THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 330 — 15 June 2020

Editor: Bo Reipurth (reipurth@ifa.hawaii.edu)

List of Contents
The Star Formation Newsletter
Editor: Bo Reipurthreipurth@ifa.hawaii.edu
Associate Editor: Anna McLeod
anna.mcleod@berkeley.edu

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Abstracts of Newly Accepted Papers . . . . . . . . . . . 6
Abstracts of Newly Accepted Major Reviews . . 42
Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Summary of Upcoming Meetings . . . . . . . . . . . . . . 47

Technical Editor: Hsi-Wei Yen
hwyen@asiaa.sinica.edu.tw
Editorial Board
Joao Alves
Alan Boss
Jerome Bouvier
Lee Hartmann
Thomas Henning
Paul Ho
Jes Jorgensen
Charles J. Lada
Thijs Kouwenhoven
Michael R. Meyer
Ralph Pudritz
Luis Felipe Rodríguez
Ewine van Dishoeck
Hans Zinnecker
The Star Formation Newsletter is a vehicle forfast distribution of information of interest for astronomers working on star and planet formationand molecular clouds. You can submit material
for the following sections: Abstracts of recently
accepted papers (only for papers sent to refereed
journals), Abstracts of recently accepted major reviews (not standard conference contributions), Dissertation Abstracts (presenting abstracts of new
Ph.D dissertations), Meetings (announcing meetings broadly of interest to the star and planet formation and early solar system community), New
Jobs (advertising jobs specifically aimed towards
persons within the areas of the Newsletter), andShort Announcements (where you can inform or request information from the community). Additionally, the Newsletter brings short overview articles
on objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

Newsletter Archive
www.ifa.hawaii.edu/users/reipurth/newsletter.htm

Cover Picture
The North America/Pelican and the Cygnus-X regions are here seen in an ultradeep wide field image.
The region was imaged by Alistair Symon, who has
uploaded to his website both this overview as well
as a much more detailed 22-image mosaic with a total of 140 hours exposure time in Hα (52 hr, green),[SII] (52 hr, red), and [OIII] (36 hours, blue). Thisis likely the deepest wide-field image taken of the
Cygnus Rift region. Higher resolution images areavailable at the website below.
Courtesy Alistair Symon
http://woodlandsobservatory.com

Submitting your abstracts
Latex
macrosfor
submitting
abstractsand dissertation abstracts (by e-mail toreipurth@ifa.hawaii.edu)
areappendedtoeach Call for Abstracts.
You can also
submitvia
theNewsletterwebinterfaceat
http://www2.ifa.hawaii.edu/starformation/index.cfm

confirmed by observations of a different linear molecule,HC3 N, but does not have a huge effect on the emergent
intensity. Fortunately, pioneers such as Sheldon Green got
interested in carrying out proper quantum calculations,and we started having reliable collision rates for simple
molecules. This is an ongoing effort over almost 50 years
since then, but methods have improved enormously andmore complex molecules can be handled. Astronomers really do need the ongoing work of this sort to make progressin interpreting observations.

Paul Goldsmith
in conversation with Bo Reipurth

Q: For your subsequent PhD you followed up with an observational study of CO using the Lick 120-inch telescope.
A: It seemed that having more than one transition of asingle molecule coud provide unique information on temperatures, densities, and other physical conditions, and I
focused on building a receiver for 230 GHz, the frequencyof the J = 2-1 transition of CO. That was a challenge, as
it was a very high frequency at the time, and technology
and tools were limited. I got enormous help from Bell
Laboratories, where Gerry Wrixon and Martin Schneider
were making low capacitance Schottky diodes that worked
reasonably well at this frequency. With those diodes, andwith a lot of help from fellow graduate student Richard
Plambeck, I built a receiver that had 11,000 K double
sideband noise temperature, which seemed very good then;
now the state of the art is close to 1000 times better! But
where to use it? No “radio” telescope had a good enoughsurface, so after checking that the thin, evaporated aluminum coating was thick enough to be a good reflector
at 1.3 mm wavelength, I decided that an optical telescopeshould work. We could only get daytime on the 120” telescope at Lick Observatory since nights were too valuable tobe given to this new type of observations. With Professor
Raymond Chiao, we took our equipment to Mt. Hamilton,
and after some embarrassing mistakes detected the CO J
= 2-1 line in several sources, and even detected the 13 CO
J = 2-1 line in Orion. The intensity of the latter relative
to J = 1-0 line indicated that even the rare isotopologue
is optically thick – a hint of how much molecular material
was present.

Q: As a graduate student in Berkeley, you were inspiredby Charles Townes to do a theoretical study of collisional
excitation of carbon monoxide in interstellar clouds, whichappeared in 1972. What was the state of affairs on thissubject back then?
A: The situation was unbelievably primitive by current
standards. There were no reliable calculations of crosssections for collisions of CO, HCN, and other widely–observed molecules with H2 , recognized as the key partner
for collisional excitation. There was work going on to understand the apparent “cooling” of the 6 cm transition offormaldehyde, indicated by its being observed in absorption against the cosmic microwave background. Different
approximate solutions led to quite different answers. But
remember, the computer codes for such calculations werecarried around in boxes of punched cards.
In any case, Charlie Townes suggested that I investigate
the collisional excitation of carbon monoxide. Only thelowest J = 1-0 rotational transition at 115 GHz had been
observed, but the J = 2 -1 line was coming soon, and I
think, with his usual impressive physical intuition, Townes
thought that the relative intensities of different transitions
would provide valuable information. I came up with aprogram that solved the equations of statistical equilibrium in the optically thin limit, but other than for collisions with electrons (in which J changes by only ±1),
I had to “guess” the rates for different J–changing collisions. With guidance from Townes, I felt that you could
likely have quite significant changes in angular momentum (so–called “hard” collisions). These had the interesting effect of overpopulating the J = 1 level and producing
weak maser emission. This was a big surprise and was met
with some skepticism at the time. This process has been

Q: In 1978 you and Bill Langer wrote a very highly cited
paper on molecular cooling and thermal balance in molecular clouds. What were the key new insights?
A: I had moved to Bell Laboratories in Holmdßel, NJ after receiving my PhD in 1975, and was working with Arno
Penzias and Bob Wilson, developing instrumentation forthe soon–to–arrive 7m millimeter telescope. Bill Langer
had been working on modeling the chemistry of molecular
clouds and had a good idea of what abundances of various species were reasonable in well–shielded regions. We
combined that information with a statistical equilibrium
plus radiative transfer code that could handle a wide variety of molecules and calculate the emission from all spec3

problem?

tral lines of relevance at modest temperatures. By adding
these up, we could calculate the total cooling. We combined this with estimates of some representative heating
rates in different types of clouds, and could thus determine
the steady–state gas temperatures. We were able to derive
what may have been the first general expression for coolingas function of temperature and density. This proved very
useful for numerous studies of thermal balance in interstellar clouds. The most enduring single result was that thebalance between molecular cooling and cosmic ray heating
predicted dark cloud temperatures in the range 8 K to 12
K. This agreed with the limited observations then available, and has held up with much more extensive surveys
of such regions that have been carried out since then.

A: I had been interested in molecular oxygen since work
on cloud cooling, as mentioned earlier. O2 was predicted
to be a significant (after CO and H2 O in importance)coolant. But was it there? You have to be above theatmosphere to look for O2 emission from Galactic sources,
and searching for this elusive species was one of the keytasks for SWAS. I started work on SWAS with Gary Melnick, the PI, when I was at UMASS, but by the time it was
launched, I had moved to Cornell University, where I was
also Director of NAIC, operating the Arecibo Observatory.
SWAS’ O2 channel ran in parallel with the channel observing the ground state water line, which we could detect andmap, but we never could unambiguously detect molecularoxygen. We knew the instrument was working as at one
point the antenna beam swung through the Earth and weeasily detected O2 in our atmosphere! The resulting upper limits on the O2 fractional abundance, on the orderof 100 times below the predictions of gas–phase chemistry,
clearly showed that something was amiss with those models. The missing piece was pinpointed in an effort led by
SWAS team member Ted Bergin, and was the impact ofinterstellar grains. In this picture, oxygen atoms stick tograin surfaces and are hydrogenated to form water ice.
The remaining gas–phase oxygen is almost entirely tied
up in CO. This model also explained the low abundanceof H2 O found by SWAS. These results encouraged development of sophisticated astrochemical models, including
grain surface depletion and chemistry, that have proven essential for understanding the many results that have beenobtained. This is an area with laboratory measurements,
theoretical calculations, and observations coming together
to explain ever more complex molecules being found withincreasingly sensitive instruments.

Q: Together with a team of collaborators you have analyzed
a unique 12 CO and 13 CO Nyquist-sampled map of 98 deg2of the Taurus clouds on a 20′′ grid. What were the key
results?
A: Just as the 7m telescope was beginning to operate,
I left Bell Laboratories to take a faculty position at the
University of Massachusetts, Amherst. There I worked
on receivers and other systems for the 14m FCRAO telescope. An excellent team including Neal Erickson developed focal plane array receivers that enabled large–scale,high spatial dynamic range imaging of interstellar clouds.
The sensitivity and large amount of time on the FCRAO
14m telescope with the SEQUOIA 32–element focal planearray made the large Taurus map possible. I think themost interesting result is that a significant fraction of themass of the cloud is in very weak, diffuse emission coming from outside the cloud boundary as it was generally
defined. This emission is tracing the interface between
the essentially totally molecular well-shielded interior, andthe atomic interstellar medium. But there is a lot more
molecular gas in these extended, low–density regions than
was recognized at that point. The 12 CO and 13 CO images, each with 3 million spectra, also revealed that theinterior of the cloud is highly nonuniform, with multiple
filaments and shell-like structures present. We also foundthat star formation (traced by embedded young stars) is
restricted to regions with visual extinctions above 6 mag.,an early demonstration of this threshold in dark clouds. In
addition, we saw that the diffuse molecular gas was clearlystriated, with structures oriented parallel to the local magnetic field, while the dense gas filaments are largely perpendicular to the field direction. These conclusions had
obvious bearing on the relationship of the magnetic fieldand gas that is potentially going to form stars,

Q: With the launch of Herschel, major new information
about cloud chemistry became available, and you and yourcollaborators performed a Galactic plane survey of [NII]
fine structure emission. What did you learn?
A: Having worked extensively on [CII] emission with the
Herschel GOTC+ project with JPL collaborators, the question of the origin of the emission from C+ had to be addressed. One of the possibilities was emission from theionized component of the ISM, and one way to estimate
this would be to quantify this component through theemission of ionized nitrogen, which is produced only inthis material, unlike C+ , which can come from neutral
and even partially molecular regions. There are two [NII]
fine structure lines, which had been previously recognized,
their ratio is an excellent tracer of the electron density inionized regions. This led to the use of the PACS instrument on Herschel, which covered both lines, albeit without
the velocity resolution to measure line profiles. The survey
was very successful in that we detected the lines through

Q: In 2000 you led a large team in search of O2 with theSubmillimeter Wave Astronomy Satellite. This led to anull result, indicating that O2 is not a major coolant. How
are these results understood in terms of chemical and dynamical cloud models and what is the present state of this4

most of the inner galaxy. The line ratio yielded the surprise that the characteristic electron density was typically
20 to 50 cm−3 - too low to be “normal” HII regions, but
far higher than the Warm Ionized Medium (WIM), which
is very extended, but typically thought to have density
0.1 to 1 cm−3 . Might this be a different phase of the ISM,
possibly very extended low density HII regions or interface
regions between ionized and neutral material? This same
electron density was determined from [NII] observationsof external galaxies, indicating that this is a widespreadcomponent of the ISM. The fraction of [CII] coming fromionized gas is modest, but has to be considered in understanding the origin of [CII] emission and how it traces starformation in the Milky Way and other galaxies. This is
one of the goals of GUSTO, an Explorer MO balloon mission, scheduled for December 2021. Obtaining images ofelectron densities that are velocity–resolved and thus giveinsight into the line of sight structure requires observationof both [NII] lines (which cannot be done from aircraft
altitude), but which is the key goal of the ASTHROS balloon mission scheduled for December 2023.

in terms of determining the “true” luminosity producedby massive young stars than are [CII] or [NII] emission,and velocity–resolved spectra are essential. Understanding how to use these fine structure lines to trace star formation, measure the effect of formation of massive stars,
and determine what controls the rate of star formation,
remains a very exciting challenge.
Q: In addition to observations and modeling, you’ve worked
on instrumentation development. What do you see as theconnection?
A: I certainly enjoy development of instrumentation for
astronomy. There is a whole range of reasons why I think
this is good for the person who does this, as well as beingof value to astronomy. For the individual, understanding how an instrument really works helps you employ itbetter and more effectively. I have focused on low–noise
radiometers for millimeter and submillimeter wavelengths,
which is where you can see that my astronomical interestslie. I feel that by getting into the “nitty gritty” of antennas, feed systems, and signal processing components, I
have understood how the data that they produce can best
be used. Working with a system on a laboratory bench
gives you a head start in appreciating what problems it
may have when mounted on a radio telescope or a spacecraft. For example, it makes you a little more suspiciousof the data, since you’ve seen strange things happening on
the bench and you don’t forget them when you are facedwith a strange spectral artifact or baseline ripple in yourdata. To me it is also exciting to come up with a new ideathat enables new astronomical observations. Sometimes
such ideas start with a suggestion from a colleague, orfrom something you read about. But if after turning theidea over in your mind, you come to the conclusion thatit could make a better system, and you get to build it,
and it does – that’s a really great feeling! And to be honest, it’s wonderful to see others using a piece of equipment
or technology you’ve helped develop, and obtaining exciting astronomical data. It’s the intersection of two worlds,
that I find personally is rewarding and very stimulating. I
only hope that the increasing specialization in instrumentation development does not preclude astronomers fromgetting involved, getting their hands dirty, and developing
new technology and thus contributing to the future of ourfield.

Q: In a 2019 paper, you have modeled the [OI] 63 µm finestructure line in PDR regions. What has this revealed?
A: The 63 µm fine structure transition of atomic oxygenis one of the strongest FIR lines, and in the warmest portions of photon dominated regions is the most importantgas coolant. It has thus been widely observed in Galactic and extragalactic surveys, but until recently almost no
velocity-resolved spectra were available. There had been
a number of studies, mostly with ISO, of [OI] 63µm seenin absorption against strong continuum sources; these implied extremely large column densities of low-excitation
O0 , plausibly associated with molecular clouds, but with
O0 /CO well in excess of unity. Other studies using the 145µm [OI] line together with the 63 µm line also suggested
very large column densities of atomic oxygen. To try andunderstand this, we obtained a large set of observations of
GMCs, with the high spectral resolution provided by the
upGREAT instrument on SOFIA. The 2019 paper suggested that significant opacity in the 63 µm line would
be revealed by self-absorption from low-excitation atoms
in the outer regions of the cloud where radiative trapping
was insufficient to thermalize the line. In realistic regionswith density gradients, this effect could be dramatic. Initial analysis of the [OI] spectra shows that a substantial
fraction of sources are characterized by very prominent
self-absorption; so strong that the line seen in emission isjust the line wings of what would be a far stronger line.
The fact that the absorbed portion of the line is almost
exactly centered on what is left of the emission profile indicates that the absorbing gas is almost certainly associatedwith the hot, dense photon–dominated region gas producing the emission. Thus, [OI] 63 µm is more problematic5

Abstracts of recently accepted papers

1.

Outflows, cores, and magnetic field orientations in W43-MM1 as seen by ALMA
C. Arce1 , F. Louvet1,2 , P. C. Cortes3,4 , F. Motte5 , C. L. H. Hull3,6,7 , V. J. M. Le Gouellec8,2 , G. Garay1 ,T. Nony5 , P. Didelon2 and L. Bronfman1
1
Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago de Chile; 2 Laboratoire AIM Paris-Saclay,
CEA/IRFU - CNRS/INSU - Université Paris Diderot, Service d’Astrophysique, Bât 709, CEA-Saclay, 91191 Gif-surYvette; 3 Join ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile; 4 National Radio Astronomy
Observarory, Charlottesville, VA 22903, USA; 5 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 6National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Cordova, Santiago, Chile; 7 NAOJ Fellow; 8European Southern Observatory, Alonso de Cordova 3788, Santiago, Chile

E-mail contact: fabien.louvet at cea.fr
It has been proposed that the magnetic field, pervasive in the ISM, plays an important role in the process of massive
star formation. To better understand its impact at the pre and protostellar stages, high-angular resolution observationsof polarized dust emission toward a large sample of massive dense cores are needed. To this end, we used the Atacama
Large Millimeter Array in Band 6 (1.3 mm) in full polarization mode to map the polarized emission from dust grains ata physical scale of ∼2700 au in the massive protocluster W43-MM1. We used these data to measure the orientation of
the magnetic field at the core scale. Then, we examined the relative orientations of the core-scale magnetic field, of the
protostellar outflows determined from CO molecular line emission, and of the major axis of the dense cores determinedfrom 2D Gaussian fit in the continuum emission. We found that the orientation of the dense cores is not random withrespect to the magnetic field. Instead, the dense cores are compatible with being oriented 20-50◦ with respect to themagnetic field. The outflows could be oriented 50-70◦ with respect to the magnetic field, or randomly oriented withrespect to the magnetic field, similar to current results in low-mass star-forming regions. In conclusion, the observedalignment of the position angle of the cores with respect to the magnetic field lines shows that the magnetic field iswell coupled with the dense material; however, the 20-50◦ preferential orientation contradicts the predictions of themagnetically-controlled core-collapse models. The potential correlation of the outflow directions with respect to themagnetic field suggests that, in some cases, the magnetic field is strong enough to control the angular momentum
distribution from the core scale down to the inner part of the circumstellar disks where outflows are triggered.
Accepted by A&A
https://arxiv.org/pdf/2005.12921

2. The velocity structure of Cygnus OB2
Becky Arnold1,2 , Simon P. Goodwin1 and Nick J. Wright3
1

Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK; 2 Department of Astronomy,
University of Massachusetts, Massachusetts, 01003, USA; 3 Astrophysics Group, Keele University, Keele, Staffordshire,
ST5 5BG, UK
E-mail contact: kpoppenhaeger at aip.de

The kinematic structure of the Cygnus OB2 association is investigated. No evidence of expansion or contraction isfound at any scale within the region. Stars that are within ∼0.5 parsecs of one another are found to have more similar
velocities than would be expected by random chance, and so it is concluded that velocity substructure exists on thesescales. At larger scales velocity substructure is not found. We suggest that bound substructures exist on scales of ∼0.5
parsecs, despite the region as a whole being unbound. We further suggest that any velocity substructure that existed
on scales > 0.5 parsecs has been erased. The results of this study are then compared to those of other kinematicstudies of Cygnus OB2.
6

Accepted by MNRAS
http://arxiv.org/pdf/2005.10260

3. On the Origin of the Bimodal Rotational Velocity Distribution in Stellar Clusters: Ro-tation on the Pre-Main Sequence
Nate Bastian1 , Sebastian Kamann1 , Louis Amard2 , Corinne Charbonnel3,4 , Lionel Haemmerlé3 andSean P. Matt2
1

Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK; 2
University of Exeter, Department of Physics & Astronomy, Stoker Road, Devon, Exeter EX4 4QL, UK; 3 Departmentof Astronomy, University of Geneva, Chemin de Pégase 51, 1290 Versoix, Switzerland; 4 IRAP, UMR 5277 CNRS andUniversité de Toulouse, 14, Av. E.Belin, 31400 Toulouse, France
E-mail contact: N.J.Bastian at ljmu.ac.uk
We address the origin of the observed bimodal rotational distribution of stars in massive young and intermediate age
stellar clusters. This bimodality is seen as split main sequences at young ages and also has been recently directly
observed in the V sin i distribution of stars within massive young and intermediate age clusters. Previous models haveinvoked binary interactions as the origin of this bimodality, although these models are unable to reproduce all of
the observational constraints on the problem. Here we suggest that such a bimodal rotational distribution is set up
early within a cluster’s life, i.e., within the first few Myr. Observations show that the period distribution of low-mass(<∼2 M⊙ ) pre-main sequence (PMS) stars is bimodal in many young open clusters and we present a series of models
to show that if such a bimodality exists for stars on the PMS that it is expected to manifest as a bimodal rotational
velocity (at fixed mass/luminosity) on the main sequence for stars with masses in excess of ∼1.5 M⊙ . Such a bimodal
period distribution of PMS stars may be caused by whether stars have lost (rapid rotators) or been able to retain(slow rotators) their circumstellar discs throughout their PMS lifetimes. We conclude with a series of predictions forobservables based on our model.
Accepted by MNRAS
http://arxiv.org/pdf/2005.01779

4. Formation of Giant Planet Satellites
Konstantin Batygin1 and Alessandro Morbidelli2
1

Division of Geological and Planetary Sciences California Institute of Technology, Pasadena, CA 91125, USA; 2
Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, CS 34229, F-06304 Nice,
FranceE-mail contact: kbatygin at gps.caltech.edu
Recent analyses have shown that the concluding stages of giant planet formation are accompanied by the developmentof large-scale meridional flow of gas inside the planetary Hill sphere. This circulation feeds a circumplanetary disk thatviscously expels gaseous material back into the parent nebula, maintaining the system in a quasi-steady state. Here
we investigate the formation of natural satellites of Jupiter and Saturn within the framework of this newly outlined
picture. We begin by considering the long-term evolution of solid material, and demonstrate that the circumplanetary
disk can act as a global dust trap, where s• ∼ 0.1–10 mm grains achieve a hydrodynamical equilibrium, facilitatedby a balance between radial updraft and aerodynamic drag. This process leads to a gradual increase in the system’s
metallicity, and eventually culminates in the gravitational fragmentation of the outer regions of the solid sub-disk into
R ∼ 100 km satellitesimals. Subsequently, satellite conglomeration ensues via pairwise collisions, but is terminatedwhen disk-driven orbital migration removes the growing objects from the satellitesimal feeding zone. The resulting
satellite formation cycle can repeat multiple times, until it is brought to an end by photo-evaporation of the parent
nebula. Numerical simulations of the envisioned formation scenario yield satisfactory agreement between our modeland the known properties of the Jovian and Saturnian moons.
Accepted by ApJ
http://arxiv.org/pdf/2005.08330

75. Photoionising feedback in spiral arm molecular clouds
Thomas J. R. Bending1 , Clare L. Dobbs1 and Matthew R. Bate1
1

School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK

E-mail contact: tb457 at exeter.ac.uk
We present simulations of a 500 pc2 region, containing gas of mass 4 × 106 M⊙ , extracted from an entire spiralgalaxy simulation, scaled up in resolution, including photoionising feedback from stars of mass >18 M⊙ . Our region
is evolved for 10 Myr and shows clustered star formation along the arm generating ≈ 5000 cluster sink particles ≈ 5%of which contain at least one of the ≈ 4000 stars of mass >18 M⊙ . Photoionisation has a noticeable effect on the gas
in the region, producing ionised cavities and leading to dense features at the edge of the HII regions. Compared to
the no-feedback case, photoionisation produces a larger total mass of clouds and clumps, with around twice as manysuch objects, which are individually smaller and more broken up. After this we see a rapid decrease in the total massin clouds and the number of clouds. Unlike studies of isolated clouds, our simulations follow the long range effects ofionisation, with some already-dense gas becoming compressed from multiple sides by neighbouring HII regions. This
causes star formation that is both accelerated and partially displaced throughout the spiral arm with up to 30% of
our cluster sink particle mass forming at distances >5 pc from sites of sink formation in the absence of feedback. At
later times, the star formation rate decreases to below that of the no-feedback case.
Accepted by MNRAS
https://arxiv.org/pdf/2005.06234

6. Possible evidence of ongoing planet formation in AB Aurigae.

A showcase of the

SPHERE/ALMA synergy
A. Boccaletti1 , E. Di Folco2 , E. Pantin3 , A. Dutrey2 , S. Guilloteau2 , Y.W. Tang4 , V. Piétu5 , E. Habart6 ,J. Milli8, T.L. Beck7 and A.-L. Maire9
1

LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris
Cité, 5 place Jules Janssen, 92195 Meudon, France; 2 Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France; 3 Laboratoire CEA, IRFU/DAp, AIM, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, CNRS, 91191 Gif-sur-Yvette, France; 4 Academia
Sinica, Institute of Astronomy and Astrophysics, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4,
Roosevelt Rd, Taipei, Taiwan; 5 IRAM, 300 rue de la piscine, Domaine Universitaire, 38406 Saint-Martin d’Hères,France; 6 Institut d’astrophysique spatiale, CNRS UMR 8617, Université Paris-Sud 11, 91405 Orsay, France; 7 Space
Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 8 CNRS, IPAG, Univ. Grenoble
Alpes, 38000 Grenoble, France; 9 STAR Institute, Université de Liege, Allée du Six Août 19c, 4000 Liege, Belgium
E-mail contact: anthony.boccaletti at obspm.fr
Context. Planet formation is expected to take place in the first million years of a planetary system through various
processes, which remain to be tested through observations. Aims. With the recent discovery, using ALMA, of two
gaseous spiral arms inside the ∼120 au cavity and connected to dusty spirals, the famous protoplanetary disk around
AB Aurigae presents a strong incentive for investigating the mechanisms that lead to giant planet formation. A
candidate protoplanet located inside a spiral arm has already been claimed in an earlier study based on the same
ALMA data.
Methods. We used SPHERE at the Very Large Telescope to perform near-infrared high-contrast imaging of AB Aur inpolarized and unpolarized light in order to study the morphology of the disk and search for signs of planet formation.
Results. SPHERE has delivered the deepest images ever obtained for AB Aur in scattered light. Among the many
structures that are yet to be understood, we identified not only the inner spiral arms, but we also resolved a featurein the form of a twist in the eastern spiral at a separation of about 30 au. The twist of the spiral is perfectly
reproduced with a planet-driven density wave model when projection effects are accounted for. We measured anazimuthal displacement with respect to the counterpart of this feature in the ALMA data, which is consistent with
Keplerian motion on a 4 yr baseline. Another point sxce is detected near the edge of the inner ring, which is likely
the result of scattering as opposed to the direct emission from a planet photosphere. We tentatively derived massconstraints for these two features.
Conclusions. The twist and its apparent orbital motion could well be the first direct evidence of a connection between8a protoplanet candidate and its manifestation as a spiral imprinted in the gas and dust distributions.
Accepted by Astronomy & Astrophysics (A&A 637, L5, 2020)
https://www.aanda.org/articles/aa/pdf/2020/05/aa38008-20.pdf

7. Protoplanetary Disks in the Orion Nebula Cluster: Gas Disk Morphologies and Kine-

matics as seen with ALMA
Ryan D. Boyden1 and Josh A. Eisner1
1

Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA

E-mail contact: rboyden at email.arizona.edu
We present Atacama Large Millimeter Array CO (3–2) and HCO+ (4–3) observations covering the central 1′′ × 1.′′ 5
region of the Orion Nebula Cluster (ONC). The unprecedented level of sensitivity (∼0.1 mJy beam−1 ) and angularresolution (∼0.′′ 09 ≈ 35 AU) of these line observations enable us to search for gas-disk detections towards the known
positions of submillimeter-detected dust disks in this region. We detect 23 disks in gas: 17 in CO (3–2), 17 in HCO+
(4–3), and 11 in both lines. Depending on where the sources are located in the ONC, we see the line detections inemission, in absorption against the warm background, or in both emission and absorption. We spectrally resolve thegas with 0.5 km s−1 channels, and find that the kinematics of most sources are consistent with Keplerian rotation.
We measure the distribution of gas-disk sizes and find typical radii of ∼50–200 AU. As such, gas disks in the ONC
are compact in comparison with the gas disks seen in low-density star-forming regions. Gas sizes are universallylarger than the dust sizes. However, the gas and dust sizes are not strongly correlated. We find a positive correlation
between gas size and distance from the massive star θ1 Ori C, indicating that disks in the ONC are influenced byphotoionization. Finally, we use the observed kinematics of the detected gas lines to model Keplerian rotation andinfer the masses of the central pre-main-sequence stars. Our dynamically-derived stellar masses are not consistent
with the spectroscopically-derived masses, and we discuss possible reasons for this discrepancy.
Accepted by ApJ
http://arxiv.org/pdf/2003.12580

8. An Analytic Model for an Evolving Protoplanetary Disk with a Disk Wind
John Chambers1
1Carnegie Institution for Science Department of Terrestrial Magnetism, 5241 Broad Branch Road, NW, Washington,
DC 20015, USA
E-mail contact: jchambers at carnegiescience.edu
We describe an analytic model for an evolving protoplanetary disk driven by viscosity and a disk wind. The disk isheated by stellar irradiation and energy generated by viscosity. The evolution is controlled by 3 parameters: (i) the
inflow velocity towards the central star at a reference distance and temperature, (ii) the fraction of this inflow causedby the disk wind, and (iii) the mass loss rate via the wind relative to the inward flux in the disk. The model gives
the disk midplane temperature and surface density as a function of time and distance from the star. It is intended toprovide an efficient way to calculate conditions in a protoplanetary disk for use in simulations of planet formation. In
the model, disks dominated by viscosity spread radially while losing mass onto the star. Radial spreading is the main
factor reducing the surface density in the inner disk. The disk mass remains substantial at late times. Temperatures in
the inner region are high at early times due to strong viscous heating. Disks dominated by a wind undergo much lessradial spreading and weaker viscous heating. These disks have a much lower mass at late times than purely viscousdisks. When mass loss via a wind is significant, the surface density gradient in the inner disk becomes shallower, andthe slope can become positive in extreme cases.
Accepted by ApJ

http://arxiv.org/pdf/2005.09132

99. Gas Kinematics of the Massive Protocluster G286.21+0.17 revealed by ALMA
Yu Cheng1 , Jonathan C. Tan2,1 , Mengyao Liu1 , Wanggi Lim3 and Morten Andersen4
1

Dept. of Astronomy, University of Virginia, Charlottesville, Virginia 22904, USA; 2 Dept. of Space, Earth &Environment, Chalmers University of Technology, Gothenburg, Sweden; 3 SOFIA-USRA, NASA Ames ResearchCenter, MS 232-12, Moffett Field, CA 94035, USA; 4 Gemini Observatory, NSFs National Optical-Infrared Astronomy
Research Laboratory Casilla 603, La Serena, Chile
E-mail contact: ycheng.astro at gmail.com
We study the gas kinematics and dynamics of the massive protocluster G286.21+0.17 with the Atacama Large Millimeter/submillimeter Array using spectral lines of C18 O(2-1), N2 D+ (3-2), DCO+ (3-2) and DCN(3-2). On the parsec
clump scale, C18 O emission appears highly filamentary around the systemic velocity. N2 D+ and DCO+ are moreclosely associated with the dust continuum. DCN is strongly concentrated towards the protocluster center, where noor only weak detection is seen for N2 D+ and DCO+ , possibly due to this region being at a relatively evolved evolutionary stage. Spectra of 76 continuum defined dense cores, typically a few 1000 AU in size, are analysed to measure theircentroid velocities and internal velocity dispersions. There are no statistically significant velocity offsets of the coresamong the different dense gas tracers. Furthermore, the majority (71%) of the dense cores have subthermal velocity
offsets with respect to their surrounding, lower density C18 O emitting gas. Within the uncertainties, the dense coresin G286 show internal kinematics that are consistent with being in virial equilibrium. On clumps scales, the core tocore velocity dispersion is also similar to that required for virial equilibrium in the protocluster potential. However,the distribution in velocity of the cores is largely composed of two spatially distinct groups, which indicates that thedense molecular gas has not yet relaxed to virial equilibrium, perhaps due to there being recent/continuous infall into
the system.
Accepted by ApJ
https://arxiv.org/pdf/2005.08197.pdf

10. Stellar Variability in a Forming Massive Star Cluster
Yu Cheng1 , Morten Andersen2 and Jonathan C. Tan3,1
1

Dept. of Astronomy, University of Virginia, Charlottesville, Virginia 22904, USA; 2 Gemini Observatory, NSFs
National Optical-Infrared Astronomy Research Laboratory Casilla 603, La Serena, Chile; 3 Dept. of Space, Earth &Environment, Chalmers University of Technology, Gothenburg, Sweden
E-mail contact: ycheng.astro at gmail.com

We present a near-infrared (NIR) variability analysis for an 6’ × 6’ region, which encompasses the massive protocluster
G286.21+0.17. The total sample comprises more than 5000 objects, of which 562 show signs of a circumstellar disk
based on their infrared colors. The data includes HST observations taken in two epochs separated by 3 years in the
F110W and F160W bands. 363 objects (7% of the sample) exhibit NIR variability at a significant level (Stetson index> 1.7), and a higher variability fraction (14%) is found for the young stellar objects (YSOs) with disk excesses. We
identified 4 high amplitude (> 0.6 mag) variables seen in both NIR bands. Follow up and archival observations of
the most variable object in this survey (G286.2032+0.1740) reveal a rising light curve over 8 years from 2011 to 2019,with a K band brightening of 3.5 mag. Overall the temporal behavior of G286.2032+0.1740 resembles that of typical
FU Ori objects, however its pre-burst luminosity indicates it has a very low mass (< 0.12 M⊙ ), making it an extreme
case of an outburst event that is still ongoing.
Accepted by ApJ
https://arxiv.org/pdf/2005.08198

11. Astrometry of H2 O Masers in W48A (G35.20-01.74) HII Region with VERA: A Com-

pact Disk-Outflow inside Core H-2a

James O. Chibueze1,2 , Takumi Nagayama3 , Toshihiro Omodaka4 , Masayuki Nagano4 , Koji Wada3 andKen Hirano3
1

Centre for Space Research, Physics Department, North-West University, Potchefstroom 2520, South Africa.; 2 Department of Physics and Astronomy, Faculty of Physical Sciences, University of Nigeria, Carver Building, 1 University
10Road, Nsukka, Nigeria.; 3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-12 Hoshigaokacho, Mizusawa, Oshu, Iwate 023-0861; 4 Graduate School of Science and Engineering, Kagoshima University, 1-21-35
Korimoto, Kagoshima 890-0065
E-mail contact: james.chibueze at nwu.ac.za
W48A core H-2a is one of the young massive protostellar objects in the W48 region. We conducted multi-epoch
astrometric observations of the water (H2 O) masers associated with the W48A core H-2a with VLBI Exploration ofRadio Astrometry (VERA). The trigonometric annual parallax of W48A core H-2a was measured to be 0.433 ± 0.026
mas corresponding to the distance of 2.31+0.15−0.13 kpc. This agrees with the revised parallax of 0.412 ± 0.014 mas by
Wu et al. (2019, ApJ, 874, 94). We obtained the systemic proper motion and LSR velocity to be (µα cos δ, µδ ) =(0.26 ± 0.73, −3.87 ± 0.33) mas yr−1 and vLSR = 41.9 ± 0.9 km s−1 , respectively. The distribution of the H2 O masers
covers an area of 70 mas × 80 mas corresponding to 160 AU × 180 AU at the distance of 2.31 kpc. The internal propermotions of the H2 O masers trace an east-west bipolar outflow. With the recent absolute position measurement of the
6.7 GHz methanol (CH3 OH) masers and their elliptical distribution whose major axis is perpendicular to the axis of thebipolar outflow, we suggest the presence of a disk-outflow system in core H-2a. The spectral energy distribution (SED)of the driving source of core H-2a was previously reported to yield a luminosity and envelope mass of 8000 ± 1000 L⊙
and 170 ± 30 M⊙ , respectively. Re-fitting the SED with the new distance, we obtained the luminosity to be 3100±388
L⊙ and derived ZAMS stellar mass to be 9±1 M⊙ . Using our distance measurement, we derived the peculiar motionof W48A to be (Us , Vs , Ws ) = (1 ± 4, 5 ± 6, −15 ± 5) km s−1 .
Accepted by PASJ

12. The Relationship between Mid-Infrared and Sub-Millimetre Variability of Deeply Em-

bedded Protostars
Carlos Contreras Pena1 , Doug Johnstone2,3 , Giseon Baek4 , Gregory J. Herczeg5 , Steve Mairs6 , Aleks
Scholz7 and Jeong-Eun Lee4
1

School of Physics, Astrophysics Group, University of Exeter, Stocker Road, Exeter EX4 4QL, UK; 2 NRC Herzberg
Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada; 3 Department of Physics
and Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada; 4 School of Space Research and Institute of
Natural Sciences, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 446-701, Korea; 5Kavli Institute for Astronomy and Astrophysics, Peking University, Yiheyuan 5, Haidian Qu, 100871 Beijing, People’s
Republic of China; 6 East Asian Observatory, 660 North Aohoku Place, University Park, Hilo, HI 96720, USA; 7
SUPA, School of Physics & Astronomy, North Haugh, St Andrews KY16 9SS, UK
E-mail contact: c.contreras at exeter.ac.uk
We study the relationship between the mid-infrared and sub-mm variability of deeply embedded protostars using themulti-epoch data from the Wide Infrared Survey Explorer (WISE/NEOWISE) and the ongoing James Clerk Maxwell
Telescope (JCMT) transient survey. Our search for signs of stochastic (random) and/or secular (roughly monotonic
in time) variability in a sample of 59 young stellar objects (YSOs) revealed that 35 are variable in at least one of thetwo surveys. This variability is dominated by secular changes. Of those objects with secular variability, 14 objects(22% of the sample) show correlated secular variability over mid-IR and sub-mm wavelengths. Variable accretion is
the likely mechanism responsible for this type of variability. Fluxes of YSOs that vary in both wavelengths follow a
relation of log10 F4.6 (t) = η log10 F850 (t) between the mid-IR and sub-mm, with η = 5.53 ± 0.29. This relationshiparises from the fact that sub-mm fluxes respond to the dust temperature in the larger envelope whereas the mid-IR
emissivity is more directly proportional to the accretion luminosity. The exact scaling relation, however, depends on
the structure of the envelope, the importance of viscous heating in the disc, and dust opacity laws.
Accepted by MNRAS
https://arxiv.org/pdf/2005.01569.pdf

13. The inner disk of RY Tau: evidence of stellar occultation by the disk atmosphere at the

sublimation rim from K-band continuum interferometry

Claire L. Davies1 , Stefan Kraus1 , Tim J. Harries1 , John D. Monnier2 , Brian Kloppenborg3 et al.
1

Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK; 2 Department
11

of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA; 3 Department of Physics and Astronomy, Georgia
State University, Atlanta, GA 30302, USA
E-mail contact: c.davies3 at exeter.ac.uk
We present models of the inner region of the circumstellar disk of RY Tau which aim to explain our near-infrared(K-band: 2.1 µm) interferometric observations while remaining consistent with the optical to near-infrared portionsof the spectral energy distribution. Our sub-milliarcsecond resolution CHARA Array observations are supplemented
with shorter baseline, archival data from PTI, KI and VLTI/GRAVITY and modeled using an axisymmetric Monte
Carlo radiative transfer code. The K-band visibilities are well-fit by models incorporating a central star illuminatinga disk with an inner edge shaped by dust sublimation at 0.210±0.005 au, assuming a viewing geometry adopted
from millimeter interferometry (65◦ inclined with a disk major axis position angle of 23◦ ). This sublimation radius isconsistent with that expected of Silicate grains with a maximum size of 0.36–0.40 µm contributing to the opacity and isan order of magnitude further from the star than the theoretical magnetospheric truncation radius. The visibilities on
the longest baselines probed by CHARA indicate that we lack a clear line-of-sight to the stellar photosphere. Instead,our analysis shows that the central star is occulted by the disk surface layers close to the sublimation rim. While we
do not see direct evidence of temporal variability in our multi-epoch CHARA observations, we suggest the aperiodic
photometric variability of RY Tau is likely related temporal and/or azimuthal variations in the structure of the disk
surface layers.
Accepted by ApJ
http://arxiv.org/pdf/2005.06932

14. Formation of Orion Fingers
Ross Dempsey1 , Nadia L. Zakamska1 , and James E. Owen2
12

Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA;
Astrophysics Group, Imperial College London, Prince Consort Road, London SW7 2AZ, UK

E-mail contact: sdempsey at princeton.edu“Orion fingers” are a system of dozens of bowshocks, with the wings of shocks pointing to a common system of origin,which is centered on a dynamically disintegrating system of several massive stars. The shock heads propagate withvelocities of up to 300–400 km s−1 , but the formation and physical properties of the “bullets” leading the shocks are
not known. Here we summarize two possible scenarios for the formation of the “bullets” and the resulting bowshocks(“fingers”). In the first scenario, bullets are self-gravitating, Jupiter-mass objects which were formed rapidly and thenejected during the strong dynamical interactions of massive stars and their disks. This scenario naturally explains
the similar timescales for the outflow of bullets and for the dynamical interaction of the massive stars, but has
some difficulty explaining the observed high velocities of the bullets. In the second scenario, bullets are formed
via hydrodynamic instabilities in a massive, infrared-driven wind, naturally explaining the high velocities and themorphology of outflow, but the bullets are not required to be self-gravitating. The processes that created the Orionfingers are likely not unique to this particular star-forming region and may result in free-floating, high-velocity, core-lessplanets.
Accepted by MNRAS
http://arxiv.org/pdf/2005.01902

15. Uncovering distinct environments in an extended physical system around the W33 com-plex
L. K. Dewangan1 , T. Baug2 and D. K. Ojha3
1

Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India.; 2 Kavli Institute for Astronomy andAstrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, P. R. China.; 3 Department of
Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India.
E-mail contact: lokeshd at prl.res.in
We present a multi-wavelength investigation of a large-scale physical system containing the W33 complex. The
12

extended system (∼50 pc × 37 pc) is selected based on the distribution of molecular gas at [29.6, 60.2] km s−1 andof 88 ATLASGAL 870 µm dust clumps at d ∼2.6 kpc. The extended system/molecular cloud traced in the mapsof 13 CO and C18 O emission contains several H ii regions excited by OB stars (age ∼0.3–1.0 Myr) and a thermallysupercritical filament (“fs1", length ∼17 pc). The filament, devoid of the ionized gas, shows dust temperature (Td ) of
∼19 K, while the H ii regions are depicted with Td of ∼21–29 K. It suggests the existence of two distinct environmentsin the cloud. The distribution of Class I young stellar objects (mean age ∼0.44 Myr) traces the early stage of starformation (SF) toward the cloud. At least three velocity components (around 35, 45, and 53 km s−1 ) are investigatedtoward the system. The analysis of 13 CO and C18 O reveals the spatial and velocity connections of cloud components
around 35 and 53 km s−1 . The observed positions of previously known sources, W33 Main, W33 A and O4-7I stars,
are found toward a complementary distribution of these two cloud components. The filament “fs1" and a previously
known object W33 B are seen toward the overlapping areas of the clouds, where ongoing SF activity is evident. A
scenario concerning the converging/colliding flows from two different velocity components appears to explain well theobserved signposts of SF activities in the system.
Accepted by MNRAS
https://arxiv.org/pdf/2005.13871.pdf

16. Investigating the physical conditions in extended system hosting mid-infrared bubble

N14

L. K. Dewangan1 , T. Baug2 , L. E. Pirogov3 and D. K. Ojha4
1

Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India.; 2 Kavli Institute for Astronomy andAstrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, P. R. China.; 3 Institute ofApplied Physics of the Russian Academy of Sciences, 46 Ulyanov st., Nizhny Novgorod 603950, Russia.; 4 Departmentof Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India.
E-mail contact: lokeshd at prl.res.in

To observationally explore physical processes, we present a multi-wavelength study of a wide-scale environment towardl = 13.7–14.9 degrees containing a mid-infrared bubble N14. The analysis of 12 CO, 13 CO, and C18 O gas at [31.6,
46] km s−1 reveals an extended physical system (extension ∼59 pc × 29 pc), which hosts at least five groups of
the ATLASGAL 870 µm dust clumps at d ∼3.1 kpc. These spatially-distinct groups/sub-regions contain unstablemolecular clumps, and are associated with several Class I young stellar objects (mean age ∼0.44 Myr). At least threegroups of ATLASGAL clumps associated with the expanding H ii regions (including the bubble N14) and embedded
infrared dark clouds, devoid of the ionized gas, are found in the system. The observed spectral indices derived using
the GMRT and THOR radio continuum data suggest the presence of non-thermal emission with the H ii regions. High
resolution GMRT radio continuum map at 1280 MHz traces several ionized clumps powered by massive B-type stars
toward N14, which are considerably young (age ∼103 –104 years). Locally, early stage of star formation is evident
toward all the groups of clumps. The position-velocity maps of 12 CO, 13 CO, and C18 O exhibit an oscillatory-likevelocity pattern toward the selected longitude range. Considering the presence of different groups/sub-regions in thesystem, the oscillatory pattern in velocity is indicative of the fragmentation process. All these observed findings favour
the applicability of the global collapse scenario in the extended physical system, which also seems to explain theobserved hierarchy.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2005.08905.pdf

17. Feedback of molecular outflows from protostars in NGC 1333, revealed by Herschel andSpitzer spectro-imaging observations
Odysseas Dionatos1 , Lars. E. Kristensen2, Mario Tafalla3 , Manuel Güdel1 and Magnus Persson4
1

Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna; 2 Centre for Star andPlanet Formation, Niels Bohr Institute and Natural History Museum of Denmark, University of Copenhagen, Øster
Voldgade 5-7, 1350 Copenhagen, Denmark; 3 Observatorio Astronómico Nacional (IGN), Alfonso XII 3, 28014 Madrid,
Spain; 4 Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory,

13

439 92, Onsala, Sweden
E-mail contact: odysseas.dionatos at univie.ac.at
Context Far infrared cooling of excited gas around protostars has been predominantly studied in the context of pointed
observations. Large scale spectral maps of star forming regions enable the simultaneous, comparative study of the gas
excitation around an ensemble of sources at a common frame of reference, therefore providing direct insights in themultitude of physical processes involved.
Aims We employ extended spectral-line maps to decipher the excitation, the kinematical and dynamical processes in
NGC 1333 as revealed by a number of different molecular and atomic lines, aiming to set a reference for the applicability and limitations of difference tracers in constraining particular physical processes.
Methods We reconstruct line maps for H2 , CO, H2 O and [CI] using data obtained with the Spitzer/IRS spectrographand the Herschel HIFI and SPIRE instruments. We compare the morphological features revealed in the maps andderive the gas excitation conditions for regions of interest employing LTE and non-LTE methods. We also calculate thekinematical and dynamical properties for each outflow tracer in a consistent manner, for all observed outflows driven
by protostars in NGC 1333. We finally measure the water abundance in outflows with respect to carbon monoxideand molecular hydrogen.
Results CO and H2 are highly excited around B-stars and at lower levels trace protostellar outflows. H2 O emission isdominated by a moderately fast component associated with outflows. H2 O also displays a weak, narrow-line component in the vicinity of B-stars associated to their UV field. This narrow component it is also present in a handful ofoutflows, indicating UV radiation generated in shocks. Intermediate J CO lines appear brightest at the locations tracedby the narrow H2 O component, indicating that beyond the dominating collisional processes, a secondary, radiative
excitation component can also be active. The morphology, kinematics, excitation and abundance variations of water
are consistent with its excitation and partial dissociation in shocks. Water abundance ranges between 5 × 10−7 and ∼10−5 , with the lower values being more representative. Water is brightest and most abundant around IRAS 4A whichis consistent with the latter hosting a hot corino source. [CI] traces dense and warm gas in the envelopes surrounding
protostars. Outflow mass flux is highest for CO and decreases by one and two orders of magnitude for H2 and H2 O,
respectively.
Conclusions Large scale spectral line maps can provide unique insights into the excitation of gas in star-forming regions. Comparative analysis of line excitation and morphologies at different locations allows to decipher the dominant
excitation conditions in each region but also isolate exceptional cases.
Accepted by A&A
http://arxiv.org/abs/2006.01087

18. Strong Hα emission and signs of accretion in a circumbinary planetary mass companion

from MUSE

Simon C. Eriksson1 , Rubén Asensio Torres2 , Markus Janson1 , Yuhiko Aoyama3,4 , Gabriel-DominiqueMarleau5,6,2 et al.
1

Institutionen för astronomi, Stockholms universitet, AlbaNova universitetscentrum, 106 91, Stockholm, Sweden; 2
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 3 Institute for Advanced Study,
Tsinghua University, Beijing 100084, People’s Republic of China; 4 Department of Astronomy, Tsinghua University,
Beijing 100084, People’s Republic of China; 5 Institut für Astronomie und Astrophysik, Tübingen, Auf der Morgenstelle
10, D-72076 Tübingen, Germany; 6 Physikalisches Institut, Universität Bern, Gesellschaftsstr. 6, CH-3012 Bern,
Switzerland
E-mail contact: simon.eriksson at astro.su.se
Context. Using intrinsic Hα emission to detect substellar companions can be advantageous for improving contrasts indirect imaging, and probing planetary formation theories through the characterisation of accreting exoplanets.
Aims. In this work we aim to characterise the young circumbinary planetary mass companion 2MASS J01033563−5515561(AB)b (Delorme 1 (AB)b) through medium resolution spectroscopy.
Methods. We have used the new Narrow-Field Mode (NFM) for the MUSE integral-field spectrograph, located on the
ESO Very Large Telescope, during SV time to obtain optical spectra of Delorme 1 (AB)b.
Results. We report the discovery of very strong Hα and Hβ emission, accompanied by He I emission, consistent with14

an active accretion scenario. We provide accretion rate estimates obtained from several independent methods and finda likely mass of 12–15 MJup for Delorme 1 (AB)b, also consistent with previous estimates.
Conclusions. Signs of active accretion in the Delorme 1 system could indicate a younger age than the ∼30–40 Myr
expected from a likely Tucana-Horologium (THA) membership. Previous works have also shown the central binary
to be overluminous, which gives further indication of a younger age. However, recent discoveries of active disks inrelatively old (∼40 Myr), very low-mass systems suggests that ongoing accretion in Delorme 1 (AB)b might not requirein and of itself that the system is younger than the age implied by its THA membership.
Accepted by A&A
http://arxiv.org/pdf/2005.11725

19. A Survey for New Stars and Brown Dwarfs in the Ophiuchus Star-forming Complex
T.L. Esplin1,2 and K.L. Luhman3,4
1

Steward Observatory, University of Arizona, Tucson, AZ, 85719, USA; 2 Strittmatter Fellow; 3 Department of
Astronomy and Astrophysics, The Penn- sylvania State University, University Park, PA 16802; 4 Center for Exoplanets
and Habitable Worlds, The Pennsyl- vania State University, University Park, PA 16802
E-mail contact: taranesplin at email.arizona.edu
We have performed a survey for new members of the Ophiuchus cloud complex using high-precision astrometry
from the second data release of Gaia, proper motions measured with multi-epoch images from the Spitzer Space
Telescope, and color-magnitude diagrams constructed with photometry from various sources. Through spectroscopyof candidates selected with those data, we have identified 155 new young stars. Based on available measurements ofkinematics, we classify 102, 47, and six of those stars as members of Ophiuchus, Upper Sco, and other populationsin Sco-Cen, respectively. We have also assessed the membership of all other stars in the vicinity of Ophiuchus thathave spectroscopic evidence of youth from previous studies, arriving at a catalog of 373 adopted members of thecloud complex. For those adopted members, we have compiled mid-IR photometry from Spitzer and the Wide-field
Infrared Survey Explorer and have used mid-IR colors to identify and classify circumstellar disks. We find that 210
of the members show evidence of disks, including 48 disks that are in advanced stages of evolution. Finally, we haveestimated the relative median ages of the populations near the Ophiuchus clouds and the surrounding Upper Sco
association using absolute K-band magnitudes (MK ) based on Gaia parallaxes. If we adopt an age 10 Myr for Upper
Sco, then the relative values of MK imply median ages of ∼2 Myr for L1689 and embedded stars in L1688, 3–4 Myr
for low-extinction stars near L1688, and ∼6 Myr for the group containing ρ Oph.
Accepted by AJ

http://arxiv.org/pdf/2005.10096

20. Seeds of Life in Space (SOLIS). IX. Chemical segregation of SO2 and SO toward thelow-mass protostellar shocked region of L1157

S. Feng1,2,3 , C. Codella4,5 , C. Ceccarelli5 , P. Caselli3 , A. Lopez-Sepulcre5,6 , R. Neri6 , F. Fontani3,4 , L.
Podio4 , B. Leﬂoch5 , H. B. Liu7 , R. Bachiller8 and S. Viti91National Astronomical Observatory of China, Datun Road 20, Chaoyang, Beijing, 100012, P. R. China; 2 CAS Key
Laboratory of FAST, NAOC, Chinese Academy of Sciences, P. R. China; 3 Max-Planck-Institut für Extraterrestrische
Physik, Gießenbachstraße 1, D-85748, Garching bei München, Germany; 4 INAF-Osservatorio Astrofisico di Arcetri,
Largo E. Fermi 5, I-50125, Florence, Italy; 5 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 6 Institut
de Radioastronomie Millimétrique, 300 rue de la Piscine, Domaine Universitaire de Grenoble, F-38406 Saint-Martind’Hères, France; 7 Academia Sinica Institute of Astronomy and Astrophysics, No.1, Sec. 4, Roosevelt Road, Taipei
10617, Taiwan, Republic of China; 8 Observatorio Astronomico Nacional (OAN, IGN), Calle Alfonso XII, 3, E-28014
Madrid, Spain; 9 Department of Physics and Astronomy, University College London, Gower Street, London WC1E
6BT, UK
E-mail contact: siyi.s.feng at gmail.com
We present observations of SO and SO2 lines toward the shocked regions along the L1157 chemically rich outflow,
taken in the context of the Seeds Of Life In Space IRAM-NOrthern Extended Millimeter Array Large Program, and15

supported by data from Submillimeter Array and IRAM-30 m telescope at 1.1–3.6 mm wavelengths. We simultaneously
analyze, for the first time, all of the brightest shocks in the blueshifted lobe, namely, B0, B1, and B2. We found thefollowing. (1) SO and SO2 may trace different gas, given that the large(-scale) velocity gradient analysis indicatesfor SO2 a volume density (105 −−106 cm−3 ) denser than that of the gas emitting in SO by a factor up to an order ofmagnitude. (2) Investigating the 0.1 pc scale field of view, we note a tentative gradient along the path of the precessing
jet. More specifically, χ(SO/SO2 ) decreases from the B0-B1 shocks to the older B2. (3) At a linear resolution of 500–
1400 au, a tentative spatial displacement between the two emitting molecules is detected, with the SO peak closer(with respect to SO2 ) to the position where the recent jet is impinging on the B1 cavity wall. Our astrochemical
modeling shows that the SO and SO2 abundances evolve on timescales less than about 1000 years. Furthermore, themodeling requires high abundances (2 × 10−6 ) of both H2 S/H and S/H injected in the gas phase due to the shock
occurrence, so pre-frozen OCS only is not enough to reproduce our new observations.
Accepted by ApJ
https://arxiv.org/pdf/2005.04629

21. The chemical structure of young high-mass star-forming clumps: (I) Deuteration
S. Feng1,2,3 , P. Caselli4, K. Wang5 , Y. Lin6 , H. Beuther7 and O. Sipilä41National Astronomical Observatory of China, Datun Road 20, Chaoyang, Beijing, 100012, P. R. China; 2 CAS
Key Laboratory of FAST, NAOC, Chinese Academy of Sciences, P. R. China; 3 National Astronomical Observatoryof Japan, 2 Chome-21-1 Osawa, Mitaka-shi, Tokyo-to 181-8588, Japan; 4 Max-Planck-Institut für Extraterrestrische
Physik, Gießenbachstraße 1, D-85748, Garching bei München, Germany; 5 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, China; 6 Max Planck Institute forRadio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany; 7 Max-Planck-Institut für Astronomie, Königstuhl
17, D-69117, Heidelberg, Germany
E-mail contact: siyi.s.feng at gmail.com
The chemical structure of high-mass star nurseries is important for a general understanding of star formation. Deuteration is a key chemical process in the earliest stages of star formation because its efficiency is sensitive to the environment.
Using the IRAM-30 m telescope at 1.3–4.3 mm wavelengths, we have imaged two parsec-scale high-mass protostellar
clumps (P1 and S) that show different evolutionary stages but are located in the same giant filamentary infrared darkcloud G28.34+0.06. Deep spectral images at subparsec resolution reveal the dust and gas physical structures of bothclumps. We find that (1) the low-J lines of N2 H+ , HCN, HNC, and HCO+ isotopologues are subthermally excited;and (2) the deuteration of N2 H+ is more efficient than that of HCO+ , HCN, and HNC by an order of magnitude.
The deuterations of these species are enriched toward the chemically younger clump S compared with P1, indicatingthat this process favors the colder and denser environment (Tkin ∼ 14K, N(NH3 ) ∼ 9 × 1015 cm−2 ). In contrast,
single deuteration of NH3 is insensitive to the environmental difference between P1 and S; and (3) single deuterationof CH3 OH (> 10%) is detected toward the location where CO shows a depletion of ∼ 10. This comparative chemical
study between P1 and S links the chemical variations to the environmental differences and shows chemical similarities
between the early phases of high- and low-mass star-forming regions.
Accepted by ApJ
https://arxiv.org/pdf/1909.00209

22.

APEX CO observations towards the photodissociation region of RCW120
M. Figueira1 , A. Zavagno2 , L. Bronfman3 , D. Russeil2, R. Finger3 , and F. Schuller4,51National Centre for Nuclear Research, ul. Pasteura 7, 02-093, Warszawa, Poland; 2 Aix Marseille Univ, CNRS, CNES,
LAM, Marseille, France; 3 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile; 4 MaxPlanck-Institut für Radioastronomie, Auf dem Hügel 69, 53121, Bonn, Germany; 5 Leibniz-Institut für Astrophysik
Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany

E-mail contact: Miguel.Figueira at ncbj.gov.pl
The edges of ionized (HII) regions are important sites for the formation of (high-mass) stars. Indeed, at least 30%of the galactic high mass star formation is observed there. The radiative and compressive impact of the HII region
could induce the star formation at the border following different mechanisms such as the Collect & Collapse (C&C)
16

or the Radiation Driven Implosion (RDI) models and change their properties. We study the properties of two zones
located in the Photo Dissociation Region (PDR) of the Galactic HII region RCW120 and discussed them as a functionof the physical conditions and young star contents found in both clumps. Using the APEX telescope, we mapped
two regions of size 1.′ 5×1.′ 5 toward the most massive clump of RCW120 hosting young massive sources and towarda clump showing a protrusion inside the HII region and hosting more evolved low-mass sources. The 12 CO(J=3–2),
13
CO(J=3–2) and C18 O(J=3–2) lines are used to derive the properties and dynamics of these clumps. We discuss theirrelation with the hosted star-formation. The increase of velocity dispersion and Tex are found toward the center of themaps, where star-formation is observed with Herschel. Furthermore, both regions show supersonic Mach number. No
strong evidences have been found concerning the impact of far ultraviolet (FUV) radiation on C18 O photodissociation.
The fragmentation time needed for the C&C to be at work is equivalent to the dynamical age of RCW120 andthe properties of region B are in agreement with bright-rimmed clouds. It strengthens the fact that, together withevidences of compression, C&C might be at work at the edges of RCW120. Additionally, the clump located at theeastern part of the PDR is a good candidate of pre-existing clump where star-formation may be induced by the RDI
mechanism.
Accepted by A&A
http://arxiv.org/pdf/2005.08810

23. Measuring turbulent motion in planet-forming disks with ALMA: A detection around

DM Tau and non-detections around MWC 480 and V4046 SgrKevin Flaherty1 , A. Meredith Hughes2 , Jacob B. Simon3,4,5 , Chunhua Qi6 , Xue-Ning Bai7,8 , Alyssa
Bulatek9 , Sean M. Andrews6 , David J. Wilner6 and Agnes Kospal10,11,12
1

Department of Astronomy and Department of Physics, Williams College, Williamstown, MA; 2 Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 USA; 3 Department of
Physics and Astronomy, Iowa State University, Ames, IA; 4 Department of Space Studies, Southwest Research Institute Boulder, CO; 5 JILA, University of Colorado and NIST, 440 UCB, Boulder, CO; 6 Harvard-Smithsonian Center
for Astrophysics, 60 Garden St, Cambridge, MA; 7 Institute for Advanced Study, Tsinghua University, Beijing 100084,
China; 8 Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China; 9 Department of Physics &Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN; 10 Konkoly Observatory Research Centre for
Astronomy and Earth Sciences, Konkoly-Thege Monklsut 15-17, 1121 Budapest, Hungary; 11 Max Planck Institute for
Astronomy, Konighstuhl 17, D-69117 Heildelberg, Germany; 12 ELTE Eotvos Lorand University, Institute of Physics,
Pazmany Peter setany 1/A, 1117 Budapest, Hungary
E-mail contact: kmf4 at williams.edu
Turbulence is a crucial factor in many models of planet formation, but it has only been directly constrained among asmall number of planet forming disks. Building on the upper limits on turbulence placed in disks around HD 163296
and TW Hya, we present ALMA CO J=2-1 line observations at ∼ 0.3 arcsec (20-50 au) resolution and 80 ms−1
channel spacing of the disks around DM Tau, MWC 480, and V4046 Sgr. Using parametric models of disk structure,
we robustly detect non-thermal gas motions around DM Tau of between 0.25 cs and 0.33 cs , with the range dominatedby systematic effects, making this one of the only systems with directly measured non-zero turbulence. Using thesame methodology, we place stringent upper limits on the non-thermal gas motion around MWC 480 (<0.08cs ) and
V4046 Sgr (<0.12 cs ). The preponderance of upper limits in this small sample, and the modest turbulence levels−3
consistent with dust studies, suggest that weak turbulence (α <∼ 10 ) may be a common, albeit not universal, featureof planet-forming disks. We explore the particular physical conditions around DM Tau that could lead this system to
be more turbulent than the others.
Accepted by ApJ
https://arxiv.org/pdf/2004.12176

24. Gas and dust dynamics in starlight-heated protoplanetary disks
Mario Flock1 , Neal J. Turner2 , Richard P. Nelson3 , Wladimir Lyra4 , Natascha Manger5 and Hubert
Klahr1
1

Max-Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Jet Propulsion Laboratory,17

California Institute of Technology, Pasadena, California 91109, USA; 3 Astronomy Unit, Queen Mary University of
London, Mile End Road, London E1 4NS, UK; 4 Department of Astronomy, New Mexico State University, MSC 4500,
Las Cruces, NM 88003, USA; 5 Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Ave, New York,NY 10010, USA
E-mail contact: flock at mpia.de
Theoretical models of the ionization state in protoplanetary disks suggest the existence of large areas with low ionization
and weak coupling between the gas and magnetic fields. In this regime hydrodynamical instabilities may become
important. In this work we investigate the gas and dust structure and dynamics for a typical T Tauri system under
the influence of the vertical shear instability (VSI). We use global 3D radiation hydrodynamics simulations covering
all 360◦ of azimuth with embedded particles of 0.1 and 1mm size, evolved for 400 orbits. Stellar irradiation heating is
included with opacities for 0.1- to 10-µm-sized dust. Saturated VSI turbulence produces a stress-to-pressure ratio ofα ≃ 10−4 . The value of α is lowest within 30 au of the star, where thermal relaxation is slower relative to the orbital
period and approaches the rate below which VSI is cut off. The rise in α from 20 to 30 au causes a dip in the surface
density near 35 au, leading to Rossby wave instability and the generation of a stationary, long-lived vortex spanningabout 4 au in radius and 40 au in azimuth. Our results confirm previous findings that mm size grains are strongly
vertically mixed by the VSI. The scale height aspect ratio for 1mm grains is determined to be 0.037, much higher thanthe value H/r = 0.007 obtained from millimeter-wave observations of the HL Tau system. The measured aspect ratio
is better fit by non-ideal MHD models. In our VSI turbulence model, the mm grains drift radially inwards and many
are trapped and concentrated inside the vortex. The turbulence induces a velocity dispersion of ∼ 12 m/s for the mm
grains, indicating that grain-grain collisions could lead to fragmentation.
Accepted by ApJ
https://arxiv.org/pdf/2005.11974.pdf

25. Enrichment of the HR 8799 planets by minor bodies and dust
K. Frantseva1,2 , M. Mueller3,4,2 , P. Pokorný5,6 , F.F.S. van der Tak2,1 , I.L. ten Kate7
1

Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands;
SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands; 3 NOVA
Netherlands Research School for Astronomy, The Netherlands; 4 Leiden Observatory, Leiden University, Leiden,
The Netherlands; 5 Department of Physics, The Catholic University of America, Washington, DC, 20064, USA; 6
Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA; 7 Department ofEarth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
2E-mail contact: frantseva at astro.rug.nl
In the Solar System, minor bodies and dust deliver various materials to planetary surfaces. Several exoplanetarysystems are known to host inner and outer belts, analogues of the main asteroid belt and the Kuiper belt. We study
the possibility that exominor bodies and exodust deliver volatiles and refractories to the exoplanets in the system
HR8799 by performing N-body simulations. The model consists of the host star, four giant planets (HR8799 e, d,c, and b), 650000 test particles representing the inner belt, and 1450000 test particles representing the outer belt.
Moreover we modelled dust populations that originate from both belts. Within a million years, the two belts evolve
towards the expected dynamical structure (also derived in other works), where mean-motion resonances with theplanets carve the analogues of Kirkwood gaps. We find that, after this point, the planets suffer impacts by objects
from the inner and outer belt at rates that are essentially constant with time, while dust populations do not contributesignificantly to the delivery process. We convert the impact rates to volatile and refractory delivery rates using ourbest estimates of the total mass contained in the belts and their volatile and refractory content. Over their lifetime,
the four giant planets receive between 10−4 and 10−3 M⊕ of material from both belts. The total amount of delivered
volatiles and refractories, 5 × 10−3 M⊕ , is small compared to the total mass of the planets, 11 × 103 M⊕ . However, if
the planets were formed to be volatile-rich, their exogenous enrichment in refractory material may well be significant
and observable, for example with JWST-MIRI. If terrestrial planets exist within the snow line of the system, volatiledelivery would be an important astrobiological mechanism and may be observable as atmospheric trace gases.
Accepted by A&A
http://arxiv.org/pdf/2005.13562

18

26. Efficient Methanol Production on the Dark Side of a Prestellar Core
Jorma Harju1,2 , Jaime E. Pineda1 , Anton I. Vasyunin1,3,4 , Paola Caselli1, Stella S.R. Oﬀner5 , Alyssa
A. Goodman6 , Mika Juvela2 , Olli Sipilä1 , Alexandre Faure7,8 , Romane Le Gal6 , Pierre Hily-Blant7,8 ,João Alves9 , Luca Bizzocchi1 , Andreas Burkert1,10 , Hope Chen6 , Rachel K. Friesen11 , Rolf Güsten12 ,Philip C. Myers6 , Anna Punanova1,3 , Claire Rist7,8 , Erik Rosolowsky13 , Stephan Schlemmer14 , Yancy
Shirley15 , Silvia Spezzano1 , Charlotte Vastel16,17 and Laurent Wiesenfeld18
1

Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, D-85748 Garching, Germany; 2 Departmentof Physics, P.O. BOX 64, FI-00014 University of Helsinki, Finland; 3 Ural Federal University, 620002, 19 Mira street,
Yekaterinburg, Russia; 4 Ventspils University of Applied Sciences, Inzenieru 101, Ventspils 3601, Latvia; 5 Astronomy
Department, University of Texas, Austin, TX 78712, USA; 6 Harvard-Smithsonian Center for Astrophysics, 60 Garden
Street, Cambridge MA 02138, USA; 7 Université Grenoble Alpes, IPAG, F-38000 Grenoble, France; 8 CNRS, IPAG,
F-38000 Grenoble, France; 9 University of Vienna, Türkenschanzstraße 17, A-1880 Vienna, Austria; 10 UniversitätsSternwarte, Ludwig-Maximilians-Universität München, Scheinerstraße 1, D-81679 München, Germany; 11 Dunlap
Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto M5S 3H4, Ontario,
Canada; 12 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 13 Department of
Physics, 4-181 CCIS, University of Alberta, Edmonton, AB T6G 2E1, Canada; 14 I. Physikalisches Institut, Universität
zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany; 15 Steward Observatory, University of Arizona, 933 North
Cherry Avenue, Tucson, AZ 85721, USA; 16 Université de Toulouse, UPS-OMP, IRAP, Toulouse, France; 17 CNRS,
IRAP, 9 Avenue du Colonel Roche, BP 44346, F-31028 Toulouse Cedex 4, France; 18 Laboratoire Aimé-Cotton, CNRS
and Université Paris-Saclay, F-91405 Orsay, France
E-mail contact: jorma.harju at helsinki.fi
We present Atacama Large Millimeter/submillimeter Array maps of the starless molecular cloud core Ophiuchus/HMM1 in the lines of deuterated ammonia (ortho-NH2 D), methanol (CH3 OH), and sulfur monoxide (SO). The dense
core is seen in NH2 D emission, whereas the CH3 OH and SO distributions form a halo surrounding the core. Because
methanol is formed on grain surfaces, its emission highlights regions where desorption from grains is particularly
efficient. Methanol and sulfur monoxide are most abundant in a narrow zone that follows the eastern side of the core.
This side is sheltered from the stronger external radiation field coming from the west. We show that photodissociationon the illuminated side can give rise to an asymmetric methanol distribution but that the stark contrast observed in
H-MM1 is hard to explain without assuming enhanced desorption on the shaded side. The region of the brightest
emission has a wavy structure that rolls up at one end. This is the signature of Kelvin-Helmholtz instability occurringin sheared flows. We suggest that in this zone, methanol and sulfur are released as a result of grain–grain collisions
induced by shear vorticity.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1903.11298.pdf

27. Tracking the evolutionary stage of protostars by the abundances of astrophysical ices
Katsuhiro Hayashi1,2 , Satoshi Yoshiike1 , Rei Enokiya1 , Shinji Fujita1,3 , Rin Yamada1 et al.
1

Department of Physics, Nagoya University, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan; 2 Institute of Space andAstronautical Science (ISAS) Japan Aerospace Exploration Agency (JAXA), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan; 3 Department of Physical Science, Graduate School of Science, Osaka Prefecture
University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
E-mail contact: khayashi at a.phys.nagoya-u.ac.jp

We report on a study of the high-mass star formation in the the HII region W28A2 by investigating the molecular
clouds extended over ∼5–10 pc from the exciting stars using the 12 CO and 13 CO (J=1–0) and 12 CO (J=2–1) datataken by the NANTEN2 and Mopra observations. These molecular clouds consist of three velocity components with
the CO intensity peaks at VLSR ∼ −4 km s−1 , 9 km s−1 and 16 km s−1 . The highest CO intensity is detected at
VLSR ∼ 9 km s−1 , where the high-mass stars with the spectral types of O6.5–B0.5 are embedded. We found bridging
features connecting these clouds toward the directions of the exciting sources. Comparisons of the gas distributions
with the radio continuum emission and 8 µm infrared emission show spatial coincidence/anti-coincidence, suggesting
physical associations between the gas and the exciting sources. The 12 CO J=2–1 to 1–0 intensity ratio shows a high19

value (>0.8) toward the exciting sources for the −4 km s−1 and +9 km s−1 clouds, possibly due to heating by the highmass stars, whereas the intensity ratio at the CO intensity peak (VLSR ∼ 9 km s−1 ) lowers down to ∼0.6, suggesting self
absorption by the dense gas in the near side of the +9 km s−1 cloud. We found partly complementary gas distributions
between the −4 km s−1 and +9 km s−1 clouds, and the −4 km s−1 and +16 km s−1 clouds. The exciting sources arelocated toward the overlapping region in the −4 km s−1 and +9 km s−1 clouds. Similar gas properties are found in
the Galactic massive star clusters, RCW 38 and NGC 6334, where an early stage of cloud collision to trigger the starformation is suggested. Based on these results, we discuss a possibility of the formation of high-mass stars in the
W28A2 region triggered by the cloud-cloud collision.
Accepted by PASJ
http://arxiv.org/pdf/2005.07933

28. Magnetic Field Structure of Orion Source I
Tomoya Hirota1,2 , Richard L. Plambeck3 , Melvyn C. H. Wright3 , Masahiro N. Machida4 , Yuko Matsushita4 ,Kazuhito Motogi5, Mi Kyoung Kim6,7 , Ross A. Burns8 and Mareki Honma6,9,10
1

Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 2
Department of Astronomical Sciences, SOKENDAI, Mitaka, Tokyo 181-8588, Japan; 3 Radio Astronomy Laboratory,
University of California, Berkeley, CA 94720, USA; 4 Department of Earth and Planetary Sciences, Faculty of Sciences,
Kyushu University, Fukuoka 819-0395, Japan; 5 Graduate School of Science and Engineering, Yamaguchi University,
Yamaguchi 753-8511, Japan; 6 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Oshu,
Iwate 023-0861, Japan; 7 Otsuma women’s university, Faculty of Home Economics, Department of Child Studies,
Chiyoda-ku, Tokyo 102-8357, Japan; 8 Joint Institute for VLBI in Europe, Postbus 2, 7990 AA, Dwingeloo, The
Netherlands; 9 Department of Astronomical Sciences, SOKENDAI, Oshu, Iwate 023-0861, Japan; 10 Department of
Astronomy, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
E-mail contact: tomoya.hirota at nao.ac.jp
We observed polarization of the SiO rotational transitions from Orion Source I (SrcI) to probe the magnetic field in
bipolar outflows from this high mass protostar. Both 43 GHz J=1-0 and 86 GHz J=2-1 lines were mapped with
∼20 AU resolution, using the VLA and ALMA, respectively. The 28 SiO transitions in the ground vibrational state
are a mixture of thermal and maser emission. Comparison of the polarization position angles in the J=1-0 and J=2-1transitions allows us to set an upper limit on possible Faraday rotation of 104 radians m−2 , which would twist the
J=2-1 position angles typically by less than 10 degrees. The smooth, systematic polarization structure in the outflow
lobes suggests a well ordered magnetic field on scales of a few hundred AU. The uniformity of the polarization suggests
a field strength of ∼30 milli-Gauss. It is strong enough to shape the bipolar outflow and possibly lead to sub-Keplerianrotation of gas at the base of the outflow. The strikingly high fractional linear polarizations of 80-90% in the 28 SiO v=0
masers require anisotropic pumping. We measured circular polarizations of 60% toward the strongest maser feature in
the v=0 J=1-0 peak. Anisotropic resonant scattering (ARS) is likely to be responsible for this circular polarization.
We also present maps of the 29 SiO ν=0 J=2-1 maser and several other SiO transitions at higher vibrational levels
and isotopologues.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2005.13077

29.

Frankenstein: Protoplanetary disc brightness profile reconstruction at sub-beam resolution with a rapid Gaussian process
Jeﬀ Jennings1 , Richard A. Booth1 , Marco Tazzari1 , Giovanni P. Rosotti2 and Cathie J. Clarke1
1

Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK; 2 Leiden Observatory,
University of Leiden, P.O. Box 9500, Leiden, NL-2300 RA, Netherlands
E-mail contact: jmj51 at ast.cam.ac.uk
Interferometric observations of the mm dust distribution in protoplanetary discs are now showing a ubiquity of annular
gap and ring substructures. Their identification and accurate characterization is critical to probing the physicalprocesses responsible. We present Frankenstein (frank), an open source code that recovers axisymmetric disc structures20

at sub beam resolution. By fitting the visibilities directly, the model reconstructs a disc’s 1D radial brightness profile
nonparametrically using a fast (less than about 1 min) Gaussian process. The code avoids limitations of current
methods that obtain the radial brightness profile by either extracting it from the disc image via nonlinear deconvolution
at the cost of reduced fit resolution, or by assumptions placed on the functional forms of disc structures to fit thevisibilities parametrically. We use mock ALMA observations to quantify the method’s intrinsic capability and its
performance as a function of baseline-dependent signal-to-noise. Comparing the technique to profile extraction from a
CLEAN image, we motivate how our fits accurately recover disc structures at a sub-beam resolution. Demonstrating
the model’s utility in fitting real high and moderate resolution observations, we conclude by proposing applications toaddress open questions on protoplanetary disc structure and processes.
Accepted by MNRAS
http://arxiv.org/pdf/2005.07709

30. Outbursts in Global Protoplanetary Disk Simulations
Kundan Kadam1 , Eduard Vorobyov2,3 , Zsolt Regály1 , Ágnes Kóspál1,4,5 and Péter Ábrahám1,5
1

Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121
Budapest, Hungary; 2 Department of Astrophysics, The University of Vienna, A-1180 Vienna, Austria; 3 Ural Federal
University, 51 Lenin Str., 620051 Ekaterinburg, Russia; 4 Max Planck Institute for Astronomy, Königstuhl 17, D69117 Heidelberg, Germany; 5 ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117
Budapest, Hungary
E-mail contact: kundan.kadam at csfk.mta.hu
While accreting through a circumstellar disk, young stellar objects are observed to undergo sudden and powerfulaccretion events known as FUor or EXor outbursts. Although such episodic accretion is considered to be an integral
part of the star formation process, the triggers and mechanisms behind them remain uncertain. We conducted global
numerical hydrodynamics simulations of protoplanetary disk formation and evolution in the thin-disk limit, assuming
both magnetically layered and fully magnetorotational instability (MRI)-active disk structure. In this paper, wecharacterize the nature of the outbursts occurring in these simulations. The instability in the dead zone of a typicallayered disk results in “MRI outbursts". We explore their progression and their dependence on the layered disk
parameters as well as cloud core mass. The simulations of fully MRI-active disks showed an instability analogous tothe classical thermal instability. This instability manifested at two temperatures–above approximately 1400 K and3500 K–due to the steep dependence of Rosseland opacity on the temperature. The origin of these thermally unstableregions is related to the bump in opacity resulting from molecular absorption by water vapor and may be viewed asa novel mechanism behind some of the shorter duration accretion events. Although we demonstrated local thermal
instability in the disk, more investigations are needed to confirm that a large-scale global instability will ensue. We
conclude that the magnetic structure of a disk, its composition, as well as the stellar mass, can significantly affect thenature of episodic accretion in young stellar objects.
Accepted by ApJ
https://arxiv.org/pdf/2005.03578

31.

Gap, shadows, spirals, streamers: SPHERE observations of binary-disk interactions in
GG Tau A
M. Keppler1 , A. Penzlin2 , M. Benisty3,4 , R. van Boekel1 , T. Henning1 et al.
1

Max Planck Institute for Astronomy, Königstuhl 17, 69117, Heidel- berg, Germany; 2 Institut für Astronomie undAstrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany; 3 Univ. Grenoble Alpes,
CNRS, IPAG, 38000 Grenoble, France; 4 Unidad Mixta Internacional Franco-Chilena de Astronomía (CNRS, UMI
3386), Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
E-mail contact: keppler at mpia.de
A large fraction of stars is found to be part of binary or higher-order multiple systems. The ubiquity of planets foundaround single stars raises the question if and how planets in binary systems may form. Protoplanetary disks are
the birthplaces of planets, and their characterization is crucial in order to understand the planet formation process.
21

Our aim is to characterize the morphology of the GG Tau A disk, one of the largest and most massive circumbinarydisks, and trace evidence for binary-disk interactions. We obtained observations in polarized scattered light of GG
Tau A using the SPHERE/IRDIS instrument in the H-band filter. We analyze the observed disk morphology andsubstructures. We run 2D hydrodynamical models simulating the evolution of the circumbinary ring over the lifetimeof the disk. The disk, as well as the cavity and the inner region are highly structured with several shadowed regions,spiral structures, and streamer-like filaments, some of them detected for the first time. The streamer-like filaments
appear to connect the outer ring with the northern arc. Their azimuthal spacing suggests that they may be generated
by periodic perturbations by the binary, tearing off material from the inner edge of the outer disk once during eachorbit. By comparing observations to hydrodynamical simulations we find that the main features, in particular the gap
size, as well as the spiral and streamer filaments, can be qualitatively explained by the gravitational interactions of abinary with semi-major axis of ∼35 au on an orbit coplanar with the circumbinary ring.
Accepted by A&A
http://arxiv.org/pdf/2005.09037

32. Multiple outflows in the high-mass cluster forming region, G25.82−0.17
Jungha Kim1,2 Mi Kyoung Kim3,4 , Tomoya Hirota2 , Kee-Tae Kim5,6 , Koichiro Sugiyama2,7 et al.
1

Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo
181-8588, Japan; 3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21 Hoshi-ga-oka,
Mizusawa-ku, Oshu, Iwate 023-0861, Japan; 4 Otsuma women’s university, Faculty of Home Economics, Departmentof Child Studies, 12 Sanban-cho, Chiyoda-ku, Tokyo 102-8357, Japan; 5 Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 34055, Republic of Korea; 6 University of Science and Technology, 217
Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea; 7 National Astronomical Research Institute of Thailand,
260 M.4, T. Donkaew, Amphur Maerim, Chiang Mai 50180, Thailand
E-mail contact: jungha.kim at grad.nao.ac.jp
We present results of continuum and spectral line observations with ALMA and 22 GHz water (H2 O) maser observations using KaVA and VERA toward a high-mass star-forming region, G25.82−0.17. Multiple 1.3 mm continuum
sources are revealed, indicating the presence of young stellar objects (YSOs) at different evolutionary stages, namely
an ultra-compact HII region, G25.82-E, a high-mass young stellar object (HM-YSO), G25.82-W1, and starless cores,
G25.82-W2 and G25.82-W3. Two SiO outflows, at N-S and SE-NW orientations, are identified. The CH3 OH 8−1 –70
E line, known to be a class I CH3 OH maser at 229 GHz is also detected showing a mixture of thermal and maser
emission. Moreover, the H2 O masers are distributed in a region ∼0.′′ 25 shifted from G25.82-W1. The CH3 OH 224 –215 E line shows a compact ring-like structure at the position of G25.82-W1 with a velocity gradient, indicating arotating disk or envelope. Assuming Keplerian rotation, the dynamical mass of G25.82-W1 is estimated to be >25
M⊙ and the total mass of 20 M⊙ –84 M⊙ is derived from the 1.3 mm continuum emission. The driving source of the
N-S SiO outflow is G25.82-W1 while that of the SE-NW SiO outflow is uncertain. Detection of multiple high-mass
starless/protostellar cores and candidates without low-mass cores implies that HM-YSOs could form in individual
high-mass cores as predicted by the turbulent core accretion model. If this is the case, the high-mass star formation
process in G25.82 would be consistent with a scaled-up version of low-mass star formation.
Accepted by ApJ
http://arxiv.org/pdf/2005.05006

33. Cloud structures in M17 SWex : Possible cloud-cloud collision
Shinichi W. Kinoshita1,2 , Fumitaka Nakamura1,2,3 , Quang Nguyen-Luong4,6 , Benjamin Wu2 , Tomomi
Shimoikura5 et al.
1

Department of Astronomy, the University of Tokyo, 7-3-1 Hongo Bunkyo, 113-0033 Tokyo, Japan; 2 National
Astronomical Observatory of Japan, NINS, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 The Graduate University
for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 4 McMaster University, 1 James St
N, Hamilton, ON, L8P 1A2, Canada; 5 Faculty of Social Information Studies, Otsuma Womens University, Chiyoda-

22

ku,Tokyo, 102-8357, Japan; 6 Graduate School of Science, Nagoya City University, Mizuho-ku, Nagoya,467-8501,
Japan
E-mail contact: kinoshita.shinichi at nao.ac.jp
Using wide-field 13 CO (J=1–0) data taken with the Nobeyama 45-m telescope, we investigate cloud structures of theinfrared dark cloud complex in M17 with SCIMES. In total, we identified 118 clouds that contain 11 large clouds withradii larger than 1 pc. The clouds are mainly distributed in the two representative velocity ranges of 10–20 km s−1
and 30–40 km s−1 . By comparing with the ATLASGAL catalog, we found that the majority of the 13 CO clouds with
10–20 km s−1 and 30–40 km s−1 are likely located at distances of 2 kpc (Sagittarius arm) and 3 kpc (Scutum arm),
respectively. Analyzing the spatial configuration of the identified clouds and their velocity structures, we attempt
to reveal the origin of the cloud structure in this region. Here we discuss three possibilities: (1) overlapping withdifferent velocities, (2) cloud oscillation, and (3) cloud-cloud collision. From the position-velocity diagrams, we foundspatially-extended faint emission between ∼20 km s−1 and ∼35 km s−1 , which is mainly distributed in the spatiallyoverlapped areas of the clouds. We also found that in some areas where clouds with different velocities overlapped, themagnetic field orientation changes abruptly. The distribution of the diffuse emission in the position-position-velocity
space and the bending magnetic fields appear to favor the cloud-cloud collision scenario compared to other scenarios.
In the cloud-cloud collision scenario, we propose that two ∼35 km s−1 foreground clouds are colliding with clouds at∼20 km s−1 with a relative velocity of 15 km s−1 . These clouds may be substructures of two larger clouds having
3−1
4
velocities of ∼35 km s−1 (>∼10 M⊙ ) and ∼20 km s (>∼10 M⊙ ), respectively.
Accepted by PASJ
http://arxiv.org/pdf/2005.10778

34. Grain growth in newly discovered young eruptive stars
Á. Kóspál1,2,3 , P. Ábrahám1,3 , A. Carmona4 , L. Chen1 , J. D. Green5 , R. van Boekel2 and J. A. White1
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121
Budapest, Hungary; 2 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 3 ELTE
Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary; 4 Institute dePlanetologie et Astrophysique de Grenoble, Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 5Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
E-mail contact: kospal at konkoly.hu
FU Orionis-type stars are young stellar objects showing large outbursts due to highly enhanced accretion from thecircumstellar disk onto the protostar. FUor-type outbursts happen in a wide variety of sources from the very embedded
ones to those with almost no sign of extended emission beyond the disk. The subsequent eruptions might graduallyclear up the obscuring envelope material and drive the protostar on its way to become a disk-only T Tauri star. We
used VLT/VISIR to obtain the first spectra that cover the 8 − 13 µm mid-infrared wavelength range in low-resolutionof five recently discovered FUors. Four objects from our sample show the 10 µm silicate feature in emission. We study
the shape and strength of the silicate feature in these objects and find that they mostly contain large amorphous grains,suggesting that large grains are typically not settled to the midplane in FUor disks. This is a general characteristic ofFUors, as opposed to regular T Tauri-type stars whose disks display anything from pristine small grains to significant
grain growth. We classify our targets by determining whether the silicate feature is in emission or in absorption, andconfront them with the evolutionary scenarios on the dispersal of the envelopes around young stars. In our sample,
all Class II objects exhibit silicate emission, while for Class I objects, the appearance of the feature in emission
or absorption depends on the viewing angle with respect to the outflow cavity. This highlights the importance ofgeometric effects when interpreting the silicate feature.
Accepted by ApJL
http://arxiv.org/pdf/2005.09364

35.

Star Cluster Formation in Orion A
Wanggi Lim1 , Fumitaka Nakamura2 , Benjamin Wu2 , Thomas G.Bisbas3,4,5, Jonathan C. Tan6,7 , Edward
Chambers1 , John Bally8 , Shuo Kong9 , Peregrine McGehee10 , Dariusz C. Lis11 , Volker Ossenkopf-Okada423

and Álvaro Sánchez-Monge4
1

SOFIA-USRA, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035, USA; 2 National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 3 National Observatory of Athens, Institute for Astronomy,
Astrophysics, Space Applications and Remote Sensing, Penteli, 15236, Athens, Greece; 4 I. Physikalisches Institut,
Universität zu Köln, Zülpicher Straße 77, Germany; 5 Department of Physics, Aristotle University of Thessaloniki,
GR-54124 Thessaloniki, Greece; 6 Department of Space, Earth & Environment, Chalmers University of Technology,
Gothenburg, Sweden; 7 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 8 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA; 9 Steward Observatory,
University of Arizona, AZ 85719; 10 Department of Earth and Space Sciences, College of the Canyons, Santa Clarita,
CA 91355, USA; 11 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena,
CA 91109, USA
E-mail contact: wanggi.lim.astro at gmail.com
We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining
the scenario of a cloud-cloud collision. We utilize the CARMA-NRO Orion survey 13 CO (1-0) data to compare
molecular gas to the properties of YSOs from the SDSS III IN-SYNC survey. We show that the increase of v13CO −vYSO
and Σ scatter of older YSOs can be signals of cloud-cloud collision. SOFIA-upGREAT 158µm [Cii] archival data
toward the northern part of Orion A are also compared to the 13 CO data to test whether the position and velocity
offsets between the emission from these two transitions resemble those predicted by a cloud-cloud collision model.
We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3 and OMC-4, shows
qualitative agreements with the cloud-cloud collision scenario, while in one of the southern regions, NGC1999, there
is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster,L1641N, shows slight tendencies of cloud-cloud collision. Overall, our results support the cloud-cloud collision process
as being an important mechanism for star cluster formation in Orion A.
Accepted by PASJ
https://arxiv.org/pdf/2004.03668

36.

The Age-Dependence of Mid-Infrared Emission Around Young Star Clusters
Zesen Lin1,2,3 , Daniela Calzetti3 , Xu Kong1,2 , A. Adamo4 , M. Cignoni5 et al.
1

Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science andTechnology of China, Hefei 230026, China; 2 School of Astronomy and Space Sciences, University of Science andTechnology of China, Hefei, 230026, China; 3 Department of Astronomy, University of Massachusetts, Amherst, MA
01003, USA; 4 Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre,
SE-106 91 Stockholm, Sweden; 5 Department of Physics, University of Pisa, Largo Pontecorvo, 3, I-56127 Pisa, Italy
E-mail contact: zesenlin at mail.ustc.edu.cn
Using the star cluster catalogs from the Hubble Space Telescope program Legacy ExtraGalactic UV survey (LEGUS)
and 8 µm images from the IRAC camera on the Spitzer Space Telescope for 5 galaxies within 5 Mpc, we investigate
how the 8 µm dust luminosity correlates with the stellar age on the 30–50 pc scale of star forming regions. We
construct a sample of 97 regions centered at local peaks of 8 µm emission, each containing one or more young starcluster candidates from the LEGUS catalogs. We find a tight anti-correlation with a Pearson correlation coefficientof r = −0.84 ± 0.05 between the mass-normalized dust-only 8 µm luminosity and the age of stellar clusters younger
than 1 Gyr; the 8 µm luminosity decreases with increasing age of the stellar population. Simple assumptions on a
combination of stellar and dust emission models reproduce the observed trend. We also explore how the scatter of theobserved trend depends on assumptions of stellar metallicity, PAH abundance, fraction of stellar light absorbed bydust, and instantaneous versus continuous star formation models. We find that variations in stellar metallicity havelittle effect on the scatter, while PAH abundance and the fraction of dust-absorbed light bracket the full range of thedata. We also find that the trend is better explained by continuous star formation, rather than instantaneous burst
models. We ascribe this result to the presence of multiple star clusters with different ages in many of the regions.
Upper limits of the dust-only 8 µm emission as a function of age are provided.
Accepted by ApJ
http://arxiv.org/pdf/2005.02446

24

Validating Scattering-Induced (Sub)millimeter Disk Polarization through the Spectral

37. Index, Wavelength-Dependent PolarizationPattern, and Polarization Spectrum: The

Case of HD 163296

Zhe-Yu Daniel Lin1 , Zhi-Yun Li1 , Haifeng Yang2 , Leslie Looney3 , Ian Stephens4 and Charles L. H.
Hull5,6
1

Deparment of Astronomy, University of Virginia, 530 McCormick Rd., Charlottesville 22904, Virginia, USA; 2
Institute for Advanced Study, Tsinghua University, Beijing, 100084, People’s Republic of China; 3 Department of
Astronomy, University of Illinois at Urbana-Champaign, Urbana IL 61801, USA; 4 Harvard-Smithsonian Center for
Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 5 National Astronomical Observatory of Japan, NAOJ
Chile Observatory, Alonso de Cordova 3788, Vitacura, Santiago, Chile; 6 Joint ALMA Observatory, Alonso de Cordova
3107, Vitacura, Santiago, Chile
E-mail contact: zdl3gk at virginia.edu
A number of young circumstellar disks show strikingly ordered (sub)millimeter polarization orientations along theminor axis, which is strong evidence for polarization due to scattering by ∼ 0.1 mm-sized grains. To test thismechanism further, we model the ALMA dust continuum and polarization data of HD 163296 using RADMC-3D.
We find that scattering by grains with a maximum size of 90 µm simultaneously reproduces the polarization observedat Band 7 and the unusually low spectral index (α ∼ 1.5) between Band 7 and Band 6 in the optically thick innerdisk as a result of more efficient scattering at the shorter wavelength. The low spectral index of ∼ 2.5 inferred forthe optically thin gaps is reproduced by the same grains, as a result of telescope beam averaging of the gaps (withan intrinsic α ∼ 4) and their adjacent optically thick rings (where α << 2). The tension between the grain sizes
inferred from polarization and spectral index disappears because the low α values do not require large mm-sizedgrains. In addition, the polarization fraction has a unique azimuthal variation: higher along the major axis than theminor axis in the gaps, but vice versa in the rings. We find a rapidly declining polarization spectrum (with p ∝ λ−3approximately) in the gaps, which becomes flattened or even inverted towards short wavelengths in the optically thickrings. These contrasting behaviors in the rings and gaps provide further tests for scattering-induced polarization via
resolved multi-wavelength observations.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/1912.10012

38. Magnetic fields in the early stages of massive star formation as revealed by ALMA
Junhao Liu1,2,3 , Qizhou Zhang3 , Keping Qiu1,2 , Hauyu Baobab Liu4 , Thushara Pillai5,6 et al.
1

School of Astronomy and Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing, Jiangsu 210023, People’s
Republic of China; 2 Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of
Education, Nanjing, Jiangsu 210023, People’s Republic of China; 3 Center for Astrophysics | Harvard & Smithsonian,
60 Garden Street, Cambridge, MA 02138, USA; 4 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box
23-141, Taipei 10617, Taiwan; 5 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany;
6
Institute for Astrophysical Research, 725 Commonwealth Ave, Boston University Boston, MA 02215, USA
E-mail contact: kpqiu at nju.edu.cn
We present 1.3 mm ALMA dust polarization observations at a resolution of ∼0.02 pc of three massive molecular clumps,
MM1, MM4, and MM9, in the infrared dark cloud G28.34+0.06. With the sensitive and high-resolution continuum
data, MM1 is resolved into a cluster of condensations. The magnetic field structure in each clump is revealed by thepolarized emission. We found a trend of decreasing polarized emission fraction with increasing Stokes I intensities
in MM1 and MM4. Using the angular dispersion function method (a modified Davis-Chandrasekhar-Fermi method),the plane-of-sky magnetic field strength in two massive dense cores, MM1-Core1 and MM4-Core4, are estimated tobe ∼1.6 mG and ∼0.32 mG, respectively. The virial parameters in MM1-Core1 and MM4-Core4 are calculated tobe ∼0.76 and ∼0.37, respectively, suggesting that massive star formation does not start in equilibrium. Using thepolarization-intensity gradient-local gravity method, we found that the local gravity is closely aligned with intensity
gradient in the three clumps, and the magnetic field tends to be aligned with the local gravity in MM1 and MM4
except for regions near the emission peak, which suggests that the gravity plays a dominant role in regulating the gas
collapse. Half of the outflows in MM4 and MM9 are found to be aligned within 10◦ of the condensation-scale (<0.05

25pc) magnetic field, indicating that the magnetic field could play an important role from condensation to disk scale in
the early stage of massive star formation. We found that the fragmentation in MM1-Core1 cannot be solely explainedby thermal Jeans fragmentation or turbulent Jeans fragmentation.
Accepted by ApJ
http://arxiv.org/pdf/2005.01705

39. VLT/SPHERE survey for exoplanets around young, early-type stars including systems

with multi-belt architectures

M. Lombart1,2 , G. Chauvin1,3 , P. Rojo4 , E. Lagadec5 P. Delorme3 et al.
1

Unidad Mixta Internacional Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile; 2 Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre
de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis,-Laval, France; 3 Univ. Grenoble Alpes, CNRS,
IPAG, F-38000 Grenoble, France; 4 Departamento de Astronomía, Universidad de Chile, Camino El Observatorio
1515, Las Condes, Santiago, Chile; 5 Université Cote d’Azur, OCA, CNRS, Lagrange, France
E-mail contact: maxime.lombart at ens-lyon.fr
Dusty debris disks around pre- and main-sequence stars are potential signposts for the existence of planetesimals
and exoplanets. Giant planet formation is therefore expected to play a key role in the evolution of the disk. This
is indirectly confirmed by extant sub-millimeter near-infrared images of young protoplanetary and cool dusty debris
disks around main sequence stars usually showing substantial spatial structures. A majority of recent discoveriesof imaged giant planets have been obtained around young, early-type stars hosting a circumstellar disk. In thiscontext, we have carried out a direct imaging program designed to maximize our chances of giant planet discovery
and targeting twenty-two young, early-type stars. About half of them show indication of multi-belt architectures.
Using the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-constrast
coronagraphic differential near-infrared images, we have conducted a systematic search in the close environment ofthese young, dusty and early-type stars. We confirmed that companions detected around HIP 34276, HIP 101800 and
HIP 117452 are stationary background sources and binary companions. The companion candidates around HIP 8832,
HIP 16095 and HIP 95619 are determined as background contamination. For stars for which we infer the presenceof debris belts, a theoretical minimum mass for planets required to clear the debris gaps can be calculated . The
dynamical mass limit is at least 0.1 MJ and can exceed 1 MJ . Direct imaging data is typically sensitive to planets
down to ∼3.6 MJ at 1′′ , and 1.7 MJ in the best case. These two limits tightly constrain the possible planetary systems
present around each target. These systems will be probably detectable with the next generation of planet imagers.
Accepted by A&A
http://arxiv.org/pdf/2005.08850

40. X-Shooter survey of disk accretion in Upper Scorpius I. Very high accretion rates atage>5 Myr

C.F. Manara1 , A. Natta2 , G.P. Rosotti3, J.M. Alcalá4 , B. Nisini5, G. Lodato6 , L. Testi1,7 , I. Pascucci8 ,L. Hillenbrand9 , J. Carpenter10 , A. Scholz11 , D. Fedele7 , A. Frasca12 , G. Mulders13 , E. Rigliaco14 , C.
Scardoni6,15 and E. Zari16
1

European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 2 Schoolof Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliams Place, Dublin 2, Ireland; 3 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 4 INAF - Osservatorio Astronomico di
Capodimonte, via Moiariello 16, 80131 Napoli, Italy; 5 INAF - Osservatorio Astronomico di Roma, via di Frascati 33,
00078 Monte Porzio Catone, Italy; 6 Dipartimento di Fisica, Universitá degli Studi di Milano, Via Giovanni Celoria
16, I-20133 Milano, Italy; 7 INAF - Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy; 8 Lunarand Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA; 9 California Institute of Technology,
1200 East California Blvd, Pasadena, CA 91125, USA; 10 Joint ALMA Observatory, Avenida Alonso de Córdova 3107,
Vitacura, Santiago, Chile; 11 SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St
Andrews, KY16 9SS, United Kingdom; 12 INAF - Osservatorio Astrofisico di Catania, via S. Sofia, 78, 95123 Catania,

26

Italy; 13 Department of the Geophysical Sciences, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL
60637, USA; 14 INAF - Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova, Italy; 15 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 OHA, UK; 16 Max Planck Institutefor Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
E-mail contact: cmanara at eso.org
Determining the mechanisms that drive the evolution of protoplanetary disks is a necessary step to understand how
planets form. Here we measure the mass accretion rate for young stellar objects with disks at age >5 Myr, a critical
test for the current models of disk evolution. We present the analysis of the spectra of 36 targets in the ∼5-10 Myr
old Upper Scorpius star-forming regions for which disk masses were measured with ALMA. We find that the massaccretion rates in this sample of old but still survived disks are similarly high as those of the younger (∼1 ? 3 Myrold) star-forming regions of Lupus and Chamaeleon I, when considering the dependence on stellar and disk mass. In
particular, several disks show high mass accretion rates > 10−9 M⊙ /yr while having low disk masses. Furthermore,
the median values of the measured mass accretion rates in the disk mass ranges where our sample is complete at alevel ∼60 - 80% are compatible in these three regions. At the same time, the spread of mass accretion rates at any
given disk mass is still >0.9 dex even at age>5 Myr. These results are in contrast with simple models of viscous
evolution, which would predict that the values of the mass accretion rate diminish with time, and a tighter correlation
with disk mass at age>5 Myr. Similarly, simple models of internal photoevaporation cannot reproduce the observed
mass accretion rates, while external photoevaporation might explain the low disk masses and high accretion rates. A
partial possible solution to the discrepancy with the viscous models is that the gas-to-dust ratio of the disks at ∼5-10
Myr is significantly different and higher than the canonical 100, as suggested by some dust and gas disk evolution
models. The results shown here require the presence of several inter-playing processes, such as detailed dust evolution,
external photoevaporation and possibly MHD winds, to explain the secular evolution of protoplanetary disks.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2004.14232

41. Orbital and mass constraints of the young binary system IRAS 16293-2422 A
Maria Jose Maureira1 , Jaime E. Pineda1 , Dominique, M. Segura-Cox1 , Paola Caselli1 , Leonardo Testi2 ,Giuseppe Lodato3 , Laurent Loinard4,5 and Antonio Hernandez-Gomez4,6,7
1

Max-Planck-Institut für extraterrestrische Physik (MPE), , Giessenbachstr. 1, D-85741 Garching, Germany; 2European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany; 3 Dipartimento di Fisica,
Universita degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy; 4 Instituto de Radioastronomia y Astrofisica,
Universidad Nacional Autónoma de México Morelia, 58089, Mexico; 5 Instituto de Astronomia, Universidad Nacional
Autonoma de Mexico,
Apartado Postal 70-264, Ciudad de Mexico 04510, Mexico; 6 Max-Planck-Institute für Radioastronomie Auf dem
Hügel 69, 53121 Bonn, Germany; 7 IRAP, Université de Toulouse CNRS, UPS, CNES, Toulouse, France
E-mail contact: maureira at mpe.mpg.de
We present 3 mm ALMA continuum and line observations at resolutions of 6.5 au and 13 au respectively, toward theClass 0 system IRAS 16293-2422 A. The continuum observations reveal two compact sources towards IRAS 16293-2422
A, coinciding with compact ionized gas emission previously observed at radio wavelengths (A1 and A2), confirming thelong-known radio sources as protostellar. The emission towards A2 is resolved and traces a dust disk with a FWHM
size of ∼12 au, while the emission towards A1 sets a limit to the FWHM size of the dust disk of ∼4 au. We also detectspatially resolved molecular kinematic tracers near the protostellar disks. Several lines of the J = 5 − 4 rotationaltransition of HNCO, NH2 CHO and t-HCOOH are detected, with which we derived individual line-of-sight velocities.
Using these together with the CS (J = 2 − 1), we fit Keplerian profiles towards the individual compact sources andderive masses of the central protostars. The kinematic analysis indicates that A1 and A2 are a bound binary system.
Using this new context for the previous 30 years of VLA observations, we fit orbital parameters to the relative motion
between A1 and A2 and find the combined protostellar mass derived from the orbit is consistent with the masses
derived from the gas kinematics. Both estimations indicate masses consistently higher (0.5 < M1 < M2 < 2 M⊙ )than previous estimations using lower resolution observations of the gas kinematics. The ALMA high-resolution data
provides a unique insight into the gas kinematics and masses of a young deeply embedded bound binary system.

27

Accepted by ApJ
https://arxiv.org/pdf/2005.11954

42. What did the seahorse swallow? APEX 170 GHz observations of the chemical conditionsin the Seahorse infrared dark cloud
Oskari Miettinen1
1

Academy of Finland, Hakaniemenranta 6, P.O. Box 131, FI-00531 Helsinki, FinlandE-mail contact: oskari.miettinen at aka.fi
Context. Infrared dark clouds (IRDCs) are useful target sources for the studies of molecular cloud substructure
evolution and early stages of star formation. Determining the chemical composition of IRDCs helps to constrain theinitial conditions and timescales (via chemical clocks) of star formation in these often filamentary, dense interstellar
clouds.
Aims. We aim to determine the fractional abundances of multiple different molecular species in the filamentary IRDC
G304.74+01.32, nicknamed the Seahorse IRDC, and to search for relationships between the abundances and potential
evolutionary trends.
Methods. We used the Atacama Pathfinder EXperiment (APEX) telescope to observe spectral lines occurring at about
170 GHz frequency towards 14 positions along the full extent of the Seahorse filament. The sample is composed of fiveclumps that appear dark in the mid-IR, eight clumps that are associated with mid-IR sources, and one clump thatis already hosting an HII region and is, hence, likely to be in the most advanced stage of evolution of all the target
sources. We also employed our previous 870 µm dust continuum imaging data of the Seahorse.
Results. Six spectral line transitions were detected (≥ 3σ) altogether, namely, SO(NJ = 44 − 33 ), H13 CN(J = 2 − 1),
H13 CO+ (J = 2 − 1), SiO(J = 4 − 3), HN13 C(J = 2 − 1), and C2 H(N = 2 − 1). While SO, H13 CO+ , and HN13 C
were detected in every source, the detection rates for C2 H and H13 CN were 92.9% and 85.7%, respectively. Only one
source (SMM 3) showed detectable SiO emission (7.1% detection rate). Three clumps (SMM 5, 6, and 7) showed theSO, H13 CN, H13 CO+ , HN13 C, and C2 H lines in absorption. Of the detected species, C2 H was found to be the mostabundant one with respect to H2 (a few times 10−9 on average), while HN13 C was found to be the least abundantspecies (a few times 10−11 ). We found three positive correlations among the derived molecular abundances, of whichthose between C2 H and HN13 C and HN13 C and H13 CO+ are the most significant (correlation coefficient r ≃ 0.9).
The statistically most significant evolutionary trends we uncovered are the drops in the C2 H abundance and in the[HN13 C]/[H13 CN] ratio as the clump evolves from an IR dark stage to an IR bright stage and then to an HII region.
Conclusions. The absorption lines detected towards SMM 6 and SMM 7 could arise from continuum radiation froman embedded young stellar object and an extragalactic object seen along the line of sight. However, the cause ofabsorption lines in the IR dark clump SMM 5 remains unclear. The correlations we found between the different
molecular abundances can be understood as arising from the gas-phase electron (ionisation degree) and atomic carbon
abundances. With the exception of H13 CN and H13 CO+ , the fractional abundances of the detected molecules in the
Seahorse are relatively low compared to those in other IRDC sources. The [C2 H] evolutionary indicator we foundis in agreement with previous studies, and can be explained by the conversion of C2 H to other species (e.g. CO)
when the clump temperature rises, especially after the ignition of a hot molecular core in the clump. The decrease of[HN13 C]/[H13 CN] as the clump evolves is also likely to reflect the increase in the clump temperature, which leads toan enhanced formation of HCN and its 13 C isotopologue. Both single-dish and high-resolution interferometric imaging
of molecular line emission (or absorption) of the Seahorse filament are required to understand the large-scale spatial
distribution of the gas and to search for possible hot, high-mass star-forming cores in the cloud.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2005.08250.pdf

43. The big sibling of AU Mic: a cold dust-rich debris disk around CP-72 2713 in the β Pic

moving group

Attila Moór1,2 , Nicole Pawellek3,4,1 , Péter Ábrahám1,2 , Ágnes Kóspál1,4,2 , Krisztián Vida1,2 et al.
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, H1121 Budapest, Hungary; 2 ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117
28

Budapest, Hungary; 3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK;
Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany

4E-mail contact: moor at konkoly.hu
Analyzing Spitzer and Herschel archival measurements we identified a hitherto unknown debris disk around the young
K7/M0 star CP-72 2713. The system belongs to the 24 Myr old β Pic moving group. Our new 1.33 mm continuum
observation, obtained with the ALMA 7-m array, revealed an extended dust disk with a peak radius of 140 au, probably
tracing the location of the planetesimal belt in the system. The disk is outstandingly large compared to known spatiallyresolved debris disks and also to protoplanetary disks around stars of comparable masses. The dynamical excitationof the belt at this radius is found to be reconcilable with planetary stirring, while self-stirring by large planetesimals
embedded in the belt can work only if these bodies form very rapidly, e.g. via pebble concentration. By analyzing
the spectral energy distribution we derived a characteristic dust temperature of 43 K and a fractional luminosity of
1.1 × 10−3 . The latter value is prominently high, we know only four other similarly dust-rich Kuiper-belt analogs
within 40 pc of the Sun.
Accepted by AJ
http://arxiv.org/pdf/2005.00861

44. Protostellar Outflows at the EarliesT Stages (POETS). IV. Statistical properties of the

22 GHz H2 O masers

L. Moscadelli1, A. Sanna2 , C. Goddi3 , V. Krishnan4 , F. Massi1 and F. Bacciotti11

INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 INAF-Istituto di Radioastronomia& Italian ALMA Regional Centre, Via P. Gobetti 101, I-40129 Bologna, Italy; 3 Department of Astrophysics/IMAPP,
Radboud University Nijmegen, PO Box 9010, NL-6500 GL Nijmegen, the Netherlands; 4 South African Radio Astronomy Observatory (SARAO), 2 Fir street, Black River Park, Observatory, Cape Town, 7925, South Africa
E-mail contact: mosca at arcetri.astro.it
Context. 22 GHz water masers are the most intense and widespread masers in star-forming regions. They are commonly
associated with protostellar winds and jets emerging from low- and high-mass young stellar objects (YSO).
Aims. We wish to perform for the first time a statistical study of the location and motion of individual water maser
cloudlets, characterized by typical sizes that are within a few au, with respect to the weak radio thermal emission
from YSOs.
Methods. For this purpose, we have been carrying out the Protostellar Outflows at the EarliesT Stages (POETS) surveyof a sample (38) of high-mass YSOs. The 22 GHz water maser positions and three-dimensional (3D) velocities were
determined through multi-epoch Very Long Baseline Array (VLBA) observations with accuracies of a few milliarcsec(mas) and a few km s−1 , respectively. The position of the ionized core of the protostellar wind, marking the YSO, wasdetermined through sensitive radio continuum, multi-frequency Jansky Very Large Array (JVLA) observations with atypical error of ≈ 20 mas.
Results. The statistic of the separation of the water masers from the radio continuum shows that 84% of the masers
are found within 1000 au from the YSO and 45% of them are within 200 au. Therefore, we can conclude that the
22 GHz water masers are a reliable proxy for locating the position of the YSO. The distribution of maser luminosity
is strongly peaked towards low values, indicating that about half of the maser population is still undetected withthe current Very Long Baseline Interferometry (VLBI) detection thresholds of 50–100 mJy beam−1. Next-generation,
sensitive (at the nJy level) radio interferometers will have the capability to exploit these weak masers for an improved
sampling of the velocity and magnetic fields around the YSOs. The average direction of the water maser propermotions provides a statistically-significant estimate for the orientation of the jet emitted by the YSO: 55% of themaser proper motions are directed on the sky within an angle of 30◦ from the jet axis. Finally, we show that ourmeasurements of 3D maser velocities statistically support models in which water maser emission arises from planar
shocks with propagation direction close to the plane of the sky.
Accepted by A&A 635, A118 (2020)
https://arxiv.org/pdf/2002.06871

29

45. The High-Mass Protostellar Population of a Massive Infrared Dark Cloud
Emily Moser1 , Mengyao Liu2 , Jonathan Tan2,3 , Wanggi Lim4 , Yichen Zhang5 and Juan Pablo Farias3
1

Cornell University, Ithaca, NY, USA; 2 University of Virginia, Charlottesville, VA, USA; 3 Chalmers University ofTechnology, Gothenburg, Sweden; 4 SOFIA Science Center, Mountain View, CA, USA; 5 RIKEN, Tokyo, Japan
E-mail contact: emm376 at cornell.edu
We conduct a census of the high-mass protostellar population of the ∼ 70, 000 M⊙ Infrared Dark Cloud (IRDC)
G028.37+00.07, identifying 35 sources based on their 70 µm emission, as reported in the Herschel Hi-GAL catalog ofMolinari et al. (2016). We perform aperture photometry to construct spectral energy distributions (SEDs), which arethen fit with the massive protostar models of Zhang & Tan (2018). We find that the sources span a range of isotropic
luminosities from ∼20 to 4,500 L⊙ . The most luminous sources are predicted to have current protostellar masses ofm∗ ∼ 10 M⊙ forming from cores of mass Mc ∼ 40 to 400 M⊙ . The least luminous sources in our sample are predicted
to be protostars with masses as low as ∼ 0.5 M⊙ forming from cores with Mc ∼ 10 M⊙, which are the minimum values
explored in the protostellar model grid. The detected protostellar population has a total estimated protostellar massof M∗ ∼ 100 M⊙ . Allowing for completeness corrections, which are constrained by comparison with an ALMA study
in part of the cloud, we estimate a star formation efficiency per free-fall time of ∼ 3% in the IRDC. Finally, analyzing
the spatial distribution of the sources, we find relatively low degrees of central concentration of the protostars. The
protostars, including the most massive ones, do not appear to be especially centrally concentrated in the protocluster
as defined by the IRDC boundary.
Accepted by ApJ
http://arxiv.org/pdf/1907.12560

46.

Magnetic Field Structure in Spheroidal Star-Forming Clouds.
Structure from Observed Maps

II. Estimating Field

Philip C. Myers1 , Ian W. Stephens1 , Sayantan Auddy2 , Shantanu Basu3 , Tyler L. Bourke4 and Charles
L. H. Hull5,61

Center for Astrophysics | Harvard and Smithsonian, Cambridge, MA 02138, USA; 2 Institute of Astronomy andAstrophysics, Academia Sinica, Taipei 10617, Taiwan; 3 Department of Physics & Astronomy, University of Western
Ontario, London, ON N6A 3K7, Canada; 4 SKA Organisation, Jodrell Bank, Lower Withington, Macclesfield, Cheshire
SK11 9FT, UK; 5 National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Córdova 3788, Office 61B,
7630422, Vitacura, Santiago, Chile; 6 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
E-mail contact: pmyers at cfa.harvard.edu
This paper presents models to estimate the structure of density and magnetic field strength in spheroidal condensations,from maps of their column density and their polarization of magnetically aligned dust grains. The density model isobtained by fitting a column density map with an embedded p = 2 Plummer spheroid of any aspect ratio and inclination.
The magnetic properties are based on the density model, on the Davis-Chandrasekhar-Fermi (DCF) model of Alfvénic
fluctuations, and on the Spheroid Flux Freezing (SFF) model of mass and flux conservation in Paper I. The fieldstrength model has the resolution of the column density map, which is finer than the resolution of the DCF estimate offield strength. The models are applied to ALMA observations of the envelope of the protostar BHR71 IRS1. Column
density fits give the density model, from (2.0 ± 0.4) × 105 cm−3 to (7 ± 1) × 107 cm−3 . The density model predicts thefield directions map, which fits the polarization map best within 1100 au, with standard deviation of angle differences17◦ . In this region the DCF mean field strength is 0.7±0.2 mG and the envelope mass is supercritical, with ratio ofmass to magnetic critical mass 1.5±0.4. The SFF field strength profile scales with the DCF field strength, from 60±10µG to 4±1 mG. The spatial resolution of the SFF field strength estimate is finer than the DCF resolution by a factor∼ 7, and the peak SFF field strength exceeds the DCF field strength by a factor ∼ 4.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2005.04307

30

47.

Cradle(s) of the Sun
Susanne Pfalzner1,2 and Kirsten Vincke2
1

Research Centre Jülich, Germany; 2 Max-Planck-Institut für Radioastronomy, Bonn, Germany

E-mail contact: s.pfalzner at fz-juelich.de
The Sun likely formed as part of a group of stars. A close stellar flyby by one of the solar siblings is probably
responsible for the sharp outer edge in the solar system‘s mass distribution. The frequency of such close flybys canbe used to determine the likely type of birth environment of the solar system. Young stellar groups develop very
quickly, expanding significantly within just a few Myr. Here we model this strong dynamical development of youngstellar groups and determine the resulting close flyby history. We find that solar system equivalents are predominantly
produced in areas with stellar densities in the range 5 × 104 pc−3 <nlocal < 2 × 105 pc−3 . Remarkably we find that
only two very distinct types of stellar groups can be considered as serious contestants as the cradle of the Sun —high-mass, extended associations (Mc > 20 000 M⊙ ) and intermediate-mass mass, compact clusters (Mc < 3000
M⊙ ). Current day counterparts would be the association NGC 2244 and the M44 cluster, respectively. In these two
types of stellar groups, close flybys take place at a sufficiently high rate, while not being too destructive either. A final
decision between these two remaining options will require incorporation of constraints from cosmo-chemical studies.
Accepted by ApJ
https://arxiv.org/pdf/2005.11260.pdf

48. X-ray irradiation and evaporation of the four young planets around V1298 Tau
K. Poppenhaeger1,2 , L. Ketzer1,2 , and M. Mallonn1
1

Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany; 2 Universität
Potsdam, Institut für Physik und Astronomie, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
E-mail contact: kpoppenhaeger at aip.de
Planets around young stars are thought to undergo atmospheric evaporation due to the high magnetic activity of thehost stars. Here we report on X-ray observations of V1298 Tau, a young star with four transiting exoplanets. We use
X-ray observations of the host star with Chandra and ROSAT to measure the current high-energy irradiation level ofthe planets, and employ a model for the stellar activity evolution together with exoplanetary mass loss to estimate
the possible evolution of the planets. We find that V1298 Tau is X-ray bright with log LX [erg s−1 ] = 30.1 and hasa mean coronal temperature of ≈9 MK. This places the star amongst the more X-ray luminous ones at this stellarage. We estimate the radiation-driven mass loss of the exoplanets, and find that it depends sensitively on the possible
evolutionary spin-down tracks of the star as well as on the current planetary densities. Assuming the planets areof low density due to their youth, we find that the innermost two planets can lose significant parts of their gaseousenvelopes, and could be evaporated down to their rocky cores depending on the stellar spin evolution. However, if
the planets are heavier and follow the mass-radius relation of older planets, then even in the highest XUV irradiation
scenario none of the planets is expected to cross the radius gap into the rocky regime until the system reaches an ageof 5 Gyr.
Accepted by MNRAS
http://arxiv.org/pdf/2005.10240

49. Illuminating a tadpole’s metamorphosis II: observing the on-going transformation with

ALMA

Megan Reiter1 , Andrés E. Guzmán2 , Thomas J. Haworth3 , Pamela D. Klaassen1 , Anna F. McLeod4,5 ,Guido Garay6 and Joseph C. Mottram7
1

UK Astronomy Technology Centre, Blackford Hill, Edinburgh, EH9 3HJ, UK; 2 National Astronomical Observatoryof Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Astronomy Unit, School of Physics and Astronomy, Queen
Mary University of London, London E1 4NS, UK; 4 Department of Astronomy, University of California Berkeley,
Berkeley, CA 94720, USA; 5 Department of Physics and Astronomy, Texas Tech University, PO Box 41051, Lubbock,TX 79409, USA; 6 Departamento de Astronomía, Universidad de Chile, Camino el Observatorio 1515, Las Condes,
31

Santiago, Chile; 7 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
E-mail contact: megan.reiter at stfc.ac.uk
We present new Atacama Large Millimeter/submillimeter Array (ALMA) observations of the tadpole, a small globulein the Carina Nebula that hosts the HH 900 jet+outflow system. Our data include 12 CO, 13 CO, C18 O J=2-1, 13 CO,
C18 O J=3-2, and serendipitous detections of DCN J=3-2 and CS J=7-6. With angular resolution comparable to
the Hubble Space Telescope (HST), our data reveal for the first time the bipolar molecular outflow in CO, seen only
inside the globule, that is launched from the previously unseen jet-driving protostar (the HH 900 YSO). The biconicalmorphology joins smoothly with the externally irradiated outflow seen in ionized gas tracers outside the globule, tracing
the overall morphology of a jet-driven molecular outflow. Continuum emission at the location of the HH 900 YSO
appears to be slightly flattened perpendicular to outflow axis. Model fits to the continuum have a best-fit spectral
index of ∼ 2, suggesting cold dust and the onset of grain growth. In position-velocity space, 13 CO and C18 O gas
kinematics trace a C-shaped morphology, similar to infall profiles seen in other sources, although the global dynamical
behaviour of the gas remains unclear. Line profiles of the CO isotopologues display features consistent with externallyheated gas. We estimate a globule mass of ∼ 1.9 M⊙ , indicating a remaining lifetime of ∼ 4 Myr, assuming a constantphotoevaporation rate. This long globule lifetime will shield the disk from external irradiation perhaps prolonging its
life and enabling planet formation in regions where disks are typically rapidly destroyed.
Accepted by MNRAS
https://arxiv.org/pdf/2005.12920

50. DC3 N observations towards high-mass star-forming regions
V. M. Rivilla1 , L. Colzi1 , F. Fontani1 , M. Melosso2, P. Caselli3 , L. Bizzocchi3 , F. Tamassia4 and L.
Dore2
1

INAF/Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125, Florence, Italy; 2 Dipartimento di Chimica“Giacomo Ciamician”, Università di Bologna, Via F. Selmi 2, 40126 Bologna, Italy; 3 Center for Astrochemical Studies,
Max Planck Institut für extraterrestrische Physik Gießenbachstraße 1, 85748 Garching bei München, Germany; 4 Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale del Risorgimento 4, 40136 Bologna,
ItalyE-mail contact: vmrivilla at gmail.com
We present the study of deuteration of cyanoacetylene (HC3 N) towards a sample of 28 high-mass star-forming cores
divided into different evolutionary stages, from starless to evolved protostellar cores. We report for the first timethe detection of DC3 N towards 15 high-mass cores. The abundance ratios of DC3 N with respect HC3 N range in
the interval 0.003−0.022, lower than those found in low-mas protostars and dark clouds. No significant trend withthe evolutionary stage, or with the kinetic temperature of the region, has been found. We compare the level of
deuteration of HC3 N with those of other molecules towards the same sample, finding weak correlation with species
formed only or predominantly in gas-phase (N2 H+ and HNC, respectively), and no correlation with species formed
only or predominantly on dust grains (CH3 OH and NH3 , respectively). We also present a single-dish map of DC3 N
towards the protocluster IRAS 05358+3543, which shows that DC3 N traces an extended envelope (∼0.37 pc) andpeaks towards two cold condensations separated from the positions of the protostars and the dust continuum. The
observations presented in this work suggest that deuteration of HC3 N is produced in the gas of the cold outer partsof massive star-forming clumps, giving us an estimate of the deuteration factor prior to the formation of denser gas.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/2005.14118

51. A 3D view of the Taurus star-forming region by Gaia and Herschel: multiple populations

related to the filamentary molecular cloudV. Roccatagliata1,2,3 , E. Franciosini2 , G.G. Sacco2 , S. Randich2 and A. Sicilia-Aguilar4
1

Dipartimento di Fisica “Enrico Fermi”, Universita’ di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy; 2 INAF-Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 3 INFN, Sezione di Pisa, Largo Bruno Pontecorvo 3,56127 Pisa, Italy; 4 SUPA, School of Science and Engineering, University of Dundee, Nethergate, DD1 4HN, Dundee,UK32

E-mail contact: veronica.roccatagliata at unipi.it
Context. Taurus represents an ideal region to study the three-dimensional distribution of the young stellar population
and relate it to the associated molecular cloud.
Aims. The second Gaia data release (DR2) enables us to investigate the Taurus complex in three dimensions, startingfrom a previously defined robust membership. The molecular cloud structured in filaments can be traced in emission
using the public far-infrared maps from Herschel.
Methods. From a compiled catalog of spectroscopically confirmed members, we analyze the 283 sources with reliable
parallax and proper motions in the Gaia DR2 archive. We fit the distribution of parallaxes and proper motions withmultiple populations described by multivariate Gaussians. We compute the cartesian Galactic coordinates (X,Y,Z)
and, for the populations associated with the main cloud, also the galactic space velocity (U,V,W). We discuss thespatial distribution of the populations in relation to the structure of the filamentary molecular cloud traced by Herschel.
Results. We discover the presence of six populations which are all well defined in parallax and proper motions, withthe only exception being Taurus D. The derived distances range between 130 and 160 pc. We do not find a uniquerelation between stellar population and the associated molecular cloud: while the stellar population seems to be on thecloud surface, both lying at similar distances, this is not the case when the molecular cloud is structured in filaments.
Taurus B is probably moving in the direction of Taurus A, while Taurus E appears to be moving towards them.
Conclusions. The Taurus region is the result of a complex star formation history which most probably occurred inclumpy and filamentary structures that are evolving independently.
Accepted by A&A
http://arxiv.org/pdf/2005.01331

52. Tracking the evolutionary stage of protostars by the abundances of astrophysical ices
W.R.M. Rocha1,2 and S. Pilling1,31Instituto de Pesquisa & Desenvolvimento (IP&D), Universidade do Vale do Paraíba, Av. Shishima Hifumi 2911,
12244-000, São José dos Campos, SP, Brazil; 2 Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K., Denmark; 3 Departamento de Física, Instituto
Tecnológico de Aeronautica, ITA - DCTA, Vila das Acácias, São José dos Campos, 12228-900, SP-Brazil
E-mail contact: willrobson88 at hotmail.com

The physical evolution of Young Stellar Objects (YSOs) is accompanied by an enrichment of the molecular complexity,
mainly triggered by the heating and energetic processing of the astrophysical ices. In this paper, a study of how theice column density varies across the protostellar evolution has been performed. Tabulated data of H2 O, CO2 , CH3 OH,
HCOOH observed by ground- and space-based telescopes toward 27 early-stage YSOs were taken from the literature.
The observational data shows that ice column density and spectral index (α), used to classify the evolutionary stage, arewell correlated. A 2D continuum radiative transfer simulation containing bare and grains covered by ices at different
levels of cosmic-ray processing were used to calculate the Spectral Energy Distributions (SEDs) in different angle
inclinations between face-on and edge-on configuration. The H2 O:CO2 ice mixture was used to address the H2 O andCO2 column density variation whereas the CH3 OH and HCOOH are a byproduct of the virgin ice after the energetic
processing. The simulated spectra were used to calculate the ice column densities of YSOs in an evolutionary sequence.
As a result, the models show that the ice column density variation of HCOOH with α can be justified by the envelope
dissipation and ice energetic processing. On the other hand, the ice column densities are mostly overestimated in thecases of H2 O, CO2 and CH3 OH, even though the physical and cosmic-ray processing effects are taken into account.
Accepted by ApJ
http://arxiv.org/pdf/2005.07744
1813
12
53. C O, CO, and CO abundances and excitation temperatures in the Orion B molecular

cloud: An analysis of the precision achievable when modeling spectral line within the
Local Thermodynamic Equilibrium approximation
Antoine Roueﬀ1 , Maryvonne Gerin2 , Pierre Gratier3 , François Levrier4 , Jérôme Pety5,2 et al.

1
Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France; 2 LERMA, Observatoire deParis, PSL Research University, CNRS, Sorbonne Universités, 75014 Paris, France 3 Laboratoire d’Astrophysique de33

Bordeaux, Univ. Bordeaux, CNRS, B18N, Allee Geoffroy Saint-Hilaire,33615 Pessac, France; 4 Laboratoire de Physiquede l’Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Sorbonne Paris
Cité, Paris, France 5 IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France.
E-mail contact: antoine.roueff at fresnel.fr
CO isotopologue transitions are routinely observed in molecular clouds to probe the column density of the gas, theelemental ratios of carbon and oxygen, and to trace the kinematics of the environment. We aim at estimating theabundances, excitation temperatures, velocity field and velocity dispersions of the three main CO isotopologues towards
a subset of the Orion B molecular cloud. We use the Cramer Rao Bound (CRB) technique to analyze and estimate
the precision of the physical parameters in the framework of local-thermodynamic-equilibrium excitation and radiativetransfer with an additive white Gaussian noise. We propose a maximum likelihood estimator to infer the physicalconditions from the 1–0 and 2–1 transitions of CO isotopologues. Simulations show that this estimator is unbiased andefficient for a common range of excitation temperatures and column densities (Tex > 6 K, N > 1×1014 –1×1015 cm−2 ).
Contrary to the general assumptions, the different CO isotopologues have distinct excitation temperatures, and theline intensity ratios between different isotopologues do not accurately reflect the column density ratios. We find mean
fractional abundances that are consistent with previous determinations towards other molecular clouds. However,significant local deviations are inferred, not only in regions exposed to UV radiation field but also in shielded regions.
These deviations result from the competition between selective photodissociation, chemical fractionation, and depletionon grain surfaces. We observe that the velocity dispersion of the C18 O emission is 10% smaller than that of 13 CO. The
substantial gain resulting from the simultaneous analysis of two different rotational transitions of the same species isrigorously quantified. The CRB technique is a promising avenue for analyzing the estimation of physical parametersfrom the fit of spectral lines.
Accepted by A&A
http://arxiv.org/pdf/2005.08317

54. Erosion of planetesimals by gas flow
Noemi Schaﬀer1 , Anders Johansen1 , Lukas Cedenblad2 , Bernhard Mehling3, and Dhrubaditya Mitra2
1

Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden;
NORDITA, Stockholm, Roslagstullsbacken 23 106 91 Stockholm, Sweden; 3 Department of Physics , Gothenburg
University, SE-41296 Gothenburg, Sweden

2

E-mail contact: noemi.schaffer at astro.lu.se
The first stages of planet formation take place in protoplanetary disks that are largely made up of gas. Understanding
how the gas affects planetesimals in the protoplanetary disk is therefore essential. In this paper, we discuss whether or
not gas flow can erode planetesimals. We estimate how much shear stress is exerted onto the planetesimal surface by
the gas as a function of disk and planetesimal properties. To determine whether erosion can take place, we compare thiswith previous measurements of the critical stress that a pebble-pile planetesimal can withstand before erosion begins.
If erosion takes place, we estimate the erosion time of the affected planetesimals. We also illustrate our estimates with
two-dimensional numerical simulations of flows around planetesimals using the lattice Boltzmann method. We findthat the wall shear stress can overcome the critical stress of planetesimals in an eccentric orbit within the innermost
regions of the disk. The high eccentricities needed to reach erosive stresses could be the result of shepherding by
migrating planets. We also find that if a planetesimal erodes, it does so on short timescales. For planetesimals residing
outside of 1 au, we find that they are mainly safe from erosion, even in the case of highly eccentric orbits.
Accepted by A&A
http://arxiv.org/pdf/2005.07951

55. Gaia 18dvy: a new FUor in the Cygnus OB3 association
E. Szegedi-Elek1 , P. Ábrahám1,2 , Ł. Wyrzykowski3 , M. Kun1 , Á. Kóspál1,4,2 , L. Chen1 , G. Marton1,2 ,A. Moór1,2 , Cs. Kiss1,2 , A. Pál1,5,2 , L. Szabados1 , J. Varga6,1 , E. Varga-Verebélyi1 , C. Andreas7 , E.
Bachelet8 , R. Bischoﬀ7 , A. Bódi1,2,9 , E. Breedt10 , U. Burgaz11,12 , T. Butterley13 , J. M. Carrasco14 , V.
Cepas15 , G. Damljanovic16 , I. Gezer3 , V. Godunova17 , M. Gromadzki3 , A. Gurgul3 , L. Hardy18 , F.
Hildebrandt7 , S. Hoﬀmann7 , M. Hundertmark19 , N. Ihanec3 , R. Janulis15 , Cs. Kalup1 , Z. Kaczmarek3 ,34

R. Könyves-Tóth1 , M. Krezinger1 , K. Kruszyńska3 , S. Littlefair18 , M. Maskoliūnas15 , L. Mészáros1 , P.
Mikołajczyk20 , M. Mugrauer7 , H. Netzel21 , A. Ordasi1 , E. Pakstienė15 , K. A. Rybicki3 , K. Sárneczky1 ,B. Seli1 , A. Simon22 , K. Siskauskaitė15, Á. Sódor1 , K. V. Sokolovsky23,24,25 , W. Stenglein7 , R. Street8 ,R. Szakáts1 , L. Tomasella26 , Y. Tsapras19 , K. Vida1,2 , J. Zdanavicius15 , M. Zieliński3, P. Zieliński3 andO. Ziółkowska3
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege út
15–17, Hungary; 2 ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest,
Hungary; 3 Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland; 4 Max
Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 5 Department of Astronomy, Loránd
Eötvös University, Pázmány P. sétány. 1/A, H-1117 Budapest, Hungary; 6 Leiden Observatory, Leiden University,
PO Box 9513, NL2300, RA Leiden, The Netherlands; 7 Astrophysikalisches Institut und Universitäts-Sternwarte, FSU
Jena, Schillergäßchen 2-3, D-07745 Jena, Germany; 8 Las Cumbres Observatory, 6740 Cortona Drive, Suite 102,93117
Goleta, CA, USA; 9 MTA CSFK Lendület Near-Field Cosmology Research Group, Konkoly Thege Miklós út 1517, H-1121 Budapest, Hungary; 10 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge,
CB3 0HA, UK; 11 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 6068502, Japan; 12 Department of Astronomy and Space Sciences, Ege University, 35100, Izmir, Turkey; 13 Centre forAdvanced Instrumentation, Durham University, UK; 14 Dept. Física Quàntica i Astrofísica, Institut de Ciències delCosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Martí Franquès 1, E08028 Barcelona, Spain 15 Institute ofTheoretical Physics and Astronomy, Vilnius University, Saulėtekio av. 3, 10257 Vilnius, Lithuania; 16 Astronomical
Observatory, Volgina 7, 11060 Belgrade, Serbia; 17 ICAMER Observatory, NAS of Ukraine, 27 Acad. Zabolotnoho
Str., 03143, Kyiv, Ukraine; 18 Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, United
Kingdom; 19 Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 1214, 69120 Heidelberg, Germany; 20 Astronomical Institute, University of Wrocław, ul. Kopernika 11, 51-622 Wrocław,
Poland; 21 Nicolaus Copernicus Centre of Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warszawa, Poland; 22
Taras Shevchenko National University of Kyiv, Glushkova ave., 4, 03127, Kyiv, Ukraine; 23 Department of Physics
and Astronomy, Michigan State University, 567 Wilson Rd, East Lansing, MI 48824, USA; 24 Sternberg AstronomicalInstitute, Moscow State University, Universitetskii pr. 13, 119992 Moscow, Russia; 25 Astro Space Center of Lebedev
Physical Institute, Profsoyuznaya St. 84/32, 117997 Moscow, Russia; 26 INAF Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5, 35122 Padova, Italy
E-mail contact: elek.elza at csfk.mta.hu
We present optical-infrared photometric and spectroscopic observations of Gaia 18dvy, located in the Cygnus OB3
association at a distance of 1.88 kpc. The object was noted by the Gaia alerts system when its lightcurve exhibiteda >∼4 mag rise in 2018-2019. The brightening was also observable at mid-infared wavelengths. The infrared colors
of Gaia 18dvy became bluer as the outburst progressed. Its optical and near-infrared spectroscopic characteristics inthe outburst phase are consistent with those of bona fide FU Orionis-type young eruptive stars. The progenitor of
the outburst is probably a low-mass K-type star with an optical extinction of ∼3 mag. A radiative transfer modelingof the circumstellar structure, based on the quiescent spectral energy distribution, indicates a disk with a mass of
4×10−3 M⊙ . Our simple accretion disk modeling implies that the accretion rate had been exponentially increasing for
more than 3 years until mid-2019, when it reached a peak value of 6.9 × 10−6 M⊙ yr−1 . In many respects, Gaia 18dvy
is similar to the FU Ori-type object HBC 722.
Accepted by ApJ
http://arxiv.org/pdf/2005.11537

56. Chemical composition in the IRAS 16562–3959 high-mass star-forming region
Kotomi Taniguchi1 , Andrés E. Guzmán2 , Liton Majumdar3 , Masao Saito2,4 and Kazuki Tokuda2,51

Department of Physics, Faculty of Science, Gakushuin University, Mejiro, Toshima, Tokyo 171-8588, Japan; 2National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences, Osawa, Mitaka, Tokyo
181-8588, Japan; 3 School of Earth and Planetary Sciences, National Institute of Science Education and Research,
HBNI, Jatni 752050, Odisha, India; 4 Department of Astronomical Science, School of Physical Science, SOKENDAI(The Graduate University for Advanced Studies), Osawa, Mitaka, Tokyo 181-8588, Japan; 5 Department of PhysicalScience, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531,
Japan
35

E-mail contact: kotomi.taniguchi at gakushuin.ac.jp
We have analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) cycle 2 data of band 6 toward theG345.4938+01.4677 massive young protostellar object (G345.5+1.47 MYSO) in the IRAS 16562–3959 high-mass starforming region with an angular resolution of ∼ 0.3 arcsec, corresponding to ∼ 760 au. We spatially resolve the central
region which consists of three prominent molecular emission cores. A hypercompact (HC) HII region (Core A) and twomolecule-rich cores (Core B and Core C) are identified using the moment zero images of the H30α line and a CH3 OH
line, respectively. Various oxygen-bearing complex organic molecules (COMs), such as (CH3 )2 CO and CH3 OCHO,
have been detected toward the positions of Core B and Core C, while nitrogen-bearing species, CH3 CN, HC3 N and
its 13 C isotopologues, have been detected toward all of the cores. We discuss the formation mechanisms of H2 CO
by comparing the spatial distribution of C18 O with that of H2 CO. The 33 SO emission, on the other hand, shows aring-like structure surrounding Core A, and it peaks on the outer edge of the H30α emission region. These results
imply that SO is enhanced in a shock produced by the expanding motion of the ionized region.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2006.01995

57. Observed sizes of planet-forming disks trace viscous evolution
Leon Trapman1 , Giovanni Rosotti1 , Arthur D. Bosman1,2 , Michiel R. Hogerheijde1,3 and Ewine F. van
Dishoeck1,4
1

Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, The Netherlands; 2 Department of
Astronomy, University of Michigan, 1085 S. University Ave, Ann Arbor, MI 48109; 3 Anton Pannekoek Institutefor Astronomy, University of Amsterdam, Science Park 904, 1090 GE Amsterdam, The Netherlands; 4 Max-Planckinstitute für Extraterrestrische Physik, Giessenbachstraße, D-85748 Garching, Germany
E-mail contact: trapman at strw.leidenuniv.nl
The evolution of protoplanetary disks is dominated by the conservation of angular momentum, where the accretionof material onto the central star is driven by viscous expansion of the outer disk or by disk winds extracting angularmomentum without changing the disk size. Studying the time evolution of disk sizes allows us therefore to distinguishbetween viscous stresses or disk winds as the main mechanism of disk evolution. Observationally, estimates of thedisk gaseous outer radius are based on the extent of the CO rotational emission, which, during the evolution, is also
affected by the changing physical and chemical conditions in the disk. We use physical-chemical DALI models to
study how the extent of the CO emission changes with time in a viscously expanding disk and investigate to what
degree this observable gas outer radius is a suitable tracer of viscous spreading and whether current observations are
consistent with viscous evolution. We find that the gas outer radius (RCO, 90% ) measured from our models matches
the expectations of a viscously spreading disk: RCO, 90% increases with time and for a given time RCO, 90% is larger
for a disk with a higher viscosity αvisc . However, in the extreme case where the disk mass is low (less than 10−4 M⊙ )and αvisc is high (larger than 10−2 ), RCO, 90% will instead decrease with time as a result of CO photodissociationin the outer disk. For most disk ages RCO, 90% is up to 12× larger than the characteristic size Rc of the disk, and
RCO, 90% /Rc is largest for the most massive disk. As a result of this difference, a simple conversion of RCO, 90% toαvisc will overestimate the true αvisc of the disk by up to an order of magnitude. We find that most observed gas
outer radii in Lupus can be explained using a viscously evolving disk that starts out small (Rc = 10 AU) and has a
low viscosity (αvisc = 10−4 − 10−3 ).
Accepted by A&A
https://arxiv.org/pdf/2005.11330.pdf

58. Complex organic molecules in low-mass protostars on solar system scales – I. Oxygen-bearing species

M. L. van Gelder1 , B. Tabone1 , Ł. Tychoniec1 , E. F. van Dishoeck1,2 , H. Beuther3 , A. C. A. Boogert4 ,A. Caratti o Garatti5 , P. D. Klaassen6 , H. Linnartz7 , H. S. P. Müller8 and V. Taquet9
1
Leiden Observatory, Leiden University, PO Box 9513, 2300RA Leiden, The Netherlands; 2 Max Planck Institut
für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany; 3 Max Planck Institute for
Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 4 Institute for Astronomy, University of Hawaii at Manoa,

362680 Woodlawn Drive, Honolulu, HI 96822, USA; 5 Dublin Institute for Advanced Studies, School of Cosmic Physics,
Astronomy and Astrophysics Section, 31 Fitzwilliam Place, D04C932 Dublin 2, Ireland; 6 UK Astronomy Technology
Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK; 7 Laboratory for Astrophysics,
Leiden Observatory, Leiden University, PO Box 9531, 2300RA Leiden, The Netherlands; 8 I. Physikalisches Institut,
Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany37 Köln, Germany; 9 INAF, Osservatorio Astrofisico di
Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
E-mail contact: vgelder at strw.leidenuniv.nl
Context. Complex organic molecules (COMs) are thought to form on icy dust grains in the earliest phase of starformation. The evolution of these COMs from the youngest Class 0/I protostellar phases toward the more evolved
Class II phase is still not fully understood. Since planet formation seems to start early, and mature disks are too cold
for characteristic COM emission lines, studying the inventory of COMs on solar system scales in the Class 0/I stage
is relevant.
Aims. The aim is to determine the abundance ratios of oxygen-bearing COMs in Class 0 protostellar systems on scalesof ∼100 AU radius. These abundances will be inter-compared, and contrasted to other low-mass protostars such as
IRAS16293-2422B and HH 212. Additionally, using both cold and hot COM lines, the gas-phase abundances can betracked from a cold to a hot component, and ultimately be compared with those in ices to be measured with the James
Webb Space Telescope (JWST). The abundance of deuterated methanol allows us to probe the ambient temperatureduring the formation of this species.
Methods. ALMA Band 3 (3 mm) and Band 6 (1 mm) observations are obtained of seven Class 0 protostars in
the Perseus and Serpens star-forming regions. By modeling the inner protostellar region using ’LTE’ models, theexcitation temperature and column densities are determined for several O-bearing COMs including methanol (CH3 OH),
acetaldehyde (CH3 CHO), methyl formate (CH3 OCHO), and dimethyl ether (CH3 OCH3 ). Abundance ratios are takenwith respect to CH3 OH.
Results. B1-c and B1-bS (both Perseus) and Serpens S68N (Serpens) show COM emission, i.e., three out of the seven of
the observed sources. No clear correlation seems to exist between the occurrence of COMs and source luminosity. The
abundances of several COMs such as CH3 OCHO, CH3 OCH3 , acetone (CH3 COCH3 ), and ethylene glycol ((CH2 OH)2 )are remarkably similar for the three COM-rich sources, and to IRAS 16293-2422B and HH 212, even though thesesources originate from four different star-forming regions (i.e., Perseus, Serpens, Ophiuchus, Orion). For other COMs
like CH3 CHO, ethanol (CH3 CH2 OH), and glycolaldehyde (CH2 OHCHO), the abundances differ by up to an orderof magnitude, indicating that local source conditions are case determining. B1-c hosts a cold (Tex ≈ 60 K), more
extended component of COM emission with a column density of typically a few % of the warm/hot (Tex ∼ 200 K),
central component. A D/H ratio of 1–3 % is derived for B1-c, S68N, and B1-bS based on the CH2 DOH/CH3 OH ratio(taking into account statistical weighting) suggesting a temperature of ∼15 K during the formation of methanol. Thisratio is consistent with other low-mass protostars, but lower than for high-mass star-forming regions.
Conclusions. The abundance ratios of most O-bearing COMs are roughly fixed between different star-forming regions,and are presumably set at an earlier cold prestellar phase. For several COMs, local source properties become important.
Future mid-infrared facilities such as JWST/MIRI will be essential to directly observe COM ices. Combining thiswith a larger sample of COM-rich sources with ALMA will allow for directly linking ice and gas-phase abundances inorder to constrain the routes that produce and maintain chemical complexity during the star formation process.
Accepted by A&A
https://arxiv.org/pdf/2005.06784

59. Is the gap in the DS Tau disc hiding a planet?
Benedetta Veronesi1,4 , Enrico Ragusa2 , Giuseppe Lodato1,4 , Hossam Aly1,3 , Christophe Pinte4,5 et al.
1

Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria, 16, Milano, I-20133, Italy; 2 School of Physics
and Astronomy, University of Leicester, Leicester, United Kingdom; 3 Univ Lyon, Univ Claude Bernard Lyon 1, Ens
de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, France; 4 Schoolof Physics and Astronomy, Monash University, Vic 3800, Australia; 5 Univ. Grenoble Alpes, CNRS, IPAG, F-38000
Grenoble, France
E-mail contact: benedetta.veronesi at unimi.it
Recent mm-wavelength surveys performed with the Atacama Large Millimeter Array (ALMA) have revealed pro-37

toplanetary discs characterized by rings and gaps. A possible explanation for the origin of such rings is the tidal
interaction with an unseen planetary companion. The protoplanetary disc around DS Tau shows a wide gap in the
ALMA observation at 1.3 mm. We construct a hydrodynamical model for the dust continuum observed by ALMA
assuming the observed gap is carved by a planet between one and five Jupiter masses. We fit the shape of the radialintensity profile along the disc major axis varying the planet mass, the dust disc mass, and the evolution time of thesystem. The best fitting model is obtained for a planet with Mp = 3.5 MJup and a disc with Mdust = 9.6 × 10−5 M⊙ .
Starting from this result, we also compute the expected signature of the planet in the gas kinematics, as traced by COemission. We find that such a signature (in the form of a “kink” in the channel maps) could be observed by ALMA
with a velocity resolution between 0.2–0.5 km s−1 and a beam size between 30 and 50 mas.
Accepted by MNRAS
http://arxiv.org/pdf/2005.04244

60. Catalogue of new Herbig Ae/Be and classical Be stars. A machine learning approach

to Gaia DR2

M. Vioque1,2 , R.D. Oudmaijer1 , M. Schreiner3 , I. Mendigutía4, D. Baines5 et al.
1

School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK; 2 Ingeniería de Sistemas para la Defensa
de España (Isdefe), XMM/Newton Science Operations Centre, ESA-ESAC Campus, PO Box 78, 28691 Villanueva dela Cañada, Madrid, Spain; 3 Desupervised, Desupervised ApS, Njalsgade 76, 2300 Copenhagen, Denmark; 4 Centrode Astrobiología (CSIC-INTA), Departamento de Astrofísica, ESA-ESAC Campus, PO Box 78, 28691 Villanueva dela Cañada, Madrid, Spain; 5 Quasar Science Resources for ESA-ESAC, ESAC Science Data Centre, PO Box 78, 28691
Villanueva de la Cañada, Madrid, Spain
E-mail contact: pymvdl at leeds.ac.uk
The intermediate-mass pre-main sequence Herbig Ae/Be stars are key to understanding the differences in formation
mechanisms between low- and high-mass stars. The study of the general properties of these objects is hamperedby the fact that few and mostly serendipitously discovered sources are known. Our goal is to identify new Herbig
Ae/Be candidates to create a homogeneous and well defined catalogue of these objects. We have applied machinelearning techniques to 4,150,983 sources with data from Gaia DR2, 2MASS, WISE, and IPHAS or VPHAS+. Several
observables were chosen to identify new Herbig Ae/Be candidates based on our current knowledge of this class, which
is characterised by infrared excesses, photometric variabilities, and Hα emission lines. Classical techniques are notefficient for identifying new Herbig Ae/Be stars mainly because of their similarity with classical Be stars, with which
they share many characteristics. By focusing on disentangling these two types of objects, our algorithm has also
identified new classical Be stars. We have obtained a large catalogue of 8470 new pre-main sequence candidates andanother catalogue of 693 new classical Be candidates with a completeness of 78.8±1.4% and 85.5±1.2%, respectively.
Of the catalogue of pre-main sequence candidates, at least 1361 sources are potentially new Herbig Ae/Be candidates
according to their position in the Hertzsprung-Russell diagram. In this study we present the methodology used,evaluate the quality of the catalogues, and perform an analysis of their flaws and biases. For this assessment, we makeuse of observables that have not been accounted for by the algorithm and hence are selection-independent, such as
coordinates and parallax based distances. The catalogue of new Herbig Ae/Be stars that we present here increases
the number of known objects of the class by an order of magnitude.
Accepted by A&A
http://arxiv.org/pdf/2005.01727

61. Thermal evolution of protoplanetary disks: from β-cooling to decoupled gas and dust

temperatures

Eduard Vorobyov1 , Ryoki Matsukoba2 , Kazuyuki Omukai2 and Manuel Guedel1
1
University of Vienna, Department of Astrophysics, Vienna, 1180, Austria; 2 Astronomical Institute, Graduate Schoolof Science, Tohoku University, Aoba, Sendai, Miyagi 980-8578, Japan

E-mail contact: eduard.vorobiev at univie.ac.at
We explore the long-term evolution of young protoplanetary disks with different approaches to computing the thermal
structure determined by various cooling and heating processes in the disk and its surroundings. Numerical hydro38

dynamics simulations in the thin-disk limit were complemented with three thermal evolution schemes: a simplified
β-cooling approach with and without irradiation, where the rate of disk cooling is proportional to the local dynamical
time; a fiducial model with equal dust and gas temperatures calculated taking viscous heating, irradiation, and radiative cooling into account; and a more sophisticated approach allowing decoupled dust and gas temperatures. We
found that the gas temperature may significantly exceed that of dust in the outer regions of young disks thanks toadditional compressional heating caused by the infalling envelope material in the early stages of disk evolution andslow collisional exchange of energy between gas and dust in low-density disk regions. However, the outer envelope
shows an inverse trend, with the gas temperatures dropping below that of dust. The global disk evolution is only
weakly sensitive to temperature decoupling. Nevertheless, separate dust and gas temperatures may affect the chemicalcomposition, dust evolution, and disk mass estimates. Constant-β models without stellar and background irradiation
fail to reproduce the disk evolution with more sophisticated thermal schemes because of the intrinsically variable natureof the β-parameter. Constant-β models with irradiation more closely match the dynamical and thermal evolution, but
the agreement is still incomplete. Models allowing separate dust and gas temperatures are needed when emphasis isplaced on the chemical or dust evolution in protoplanetary disks, particularly in subsolar metallicity environments.
Accepted by Astronomy & Astrophysics

62.

A Study of Millimeter Variability in FUor Objects
John Wendeborn1 , Catherine C. Espaillat1 , Enrique Macias1,2 , Orsolya Feher3 , Agnes Kospal4,5 , Lee
Hartmann6 , Zhaohuan Zhu7 , Michael M. Dunham8 and Marina Kounkel91

Department of Astronomy & Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue,
Boston MA, 02215, USA; 2 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago 763-0355, Chile;
3
IRAM, 300 Rue de la Piscine, 38046 Saint Martin d’Heres, France; 4 Konkoly Observatory, Research Centre for
Astronomy and Earth Sciences, Konkoly-Thege Miklos ut 15-17, 1121 Budapest, Hungary; 5 Max Planck Institutefor Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany; 6 Department of Astronomy, University of Michigan, 500
Church Street, Ann Arbor MI, 41809, USA; 7 Department of Physics and Astronomy, University of Nevada, Las
Vegas, 4505 South Maryland Parkway, Las Vegas NV, 89154, USA; 8 Department of Physics, State University of New
York at Fredonia, 280 Central Avenue, Fredonia NY, 14063, USA; 9 Department of Physics and Astronomy, Western
Washington University, 516 High Street, Bellingham, WA 98225, USA
E-mail contact: wendebo2 at bu.edu
FU Orionis objects (FUors) are rapidly-accreting, pre-main sequence objects that are known to exhibit large outbursts
at optical and near-infrared wavelengths, with post-eruption, small-scale photometric variability superimposed on
longer-term trends. In contrast, little is known about the variability of FUors at longer wavelengths. To explore thisfurther, we observed six FUor objects using the NOrthern Extended Millimeter Array (NOEMA) and for a subsetof three objects we obtained coordinated observations with NOEMA and the Lowell Discovery Telescope (LDT). In
combination with previously published NOEMA observations from 2014, our 2017 observations of V1735 Cyg provide
the first detection of variability in an FUor object at 2.7 mm. In the absence of significant optical variability, we
discount the possibility that the mm flux density changed as a result of irradiation from the central disk. In addition,a change in the dust mass due to infall is highly unlikely. A plausible explanation for the change in 2.7 mm flux density
is variability in free-free emission due to changes in the object’s jet/wind. Thus, it may be that free-free emission
in some FUor objects is significant at ∼3 mm and must be considered when deriving disk masses in order to help
constrain the mechanism responsible for triggering FUor outbursts.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2005.10371.pdf

63. Non-ideal magnetohydrodynamics vs turbulence I: Which is the dominant process inprotostellar disc formation?

James Wurster1,2 and Benjamin T. Lewis3
1

Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North
Haugh, St Andrews, Fife KY16 9SS, UK; 2 School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter
EX4 4QL, UK; 3 School of Physics and Astronomy, Rochester Institute of Technology, Rochester N.Y. 14623, U.S.A.
39

E-mail contact: jhw5 at st-andrews.ac.uk
Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate the effect of magnetic fields (ideal
and non-ideal) and turbulence (sub- and transsonic) on the formation of circumstellar discs that form nearly simultaneously with the formation of the protostar. This is done by modelling the gravitational collapse of a 1 M⊙ gas
cloud that is threaded with a magnetic field and imposed with both rotational and turbulent velocities. We investigate
magnetic fields that are parallel/anti-parallel and perpendicular to the rotation axis, two rotation rates and four Mach
numbers. Disc formation occurs preferentially in the models that include non-ideal MHD where the magnetic field
is anti-parallel or perpendicular to the rotation axis. This is independent of the initial rotation rate and level of
turbulence, suggesting that subsonic turbulence plays a minimal role in influencing the formation of discs. Aside fromfirst core outflows which are influenced by the initial level of turbulence, non-ideal MHD processes are more important
than turbulent processes during the formation of discs around low-mass stars.
Accepted by MNRAS
http://arxiv.org/pdf/2005.05345

64. Non-ideal magnetohydrodynamics vs turbulence II: Which is the dominant process instellar core formation?

James Wurster1,2 and Benjamin T. Lewis3
1

Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North
Haugh, St Andrews, Fife KY16 9SS, UK; 2 School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter
EX4 4QL, UK; 3 School of Physics and Astronomy, Rochester Institute of Technology, Rochester N.Y. 14623, U.S.A.
E-mail contact: jhw5 at st-andrews.ac.uk
Non-ideal magnetohydrodynamics (MHD) is the dominant process. We investigate the effect of magnetic fields (ideal
and non-ideal) and turbulence (sub- and transsonic) on the formation of protostars by following the gravitational
collapse of 1 M⊙ gas clouds through the first hydrostatic core to stellar densities. The clouds are imposed with bothrotational and turbulent velocities, and are threaded with a magnetic field that is parallel/anti-parallel or perpendicular
to the rotation axis; we investigate two rotation rates and four Mach numbers. The initial radius and mass of thestellar core are only weakly dependent on the initial parameters. In the models that include ideal MHD, the magnetic
field strength implanted in the protostar at birth is much higher than observed, independent of the initial level of
turbulence; only non-ideal MHD can reduce this strength to near or below the observed levels. This suggests that
not only is ideal MHD an incomplete picture of star formation, but that the magnetic fields in low mass stars are
implanted later in life by a dynamo process. Non-ideal MHD suppresses magnetically launched stellar core outflows,
but turbulence permits thermally launched outflows to form a few years after stellar core formation.
Accepted by MNRAS

http://arxiv.org/pdf/2005.05348

65.

The role of Galactic H ii regions in the formation of filaments
High-resolution submilimeter imaging of RCW 120 with ArTéMiS
A. Zavagno1,2 , Ph. André3 , F. Schuller3,4 , N. Peretto5 , Y. Shimajiri3,6 , D. Arzoumanian7 , T. Csengeri8 ,M. Figueira9 , G.A. Fuller10 , V. Konyves11 , A. Men’shchikov3 , P. Palmeirim7 , H. Roussel12 , D. Russeil1,
N. Schneider8,13 and S. Zhang1
1

Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France; 2 Institut Universitaire de France, France; 3 Laboratoired’Astrophysique (AIM), CEA/DRF, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris-Cité,
91191 Gif-sur-Yvette, France; 4 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam,
Germany; 5 School of Physics & Astronomy, Cardiff University, Cardiff CF24 3AA, UK; 6 Department of Physics
and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima,
Kagoshima 890-0065, Japan; 7 Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das
Estrelas, PT4150-762 Porto, Portugal; 8 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N,
allée Geoffroy Saint-Hilaire, 33615 Pessac, France; 9 National Centre for Nuclear Research, Ul. Pasteura 7, 02-093,
Warsaw, Poland; 10 Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of40

Manchester, Oxford Road, Manchester M13 9PL, UK; 11 Jeremiah Horrocks Institute, University of Central Lancashire,
Preston PR1 2HE, UK; 12 Institut d’Astrophysique de Paris, Sorbonne Université, CNRS (UMR7095), 75014 Paris,
France; 13 I. Physik. Institut, University of Cologne, 50937, Cologne, Germany; 14 Aix Marseille Univ, CNRS, CNES,
LAM, Marseille, France; 15 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy
Saint-Hilaire, 33615 Pessac, France; 16 Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
E-mail contact: annie.zavagno at lam.fr
Massive stars and their associated ionized (H ii) regions could play a key role in the formation and evolution of filamentsthat host star formation. However, the properties of filaments that interact with H ii regions are still poorly known.
To investigate the impact of H ii regions on the formation of filaments, we imaged the Galactic H ii region RCW 120
and its surroundings where active star formation takes place and where the role of ionization feedback on the starformation process has already been studied.
We used the large-format bolometer camera ArTéMiS on the APEX telescope and combined the high-resolution
ArTéMiS data at 350 µm and 450 µm with Herschel -SPIRE/HOBYS data at 350 and 500 µm to ensure good sensitivity
to a broad range of spatial scales. This allowed us to study the dense gas distribution around RCW 120 with a resolutionof 8 arcsec or 0.05 pc at a distance of 1.34 kpc.
Our study allows us to trace the median radial intensity profile of the dense shell of RCW 120. This profile isasymmetric, indicating a clear compression from the H ii region on the inner part of the shell. The profile is observed
to be similarly asymmetric on both lateral sides of the shell, indicating a homogeneous compression over the surface.
On the contrary, the profile analysis of a radial filament associated with the shell, but located outside of it, reveals asymmetric profile, suggesting that the compression from the ionized region is limited to the dense shell. The mean
intensity profile of the internal part of the shell is well fitted by a Plummer-like profile with a deconvolved Gaussian
full width at half maximum (FWHM) of 0.09 pc, as observed for filaments in low-mass star-forming regions.
Using ArTéMiS data combined with Herschel-SPIRE data, we found evidence for compression from the inner partof the RCW 120 ionized region on the surrounding dense shell. This compression is accompanied with a significant(factor 5) increase of the local column density. This study suggests that compression exerted by H ii regions may playa key role in the formation of filaments and may further act on their hosted star formation. ArTéMiS data also suggestthat RCW 120 might be a 3D ring, rather than a spherical structure.
Accepted by Astronomy and Astrophysics
http://arxiv.org/pdf/2004.05604

41

Abstracts of recently accepted major reviews

Star clusters near and far; tracing star formation across cosmic time
Angela Adamo1 , Peter Zeidler2 , J. M. Diederik Kruijssen3 , Mélanie Chevance3 , Mark Gieles4,5 et al.
1

Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre, SE-106 91
Stockholm, Sweden; 2 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USASpace Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD-21218, USA; 3 Astronomisches RechenInstitut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany; 4Institut de Ciències del Cosmos (ICCUB-IEEC), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain;
5
ICREA, Pg. Lluis Companys 23, 08010 Barcelona, Spain
E-mail contact: adamo at astro.su.se
Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In thisreview, we will first focus on their constituents, i.e. detailed insight into their stellar populations and their surrounding
ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations
at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At
high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe
the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how
numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe,
are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation
and assembly that is carried by globular cluster populations.
Accepted by Space Science Reviews
http://arxiv.org/pdf/2005.06188

Physical Processes in Star Formation
Philipp Girichidis1 , Stella S.R. Oﬀner2 , Alexei G. Kritsuk3 , Ralf S. Klessen4, Patrick Hennebelle5,6 etal.
1Leibniz-Institut für Astrophysik (AIP) - Potsdam, Germany; 2 The University of Texas at Austin - Austin TX, USA;
University of California, San Diego; La Jolla, California, 92093-0424, USA; 4 Universität Heidelberg, Zentrum fürAstronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 5 Laboratoire
AIM, Paris-Saclay, CEA/IRFU/SAp CNRS Université Paris Diderot, 91191 Gif-sur-Yvette Cedex, France; 6 LERMA(UMR CNRS 8112), Ecole Normale Supérieure, 75231 Paris Cedex, France

3

E-mail contact: philipp at girichidis.com
Star formation is a complex multi-scale phenomenon that is of significant importance for astrophysics in general. Stars
and star formation are key pillars in observational astronomy from local star forming regions in the Milky Way up to
high-redshift galaxies. From a theoretical perspective, star formation and feedback processes (radiation, winds, andsupernovae) play a pivotal role in advancing our understanding of the physical processes at work, both individuallyand of their interactions. In this review we will give an overview of the main processes that are important for theunderstanding of star formation. We start with an observationally motivated view on star formation from a global
perspective and outline the general paradigm of the life-cycle of molecular clouds, in which star formation is the key
process to close the cycle. After that we focus on the thermal and chemical aspects in star forming regions, discussturbulence and magnetic fields as well as gravitational forces. Finally, we review the most important stellar feedback
mechanisms.
Accepted by Space Science Reviews
http://arxiv.org/pdf/2005.06472

42

The Physics of Star Cluster Formation and Evolution
Martin G.H. Krause1 , Stella S.R. Oﬀner2 , Corinne Charbonnel3 , Mark Gieles4,5, Ralf S. Klessen6 et al.
1

Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire,College Lane, Hatfield, Hertfordshire AL10 9AB, UK; 2 Department of Astronomy, The University of Texas, Austin
TX, 78712, U.S.A.; 3 Department of Astronomy, University of Geneva, Chemin de Pegase 51, 1290 Versoix, Switzerland;
IRAP, CNRS & Univ. of Toulouse, 14, av.E.Belin, 31400 Toulouse, France; 4 Institut de Ciències del Cosmos (ICCUBIEEC), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain; 5 ICREA, Pg. Lluis Companys 23,
08010 Barcelona, Spain; 6 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik,
Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
E-mail contact: M.G.H.Krause at herts.ac.uk
Star clusters form in dense, hierarchically collapsing gas clouds. Bulk kinetic energy is transformed to turbulence withstars forming from cores fed by filaments. In the most compact regions, stellar feedback is least effective in removing
the gas and stars may form very efficiently. These are also the regions where, in high-mass clusters, ejecta from somekind of high-mass stars are effectively captured during the formation phase of some of the low mass stars and effectively
channeled into the latter to form multiple populations. Star formation epochs in star clusters are generally set by gas
flows that determine the abundance of gas in the cluster. We argue that there is likely only one star formation epoch
after which clusters remain essentially clear of gas by cluster winds. Collisional dynamics is important in this phaseleading to core collapse, expansion and eventual dispersion of every cluster. We review recent developments in thefield with a focus on theoretical work.
Accepted by Space Science Reviews Topical collection “Star formation”
http://arxiv.org/pdf/2005.00801

On the Mass Accretion Rates of Herbig Ae/Be Stars. Magnetospheric Accretion or
Boundary Layer?
I. Mendigutía1
1

Centro de Astrobiología (CSIC-INTA), Departamento de Astrofísica, ESA-ESAC Campus, 28691 Madrid, Spain

E-mail contact: imendigutia at cab.inta-csic.es
Understanding how young stars gain their masses through disk-to-star accretion is of paramount importance in astrophysics. It affects our knowledge about the early stellar evolution, the disk lifetime and dissipation processes, theway the planets form on the smallest scales, or the connection to macroscopic parameters characterizing star-forming
regions on the largest ones, among others. In turn, mass accretion rate estimates depend on the accretion paradigm assumed. For low-mass T Tauri stars with strong magnetic fields there is consensus that magnetospheric accretion (MA)is the driving mechanism, but the transfer of mass in massive young stellar objects with weak or negligible magnetic
fields probably occurs directly from the disk to the star through a hot boundary layer (BL). The intermediate-mass
Herbig Ae/Be (HAeBe) stars bridge the gap between both previous regimes and are still optically visible during the
pre-main sequence phase, thus constituting a unique opportunity to test a possible change of accretion mode from MA
to BL. This review deals with our estimates of accretion rates in HAeBes, critically discussing the different accretion
paradigms. It shows that although mounting evidence supports that MA may extend to late-type HAes but not toearly-type HBes, there is not yet a consensus on the validity of this scenario versus the BL one. Based on MA and BL
shock modeling, it is argued that the ultraviolet regime could significantly contribute in the future to discriminating
between these competing accretion scenarios.
Accepted by Galaxies (2020, 8, 39) in Special Issue "Star Formation in the Ultraviolet" (Ed. Jorick Vink)
http://arxiv.org/pdf/2005.01745

The UV Perspective of Low-Mass Star Formation
P.C. Schneider1,4 , H.M. Günther2 , K. France3
1

Hamburger Sternwarte; 2 Massachusetts Institute of Technology, Kavli Institute for Astrophysics and Space Research;
Department of Astrophysical and Planetary Sciences Laboratory for Atmospheric and Space Physics, University ofColorado 4 Current address: Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
343

E-mail contact: astro at pcschneider.eu
The formation of low-mass stars in molecular clouds involves accretion disks and jets, which are of broad astrophysicalinterest. Accreting stars represent the closest examples of these phenomena. Star and planet formation are also
intimately connected, setting the starting point for planetary systems like our own. The ultraviolet (UV) spectral
range is particularly suited to study star formation, because virtually all relevant processes radiate at temperaturesassociated with UV emission processes or have strong observational signatures in the UV. In this review, we describe
how UV observations provide unique diagnostics for the accretion process, the physical properties of the protoplanetarydisk, and jets and outflows.
Accepted by Galaxies special issue: “Star Formation in the UV”
http://arxiv.org/pdf/2005.10031

Star Formation in the Ultraviolet
Jorick S Vink1
1

Armagh Observatory and Planetarium

E-mail contact: jorick.vink at armagh.ac.uk
With the launch of JWST and the upcoming installation of extremely large telescopes, the first galaxies in our Universe
will finally be revealed. Their light will be dominated by massive stars, which peak in in the ultra-violet (UV) part ofthe electromagnetic spectrum. Star formation is the key driver of the evolution of our Universe. At young ages, within
10 Million years, both high and low mass stars generate complex UV emission processes which are poorly understood
yet are vital for interpreting high red-shift line emission. For these reasons, the Hubble Space Telescope (HST) will
devote 1000 orbits to obtaining a UV Legacy Library of Young Stars as Essential Standards (ULLYSES). The purposeof this Overview is to outline the basic physical principles driving UV emission processes from local (within 100 parsecsof) star formation, ranging from huge star-forming complexes containing hundreds of massive and very-massive stars(VMS), such as 30 Doradus (the Tarantula Nebula) in the neighbouring Magellanic Clouds (only 50 kpc away), togalaxies near and far, out to the epoch of Cosmic Reionization.
Accepted by Galaxies
http://arxiv.org/pdf/2005.01753

44

Meetings

Star Formation: From Clouds to Discs
A Tribute to the Career of Lee Hartmann
Due to the continuing restrictions in place with regard to COVID-19 (Coronavirus) and following the advice of the Irish
Health Service Executive and the Dublin Institute for Advanced Studies, as organisers, we have decided to postpone
the conference “Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann”. With many
countries and their academic institutes indefinitely restricting travel, we feel it is not possible to proceed in 2020. The
conference will now take place on 16th - 19th August 2021, in Malahide, County Dublin, Ireland.
Abstract submission and registration will be re-opened on 1st February 2021. Everyone who is interested in attending
can submit a new registration form following the revised calendar. We look forward to welcoming everyone to Dublin
in 2021.
For more details, please see: https://www.dias.ie/cloudstodiscs/

EPSC2020 conference – EXO3 session "From Protoplanetary Disks to
Small Bodies, Planets, and their Atmospheres"
Dear colleagues,
we would like to bring to your attention the following session that will take place during the Europlanet Science
Congress 2020 (www.epsc2020.eu), as part of the Exoplanets and Origins of Planetary Systems group:
EXO3
From Protoplanetary Disks to Small Bodies, Planets, and their Atmospheres
Since the discovery of the first exoplanet in 1995 more than 4000 exoplanets have been detected to date. This indicatesthat planet formation is a robust mechanism and nearly every star in our Galaxy should host a system of planets.
However, many crucial questions about the origin of planets are still unanswered: How and when planets formed in
the Solar System and in extra-solar systems? Are protoplanetary disks massive enough to form the planets cores?
And what chemical composition do planets and primitive Solar System bodies inherit from their natal environment?
Is the chemical composition passed unaltered from the earliest stages of the formation of a star to its disk and thento the bodies which assemble in the disk? Or does it reflects chemical processes occurring in the disk and/or during
the planet formation process?
A viable way to answer these questions is to study the planets formation site, i.e. protoplanetary disks. In the
recent years, the advent of ALMA and near-infrared/optical imagers aided by extreme adaptive optics revolutionised
our comprehension of planet formation by providing unprecedented insights on the protoplanetary disks structure,both in its gaseous and solid components. The aim of this session is to review the latest results on protoplanetarydisks; to foster a comparison with the recent outcomes of small bodies space missions (e.g. Rosetta, Dawn, Hayabusa
2, OSIRIS-REX) and ground-based observations; and to discuss how these will affect the current models of planet
formation and can guide us to investigate the origin of planets and small bodies and of their chemical composition.
Deadlines & Milestones- EPSC2020 will be held as a virtual meeting on 21 September - 9 October 2020.
- Abstract submission is due *** 24 June 2020, 13:00 CEST ***.
45

- Talks and posters will be announced on July 10.
- Talks and posters upload by September 7.
We would like to encourage all people interested in this topic to submit an abstract, in particular early career scientists.
For questions, you are welcome to contact Linda Podio (lpodio@arcetri.astro.it) or other members of the SOC.
Linda Podio, Mauro Ciarniello, Cecile Favre, Carlo Felice Manara, and Francesco Marzari
https://meetingorganizer.copernicus.org/EPSC2020/session/38481

Abstract submission deadline
The deadline for submitting abstracts and othersubmissions is the first day of the month. Abstracts
submitted after the deadline will appear in the following month’s issue.

46Summary of Upcoming Meetings

Check the websites of these meetings for the latest information on how they are aﬀected by Covid-19
Astrochemical Frontiers – Quarantine Edition
15 - 19 June 2020 via Zoom
https://sites.google.com/cfa.harvard.edu/astrochemicalfrontiers
Planet Formation: From Dust Coagulation to Final Orbital Assembly
1 - 26 June 2020, Munich, Germany
http://www.munich-iapp.de/planetformation
Illuminating the Dusty Universe: A Tribute to the Work of Bruce Draine
6 - 10 July 2020, Florence, Italy
https://web.astro.princeton.edu/IlluminatingTheDustyUniverse
The Early Phase of Star Formation
12 - 17 July 2020, Ringberg, Germany
http://www.mpia.de/homes/stein/EPoS/2020/2020.php
Star Formation in Diﬀerent Environments 202024 - 28 August 2020, Quy Nhon, Vietnam
http://icisequynhon.com/conferences/sfde/
Planetary Science: The Young Solar System
6 - 12 September 2020, Quy Nhon, Vietnam
http://www.icisequynhon.com/conferences/planetary_science/
Wheel of Star Formation: A conference dedicated to Prof. Jan Palouš
14 - 18 September 2020, Prague, Czech Republic
https://janfest2020.asu.cas.cz
Conditions and Impact of Star Formation - Across Times and Scales
28 September - 2 October 2020, Chile
https://astro.uni-koeln.de/symposium-star-formation-2020.html
From Clouds to Planets II: The Astrochemical Link
28 September - 2 October 2020, Berlin, Germany
https://events.mpe.mpg.de/event/12/
The Aftermath of a Revolution: Planet Formation Five Years after HL Tau
7 - 11 December 2020, Chile
https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org
Cool Stars, Stellar Systems, and the Sun 21
postponed to summer 2021, Toulouse, France
https://coolstars21.github.io/Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann
16 - 19 August 2021, Malahide, Ireland
https://www.dias.ie/cloudstodiscs/
Chemical Processes in Solar-type Star Forming Regions
13 - 17 September 2021, Torino, Italy47

https://sites.google.com/inaf.it/aco-conference
The Physics of Star Formation: From Stellar Cores to Galactic Scales∼June - July 2022, Lyon, France
http:/staratlyon.univ-lyon1.fr/en

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48