THE STAR FORMATION NEWSLETTER - CiteSeerX

THE STAR FORMATION NEWSLETTERAn electronic publication dedicated to early stellar/planetary evolution and molecular clouds

No. 258 — 6 June 2014 Editor: Bo Reipurth ([email protected])

The Star Formation Newsletter

Editor: Bo [email protected]

Technical Editor: Eli [email protected]

Technical Assistant: Hsi-Wei [email protected]

Editorial Board

Joao AlvesAlan Boss

Jerome BouvierLee Hartmann

Thomas HenningPaul Ho

Jes JorgensenCharles J. Lada

Thijs KouwenhovenMichael R. MeyerRalph Pudritz

Luis Felipe RodrıguezEwine van Dishoeck

Hans Zinnecker

The Star Formation Newsletter is a vehicle forfast distribution of information of interest for as-tronomers working on star and planet formationand molecular clouds. You can submit materialfor the following sections: Abstracts of recentlyaccepted papers (only for papers sent to refereedjournals), Abstracts of recently accepted major re-views (not standard conference contributions), Dis-sertation Abstracts (presenting abstracts of newPh.D dissertations), Meetings (announcing meet-ings broadly of interest to the star and planet for-mation and early solar system community), NewJobs (advertising jobs specifically aimed towardspersons within the areas of the Newsletter), andShort Announcements (where you can inform or re-quest information from the community). Addition-ally, the Newsletter brings short overview articleson objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

Newsletter Archivewww.ifa.hawaii.edu/users/reipurth/newsletter.htm

List of Contents

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

My Favorite Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Abstracts of Newly Accepted Papers . . . . . . . . . . 12

Abstracts of Newly Accepted Major Reviews . 41

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

New and Upcoming Meetings . . . . . . . . . . . . . . . . . 44

Cover Picture

The cover shows a first-light image with ESO’sSPHERE - the Spectro-Polarimetric High-contrastExoplanet REsearch instrument mounted on theVLT. SPHERE’s main goal is to find and character-ize giant exoplanets orbiting nearby stars by directimaging. SPHERE combines adaptive optics witha coronagraph and differential imaging. The imageshows the well known dust ring around HR4796A, aprobable member of the TW Hya association. Thestar, which is a component in a 7.7 arcsec visual bi-nary, is young, about 8 Myr, with a spectral type ofA0 V. It is surrounded by a dust ring with a radiusof 75 AU.

Image courtesy ESO/J.-L. Beuzit et al./SPHEREConsortium

Submitting your abstracts

Latex macros for submitting abstractsand dissertation abstracts (by e-mail [email protected]) are appended toeach Call for Abstracts. You can alsosubmit via the Newsletter web inter-face at http://www2.ifa.hawaii.edu/star-formation/index.cfm

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Luis Felipe Rodrıguezin conversation with Bo Reipurth

Q:Who was your Ph. D. thesis adviser and what was yourthesis about?

A: I did my undergraduate thesis in Physics at the Na-tional University of Mexico, under the direction of SilviaTorres-Peimbert (who is now President-elect of the Inter-national Astronomical Union). The thesis was on ioniza-tion structures of planetary nebulae, a topic of optical as-tronomy with a long tradition in my country. At that time(1974) we did not have graduate programs in Astronomyin Mexico, so I applied and was accepted at Harvard.

I left for Harvard with the belief that I was going to con-tinue working on optical astronomy, but after taking thefirst classes I was astounded by the relevance of multiwave-length astronomy and decided that I had to learn one ofthese relatively new astronomies and later start it in Mex-ico. Interestingly, Riccardo Giaconni was my first adviserat Harvard and I guess I could have specialized in X-rayastronomy, but in those days I got the impression that todo observational work in this spectral window you neededto be in the USA or Europe and I wanted to return to mycountry. So, the obvious choice was radio astronomy, thatwas mature enough for one to be able to do research fromany place in the world, using well-established facilities.

My Ph. D. thesis adviser was Eric Chaisson, an expert insingle-dish observations and in the study of radio recom-bination lines. Since a lot of work was already done instudying galactic HII regions in the recombination lines,we decided to study the ionized gas around the galacticcenter. The recombination lines from this region are muchwider (hundreds of km/sec) than those of normal galacticHII regions (tens of km/sec) and combining our data withline observations of other tracers we came to the conclu-sion that the kinematics of the ionized gas around Sgr A*was best explained by a combination of the known stellar

population plus a supermassive black hole (conservatively,we called it a central mass point), with a mass of aboutfive million solar masses. However, this evidence for theexistence of a supermassive black hole at the center of theMilky Way was not considered fully convincing, since thekinematics of gas can be affected by things such as super-nova explosions and pressure gradients. As we all know,most astronomers became convinced of the presence of asupermassive black hole there with the fantastic work ofthe groups of Reinhard Genzel and Andrea Ghez, that wasmade with the motion of stars and was unquestionable.

Q: How did you become an expert in centimeter radio in-terferometry?

A: In the last two years of my Ph. D. I realized that toget high angular resolution information in the radio youneeded, of course, to learn interferometry. I started work-ing under the guidance of Jim Moran, one of the world’sforemost experts in the field. I remember our first trip tothe yet uncompleted Very Large Array in New Mexico todo observations of the surroundings of Herbig-Haro can-didates, searching for their exciting sources. I learned alot from Jim, as well as from the very knowledgeable staffof the US National Radio Astronomy Observatory. I stillpublish occassionally with Jim and, yes, I am still learningfrom him.

Q: You have studied thermal radio jets in many regions.What have you learned about the collimation and otherparameters of such jets?

A: The study of thermal jets has been very useful. Theylocate accurately the position of the exciting sources ofoutflows and allow the study of the phenomenon very closeto the young star. One can also get an estimate of the ion-ized mass loss rate and of the direction of the gas ejectedby the system in the last years or decades. The observa-tions suggest that within 100 AU or so from the star thejet has modest collimation, but that collimation increasesfarther away. In particular, most HH objects suggest highcollimation at large distances from the exciting star.

Q: You have used the VLA extensively to study Herbig-Haro objects and their driving sources. Especially the clas-sical system HH 1/2 has provided beautiful results. Are youcontinuing these studies?

A: Indeed, HH 1/2 has been a key object in the study ofthe outflow phenomenon in star formation. They were thefirst HH objects, discovered by Herbig and Haro back inthe 1950s. The 1981 paper of Herbig and Jones reportinglarge diverging proper motions for these two objects indi-cated that they shared an exciting source, somewhere inbetween them. We were part of the US-Mexico collabora-tion that in 1986 reported the VLA detection of a radiosource right at the middle of the system, that was iden-tified as the exciting source. These and other important

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contributions consolidated a new paradigm for star for-mation, in which the forming star not only accretes gas,but also ejects it in collimated jets that produce the HHobjects and the bipolar molecular outflows.

Q: You have published many papers on the Cepheus Aoutflow region. What makes this region so interesting?

A: Cepheus A is very important because it was the firsthigh-mass young star that exhibited similar phenomenato that seen in low-mass protostars, that is, collimatedoutflows and the possible presence of a circumstellar disk.These results pointed to the idea that stars of all massesshare the same formation mechanism.

Q: Among the many Herbig-Haro energy sources you havestudied, L1551 IRS5 has been the subject of many of youranalyses. What have you learned by studying this source?

A: For many years we all thought that L1551 IRS5 wasa single star, producing a single outflow. However, in the1990s it became clear that it was a relatively close binarysystem (with a projected separation in the sky of about45 AU), with each star having its own disk and its ownjet system. We learnt that star formation via the disk-jet combination is a very robust mechanism, taking placeeven in close binary systems.

Q: You and Salvador Curiel and other team members havediscovered and studied the Serpens triple radio source. Whatmakes this source so special?

A: The Serpens triple is a neat system that clearly showsproper motions. It was also one of the first systems thatshowed evidence of non-thermal (synchrotron) emission inits lobes. I have had the pleasure to work with other ob-servers such as Salvador Curiel, Jose M. Torrelles, andyourself, as well as with theoreticians like Jorge Canto,Susana Lizano, Alex Raga and Paola D’Alessio. Star for-mation is one of the strongest science fields in Mexico,thanks to the contribution of many researchers.

Q: Laurent Loinard and you and other team members haveused radio parallaxes to determine distances to nearby starforming regions with unprecedented accuracy. How accu-rate can this be done, and how many regions are amenableto such analysis?

A: For the best cases, one can get accuracies below 1%. Ilove to give my radio parallax talk to physicists, who usu-ally believe that astronomy is an order of magnitude sci-ence, and are shocked by these results. Laurent does thiswork using the compact gyrosynchrotron emission from ac-tive magnetospheres of low-mass young stars. Mark Reidand Karl Menten head a similar effort that uses maseremission and is better suited for regions of massive starformation. The synchrotron technique is good to a fewkpc and the maser technique can be applied to most ofthe galaxy.

Q: Your team have measured proper motions of the Becklin-Neugebauer object and Radio Source I in Orion. What areyour conclusions, and are you continuing to study this re-gion?

A: Luis Zapata, a young researcher at our Center, leadsthis effort. As the star-disk paradigm becomes strongeras an explanation for the formation of stars of all masses,on the other hand we have this amazing region where anexplosion that can be observed in the gas and stars tookplace some 500 years ago and may point to the formationof a close binary or even to the fusion of two stars. We needto find more examples of these explosions and understandwhat they mean. Recently, Luis reported a similar casein DR21, so perhaps they are not as rare as previouslythought. We are searching for other examples.

Q: You and Felix Mirabel have discovered and studied anumber of relativistic jets inside our Galaxy.

A: During a sabbatical I took at the VLA, I had the op-portunity of discovering the first example of superluminalmotions for a galactic source. These sources are X-raybinaries that are sometimes called microquasars becausethey mimic, in small scale, the phenomena observed inquasars. Felix believed that jets should be present in stel-lar mass black holes (as they are in supermassive blackholes at the centers of galaxies) and this work showed thatthe physics around black holes is similar, regardless of themass of the black hole.

Q: You founded the UNAM-Morelia Center, with a strongfocus on star formation studies, and you were director formany years. Was that a difficult process, and how is theCenter doing?

A: I hate doing administration, but sometimes it is im-possible to avoid it. I was first Director of the big MexicoCity Astronomy institute and later, Yolanda Gomez, Su-sana Lizano, Stan Kurtz, Enrique Vazquez, myself andother colleagues started the Morelia Center. It was a dif-ficult process because resources are scarce in Mexico andthe established institutions always see the new ones as po-tential competitors. Altogether, the experience has beenvery rewarding for all of us. The Center is small (about 20researchers) but the bibliometric indicators place us as oneof the Mexican institutions with the largest internationalimpact.

Q: Astronomy has in recent years been suffering all overthe world due to the financial crisis. What is the situationfor Mexican astronomy?

A: The investment in science in Mexico is not only smallbut many times it is also poorly used. In terms of peo-ple, we have a great potential, but we have to get betterorganized and use these modest resources wisely.

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My Favorite ObjectChamaeleon-MMS1

Miikka Vaisala

Chamaeleon-MMS1 (Cha-MMS1) is a very young proto-stellar core which is associated with the reflection nebulaCederblad 110 located in the centre of the Chamaeleon I(Cha I) cloud complex. Cederblad 110 is considered to bean active site of star formation within Cha I (e.g., Prusti etal. 1991; Persi et al. 2001). As such, Cha-MMS1 is locatednear a small cluster of young stellar objects (YSOs) calledCed 110 IRS2, IRS4, and IRS6. Distance to Cha-MMS1is ∼ 160 pc which makes it a relatively nearby object. Alook into some features of the core and its environmentcan be seen in the Fig. 1.

Cha-MMS1 was discovered by Reipurth et al. (1996),based on a λ = 1.3 mm survey. It is a cold, dense corewhich is particularly interesting, because it has been sug-gested by Belloche et al. (2006, 2011), Cordiner et al.(2012) and Tsitali et al. (2013) to be still in the first hydro-static core (FHSC, see Larson 1969) stage of development.As the FSHC is such a brief stage within the process of corecollapse, Cha-MMS1 might provide a rare opportunity toobserve this phenomenon. And to add more complexityin the mix, Cha-MMS1 is apparently hit by a molecularoutflow emitted by Ced110 IRS4 (Hiramatsu et al. 2007;Ladd et al. 2011). Cha-MMS1 being virially unstable, theoutflow could further destabilize the core against collapse.

My personal interest concerning the Cha-MMS1 is con-nected with our study based on high-resolution ammoniaobservations of the Cha-MMS1 with the Australian Tele-scope Compact Array or ATCA (Vaisala et al. 2014). Inour study, we found that the ammonia core possesses arotating bar-like structure, and we considered the possi-bility that a very early stage molecular outflow could bepresent deep within the core.

Evolutionary state of Chamaeleon-MMS1

The question of the evolutionary state of Cha-MMS1 isimportant, because the core might be an example of avery transient stage in star formation. Originally Larson(1969) predicted a stage in the core collapse, where afterthe initial collapse the internal pressure within the corewould grow strong enough to resist the collapse. How-ever, this first hydrostatic core would last a relatively shorttime (within a few thousand years) until the dissociationof molecular hydrogen would allow the core to collapseeven further.

Belloche et al. (2006) have suggested that Cha-MMS1 isat the stage just prior to the Class 0 stage, namely FHSC.First, they suspect this because of deuterium fractiona-

tion. Their observed fractionation, [N2D+]

[N2H+] = 11 ± 3%,

comes between the fractionation observed in L1544 (16−23%) and L1521F (5−10%) (Crapsi et al. 2005), a knownClass 0 protostar. In addition, they see no sign of molec-ular outflow originating from Cha-MMS1. Instead theyattribute the origin of Herbig-Haro objects HH 49/50 tothe Class I protostar Ced 110 IRS 4, instead of Cha-MMS1as suggested originally by Reipurth et al. (1996). Further-more, Tsitali et al. (2013) point out that the 70 µm fluxdensity of the central source would imply a very low lumi-nosity which in turn would be consistent with an FHSC,as it would be clearly too low for a true protostar.

On the other hand, Cha-MMS1 has a large abundanceof carbon-chain-bearing species, in similar amounts com-pared to other carbon-chair-rich interstellar clouds (Cor-diner et al. 2012). This may hint that oxygen is frozen-outwithin the core, but another option is that the core mightbe heated by a protostar inside.

In Vaisala et al. (2013) we analysed the SED of Cha-MMS1 by fitting model SEDs to the observed flux den-sities. The model SEDs were based on YSO models byRobitaille et al. (2006, 2007) which consists of a grid of20 000 two-dimensional YSO radiation transfer models.The best fit acquired suggests the luminosity of 0.6 L⊙,which is higher than what just a FHSC would produce. Assuch, the model indicates that the Cha-MMS1 would havereached already to the Class 0 stage. However, the datapoint at 70 µm does not fit very well with the models, andthe models of Robitaille et al. (2006) only cover YSOs withcentral temperatures above 2000 K. As Commercon et al.(2012) suggests, it is very difficult to distinguish betweenFHSCs and Class 0 YSOs just based on SED information.

However, an observation of a molecular outflow might notsettle the question either. It is theoretically feasible thata slow, weakly collimated outflow might be produced al-ready during the FHSC stage of core collapse (see e.g.Machida et al. 2008). There exists some candidate out-flows from FHSCs or very low luminosity objects such as

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Figure 1: Left: Intensity of thermal dust emission at the wavelength λ = 250 µm in a region of 5′ × 5′ aroundCha-MMS1. The Spitzer 24-µm peak is indicated with a red triangle. The red circle in the top right corresponds tothe average Herschel beamsize (FWHM, 18′′) at 250 µm. The small white ellipse shows the synthesised ATCA beam(∼ 7′′). Middle: Dust temperature in the same region. The red circle in the top right represents the resolution ofthe calculated Tdust and H2 column density maps (40′′). Right: H2 column density derived from the 250-µm opticalthickness. The dust temperature and column density maps are derived by fitting a modified blackbody function tothe Herschel intensity maps. The locations of three prominent YSOs, Ced110 IRS2 (right), IRS4 (middle), and IRS6(left), are indicated with asterisks. The plus sign indicates the location of the millimetre source Cha-MMS1a (Reipurthet al. 1996). The white contour shows the integrated intensity level 5 K km s−1 of the NH3(1, 1) satellites as observedwith ATCA. The yellow contours show the integrated intensity of the NH3(1, 1) line emission (K km s−1) observed atParkes Radio Telescope. The Parkes beam is shown with the large yellow circle in the top right. (Credit: Vaisala etal., A&A, 564, A99, 2014, reproduced with permission c© ESO.)

L673-7 (Dunham et al. 2010), Per-Bolo 58 (Enoch et al.2010; Dunham et al. 2011), L1448 IRS 2E (Chen et al.2010); L1451 (Pineda et al. 2011), CB 17 MMS (Chenet al. 2012), and L1521F-IRS (Takahashi et al. 2013), al-though also in these cases making a distinction between anFHSC and a very low luminosity Class 0 object is difficult.

Presence of an outflow?

Considering the state of the evolution of the Cha-MMS1core, the question of outflow still remains. Despite thatBelloche et al. (2006) do not see any clear signs of out-flows, some features of our NH3 (1, 1) observations havemade us to ask the question if an actual early stage molec-ular outflow could really be present within the core. Itwould be reasonable to consider the presence of an out-flow even in the case of FHSC, because such candidatesexist.

By making a two-layer fit to the NH3 (1, 1) spectral lines,we found that the background component is highly excitedalong the axis of rotation (see Fig. 2, Vaisala et al. 2014).This hints toward a presence of some energetic process

inside. The elongated geometry of the excited componentcould be caused by an early molecular outflow seen nearlyin the plane of the sky. The projected total length of thehypothetical outflow is approximately 9000 AU.

We also found tentative 1.3 cm continuum emission alignedwith the assumed rotation axis (Vaisala et al. 2014). Thisstring of weak sources near the ammonia maximum is only3–4 times stronger than the rms noise in the area. There-fore, this observation should be confirmed, or disprovedby more sensitive observations of the 1.3 cm continuum.Regardless, such emission could be a result of shocked gasdue to outflow within the core.

No CO outflow originating in Cha-MMS1 has been de-tected. If there is indeed an outflow present, the likelyreason for non-detection is that the high-velocity wings ofthe spectra may still be confined in the very inner regionsof the core. Therefore, it can have escaped the previoussingle-dish surveys.

However, with our observations we cannot conclusivelyconfirm a presence of an outflow cavity within the core. Amore definitive solution would require more detailed andsensitive observations.

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Figure 2: The region where the two-layer fit is applicableis shown with white diamonds on the integrated bright-ness temperature map of the NH3 (1, 1) satellites. Blueplus signs indicate positions where Tex,bg > 11 K, i.e.,where the excitation temperature of the background com-ponent exceeds the average kinetic temperature of thecore. (Credit: Vaisala et al., A&A, 564, A99, 2014, re-produced with permission c© ESO.)

Interaction with Ced 110 IRS4 outflow

Regardless of outflow within the Cha-MMS1 core itself,observations by Hiramatsu et al. (2007) and Ladd et al.(2011) have shown that the blueshifted lobe of the out-flow from the Ced 110 IRS 4 collides with the Cha-MMS1core. In addition Ladd et al. (2011) state that some ofthe material is displaced by the collision between the coreand the outflow. Here, Ladd et al. (2011) consider twopossibilities: a direct collision or a glancing blow. Theiranalysis supports more of the glancing blow scenario.

The reason for this is due to the ablated material by thecollision. With a direct collision, the outflow would haveenough momentum to just plough through the core. Incase of the direct collision a ”splash” may be produced,which might explain the displaced material. However,Ladd et al. (2011) do not see any sign of interaction inthe bulk of N2H

+ emission from Cha-MMS1, which shouldbe present considering the direction of HH 49/50, if thecollision was indeed a direct one.

In our high-resolution ammonia emission map, we do notsee any strong signs of a direct collision (Vaisala et al.

2014). However, perhaps the steeper velocity gradient inthe northeast part of the core might be explained by anindirect collision of the outflow. Alternatively we see abar-like density distribution with apparent rotation, whereammonia shows strong signs of self-absorption.

Things to look for

Although there are reasons to consider the presence ofan outflow within Cha-MMS1, our ammonia observationsby themselves cannot confirm the existence of it. There-fore, future high-resolution observations, such as a searchfor a compact CO outflow, could likely either confirm ordeny its existence. In addition, probing the distributionand kinematics of dense gas in the neighbourhood of theSpitzer 24 µm source would be fruitful, perhaps even of-fering some insight into how the collision from the IRS4outflow dynamically affects the whole system.

References:

Belloche, A., Parise, B., van der Tak, F. F. S., et al. 2006, A&A,

454, L51

Belloche, A., Schuller, F., Parise, B., et al. 2011, A&A, 527, A145

Chen, X., Arce, H. G., Zhang, Q., et al. 2010, ApJ, 715, 1344

Chen, X., Arce, H. G., Dunham, M. M., et al. 2012, ApJ, 751, 89

Commercon, B., Launhardt, R., Dullemond, C., Henning, T. 2012,

A&A, 545, A98

Cordiner, M. A., Charnley, S. B., Wirstrom, E. S., Smith, R. G.

2012, ApJ, 744, 131

Crapsi, A., Caselli, P., Walmsley, C. M., Myers, P. C., Tafalla, M.,

Lee, C. W., Bourke, T. L. 2005, ApJ, 619, 379

Dunham, M. M., Evans, N. J., Bourke, T. L., et al. 2010, ApJ, 721,

995

Dunham, M. M., Chen, X., Arce, H. G., et al. 2011, ApJ, 742, 1

Enoch, M. L., Lee, J.-E., Harvey, P., Dunham, M. M., Schnee, S.

2010, ApJ, 722, L33

Hiramatsu, M., Hayakawa, T., Tatematsu, K., et al. 2007, ApJ, 664,

964

Ladd, E. F., Wong, T., Bourke, T. L., Thompson, K. L. 2011, ApJ,

743, 108

Larson, R. B. 1969, MNRAS, 145, 271

Machida, M. N., Inutsuka, S.-i., Matsumoto, T. 2008, ApJ, 676, 1088

Persi, P., Marenzi, A. R., Gomez, M., Olofsson, G. 2001, A&A, 376,

907

Pineda, J. E., Arce, H. G., Schnee, S., et al. 2011, ApJ, 743, 201

Prusti, T., Clark, F. O., Whittet, D. C. B., Laureijs, R. J., Zhang,

C. Y. 1991, MNRAS, 251, 303

Reipurth, B., Nyman, L.-., Chini, R. 1996, A&A, 314, 258

Robitaille, T. P., Whitney, B. A., Indebetouw, R., Wood, K., Denz-

more, P. 2006, ApJS, 167, 256

Robitaille, T. P., Whitney, B. A., Indebetouw, R., Wood, K. 2007,

ApJS, 169, 328

Takahashi, S., Ohashi, N., Bourke, T. L. 2013, ApJ, 774, 20

Tsitali, A. E., Belloche, A., Commeron, B., Menten, K. M. 2013,

A&A, 557, A98

Vaisala, M.S., Harju, J., Mantere, M.J., Miettinen, O., Sault, R. S.,

Walmsley, C.M., Whiteoak, J. B. 2014, A&A, 564, 99

7

Perspective

Observing ProtoplanetaryDisks using Chondrules

Steve Desch

The properties of protoplanetary disks are difficult to probewith astronomical observations. Meteorites one can holdin one’s hand provide a wealth of specific detail about theconditions and physical properties in disks. As much aboutdisks has been learned from microscopes as from telescopes...

1 Telescopes vs. microscopes

Protoplanetary disks have been recognized as the birth-places of planets and solar systems since Laplace and Kant,but detailed data took until the 20th century to acquireand are still incomplete. To understand disk evolution andthe formation of planets, modelers need such informationas the mass Md of the disk, and the surface density Σ(r)and temperature T (r) within the disk as functions of dis-tance r from the star. Modelers also require constraintson the mechanisms of angular momentum transport in thedisk and the timescales over which the disk mass is lostand accreted onto the central star. These data are difficultto obtain through astronomical observation.

Only in recent decades have astronomical observationssupplied some of this information, and our knowledge re-mains incomplete. Just to see the silhouetted protoplan-etary disks in the Orion Nebula (Figure 1) required useof the Hubble Space Telescope (McCaughrean & O’Dell1996), and each of the methods used to obtain the neededdata faces limitations. Surveys (Haisch et al. 2001) suggesttypical disk lifetimes of 3 to 6 Myr, but these observationsof infrared excesses do not probe the disk more than 1

AU from the star, where considerable planet-forming massmay reside. Disk temperatures are constrained by infraredspectral energy distributions, but these probe only the sur-face temperatures of disks and not the more importanttemperatures at the midplanes. Disk mass is constrainedby the flux emitted at millimeter wavelengths, providedthe solid particles emitting the radiation are smaller thanmillimeter-sized (e.g., Eisner & Carpenter 2006); but suchobservations are blind to any solids mass locked up inplanets. While the Atacama Large Millimeter Array maychange the picture, observations until now have lacked thespatial resolution to measure surface densities within ∼ 10AU. For the same reason it has not been possible to ob-serve spiral shocks in protoplanetary disks that might in-dicate angular momentum transport through gravitationalinstabilities. Astronomical observations alone cannot sup-ply all the information needed to model planet formation.

Instead, meteorites can supply an enormous amount of in-formation about protoplanetary disks, at least the one oursolar system formed from. They can be analyzed for ele-mental and isotopic compositions, with precisions that areastounding compared to astronomical data, usually at theparts per million level. Radiometric dating of meteoritesis how we know that the solar system and Sun formed 4568Myr ago (Bouvier & Wadhwa 2010), and many events canbe timed to within ∼ 105 years (a precision < 0.01%!).In combination with astrophysical modeling, one can inferthe pressures, temperatures, and physical processes actingin the protoplanetary disk. My purpose here is to describethe type of data obtained from meteorites, especially fromchondrules within chondrites (unmelted meteorites), andto explain what such measurements and models have re-vealed about our protoplanetary disk.

2 Data about chondrule formation

The study of meteorites has traditionally divided alongdisciplinary lines. Developing quantitative physical mod-els to describe events in the Sun’s protoplanetary disk isthe domain of the astrophysicists, but often this commu-nity is unaware of the richness of meteoritic data. Partlythis is because the rocks themselves are described by me-teoriticists with backgrounds in geology, using jargon andterminology that initially can be opaque to astrophysi-cists. But the essential information, as follows, is eas-ily learned. Meteorites are asteroid fragments that inter-cept the Earth. Asteroids that melt from internal heatingby radionuclides produce iron meteorites or stony achon-drites. Meteorites from unmelted bodies are called chon-drites, because they contain chondrules, in addition tocalcium-rich, aluminum-rich inclusions (CAIs), and micron-sized matrix grains. Each component provides useful con-straints on events in the solar nebula.

8

Figure 1: Silhouetted protoplanetary disk in the OrionNebula seen with the Hubble Space Telescope (McCaugh-rean & O’Dell 1996). Data such as midplane density andtemperature at 1 AU are difficult to obtain from such im-ages. Scale is about 1000 AU across.

CAIs are typically large, up to centimeter-sized, and com-posed of refractory minerals predicted to condense firstfrom a cooling solar-composition gas. They are believedto be the first solids formed in the solar system. At thetime of their formation, they contained abundant 26Al, ashort-lived radionuclide with a half life of 0.7 Myr. Ma-trix grains contain a mix of condensates as well as frag-ments of chondrules and CAIs. Chondrules (see reviewsby Connolly & Desch 2004, Desch et al. 2005, 2010) aretypically a few hundred microns to a millimeter in diam-eter, contained live 26Al when they formed (but not asmuch as CAIs), are composed of ferromagnesian (Fe- andMg-bearing) silicates. They also have igneous textures,meaning they contain crystals whose sizes and shapes in-dicate that chondrules crystallized from a melt (Figure 2).This was recognized as long ago as 1877 when Sorby calledthem “drops of fiery rain”. What melted the chondrulesis a central mystery in meteoritics. In a typical chondrite,chondrules make up 50-80% of the mass, and the aster-oid belt contains at least 1024 g of chondrules (Desch etal. 2012). Meteoriticists have long presented ideas aboutwhat could have melted that much rock, but quantitativemodels and rigorous tests require astrophysical modeling.

A successful astrophysical model of chondrule formationmust explain the following, detailed information aboutchondrules (see review by Desch et al. 2012 for references).Chondrules contain primary S, which only condenses be-

Figure 2: Thin section of a chondrule from the CV3chondrite NWA 6207, seen through a petrographic mi-croscope, illuminated by cross-polarized light, revealinga porphyritic igneous texture: hundreds of crystals thatgrew relatively slowly from a melt. This chondrule alsocontains large relict grains that are fragments of previouslycreated chondrules with other textures. Scale is about 1millimeter across. (http://meteorite-times.com/micro-visions/seeing-processing-in-a-cv3)

low 650 K, so chondrules formed in a region of the diskcooler than this. The majority (≈ 85% in ordinary chon-drites) of chondrules have porphyritic textures (depictedin Figure 1), with hundreds of well-shaped crystals. Thisrequires that chondrules reached peak temperatures suffi-cient to melt most but not all seed nuclei, and then cooledslowly enough for crystals to form. Experiments, in whichartificial chondrules are melted in furnaces, indicate thatpeak temperatures ≈ 1750− 2100 K are needed, and thatchondrules must cool at rates ∼ 10− 1000Khr−1 throughthe crystallization temperatures ≈ 1400 − 1800K. Thecooling rate from the peak itself may have been faster:volatile species like K, Na and S should have been lostwithin minutes from a fully molten chondrules; since chon-drules retain these, cooling rates from the peak∼ 104Khr−1

are inferred. Likewise, the heating of chondrules musthave been rapid, only minutes. Even during the crystal-lization stage, retention of volatiles requires a high partialpressure of these species in the gas, which in turn placesconstraints (Cuzzi & Alexander 2006) on the density ofchondrules (∼ 10−5 cm−3) and the size of the region overwhich chondrules were melted (> 103 km). It also requireshigh pressures, > 10−3 bar. Alexander et al. (2008) haveargued for a partial pressure∼ 10−3 bar of Na vapor alone.It is known that 5% of chondrules are compound, stuckto another chondrule while both were plastic. This also

9

argues for a number density of chondrules ∼ 10−5 cm−3.From radiometric dating using 26Al, we know that mostchondrules in our collections formed over a range of times2 to 3 Myr after CAIs. Chondrules often contain frag-ments of previously formed chondrules (Figure 2). Chon-drules and matrix grains often appear chemically comple-mentary, meaning that matrix grains are enriched in someelements, and chondrules depleted in the same elements(compared to a solar composition). This strongly sug-gests chondrules and matrix grains formed from the samebatch of solar-composition material, implying that chon-drules formed locally, about 2 to 3 AU from the Sun inthe protoplanetary disk. Astrophysical models of chon-drule formation are constrained by a remarkable wealth ofdata about chondrules.

3 Melting of chondrules by shocks

To date, the model that most successfully explains thesedata is the nebular shock model (Connolly & Love 1998;Iida et al. 2001; Desch & Connolly 2002; Ciesla & Hood2002; Morris & Desch 2010; Morris et al. 2012; Boley etal. 2013), in which chondrules were melted as they passedthrough a shock wave in the gas of the protoplanetary disk.Critiques of alternative models were provided by Desch etal. (2010, 2012). Many (lightning, X winds) simply do notmatch the data. Other models (asteroid impacts) mightbe applicable to some chondrules, but have not been quan-titatively developed enough to be tested. The shock wavemodel has been fully developed, taking into account theseparate hydrodynamics of gas and particles, dissociationof H2 molecules, radiative transfer through dust and chon-drules, etc., into detailed numerical codes. The shock wavemodel makes several quantitative predictions that matchwhat is known about chondrules.

The shock wave melts chondrules through the followingsequence of events (Desch & Connolly 2002, Desch et al.2005; Morris & Desch 2010). As the shock wave advancestoward a region in the nebula at speeds ≈ 7 to 8 kms−1,chondrule precursors (clumps of dust, previous chondrulefragments, and possibly C or ice) are heated by the in-frared radiation emitted by solids already heated behindthe shock. The precursors are already partially liquidby the time the shock itself arrives, at which point thechondrule is immersed in gas streaming past it at about6 kms−1. The friction of the streaming gas accelerates thechondrules within 1 minute, during which time chondrulesare considerably heated. During this first minute, chon-drules cool several hundred K, at a rate ∼ 104Khr−1.After this, chondrules are immersed in the hot (> 2000K), compressed gas behind the shock. The gas and chon-drules form a thermally coupled system, and both compo-nents cool only as fast as they can travel several opticaldepths away from the shock front. For a large-scale shock

(≫ 105 km in lateral extent), this typically requires dis-tances > 105 km, taking many hours. During this interval,chondrules (and the gas) cool at rates of tens of K perhour. For a shock with lateral extent < 104 km, cooling ismuch more rapid, typically at ∼ 1000− 3000Khr−1 (Bo-ley et al. 2013; Morris et al. 2012). In the same region inwhich chondrules form, micron-sized mineral grains cancondense from the gas. Eventually the chondrules andcondensed grains cool and mix with other nebular mate-rials that have not been heated by the shock.

The timescales and thermal histories above assume a gasdensity ρg ∼ 10−9 g cm−3, and a chondrule-to-gas mass ra-tio ≈ 0.04. With these parameters, all aspects of the ther-mal histories of chondrules in solar nebula shocks matchthe meteoritic constraints. These parameters are also con-sistent with the other constraints, such as the chondruledensity implied from the compound chondrule frequency.These are plausible parameters: at a few AU, the mini-mum mass solar nebula model of Weidenschilling (1977)predicts ρg ∼ 10−10 g cm−3, so these densities require adisk mass ∼ 0.1M⊙, but this is not unreasonable (Desch2007). A moderate but reasonable amount of gravitationalsettling of chondrules to the disk midplane is also implied.

The other meteoritic constraints also can be met by theshock model, provided that shocks ≈ 8 kms−1 can be gen-erated, repeatably, over many Myr. Shocks must act atthe midplane of the 2-3 AU region of the disk. Largeshocks (lateral extent ≫ 105 km) more easily meet theconstraints on cooling rates, but smaller shocks (∼ 103

km) may also comply.

4 Shocks in protoplanetary disks

Meteoritic data, coupled with numerical modeling of chon-drule formation, point to two sources of shocks: large “spi-ral” shocks in the solar nebula, driven by gravitationalinstabilities (Wood 1984; Boss & Durisen 2005; Boley &Durisen 2008); or bow shocks around large planetary bod-ies on eccentric orbits (Hood 1998; Weidenschilling 1998;Ciesla et al. 2004; Morris et al. 2012; Boley et al. 2013).Shocks driven by gravitational instabilities are large, withlateral extent ≫ 106 km. Figure 3 illustrates how gravita-tional instabilities may manifest themselves in disks andcreate shocks. Bow shocks capable of melting chondruleswould arise around planetary embryos several ×103 kmin radius, if they are driven into orbital resonances sothat they acquire orbits with high eccentricity (> 0.3 ormore). Figure 4 shows the gas temperatures surroundingsuch a body moving with speed 8 kms−1 with respect tothe gas in Keplerian rotation. Chondrules in gravitationalinstability-driven shocks cool more slowly, easily match-ing the meteoritic constraints, while chondrules melted inbow shocks tend to cool at rates > 103Khr−1, consis-

10

Figure 3: False color representation of the midplane den-sities in the gravitationally unstable disk model of Boss &Durisen (2005). Region shown is 20 AU in radius, and a1M⊙ protostar lies at the center of the disk, whose innerboundary is 2 AU in radius. A strong shock between verylow-density material (black) and moderate- density mate-rial (purple) is seen at the 12 o’clock position, extendingfrom 2 AU to about 4 AU in radius.

Figure 4: Temperatures of gas in the bow shock regionaround a planetary embryo moving at 8 kms−1 to theright, as calculated by Boley et al. (2013). The trajecto-ries of chondrule precursors and chondrules are shown inblue (moving from right to left with respect to the body).

tent with the constraints but just barely. On the otherhand, passage of chondrules through the atmospheres ofthese bodies may explain the high Na vapor pressures dur-ing chondrule formation, something impossible to explainusing nebular shocks. Further investigations will revealwhich type of shock melted chondrules. Of course, bothmay have: the two models are not exclusive.

Either model has profound implications for protoplanetarydisks. Gravitational instabilities require massive disks,∼ 0.1M⊙, as do the thermal constraints. While not im-plausible, the majority of disks weighed by measuring theirmillimeter fluxes have lower masses, ∼ 0.005M⊙ (Eisner& Carpenter 2006). The planetary bow shock model re-quires planetary embryos to form before the time of chon-drule formation, < 2 Myr after CAIs. Chondrules wouldnot represent the building blocks of planets, but ratherthe crumbs left over after planet formation. Importantly,a substantial fraction of the solids mass in protoplanetarydisks, even young disks < 2 Myr in age, must be lockedin planets and hidden from millimeter observations. Themasses of protoplanetary disks are very likely grossly un-derestimated by astronomical observations.

This is just one of the many insights gained by leveragingchondrules and meteoritic data and using microscopes, nottelescopes, to observe a protoplanetary disk.

References:

Alexander, C. M. O.’D., Grossman, J. N., Ebel, D. S. & Ciesla, F.

J. 2008, Science 320, 1617.

Boley, A. C. & Durisen, R. H. 2008, ApJ 685, 1193.

Boley, A. C., Morris, M. A. & Desch, S. J. 2013, ApJ 776, 101.

Boss, A. P. & Durisen, R. H. 2005, ApJ 621, L137.

Bouvier, A. & Wadhwa, M. 2010, Nature Geoscience 3, 637.

Ciesla, F. J. & Hood, L. L. 2002, Icarus 158, 281.

Ciesla, F. J., Hood, L. L. & Weidenschilling, S. J. 2004, Icarus 158,

281.

Connolly, Jr., H. C. & Desch, S. J. 2004, Chemie der Erde 64, 95.

Connolly, Jr., H. C. & Love, S. G. 1998, Science, 280, 62.

Cuzzi, J. N. & Alexander, C. M. O’D. 1996, Nature 441, 483.

Desch, S. J. 2007, ApJ 671, 878.

Desch, S. J. & Connolly, Jr., H. C. 2002, Meteorit. and Planet. Sci.

37, 183.

Desch, S. J., Ciesla, F. J., Hood, L. L. & Nakamoto, T. 2005, in

Chondrites and the Protoplanetary Disk, eds. A. Krot, E. R. D.

Scott and B. Reipurth, Astronomical Society of the Pacific Confer-

ence Series 341, 849.

Desch, S. J., Morris, M. A., Connolly, Jr., H. C. & Boss, A. P. 2010,

ApJ 725, 692.

Desch, S. J., Morris, M. A., Connolly, Jr., H. C. & Boss, A. P. 2012,

Meteorit. and Planet. Sci. 47, 1139.

Eisner, J. A. & Carpenter, J. M. 2006, ApJ 641, 1162.

Haisch, Jr., K. E., Lada, E. A. & Lada, C. J. 2001, ApJL 553, L153.

Iida, A., Nakamoto, T., Susa, H. & Nakagawa, Y. 2001, Icarus 153,

430.

McCaughrean, M. J. & O’Dell, R. C. 1996, AJ 111, 1977.

Morris, M. A. & Desch, S. J. 2010, ApJ 722, 1474.

Morris, M. A., Boley, A. C., Desch, S. J. & Athanassiadou, T. 2012,

ApJ 752, 27.

Weidenschilling, S. J. 1977, Ap&SS 51, 153.

Wood, J. A. 1984, Meteoritics 19, 339.

11

Abstracts of recently accepted papers

Distributions of Short-Lived Radioactive Nuclei Produced by Young Embedded StarClusters

Fred C. Adams1, Marco Fatuzzo2 and Lisa Holden3

1 University of Michigan, USA2 Xavier University, USA3 Northern Kentucky University, USA

E-mail contact: fca at umich.edu

Most star formation in the Galaxy takes place in clusters, where the most massive members can affect the propertiesof other constituent solar systems. This paper considers how clusters influence star formation and forming planetarysystems through nuclear enrichment from supernova explosions, where massive stars deliver short-lived radioactivenuclei (SLRs) to their local environment. The decay of these nuclei leads to both heating and ionization, and therebyaffects disk evolution, disk chemistry, and the accompanying process of planet formation. Nuclear enrichment cantake place on two spatial scales: [1] Within the cluster itself (ℓ ∼ 1pc), the SLRs are delivered to the circumstellardisks associated with other cluster members. [2] On the next larger scale (ℓ ∼ 2 − 10pc), SLRs are injected into thebackground molecular cloud; these nuclei provide heating and ionization to nearby star-forming regions, and to thenext generation of disks. For the first scenario, we construct the expected distributions of radioactive enrichment levelsprovided by embedded clusters. Clusters can account for the SLR mass fractions inferred for the early Solar Nebula,but typical SLR abundances are lower by a factor of ∼ 10. For the second scenario, we find that distributed enrichmentof SLRs in molecular clouds leads to comparable abundances. For both the direct and distributed enrichment processes,the masses of 26Al and 60Fe delivered to individual circumstellar disks typically fall in the range 10− 100pM⊙ (where1pM⊙ = 10−12M⊙). The corresponding ionization rate due to SLRs typically falls in the range ζSLR ∼ 1− 5× 10−19

sec−1. This ionization rate is smaller than that due to cosmic rays, ζCR ∼ 10−17 sec−1, but will be important inregions where cosmic rays are attenuated (e.g., disk mid-planes).

Accepted by The Astrophysical Journal

http://arXiv.org/pdf/1405.5142

Herschel’s view of the large-scale structure in the Chamaeleon dark clouds

C. Alves de Oliveira1, N. Schneider2,3, B. Merın1, T. Prusti4, A. Ribas1,5,6, N. L. J. Cox7, R. Vavrek1,V. Konyves8,9, D. Arzoumanian9, E. Puga1,10, G. L. Pilbratt4, A. Kospal4, Ph. Andre8, P. Didelon8,A. Men’shchikov8, P. Royer7, C. Waelkens7, S. Bontemps2,3, E. Winston4 and L. Spezzi11

1 European Space Agency (ESA/ESAC, SRE-O), P.O. Box 78, 28691 Villanueva de la Canada (Madrid), Spain2 Universite de Bordeaux, Laboratoire d’Astrophysique de Bordeaux, CNRS/INSU, 33270 Floirac, France3 CNRS, LAB, UMR 5804, 33270, Floirac, France4 European Space Agency (ESA/ESTEC, SRE-S), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands5 Ingenierıa y Servicios Aeroespaciales, European Space Agency (ESA/ESAC, SRE-O), P.O. Box 78, 28691 Villanuevade la Canada (Madrid), Spain6 Centro de Astrobiologia (INTA-CSIC), P.O. Box 78, 28691 Villanueva de la Canada (Madrid), Spain7 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, bus 2401, 3001 Leuven, Belgium8 Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SAp, CEA Saclay, Orme des Merisiers, 91191Gif-sur-Yvette, France9 IAS, CNRS (UMR 8617), Universite Paris-Sud 11, Batiment 121, 91400 Orsay, France10 Vega, European Space Agency (ESA/ESAC, SRE-O), P.O. Box 78, 28691, Villanueva de la Canada (Madrid), Spain11 European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany

12


E-mail contact: calves at sciops.esa.int

Context. The Chamaeleon molecular cloud complex is one of the nearest star-forming sites encompassing threemolecular clouds (Cha I, II, and III) with a different star-formation history, from quiescent (Cha III) to activelyforming stars (Cha II), and reaching the end of star-formation (Cha I).Aims. We aim at characterising the large-scale structure of the three sub-regions of the Chamaeleon molecular cloudcomplex by analysing new far-infrared images taken with the Herschel Space Observatory.Methods. We derived column density and temperature maps using PACS and SPIRE observations from the HerschelGould Belt Survey, and applied several tools, such as filament tracing, power-spectra, ∆-variance, and probabilitydistribution functions of column density (PDFs), to derive physical properties.Results. The column density maps reveal a different morphological appearance for the three clouds, with a ridge-like structure for Cha I, a clump-dominated regime for Cha II, and an intricate filamentary network for Cha III. Thefilament width is measured to be around 0.12±0.04 pc in the three clouds, and the filaments found to be gravitationallyunstable in Cha I and II, but mostly subcritical in Cha III. Faint filaments (striations) are prominent in Cha I showinga preferred alignment with the large-scale magnetic field. The PDFs of all regions show a lognormal distribution atlow column densities. For higher densities, the PDF of Cha I shows a turnover indicative of an extended higher densitycomponent, culminating with a power-law tail. Cha II shows a power-law tail with a slope characteristic of gravity.The PDF of Cha III can be best fit by a single lognormal.Conclusions. The turbulence properties of the three regions are found to be similar, pointing towards a scenario wherethe clouds are impacted by large-scale processes. The magnetic field could possibly play an important role for thestar-formation efficiency in the Chamaeleon clouds if proven that it can effectively channel material on Cha I, andpossibly Cha II, but probably less efficiently on the quiescent Cha III cloud.

Accepted by A&A

http://arxiv.org/pdf/1404.6526

Recent outburst of the young star V1180 Cas

S. Antoniucci1, A. A. Arkharov2, A. Di Paola1, T. Giannini1, A. Harutyunyan3, E. N. Kopatskaya4, V.M. Larionov2,4, G. Li Causi1,5, D. Morozova4, B. Nisini1 and F. Vitali1

1 INAF-Osservatorio Astronomico di Roma, Via Frascati 33, Monte Porzio Catone (RM), Italy2 Central Astronomical Observatory of Pulkovo, Pulkovskoe shosse 65, 196140 St. Petersburg, Russia3 Fundacion Galileo Galilei - INAF, Telescopio Nazionale Galileo, 38700 Santa Cruz de la Palma, Tenerife, Spain4 Astronomical Institute of St. Petersburg University, Russia5 INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Roma, Italy

E-mail contact: simone.antoniucci at oa-roma.inaf.it

We report on the ongoing outburst of the young variable V1180 Cas, which is known to display characteristics incommon with EXor eruptive variables. We present results that support the scenario of an accretion-driven natureof the brightness variations of the object and provide the first evidence of jet structures around the source. Wemonitored the recent flux variations of the target in the RC , J , H , and K bands. New optical and near-IR spectrataken during the current high state of V1180 Cas are presented, in conjunction with H2 narrow-band imaging ofthe source. Observed near-IR colour variations are analogous to those observed in EXors and consistent with excessemission originating from an accretion event. The spectra show numerous emission lines, which indicates accretion,ejection of matter, and an active disc. Using optical and near-IR emission features we derive a mass accretion rate of∼ 3 × 10−8M⊙ yr−1, which is an order of magnitude lower than previous estimates. In addition, a mass loss rate of∼ 4× 10−9 and ∼ 4× 10−10M⊙ yr−1 are estimated from atomic forbidden lines and H2, respectively. Our H2 imagingreveals two bright knots of emission around the source and the nearby optically invisible star V1180 Cas B, clearlyindicative of mass-loss phenomena. Higher resolution observations of the detected jet will help to clarify whetherV1180 Cas is the driving source and to determine the relation between the observed knots.

Accepted by A&A


13



HD100546 Multi-Epoch Scattered-Light Observations

Henning Avenhaus1, Sascha P. Quanz1, Michael R. Meyer1, Sean D. Brittain2, John S. Carr3 and JoanR. Najita4

1 ETH Zurich, Institute for Astronomy, Wolfgang-Pauli- Strasse 27, 8093 Zurich, Switzerland2 Department of Physics & Astronomy, 118 Kinard Labora- tory, Clemson University, Clemson, SC 29634, USA3 Naval Research Laboratory, Code 7211, Washington, DC 20375, USA4 National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85719, USA

E-mail contact: havenhaus at phys.ethz.ch

We present H , Ks and L′ filter polarimetric differential imaging (PDI) data for the transitional disk around HD100546obtained in 2013, together with an improved re-reduction of previously published 2006 data. We reveal the disk inpolarized scattered light in all three filters, achieving an inner working angle of ∼0.1 arcsec. Additional, short-exposureobservations in the H and Ks filter probe the surrounding of the star down to ∼0.03 arcsec (∼3 AU). HD100546 isfascinating because of its variety of sub-structures possibly related to forming planets in the disk, and PDI is currentlythe best technique to image them in the near-IR. Our key results are: (1) For the first time ever, we detect a disk inL-band PDI data. (2) We constrain the outer radius of the inner hole to 14±2 AU and its eccentricity to < 0.133.(3) We detect a dark lane between ∼0.2-0.6 arcsec AU in the front side of the disk, which is likely an effect of thescattering angle and the scattering function of the grains. (4) We find a spiral arm in the northeast which has noobvious connection to spiral arms seen before by other authors further out in the disk, but winds in the same direction(clockwise). (5) The two bright scattering peaks along the semi-major axis are asymmetric, with the southeastern onebeing significantly brighter. This could be related to the inner companion candidate that is close to the brighter sideof the disk at the time of the observations. (6) The scattering color is close to grey between H and Ks filter ([H ]-[Ks]= 0.19±0.11), but the scattering in L′ filter is significantly weaker ([H ]-[L′] = -1.08±0.35, [Ks]-[L

′] = -1.27±0.35).(7) We measure the position angle of the disk to be 138±3, consistent with previous observations. (8) We derivethe dust scattering function in the H and Ks filter between ∼35 and ∼130 at two different radii (30-50 and 80-110AU) and show that our results are consistent with a disk that is more strongly flared in the outer regions.

Accepted by ApJ


The statistical properties of stars and their dependence on metallicity: the effects ofopacity

Matthew R. Bate1

1 School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom

E-mail contact: mbate at astro.ex.ac.uk

We report the statistical properties of stars and brown dwarfs obtained from four radiation hydrodynamical simulationsof star cluster formation that resolve masses down to the opacity limit for fragmentation. The calculations are identicalexcept for their dust and gas opacities. Assuming dust opacity is proportional to metallicity, the calculations spana range of metallicities from 1/100 to 3 times solar, although we emphasise that changing the metallicity has otherthermodynamic effects that the calculations do not capture (e.g. on the thermal coupling between gas and dust).All four calculations produce stellar populations whose statistical properties are difficult to distinguish from observedstellar systems, and we find no significant dependence of stellar properties on opacity. The mass functions andproperties of multiple stellar systems are consistent with each other. However, we find protostellar mergers aremore common with lower opacities. Combining the results from the three calculations with the highest opacities, weobtain a stellar population consisting of more than 500 stars and brown dwarfs. Many of the statistical propertiesof this population are in good agreement with those observed in our Galaxy, implying that gravity, hydrodynamics,and radiative feedback may be the primary ingredients for determining the statistical properties of low-mass stars.However, we do find indications that the calculations may be slightly too dissipative. Although further calculationswill be required to understand all of the effects of metallicity on stellar properties, we conclude that stellar propertiesare surprisingly resilient to variations of the dust and gas opacities.

Accepted by MNRAS

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Preprint at: http://arxiv.org/pdf/1405.5583Animations available at: http://www.astro.ex.ac.uk/people/mbate/Research/Cluster/clusterMetallicity.htmlDataset available at: http://hdl.handle.net/10871/14881

The Onset of Massive Star Formation: The Evolution of Temperature and DensityStructure in an Infrared Dark Cloud

Cara Battersby1,2, Adam Ginsburg2,3, John Bally2, Steve Longmore4, Miranda Dunham5, and JeremyDarling2

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA2 Center for Astrophysics and Space Astronomy, University of Colorado, UCB 389, Boulder, CO 80309, USA3 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen, Germany4 Astrophysics Research Institute, Liverpool JohnMoores University, Twelve Quays House, EgertonWharf, BirkenheadCH41 1LD, UK5 Department of Astronomy, Yale University, New Haven, CT 06520, USA

E-mail contact: cbattersby at cfa.harvard.edu

We present new NH3 (1,1), (2,2), and (4,4) observations from the Karl G. Jansky Very Large Array (VLA) compiledwith work in the literature to explore the range of conditions observed in young, massive star-forming regions. Tosample the effects of evolution independent from those of distance/resolution, abundance, and large-scale environment,we compare clumps in different evolutionary stages within a single Infrared Dark Cloud (IRDC), G32.02+0.06. Wefind that the early stages of clustered star formation are characterized by dense, parsec-scale filamentary structuresinterspersed with complexes of dense cores (<0.1 pc cores clustered in complexes separated by ∼1 pc) with masses fromabout 10 to 100 M⊙. The most quiescent core is the most extended while the star forming cores are denser and morecompact, showing very similar column density structure before and shortly after the onset of massive star formation,with peak surface densities Σ >∼ 1 g cm−2. Quiescent cores and filaments show smoothly varying temperatures from10-20 K, rising to over 40 K in star-forming cores. We calculate virial parameters for 16 cores and find that the levelof support provided by turbulence is generally insufficient to support them against gravitational collapse (〈αvir〉 ∼0.6). The star-forming filaments show smooth velocity fields, punctuated by discontinuities at the sites of active starformation. We discuss the Massive Molecular Filament (MMF; M ∼ 105 M⊙, length > 60 pc) hosting the IRDC,hypothesizing that it may have been shaped by previous generations of massive stars

Accepted by ApJ


http://adsabs.harvard.edu/abs/2014ApJ...787..113B

The Comparison of Physical Properties Derived from Gas and Dust in a Massive Star-forming Region

Cara Battersby1,2, John Bally1, Miranda Dunham3, Adam Ginsburg1,4,3, , Steve Longmore5, andJeremy Darling1

1 Center for Astrophysics and Space Astronomy, University of Colorado, UCB 389, Boulder, CO 80309, USA2 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA3 Department of Astronomy, Yale University, New Haven, CT 06520, USA4 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Munchen, Germany5 Astrophysics Research Institute, Liverpool JohnMoores University, Twelve Quays House, EgertonWharf, BirkenheadCH41 1LD, UK

E-mail contact: cbattersby at cfa.harvard.edu

We explore the relationship between gas and dust in massive star-forming regions by comparing the physical propertiesderived from each. We compare the temperatures and column densities in a massive star-forming Infrared Dark Cloud(IRDC, G32.02+0.05), which shows a range of evolutionary states, from quiescent to active. The gas properties werederived using radiative transfer modeling of the (1,1), (2,2), and (4,4) transitions of NH3 on the Karl G. JanskyVery Large Array (VLA), while the dust temperatures and column densities were calculated using cirrus-subtracted,

15


http://www.astro.ex.ac.uk/people/mbate/Research/Cluster/clusterMetallicity.html

http://hdl.handle.net/10871/14881



modified blackbody fits to Herschel data. We compare the derived column densities to calculate an NH3 abundance,χNH3

= 4.6 × 10−8. In the coldest star-forming region, we find that the measured dust temperatures are lower thanthe measured gas temperatures (mean and standard deviations Tdust,avg ∼ 11.6 ± 0.2 K vs. Tgas,avg ∼ 15.2 ± 1.5K), which may indicate that the gas and dust are not well-coupled in the youngest regions (∼0.5 Myr) or that theseobservations probe a regime where the dust and/or gas temperature measurements are unreliable. Finally, we calculatemillimeter fluxes based on the temperatures and column densities derived from NH3 which suggest that millimeter dustcontinuum observations of massive star-forming regions, such as the Bolocam Galactic Plane Survey or ATLASGAL,can probe hot cores, cold cores, and the dense gas lanes from which they form, and are generally not dominated bythe hottest core.

Accepted by ApJ



An Observational Method to Measure the Relative Fractions of Solenoidal and Com-pressible Modes in Interstellar Clouds

C.M. Brunt1 and C. Federrath2,3

1 Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK2 Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Vic 3800, Australia3 Zentrum fur Astronomie der Universitat Heidelberg, Institut fur Theoretische Astrophysik, Albert-Uerberle-Str. 2,69120 Heidelberg, Germany

E-mail contact: brunt at astro.ex.ac.uk

We introduce a new method for observationally estimating the fraction of momentum density (ρv) power containedin solenoidal modes (for which ∇ · ρv = 0) in molecular clouds. The method is successfully tested with numericalsimulations of supersonic turbulence that produce the full range of possible solenoidal/compressible fractions. Atpresent the method assumes statistical isotropy, and does not account for anisotropies caused by (e.g.) magneticfields. We also introduce a framework for statistically describing density–velocity correlations in turbulent clouds.

Accepted by MNRAS


Imaging the disk around IRAS20126+4104 at subarcsecond resolution

R. Cesaroni1, D. Galli1, R. Neri2 and C.M. Walmsley1,3

1 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy2 IRAM, 300 rue de la Piscine, 38406, Saint Martin d’Heres, France3 Dublin Institute for Advanced Studies (DIAS), 31 Fitzwilliam Place, Dublin 2, Ireland

E-mail contact: cesa at arcetri.astro.it

The existence of disks around high-mass stars has yet to be established on a solid ground, as only few reliablecandidates are known to date. The disk rotating about the ∼104 L⊙ protostar IRAS20126+4104 is probably themost convincing of these. We would like to resolve the disk structure in IRAS20126+4104 and, if possible, investigatethe relationship between the disk and the associated jet emitted along the rotation axis. We performed observationsat 1.4 mm with the IRAM Plateau de Bure interferometer attaining an angular resolution of ∼0.4′′ (∼660 AU). Weimaged the methyl cyanide J=12→11 ground state and vibrationally excited transitions as well as the CH3

13CNisotopologue, which had proved to be disk tracers. Our findings confirm the existence of a disk rotating about a∼7–10 M⊙ star in IRAS20126+4104, with rotation velocity increasing at small radii. The dramatic improvement insensitivity and spectral and angular resolution with respect to previous observations allows us to establish that higherexcitation transitions are emitted closer to the protostar than the ground state lines, which demonstrates that the gastemperature is increasing towards the centre. We also find that the material is asymmetrically distributed in the diskand speculate on the possible origin of such a distribution. Finally, we demonstrate that the jet emitted along thedisk axis is co-rotating with the disk. We present iron-clad evidence of the existence of a disk undergoing rotationaround a B-type protostar, with rotation velocity increasing towards the centre. We also demonstrate that the disk

16




is not axially symmetric. These results prove that B-type stars may form through disk-mediated accretion as theirlow-mass siblings do, but also show that the disk structure may be significantly perturbed by tidal interactions with(unseen) companions, even in a relatively poor cluster such as that associated with IRAS20126+4104.

Accepted by A&A

http://www.arcetri.astro.it/science/starform/preprints/cesa_24.pdf

Study of background star polarization and polarization efficiency of three selected Bokglobules CB56, CB60 and CB69

A. Chakraborty1, H.S. Das1, and D. Paul2

1 Department of Physics, Assam University, Silchar 788011, India2 Department of Physics, Ramkrishna Nagar College, Ramkrishna Nagar 788166, India

E-mail contact: hsdas at iucaa.ernet.in

We present the polarization maps of three selected Bok globules CB56, CB60 and CB69 constructed using a V-banddata from a CCD imaging polarimeter. The aim of this work is to measure the optical polarization (pv) of backgroundfield stars in order to determine the polarization efficiency, pv/Av. We find that the local magnetic field of thecloud CB56 is almost aligned with the galactic field, but not in CB60 and CB69. A trend of decreasing polarizationefficiency with increasing extinction (Av) is observed: it can be well represented by a power law, pv/Av ∝ A−α

v , whereα = −0.56±0.36, −0.59±0.51 and −0.52±0.49 for CB56, CB60 and CB69 respectively. This indicates that the linearpolarization of the starlight due to aligned dust grains in these clouds is produced more efficiently in low extinctionregions, compared with high obscured lines of sight.

Accepted by MNRAS


The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfsat wide orbits: II- Survey description, results and performances

G. Chauvin1, A. Vigan2, M. Bonnefoy3, S. Desidera4, M. Bonavita4, D. Mesa4, A. Boccaletti5, E.Buenzli3, J. Carson6,3, P. Delorme1, J. Hagelberg7, G. Montagnier2, C. Mordasini3, S.P. Quanz8, D.Segransan7, C. Thalmann8, J.-L. Beuzit1, B. Biller3, E. Covino9, M. Feldt3, J. Girard10, R. Gratton4,T. Henning3, M. Kasper11, A.-M. Lagrange1, S. Messina12, M. Meyer8, D. Mouillet1, C. Moutou2, M.Reggianni8, J.E. Schlieder3, and A. Zurlo2

1 UJF-Grenoble1/CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble UMR 5274, Grenoble, F-38041, France2 Aix Marseille Universite, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille,France3 Max Planck Institute for Astronomy, Konigstuhl 17, D-69117 Heidelberg, Germany4 INAF - Osservatorio Astronomico di Padova, Vicolo dell Osservatorio 5, 35122, Padova, Italy5 LESIA, Observatoire de Paris Meudon, 5 pl. J. Janssen, 92195 Meudon, France6 Department of Physics & Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424, USA7 Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland8 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland9 INAF Osservatorio Astronomico di Capodimonte Via Moiarello 16 80131 Napoli Italy10 European Southern Observatory, Casilla 19001, Santiago 19, Chile11 European Southern Observatory, Karl Schwarzschild St, 2, D-85748 Garching, Germany12 INAF - Catania Astrophysical Observatory, via S. So a 78 I-95123 Catania, Italy

E-mail contact: gael.chauvin at obs.ujf-grenoble.fr

In anticipation of the VLT/SPHERE planet imager guaranteed time programs, we have conducted a preparatorysurvey of 86 stars between 2009 and 2013 in order to identify new faint comoving companions to ultimately carry outa comprehensive analysis of the occurence of giant planets and brown dwarf companions at wide (10–2000 AU) orbitsaround young, solar-type stars. We used NaCo at VLT to explore the occurrence rate of giant planets and brown dwarfs

17

http://www.arcetri.astro.it/science/starform/preprints/cesa_24.pdf


between typically 0.1 and 8′′. Diffraction-limited observations in H-band combined with angular differential imagingenabled us to reach primary star-companion brightness ratios as small as 10−6 at 1.′′5. 12 systems were resolved asnew binaries, including the discovery of a new white dwarf companion to the star HD 8049. Around 34 stars, at leastone companion candidate was detected in the observed field of view. More than 400 faint sources were detected, 90%of them in 4 crowded fields. With the exception of HD8049B, we did not identify any new comoving companions.The survey also led to spatially resolved images of the thin debris disk around HD61005 that have been publishedearlier. Finally, considering the survey detection limits, we derive a preliminary upper limit on the frequency of giantplanets for semi-major axes of [10,2000] AU: typically less than 15% between 100 and 500 AU, and less than 10%between 50 and 500 AU for exoplanets more massive than 5 MJup and 10 MJup respectively, considering a uniforminput distribution and with a confidence level of 95%.

Accepted by A&A


Near Infrared Spectroscopy of Young Brown Dwarfs in Upper Scorpius

P. Dawson1, A. Scholz2, T.P. Ray1, D.E. Peterson3, D. Rodgers-Lee1, V. Geers1

1 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland2 School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS, UK3 Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA

E-mail contact: pdawson at cp.dias.ie

Spectroscopic follow-up is a pre-requisite for studies of the formation and early evolution of brown dwarfs. Here wepresent IRTF/SpeX near-infrared spectroscopy of 30 candidate members of the young Upper Scorpius association,selected from our previous survey work. All 24 high confidence members are confirmed as young very low mass objectswith spectral types from M5 to L1, 15–20 of them are likely brown dwarfs. This high yield confirms that brown dwarfsin Upper Scorpius can be identified from photometry and proper motions alone, with negligible contamination fromfield objects (<4%). Out of the 6 candidates with lower confidence, 5 might still be young very low mass membersof Upper Scorpius, according to our spectroscopy. We demonstrate that some very low mass class II objects exhibitradically different near infrared (0.6–2.5 µm) spectra from class III objects, with strong excess emission increasingtowards longer wavelengths and partially filled in features at wavelengths shorter than 1.25 µm. These characteristicscan obscure the contribution of the photosphere within such spectra. Therefore, we caution that near infrared derivedspectral types for objects with discs may be unreliable. Furthermore, we show that the same characteristics can beseen to some extent in all class II and even a significant fraction of class III objects (∼40%), indicating that some ofthem are still surrounded by traces of dust and gas. Based on our spectra, we select a sample of objects with spectraltypes of M5 to L1, whose near-infrared emission represents the photosphere only. We recommend the use of theseobjects as spectroscopic templates for young brown dwarfs in the future.

Accepted by MNRAS


The VLT/NaCo Large program to probe the occurrence of exoplanets and brown dwarfsin wide orbits: I- Sample definition and characterization

S. Desidera1, E. Covino2, S. Messina3, J. Carson4,5, J. Hagelberg6, J.E. Schlieder5, K. Biazzo3, J.M.Alcala2, G. Chauvin7, A. Vigan8, J.L. Beuzit7, M. Bonavita1, M. Bonnefoy5, P. Delorme7, V. D’Orazi9,1,M. Esposito10,2, M. Feldt5, L. Girardi1, R. Gratton1, T. Henning5, A.M. Lagrange7, A.C. Lanzafame3,11,R. Launhardt5, M. Marmier6, C. Melo12, M. Meyer13, D. Mouillet7, C. Moutou8, D. Segransan6, S.Udry6, and C.M. Zaidi7

1 INAF-Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, 35122 Padova, Italy2 INAF-Osservatorio Astronomico di Napoli, Salita Moiariello 16, 80131, Napoli, Italy3 INAF-Osservatorio Astrosico di Catania, Via S. Soa 78, 95123 Catania, Italy4 Department of Physics & Astronomy, College of Charleston, 58 Coming St. Charleston, SC 29424, USA5 Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117, Heidelberg, Germany

18



6 Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland7 Institut de Planetologie et dAstrophysique de Grenoble, UJF, CNRS, 414 rue de la piscine, 38400 Saint Martind’Heres, France8 Aix Marseille Universite, CNRS, LAM (Laboratoire dAstrophysique de Marseille) UMR 7326, 13388, Marseille,France9 Department of Physics and Astronomy, Faculty of Science, Macquarie University, Sydney, NSW, 2109, Australia10 Instituto de Astrosica de Canarias, C/ Via Lactea, s/n, E38205 - La Laguna (Tenerife), Spain11 Universita di Catania, Dipartimento di Fisica e Astronomia, Via S. Soa 78, 95123 Catania, Italy12 European Southern Observatory, Casilla 19001, Santiago 19, Chile13 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli Strasse 27, 8093 Zurich, Switzerland

E-mail contact: gael.chauvin at obs.ujf-grenoble.fr

Young, nearby stars are ideal targets to search for planets using the direct imaging technique. The determinationof stellar parameters is crucial for the interpretation of imaging survey results particularly since the luminosity ofsubstellar objects has a strong dependence on system age. We have conducted a large program with NaCo at theVLT in order to search for planets and brown dwarfs in wide orbits around 86 stars. A large fraction of the targetsobserved with NaCo were poorly investigated in the literature. We performed a study to characterize the fundamentalproperties (age, distance, mass) of the stars in our sample. To improve target age determinations, we compiled andanalyzed a complete set of age diagnostics. We measured spectroscopic parameters and age diagnostics using dedicatedobservations acquired with FEROS and CORALIE spectrographs at La Silla Observatory. We also made extensiveuse of archival spectroscopic data and results available in the literature. Additionally, we exploited photometric time-series, available in ASAS and Super-WASP archives, to derive rotation period for a large fraction of our programstars. We provided updated characterization of all the targets observed in the VLT NaCo Large program, a surveydesigned to probe the occurrence of exoplanets and brown dwarfs in wide orbits. The median distance and age of ourprogram stars are 64 pc and 100 Myr, respectively. Nearly all the stars have masses between 0.70 and 1.50 M⊙, witha median value of 1.01 M⊙. The typical metallicity is close to solar, with a dispersion that is smaller than that ofsamples usually observed in radial velocity surveys. Several stars are confirmed or proposed here to be members ofnearby young moving groups. Eight spectroscopic binaries are identified.

Accepted by A&A


Structure and Dynamics of the Accretion Process and Wind in TW Hya

A.K. Dupree1, N.S. Brickhouse1, S.R. Cranmer1, P. Berlind1,2, Jay Strader1,3, Graeme H. Smith4

1 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA2 Fred L. Whipple Observatory, Amado, AZ, USA3 Michigan State University, East Lansing, MI, USA4 University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064, USA

E-mail contact: dupree at cfa.harvard.edu

Time-domain spectroscopy of the classical accreting T Tauri star, TW Hya, covering a decade and spanning the farUV to the near-infrared spectral regions can identify the radiation sources, the atmospheric structure produced byaccretion,and properties of the stellar wind. On time scales from days to years, substantial changes occur in emissionline profiles and line strengths. Our extensive time-domain spectroscopy suggests that the broad near-IR, optical, andfar-uv emission lines, centered on the star, originate in a turbulent post-shock region and can undergo scattering bythe overlying stellar wind as well as some absorption from infalling material. Stable absorption features appear in Hα,apparently caused by an accreting column silhouetted in the stellar wind. Inflow of material onto the star is revealed bythe near-IR He i 10830A line, and its free-fall velocity correlates inversely with the strength of the post-shock emission,consistent with a dipole accretion model. However, the predictions of hydrogen line profiles based on accretion streammodels are not well-matched by these observations. Evidence of an accelerating warm to hot stellar wind is shownby the near-IR He i line, and emission profiles of C ii, C iii, C iv, N v, and O vi. The outflow of material changessubstantially in both speed and opacity in the yearly sampling of the near-IR He i line over a decade. Terminal outflowvelocities that range from 200 km s−1 to almost 400 km s−1 in He i appear to be directly related to the amount ofpost- shock emission, giving evidence for an accretion-driven stellar wind. Calculations of the emission from realistic

19


post- shock regions are needed.

Accepted by ApJ


Deep VLA Images of the HH 124 IRS Radio Cluster and its Surroundings and a NewDetermination of the Distance to NGC 2264

Sergio A. Dzib1,2, Laurent Loinard1, Luis F. Rodriguez1,3 and Phillip Galli4

1 Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico. Apartado Postal 3-72, 58090,Morelia, Michoacan, Mexico.2 Max-Planck-Institute fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany.3 King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia4 Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226 , CidadeUniversitaria, 05508-900, Sao Paulo, SP, Brazil

E-mail contact: sdzib at mpifr-bonn.mpg.de

We present new deep (σ ∼ 6 µJy) radio images of the HH 124 IRS Radio Cluster at 4.8 and 7.5 GHz. We detect atotal of 50 radio sources, most of them compact. Variability and spectral indices were analyzed in order to determinethe nature of the sources and of their radio emission. A proper motion study was also performed for several of theseradio sources using radio observation previously reported. Our analysis shows that 11 radio sources can be relatedwith Galactic objects, most of them probably young stars. Interestingly, eight of these sources are in an area lessthan 1 square arcminute in size. The importance of such compact clusters resides in that all its members can beobserved in a single pointing with most telescopes, and are, therefore, ideal for multi-wavelength studies of variability.Another 4 of the detected sources are clearly extragalactic. Finally, we propose from statistical arguments that fromthe remaining sources, about 10 are Galactic, but our study does not allow us to identify which of the sources fall inthat specific category. The relatively large proper motions observed for the sources in HH 124 IRS suggest that thisregion is located at about 400 pc from the Sun. This is significantly smaller than the ∼800–900 pc distance usuallyassigned to the nearby open cluster NGC 2264 with which HH 124 is thought to be associated. However, a reanalysisof the Hipparcos parallaxes for members of NGC 2264, a convergent point approach, and a kinematic analysis all arguein favor of a distance of order 400 pc for NGC 2264 as well.


http://adsabs.harvard.edu/abs/2014arXiv1404.7543D

Dynamical star-disk interaction in the young stellar system V354 Mon

N. N. J. Fonseca1,2,3, S. H. P. Alencar1, J. Bouvier2, F. Favata4 and E. Flaccomio5

1 Departamento de Fısica - ICEx - UFMG, Av. Antonio Carlos, 6627, 31270-901, Belo Horizonte, MG, Brazil2 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Greno-ble, F-38041, France3 CAPES Foundation, Ministry of Education of Brazil, Brasılia - DF 70040-020, Brazil4 European Space Agency, 8-10 rue Mario Nikis, 75738 Paris Cedex 15, France5 Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Palermo G.S. Vaiana, Piazza del Parlamento 1, 90134Palermo, Italy

E-mail contact: nath at fisica.ufmg.br

The main goal of this work is to characterize the mass accretion and ejection processes of the classical T Tauri star V354Mon, a member of the young stellar cluster NGC 2264. In March 2008, photometric and spectroscopic observationsof V354 Mon were obtained simultaneously with the CoRoT satellite, the 60 cm telescope at the Observatorio Picodos Dias (LNA - Brazil) equipped with a CCD camera and Johnson/Cousins BV(RI)c filters, and the SOPHIEechelle spectrograph at the Observatoire de Haute-Provence (CNRS - France). The light curve of V354 Mon showsperiodical minima (P = 5.26 ± 0.50 days) that vary in depth and width at each rotational cycle. The BV(RI)cobservations indicate that the system becomes slightly bluer as the flux increases. The spectra of this T Tauri starexhibit variable emission lines, with blueshifted and redshifted absorption components associated with a disk wind

20


http://adsabs.harvard.edu/abs/2014arXiv1404.7543D

and with the accretion process, respectively, confirming the magnetospheric accretion scenario. From the analysis ofthe photometric and spectroscopic data, it is possible to identify correlations between the emission line variability andthe light-curve modulation of the young system, such as the occurrence of pronounced redshifted absorption in theHα line at the epoch of minimum flux. This is evidence that during photometric minima we see the accretion funnelprojected onto the stellar photosphere in our line of sight, implying that the hot spot coincides with the light-curveminima. We applied models of cold and hot spots and a model of occultation by circumstellar material to investigatethe source of the observed photometric variations. We conclude that nonuniformly distributed material in the innerpart of the circumstellar disk is the main cause of the photometric modulation, which does not exclude the presenceof hot and cold spots at the stellar surface. It is believed that the distortion in the inner part of the disk is createdby the dynamical interaction between the stellar magnetosphere, inclined with respect to the rotation axis, and thecircumstellar disk, as also observed in the classical T Tauri star AA Tau and predicted by magnetohydrodynamicalnumerical simulations.

Accepted by Astronomy & Astrophysics


A CGPS Look at the Spiral Structure of the Outer Milky Way I: Distances and Velocitiesto Star Forming Regions

Tyler J. Foster1,2 and Christopher M. Brunt3

1 Department of Physics & Astronomy, Brandon University, Brandon, Manitoba, Canada2 National Research Council Canada, Penticton, British Columbia, Canada3 Astrophysics Group, School of Physics, University of Exeter, Exeter, United Kingdom

E-mail contact: FosterT at BrandonU.CA

We present a new catalogue of spectrophotometric distances and line-of-sight systemic velocities to 103 Hii regionsbetween 90 ≤ l ≤ 195 (longitude quadrants II and part of III). Two new velocities for each region are independentlymeasured using 1′ resolution 21 cm H i and 2.6 mm 12CO line maps (from the Canadian Galactic Plane Survey andFCRAO Outer Galaxy Surveys) that show where gaseous shells are observed around the periphery of the ionized gas.Known and neighbouring OB-type stars with published UBV photometry and MK classifications are overlaid onto21 cm continuum maps, and those stars observed within the boundary of the H ii emission (and whose distance isnot more than 3 times the standard deviation of the others) are used to calculate new mean stellar distances to eachof the 103 nebulae. Using this approach of excluding distance outliers from the mean distance to a group of manystars in each H ii region lessens the impact of anomalous reddening for certain individuals. Final mean distancesof 9 common objects with VLBI parallax distances show a 1:1 correspondence. Further, comparison with previouscatalogues of H ii regions in these quadrants shows a 50% reduction in scatter for the distance to Perseus spiral armobjects in the same region, and a reduction by ∼1/

√2 in scatter around a common angular velocity relative to the Sun

Ω−Ω0(km s−1 kpc−1). The purpose of the catalogue is to provide a foundation for more detailed large-scale Galacticspiral structure and dynamics (rotation curve, density wave streaming) studies in the 2nd and 3rd quadrants, whichfrom the Sun’s location is the most favourably viewed section of the Galaxy.

Accepted by AJ


Shaping a high-mass star-forming cluster through stellar feedback. The case of theNGC 7538 IRS 1–3 complex.

Pau Frau1,2, Josep Miquel Girart3, Qizhou Zhang4 and Ramprasad Rao5

1 Instituto de Ciencia de Materiales de Madrid (CSIC), Sor Juana Ines de la Cruz 3, E-28049 Madrid, Spain2 Observatorio Astronomico Nacional, Alfonso XII 3, E-28014 Madrid, Spain3 Institut de Ciencies de l’Espai, CSIC-IEEC, Campus UAB, Facultat de Ciencies, Torre C5p 2, E-08193 Bellaterra,Catalonia, Spain4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA5 Institute of Astronomy and Astrophysics, Academia Sinica, 645 N. Aohoku Place, Hilo HI 96720, USA

E-mail contact: p.frau at oan.es

21



Context. NGC 7538 IRS 1–3 is a high-mass star-forming cluster with several detected dust cores, infrared sources,(ultra)compact H II regions, molecular outflows, and masers. In such a complex environment, important interactionsand feedback among the embedded objects are expected to play a major role in the evolution of the region.Aims. We study the dust, kinematic, and polarimetric properties of the NGC 7538 IRS 1–3 region to investigate therole of the different forces interplaying in the formation and evolution of high-mass star-forming clusters.Methods. We perform SMA high angular resolution observations at 880 µmwith the compact configuration. We developthe RATPACKS code to generate synthetic velocity cubes from models of choice to be compared to the observationaldata. We develop the “mass balance” analysis to quantify the stability against gravitational collapse accounting forall the energetics at core scales.Results. We detect 14 dust cores from 3.5 M⊙ to 37 M⊙ arranged in two larger scale structures: a central bar anda filamentary spiral arm. The spiral arm presents large scale velocity gradients in H13CO+ 4–3 and C17O 3–2, andmagnetic field segments well aligned to the dust main axis. The velocity gradient is well reproduced by a spiral armexpanding at 9 km s−1 with respect to the central core MM1, which is known to power a large precessing outflow.The energy of the outflow is comparable with the spiral arm kinetic energy, which is dominant over gravitational andmagnetic energies. In addition, the dynamical ages of the outflow and spiral arm are comparable. At core scales, thoseembedded in the central bar seem to be unstable against gravitational collapse and prone to form high-mass stars,while those in the spiral arm have lower masses that seem to be supported by non-thermal motions and magneticfields.Conclusions. The NGC 7538 IRS 1–3 cluster seems to be dominated by proto-stellar feedback. The dusty spiral armappears to be formed in a snow-plow fashion due to the outflow from the MM1 core. We speculate that the externalpressure from the red-shifted lobe of the outflow could trigger star formation in the spiral arm cores. This scenariowould form a small cluster with a few central high-mass stars, surrounded by a number of low-mass stars formedthrough proto-stellar feedback.

Accepted by A&A


Long Term Evolution of Planet-Induced Vortices in Protoplanetary Disks

Wen Fu1,2, Hui Li2, Stephen Lubow3, and Shengtai Li2

1 Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA2 Los Alamos National Laboratory, Los Alamos, NM 87545, USA3 Space Telescope Science Institute, Baltimore, MD 21218, USA

E-mail contact: wf5 at rice.edu

Recent observations of large-scale asymmetric features in protoplanetary disks suggest that large-scale vortices exist insuch disks. Massive planets are known to be able to produce deep gaps in protoplanetary disks. The gap edges couldbecome hydrodynamically unstable to the Rossby wave/vortex instability and form large-scale vortices. In this studywe examine the long term evolution of these vortices by carrying out high-resolution two dimensional hydrodynamicsimulations that last more than 104 orbits (measured at the planet’s orbit). We find that the disk viscosity has astrong influence on both the emergence and lifetime of vortices. In the outer disk region where asymmetric featuresare observed, our simulation results suggest that the disk viscous α needs to be low ∼10−5–10−4 to sustain vorticesto thousands and up to 104 orbits in certain cases. The chance of finding a vortex feature in a disk then decreaseswith smaller planet orbital radius. For α ∼ 10−3 or larger, even planets with masses of 5 Jupiter-masses will havedifficulty either producing or sustaining vortices. We have also studied the effects of different disk temperatures andplanet masses. We discuss the implications of our findings on current and future protoplanetary disk observations.

Accepted by ApJL


A CO survey in planet-forming disks: characterizing the gas content in the epoch ofplanet formation

A.S. Hales1,2, I. De Gregorio-Monsalvo1,3, B. Montesinos4, S. Casassus5, W.F.R. Dent1,3, C. Dougados6,C. Eiroa7, A.M. Hughes8, G. Garay5, D. Mardones5, F. Menard6, Aina Palau9, S. Perez5, N. Phillips1,3,J.M. Torrelles10 and D. Wilner11

22



1 Atacama Large Millimeter/Submillimeter Array, Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago - Chile2 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia, 22903-2475, United States3 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748, Garching bei Mnchen, Germany4 Department of Astrophysics, Centre for Astrobiology (CAB, CSIC-INTA), ESAC Campus, P.O. Box 78, 28691Villanueva de la Canada, Madrid, Spain5 Departamento de Astronomıa, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile6 UMI-FCA, CNRS/INSU, France (UMI 3386), and Dept. de Astronomıa, Universidad de Chile, Santiago, Chile7 Departamento de Fısica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, 28049,Madrid, Spain8 Department of Astronomy, University of California, Berkeley, CA 94720, USA9 Institut de Ciencies de l’Espai (CSIC-IEEC), Campus UAB-Facultat de Ciencies, Torre C5-parell 2, 08193 Bellaterra,Catalunya, Spain10 Institut de Ciencies de l’Espai (CSIC-IEEC) and Institut de Ciencies del Cosmos (UBIEEC), Martı i Franqu‘es 1,08028 Barcelona, Spain11 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

E-mail contact: ahales at alma.cl

We carried out a 12CO (3–2) survey of 52 southern stars with a wide range of IR excesses (LIR/L∗) using the single dishtelescopes APEX and ASTE. The main aims were (1) to characterize the evolution of molecular gas in circumstellardisks using LIR/L∗ values as a proxy of disk dust evolution, and (2) to identify new gas-rich disk systems suitable fordetailed study with ALMA. About 60% of the sample (31 systems) have LIR/L∗ > 0.01 typical of T-Tauri or HerbigAeBe stars, and the rest (21 systems) have LIR/L∗ < 0.01 typical of debris disks. We detect CO (3–2) emission from20 systems, and 18 (90%) of these have LIR/L∗ > 0.01. However, the spectra of only four of the newly detectedsystems appear free of contamination from background or foreground emission from molecular clouds. These includethe early-type stars HD 104237 (A4/5V, 116 pc) and HD 98922 (A2 III, 507 pc, as determined in this work), whereour observations reveal the presence of CO-rich circumstellar disks for the first time. Of the other detected sources,many could harbor gaseous circumstellar disks, but our data are inconclusive. For these two newly discovered gas-richdisks, we present radiative transfer models that simultaneously reproduce their spectral energy distributions and the12CO (3–2) line profiles. For both of these systems, the data are fit well by geometrically flat disks, placing them inthe small class of non-flaring disks with significant molecular gas reservoirs.

Accepted by AJ


The Disappearing Envelope around the Transitional Class I Object L43

Shin Koyamatsu1,2, Shigehisa Takakuwa3, Masahiko Hayashi4, Satoshi Mayama5 and Nagayoshi Ohashi2

1 Department of Astronomy, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo113-0033, Japan2 Subaru Telescope, 650 North A’ohoku Place, Hilo, HI 96720, U.S.A.3 Institute of Astronomy and Astrophysics, Academia Sinica, P. O. Box 23-141, Taipei 10641, Taiwan4 National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, 181-8588, Japan5 Graduate University for Advanced Studies, Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193, Japan

E-mail contact: shin.koyamatsu at nao.ac.jp

We present SMA interferometric observations of the 12CO (J = 2–1), 13CO (J = 2–1), and C18O (J = 2–1) lines and225 GHz continuum emission and SMT single-dish observations of C18O (J = 2–1) toward L43, a protostellar objectin transition from Class I to II. The 225 GHz continuum emission shows a weak (∼ 23.6mJy), compact (< 1000AU)component associated with the central protostar. Our simulated observations show that it can be explained by dustthermal emission arising from an envelope which has a hole or a constant intensity region within a few hundred AUof the protostar. This suggests the disappearance or a lower concentration distribution of the envelope on a smallscale. The 12CO and 13CO emission exhibit molecular outflows to the south and north. The C18O emission shows twomolecular blobs, which correspond to the reflection nebulosity seen in near-infrared images, while there is no C18O

23


emission associated with the protostar. The near-infrared features are likely due to the scattering at the positions ofthe blobs. The visible scattering features should result from the optical thinness of the envelope material, which isconsistent with the less-concentrated distribution in the continuum emission. From single-dish observations, we foundthat the mass of the envelope (∼ 1.5M⊙) + protostar (∼ 0.5M⊙) is comparable with the virial mass of Mvir = 1.0M⊙

within 40 arcsec. This suggests that the envelope is likely gravitationally bound. We suggest that the protostellarenvelope of L43 has been disappearing by consumption through accretion, at least in the close vicinity of the protostar.



Feedback by massive stars and the emergence of superbubbles II. X-ray properties

Martin Krause1,2, Roland Diehl1,2, Hans Bohringer1,2, Michael Freyberg1, and Daniel Lubos1

1 Max-Planck-Institut fur extraterrestrische Physik, Giessenbachstr. 1, 85741 Garching, Germany2 Excellence Cluster Universe, Technische Universitat Munchen, Boltzmannstrasse 2, 85748 Garching, Germany

E-mail contact: krause at mpe.mpg.de

In a previous paper we investigated the energy transfer of massive stars to the interstellar medium as a function of timeand the geometrical configuration of three massive stars via 3D-mesh-refining hydrodynamics simulations, followingthe complete evolution of the massive stars and their supernovae except non-thermal processes. We analysed our ISMsimulation results with the help of spectra for plasma temperatures between 0.1 and 10 keV and computed the spectralevolution and the spatio-temporal distribution of the hot gas. Despite significant input of high temperature gas fromsupernovae and fast stellar winds, the resulting thermal X-ray spectra are generally very soft, with most of the emissionwell below 1 keV. We show that this is due to mixing triggered by resolved hydrodynamic instabilities. Supernovaeenhance the X-ray luminosity of a superbubble by 1–2 orders of magnitude for a time span of about 0.1 Myr; longerif a supernova occurs in a larger superbubble and shorter in higher energy bands. Peak superbubble luminosities ofthe order of 1036 erg s−1 are reproduced well. The strong decay of the X-ray luminosity is due to bubble expansion,hydrodynamic instabilities related to the acceleration of the superbubble’s shell thanks to the sudden energy input, andsubsequent mixing. We also find global oscillations of our simulated superbubbles, which produce spatial variations ofthe X-ray spectrum, similar to what we see in the Orion-Eridanus cavity. We calculated the fraction of energy emittedin X-rays and find that with a value of a few times 10−4, it is about a factor of ten below the measurements for nearbygalaxies.

Accepted by A&A


Star-forming regions of the Aquila rift cloud complex. II. Turbulence in molecular coresprobed by NH3 emission

S.A. Levshakov1,2,3, C. Henkel4,5, D. Reimers1, and M. Wang6

1 Hamburger Sternwarte, Universitat Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany2 Ioffe Physical-Technical Institute, Polytekhnicheskaya Str. 26, 194021 St. Petersburg, Russia3 St. Petersburg Electrotechnical University ‘LETI’, Prof. Popov Str. 5, 197376 St. Petersburg, Russia4 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany5 Astronomy Department, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia6 Purple Mountain Observatory, Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008,P. R. China

E-mail contact: lev at astro.ioffe.rssi.ru

Aims. We intend to derive statistical properties of stochastic gas motion inside the dense low mass star formingmolecular cores traced by NH3(1,1) and (2,2) emission lines. Methods. We use the spatial two-point autocorrelation(ACF) and structure functions calculated from maps of the radial velocity fields.Results. We find oscillating ACFs which eventually decay to zero with increasing lags on scales of 0.04 ≤ l ≤ 0.5 pc.The current paradigm supposes that the star formation process is controlled by the interplay between gravitation andturbulence, the latter preventing molecular cores from a rapid collapse due to their own gravity. Thus, oscillating

24



ACFs may indicate a damping of the developed turbulent flows surrounding the dense but less turbulent core - atransition to dominating gravitational forces and, hence, to gravitational collapse.

Accepted by A&A


On filament L1482 in the California molecular cloud

D.L. Li1,2, J. Esimbek1,3, J.J. Zhou1,3, Y.-Q. Lou4, G. Wu1,2,3, X.D. Tang1,2, and Y.X. He1,2

1 Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, P. R. China2 University of the Chinese Academy of Sciences, Beijing 100080, P. R. China3 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Urumqi 830011, P. R. China4 Department of Physics and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing 100084, P. R.China

E-mail contact: lidalei at xao.ac.cn

Aims. The process of gravitational fragmentation in the L1482 molecular filament of the California Molecular Cloudis studied by combining several complementary observations and physical estimates. We investigate the kinematicand dynamical states of this molecular filament and physical properties of several dozens of dense molecular clumpsembedded therein.Methods. We present and compare molecular line emission observations of the J=2–1 and J=3–2 transitions of 12COin this molecular complex, using the KOSMA 3-meter telescope. These observations are complemented with archivaldata observations and analyses of the 13CO J=1–0 emission obtained at the Purple Mountain Observatory 13.7-meter radio telescope at Delingha Station in QingHai Province of west China, as well as infrared emission mapsfrom the Herschel Space Telescope online archive, obtained with the SPIRE and PACS cameras. Comparison ofthese complementary datasets allow for a comprehensive multi-wavelength analysis of the L1482 molecular filament.Results. We have identified 23 clumps along the molecular filament L1482 in the California Molecular Cloud. Allthese molecular clumps show supersonic non-thermal gas motions. While surprisingly similar in mass and size to themuch more well-known Orion Molecular Cloud, the formation rate of high-mass stars appears to be suppressed in theCalifornia Molecular Cloud relative to that in the Orion Molecular Cloud based on the mass-radius threshold derivedfrom the static Bonnor Ebert sphere. Our analysis suggests that these molecular filaments are thermally supercriticaland molecular clumps may form by gravitational fragmentation along the filament. Instead of being static, thesemolecular clumps are most likely in processes of dynamic evolution.

Accepted by A&A


ALMA observations of the kinematics and chemistry of disc formation

Johan E. Lindberg1,2, Jes K. Jørgensen2,1, Christian Brinch2,1, Troels Haugbølle1,2, Edwin A. Bergin3,Daniel Harsono4,5, Magnus V. Persson4, Ruud Visser3 and Satoshi Yamamoto6

1 Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, ØsterVoldgade 5-7, DK-1350 Copenhagen K, Denmark2 Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark3 Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109-1042, USA4 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands5 SRON Netherlands Institute for Space Research, P.O. Box 800, NL-9700 AV, Groningen, The Netherlands6 Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan

E-mail contact: jolindbe at gmail.com

Context: The R CrA cloud hosts a handful of Class 0/I low-mass young stellar objects. The chemistry and physics atscales > 500 AU in this cloud are dominated by the irradiation from the nearby Herbig Be star R CrA. The luminouslarge-scale emission makes it necessary to use high-resolution spectral imaging to study the chemistry and dynamicsof the inner envelopes and discs of the protostars.Aims: We aim to better understand the structure of the inner regions of these protostars and, in particular, the

25



interplay between the chemistry and the presence of discs.Methods: Using Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution spectral imaging interfer-ometry observations, we study the molecular line and dust continuum emission at submillimetre wavelengths.Results: We detect dust continuum emission from four circumstellar discs around Class 0/I objects within the RCrA cloud. Towards IRS7B we detect C17O emission showing a rotation curve consistent with a Keplerian disc witha well-defined edge that gives a good estimate for the disc radius at 50 AU. We derive the central object mass to2.3M⊙ and the disc mass to 0.024M⊙. The observations are also consistent with a model of material infalling underconservation of angular momentum; however, this model provides a worse fit to the data. We also report a likelydetection of faint CH3OH emission towards this point source, as well as more luminous CH3OH emission in an outfloworthogonal to the major axis of the C17O emission.Conclusions: The faint CH3OH emission seen towards IRS7B can be explained by a flat density profile of the innerenvelope caused by the disc with a radius <∼50 AU. We propose that the regions of the envelopes where complexorganic molecules are present in Class 0/I young stellar objects can become quenched as the disc grows.

Accepted by A&A


Constraints to the magnetospheric properties of T Tauri stars. I. The C II], Fe II] andSi II] ultraviolet features

Fatima Lopez-Martınez1 and Ana Ines Gomez de Castro1

1 AEGORA Research Group, Universidad Complutense de Madrid, Plaza de Ciencias 3, 28040 Madrid, Spain

E-mail contact: fatimalopezmar at gmail.com

The C II] feature at ∼2325 A is very prominent in the spectra of T Tauri stars (TTSs). This feature is a quintupletof semiforbidden transitions excited at electron temperatures around 10,000 K that, together with the nearby SiII] and Fe II] features, provides a reliable optically thin tracer for accurate measurement of the plasma propertiesin the magnetospheres of TTSs. The spectra of 20 (out of 27) TTSs observed with the Space Telescope ImagingSpectrograph (STIS) on board the Hubble Space Telescope (HST) have good enough signal to noise ratio (S/N) at theC II] wavelength. For these stars we have determined electron densities (ne) and temperatures (Te) in the line emissionregion as well as the profile broadening (σ). For most of the stars in the sample (17) we obtain 104.1 < Te < 104.5 Kand 108 < ne < 1012 cm−3. These stars have suprathermal line broadening (35 < σ < 165 km s−1), except TW Hyaand CY Tau with thermal line broadening. Both C II] line luminosity and broadening are found to correlate with theaccretion rate. Line emission seems to be produced in the magnetospheric accretion flow, close to the disk. There arethree exceptions: DG Tau, RY Tau and FU Ori. The line centroids are blueshifted indicating that the line emissionin these three stars is dominated by the outflow.

Accepted by MNRAS


Mid- and Far-Infrared Variability of PV Cep

Dario Lorenzetti1, Simone Antoniucci1, Teresa Giannini1, Gianluca Li Causi1, Andrea Di Paola1,Arkady A. Arkharov2 and Valeri M. Larionov2,3

1 INAF - Osservatorio Astronomico di Roma - Via Frascati 33 - 00040 Monte Porzio Catone, Italy2 Central Astronomical Observatory of Pulkovo - Pulkovskoe shosse 65, 196140 St.Petersburg, Russia3 Astronomical Institute of St.Petersburg University, Russia

E-mail contact: dario.lorenzetti at oa-roma.inaf.it

We present the collection of all the mid- and far-IR observations (λ=3-170µm) of the young eruptive variable PV Cepavailable so far in the literature. These data allow us to confirm that flux variability is a prominent feature at mid-IRwavelengths (λ=3-25µm). Color-magnitude plots clearly indicate that the observed variability is not extinction-driven,but mainly influenced by fluctuations of the mass accretion rate. We interpret such variability as due to a hot spotcreated onto the stellar surface by the column of accreting matter, which heats the inner parts of the disk anddetermines the observed increase of the near- mid-IR luminosity. A quantitative characterization is given for both the

26



spot itself and the additional thermal component created by it. Far-IR data (λ=60-170µm) are consistent with thepresence of a temperature stratification in a massive and quite un-evolved circumstellar disk.

Accepted by Astrophysics and Space Science


The W43-MM1 mini-starburst ridge, a test for star formation efficiency models

Fabien Louvet1, Frederique Motte1, Patrick Hennebelle1, Anaelle Maury1, Ian Bonnell2, Sylvain Bontemps3,Antoine Gusdorf4, Tracey Hill5, Frederic Gueth6, Nicolas Peretto7, Ana Duarte-Cabral8, GwendolineStephan9, Peter Schilke9, Timea Csengeri10, Quang Nguyen-Luong11 and Darek Lis12

1 Laboratoire AIM Paris-Saclay, CEA/IRFU - CNRS/INSU - Universite Paris Diderot, Service d’Astrophysique, Bat.709, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex, France2 Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North Haugh,St Andrews, Fife KY16 9SS, UK3 OASU/LAB-UMR 5804, CNRS/INSU - Universite Bordeaux 1, 2 rue de l’Observatoire, BP 89, F-33270 Floirac,France4 LERMA, UMR 8112 du CNRS, Observatoire de Paris, Ecole Normale Superieure, 24 rue Lhomond, 75231 ParisCedex 05, France5 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile6 Institut de Radioastronomie Millimetrique (IRAM), 300 rue de la Piscine, 38406 Saint Martin d’Heres, France7 School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK8 School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK9 Physikalisches Institut, Universitat zu Koln, Zulpicher Str. 77, D-50937 Koln, Germany10 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany11 Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ONM5S 3H8,Canada12 Sorbonne Universites, Universite Pierre et Marie Curie, Paris 6, CNRS, Observatoire de Paris, UMR 8112, LERMA,Paris, France

E-mail contact: fabien.louvet at cea.fr

Star formation efficiency (SFE) theories are currently based on statistical distributions of turbulent cloud structuresand a simple model of star formation from cores. They remain poorly tested, especially at the highest densities. Weinvestigate the effects of gas density on the SFE through measurements of the core formation efficiency (CFE). With atotal mass of ∼2×104 M⊙, the W43-MM1 ridge is one of the most convincing candidate precursor of Galactic starburstclusters and thus one of the best places to investigate star formation. We used high-angular resolution maps obtainedat 3 mm and 1 mm within the W43-MM1 ridge with the IRAM Plateau de Bure Interferometer to reveal a cluster of11 massive dense cores (MDCs), and, one of the most massive protostellar cores known. An Herschel column densityimage provided the mass distribution of the cloud gas. We then measured the ‘instantaneous’ CFE and estimatedthe SFE and the star formation rate (SFR) within subregions of the W43-MM1 ridge. The high SFE found in theridge (∼6% enclosed in ∼8 pc3) confirms its ability to form a starburst cluster. There is however a clear lack of densecores in the northern part of the ridge, which may be currently assembling. The CFE and the SFE are observed toincrease with volume gas density while the SFR per free fall time steeply decreases with the virial parameter, αvir .Statistical models of the SFR may well describe the outskirts of the W43-MM1 ridge but struggle to reproduce itsinner part, which corresponds to measurements at low αvir. It may be that ridges do not follow the log-normal densitydistribution, Larson relations, and stationary conditions forced in the statistical SFR models.



Rosette Globulettes and Shells in the Infrared

Minja M. Makela1, Lauri K. Haikala2,1 and Gosta F. Gahm3

1 Department of Physics, Division of Geophysics and Astronomy, P.O. Box 64, 00014 University of Helsinki, Finland

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2 Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vaisalantie 20, 21500 Piikkio, Finland3 Stockholm Observatory, AlbaNova University Centre, Stockholm University, SE-106 91 Stockholm, Sweden

E-mail contact: minja.makela at helsinki.fi

Context. Giant galactic HII regions surrounding central young clusters show compressed molecular shells, which havebroken up into clumps, filaments, and elephant trunks interacting with UV light from central OB stars. Tiny, denseclumps of sub-solar mass, called globulettes, form in this environment.Aims. We observe and explore the nature and origin of the infrared emission and extinction in such cool, dusty shellfeatures and globulettes in one such HII region, the Rosette Nebula, and search for associated newborn stars.Methods. We imaged the northwestern quadrant of the Rosette Nebula in the near-infrared (NIR) through wide-bandJHKs filters and narrow-band H2 1–0 S(1) and Pβ plus continuum filters using SOFI at the New Technology Telescope(NTT) at ESO. NIR images were used to study the surface brightness of the globulettes and associated bright rims.NIR JHKs photometry was used to create a visual extinction map and to search for objects with NIR excess emission.In addition, archival images from Spitzer IRAC and MIPS 24 µm and Herschel PACS observations, covering severalbands in the mid-infrared (MIR) and far-infrared (FIR), were used to further analyze the stellar population, to examinethe structure of the trunks and other shell structures and to study this Rosette Nebula photon-dominated region inmore detail.Results. The globulettes and elephant trunks have bright rims in the Ks band, which are unresolved in our images,on the sides facing the central cluster. Analysis of 21 globulettes where surface brightness in the H2 1–0 S(1) lineat 2.12 µm is detected shows that approximately a third of the surface brightness observed in the Ks filter is due tothis line: the observed average of the H2/Ks surface brightness is 0.26±0.02 in the globulettes cores and 0.30±0.01in the rims. The estimated H2 1–0 S(1) surface brightness of the rims is ∼ 3–8×10−8 Wm−2sr−1µm−1. The ratio ofthe surface brightnesses support fluorescence instead of shocks as the H2 excitation mechanism. The globulettes havenumber densities of n(H2) ∼ 10−4 cm−3 or higher. Masses of individual globulettes were estimated and comparedto the results from previous optical and radio molecular line surveys. We confirm that the larger globulettes containvery dense cores, that the density is high also farther out from the core, and that their mass is sub-solar. Two NIRprotostellar objects were found in an elephant trunk and one in the most massive globulette in our study.



Revisiting the universality of (multiple) star formation in present-day star formationregions

Michael Marks1, Nathan Leigh2,3, Mirek Giersz4, Susanne Pfalzner5, Jan Pamm-Altenburg1, SeungkyungOh1

1 Helmholtz-Institut fur Strahlen- und Kernphysik, University of Bonn, Nussallee 14-16, D-53115 Bonn2 Department of Astrophysics, American Museum of Natural History, Central Park West and 79th Street, NY 10024,USA3 Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB T6G 2E1, Canada4 Nicolaus Copernicus Astronomical Centre, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland5 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany

E-mail contact: mmarks at astro.uni-bonn.de

Populations of multiple stars inside clustered regions are known to change through dynamical interactions. The effi-ciency of binary disruption is thought to be determined by stellar density. King and collaborators recently investigatedthe multiplicity properties in young star forming regions and in the Galactic field. They concluded that stellar density-dependent modification of a universal initial binary population (the standard or null hypothesis model) cannot explainthe observations. We re-visit their results, analyzing the data within the framework of different model assumptions,namely non-universality without dynamical modification and universality with dynamics. We illustrate that the stan-dard model does account for all known populations if regions were significantly denser in the past. Some of the effectsof using present-day cluster properties as proxies for their past values are emphasized and that the degeneracy betweenage and density of a star forming region can not be omitted when interpreting multiplicity data. A new analysis ofthe Corona Australis region is performed within the standard model. It is found that this region is likely as unevolvedas Taurus and an initial density of ≈ 190 M⊙ pc−3 is required to produce the presently observed binary population,

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which is close to its present-day density.

Accepted by MNRAS


Stellar parameters and accretion rate of the transition disk star HD 142527 from X-Shooter

I. Mendigutıa1, J. Fairlamb1, B. Montesinos2, R.D. Oudmaijer1, J.R. Najita3, S.D. Brittain4, and M.E.van den Ancker5

1 School of Physics & Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK2 Centro de Astrobiologıa, Departamento de Astrofısica (CSIC-INTA), ESAC Campus, P.O. Box 78, 28691 Villanuevade la Canada, Madrid, Spain3 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA4 Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA5 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching b. Munchen, Germany

E-mail contact: I.Mendigutia at leeds.ac.uk

HD 142527 is a young pre-main sequence star with properties indicative of the presence of a giant planet or/and alow-mass stellar companion. We have analyzed an X-Shooter/Very Large Telescope spectrum to provide accuratestellar parameters and accretion rate. The analysis of the spectrum, together with constraints provided by the SEDfitting, the distance to the star (140±20 pc) and the use of evolutionary tracks and isochrones, lead to the followingset of parameters Teff = 6550 ± 100 K, log g = 3.75 ± 0.10, L∗/L⊙ = 16.3 ± 4.5, M∗/M⊙ = 2.0 ± 0.3 and an age of5.0 ± 1.5 Myr. This stellar age provides further constrains to the mass of the possible companion estimated by Billeret al. (2012), being in-between 0.20 and 0.35 M⊙. Stellar accretion rates obtained from UV Balmer excess modelling,optical photospheric line veiling, and from the correlations with several emission lines spanning from the UV to thenear-IR, are consistent to each other. The mean value from all previous tracers is (2±1) × 10−7 M⊙ yr−1, which iswithin the upper limit gas flow rate from the outer to the inner disk recently provided by Cassasus et al. (2013). Thissuggests that almost all gas transferred between both components of the disk is not trapped by the possible planet(s)in-between but fall onto the central star, although it is discussed how the gap flow rate could be larger than previouslysuggested. In addition, we provide evidence showing that the stellar accretion rate of HD 142527 has increased by afactor ∼7 on a timescale of 2–5 years.

Accepted by ApJ


Very deep images of the innermost regions of the β Pictoris debris disc at L′

J. Milli1,2, A.-M. Lagrange1, D. Mawet2, O. Absil3, J.-C. Augereau1, D. Mouillet1, A. Boccaletti4, J.H.Girard2, and G. Chauvin1

1 Universite Grenoble Alpes, IPAG, F-38000 Grenoble, FranceCNRS, IPAG, F-38000 Grenoble, France 2 European Southern Observatory (ESO), Alonso de Cordova 3107, Vitacura,Casilla 19001, Santiago, Chile3 Departement d’Astrophysique, Geophysique et Oceanographie (AGO), Universite de Liege, 17 Allee du Six Aout,B-4000 Liege, Belgium4 LESIA, Observatoire de Paris, CNRS, Universit Pierre et Marie Curie 6 and Universit Denis Diderot Paris 7, 5 placeJules Janssen, 92195 Meudon, France

E-mail contact: jmilli at eso.org

Very few debris discs have been imaged in scattered light at wavelengths beyond 3 µm because the thermal emissionfrom both the sky and the telescope is generally too strong with respect to the faint emission of a debris disc. Wepresent here the first analysis of a high angular resolution image of the disc of β Pictoris at 3.8 µm. Our primaryobjective is to probe the innermost parts of the β Pictoris debris disc and describe its morphology. We performedextensive forward modelling to correct for the biases induced by angular differential imaging on extended objectsand derive the physical parameters of the disc. This work relies on a new analysis of seven archival datasets of β

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Pictoris observed with VLT/NaCo in the L′ band, associated with disc forward modelling to correct for the biasesinduced by that technique. The disc is detected above a 5σ level between 0.′′4 and 3.′′8. The two extensions have asimilar brightness within error bars. We confirm an asymmetry previously observed at larger distances from the starand at shorter wavelengths: the isophotes are more widely spaced on the north-west side (above the disc apparentmidplane) than on the south-east side. This is interpreted as a small inclination of the disc combined with anisotropicscattering. Our best-fit model has an inclination of 86 with an anisotropic Henyey- Greenstein coefficient of 0.36.This interpretation is supported by a new asymmetry detected in the disc: the disc is significantly bowed towards thenorth-west within 3′′ (above the apparent midplane). We also detect a possible new asymmetry within 1′′, but at thisstage we cannot discern between a real feature and an underlying speckle.

Accepted by A&A


Grain growth in the envelopes and disks of Class I protostars

A. Miotello1,2, L. Testi1,3,4, G. Lodato2, L. Ricci5, G. Rosotti4,6, K. Brooks7, A. Maury8 and A. Natta3,9

1 European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany2 Universit degli Studi di Milano, Dipartimento di Fisica, Via Celoria 16, I-20133 Milano, Italy3 INAF-Osservatorio Astrofidico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy4 Excellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, Germany5 Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA6 Max-Planck-institute fr extraterrestrische Physik, Giessenbachstraße, D-85748 Garching, Germany7 Australia Telescope National Facility, P.O. Box 76, Epping NSW 1710, Australia8 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA9 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland

E-mail contact: miotello at mpe.mpg.de

We present new 3 mm ATCA data of two Class I Young Stellar Objects in the Ophiucus star forming region: Elias29and WL12. For our analysis we compare them with archival 1.1 mm SMA data. In the (u, v) plane the two sourcespresent a similar behavior: a nearly constant non-zero emission at long baselines, which suggests the presence of anunresolved component and an increase of the fluxes at short baselines, related to the presence of an extended envelope.Our data analysis leads to unusually low values of the spectral index α1.1−3mm, which may indicate that mm-sized dustgrains have already formed both in the envelopes and in the disk-like structures at such early stages. To explore thepossible scenarios for the interpretation of the sources we perform a radiative transfer modeling using a Monte Carlocode, in order to take into account possible deviations from the Rayleigh-Jeans and optically thin regimes. Comparisonbetween the model outputs and the observations indicates that dust grains may form aggregates up to millimeter sizealready in the inner regions of the envelopes of Class I YSOs. Moreover, we conclude that the embedded disk-likestructures in our two Class Is are probably very compact, in particular in the case of WL12, with outer radii down totens of AU.

Accepted by A&A


Chemistry in an Evolving Protoplanetary Disk: Effects on Terrestrial Planet Composi-tion

John Moriarty1, Nikku Madhusudhan2,3, and Debra Fischer1

1 Department of Astronomy, Yale University, New Haven, CT 06511, USA2 Departments of Physics and Astronomy, Yale University, New Haven, CT 06511, USA3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

E-mail contact: john.c.moriarty at yale.edu

The composition of planets is largely determined by the chemical and dynamical evolution of the disk during planetes-imal formation and growth. To predict the diversity of exoplanet compositions, previous works modeled planetesimalcomposition as the equilibrium chemical composition of a protoplanetary disk at a single time. However, planetes-

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imals form over an extended period of time, during which, elements sequentially condense out of the gas as the diskcools and are accreted onto planetesimals. To account for the evolution of the disk during planetesimal formation,we couple models of disk chemistry and dynamics with a prescription for planetesimal formation. We then followthe growth of these planetesimals into terrestrial planets with N-body simulations of late stage planet formation toevaluate the effect of sequential condensation on the bulk composition of planets. We find that our model producesresults similar to those of earlier models for disks with C/O ratios close to the solar value (0.54). However, in diskswith C/O ratios greater than 0.8, carbon rich planetesimals form throughout a much larger radial range of the disk.Furthermore, our model produces carbon rich planetesimals in disks with C/O ratios as low as ∼0.65, which is notpossible in the static equilibrium chemistry case. These results suggest that (1) there may be a large population ofshort period carbon rich planets around moderately carbon enhanced stars (0.65 < C/O < 0.8) and (2) carbon richplanets can form throughout the terrestrial planet region around carbon rich stars (C/O > 0.8).

Accepted by ApJ


Discovery of a wide planetary-mass companion to the young M3 star GU Psc

Marie-Eve Naud1, Etienne Artigau1, Lison Malo1, Loıc Albert1, Rene Doyon1, David Lafreniere1,Jonathan Gagne1, Didier Saumon2, Caroline V. Morley3, France Allard4, Derek Homeier4, Charles A.Beichman5, Christopher R. Gelino5,6, and Anne Boucher1

1 Departement de physique and Observatoire du Mont-Megantic, Universite de Montreal, Montreal H3C 3J7, Canada2 Los Alamos National Laboratory, Los Alamos, NM 87545, USA3 Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA4 Centre de Recherche Astrophysique de Lyon, UMR 5574 CNRS, Universite de Lyon, Ecole Normale Superieure deLyon, 46 Allee d’Italie, F-69364 Lyon Cedex 07, France5 Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125, USA6 NASA Exoplanet Science Institute, California Institute of Technology, 770 S. Wilson Ave., Pasadena, CA 91125,USA

E-mail contact: naud at astro.umontreal.ca

We present the discovery of a co-moving planetary-mass companion ∼42′′ (∼2000 AU) from a young M3 star, GUPsc, likely member of the young AB Doradus Moving Group (ABDMG). The companion was first identified via itsdistinctively red i−z color (>3.5) through a survey made with Gemini-S/GMOS. Follow-up Canada-France-HawaiiTelescope/WIRCam near-infrared (NIR) imaging, Gemini-N/GNIRS NIR spectroscopy and Wide-field Infrared SurveyExplorer photometry indicate a spectral type of T3.5±1 and reveal signs of low gravity which we attribute to youth.Keck/Adaptive Optics NIR observations did not resolve the companion as a binary. A comparison with atmospheremodels indicates Teff = 1000–1100 K and log g = 4.5–5.0. Based on evolution models, this temperature corresponds toa mass of 9–13 MJup for the age of ABDMG (70–130 Myr). The relatively well-constrained age of this companion andits very large angular separation to its host star will allow its thorough characterization and will make it a valuablecomparison for planetary-mass companions that will be uncovered by forthcoming planet-finder instruments such asGemini Planet Imager and SPHERE.

Accepted by ApJ


Accreting planets as dust dams in ‘transition’ discs

James E. Owen1

1 Canadian Institute for Theoretical Astrophysics, 60 St. George St., Toronto, M5S 3H8, Canada

E-mail contact: jowen at cita.utoronto.ca

We investigate under what circumstances an embedded planet in a protoplanetary disc may sculpt the dust distributionsuch that it observationally presents as a ‘transition’ disc. We concern ourselves with ‘transition’ discs that have largeholes (>∼10 AU) and high accretion rates (∼10−9–10−8 M⊙ yr−1). Particularly, those discs which photoevaporativemodels struggle to explain. Assuming the standard picture for how massive planets sculpt their parent discs, along

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with the observed accretion rates in ‘transition’ discs, we find that the accretion luminosity from the forming planetis significant, and can dominate over the stellar luminosity at the gap edge. This planetary accretion luminosity canapply a significant radiation pressure to small (s<∼ 1 µm) dust particles provided they are suitably decoupled from thegas. Secular evolution calculations that account for the evolution of the gas and dust components in a disc with anembedded, accreting planet, show that only with the addition of the radiation pressure can we explain the full observedcharacteristics of a ‘transition’ disc (NIR dip in the SED, mm cavity and high accretion rate). At suitably high planetmasses (>∼3–4 MJ), radiation pressure from the accreting planet is able to hold back the small dust particles, producinga heavily dust-depleted inner disc that is optically thin (vertically and radially) to Infra-Red radiation. We use ourmodels to calculate synthetic observations and present a observational evolutionary scenario for a forming planet,sculpting its parent disc. The planet-disc system will present as a ‘transition’ disc with a dip in the SED, only whenthe planet mass and planetary accretion rate is high enough. At other times it will present as a disc with a primordialSED, but with a cavity in the mm, as observed in a handful of protoplanetary discs.

Accepted by ApJ


Resolved images of the protoplanetary disk around HD 100546 with ALMA

Jaime E. Pineda1, Sascha P. Quanz1, Farzana Meru1, Gijs D. Mulders2, Michael R. Meyer1, Olja Panic3,and Henning Avenhaus1

1 Institute for Astronomy, ETH Zurich, Wolfgang-PauliStrasse 27, 8093 Zurich, Switzerland2 Lunar and Planetary Laboratory, The University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA3 Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK

E-mail contact: pjaime at phys.ethz.ch

The disk around the Herbig Ae/Be star HD 100546 has been extensively studied and it is one of the systems for whichthere are observational indications of ongoing and/or recent planet formation. However, up until now no resolvedimage of the millimeter dust emission or the gas has been published. We present the first resolved images of thedisk around HD 100546 obtained in Band 7 with the ALMA observatory. The CO (3–2) image reveals a gas diskthat extends out to 350 AU radius at the 3σ level. Surprisingly, the 870 µm dust continuum emission is compact(radius <60 AU) and asymmetric. The dust emission is well matched by a truncated disk with outer radius of ∼50AU. The lack of millimeter-sized particles outside the 60 AU is consistent with radial drift of particles of this size.The protoplanet candidate, identified in previous high-contrast NACO/VLT L′ observations, could be related to thesharp outer edge of the millimeter-sized particles. Future higher angular resolution ALMA observations are needed todetermine the detailed properties of the millimeter emission and the gas kinematics in the inner region (<2′′). Suchobservations could also reveal the presence of a planet through the detection of circumplanetary disk material.

Accepted by ApJL


The Herschel view of circumstellar discs: a multiwavelength study of Chamaeleon I

Donna Rodgers-Lee1, Alexander Scholz1,2, Antonella Natta1,3 and Tom Ray1

1 School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland2 School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife, KY16 9SS3 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 1-50125, Firenze, Italy

E-mail contact: donna at cp.dias.ie

We present the results of a multi-wavelength study of circumstellar discs around 44 young stellar objects in the 3 Myrold nearby Chamaeleon-I star-forming region. In particular, we explore the far-infrared/submm regime using Herschelfluxes. We show that Herschel fluxes at 160-500µm can be used to derive robust estimates of the disc mass. The mediandisc mass is 0.005M⊙ for a sample of 28 Class IIs and 0.006M⊙ for 6 transition disks (TDs). The fraction of objectsin Chamaeleon I with at least the ‘minimum mass solar nebula’ is 2-7%. This is consistent with previously publishedresults for Taurus, IC348, ρ Oph. Diagrams of spectral slopes show the effect of specific evolutionary processes incircumstellar discs. Class II objects show a wide scatter that can be explained by dust settling. We identify acontinuous trend from Class II to TDs. Including Herschel fluxes in this type of analysis highlights the diversity of

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TDs. We find that TDs are not significantly different to Class II discs in terms of far-infrared luminosity, disc mass ordegree of dust settling. This indicates that inner dust clearing occurs independently from other evolutionary processesin the discs.

Accepted by MNRAS


Radio Continuum Sources associated with the HH 92 and HH 34 Jets

Luis F. Rodrıguez1,2, Bo Reipurth3,4 and Hsin-Fang Chiang3,4

1 Centro de Radioastronomıa y Astrofısica, Universidad Nacional Autonoma de Mexico, Campus Morelia2 Astronomy Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia3 Institute for Astronomy, University of Hawaii at Manoa, Hilo, HI, USA4 NASA Astrobiology Institute, University of Hawaii at Manoa, Hilo, HI, USA

E-mail contact: l.rodriguez at crya.unam.mx

We present high angular resolution, high sensitivity 8.46 GHz (3.6 cm) radio continuum observations made towardthe core of the HH 92 outflow with the Very Large Array in 2002-2003 and with the Expanded Very Large Array in2011. We detect a group of three compact sources distributed in a region 2′′ in extension and discuss their nature.We conclude that one of the objects (VLA 1) is the exciting source of the giant outflow associated with HH 92. In thecase of HH 34 we present new 43.3 GHz (7 mm) observations that reveal the presence of a structure associated withthe exciting source and elongated perpendicular to the highly collimated optical jet in the region. We propose thatthis 7 mm source is a circumstellar disk with radius of ∼80 AU and mass of ∼0.21 M⊙.

Accepted by Revista Mexicana de Astronomıa y Astrofısica


Diversity of planetary systems in low-mass disks: Terrestrial-type planet formation andwater delivery

M.P. Ronco1 and G.C. de Elıa1

1 Facultad de Ciencias Astronomicas y Geofısicas, Universidad Nacional de La Plata and Instituto de Astrofsica deLa Plata, CCT La Plata-CONICET-UNLP, Paseo del Bosque S/N (1900), La Plata, Argentina

E-mail contact: mpronco at fcaglp.unlp.edu.ar

Several studies, observational and theoretical, suggest that planetary systems with only rocky planets should be themost common in the Universe. We study the diversity of planetary systems that might form around Sun-like starsin low-mass disks without giant planets. We focus on the formation process of terrestrial planets in the habitablezone (HZ) and analyze their water contents with the goal to determine systems of astrobiological interest. Besides, westudy the formation of planets on wide orbits because they can be detected with the microlensing technique. N-bodysimulations of high resolution (embryos + planetesimals) are developed for a wide range of surface density profiles.The surface density profile combines a power law to the inside of the disk of the form r−γ , with an exponential decayto the outside. We adopt a disk of 0.03 M⊙ and values of γ = 0.5, 1 and 1.5. All our simulations form planets inthe HZ with different masses and final water contents depending on the 3 profiles. For γ = 0.5, we produce 3 planetsin the HZ with masses between 0.03 M⊕ to 0.1 M⊕ and water contents between 0.2 and 16 Earth oceans. For γ =1, 3 planets form in the HZ with masses between 0.18 M⊕ and 0.52 M⊕ and water contents from 34 to 167 Earthoceans. For γ = 1.5, we find 4 planets in the HZ with masses from 0.66 M⊕ to 2.21 M⊕ and water contents between192 and 2326 Earth oceans. This profile shows distinctive results because it is the only one of those studied here thatleads to the formation of water worlds. Since planetary systems with γ = 1 and 1.5 present planets in the HZ withsuitable masses to retain a long-live atmosphere and to maintain plate tectonics, they seem to be the most outstandingcandidates to be potentially habitable. Particularly, these systems form Earths and Super-Earths near the snow linewhich can be discovered by microlensing.

Accepted by A&A


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Numerical simulations of stellar jets and comparison between synthetic and observedmaps: clues to the launch mechanism

F. Rubini1, L. Maurri1, G. Inghirami1,2, F. Bacciotti3, and L. Del Zanna1,2,3

1 Dipartimento di Fisica e Astronomia, Universita di Firenze, Via G. Sansone 1, I-50019, Sesto F. no (Firenze), Italy2 INFN - Sezione di Firenze, Via G. Sansone 1, I-50019, Sesto F. no (Firenze), Italy3 INAF - Osservatorio Astrosico di Arcetri, Largo E. Fermi 5, I-50125, Firenze, Italy

E-mail contact: rubini at arcetri.astro.it

High angular resolution spectra obtained with the Hubble Space Telescope Imaging Spectrograph (HST/STIS) providerich morphological and kinematical information about the stellar jet phenomenon, which allows us to test theoreticalmodels efficiently. In this work, numerical simulations of stellar jets in the propagation region are executed with thePLUTO code, by adopting inflow conditions that arise from former numerical simulations of magnetized outflows,accelerated by the disk-wind mechanism in the launching region. By matching the two regions, information about themagneto-centrifugal accelerating mechanism underlying a given astrophysical object can be extrapolated by comparingsynthetic and observed position-velocity diagrams (PVDs). We show that quite different jets, like those from the youngT Tauri stars DG-Tau and RW-Aur, may originate from the same disk-wind model for different configurations of themagnetic field at the disk surface. This result supports the idea that all the observed jets may be generated by thesame mechanism.

Accepted by A&A


Old pre-main-sequence Stars: Disc reformation by Bondi-Hoyle accretion

P. Scicluna1,2, G. Rosotti3,4,5, J.E. Dale4 and L. Testi2,6

1 ITAP, Universitaet zu Kiel, Leibnizstr. 15, 24118 Kiel, Germany2 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching b. Muenchen, Germany3 Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrae, D-85748 Garching, Germany4 Excellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, Germany5 Universitats-Sternwarte Muenchen, Scheinerstrae 1, D-81679 Muenchen, Germany6 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

E-mail contact: pscicluna at astrophysik.uni-kiel.de

Young stars show evidence of accretion discs which evolve quickly and disperse with an e-folding time of ∼ 3Myr. Thisis in striking contrast with recent observations that suggest evidence for numerous> 30 Myr old stars with an accretiondisc in large star-forming complexes. We consider whether these observations of apparently old accretors could beexplained by invoking Bondi-Hoyle accretion to rebuild a new disc around these stars during passage through a clumpymolecular cloud. We combine a simple Monte Carlo model to explore the capture of mass by such systems with aviscous evolution model to infer the levels of accretion that would be observed. We find that a significant fraction ofstars may capture enough material via the Bondi-Hoyle mechanism to rebuild a disc of mass >∼ 1 minimum-mass solarnebula, and <∼10% accrete at observable levels at any given time. A significant fraction of the observed old accretorsmay be explained with our proposed mechanism. Such accretion may provide a chance for a second epoch of planetformation, and have unpredictable consequences for planetary evolution.

Accepted by A&A


Gravito-Turbulent Disks in 3D: Turbulent Velocities vs. Depth

Ji-Ming Shi1,2 and Eugene Chiang1,2,3

1 Department of Astronomy, UC Berkeley, Hearst Field Annex B-20, Berkeley, CA 94720-3411, USA2 Center for Integrative Planetary Science, UC Berkeley, Hearst Field Annex B-20, Berkeley, CA 94720-3411, USA3 Department of Earth and Planetary Science, UC Berkeley, 307 McCone Hall, Berkeley, CA 94720-4767, USA

E-mail contact: jmshi at berkeley.edu

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Characterizing turbulence in protoplanetary disks is crucial for understanding how they accrete and spawn planets.Recent measurements of spectral line broadening promise to diagnose turbulence, with different lines probing differentdepths. We use 3D local hydrodynamic simulations of cooling, self-gravitating disks to resolve how motions drivenby “gravito-turbulence” vary with height. We find that gravito-turbulence is practically as vigorous at altitude asat depth: even though gas at altitude is much too rarefied to be itself self-gravitating, it is strongly forced by self-gravitating overdensities at the midplane. The long-range nature of gravity means that turbulent velocities are nearlyuniform vertically, increasing by just a factor of 2 from midplane to surface, even as the density ranges over nearly threeorders of magnitude. The insensitivity of gravito-turbulence to height contrasts with the behavior of disks afflicted bythe magnetorotational instability (MRI); in the latter case, non-circular velocities increase by at least a factor of 15from midplane to surface, with various non-ideal effects only magnifying this factor. The distinct vertical profiles ofgravito-turbulence vs. MRI turbulence may be used in conjunction with measurements of non-thermal linewidths atvarious depths to identify the source of transport in protoplanetary disks.

Accepted by ApJ


The Gaia-ESO Survey: the first abundance determination of the pre-main-sequencecluster Gamma Velorum

L. Spina1,2, S. Randich1, F. Palla1, G.G. Sacco1, L. Magrini1, E. Franciosini1, L. Morbidelli1, L.Prisinzano3, E.J. Alfaro4, K. Biazzo5, A. Frasca5, J.I. Gonzalez Hernandez6,7, S.G. Sousa8,9, V. Adibekyan8,E. Delgado-Mena8, D. Montes10, H. Tabernero10, A. Klutsch5, G. Gilmore11, S. Feltzing12, R.D.Jeffries13, G. Micela3, A. Vallenari14, T. Bensby11, A. Bragaglia15, E. Flaccomio13, S. Koposov10, A.C.Lanzafame16, E. Pancino15, A. Recio-Blanco18, R. Smiljanic19,20, M. T. Costado4, F. Damiani3, V. Hill18,A. ourihane10, P. Jofre10, P. de Laverny18, T. Masseron10, C. Worley11

1 INAFOsservatorio Astrosico di Arcetri, Largo E. Fermi, 5, I-50125 Firenze, Italy2 Universita degli Studi di Firenze, Dipartimento di Fisica e Astrosica, Sezione di Astronomia, Largo E. Fermi, 2,I-50125, Firenze, Italy3 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134, Palermo, Italy4 Instituto de Astrofısica de Andalucıa-CSIC, Apdo. 3004, 18080 Granada, Spain5 INAFOsservatorio Astrosico di Catania, via S. Soa, 78, I-95123 Catania, Italy6 Instituto de Astrosica de Canarias (IAC), E-38205 La Laguna, Tenerife, Spain7 Depto. Astrosica, Universidad de La Laguna (ULL), E-38206 La Laguna, Tenerife, Spain8 Centro de Astrosica, Universidade do Porto, Rua das Estrelas, 4150-762, Porto, Portugal9 Departamento de Fısica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal10 Departamento de Astrosica, Universidad Complutense de Madrid (UCM), Spain11 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom12 Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-221 00 Lund, Sweden13 Astrophysics Group, Research Institute for the Environment, Physical Sciences and Applied Mathematics, KeeleUniversity, Keele, Staordshire ST5 5BG, United Kingdom14 INAF - Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy15 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127, Bologna, Italy16 Dipartimento di Fisica e Astronomia, Sezione Astrosica, Universita di Catania, via S. Soa 78, 95123, Catania, Italy17 ASI Science Data Center, Via del Politecnico SNC, 00133 Roma, Italy18 Universite de Nice Sophia Antipolis, CNRS, Observatoire de la Cote d’Azur, BP 4229, F-06304, Nice Cedex 4,France19 Department for Astrophysics, Nicolaus Copernicus Astronomical Center, ul. Rabianska 8, 87-100 Torun, Poland20 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Munchen, Germany

E-mail contact: lspina at arcetri.astro.it

Knowledge of the abundance distribution of star forming regions and young clusters is critical to investigate a varietyof issues, from triggered star formation and chemical enrichment by nearby supernova explosions to the ability toform planetary systems.In spite of this, detailed abundance studies are currently available for relatively few regions.

35


In this context, we present the analysis of the metallicity of the Gamma Velorum cluster, based on the productsdistributed in the first internal release of the Gaia-ESO Survey. The Gamma Velorum candidate members havebeen observed with FLAMES, using both UVES and Giraffe, depending on the target brightness and spectral type.In order to derive a solid metallicity determination for the cluster, membership of the observed stars must be firstassessed. To this aim, we use several membership criteria including radial velocities, surface gravity estimates, and thedetection of the photospheric lithium line. Out of the 80 targets observed with UVES, we identify 14 high-probabilitymembers. We find that the metallicity of the cluster is slightly subsolar, with a mean [Fe/H] = −0.057± 0.018 dex.Although J08095427−4721419 is one of the high-probability members, its metallicity is significantly larger than thecluster average. We speculate about its origin as the result of recent accretion episodes of rocky bodies of ∼60 M⊕

hydrogen-depleted material from the circumstellar disk.

Accepted by A&A


Rapidly increasing collimation and magnetic field changes of a protostellar H2O maseroutflow

G. Surcis1, W.H.T. Vlemmings2, H.J. van Langevelde1,3, C. Goddi1, J.M. Torrelles4, J. Canto5, S.Curiel5, S.-W. Kim6 and J.-S. Kim7

1 Joint Institute for VLBI in Europe, Postbus 2, 79990 AA Dwingeloo, The Netherlands2 Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala, Sweden3 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands4 Institut de Ciencies de l’Espai (CSIC)-Institut de Ciencies del Cosmos (UB)/IEEC, E-08028 Barcelona, Spain5 Instituto de Astronomıa (UNAM), Apdo Postal 70-264, Cd. Universitaria, 04510-Mexico D.F., Mexico6 Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 305-348, Republic of Korea7 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

E-mail contact: surcis at jive.nl

Context. W75N(B) is a massive star-forming region that contains three radio continuum sources (VLA1, VLA2, andVLA3), which are thought to be three massive young stellar objects at three different evolutionary stages. VLA1 isthe most evolved and VLA2 the least evolved source. The 22 GHz H2O masers associated with VLA1 and VLA2 havebeen mapped at several epochs over eight years. While the H2O masers in VLA 1 show a persistent linear distributionalong a radio jet, those in VLA2 are distributed around an expanding shell. Furthermore, H2O maser polarimetricmeasurements revealed magnetic fields aligned with the two structures.Aims. Using new polarimetric observations of H2O masers, we aim to confirm the elliptical expansion of the shell-like structure around VLA2 and, at the same time, to determine if the magnetic fields around the two sources havechanged.Methods. The NRAO Very Long Baseline Array was used to measure the linear polarization and the Zeeman-splittingof the 22 GHz H2O masers towards the massive star-forming region W75N(B).Results. The H2O maser distribution around VLA1 is unchanged from that previously observed. We made an ellipticalfit of the H2O masers around VLA2. We find that the shell-like structure is still expanding along the direction parallelto the thermal radio jet of VLA1. While the magnetic field around VLA1 has not changed in the past ∼7 years,the magnetic field around VLA2 has changed its orientation according to the new direction of the major-axis of theshell-like structure and it is now aligned with the magnetic field in VLA 1.

Accepted by Astronomy & Astrophysics Letters

Distribution of CCS and HC3N in L1147, an Early Phase Dark Cloud

Taiki Suzuki1, Masatoshi Ohishi1,2, and Tomoya Hirota1,2

1 Department of Astronomical Science, the Graduate University for Advanced Studies (SOKENDAI), Osawa 2-21-1,Mitaka, Tokyo 181-8588, Japan2 National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan

E-mail contact: taiki.suzuki at nao.ac.jp

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We used the Nobeyama 45 m radio telescope to reveal spatial distributions of CCS and HC3N in L1147, one of carbon-chain producing regions (CCPRs) candidates, where carbon-chain molecules are dominant rather than NH3. We foundthat three cores (two CCS cores and one HC3N core) exist along the NE–SW filament traced by the 850 µm dustcontinuum, which are away from a Very Low Luminosity Object (VeLLO - a source that may turn into sub-stellarmass brown dwarf). The column densities of CCS are 3–7 × 1012 cm−2 and those of HC3N are 2–6 × 1012 cm−2,respectively, much lower than those previously reported towards other CCPRs. We also found that two CCS peaksare displaced from that of HC3N. In order to interpret such interleaved distributions, we conducted chemical reactionnetwork simulations, and found that slightly different gas densities could lead to large variation of CCS-to-HC3N ratioin the early phase of dark cloud evolution. Such a chemical “variation” may be seen in other CCPRs. Finally we wereable to confirm that the L1147 filament can be regarded as a CCPR.

Accepted by ApJ


Multilayer formation and evaporation of deuterated ices in prestellar and protostellarcores

Vianney Taquet1,2, Steven B. Charnley2, and Olli Sipila3

1 NASA Postdoctoral Program Fellow2 Astrochemistry Laboratory and The Goddard Center for Astrobiology, Mailstop 691, NASA Goddard Space FlightCenter, 8800 Greenbelt Road, Greenbelt, MD 20770, USA3 Department of Physics, PO Box 64, 00014 University of Helsinki, Finland

E-mail contact: vianney.taquet at nasa.gov

Extremely large deuteration of several molecules has been observed towards prestellar cores and low-mass protostarsfor a decade. New observations performed towards low-mass protostars suggest that water presents a lower deuterationin the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimension model of collapsing core to properly follow the formation and the deuteration of interstellar ices as wellas their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial andtemporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of iceswith a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin statesof H2 and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous andshow an increase of their deuterium fractionation towards the surface. The differentiation of the deuteration in icesinduces an evolution of the deuteration within protostellar envelopes. The warm inner region is poorly deuteratedbecause it includes the whole molecular content of ices while the deuteration predicted in the cold external envelopescales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuterationwithin protostellar envelopes but we are still unable to predict the super-high deuteration observed for formaldehydeand methanol. Finally, the extension of this study to the deuteration of complex organics (COMs), important for theprebiotic chemistry, shows a good agreement with the observations, suggesting that we can use the deuteration toretrace their mechanisms and their moments of formation.

Accepted by ApJ


Thermal Starless Ammonia Core Surrounded by CCS in the Orion A Cloud

Ken’ichi Tatematsu1,2, Tomoya Hirota1,2, Satoshi Ohashi3, Minho Choi4, Jeong-Eun Lee5, SatoshiYamamoto6, Tomofumi Umemoto1,2, Ryo Kandori1, Miju Kang4 and Norikazu Mizuno1,3

1 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan2 Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa,Mitaka, Tokyo 181-8588, Japan3 Department of Astronomy, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan4 Korea Astronomy and Space Science Institute, Daedeokdaero 776, Yuseong, Daejeon 305-348, South Korea5 School of Space Research, Kyung Hee University, Seocheon-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-Do, 446-701,

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South Korea6 Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

E-mail contact: k.tatematsu at nao.ac.jp

We imaged two starless molecular cloud cores, TUKH083 and TUKH122, in the Orion A giant molecular cloud (GMC)in the CCS and ammonia (NH3) emission with the Very Large Array. TUKH122 contains one NH3 core “TUKH122-n,” which is elongated and has a smooth oval boundary. Where observed, the CCS emission surrounds the NH3 core.This configuration resembles that of the N2H

+ and CCS distribution in the Taurus starless core L1544, a well-studiedexample of a dense prestellar core exhibiting infall motions. The linewidth of TUKH122-n is narrow (0.20 km s−1)in the NH3 emission line and therefore dominated by thermal motions. The smooth oval shape of the core boundaryand narrow linewidth in N2H

+ seem to imply that TUKH122-n is dynamically relaxed and quiescent. TUKH122-nis similar to L1544 in the kinetic temperature (10 K), linear size (0.03 pc), and virial mass (∼ 2 M⊙). Our resultsstrongly suggest that TUKH122-n is on the verge of star formation. TUKH122-n is embedded in the 0.2 pc massive(virial mass ∼ 30 M⊙) turbulent parent core, while the L1544 NH3 core is embedded in the 0.2 pc less-massive (virialmass ∼ 10 M⊙) thermal parent core. TUKH083 shows complicated distribution in NH3, but was not detected in CCS.The CCS emission toward TUKH083 appears to be extended, and is resolved out in our interferometric observations.

Accepted by Astrophysical Journal


ALMA observations of a high density core in Taurus: dynamical gas interaction at thepossible site of a multiple star formation

Kazuki Tokuda1, Toshikazu Onishi1, Kazuya Saigo2, Akiko Kawamura2, Yasuo Fukui3, Tomoaki Matsumoto4,Shu-ichiro Inutsuka3, Masahiro N. Machida5, Kengo Tomida6,7 and Kengo Tachihara3

1 Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,Sakai, Osaka 599-8531, Japan2 National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan3 Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan4 Faculty of Humanity and Environment, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan5 Department of Earth and Planetary Sciences, Kyushu University, Fukuoka 812-8581, Japan6 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA7 Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan

E-mail contact: s k.tokuda at p.s.osakafu-u.ac.jp

Starless dense cores eventually collapse dynamically to form protostars in them, and the physical properties of thecores determine the nature of the forming protostars. We report ALMA observations of dust continuum emissionand molecular rotational lines toward MC27 or L1521F, which is considered to be very close to a moment of the firstprotostellar core phase. We found a few starless high-density cores, one of which has a very high density of sim107cm−3,within a region of several hundred AU around a very low luminosity protostar detected by the Spitzer. A very compactbipolar outflow with a dynamical time scale of a few hundred years was found toward the protostar. The molecularline observation shows several cores with arc-like structure, possibly due to the dynamical gas interaction. Thesecomplex structures revealed in the present observations suggest that the initial condition of star formation is highlydynamical in nature, which is considered to be a key factor to understand fundamental issues of star formation suchas the formation of multiple stars and the origin of the initial mass function of stars.

Accepted by Astrophysical Journal Letters


Core and filament formation in magnetized, self-gravitating isothermal layers.

Sven Van Loo1, Eric Keto1 and Qizhou Zhang1

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

E-mail contact: svanloo at cfa.harvard.edu

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We examine the role of the gravitational instability in an isothermal, self-gravitating layer threaded by magnetic fieldson the formation of filaments and dense cores. Using numerical simulation we follow the non-linear evolution of aperturbed equilibrium layer. The linear evolution of such a layer is described in the analytic work of Nagai et al(1998). We find that filaments and dense cores form simultaneously. Depending on the initial magnetic field, theresulting filaments form either a spiderweb-like network (for weak magnetic fields) or a network of parallel filamentsaligned perpendicular to the magnetic field lines (for strong magnetic fields). Although the filaments are radiallycollapsing, the density profile of their central region (up to the thermal scale height) can be approximated by ahydrodynamical equilibrium density structure. Thus, the magnetic field does not play a significant role in settingthe density distribution of the filaments. The density distribution outside of the central region deviates from theequilibrium. The radial column density distribution is then flatter than the expected power law of r−4 and similar tofilament profiles observed with Herschel. Our results does not explain the near constant filament width of ∼ 0.1pc.However, our model does not include turbulent motions. It is expected that accretion-driven amplification of theseturbulent motions provides additional support within the filaments against gravitational collapse. Finally, we interpretthe filamentary network of the massive star forming complex G14.225-0.506 in terms of the gravitational instabilitymodel and find that the properties of the complex are consistent with being formed out of an unstable layer threadedby a strong, parallel magnetic field.

Accepted by Astrophysical Journal


Accurate water maser positions from HOPS

Andrew J. Walsh1, Cormac R. Purcell2, Steven N. Longmore3, Shari L. Breen4, James A. Green5, LisaHarvey-Smith4, Christopher H. Jordan6 and Christopher MacPherson1

1 ICRAR/Curtin University2 University of Sydney3 Liverpool John Moores University4 CSIRO Astronomy and Space Science5 SKA Organisation6 University of Tasmania

E-mail contact: andrew.walsh at curtin.edu.au

We report on high spatial resolution water maser observations, using the Australia Telescope Compact Array, towardswater maser sites previously identified in the H2O southern Galactic Plane Survey (HOPS). Of the 540 masers identifiedin the single-dish observations of Walsh et al. (2011), we detect emission in all but 31 fields. We report on 2790 spectralfeatures (maser spots), with brightnesses ranging from 0.06 Jy to 576Jy and with velocities ranging from −238.5 to+300.5km/s. These spectral features are grouped into 631 maser sites. We have compared the positions of these sitesto the literature to associate the sites with astrophysical objects. We identify 433 (69 per cent) with star formation,121 (19 per cent) with evolved stars and 77 (12 per cent) as unknown. We find that maser sites associated with evolvedstars tend to have more maser spots and have smaller angular sizes than those associated with star formation. Wepresent evidence that maser sites associated with evolved stars show an increased likelihood of having a velocity rangebetween 15 and 35 km/s compared to other maser sites. Of the 31 non-detections, we conclude they were not detecteddue to intrinsic variability and confirm previous results showing that such variable masers tend to be weaker and havesimpler spectra with fewer peaks.

Accepted by MNRAS


The full preprint (718 pages, 21MB) can be downloaded from this http://www.hops.org.au under ”Publications”

Rapid Evolution of the Innermost Dust Disk of Protoplanetary Disks SurroundingIntermediate-mass Stars

Chikako Yasui1, Naoto Kobayashi2, Alan T. Tokunaga3 and Masao Saito4,5

1 Department of Astronomy, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-

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http://www.hops.org.au

0033, Japan2 Institute of Astronomy, School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan3 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA4 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan5 Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago, Chile

E-mail contact: ck.yasui at astron.s.u-tokyo.ac.jp

We derived the intermediate-mass (≃1.5–7M⊙) disk fraction (IMDF) in the near-infrared JHK photometric bands aswell as in the mid-infrared (MIR) bands for young clusters in the age range of 0 to ∼10Myr. From the JHK IMDF, thelifetime of the innermost dust disk (∼0.3AU; hereafter the K disk) is estimated to be ∼3Myr, suggesting a stellar mass(M∗) dependence of K-disk lifetime ∝ M−0.7

∗ . However, from the MIR IMDF, the lifetime of the inner disk (∼5AU;hereafter the MIR disk) is estimated to be ∼6.5Myr, suggesting a very weak stellar mass dependence (∝ M−0.2

∗ ). Themuch shorter K-disk lifetime compared to the MIR-disk lifetime for intermediate-mass (IM) stars suggests that IMstars with transition disks, which have only MIR excess emission but no K-band excess emission, are more commonthan classical Herbig Ae/Be stars, which exhibit both. We suggest that this prominent early disappearance of the Kdisk for IM stars is due to dust settling/growth in the protoplanetary disk, and it could be one of the major reasonsfor the paucity of close-in planets around IM stars.

Accepted by MNRAS

http://arxiv.org/pdf/1405.5284v2.pdf

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http://arxiv.org/pdf/1405.5284v2.pdf

Abstracts of recently accepted major reviews

Exploring the Origins of Carbon in Terrestrial Worlds

Edwin Bergin1, L. Ilsedore Cleeves1, Nathan Crockett2 and Geoffrey Blake2

1 University of Michigan, Department of Astronomy, 500 Church St., Ann Arbor, MI 48109 USA2 California Institute of Technology, Division of Geological & Planetary Sciences, MS 150-21, Pasadena, CA 91125,USA

E-mail contact: ebergin at umich.edu

Given the central role of carbon in the chemistry of life, it is a fundamental question as to how carbon is supplied tothe Earth, in what form and when. We provide an accounting of carbon found in solar system bodies, in particular acomparison between the organic content of meteorites and that in identified organics in the dense interstellar medium(ISM). Based on this accounting identified organics created by the chemistry of star formation could contain at most∼15% of the organic carbon content in primitive meteorites and significantly less for cometary organics, which representthe putative contributors to starting materials for the Earth. In the ISM ∼ 30% of the elemental carbon is found inCO, either in the gas or ices, with a typical abundance of ∼ 10−4 (relative to H2). Recent observations of the TW Hyadisk find that the gas phase abundance of CO is reduced by an order of magnitude compared to this value. We explorea solution where the volatile CO is destroyed via a gas phase processes, providing an additional source of carbonfor organic material to be incorporated into planetesimals and cometesimals. This chemical processing mechanismrequires warm grains (> 20 K), partially ionized gas, and sufficiently small (agrain < 10 µm) grains, i.e. a larger totalgrain surface area, such that freeze-out is efficient. Under these conditions static (non-turbulent) chemical modelspredict that a large fraction of the carbon nominally sequestered in CO can be the source of carbon for a wide varietyof organics that are present as ice coatings on the surfaces of warm pre-planetesimal dust grains.

Accepted by Faraday Disc., 2014, Vol. 168, DOI: 10.1039/C4FD00003J


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Meetings

The Filamentary Structure in Molecular Clouds10-11 October 2014 Charlottesville, Virginia, USA

A North America ALMA Science Center (NAASC) Workshop

Filamentary structure in molecular clouds has been observed dating back many years. However, recent Herschelobservations of nearby dust clouds have highlighted that the dense gas is distributed predominantly in filaments. Ithas been suggested that such filamentary structure may be ubiquitous in the internal structure of all molecular cloudsand may be preferential formation sites of dense cores that eventually collapse to form stars.

If such filamentary structures were universal in all molecular clouds of low mass and high mass star formation, thenthe whole paradigm of cloud formation and evolution leading to star formation would be placed on a more definitiveframework that centers on cloud condensation into filaments and filament fragmentation into cores. This frameworkwould focus the theoretical and observational studies of star formation in molecular clouds on the origin and evolutionof dense filaments as one of the fundamental steps.

This NAASC Workshop aims to bring together experts, postdoctoral fellows, and students, to discuss the currentevidence for such a picture and to help formulate future projects on ALMA and other facilities - CARMA, SMA,SMT, GBT, VLA, JCMT, LMT, CCAT, etc. - and theoretical investigations to verify whether such filamentarystructure is universal in molecular clouds in different environments and to study the physical conditions of suchstructures.

A sample of outstanding issues to be addressed include:

1. Is filamentary structure in molecular clouds universal?

2. What are the kinematic characteristics of filaments and their local environment that would inform us on theirorigins? Do the filaments we observe arise from converging, super-Alfvenic gas flows, stretching and shearing ofpre-existing features, or sub-Alfvenic flows along magnetic fields, and self-gravity?

3. How important is filamentary structure for star formation? Would the IMF be different if filaments were different?

4. What is the connection between the filamentary structure in molecular clouds and the shell-like structure of the HImedium? And, what is the relationship to the ionized regions?

5. What further observations would be needed to fully characterize the internal (filamentary) structure of molecularclouds in various environments?

6. The viability of similar studies of molecular clouds in the Magellanic Clouds, nearby Local Group galaxies andperhaps the nearest starburst galaxies, such as NGC253.

Through this focused workshop, it is hoped that interested members of the community can formulate key projects onALMA and other telescopes that will further define the internal structure of molecular clouds in various environmentsin the Galaxy. The workshop will take at NRAO in Charlottesville from 10-11 October 2014. Attendance will belimited to 60 participants.

Further information will be made available at http://science/nrao.edu

Science Organizing Committee:

Fred Lo, Chair (NRAO), Neal Evans (Texas), James di Francesco (HIA), Paul Goldsmith (JPL/Caltech), Mark Heyer(UMass), Zhi Yun Li (Virginia), Lee Mundy (CARMA), Phil Myers (CfA), Eve Ostriker (Princeton), Juergen Ott(NRAO), Enrique Vazquez (UNAM)

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http://science/nrao.edu

The Early Life of Stellar Clusters: Formation and Dynamics

3-7 November 2014, Copenhagen, Denmark

http://www.nbia.dk/nbia-clusters-2014

The goal of the workshop is to bridge the artificial divide between the fields of star formation and stellar dynamics.Star formation provides the initial conditions for the long term evolution of stellar clusters, while the dynamics ofstars in clusters after star formation has ceased can inform on the conditions that have prevailed in the environmentin which the clusters have formed. The central topics of the workshop will thus focus on:

• Reviewing the status of observations of star forming regions and young stellar clusters and discuss the prospectswith current and future ground based and space-borne telescopes

• Characterizing the dependence of the IMF, the SFE, binarity, sub-clustering, mass segregation, ages spreads onthe environment in which stars form

• Exploring the effects of any variability in the outcome of the star formation process on the dynamical evolutionof stellar clusters

• Assessing the importance of the different modes of stellar feedback and highlightng their importance on theclusters SFE, dynamics, and survival

• Discussing the advances in the numerical modeling of star formation and the dynamical evolution of stellarclusters and the necessity of having platforms that integrate all the required physics.

Workshop Organisers:

Sami Dib (NBIA & StarPlan)Paolo Padoan (ICC, Barcelona)Simon Portegies Zwart (Leiden)Susanne Pfalzner (MPIfR, Bonn)Barabara Ercolano (USM, Munich)Inti Pelupessy (Leiden)Seyit Houk (Groningen)Troels Haugblle (StarPlan & NBI)

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Summary of Upcoming Meetings

The Submillimeter Array: First Decade of Discovery9 - 10 June, 2014, Cambridge, MA, USAhttp://www.cfa.harvard.edu/sma/events/smaConf/

The 18th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun9 - 13 June 2014 Flagstaff, Arizona, USAhttp://www2.lowell.edu/workshops/coolstars18/

Summer School on Protoplanetary Disks: Theory and Modeling meet Observations16 - 20 June 2014 Groningen, The Netherlandshttp://www.diana-project.com/summer-school

Workshop on Dense Cores: Origin, Evolution, and Collapse27 - 30 July 2014 Monterey, CA, USAhttp://www.aas.org/meetings/aastcs4

Characterizing Planetary Systems Across the HR Diagram28 July - 1 August 2014 Inst. for Astronomy, Cambridge, USAhttp://www.ast.cam.ac.uk/meetings/2013/AcrossHR

Planet Formation and Evolution 20148 - 10 September 2014 Kiel, Germanyhttp://www.astrophysik.uni-kiel.de/kiel2014

Living Together: Planets, Stellar Binaries and Stars with Planets8 - 12 September 2014 Litomysl Castle, Litomysl, Czech Republichttp://astro.physics.muni.cz/kopal2014/

Galactic and Extragalactic Star Formation8 - 12 September 2014 Marseille, Francehttp://gesf2014.lam.fr

Thirty Years of Beta Pic and Debris Disk Studies8 - 12 September 2013 Paris, Francehttp://betapic30.sciencesconf.org

Towards Other Earths II. The Star-Planet Connection15 - 19 September 2014 Portugalhttp://www.astro.up.pt/toe2014

The Early Life of Stellar Clusters: Formation and Dynamics3 - 7 November 2014, Copenhagen, Denmarkhttp://www.nbia.dk/nbia-clusters-2014

Star Formation Across Space and Time11-14 November 2014 Noordwijk, The Netherlandshttp://congrexprojects.com/14a09/

45th “Saas-Fee Advanced Course”:From Protoplanetary Disks to Planet Formation15-20 March 2015, Switzerlandno website yet

Other meetings: http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

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http://www.cfa.harvard.edu/sma/events/smaConf/

http://www2.lowell.edu/workshops/coolstars18/

http://www.diana-project.com/summer-school

http://www.aas.org/meetings/aastcs4

http://www.ast.cam.ac.uk/meetings/2013/AcrossHR

http://www.astrophysik.uni-kiel.de/kiel2014

http://astro.physics.muni.cz/kopal2014/

http://gesf2014.lam.fr

http://betapic30.sciencesconf.org

http://www.astro.up.pt/toe2014

http://www.nbia.dk/nbia-clusters-2014

http://congrexprojects.com/14a09/

http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

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