THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 327 — 16 March 2020

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

List of Contents
The Star Formation Newsletter
Abstracts of Newly Accepted Papers . . . . . . . . . . . 3
Editor: Bo Reipurthreipurth@ifa.hawaii.edu

Abstracts of Newly Accepted Major Reviews . . 24

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

Summary of Upcoming Meetings . . . . . . . . . . . . . . 28

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 26

Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 29

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

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

Cover Picture
NGC 1333 is a mini-starburst of low-mass star formation generating numerous Herbig-Haro objects.
The large shocked region that dominates the image
is HH 12, and the chain of knots at the bottom of
the image is HH 7-11. The faint collimated jet atthe top is HH 333, which is the HH jet with thehighest collimation known. For identifications ofother objects, see Walawender et al. Astron. J.
129, 2308, 2005. The color figure is a composite of
Hα, [SII], and I-band images obtained at the Mayall
4m telescope.
Processing: Jon Talbot
http://www.starscapeimaging.com

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

Abstracts of recently accepted papers

Optimization in Extrasolar Planetary Systems:
1 Energy
The Transition from Peas-in-a-Pod to Runaway GrowthFred C Adams1 , Konstantin Batygin2 , Anthony M Bloch3 and Gregory Laughlin4
1

Physics Department, University of Michigan, Ann Arbor, MI 48109; 2 Division of Geological and Planetary Sciences,
California Institute of Technology, Pasadena, CA 91125; 3 Math Department, University of Michigan, Ann Arbor, MI
48109; 4 Astronomy Department, Yale University, New Haven, CT 06511
E-mail contact: fca at umich.edu

Motivated by the trends found in the observed sample of extrasolar planets, this paper determines tidal equilibrium
states for forming planetary systems — subject to conservation of angular momentum, constant total mass, and fixed
orbital spacing. In the low-mass limit, valid for superearth-class planets with masses of order mp ∼ 10M⊕ , previous
work showed that energy optimization leads to nearly equal mass planets, with circular orbits confined to a plane.
The present treatment generalizes previous results by including the self-gravity of the planetary bodies. For systems
with sufficiently large total mass mT in planets, the optimized energy state switches over from the case of nearly equalmass planets to a configuration where one planet contains most of the material. This transition occurs for a criticalmass threshold of approximately mT >∼ mC ∼ 40M⊕ (where the value depends on the semimajor axes of the planetary
orbits, the stellar mass, and other system properties). These considerations of energy optimization apply over a wide
range of mass scales, from binary stars to planetary systems to the collection of moons orbiting the giant planets inour solar system.
Accepted by Monthly Notices of the Royal Astronomical Society
http://arXiv.org/pdf/2002.10661

connection in the newly discovered young stellar stream Psc-Eri (Mein2 Lithium-rotation
gast 1)
J. Arancibia-Silva1,2 , J. Bouvier3 , A. Bayo1,2 , P.A.B. Galli4 , W. Brandner5 , H. Bouy4 and D. Barrado6
1

Instituto de Física y Astronomía, Universidad de Valparaíso, Chile; 2 Núcleo Milenio Formación Planetaria - NPF,
Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile; 3 IPAG, Univ. Grenoble Alpes, 38000 Grenoble,
France; 4 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire,
33615, Pessac, France; 5 Max Planck Institute for Astronomy, Heidelberg, Germany; 6 Depto. Astrofísica, Centro de
Astrobiología (INTA-CSIC), ESAC Campus, Camino Bajo del Castillo s/n, 28692, Villanueva de la Cañada, Spain
E-mail contact: javier.arancibia at postgrado.uv.cl
Context. As a fragile element, lithium is a sensitive probe of physical processes occurring in stellar interiors. Aims.
We aim to investigate the relationship between lithium abundance and rotation rate in low-mass members of the newly
discovered 125 Myr-old Psc-Eri stellar stream. Methods. We obtained high-resolution optical spectra and measured
the equivalent width of the 607.8 nm LiI line for 40 members of the Psc-Eri stream, whose rotational periods havebeen derived by Curtis et al. 2019. Results. We show that a tight correlation exists between lithium content androtation rate among the late-G to early-K-type stars of the Psc-Eri stream. Fast rotators are systematically Li rich,
while slow rotators are Li depleted. This trend mimics that previously reported for the similar age Pleiades cluster.
Conclusions. The lithium-rotation connection thus seems to be universal over a restricted effective temperature range
for low-mass stars at or close to the zero-age main sequence, and does not depend on environmental conditions.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2002.10556

3

Dynamics of Planetary Systems Within Star Clusters: Aspects of the Solar System’s

3 Early Evolution

Konstantin Batygin1 , Fred C. Adams2,3 , Yuri K. Batygin4 and Erik A. Petigura5
1

Division of Geological and Planetary Sciences California Institute of Technology, Pasadena, CA 91125, USA; 2 Physics
Department, University of Michigan, Ann Arbor, MI 48109, USA; 3 Astronomy Department, University of Michigan,
Ann Arbor, MI 48109, USA; 4 Los Alamos National Laboratory, Los Alamos, NM 87545, USA; 5 Department of
Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
E-mail contact: kbatygin at gps.caltech.edu
Most planetary systems — including our own — are born within stellar clusters, where interactions with neighboringstars can help shape the system architecture. This paper develops an orbit-averaged formalism to characterize thecluster’s mean-field effects as well as the physics of long-period stellar encounters. Our secular approach allows for ananalytic description of the dynamical consequences of the cluster environment on its constituent planetary systems. We
analyze special cases of the resulting Hamiltonian, corresponding to eccentricity evolution driven by planar encounters,
as well as hyperbolic perturbations upon dissipative disks. We subsequently apply our results to the early evolutionof our solar system, where the cluster’s collective potential perturbs the solar system’s plane, and stellar encounters
act to increase the velocity dispersion of the Kuiper belt. Our results are two-fold: first, we find that cluster effects◦◦
can alter the mean plane of the solar system by <∼1 , and are thus insufficient to explain the ψ ≈ 6 obliquity of thesun. Second, we delineate the extent to which stellar flybys excite the orbital dispersion of the cold classical Kuiper
belt, and show that while stellar flybys may grow the cold belt’s inclination by the observed amount, the resulting
distribution is incompatible with the data. Correspondingly, our calculations place an upper limit on the product of
4−3
the stellar number density and residence time of the sun in its birth cluster, ητ <∼ 2 × 10 Myr pc .
Accepted by AJ
http://arxiv.org/pdf/2002.05656

evolution of fractal structures in star-forming regions
4 Dynamical
Emma C. Daffern-Powell , Richard J. Parker
1

1

1

Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3
7RH, UK
E-mail contact: ecdaffern1 at sheffield.ac.uk
The Q-parameter is used extensively to quantify the spatial distributions of stars and gas in star-forming regions aswell as older clusters and associations. It quantifies the amount of structure using the ratio of the average length of aminimum spanning tree, m̄, to the average length within the complete graph, s̄. The interpretation of the Q-parameter
often relies on comparing observed values of Q, m̄ and s̄ to idealised synthetic geometries, where there is little or nomatch between the observed star-forming regions and the synthetic regions. We measure Q, m̄ and s̄ over 10 Myr
in N-body simulations which are compared to IC 348, NGC 1333, and the ONC. For each star-forming region weset up simulations that approximate their initial conditions for a combination of different virial rations and fractal
dimensions. We find that dynamical evolution of idealised fractal geometries can account for the observed Q, m̄ and s̄
values in nearby star-forming regions. In general, an initially fractal star-forming region will tend to evolve to become
more smooth and centrally concentrated. However, we show that initial conditions, as well as where the edge of theregion is defined, can cause significant differences in the path that a star-forming region takes across the m̄–s̄ plot as it
evolves. We caution that the observed Q-parameter should not be directly compared to idealised geometries. Instead,
it should be used to determine the degree to which a star-forming region is either spatially substructured or smoothand centrally concentrated.
Accepted by MNRAS

http://arxiv.org/pdf/2002.11140

Instability in Diamagnetic, Misaligned Protostellar Discs
5 Magnetorotational
Ebru Devlen , Ayse Ulubay and E. Rennan Pekünlü
1

1

2,3

1

Faculty of Science, Department of Astronomy and Space Sciences, Ege University, 35100, Bornova/Izmir, Turkey;
4

2

Faculty of Science, Department of Physics, Istanbul University, 34134, Vezneciler, Istanbul, Turkey; 3 Feza Gürsey
Center for Physics and Mathematics, Bogazici University, 34684, Cengelköy, Istanbul, Turkey
E-mail contact: ebru.devlen at ege.edu.tr
In the present study, we addressed the question of how the growth rate of the magnetorotational instability is modified
when the radial component of the stellar dipole magnetic field is taken into account in addition to the verticalcomponent. Considering a fiducial radius in the disc where diamagnetic currents are pronounced, we carried out alinear stability analysis to obtain the growth rates of the magnetorotational instability for various parameters such as
the ratio of the radial-to-vertical component and the gradient of the magnetic field, the Alfvenic Mach number and the
diamagnetization parameter. Our results show that the interaction between the diamagnetic current and the radial
component of the magnetic field increases the growth rate of the magnetorotational instability and generates a force
perpendicular to the disc plane which may induce a torque. It is also shown that considering the radial component of
the magnetic field and taking into account a radial gradient in the vertical component of the magnetic field causes anincrease in the magnitudes of the growth rates of both the axisymmetric (m = 0) and the non-axisymmetric (m = 1)
modes.
Accepted by MNRAS
http://arxiv.org/pdf/2002.02254

origin of s-process isotope heterogeneity in the solar protoplanetary disk
6 The
Mattias Ek , Alison C. Hunt , Maria Lugaro , Maria Schönbächler
1,2

1

3,4

1

1

Institute for Geochemistry and Petrology, ETH Zürich, Clausiusstrasse 25, 8092 Zürich, Switzerland; 2 Bristol
Isotope Group, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen’s Road, Bristol BS8
1RJ, United Kingdom; 3 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, MTA Centre for
Excellence, H-1121 Budapest, Hungary; 4 Monash Centre for Astrophysics, School of Physics and Astronomy, Monash
University, VIC 3800, Australia
E-mail contact: mattias.ek at bristol.ac.uk
Rocky asteroids and planets display nucleosynthetic isotope variations that are attributed to the heterogeneous distribution of stardust from different stellar sources in the solar protoplanetary disk. Here we report new high precision
palladium isotope data for six iron meteorite groups, which display smaller nucleosynthetic isotope variations thanthe more refractory neighbouring elements. Based on this observation we present a new model in which thermal destruction of interstellar medium dust results in an enrichment of s-process dominated stardust in regions closer to theSun. We propose that stardust is depleted in volatile elements due to incomplete condensation of these elements into
dust around asymptotic giant branch (AGB) stars. This led to the smaller nucleosynthetic variations for Pd reported
here and the lack of such variations for more volatile elements. The smaller magnitude variations measured in heavier
refractory elements suggest that material from high-metallicity AGB stars dominated stardust in the Solar System.
These stars produce less heavy s-process elements compared to the bulk Solar System composition.
Accepted by Nature Astronomy
http://arxiv.org/pdf/2002.02155

of Life in Space (SOLIS).VII. Discovery of a cold dense methanol blob toward the
7 Seeds
L1521F VeLLO system
C. Favre1 , C. Vastel2 , I. Jimenez-Serra3 , D. Quénard4 , P. Caselli5 et al.
1

Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble,
France; 2 IRAP, Université de Toulouse, CNRS, CNES, UPS, (Toulouse), France; 3 Centro de Astrobiología (CSIC,
INTA), Ctra. de Torrejon a Ajalvir km4, Torrejón de Ardoz, 28850 Madrid, Spain; 4 School of Physics and Astronomy, Queen Mary University of Lon- don, 327 Mile End Road, London, E1 4NS, UK; 5 Max-Planck-Institut für
extraterrestrische Physik (MPE), 85748 Garching, Germany
E-mail contact: cecile.favre at univ-grenoble-alpes.fr
The SOLIS (Seeds Of Life In Space) IRAM/NOEMA Large Program aims at studying a set of crucial complex organic
5molecules in a sample of sources, with well-known physical structure, covering the various phases of Solar-type starformation. One representative object of the transition from the prestellar core to the protostar phases has been

8

9

star DG Tau B. Images of the continuum emission reveals a dust disk with rings and, putatively, a leading spiral arm.
The disk, as well as the prominent outflow cavities, are detected in CO, H2 CO, CS, and CN while they remain undetected in SO2 , HDO, and CH3 OH. From the absorption of the back-side outflow, we inferred that the disk emission is
optically thick in the inner 50 au. This morphology explains why no line emission is detected from this inner region
and poses some limitations toward the calculation of the dust mass and the characterization of the inner gaseous disk.
The H2 CO and CS emission from the inner 200 au is mostly from the disk and their morphology is very similar. The
CN emission significantly differs from the other two molecules as it is observed only beyond 150 au. This ring-likemorphology is consistent with previous observations and the predictions of thermochemical disk models. Finally, weconstrained the disk-integrated column density of all molecules. In particular, we found that the CH3 OH/H2 CO ratio
must be smaller than 2, making the methanol non-detection still consistent with the only such a ratio available fromthe literature (1.27 in TW Hya).
Accepted by A&A
https://arxiv.org/pdf/2002.10195

Survey for Young Substellar Objects with the W-band filter II. The Coolest
10 AandNovel
Lowest Mass Members of the Serpens-South Star-forming Region
Jessy Jose1,5 , Beth A. Biller2,11 , Loïc Albert3 , Sophie Dubber2,11 , Katelyn Allers4 , Gregory J. Herczeg5 ,Michael C. Liu6 , Samuel Pearson2 , Bhavana Lalchand7 , Wen-Ping Chen7 , Mickaël Bonnefoy8 , Etienne
Artigau9 , Philippe Delorme8 , Po-shih Chiang7 , Zhoujian Zhang6 and Yumiko Oasa10
1

Indian Institute of Science Education and Research (IISER) Tirupati, Rami Reddy Nagar, Karakambadi Road,
Mangalam (P.O.), Tirupati 517 507, India; 2 SUPA, Institute for Astronomy, University of Edinburgh, Blackford
Hill, Edinburgh EH9 3HJ, UK; 3 Institut de recherche sur les exoplanètes, Université de Montréal, Montréal, H3C
3J7, Canada; 4 Bucknell University; Department of Physics and Astronomy; Lewisburg, PA 17837, USA; 5 Kavli
Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871, China; 6Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA; 7 Graduate
Institute of Astronomy, National Central University, 300 Jhongda Road, Zhongli, Taoyuan 32001, Taiwan; 8 Institutde Planétologie et d’Astrophysique de Grenoble, Université Grenoble Alpes, CS 40700, 38058 Grenoble Cédex 9,France; 9 Institut de recherche sur les exoplanètes, Université de Montréal, Montréal, H3C 3J7, Canada; 10 Facultyof Education / Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura, Saitama,
Saitama 338-8570, Japan; 11 Centre for Exoplanet Science, University of Edinburgh, Edinburgh, UK
E-mail contact: jessyvjose1 at gmail.com
Given its relative proximity (∼430 pc), compact size (< 20′ ), young age (∼ 0.5 Myr) and rich number of youngstellar objects, the Serpens-South star forming region is a promising site for studying young sub-stellar objects, yet
the low-mass members of this region remain largely undiscovered. In this paper we report on a deep photometricsurvey using a custom 1.45 µm filter (W -band), as well as standard J and H near-IR filters, in order to identify
candidate low-mass young brown-dwarfs in the Serpens-South region. We constructed a reddening-insensitive index(Q) by combining J, H and W -band photometry for survey objects, in order to identify candidate low-mass membersof Serpens based on the strength of the water absorption feature at 1.45 µm in the atmospheres of mid-M and later
objects. We then conducted spectroscopic follow up to confirm youth and spectral type for our candidates. This is thefirst survey to identify the very low-mass and coolest members of Serpens-South. We identify 4 low-mass candidate
Serpens members, which all display IR excess emission, indicating the likely presence of circumstellar disks aroundthem. One of the four candidate low-mass members in our list, SERP182918-020245, exhibits P aβ and Brγ emission
features, confirming its youth and ongoing magnetospheric accretion. Our new candidate members have spectral types>M4 and are the coolest and lowest mass candidate members yet identified in Serpens-South.
Accepted by ApJ
https://arxiv.org/pdf/2002.02473.pdf

constraints for 15 protoplanetary disks from HD 1-0
11 Mass
Mihkel Kama , Leon Trapman , Davide Fedele , Simon Bruderer , Michiel R. Hogerheijde , Anna
1,2

3

4

5

3,6

Miotello , Ewine F. van Dishoeck , Cathie Clarke and Edwin A. Bergin
7

3

2

7

8

1

Tartu Observatory, Observatooriumi 1, Tõravere 61602, Tartu, Estonia; 2 Institute of Astronomy, University ofCambridge, Madingley Road, Cambridge CB3 0HA, UK; 3 Leiden Observatory, Leiden University, Niels Bohrweg 2,2333 CA Leiden, The Netherlands; 4 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze,
Italy; 5 Max-Planck-institut für extraterrestrische Physic, Giessenbachstrasse, 85748 Garching bei München, Germany;
6
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1090 GE Amsterdam, The
Netherlands; 7 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany;
8
Department of Astronomy, University of Michigan, 1085 S. University Ave, Ann Arbor, MI 48109, USA
E-mail contact: mihkel.kama at ut.ee

Hydrogen deuteride (HD) rotational line emission can provide reliable protoplanetary disk gas mass measurements,
but it is difficult to observe and detections have been limited to three T Tauri disks. No new data have been available
since the Herschel Space Observatory mission ended in 2013. We set out to obtain new disk gas mass constraints byanalysing upper limits on HD 1-0 emission in Herschel /PACS archival data from the DIGIT key programme. Witha focus on the Herbig Ae/Be disks, whose stars are more luminous than T Tauris, we determine upper limits for
HD in data previosly analysed for its line detections. Their significance is studied with a grid of models run with
the DALI physical-chemical code, customised to include deuterium chemistry. Nearly all the disks are constrained to
Mgas ≤ 0.1 M⊙ , ruling out global gravitational instability. A strong constraint is obtained for the HD 163296 disk
mass, Mgas ≤ 0.067 M⊙, implying ∆g/d ≤ 100. This HD-based mass limit is towards the low end of CO-based massestimates for the disk, highlighting the large uncertainty in using only CO and suggesting that gas-phase CO depletionin HD 163296 is at most a factor of a few. The Mgas limits for HD 163296 and HD 100546, both bright disks withmassive candidate protoplanetary systems, suggest disk-to-planet mass conversion efficiencies of Mp /(Mgas +Mp )≈ 10
to 40% for present-day values. Near-future observations with SOFIA/HIRMES will be able to detect HD in thebrightest Herbig Ae/Be disks within 150pc with ≈ 10 h integration time.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1912.11883

of a gap formed by a planet with fast inward migration
12 ModelKazuhiro D. Kanagawa , Hideko Nomura , Takashi Tsukagoshi , Takayuki Muto , Ryohei Kawabe
1

2

2

3

2,4,5

1

Research Center for the Early Universe, Graduate School of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo
113-0033, Japan; 2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;
3
Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677, Japan; 4 The
Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 5 Departmentof Astronomy, The University of Tokyo, Hongo, Tokyo 113-0033, Japan
E-mail contact: kazuhiro.kanagawa at utap.phys.s.u-tokyo.ac.jp
A planet is formed within a protoplanetary disk. Recent observations have revealed substructures such as gaps andrings, which may indicate forming planets within the disk. Due to disk–planet interaction, the planet migrates within
the disk, which can affect a shape of the planet-induced gap. In this paper, we investigate effects of fast inward
migration of the planet on the gap shape, by carrying out hydrodynamic simulations. We found that when the
migration timescale is shorter than the timescale of the gap-opening, the orbital radius is shifted inward as comparedto the radial location of the gap. We also found a scaling relation between the radial shift of the locations of the planet
and the gap as a function of the ratio of the timescale of the migration and gap-opening. Our scaling relation alsoenables us to constrain the gas surface density and the viscosity when the gap and the planet are observed. Moreover,
we also found the scaling relation between the location of the secondary gap and the aspect ratio. By combining
the radial shift and the secondary gap, we may constrain the physical condition of the planet formation and how theplanet evolves in the protoplanetary disk, from the observational morphology.
Accepted by ApJ
http://arxiv.org/pdf/2002.08217

13 Distortion of Magnetic Fields in BHR 71

Ryo Kandori1 , Motohide Tamura1,2,3 , Masao Saito2 , Kohji Tomisaka2 , Tomoaki Matsumoto4 , Ryo
Tazaki5 , Tetsuya Nagata6 , Nobuhiko Kusakabe1 , Yasushi Nakajima7 , Jungmi Kwon3 , Takahiro Nagayama88and Ken’ichi Tatematsu2
1

Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatoryof Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of Astronomy, The University of Tokyo, 7-3-1,
Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 4 Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyodaku, Tokyo 102-8160, Japan; 5 Astronomical Institute, Graduate School of Science, Tohoku University, 6-3 Aramaki,
Aoba-ku, Sendai 980-8578, Japan; 6 Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;
7
Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601, Japan; 8 Kagoshima University, 1-21-35 Korimoto,Kagoshima 890-0065, Japan
E-mail contact: r.kandori at gmail.com
The magnetic field structure of a star-forming Bok globule BHR 71 was determined based on near-infrared polarimetricobservations of background stars. The magnetic field in BHR 71 was mapped from 25 stars. By using a simple 2D
parabolic function, the plane-of-sky magnetic axis of the core was found to be θmag = 125◦ ± 11◦ . The plane-of-sky
mean magnetic field strength of BHR 71 was found to be Bpos = 8.8 − 15.0 µG, indicating that the BHR 71 core ismagnetically supercritical with λ = 1.44 − 2.43. Taking into account the effect of thermal/turbulent pressure and theplane-of-sky magnetic field component, the critical mass of BHR 71 was Mcr = 14.5 − 18.7 M⊙ , which is consistent
with the observed core mass of Mcore ≈ 14.7 M⊙ (Yang et al. 2017). We conclude that BHR 71 is in a condition
close to a kinematically critical state, and the magnetic field direction lies close to the plane of sky. Since BHR 71 isa star-forming core, a significantly subcritical condition (i.e., the magnetic field direction deviating from the plane ofsky) is unlikely, and collapsed from a condition close to a kinematically critical state. There are two possible scenarios
to explain the curved magnetic fields of BHR 71, one is an hourglass-like field structure due to mass accumulationand the other is the Inoue & Fukui (2013) mechanism, which proposes the interaction of the core with a shock wave
to create curved magnetic fields wrapping around the core.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/2002.12512

and Solution of the Time-Dependent Bondi-Parker Flow
14 Stability
Eric Keto1

1

Institute for Theory and Computation, Harvard College Observatory

E-mail contact: eketo at cfa.harvard.edu
Bondi (1952) and Parker(1958) derived a steady-state solution for Bernouilli’s equation in spherical symmetry arounda point mass for two cases, respectively, an inward accretion flow and an outward wind. Left unanswered were thestability of the steady-state solution, the solution itself of time-dependent flows, whether the time-dependent flows
would evolve to the steady-state, and under what conditions a transonic flow would develop. In a Hamiltonian
description, we find that the steady state solution is equivalent to the Lagrangian implying that time-dependent flows
evolve to the steady state. We find that the second variation is definite in sign for isothermal and adiabatic flows,
implying at least linear stability. We solve the partial differential equation for the time-dependent flow as an initialvalue problem and find that a transonic flow develops under a wide range of realistic initial conditions. We present
some examples of time-dependent solutions.
Accepted by MNRAS
https://arxiv.org/pdf/2002.09004

Depletion in Prestellar Cores
15 CS
Shinyoung Kim , Chang Won Lee , Maheswar Gopihathan , Mario Tafalla , Jungjoo Sohn , Gwan1,2

1,2

3

4

5

jeong Kim6 , Mi-Ryang Kim1 , Archana Soam7 and Philip C. Myers8
1
Korea Astronomy and Space science Institute, Daejeon 34055, Republic of Korea; 2 University of Science and Technology, Korea, Daejeon 34113, Republic of Korea; 3 Indian Institute of Astrophysics, Karnataka 560034, India; 4 IGN,
Observatorio Astronómico Nacional, E-28014 Madrid, Spain; 5 Korea National University of Education, Chungbuk
28173, Republic of Korea; 6 National Astronomical Observatory of Japan, Nagano 384-1305, Japan; 7 SOFIA Science9Center, USRA, NASA Ames Research Center, CA 94035, USA; 8 Center for Astrophysics, Harvard & Smithsonian,
MA 02138, USA
E-mail contact: shinykim at kasi.re.kr
The CS molecule is known to be adsorbed onto dust in the cold and dense conditions, causing it to get significantly
depleted in the central region of cores. This study is aimed to investigate the depletion of the CS molecule using theoptically thin C34 S molecular line observations. We mapped five prestellar cores, L1544, L1552, L1689B, L694-2 andL1197 using two molecular lines, C34 S (J = 2 − 1) and N2 H+ (J = 1 − 0) with the NRO 45-m telescope, doubling
the number of cores where the CS depletion was probed using C34 S. In most of our targets, the distribution of C34 S
emission shows features that suggest that the CS molecule is generally depleted in the center of the prestellar cores.
The radial profile of the CS abundance with respect to H2 directly measured from the CS emission and the Herscheldust emission indicates that the CS molecule is depleted by a factor of ∼ 3 toward the central regions of the coreswith respect to their outer regions. The degree of the depletion is found to be even more enhanced by an order ofmagnitude when the contaminating effect introduced by the presence of CS molecules in the surrounding envelopethat lie along the line-of-sight is removed. Except for L1197 which is classified as relatively the least evolved core in
our targets based on its observed physical parameters, we found that the remaining four prestellar cores are sufferingfrom significant CS depletion at their central region regardless of the relative difference in their evolutionary status.
Accepted by ApJ
https://arxiv.org/pdf/2002.06857

structures in an embedded protostellar disk driven by envelope accretion
16 Spiral
Chin-Fei Lee , Zhi-Yun Li and Neal J. Turner
1,2

3

4

1

Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 2 Graduate Instituteof Astronomy and Astrophysics, National Taiwan University, Taipei, Taiwan; 3 Astronomy Department, University ofVirginia, Charlottesville, VA, USA; 4 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA,USA
E-mail contact: cflee at asiaa.sinica.edu.tw
Hydrodynamical simulations show that a pair of spiral arms can form in the disk around a rapidly growing young starand that the arms are crucial in transporting angular momentum as the disk accretes material from the surrounding
envelope. Here we report the detection of a pair of symmetric spiral structures in a protostellar disk, supporting theformation of spiral arms in the disk around a forming star. The HH 111 VLA 1 source is a young Class I source
embedded in a massive infalling protostellar envelope and is actively accreting, driving the prominent HH 111 jet.
Previous observations showed a ring of shock emission around the disk’s outer edge, indicating accretion of the envelopematerial onto the disk at a high rate. Now with ALMA observations of thermal emission from dust particles, we detecta pair of spiral arms extending from the inner region to the disk’s outer edge, similar to that seen in many simulations.
Additionally, the disk is massive, with a Toomre Q parameter near unity in the outer parts where the spiral structures
are detected, supporting the notion that envelope accretion is making the outer disk gravitationally unstable. In ourobservations, another source, HH 111 VLA 2, is spatially resolved for the first time, showing a disk-like structure witha diameter of ∼26 au and an orientation nearly orthogonal to that of the HH 111 VLA 1 disk.
Accepted by Nature Astronomy
https://www.nature.com/articles/s41550-019-0905-x

motions in OB-associations with Gaia DR2
17 Internal
A.M. Melnik and A.K. Dambis
11

1

Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskii pr. 13, Moscow, 119991
RussiaE-mail contact: anna at sai.msu.ru
We study the motions inside 28 OB-associations with the use of Gaia DR2 proper motions. The average velocity
dispersion calculated for 28 OB-associations including more than 20 stars with Gaia DR2 proper motion is σv = 4.5
10km s−1 . The median virial and stellar masses of OB-associations are Mvir = 8.9 × 105 and Mst = 8.1 × 103 M⊙ ,respectively. The median star-formation efficiency in parent giant molecular clouds appears to be ǫ = 1.2 per cent.
Gaia DR2 proper motions confirm the expansion in the Per OB1, Car OB1 and Sgr OB1 associations found earlier
with Gaia DR1 data. We also detect the expansion in Gem OB1, Ori OB1 and Sco OB1 associations which became
possible for the first time now when analyzed with Gaia DR2 proper motions. The analysis of the distribution of
OB-stars in the Per OB1 association shows the presence of a shell-like structure with the radius of 40 pc. Probably,
the expansion of the Per OB1 association started with the velocity greater than the present-day expansion velocity
equal to 5.0±1.7 km s−1 .
Accepted by MNRAS
http://arxiv.org/pdf/2002.05044

the turbulence driving mode of expanding HII regions
18 On
Shyam H. Menon , Christoph Federrath , Rolf Kuiper
1

1

2

1

Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia;
Institute of Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen,Germany

2E-mail contact: Shyam.Menon at anu.edu.au
We investigate the turbulence driving mode of ionizing radiation from massive stars on the surrounding interstellar
medium (ISM). We run hydrodynamical simulations of a turbulent cloud impinged by a plane-parallel ionization front.
We find that the ionizing radiation forms pillars of neutral gas reminiscent of those seen in observations. We quantify
the driving mode of the turbulence in the neutral gas by calculating the driving parameter b, which is characterised by
the relation σs2 = ln(1 + b2 M2 ) between the variance of the logarithmic density contrast σs2 (where s = ln(ρ/ρ0 ) withthe gas density ρ and its average ρ0 ), and the turbulent Mach number M. Previous works have shown that b ∼ 1/3
indicates solenoidal (divergence-free) driving and b ∼ 1 indicates compressive (curl-free) driving, with b ∼ 1 producing
up to ten times higher star formation rates than b ∼ 1/3. The time variation of b in our study allows us to infer thationizing radiation is inherently a compressive turbulence driving source, with a time-averaged b ∼ 0.76 ± 0.08. We
also investigate the value of b of the pillars, where star formation is expected to occur, and find that the pillars arecharacterised by a natural mixture of both solenoidal and compressive turbulent modes (b ∼ 0.4) when they form,
and later evolve into a more compressive turbulent state with b ∼ 0.5–0.6. A virial parameter analysis of the pillar
regions supports this conclusion. This indicates that ionizing radiation from massive stars may be able to trigger starformation by producing predominately compressive turbulent gas in the pillars.
Accepted by MNRAS
http://arxiv.org/pdf/2002.08707

Outflows at the EarliesT Stages (POETS). IV. Statistical properties of the
19 Protostellar
22 GHz H O masers
2

L. Moscadelli1, A. Sanna2,3 , C. Goddi4,5 , V. Krishnan1,6 , F. Massi1 , and F. Bacciotti11INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 INAF-Istituto di Radioastronomia& Italian ALMA Regional Centre, Via P. Gobetti 101, I-40129 Bologna, Italy; 3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 4 Leiden Observatory, Leiden University, PO Box 9513, 2300
RA Leiden, The Netherlands; 5 Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL,
Nijmegen, The Netherlands; 6 South African Radio Astronomy Observatory (SARAO), 2 Fir street, Black River Park,
Observatory, Cape Town, 7925, South Africa
E-mail contact: mosca at arcetri.astro.it
We wish to perform a statistical study of the location and motion of individual 22 GHz water maser cloudlets,characterized by sizes that are within a few au, with respect to the radio thermal emission from young stellar objects(YSO). For this purpose, we have been carrying out the Protostellar Outflows at the EarliesT Stages (POETS)
survey of a sample (38) of high-mass YSOs. The water maser positions and three-dimensional (3D) velocities were
determined through Very Long Baseline Array observations with accuracies of a few milliarcsec (mas) and a few
11km s−1 , respectively. The position of the ionized core of the protostellar wind, marking the YSO, was determinedthrough sensitive continuum Jansky Very Large Array observations with a typical error of 20 mas. The statistic of theseparation of the water masers from the radio continuum shows that 84% of the masers are found within 1000 au fromthe YSO and 45% of them are within 200 au. Therefore, we can conclude that the 22 GHz water masers are a reliable
proxy for the YSO position. The distribution of maser luminosity is strongly peaked towards low values, indicating thatabout half of the maser population is still undetected with the current Very Long Baseline Interferometry detection
thresholds of 50–100 mJy beam−1 . Next-generation, sensitive radio interferometers will exploit these weak masers for
an improved sampling of the velocity and magnetic fields around the YSOs. The average direction of the water maser
proper motions provides a statistically-significant estimate for the orientation of the jet emitted by the YSO: 55% of
the maser proper motions are directed on the sky within an angle of 30◦ from the jet axis. Finally, we show that ourmeasurements of 3D maser velocities statistically support models in which water maser emission arises from planar
shocks with propagation direction close to the plane of the sky.
Accepted by A&A
http://arxiv.org/pdf/2002.06871

20 Rocking shadows in broken circumbinary discs

Rebecca Nealon1 , Daniel J. Price2 and Christophe Pinte2

1

Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, United Kingdom; 2 School ofPhysics and Astronomy, Monash University, Clayton Vic 3800, Australia
E-mail contact: rebecca.nealon at leicester.ac.uk

We use three dimensional simulations with coupled hydrodynamics and Monte Carlo radiative transfer to show thatshadows cast by the inner disc in broken circumbinary discs move within a confined range of position angles on theouter disc. Over time, shadows appear to rock back and forth in azimuth as the inner disc precesses. The effect occurs
because the inner disc precesses around a vector that is not the angular momentum vector of the outer disc. We relate
our findings to recent observations of shadows in discs
Accepted by MNRAS Letters
http://arxiv.org/pdf/2002.02983

21

in the accretion process, either protostellar accretion is more variable or episodicity is easier to detect in high-massstar-forming regions than in nearby clouds. The timescale found between accretion events could be resulting from disk
instabilities, associated with bursts of inflowing gas arising from the dynamical environment of high-mass star-forming
cores.
Accepted by A&A
http://arxiv.org/pdf/2002.05720

22 GG Tau A: gas properties and dynamics from the cavity to the outer disk

N.T. Phuong1,2,3 , A. Dutrey1 , P. N. Diep2,3 , S. Guilloteau1 , E. Chapillon1,4 , E. Di Folco1 , Y-W. Tang5 ,V. Piétu6 , J. Bary7 , T. Beck8 , F. Hersant1 , D.T Hoai2 , J.M. Huré1 , P.T. Nhung2 , A. Pierens1 and P.
Tuan-Anh2
1

Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire,
F-33615 Pessac; 2 Department of Astrophysics, Vietnam National Space Center, Vietnam Academy of Science andTechonology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; 3 Graduate University of Science and Technology,
Vietnam Academy of Science and Techonology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam; 4 Graduate Universityof Science and Technology, Vietnam Academy of Science and Techonology, 18 Hoang Quoc Viet, Cau Giay, Hanoi,
Vietnam; 5 IRAM, 300 rue de la piscine, F-38406 Saint Martin d’Hères Cedex, France; 6 Academia Sinica Institute of
Astronomy and Astrophysics, PO Box 23-141, Taipei 106, Taiwan; 7 Department of Physics and Astronomy, Colgate
University, 13 Oak Drive, Hamilton, New York 13346, USA; 8 Space Telescope Science Institute, 3700 San Martin
Drive, Baltimore, Maryland 21218, USA
E-mail contact: thi-phuong.nguyen at u-bordeaux.fr
GG Tau A is the prototype of a young triple T Tauri star that is surrounded by a massive and extended Keplerianouter disk. The central cavity is not devoid of gas and dust and at least GG Tau Aa exhibits its own disk of gas anddust emitting at millimeter wavelengths. Its observed properties make this source an ideal laboratory for investigating
planet formation in young multiple solar-type stars. We used new ALMA 13 CO(3–2) and C18 O(3–2) observations
obtained at high angular resolution (∼ 0.2′′ ) together with previous CO(3–2) and (6–5) ALMA data and continuum
maps at 1.3 and 0.8 mm in order to determine the gas properties (temperature, density, and kinematics) in the cavity
and to a lesser extent in the outer disk.
By deprojecting, we studied the radial and azimuthal gas distribution and its kinematics. We also applied a new method
to improve the deconvolution of the CO data and in particular better quantify the emission from gas inside the cavity.
We perform local nonlocal thermodynamic equilibrium studies in order to determine the excitation conditions andrelevant physical parameters inside the ring and in the central cavity.
Residual emission after removing a smooth-disk model indicates unresolved structures at our angular resolution,
probably in the form of irregular rings or spirals. The outer disk is cold, with a temperature < 20 K beyond 250 authat drops quickly (∝ r−1 ). The kinematics of the gas inside the cavity reveals infall motions at about 10% of the
Keplerian speed. We derive the amount of gas in the cavity, and find that the brightest clumps, which contain about
10% of this mass, have kinetic temperatures 40 − 80 K, CO column densities of a few 1017 cm−2 , and H2 densities
around 107 cm−3 .
Although the gas in the cavity is only a small fraction of the disk mass, the mass accretion rate throughout the cavity
is comparable to or higher than the stellar accretion rate. It is accordingly sufficient to sustain the circumstellar disks
on a long timescale.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2001.08147

23 Planet induced spirals in the circumbinary disk of GG Tau A

N.T. Phuong1 , A. Dutrey 2 , E. Di Folco2 , S. Guilloteau2 , A. Pierens2 , J. Bary3 , Tracy L. Beck4 , E.
Chapillon2,5 , O. Denis-Alpizar6 , P.N. Diep1 , L. Majumdar7 , , V. Piétu5 , and Y-W. Tang8 ,1

Department of Astrophysics, Vietnam National Space Center, Vietnam Academy of Science and Techonology, 18
Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam

13

2

Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, F33615 Pessac, France
3
Department of Physics and Astronomy, Colgate University, 13 Oak Drive, Hamilton, New York 13346, USA
4Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA
5
IRAM, 300 rue de la piscine, F-38406 Saint Martin d’Hères Cedex, France
6
Instituto de Ciencias Químicas Aplicadas, Facultad de Ingeniería, Universidad Autónoma de Chile, Av. Pedro deValdivia 425, 7500912 Providencia, Santiago, Chile
7
School of Earth and Planetary Sciences, National Institute of Science Education and Research, HBNI, Jatni 752050,
Odisha, India
8
Academia Sinica Institute of Astronomy and Astrophysics, PO Box 23-141, Taipei 106, Taiwan
E-mail contact: ntphuong02@vnsc.org.vn
ALMA high angular resolution observations of the dust and CO emission have already revealed signatures of protoplanets embedded in protoplanetary disks. These detections are around single T Tauri stars while exo-planet surveys
reveal that planets can also form in binary (or multiple) systems, either in circumstellar or circumbinary orbits. We
searched for indirect evidence for planet formation in the multiple system GG Tau A that harbors the most massive
circumbinary disk among T Tauri stars.
We performed CO(2–1) ALMA Cycle 6 observations of GG Tau A at 0.3′′ resolution. The images confirm the “hotspot” detected at higher frequencies, but also reveal prominent spiral-like features. We model these features by using
the analytic prescription for the linear perturbation regime induced by low-mass planets.
The brightest spiral is well reproduced by a density wave excited by a protoplanet (GG Tau Ac) at the hot-spot
location (290 au), just outside the dust ring. The absence of a clear gap (in gas or dust) at the planet location implies
that its mass is significantly lower than that of Jupiter, i.e. of the order of the mass of Neptune or less. Furthermore,other prominent (trailing) spiral patterns can be represented by adding one (or more) planet(s) at larger orbital radii,
with the most obvious candidate located near the 2:1 mean-motion resonance with GG Tau Ac.
The (proto-)planet GG Tau Ac appears to externally confine the ring in a stable configuration, explaining its highmass. Our results also suggest that planets similar in mass to Neptune may form in dense circumbinary disks orbiting(wide) binary stars. In the GG Tau case, orbital resonances appear to play an important role in shaping this multiple
circumbinary planet system.
Accepted by Astronomy and Astrophysics (A&A Letters)

Along Accretion Streams in a Viscously-Evolving Protoplanetary Disk
24 Chemistry
Ellen M. Price , L. Ilsedore Cleeves , and Karin I. Öberg
1

2

1

1

Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138; 2 University of Virginia,
Department of Astronomy, 530 McCormick Rd., Charlottesville, VA 22904
E-mail contact: ellen.price at cfa.harvard.edu
The composition of a protoplanetary disk is set by a combination of interstellar inheritance and gas and grain surface
chemical reactions within the disk. The survival of inherited molecules, as well as the disk in situ chemistry depends
on the local temperature, density and irradiation environment, which can change over time due to stellar and disk
evolution, as well as transport in the disk. We address one aspect of this coupling between the physical and chemical
evolution in disks by following accretion streamlines of gas and small grains in the disk midplane, while simultaneously
taking the evolving star into account. This approach is computationally efficient and enables us to take into accountchanging physical conditions without reducing the chemical network. We find that many species are enhanced in the
inner disk midplane in the dynamic model due to inward transport of cosmic-ray driven chemical products, resulting
in, e.g., orders-of magnitude hydrocarbon enhancements at 1 au, compared to a static disk. For several other chemicalfamilies, there is no difference between the static and dynamic models, indicative of a robust chemical reset, while yetothers show differences between static and dynamic models that depend on complex interactions between physics andchemistry during the inward track. The importance of coupling dynamics and chemistry when modeling the chemical
evolution of protoplanetary disks is thus depends on what chemistry is of interest.
Accepted by ApJ
http://arxiv.org/pdf/2002.04651

14Young Runaway Star in W49 North
25 ALuisMassive
F. Rodriguez , Roberto Galvan-Madrid , Joel Sanchez-Bermudez and Christopher G. De Pree
1,2

1

3,4

5

1

Instituto de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacan, Mexico; 2 Mesoamerican Center for Theoretical Physics, Universidad Autonoma de
Chiapas, Carretera Emiliano Zapata Km.4, Real del Bosque. 29050 Tuxtla Gutierrez, Chiapas, Mexico; 3 Institutode Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70264, Ciudad de Mexico 04510, exico;
4
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 5 Department of Physics &Astronomy, Agnes Scott College, 141 East College Avenue, Decatur, GA 30030, USA
E-mail contact: l.rodriguez at irya.unam.mx
We analyzed high-angular resolution 45.5 GHz images of the W49 North massive star-forming region obtained in 1998
and 2016 with the Very Large Array. Most of the ultracompact H II regions show no detectable changes over the timeinterval of the observations. However, subcomponents B1, B2, G2a, and G2c have increased its peak flux densities byvalues in the range of 3.8 to 21.4%. Most interestingly, the cometary region C clearly shows proper motions that at
the distance of the region are equivalent to a velocity of 76±6 km s−1 in the plane of the sky. We interpret this region
as the ionized bowshock produced by a runaway O6 ZAMS star that was ejected from the eastern edge of Welch’s ring
about 6400 yr ago.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2002.02894

Motions of the Radio Source Orion MR, Formerly Known as Orion n, and New
26 Proper
Sources with Large Proper Motions in Orion BN/KL
Luis F. Rodriguez1,2, Sergio A. Dzib3 , Luis Zapata1 , Susana Lizano1 , Laurent Loinard1,4 , Karl M.
Menten3 and Laura Gomez5
1Instituto de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 3-72 (Xangari),
58089 Morelia, Michoacan, Mexico; 2 Mesoamerican Center for Theoretical Physics, Universidad Autonoma de Chiapas,
Carretera Emiliano Zapata km. 4, Real del Bosque (Teran). 29050 Tuxtla Gutierrez, Chiapas, Mexico; 3 Max-PlanckInstitut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany; 4 Instituto de Astronomia, Universidad
Nacional Autonoma de Mexico, Apartado Postal 70-264, CdMx, CP 04510, Mexico; 5 Joint ALMA Observatory,
Alonso de Cordova 3107, Vitacura, Santiago, Chile
E-mail contact: l.rodriguez at irya.unam.mx
The infrared source known as Orion n was detected in 1980 with observations made with the 3.8-m United Kingdom
Infrared Telescope. About two decades later, sensitive observations made with the Very Large Array revealed thepresence of a mJy double radio source apparently coincident in position with the infrared source n. The radio source
was assumed to be the counterpart of the infrared source. However, over the years it has been concluded that theradio source shows large proper motions to the south while the infrared source n is stationary. Here we reanalyze theproper motions of the radio source adding both older and newer VLA observations than previously used. We confirm
the proper motions of the radio source that at present no longer coincides positionally with the infrared source. The
solution to this problem is, most probably, that the infrared source n and the radio source are not the same object: theinfrared source is a stationary object in the region while the radio counterpart is moving as a result of the explosionthat took place in this region some 500 years ago and that expelled large amounts of molecular gas as well as several
compact sources. Considering the paper where it was first reported, we refer to this double radio source as Orion MR.
In addition, we use these new observations to fully confirm the large proper motions of the sources IRc23 and Zapata
11. Together with sources BN, I, Orion MR, and x, there are at least six compact sources that recede from a pointin common in Orion BN/KL. However, IRc23 is peculiar in that its ejection age appears to be only ∼300 years. The
relatively large number of sources rules out as a possible mechanism the classic three-body scenario since then only
two escaping bodies are expected: a tight binary plus the third star involved in the encounter.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2002.12513

15

study of the young massive cluster Westerlund 2 with the Hubble Space27 Time-domain
Telescope. I
E. Sabbi1 , M. Gennaro1 , J. Anderson1 , V. Bajaj1 , N. Bastian2 et al.
1

Space Telescope Science Institute, 3700 San Martin Dr Baltimore, MD 21218, USA; 2 Astrophysics Research Institute,
Liverpool John Moores University, 146 Brownlow Hill Liverpool L3 5RF, UK
E-mail contact: sabbi at stsci.edu

Time-domain studies of pre-main sequence stars have long been used to investigate star properties during their early
evolutionary phases and to trace the evolution of circumstellar environments. Historically these studies have been
confined to the nearest, low-density, star forming regions. We used the Wide Field Camera 3 on board of the Hubble
Space Telescope to extend, for the first time, the study of pre-main sequence variability to one of the few young massive
clusters in the Milky Way, Westerlund 2. Our analysis reveals that at least 1/3 of the intermediate and low-mass
pre-main sequence stars in Westerlund 2 are variable. Based on the characteristics of their light curves, we classified∼11% of the variable stars as weak-line T-Tauri candidates, ∼52% as classical T-Tauri candidates, ∼5% as dippersand ∼26% as bursters. In addition, we found that 2% of the stars below 6 M⊙ (∼6% of the variables) are eclipsingbinaries, with orbital periods shorter than 80 days. The spatial distribution of the different populations of variable
pre-main sequence stars suggests that stellar feedback and UV-radiation from massive stars play an important role on
the evolution of circumstellar and planetary disks.
Accepted by ApJ
http://arxiv.org/pdf/2002.04574

the coexistence of the streaming instability and the vertical shear instability in
28 On
protoplanetary disks
Urs Schäfer1,2 , Anders Johansen2 , and Robi Banerjee1
1

Hamburg Observatory, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany; 2 Lund Observatory,
Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden
E-mail contact: urs.schaefer at hs.uni-hamburg.de
The streaming instability is a leading candidate mechanism to explain the formation of planetesimals. Yet, therole of this instability in the driving of turbulence in protoplanetary disks, given its fundamental nature as a linearhydrodynamical instability, has so far not been investigated in detail. We study the turbulence that is induced by
the streaming instability as well as its interaction with the vertical shear instability. For this purpose, we employ the
FLASH Code to conduct two-dimensional axisymmetric global disk simulations spanning radii from 1 au to 100 au,
including the mutual drag between gas and dust as well as the radial and vertical stellar gravity. If the streaming
instability and the vertical shear instability start their growth at the same time, we find the turbulence in the dust
mid-plane layer to be primarily driven by the streaming instability. It gives rise to vertical gas motions with a Mach
number of up to ∼10−2. The dust scale height is set in a self-regulatory manner to about 1% of the gas scale height. In
contrast, if the vertical shear instability is allowed to saturate before the dust is introduced into our simulations, thenit continues to be the main source of the turbulence in the dust layer. The vertical shear instability induces turbulencewith a Mach number of ∼10−1 and thus impedes dust sedimentation. Nonetheless, we find the vertical shear instability
and the streaming instability in combination to lead to radial dust concentration in long-lived accumulations which
are significantly denser than those formed by the streaming instability alone. Thus, the vertical shear instability may
promote planetesimal formation by creating weak overdensities that act as seeds for the streaming instability.
Accepted by A&A
http://arxiv.org/pdf/2002.07185

of Complex Organic Molecules in Starless and Prestellar Cores within the
29 Prevalence
Taurus Molecular Cloud
Samantha Scibelli1 and Yancy Shirley1
1

Steward Observatory University of Arizona Tucson, AZ 85721
16

E-mail contact: sscibelli at email.arizona.edu
The detection of complex organic molecules (COMs) toward dense, collapsing prestellar cores has sparked interestin the fields of astrochemistry and astrobiology, yet the mechanisms for COM formation are still debated. It was
originally believed that COMs initially form in ices which are then irradiated by UV radiation from the surrounding
interstellar radiation field as well as forming protostars and subsequently photodesorbed into the gas-phase. However,starless and prestellar cores do not have internal protostars to heat-up and sublimate the ices. Alternative models
using chemical energy have been developed to explain the desorption of COMs, yet in order to test these models robust
measurements of COM abundances are needed toward representative samples of cores. We’ve conducted a large-sample
survey of 31 starless and prestellar cores in the Taurus Molecular Cloud, detecting methanol (CH3 OH) in 100% of thecores targeted and acetaldehyde (CH3 CHO) in 70%. At least two transition lines of each molecule were measured,
allowing us to place tight constraints on excitation temperature, column density and abundance. Additional mappingof methanol revealed extended emission, detected down to AV as low as ∼3 mag. We find complex organic molecules
are detectable in the gas-phase and are being formed early, at least hundreds of thousands of years prior to star andplanet formation. The precursor molecule, CH3 OH, may be chemically linked to the more complex CH3 CHO, however
higher spatial resolution maps are needed to further test chemical models.
Accepted by ApJ
http://arxiv.org/pdf/2002.02469

gap opening across stellar masses
30 Planet
Catriona A. Sinclair , Giovanni P. Rosotti , Attila Juhasz and Cathie J. Clarke
1

1,2

1

1

1

Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, UK; 2 Leiden Observatory, Leiden University, PO
Box 9513, NL-2300 RA Leiden, the Netherlands
E-mail contact: cas213 at cam.ac.uk

Annular structures in proto-planetary discs, such as gaps and rings, are now ubiquitously found by high-resolution
ALMA observations. Under the hypothesis that they are opened by planets, in this paper we investigate how theminimum planet mass needed to open a gap varies across different stellar host masses and distances from the star.
The dependence on the stellar host mass is particularly interesting because, at least in principle, gap opening aroundlow mass stars should be possible for lower mass planets, giving us a look into the young, low mass planet population.
Using dusty hydrodynamical simulations, we find however the opposite behaviour, as a result of the fact that discs
around low mass stars are geometrically thicker: gap opening around low mass stars can require more massive planets.
Depending on the theoretical isochrone employed to predict the relationship between stellar mass and luminosity, thegap opening planet mass could also be independent of stellar mass, but in no case we find that gap opening becomeseasier around low mass stars. This would lead to the expectation of a lower incidence of such structures in lower mass
stars, since exoplanet surveys show that low mass stars have a lower fraction of giant planets. More generally, ourstudy enables future imaging observations as a function of stellar mass to be interpreted using information on themass vs. luminosity relations of the observed samples.
Accepted by MNRAS
https://arxiv.org/pdf/2002.11036

Cloud Factory I: Generating resolved filamentary molecular clouds from galactic31 The
scale forces
Rowan J. Smith1 , Robin G. Tress2 , Mattia C. Sormani2 , Simon C.O. Glover2 , Ralf S. Klessen2, Paul
C. Clark3 , Andres F. Izquierdo1 , Ana Duarte-Cabral3 and Catherine Zucker4
1

Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, University of Manchester, Oxford
Road, Manchester M13 9PL, UK; 2 Universität Heidelberg, Zentrum für Astronomie, Institut für theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg, Germany; 3 School of Physics and Astronomy, Queens Buildings,
The Parade, Cardiff University, Cardiff CF24 3AA, UK; 4 Harvard Astronomy, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
E-mail contact: rowan.smith at manchester.ac.uk
17

We introduce a new suite of simulations, ‘The Cloud Factory’, which self-consistently forms molecular cloud complexes
at high enough resolution to resolve internal substructure (up to 0.25 Msol in mass) all while including galactic-scale
forces. We use a version of the AREPO code modified to include a detailed treatment of the physics of the cold
molecular ISM, and an analytical galactic gravitational potential for computational efficiency. The simulations havenested levels of resolution, with the lowest layer tied to tracer particles injected into individual cloud complexes. These
tracer refinement regions are embedded in the larger simulation so continue to experience forces from outside the cloud.
This allows the simulations to act as a laboratory for testing the effect of galactic environment on star formation. Here
we introduce our method and investigate the effect of galactic environment on filamentary clouds. We find that cloudcomplexes formed after a clustered burst of feedback have shorter lengths and are less likely to fragment compared
to quiescent clouds (e.g. the Musca filament) or those dominated by the galactic potential (e.g. Nessie). Spiral arms
and differential rotation preferentially align filaments, but strong feedback randomises them. Long filaments formed
within the cloud complexes are necessarily coherent with low internal velocity gradients, which has implications forthe formation of filamentary star-clusters. Cloud complexes formed in regions dominated by supernova feedback havefewer star-forming cores, and these are more widely distributed. These differences show galactic-scale forces can havea significant impact on star formation within molecular clouds.
Accepted by MNRAS
https://ui.adsabs.harvard.edu/abs/2020MNRAS.492.1594S/abstract

the vortex evolution in non-isothermal protoplanetary discs
32 On
D. Tarczay-Nehéz , Zs. Regály and E. Vorobyov
1,2

1

3,4,5

1

Konkoly Observatory, Research Centre for Astronomy and Earth Science, Konkoly-Thege Miklós 15-17, 1121, Budapest, Hungary; 2 MTA CSFK Lendület Near-Field Cosmology Research Group; 3 Department of Astrophysics,
University of Vienna, 1180, Vienna, Austria; 4 Research Institute of Physics, Southern Federal University, Stachki
Ave. 194, 344090, Rostov-on-Don, Russia; 5 Ural Federal University, 51 Lenin Str., 620051 Ekaterinburg, Russia
E-mail contact: tarczaynehez.dora at csfk.mta.hu
It is believed that large-scale horseshoe-like brightness asymmetries found in dozens of transitional protoplanetary
discs are caused by anticyclonic vortices. These vortices can play a key role in planet formation, as mm-sized dust
— the building blocks of planets — can be accumulated inside them. Anticyclonic vortices are formed by the Rossby
wave instability, which can be excited at the gap edges opened by a giant planet or at sharp viscosity transitionsof accretionally inactive regions. It is known that vortices are prone to stretching and subsequent dissolution due
to disc self-gravity for canonical disc masses in the isothermal approximation. To improve the hydrodynamic modelof protoplanetary discs, we include the disc thermodynamics in our model. In this paper, we present our results on
the evolution of the vortices formed at the outer edge of an accretionally inactive region (dead zone) assuming an
ideal equation of state and taking PdV work, disc cooling in the β-approximation, and disc self-gravity into account.
Thermodynamics affects the offset and the mode number (referring to the number of small vortices at the early phase)of the RWI excitation, as well as the strength, shape, and lifetime of the large-scale vortex formed through merging of
the initial small vortices. We found that the inclusion of gas thermodynamics results in stronger, however decreased
lifetime vortices. Our results suggest that a hypothetical vortex-aided planet formation scenario favours effectively
cooling discs.
Accepted by MNRAS
http://arxiv.org/pdf/2002.02203

Accretion onto Protoplanet Host Star PDS 70
33 VariableThanawuth Thanathibodee , Brandon Molina , Nuria Calvet , Javier Serna , Jaehan Bae et al.
1

2

1

1

3

4

Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA;
Department of Climate and Space Sciences and Engineering, University of Michigan, 2455 Hayward Street, Ann
Arbor, MI 48109, USA; 3 Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, México; 4
Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington,
DC 20015, USA218

E-mail contact: thanathi at umich.edu
The PDS 70 system has been subject to many studies in the past year following the discovery of two accreting planetsin the gap of its circumstellar disk. Nevertheless, the mass accretion rate onto the star is still not well known. Here
we determined the stellar mass accretion rate and its variability based on TESS and HARPS observations. The stellar
light curve shows a strong signal with a 3.03±0.06 days period, which we attribute to stellar rotation. Our analysisof the HARPS spectra shows a rotational velocity of v sin i = 16.0 ± 0.5 km s−1 , indicating that the inclination of therotation axis is 50±8 degrees. This implies that the rotation axes of the star and its circumstellar disk are parallel
within the measurement error. We apply magnetospheric accretion models to fit the profiles of the Hα line and derive
mass accretion rates onto the star in the range of 0.6–2.2 × 10−10 M⊙ yr−1 , varying over the rotation phase. The
measured accretion rates are in agreement with those estimated from NUV fluxes using accretion shock models. The
derived accretion rates are higher than expected from the disk mass and planets properties for the low values of theviscous parameter α suggested by recent studies, potentially pointing to an additional mass reservoir in the inner disk
to feed the accretion, such as a dead zone. We find that the He I λ10830 line shows a blueshifted absorption feature,indicative of a wind. The mass-loss rate estimated from the line depth is consistent with an accretion-driven innerdisk MHD wind.
Accepted by ApJ
http://arxiv.org/pdf/2002.07283

of membership probability in nearby young moving groups with Gaia DR2
34 Analysis
K. Ujjwal , Sreeja S. Kartha , Blesson Mathew , P. Manoj and Mayank Narang
1

1

1

2

2

1

Department of Physics and Electronics, CHRIST (Deemed to be University), Bangalore 560029, India 2 Departmentof Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005
E-mail contact: sreeja.kartha at christuniversity.in
We analyze the membership probability of young stars belonging to nearby moving groups with Gaia DR2 data. The
sample of 1429 stars were identified from ‘The Catalog of Suspected Nearby Young Moving Group Stars’. Goodquality parallax and proper motion values were retrieved for 890 stars from Gaia DR2 database. The analysis formembership probability is performed in the framework of LACEwING algorithm. From the analysis it is confirmedthat 279 stars do not belong to any of the known moving groups. We estimated the U, V, W space velocity values
for 250 moving group members, which were found to be more accurate than previous values listed in the literature.
The velocity ellipses of all the moving groups are well constrained within the “good box”, a widely used criterion to
identify moving group members. The age of moving group members are uniformly estimated from the analysis of Gaia
Color-Magnitude Diagram with MIST isochrones. We found a spread in the age distribution of stars belonging tosome moving groups, which needs to be understood from further studies.
Accepted by AJ
http://arxiv.org/pdf/2002.04801

spectroscopy of massive young stellar objects in the 30 Doradus region
35 VLT/X-shooterof the Large Magellanic Cloud
M. L. van Gelder1,2 , L. Kaper1 , J. Japelj1 , M. C. Ramírez-Tannus1,3 , L. E. Ellerbroek1 , R. H. Barbá4 ,J. M. Bestenlehner5 , A. Bik6 , G. Gräfener7 , A. de Koter1,8 , S. E. de Mink1,9 , E. Sabbi10 , H. Sana8 , M.
Sewiło11,12 , J. S. Vink13 and N. R. Walborn10
1Anton Pannekoek Institute, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The Netherlands;
Leiden Observatory, Leiden University, PO Box 9513, 2300RA Leiden, The Netherlands; 3 Max-Planck-Institutefor Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 4 Departamento de Fisica y Astronomia, Universidad
de La Serena, Av. cisternas 1200 norte, La Serena, Chile; 5 Department of Physics and Astronomy, University of
Sheffield, Sheffield S3 7RH, UK; 6 Department of Astronomy, Stockholm University, AlbaNova University Centre,
106 91 Stockholm, Sweden; 7 Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121
Bonn, Germany; 8 Institute of Astrophysics, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium; 9 Center
for Astrophysics, Harvard-Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; 10 Space Telescope Science219Institute, 2700 San Martin Drive, MD 21218, Baltimore, USA; 11 Department of Astronomy, University of Maryland,College Park, MD 20742, USA; 12 CRESST II and Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard
Space Flight Center, Greenbelt, MD 20771,USA; 13 Armagh Observatory, College Hill, Armagh BT61 9DG, UK
E-mail contact: vgelder at strw.leidenuniv.nl
The process of massive star (M ≥ 8 M⊙ ) formation is still poorly understood. Observations of massive young stellar
objects (MYSOs) are challenging due to their rarity, short formation timescale, large distances, and high circumstellar
extinction. Here, we present the results of a spectroscopic analysis of a population of MYSOs in the Large Magellanic
Cloud (LMC). We took advantage of the spectral resolution and wavelength coverage of X-shooter (300-2500 nm),mounted on the European Southern Observatory Very Large Telescope, to detect characteristic spectral featuresin a dozen MYSO candidates near 30 Doradus, the largest starburst region in the Local Group hosting the most
massive stars known. The X-shooter spectra are strongly contaminated by nebular emission. We used a scaling
method to subtract the nebular contamination from our objects. We detect Hα, β, [O i] 630.0 nm, Ca ii infrared
triplet, [Fe ii] 1643.5 nm, fluorescent Fe ii 1687.8 nm, H2 2121.8 nm, Brγ, and CO bandhead emission in the spectraof multiple candidates. This leads to the spectroscopic confirmation of ten candidates as bona fide MYSOs. We
compare our observations with photometric observations from the literature and find all MYSOs to have a strong
near-infrared excess. We compute lower limits to the brightness and luminosity of the MYSO candidates, confirming
the near-infrared excess and the massive nature of the objects. No clear correlation is seen between the Brγ luminosityand metallicity. Combining our sample with other LMC samples results in a combined detection rate of disk features
such as fluorescent Fe ii and CO bandheads which is consistent with the Galactic rate (40%). Most of our MYSOs
show outflow features.
Accepted by A&A
https://arxiv.org/pdf/2002.02690

disk formation by a non-rotating, non-axisymmetric collapsing cloud: model
36 Protostellar
and comparison with observations
Antoine Verliat1 , Patrick Hennebelle1,2, Anaëlle J. Maury1,3 , and Mathilde Gaudel1
1

Laboratoire AIM, Paris-Saclay, CEA Saclay/IRFU/DAp – CNRS – Université Paris Diderot, 91191 Gif-sur-Yvette
Cedex, France; 2 LERMA (UMR CNRS 8112), Ecole Normale Supérieure, 75231 Paris Cedex, France; 3 HarvardSmithsonian Center for Astrophysics, 60 Garden street, Cambridge, MA 02138, USA
E-mail contact: antoine.verliat at cea.fr
Planet-forming disks are fundamental objects thought to be inherited from large scale rotation, through the conservation of angular momentum during the collapse of a prestellar dense core. We investigate the possibility for a
protostellar disk to be formed from a motionless dense core which contains non-axisymmetric density fluctuations.
The rotation is thus generated locally by the asymmetry of the collapse. We study the evolution of the angularmomentum in a non-axisymmetric collapse of a dense core from an analytical point of view. To test the theory, we
perform three-dimensional simulations of a collapsing prestellar dense core using adaptative mesh refinement. We
start from a non-axisymmetrical situation, considering a dense core with random density perturbations that follow
a turbulence spectrum. We analyse the emerging disk comparing the angular momentum it contains with the one
expected from our analytic development. We study the velocity gradients at different scales in the simulation as it isdone with observations. We show that the angular momentum in the frame of a stellar object which is not locatedat the center of mass of the core is not conserved, due to inertial forces. Our simulations of such non-axisymmetricalcollapse quickly produce accretion disks at the small scales in the core. The analysis of the kinematics at different
scales in the simulated core reveals projected velocity gradients of amplitudes similar to the ones observed in protostellar cores, and which directions vary, sometimes even reversing when small and large scales are compared. These
complex kinematics patterns appear in recent observations, and could be a discriminating feature with models whererotation is inherited from large scales. Our results from simulations without initial rotation are more consistent withthese recent observations than when solid-body rotation is initially imprinted.
Accepted by A&A

http://arxiv.org/pdf/2002.02144

20

planet migration and the formation of multiple dust rings and gaps in
37 Intermittent
protoplanetary disks
Gaylor Wafflard-Fernandez1 , Clément Baruteau11

IRAP, Université de Toulouse, CNRS, UPS, F-31400 Toulouse, France

E-mail contact: gwafflard at irap.omp.eu
A key challenge for protoplanetary disks and planet formation models is to be able to make a reliable connection
between observed structures in the disks emission, like bright and dark rings or asymmetries, and the supposed
existence of planets triggering these structures. The observation of N dark rings of emission is often interpreted as
evidence for the presence of N planets which clear dust gaps around their orbit and form dust-trapping pressure
maxima in the disk. The vast majority of the models that studied the impact of planets on the dynamics of dust
and gas in a protoplanetary disk assumed planets on fixed orbits. Here we go a different route and examine how thelarge-scale inward migration of a single planet structures the dust content of a massive disk. In many circumstances,the migration of a partial gap-opening planet with a mass comparable to Saturn is found to run away intermittently.
By means of 2D gas and dust hydrodynamical simulations, we show that intermittent runaway migration can form
multiple dust rings and gaps across the disk. Each time migration slows down, a pressure maximum forms beyond
the planet gap that traps the large dust. Post-processing of our simulations results with 3D dust radiative transfer
calculations confirms that intermittent runaway migration can lead to the formation of multiple sets of bright anddark rings of continuum emission in the (sub)millimeter beyond the planet location.
Accepted by MNRAS
http://arxiv.org/pdf/2002.02280

of three-planet systems predicted from the observed protoplanetary disk
38 Architectureof HL Tau
Shijie Wang1 , Kazuhiro D. Kanagawa2 , Toshinori Hayashi1 , Yasushi Suto1,2
1

Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan; 2 Research Center for the Early Universe,
School of Science, Tokyo 113-0033, Japan
E-mail contact: wang at utap.phys.s.u-tokyo.ac.jp
A number of protoplanetary disks observed with ALMA potentially provide direct examples of initial conditions forplanetary systems. In particular, the HL Tau disk has been intensively studied, and its rings/gaps are conventionallyinterpreted to be a result of unseen massive planets embedded in the gaps. Based on this interpretation, we carriedout N-body simulations to investigate orbital evolution of planets within the protoplanetary disk and after the disk
dispersal. Before the disk dispersal, our N-body simulations include both migration and mass-growth of the planet
coupled with evolution of the disk. By varying the disk parameters, we produce a variety of widely-separated planetarysystems consisting of three super-Jupiters at the end of disk dispersal. We found the outer planet is more massive
than the inner one, and the migration of the innermost planet is inefficient due to the accretion of outer planet(s).
We also showed how the final configuration and the final planetary mass depend on disk parameters. The migration
is found to be convergent and no planet-pair has a period ratio less than 2. After the disk dispersal, we switch to puregravitational N-body simulations and integrate the orbits up to 10 Gyr. Most simulated systems remain stable for atleast 10 Gyr. We discuss implications of our result in terms of the observed widely-separated planetary systems HR
8799 and PDS 70.
Accepted by ApJ
http://arxiv.org/pdf/2002.08036

Collisions as Triggers of Star Formation. VII. The Effect of Magnetic Field
39 GMCStrength on Star Formation
Benjamin Wu1 , Jonathan C. Tan2,3 , Duncan Christie3 and Fumitaka Nakamura1
1
National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 2 Department of Space, Earth andEnvironment, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden; 3 Department of Astronomy,

21

University of Virginia, Charlottesville, VA 22904, USA
E-mail contact: benwu.astro at gmail.com
We investigate the formation of stars within giant molecular clouds (GMCs) evolving in environments of different global
magnetic field strength and large-scale dynamics. Building upon a series of magnetohydrodynamic (MHD) simulationsof non-colliding and colliding GMCs, we employ density- and magnetically-regulated star formation sub-grid models
in clouds which range from moderately magnetically supercritical to near critical. We examine gas and star cluster
morphologies, magnetic field strengths and relative orientations, pre-stellar core densities, temperatures, mass-to-flux
ratios and velocities, star formation rates and efficiencies over time, spatial clustering of stars, and kinematics of thestars and natal gas. The large scale magnetic criticality of the region greatly affects the overall gas evolution andstar formation properties. GMC collisions enhance star formation rates and efficiencies in magnetically supercriticalconditions, but may actually inhibit them in the magnetically critical case. This may have implications for starformation in different Galactic environments such as the Galactic Center and the main Galactic disk.
Accepted by ApJ
https://arxiv.org/pdf/1911.03141.pdf

the Infalling Envelope Models of Embedded Protostars: BHR 71 and its
40 Constraining
Hot Corino
Yao-Lun Yang1,2 , Neal J. Evans II1,3,4 , Aaron Smith5,6 , Jeong-Eun Lee7 , John J. Tobin8,9 , Susan
Terebey10 , Hannah Calcutt11 , Jes K. Jørgensen12 , Joel D. Green13,1 and Tyler L. Bourke14
1

The University of Texas at Austin, Department of Astronomy, 2515 Speedway, Stop C1400, Austin, TX 78712, USA;RIKEN Cluster for Pioneering Research, Wako-shi, Saitama, 351-0106, Japan; 3 Korea Astronomy and Space Science
Institute, 776 Daedeokdae-ro, Yuseong-gu,
41.33.073(a)-6.01443(o)-6.0149(,)-72679(d)-323.82(o)-6.01552(f)-332.98(n)1.34781(s)-3.1391
Daejeon 34055, Korea; 4 Humanitas College, Global Camp, 1368(0)61735

22679(m)-383.45(c)-1.3136()i)0.725003(g)-6.0149(e)-362.683(f)4.35587(r)-5.9149(r)-5.9144,)-300.451(90)-6.01368(r)-5.9156(a)-6.01613(l)]TJ.0136

Evolution of Volatile CO from the Protostellar Disk Stage to the Protoplanetary
41 Rapid
Disk StageKe Zhang1,2 , Kamber Schwarz3,4 and Edwin A. Bergin1
1

Department of Astronomy, University of Michigan, 323 West Hall, 1085 S. University Avenue, Ann Arbor, MI 48109,
USA; 2 Hubble Fellow; 3 Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Boulevard,
Tucson, AZ 85721, USA; 4 Sagan Fellow
E-mail contact: kezhang at umich.edu
Recent observations show that the CO gas abundance, relative to H2 , in many 1–10 Myr old protoplanetary disks may
be heavily depleted, by a factor of 10–100 compared to the canonical interstellar medium value of 10−4 . When andhow this depletion happens can significantly affect compositions of planetesimals and atmospheres of giant planets.
It is therefore important to constrain if the depletion occurs already at the earliest protostellar disk stage. Here we
present spatially resolved observations of C18 O, C17 O, and 13 C18 O J=2–1 lines in three protostellar disks. We showthat the C18 O line emits from both the disk and the inner envelope, while C17 O and 13 C18 O lines are consistent witha disk origin. The line ratios indicate that both C18 O and C17 O lines are optically thick in the disk region, and only
13 18
C O line is optically thin. The line profiles of the 13 C18 O emissions are best reproduced by Keplerian gaseousdisks at similar sizes as their mm-continuum emissions, suggesting small radial separations between the gas and mmsized grains in these disks, in contrast to the large separation commonly seen in protoplanetary disks. Assuming a
gas-to-dust ratio of 100, we find that the CO gas abundances in these protostellar disks are consistent with the ISM
abundance within a factor of 2, nearly one order of magnitude higher than the average value of 1–10 Myr old disks.
These results suggest that there is a fast, ∼1 Myr, evolution of the abundance of CO gas from the protostellar disk
stage to the protoplanetary disk stage.
Accepted by ApJL
http://arxiv.org/pdf/2002.08522

C/H in Protoplanetary Disk Gas from Icy Pebble Drift across the CO Snowline
42 Excess
Ke Zhang , Arthur D. Bosman and Edwin A. Bergin
1,2

1

1

1

Department of Astronomy, University of Michigan, 323 West Hall, 1085 S. University Avenue, Ann Arbor, MI 48109,
USA; 2 Hubble Fellow
E-mail contact: kezhang at umich.edu
The atmospheric composition of giant planets carries the information of their formation history. Superstellar C/Hratios are seen in atmospheres of Jupiter, Saturn, and various giant exoplanets. Also, giant exoplanets show a wide
range of C/O ratio. To explain these ratios, one hypothesis is that protoplanets accrete carbon-enriched gas when alarge number of icy pebbles drift across the CO snowline. Here we report the first direct evidence of an elevated C/Hratio in disk gas. We use two thermo-chemical codes to model the 13 C18 O, C17 O, and C18 O (2–1) line spectra of the
HD 163296 disk. We show that the gas inside the CO snowline (∼70 au) has a C/H ratio of 1–2 times higher than
the stellar value. This ratio exceeds the expected value substantially, as only 25–60% of the carbon should be in gas
at these radii. Although we cannot rule out the case of a normal C/H ratio inside 70 au, the most probable solution
is an elevated C/H ratio of 2–8 times higher than the expectation. Our model also shows that the gas outside 70 au
has a C/H ratio of 0.1× the stellar value. This picture of enriched C/H gas at the inner region and depleted gas at
the outer region is consistent with numerical simulations of icy pebble growth and drift in protoplanetary disks. Our
results demonstrate that the large-scale drift of icy pebble can occur in disks and may significantly change the disk
gas composition for planet formation.
Accepted by ApJL
http://arxiv.org/pdf/2002.08529

VMC survey – XXXVI. Young stellar variability in the Large Magellanic Cloud
43 TheViktor Zivkov , Joana M. Oliveira , Monika G. Petr-Gotzens , Stefano Rubele , Maria-Rosa L.
1,2

1

2,12

3,4

Cioni5 , Jacco Th. van Loon1 , Richard de Grijs6,7,8 , Jim Emerson9 , Valentin D. Ivanov2 , Marcella23

Marconi10 , Maria Ida Moretti10 , Vincenzo Ripepi10, Florian Niederhofer5 and Ning-Chen Sun11
1

Lennard-Jones Laboratories, School of Chemical and Physical Sciences, Keele University, ST5 5BG, UK; 2 European
Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany; 3 Dipartimento di Fisica
e Astronomia, Università di Padova, Vicolo dell’Osservatorio 2, I-35122 Padova, Italy; 4 Osservatorio Astronomico
di Padova – INAF, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy; 5 Leibniz-Institut für Astrophysik Potsdam,
An der Sternwarte 16, D-14482 Potsdam, Germany; 6 Department of Physics and Astronomy, Macquarie University,
Balaclava Road, Sydney NSW 2109, Australia; 7 Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie
University, Balaclava Road, Sydney NSW 2109, Australia; 8 International Space Science Institute–Beijing, 1 Nanertiao,
Zhongguancun, Hai Dian District, Beijing 100190, China; 9 Astronomy Unit, School of Physics and Astronomy,
Queen Mary University of London, Mile End Road, London E1 4NS, UK; 10 INAF-Osservatorio Astronomico di
Capodimonte, via Moiariello 16, I-80131, Naples, Italy; 11 Department of Physics and Astronomy, University of
Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK; 12 Universitäts-Sternwarte, Ludwig-MaximiliansUniversität München, Scheinerstr 1, D-81679 München, Germany
E-mail contact: v.zivkov at keele.ac.uk
Studies of young stellar objects (YSOs) in the Galaxy have found that a significant fraction exhibit photometricvariability. However, no systematic investigation has been conducted on the variability of extragalactic YSOs. Here
we present the first variability study of massive YSOs in a ∼ 1.5 deg2 region of the Large Magellanic Cloud (LMC).
The aim is to investigate whether the different environmental conditions in the metal-poor LMC (∼ 0.4 − 0.5 Z⊙)
have an impact on the variability characteristics. Multi-epoch near-infrared (NIR) photometry was obtained fromthe VISTA Survey of the Magellanic Clouds (VMC) and our own monitoring campaign using the VISTA telescope.
By applying a reduced χ2 -analysis, stellar variability was identified. We found 3062 candidate variable stars from a
population of 362 425 stars detected. Based on several Spitzer studies, we compiled a sample of high-reliability massive
YSOs: a total of 173 massive YSOs have NIR counterparts (down to Ks ∼ 18.5 mag) in the VMC catalogue, of which
39 display significant (> 3σ) variability. They have been classified as eruptive, fader, dipper, short-term variable andlong-period variable YSOs based mostly on the appearance of their Ks band light curves. The majority of YSOs are
aperiodic, only five YSOs exhibit periodic lightcurves. The observed amplitudes are comparable or smaller than thosefor Galactic YSOs (only two Magellanic YSOs exhibit ∆Ks > 1 mag), not what would have been expected from thetypically larger mass accretion rates observed in the Magellanic Clouds.
Accepted by MNRAS
http://arxiv.org/pdf/2002.12291

Abstracts of recently accepted major reviews

Molecular jets from low-mass young protostellar objects
Chin-Fei Lee1
1

Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan

E-mail contact: cflee at asiaa.sinica.edu.tw
Molecular jets are seen coming from the youngest protostars in the early phase of low-mass star formation. They aredetected in CO, SiO, and SO at (sub)millimeter wavelengths down to the innermost regions, where their associatedprotostars and accretion disks are deeply embedded and where they are launched and collimated. They are not only
the fossil records of accretion history of the protostars but also are expected to play an important role in facilitating theaccretion process. Studying their physical properties (e.g., mass-loss rate, velocity, rotation, radius, wiggle, molecular
content, shock formation, periodical variation, magnetic field, etc) allows us to probe not only the jet launching andcollimation, but also the disk accretion and evolution, and potentially binary formation and planetary formation in
the disks. Here I review recent exciting results obtained with high-spatial and high-velocity resolution observations
24

of molecular jets in comparison to those obtained in the optical jets in the later phase of star formation. Future
observations of molecular jets with a large sample at high spatial and velocity resolution with ALMA are expected tolead to a breakthrough in our understanding of jets from young stars.
Accepted by Astronomy and Astrophysics Review
https://arxiv.org/abs/2002.05823

Impact of low-energy cosmic rays on star formation
Marco Padovani1 , Alexei V. Ivlev2 , Daniele Galli1 , Stella S. R. Offner3 , Nick Indriolo4 , Donna RodgersLee5 , Alexandre Marcowith6 , Philipp Girichidis7 , Andrei M. Bykov8 and J. M. Diederik Kruijssen91INAF-Osservatorio Astrofisico di Arcetri - Firenze, Italy; 2 Max-Planck-Institut für extraterrestrische Physik Garching, Germany; 3 Department of Astronomy, The University of Texas - Austin, USA; 4 ALMA Project, National
Astronomical Observatory of Japan, National Institutes of Natural Sciences - Tokyo, Japan; 5 School of Physics,
Trinity College Dublin, University of Dublin - Dublin, Ireland; 6 Laboratoire Univers et Particules d81(b3311.34781(l4781(o)-6.0

Dissertation Abstracts

Understanding Protostellar Jet Feedback on Disc and Cloud Scales
Christopher Nolan

Thesis work conducted at: Australian National University
Mt Stromlo Observatory, Cotter Rd, Weston Creek, ACT 2611, Australia
Current address: Max-Planck-Institut für extraterrestrische Physik
Giessenbachstrasse 1 85748 Garching Germany
Electronic mail: cnolan at mpe.mpg.de
Ph.D dissertation directed by: Raquel Salmeron and Christoph FederrathPh.D degree awarded: December 2019

Protostellar jets are a vital part of the star formation process. They are responsible for the removal of excess angularmomentum critical to the growth of protostars, while feeding that angular momentum back into molecular clouds
to regulate the formation of stellar cores and gravitational collapse. To better understand the origin and impact ofprotostellar jets, this thesis investigates the launching of protostellar disc winds and the driving of non-isothermal
turbulence in the interstellar medium.
In the first part of this thesis, we explore how the structure of protostellar discs relates to the properties of the windlaunching region, which directly effects the large-scale properties of the jet. In order to study the launching of discwinds, we first design a 1+1.5D magnetohydrodynamic (MHD) model of the launching region in the [r,z] plane. We
take into account the three diffusion mechanisms of non-ideal MHD (Ohm, Hall, and ambipolar) by calculating theircontributions at the disc midplane and using a simplified, vertically-scaled approach for higher z. We observe thatmost of the mass launched by the wind is concentrated within a radially localized region a fraction of an astronomical
unit (au) in width, in agreement with current observations. We find that the footprint radius and the wind efficiency,
measured by the ratio of the wind mass-loss rate to the rate of material accreted onto the star, are a strong functionof the model parameters, namely the mass accretion rate, magnetic field strength, and surface density profile of thedisc. Understanding the structure of the wind-launching region has important
We subsequently improve the 1+1.5D models by removing the vertical scaling approximation to the non-ideal MHD
terms and calculate the magnetic diffusivities self-consistently at all heights above the disc midplane. This results inincreased field-matter coupling surrounding the midplane, increasing the poloidal magnetic field bending and compressing the disc via enhanced magnetic pressure gradients. It also shifts the wind-launching region to smaller radii,
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decreases the overall wind mass-loss rate by an order of magnitude, and generates a radially symmetric wind mass-loss
profile.
In the second part of this thesis, we investigate the properties of driven, turbulent, adiabatic gas. The density variance–
Mach number relation of the turbulent interstellar medium is a key ingredient for analytical models of star formation.
We examine the robustness of the standard, isothermal form of this relation in the non-isothermal regime, specificallytesting ideal gases with diatomic molecular and monatomic adiabatic indices. Stirring the gas with purely solenoidal
forcing at low wavenumbers, we find that as the gas heats in adiabatic compressions, it evolves along a curve in thedensity variance-Mach number plane, but deviates significantly from the standard isothermal relation. We provide
new empirical and theoretical relations that take the adiabatic index into account and provide good fits for a range ofMach numbers.

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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.

27Summary of Upcoming Meetings

Interstellar Shocks School
22 - 27 March 2020, Les Houches, France
https://www.sciencesconf.org/browse/conference/?confid=8899
Linking Dust, Ice, and Gas in Space19 - 24 April 2020, Capri Islands, Italy
http://www.frcongressi.it/ecla2020/
AIP Thinkshop on Protoplanetary Disk Chemodynamics
11 - 15 May 2020, Leibnitz Institute for Astrophysics Potsdam, Germany
https://meetings.aip.de/event/1
Planet Formation: From Dust Coagulation to Final Orbital Assembly
1 - 26 June 2020, Munich, Germany
http://www.munich-iapp.de/planetformation
Cool Stars, Stellar Systems, and the Sun 21
21 - 26 June 2020, Toulouse, France
https://coolstars21.github.io/
The Physics of Star Formation: From Stellar Cores to Galactic Scales; 29 June - 3 July 2020, Lyon,
Francehttp:/staratlyon.univ-lyon1.fr/en
Illuminating the Dusty Universe: A Tribute to the Work of Bruce Draine
6 - 10 July 2020, Florence, Italy
https://web.astro.princeton.edu/IlluminatingTheDusty Universe
The Early Phase of Star Formation
12 - 17 July 2020, Ringberg, Germany
http://www.mpia.de/homes/stein/EPoS/2020/2020.php
Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann
17 - 20 August 2020, Malahide, Ireland
https://www.dias.ie/cloudstodiscs/
Star Formation in Different Environments 202024 - 28 August 2020, Quy Nhon, Vietnam
http://icisequynhon.com/conferences/sfde/
Planetary Science: The Young Solar System
6 - 12 September 2020, Quy Nhon, Vietnam
http://www.icisequynhon.com/conferences/planetary_science/
Wheel of Star Formation: A conference dedicated to Prof. Jan Palouš
14 - 18 September 2020, Prague, Czech Republic
https://janfest2020.asu.cas.cz
Conditions and Impact of Star Formation - Across Times and Scales
28 September - 2 October 2020, Chile
https://astro.uni-koeln.de/symposium-star-formation-2020.html
From Clouds to Planets II: The Astrochemical Link
28 September - 2 October 2020, Berlin, Germany
https://events.mpe.mpg.de/event/12/

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The Aftermath of a Revolution: Planet Formation Five Years after HL Tau
7 - 11 December 2020, Chile
https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org

Short Announcements

In Fall 2020, the SOFIA Observatory anticipates offering a new, next generation, scientific instrument: the High
Resolution Mid-Infrared Spectrometer (HIRMES). HIRMES will enable mid- to far-infrared spectroscopy (25 – 122µm) with selectable spectral resolving powers of R ∼ 300-600, 12,000, and 50,000-100,000, covering the wavelength
gap between JWST MIRI (28 µm) and Herschel PACS (55 µm). In its highest resolution mode, HIRMES is expected
to provide 100x higher spectral resolution with similar or slightly better sensitivity compared with Herschel PACS.
Thus, HIRMES is expected to enable a wide variety of science by spectrally resolving gas emission lines (including 63µm [OI] and other fine-structure lines, HD 1-0, and many water lines) and providing access to a variety of solid-state
emission features, including the elusive 43 µm solid-state water ice feature. Finally, HIRMES offers a fast spectral
mapping mode for selected lines, including the 88.4 µm [OIII] and 121.9 µm [NII] lines.
The HIRMES Science Working Group is organizing a workshop for the astronomical community June 22-24, 2020 tobe held at Space Telescope Science Institute on the campus of Johns Hopkins University. The goal of the workshop is
to raise the community’s awareness to the upcoming availability of HIRMES, discuss the science that could be enabledby this new capability, and provide technical support for attendees interested in submitting HIRMES proposals. The
SOFIA project is enthusiastic about engaging the broader astronomical community and hearing about the sciencethat HIRMES will enable. The project would like to support HIRMES observing by providing early opportunities
to propose for telescope time if the community is interested. There are no fees associated with participating in theworkshop. For more information, please go to https://www.hirmes.org/2020-workshop

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