THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 331 — 15 July 2020

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

List of Contents
The Star Formation Newsletter
Editor: Bo Reipurthreipurth@ifa.hawaii.edu

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Abstracts of Newly Accepted Papers . . . . . . . . . . . 6
Abstracts of Newly Accepted Major Reviews . . 38

Associate Editor: Anna McLeod
anna.mcleod@berkeley.edu

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 40

Technical Editor: Hsi-Wei Yen
hwyen@asiaa.sinica.edu.tw

Summary of Upcoming Meetings . . . . . . . . . . . . . . 43

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 44

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

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

Cover Picture
The cover shows a region of the Serpens star forming cloud as imaged by HST. A disk around the
young star HBC 672 = EC82 (to the upper right)
casts a large shadow over its surroundings. See theabstract by Pontoppidan et al. in this issue.
Image courtesy NASA, ESA, and Klaus Pontoppidan (STScI).

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

familiar with Kippenhahn’s code, and when I returned toGermany in the second half of 1967, I joined his theory
group. Kippenhahn’s code was hydrostatic and Newtonian, but the quasar model required a dynamical and relativistic code. Therefore, I modified Kippenhahn’s code in
two steps: First I replaced the hydrostatic equation witha Newtonian equation of motion. After the resulting Newtonian dynamical code was running, I replaced the Newtonian equations by the corresponding relativistic equations. The numerical results showed that Fowler’s quasar
model could not explain the quasars. Therefore, I retired
the relativistic code and applied the Newtonian version
to various problems of stellar physics, including star formation via the contraction and collapse of interstellar gas
clouds. A few years earlier Richard Larson and others
had demonstrated that the outcome of such computations
was a ’protostar’, consisting of a hydrostatic core, which
was accreting matter from an extended envelope. Simulations, carried out together with Werner Tscharnuter,
confirmed this result for different parameters and different initial conditions. As our code included the energy
production by nuclear reactions, we could simulate theevolution of more massive protostars, where the hydrostatic evolutionary time scale of the core becomes shorter
than the accretion time scale. For an initially 60 M⊙ protostar we found that the mass accretion was halted andthe remaining envelope was blown away, soon after hydrogen burning had started in the core. Our code did notinclude rotation, but we expected that with rotation theoutcome would have been qualitatively similar.

Immo Appenzellerin conversation with Bo Reipurth

Q: First of all, congratulations on your 80th birthday. You
have witnessed essentially the whole development of thesubject of star formation. How did your own involvementwith the subject start?
A: Thanks, Bo, for the congratulations and for inviting me
to your interview series. To your question: I got involvedin star formation as a by-product of work on quasars. I
had studied physics at the universities of Tübingen andGöttingen. After graduating in 1966 with a thesis on thethe local interstellar magnetic field, as traced by the interstellar polarization, I spent some time at the Universityof Chicago. There I built a new and more sensitive polarimeter, which I used at the telescopes of the McDonald
Observatory in Texas. Among my targets were the newly
discovered quasars, which were the most discussed objectsof that time. To test one of the mechanisms, which had
been proposed to explain quasars, I carried out numerical model computations, and as a by-product I obtained
a computer code that was suitable for simulating star formation.

Q: You then returned to observations and wrote a series of
papers on the so-called YY Orionis-type stars, like S CrA
and RW Aur.
A: I enjoyed doing theoretical work in Kippenhan’s group,
but I never completely abandoned observational astronomy. When ESO’s La Silla Observatory in Chile was officially opened in 1969, I started using the first small telescopes there. With larger telescopes under construction at
ESO and the creation of the German-Spanish Astronomical Center on Calar Alto in Spain, observational astronomy became attractive again in Germany. Thus, when
I was offered a professorship at the University of Heidelberg in 1975, I accepted with the aim of forming a researchgroup, which combined theory and observations. One of
our first programs in Heidelberg was identifying observational counterparts of the predicted protostars. Amongthe prime candidates were the T Tauri stars. They were
known to be young, and they showed chromospheric emission spectra which resembled those predicted for the cooling zones of protostellar accretion shocks. Already in 1948
Jesse Greenstein had suggested that the properties of the
T Tauri stars resulted from mass infall on forming stars.
This suggestion was supported by Merle Walker, who in

Q: Could you explain this in more detail? Why did you
switch to theory and how did this lead to your investigations of massive protostars? And what were your conclusions?
A: My initial aim was to investigate a quasar model, which
had been proposed in 1966 by William Fowler. He had suggested that quasars resulted from relaxation oscillations of
unstable supermassive (M ≥ 105 M⊙ ) stars. To test this
scenario I planned numerical simulations using the stellar
evolution code of Rudolf Kippenhahn. Kippenhahn had
started developing this code at the Max-Planck-Institutefor Astrophysics in Munich, but in 1965 he had moved to
Göttingen, where he formed a new group for theoretical astrophysics. To earn money, I had done some programmingfor his group while working on my thesis. Therefore, I was3

A: This was a joint project with an astronomy group,
which at that time existed at the Norwegian Universityof Tromsø. Tromsø is located about 350 km north of the
Arctic Circle. Thus, at midwinter the sun remains below the horizon for about 50 days, and the sky remains
dark for about three weeks. Tromsø itself is not a suitable observatory site, as the winters bring fog, clouds, andheavy snowfall. But its University operated a 50 cm Telescope about 50 km east of Tromsø, in the Skibotn valley,
which belongs to the places with the highest percentage ofclear sky in Norway. As the Skibotn telescope did not havespectroscopic equipment, we brought a fiber-coupled spectrometer with a two-stage image tube from Heidelberg.
The observations were carried out jointly by students and
Q: You were among the first to explore the ultraviolet spec- staff from Tromsø and Heidelberg. As you mentioned, thetrum of young stars using the newly launched IUE satel- main target was the YY Ori star RW Aur, which could
be observed, with minor interruptions, for about 12 days.
lite. What did you learn?
Our results disagreed with most of the mechanisms which
A: In addition to a chromospheric line spectrum, proto- had been suggested for the irregular spectral variations ofstars were predicted to emit a strong UV flux originating RW Aur, but they were consistent with the assumption ofin the accretion shocks. Indications that this was actu- variable mass accretion being the main cause of the varially observed, were the UV excess at the U band, and the ations.
increase of the flux between the U band and the atmospheric cutoff, which was seen on spectrograms observed Q: In 1983, you and David Dearborn used models of variby Merle Walker with a Lallemand camera. The launch of able surface magnetic fields in T Tauri stars for comparthe IUE satellite provided a chance to measure the extent ison with their observed photometric observations. Whatand shape of the UV continuum and to derive its contri- resulted from this study?
bution to the total luminosity. Therefore, as soon as IUE A: I met Dave during the winter 1982/1983, when I spentbecame operational, we applied for observing time. For part of a sabbatical in Tucson. When I learned about
S CrA, the at that time brightest known YY Ori star, we Dave’s stellar evolution code, which included the effects ofcombined the IUE data with groundbased IR photome- star spots produced by magnetic fields, I proposed to apply
try to derive the continuum between 15 nm and 22 µm. this code to PMS stars. The presence of star spots in PMS
The observed UV continuum, corrected for interstellar ab- and T Tauri stars had been suggested by many different
sorption, was found to peak near 200 nm. Only a minor authors to explain the irregular as well as the rotationfraction of the total luminosity of S CrA was found to related cyclic light variations. We calculated a series oforiginate from the stellar photosphere. Among the other models, with different initial conditions and values of theobserved T Tau stars, the results for GQ Lup (at that total surface magnetic flux between zero and the maximum
time known as CoD -35 10525) and for DR Tau were par- value consistent with an equilibrium of the gas and theticularly interesting. GQ Lup has a typical YY Ori spec- magnetic pressures at the surface. For all models we detrum, with photospheric absorption lines corresponding to rived the V-magnitude change, the total spot area, and thea spectral type K7 and clearly visible redward displaced effective temperatures of the spots and of the spot-free surabsorption components at the higher Balmer lines. But face area. As a result we found that in purely hydrostatic
its UV flux was found to be much weaker than in S CrA. PMS stars the spots could cause irregular V-magnitude
On the other hand, DR Tau, which often has only week variations up to about 3.5 mag and cyclic variations up
redward displaced absorption features, was found to emit to about 2.2 mag. If accretion shocks contribute to thea UV flux even larger than that of S CrA. This confirmed continuum at the V band, these upper limits are someearlier indications that the strength of the Balmer contin- what lower. Nevertheless, we concluded that all observed
uum and of the Balmer emission lines are the most reliable cyclic variations and part of the observed irregular variameasures of the mass accretion. Compared to the visual tions could, in principle, be explained by star spots. But
spectra, the UV emission line spectra were found to vary for YY Ori stars with larger irregular variations (such as
more strongly between the individual T Tauri stars.
DR Tau) variable mass accretion remained the only viable
Q: In the winter of 1981 you and your collaborators took explanation. Other conclusions were that the observed efadvantage of the long nights in northern Norway to spec- fective temperature depends on the relative contributionof the spots to the total surface, and that spectral types
troscopically monitor T Tauri stars, especially RW Aur.
1972 identified a subclass of the T Tauri stars, which hecalled ‘YY Ori stars’, and which were characterized by astrong UV excess at the U band and redward displaced
absorption components at the higher Balmer lines. The
observed velocity shifts were close to the expected free-fallvelocities of low-mass PMS stars. To investigate the suggested protostellar nature of the T Tauri stars, we combined non-LTE line profile calculations, done mainly by
Claude Bertout and Ulrich Bastian, with spectroscopic
observations, carried out by Claude Bertout, Bernhard
Wolf, Joachim Krautter, Reinhard Mundt, Carlos Chavarria, and others. We found signs for mass accretion in the
spectra of most classical T Tau stars and redward displaced absorption at many different spectral lines.

4

derived from the photospheric absorption lines depend on
the spectral range observed. This, and the contributionof shock emission to the luminosity, has to be taken into
account, when trying to place T Tauri stars in an HR diagram. Finally, we found the reduction of the photosphericemission by the spots to increase the hydrostatic evolutionary time scale during the fully convective PMS phase.

Bertout. The presence of rotation, disks, and jets makethe T Tauri systems, on first approximation, rotationallysymmetric. Therefore, a dependence of their observed appearance on the angle between the symmetry axis and theline of sight had been suggested. Earlier searches for thiseffect failed, as the inclination angles could not be derived
with sufficient accuracy. Claude and I started a new attempt, when images of T Tauri disks, resolved by optical,
IR and mm-wave interferometry, became available. Assuming that the disks are intrinsically circular, and thatthe disk axes are the system axes, we used the oblatenessof the disk images to derive the inclination. A clear inclination dependence was found for the velocities of the forbidden lines, for the wind absorption components of theBalmer lines and for the properties of the Helium lines.
And, knowing the inclination, we could derive the true,
deprojected flow velocities of the jets.

Q: In the late 1980s you led a series of studies of theabsorption and emission line spectra of T Tauri stars using
high-resolution echelle spectra.
A: At the beginning of the 1980s, the more sensitive andlinear CCDs replaced photographic plates and image tubes.
This resulted in an improved flux calibration and a bettersky background subtraction. And it became possible tosubtract the photospheric spectra from the emission lines(and vice versa) more accurately. As CCDs could not be
fitted well to the coudé spectrographs of that time, echelle
spectrometers became the main instruments for high resolution spectroscopy. We used these new instrumental capabilities to study the T Tauri spectra with higher spectral
resolution and better S/N. And by accurately subtracting
the photospheric spectra, we could derive the true line profiles of the infalling matter. Among the new results was thedetection of the systematic blueshift of the forbidden emission lines. As such lines had been observed to originate inbipolar outflows and jets from young stars, we suggested
that the systematic blueshift resulted from the fact that
only the jet flows directed towards us could be observed,
while the receding counter jets were hidden by an opaqueaccretion disk. Accretion disks had been predicted theoretically and inferred from the IR spectra of young stars,
but they had not yet been observed directly. The simultaneous presence of accretion disks and infall with nearly
free-fall velocities resulted in the current magnetosphericmodel of the T Tauri stars, where matter in the disk isslowly moving inward, until the radius of co-rotation between the disk and the stellar surface is reached. Inside
this radius the model assumes the matter to be in free fallalong magnetic field lines, until stopped at the accretion
shock. The magnetic fields also explained the removal ofangular momentum and the jets. Although I continued tofollow the progress in star formation with great interest,
after 1990 I devoted most of my time (again) to quasars,
AGN, and hot stars, were progress in X-ray astronomy andfar and extreme UV spectroscopy lead to new opportunities. And when ESO’s VLT became operational, distantextragalactic objects became my favorite subjects.

Q: During the more than half century of research thatyou have witnessed, star formation studies have developed
from a quiet backwater to one of the main pillars of astrophysics. What are your views on the role of technology inthis amazing progress?
A: Technological advances always played a decisive rolefor progress in astronomy. Most important for star formation was probably the invention and the development ofcomputers. In the older literature on star formation, one
finds plenty of ideas and interesting speculations. Someof these ideas, such as Greenstein’s T Tauri scenario, wereeven correct. But, as experiments are rarely possible inastrophysics, reliable tests of such ideas became feasible
only after physical processes could be simulated numerically. Computers also play a pivotal role for today’s detectors and receivers. CCDs, which initially were developed as shift registers for computers, require computer
hardware for the readout and the image reconstruction.
Many techniques used for star formation studies, such asactive and adaptive optics, and interferometric imaging,had been proposed a long time ago, but could be realized
only after the required computing power became available.
The important role of improved detectors has already been
mentioned. Other technical advances enabling progressin star formation, were astronomy from space and from
airplanes, and the improvements in the telescope and interferometer technologies. Following these technologicaladvances and the resulting scientific progress over half acentury was highly interesting, and a great pleasure.

Q: Most recently you and Claude Bertout have studied inclination effects in T Tauri spectra. What were your conclusions?
A: Although my main activities were in other fields, occasionally I still tried to contribute a bit to star formation.
An example is the paper on inclination effects with Claude
5

Abstracts of recently accepted papers ;1.

Chemical Variation among Protostellar Cores: Dependence on Prestellar Core Conditions
Yuri Aikawa1 , Kenji Furuya2 , Satoshi Yamamoto3 and Nami Sakai4
Department of Astronomy, The University of Tokyo; 2 National Astronomical Observatory of Japan; 3 Departmentof Physics, The University of Tokyo; 4 RIKEN

1

E-mail contact: aikawa at astron.s.u-tokyo.ac.jp
Hot corino chemistry and warm carbon chain chemistry (WCCC) are driven by gas-grain interactions in star-forming
cores: radical-radical recombination reactions to form complex organic molecules (COMs) in the ice mantle, sublimation of CH4 and COMs, and their subsequent gas-phase reactions. These chemical features are expected to dependon the composition of ice mantle which is set in the prestellar phase. We calculated the gas-grain chemical reaction
network considering a layered ice-mantle structure in star-forming cores, to investigate how the hot corino chemistry
and WCCC depend on the physical condition of the static phase before the onset of gravitational collapse. We foundthat WCCC becomes more active, if the temperature is lower, or the visual extinction is lower in the static phase, orthe static phase is longer. Dependence of hot corino chemistry on the static-phase condition is more complex. While
CH3 OH is less abundant in the models with warmer static phase, some COMs are formed efficiently in those warm
models, since there are various formation paths of COMs. If the visual extinction is lower, photolysis makes COMsless abundant in the static phase. Once the collapse starts and visual extinction increases, however, COMs can beformed efficiently. Duration of the static phase does not largely affect COM abundances. Chemical diversity between
prototypical hot corinos and hybrid sources, in which both COMs and carbon chains are reasonably abundant, canbe explained by the variation of prestellar conditions. Deficiency of gaseous COMs in prototypical WCCC sources is,however, hard to reproduce within our models.
Accepted by ApJ
http://arxiv.org/pdf/2006.11696

2.

Three generations of stars: a possible case of triggered star formation
M.B. Areal1 , A. Buccino1,2 , S. Paron1 , C. Fariña3,4 and M.E. Ortega1
CONICET-Universidad de Buenos Aires. Instituto de Astronomía y Física del Espacio CC 67, Suc. 28, 1428 Buenos
Aires, Argentina; 2 Departamento de Física. FCEyN-Universidad de Buenos Aires, Buenos Aires, Argentina; 3 Isaac
Newton Group of Telescopes, E38700, La Palma, Spain; 4 Instituto de Astrofísica de Canarias (IAC) and Universidad
de La Laguna, Dpto. Astrofísica, Spain
1

E-mail contact: mbareal at iafe.uba.ar
Evidence for triggered star formation linking three generations of stars is difficult to assemble, as it requires convincingly
associating evolved massive stars with Hii regions that, in turn, would need to present signs of active star formation.
We present observational evidence for triggered star formation relating three generations of stars in the neighbourhoodof the star LS II +26 8. We carried out new spectroscopic observations of LS II +26 8, revealing that it is a B0 III-type
star. We note that LS II +26 8 is located exactly at the geometric centre of a semi-shell-like Hii region complex. The
most conspicuous component of this complex is the Hii region Sh2-90, which is probably triggering a new generationof stars. The distances to LS II +26 8 and to Sh2-90 are in agreement (between 2.6 and 3 kpc). Analysis of theinterstellar medium on a larger spatial scale shows that Hii region complex lies on the northwestern border of an
extended H2 shell. The radius of this molecular shell is about 13 pc, which is in agreement with what an O9V star(the probable initial spectral type of LS II +26 8 as inferred from evolutive tracks) can generate through its winds inthe molecular environment. In conclusion, the spatial and temporal correspondences derived in our analysis enable us
to propose a probable triggered star formation scenario initiated by the evolved massive star LS II +26 8 during its
6main sequence stage, followed by stars exciting the Hii region complex formed in the molecular shell, and culminatingin the birth of YSOs around Sh2-90.
Accepted by MNRAS
http://arxiv.org/pdf/2006.00120

3.

An evolutionary study of volatile chemistry in protoplanetary disks
Jennifer B. Bergner1,2 , KarinI. Öberg3 , Edwin A. Bergin4 , Sean M. Andrews3 , Geoﬀrey A. Blake5 etal.
1

University of Chicago Department of the Geophysical Sciences, Chicago, IL 60637, USA; 2 NASA Sagan Fellow;
Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138, USA; 4 Department of Astronomy,
University of Michigan, Ann Arbor, MI 48109, USA; 5 Division of Geological & Planetary Sciences, California Instituteof Technology, Pasadena, CA 91125, USA

3E-mail contact: jbergner at uchicago.edu
The volatile composition of a planet is determined by the inventory of gas and ice in the parent disk. The volatile
chemistry in the disk is expected to evolve over time, though this evolution is poorly constrained observationally. We
present ALMA observations of C18 O, C2 H, and the isotopologues H13 CN, HC15 N, and DCN towards five Class 0/I
disk candidates. Combined with a sample of fourteen Class II disks presented in Bergner et al. (2019b), this data set
offers a view of volatile chemical evolution over the disk lifetime. Our estimates of C18 O abundances are consistent
with a rapid depletion of CO in the first ∼0.5–1 Myr of the disk lifetime. We do not see evidence that C2 H and HCN
formation are enhanced by CO depletion, possibly because the gas is already quite under-abundant in CO. Further
CO depletion may actually hinder their production by limiting the gas-phase carbon supply. The embedded sources
show several chemical differences compared to the Class II stage, which seem to arise from shielding of radiationby the envelope (impacting C2 H formation and HC15 N fractionation) and sublimation of ices from infalling material(impacting HCN and C18 O abundances). Such chemical differences between Class 0/I and Class II sources may affectthe volatile composition of planet-forming material at different stages in the disk lifetime.
Accepted by ApJ
http://arxiv.org/pdf/2006.12584

4.

Star-forming sites IC 446 and IC 447: an outcome of end-dominated collapse of Monoceros R1 filament
N. K. Bhadari1,2 , L. K. Dewangan1 , L. E. Pirogov3 and D. K. Ojha4
Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India.; 2 Indian Institute of Technology Gandhinagar Palaj, Gandhinagar - 382355, India.; 3 Institute of Applied Physics of the Russian Academy of Sciences,
46 Ulyanov st., Nizhny Novgorod 603950, Russia.; 4 Department of Astronomy and Astrophysics, Tata Institute ofFundamental Research, Homi Bhabha Road, Mumbai 400 005, India.

1

E-mail contact: naval at prl.res.in
We present an analysis of multi-wavelength observations of Monoceros R1 (Mon R1) complex (at d ∼760 pc). An
elongated filament (length ∼14 pc, mass ∼1465 M⊙ ) is investigated in the complex, which is the most prominent
structure in the Herschel column density map. An analysis of the FUGIN 12 CO(1–0) and 13 CO(1–0) line data
confirms the existence of the filament traced in a velocity range of [−5, +1] km s−1 . The filament is found to host two
previously known sites IC 446 and IC 447 at its opposite ends. A massive young stellar object (YSO) is embedded
in IC 446, while IC 447 contains several massive B-type stars. The Herschel temperature map reveals the extended
warm dust emission (at Td ∼ 15–21 K) toward both the ends of the filament. The Spitzer ratio map of 4.5 µm/3.6µm emission suggests the presence of photo-dissociation regions and signature of outflow activity toward IC 446 andIC 447. Based on the photometric analysis of point-like sources, clusters of YSOs are traced mainly toward thefilament ends. The filament is found to be thermally supercritical showing its tendency of fragmentation, which isfurther confirmed by the detection of a periodic oscillatory pattern (having a period of ∼3–4 pc) in the velocity profile
of 13 CO. Our outcomes suggest that the fragments distributed toward the filament ends have rapidly collapsed, andhad formed the known star-forming sites. Overall, the elongated filament in Mon R1 is a promising sample of the7

“end-dominated collapse" scenario, as discussed by Pon et al. (2011, 2012).
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2006.13894.pdf

5.

Shape Analysis of Hii Regions – II. Synthetic Observations
Justyn Campbell-White1,2, Ahmad A. Ali3 , Dirk Froebrich2 and Alfred Kume4
SUPA, School of Science and Engineering, University of Dundee, Nethergate, Dundee DD1 4HN, U.K.; 2 Centre for
Astrophysics and Planetary Science, The University of Kent, Canterbury, CT2 7NH, U.K.; 3 Department of Physics
and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, U.K.; 4 School of Mathematics, Statistics andActuarial Sciences, The University of Kent, Canterbury, CT2 7FS, U.K.

1

E-mail contact: JCampbellWhite001 at dundee.ac.uk
The statistical shape analysis method developed for probing the link between physical parameters and morphologies
of Galactic Hii regions is applied here to a set of synthetic observations (SOs) of a numerically modelled Hii region.
The systematic extraction of Hii region shape, presented in the first paper of this series, allows for a quantifiableconfirmation of the accuracy of the numerical simulation, with respect to the real observational counterparts of
the resulting SOs. A further aim of this investigation is to determine whether such SOs can be used for directinterpretation of the observational data, in a future supervised classification scheme based upon Hii region shape. The
numerical Hii region data was the result of photoionisation and radiation pressure feedback of a 34 M⊙ star, in a 1000
M⊙ cloud. The SOs analysed herein comprised four evolutionary snapshots (0.1, 0.2, 0.4 and 0.6 Myr), and multiple
viewing projection angles. The shape analysis results provided conclusive evidence of the efficacy of the numericalsimulations. When comparing the shapes of the synthetic regions to their observational counterparts, the SOs weregrouped in amongst the Galactic Hii regions by the hierarchical clustering procedure. There was also an association
between the evolutionary distribution of regions and the respective groups. This suggested that the shape analysis
method could be further developed for morphological classification of Hii regions by using a synthetic data training
set, with differing initial conditions of well-defined parameters.
Accepted by MNRAS
https://arxiv.org/pdf/2006.06506

6.

The distances to molecular clouds in the fourth Galactic quadrant
Bingqiu Chen1 , Shu Wang2 , Ligang Hou2 , Yihong Yang1,3 , Zhiwen Li1,3 et al.
1South-Western Institute for Astronomy Research, Yunnan University, Kunming, 650500, P. R. China; 2 National
Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, P. R. China; 3 School of Physics andAstronomy, Yunnan University, Kunming, 650500, P. R. China

E-mail contact: bchen at ynu.edu.cn
Distance measurements to molecular clouds are essential and important. We present directly measured distances to
169 molecular clouds in the fourth quadrant of the Milky Way. Based on the near-infrared photometry from the Two
Micron All Sky Survey and the Vista Variables in the Via Lactea Survey, we select red clump stars in the overlapping
directions of the individual molecular clouds and infer the bin averaged extinction values and distances to these stars.
We track the extinction versus distance profiles of the sightlines toward the clouds and fit them with Gaussian dust
distribution models to find the distances to the clouds. We have obtained distances to 169 molecular clouds selectedfrom Rice et al. The clouds range in distances between 2 and 11 kpc from the Sun. The typical internal uncertainties
in the distances are less than 5 per cent and the systematic uncertainty is about 7 per cent. The catalogue presented
in this work is one of the largest homogeneous catalogues of distant molecular clouds with the direct measurement of
distances. Based on the catalogue, we have tested different spiral arm models from the literature.
Accepted by MNRAS
http://arxiv.org/pdf/2006.119668

7.

Evolutionary study of complex organic molecules in high-mass star-forming regions
Alessandro Coletta1 , Francesco Fontani2 , Victor Manuel Rivilla2 , Chiara Mininni1,2 , Laura Colzi1,2 ,Alvaro Sanchez-Monge3 and Maria T. Beltran2
1
3

Dipartimento di Fisica e Astronomia - Universita’ degli Studi di Firenze; 2 INAF - Osservatorio Astrofisico di Arcetri;
I. Physikalisches Institut - Universitat zu Koln

E-mail contact: alessandro.coletta at stud.unifi.it
We have studied four complex organic molecules (COMs), the oxygen-bearing methyl formate (CH3 OCHO) anddimethyl ether (CH3 OCH3 ) as well as the nitrogen-bearing formamide (NH2 CHO) and ethyl cyanide (C2 H5 CN),
towards a large sample of 39 high-mass star-forming regions representing different evolutionary stages, from early to
evolved phases. We aim to identify potential correlations and chemical links between the molecules and to trace theirevolutionary sequence through the star formation process.
We analysed spectra obtained at 3, 2, and 0.9 mm with the IRAM-30m telescope. We derived the main physicalparameters for each species by fitting the molecular lines. We compared them and evaluated their evolution while also
taking several other interstellar environments into account.
We report detections in 20 sources, revealing a clear dust absorption effect on column densities. Derived abundances
range between ∼10−10 − 10−7 for CH3 OCHO and CH3 OCH3 , ∼10−12 − 10−10 for NH2 CHO, and ∼10−11 − 10−9 forC2 H5 CN. The abundances of CH3 OCHO, CH3 OCH3 , and C2 H5 CN are very strongly correlated (r ≥ 0.92) across ∼4orders of magnitude. We note that CH3 OCHO and CH3 OCH3 show the strongest correlations in most parameters,
and a nearly constant ratio (∼1) over a remarkable ∼9 orders of magnitude in luminosity for the following wide variety
of sources: pre-stellar to evolved cores, low- to high-mass objects, shocks, Galactic clouds, and comets. This indicatesthat COMs chemistry is likely early developed and then preserved through evolved phases. Moreover, the molecularabundances clearly increase with evolution, covering ∼6 orders of magnitude in the luminosity/mass ratio.
We consider CH3 OCHO and CH3 OCH3 to be most likely chemically linked. They could, for example, share a common
precursor, or be formed one from the other. Based on correlations, ratios, and the evolutionary trend, we propose
a general scenario for all COMs, involving a formation in the cold, earliest phases of star formation and a following
increasing desorption with the progressive thermal and shock-induced heating of the evolving core.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2006.15413

8.

Carbon isotopic fractionation in molecular clouds
Laura Colzi1,2 , Olli Sipilä3 , Evelyne Roueﬀ4 , Paola Caselli3 and Francesco Fontani2
Università degli studi di Firenze, Dipartimento di fisica e Astronomia, Via Sansone 1, 50019 Sesto Fiorentino, Italy;
INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Florence, Italy; 3 Max-Planck-Institüt für
extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching bei München, Germany; 4 Sorbonne Université,
Observatoire de Paris, Université PSL, CNRS, LERMA, 92190 Meudon, France

1

2

E-mail contact: lcolzi.astro at gmail.com
C-fractionation has been studied from a theoretical point of view with different models of time-dependent chemistry,including both isotope-selective photodissociation and low-temperature isotopic exchange reactions. Recent chemical
models predict that the latter may lead to a depletion of 13 C in nitrile-bearing species, with 12 C/13 C ratios two times
higher than the elemental abundance ratio of 68 in the local interstellar medium. Since the carbon isotopic ratio
is commonly used to evaluate the 14 N/15 N ratios with the double-isotope method, it is important to study carbon
fractionation in detail to avoid incorrect assumptions. In this work we implemented a gas-grain chemical model withnew isotopic exchange reactions and investigated their introduction in the context of dense and cold molecular gas. In
particular, we investigated the 12 C/13 C ratios of HNC, HCN, and CN using a grid of models, with temperatures anddensities ranging from 10 to 50 K and 2×103 to 2×107 cm−3 , respectively.
We suggest a possible 13 C exchange through the 13 C + C3 → 12 C +13 CC2 reaction, which does not result in dilution,
but rather in 13 C enhancement, for molecules that are formed starting from atomic carbon. This effect is efficientin a range of time between the formation of CO and its freeze-out on grains. Furthermore, the parameter-space
exploration shows, on average, that the 12 C/13 C ratios of nitriles are predicted to be a factor 0.8–1.9 different fromthe local 12 C/13 C of 68 for high-mass star-forming regions. This result also affects the 14 N/15 N ratio: a value of 330
9obtained with the double-isotope method is predicted to vary in the range 260–630, up to 1150, depending on thephysical conditions. Finally, we studied the 12 C/13 C ratios of nitriles by varying the cosmic-ray ionization rate, ζ: the12
C/13 C ratios increase with ζ because of secondary photons and cosmic-ray reactions.
Accepted by A&A
https://arxiv.org/pdf/2006.03362.pdf

9.

Seeds of Life in Space (SOLIS). X. Interstellar Complex Organic Molecules in the NGC
1333 IRAS 4A outflows
Marta De Simone1 , C. Codella2,1 , C. Ceccarelli1 , A. López-Sepulcre3,1 , A. Witzel1 , R. Neri3 , N.
Balucani4,1 , P. Caselli5 , C. Favre1 , F. Fontani2 , B. Leﬂoch1 , J. Ospina-Zamudio1 , J. E. Pineda5 and
V. Taquet2
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 INAF, Osservatorio Astrofisico di Arcetri, Largo
E. Fermi 5, 50125 Firenze, Italy; 3 Institut de Radioastronomie Millimetrique (IRAM), 300 rue de la Piscine, 38400
Saint-Martin d’Hères, France; 4 Dipartimento di Chimica, Biologia e Biotecnologie, Universit degli Studi di Perugia, Perugia 06123, Italy; 5 Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748
Garching, Germany
1E-mail contact: marta.de.smn at gmail.com
Context. The interstellar Complex Organic Molecules (iCOMs) are C-bearing molecules containing at least six atoms;
two main approaches of their formation are invoked: a direct formation in the icy mantle of the dust grains, or
through the reaction in gas phase of released grain mantle species. The shocked gas along outflows driven by low-mass
protostars is a unique environment to study how the iCOMs can be formed, as the composition of the dust mantles is
sputtered into the gas phase.
Aims. The chemical richness in shocked material associated with low-mass protostellar outflows has been so far studied
in the prototypical L1157 blue shifted outflow to investigate the iCOMs formation routes. To understand whether thecase of L1157-B1 is unique, we imaged and studied the IRAS 4A outflows in the NGC 1333 star forming region.
Methods. We used the NOEMA (NOrthern Extended Millimeter Array) interferometer as part of the IRAM SOLIS(Seeds Of Life in Space) Large Program to image the large scale bipolar outflows driven by the IRAS 4A system inthe 3 mm band, and we compared the observation with the GRAINOBLE+ astrochemical model.
Results. We report the first detection, in the IRAS 4A outflows, of several iCOMs: six lines of methanol (CH3OH),
eight of acetaldehyde (CH3CHO), one of formamide (NH2CHO) and four of dimethyl ether (CH3OCH3), all sampling
upper excitation energy up to ?30 K. We found a significant chemical differentiation between the south east outflow
driven by the IRAS 4A1 protostar, showing a richer molecular content, and the north-south west one driven by the
IRAS 4A2 hot corino. The CH3OH/CH3CHO abundance ratio is lower by a factor ∼4 in the former; furthermore theratio in the IRAS 4A outflows is lower by a factor ∼10 with respect to the values found in different hot corinos.
Conclusions. After L1157-B1, IRAS 4A outflow is now the second outflow to show an evident chemical complexity.
Given that CH3OH is a grain surface species, the astrochemical gas phase model run with GRAINOBLE+ reproduced
our observation assuming that acetaldehyde is formed mainly through the gas phase reaction of ethyl radical (CH3CH2)
and atomic oxygen. Furthermore, the chemical differentiation between the two outflows suggests that the IRAS 4A1
outflow is likely younger than the IRAS 4A2 one.Further investigation is needed to constrain the age of the outflow.
In addition, observation of even younger shocks are necessary. In order to provide strong constraints on the CH3CHO
formation mechanisms it would be interesting to observe CH3CH2, but given that its frequencies are not known, future
spectroscopic studies on this species are needed.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2006.09925

10. Hot Corinos Chemical Diversity: Myth or Reality?
Marta De Simone1 , Cecilia Ceccarelli1 , Claudio Codella1,2 , Brian E. Svoboda3,4 , Claire Chandler3 ,Mathilde Bouvier1 , Satoshi Yamamoto5 , Nami Sakai6 , Paola Caselli7, Cecile Favre1 , Laurent Loinard8 ,Bertrand Leﬂoch1 , Hauyu Baobab Liu9 , Ana López-Sepulcre1,10 , Jaime E. Pineda7 , Vianney Taquet2and Leonardo Testi2,11,12
10

Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 2 INAF, Osservatorio Astrofisico di Arcetri, Largo E.
Fermi 5, 50125 Firenze, Italy; 3 National Radio Astronomy Observatory,131003 Lopezville Road, Socorro, NM 87801,
USA; 4 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 5 Departmentof Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan; 6 The Institute of Physical and Chemical
Research(RIKEN),2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan; 7 Max-Planck-Institut für extraterrestrische
Physik(MPE), Giessenbachstrasse 1, D-85748 Garching, Germany; 8 Instituto de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apartado 58090, Morelia, Michoacan, Mexico; 9 Academia Sinica Instituteof Astronomy and Astrophysics(ASIAA), No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan; 10 Institut deRadioastronomie Millimetrique(IRAM), 300 rue de la Piscine, F-38400 Saint-Martin d’Héres, France; 11 ESO, Karl
Schwarzchild Srt. 2, D-85478 Garching bei München, Germany; 12 Excellence Cluster Origins, Boltzmannstrasse 2,
D-85748 Garching bei München, Germany
1E-mail contact: marta.desimone at univ-grenoble-alpes.fr
After almost 20 years of hunting, only about a dozen hot corinos, hot regions enriched in interstellar complex organic
molecules(iCOMs), are known. Of them, many are binary systems with the two components showing drasticallydifferent molecular spectra. Two obvious questions arise. Why are hot corinos so difficult to find and why do theirbinary components seem chemically different? The answer to both questions could be a high dust opacity that would
hide the molecular lines. To test this hypothesis, we observed methanol lines at centimeter wavelengths, where dust
opacity is negligible, using the Very Large Array interferometer. We targeted the NGC1333 IRAS 4A binary system,
for which one of the two components, 4A1, has a spectrum deprived of iCOMs lines when observed at millimeter
wavelengths, while the other component, 4A2, is very rich in iCOMs. We found that centimeter methanol lines are
similarly bright toward 4A1 and 4A2. Their non-LTE analysis indicates gas density and temperature( ≥ 2 × 106 cm−3
and 100-190 K), methanol column density(∼1019 cm−2 ), and extent(∼35 au in radius)similar in 4A1 and 4A2, provingthat both are hot corinos. Furthermore, the comparison with previous methanol line millimeter observations allows
us to estimate the optical depth of the dust in front of 4A1 and 4A2,respectively. The obtained values explain theabsence of iCOMs line emission toward 4A1 at millimeter wavelengths and indicate that the abundances toward 4A2
are underestimated by ∼30%. Therefore, centimeter observations are crucial for the correct study of hot corinos, theircensus, and their molecular abundances
Accepted by ApJ Letters
https://arxiv.org/pdf/2006.04484

11. Probing the physical conditions and star formation processes in the Galactic HII region

S305

L. K. Dewangan1 , Saurabh Sharma2 , Rakesh Pandey2 , S. del Palacio3 , D. K. Ojha4 , P. Benaglia3 , T.
Baug5 and S. R. Das6
Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India.; 2 Aryabhatta Research Institute ofObservational Sciences, Manora Peak, Nainital 263 002, India.; 3 Instituto Argentino de Radioastronomía, Argentina.;
4
Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai
400 005, India.; 5 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian
District, Beijing 100871, P. R. China.; 6 Indian Institute of Space Science and Technology, Trivandrum 695547, India.

1

E-mail contact: lokeshd at prl.res.in
We present multi-scale and multi-wavelength observations of the Galactic H ii region S305, which is excited by massive
O8.5V and O9.5V stars. Infrared images reveal an extended sphere-like shell (extension ∼7.5 pc; at Td = 17.5–
27 K) enclosing the S305 H ii region (size ∼5.5 pc; age ∼1.7 Myr). The extended structure observed in the Herscheltemperature map indicates that the molecular environment of S305 is heated by the massive O-type stars. Regularly
spaced molecular condensations and dust clumps are investigated toward the edges of the infrared shell, where the
PAH and H2 emission is also observed. The molecular line data show a signature of an expanding shell of molecular gas
in S305. GMRT 610 and 1280 MHz continuum maps reveal overdensities of the ionized emission distributed around
two O-type stars, which are surrounded by the horseshoe envelope (extension ∼2.3 pc). A molecular gas deficientregion/cavity is identified toward the center of the horseshoe envelope, which is well traced with PAH, H2 , molecular,
and dust emission. The edges of the infrared shell are found to be located in the front of the horseshoe envelope. All
these outcomes provide the observational evidence of the feedback of O-type stars in S305. Moreover, non-thermal
11radio emission is detected in S305 with an average spectral index α ∼ −0.45. The variations in α, ranging from −1.1
to 1.3, are explained due to soft synchrotron emission and either optically-thicker thermal emission at high frequencies
or a suppression of the low-frequency emission by the Razin-Tsytovich effect.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2006.03244.pdf

12. Tidal tails of open star clusters as probes to early gas expulsion I: A semi-analytic model
Frantisek Dinnbier1 and Pavel Kroupa2,3
1

I.Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany; 2 Helmholtz-Institut fürStrahlen- und Kernphysik, University of Bonn, Nussallee 14-16, 53115 Bonn, Germany; 3 Charles University in Prague,
Faculty of Mathematics and Physics, Astronomical Institute, V Holesovickách 2, 180 00 Praha 8, Czech Republic
E-mail contact: dinnbier at ph1.uni-koeln.de
Star clusters form out of the densest parts of infrared dark clouds. The emergence of massive stars expels theresidual gas, which has not formed stars yet. Gas expulsion lowers the gravitational potential of the embedded cluster,
unbinding many of the cluster stars. These stars then move on their own trajectories in the external gravitational
field of the Galaxy, forming a tidal tail. We investigate the formation and evolution of the tidal tail forming due
to expulsion of primordial gas under various scenarios of gas expulsion to provide predictions for tidal tails around
dynamically evolved (age > 100 Myr) galactic star clusters, which can be possibly detected by the Gaia mission.
We provide a semi-analytical model for the tail evolution. We find that tidal tails released during gas expulsion
have different kinematic properties than the tails gradually forming due to evaporation. The gas expulsion tidal tailshows non-monotonic expansion with time, where longer epochs of expansion are interspersed with shorter epochs ofcontraction. The tail thickness and velocity dispersions strongly, but not exactly periodically, vary with time. The
times of minima of tail thickness and velocity dispersions are given only by the properties of the galactic potential,
and not by the properties of the cluster. The estimates provided by the (semi-)analytical model for the extent of thetail, the minima of tail thickness, and velocity dispersions are in a very good agreement with the nbody6 simulations.
This implies that the semi-analytic model can be used for estimating the properties of the gas expulsion tidal tail fora cluster of a given age and orbital parameters without the necessity of performing numerical simulations. A study
with a more extended parameter space of the initial conditions is performed in the follow up paper.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2006.14087

13. The JCMT BISTRO Survey: Magnetic fields associated with a network of filaments in

NGC 1333

Yasuo Doi1 , Tetsuo Hasegawa2 , Ray S. Furuya3,4 , and 131 co-authors
Department of Earth Science and Astronomy, Graduate School of Arts and Sciences, The University of Tokyo,
3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan; 2 National Astronomical Observatory of Japan, National Institutes of
Natural Sciences, Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Tokushima University, Minami Jousanajima-machi 1-1,
Tokushima 770-8502, Japan; 4 Institute of Liberal Arts and Sciences, Tokushima University, Minami Jousanajimamachi 1-1, Tokushima 770-8502, Japan1

E-mail contact: lvferrero at unc.edu.ar
We present a multi-wavelength study of two HH objects (137 and 138) that may be associated. We use Gemini H2(2.12 µm) and K (2.2 µm) images, as well as APEX molecular line observations and Spitzer image archives. Several
H2 knots, linked to the optical chain of knots of HH 137, are identified in the Gemini and Spitzer 4.5 µm images. New
shock excited regions related to the optical knots delineating HH 138 are also reported. In addition, a bright 4.5 µm
0.09 pc-long arc-shaped structure, roughly located mid-way between HH 137 and HH 138, is found to be associatedwith two Spitzer Class I/II objects, which are likely to be the exciting stars. These sources are almost coincident witha high-density molecular clump detected in 12 CO(3-2), 13 CO(3-2), C18 O(3-2), HCO+ (3-2) and HCN(3-2) molecularlines with an LTE mass of 36 M⊙ . The 12 CO(3-2) emission distribution over the observed region reveals molecularmaterial underlying three molecular outflows. Two of them (outflows 1 and 2) are linked to all optical knots of HH 137
12

and HH 138 and to the H2 and 4.5 µm shock emission knots. In fact, the outflow 2 shows an elongated 12 CO blue
lobe that coincides with all the H2 knots of HH 137 which end at a terminal H2 bow shock. We propose a simple
scenario that connects the outflows to the dust clumps detected in the region. A third possible outflow is located to
the north-east projected towards a secondary weak and cold dust clump.
Accepted by MNRAS
http://arxiv.org/pdf/2006.16287

14.

Is T Tauri North a ‘Classical’ T Tauri star?
Christian Flores1 , Bo Reipurth1 and Michael S. Connelley1
1Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI 96720, USA

E-mail contact: caflores at hawaii.edu
We present high-resolution H- and K-band spectroscopic observations of the archetypal T Tauri star T Tau North.
Synthetic spectral modeling is used to derive the K-band temperature, surface gravity, magnetic field strength, androtational velocity for this star. The K-band spectroscopic temperature measured is TK−band = 3976 ± 90K, whichis ∼ 1000 K cooler than the temperature measured from optical observations. Our K-band temperature measurement
for T Tau N is confirmed using equivalent width line ratio vs. temperature relations in the H-band, from which a
TH−band = 4085 ± 155K is derived. This optical vs. IR temperature difference is interpreted as cool or hot spots, orboth, covering a significant part of the surface of T Tau N. The gravity derived for T Tau N log g = 3.45 ± 0.14 islower than the gravity of nearly every other star in a sample of 24 classical T Tauri stars in Taurus. Combining thesetemperature and gravity results with magnetic stellar evolutionary models, we find the age of T Tau N to be less than
1 Myr old. These results suggest that T Tau N is in an earlier evolutionary stage than most classical T Tauri stars in
Taurus, arguing that it is a protostar ejected from the embedded southern binary system shortly after its formation.
Accepted by ApJ
https://arxiv.org/pdf/2006.10139.pdf

15.

ISO-ChaI 52: a weakly-accreting young stellar object with a dipper light curve
A. Frasca1 , C.F. Manara2 , J.M. Alcalá3 , K. Biazzo4 , L. Venuti5,6 et al.
INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy; 2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 3 INAF – Osservatorio Astronomico di
Capodimonte, via Moiariello, 16, 80131 Napoli, Italy; 4 INAF – Osservatorio Astronomico di Roma, Via Frascati 33,
00078 Monte Porzio Catone, Italy; 5 NASA Ames Research Center, Moffett Blvd, Mountain View, CA 94035, USA; 6
INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
1E-mail contact: antonio.frasca at inaf.it
We report on the discovery of periodic dips in the multiband lightcurve of ISO-ChaI 52, a young stellar object in the
Chamaeleon I dark cloud. This is one among the peculiar objects that display very low or negligible accretion both intheir UV continuum and spectral lines, although they present a remarkable infrared excess emission characteristic of
optically-thick circumstellar disks. We have analyzed a VLT/X-Shooter spectrum with the tool ROTFIT to determine
the stellar parameters. The latter, along with photometry from our campaign with the REM telescope and from theliterature, have allowed us to model the spectral energy distribution and to estimate the size and temperature of theinner and outer disk. From the rotational period of the star/disk system of 3.45 days we estimate a disk inclinationof 36◦ . The depth of the dips in different bands has been used to gain information about the occulting material. A
single extinction law is not able to fit the observed behavior, while a two-component model of a disk warp composedof a dense region with a gray extinction and an upper layer with an ISM-type extinction provides a better fit of thedata.
Accepted by A&A
http://arxiv.org/pdf/2006.07921

13

16. A low-velocity bipolar outflow from a deeply embedded object in Taurus revealed by

the Atacama Compact Array

Kakeru Fujishiro1 , Kazuki Tokuda2,3 , Kengo Tachihara1 , Tatsuyuki Takashima2 , Yasuo Fukui1,4 , Sarolta
Zahorecz2,3 , Kazuya Saigo3 , Tomoaki Matsumoto5 , Kengo Tomida6 , Masahiro N. Machida7 , Shu-ichiro
Inutsuka1 , Philippe André8 , Akiko Kawamura3 and Toshikazu Onishi2
Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan; 2 Dept. of Physical Science,
Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan;
3
National Astron. Obs. of Japan, National Institutes of Natural Science, 2-21-1 Osawa, Mitaka, Tokyo 181-8588,
Japan; 4 Inst. for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan; 5 Facultyof Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan; 6 Astron. Institute, Tohoku
University, 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan; 7 Dep. of Earth and Planetary Sciences, Facultyof Sciences, Kyushu University, Nishi-ku, Fukuoka 819-0395, Japan; 8 Laboratoire d’Astrophysique (AIM), CEA,
CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
1

E-mail contact: tokuda at p.s.osakafu-u.ac.jp
The first hydrostatic core, the first quasi-hydrostatic object formed during the star formation process, is still theobservational missing link between the prestellar and protostellar phases, mainly due to its short lifetime. Although wehave not established a clear method to identify this rare object, recent theoretical studies predict that the first core has
millimeter continuum emission and low-velocity outflow with a wide opening angle. An extensive continuum/outflow
survey toward a large number of “starless” cores in nearby star-forming regions works as a pathfinder. We observed
32 prestellar cores in Taurus with an average density of >105 cm−3 in 1.3 mm continuum and molecular lines using
the ALMA-ACA stand-alone mode. Among the targets, MC35-mm centered at one of the densest “starless” cores in
Taurus has blueshifted/redshifted wings in the 12 CO (2–1) line, indicating that there is deeply embedded object driving
molecular outflow. The observed velocities and sizes of the possible outflow lobes are 2–4 km s−1, and ∼2 × 103 au,
respectively, and the dynamical time is calculated to be ∼103 yr. In addition to this, the core is one of the strongest
N2 D+ (3–2) emitter in our sample. All the observed signatures do not conflict with any of the theoretical predictions
about the first hydrostatic core so far, and thus MC35-mm is unique as the only first-core candidate in the Taurus
molecular cloud.
Accepted by ApJL
https://arxiv.org/pdf/2006.06378

17. Analysis of Methanol Maser Flares in G107.298+5.63 and S255-NIRS3
M. D. Gray1,2 , S. Etoka1 and B. Pimpanuwat1,2
1
2

Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, M13 9PL, UK;
National Astronomical Research Institute, 260 Moo 4, T. Donkaew, A. Maerim, Chiangmai 50180, Thailand

E-mail contact: Malcolm.Gray at manchester.ac.uk
A 3D maser model has been used to perform an inverse problem on the light curves from three high-amplitude maser
flares, selected on the basis of contemporaneous infra-red observations. Plots derived from the model recover the sizeof the maser cloud, and two parameters linked to saturation, from three observational properties of the light curve.
Recovered sizes are consistent with independent interferometric measurements. Maser objects transition between weak
and moderate saturation during a flare.
Accepted by MNRAS
https://arxiv.org/pdf/2006.13124

18. Global Hydromagnetic Simulations of Protoplanetary Disks with Stellar Irradiation and

Simplified Thermochemistry
Oliver Gressel1,2, Jon P. Ramsey3 , Christian Brinch2 , Richard P. Nelson4 , Neal J. Turner5 and Simon
Bruderer6
1

Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482, Potsdam, Germany; 2 Astrophysics& Planetary Science, The Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen, Denmark; 3 Department
14

of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 4 Astronomy Unit, Queen Mary Universityof London, Mile End Road, London E1 4NS, UK; 5 Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA 91109, USA; 6 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching,
Germany
E-mail contact: ogressel at aip.de
Outflows driven by large-scale magnetic fields likely play an important role in the evolution and dispersal of protoplanetary disks and in setting the conditions for planet formation. We extend our 2D-axisymmetric nonideal MHD
model of these outflows by incorporating radiative transfer and simplified thermochemistry, with the dual aims of
exploring how heating influences wind launching and illustrating how such models can be tested through observationsof diagnostic spectral lines. Our model disks launch magnetocentrifugal outflows primarily through magnetic tension
forces, so the mass-loss rate increases only moderately when thermochemical effects are switched on. For typical fieldstrengths, thermochemical and irradiation heating are more important than magnetic dissipation. We furthermore
find that the entrained vertical magnetic flux diffuses out of the disk on secular timescales as a result of nonideal
MHD. Through postprocessing line radiative transfer, we demonstrate that spectral line intensities and moment-1
maps of atomic oxygen, the HCN molecule, and other species show potentially observable differences between a modelwith a magnetically driven outflow and one with a weaker, photoevaporative outflow. In particular, the line shapes
and velocity asymmetries in the moment-1 maps could enable the identification of outflows emanating from the disk
surface.
Accepted by ApJ
http://arxiv.org/pdf/2005.03431

19. The relative orientation between the magnetic field and gradients of surface brightness

within thin velocity slices of 12 CO and 13 CO emission from the Taurus molecular cloudMark Heyer1 , Juan Soler2 and Blakesley Burkhart3

Department of Astronomy, Lederle Research Building, University of Massachusetts, Amherst, MA 01003, USA;Max Planck Institute for Astronomy, Königsthul, 17, 69117, Heidelberg, Germany; 3 Department of Physics andAstronomy, Rutgers University, 136 Frelinghuysen Rd, Piscataway, NJ 08854, USA
1

2E-mail contact: heyer at astro.umass.edu
We examine the role of the interstellar magnetic field to modulate the orientation of turbulent flows within the Taurus
molecular cloud using spatial gradients of thin velocity slices of 12 CO and 13 CO antenna temperatures. Our analysis
accounts for the random errors of the gradients that arise from the thermal noise of the spectra. The orientations of thevectors normal to the antenna temperature gradient vectors are compared to the magnetic field orientations that arecalculated from Planck 353 GHz polarization data. These relative orientations are parameterized with the projected
Rayleigh statistic and mean resultant vector. For 12 CO, 28% and 39% of the cloud area exhibit strongly parallel orstrongly perpendicular relative orientations respectively. For the lower opacity 13 CO emission, strongly parallel andstrongly perpendicular orientations are found in 7% and 43% of the cloud area respectively. For both isotopologues,
strongly parallel or perpendicular alignments are restricted to localized regions with low levels of turbulence. If
the relative orientations serve as an observational proxy to the Alfvénic Mach number then our results imply local
variations of the Alfvénic Mach number throughout the cloud.
Accepted by MNRAS
https://arxiv.org/pdf/2006.10775.pdf

20. The Effect of Misalignment between Rotation Axis and Magnetic Field on Circumstellar

Disk

Shingo Hirano1 , Yusuke Tsukamoto2 , Shantanu Basu3 and Masahiro N. Machida1,3
Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan;
Department of Earth and Space Science, Graduate Schools of Science and Engineering, Kagoshima University,
Kagoshima 890-0065, Japan; 3 Department of Physics and Astronomy, The University of Western Ontario, London,
ON N6A 3K7, Canada
1

2

15

E-mail contact: hirano.shingo.821 at m.kyushu-u.ac.jp
The formation of circumstellar disks is investigated using three-dimensional resistive magnetohydrodynamic simulations, in which the initial prestellar cloud has a misaligned rotation axis with respect to the magnetic field. We
examine the effects of (i) the initial angle difference between the global magnetic field and the cloud rotation axis (θ0 )and (ii) the ratio of the thermal to gravitational energy (α0 ). We study 16 models in total and calculate the cloud
evolution until ∼ 5000 yr after protostar formation. Our simulation results indicate that an initial non-zero θ0 (> 0)
promotes the disk formation but tends to suppress the outflow driving, for models that are moderately gravitationallyunstable, α0 <∼ 1. In these models, a large-sized rotationally-supported disk forms and a weak outflow appears, incontrast to a smaller disk and strong outflow in the aligned case (θ0 = 0). Furthermore, we find that when the initialcloud is highly unstable with small α0 , the initial angle difference θ0 does not significantly affect the disk formationand outflow driving.
Accepted by ApJ
https://arxiv.org/pdf/2006.13233

21. Determining the Physical Conditions of an Extremely Young Class 0 Circumbinary Disk

around VLA 1623A

Cheng-Han Hsieh1,2, Shih-Ping Lai1,3,4 , Pou-Ieng Cheong3 , Chia-Lin Ko3,5 , Zhi-Yun Li6 and Murillo
Nadia M.7
Department of Physics, National Tsing Hua University, 101 Section 2 Kuang Fu Road, 30013 Hsinchu, Taiwan; 2
Department of Astronomy, Yale University, New Haven, CT 06511, USA; 3 Institute for Astronomy, National Tsing
Hua University,101 Section 2 Kuang Fu Road, 30013 Hsinchu, Taiwan; 4 Academia Sinica Institute of Astronomy andAstrophysics, P.O. Box 23-141, 10617 Taipei, Taiwan; 5 Department of Physics, National Taiwan Normal University,
No. 162, Section 1, Heping East Road, Taipei 10610, Taiwan; 6 Department of Astronomy, University of Virginia,
530 McCormick Road, Charlottesville, VA, USA; 7 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA
Leiden, The Netherlands
1E-mail contact: cheng-han.hsieh at yale.edu
We present a detailed analysis of high-resolution C18O (2-1), SO (88-77), CO (3-2), and DCO+ (3-2) data obtainedby the Atacama Large Millimeter/submillimeter Array toward a class 0 Keplerian circumbinary disk around VLA
1623A, which represents one of the most complete analyses toward a class 0 source. From the dendrogram analysis,
we identified several accretion flows feeding the circumbinary disk in a highly anisotropic manner. Stream-like SO
emission around the circumbinary disk reveals the complicated shocks caused by the interactions between the disk,
accretion flows, and outflows. A wall-like structure is discovered south of VLA1623B. The discovery of two outflow
cavity walls at the same position traveling at different velocities suggests that the two outflows from both VLA 1623A
and VLA 1623B are on top of each other in the plane of the sky. Our detailed flat and flared disk modeling showsthat Cycle 2 C18O J = 2-1 data are inconsistent with the combined binary mass of 0.2 Msun, as suggested by early
Cycle 0 studies. The combined binary mass for VLA 1623A should be modified to 0.3-0.5 Msun.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1904.00133

22. ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): I. Detection of

New Hot Corinos with ACA
Shih-Ying Hsu1,2 , Sheng-Yuan Liu2 , Tie Liu3 , Dipen Sahu2 , Naomi Hirano2 et al.
1

National Taiwan University (NTU), Taiwan (R.O.C.); 2 Institute of Astronomy and Astrophysics, Academic Sinica,
Taipei, Taiwan (R.O.C.)
E-mail contact: syliu at asiaa.sinica.edu.tw
We report the detection of four new hot corino sources, G211.47−19.27S, G208.68−19.20N1, G210.49−19.79W and
G192.12−11.10 from a survey study of Planck Galactic Cold Clumps in the Orion Molecular Cloud Complex with the
Atacama Compact Array (ACA). Three sources had been identified as low mass Class 0 protostars in the Herschel Orion

16

Protostar Survey (HOPS). One source in the lambda Orionis region is firstly reported as a protostellar core. We haveobserved abundant complex organic molecules (COMs), primarily methanol but also other oxygen-bearing COMs
(in G211.47−19.27S and G208.68−19.20N1) and the molecule of prebiotic interest NH2 CHO (in G211.47−19.27S),
signifying the presence of hot corinos. While our spatial resolution is not sufficient for resolving most of the molecularemission structure, the large linewidth and high rotational temperature of COMs suggest that they likely reside in thehotter and innermost region immediately surrounding the protostar. In G211.47−19.27S, the D/H ratio of methanol([CH2 DOH]/[CH3 OH]) and the 12 C/13 C ratio of methanol ([CH3 OH]/[13 CH3 OH]) are comparable to those of otherhot corinos. Hydrocarbons and long carbon-chain molecules such as c-C3 H2 and HCCCN are also detected in the four
sources, likely tracing the outer and cooler molecular envelopes.
Accepted by ApJ
http://arxiv.org/pdf/2006.15850

23. BV (RI)c photometric study of three variable PMS stars in the field of V733 Cephei
Sunay Ibryamov1 , Evgeni Semkov2 , Stoyanka Peneva2 and Kristina Gocheva1
Department of Physics and Astronomy, University of Shumen, 115, Universitetska Str., 9700 Shumen, Bulgaria;
Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, 72, Tsarigradsko
Shose Blvd., 1784 Sofia, Bulgaria

1
2

E-mail contact: sibryamov at shu.bg
This paper report results from the first long-term BV (RI)c photometric CCD observations of three variable pre-mainsequence stars collected during the period from February 2007 to January 2020. The investigated stars are locatedin the field of the PMS star V733 Cep within the Cepheus OB3 association. All stars from our study show rapid
photometric variability in all-optical passbands. In this paper, we describe and discuss the photometric behavior ofthese stars and the possible reasons for their variability. In the light variation of two of the stars we found periodicity.
Accepted by Research in Astronomy and Astrophysics
https://arxiv.org/pdf/2006.02498

24. The ionized warped disk and disk wind of the massive protostar Monoceros R2-IRS2

seen with ALMA

Izaskun Jiménez-Serra1 , Alejandro Báez-Rubio1 , Jesús Martín-Pintado1 , Qizhou Zhang2 and Víctor
M. Rivilla3
Centro de Astrobiología (CSIC-INTA), Ctra. de Torrejón a Ajalvir km 4, 28850, Torrejón de Ardoz, Spain; 2 Center
for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138 USA; 3 INAF-Osservatorio Astrofisico
di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
1E-mail contact: ijimenez at cab.inta-csic.es
Theories of massive star formation predict that massive protostars accrete gas through circumstellar disks. Althoughseveral cases have been found already thanks to high-angular resolution interferometry, it remains unknown the internal
physical structure of these disks and, in particular, whether they present warps or internal holes as observed in lowmass proto-planetary disks. Here, we report very high angular resolution observations of the H21α radio recombinationline carried out in Band 9 with the Atacama Large Millimeter/submillimeter Array (beam of 80 mas×60 mas, or
70 au×50 au) toward the IRS2 massive young stellar object in the Monoceros R2 star-forming cluster. The H21α line
shows maser amplification, which allows us to study the kinematics and physical structure of the ionised gas aroundthe massive protostar down to spatial scales of ∼1-2 au. Our ALMA images and 3D radiative transfer modelling revealthat the ionized gas around IRS2 is distributed in a Keplerian circumstellar disk and an expanding wind. The H21αemission centroids at velocities between −10 and 20 km s−1 deviate from the disk plane, suggesting a warping for the
disk. This could be explained by the presence of a secondary object (a stellar companion or a massive planet) within
the system. The ionized wind seems to be launched from the disk surface at distances ∼11 au from the central star,consistent with magnetically-regulated disk wind models. This suggests a similar wind launching mechanism to thatrecently found for evolved massive stars such as MWC349A and MWC922.

17

Accepted by Astrophysical Journal Letters
http://arxiv.org/pdf/2006.15853

25. Spin-orbit alignment of the β Pictoris planetary system
Stefan Kraus1 , Jean-Baptiste LeBouquin2 , Alexander Kreplin1 , Claire L. Davies1 , Edward Hone1 , John
D. Monnier3 , Tyler Gardner3 , Grant Kennedy4 and Sasha Hinkley1
1
3

School of Physics and Astronomy, University of Exeter, UK; 2 Universite d’Grenoble Alpes, Grenoble, France;
Dept of Astron., Univ. of Michigan, Ann Arbor, USA; 4 Dept of Physics, Univ. of Warwick, Coventry, UK

E-mail contact: s.kraus at exeter.ac.uk
A crucial diagnostic that can tell us about processes involved in the formation and dynamical evolution of planetarysystems is the angle between the rotation axis of a star and a planet’s orbital angular momentum vector ("spin-orbit"
alignment or "obliquity"). Here we present the first spin-orbit alignment measurement for a wide-separation exoplanetary system, namely on the directly imaged planet β Pictoris b. We use VLTI/GRAVITY spectro-interferometry withan astrometric accuracy of 1 µas (microarcsecond) in the Brγ photospheric absorption line to measure the photocenter
displacement associated with the stellar rotation. Taking inclination constraints from astroseismology into account,we constrain the three-dimensional orientation of the stellar spin axis and find that β Pic b orbits its host star on
a prograde orbit. The angular momentum vectors of the stellar photosphere, the planet, and the outer debris disk
are well aligned with mutual inclinations 3◦ ± 5◦ , which indicates that β Pic b formed in a system without significant
primordial misalignments. Our results demonstrate the potential of infrared interferometry to measure the spin-orbitalignment for wide-separation planetary systems, probing a highly complementary regime to the parameter space
accessible with the Rossiter-McLaughlin effect. If the low obliquity is confirmed by measurements on a larger sampleof wide-separation planets, it would lend support to theories that explain the obliquity in Hot Jupiter systems withdynamical scattering and the Kozai-Lidov mechanism.
Accepted by ApJL
https://arxiv.org/pdf/2006.10784

26. Ionization: a possible explanation for the difference of mean disk sizes in star-forming

regions
M. Kuﬀmeier1, B. Zhao2 and P. Caselli2
Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany; 2 Max-PlanckInstitute for Extraterrestrial Physics, Garching, Germany

1E-mail contact: kueffmeier at gmail.com
Surveys of protoplanetary disks in star-forming regions of similar age revealed significant variations in average disk
mass in some regions. For instance, disks in the Orion Nebular Cluster (ONC) and Corona Australis (CrA) areon average smaller than disks observed in Lupus, Taurus, Chamaeleon I, or Ophiuchus. In contrast to previous
models that studied the truncation of disks at a late stage of their evolution, we investigate whether disks may
already be born with systematically smaller disk sizes in more massive star-forming regions as a consequence of higher
ionization rates. Assuming various cosmic-ray ionization rates, we computed the resistivities for ambipolar diffusion
and Ohmic dissipation with a chemical network, and performed 2D nonideal magnetohydrodynamical protostellar
collapse simulations. A higher ionization rate leads to stronger magnetic braking, and hence to the formation ofsmaller disks. Accounting for recent findings that protostars act as forges of cosmic rays and considering only mild
attenuation during the collapse phase, we show that a high average cosmic-ray ionization rate in star-forming regions
such as the ONC or CrA can explain the detection of smaller disks in these regions. Our results show that on average,a higher ionization rate leads to the formation of smaller disks. Smaller disks in regions of similar age can therefore
be the consequence of different levels of ionization, and may not exclusively be caused by disk truncation throughexternal photoevaporation. We strongly encourage observations that allow measuring the cosmic-ray ionization degrees
in different star-forming regions to test our hypothesis.
Accepted by A&A
https://arxiv.org/pdf/2006.00019

18

27. Linear dust polarization during the embedded phase of protostar formation: Synthetic

observations of bridge structures

M. Kuﬀmeier1, S. Reissl1, S. Wolf2 , I. Stephens3 and H. Calcutt4
Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany; 2 Institut fürTheoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstrasse 15, 24118 Kiel, Germany;3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 4 Department ofSpace, Earth and Environment, Chalmers University of Technology, 412 96, Gothenburg, Sweden
1E-mail contact: kueffmeier at gmail.com
Measuring polarization from thermal dust emission can provide important constraints on the magnetic field structurearound embedded protostars. However, interpreting the observations is challenging without models that consistently
account for both the complexity of the turbulent protostellar birth environment and polarization mechanisms. We
aim to provide a better understanding of dust polarization maps of embedded protostars with a focus on bridgelike structures such as the structure observed toward the protostellar multiple system IRAS 16293–2422 by comparing
synthetic polarization maps of thermal reemission with recent observations. We analyzed the magnetic field morphology
and properties associated with the formation of a protostellar multiple based on ideal magnetohydrodynamic 3D
zoom-in simulations carried out with the ramses code. To compare the models with observations, we postprocessed asnapshot of a bridge-like structure that is associated with a forming triple star system with the radiative transfer codepolaris and produced multiwavelength dust polarization maps. The typical density in the most prominent bridgeof our sample is about 10−16 g cm−3 , and the magnetic field strength in the bridge is about 1 to 2 mG. Inside thebridge, the magnetic field structure has an elongated toroidal morphology, and the dust polarization maps trace thecomplex morphology. In contrast, the magnetic field strength associated with the launching of asymmetric bipolar
outflows is significantly more magnetized (∼100 mG). At λ = 1.3 mm, and the orientation of the grains in the bridge
is very similar for the case accounting for radiative alignment torques (RATs) compared to perfect alignment withmagnetic field lines. However, the polarization fraction in the bridge is three times smaller for the RAT scenario thanwhen perfect alignment is assumed. At shorter wavelength (λ < 200µm), however, dust polarization does not trace
the magnetic field because other effects such as self-scattering and dichroic extinction dominate the orientation of thepolarization. Compared to the launching region of protostellar outflows, the magnetic field in bridge-like structures isweak. Synthetic dust polarization maps of ALMA Bands 6 and 7 (1.3 mm and 870 µm, respectively) can be used asa tracer of the complex morphology of elongated toroidal magnetic fields associated with bridges.
Accepted by A&A
https://ui.adsabs.harvard.edu/pdf/2020arXiv200601297K/abstract

28. The Formation of a Stellar Association in the NGC 7000/IC 5070 Complex:

Results from Kinematic Analysis of Stars and Gas

Michael A. Kuhn1 , Lynne A. Hillenbrand1 , John M. Carpenter2 and Angel Rodrigo Avelar Menendez1
Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA; 2 Joint ALMA Observatory,
Alonso de Córdova 3107 Vitacura, Santiago, Chile
1

E-mail contact: mkuhn at astro.caltech.edu
We examine the clustering and kinematics of young stellar objects (YSOs) in the North America/Pelican Nebulae, as
revealed by Gaia astrometry, in relation to the structure and motions of the molecular gas, as indicated in molecularline maps. The Gaia parallaxes and proper motions allow us to significantly refine previously published lists of YSOs,
demonstrating that many of the objects previously thought to form a distributed population turn out to be nonmembers. The members are subdivided into at least 6 spatio-kinematic groups, each of which is associated with its
own molecular cloud component or components. Three of the groups are expanding, with velocity gradients of 0.3–
0.5 km s−1 pc−1 , up to maximum velocities of ∼8 km s−1 away from the groups’ centers. The two known O-type stars
associated with the region, 2MASS J20555125+4352246 and HD 199579, are rapidly escaping one of these groups,
following the same position–velocity relation as the low-mass stars. We calculate that a combination of gas expulsion
and tidal forces from the clumpy distribution of molecular gas could impart the observed velocity gradients within thegroups. However, on a global scale, the relative motions of the groups do not appear either divergent or convergent.
The velocity dispersion of the whole system is consistent with the kinetic energy gained due to gravitational collapse
19

of the complex. Most of the stellar population has ages similar to the free-fall timescales for the natal clouds. Thus,
we suggest the nearly free-fall collapse of a turbulent molecular cloud as the most likely scenario for star formation inthis complex.
Accepted by ApJ
http://arxiv.org/pdf/2006.08622

29. The Mass-Size Relation and the Constancy of GMC Surface Densities in the Milky Way
Charles J. Lada1 and T.M. Dame1
1

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

E-mail contact: clada at cfa.harvard.edu
We use two existing molecular cloud catalogs derived from the same CO survey and two catalogs derived from local
dust extinction surveys to investigate the nature of the GMC mass-size relation in the Galaxy. We find that the four
surveys are well described by MGMC ∼ R2 implying a constant mean surface density, ΣGMC , for the cataloged clouds.
However, the scaling coefficients and scatter differ significantly between the CO and extinction derived relations. We
find that the additional scatter seen in the CO relations is due to a systematic variation in ΣGMC with Galactic radiusthat is unobservable in the local extinction data. We decompose this radial variation of ΣGMC into two components,
a linear negative gradient with Galactic radius and a broad peak coincident with the molecular ring and superposedon the linear gradient. We show that the former may be due to a radial dependence of XCO on metallicity while thelatter likely results from a combination of increased surface densities of individual GMCs and a systematic upwardbias in the measurements of ΣGMC due to cloud blending in the molecular ring. We attribute the difference in scalingcoefficients between the CO and extinction data to an underestimate of XCO . We recalibrate the CO observationsof nearby GMCs using extinction measurements to find that locally XCO = 3.6±0.3 × 1020 cm−2 (K-km/s)−1 . We
conclude that outside the molecular ring the GMC population of the Galaxy can be described to relatively goodprecision by a constant ΣGMC of 35 M⊙ pc−2 .
Accepted by Astrophysical Journal
https://arxiv.org/pdf/2006.08632.pdf

30. The Future of IMF studies with the ELT and MICADO: The local Universe as a resolved

IMF laboratory

Kieran Leschinski1 and João Alves1
1

University of Vienna, Department of Astrophysics, Vienna, Austria

E-mail contact: kieran.leschinski at univie.ac.at
In this work, we aim to estimate the lowest stellar mass that MICADO at the ELT will be able to reliably detect
given a stellar density and distance. We also show that instrumental effects that will play a critical role, and report
the number of young clusters that will be accessible for IMF studies in the local Universe with the ELT. We used
SimCADO, theinstrument simulator package for the MICADO camera, to generate observations of 56 dense stellar
22rr lvaregions withdensities similart
wi a kpe anddirect measurements of the Salpeter slope of the IMF will be possible in over 1500 young clusters out to a distanceof 5 Mpc. MICADO on the ELT will be able to measure resolved IMFs for a large ensemble of young clusters understarkly different environments and test the universality of the IMF in the local Universe.
Accepted by A&A
https://arxiv.org/pdf/2006.07619.pdf

31. The origin of a distributed stellar population in the star-forming region W4
Beomdu Lim1 , Jongsuk Hong2 , Hyeong-Sik Yun1 , Narae Hwang3 , Jinyoung S. Kim4 et al.
School of Space Research, Kyung Hee University 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi- do 17104,
Republic of Korea; 2 Dept of Astronomy, Yonsei Univ. 50, Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
3Korea Astronomy and Space Science Institute, 776; 3 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Korea; 4 Steward
Observatory, University of Arizona, 933 N. Cherry Ave. Tucson, AZ 85721-0065, USA; 5 Astronomy and Space Science
Major, Univ. of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea

1E-mail contact: blim at khu.ac.kr
Stellar kinematics provides the key to understanding the formation process and dynamical evolution of stellar systems.
Here, we present a kinematic study of the massive star-forming region W4 in the Cassiopeia OB6 association using
the Gaia Data Release 2 and high-resolution optical spectra. This star-forming region is composed of a core cluster(IC 1805) and a stellar population distributed over 20 pc, which is a typical structural feature found in many OB
associations. According to a classical model, this structural feature can be understood in the context of the dynamical
evolution of a star cluster. The core-extended structure exhibits internally different kinematic properties. Stars in
the core have an almost isotropic motion, and they appear to reach virial equilibrium given their velocity dispersion(0.9±0.3 km s−1 ) comparable to that in a virial state (∼0.8 km s−1 ). On the other hand, the distributed populationshows a clear pattern of radial expansion. From the N-body simulation for the dynamical evolution of a model clusterin subvirial state, we reproduce the observed structure and kinematics of stars. This model cluster experiences collapse
for the first 2 Myr. Some members begin to radially escape from the cluster after the initial collapse, eventually forminga distributed population. The internal structure and kinematics of the model cluster appear similar to those of W4.
Our results support the idea that the stellar population distributed over 20 pc in W4 originate from the dynamical
evolution of IC 1805.
Accepted by ApJ
http://arxiv.org/pdf/2006.15262

32. An unbiased ALMA spectral survey of the LkCa 15 and MWC 480 protoplanetary disks
Ryan A. Loomis1, Karin I. Öberg2 , Sean M. Andrews2 , Edwin Bergin3 , Jennifer Bergner2 et al.
National Radio Astronomy Observatory, Charlottesville, VA 22903, USA; 2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; 3 University of Michigan, Ann Arbor, MI 48109, USA
1E-mail contact: rloomis at cfa.harvard.edu
The volatile contents of protoplanetary disks both set the potential for planetary chemistry and provide valuable
probes of defining disk system characteristics such as stellar mass, gas mass, ionization, and temperature structure.
Current disk molecular inventories are fragmented, however, giving an incomplete picture: unbiased spectral line
surveys are needed to assess the volatile content. We present here an overview of such a survey of the protoplanetarydisks around the Herbig Ae star MWC 480 and the T Tauri star LkCa 15 in ALMA Band 7, spanning ∼36 GHz from
275–317 GHz and representing an order of magnitude increase in sensitivity over previous single-dish surveys. We
detect 14 molecular species (including isotopologues), with 5 species (C34 S, 13 CS, H2 CS, DNC, and C2 D) detected forthe first time in protoplanetary disks. Significant differences are observed in the molecular inventories of MWC 480
and LkCa 15, and we discuss how these results may be interpreted in light of the different physical conditions of thesetwo disk systems.
Accepted by ApJ
http://arxiv.org/pdf/2006.16187

21

33. Dual-Wavelength ALMA Observations of Dust Rings in Protoplanetary Disks
Feng Long1,2 , Paola Pinilla3 , Gregory J. Herczeg2 , Sean M. Andrews1 , Daniel Harsono4,5 et al.
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 2 Kavli Institutefor Astronomy and Astrophysics, Peking University, Beijing 100871, China; 3 Max-Planck-Institut für Astronomie,
Königstuhl 17, 69117, Heidelberg, Germany; 4 Leiden Observatory, Leiden University, P.O. box 9513, 2300 RA Leiden,
The Netherlands; 5 Institute of Astronomy and Astrophysics, Academia Sinica, No. 1, Sec. 4 Roosevelt Rd., Taipei
10617, Taiwan, Republic of China
1E-mail contact: feng.long at cfa.harvard.edu
We present new Atacama Large Millimeter/submillimeter Array (ALMA) observations for three protoplanetary disks
in Taurus at 2.9 mm and comparisons with previous 1.3 mm data both at an angular resolution of ∼0.′′ 1 (15 au forthe distance of Taurus). In the single-ring disk DS Tau, double-ring disk GO Tau, and multiple-ring disk DL Tau,
the same rings are detected at both wavelengths, with radial locations spanning from 50 to 120 au. To quantify thedust emission morphology, the observed visibilities are modeled with a parametric prescription for the radial intensity
profile. The disk outer radii, taken as 95% of the total flux encircled in the model intensity profiles, are consistent at
both wavelengths for the three disks. Dust evolution models show that dust trapping in local pressure maxima in theouter disk could explain the observed patterns. Dust rings are mostly unresolved. The marginally resolved ring in DS
Tau shows a tentatively narrower ring at the longer wavelength, an observational feature expected from efficient dust
trapping. The spectral index (αmm ) increases outward and exhibits local minima that correspond to the peaks of dust
rings, indicative of the changes in grain properties across the disks. The low optical depths (τ ∼ 0.1–0.2 at 2.9 mm
and 0.2–0.4 at 1.3 mm) in the dust rings suggest that grains in the rings may have grown to millimeter sizes. The
ubiquitous dust rings in protoplanetary disks modify the overall dynamics and evolution of dust grains, likely paving
the way towards the new generation of planet formation.
Accepted by ApJ
http://arxiv.org/pdf/2006.03120

34. Ongoing flyby in the young multiple system UX Tauri
F. Ménard1 , N. Cuello1,2,3, C. Ginski4,5 , G. van der Plas1 , M. Villenave1,6 et al.
Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 2 Instituto de Astrofísica, Pontificia Universidad
Católica de Chile, Santiago, Chile; 3 Univ Lyon, Univ Claude Bernard Lyon1, Ens de Lyon, CNRS, Centre de Recherche
Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, France; 4 Sterrenkundig Instituut Anton Pannekoek,
Science Park 904, 1098 XH Amsterdam, The Netherlands; 5 Leiden Observatory, Leiden University, PO Box 9513, 2300
RA Lei- den, The Netherlands; 6 European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura,Santiago, Chile
1

E-mail contact: francois.menard at univ-grenoble-alpes.fr
We present observations of the young multiple system UX Tauri to look for circumstellar disks and for signs ofdynamical interactions. We obtained SPHERE/IRDIS deep differential polarization images in the J and H bands.
We also used ALMA archival CO data. Large extended spirals are well detected in scattered light coming out ofthe disk of UX Tau A. The southern spiral forms a bridge between UX Tau A and C. These spirals, including thebridge connecting the two stars, all have a CO (3–2) counterpart seen by ALMA. The disk of UX Tau C is detectedin scattered light. It is much smaller than the disk of UX Tau A and has a major axis along a different position
angle, suggesting a misalignment. We performed PHANTOM SPH hydrodynamical models to interpret the data. The
scattered light spirals, CO emission spirals and velocity patterns of the rotating disks, and the compactness of thedisk of UX Tau C all point to a scenario in which UX Tau A has been perturbed very recently (about 1000 years) by
the close passage of UX Tau C.
Accepted by A&A Letters
http://arxiv.org/pdf/2006.02439

2235. Substructure Formation in a Protostellar Disk of L1527 IRS
Riouhei Nakatani1 , Hauyu Baobab Liu2 , Satoshi Ohashi1 , Yichen Zhang1 , Tomoyuki Hanawa3 et al.
RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan; 2 Academia Sinica
Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan; 3 Center for Frontier Science, Chiba
University, 1-33 Yayoi-cho, Inage-ku, Chiba, Chiba 263-8522, Japan1

E-mail contact: ryohei.nakatani at riken.jp
We analyze multi-frequency, high-resolution continuum data obtained by ALMA and JVLA to study detailed structureof the dust distribution in the infant disk of a Class 0/I source, L1527 IRS. We find three clumps aligning in thenorth-south direction in the 7 mm radio continuum image. The three clumps remain even after subtracting free-freecontamination, which is estimated from the 1.3 cm continuum observations. The northern and southern clumps arelocated at a distance of ∼15 au from the central clump and are likely optically thick at 7 mm wavelength. The clumps
have similar integrated intensities. The symmetric physical properties could be realized when a dust ring or spiralarms around the central protostar is projected to the plane of the sky. We demonstrates for the first time that such
substructure may form even in the disk-forming stage, where the surrounding materials actively accrete toward a
disk-protostar system.
Accepted by ApJ
http://arxiv.org/pdf/2004.14122

36. A planet within the debris disk around the pre-main-sequence star AU Microscopii
Peter Plavchan1 , Thomas Barclay2,5 , Jonathan Gagné3 , Peter Gao4 , Bryson Cale1 et al.
Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA; 2 Center for Space Sciences
and Technology, University of Maryland Baltimore County (UMBC), Baltimore, MD, USA; 3 Institute for Research
on Exoplanets, Département de Physique, Université de Montréal, Montréal, Quebec, Canada; 4 Department of
Astronomy, University of California, Berkeley, CA, USA; 5 Exoplanets and Stellar Astrophysics Laboratory, NASA
Goddard Space Flight Center, Greenbelt, MD, USA

1E-mail contact: plavchan at gmail.com
AU Microscopii (AU Mic) is the second closest pre main sequence star, at a distance of 9.79 parsecs and with an ageof 22 million years. AU Mic possesses a relatively rare and spatially resolved edge-on debris disk extending from about
35 to 210 astronomical units from the star, and with clumps exhibiting non-Keplerian motion. Detection of newly
formed planets around such a star is challenged by the presence of spots, plage, flares and other manifestations ofmagnetic activity on the star. Here we report observations of a planet transiting AU Mic. The transiting planet, AU
Mic b, has an orbital period of 8.46 days, an orbital distance of 0.07 astronomical units, a radius of 0.4 Jupiter radii,
and a mass of less than 0.18 Jupiter masses at 3σ confidence. Our observations of a planet co-existing with a debris
disk offer the opportunity to test the predictions of current models of planet formation and evolution.
Accepted by Nature
http://arxiv.org/pdf/2006.13248

37. Variability of the Great Disk Shadow in Serpens
Klaus M. Pontoppidan1 , Joel D. Green1 , Tyler A. Pauly1 , Colette Salyk2 and Joseph DePasquale1
Space Telescope Science Institute 3700 San Martin Drive Baltimore, MD 21218, USA; 2 Vassar College 124 Raymond
Ave Poughkeepsie, NY 12604, USA
1E-mail contact: pontoppi at stsci.edu
We present multi-epoch Hubble Space Telescope imaging of the Great Disk Shadow in the Serpens star-forming region.
The near-infrared images show strong variability of the disk shadow, revealing dynamics of the inner disk on timescales of months. The Great Shadow is projected onto the Serpens reflection nebula by an unresolved protoplanetary
disk surrounding the young intermediate-mass star SVS2/CK3/EC82. Since the shadow extends out to a distance ofat least 17,000 au, corresponding to a light travel time of 0.24 years, the images may reveal detailed changes in the23

disk scale height and position angle on time scales as short as a day, corresponding to the angular resolution of theimages, and up to the 1.11 year span between two observing epochs. We present a basic retrieval of temporal changes
in the disk density structure, based on the images. We find that the inner disk changes position angle on time scalesof months, and that the change is not axisymmetric, suggesting the presence of a non-axisymmetric dynamical forcing
on ∼1 au size scales. We consider two different scenarios, one in which a quadrupolar disk warp orbits the central
star, and one in which an unequal-mass binary orbiting out of the disk plane displaces the photo-center relative tothe shadowing disk. Continued space-based monitoring of the Serpens Disk Shadow is required to distinguish between
these scenarios, and could provide unique, and detailed, insight into the dynamics of inner protoplanetary disks notavailable through other means.
Accepted by ApJ
http://arxiv.org/pdf/2006.05965

38. The circumstellar environment of EX Lup: SPHERE and SINFONI views
Elisabetta Rigliaco1 , R. Gratton1 , Á. Kóspál2,3,4 , D. Mesa1 , V. D’Orazi1 , P. Ábrahám2,4 , S. Desidera1 ,C. Ginski5,6 , R. G. van Holstein6,7, C. Dominik5 , A. Garuﬁ8 , T. Henning9 , F. Menard10 , A. Zurlo11,12,13 ,D. Maurel10 , P. Blanchard14 and L. Weber15
INAF/Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy; 2 Konkoly Observatory,
Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary; 3 MPIA,
Königstuhl 17, D-69117 Heidelberg, Germany; 4 ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter
sétány 1/A, 1117 Budapest, Hungary; 5 Anton Pannekoek Inst for Astronomy, Univ of Amsterdam, Science Park 904,
Amsterdam, The Netherlands; 6 Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands; 7 ESO,
Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago, Chile; 8 INAF/Osservatorio Astrofisico di Arcetri, Largo
Enrico Fermi 5, 50125 Firenze, Italy; 9 MPIA, Königstuhl 17, D-69117 Heidelberg, Germany; 10 Univ. Grenoble Alpes,
IPAG, F-38000 Grenoble, France; 11 Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Univ Diego Portales,
Santiago, Chile; 12 Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Univ Diego Portales, Santiago,
Chile; 13 Aix Marseille Univ., CNRS, LAM, Marseille, France; 14 Aix Marseille Univ., CNRS, CNES, LAM, Marseille,
France; 15 Geneva Observatory, Univ of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland
1

E-mail contact: elisabetta.rigliaco at inaf.it
EX Lup is a well-studied T Tauri star that represents the prototype of young eruptive stars known as EXors. They
are characterized by repetitive outbursts that are due to enhanced accretion from the circumstellar disk onto thestar. In this paper, we analyze new adaptive optics imaging and spectroscopic observations to study EX Lup and its
circumstellar environment in near-infrared in its quiescent phase. We aim to provide a comprehensive understandingof the circumstellar environment around EX Lup in quiescence, building upon the vast store of data provided by
the literature. We observed EX Lup in quiescence with the high contrast imager SPHERE/IRDIS in the dual-beampolarimetric imaging mode to resolve the circumstellar environment in near-infrared scattered light. We complemented
the data with earlier SINFONI spectroscopy, which was also taken in quiescence. We resolve, for the first time inscattered light, a compact feature around EX Lup azimuthally extending from ∼280◦ to ∼360◦ and radially extending
from ∼0.3′′ to ∼0.55′′ in the plane of the disk. We explore two different scenarios for the detected emission. The
first one accounts for the emission as coming from the brightened walls of the cavity excavated by the outflow whose
presence was suggested by ALMA observations in the J = 3 − 2 line of 12 CO. The second attributes the emission
to an inclined disk. In this latter case, we detect, for the first time, a more extended circumstellar disk in scattered
light, which shows that a region between ∼10 and ∼30 au is depleted of µm-size grains. We compare the J−, H−, andK−band spectra obtained with SINFONI in quiescence with the spectra taken during the outburst, showing that all
the emission lines result from the episodic accretion event. Based on the morphology analysis, we favor the scenariothat assumes the scattered light is coming from a circumstellar disk rather than the outflow around EX Lup. We
determine the origin of the observed feature as either coming from a continuous circumstellar disk with a cavity, fromthe illuminated wall of the outer disk, or from a shadowed disk. Moreover, we discuss the potential origins of thedepleted region of µm-size grains, exploring the possibility that a sub-stellar companion may be the source of thisfeature.
Accepted by A&A
http://arxiv.org/2006.09787

2439. Ring formation and dust dynamics in wind-driven protoplanetary discs: global simula-tions

A. Riols1 , G. Lesur1 and F. Menard1
Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), F-38000, Grenoble,
France1E-mail contact: antoine.riols at univ-grenoble-alpes.fr
Large-scale vertical magnetic fields are believed to play a key role in the evolution of protoplanetary discs. Associatedwith non-ideal effects, such as ambipolar diffusion, they are known to launch a wind that could drive accretion in
the outer part of the disc (R > 1 AU). They also potentially lead to self-organisation of the disc into large-scale
axisymmetric structures, similar to the rings recently imaged by sub-millimetre or near-infrared instruments (ALMAand SPHERE). The aim of this paper is to investigate the mechanism behind the formation of these gaseous rings,
but also to understand the dust dynamics and its emission in discs threaded by a large-scale magnetic field. To
this end, we performed global magneto-hydrodynamics (MHD) axisymmetric simulations with ambipolar diffusion
using a modified version of the PLUTO code. We explored different magnetisations with the midplane β parameter
ranging from 105 to 103 and included dust grains – treated in the fluid approximation – ranging from 100 µm to 1
cm in size. We first show that the gaseous rings (associated with zonal flows) are tightly linked to the existence of
MHD winds. Secondly, we find that millimetre-size dust is highly sedimented, with a typical scale height of 1 AU at
R = 100 AU for β = 104 , compatible with recent ALMA observations. We also show that these grains concentrate
into pressure maxima associated with zonal flows, leading to the formation of dusty rings. Using the radiative transfer
code MCFOST, we computed the dust emission and make predictions on the ring-gap contrast and the spectral index
that one might observe with interferometers like ALMA.
Accepted by A&A
http://arxiv.org/pdf/2006.01194

40. Characterizing the radio continuum nature of sources in the massive star-forming region

W75N (B)A. Rodríguez-Kamenetzky1 , C. Carrasco-González2 , J. M. Torrelles3 , W. H. T. Vlemmings5, L. F.
Rodríguez2 , G. Surcis6 , J. F. Gómez7 , J. Cantó8 , C. Goddi9,10 , J. S. Kim11 , S. -W. Kim11 , N. AñezLópez3,4 , S. Curiel8 and H. J. van Langevelde12,13
1 Instituto de Astronomia Teorica y Experimental, (IATE-UNC), X5000BGR Cordoba, Argentina; 2 Instituto deRadioastronomia y Astrofisica (IRyA-UNAM), 58089 Morelia, Mexico; 3 Institut de Ciencies de l’Espai (ICE, CSIC),Can Magrans s/n, E-08193, Cerdanyola del Valles, Spain; 4 Institut d’Estudis Espacials de Catalunya (IEEC), E08034, Barcelona, Spain; 5 Department of Earth and Space Sciences, Chalmers University of Technology, SE-43992
Onsala, Sweden; 6 INAF-Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy; 7
Instituto de Astrofisica de Andalucia, CSIC, Glorieta de la Astronomia s/n, E-18008 Granada, Spain; 8 Institutode Astronomia, Universidad Nacional Autonoma de Mexico (UNAM), Apartado Postal 70-264, DF 04510 Mexico; 9
ALLEGRO/Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands; 10 Departmentof Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands; 11
Korea Astronomy and Space Science Institute, 776 Daedeokdaero, Yuseong, Daejeon 305-348, Republic of Korea; 12
Joint Institute for VLBI ERIC (JIVE), Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands; 13 Leiden
Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands
1E-mail contact: adriana.rodriguez at unc.edu.ar
The massive star-forming region W75N (B) is thought to host a cluster of massive protostars (VLA 1, VLA 2, andVLA 3) undergoing different evolutionary stages. In this work, we present radio continuum data with the highest
sensitivity and angular resolution obtained to date in this region, using the VLA-A and covering a wide range of
frequencies (4-48 GHz), which allowed us to study the morphology and the nature of the emission of the different
radio continuum sources. We also performed complementary studies with multi-epoch VLA data and ALMA archive
data at 1.3 mm wavelength. We find that VLA 1 is driving a thermal radio jet at scales of ≈0.1 arcsec (≈130 au), butalso shows signs of an incipient hyper-compact HII region at scales of <∼ 1 arcsec (<∼ 1300 au). VLA 3 is also drivinga thermal radio jet at scales of a few tenths of arcsec (few hundred of au). We conclude that this jet is shock-exciting25

the radio continuum sources Bc and VLA 4 (obscured HH objects), which show proper motions moving outward from
VLA 3 at velocities of ≈112–118 km/s. We have also detected three new weak radio continuum sources, two of themassociated with millimeter continuum cores observed with ALMA, suggesting that these two sources are also embedded
YSOs in this massive star-forming region.
Accepted by MNRAS
https://arxiv.org/pdf/2006.08566v1

41. The Role of Outflows, Radiation Pressure, and Magnetic Fields in Massive Star Forma-tion

Anna L. Rosen1 and Mark R. Krumholz2,3Center for Astrophysics | Harvard & Smithsonian, 60 Garden St, Cambridge, MA 02138, USA; 2 Research Schoolof Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 Australia; 3 ARC Centre of
Excellence for Astronomy in Three Dimensions (ASTRO-3D), Canberra, ACT 2611 Australia

1E-mail contact: anna.rosen at cfa.harvard.edu
Stellar feedback in the form of radiation pressure and magnetically-driven collimated outflows may limit the maximum
mass that a star can achieve and affect the star-formation efficiency of massive pre-stellar cores. Here we present a
series of 3D adaptive mesh refinement radiation-magnetohydrodynamic simulations of the collapse of initially turbulent,
massive pre-stellar cores. Our simulations include radiative feedback from both the direct stellar and dust-reprocessedradiation fields, and collimated outflow feedback from the accreting stars. We find that protostellar outflows punches
holes in the dusty circumstellar gas along the star’s polar directions, thereby increasing the size of optically thinregions through which radiation can escape. Precession of the outflows as the star’s spin axis changes due to theturbulent accretion flow further broadens the outflow, and causes more material to be entrained. Additionally, thepresence of magnetic fields in the entrained material leads to broader entrained outflows that escape the core. We
compare the injected and entrained outflow properties and find that the entrained outflow mass is a factor of ∼3larger than the injected mass and the momentum and energy contained in the entrained material are ∼25% and ∼5%of the injected momentum and energy, respectively. As a result, we find that, when one includes both outflows andradiation pressure, the former are a much more effective and important feedback mechanism, even for massive stars
with significant radiative outputs.
Accepted by ApJ
http://arxiv.org/pdf/2006.04829

42.

Planet Migration in Self-Gravitating Discs: Survival of Planets
Sahl Rowther1,2 and Farzana Meru1,2
1

Centre for Exoplanets and Habitability, University of Warwick, Coventry CV4 7AL, UK; 2 Department of Physics,
University of Warwick, Coventry CV4 7AL, UK
E-mail contact: sahl.rowther at warwick.ac.uk
We carry out three-dimensional SPH simulations to study whether planets can survive in self-gravitating protoplanetary
discs. The discs modelled here use a cooling prescription that mimics a real disc which is only gravitationally unstablein the outer regions. We do this by modelling the cooling using a simplified method such that the cooling time inthe outer parts of the disc is shorter than in the inner regions, as expected in real discs. We find that both giant(> MSat ) and low mass (< MNep ) planets initially migrate inwards very rapidly, but are able to slow down in the inner
gravitationally stable regions of the disc without needing to open up a gap. This is in contrast to previous studies
where the cooling was modelled in a more simplified manner where regardless of mass, the planets were unable toslow down their inward migration. This shows the important effect the thermodynamics has on planet migration. In
a broader context, these results show that planets that form in the early stages of the discs’ evolution, when they arestill quite massive and self-gravitating, can survive.
Accepted by MNRAS
https://arxiv.org/pdf/2006.03077
2643. A census of young stellar population associated with the Herbig Be star HD 200775
Piyali Saha1,2 , Maheswar Gopinathan1 , Umanath Kamath1 , Chang Won Lee3,4 , Manoj Puravankara5 ,Blesson Mathew6 and Ekta Sharma1
Indian Institute of Astrophysics (IIA), Sarjapur Road, Koramangala, Bangalore 560034, Karnataka, India; 2 Pt. Ravishankar Shukla University, Amanaka G.E. Road, Raipur 492010, Chhatisgarh, India; 3 Korea Astronomy and Space
Science Institute (KASI), 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, South Chungcheong, Republic of Korea;
4
University of Science and Technology, Korea, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, South Chungcheong,Republic of Korea.; 5 Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, Maharashtra,
India; 6 Department of Physics and Electronics, CHRIST, Bangalore 560029, Karnataka, India
1

E-mail contact: s.piyali16 at gmail.com
The region surrounding the well-known reflection nebula, NGC 7023, illuminated by a Herbig Be star, HD 200775,
located in the dark cloud L1174 is studied in this work. Based on the distances and proper motion values from Gaia
DR2 of 20 previously known young stellar object (YSO) candidates, we obtained a distance of 335 ± 11 pc to thecloud complex L1172/1174. Using polarization measurements of the stars projected on the cloud complex, we show
additional evidence for the cloud to be at ∼ 335 pc distance. Using this distance and proper motion values of the YSO
candidates, we searched for additional comoving sources in the vicinity of HD 200775 and found 20 new sources, whichshow low infrared excess emission and are of age ∼ 1 Myr. Among these, 10 YSO candidates and 4 newly identified
comoving sources are found to show X-ray emission. Three of the four new sources for which we have obtained optical
spectra show H α in emission. About 80 per cent of the total sources are found within ∼ 1 pc distance from HD
200775. Spatial correlation of some of the YSO candidates with the Herschel dust column density peaks suggests thatstar formation is still active in the region and may have been triggered by HD 200775.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/2005.00519

44. Twin Jets and Close Binary Formation
Yu Saiki1 and Masahiro N. Machida11Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan

E-mail contact: saiki.yu.868 at s.kyushu-u.ac.jp
The formation of a close binary system is investigated using a three-dimensional resistive magnetohydrodynamics
simulation. Starting from a prestellar cloud, the cloud evolution is calculated until ∼ 400 yr after protostar formation.
Fragmentation occurs in the gravitationally collapsing cloud and two fragments evolve into protostars. The protostars
orbit each other and a protobinary system appears. A wide-angle low-velocity outflow emerges from the circumbinary
streams that encloses two protostars, while each protostar episodically drives high-velocity jets. Thus, the two high−1
velocity jets are surrounded by the low-velocity circumbinary outflow. The speed of the jets exceeds >∼100 km s .
Although the jets have a collimated structure, they are swung back on the small scale and are tangled at the large
scale due to the binary orbital motion. A circumstellar disk also appears around each protostar. In the early mainaccretion phase, the binary orbit is complicated, while the binary separation is within < 30 au. For the first time,
all the characteristics of protobinary systems recently observed with large telescopes are reproduced in a numericalsimulation.
Accepted by ApJL
https://arxiv.org/pdf/2006.10243

45. Bipolar molecular outflow of the very low-mass star Par-Lup3-4
A. Santamaría-Miranda1,2,3 , I. de Gregorio-Monsalvo1 , N. Huélamo4 , A.L. Plunkett5 , ’A. Ribas1 , F.
Comerón6 , M.R. Schreiber2,3 , C. López7 , K. Muzić8 , L. Testi6,9European Southern Observatory, 3107, Alonso de Córdova, Santiago de Chile; 2 Instituto de Física y Astronomía,
Universidad de Valparaíso, Av. Gran Bretaña 1111, 5030 Casilla, Valparaíso, Chile; 3 Núcleo Milenio Formación
Planetaria - NPF, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile; 4 Centro de Astrobiología(INTA-CSIC); ESAC campus, Camino bajo del Castillo s/n, Urb. Villafranca del Castillo, 28692 Villanueva de la127

Cañada, Madrid, Spain; 5 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903,
U.S.A; 6 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 7Joint ALMA Observatory, 3107 Alonso de Córdova, Vitacura, Casilla 19001, Santiago, Chile; 8 CENTRA, Faculdadede Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal; 9 INAF/Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
E-mail contact: asantama at eso.org
Very low-mass stars are known to have jets and outflows, which is indicative of a scaled-down version of low-massstar formation. However, only very few outflows in very low-mass sources are well characterized. We characterize thebipolar molecular outflow of the very low-mass star Par-Lup3-4, a 0.12 M⊙ object known to power an optical jet. We
observed Par-Lup3-4 with ALMA in Bands 6 and 7, detecting both the continuum and CO molecular gas. In particular,
we studied three main emission lines: CO(2-1), CO(3-2), and 13 CO(3-2). Our observations reveal for the first time thebase of a bipolar molecular outflow in a very low-mass star, as well as a stream of material moving perpendicular tothe primary outflow of this source. The primary outflow morphology is consistent with the previously determined jet
orientation and disk inclination. The outflow mass is 9.5×10−7M⊙ , with an outflow rate of 4.3×10−9M⊙ /yr. A new
fitting to the spectral energy distribution suggests that Par-Lup3-4 may be a binary system. We have characterized
Par-Lup3-4 in detail, and its properties are consistent with those reported in other very low-mass sources. This source
provides further evidence that very low-mass sources form as a scaled-down version of low-mass stars.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2006.03063

46. Orbital Motion, Variability, and Masses in the T Tauri Triple System
G. H. Schaefer1 , Tracy L. Beck2 , L. Prato3 and M. Simon4
The CHARA Array of Georgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023, USA; 2
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 3 Lowell Observatory, 1400
West Mars Hill Road, Flagstaff, AZ 86001, USA; 4 Department of Physics and Astronomy, Stony Brook University,
Stony Brook, NY 11794, USA

1E-mail contact: schaefer at chara-array.org
We present results from adaptive optics imaging of the T Tauri triple system obtained at the Keck and Gemini
Observatories in 2015−2019. We fit the orbital motion of T Tau Sb relative to Sa and model the astrometric motionof their center of mass relative to T Tau N. Using the distance measured by Gaia, we derived dynamical masses of
MSa = 2.05 ± 0.14 M⊙ and MSb = 0.43 ± 0.06 M⊙ . The precision in the masses is expected to improve with continued
observations that map the motion through a complete orbital period; this is particularly important as the systemapproaches periastron passage in 2023. Based on published properties and recent evolutionary tracks, we estimate
a mass of ∼ 2 M⊙ for T Tau N, suggesting that T Tau N is similar in mass to T Tau Sa. Narrow-band infrared
photometry shows that T Tau N remained relatively constant between late 2017 and early 2019 with an average valueof K = 5.54 ± 0.07 mag. Using T Tau N to calibrate relative flux measurements since 2015, we found that T Tau
Sa varied dramatically between 7.0 to 8.8 mag in the K-band over timescales of a few months, while T Tau Sb faded
steadily from 8.5 to 11.1 mag in the K-band. Over the 27 year orbital period of the T Tau S binary, both components
have shown 3–4 magnitudes of variability in the K-band, relative to T Tau N.
Accepted by Astronomical Journal
https://arxiv.org/pdf/2006.03183

47. Discovery of a jet from the single HAe/Be star HD 100546
P. C. Schneider1 , C. Dougados2 , E. T. Whelan3 , J. Eisloeﬀel4, H. M. Guenther5 , N. Huelamo6 , I.
Mendigutia6 , R. D. Oudmaijer7 and Tracy L. Beck8
Hamburger Sternwarte; 2 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 3 Maynooth University
Department of Experimental Physics, National University of Ireland Maynooth, Maynooth Co. Kildare, Ireland; 4
Thueringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany; 5 Massachusetts Institute of Technology,
Kavli Institute for Astrophysics & Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; 6 Centro
128

de Astrobiologia (CSIC-INTA), Departamento de Astrofisica, ESA-ESAC Campus, PO Box 78, 28692, Villanueva dela Canada, Madrid, Spain; 7 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK; 8 Space
Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
E-mail contact: cschneider at hs.uni-hamburg.de
Young accreting stars drive outflows that collimate into jets, which can be seen hundreds of au from their driving
sources. Accretion and outflow activity cease with system age, and it is believed that magneto-centrifugally launcheddisk winds are critical agents in regulating accretion through the protoplanetary disk. Protostellar jets are well studiedin classical T Tauri stars (M⋆ <∼ 2 M⊙ ), while few nearby (d <∼ 150 pc) intermediate-mass stars (M⋆ = 2 − 10 M⊙),known as Herbig Ae/Be stars, have detected jets. We report VLT/MUSE observations of the Herbig Ae/Be star
HD 100546 and the discovery of a protostellar jet. The jet is similar in appearance to jets driven by low-mass stars
and compares well with the jet of HD 163296, the only other known optical jet from a nearby Herbig Ae/Be star. We
derive a (one-sided) mass-loss rate in the jet of log Ṁjet ∼ −9.5 (in M⊙ yr−1 ) and a ratio of outflow to accretion ofroughly 3 × 10−3 , which is lower than that of CTTS jets.
The discovery of the HD 100546 jet is particularly interesting because the protoplanetary disk around HD 100546
shows a large radial gap, spiral structure, and might host a protoplanetary system. A bar-like structure previously
seen in Hα with VLT/SPHERE shares the jet position angle, likely represents the base of the jet, and suggests a
jet-launching region within about 2 au. We conclude that the evolution of the disk at radii beyond a few au does notaffect the ability of the system to launch jets.
Accepted by A&A letters
https://arxiv.org/pdf/2006.00573

48. Rapid Elimination of Small Dust Grains in Molecular Clouds
Kedron Silsbee1, Alexei V. Ivlev1 , Olli Sipilä1 , Paola Caselli1 , and Bo Zhao1
1

Max-Planck-Institut für Extraterrestrische Physik, 85748 Garching, Germany

E-mail contact: ksilsbee at mpe.mpg.de
We argue that impact velocities between dust grains with sizes less than ∼0.1 µm in molecular cloud cores are
dominated by drift arising from ambipolar diffusion. This effect is due to the size dependence of the dust coupling
to the magnetic field and the neutral gas. Assuming perfect sticking in collisions up to ≈50 m s−1 , we show that
this effect causes rapid depletion of small grains — consistent with starlight extinction and IR/microwave emission
measurements, both in the core center (n ∼ 106 cm−3 ) and envelope (n ∼ 104 cm−3 ). The upper end of the size
distribution does not change significantly if only velocities arising from this effect are considered. We consider the
impact of an evolved dust size distribution on the gas temperature, and argue that if the depletion of small dust grains
occurs as would be expected from our model, then the cosmic ray ionization rate must be well below 10−16 s−1 at anumber density of 105 cm−3 .
Accepted by A&A
http://arxiv.org/pdf/2006.13225

49. Seeds of Life in Space (SOLIS) VIII. SiO isotopic fractionation and a new insight in theshocks of L1157-B1

S. Spezzano1 , C. Codella2,3 , L. Podio2 , C. Ceccarelli3 , P. Caselli1 et al.
1
Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany; 2 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 3 Univ. Grenoble Alpes, CNRS, Institut dePlant́ologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France

E-mail contact: spezzano at mpe.mpg.de
L1157-B1 is one of the outflow shocked regions along the blue-shifted outflow driven by the Class 0 protostar L1157mm, and is an ideal laboratory to study the material ejected from the grains in very short timescales, i.e. its chemicalcomposition is representative of the composition of the grains. We imaged 28 SiO, 29 SiO and 30 SiO J = 2–1 emission
towards L1157-B1 and B0 with the NOrthern Extended Millimeter Array (NOEMA) interferometer as part of the29

Seeds of Life in Space (SOLIS) large project. We present here a study of the isotopic fractionation of SiO towards
L1157-B1. Furthermore, we use the high spectral resolution observations on the main isotopologue, 28 SiO, to study
the jet impact on the dense gas. We present here also single-dish observations obtained with the IRAM 30m telescopeand Herschel-HIFI. We carried out a non-LTE analysis using a Large Velocity Gradient (LVG) code to model thesingle-dish observations. From our observations we can show that (i) the (2–1) transition of the main isotopologue is
optically thick in L1157-B1 even at high velocities, and (ii) the [29 SiO/30 SiO] ratio is constant across the source, andconsistent with the solar value of 1.5. We report the first isotopic fractionation maps of SiO in a shocked region andshow the absence of a mass dependent fractionation in 29 Si and 30 Si across L1157-B1. A high-velocity bullet in 28 SiO
has been identified, showing the signature of a jet impacting on the dense gas. With the dataset presented in thispaper, both interferometric and single-dish, we were able to study in great detail the gas shocked at the B1a position
and its surrounding gas.
Accepted by A&A
http://arxiv.org/pdf/2006.05772

50. Circumbinary Disks of the Protostellar Binary Systems in the L1551 Region
Shigehisa Takakuwa1,2 , Kazuya Saigo3 , Tomoaki Matsumoto4 , Masao Saito5 , Jeremy Lim6 , Hsi-Wei
Yen2 , Nagayoshi Ohashi2 , Paul T. P. Ho2,7 and Leslie W. Looney8
Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35
Korimoto, Kagoshima, Kagoshima 890-0065, Japan; 2 Academia Sinica Institute of Astronomy and Astrophysics, 11F
of Astro-Math Bldg, 1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan; 3 ALMA Project Office, National Astronomical
Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 4 Faculty of Humanity and Environment, Hosei
University, Chiyoda-ku, Tokyo 102-8160; 5 TMT-J Project Office, National Astronomical Observatory of Japan, Osawa
2-21-1, Mitaka, Tokyo 181-8588, Japan; 6 Department of Physics, University of Hong Kong, Pokfulam Road, HongKong; 7 East Asian Observatory, 660 N. A’ohoku Place, University Park, Hilo, Hawaii 96720, U.S.A.; 8 Departmentof Astronomy, University of Illinois, Urbana, IL, U.S.A.
1

E-mail contact: takakuwa at asiaa.sinica.edu.tw
We report ALMA Cycle 4 observations of the Class I binary protostellar system L1551 IRS 5 in the 0.9-mm continuum
emission, C18 O (J=3–2), OCS (J=28–27), and four other Band 7 lines. At ∼0.′′ 07 (= 10 au) resolution in the 0.9 mm
emission, two circumstellar disks (CSDs) associated with the binary protostars are separated from the circumbinary
disk (CBD). The CBD is resolved into two spiral arms, one connecting to the CSD around the northern binary source,
Source N, and the other to Source S. As compared to the CBD in the neighboring protobinary system L1551 NE, the
CBD in L1551 IRS 5 is more compact (r ∼150 au) and the m=1 mode of the spirals found in L1551 NE is less obvious
in L1551 IRS 5. Furthermore, the dust and molecular-line brightness temperatures of CSDs and CBD reach >260 K
and >100 K, respectively, in L1551 IRS 5, much hotter than those in L1551 NE. The gas motions in the spiral arms arecharacterized by rotation and expansion. Furthermore, the transitions from the CBD to the CSD rotations at aroundthe L2 and L3 Lagrangian points and gas motions around the L1 point are identified. Our numerical simulations
reproduce the observed two spiral arms and expanding gas motion as a result of gravitational torques from the binary,transitions from the CBD to the CSD rotations, and the gas motion around the L1 point. The higher temperature in
L1551 IRS 5 likely reflects the inferred FU-Ori event.
Accepted by ApJ
http://arxiv.org/pdf/2006.05723

51. An infrared study of the high-mass, multi-stage star-forming region IRAS 12272-6240
Mauricio Tapia1 , Paolo Persi2 , Miguel Roth3 and Davide Elia2
Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada, B.C., CP 22830, Mexico; 2 INAFIstituto Astrofisica e Planetologia Spaziale, Via Fosso del Cavaliere 100, 00133 Roma, Italy; 3 Las Campanas Observatory, Carnegie Institution of Washington, La Serena, Chile
1

E-mail contact: mt at astro.unam.mx
IRAS 12272-6240 is a complex star forming region with a compact massive dense clump and several associated masers,
30

located at a well-determined distance of d = 9.3 kpc from the Sun. For this study, we obtained sub-arcsec broadand narrow-band near-IR imaging and low-resolution spectroscopy with the Baade/Magellan telescope and its camera
PANIC. Mosaics of siw0se

52.

53.

Early evolution of disk, outflow, and magnetic field of young stellar objects: Impact of
dust model
Y. Tsukamoto1 , M.N. Machida2 H. Susa3 , H. Nomura4 , and S. Inutsuka5
Graduate Schools of Science and Engineering, Kagoshima University, Kagoshima, Japan; 2 Department of Earthand Planetary Sciences, Kyushu University, Fukuoka, Japan; 3 Department of Physics, Konan University, Okamoto,
Kobe, Japan; 4 Division of Science, National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan 5Departmentof Physics, Nagoya University, Aichi, Japan1

E-mail contact: tsukamoto.yusuke at sci.kagoshima-u.ac.jp
The formation and early evolution of low mass young stellar objects (YSOs) are investigated using three-dimensional
non-ideal magneto-hydrodynamics simulations. We investigate the evolution of YSOs up to ∼104 yr after protostar
formation, at which protostellar mass reaches ∼0.1 M⊙ . We particularly focus on the impact of the dust model on
the evolution. We found that a circumstellar disk is formed in all simulations regardless of the dust model. Disk size
is approximately 10 AU at the protostar formation epoch, and it increases to several tens of AU at ∼104 yr after
protostar formation. Disk mass is comparable to central protostellar mass and gravitational instability develops. In
the simulations with small dust size, the warp of the pseudodisk develops ∼104 yr after protostar formation. The warp
strengthens magnetic braking in the disk and decreases disk size. Ion-neutral drift can occur in the infalling envelope>
under the conditions that the typical dust size is a >∼ 0.2 µm and the protostar (plus disk) mass is M ∼ 0.1 M⊙ . The
outflow activity is anti-correlated to the dust size and the strong outflow appears with small dust grains.
Accepted by ApJ
http://arxiv.org/pdf/2006.16458

54. Dust masses of young disks: constraining the initial solid reservoir for planet formationŁukasz Tychoniec1 , Carlo F. Manara2 , Giovanni P. Rosotti1, Ewine F. van Dishoeck1,3 , Alexander J.
Cridland1 , Tien-Hao Hsieh4 , Nadia M. Murillo5 , Dominique Segura-Cox6 , Sierk E. van Terwisga6 andJohn J. Tobin7
Leiden Observatory, Leiden University, Leiden, The Netherlands; 2 European Southern Observatory, Garching
bei München, Germany; 3 Max-Planck-Institut für Extraterrestrische Physik, Garching bei München, Germany; 4Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan; 5 The Institute of Physical and Chemical Research(RIKEN), Hirosawa, Wako-shi, Saitama, Japan; 6 Max Planck Institute for Astronomy, Heidelberg, Germany; 7
National Radio Astronomy Observatory, Charlottesville, VA, US

1E-mail contact: tychoniec at strw.leidenuniv.nl
In recent years evidence has been building that planet formation starts early, in the first ∼ 0.5 Myr. Studying thedust masses available in young disks enables understanding the origin of planetary systems since mature disks arelacking the solid material necessary to reproduce the observed exoplanetary systems, especially the massive ones. We
aim to determine if disks in the embedded stage of star formation contain enough dust to explain the solid content of
the most massive exoplanets. We use Atacama Large Millimeter/submillimeter Array (ALMA) Band 6 observationsof embedded disks in the Perseus star-forming region together with Very Large Array (VLA) Ka-band (9 mm) data
to provide a robust estimate of dust disk masses from the flux densities. Using the DIANA opacity model including
large grains, with a dust opacity value of κ9 mm = 0.28 cm2 g−1 , the median dust masses of the embedded disks in
Perseus are 158 M⊕

55.

Accretion bursts in low-metallicity protostellar disks
Eduard I. Vorobyov1,2,3 , Vardan G. Elbakyan3 , Kazuyuki Omukai4 , Takashi Hosokawa5 , Ryoki Matsukoba4 ,and Manuel Guedel1
University of Vienna, Department of Astrophysics, Türkenschanzstr. 17, Vienna, 1180, Austria; 2 Ural Federal
University, 51 Lenin Str., 620051 Ekaterinburg, Russia; 3 Research Institute of Physics, Southern Federal University,
Rostov-on-Don, 344090 Russia; 4 Astronomical Institute, Graduate School of Science, Tohoku University, Aoba, Sendai,
Miyagi 980-8578, Japan; 5 Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan1

E-mail contact: eduard.vorobiev at univie.ac.at
The early evolution of protostellar disks with metallicities in the Z = 1.0–0.01 Z⊙ range was studied with a particular emphasis on the strength of gravitational instability and the nature of protostellar accretion in low-metallicity
systems. Numerical hydrodynamics simulations in the thin-disk limit were employed that feature separate gas anddust temperatures, and disk mass-loading from the infalling parental cloud cores. Models with cloud cores of similar
initial mass and rotation pattern, but distinct metallicity were considered to distinguish the effect of metallicity fromthat of initial conditions. The early stages of disk evolution in low-metallicity models are characterized by vigorous
gravitational instability and fragmentation. Disk instability is sustained by continual mass-loading from the collapsingcore. The time period that is covered by this unstable stage is much shorter in the Z = 0.01 Z⊙ models as comparedto their higher metallicity counterparts thanks to the higher mass infall rates caused by higher gas temperatures (thatdecouple from lower dust temperatures) in the inner parts of collapsing cores. Protostellar accretion rates are highlyvariable in the low-metallicity models reflecting a highly dynamical nature of the corresponding protostellar disks. The
low-metallicity systems feature short, but energetic episodes of mass accretion caused by infall of inward-migrating
gaseous clumps that form via gravitational fragmentation of protostellar disks. These bursts seem to be more numerous and last longer in the Z = 0.1 Z⊙ models in comparison to the Z = 0.01 Z⊙ case. Variable protostellar accretion
with episodic bursts is not a particular feature of solar metallicity disks. It is also inherent to gravitationally unstabledisks with metallicities up to 100 times lower than solar.
Accepted by A&A
http://arxiv.org/pdf/2006.16598

56.

Promoted Mass Growth of Multiple, Distant Giant Planets through Pebble Accretion
and Planet-Planet Collision
John Wimarsson1, Beibei Liu1 and Masahiro Ogihara2
Department of Astronomy and Theoretical Physics, Lund Observatory, Box 43, SE–221 00, Lund, Sweden; 2 Divisionof Science, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, 181-8588 Tokyo, Japan1

E-mail contact: bbliu at astro.lu.se
We propose a pebble-driven planet formation scenario to form giant planets with high multiplicity and large orbital
distances in the early gas disk phase. We perform N-body simulations to investigate the growth and migration of
low-mass protoplanets in the disk with inner viscously heated and outer stellar irradiated regions. The key featureof this model is that the giant planet cores grow rapidly by a combination of pebble accretion and planet-planet
collisions. This consequently speeds up their gas accretion. Because of efficient growth, the planet transitions fromrapid type I migration to slow type II migration early, reducing the inward migration substantially. Multiple giant
planets can sequentially form in this way with increasing semimajor axes. Both mass growth and orbital retention
are more pronounced when a large number of protoplanets are taken into account compared to the case of single
planet growth. Eventually, a few numbers of giant planets form with orbital distances of a few to a few tens of AUs
within 1.5–3 Myr after the birth of the protoplanets. The resulting simulated planet populations could be linked tothe substructures exhibited in disk observations as well as large orbital distance exoplanets observed in radial velocity
and microlensing surveys.
Accepted by MNRAS
http://arxiv.org/pdf/2006.06451

33

57. Testing viscous disc theory using the balance between stellar accretion and external

photoevaporation of protoplanetary discs

Andrew J. Winter1,2 , Megan Ansdell3,4 , Thomas J. Haworth5 , and J.M. Diederik Kruijssen1
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120
Heidelberg, Germany; 2 School of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK; 3 Flatiron
Institute, Simons Foundation, 162 Fifth Ave, New York, NY 10010, USA; 4 NASA Headquarters, 300 E Street SW,
Washington, DC 20546, USA; 5 Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London,
Mile End Road, London, United Kingdom
1E-mail contact: andrew.winter at uni-heidelberg.de
The nature and rate of (viscous) angular momentum transport in protoplanetary discs (PPDs) has important consequences for the formation process of planetary systems. While accretion rates onto the central star yield constraints
on such transport in the inner regions of a PPD, empirical constraints on viscous spreading in the outer regions remainchallenging to obtain. Here we demonstrate a novel method to probe the angular momentum transport at the outeredge of the disc. This method applies to PPDs that have lost a significant fraction of their mass due to thermal
winds driven by UV irradiation from a neighbouring OB star. We demonstrate that this external photoevaporation
can explain the observed depletion of discs in the 3–5 Myr old σ Orionis region, and use our model to make predictions motivating future empirical investigations of disc winds. For populations of intermediate-age PPDs, in viscousmodels we show that the mass flux outwards due to angular momentum redistribution is balanced by the mass-loss
in the photoevaporative wind. A comparison between wind mass-loss and stellar accretion rates therefore offers an
independent constraint on viscous models in the outer regions of PPDs.
Accepted by MNRAS Letters
http://arxiv.org/pdf/2006.04819

58. Rotation of Two Micron All Sky Survey Clumps in Molecular Clouds
Xuefang Xu1,2 , Di Li1,2,3 , Y.Sophia Dai4 , Paul F. Goldsmith5 and Gary A. Fuller6
CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101,
China; 2 University of Chinese Academy of Sciences, Beijing 100049, China; 3 NAOC-UKZN Computational Astrophysics Centre, University of KwaZulu-Natal, Durban 4000, South Africa; 4 Chinese Academy of Sciences SouthAmerica Center for Astronomy (CASSACA), NAOC, Beijing 100101, China; 5 Jet Propulsion Laboratory, California
Institute of Technology, Pasadena, CA 91109, USA; 6 Jodrell Bank Centre for Astrophysics, Department of Physics
and Astronomy, the University of Manchester, Oxford Road, Manchester, M13 9PL, UK
1

E-mail contact: xfxu at nao.cas.cn
We have analyzed the rotational properties of 12 clumps using 13 CO (1–0) and C18 O (1–0) maps of the Five College
Radio Astronomy Observatory 13.7 m radio telescope. The clumps, located within molecular clouds, have radii (R)in the range of 0.06 – 0.27 pc. The direction of clump elongation is not correlated with the direction of the velocity
gradient. We measured the specific angular momentum (J/M) to be between 0.0022 and 0.025 pc km s−1 based on 13 CO
images, and between 0.0025 and 0.021 pc km s−1 based on C18 O images. The consistency of J/M based on different
tracers indicates the 13 CO and C18 O in dense clumps trace essentially the same material despite significantly different
opacities. We also found that J/M increases monotonically as a function of R in power–law form, J/M ∝ R1.58 ± 0.11 .
The ratio between rotation energy and gravitational energy, β, ranges from 0.0012 to 0.018. The small values of β
imply that rotation alone is not sufficient to support the clump against gravitational collapse.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/2006.04309

59.

Super-resolution Imaging of the Protoplanetary Disk HD 142527 Using Sparse Modeling
Masayuki Yamaguchi1,2 , Kazunori Akiyama2,3,4,5 , Takashi Tsukagoshi2 , Takayuki Muto6 , Akimasa Kataoka2,7et al.
1

Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo
34

113-0033, Japan; 2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3
National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA; 4 Massachusetts Instituteof Technology, Haystack Observatory, 99 Millstone Rd, Westford, MA 01886, USA; 5 Black Hole Initiative, Harvard
University, 20 Garden Street, Cambridge, MA 02138, USA; 6 Division of Liberal Arts, Kogakuin University, 1-242 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677, Japan; 7 Department of Astronomical Science, School of PhysicalSciences, Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
E-mail contact: masayuki.yamaguchi.astro at gmail.com
With an emphasis on improving the fidelity even in super-resolution regimes, new imaging techniques have been
intensively developed over the last several years, which may provide substantial improvements to the interferometricobservation of protoplanetary disks. In this study, sparse modeling (SpM) is applied for the first time to observational
data sets taken by the Atacama Large Millimeter/submillimeter Array (ALMA). The two data sets used in this study
were taken independently using different array configurations at Band 7 (330 GHz), targeting the protoplanetary disk
around HD 142527; one in the shorter-baseline array configuration (∼430 m), and the other in the longer-baselinearray configuration (∼1570 m). The image resolutions reconstructed from the two data sets are different by a factorof ∼3. We confirm that the previously known disk structures appear on the images produced by both SpM and
CLEAN at the standard beam size. The image reconstructed from the shorter-baseline data using the SpM matches
that obtained with the longer-baseline data using CLEAN, achieving a super-resolution image from which a structure
finer than the beam size can be reproduced. Our results demonstrate that on-going intensive development in the SpM
imaging technique is beneficial to imaging with ALMA.
Accepted by ApJ
http://arxiv.org/pdf/2004.10989

60. Distances and statistics of local molecular clouds in the first Galactic quadrant
Qing-Zeng Yan1 , Ji Yang1 , Yang Su1 , Yan Sun1 and Chen Wang1
Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing
210034, People’s Republic of China
1E-mail contact: jiyang at pmo.ac.cn
We present an analysis of local molecular clouds (−6 < VLSR < 30 km s−1 , i.e., <1.5 kpc) in the first Galactic quadrant(25.◦ 8 < l < 49.◦ 7 and |b| < 5◦ ), a pilot region of the Milky Way Imaging Scroll Painting (MWISP) CO survey. Using
the SCIMES algorithm to divide large molecular clouds into moderate-sized ones, we determined distances to 28
molecular clouds with the background-eliminated extinction-parallax (BEEP) method using the Gaia DR2 parallax
measurements aided by AG and AV , and the distance ranges from 250 pc to about 1.5 kpc. These incomplete distancesamples indicate a linear relationship between the distance and the radial velocity (VLSR ) with a scatter of 0.16 kpc,
and kinematic distances may be systematically larger for local molecular clouds. In order to investigate fundamental
properties of molecular clouds, such as the total sample number, the linewidth, the brightness temperature, thephysical area, and the mass, we decompose the spectral cube using the DBSCAN algorithm. Post selection criteria areimposed on DBSCAN clusters to remove the noise contamination, and we found that the separation of molecular cloud
individuals is reliable based on a definition of independent consecutive structures in l-b-V space. The completenessof the local molecular cloud flux collected by the MWISP CO survey is about 80%. The physical area, A, shows apower-law distribution, dN/dA ∝ A−2.20±0.18 , while the molecular cloud mass also follows a power-law distribution
but slightly flatter, dN/dM ∝ M −1.96±0.11 .
Accepted by ApJ
http://arxiv.org/pdf/2006.13654

61. Resolution-dependent Subsonic Non-thermal Line Dispersion Revealed by ALMA
Nannan Yue1 , Di Li1 , Qizhou Zhang2 , Lei Zhu1 , Jonathan Henshaw3 , Diego Mardones4 and Zhiyuan
Ren1
National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012; 2 Harvard-Smithsonian Center
for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 3 Max-Planck-Institut für Astronomie, Königstuhl
135

17, D-69117 Heidelberg, Germany; 4 Departameto de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
E-mail contact: nnyue at nao.cas.cn
We report here Atacama Large Millimeter/submillimeter Array (ALMA) N2 H+ (1-0) images of the Orion Molecular
Cloud 2 and 3 (OMC-2/3) with high angular resolution (3” or 1200 au) and high spatial dynamic range. Combining
dataset from the ALMA main array, ALMA Compact Array (ACA), the Nobeyama 45m Telescope, and the JVLA
(providing temperature measurement on matching scales), we find that most of the dense gas in OMC-2/3 is subsonic(σNT /cs = 0.62) with a mean line width (∆υ) of 0.39 km s−1 FWHM. This is markedly different from the majorityof previous observations of massive star-forming regions. In contrast, line widths from the Nobeyama Telescope aretransonic at 0.69 km s−1 (σNT /cs = 1.08). We demonstrated that the larger line widths obtained by the single-dishtelescope arose from unresolved sub-structures within their respective beams. The dispersions from larger scales σls2222(as traced by the Nobeyama Telescope) can be decomposed into three components σls
= σss
+ σbm
+ σrd
, wheresmall-scale σss is the line dispersion of each ALMA beam, bulk motion σbm is dispersion between peak velocity of each
ALMA beam, and σrd is the residual dispersion. Such decomposition, though purely empirical, appears to be robust
throughout our data cubes. Apparent supersonic line widths, commonly found in massive molecular clouds, are thus
likely due to the effect of poor spatial resolution. The observed non-thermal line dispersion (sometimes referred toas ’turbulence’) transits from supersonic to subsonic at ∼ 0.05 pc scales in OMC-2/3 region. Such transition could
be commonly found with sufficient spatial (not just angular) resolution, even in regions with massive young clusters,such as Orion molecular clouds studied here.
Accepted by Research in Astronomy and Astrophysics
http://arxiv.org/pdf/2006.04168

62. Filament Intersections and Cold Dense Cores in Orion A North
Chao Zhang1 , Zhiyuan Ren1 , Jingwen Wu1 , Di Li1,2,3 , Lei Zhu7 et al.
National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Chaoyang District, Beijing
100101, China; 2 University of Chinese Academy of Sciences, Beijing 100049, China; 3 NAOC-UKZN Computational
Astrophysics Centre (NUCAC), University of KwaZulu-parental, Durban 4000, South Africa; 4 Chinese Academy of
Sciences South America Center for Astronomy

1E-mail contact: renzy at nao.cas.cn
We studied the filament structures and dense cores in OMC-2,3 region in Orion A North molecular cloud using thehigh-resolution N2 H+ (1–0) spectral cube observed with the Atacama Large Millimeter/Submillimeter Array (ALMA).
The filament network over a total length of 2 pc is found to contain 170 intersections and 128 candidate dense cores.
The dense cores are all displaced from the infrared point sources (possible young stars), and the major fraction of cores(103) are located around the intersections. Towards the intersections, there is also an increasing trend for the total
column density Ntot as well as the the power-law index of the column-density Probability Distribution Function (NPDF), suggesting that the intersections would in general have more significant gas assembly than the other part of thefilament paths. The virial analysis shows that the dense cores mostly have virial mass ratio of αvir = Mvir /Mgas < 1.0,
suggesting them to be bounded by the self gravity. In the mean time, only about 23 percent of the cores have criticalmass ratio of αcrit = Mcrit /Mgas < 1.0, suggesting them to be unstable against core collapse. Combining these results,
it shows that the major fraction of the cold starless and possible prestellar cores in OMC-2,3 are being assembled
around the intersections, and currently in a gravitationally bound state. But more extensive core collapse and starformation may still require continuous core-mass growth or other perturbation.
Accepted by MNRAS
http://arxiv.org/pdf/2006.13410

63. The Ophiuchus DIsc Survey Employing ALMA (ODISEA). II. The effect of stellar

multiplicity on disc properties

Alice Zurlo1,2 , Lucas A. Cieza1 , Sebastián Pérez3 , Valentin Christiaens4 , Jonathan P. Williams5 et al.
Núcleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 2
Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441,136Santiago, Chile; 3 Universidad de Santiago de Chile, Av. Libertador Bernardo O’Higgins 3363, Estación Central,
Santiago, Chile; 4 School of Physics and Astronomy, Monash University, VIC 3800, Australia; 5 Institute for Astronomy,
University of Hawaii at Manoa, Honolulu, HI, 96822, USA
E-mail contact: alice.zurlo at mail.udp.cl
We present Adaptive Optics (AO) near infrared (NIR) observations using VLT/NACO and Keck/NIRC2 of ODISEA
targets. ODISEA is an ALMA survey of the entire population of circumstellar discs in the Ophiuchus molecular cloud.
From the whole sample of ODISEA we select all the discs that are not already observed in the NIR with AO and thatare observable with NACO or NIRC2. The NIR-ODISEA survey consists of 147 stars observed in NIR AO imaging
for the first time, as well as revisiting almost all the binary systems of Ophiuchus present in the literature (20 out of21). In total, we detect 20 new binary systems and one triple system. For each of them we calculate the projected
separation and position angle of the companion, as well as their NIR and millimeter flux ratios. From the NIR contrast
we derived the masses of the secondaries, finding that 9 of them are in the sub-stellar regime (30–50 MJup ). Discs inmultiple systems reach a maximum total dust mass of ∼50 M⊕ , while discs in single stars can reach a dust mass of
200 M⊕ . Discs with masses above 10 M⊕ are found only around binaries with projected separations larger than ∼110
au. The maximum disc size is also larger around single star than binaries. However, since most discs in Ophiuchus
are very small and low-mass, the effect of visual binaries is relatively weak in the general disc population.
Accepted by MNRAS
http://arxiv.org/pdf/2006.16259

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

37

Abstracts of recently accepted major reviews

From diffuse gas to dense molecular cloud cores
Javier Ballesteros-Paredes1 , Philippe André2 , Patrick Hennebelle3, Ralf S. Klessen4,5, Shu-ichiro Inutsuka et al.
Instituto de Radioastronomía y Astrofísica, UNAM, Campus Morelia, Antigua Carretera a Patzcuaro 8701. 58090
Morelia, Michoacan, Mexico 2 Laboratoire d’Astrophysique (AIM), CEA/DRF, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France; 3 AIM, CEA, CNRS, Université Paris-Saclay,
Université Paris Diderot, Sorbonne Paris Cité, 91191, Gif- sur-Yvette, France; 4 Universität Heidelberg, Zentrum fürAstronomie, Institut für Theoretische Astrophysik, Albert-Ueberle- Str. 2, 69120 Heidelberg, Germany; 5 Departmentof Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan1

E-mail contact: j.ballesteros at irya.unam.mx
Molecular clouds are a fundamental ingredient of galaxies: they are the channels that transform the diffuse gas intostars. The detailed process of how they do it is not completely understood. We review the current knowledge ofmolecular clouds and their substructure from scales ∼1 kpc down to the filament and core scale. We first review
the mechanisms of cloud formation from the warm diffuse interstellar medium down to the cold and dense molecular
clouds, the process of molecule formation and the role of the thermal and gravitational instabilities. We also discuss
the main physical mechanisms through which clouds gather their mass, and note that all of them may have a roleat various stages of the process. In order to understand the dynamics of clouds we then give a critical review of thewidely used virial theorem, and its relation to the measurable properties of molecular clouds. Since these properties
are the tools we have for understanding the dynamical state of clouds, we critically analyse them. We finally discuss
the ubiquitous filamentary structure of molecular clouds and its connection to prestellar cores and star formation.
Accepted by Space Science Reviews Topical collection “Star formation”
http://arxiv.org/pdf/2006.01326

Astrochemistry During the Formation of Stars
Jes K. Jørgensen1 , Arnaud Belloche2 and Robin T. Garrod3
Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark; 2 Max-Planck-Institut für Radioastronomie,Bonn, Germany; 3 Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, Virginia, USA

1E-mail contact: jeskj at nbi.ku.dk
Star-forming regions show a rich and varied chemistry, including the presence of complex organic molecules – bothin the cold gas distributed on large scales, and in the hot regions close to young stars where protoplanetary disksarise. Recent advances in observational techniques have opened new possibilities for studying this chemistry. In
particular, the Atacama Large Millimeter/submillimeter Array (ALMA) has made it possible to study astrochemistry
down to Solar System size scales, while also revealing molecules of increasing variety and complexity. In this review, we
discuss recent observations of the chemistry of star-forming environments, with a particular focus on complex organic
molecules, taking context from the laboratory experiments and chemical models that they have stimulated. The key
takeaway points are:
• The physical evolution of individual sources plays a crucial role in their inferred chemical signatures, and remains
an important area for observations and models to elucidate.
• Comparisons of the abundances measured toward different star-forming environments (high-mass versus lowmass, Galactic center versus Galactic disk) reveal a remarkable similarity, an indication that the underlying
chemistry is relatively independent of variations in their physical conditions.
38• Studies of molecular isotopologs in star-forming regions provide a link with measurements in our own Solar
System, and thus may shed light on the chemical similarities and differences expected in other planetary systems.
Accepted by Annual Reviews of Astronomy and Astrophysics
https://arxiv.org/pdf/2006.07071

The Origin of the Stellar Mass Distribution and Multiplicity
Yueh-Ning Lee1 , Stella S.R. Oﬀner2 , Patrick Hennebelle3, Philippe André3 , Hans Zinnecker et al.
Department of Earth Sciences, National Taiwan Normal University, 88, Sec. 4, Ting-Chou Road, Taipei City 11677,
Taiwan; 2 The University of Texas, Austin, TX 78712, USA; 3 Laboratoire AIM, Paris-Saclay, CEA/IRFU/DAp CNRS-Université Paris Diderot, 91191 Gif-sur- Yvette Cedex, France; 4 Universidad Autonoma de Chile, Nucleo deAstroquimica y Astrofisica, Avda Pedro de Valdivia 425, Providencia, Santiago de Chile, Chile
1

E-mail contact: ynlee at ntnu.edu.tw
In this chapter, we review some historical understanding and recent advances on the Initial Mass Function (IMF)
and the Core Mass Function (CMF), both in terms of observations and theories. We focus mostly on star formationin clustered environment since this is suggested by observations to be the dominant mode of star formation. The
statistical properties and the fragmentation behaviour of turbulent gas is discussed, and we also discuss the formationof binaries and small multiple systems.
Accepted by Space Science Reviews
http://arxiv.org/pdf/2006.05778

Setting the Stage: Planet formation and Volatile Delivery
Julia Venturini1 , Maria Paula Ronco2,3 , Octavio Miguel Guilera4,2,3International Space Science Institute. Hallerstrasse 6, 3012, Bern, Switzerland; 2 Instituto de Astrofísica. Pontificia
Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Santiago 8970117, Chile; 3 Núcleo Milenio Formación
Planetaria - NPF, Chile; 4 Instituto de Astrofísica de La Plata (CONICET-UNLP), Paseo del Bosque S/N, La Plata
1900, Argentina
1E-mail contact: julia.venturini at issibern.ch
The diversity in mass and composition of planetary atmospheres stems from the different building blocks present inprotoplanetary discs and from the different physical and chemical processes that these experience during the planetaryassembly and evolution. This review aims to summarise, in a nutshell, the key concepts and processes operating during
planet formation, with a focus on the delivery of volatiles to the inner regions of the planetary system.
Accepted by Space Science Reviews
http://arxiv.org/pdf/2006.07127

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Dissertation Abstracts

Traces of Planets imprinted in the Dust of Protoplanetary Disks
Philipp Weber

Thesis work conducted at: Niels Bohr Institute, University of Copenhagen, Denmark
Current address: The Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen Ø, Denmark
Electronic mail: philipppweber@gmail.com
Ph.D dissertation directed by: Oliver Gressel, Pablo Benítez-Llambay
Ph.D degree awarded: June 2020

When a molecular cloud collapses to form a star, not all material is accreted instantaneously. To conserve the total
angular momentum of the system, a disk of rotating gas and dust is formed around the protostar, which then, slowly
accretes onto the star. These disks represent the stage for planet formation. They are therefore product-orientedlabelled protoplanetary disks (PPDs).
A very massive planet, such as Jupiter, displaces the material along its orbit by its gravitational influence. Consequently, it forms a gap in the disk - a ring-shaped area of depleted gas and dust material. This automatically divides
the disk into an outer part and an inner part. While gas still flows from the outer region through the planetary gap
towards the central star, the behaviour of dust grains is more ambiguous. We studied the effect of this gap onto radial
dust transport by carrying out two-dimensional hydrodynamical simulations with the code FARGO3D, investigating,whether or not the solid material that is initially located in the outer parts of the disk is transported towards theinner system. We find that this mainly depends on the size of the dust grains and on the characteristics of the disk
model. Yet, in all the cases, there is a critical grain size above which the dust is halted at the outer edge of the gap,
where it starts to accumulate. Consequently, the inner system is depleted from these larger grains.
What we inferred from this allowed us to explain a long-known phenomenon in the Solar System - the absence of
calcium-aluminium-rich inclusions (CAIs) in meteorites that originate from the inner Solar System. Motivated by ournumerical results we found tiny CAIs in the meteorite NWA 5697, which is expected to have formed in the inner
system. This detection supports the idea that large CAIs have been halted by Jupiter’s presence in the outer system(where they are a common constituent of meteoritic bodies), and only small CAIs were permitted to be transported
inwards.
In a further project, we investigated the dust structure if a Neptune-sized planet is embedded in the disk. In somecases, the planet induces three concentric rings to form in and around its orbit. We show that from the mutualspacing of these rings, one can infer the planet’s migration behaviour. This can tells, whether and how a planet ischanging its distance to the star in the PPD. Additionally, we performed radiative transfer simulations and image
synthesis. This showed that the predicted effect is visible through highly resolved observations with the Atacama
Milimeter-/Submillimeter Array (ALMA).
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Meetings

Five years after HL Tau: a new era in planet formation
Virtual conference, Dec 7 - Dec 11, 2020
Six years ago, somewhere in an email thread at the Joint ALMA Observatory:
Re: Suggestions for Science Verification targets for Long Baselines
HL Tau @ 04 31 38.45 +18:13:59.0
Band 6 total flux around 1 Jy. Observations would be continuum in whatever bands are available.
Band 3 might be most interesting to compare with the VLA data.
A few months after these words were written, the ALMA antennas pointed toward HL Tau, the first protoplanetary
disk to be imaged with the ALMA long baselines. These observations marked the start of a revolution that has shaken
the foundations of our understanding of planet formation and protoplanetary disk evolution. Now, 5 years after the
publication of the iconic image of HL Tau, we aim to celebrate its anniversary with a conference that will discuss themost important advances in this new era in planet formation.
The conference will be online, and it will take place from Dec 7 to Dec 11, 2020. The conference will consist of a series
of invited talks, live discussions, contributed talks (live or pre-recorded), and virtual posters. All talks will be recorded
and made available to all the participants in order to facilitate discussions across different timezones. Registration will
be free of charge. Pre-registration is now open, and the specific format and logistical details will be confirmed in thenear future. The program will offer a broad view of the field, covering from the early stages of disks still embedded intheir parental envelope to the times when full planetary systems are formed and only a few remnants of the progenitor
disk are left. It will also explore the future of planet formation studies, as well as the impact and potential of upcoming
instrumentation and telescopes (e.g. E-ELT, JWST), with particular focus on ngVLA. With this workshop, we aim
at creating a more unified view of the exciting discoveries that have taken place in recent years. Some of the specifictopics that will be discussed are:
- Planet formation in embedded protoplanetary disks- Role and origin of disk substructures- Dust evolution and planetesimal formation- Disk polarization and magnetic fields- Planet formation in multiple systems- Chemistry in protoplanetary disks- Protoplanetary disk demographics- Disk evolution and dispersal- Gas kinematics in protoplanetary disks- Detection and characterization of young exoplanets and circumplanetary disks- Debris disks
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The list of confirmed invited speakers so far includes Nicolás Cuello, Barbara Ercolano, Meredith Hughes, Andrea
Isella, Akimasa Kataoka, Anna Miotello, Paola Pinilla, Christophe Pinte, Didier Queloz, Patrick Sheehan, and Alice
Zurlo.
More information can be found on our website: https://www.eso.org/sci/meetings/2020/hltau2020.html
LOC: Álvaro Ribas (co-chair), Antonio Hales (co-chair), Enrique Macías (co-chair), Bill Dent, Itziar de GregorioMonsalvo, John Carpenter, Julien Milli.
SOC: Álvaro Ribas (co-chair), Antonio Hales (co-chair), Enrique Macías (co-chair), John Carpenter (co-chair), Bill
Dent, Catherine Espaillat, Inga Kamp, Itziar de Gregorio-Monsalvo, Joan Najita, Julien Milli, Laura Pérez, Lucas
Cieza, Misato Fukagawa, Viviana Guzmán.

AGU Fall Meeting Session ’Accretion and differentiation of rocky planets:cilsilseng

Summary of Upcoming Meetings

Check the websites of these meetings for the latest information on how they are aﬀected by Covid-19
Astrochemical Frontiers – Quarantine Edition
15 - 19 June 2020 via Zoom
https://sites.google.com/cfa.harvard.edu/astrochemicalfrontiers
Planet Formation: From Dust Coagulation to Final Orbital Assembly
1 - 26 June 2020, Munich, Germany
http://www.munich-iapp.de/planetformation
Illuminating the Dusty Universe: A Tribute to the Work of Bruce Draine
6 - 10 July 2020, Florence, Italy
https://web.astro.princeton.edu/IlluminatingTheDustyUniverse
The Early Phase of Star Formation
12 - 17 July 2020, Ringberg, Germany - CANCELLED
http://www.mpia.de/homes/stein/EPoS/2020/2020.php
Star Formation in Diﬀerent Environments 202024 - 28 August 2020, Quy Nhon, Vietnam
http://icisequynhon.com/conferences/sfde/
IMPRS Summer School: Planet Formation in Protoplanetary Disks
31 Aug - 4 Sept 2020, Heidelberg, Germany
https://www.imprs-hd.mpg.de/Summer-School
Planetary Science: The Young Solar System
6 - 12 September 2020, Quy Nhon, Vietnam
http://www.icisequynhon.com/conferences/planetary_science/
Conditions and Impact of Star Formation - Across Times and Scales
28 September - 2 October 2020, Chile
https://astro.uni-koeln.de/symposium-star-formation-2020.html
From Clouds to Planets II: The Astrochemical Link
28 September - 2 October 2020, Berlin, Germany
https://events.mpe.mpg.de/event/12/
Five Years after HL Tau: A New Era in Planet Formation – VIRTUAL MEETING
7 - 11 December 2020, Chile
https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org
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
Summer 2021, Toulouse, France
https://coolstars21.github.io/43

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
The Physics of Star Formation: From Stellar Cores to Galactic Scales∼June - July 2022, Lyon, France
http:/staratlyon.univ-lyon1.fr/en
From Clouds to Planets II: The Astrochemical Link
3 - 7 October 2022, Berlin, Germany
https://events.mpe.mpg.de/event/12/

Short Announcements

Galaxies is a peer-reviewed open access journal of astronomy, astrophysics, and cosmology published by the Multidisciplinary Digital Publishing Institute. It runs special issues to create collections of papers on specific topics led by
Guest Editors.
The Special Issue Star Formation in the Ultraviolet
https://www.mdpi.com/journal/galaxies/special_issues/StarFormation
has come out as the Hubble Space Telescope (HST) is preparing to devote 1000 orbits to obtain a UV Legacy Libraryof Young Stars as Essential Standards (ULLYSES) with UV spectroscopy of both low mass T Tauri stars (500 orbits)
and 500 orbits for massive OB stars that provide the UV radiation in Extra-galactic star formation regions.
These are the review articles:
1. Overview: Star Formation in the Ultraviolet - Jorick S. Vink (Guest Editor)
2. The UV Perspective of Low-Mass Star Formation - Schneider, Günther & France
3. On the mass accretion rates of Herbig Ae/Be stars - Ignacio Mendigutia
4. UV Spectroscopy of massive stars - John Hillier
5. Massive Star Formation in the Ultraviolet observed with HST - Claus Leitherer
6. Applications of Stellar Population Synthesis in the Distant Universe - Elizabeth Stanway
Jorick Vink
Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DB, UK

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