THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 334 — 24 October 2020

Editor: João Alves (joao.alves@univie.ac.at)List of Contents
The Star Formation Newsletter
Editor: João Alves
joao.alves@univie.ac.at
Editorial Board
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

Editorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Abstracts of Newly Accepted Papers . . . . . . . . . . . 7
New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Summary of Upcoming Meetings . . . . . . . . . . . . . . 41
Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 42

Cover Picture
The L1495 cloud in Taurus contains many small
groupings of young low-mass stars. The image
shows the region around V1096 Tau, seen as a nebulous star near the center of the image, and thesmall compact group of young stars seen further tothe south, including CW Tau, V773 Tau, and FM
Tau. The red nebulous object is Herbig-Haro object
HH 827.
Image courtesy Adam Block
http://adamblockphotos.com
http://caelumobservatory.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

Editorial
Do we still need a Star Formation Newsletter?
This is a fair question. It’s 2020, and there is an abundance of services that will filter the astro-ph river into amanageable number of papers on a specific topic. Why continue with the Star Formation Newsletter (SFN)? In
October 1992, Bo Reipurth introduced the SFN, the first electronic newsletter in Astronomy, to allow easy distributionof abstracts of the recent papers in the field. Back then, one would need to physically go to the local library, sit
down, and read about the field’s latest results. Over the following 28 years, Bo created much more than a list ofmonthly Abstracts; he created a community. The SFN has been connecting astronomers working on star and planet
formation across the planet since 1992 and is today the authoritative reference for the latest in Star and Planet
Formation research, from Abstracts and Reviews listings to Perspectives, from the latest Jobs and Meetings listings tocommunity Announcements. The section “Interviews” is now the de facto community legacy’s repository: describing
inspiring scientific life achievements and the human story behind them.
After 333 months at the helm of the successful SFN, Bo has asked me to become the editor. The thought of leading
the SFN is exciting and honoring but also terrifying. How does one follow Bo and how not to drop the ball? Bo wastransparent about the challenges, and I accepted, with joy and fear, the editor’s role from SFN 334. The immediate
plan is to transition the SFN into a sustainable web page, where the various sections of the SFN will become readily
accessible web pages. In some future, I would like to include a new section on resources for the community, like acurated list of high-quality star and planet formation illustrations and images to be used in teaching and presentations,among other ideas.
An essential goal of the SFN is to welcome young researchers into the field, help them navigate the community, andinspire them to make their mark. A paradox in today’s incredibly easy access to large amounts of information is
PhD students’ hyper-specialization. In part, this is a structural problem arising from what is expected from young
researchers to succeed. The SFN web will minimize this drawback and avoid dividing the SFN into sub-fields to expose
the reader to a broader view, following Bo’s original design. Given the current information growth, this will be difficult
to tread, but the spirit will be kept.
Finally, the SFN is done by the community and for the community. I invite anyone to contribute to the content andthe design of the SFN. All ideas are welcome. I plan to put together a group of Contributing Editors and an Editorial
Advisory Board to strengthen and guide the SFN through the 2020s. This transition will take some time, so thecurrent submission platform and the PDF file will be with us a little longer. The SFN mailing list will be hosted at
the University of Vienna, under the new General Data Protection Regulation (GDPR) of the European Union. You
will be able to opt-in/out easily and register via a web interface of the University.
I thank Bo for the trust and wish him a wonderful retirement from the 333 months he dedicated to the SFN. My wish
for the SFN is to allow it to grow, with your help, as a useful reference for the Star and Planet Formation community.
João Alves
Vienna, October 20203

every data sample. It might seem crazy to degrade theresolution of the world’s smallest radio telescope, but thetechnique allowed us to well sample large areas of the sky
very rapidly, and the angular resolution was still more thanadequate for comparison with the high-energy gamma ray
surveys that were being obtained around the same time by
the SAS-II and COS-B satellites. Pat and I collaborated
with the COS-B group on such a comparison (Lebrun etal. 1983) that provided the first gamma-ray calibration of
the CO-to-H2 conversion factor - what we unimaginatively
named the “X factor” in the paper.

Tom Damein conversation with Bo Reipurth

Q: A few years later you and a team of collaborators presented a composite survey of the entire Milky Way. Thiswas something of a revolution in millimeter astronomy,
and the paper has been cited over 800 times. What were
the key conclusions?
A: Even though that 1987 paper was cited so many times,
I suspect that most older researchers today have forgotten about it and most younger ones have never heard of
it. That’s because the ’87 whole-Galaxy survey was superseded by a higher-resolution version that we publishedin 2001; the former survey was a composite of 0.5◦ “superbeam” surveys while the latter was largely beam width
sampled. Both journal papers included unique 5-page foldouts displaying the whole-Galaxy lb and lv maps and inboth cases we put those same maps on wall posters thatwere widely distributed. Because our research group –along with the northern 1.2 m telescope – moved from
Columbia to CfA in 1986, the former survey is generally
called the Columbia CO survey and the latter one the CfA
survey. Together these two surveys incorporate the datafrom most of the 24 people who have obtained their PhDs
with the northern and southern 1.2 m telescopes.

Q: What was the topic of your 1983 PhD, and who wasyour advisor?
A: For my thesis work I was fortunate to be in the rightplace at the right time. Just after passing my qualifying exams, I was contacted by Pat Thaddeus who told me
about the little radio telescope that he was building on theroof of the physics building on the Columbia campus. Pat
was a brilliant and inspiring scientist who sold me on theimportance of the work right away. Several of his graduate students, including Gordon Chin, Hong-Ih Cong, andRichard Cohen, had been working hard for the previous
few years on building the 1.2 m telescope, so by the time
I joined the group it was ready to begin large-scale COsurveys of the Galaxy. My thesis was entitled “Molecular Clouds and Galactic Spiral Structure” and dealt withsome subjects which at the time were very controversial:the confinement of molecular clouds to the spiral arms andtheir lifetimes. Based on modeling of the spiral features
evident in my CO survey of the first Galactic quadrant, I
argued that molecular clouds were tightly confined to thearms and so couldn’t live longer than a spiral arm crossing
time of a few 107 years. Since then, interferometric CO
surveys of many external spirals have shown that molecular clouds are indeed excellent tracers of spiral structure.

Thanks to the superbeam technique, we were able to get
our first look at the molecular Milky Way 15 years earlier than would otherwise have been possible. Owing to
its wide latitude coverage, the Columbia survey was especially valuable for studying local molecular clouds. We
cataloged 23 within 1 kpc of the Sun, plotted their locations on the Galactic plane, and used them to determine
the mean molecular surface density and scale height in thesolar neighborhood. It was reassuring that these direct
measurements agreed well with values obtained for the inQ: Your first paper with Pat Thaddeus presented a CO ner Galaxy using kinematic distances and axisymmetricsurvey of the first Galactic quadrant with 1 degree angular modeling.
resolution. How and why did you carry out such a survey?
Q: In 1986 you and your colleagues published a paper on
A: That 1985 paper presented the first of our so-called “su- the largest molecular clouds in the first Galactic quadrant,
perbeam” surveys for which we degraded the telescope’s aiming to characterize their distribution and properties.
angular resolution by offsetting the pointing through a What did you learn?
square raster of points separated by a beam width (∼1/8deg) during an observation; it bore some resemblance to A: This was an early attempt to decompose the CO emismodern day on-the-fly mapping except that our Data Gen- sion in the first quadrant into its component clouds. We
eral Nova minicomputer was not up to the task of saving focused on the few dozen largest and brightest objects,

4what we called “complexes”, because they were the best
defined and I knew from my thesis work that such objects contained most of the molecular mass. Unlike themany subsequent attempts that relied on programs suchas clumpfind, this analysis was largely done by hand, particularly when it came to resolving the kinematic distanceambiguity. We had an appendix which gave a “lawyer’s
brief” of evidence for each cloud supporting either the nearor far distance.

to one part in 105 and yielded spectra that almost did
not require baseline removal. Although we could not resolve individual clouds, we obtained robust results on themolecular radial distribution. We found that beyond aradius of ∼8 kpc M31 and the Milky Way have comparable amounts of gas, both atomic and molecular, and bothhave central gas holes. We suggested that the essential
difference between the two galaxies may be the larger sizeof the hole in M31 (∼8 kpc) compared with that in theI think this work was important because it broke a long- Milky Way (∼3 kpc).
standing stalemate as to whether the apparent spiral struc- Q: In 2001 you published, together with Dap Hartmann
ture in lv diagrams was due to velocity or gas density vari- and Pat Thaddeus, your magnum opus, a new complete
ations along the line of sight. Very influential work by W. CO survey of the molecular clouds in the Milky Way. With
Butler Burton in the early 1970s had shown that in the almost 1500 citations, this study evidently has been highlycase of 21 cm lv diagrams, the apparent spiral structure influential. Please tell us about the survey.
might be just “kinematic illusions” produced by density A: This was our second whole-Galaxy CO survey, alreadywave streaming motions. In our case we definitely had mentioned earlier. The many citations to this paper are
real, well-defined objects, and we were able to locate them largely owing to the fact that molecular clouds, along
one by one on the Galactic plane, and they lined up nicely with their associated dust and star formation, influence
along the spiral arms. We also confirmed and extended the the large-scale Galactic emission in every major waveradius-linewidth relation of Larson to much higher cloud length band. In many cases, our CO survey provides
masses and showed that the clouds were in approximate the crucial third dimension of velocity or kinematic disvirial equilibrium.
tance that is lacking in continuum surveys such as those in
Q: Besides the Milky Way, the 1.2 m telescopes also obtained the first complete CO surveys of the LMC and M31.
Can you tell us about those surveys?

gamma rays and the infrared. Much of my work in recent
years has been in collaboration with astronomers studying the Galaxy at other wavelengths. I’m proud of the fact
A: The Magellanic Clouds, along with the Galactic cen- that our small telescopes, largely operated by students forter, were prime targets for the second 1.2 m telescope, about $25K per year, have provided data that were essenwhich was built and tested on the roof of the Goddard tial for the interpretation of satellite surveys costing tens
Institute for Space Studies in New York City before being to hundreds of millions of dollars.
transported to CTIO in Chile in 1982. Certainly the most Q: In the past decade or so you and Pat have discovered
spectacular discovery of the LMC survey was the enor- two new spiral arm structures in the Milky Way. How did
mous concentration of molecular clouds extending south these discoveries come about and what are their signififrom the giant HII region 30 Doradus for nearly 2400 pc cance?
and containing about 60 million solar masses of molecular A: During my thesis work I developed a great familiaritygas. There is really nothing comparable to that struc- with and, some would say, bizarre fondness for 21 cm andture in the Milky Way. Perhaps it is the solid body rota- CO longitude-velocity diagrams. My feeling is that anytion of the LMC that allows such structures to form. We gaseous spiral feature must be evident in the lv diagram–found that individual GMCs in the LMC were similar to essentially the raw data of a spectral line survey–otherwise
those in the Milky Way, except that they were about 6 it’s crazy to think that it is going to suddenly appear after
times fainter in CO, suggesting that the CO luminosity in a complex transformation into the plane of the Galaxy. I
a galaxy scales roughly with its metallicity.
spotted the far-side counterpart of the long-known “Ex-Our complete CO survey of M31 was the most difficult
ever undertaken with either of the 1.2 m telescopes. Beamdilution and velocity gradients across our 1.7 kpc beam
resulted in extremely weak (∼0.01 K) and broad (50-100
km s−1 ) lines that required exceptionally flat baselines for
detection. Only mm-wave observing aficionados will appreciate this, but we developed a unique azimuth-switching
technique in which we slightly adjusted the elevation of the
OFF after every switching cycle to cancel out any accumulated ON-OFF power to that point in the scan. This
active feedback technique balanced the ON-OFF powers

panding 3-kpc Arm” while preparing a review talk on CO
spiral structure for the June 2008 AAS meeting. I wastrying to make lv diagrams that showed the CO spiralstructure most clearly when the so-called “Far 3-kpc Arm”
revealed itself. I was a bit skeptical at first, but subsequently calculated that all of its physical characteristics
closely matched those of the near-side Expanding Arm.
My review talk turned into a report on this new spiralfeature, which was very exciting and fun. Scott Tremaine
called it the first direct evidence for a two-fold symmetry
in the Galaxy.
5

Oddly enough, I came upon the Outer Scutum-Centaurus
Arm in a similar manner – while preparing a review talkfor an ESO conference in Chile. In this case the arm was
first visible only in 21 cm emission. Since it was located a
few degrees above the plane in the distant outer Galaxy,no CO survey had covered the region. Concerned thatthe arm might be considered a “kinematic illusion” of thesort discussed earlier, Pat and I began very sensitive CO
observations of the structure with the CfA telescope. We
concentrated on HI peaks and ultimately found molecular
clouds at about a dozen locations along the arm. Molecular clouds are so rare in the distant outer Galaxy thatthese detections strongly supported the idea that this wasa major spiral arm structure. In our 2011 paper, we argued
that it was most likely the far end of the mighty Sct-Cen
arm, which originates at the end of the central bar before spiraling through the first and fourth quadrants andthen back around to the first quadrant again in the outer
Galaxy. This result too argued for a degree of Galactic
symmetry, since the Outer Sct-Cen arm appears to be thedistant counterpart of the Perseus spiral arm in the third
quadrant.

mass stars (Reid et al. 2019). One of my main roles in
the project has been to pick out maser targets based on
their locations in the lv diagram and their potential forclarifying the structure of particular spiral arms. Having
struggled throughout my career to locate the Galactic spiral arms using kinematic distances, it’s thrilling to finallybe pinning down the arms with such high precision. I canhardly wait to see results start to come in from the southern counterpart of BeSSeL, which is scheduled to startsoon using an array of telescopes in Australia and New
Zealand.

Q: What are you currently focused on?
A: Both 1.2 m telescopes are still in operation, the northern one just a few years shy of its 50th anniversary. The
CfA telescope recently completed a very long-term projectto map the entire northern sky in CO. This was a background observing project for about a decade, and mostof the data were obtained at night and on weekends byseveral generations of Harvard undergraduate observers.
I’m working now on the final reduction and publicationof this massive survey. I think Pat, who passed away in2017, would have agreed that completion of that survey
is an appropriate endpoint to what he called the “zerothorder experiment”, to determine the overall distributionof molecular gas in the Milky Way. Accordingly, over the
past year or so we have been tuning the telescope to othermolecules of interest, most notably HCN at 89 GHz. Extragalactic observers have long favored this high dipole
moment molecule for tracing dense gas (Gao & Solomon2004), but interpretation of their data has been stymied by
the lack of nearby Galactic clouds that have been mappedin HCN. Completing such maps is an ideal project for ourtelescope, so we are currently planning modifications to
our receiver that will double its sensitivity at the HCNline while maintaining its current sensitivity at CO.
Besides such observing projects and other collaborations
involving our surveys, I’ve been very excited to be involvedin the BeSSeL maser survey led by Mark Reid at the CfA.
This project has recently completed a five-year run on the
Very Long Baseline Array during which highly accurate
parallaxes and proper motions were measured for about
200 molecular masers associated with very young high-6

Abstracts of recently accepted papers

1. Gravitoviscous Protoplanetary Discs with a Dust Component. IV. Disc Outer Edges,

Spectral Indices, and Opacity Gaps

Vitaly Akimkin1 , Eduard Vorobyov2,3 , Yaroslav Pavlyuchenkov1 and Olga Stoyanovskaya4,5Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya str. 48, 119017, Russia; 2 University of Vienna,
Department of Astrophysics, Vienna, 1180, Austria; 3 Research Institute of Physics, Southern Federal University,
Rostov-on-Don, 344090 Russia; 4 Lavrentiev Institute of Hydrodynamics, Siberian Branch of Russian Academy of
Sciences, Lavrentieva ave. 15, 630090, Russia; 5 Novosibirsk State University, Novosibirsk, 630090 Russia
1E-mail contact: akimkin at inasan.ru
The crucial initial step in planet formation is the agglomeration of micron-sized dust into macroscopic aggregates.
This phase is likely to happen very early during the protostellar disc formation, which is characterised by active gas
dynamics. We present numerical simulations of protostellar/protoplanetary disc long-term evolution, which includes
gas dynamics with self-gravity in the thin-disc limit, and bidisperse dust grain evolution due to coagulation, fragmentation, and drift through the gas. We show that the decrease of the grain size to the disc periphery leads to sharp outeredges in dust millimetre emission, which are explained by a drop in dust opacity coefficient rather than by dust surface
density variations. These visible outer edges are at the location where average grain size ≈ λ/2π, where λ is the observational wavelength, so discs typically look more compact at longer wavelengths if dust size decreases outwards. This
allows a simple recipe for reconstructing grain sizes in disc outer regions. Discs may look larger at longer wavelengths
if grain size does not reach λ/2π for some wavelength. Disc visible sizes evolve non-monotonically over the first million
years and differ from dust and gas physical sizes by factor of a few. We compare our model with recent observation
data on gas and dust disc sizes, far-infrared fluxes and spectral indices of protoplanetary discs in Lupus. We also
show that non-monotonic variations of the grain size in radial direction can cause wavelength-dependent opacity gaps,
which are not associated with any physical gaps in the dust density distribution.
Accepted by MNRAS
https://arxiv.org/pdf/2010.06566

2. Hints for icy pebble migration feeding an oxygen-rich chemistry in the inner planet-

forming region of disks
Andrea Banzatti1,2 , Ilaria Pascucci2,3 , Arthur D. Bosman4 , Paola Pinilla5 , Colette Salyk6 , Greg J.
Herczeg7 , Klaus M. Pontoppidan8 , Ivan Vazquez1 , Andrew Watkins1 , Sebastiaan Krijt9,3,10 , Nathan
Hendler2 and Feng Long11
Department of Physics, Texas State University, 749 N Comanche Street, San Marcos, TX 78666, USA; 2 Department
of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, USA; 3 Earths in
Other Solar Systems Team, NASA Nexus for Exoplanet System Science; 4 Department of Astronomy, University ofMichigan, 1085 S. University Ave, Ann Arbor, MI 48109; 5 Max-Planck-Institut für Astronomie, Königstuh l17, 69117
Heidelberg, Germany; 6 Department of Physics and Astronomy, Vassar College, 124 Raymond Avenue, Poughkeepsie,
NY 12604, USA; 7 Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China; 8 Space
Telescope Science Institute 3700 San Martin Drive Baltimore, MD 21218, USA; 9 Department of Astronomy, The
University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 10 Hubble Fellow; 11 Harvard-Smithsonian
Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
1E-mail contact: banzatti at txstate.edu
We present a synergic study of protoplanetary disks to investigate links between inner disk gas molecules and thelarge-scale migration of solid pebbles. The sample includes 63 disks where two types of measurements are available: i)spatially-resolved disk images revealing the radial distribution of disk pebbles (mm-cm dust grains), from millimeter7

observations with ALMA or the SMA, and ii) infrared molecular emission spectra as observed with Spitzer. The line
flux ratios of H2 O with HCN, C2 H2 , and CO2 all anti-correlate with the dust disk radius Rdust , expanding previous
results found by Najita et al. (2013) for HCN/H2 O and the dust disk mass. By normalization with the dependence on
accretion luminosity common to all molecules, only the H2 O luminosity maintains a detectable anti-correlation withdisk radius, suggesting that the strongest underlying relation is between H2 O and Rdust . If Rdust is set by large-scale
pebble drift, and if molecular luminosities trace the elemental budgets of inner disk warm gas, these results can benaturally explained with scenarios where the inner disk chemistry is fed by sublimation of oxygen-rich icy pebbles
migrating inward from the outer disk. Anti-correlations are also detected between all molecular luminosities and theinfrared index n13−30 , which is sensitive to the presence and size of an inner disk dust cavity. Overall, these relations
suggest a physical interconnection between dust and gas evolution both locally and across disk scales. We discuss
fundamental predictions to test this interpretation and study the interplay between pebble drift, inner disk depletion,and the chemistry of planet-forming material.
Accepted by ApJ
https://arxiv.org/pdf/2009.13525

3. Gravity and rotation drag the magnetic field in high-mass star formation
H. Beuther1 , J.D. Soler1 , H. Linz1 , Th. Henning1 , C. Gieser1 , R. Kuiper2 , W. Vlemmings3, P. Hennebelle4,
S. Feng5 , R. Smith6 and A. Ahmadi7
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Institute of Astronomy andAstrophysics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany; 3 Department of Earthand Space Sciences Chalmers University of Technology, Onsala Space Observatory, 439 92, Onsala, Sweden; 4 AIM,
CEA, CNRS, Universite Paris-Saclay, Universite Paris Diderot, Sorbonne Paris Cite, 91191 Gif-sur-Yvette, France; 5Chinese Academy of Sciences Key Laboratory of FAST, National Astronomical Observatory of China, Datun Road
20, Chaoyang, Bejing, 100012, P. R. China; 6 Jodrell Bank Centre for Astrophysics, Department of Physics andAstronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK; 7 Leiden University, Niels Bohrweg
2, 2333 CA Leiden, Netherlands
1E-mail contact: beuther at mpia.de
The formation of hot stars out of the cold interstellar medium lies at the heart of astrophysical research. Understanding the importance of magnetic fields during star formation remains a major challenge. With the advent of the
Atacama Large Millimeter Array, the potential to study magnetic fields by polarization observations has tremendously
progressed. However, the major question remains how much magnetic fields shape the star formation process orwhether gravity is largely dominating. Here, we show that for the high-mass star-forming region G327.3 the magnetic
field morphology appears to be dominantly shaped by the gravitational contraction of the central massive gas core
where the star formation proceeds. We find that in the outer parts of the region, the magnetic field is directed toward
the gravitational center of the region. Filamentary structures feeding the central core exhibit U-shaped magnetic fieldmorphologies directed toward the gravitational center as well, again showing the gravitational drag toward the center.
The inner part then shows rotational signatures, potentially associated with an embedded disk, and there the magnetic
field morphology appears to be rotationally dominated. Hence, our results demonstrate that for this region gravity
and rotation are dominating the dynamics and shaping the magnetic field morphology.
Accepted by Astrophysical Journal
https://www2.mpia-hd.mpg.de/homes/beuther/papers.html

4. Observations of the Onset of Complex Organic Molecule Formation in Interstellar Ices
Laurie E. U. Chu1 , Klaus W. Hodapp1 and Adwin Boogert2
Institute for Astronomy, 640 N. Auhoku Pl. #209, Hilo, HI 96720 USA; 2 Institute for Astronomy, 2680 Woodlawn
Dr., Honolulu, HI 96822 USA
1E-mail contact: lurban at hawaii.edu
Isolated dense molecular cores are investigated to study the onset of complex organic molecule formation in interstellar
ice. Sampling three cores with ongoing formation of low-mass stars (B59, B335, and L483) and one starless core (L694-82) we sample lines of sight to nine background stars and five young stellar objects (YSOs; AK ∼0.5 - 4.7). Spectra ofthese stars from 2-5 µm with NASA’s Infrared Telescope Facility (IRTF) simultaneously display signatures from thecores of H2 O (3.0 µm), CH3 OH (C-H stretching mode, 3.53 µm) and CO (4.67 µm) ices. The CO ice is traced by ninestars in which five show a long wavelength wing due to a mixture of CO with polar ice (COr ), presumably CH3 OH.
Two of these sight lines also show independent detections of CH3 OH. For these we find the ratio of the CH3 OH:COr
is 0.55±0.06 and 0.73±0.07 from L483 and L694-2, respectively. The detections of both CO and CH3 OH for the firsttime through lines of sight toward background stars observationally constrains the conversion of CO into CH3 OH ice.
Along the lines of sight most of the CO exists in the gas phase and ≤15% of the CO is frozen out. However, CH3 OH
ice is abundant with respect to CO (∼50%) and exists mainly as a CH3 OH-rich CO ice layer. Only a small fractionof the lines of sight contains CH3 OH ice, presumably that with the highest density. The high conversion of CO to
CH3 OH can explain the abundances of CH3 OH ice found in later stage Class 1 low mass YSO envelopes (CH3 OH:COr
0.5-0.6). For high mass YSOs and one Class 0 YSO this ratio varies significantly implying local variations can affectthe ice formation. The large CH3 OH ice abundance indicates that the formation of complex organic molecules is likely
during the pre-stellar phase in cold environments without higher energy particle interactions (e.g. cosmic rays).
Accepted by ApJ
https://arxiv.org/pdf/2010.05917

5.

SiO emission as a probe of Cloud-Cloud Collisions in Infrared Dark Clouds
G. Cosentino1 , I. Jiménez-Serra2 , J.D. Henshaw3 , P. Caselli4, S. Viti5 , A.T. Barnes6 , J.C. Tan1,7 , F.
Fontani8 and B. Wu9Space, Earth and Environment Department, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden;
Centro de Astrobiología (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4, Madrid, Spain; 3 Max Planck Institutefor Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 4 Max Planck Institute for Extraterrestrial Physics,
Giessenbachstrasse 1, 85748 Garching bei München, Germany; 5 Department of Physics and Astronomy, University
College London, Gower Street, London WC1E6BT, UK; 6 Argelander-Institut für Astronomie, Universität Bonn, Auf
dem Hügel 71, 53121, Bonn, Germany; 7 Department of Astronomy, University of Virginia, 530 McCormick Road
Charlottesville, 22904-4325 USA; 8 INAF Osservatorio Astronomico di Arcetri, Largo E. Fermi 5, 50125 Florence,
Italy; 9 National Astronomical Observatory of Japan, Yubinbango 181-8588 Tokio, Mitaka, Osawa 2-21-1, Japan1

2

E-mail contact: giuliana.cosentino at chalmers.se
Infrared Dark Clouds (IRDCs) are very dense and highly extincted regions that host the initial conditions of star andstellar cluster formation. It is crucial to study the kinematics and molecular content of IRDCs to test their formation
mechanism and ultimately characterise these initial conditions. We have obtained high-sensitivity Silicon Monoxide,
SiO(2-1), emission maps toward the six IRDCs, G018.82−00.28, G019.27+00.07, G028.53−00.25, G028.67+00.13,
G038.95−00.47 and G053.11+00.05 (cloud A, B, D, E, I and J, respectively), using the 30-m antenna at the Institutode Radioastronomía Millimétrica (IRAM30m). We have investigated the SiO spatial distribution and kinematic
structure across the six clouds to look for signatures of cloud-cloud collision events that may have formed the IRDCs
and triggered star formation within them. Toward clouds A, B, D, I and J we detect spatially compact SiO emission
with broad line profiles which are spatially coincident with massive cores. Toward the IRDCs A and I, we report an
additional SiO component that shows narrow line profiles and that is widespread across quiescent regions. Finally,
we do not detect any significant SiO emission toward cloud E. We suggest that the broad and compact SiO emission
detected toward the clouds is likely associated with ongoing star formation activity within the IRDCs. However, theadditional narrow and widespread SiO emission detected toward cloud A and I may have originated from the collision
between the IRDCs and flows of molecular gas pushed toward the clouds by nearby HII regions.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/2009.13890

6.

Chemical evolution during the formation of a protoplanetary disk
A. Coutens1 , B. Commerçon2 and V. Wakelam1
Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac,
France; 2 Centre de Recherche Astrophysique de Lyon UMR5574, ENS de Lyon, Univ. Lyon1, CNRS, Université de19Lyon, 69007 Lyon, France
E-mail contact: audrey.coutens at u-bordeaux.fr
The chemical composition of protoplanetary disks is expected to impact the composition of the forming planets.
Characterizing the diversity of chemical composition in disks and the physicochemical factors that lead to this diversity
is consequently of high interest. The aim of this study is to investigate the chemical evolution from the prestellar
phase to the formation of the disk, and to determine the impact that the chemical composition of the cold and dense
core has on the final composition of the disk. We performed 3D nonideal magneto-hydrodynamic (MHD) simulationsof a dense core collapse using the adaptive-mesh-refinement RAMSES code. For each particle ending in the young
rotationally supported disk, we ran chemical simulations with the three-phase gas-grain chemistry code Nautilus. Two
different sets of initial abundances, which are characteristic of cold cores, were considered. The final distributions of
the abundances of common species were compared to each other, as well as with the initial abundances of the coldcore. We find that the spatial distributions of molecules reflect their sensitivity to the temperature distribution. The
main carriers of the chemical elements in the disk are usually the same as the ones in the cold core, except for the
S-bearing species, where HS is replaced by H2 S3 , and the P-bearing species, where atomic P leads to the formationof PO, PN, HCP, and CP. However, the abundances of less abundant species change over time. This is especially thecase for “large” complex organic molecules (COMs) such as CH3 CHO, CH3 NH2 , CH3 OCH3 , and HCOOCH3 which
see their abundances significantly increase during the collapse. These COMs often present similar abundances in thedisk despite significantly different abundances in the cold core. In contrast, the abundances of many radicals decrease
with time. A significant number of species still show the same abundances in the cold core and the disk, whichindicates efficient formation of these molecules in the cold core. This includes H2 O, H2 CO, HNCO, and “small” COMs
such as CH3 OH, CH3 CN, and NH2 CHO. We computed the MHD resistivities within the disk for the full gas–grainchemical evolution and find results in qualitative agreement with the literature assuming simpler chemical networks.
In conclusion, the chemical content of prestellar cores is expected to affect the chemical composition of disks. The
impact is more or less important depending on the type of species. Users of stand-alone chemical models of disks
should pay special attention to the initial abundances they choose.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2010.05108

7.

Time-Variable Radio Recombination Line Emission in W49A
C. G. DePree1 , D. J. Wilner2 , L. E. Kristensen3,2 , R. Galván-Madrid4 , W. M. Goss5 , R. S. Klessen6,7,
M.-M. Mac Low7,8 , T. Peters10 , A. Robinson1, M. Rao1 and S. Sloman1
Department of Physics & Astronomy, Agnes Scott College, Decatur, GA, United States; 2 Center for Astrophysics;
Harvard & Smithsonian, Cambridge, MA, United States; 4 Niels Bohr Institute & Centre for Star and Planet
Formation, Copenhagen University, Denmark; 5 Instituto de Radioastronomía y Astrofísica (IRyA), UNAM, Morelia,
Michoacán, Mexico; 6 National Radio Astronomy Observatory, Socorro, NM, United States; 7 Universität Heidelberg,
Zentrum für Astronomie, Institut für Theoretische Astrophysik, Heidelberg, Germany; 8 Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Heidelberg, Germany; 9 Department of Astrophysics, American
Museum of Natural History, New York, NY, USA; 10 Center for Computational Astrophysics, Flatiron Institute, New
York, NY, United States
1

3

E-mail contact: cdepree at agnesscott.edu
We present new Jansky Very Large Array (VLA) images of the central region of the W49A star-forming region at
3.6 cm and at 7 mm at resolutions of 0.15′′ (1650 au) and 0.04′′ (440 au), respectively. The 3.6 cm data reveal new
morphological detail in the ultracompact HII region population, as well as several previously unknown and unresolved
sources. In particular, source A shows elongated, edge-brightened, bipolar lobes, indicative of a collimated outflow,
and source E is resolved into three spherical components. We also present VLA observations of radio recombinationlines at 3.6 cm and 7 mm, and IRAM Northern Extended Millimeter Array (NOEMA) observations at 1.2 mm.
Three of the smallest ultracompact HII regions (sources A, B2 and G2) all show broad kinematic linewidths, with
∆VF W HM >40 km s−1 . A multi-line analysis indicates that broad linewidths remain after correcting for pressure
broadening effects, suggesting the presence of supersonic flows. Substantial changes in linewidth over the 21 year timebaseline at both 3.6 cm and 7 mm are found for source G2. At 3.6 cm, the linewidth of G2 changed from 31.7±1.8
km s−1 to 55.6±2.7 km s−1 , an increase of +23.9±3.4 km s−1 . The G2 source was previously reported to have shown10

a 3.6 cm continuum flux density decrease of 40% between 1994 and 2015. This source sits near the center of a very
young bipolar outflow whose variability may have produced these changes.
Accepted by The Astronomical Journal
http://arXiv.org/pdf/2010.04656

8.

New insights in the HII region G18.88−0.49: hub-filament system and accreting filaments
L. K. Dewangan1 , D. K. Ojha2 , Saurabh Sharma3 , S. del Palacio4 , N. K. Bhadari1,5 and A. Das6
1

Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India.; 2 Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai - 400005, India.; 3 Aryabhatta ResearchInstitute of Observational Sciences (ARIES), Manora Peak, Nainital, 263002, India.; 4 Instituto Argentino de Radioastronomía (CCT La Plata, CONICET; CICPBA; UNLP), C.C.5, (1894) Villa Elisa, Buenos Aires, Argentina.; 5 Indian
Institute of Technology Gandhinagar Palaj, Gandhinagar, 382355, India.; 6 University of Hyderabad, Hyderabad 500046, India.
E-mail contact: lokeshd at prl.res.in
We present an analysis of multi-wavelength observations of an area of 0.27 deg × 0.27 deg around the Galactic H ii
region G18.88−0.49, which is powered by an O-type star (age ∼105 years). The Herschel column density map reveals
a shell-like feature of extension ∼12 pc × 7 pc and mass ∼2.9 ×104 M⊙ around the H ii region; its existence is further
confirmed by the distribution of molecular (12 CO, 13 CO, C18 O, and NH3 ) gas at [60, 70] km s−1 . Four subregions
are studied toward this shell-like feature, and show a mass range of ∼0.8–10.5 ×103 M⊙ . These subregions associatedwith dense gas are dominated by non-thermal pressure and supersonic non-thermal motions. The shell-like feature
is associated with the H ii region, Class I protostars, and a massive protostar candidate, illustrating the ongoingearly phases of star formation (including massive stars). The massive protostar is found toward the position of the
6.7 GHz methanol maser, and is associated with outflow activity. Five parsec-scale filaments are identified in thecolumn density and molecular maps, and appear to be radially directed to the dense parts of the shell-like feature.
This configuration is referred to as a “hub-filament" system. Significant velocity gradients (0.8–1.8 km s−1 pc−1 ) are
observed along each filament, suggesting that the molecular gas flows towards the central hub along the filaments.
Overall, our observational findings favor a global non-isotropic collapse scenario as discussed in Motte et al. (2018),
which can explain the observed morphology and star formation in and around G18.88−0.49.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2009.05249.pdf

9.

The structure and characteristic scales of molecular clouds
Sami Dib1 , Sylvain Bontemps1 , Nicola Schneider2 , Davide Elia3 , Volker Ossenkopf-Okada2 , Mohsen
Shadmehri4 , Doris Arzoumanian5 , Frédérique Motte6 , Mark Heyer7 , Åke Nordlund8 and Bilal Ladjelate9
1

Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire,
33615, Pessac, France; 2 I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany; 3Istituto di Astrofisica e Planetologia Spazialli, INAF, via Fosso del Cavaliere 100, Roma, 00133, Italy; 4 Departmentof Physics, Faculty of Sciences, Golestan University, Gorgan 49138-15739, Iran; 5 nstituto de Astrofísica e Ciências
do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762, Porto, Portugal; 6 Institut de Planétologie
et d’Astrophysique de Grenoble, Université Grenoble Alpes, CNRS, Grenoble, France; 7 Department of Astronomy,
University of Massachusetts, Amherst, MA 01003, USA; 8 Centre for Star and Planet Formation, the Niels Bohr
Institute and the Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, DK-1350,
Denmark; 9 Instituto de Radioastronomía Milimétrica, IRAM Avenida Divina Pastora 7, Local 20, 18012, Granada,
Spain
E-mail contact: sami.dib at gmail.com
The structure of molecular clouds holds important clues on the physical processes that lead to their formation andsubsequent dynamical evolution. While it is well established that turbulence imprints a self-similar structure to theclouds, other processes, such as gravity and stellar feedback, can break their scale-free nature. The break of self-11

similarity can manifest itself in the existence of characteristic scales that stand out from the underlying structure
generated by turbulent motions. In this work, we investigate the structure of the Cygnus-X North and the Polaris
Flare molecular clouds which represent two extremes in terms of their star formation activity. We characterize thestructure of the clouds using the delta-variance (∆-variance) spectrum. In the Polaris Flare, the structure of the cloudis self-similar over more than one order of magnitude in spatial scales. In contrast, the ∆-variance spectrum of CygnusX North exhibits an excess and a plateau on physical scales of ≈ 0.5 − 1.2 pc. In order to explain the observations
for Cygnus-X North, we use synthetic maps in which we overlay populations of discrete structures on top of a fractal
Brownian motion (fBm) image. The properties of these structures such as their major axis sizes, aspect ratios, andcolumn density contrasts with the fBm image are randomly drawn from parameterized distribution functions. We areable to show that under plausible assumptions, it is possible to reproduce a ∆-variance spectrum that resembles theone of the Cygnus-X North region. We also use a "reverse engineering" approach in which we extract the compact
structures in the Cygnus-X North cloud and re-inject them on an fBm map. The calculated ∆-variance spectrum using
this approach deviates from the observations and is an indication that the range of characteristic scales (≈ 0.5 − 1.2pc) observed in Cygnus-X North is not only due to the existence of compact sources, but is a signature of the whole
population of structures that exist in the cloud, including more extended and elongated structures
Accepted by Astronomy & Astrophysics
https://ui.adsabs.harvard.edu/pdf/2020arXiv200708533D/abstract

10. The First Extensive Spectroscopic Study of Young Stars in the North America andPelican Nebulae Region

Min Fang1 , Lynne A. Hillenbrand1 , Jinyoung Serena Kim2 , Krzysztof Findeisen3, Gregory J. Herczeg4 ,John M. Carpenter5 , Luisa M. Rebull6 and Hongchi Wang7
Department of Astronomy, California Institute of Technology, Pasadena CA 91125; 2 Department of Astronomy,
University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 3 University of Washington, Department of
Astronomy, Seattle, WA, 98195, U.S.A; 4 Kavli Institute for Astronomy and Astrophysics, Peking University, Yiheyuan
5, Haidian Qu, 100871 Beijing, China; 5 Joint ALMA Observatory, Alonso de Cordova 3107 Vitacura, Santiago, Chile;
6
Infrared Science Archive (IRSA), IPAC, 1200 E. California Blvd., California Institute of Technology, Pasadena, CA
91125, USA; 7 Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences,
2 West Beijing Road, 210008 Nanjing, China
1E-mail contact: mfang.cn at gmail.com
We present a spectroscopic survey of over 3400 potential members in the North America and Pelican nebulae (NAP)
using several low-resolution (R≈1300-2000) spectrographs: Palomar/Norris, WIYN/HYDRA, Keck/DEIMOS, and
MMT/Hectospec. We identify 580 young stars as likely members of the NAP region based on criteria involving
infrared excess, Li I 6708 absorption, X-ray emission, parallax, and proper motions. The spectral types of individual
spectra are derived by fitting them with templates that are either empirical spectra of pre-main sequence stars, ormodel atmospheres. The templates are artificially veiled, and a best-fit combination of spectral type and veilingparameter is derived for each star. We use the spectral types with archival photometry to derive V-band extinction
and stellar luminosity. From the H-R diagram, the median age of the young stars is about 1 Myr, with a luminosity
dispersion of ∼0.3–0.4 dex. We investigate the photometric variability of the spectroscopic member sample using ZTF
data, and conclude that photometric variability, while present, does not significantly contribute to the luminosity
dispersion. While larger than the formal errors, the luminosity dispersion is smaller than if veiling were not taken
into account in our spectral typing process. The measured ages of stellar kinematic groups, combined with inferredages for embedded stellar populations revealed by Spitzer, suggests a sequential history of star formation in the NAP
region.
Accepted by ApJ
https://arxiv.org/pdf/2009.11995

11.

The chemical structure of young high-mass star-forming clumps: (II) parsec-scale COdepletion and deuterium fraction of HCO+
S. Feng1,2,3 , D. Li1,4 , P. Caselli5 , F. Du6,7 , Y. Lin8 , O. Sipilä5 , H. Beuther9 , Patricio Sanhueza3 , K.

12

Tatematsu10,11 , S. Y. Liu2 , Q. Zhang12 , Y. Wang9 , T. Hogge13 , I. Jimenez-Serra14 , X. Lu3 , T. Liu15 , K.
Wang16 , Z. Y. Zhang17 , S. Zahorecz3,18 , G. Li19 , H. B. Liu2 and J. Yuan1
National Astronomical Observatories, Chinese Academy of Science, Beijing 100101, People’s Republic of China; 2
Academia Sinica Institute of Astronomy and Astrophysics, No.1, Section 4, Roosevelt Road, Taipei 10617, Taiwan,
Republic of China; 3 National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1
Osawa, Mitaka, Tokyo 181-8588, Japan; 4 NAOC-UKZN Computational Astrophysics Centre, University of KwaZuluNatal, Durban 4000, South Africa; 5 Max-Planck-Institut für Extraterrestrische Physik, Gießenbachstraße 1, D-85748,
Garching bei München, Germany; 6 Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210023, People’s Republic of China; 7 School of Astronomy and Space Science,
University of Science and Technology of China, Hefei 230026, People’s Republic of China; 8 Max Planck Institute forRadio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany; 9 Max-Planck-Institut für Astronomie, Königstuhl
17, D-69117, Heidelberg, Germany; 10 Nobeyama Radio Observatory, National Astronomical Observatory of Japan,
National Institutes of Natural Sciences, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; 11 Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka,
Tokyo, 181-8588, Japan; 12 Center for Astrophysics; 13 Harvard and Smithsonian, 60 Garden Street, Cambridge,
MA 02138, USA; 14 Institute for Astrophysical Research, Boston University, Boston, MA 02215, USA; 15 Centrode Astrobiología (CSIC, INTA), Ctra. de Torrejón a Ajalvir km. 4, Torrejón de Ardoz, E-28850 Madrid, Spain;
16
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s
Republic of China; 17 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian
District, Beijing 100871, People’s Republic of China; 18 School of Astronomy and Space Science, Nanjing University,
163 Xianlin Avenue, Nanjing 210023, People’s Republic of China; 19 Department of Physical Science, Graduate Schoolof Science, Osaka Prefecture University, 1-1 Gakuen-cho,Naka-ku, Sakai, Osaka 599-8531, Japan1

E-mail contact: siyi.s.feng at gmail.com
The physical and chemical properties of cold and dense molecular clouds are key to understanding how stars form.
Using the IRAM 30 m and NRO 45 m telescopes, we carried out a Multiwavelength line-Imaging survey of the 70 µm
dark and bright clOuds (MIAO). At a linear resolution of 0.1–0.5 pc, this work presents a detailed study of parsec-scale
CO depletion and HCO+ deuterium (D-) fractionation toward four sources (G 11.38+0.81, G 15.22-0.43, G 14.49-0.13,
and G 34.74-0.12) included in our full sample. In each source with T < 20 K and nH ∼ 104 –105 cm−3 , we comparedpairs of neighboring 70 µm bright and dark clumps and found that (1) the H2 column density and dust temperatureof each source show strong spatial anticorrelation; (2) the spatial distribution of CO isotopologue lines and dense
gas tracers, such as 1–0 lines of H13 CO+ and DCO+ , are anticorrelated; (3) the abundance ratio between C18 O and
DCO+ shows a strong correlation with the source temperature; (4) both the C18 O depletion factor and D-fractionof HCO+ show a robust decrease from younger clumps to more evolved clumps by a factor of more than 3; and (5)preliminary chemical modeling indicates chemical ages of our sources are ∼8 × 104 yr, which is comparable to theirfree-fall timescales and smaller than their contraction timescales, indicating that our sources are likely dynamicallyand chemically young.
Accepted by ApJ
https://doi.org/10.3847/1538-4357/abada3

Hydrodynamical simulations of protoplanetary disks including irradiation of stellar pho-

12. tons. I. Resolution study for Vertical Shear Instability (VSI)
Lizxandra Flores-Rivera1 , Mario Flock1 and Ryohei Nakatani2
1

Max Planck Institute for Astronomy, Germany; 2 RIKEN, Japan

E-mail contact: flores at mpia.de
In recent years hydrodynamical (HD) models have become important to describe the gas kinematics in protoplanetarydisks, especially in combination with models of photoevaporation and/or magnetic-driven winds. Our aim is toinvestigate how the Vertical Shear Instability (VSI) could influence the thermally-driven winds on the surface of
protoplanetary disks. In this first part of the project, we focus on diagnosing the conditions of the VSI at the highest
numerical resolution ever recorded and allude at what resolution per scale height we obtain convergence. At the sametime, we want to investigate the vertical extent of VSI activity. Finally, we determine the regions where EUV, FUV

13and X-Rays are dominant in the disk. We perform global HD simulations using the PLUTO code. We adopt a global
isothermal accretion disk setup, 2.5D (2 dimensions, 3 components) which covers a radial domain from 0.5 to 5.0 and an
approximately full meridional extension. Our simulation runs cover a resolution from 12 to 203 cells per scale height.
We determine the 50 cells per scale height to be the lower limit to resolve the VSI. For higher resolutions, greaterthan 50 cells per scale height, we observe the convergence for the saturation level of the kinetic energy. We are alsoable to identify the growth of the ‘body’ modes, with higher growth rate for higher resolution. Full energy saturation
and a turbulent steady state is reached after 70 local orbits. We determine the location of the EUV-heated region
defined by the radial column density to be 1019 cm−2 located at HR ∼9.7 and the FUV/X-Rays-heated boundary
layer defined to be 1022 cm−2 located at HR ∼6.2, making it necessary to introduce the need of a hot atmosphere.
For the first time, we report the presence of small scale vortices in the r-Z plane, between the characteristic layers oflarge scale vertical velocity motions. Such vortices could lead to dust concentration, promoting grain growth. Our
results highlight the importance to combine photoevaporation processes in the future high-resolution studies of the
turbulence and accretion processes in disks.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2010.06711

13.

Lupus DANCe. Census of stars and 6D structure with Gaia-DR2 data
P.A.B. Galli1 , H. Bouy1 , J. Olivares1 , N. Miret-Roig1, R.G. Vieira2 , L.M. Sarro3 , D. Barrado4 , A.
Berihuete5 , C. Bertout6 , E. Bertin6 and J.C. Cuillandre7
Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hillaire, F-33615
Pessac, France; 2 Departamento de Física, Universidade Federal de Sergipe, São Cristóvão, SE, Brazil; 3 Depto.
de Inteligencia Artificial, UNED, Juan del Rosal, 16, 28040 Madrid, Spain; 4 Centro de Astrobiología, Depto. de
Astrofísica, INTA-CSIC, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid,
Spain; 5 Dept. Statistics and Operations Research, University of Cádiz, Campus Universitario Río San Pedro s/n,
11510 Puerto Real, Cádiz, Spain; 6 Institut d’Astrophysique de Paris, CNRS UMR 7095 and UPMC, 98bis bd Arago,
75014 Paris, France; 7 AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot, Orme des Merisiers,
France1E-mail contact: phillip.galli at u-bordeaux.fr
Context: Lupus is recognised as one of the closest star-forming regions, but the lack of trigonometric parallaxes in the
pre-Gaia era hampered many studies on the kinematic properties of this region and led to incomplete censuses of its
stellar population.
Aims: We use the second data release of the Gaia space mission combined with published ancillary radial velocity
data to revise the census of stars and investigate the 6D structure of the Lupus complex.
Methods: We performed a new membership analysis of the Lupus association based on astrometric and photometricdata over a field of 160 deg2 around the main molecular clouds of the complex and compared the properties of thevarious subgroups in this region.
Results: We identified 137 high-probability members of the Lupus association of young stars, including 47 stars
that had never been reported as members before. Many of the historically known stars associated with the Lupus
region identified in previous studies are more likely to be field stars or members of the adjacent Scorpius-Centaurus
association. Our new sample of members covers the magnitude and mass range from G ≃ 8 to G ≃ 18 mag and from0.03 to 2.4 M⊙ , respectively. We compared the kinematic properties of the stars projected towards the molecular
clouds Lupus 1 to 6 and showed that these subgroups are located at roughly the same distance (about 160 pc) andmove with the same spatial velocity. Our age estimates inferred from stellar models show that the Lupus subgroups
are coeval (with median ages ranging from about 1 to 3 Myr). The Lupus association appears to be younger thanthe population of young stars in the Corona-Australis star-forming region recently investigated by our team using
a similar methodology. The initial mass function of the Lupus association inferred from the distribution of spectral
types shows little variation compared to other star-forming regions.
Conclusions: In this paper, we provide an updated sample of cluster members based on Gaia data and construct themost complete picture of the 3D structure and 3D space motion of the Lupus complex.
Accepted by A&A
http://arxiv.org/pdf/2010.00233
14

14.

A photoionized accretion disk around a young high-mass star
Andres E. Guzman1 , Paricio Sanhueza1,2 , Luis Zapata3 , Guido Garay4 and Luis Felipe Rodriguez3
National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo
181-8588, Japan; 2 Department of Astronomical Sciences, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Instituto de Radioastronomía y Astrofísica, Universidad Nacional
Autónoma de México, P.O. Box 3-72, 58090, Morelia, Michoacán, México; 4 Departamento de Astronomía, Universidad
de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile

1

E-mail contact: andres.guzman at nao.ac.jp
We present high spatial resolution (52 au) observations of the high-mass young stellar object (HMYSO) G345.4938+01.4677
made using the Atacama Large Millimeter/sub-millimeter Array (ALMA). This O-type HMYSO is located at 2.38
kpc and it is associated with a luminosity of 1.5 × 105 L⊙ . We detect circumstellar emission from the H38β hydrogen
recombination line showing a compact structure rotating perpendicularly to the previously detected radio jet. We
interpret this emission as tracing a photo-ionized accretion disk around the HMYSO. While this disk-like structure
seems currently too small to sustain continued accretion, the data present direct observational evidence of how disks
can effectively survive the photo-ionization feedback from young high-mass stars. We also report the detection of alow-mass young stellar object in the vicinity of the HMYSO and suggest that it forms a high-mass and low-mass starbinary system.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2010.00244
7−3
towards OMC-1
15. APEX-SEPIA660 Early Science: Gas at densities above 10 cm
1,2
1,3
4
1
A. Hacar , M. R. Hogerheijde , D. Harsono , S. Portegies Zwart , C. De Breuck5 , K. Torstensson5 ,W. Boland6 , A. M. Baryshev6 , R. Hesper6 , J. Barkhof6 , J. Adema6 , M. E. Bekema6 , A. Koops6 , A.
Khudchenko6 and R. Stark7

Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands; 2 University of Vienna,
Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria; 3 Anton Pannekoek Institute for Astonomy, University of Amsterdam, the Netherlands; 4 Institute of Astronomy and Astrophysics, Academia Sinica, No.1,
Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.; 5 European Southern Observatory, Karl Schwarzschild Strasse 2,85748 Garching, Germany; 6 Netherlands Research School for Astronomy (NOVA), Kapteyn Astronomical Institute,
Landleven 12, 9747 AD Groningen, The Netherlands; 7 Netherlands Research School for Astronomy (NOVA), Leiden
Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands
1E-mail contact: alvaro.hacar at univie.ac.at
Context: The star formation rates and stellar densities found in young massive clusters suggest that these stellar
systems originate from gas at densities n(H2 )=107 cm−3 . Until today, however, the physical characterization of thisultra high density material remains largely unconstrained in observations.
Aims. We investigated the density properties of the star-forming gas in the OMC-1 region located in the vicinity of
the Orion Nebula Cluster (ONC).
Methods: We mapped the molecular emission at 652 GHz in OMC-1 as part of the APEX-SEPIA660 Early Science.
Results: We detect bright and extended N2 H+ (J=7-6) line emission along the entire OMC-1 region. Comparisonswith previous ALMA data of the (J=1-0) transition and radiative transfer models indicate that the line intensities
observed in this N2 H+ (7-6) line are produced by large mass reservoirs of gas at densities n(H2 )=107 cm−3 .
Conclusions: The first detection of this N2 H+ (7-6) line at parsec-scales demonstrates the extreme density conditionsof the star- forming gas in young massive clusters such as the ONC. Our results highlight the unique combinationof sensitivity and mapping capabilities of the new SEPIA660 receiver for the study of the ISM properties at highfrequencies.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2009.12549

15

16.

Misaligned Twin Molecular Outflows From Class-0 Proto-stellar Binary System VLA
1623A Unveiled by ALMA
Chihomi Hara1,2,3 , Ryohei Kawabe2,3,4 , Fumitaka Nakamura2,3,4 , Naomi Hirano5 , Shigehisa Takakuwa6 ,Yoshito Shimajiri2 , Takeshi Kamazaki2 , James Di Francesco7 , Masahiro N. Machida8 , Motohide Tamura3 ,Kazuya Saigo2 , Tomoaki Matsumoto9 and Kengo Tomida10
NEC Coorporation, Fuchu, Tokyo 183-8501, Japan; 2 National Astronomical Observatory of Japan, Mitaka, Tokyo
181-8588, Japan; 3 Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033,
Japan; 4 The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;
5
Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No.1,
Sec. 4, Roosevelt Rd, Taipei, 10617, Taiwan; 6 Department of Physics and Astronomy, Graduate School of Science andEngineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan; 7 NRC Herzberg Instof Astrophysics, 5071 W Saanich Rd, Victoria BC V9E 2E7, British Columbia, Canada; 8 Department of Earth andPlanetary Science, Faculty of Science, Kyushu University, Motooka 744 , Nishi-ku, Fukuoka 819-0395, Japan; 9 acultyof Sustainability Studies, Hosei University,Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan; 10 Astronomical Institute,
Tohoku University, Sendai, Miyagi 980-8578, Japan1

E-mail contact: fumitaka.nakamura at nao.ac.jp
We present the results of ALMA observations toward the low-mass Class-0 binary system, VLA 1623Aab in theOphiuchus molecular cloud in 12 CO, 13 CO, and C18 O(2–1) lines. Our 12 CO (J=2–1) data reveal that the VLA 1623
outflow consists of twin spatially overlapped outflows/jets. The redshifted northwestern jet exhibits the three cyclesof wiggle with a spatial period of 1360pm10 au, corresponding to a time period of 180 yr. The wiggle-like structureis also found in the position-velocity (PV) diagram, showing an amplitude in velocity of about 0.9 km s−1 . Both theperiod and the velocity amplitude of the wiggle are roughly consistent with those expected from the binary parameters,i.e., the orbital period (460pm20 yr) and the Keplerian velocity (2.2 km s−1 ). Our 13 CO and C18 O images reveal thenature of the dense gas in the two cm/mm sources, VLA 1623-B and -W, and its relation to the outflows, and strongly
support the previous interpretation that both are shocked cloudlets. The driving sources of the twin molecular outflows
are, therefore, likely to be within the VLA 1623Aab binary. The axes of the two molecular outflows are estimatedto be inclined by 70◦ from each other across the plane of sky, implying that the associated protostellar disks are also
misaligned by 70◦ . Such a misalignment, together with a small binary separation of 34 au in the one of the youngest
protobinary systems known, is difficult to explain by models of disk fragmentation in quiescent environments. Instead,other effects such as turbulence probably play roles in misaligning the disks.
Accepted by ApJ

CMZoom II: Catalog of Compact Submillimeter Dust Continuum Sources in the Milky

17. Way’s Central Molecular Zone

H Perry Hatchfield1 , Cara Battersby1,2 , Eric Keto2 , Daniel Walker1,3,4 , Ashley Barnes5 , Daniel Callanan2,6 ,Adam Ginsburg7 , Jonathan D. Henshaw8 , Jens Kauffmann9 , J. M. Diederik Kruijssen10 , Steve N.
Longmore6 , Xing Lu4 , Elisabeth A. C. Mills11, Thushara Pillai12 , Qizhou Zhang13 , John Bally14 , Natalie Butterfield15 , Yanett A. Contreras16 , Luis C. Ho17,18 , J19 , Nimesh Patel2 and Volker Tolls2
University of Connecticut, Department of Physics, 196A Auditorium Road, Unit 3046, Storrs, CT 06269, USA; 2Center for Astrophysics, Harvard & Smithsonian, MS-78, 60 Garden Street, Cambridge, MA 02138, USA; 3 Joint
ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 4 National Astronomical Observatory ofJapan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan; 5 Argelander-Institut für Astronomie, Universität Bonn, Auf
dem Hügel 71, D-53121, Bonn, DE, Germany; 6 Astrophysics Research Institute, Liverpool John Moores University,
146 Brownlow Hill, Liverpool L3 5RF, UK; 7 University of Florida Department of Astronomy, Bryant Space Science
Center, Gainesville, FL, 32611, USA; 8 Max-Planck-Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg,
Germany; 9 Haystack Observatory, Massachusetts Institute of Technology, 99 Millstone Road, Westford, MA 01886,
USA; 10 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14,
D-69120 Heidelberg, Germany; 11 Department of Physics and Astronomy, University of Kansas, 1251 Wescoe Hall
Drive, Lawrence, KS 66045, USA; 12 Boston University Astronomy Department, 725 Commonwealth Avenue, Boston,
MA 02215, USA; 13 Center for Astrophysics, Harvard & Smithsonian, MS-42, 60 Garden Street, Cambridge, MA
02138, USA; 14 CASA, University of Colorado, 389-UCB, Boulder, CO 80309, USA; 15 Green Bank Observatory, 1551

16

Observatory Road, P.O. Box 2, Green Bank, WV 24944, USA; 16 Leiden Observatory, Leiden University, P.O. Box
9513, NL 2300 RA Leiden, The Netherlands; 17 Kavli Institute for Astronomy and Astrophysics, Peking University,
Beijing 100871, People’s Republic of China; 18 Department of Astronomy, School of Physics, Peking University, Beijing
100871, People’s Republic of China; 19 National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM
87801, USA
E-mail contact: h.hatchfield at uconn.edu
In this paper we present the CMZoom Survey’s catalog of compact sources (≤ 10 arcsec, ∼0.4pc) within the CentralMolecular Zone (CMZ). CMZoom is a Submillimeter Array (SMA) large program designed to provide a complete
and unbiased map of all high column density gas (N(H2 ) ≥ 1023 cm−2 ) of the innermost 500pc of the Galaxy inthe 1.3mm dust continuum. We generate both a robust catalog designed to reduce spurious source detections, and asecond catalog with higher completeness, both generated using a pruned dendrogram. In the robust catalog, we report
285 compact sources, or 816 in the high completeness catalog. These sources have effective radii between 0.04-0.4 pc,
and are the potential progenitors of star clusters. The masses for both catalogs are dominated by the Sagittarius B2
cloud complex, where masses are likely unreliable due to free-free contamination, uncertain dust temperatures, andline-of-sight confusion. Given the survey selection and completeness, we predict that our robust catalog accounts formore than ∼99% of compact substructure capable of forming high mass stars in the CMZ. This catalog provides a
crucial foundation for future studies of high mass star formation in the Milky Way’s Galactic Center.
Accepted by ApJ Supplement Series
https://arxiv.org/pdf/2009.05052

18.

Transport, destruction and growth of pebbles in the gas envelope of a protoplanet
Anders Johansen1 and Åke Nordlund2
Lund Observatory, Lund University and GLOBE Institute, University of Copenhagen; 2 Niels Bohr Institute, University of Copenhagen
1E-mail contact: Anders.Johansen at sund.ku.dk
We analyse the size evolution of pebbles accreted into the gaseous envelope of a protoplanet growing in a protoplanetary
disc, taking into account collisions driven by the relative sedimentation speed as well as the convective gas motion.
Using a simple estimate of the convective gas speed based on the pebble accretion luminosity, we find that the speed of
the convective gas is higher than the sedimentation speed for all particles smaller than 1 mm. This implies that both
pebbles and pebble fragments are strongly affected by the convective gas motion and will be transported by large-scaleconvection cells both towards and away from the protoplanet’s surface. We present a simple scheme for evolving thecharacteristic size of the pebbles, taking into account the effects of erosion, mass transfer and fragmentation. Including
the downwards motion of convective cells for the transport of pebbles with an initial radius of 1 millimeter, we findpebble sizes between 100 microns and 1 millimeter near the surface of the protoplanet. These sizes are generally
amenable to accretion at the base of the convection flow. Small protoplanets far from the star (> 30 AU) neverthelesserode their pebbles to sizes below 10 microns; future hydrodynamical simulations will be needed to determine whether
such small fragments can detach from the convection flow and become accreted by the protoplanet.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2009.07837

19.

Resolved star formation in the metal poor star-forming region Magellanic Bridge C
V. M. Kalari1,2 , M. Rubio2 , Hugo P. Saldaño3 and Alberto D. Bolatto4
1
Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile; 2 Departamento de
Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile; 3 Observatorio Astronómico, Universidad Nacionalde Córdoba, Córdoba, Argentina; 4 Department of Astronomy, University of Maryland, College Park, MD 20742, USA

E-mail contact: vkalari at gemini.edu
Magellanic Bridge C (MB-C) is a metal-poor (∼1/5 Z⊙) low-density star-forming region located 59 kpc away in the
Magellanic Bridge, offering a resolved view of the star formation process in conditions different to the Galaxy. From
17

Atacama Large Millimetre Array CO (1-0) observations, we detect molecular clumps associated to candidate youngstellar objects (YSOs), pre-main sequence (PMS) stars, and filamentary structure identified in far-infrared imaging.
YSOs and PMS stars form in molecular gas having densities between 17–200 M⊙ pc−2 , and have ages between <∼0.1–
3 Myr. YSO candidates in MB -C have lower extinction than their Galactic counterparts. Otherwise, our results
suggest that the properties and morphologies of molecular clumps, YSOs, and PMS stars in MB -C present no patentdifferences with respect to their Galactic counterparts, tentatively alluding that the bottleneck to forming stars inregions similar to MB-C is the conversion of atomic gas to molecular.
Accepted by MNRAS
https://arxiv.org/pdf/2009.11868

Mapping the H2 D+ and N2 H+ emission towards prestellar cores. Testing dynamical

20. models of the collapse using gas tracers

E. Koumpia1 , L. Evans2,3 , J. Di Francesco4 , F. F. S. van der Tak5,6 and R. D. Oudmaijer1
School of Physics & Astronomy, University of Leeds, Woodhouse Lane, LS2 9JT Leeds, UK; 2 IRAP, Université deToulouse, CNRS, UPS, CNES, F-31400 Toulouse, France; 3 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi
5,I-50125, Florence, Italy; 4 Herzberg Astronomy and Astrophysics Research Centre, National Research Council of
Canada, Victoria, BC, Canada; 5 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen,
The Netherlands; 6 Kapteyn Astronomical Institute, University of Groningen, The Netherlands

1E-mail contact: ev.koumpia at gmail.com
The study of prestellar cores is critical as they set the initial conditions in star formation and determine the final massof the stellar object. To date, several hypotheses are describing their gravitational collapse. We perform detailed line
analysis and modelling of H2 D+ 110 -111 and N2 H+ 4-3 emission at 372 GHz, using 2’x2’ maps (JCMT). Our goal
is to test the most prominent dynamical models by comparing the modelled gas kinematics and spatial distribution(H2 D+ and N2 H+ ) with observations towards four prestellar (L1544, L183, L694-2, L1517B) and one protostellar
core (L1521f). We perform a detailed non-LTE radiative transfer modelling using RATRAN, where we compare thepredicted spatial distribution and line profiles of H2 D+ and N2 H+ with observations towards all cores. To do so,
we adopt the physical structure for each core predicted by three different dynamical models taken from literature:
Quasi-Equilibrium Bonnor-Ebert Sphere (QE-BES), Singular Isothermal Sphere (SIS), and Larson-Penston (LP) flow.
Our analysis provides an updated picture of the physical structure of prestellar cores. We find that the SIS model can
be clearly excluded in explaining the gas emission towards the cores, but a larger sample is required to differentiate
clearly between the LP flow, the QE-BES and the static models. All models of collapse underestimate the intensityof the gas emission by up to several factors towards the only protostellar core in our sample, indicating that different
dynamics take place in different evolutionary core stages. If the LP model is confirmed towards a larger sample ofprestellar cores, it would indicate that they may form by compression or accretion of gas from larger scales. If the
QE-BES model is confirmed, it means that quasi hydrostatic cores can exist within turbulent ISM.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2009.08857

21. Supernovae in the Orion: the missing link in the star forming history of the region
Marina Kounkel11Western Washington University

E-mail contact: Marina.Kounkel at wwu.edu
The Orion Complex is a notable star forming region, that it is fragmented into several different populations that havesubstantial difference in their phase space. I propose a model that attempts to explain the how the Complex has evolved
to this current configuration. In this model, the large scale expansion can be attributable to a supernova that has
exploded 6 Myr ago. The remnant of which can be seen as Barnard’s loop, as the center of the expansion is consistent
with the geometrical center of the HII bubble. This is similar to the HII bubble and the ballistic expansion that is
associated with λ Ori, a region which has also been a site of an ancient supernova. Assuming that the Orion Complex
has originally been forming as one long filament spanning from the bottom of Orion A to ψ 2 Ori (or, potentially,18

as far as λ Ori), Barnard’s loop supernova could have split the cloud, which lead to the formation of Orion C & D.
Furthermore, the shockwave that has propagated into the filament could have swept along the gas through several pc,
which lead to the formation of the singularly most massive cluster in the Solar Neighborhood, the ONC. I also discuss
other related nearby events, such as the formation of the Monogem ring, and various runaways that have been ejectedfrom the Orion Complex.
Accepted by ApJ
https://arxiv.org/pdf/2007.09160

22.

Untangling the Galaxy. II. Structure within 3 kpc
Marina Kounkel1 , Kevin Covey1 and Keivan Stassun2
1

Western Washington University; 2 Vanderbilt University

E-mail contact: Marina.Kounkel at wwu.edu
We present the results of the hierarchical clustering analysis of the Gaia DR2 data to search for clusters, co-moving
groups, and other stellar structures. The current paper builds on the sample from the previous work, extending it
in distance from 1 kpc to 3 kpc, increasing the number of identified structures up to 8292. To aid in the analysis of
the population properties, we developed a neural network called Auriga to robustly estimate the age, extinction, anddistance of a stellar group based on the input photometry and parallaxes of the individual members. We apply Auriga
to derive the properties of not only the structures found in this paper, but also previously identified open clusters.
Through this work, we examine the temporal structure of the spiral arms. Specifically, we find that the Sagittarius
arm has moved by >500 pc in the last 100 Myr, and the Perseus arm has been experiencing a relative lull in starformation activity over the last 25 Myr. We confirm the findings from the previous paper on the transient nature of
the spiral arms, with the timescale of transition of a few 100 Myr. Finally, we find a peculiar ∼1 Gyr old stream ofstars that appears to be heliocentric. It is unclear what is the origin of it.
Accepted by AJ
https://arxiv.org/pdf/2004.07261

Makemake + Sedna:
23. A Continuum Radiation Transport and Photoionization Framework for Astrophysical
Newtonian Fluid Dynamics
Rolf Kuiper1 , Harold W. Yorke2 and Andrea Mignone3
1
Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany; 2 SOFIA Science Center, Universities Space Research Association (USRA), M/S 232-12, Moffett Field, CA
94035-1000, USA; 3 Dipartimento di Fisica Generale, Universita di Torino, via Pietro Giuria 1, 10125 Torino, Italy

E-mail contact: rolf.kuiper at uni-tuebingen.de
Astrophysical fluid flow studies often encompass a wide range of physical processes to account for the complexity ofthe system under consideration. In addition to gravity, a proper treatment of thermodynamic processes via continuum
radiation transport and/or photoionization is becoming the state of the art.
We present a major update of our continuum radiation transport module, MAKEMAKE, and a newly developed module for photoionization, SEDNA, coupled to the magnetohydrodynamics code PLUTO. These extensions are currently
not publicly available; access can be granted on a case-by-case basis.
We explain the theoretical background of the equations solved, elaborate on the numerical layout, and present acomprehensive test suite for radiation–ionization hydrodynamics. The grid based radiation and ionization modules
support static one-dimensional, two-dimensional, and three-dimensional grids in Cartesian, cylindrical, and spherical coordinates. Each module splits the radiation field into two components, one originating directly from a point
source – solved using a ray-tracing scheme – and a diffuse component – solved with a three-dimensional flux-limited
diffusion (FLD) solver. The FLD solver for the continuum radiation transport makes use of either the equilibrium
one-temperature approach or the linearization two-temperature approach. The FLD solver for the photoionization
module enables accounting for the temporal evolution of the radiation field from direct recombination of free electrons
into the hydrogen ground state as an alternative to the on-the-spot approximation.
19

A brief overview of completed and ongoing scientific studies is given to explicitly illustrate the multipurpose nature of
the numerical framework presented.
Accepted by ApJS, vol. 250
http://arxiv.org/pdf/2009.12374

24.

The physical parameters of clumps associated with class I methanol masers
Dmitry A. Ladeyschikov1 , James S. Urquhart2 , Andrey M. Sobolev1 , Shari L. Breen3 and Olga S.
Bayandina4
1

Ural Federal University, 51 Lenin Str., 620051 Ekaterinburg, Russia; 2 Centre for Astrophysics and Planetary Science,
University of Kent, Canterbury CT2 7NH, UK; 3 SKA Organisation, Jodrell Bank Observatory, SK11 9DL, UK; 4
Joint Institute for VLBI ERIC Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
E-mail contact: dmitry.ladeyschikov at urfu.ru
We present a study of the association between class I methanol masers and cold dust clumps from the ATLASGAL
survey. It was found that almost 100% of class I methanol masers are associated with objects listed in the ATLASGAL
compact source catalog. We find a statistically significant difference in the flux density, luminosity, number and column
density and temperature distributions of ATLASGAL sources associated with 95/44 GHz methanol masers comparedwith those ATLASGAL sources devoid of 95 GHz methanol masers. The masers tend to arise in clumps with higher
densities, luminosities and temperatures compared with both the full sample of the ATLASGAL clumps, as well as the
sample of ATLASGAL sources that were cross-matched with positions previously searched for methanol masers butwith no detections. Comparison between the peak position of ATLASGAL clumps and the interferometric positionsof the associated class I and II methanol masers reveals that class I masers are generally located at larger physicaldistances from the peak submillimetre emission than class II masers. We conclude that the tight association between
ATLASGAL sources and class I methanol masers may be used as a link toward understanding the conditions of thepumping of these masers and evolutionary stages at which they appear.
Accepted by Astronomical Journal
http://maserdb.net/ATLASGAL.MMI.accepted.pdf

25. A statistical analysis of dust polarization properties in ALMA observations of Class 0

protostellar cores

Valentin J. M. Le Gouellec1,2 , Anaëlle J. Maury2,3 , Vincent Guillet4,5, Charles L. H. Hull6,7,11 , Josep
Miquel Girart8,9 , Antoine Verliat2 , Raphaël Mignon-Risse2,10, Valeska Valdivia2 , Patrick Hennebelle2,
Matthias Gonzàlez2,10 and Fabien Louvet2
European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago , Chile; 2 Université
Paris-Saclay, CNRS, CEA, Astrophysique, Instrumentation et Modélisation de Paris-Saclay, 91191, Gif-sur-Yvette,
France; 3 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; 4 Université Paris-Saclay,
CNRS, Institut d’astrophysique spatiale, 91405, Orsay, France; 5 Laboratoire Univers et Particules de Montpellier,
Université de Montpellier, CNRS/IN2P3, CC 72, Place Eugene Bataillon, 34095, Montpellier Cedex 5, France; 6National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Cordova 3788, Office 61B, 7630422, Vitacura,Santiago, Chile; 7 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile; 8 Institut de Ciències
de l’Espai (ICE-CSIC), Campus UAB, Carrer de Can Magrans S/N, E-08193 Cerdanyola del Valles, Catalonia, Spain;
9
Institut d’Estudis Espacials de Catalunya, E-08030 Barcelona, Catalonia, Spain; 10 Universié de Paris, AIM, F-91191,
Gif-sur-Yvette, France; 11 NAOJ Fellow
1E-mail contact: valentin.le.gouellec at gmail.com
Recent observational progress has challenged the dust grain-alignment theories used to explain the polarized dust
emission routinely observed in star-forming cores. In an effort to improve our understanding of the dust grain alignment
mechanism(s), we have gathered a dozen ALMA maps of (sub)millimeter-wavelength polarized dust emission fromClass 0 protostars, and carried out a comprehensive statistical analysis of dust polarization quantities. We analyze
the statistical properties of the polarization fraction Pfrac and dispersion of polarization position angles S. Morespecifically, we investigate the relationship between S and Pf rac as well as the evolution of the product S×Pf rac
20

as a function of the column density of the gas in the protostellar envelopes. We compare the observed trends withthose found in polarization observations of dust in the interstellar medium and in synthetic observations of non-ideal
magneto-hydrodynamic (MHD) simulations of protostellar cores. We find a significant S ∝ Pfrac −0.79 correlation in
the polarized dust emission from protostellar envelopes seen with ALMA; the power-law index differs significantly
from the one observed by Planck in star-forming clouds. The product S×Pf rac , which is sensitive to the dust grainalignment efficiency, is approximately constant across three orders of magnitude in envelope column density (fromNH2 = 1022 cm−2 to NH2 = 1025 cm−2 , with a mean value of 0.36+0.10−0.17 . This suggests that the grain alignment
mechanism producing the bulk of the polarized dust emission in star-forming cores may not depend systematicallyon the local conditions such as local gas density. However, in the lowest-luminosity sources in our sample, we finda hint of less efficient dust grain alignment with increasing column density. Our observations and their comparison
with synthetic observations of MHD models suggest that the total intensity versus the polarized dust are distributed
at different intrinsic spatial scales, which can affect the statistics from the ALMA observations, for example byproducing artificially high Pfrac . Finally, synthetic observations of MHD models implementing radiative alignment
torques (RATs) show that the statistical estimator S × Pfrac is sensitive to the strength of the radiation field in thecore. Moreover, we find that the simulations with a uniform perfect alignment (PA) of dust grains yield on averagemuch higher S×Pf rac values than those implementing RATs; the ALMA values lie among those predicted by PA,
and are significantly higher than the ones obtained with RATs, especially at large column densities. Ultimately, ourresults suggest dust alignment mechanism(s) are efficient at producing dust polarized emission in the various local
conditions typical of Class 0 protostars. The grain alignment efficiency found in these objects seems to be higher
than the efficiency produced by the standard RAT alignment of paramagnetic grains. Further study will be needed tounderstand how more efficient grain alignment via, e.g., different irradiation conditions, dust grain characteristics, oradditional grain alignment mechanisms can reproduce the observations.
Accepted by A&A
https://arxiv.org/pdf/2009.07186

26.

Young Faithful: The Eruptions of EC 53 as It Cycles through Filling and Draining theInner Disk
Yong-Hee Lee1 , Doug Johnstone2,3 , Jeong-Eun Lee1 , Gregory Herczeg4,5 , Steve Mairs6 , Watson Varricatt7 ,Klaus W. Hodapp7 , Tim Naylor8 , Carlos Contreras Peña8 , Giseon Baek1 , Martin Haas9 and Rolf
Chini9,10
School of Space Research and Institute of Natural Sciences, Kyung Hee University, 1732 Deogyeong-daero, Giheunggu, Yongin-si, Gyeonggi-do 446-701, Korea; 2 Department of Physics and Astronomy, University of Victoria, Victoria,
BC, V8P 1A1, Canada; 3 NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd, Victoria, BC, V9E
2E7, Canada; 4 Kavli Institute for Astronomy and Astrophysics, Peking University, Yiheyuan 5, Haidian Qu, 100871
Beijing, China; 5 Department of Astronomy, Peking University, Yiheyuan 5, Haidian Qu, 100871 Beijing, China; 6 East
Asian Observatory, 660 N. A‘ohōkū Place, Hilo, HI 96720, USA; 7 Institute for Astronomy, University of Hawaii, 640
N. A’ohoku Place, Hilo, HI 96720, USA; 8 School of Physics, Astrophysics Group, University of Exeter, Stocker Road,
Exeter EX4 4QL, UK; 9 Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstraße 150, 44801 Bochum,
Germany; 10 Instituto de Astronomia, Universidad Catolica del Norte, Avenida Angamos 0610, Antofagasta, Chile
1

E-mail contact: ieehee at khu.ac.kr
While young stellar objects sometimes undergo bursts of accretion, these bursts usually occur sporadically, making
them challenging to study observationally and to explain theoretically. We build a schematic description of cyclicalbursts of the young stellar object EC 53 using near-IR and sub-mm monitoring obtained over six cycles, each lasting≈ 530 days. EC 53 brightens over 0.12 yr by 0.3 mag at 850 µm, 2 mag at 3.35 µm, and 1.5 mag at near-IR wavelengths,
to a maximum luminosity consistent with an accretion rate of ∼ 8 × 10−6 M⊙ yr−1 . The emission then decays with an
e-folding timescale of ≈ 0.74 yr until the accretion rate is ∼ 1 × 10−6 M⊙ yr−1 . The next eruption then occurs, likely
triggered by the buildup of ∼ 5 × 10−6 M⊙ of mass in the inner disk, enough that it becomes unstable and drains onto
the star. Just before outburst, when the disk is almost replenished, the near-IR colors become redder, indicating an
increase in the geometrical height of the disk by this mass buildup. The reddening disappears soon after the initial
burst, as much of the mass is drained from the disk. We quantify physical parameters related to the accretion process
in EC 53 by assuming an α-disk formulation, constrained by the observed disk properties and accretion rate. While21

we can only speculate about the possible trigger for these faithful eruptions, we hope that our quantified schematic
will motivate theorists to test the hypothesized mechanisms that could cause the cyclical buildup and draining of massin the inner disk.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2009.05268

The ALMA Survey of 70 µm Dark High-mass Clumps in Early Stages (ASHES). II:

27. Molecular Outflows in the Extreme Early Stages of Protocluster Formation

Shanghuo Li1,2,3,4 , Patricio Sanhueza5,6 , Qizhou Zhang2 , Fumitaka Nakamura5,6 , Xing Lu5 , Junzhi
Wang1 , Tie Liu1 , Ken’ichi Tatematsu5 , James M. Jackson7 , Andrea Silva5 , Andrés E. Guzmán5 , Takeshi
Sakai8 , Natsuko Izumi5,9 , Daniel Tafoya10 , Fei Li1,3 , Yanett Contreras11 , Kaho Morii12 and Kee-Tae
Kim13
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China; 2
CfA, 60 Garden Street, Cambridge, MA 02138, USA; 3 University of Chinese Academy of Sciences, 19A Yuquanlu,
Beijing 100049, China; 4 KASI, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; 5 National
Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588,
Japan; 6 Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1
Osawa, Mitaka, Tokyo 181-8588, Japan; 7 SOFIA Science Center, USRA, NASA Ames Research Center, Moffett
Field CA 94045, USA; 8 Graduate School of Informatics and Engineering, The University of Electro-Communications,
Chofu, Tokyo 182-8585, Japan.; 9 College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan;
10
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory,
439 92 Onsala, Sweden; 11 Leiden Observatory, PO Box 9513, NL-2300 RA Leiden, the Netherlands; 12 Departmentof Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1, Osawa, Mitaka, Tokyo 181-0015, Japan;
13
University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
1E-mail contact: shanghuo.li at gmail.com
We present a study of outflows at extremely early stages of high-mass star formation obtained from the ALMA
Survey of 70 µm dark High-mass clumps in Early Stages (ASHES). Twelve massive 3.6−70 µm dark prestellar clumpcandidates were observed with the Atacama Large Millimeter/submillimeter Array (ALMA) in Band 6. Forty-threeoutflows are identified toward 41 out of 301 dense cores using the CO and SiO emission lines, yielding a detection rateof 14%. We discover 6 episodic molecular outflows associated with low- to high-mass cores, indicating that episodic
outflows (and therefore episodic accretion) begin at extremely early stages of protostellar evolution for a range ofcore masses. The time span between consecutive ejection events is much smaller than those found in more evolved
stages, which indicates that the ejection episodicity timescale is likely not constant over time. The estimated outflow
dynamical timescale appears to increase with core masses, which likely indicates that more massive cores have longer
accretion timescales than less massive cores. The lower accretion rates in these 70 µm dark objects compared to themore evolved protostars indicate that the accretion rates increase with time. The total outflow energy rate is smaller
than the turbulent energy dissipation rate, which suggests that outflow induced turbulence cannot sustain the internal
clump turbulence at the current epoch. We often detect thermal SiO emission within these 70 µm dark clumps that isunrelated to CO outflows. This SiO emission could be produced by collisions, intersection flows, undetected protostars,
or other motions.
Accepted by ApJ
https://arxiv.org/pdf/2009.05506

28.

The role of collision speed, cloud density, and turbulence in the formation of young
massive clusters via cloud-cloud collisions
Kong You Liow1 and Clare L. Dobbs1
1

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

E-mail contact: kl457 at exeter.ac.uk
Young massive clusters (YMCs) are recently formed astronomical objects with unusually high star formation rates. We
propose the collision of giant molecular clouds (GMCs) as a likely formation mechanism of YMCs, consistent with the22

YMC conveyor-belt formation mode concluded by other authors. We conducted smoothed particle hydrodynamical
simulations of cloud-cloud collisions and explored the effect of the clouds collision speed, initial cloud density, andthe level of cloud turbulence on the global star formation rate and the properties of the clusters formed from thecollision. We show that greater collision speed, greater initial cloud density and lower turbulence increase the overall
star formation rate and produce clusters with greater cluster mass. In general, collisions with relative velocity ≥ 25
km/s, initial cloud density ≥ 250 cm−3 , and turbulence of ≈ 2.5 km/s can produce massive clusters with properties
resembling the observed Milky Way YMCs.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/2009.07857

The SOFIA Massive (SOMA) Star Formation Survey. III. From Intermediate- to High-

29. Mass Protostars

Mengyao Liu1 , Jonathan C. Tan2,1 , James M. De Buizer3 , Yichen Zhang4 , Emily Moser5 , Maria T.
Beltrán6 , Jan E. Staff7 , Kei E. I. Tanaka8 , Barbara Whitney9 , Viviana Rosero10 , Yao-Lun Yang1 andRubén Fedriani2
Dept. of Astronomy, University of Virginia, Charlottesville, Virginia 22904, USA; 2 Dept. of Space, Earth &Environment, Chalmers University of Technology, 412 93 Gothenburg, Sweden; 3 SOFIA-USRA, NASA Ames ResearchCenter, MS 232-12, Moffett Field, CA 94035, USA; 4 Star and Planet Formation Laboratory, RIKEN Cluster for
Pioneering Research, Wako, Saitama 351-0198, Japan; 5 Dept. of Astronomy, Cornell University, Ithaca, NY 14853,
USA; 6 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 7 College of Science andMath, University of Virgin Islands, St. Thomas, United States Virgin Islands 00802; 8 ALMA Project, NAOJ, Mitaka,
Tokyo 181-8588, Japan; 9 Dept. of Astronomy, University of Wisconsin-Madison, 475 N. Charter St, Madison, WI
53706, USA; 10 NRAO, 1003 Lópezville Rd., Socorro, NM 87801, USA
1E-mail contact: ml7hc at virginia.edu
We present ∼ 10−40 µm SOFIA-FORCAST images of 14 intermediate-mass protostar candidates as part of the SOFIA
Massive (SOMA) Star Formation Survey. We build spectral energy distributions (SEDs), also utilizing archival Spitzer,
Herschel and IRAS data. We then fit the SEDs with radiative transfer (RT) models of Zhang & Tan (2018), based on
Turbulent Core Accretion theory, to estimate key protostellar properties. With the addition of these intermediate-masssources, SOMA protostars span luminosities from ∼ 102 − 106 L⊙ , current protostellar masses from ∼ 0.5 − 30 M⊙ andambient clump mass surface densities, Σcl from 0.1 − 3 g cm−2 . A wide range of evolutionary states of the individual
protostars and of the protocluster environments are also probed. We have also considered about 50 protostars identified
in Infrared Dark Clouds and expected to be at the earliest stages of their evolution. With this global sample, mostof the evolutionary stages of high- and intermediate-mass protostars are probed. From the best fitting models, there
is no evidence of a threshold value of protocluster clump mass surface density being needed to form protostars up to−2∼ 25 M⊙ . However, to form more massive protostars, there is tentative evidence that Σcl needs to be >∼1 g cm . We
discuss how this is consistent with expectations from core accretion models that include internal feedback from theforming massive star.
Accepted by ApJ
https://arxiv.org/pdf/2006.06424

30. ALMA observations and modeling of the rotating outflow in Orion Source I
J. A. López-Vázquez1 , Luis A. Zapata1 , Susana Lizano1 and Jorge Cantó2
Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apartado Postal 3-72, 58089
Morelia, Michoacán, México; 2 Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal
70-264, 04510, CDMX, México
1

E-mail contact: j.lopez at irya.unam.mx
We present 29 SiO(J=8–7) ν=0, SiS (J=19–18) ν=0, and 28 SiO (J=8–7) ν=1 molecular line archive observations madewith the Atacama Large Millimeter/Submillimeter Array (ALMA) of the molecular outflow associated with Orion
Source I. The observations show velocity asymmetries about the flow axis which are interpreted as outflow rotation.

23

We find that the rotation velocity (∼4–8 km s−1 ) decreases with the vertical distance to the disk. In contrast, thecylindrical radius (∼100–300 au), the expansion velocity (∼2–15 km s−1 ), and the axial velocity vz (∼-1–10 km s−1 )increase with the vertical distance. The mass estimated of the molecular outflow Moutflow ∼0.66–1.3 M⊙ . Given akinematic time ∼130 yr, this implies a mass loss rate Ṁoutflow ∼ 5.1 − 10 × 10−3 M⊙ yr−1 . This massive outflow sets
important contraints on disk wind models. We compare the observations with a model of a shell produced by theinteraction between an anisotropic stellar wind and an Ulrich accretion flow that corresponds to a rotating molecularenvelope in collapse. We find that the model cylindrical radii are consistent with the 29 SiO(J=8–7) ν=0 data. The
expansion velocities and the axial velocities of the model are similar the observed values, except close to the disk(z ∼ ±150 au) for the expansion velocity. Nevertheless, the rotation velocities of the model are a factor ∼3–10 lower
than the observed values. We conclude that the Ulrich flow alone cannot explain the rotation observed and otherpossibilities should be explored, like the inclusion of the angular momentum of a disk wind.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2010.00132.pdf

31. Failed and delayed protostellar outflows with high mass accretion rates
Masahiro N. Machida1 and Takashi Hosokawa2
Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka, Fukuoka, Japan; 2
Department of Physics, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan1

E-mail contact: machida.masahiro.018 at m.kyushu-u.ac.jp
The evolution of protostellar outflows is investigated under different mass accretion rates in the range ∼ 10−5 –10−2 M⊙ yr−1 with three-dimensional magnetohydrodynamic simulations. A powerful outflow always appears instrongly magnetized clouds with B0 > B0,cr = 10−4 (Mcl /100 M⊙) G, where Mcl is the cloud mass. When a cloud
has a weaker magnetic field, the outflow does not evolve promptly with a high mass accretion rate. In some caseswith moderate magnetic fields B0 slightly smaller than B0,cr , the outflow growth is suppressed or delayed until theinfalling envelope dissipates and the ram pressure around the protostellar system is significantly reduced. In such anenvironment, the outflow begins to grow and reaches a large distance only during the late accretion phase. On theother hand, the protostellar outflow fails to evolve and is finally collapsed by the strong ram pressure when a massive(> 100M⊙) initial cloud is weakly magnetized with B0 < 100 µG. The failed outflow creates a toroidal structure that is
supported by magnetic pressure and encloses the protostar and disk system. Our results indicate that high-mass stars
form only in strongly magnetized clouds, if all high-mass protostars possess a clear outflow. If we would observe either
very weak or no outflow around evolved protostars, it means that strong magnetic fields are not necessarily requiredfor high-mass star formation. In any case, we can constrain the high-mass star formation process from observationsof outflows.
Accepted by MNRAS
http://arxiv.org/pdf/2010.04866

32. Exploring the nature of compact radio sources associated to UCHII regions
J.M. Masqué1 , L.F. Rodríguez2,3 , S.A. Dzib4 , S.N. Medina4 , L. Loinard2 , M.A. Trinidad1 , S.E. Kurtz2
and C. A Rodríguez-Rico1
Departamento de Astronomía, Universidad de Guanajuato, Apdo. Postal 144, 36000 Guanajuato, México; 2 Institutode Radioastronomía y Astrofísica, UNAM, Morelia 58089, México; 3 Mesoamerican Center for Theoretical Physics,
Universidad Autónoma de Chiapas, Carretera Emiliano Zapata Km. 4, Real del Bosque (Terán), 29050 Tuxtla
Gutiérrez, Chiapas, México; 4 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany

1E-mail contact: jmasque at astro.ugto.mx
We present Very Large Array 7 mm continuum observations of four Ultra-Compact (UC)HII regions, observed previously at 1.3 cm, in order to investigate the nature of the compact radio sources associated with these regions. We
detected a total of seven compact radio sources, four of them with thermal emission, and two compact radio sources
have clear non-thermal emission. The thermal emission is consistent with the presence of an ionized envelope, either
static (i.e., trapped in the gravitational radius of an associated massive star) or flowing away (i.e., a photo-evaporativeflow). On the other hand, the nature of the non-thermal sources remains unclear and several possibilities are pro24

posed. The possibility that most of these compact radio sources are photo-evaporating objects and the remaining ones
more-evolved objects is consistent with previous studies on UCHII regions.
Accepted by Revista Mexicana de Astronomía y Astrofísica
http://arxiv.org/pdf/2010.02992

33.

ALMA observations of envelopes around first hydrostatic core candidates
María José Maureira1,2 , Héctor G. Arce1 , Michael M. Dunham3,4 , Diego Mardones5,2 , Andrés E.
Guzmán6 , Jaime E. Pineda2 and Tyler L. Bourke7,3Astronomy Department, Yale University, New Haven, CT 06511, USA; 2 Max-Planck-Institut für extraterrestrische
Physik (MPE), Giessenbachstr. 1, D-85741 Garching, Germany; 3 Center for Astrophysics ; 4 Harvard & Smithsonian,
Cambridge, MA 02138, USA; 5 Department of Physics, State University of New York Fredonia, Fredonia, New York
14063, USA; 6 Dept. de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile; 7 National Astronomical
Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan1

E-mail contact: maureira at mpe.mpg.de
We present ALMA 3 mm molecular line and continuum observations with a resolution of 3.5" towards five firsthydrostatic core (FHSC) candidates (L1451-mm, Per-bolo 58, Per-bolo 45, L1448-IRS2E and Cha-MMS1). Our goal
is to characterize their envelopes and identify the most promising sources that could be bona fide FHSCs. We identify
two candidates which are consistent with an extremely young evolutionary state (L1451-mm and Cha-MMS1), with
L1451-mm being the most promising FHSC candidate. Although our envelope observations cannot rule out ChaMMS1 as a FHSC yet, the properties of its CO outflow and SED published in recent studies are in better agreementwith the predictions for a young protostar. For the remaining three sources, our observations favor a prestellar nature
for Per-bolo 45 and rule out the rest as FHSC candidates. Per-bolo 58 is fully consistent with being a Class 0, while
L1448 IRS2E shows no emission of high-density tracers (NH2D and N2H+) at the location of the previously identified
compact continuum source, which is also undetected in our observations. Thus we argue that there is no embedded
source at the presumptive location of the FHSC candidate L1448 IRS2E. We propose instead, that what was thought
to be emission from the presumed L1448 IRS2E outflow corresponds to outflow emission from a nearby Class 0 system,
deflected by the dense ambient material. We compare the properties of the FHSC candidates studied in this work andthe literature, which shows that L1451-mm appears as possibly the youngest source with a confirmed outflow.
Accepted by MNRAS
https://arxiv.org/pdf/2009.08740

34.

Carbon depletion observed inside T Tauri inner rims: Formation of icy, kilometer size
planetesimals by 1 Myr
M. K. McClure1
Marie Curie Postdoctoral Fellow, Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science
Park 904, 1098 XH Amsterdam, Netherlands

1E-mail contact: mcclure at strw.leidenuniv.nl
Context: The carbon content of protoplanetary disks is an important parameter to characterize planets formed at
different disk radii. There is some evidence from far-infrared and submillimeter observations that gas in the outer disk
is depleted in carbon, with a cor- responding enhancement of carbon-rich ices at the disk midplane. Observations of
the carbon content inside of the inner sublimation rim could confirm how much carbon remains locked in kilometersize bodies in the disk.
Aims: I aim to determine the density, temperature, and carbon abundance inside the disk dust sublimation rim in aset of T Tauri stars with full protoplanetary disks.
Methods: Using medium-resolution, near-infrared (0.8 to 2.5 µm) spectra and the new GAIA DR 2 distances, I selfconsistently determine the stellar, extinction, veiling, and accretion properties of the 26 stars in my sample. Fromthese values, and non-accreting T Tauri spectral templates, I extract the inner disk excess of the target stars fromtheir observed spectra . Then I identify a series of C0 recombination lines in 18 of these disks and use the CHIANTI
atomic line database with an optically thin slab model to constrain the average ne, Te, and nC for these lines in thefive disks with a complete set of lines. By comparing these values with other slab models of the inner disk using the25

Cloudy photoionization code, I also constrain nH and the carbon abundance, XC , and hence the amount of carbon’missing’ from the slab. For one disk, DR Tau, I use relative abundances for the accretion stream from the literature
to also determine XS i and XN .
Results: The inner disks modeled here are extremely dense (nH ∼ 1016 cm−3 ), warm (Te ∼ 4500 K), and moderately
ionized (logXe ∼ 3.3). Three of the five modeled disks show robust carbon depletion up to a factor of 42 relative
to the solar value. I discuss multiple ways in which the ’missing’ carbon could be locked out of the accreting gas.
Given the high-density inner disk gas, evidence for radial drift, and lack of obvious gaps in these three systems, theircarbon depletion is most consistent with the ’missing’ carbon being sequestered in kilometer size bodies. For DR Tau,
nitrogen and silicon are also depleted by factors of 45 and 4, respectively, suggesting that the kilometer size bodies
into which the grains are locked were formed beyond the N2 snowline. I explore briefly what improvements in themodels and observations are needed to better address this topic in the future.
Accepted by A&A
https://arxiv.org/pdf/1910.06029.pdf

35. Measuring the atomic composition of planetary building blocks
Melissa McClure1 , Carsten Dominik2 and Mihkel Kama3
Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands; 2 Anton Pannekoek
Institute for Astronomy, University of Amsterdam, Science Park 904 1098 XH Amsterdam, Netherlands; 3 Departmentof Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
1E-mail contact: mcclure at strw.leidenuniv.nl
Context: Volatile molecules are critical to terrestrial planetary habitability, yet they are difficult to observe directly
where planets form at the midplanes of protoplanetary disks. It is unclear whether the inner ?1 AU of disks arevolatile-poor or if this region is resupplied with ice-rich dust from colder disk regions. Dust traps at radial pressure
maxima bounding disk gaps can cut off the inner disk from these types of volatile reservoirs. However, the trap
retention efficiency and atomic composition of trapped dust have not been measured.
Aims: We present a new technique to measure the absolute atomic abundances in the gas accreting onto T Tauristars and infer the bulk atomic composition and distribution of midplane solids that have been retained in the disk
around the young star TW Hya. Methods. We identify near-infrared atomic line emission from gas-phase material
inside the dust sublimation rim of TW Hya. Gaus- sian decomposition of the strongest H Paschen lines isolates theinner disk hydrogen emission. We measure several key elemental abundances, relative to hydrogen, using a chemical
photoionization model and infer dust retention in the disk. With a 1D transport model, we determine approximate
radial locations and retention efficiencies of dust traps for different elements.
Results: Volatile and refractory elements are depleted from TW Hya’s hot gas by factors of ?102 and up to 105,
respectively. The abundances of the trapped solids are consistent with a combination of primitive Solar Systembodies. Dust traps beyond the CO and N2 snowline cumulatively sequester 96% of the total dust flux, while the trap
at 2 AU, near the H2 O snowline, retains 3%. The high depletions of Si, Mg, and Ca are explained by a third trap at
0.3 AU with >95% dust retention.
Conclusion: TW Hya sports a significant volatile reservoir rich in C- and N-ices in its outer submillimeter ring structure.
However, unless the inner disk was enhanced in C by earlier radial transport, typical C destruction mechanisms andthe lack of a C resupply should leave the terrestrial planet-forming region of TW Hya ’dry’ and carbon-poor. Any
planets that form within the silicate dust trap at 0.3 AU could resemble Earth in terms of the degree of their volatile
depletion.
Accepted by A&A Letters
https://www.aanda.org/articles/aa/pdf/2020/10/aa38912-20.pdf

36.

Dust trapping around Lagrangian points in protoplanetary disks
Matías Montesinos1,2,3, Juan Garrido-Deutelmoser4,3 , Johan Olofsson1,3 , Cristian A. Giuppone5 , Jorge
Cuadra6,3 , Amelia Bayo1,3 , Mario Sucerquia1,3 and Nicolás Cuello7
Instituto de Física y Astronomía, Universidad de Valparaíso, Chile; 2 Chinese Academy of Sciences South America
Center for Astronomy, National Astronomical Observatories, CAS, Beijing 100012, China; 3 Núcleo Milenio de For-126

mación Planetaria (NPF), Chile; 4 Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Santiago, Chile;
5
Universidad Nacional de Córdoba, Observatorio Astronómico - IATE. Laprida 854, 5000 Córdoba, Argentina; 6Departamento de Ciencias, Facultad de Artes Liberales, Universidad Adolfo Ibáñez, Av. Padre Hurtado 750, Viña delMar, Chile; 7 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France
E-mail contact: matias.montesinos at uv.cl
Trojans are defined as objects that share the orbit of a planet at the stable Lagrangian points L4 and L5 . In the
Solar System, these bodies show a broad size distribution ranging from micrometer(µm) to centimeter(cm) particles(Trojan dust) and up to kilometer (km) rocks (Trojan asteroids). It has also been theorized that earth-like Trojans
may be formed in extra-solar systems. The Trojan formation mechanism is still under debate, especially theories
involving the effects of dissipative forces from a viscous gaseous environment. We perform hydro-simulations to follow
the evolution of a protoplanetary disk with an embedded 1–10 Jupiter-mass planet. On top of the gaseous disk, we set
a distribution of µm–cm dust particles interacting with the gas. This allows us to follow dust dynamics as solids gettrapped around the Lagrangian points of the planet. We show that large vortices generated at the Lagrangian points
are responsible for dust accumulation, where the leading Lagrangian point L4 traps a larger amount of submillimeter(submm) particles than the trailing L5 , which traps mostly mm–cm particles. However, the total bulk mass, withtypical values of ∼ Mmoon, is more significant in L5 than in L4 , in contrast to what is observed in the current Solar
System a few gigayears later. Furthermore, the migration of the planet does not seem to affect the reported asymmetry
between L4 and L5 . The main initial mass reservoir for Trojan dust lies in the same co-orbital path of the planet,
while dust migrating from the outer region (due to drag) contributes very little to its final mass, imposing strong massconstraints for the in situ formation scenario of Trojan planets.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2009.10768

37. ALMA Observations of Giant Molecular Clouds in M33. II. Triggered High-mass Star

Formation by Multiple Gas Colliding Events at the NGC 604 Complex

Kazuyuki Muraoka1 , Hiroshi Kondo1 , Kazuki Tokuda1,2 , Atsushi Nishimura1 , Rie E. Miura2 , Sachiko
Onodera3 , Nario Kuno4,5 , Sarolta Zahorecz1,2 , Kisetsu Tsuge6 , Hidetoshi Sano2 , Shinji Fujita1 , Toshikazu
Onishi1, Kazuya Saigo2 , Kengo Tachihara6 , Yasuo Fukui6,7 and Akiko Kawamura2
Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan; 2 National Astronomical Observatory of Japan, National Institutes of Natural
Science, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Meisei University, 2-1-1 Hodokubo, Hino, Tokyo 191-0042,
Japan; 4 Department of Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai,
Tsukuba, Ibaraki 305-8577, Japan; 5 Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba,
Ibaraki 305-8571, Japan; 6 Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan; 7 Institutefor Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan1

E-mail contact: kmuraoka at p.s.osakafu-u.ac.jp
We present the results of ALMA observations in 12 CO(J = 2 − 1), 13 CO(J = 2 − 1), and C18 O(J = 2 − 1) lines and1.3 mm continuum emission toward a massive (∼ 106 M⊙ ) giant molecular cloud associated with the giant H ii region
NGC 604 in one of the nearest spiral galaxy M33 at an angular resolution of 0”.44 × 0”.27 (1.8 pc × 1.1 pc). The
12
CO and 13 CO images show highly complicated molecular structures composed of a lot of filaments and shells whose
lengths are 5 – 20 pc. We found three 1.3 mm continuum sources as dense clumps at edges of two shells and also at
an intersection of several filaments. We examined the velocity structures of 12 CO(J = 2 − 1) emission in the shells
and filaments containing dense clumps, and concluded that expansion of the H ii regions cannot explain the formationof such dense cores. Alternatively, we suggest that cloud–cloud collisions induced by an external H i gas flow and thegalactic rotation compressed the molecular material into dense filaments/shells as ongoing high-mass star formationsites. We propose that multiple gas converging/colliding events with a velocity of a few tens km s−1 are necessary tobuild up NGC 604, the most significant cluster-forming complex in the Local Group of galaxies.
Accepted by ApJ
https://arxiv.org/pdf/2009.05804

27

38.

The dipper light curve of V715 Per: is there dust in the magnetosphere?
Erick Nagel1 and Jerome Bouvier2
1
2

Departamento de Astronomía, Universidad de Guanajuato, Callejón de Jalisco S/N,Guanajuato,Gto,36240,México;
IPAG, Université Grenoble Alpes 38000 Grenoble, France

E-mail contact: e.nagel at ugto.mx
The dipper optical light curves in young stellar objects are commonly interpreted as partial or total occultation of thestellar radiation by dust surrounding the star.
In this work, we analyze the amplitude of the optical light curve of V715 Per, located in the young star forming region
IC 348. Observations gathered over the years suggest that the light curve can be explained by dust extinction events.
In our model, the dust is distributed inside the magnetosphere according to the strength of the stellar magnetic field.
The dust distribution is modulated by the vertical component of the field, whose axis is misaligned with respect to therotational axis. We include a model for the evaporation of the dust reaching the magnetosphere in order to consistently
calculate its distribution.
For V715 Per, there is dust in the optically thick warp at the disk truncation radius. We suggest that the optical light
curve is explained by extinction caused by dust reaching inside the magnetosphere. The dust distribution is opticallythin and due to the high temperature and low density, it cannot survive for a long time. However because the grains
rapidly move towards the stellar surface and the sublimation is not instantaneous, there is a layer of dust covering themagnetosphere responsible for the extinction.
Dust surviving the harsh conditions of the magnetospheric accretion flow may be responsible for some of the dipper
light curves.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2010.05973

39. A new parameterization of the star formation rate-dense gas mass relation: embracinggas density gradients

G. Parmentier1 and A. Pasquali1
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120
Heidelberg, Germany

1E-mail contact: gparm at ari.uni-heidelberg.de
It is well-established that a gas density gradient inside molecular clouds and clumps raises their star formation ratecompared to what they would experience from a gas reservoir of uniform density. This effect should be observed in
the relation between dense-gas mass Mdg and star formation rate SF R of molecular clouds and clumps, with steeper
gas density gradients yielding higher SF R/Mdg ratios. The content of this paper is two-fold. Firstly, we build on thenotion of magnification factor introduced by Parmentier (2019) to redefine the dense-gas relation (i.e. the relation
between Mdg and SF R). Not only does the SF R/Mdg ratio depend on the mean free-fall time of the gas and on its(intrinsic) star formation efficiency per free-fall time, it also depends on the logarithmic slope −p of the gas density
profile and on the relative extent of the constant-density region at the clump center. Secondly, we show that nearby
molecular clouds follow the newly-defined dense-gas relation, provided that their dense-gas mass is defined based on
a volume density criterion. We also find the same trend for the dense molecular clouds of the Central Molecular Zone
(CMZ) of the Galaxy, although this one is scaled down by a factor of 10 compared to nearby clouds. The respective
locii of both nearby and CMZ clouds in the (p, SF R/Mdg ) parameter space is discussed.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2009.10652

28

40. The brown dwarf population in the star forming region NGC2264
Samuel Pearson1 , Aleks Scholz1 , Paula S Teixeira1 , Koraljka Muzic2 and Jochen Eisloffel3
SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, United
Kingdom; 2 CENTRA, Faculdade de Ciencias, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa,
Portugal; 3 Thuüringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany
1E-mail contact: sp246 at st-andrews.ac.uk
The brown dwarf population in the canonical star forming region NGC2264 is so far poorly explored. We present
a deep, multi-wavelength, multi-epoch survey of the star forming cluster NGC2264, aimed to identify young browndwarf candidates in this region. Using criteria including optical/near-infrared colours, variability, Spitzer mid-infrared
colour excess, extinction, and Gaia parallax and proper motion (in order of relevance), we select 902 faint red sources
with indicators of youth. Within this sample we identify 429 brown dwarf candidates based on their infrared colours.
The brown dwarf candidates are estimated to span a mass range from 0.01 to 0.08 M⊙. We find rotation periods for
44 sources, 15 of which are brown dwarf candidates, ranging from 3.6 hours to 6.5 days. A subset of 38 brown dwarf
candidates show high level irregular variability indicative of ongoing disc accretion, similar to the behaviour of youngstars.
Accepted by MNRAS
https://arxiv.org/pdf/2009.14749.pdf

41. From the CMF to the IMF: Beyond the Core-Collapse Model
V.-M. Pelkonen1 , P. Padoan1,2 , T. Haugbolle3, A. Nordlund1
Institut de Ciències del Cosmos, Universitat de Barcelona, Spain; 2 ICREA, Spain; 3 Niels Bohr Institute, Universityof Copenhagen;1

E-mail contact: s.pfalzner at fz-juelich.deObservations have indicated that the prestellar core mass function (CMF) is similar to the stellar initial mass function(IMF), except for an offset towards larger masses. This has led to the idea that there is a one-to-one relation between
cores and stars, such that the whole stellar mass reservoir is contained in a gravitationally-bound prestellar core,as postulated by the core-collapse model, and assumed in recent theoretical models of the stellar IMF. We test thevalidity of this assumption by comparing the final mass of stars with the mass of their progenitor cores in a highresolution star-formation simulation that generates a realistic IMF under physical conditions characteristic of observed
molecular clouds. Using a definition of bound cores similar to previous works we obtain a CMF that converges withincreasing numerical resolution. We find that the CMF and the IMF are closely related in a statistical sense only; forany individual star there is only a weak correlation between the progenitor core mass and the final stellar mass. In
particular, for high mass stars only a small fraction of the final stellar mass comes from the progenitor core, and evenfor low mass stars the fraction is highly variable, with a median fraction of only about 50%. We conclude that thecore-collapse scenario and related models for the origin of the IMF are incomplete.
Accepted by MNRAS
http://arxiv.org/abs/2008.02192

42.

Oumuamuas passing through molecular clouds
Susanne Pfalzner1,2 , Melvyn B. Davies3 , Giorgi Kokaia3 and Michele Bannister4
Jülich Supercomputing Center, Forschungszentrum Jülich, 52428 Jülich, Germany; 2 Max Planck Institute for Radio
Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany; 3 Lund Observatory, Department of Astronomy and Theoretical
Physics, Box 43, SE-221 00 Lund, Sweden; 4 School of Physical and Chemical Sciences — Te Kura Matū, Universityof Canterbury, Private Bag 4800, Christchurch 8140, New Zealand
1E-mail contact: s.pfalzner at fz-juelich.de
The detections of 1I/Oumuamua and 2I/Borisov within just two years demonstrate impressively that interstellar
objects (ISOs) must be common in the Milky Way. Once released from their parent system, these ISOs travel for Gyr29

through interstellar space. While often imagined as empty, interstellar space contains gas and dust most prominent in
the form of molecular clouds. Performing numerical simulations, we test how often ISOs cross such molecular clouds.
We find that the ISOs pass amazingly often through molecular clouds. In the solar neighbourhood, ISOs typicallyspend 0.1-0.2% of their journey inside molecular clouds, for relative slow ISOs (< 5 km/s) this can increase to 1-2%,
equivalent to 10 - 20 Myr per Gyr. Thus the dynamically youngest ISOs spend the longest time in molecular clouds.
In other words, molecular clouds must mainly contain relatively young ISOs (< 1-2 Gyr). Thus the half-life of theseeding process by ISOs is substantially shorter than a stellar lifetime. The actual amount of time spent in MCs
decreases with distance to the Galactic Centre. We find that ISOs pass so often through MCs that backtracing theirpath to find their parent star beyond 250 Myr seems beyond the point. Besides, we give a first estimate of the ISO
density depending on the galactic centre distance based on the stellar distribution.
Accepted by ApJ
http://arxiv.org/pdf/2009.08773

43.

Magnetized filamentary gas flows feeding the young embedded cluster in Serpens SouthThushara G.S. Pillai1,2 , Dan P. Clemens1 , Stefan Reissl3, Philip C. Myers4 , Jens Kauffmann5 , Enrique
Lopez-Rodriguez6 , Felipe O. Alves7 , Gabriel A.P. Franco8 , Jonathan Henshaw9 , Karl M. Merten2 ,Fumitaka Nakamura10 , Daniel Seifried11 , Koji Sugitani12 and Helmut Wiesemeyer2
Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston MA, 02215, USA; 2
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 3 Universität Heidelberg,
Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 4Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA; 5 Haystack Observatory,
Massachusetts Institute of Technology, Westford, MA 01886, USA; 6 SOFIA Science Center, NASA Ames ResearchCenter, Moffett Field, CA 94035, USA; 7 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1, 85748
Garching, Germany; 8 Departamento de Física - ICEx - UFMG, Caixa Postal 702, 30.123-970 Belo Horizonte, Brazil;
9
Max-Planck-Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany; 10 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 11 Universität zu Köln, I. Physikalisches Institut,
Zülpicher Str. 77, 50937 Köln, Germany; 12 Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku,
Nagoya, Aichi 467-8501, Japan1

E-mail contact: tpillai.astro at gmail.com
Observations indicate that molecular clouds are strongly magnetized, and that magnetic fields influence the formationof stars. A key observation supporting the conclusion that molecular clouds are significantly magnetized is that theorientation of their internal structure is closely related to that of the magnetic field. At low column densities the
structure aligns parallel with the field, whereas at higher column densities, the gas structure is typically oriented
perpendicular to magnetic fields, with a transition at visual extinctions AV ≥ 3 mag. Here we use far-infrared
polarimetric observations from the HAWC+ polarimeter on SOFIA to report the discovery of a further transition in
relative orientation, i.e., a return to parallel alignment at AV ≥ 21 mag in parts of the Serpens South cloud. Thistransition appears to be caused by gas flow and indicates that magnetic supercriticality sets in near AV ≥ 21 mag,allowing gravitational collapse and star cluster formation to occur even in the presence of relatively strong magnetic
fields.
Accepted by Nature Astronomy
https://doi.org/10.1038/s41550-020-1172-6
https://arxiv.org/pdf/2009.14100.pdf

A “head/tail” plasmon model with a Hubble law velocity profile
44. A. C. Raga1 , A. Rodriguez-Gonzalez1 , L. Hernandez-Ramirez1 , J. Canto2 and A. Castellanos-Ramirez2
1

ICN, UNAM, Mexico; 2 IA, UNAM, Mexico

E-mail contact: raga at nucleares.unam.mx
We present a model of a hypersonic, collimated, “single pulse” outflow, produced by an event with an ejection velocity
that first grows, reaches a peak, and then decreases again to zero velocity in a finite time (simultaneously, the ejection30

density can have an arbitrary time-variability). We obtain a flow with a leading “head” and a trailing “tail’ that for
times greater than the width of the pulse develops a linear, “Hubble law” velocity vs. position. We present an analytic
model for a simple pulse with a parabolic ejection velocity vs. time and time-independent mass-loss rate, and compare
it to an axisymmetric gasdynamic simulation with parameters appropriate for fast knots in planetary nebulae. This
“head/tail plasmon” flow might be applicable to other high-velocity clumps with “Hubble law” tails.
Accepted by MNRAS, letters
https://bigbang.nucleares.unam.mx/astroplasmas/

45.

First sample of N2 H+ nitrogen isotopic ratio measurements in low-mass protostars
Elena Redaelli1, Luca Bizzocchi1 and Paola Caselli1
1

Max Planck for Extraterrestrial Physics, Giessenbachstrasse 1, D-85749 Garching bei Muenchen, Germany

E-mail contact: eredaelli at mpe.mpg.deContext. The nitrogen isotopic ratio is considered an important diagnostic tool of the star formation process, andN2 H+ is particularly important because it is directly linked to molecular nitrogen N2 . However, theoretical models
still lack to provide an exhaustive explanation for the observed 14 N/15 N values.
Aims. Recent theoretical works suggest that the 14 N/15 N behaviour is dominated by two competing reactions that
destroy N2 H+ : dissociative recombination and reaction with CO. When CO is depleted from the gas phase, if N2 H+
recombination rate is lower with respect to the N15 NH+ one, the rarer isotopologue is destroyed faster. In prestellar
cores, due to a combination of low temperatures and high densities, most CO is frozen in ices onto the dust grains,
leading to high levels of depletion. On the contrary, in protostellar cores, where temperature are higher, CO ices
evaporate back to the gas phase. This implies that the N2 H+ isotopic ratio in protostellar cores should be lower thanthe one in prestellar cores, and consistent with the elemental value of ≈ 440. We aim to test this hypothesis, producing
the first sample of N2 H+ /N15 NH+ measurements in low mass protostars.
Methods. We observe the N2 H+ and N15 NH+ lowest rotational transition towards six young stellar objects in Perseus
and Taurus molecular clouds. We model the spectra with a custom python code using a constant Tex approach to fit
the observations. We discuss in appendix the validity of this hypothesis. The derived column densities are used tocompute the nitrogen isotopic ratios.
Results. Our analysis yields an average of 14 N/15 N|pro = 420 ± 15 in the protostellar sample. This is consistent withthe protosolar value of 440, and significantly lower than the average value previously obtained in a sample of prestellar
objects.
Conclusions. Our results are in agreement with the hypothesis that, when CO is depleted from the gas-phase,dissociative recombinations with free electrons destroy N15 NH+ faster than N2 H+ , leading to high isotopic ratios inprestellar cores, where carbon monoxide is frozen onto dust grains.
Accepted by A&A

46. NGC 7538 IRS1 - An O Star Driving an Ionized Jet and Giant N-S Outflow
G. Sandell1 , M. Wright2 , R. Güsten3 , H. Wiesemeyer3 , N. Reyes3 , B. Mookerjea4 and S. Corder5
1

Institute for Astronomy, University of Hawaii, Hilo, HI 96720, USA; 2 Radio Astronomy Laboratory, University ofCalifornia, Berkeley, CA 94720, USA; 3 Max Planck Institut für Radioastronomie, Auf dem Hg̈el 69, 53121 Bonn,
Germany; 4 Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India; 5 ALMA, Av
Apoquindo 3946 Piso 19, Las Condes, Santiago, Chile
E-mail contact: gsandell at hawaii.edu
NGC 7538 IRS 1 is a very young embedded O star driving an ionized jet and accreting mass with an accretion rate
>10−4 M⊙ /year, which is quenching the hypercompact HII region. We use SOFIA GREAT data, Herschel PACS
and SPIRE archive data, SOFIA FORCAST archive data, Onsala 20m and CARMA data, and JCMT archive data
to determine the properties of the O star and its outflow. IRS 1 appears to be a single O-star with a bolometricluminosity > 1 × 105 l⊙ , i.e. spectral type O7 or earlier. We find that IRS 1 drives a large molecular outflow withthe blue-shifted northern outflow lobe extending to ∼ 280 arcsec or 3.6 pc from IRS 1. Near IRS 1 the outflow is wellaligned with the ionized jet. The dynamical time scale of the outflow is ∼ 1.3 × 105 yr. The total outflow mass31

is ∼ 130 M⊙ . We determine a mass outflow rate of 1.0 ×10−3 M⊙ yr−1 , roughly consistent with the observed massaccretion rate. We observe strong high velocity [C ii] emission in the outflow, confirming that strong UV radiationfrom IRS 1 escapes into the outflow lobes and is ionizing the gas. Many O stars may form like low mass stars, butwith a higher accretion rate and in a denser environment. As long as the accretion stays high enough to quench the
HII region, the star will continue to grow. When the accretion rate drops, the HII region will rapidly start to expand.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2010.04289

FEEDBACK: a SOFIA Legacy Program to Study Stellar Feedback in Regions of Massive

47. Star Formation

N. Schneider1 , R. Simon1 , C. Guevara1 , C. Buchbender1 , R.D. Higgins1, Y. Okada1 , J. Stutzki1 ,R. Guesten2 , L.D. Anderson3 , J. Bally4 , H. Beuther5 , L. Bonne6 , S. Bontemps6 , E. Chambers7 , T.
Csengeri6 , U.U. Graf1 , A. Gusdorf8 , K. Jacobs1 , M. Justen1 , S. Kabanovic1 , R. Karim9 , M. Luisi3 , K.
Menten2 , M. Mertens1 , B. Mookerjea10 , V. Ossenkopf-Okada1 , C. Pabst11 , M.W. Pound9 , H. Richter12 ,N. Reyes2 , O. Ricken2 , M. Roellig1, D. Russeil13, A. Sanchez-Monge1 , G. Sandell14 , M. Tiwari9 , H.
Wiesemeyer2, M. Wolfire9 , F. Wyrowski2 , A. Zavagno13 and A.G.G.M. Tielens9,111

I. Physik. Institut, University of Cologne, Germany; 2 MPIfR Bonn, Germany; 3 Dep. of Physics and Astronomy,West Virginia University, USA; 4 Center for Astrophysics and Space Astronomy, University of Colorado, USA; 5 MPA,
Heidelberg, Germany; 6 LAB, University of Bordeaux, France; 7 USRA/SOFIA, NASA Ames Research Center, USA;
8
LPENS, Sorbonne Universite, Paris, France; 9 Department of Astronomy, University of Maryland, USA; 10 Tata
Institute of Fundamental Research, Mumbai, India; 11 Leiden Observatory, Leiden University, The Netherlands; 12
DLR, Berlin, Germany; 13 Aix Marseille Universite, LAM, Marseille, France; 14 Institute for Astronomy, Universityof Hawaii, USA
E-mail contact: nschneid at ph1.uni-koeln.de
FEEDBACK is a SOFIA (Stratospheric Observatory for Infrared Astronomy) legacy program dedicated to study theinteraction of massive stars with their environment. It performs a survey of 11 galactic high mass star forming regionsin the 158 µm (1.9 THz) line of [C ii] and the 63 µm (4.7 THz) line of [O I]. We employ the 14 pixel Low frequency
Array (LFA) and 7 pixel High Frequency Array (HFA) upGREAT heterodyne instrument to spectrally resolve (0.24
MHz) these far-infrared fine structure lines. With a total observing time of 96h, we will cover ∼6700 arcmin2 at
14.1′′ angular resolution for the [C ii] line and 6.3′′ for the [O I] line. The observations started in spring 2019 (Cycle
7). Our aim is to understand the dynamics in regions dominated by different feedback processes from massive stars
such as stellar winds, thermal expansion, and radiation pressure, and to quantify the mechanical energy injection andradiative heating efficiency. This is an important science topic because feedback of massive stars on their environment
regulates the physical conditions and sets the emission characteristics in the interstellar medium (ISM), influences thestar formation activity through molecular cloud dissolution and compression processes, and drives the evolution of the
ISM in galaxies. The [C ii] line provides the kinematics of the gas and is one of the dominant cooling lines of gas for
low to moderate densities and UV fields. The [O I] line traces warm and high-density gas, excited in photodissociations
regions with a strong UV field or by shocks. The source sample spans a broad range in stellar characteristics fromsingle OB stars, to small groups of O stars, to rich young stellar clusters, to ministarburst complexes. It contains
well-known targets such as Aquila, the Cygnus X region, M16, M17, NGC7538, NGC6334, Vela, and W43 as well asa selection of H II region bubbles, namely RCW49, RCW79, and RCW120. These [C ii] maps, together with the less
explored [O I] 63 µm line, provide an outstanding database for the community. They will be made publically available
and will trigger further studies and follow-up observations.
Accepted by PASP (Vol. 132, No. 1016)
https://iopscience.iop.org/journal/1538-3873
https://arxiv.org/pdf/2009.08730

32

Constraining the Chemical Signatures and the Outburst Mechanism of the Class 0
48. Protostar HOPS 383
Rajeeb Sharma1 , John J. Tobin2 , Patrick D. Sheehan2 , S. Thomas Megeath3 , William J. Fischer4 , Jes
K. Jørgensen5 , Emily J. Safron6 and ZSofia Nagy7
Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman,
OK, 73019, USA; 2 National Radio Astronomy Observatory, Charlottesville, VA, 22901, USA; 3 Ritter AstrophysicalObservatory, Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA; 4 Space Telescope
Science Institute, Baltimore, MD, USA; 5 Niels Bohr Institute, University of Copenhagen, Øster Voldgade 5-7, DK1350, Copenhagen K, Denmark; 6 Department of Physics and Astronomy, Louisiana State University, Baton Rouge,
LA, USA; 7 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly
Thege út 15–17, Hungary
1E-mail contact: rajeeb.sharma-1 at ou.edu
We present observations toward HOPS 383, the first known outbursting Class 0 protostar located within the Orion
molecular cloud using ALMA, VLA, and SMA. The SMA observations reveal envelope scale continuum and molecularline emission surrounding HOPS 383 at 0.85 mm, 1.1 mm, and 1.3 mm.The images show that HCO+ and H13 CO+
peaks on or near the continuum, while N2 H+ is reduced at the same position. This reflects the underlying chemistrywhere CO evaporating close to the protostar destroys N2 H+ while forming HCO+ . We also observe the molecular
outflow traced by 12 CO (J = 2 → 1) and (J = 3 → 2). A disk is resolved in the ALMA 0.87 mm dust continuum,
orthogonal to the outflow direction, with an apparent radius of ∼62 AU. Radiative transfer modeling of the continuum
gives disk masses of 0.02 M⊙ when fit to the ALMA visibilities. The models including VLA 8 mm data indicatethat the disk mass could be up to a factor of 10 larger due to lower dust opacity at longer wavelengths. The disk
temperature and surface density profiles from the modeling, and an assumed protostar mass of 0.5 M⊙ suggest that
the Toomre Q parameter < 1 before the outburst, making gravitational instability a viable mechanism to explain
outbursts at an early age if the disk is sufficiently massive.
Accepted by ApJ
https://arxiv.org/pdf/2010.05939.pdf

49.

Investigating episodic accretion in a very low-mass young stellar object
Camille Stock1,2 , Alessio Caratti o Garatti1,3 , Pauline McGinnis1 , Rebeca Garcia Lopez1,3 , Simone
Antoniucci4 , Ruben Fedriani5 and Tom P. Ray1,2
Dublin Institute for Advanced Studies (DIAS), School of Cosmic Physics, Astronomy and Astrophysics Section, 31
Fitzwilliam Place, Dublin 2, Ireland; 2 School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland;
3
School of Physics, University College Dublin, Belfield, Dublin 4, Ireland; 4 INAF, Osservatorio Astronomico diRoma, via di Frascati 33, 00040 Monte Porzio Catone, Italy; 5 Department of Space, Earth & Environment, Chalmers
University of Technology, 412 93 Gothenburg, Sweden
1E-mail contact: cstock at cp.dias.ie
Very low-mass Class I protostars have been investigated very little thus far. Variability of these young stellar objects(YSOs) and whether or not they are capable of strong episodic accretion is also left relatively unstudied. We investigate
accretion variability in IRS 54 (YLW52), a Class I very low-mass protostar with a mass of M⋆ ∼ 0.1 − 0.2 M⊙ . We
obtained spectroscopic and photometric data with VLT/ISAAC and VLT/SINFONI in the near-infrared (J, H, andK bands) across four epochs (2005, 2010, 2013, and 2014). We used accretion-tracing lines (Paβ and Brγ) andoutflow-tracing lines (H2 and [FeII]) to examine physical properties and kinematics of the object. A large increase inluminosity was found between the 2005 and 2013 epochs of more than 1 magnitude in the K band, followed in 2014 bya steep decrease. Consistently, the mass accretion rate (Ṁacc ) rose by an order of magnitude from ∼ 10−8 M⊙ yr−1
to ∼ 10−7 M⊙ yr−1 between the two early epochs. The visual extinction (AV ) has also increased from ∼ 15 mag in2005 to ∼ 24 mag in 2013. This rise in AV in tandem with the increase in Ṁacc is explained by the lifting up of a large
amount of dust from the disc of IRS 54, following the augmented accretion and ejection activity in the YSO, whichintersects our line of sight due to the almost edge-on geometry of the disc. Because of the strength and timescales
involved in this dramatic increase, this event is believed to have been an accretion burst possibly similar to burstsof EXor-type objects. IRS 54 is the lowest mass Class I source observed to have an accretion burst of this type, and33

therefore potentially one of the lowest mass EXor-type objects known so far.
Accepted by A&A
https://arxiv.org/pdf/2009.12281

Planet migration, resonant locking and accretion streams in PDS70: Comparing models

50. and data

Claudia Toci1,2 , Giuseppe Lodato1 , Valentin Christiaens3 , Davide Fedele4 , Christophe Pinte3 , Daniel
J. Price3 and Leonardo Testi5
1

Dipartimento di Fisica, Universitá degli Studi di Milano, Via Celoria 16, 20133 Milano MI, Italy; 2 INAF OA Brera,
via Brera 28, 20121, Milano MI, Italy; 3 School of Physics and Astronomy, Monash University, VIC 3800, Australia;
4
INAF OA Arcetri, Largo Enrico Fermi 5, 50125 Firenze FI; 5 European Southern Observatory, Karl-SchwarzschildStrasse 2, 85748 Garching bei Munchen, Germany
E-mail contact: claudia.toci at inaf.it
The disc surrounding PDS 70, with two directly imaged embedded giant planets, is an ideal laboratory to study
planet-disc interaction. We present three-dimensional smoothed particle hydrodynamics simulations of the system.
In our simulations, planets, which are free to migrate and accrete mass, end up in a locked resonant configurationthat is dynamically stable. We show that features observed at infrared (scattered light) and millimetre (thermal
continuum) wavelengths are naturally explained by the accretion stream onto the outer planet, without requiring acircumplanetary disc around planet c. We post-processed our near-infrared synthetic images in order to account for
observational biases known to affect high-contrast images. Our successful reproduction of the observations indicatesthat planet-disc dynamical interactions alone are sufficient to explain the observations of PDS 70.
Accepted by MNRAS
https://arxiv.org/pdf/2009.11893

Moving ... ??
If you move or your e-mail address changes, please
send the editor your new address. If the Newsletterbounces back from an address for three consecutive
months, the address is deleted from the mailing list.

34

New Jobs

2x ALMA related PhD positions in Vienna (EMERGE ERC-StG)
The Department of Astrophysics at the University of Vienna is offering 2xPhD positions at the Interstellar Medium
Astrophysics group of Dr. Alvaro Hacar. We seek an outstanding candidates to work on high-mass star formation
studies using ALMA interferometric observations as part of the new EMERGE ERC-StG project ().
PhD#1 - ALMA observations of complex fiber networks (ERC funds)
High-mass stars drive the physical and chemical evolution of the Universe. However, the connection of these massive
objects with the initial properties of their gas embryos remains largely controversial.
Large-scale molecular surveys have demonstrated the existence of a new and fundamental filamentary gas unit, theso-called fibers. Fibers play a pivotal role in the star-formation process. Fibers are the first objects decoupled fromthe turbulent cascade and the first gas structures dominated by gravity inside clouds. Fibers also fragment and form
most of the stars in the solar neighbourhood. Recent Atacama Large Millimeter Array (ALMA) observations haveidentified complex fiber networks as the birthplace of high-mass stars in regions such as Orion. The discovery of thesefiber systems opens a new route to investigate the origin of some of the most massive stars and clusters in our Galaxy.
As part of the new EMERGE ERC-StG project this PhD work will explore a novel large-scale ALMA survey of massive fiber networks extracted from its public archive. By developing a new set of state-of-the-art analysis techniques,
this PhD research will characterise the statistical properties of these new fiber systems (mass, internal kinematics,
spatial distribution) across the Milky Way. In its main scientific goal, this project aims to investigate how multi-scale
phenomena in complex fiber networks such as collisions, mergers, and self-gravity determine the initial conditions forthe formation of high-mass stars.
PhD#2 - A dynamical origin of the IMF (potentially funded via VISESS fellowship)
Most of the stars in the Universe are formed following a precise mass distribution known as the Initial Mass Function(IMF). Still, the origin of this stellar mass distribution is one of the major open questions in astrophysics.
Different surveys in nearby clouds suggest that the IMF may be originated from a pre-existing distribution of dense
gas clumps, namely, the Core Mass Function (CMF). The connection between the IMF and CMF implies a direct
and uniform conversion between the initial (cores) and final (stars) gas masses with constant efficiency. This static
description also assumes the cores as single objects isolated from their environment. On the contrary, recent observations demonstrate that most dense cores are originated inside filaments. The fragmentation process of these filaments
connects the cores with their environments and provides with a more dynamical environment than previously thought.
For the first time, this PhD project aims to connect the physical evolution of the gas during the entire formation process of cores and stars in different mass regimes. Using ALMA observations of large core populations in clouds suchas Orion, this project will statistically characterise the gas fragmentation, accretion, and collapse processes at scalesof > 105 AU (filaments), ∼ 104 (cores) and 100 AU (disks + stars). This project aims to provide a first dynamical
description of the conversion of gas (CMF) and stars (IMF). This PhD project will be carried out in collaboration
with the EMERGE ERC-StG team.
Both PhDs will join the new Vienna International School of Earth and Space Sciences (VISESS)
website: https://visess.univie.ac.at/More info + application form: https://jobregister.aas.org/ad/2bb56b58
Application deadline: November 15, 2020
Questions? email: alvaro.hacar@univie.ac.at35

Star Formation in the Local Galaxy with Gaia and VISIONS
2 PhD positions in Vienna
The Department of Astrophysics of the University of Vienna is offering 2 PhD positions in Star Formation in the
Local Galaxy with ESA Gaia and VISIONS (http://visions.univie.ac.at) an ESO Large Public Survey led by
the group of Prof. João Alves. When completed, in 2021, VISIONS will be the most sensitive and complete NIR
survey of local star formation and will feed the next generation of telescopes (e.g., ELT) with new targets for star andplanet formation studies. Together with Gaia, VISIONS will reveal the 3D dynamics of the nearby stellar nurseries,
as well as of the clouds spawning them, allowing the community to explore resolved star formation in a robust, large,
and contextual manner, from cloud formation to the build-up of the Milky Way field population. The goal of these
PhD projects is centered on a fundamental ISM measurement, yet to be made, namely its 3D motion.
The two PhD projects offered are:
PhD 1: The 3D space motion of the local Interstellar Medium (4 years, fully funded)
PhD 2: The origin and evolution of the Radcliffe Wave (4 years, fully funded)
Both PhDs will join the new Vienna International School of Earth and Space Sciences (VISESS)
website: https://visess.univie.ac.at/More info + application form: https://jobregister.aas.org/ad/2bb56b58
Application deadline: November 15, 2020
Questions? email: joao.alves@univie.ac.at

ECOGAL hires a postdoctoral associate to decipher magnetic fields instar-forming cores
The ERC synergy project ’ECOGAL: Understanding our Galactic ecosystem - From the disk of the Milky Way tothe formation sites of stars and planets’ aims at building a unifying predictive model of star and planet formation in
the Milky Way and to understand the Galaxy as a complex dynamically evolving ecosystem. Several large researchgroups are now hiring across Europe (PIs Hennebelle, Klessen, Testi, Molinari - a project led jointly by CEA Saclay,
Heidelberg University, INAF Rome, and ESO Garching).
The team at CEA-Saclay is seeking candidates to participate to the scientific exploitation of interferometric polarization
datasets. A significant fraction of the work during the first year will be dedicated to the testing and validationof polarization observations carried out with the IRAM/NOEMA observatory, a capability development currently
supported by the ECOGAL/MagneticYSOs efforts. This program will produce a rich dataset probing the millimeterpolarized dust emission in a sample of protostars: the postdoctoral research fellow will be leading the scientific analysis
with the aim to characterize the magnetic field properties in young star-forming cores (with comparison to synthetic
observations of MHD models produced in the consortium). Our team was one of the very first to show that thevery young disks around the first star embryos (Class 0 protostars) are so compact that it is absolutely necessary toconsider star formation scenarios including the dynamic role of the magnetic field. The CEA teams are also pioneers
in the observation of magnetic fields at work during the initial phases of star formation: thanks to the combinationof interferometric observations and numerical models, we have recently obtained the first observational proof of theefficiency of magnetic braking to regulate the formation of stars and their disks. The ECOGAL observations andmodels will allow us to further investigate the dynamic role of the magnetic field and its coupling with dust.
The Astrophysics department of CEA is a major astrophysics laboratory located on the campus of the Paris-Saclay
University, about 20 km south-west of Paris. The appointment will be for a period of two to three years, dependingon the evolution of the project and data collection timelines. The position includes comprehensive benefits such astransportation and lunch subsidies, as well as a generous travel allowance.
As data is expected to start being collected in the coming months, the successful candidate is expected to start activities
in the Spring 2021 timeframe. Flexible starting dates could be accommodated: don’t let incompatible timelines stop
you from applying if you are highly motivated to come work with us, contact us with your questions !
Applicants should have a PhD in astronomy, astrophysics, or a closely related field. Previous experiences in analysisof datasets from star-forming structures, and expertize in submillimetre/radio interferometric observations, especially36

in interferometric polarization techniques, will be considered as assets. We also encourage female/under-represented
community applications. Applications will be handled according to CEA rules and procedures. Applicants should
send a CV, list of publications, brief statement of research interests and relevant expertise for the job to Dr. Analle
Maury (anaelle.maury@cea.fr) by November 1st.
https://jobregister.aas.org/ad/5e7aa1bf

McLaughlin Postdoctoral Fellowship
The University of Michigan Department of Astronomy invites applications for its McLaughlin Postdoctoral Fellowship.
The Department of Astronomy has a strong emphasis in star and planet formation research, as well as exoplanet
detection and characterization.
Fellows are afforded the opportunity to construct and pursue an independent research program in an energetic anddiverse research environment. The Department has guaranteed access to the 6.5 Magellan telescopes in Chile, the1.2m and 2.4m MDM telescopes in Arizona, the NOEMA sub-mm interferometer in France, and the Swift UV/Xray/Gamma-ray telescope. Observational and theoretical efforts within the department span topics including exoplanets, young stars, galaxy groups and clusters, galaxy evolution, cosmology, black holes and neutron stars, transient
events, and time-domain astronomy, dark matter, and dark energy. Instrumentation efforts are also ongoing within
the Department.
The salary for the fellowship will start at 69,000 USD, with an annual research stipend of 6,000 USD. A full benefits
package is included.
Fellowships will commence in September 2021, the expected term is three years, dependent on performance andfunding. Applicants need to have completed a Ph. D. in astronomy, physics, or a closely related field prior to thestart of the fellowship. Applicants should send a cover letter, statement of past research, statement of proposed
research, CV, and publications list (with three ’key’ papers specifically highlighted) to mclfellows@umich.edu. Lettersfrom three references are also required and should be sent to the same address. Applications that are complete by
December 1, 2020, will receive full attention.
We encourage applications from people holding any identity(ies) that have been traditionally underrepresented in thefield of astronomy.
To learn more about our research interests please visit https://lsa.umich.edu/astro/research/stars-exoplanets.html
or contact any member of our program.

Post-doctoral research positions in exoplanet science at the University ofMichigan
The Department of Astronomy at the University of Michigan welcomes applications for post-doctoral positions to join
the Formation and Evolution of Planetary Systems research group (https://sites.lsa.umich.edu/feps/). Applications are especially welcome in the areas of high contrast imaging, exoplanet detection/spectral characterization,and infrared instrumentation (especially detector expertise), as well as exoplanet population statistics, and planet
formation. Our lab is involved in a funded effort to develop new mid-infrared detectors for use with adaptive optics
on large ground-based telescopes. Successful applicants will have access to departmental facilities such as the Magellan telescopes, the MDM Observatories, NOEMA, SWIFT, high performance computing clusters, and other facilities(please see http://www.lsa.umich.edu/astro/). Members of the research team have a chance to collaborate on on-goingprojects (such as planned observations with the James Webb Space Telescope), and work with students (if appropriate). Interdisciplinary collaborations with the Departments of Astronomy, Physics, Earth Sciences, as well as Climate
and Space Sciences, are supported through the Michigan Institute for Research in Astrophysics. The University ofMichigan is recognized as a top academic employer and Ann Arbor, Michigan is routinely recognized for its high qualityof life. Please send a cover letter, CV, description of research accomplishments and plans (suggested length 8 pages
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total), list of publications, and arrange for three letters of recommendation to be sent directly to Professor Michael
R. Meyer at mrmeyer@umich.edu by 4 January 2020 for full consideration. We encourage applications from people
holding any identity(ies) that have been traditionally underrepresented in the field of astronomy. The Department of
Astronomy has a specific commitment to enhance diversity, equity, and inclusion within our department, and the field(https://sites.google.com/umich.edu/astro-dei).

Postdoctoral Position in Exoplanets, Sub-Stellar Objects or Planet
Formation - Cornell University
Applications are invited for a postdoctoral position at Cornell University. The successful candidate will work withProfessor Ray Jayawardhana and his collaborators on observational and analytical studies of extra-solar planets andrelated topics such as sub-stellar objects and planet formation. Spectroscopic and photometric characterization of
exoplanets is of particular interest. Prof. Jayawardhana’s research group currently includes two postdocs and two
graduate students.
Group members lead a recently accepted Large Program at the Gemini Observatory focused on high-resolution spectroscopy of exoplanet atmospheres. The program plans to observe 50+ targets, spanning a range of properties, over the
next three years. Prof. Jayawardhana is also on the JWST/NIRISS science team, with 200 hours of GTO dedicated to
exoplanet characterization. In addition, team members use data from TESS, Kepler, CHEOPS, Subaru, Keck, VLT,
CFHT, and other major observatories.
The position is for two years, with extension to a third year possible, and comes with a competitive salary and funds
for research expenses. Start date is flexible, ideally between January-September 2021.
Applicants should send their curriculum vitae, a description of research interests and plans and a list of publications,and should arrange for three letters of recommendation to be sent directly to Lynda Sovocool (lmk3@cornell.edu).
All materials should be submitted electronically to her e-mail address. Applications are accepted until the positionis filled, and those received before December 1, 2020 will receive full consideration. Early expressions of interestand inquiries are encouraged, and should be made to rayjay@cornell.edu Candidates interested in applying for a
Klarman Fellowship (https://as.cornell.edu/klarman-postdoctoral-fellowships) at Cornell, or bringing otherindependent fellowships to Cornell, are also encouraged to contact Prof. Jayawardhana.
Application deadline: December 1, 2020
More information: https://astro.cornell.edu/ray-jayawardhana
https://astro.cornell.edu/

Chalmers Cosmic Origins Fellowships
Applications are invited for several postdoctoral fellowships at Chalmers University of Technology (Gothenburg, Sweden) and partner institutes as part of the Chalmers Initiative on Cosmic Origins (CICO):
1) Chalmers Cosmic Origins Fellowship: One or more positions are 3-year fellowships at Chalmers;
2) Chalmers-UVA Cosmic Origins Fellowship: One fellowship is part of the Chalmers-UVA fellowship that is a 4-year
position, shared between Chalmers (2 years) and Dept. of Astronomy, Univ. of Virginia, Charlottesville, VA, USA (2years).
A successful applicant will lead an ambitious, independent research program related to Cosmic Origins science, expected
to align with the wide range of research at Chalmers and partner institutes. Relevant themes include galaxy formationand evolution, ISM, astrochemistry, star cluster formation, high- and low-mass star formation, astrochemistry andplanet formation and evolution, from both theoretical and observational perspectives. See www.cosmicorigins.space

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for more information.
http://cosmicorigins.space/job-openings
https://jobregister.aas.org/ad/12f4d49a
Application deadline: December 15th, 2020

Virginia Cosmic Origins Fellowships
The University of Virginia (UVA) invites applications for Postdoctoral Research Associate positions as part of theinterdisciplinary Virginia Initiative on Cosmic Origins (VICO).
The incumbents will lead ambitious, independent research programs related to Cosmic Origins science, expected toalign with the wide range of research at UVA, as well as at the National Radio Astronomy Observatory (NRAO) on
the grounds of the University. The relevant themes include star formation, planet formation and evolution, planetaryscience, astrochemistry, quantum chemistry and astrobiology, from both theoretical and observational perspectives.
See www.cosmicorigins.space for more information.
The Postdoctoral Research Associates will participate in departmental activities and promote collaboration bothwithin VICO and with its partner institutes, Chalmers University of Technology, Gothenburg, Sweden and the Center
for Astrochemical Studies at the Max Planck Institute for Extraterrestrial Physics (MPE), Garching, Germany.
There are two types of research programs being advertised this year: 1) Virginia Cosmic Origins Program; (2) VirginiaChalmers Cosmic Origins Program. Applicants should indicate in their cover letter if they have preferences among
these research programs.
http://cosmicorigins.space/job-openings
https://jobregister.aas.org/ad/ea51cd16
Application deadline: December 15, 2020

Tenure-track Assistant Professor Faculty Position in Star Formation
The Department of Physics and Astronomy at Rice University invites applications for a tenure-track faculty positionin astronomy in the general field of galactic star formation, including the formation and evolution of planetary systems.
We seek an outstanding theoretical, observational, or computational astronomer whose research will complement andextend existing activities in these areas within the Department. In addition to developing an independent and vigorous
research program, the successful applicant will be expected to teach, on average, one undergraduate or graduate course
each semester, and contribute to the service missions of the Department and University. The Department anticipatesmaking the appointment at the assistant professor level. A Ph.D. in astronomy/astrophysics or related field is required.
Applications for this position must be submitted electronically at http://jobs.rice.edu/postings/24588. Applicants will be required to submit the following: (1) cover letter; (2) curriculum vitae; (3) statement of research; (4)statement on teaching, mentoring, and outreach; (5) PDF copies of up to three publications; and (6) the names,
affiliations, and email addresses of three professional references. Rice University is committed to a culturally diverse
intellectual community. In this spirit, we particularly welcome applications from all genders and members of historically underrepresented groups who exemplify diverse cultural experiences and who are especially qualified to mentor
and advise all members of our diverse student population. We will begin reviewing applications on December 1, 2020.
To receive full consideration, all application materials must be received by January 1, 2021. The appointment is
expected to begin in July 2021.
Rice University is an Equal Opportunity Employer with a commitment to diversity at all levels and considers for
employment qualified applicants without regard to race, color, religion, age, sex, sexual orientation, gender identity,
national or ethnic origin, genetic information, disability, or protected veteran status. We encourage applicants fromdiverse backgrounds to apply.

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Meetings

Protostars and Planets VII
Dear Scientists interested in Protostars and Planets VII,We sincerely hope that all of you remain safe. We would like to announce the rescheduling of the Protostars andPlanets VII Conference at Kyoto. Since the COVID-19 Pandemic still strongly affects the international travel, we
decided to postpone the conference by approximately one year. The new conference dates are from 21st to 27th ofMarch, 2022. See for current schedule: http://ppvii.org/schedule/index.html
We are looking forward to seeing you at Kyoto in March 2022.
Best wishes, Shu-ichiro Inutsuka, on behalf of PP7 Editors

Planetesimal Formation Meeting - A Virtual Workshop
We are happy to announce a virtual interdisciplinary workshop on planetesimal formation via the streaming instability
that explores the connection to protoplanetary disc observations and the Solar System minor bodies.
17-20 November 2020
https://michiellambrechts.bitbucket.io/pfmeet.html
Main organisers: Michiel Lambrechts and Anders Johansen
SOC:
Pablo Benitez-Llambay
Anders Johansen
Michiel Lambrechts
Jake Simon
Kelsi Singer

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Summary of Upcoming Meetings

Check the websites of these meetings for the latest information on how they are affected by Covid-19
Threats from the Surroundings – VIRTUAL MEETING
10 - 12 November 2020
http://www.eso.org/sci/meetings/2020/tfts2020.html
Planetesimal Formation Meeting - A Virtual Workshop 17 - 20 November 2020
https://michiellambrechts.bitbucket.io/pfmeet.html
Five Years after HL Tau: A New Era in Planet Formation – VIRTUAL MEETING
7 - 11 December 2020
https://www.eso.org/sci/meetings/2020/hltau2020.html
Gordon Conference on Origins of Solar Systems
19 - 25 June 2021, MA, USA
https://www.grc.org/origins-of-solar-systems-conference/2021
Cool Stars, Stellar Systems, and the Sun 21
5 - 9 July 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, Italy
https://sites.google.com/inaf.it/aco-conference
Wheel of Star Formation: A conference dedicated to Prof. Jan Palouš
20 - 24 September 2020, Prague, Czech Republic
https://janfest2020.asu.cas.cz
Protostars & Planets VII
21 - 27 March 2022, Kyoto, Japan
http://www.ppvii.org
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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Short Announcements

Fizeau exchange visitors program in optical interferometry - call for
applications - European Interferometry Initiative
The Fizeau exchange visitors program in optical interferometry funds (travel and accommodation) visits of researchers
to an institute of his/her choice (within the European Community) to perform collaborative work and training on
one of the active topics of the European Interferometry Initiative. The visits will typically last for one month, andstrengthen the network of astronomers engaged in technical, scientific and training work on optical/infrared interferometry. The program is open for all levels of astronomers (Ph.D. students to tenured staff), with priority given to
PhD students and young postdocs. Non-EU based missions will only be funded if considered essential by the Fizeau
Committee. From January 2021 onwards, applications to travel to VLTI Expertise Centres are priority, given the newfinancial rules applying to the programme. Applicants are strongly encouraged to seek also partial support from theirhome or host institutions.
The deadline for applications is November 15. Fellowships can be awarded for missions to be carried out between mid
January 2021 and July 2021!
Further informations and application forms can be found at: www.european-interferometry.eu
The program is funded by OPTICON/H2020.
Please distribute this message also to potentially interested colleagues outside of your community!
Looking forward to your applications,Josef Hron & Péter Ábrahám(for the European Interferometry Initiative)

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