THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 320 — 15 August 2019

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

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

Abstracts of Newly Accepted Papers . . . . . . . . . . . 3
Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 23
New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Summary of Upcoming Meetings . . . . . . . . . . . . . 27

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 Rodrı́guez
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.

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Cover Picture
An excerpt from an HST image of Messier 8.
Courtesy STScI.

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Abstracts of recently accepted papers

1

The role of molecular filaments in the origin of the prestellar core mass function andstellar initial mass function
Philippe André1 , Doris Arzoumanian2,3,1 , Vera Könyves4,1 , Yoshito Shimajiri5,1,6 , Pedro Palmeirim3
1

Laboratoire d’Astrophysique (AIM), CEA/DRF, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne
Paris Cité, 91191 Gif-sur-Yvette, France; 2 Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya
464-8602, Japan; 3 Instituto de Astrofı́sica e Ciências do Espaço, Universidade do Porto, Rua das Estrelas, PT4150-762
Porto, Portugal; 4 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, United Kingdom;
5
Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35
Korimoto, Kagoshima, Kagoshima 890-0065, Japan; 6 National Astronomical Observatory of Japan, Osawa 2-21-1,
Mitaka, Tokyo 181-8588, Japan
E-mail contact: pandre at cea.fr
Context: The origin of the stellar initial mass function (IMF) is one of the most debated issues in astrophysics.
Aims: Here, we explore the possible link between the quasi-universal filamentary structure of star-forming molecular
clouds and the origin of the IMF.
Methods: Based on our recent comprehensive study of filament properties from Herschel Gould Belt survey observations(Arzoumanian et al.), we derive, for the first time, a good estimate of the filament mass function (FMF) and filamentline mass function (FLMF) in nearby molecular clouds. We use the observed FLMF to propose a simple toy model forthe origin of the prestellar core mass function (CMF), relying on gravitational fragmentation of thermally supercriticalbut virialized filaments.
Results: We find that the FMF and the FLMF have very similar shapes and are both consistent with a Salpeter−1.5±0.1
like power-law function (dN /dlogMline ∝ Mline) in the regime of thermally supercritical filaments (Mline >16 M⊙/pc). This is a remarkable result since, in contrast, the mass distribution of molecular clouds and clumps is
known to be significantly shallower than the Salpeter power-law IMF, with dN /dlogMcl ∝ Mcl−0.7 .
Conclusions: Since the vast majority of prestellar cores appear to form in thermally transcritical or supercriticalfilaments, we suggest that the prestellar CMF and by extension the stellar IMF are at least partly inherited from the
FLMF through gravitational fragmentation of individual filaments.
Accepted by Astronomy and Astrophysics Letters
http://arxiv.org/pdf/1907.13448

2

The Transition from a Lognormal to a Power-law Column Density Distribution in Molecular Clouds: An Imprint of the Initial Magnetic Field and Turbulence
Sayantan Auddy1 , Shantanu Basu2 and Takahiro Kudoh3
1

Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan; 2 Department of Physics andAstronomy, The University of Western Ontario, London, ON N6A 3K7, Canada; 3 Faculty of Education, Nagasaki
University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
E-mail contact: sauddy at asiaa.sinica.edu.tw
We introduce a theory for the development of a transitional column density ΣTP between the lognormal and the powerlaw forms of the probability distribution function (PDF) in a molecular cloud. Our turbulent magnetohydrodynamic
simulations show that the value of ΣTP increases as the strength of both the initial magnetic field and turbulence
increases. We develop an analytic expression for ΣTP based on the interplay of turbulence, a (strong) magnetic field,
and gravity. The transition value ΣTP scales with M20 , the square of the initial sonic Mach number, and β0 , the initialratio of gas pressure to magnetic pressure. We fit the variation of ΣTP among different model clouds as a function ofM20 β0 , or equivalently the square of the initial Alfvénic Mach number M2A0 . This implies that the transition value
3ΣTP is an imprint of cloud initial conditions and is set by turbulent compression of a magnetic cloud. Physically, thevalue of ΣTP denotes the boundary above which the mass-to-flux ratio becomes supercritical and gravity drives theevolution.
Accepted by ApJL
https://arxiv.org/pdf/1907.09783

3

The Concentration and Growth of Solids in Fragmenting Circumstellar Disks
Hans Baehr1 and Hubert Klahr1
1

Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany

E-mail contact: baehr at mpia.de
Due to the gas rich environments of early circumstellar disks, the gravitational collapse of cool, dense regions of thedisk form fragments largely composed of gas. During formation, disk fragments may attain increased metallicities as
they interact with the surrounding disk material, whether through particle migration to pressure maxima or throughmutual gravitational interaction. In this paper, we investigate the ability of fragments to collect and retain a significant
solid component through gas-particle interactions in high-resolution 3D self-gravitating shearing box simulations. The
formation of axissymmetric perturbations associated with gravitational instabilities allows particles of intermediate
sizes to concentrate through aerodynamic drag forces. By the onset of fragmentation, the mass of local particle
concentrations within the fragment are comparable to that of the gas component and the sebsequent gravitational
collapse results in the formation of a solid core. We find that these cores can be up to several tens of Earth masses,
depending on grain size, before the fragment center reaches temperatures which would sublimate solids. The solid
fraction and total mass of the fragment also depend on the metallicity of the young parent protoplanetary disk, withhigher initial metallicities resulting in larger fragments and larger solid cores. Additionally, the extended atmospheresof these soon-to-be gas giants or brown dwarfs are occasionally enriched above the initial metallicity, provided no solidcore forms in the center and are otherwise lacking in heavier elements when a core does form.
Accepted by ApJ
http://arxiv.org/pdf/1907.01290

4

OH maser emission in the THOR survey of the northern Milky Way
H. Beuther1 , A. Walsh2 , Y. Wang1 , M. Rugel1,3, J. Soler1 , H. Linz1 , R.S. Klessen4, L.D. Anderson5,10,11 ,J.S. Urquhart6 , S.C.O. Glover4 , S.J. Billington6, J. Kainulainen7,1 , K.M. Menten3 , N. Roy8 , S.N.
Longmore9 and F. Bigiel12
1

Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Research Centre for Astronomy,
Astrophysics, and Astrophotonics, Macquarie University, NSW 2109, Australia; 3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 4 Universität Heidelberg, Zentrum für Astronomie, Institut für
Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg, Germany; 5 Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA; 6 School of Physical Sciences, University of Kent,
Ingram Building, Canterbury, Kent CT2 7NH, UK; 7 Chalmers University of Technology, Department of Space, Earthand Environment, SE-412 93 Gothenburg, Sweden; 8 Department of Physics, Indian Institute of Science, Bangalore
560012, India; 9 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool
L3 5RF, UK; 10 Center for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research
Building, Morgantown, WV 26505, USA; 11 Adjunct Astronomer at the Green Bank Observatory, P.O. Box 2, Green
Bank, WV 24944, USA; 12 Argelander-Institute for Astronomy, University of Bonn, Auf dem Hügel 71, 53121 Bonn,
Germany
E-mail contact: beuther at mpia.de
Context: OH masers trace diverse physical processes, from the expanding envelopes around evolved stars to starforming regions or supernovae remnants. Providing a survey of the ground-state OH maser transitions in the northernhemisphere inner Milky Way facilitates the study of a broad range of scientific topics.
Aims: We want to identify the ground-state OH masers at ∼18 cm wavelength in the area covered by “The HI/OH/Recombinationline survey of the Milky Way (THOR)”. We will present a catalogue of all OH maser features and their possible asso4

ciated environments.
Methods: The THOR survey covers longitude and latitude ranges of 14.3◦ < l < 66.8◦ and b < ±1.25◦ . All OH groundstate lines 2 Π3/2 (J=3/2) at 1612 (F=1-2), 1665 (F=1-1), 1667 (F=2-2) and 1720 MHz (F=2-1) have been observed,
employing the Very Large Array (VLA) in its C configuration. The spatial resolution of the data varies between 12.5′′
and 19′′ , the spectral resolution is 1.5 km s−1 , and the rms sensitivity of the data is ∼10 mJy beam−1 per channel.
Results: We identify 1585 individual maser spots (corresponding to single spectral features) distributed over 807 maser
sites (regions of size ∼ 103 − 104 AU). Based on different criteria from spectral profiles to literature comparison, we
try to associate the maser sites with astrophysical source types. Approximately 51% of the sites exhibit the doublehorned 1612 MHz spectra typically emitted from the expanding shells of evolved stars. The separations of the twomain velocity features of the expanding shells typically vary between 22 and 38 km s−1 . In addition to this, at least
20% of the maser sites are associated with star-forming regions. While the largest fraction of 1720 MHz maser spots(21 out of 53) is associated with supernova remnants, a significant fraction of the 1720 MHz maser spots (17) are also
associated with star-forming regions. We present comparisons to the thermal 13 CO(1–0) emission as well as to othersurveys of class II CH3 OH and H2 O maser emission. The catalogue attempts to present associations to astrophysicalsources where available, and the full catalogue is available in electronic form.
Conclusions: This OH maser catalogue presents a unique resource of stellar and interstellar masers in the northernhemisphere. It provides the basis for a diverse range of follow-up studies from envelopes around evolved stars tostar-forming regions and Supernova remnants.
Accepted by Astronomy and Astrophysics
http://www.mpia.de/homes/beuther/papers.html

5First detections of H13CO+ and HC15N in the disk around HD 97048: Evidence for acold gas reservoir in the outer disk
Alice S. Booth1 , Catherine Walsh1 and John D. Ilee1
1

University of Leeds, Leeds LS2 9JT, UK

E-mail contact: pyasb at leeds.ac.uk
Observations of different molecular lines in protoplanetary disks provide valuable information on the gas kinematics, aswell as constraints on the radial density and temperature structure of the gas.With ALMA we have detected H13CO+(J=4-3) and HC15N (J=4-3) in the HD 97048 protoplanetary disk for the first time.We compare these new detections
to the ringed continuum mm-dust emission and the spatially resolved CO (J=3-2) and HCO+ (J=4-3) emission. The
radial distributions of the H13CO+ and HC15N emission show hints of ringed sub-structure whereas, the opticallythick tracers, CO and HCO+, do not. We calculate the HCO+/H13CO+ intensity ratio across the disk and findthat it is radially constant (within our uncertainties). We use a physio-chemical parametric disk structure of the HD
97048 disk with an analytical prescription for the HCO+ abundance distribution to generate synthetic observationsof the HCO+ and H13CO+ disk emission assuming LTE. The best by-eye fit models require radial variations in the
HCO+/H13CO+ abundance ratio and an overall enhancement in H13CO+ relative to HCO+. This highlights theneed to consider isotope selective chemistry and in particular low temperature carbon isotope exchange reactions. This
also points to the presence of a reservoir of cold molecular gas in the outer disk (T <10 K, R > 200 au). Chemical
models are required to confirm that isotope-selective chemistry alone can explain the observations presented here.
With these data, we cannot rule out that the known dust substructure in the HD 97048 disk is responsible for theobserved trends in molecular line emission, and higher spatial resolution observations are required to fully explore thepotential of optically thin tracers to probe planet-carved dust gaps. We also report non-detections of H13CO+ and
HC15N in the HD 100546 protoplanetary disk.
Accepted by A&A
https://arxiv.org/pdf/1907.08060

6

Fragmentation, rotation, and outflows in the high-mass star-forming region
IRAS 23033+5951. A case study of the IRAM NOEMA large program CORE
Felix Bosco1,2 , Henrik Beuther1 , Aida Ahmadi1,2 , Joseph C. Mottram1 , Rolf Kuiper3,1 , Hendrik Linz1 ,Luke Maud4 , Jan M. Winters5 , Thomas Henning1 , Siyi Feng6,7 , Thomas Peters8 , Dmitry Semonov1,9 ,5Pamela D. Klaassen10 , Peter Schilke11 , James S. Urquhart12 , Maria T. Beltrán13 , Stuart L. Lumsden14 ,Silvia Leurini15 , Luca Moscadelli13, Riccardo Cesaroni13 , Álvaro Sánchez-Monge16 , Aina Palau17 , Ralph
Pudritz18 , Friedrich Wyrowski11 and Steven Longmore19
1

Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 2 Fellow of the International Max
Planck Research School on Astronomy and Cosmic Physics at the University of Heidelberg; 3 Institute of Astronomy
and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany; 4 Leiden Observatory,
Leiden University, 2300 RA Leiden, Netherlands; 5 IRAM, 300 rue de la Piscine, Domaine Universitaire, F-38406
Saint Martin d’Hères, France; 6 East Asian Core Observatories Association; 7 National Astronomical Observatory of
China, Datun Road 20, Chaoyang, Beijing, China; 8 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1,
85748 Garching, Germany; 9 Department of Chemistry, Ludwig Maximilian University, Butenandtstr. 5-13, 81377
Munich, Germany; 10 UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinbugh
EH9 3HJ, UK; 11 Max-Planck-Institut für Radioastronomie, Auf dem Hgel 69, 53121 Bonn, Germany; 12 Centre
for Astrophysics and Planetary Science, University of Kent, Canterbury, CT2 7NH, UK; 13 INAF - Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 14 School of Physics and Astronomy, The Universityof Leeds, Woodhouse Lane, Leeds LS2 9JT, UK; 15 INAF - Osservatorio Astronomico di Cagliari, via della Scienza
5, 09047, Selargius (CA), Italy; 16 I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937 Köln,Germany; 17 Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, P.O. Box 3-72,
58090, Morelia, Michoacán, México; 18 McMaster University, 1280 MAIN ST W, L8S 4M1 Hamilton, ON, Canada; 19
Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
E-mail contact: bosco at mpia.de
The formation process of high-mass stars (> 8 M⊙ ) is poorly constrained, particularly the effects of clump fragmentation creating multiple systems and the mechanism of mass accretion onto the cores. We study the fragmentationof dense gas clumps, and trace the circumstellar rotation and outflows by analyzing observations of the high-mass(∼ 500 M⊙) star-forming region IRAS 23033+5951. Using the Northern Extended Millimeter Array (NOEMA) in
three configurations and the IRAM 30m single-dish telescope at 220 GHz, we probe the gas and dust emission at anangular resolution of ∼0.45 arcsec, corresponding to 1900 au. In the millimeter (mm) continuum emission, we identify
a protostellar cluster with at least four mm-sources, where three of them show a significantly higher peak intensity
well above a signal-to-noise ratio of 100. Hierarchical fragmentation from large to small spatial scales is discussed.
Two fragments are embedded in rotating structures and drive molecular outflows, traced by 13 CO (2–1) emission. The
velocity profiles across two of the cores are similar to Keplerian but are missing the highest-velocity components close
to the center of rotation, which is a common phenomena from observations like these, and other rotation scenarios
are not excluded entirely. Position–velocity diagrams suggest protostellar masses of ∼ 6 and 19 M⊙ . Rotational temperatures from fitting CH3 CN (12K − 11K ) spectra are used for estimating the gas temperature and thereby also thedisk stability against gravitational fragmentation, utilizing Toomre’s Q parameter. Assuming that the candidate disk
is in Keplerian rotation about the central stellar object and considering different disk inclination angles, we identify
only one candidate disk as being unstable against gravitational instability caused by axisymmetric perturbations. The
dominant sources cover different evolutionary stages within the same maternal gas clump. The appearance of rotationand outflows of the cores are similar to those found in low-mass star-forming regions.
Accepted by Astronomy & Astrophysics
http://www.mpia.de/homes/beuther/bosco2019.pdf

7High-Resolution Near Infrared Spectroscopy of HD 100546: IV. Orbiting Companion
Disappears on Schedule
Sean D. Brittain1 , Joan R. Najita2 and John S. Carr3
1

Clemson University, 118 Kinard Lab, Clemson, SC, 29634-0978, USA; 2 National Optical Astronomy Observatory,
950. N. Cherry Ave., Tucson, AZ 85719, USA; 3 Department of Astronomy, University of Maryland, College Park,
MD 20742, USA
E-mail contact: sbritt at clemson.edu

HD 100546 is a Herbig Ae/Be star surrounded by a disk with a large central region that is cleared of gas and dust
(i.e., an inner hole). High-resolution near-infrared spectroscopy reveals a rich emission spectrum of fundamental ro-

6vibrational CO emission lines whose time variable properties point to the presence of an orbiting companion within
the hole. The Doppler shift and spectroastrometric signal of the CO v=1-0 P26 line, observed from 2003 to 2013, areconsistent with a source of excess CO emission that orbits the star near the inner rim of the disk. The properties of theexcess emission are consistent with those of a circumplanetary disk. In this paper, we report follow up observations
that confirm our earlier prediction that the orbiting source of excess emission would disappear behind the near sideof the inner rim of the outer disk in 2017. We find that while the hotband CO lines remained unchanged in 2017, thev=1-0 P26 line and its spectroastrometric signal returned to the profile observed in 2003. With these new observations,
we further constrain the origin of the emission and discuss possible ways of confirming the presence of an orbiting
planetary companion in the inner disk.
Accepted by ApJ
https://arxiv.org/pdf/1908.00132

8

Polarization reversal of scattered thermal dust emission in protoplanetary disks at submillimetre wavelengths
Robert Brunngräber1 and Sebastian Wolf1
1

Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 15, 24118
Kiel, Germany
E-mail contact: rbrunngraeber at astrophysik.uni-kiel.de
Investigation of the polarized light of protoplanetary disks is key for constraining dust properties, disk morphology,
and embedded magnetic fields. However, different polarization mechanisms and the diversity of dust grain shapes
and compositions lead to ambiguities in the polarization pattern. The so-called self-scattering of thermal, re-emitted
radiation in the infrared and millimetre and submillimetre wavelengths is discussed as a major polarization mechanism.
If the net flux of the radiation field is in the radial direction, it is commonly assumed that the polarization patternproduced by scattering in a protoplanetary disk shows concentric rings for disks seen in face-on orientation. We
show that a change of 90◦ of the polarization vector orientation may occur and mimic the typical pattern of dichroic
emission of dust grains aligned by a toroidal magnetic field in disks seen close to face-on. Furthermore, this effect ofpolarization reversal is a fast-changing function of wavelength and grain size, and is thus a powerful tool to constrain
grain composition and size distribution present in protoplanetary disks. In addition, the effect may also provide uniqueconstraints for the disk inclination, especially if the disk is seen close to face-on.
Accepted by A&A
http://arxiv.org/pdf/1907.02705
https://www.aanda.org/articles/aa/pdf/2019/07/aa35169-19/aa35169-19.html

9

NH3 Observations of the S235 Star Forming Region: Dense Gas in Inter-core Bridges
Ross A. Burns1,2,3,4 , Toshihiro Handa5 , Toshihiro Omodaka4 , Andrej M. Sobolev6 , Maria S. Kirsanova6,7,8 ,Takumi Nagayama9 , James O. Chibueze10,11 , Mikito Kohno12 , Makoto Nakano13 , Kazuyoshi Sunada9
and Dmitry A. Ladeyschikov6
1

Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588,
Japan; 2 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon, 34055, Republic ofKorea; 3 Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands; 4 Graduate
School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan;
5
Amanogawa Galaxy Astronomy Research Center, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima
890-0065, Japan; 6 Ural Federal University, 19 Mira St. 620002, Ekaterinburg, Russia; 7 Institute of Astronomy,
Russian Academy of Sciences, 48 Pyatnitskaya Str. 119017, Moscow, Russia; 8 Moscow Institute of Physics andTechnology, 141701, 9 Institutskiy per., Dolgoprudny, Moscow Region, Russia; 9 Mizusawa VLBI observatory, NAOJ
2-12, Hoshigaoka, Mizusawa, Oshu, Iwate 023-0861, Japan; 10 Space Research Unit, Physics Department, NorthWest University, Potchefstroom, 2520, South Africa; 11 Department of Physics and Astronomy, University of Nigeria,
Carver Building, 1 University Road, Nsukka, 410001, Nigeria; 12 Department of Physics, Nagoya University, Furo-cho,
Chikusa-ku, Nagoya, Aichi 464-8601, Japan; 13 Faculty of Science and Technology, Oita University, 700 Dannoharu,

7

Oita, Oita 870-1192, Japan
E-mail contact: ross.burns at nao.ac.jp
Star formation is thought to be driven by two groups of mechanisms; spontaneous collapse and triggered collapse.
Triggered star formation mechanisms further diverge into cloud-cloud collision (CCC), ”collect and collapse” (C&C)
and shock induced collapse of pre-existing, gravitationally stable cores, or ’radiation driven implosion’ (RDI). To
evaluate the contributions of these mechanisms and establish whether these processes can occur together within thesame star forming region we performed mapping observations of radio frequency ammonia, and water maser emission
lines in the S235 massive star forming region. Via spectral analyses of main, hyperfine and multi-transitional ammonialines we explored the distribution of temperature and column density in the dense gas in the S235 and S235AB star
forming region. The most remarkable result of the mapping observations is the discovery of high density gas in intercore bridges which physically link dense molecular cores that house young proto-stellar clusters. The presence of dense
gas implies the potential for future star formation within the system of cores and gas bridges. Cluster formation
implies collapse and the continuous physical links, also seen in re-imaged archival CS and 13 CO maps, suggests a
common origin to the molecular cores housing these clusters, i.e the structure condensed from a single, larger parent
cloud, brought about by the influence of a local expanding HII region. An ammonia absorption feature co-locatingwith the center of the extended HII region may be attributed to an older gas component left over from the period prior
to formation of the HII region. Our observations also detail known and new sites of water maser emission, highlighting
regions of active ongoing star formation.
Accepted by Publications of the Astronomical Society of Japan (PASJ)
https://arxiv.org/pdf/1908.00954.pdf

10Forming Pop III binaries in self-gravitating discs: how to keep the orbital angularmomentum
Sunmyon Chon1 and Takashi Hosokawa2
1

Astronomical Institute, Tohoku University, Aoba, Sendai 980-8578, Japan; 2 Department of Physics, Kyoto University, Kyoto 606-8502, Japan
E-mail contact: sunmyon.chon at astr.tohoku.ac.jp

The disk fragmentation is a possible process leading to the formation of Population III stellar binary systems. However,numerical simulations show diverse fates of the fragments; some evolve into stable binaries and others merge away witha central star. To clarify the physics behind such diversity, we perform a series of three dimensional hydrodynamics
simulations in a controlled manner. We insert a point particle mimicking a fragment in a self-gravitating disk, where
the initial mass and position are free parameters, and follow the orbital evolution for several tens of orbits. The
results show great diversity even with such simple experiments. Some particles shortly merge away after migrating
inward, but others survive as the migration stalls with the gap-opening in the disk. We find that our results arewell interpreted postulating that the orbital angular momentum is extracted by (i) the gravitational torque from thedisk spiral structure, and (ii) tidal disruption of a gravitationally-bound envelope around the particle. Our analytic
evaluations show the processes (i) and (ii) are effective in an outer and inner part of the disk respectively. There is awindow of the gap-opening in the middle, if the envelope mass is sufficiently large. These all agree with our numericalresults. We further show that the binaries, which appear for the “survival” cases, gradually expand while accretingthe disk gas. Our theoretical framework is freely scalable to be applied for the present-day star and planet formation.
Accepted by MNRAS
https://arxiv.org/pdf/1904.06352

11

Cometary compositions compared with protoplanetary disk midplane chemical evolution. An emerging chemical evolution taxonomy for comets
Christian Eistrup1,2 , Catherine Walsh3 and Ewine F. van Dishoeck1,4
1

Leiden Observatory, Leiden University, P. O. Box 9531, 2300 RA Leiden, The Netherlands; 2 Department of Astronomy, University of Virginia, 530 McCormick Road, 22903 Charlottesville, VA, USA; 3 School of Physics and Astronomy,
University of Leeds, Leeds, LS2 9JT, UK; 4 Max-Planck-Institut für Extraterrestriche Physik, Giessenbackstrasse 1,
8

85748 Garching, Germany
E-mail contact: eistrup at virginia.edu
With a growing number of molecules observed in many comets, and an improved understanding of chemical evolution
in protoplanetary disk midplanes, comparisons can be made between models and observations that could potentiallyconstrain the formation histories of comets. A χ2 -method was used to determine maximum likelihood surfaces for 14
different comets that formed at a given time (up to 8 Myr) and place (out to beyond the CO iceline) in the pre-solar
nebula midplane. This was done using observed volatile abundances for the 14 comets and the evolution of volatileabundances from chemical modelling of disk midplanes. Considering all parent species (ten molecules) in a scenariothat assumed reset initial chemistry, the χ2 likelihood surfaces show a characteristic trail in the parameter space withhigh likelihood of formation around 30 AU at early times and 12 AU at later times for ten comets. This trail roughly
traces the vicinity of the CO iceline in time. The formation histories for all comets were thereby constrained to thevicinity of the CO iceline, assuming that the chemistry was partially reset early in the pre-solar nebula. This is found,both when considering carbon-, oxygen-, and sulphur-bearing molecules (ten in total), and when only considering
carbon- and oxygen-bearing molecules (seven in total). Since these 14 comets did not previously fall into the sametaxonomical categories together, this chemical constraint may be proposed as an alternative taxonomy for comets.
Based on the most likely time for each of these comets to have formed during the disk chemical evolution, a formation
time classification for the 14 comets is suggested.
Accepted by A&A
http://arxiv.org/pdf/1907.11255

Interstellar Glycolaldehyde, Methyl Formate, and Acetic Acid I: A Bi-modal Abundance

12 Pattern in Star Forming Regions

Samer El-Abd1,2 , Crystal Brogan2 , Todd Hunter2 , Eric Willis3, Robin Garrod3,1 and Brett McGuire2,4
1

Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA, 22903; 2 National Radio
Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903; 3 Department of Chemistry, University ofVirginia, 409 McCormick Road, Charlottesville, VA, 22903; 4 Havard-Smithsonian Center for Astrophysics, 60 Garden
St, Cambridge, MA, 02138
E-mail contact: sje2tu at virginia.edu
The relative column densities of the structural isomers methyl formate, glycolaldehyde, and acetic acid are derived
for a dozen positions towards the massive star-forming regions MM1 and MM2 in the NGC 6334I complex, which areseparated by ∼4000 AU. Relative column densities of these molecules are also gathered from the literature for 13 otherstar-forming regions. In this combined dataset, a clear bi-modal distribution is observed in the relative column densities
of glycolaldehyde and methyl formate. No such distribution is evident with acetic acid. The two trends are comprisedof star-forming regions with a variety of masses, suggesting that there must be some other common parameter thatis heavily impacting the formation of glycolaldehyde. This is indicative of some demonstrable differentiation in thesecores; studying the abundances of these isomers may provide a clue as to the integral chemical processes ongoing in avariety of protostellar environments.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1907.13551

A Survey for New Members of Taurus from Stellar to Planetary Masses

13 T.L. Esplin1,2 and K.L. Luhman3,4
1

Steward Observatory, University of Arizona, Tucson, AZ, 85719, USA; 2 Strittmatter Fellow; 3 Department of
Astronomy and Astrophysics, The Pennsyl- vania State University, University Park, PA 16802, USA; 4 Center for
Exoplanets and Habitable Worlds, The Pennsyl- vania State University, University Park, PA 16802, USA
E-mail contact: taranesplin at email.arizona.edu
We present a large sample of new members of the Taurus star-forming region that extend from stellar to planetary
masses. To identify candidate members at substellar masses, we have used color-magnitude diagrams and proper9motions measured with several wide-field optical and infrared (IR) surveys. At stellar masses, we have considered thecandidate members that were found in a recent analysis of high-precision astrometry from the Gaia mission. Using
new and archival spectra, we have measured spectral types and assessed membership for these 161 candidates, 79 ofwhich are classified as new members. Our updated census of Taurus now contains 519 known members. According
to Gaia data, this census should be nearly complete for spectral types earlier than M6–M7 at AJ < 1. For a large
field encompassing ∼72% of the known members, the census should be complete for K < 15.7 at AJ < 1.5, whichcorresponds to ∼5–13 MJup for ages of 1–10 Myr based on theoretical evolutionary models. Our survey has doubled
the number of known members at greater or equal to M9 and has uncovered the faintest known member in MK , whichshould have a mass of ∼3–10 MJup for ages of 1–10 Myr. We have used mid-IR photometry from the Spitzer Space
Telescope and the Wide-field Infrared Survey Explorer to determine whether the new members exhibit excess emissionthat would indicate the presence of circumstellar disks. The updated disk fraction for Taurus is ∼0.7 at less than orequal to M3.5 and ∼0.4 at >M3.5.
Accepted by AJ
http://arxiv.org/pdf/1907.00055

14

Circumbinary disk inner radius as a diagnostic for disk–binary misalignment
Alessia Franchini1 , Stephen H. Lubow2 and Rebecca G. Martin1
1

Department of Physics and Astronomy, University of Nevada 4505 South Maryland Parkway, Las Vegas, NV 89154,
USA; 2 Space Telescope Science Institute 3700 San Martin Drive, Baltimore, MD 21218, USA

E-mail contact: alessia.franchini at unlv.edu
We investigate the misalignment of the circumbinary disk around the binary HD 98800 BaBb with eccentricity e ≈ 0.8.
Kennedy et al. (2019) observed the disk to be either at an inclination of 48◦ or polar aligned to the binary orbital plane.
Their simulations showed that alignment from 48◦ to a polar configuration can take place on a shorter timescale than
the age of this system. We perform hydrodynamical numerical simulations in order to estimate the cavity size carved
by the eccentric binary for different disk inclinations as an independent check of polar alignment. Resonance theory
suggests that torques on the inner parts of a polar disk around such a highly eccentric binary are much weaker than in
the coplanar case, indicating a significantly smaller central cavity than in the coplanar case. We show that the inferredinner radius (from carbon monoxide measurements) of the accretion disk around BaBb can exclude the possibility of
it being mildly inclined with respect to the binary orbital plane and therefore confirm the polar configuration. This
study constitutes an important diagnostic for misaligned circumbinary disks, since it potentially allows us to infer the
disk inclination from observed gas disk inner radii.
Accepted by ApJL
http://arxiv.org/pdf/1907.05437

15

Dust Transport and Processing in Centrifugally Driven Protoplanetary Disk Winds
Steven Giacalone1 , Seth Teitler2 , Arieh Königl3 , Sebastiaan Krijt4 and Fred J. Ciesla5
1Department of Astronomy, University of California Berkeley, 501 Campbell Hall, Berkeley, CA 94720, USA; 2 National
Academic Quiz Tournaments, LLC, 11521 W 69th Street, Shawnee, KS 66203, USA; 3 Department of Astronomy andAstrophysics,The University of Chicago, 5640 S Ellis Ave, Chicago, IL 60637, USA; 4 Department of Astronomy and
Steward Observatory, The University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721, USA; 5 Department of
the Geophysical Sciences, The University of Chicago, 5734 S Ellis Avenue, Chicago, IL 60637, USA
E-mail contact: akonigl at uchicago.edu
There is evidence that protoplanetary disks—including the protosolar one—contain crystalline dust grains on spatial
scales where the dust temperature is lower than the threshold value for their formation through thermal annealing ofamorphous interstellar silicates. We interpret these observations in terms of an extended, magnetocentrifugally driven
disk wind that transports grains from the inner disk—where they are thermally processed by the stellar radiation
after being uplifted from the disk surfaces—to the outer disk regions. For any disk radius r there is a maximum grain
size amax (r) that can be uplifted from that location: grains of size a ≪ amax are carried away by the wind, whereas
those with a <∼ amax reenter the disk at larger radii. A significant portion of the reentering grains converge to—and10

subsequently accumulate in—a narrow region just beyond rmax (a), the maximum radius from which grains of size a
can be uplifted. We show that this model can account for the inferred crystallinity fractions in classical T Tauri and
Herbig Ae disks and for their indicated near constancy after being established early in the disk evolution. It is also
consistent with the reported radial gradients in the mean grain size, crystallinity, and crystal composition. In addition,
this model yields the properties of the grains that remain embedded in the outflows from protoplanetary disks andnaturally explains the inferred persistence of small grains in the surface layers of these disks.
Accepted by ApJ
http://arxiv.org/pdf/1907.04961

16

Fragmentation of Filamentary Cloud Permeated by Perpendicular Magnetic Field II.
Dependence on the Initial Density Profile
Tomoyuki Hanawa1 , Takahiro Kudoh2 and Kohji Tomisaka3,4
1

Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba, Chiba 263-8522, Japan; 2 Faculty of
Education, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, Nagasaki 852-8521, Japan; 3 Division of Theoretical
Astronomy, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 Departmentof Astronomical Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies),
Mitaka, Tokyo 181-8588, Japan
E-mail contact: hanawa at faculty.chiba-u.jp
We examine the linear stability of a filamentary cloud permeated by a perpendicular magnetic field. The initial
magnetic field is assumed to be uniform and perpendicular to the cloud axis. The model cloud is assumed to havea Plummer-like density profile and to be supported against the self-gravity by turbulence. The effects of turbulence
are taken into account by enhancing the effective pressure of a low density gas. We derive the effective pressure as afunction of the density from the condition of the hydrostatic balance. It is shown that the model cloud is more unstableagainst radial collapse, when the radial density slope is shallower. When the magnetic field is mildly strong, the radialcollapse is suppressed. If the displacement vanishes in the region very far from the cloud axis, the model cloud is
stabilized completely by a mildly strong magnetic field. If rearrangement of the magnetic flux tubes is permitted,
the model cloud is unstable even when the magnetic field is extremely strong. The stability depends on the outerboundary condition as in case of the isothermal cloud. The growth rate of the rearrangement mode is smaller when
the radial density slope is shallower.
Accepted by ApJ
http://arxiv.org/pdf/1907.03384

17

Formation of rocky and icy planetesimals inside and outside the snow line: Effects ofdiffusion, sublimation and back-reaction
Ryuki Hyodo1 , Shigeru Ida1 , and Sébastien Charnoz2
1

Earth-Life Science Institute/Tokyo Institute of Technology, 2-12-1 Tokyo, Japan; 2 Institut de Physique du Globe/Université
Paris Diderot 75005 Paris, France
E-mail contact: hyodo at elsi.jp
It is important to clarify where and when rocky and icy planetesimals are formed in a viscously evolving disk. We wish
to understand how local runaway pile-up of solids occurs inside or outside the snow line. We assume an icy pebble
contains micron-sized silicate grains that are uniformly mixed with ice and are released during the ice sublimation.
Using a local one-dimensional code, we solve the radial drift and the turbulent diffusion of solids and the water vapor,taking account of their sublimation/condensation around the snow line. We systematically investigate effects of backreactions of the solids to gas on the radial drift and diffusion of solids, scale height evolution of the released silicate
particles, and possible difference in effective viscous parameters between that for turbulent diffusion (αtur ) and thatfor the gas accretion rate onto the central star (αacc ). We study the dependence on the ratio of the solid mass flux tothe gas (Fp/g ). We show that the favorable locations for the pile-up of silicate grains and icy pebbles are the regionsin the proximity of the water snow line inside and outside it, respectively. We found that runaway pile-ups occur
when both the back-reactions for radial drift and diffusion are included. In the case with only the back-reaction for11the radial drift, no runaway pile-up is found except for extremely high pebble flux, while the condition of streaming
instability can be satisfied for relatively large Fp/g as found in the past literatures. If the back-reactions for radial
diffusion is considered, the runaway pile-up occurs for reasonable value of pebble flux. The runaway pile-up of silicate
grains that would lead to formation of rocky planetesimals occurs for αtur ≪ αacc , while the runaway pile-up of icy
pebbles is favored for αtur ∼ αacc .
Accepted by A&A
http://arxiv.org/pdf/1907.04621

18

New constraints on the dust and gas distribution in the LkCa 15 disk from ALMA
Sheng Jin1 , Andrea Isella2 , Pinghui Huang1,2,3,4 , Shengtai Li3 , Hui Li3 and Jianghui Ji1
1

CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing
210008, China; 2 Department of Physics and Astronomy, Rice University, 6100 Main St., Houston, TX 77005, USA; 3
Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; 4 University of Chinese Academyof Sciences, Beijing 100049, Peoples Republic of China
E-mail contact: shengjin at pmo.ac.cn
We search a large parameter space of the LkCa 15’s disk density profile to fit its observed radial intensity profile of12
CO (J = 3–2) obtained from ALMA. The best-fit model within the parameter space has a disk mass of 0.1 M⊙(using an abundance ratio of 12 CO/H2 = 1.4 × 10−4 in mass), an inner cavity of 45 AU in radius, an outer edge at∼600 AU, and a disk surface density profile follows a power-law of the form ρr ∝ r−4 . For the disk density profiles
that can lead to a small reduced χ2 of goodness-of-fit, we find that there is a clear linear correlation between the disk
mass and the power-law index γ in the equation of disk density profile. This suggests that the 12 CO disk of LkCa 15
is optically thick and we can fit its 12 CO radial intensity profile using either a lower disk mass with a smaller γ or ahigher disk mass with a bigger γ. By comparing the 12 CO channel maps of the best-fit model with disk models withhigher or lower masses, we find that a disk mass of ∼0.1 M⊙ can best reproduce the observed morphology of the 12 CO
channel maps. The dust continuum map at 0.87 mm of the LkCa 15 disk shows an inner cavity of the similar sizeof the best-fit gas model, but its out edge is at ∼200 AU, much smaller than the fitted gas disk. Such a discrepancy
between the outer edges of the gas and dust disks is consistent with dust drifting and trapping models.
Accepted by ApJ
http://arxiv.org/pdf/1907.00571

19

Dusty disk winds at the sublimation rim of the highly inclined, low mass YSO
SU Aurigae
A. Labdon1 , S. Kraus1 , C. Davies1 , A. Kreplin1 , J. Kluska1 , T. Harries1 , J. Monnier2 , T. ten Brummelaar3 ,F. Baron4 , R. Millan-Gabet5 , B. Kloppenberg4, J. Eisner6 , J. Sturmann3 and L. Sturnann4
1

University of Exeter, School of Physics and Astronomy, Astrophysics Group, Stocker Road, Exeter, EX4 4QL, UK;
University of Michigan, Dept of Astronomy, S University Ave, Ann Arbor, MI 48109, USA; 3 The CHARA Array ofGeorgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023, USA; 4 Department of Physics andAstronomy, Georgia State University, Atlanta, GA, USA; 5 IPAC, California Institute of Technology, Pasadena, CA,
91125, USA; 6 Steward Observatory, University of Arizona, Tucson, AZ, 85721, USA
2E-mail contact: al612 at exeter.ac.uk

T Tauri stars are low-mass young stars whose disks provide the setting for planet formation. Despite this, theirstructure is poorly understood. We present new infrared interferometric observations of the SU Aurigae circumstellar
environment that offer resolution that is three times higher and a better baseline position angle coverage than previous
observations. We aim to investigate the characteristics of the circumstellar material around SU Aur, constrain the disk
geometry,The CHARA array offers unique opportunities for long baseline observations, with baselines
ur7-290.4
up0Td[ea [(to)-5.8U93(s)-3.4853

disks. Our implementation is motivated by theoretical models of dusty disk winds, where magnetic field lines drive
dust above the disk plane close to the sublimation zone. Image reconstruction reveals an inclined disk with slightasymmetry along its minor-axis, likely due to inclination effects obscuring the inner disk rim through absorption ofincident star light on the near-side and thermal re-emission and scattering of the far-side. Geometric modelling ofa skewed ring finds the inner rim at 0.17 ± 0.02 au with an inclination of 50.9 ± 1.0◦ and minor axis position angle
60.8 ± 1.2◦. Radiative transfer modelling shows a flared disk with an inner radius at 0.18 au which implies a grain sizeof 0.4 µm assuming astronomical silicates and a scale height of 15.0 au at 100 au. Among the tested radiative transfer
models, only the dusty disk wind successfully accounts for the K-band excess by introducing dust above the mid-plane.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1905.11907

Effects of infall and outflow on massive star-forming regions

20 Qiang Li1,3, Jianjun Zhou1,2, Jarken Esimbek1,2, Yuxin He1,2, Willem Baan1,4 , Dalei Li1,2, Gang Wu1,2,
Xindi Tang1,2 , Weiguang Ji1 , Toktarkhan Komesh1,3,5 , Serikbek Sailanbek1,3,5
1

Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi 830011, P. R. China; 2 Key Laboratoryof Radio Astronomy, Chinese Academy of Sciences, Urumqi 830011, P. R. China; 3 University of the Chinese Academyof Sciences, Beijing 100080, P. R. China; 4 Netherlands Institute for Radio Astronomy, 7991 PD Dwingeloo, The
Netherlands; 5 Department of Solid State Physics and Nonlinear Physics, Faculty of Physics and Technology, ALFarabi Kazakh National University, Almaty 050040, Kazakhstan
E-mail contact: liqiang at xao.ac.cn
A total of 188 high-mass outflows have been identified from a sample of 694 clumps from the Millimetre Astronomy
Legacy Team 90 GHz survey, representing a detection rate of approximately 27%. The detection rate of outflows
increases from the protostellar stage to the H II stage, but decreases again at the photodissociation (PDR) stage suggesting that outflows are being switched off during the PDR stage. An intimate relationship is found between outflow
action and the presence of masers, and water masers appear together with 6.7 GHz methanol masers. Comparing theinfall detection rate of clumps with and without outflows, we find that outflow candidates have a lower infall detection
rate. Finally, we find that outflow action has some influence on the local environment and the clump itself, and thisinfluence decreases with increasing evolutionary time as the outflow action ceases.
Accepted by MNRAS
http://arxiv.org/pdf/1907.10224

The GeV emission in the field of the star-forming region W30 revisited

21 Bing Liu1,2, Rui-zhi Yang2 , Xiao-na Sun1, Felix Aharonian2,3,4,5, and Yang Chen1,6
1School of Astronomy & Space Science, Nanjing University, 163 Xinlin Avenue, Nanjing 210023, China; 2 Max-PlanckInstitut für Kernphysik, P.O. Box 103980, 69029 Heidelberg, Germany; 3 Dublin Institute for Advanced Studies,
31 Fitzwilliam Place, Dublin 2, Ireland; 4 Gran Sasso Science Institute, 7 viale Francesco Crispi, 67100 L’Aquila(AQ), Italy; 5 MEPHI, Kashirskoe shosse 31, 115409 Moscow, Russia; 6 Key Laboratory of Modern Astronomy andAstrophysics, Nanjing University, Ministry of Education, China
E-mail contact: liubing1326 at foxmail.com
We present a detailed study of the γ-ray emission from the direction of the star-forming region W30 based on a decadeof the Fermi Large Area Telescope data in the 0.3–300 GeV photon energy range. The morphological and spectral
analyses allow us to resolve the γ-ray emission into two extended structures from different origins. One of them mostly
overlaps with the supernova remnant (SNR) G8.7−0.1 and has a soft spectrum that resembles with the spectra of othermiddle-aged SNRs interacting with molecular clouds. The other shows remarkable spatial and spectral consistency
with the TeV emission from HESS J1804−216, and its spectrum could be naturally explained by inverse Compton
scattering of electrons like a number of TeV gamma-ray emitting pulsar wind nebulae. Thus we attribute this source
to the nebula around the pulsar PSR J1803−2137.
Accepted by ApJ
http://arxiv.org/pdf/1907.00180

13

Compact Disks in a High Resolution ALMA Survey of Dust Structures in the Taurus

22 Molecular Cloud

Feng Long1,2 , Gregory J. Herczeg1 , Daniel Harsono3 , Paola Pinilla4 , Marco Tazzari5 , Carlo F. Manara6 ,Ilaria Pascucci7 , Sylvie Cabrit8 , Brunella Nisini9, Doug Johnstone10 , Suzan Edwards11 , Colette Salyk12 ,Francois Menard13 , Giuseppe Lodato14 , Yann Boehler13 , Gregory N. Mace15 , Yao Liu16 , Gijs D.
Mulders17 , Nathanial Hendler7 , Enrico Ragusa18 , William J. Fischer19 , Andrea Banzatti7 , Elisabetta
Rigliaco20 , Gerrit van de Plas13 , Giovanni Dipierro18 , Michael Gully-Santiago21 and Ricardo LopezValdivia15
1

Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China; 2 Department of Astronomy, School of Physics, Peking University, Beijing 100871, China; 3 Leiden Observatory, Leiden University, P.O.
box 9513, 2300 RA Leiden, The Netherlands; 4 Department of Astronomy/Steward Observatory, The University of
Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 5 Institute of Astronomy, University of Cambridge,
Madingley Road, Cambridge CB3 0HA, UK; 6 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748
Garching bei München, Germany; 7 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA;
8
Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, F-75014 Paris, France; 9 INAFOsservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy; 10 NRC Herzberg Astronomy
and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada; 11 Five College Astronomy Department,
Smith College, Northampton, MA 01063, USA; 12 Vassar College Physics and Astronomy Department, 124 Raymond
Avenue, Poughkeepsie, NY 12604, USA; 13 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 14 Dipartimento di Fisica, Universita Degli Studi di Milano, Via Celoria, 16, I-20133 Milano, Italy; 15 McDonald Observatory
and Department of Astronomy, University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205,
USA; 16 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748, Garching, Germany; 17 Department of the Geophysical Sciences, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA;18
Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK; 19 Space Telescope Science
Institute Baltimore, MD 21218, USA; 20 INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122
Padova, Italy; 21 NASA Ames Research Center and Bay Area Environmental Research Institute, Moffett Field, CA
94035, USA
E-mail contact: longfengshine at gmail.com
We present a high-resolution (∼ 0.′′ 12, ∼ 16 au, mean sensitivity of 50 µJy beam−1 at 225 GHz) snapshot survey of
32 protoplanetary disks around young stars with spectral type earlier than M3 in the Taurus star-forming region using
Atacama Large Millimeter Array (ALMA). This sample includes most mid-infrared excess members that were notpreviously imaged at high spatial resolution, excluding close binaries and highly extincted objects, thereby providing amore representative look at disk properties at 1–2 Myr. Our 1.3 mm continuum maps reveal 12 disks with prominent
dust gaps and rings, 2 of which are around primary stars in wide binaries, and 20 disks with no resolved features atthe observed resolution (hereafter smooth disks), 8 of which are around the primary star in wide binaries. The smoothdisks were classified based on their lack of resolved substructures, but their most prominent property is that they are
all compact with small effective emission radii (Reff,95% < 50 au). In contrast, all disks with Reff,95% of at least 55 au
in our sample show detectable substructures. Nevertheless, their inner emission cores (inside the resolved gaps) have
similar peak brightness, power law profiles, and transition radii to the compact smooth disks, so the primary difference
between these two categories is the lack of outer substructures in the latter. These compact disks may lose their outerdisk through fast radial drift without dust trapping, or they might be born with small sizes. The compact dust disks,
as well as the inner disk cores of extended ring disks, that look smooth at the current resolution will likely show
small-scale or low-contrast substructures at higher resolution. The correlation between disk size and disk luminosity
correlation demonstrates that some of the compact disks are optically thick at millimeter wavelengths.
Accepted by ApJ
https://arxiv.org/pdf/1906.10809

23

Characterization of Ring Substructures in the Protoplanetary Disk of HD 169142 from
Multi-Wavelength ALMA Observations
Enrique Macı́as1 , Catherine Espaillat1 , Mayra Osorio2, Guillem Anglada2 , José M. Torrelles3 , Carlos
Carrasco-González4 , Mario Flock5 , Hendrik Linz5 , Gesa H.-M. Bertrang5 , Thomas Henning5 , José F.

14

Gómez2 , Nuria Calvet6 and William R. F. Dent7
1

Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA; 2 Institutode Astrofı́sica de Andalucı́a (CSIC) Glorieta de la Astronomı́a s/n E-18008 Granada, Spain; 3 Institut de Ciències
de l’Espai (CSIC) and Institut d’Estudis Espacials de Catalunya (IEEC), Can Magrans S/N, Cerdanyola del Vallès(Barcelona), Spain; 4 Instituto de Radioastronomı́a y Astrofı́sica UNAM, Apartado Postal 3-72 (Xangari), 58089
Morelia, Michoacán, Mexico; 5 Max-Planck Institute for Astronomy, Königstuhl 17, 69117, Heidelberg, Germany; 6
Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI4810, USA; 7 ALMA
JAO, Alonso de Cordova 3107, Santiago, Chile
E-mail contact: emacias at bu.edu
We present a detailed multi-wavelength characterization of the multi-ring disk of HD 169142. We report new ALMA
observations at 3 mm and analyze them together with archival 0.89 and 1.3 mm data. Our observations resolve
three out of the four rings in the disk previously seen in high-resolution ALMA data. A simple parametric model isused to estimate the radial profile of the dust optical depth, temperature, density, and particle size distribution. We
find that the multiple ring features of the disk are produced by annular accumulations of large particles, probably
associated with gas pressure bumps. Our model indicates that the maximum dust grain size in the rings is ∼ 1 cm,
with slightly flatter power-law size distributions than the ISM-like size distribution (p ∼ 3.5) found in the gaps. In
particular, the inner ring (∼ 26 au) is associated with a strong and narrow buildup of dust particles that could harbor
the necessary conditions to trigger the streaming instability. According to our analysis, the snowlines of the mostimportant volatiles do not coincide with the observed substructures. We explore different ring formation mechanisms
and find that planet-disk interactions are the most likely scenario to explain the main features of HD 169142. Overall,
our multi-wavelength analysis provides some of the first unambiguous evidence of the presence of radial dust traps in
the rings of HD 169142. A similar analysis in a larger sample of disks could provide key insights on the impact that24

eight secondary and one tertiary stars. The dust radii of disks around multiple stellar systems are smaller than thosearound single stars in the same stellar mass range and in the same region. The disks in multiple stellar systems havealso a steeper decay of the mm-continuum emission at the outer radius than disks around single stars, suggestive of the
impact of tidal truncation on the shape of the disks in multiple systems. However, the observed ratio between the dust
disk radii and the observed separation of the stars in the multiple systems is consistent with analytic predictions of
the effect of tidal truncation only if the eccentricities of the binaries are rather high (typically >0.5), or if the observed
dust radii are a factor of two smaller than the gas radii, as is typical for isolated systems. Similar high resolution
studies targeting the gaseous emission from disks in multiple stellar systems are required to resolve this question.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1907.03846

25

Massive stars in the young cluster VVV CL074
F. Martins1 , A.-N. Chené2 , J.-C. Bouret3 , J. Borissova4,5 , J. Groh6 , S. Ramı́rez Alegrı́a7 , and D.
Minniti8
1

LUPM, Université de Montpellier, CNRS, Place Eugène Bataillon, F-34095 Montpellier, France; 2 Gemini Observatory, Northern Operations Center, 670 N. A’ohoku Place, Hilo, Hawaii, 96720, USA; 3 Aix Marseille Université, CNRS,
CNES, LAM, Marseille, France; 4 Instituto de Fı́sica y Astronomı́a, U. de Valparaı́so, Av. Gran Bretaña 1111, Playa
Ancha, 5030 Casilla, Chile; 5 Millennium Institute of Astrophysics, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile; 6 Trinity College Dublin, The University of Dublin, Dublin 2, Ireland; 7 Centro de Astronomı́a (CITEVA),
Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile; 8 Departamento de Ciencias Fı́sicas,
Facultad de Ciencias Exactas, Universidad Andrés Bello, Av. Fernández Concha 700, Las Condes, Santiago, Chile
E-mail contact: fabrice.martins at umontpellier.fr
We obtained K-band spectroscopy of the brightest members of the cluster VVV CL074 in order to identify themassive star population. We also determined the stellar properties of the cluster’s massive stars to better quantify
the evolutionary sequences linking different types of massive stars. We collected integral field spectroscopy of selected
fields in the cluster VVV CL074 with SINFONI on the ESO/VLT. We performed a spectral classification based on the
K-band spectra and comparison to infrared spectral atlases. We determined the stellar parameters of the massive stars
from analysis with atmosphere models computed with the code CMFGEN. We uncover a population of 25 early-type(OB and Wolf-Rayet) stars, 19 being newly discovered by our observations out of which 15 are likely cluster members.
The cluster’s spectrophotometric distance is 10.2±1.6 kpc, placing it close to the intersection of the galactic bar andthe Norma arm, beyond the galactic center. This makes VVV CL074 one the farthest young massive clusters identified
so far. Among the massive stars population, three objects are Wolf-Rayet stars, the remaining are O and B stars.
From the Hertzsprung-Russell diagram we find that most stars have an age between 3 and 6 Myr according to the
Geneva evolutionary tracks. WN8 and WC8-9 stars are the descendants of stars with initial masses between 40 and
60 M⊙ . The massive star population of VVV CL074 is very similar to that of the cluster DBS2003-179 and to a lesser
extent to that of the Quintuplet cluster, indicating the same age. The central cluster of the Galaxy is ∼3 Myr older.
From the comparison of the massive stars populations in these four clusters, one concludes that galactic stars with an
initial mass in the range 40 to 60 M⊙ likely go through a WN8-9 phase.
Accepted by A&A
http://arxiv.org/pdf/1907.02357

26

Substructures in the Keplerian disc around the O-type (proto-)star G17.64+0.16
L. T. Maud1,2 , R. Cesaroni3 , M. S. N. Kumar4 , V. M. Rivilla3 , A. Ginsburg5 , P. D. Klaassen6 , D.
Harsono2 , A. Sanchez-Monge7 , A. Ahmadi8 , V. Allen9 , M. T. Beltran3 , H. Beuther8 , R. GalvanMadrid10 , C. Goddi2,11 , M. G. Hoare12 , M. R. Hogerheijde2,13, K. G. Johnston12 , R. Kuiper14 , L.
Moscadelli3, T. Peters15 , L. Testi1,3 , F. F. S. van der Tak16,17 and W. J. de Wit18
1

European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany; 2 Leiden
Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 3 INAF, Osservatorio Astrofisico
di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 4 Instituto de Astrofisica e Ciencias do Espao, Universidade do

16Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal; 5 National Radio Astronomy Observatory, 1003 LopezvilleRoad, Socorro, NM 87801, USA; 6 UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill,
Edinburgh EH9 3HJ, UK; 7 I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany;
8
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 9 NASA Goddard Space Flight
Center, Greenbelt, MD 20771, USA; 10 Universidad Nacional Autonoma de Mexico, Instituto de Radioastronomia y
Astrofisica, Morelia, Michoacan 58089, Mexico; 11 Department of Astrophysics/IMAPP, Radboud University, PO Box
9010, 6500 GL Nijmegen, The Netherlands; 12 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT,
UK; 13 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam,
The Netherlands; 14 Institute of Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, 72076
Tübingen, Germany; 15 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str.1, 85748 Garching, Germany;
16
Kapteyn Astronomical Institute, University of Groningen, The Netherlands; 17 SRON, Landleven 12, 9747 AD
Groningen, The Netherlands; 18 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla, 19001
Santiago de Chile, Chile
E-mail contact: lmaud at eso.org
We present the highest angular resolution (20x15mas - 44x33au) atacama Large Millimeter/sub-millimeter Array(ALMA) observations that are currently possible of the proto-O-star G17.64+0.16 in Band 6. The Cycle 5 observations
with baselines out to 16 km probe scales <50 au and reveal the rotating disc around G17.64+0.16, a massive forming
O-type star. The disc has a ring-like enhancement in the dust emission that is especially visible as arc structures tothe north and south. The Keplerian kinematics are most prominently seen in the vibrationally excited water line, H2O
ν2 = 1 (Eu = 3461.9 K). The mass of the central source found by modelling the Keplerian rotation is consistent with45±10 M⊙ . The H30 α (231.9 GHz) radio-recombination line and the SiO (5-4) molecular line were detected at up tothe ∼10σ level. The estimated disc mass is 0.6-2.6 M⊙ under the optically thin assumption. Analysis of the Toomre
Q parameter in the optically thin regime indicates that the disc stability is highly dependent on temperature. The
disc currently appears stable for temperatures >150 K; this does not preclude that the substructures formed earlier
through disc fragmentation.
Accepted by A&A
http://arxiv.prg/pdf/1906.06548

27

IC 4665 DANCe I. Members, empirical isochrones, magnitude distributions, present-day
system mass function, and spatial distribution
N. Miret-Roig1, H. Bouy1 , J. Olivares1 , L.M. Sarro2 , M. Tamura3,4,5 , L. Allen6 , E. Bertin7 , S. Serre1 ,A. Berihuete8 , Y. Beletsky9 , D. Barrado10 , N. Huélamo10 , J.-C. Cuillandre11 , E. Moraux12 , and J.
Bouvier12
1

Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac,
France; 2 Depto. de Inteligencia Artificial , UNED, Juan del Rosal, 16, 28040 Madrid, Spain; 3 Department of
Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 4 National Astronomical
Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588, Japan; 5 Astrobiology Center, 2-21-1, Osawa, Mitaka,
Tokyo, 181-8588, Japan; 6 National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719,
USA; 7 Institut d’Astrophysique de Paris, CNRS UMR 7095 and UPMC, 98bis bd Arago, F-75014 Paris, France;
8
Depto. Statistics and Operations Research, University of Cádiz, Campus Universitario Rı́o San Pedro s/n, 11510
Puerto Real, Cádiz, Spain; 9 Las Campanas Observatory, Carnegie Institution of Washington, Colina el Pino, 601
Casilla, La Serena, Chile; 10 Centro de Astrobiologı́a (CSIC-INTA), ESAC Campus, Camino Bajo del Castillo s/n,
28692 Villanueva de la Cañada, Madrid, Spain; 11 AIM Paris Saclay, CNRS/INSU, CEA/Irfu, Université Paris Diderot,
Orme des Merisiers, France; 12 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
E-mail contact: nuria.miret-roig at u-bordeaux.fr
Context. The study of star formation is extremely challenging due to the lack of complete and clean samples of young,nearby clusters, and star forming regions. The recent Gaia DR2 catalogue complemented with the deep, ground based
COSMIC DANCe catalogue offers a new database of unprecedented accuracy to revisit the membership of clusters
and star forming regions. The 30 Myr open cluster IC 4665 is one of the few well-known clusters of this age and it isan excellent target where to test evolutionary models and study planetary formation.
Aims. We aim to provide a comprehensive membership analysis of IC 4665 and to study the following properties:
17

empirical isochrones, distance, magnitude distribution, present-day system mass function, and spatial distribution.
Methods. We use the Gaia DR2 catalogue together with the DANCe catalogue to look for members using a probabilistic
model of the distribution of the observable quantities in both the cluster and background populations.
Results. We obtain a final list of 819 candidate members which cover a 12.4 magnitude range (7 < J < 19.4). We
find that 50% are new candidates, and we estimate a conservative contamination rate of 20%. This unique sample ofmembers allows us to obtain a present-day system mass function in the range of 0.02–6 M⊙ , which reveals a numberof details not seen in previous studies. In addition, they favour a spherically symmetric spatial distribution for thisyoung open cluster.
Conclusions. Our membership analysis represents a significant increase in the quantity and quality (low-contamination)with respect to previous studies. As such, it offers an excellent opportunity to revisit other fundamental parameterssuch as the age.
Accepted by A&A
http://arxiv.org/pdf/1907.10064

What is wrong with steady accretion discs?

28 C.J. Nixon1 and J.E. Pringle1,2
1

Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK; 2 Institute of Astronomy,
Madingley Road, Cambridge, CB3 0HA, UK
E-mail contact: cjn at leicester.ac.uk
In a standard, steady, thin accretion disc, the radial distribution of the dissipation of the accretion energy is determined
simply by energy considerations. Here we draw attention to the fact that while the (quasi-)steady discs in dwarf novae
in outburst are in agreement with the expected emission distribution, the steady discs in the nova-like variables arenot. We note that essentially the only difference between these two sets of discs is the time for which they havebeen in the high viscosity, high accretion rate state. In such discs, the major process by which angular momentumis transported outwards is MHD turbulence. We speculate that such turbulence gives rise to corona-like structures(here called magnetically controlled zones, or MCZs) which are also able to provide non-negligible angular momentum
transport, the magnitude of which depends on the spatial scale L of the magnetic field structures in such zones. For
short-lived, high accretion rate discs (such as those in dwarf novae) we expect L ∼ H and the MCZ to have little
effect. But, with time (such as in the nova-like variables) an inverse cascade in the MHD turbulence enables L, andthe net effect of the MCZ, to grow. We present a simple toy model which demonstrates that such ideas can provide
an explanation for the difference between the dwarf novae and the nova-like variable discs.
Accepted by A&A
http://arxiv.org/pdf/1907.08206

Ambipolar diffusion and the molecular abundances in prestellar cores

29 Felix D. Priestley1, James Wurster2 and Serena Viti3
1

School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, UK; 2
School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK; 3 Department of Physics
and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
E-mail contact: priestleyf at cardiff.ac.uk

We investigate differences in the molecular abundances between magnetically super- and sub-critical prestellar cores,
performing three-dimensional non-ideal magnetohydrodynamical (MHD) simulations with varying densities and magnetic field strengths, and post-processing the results with a time-dependent gas-grain chemical code. Most molecularspecies show significantly more central depletion in subcritical models, due to the longer duration of collapse. However,the directly observable quantities — the molecule to hydrogen column density ratios — are generally too similar for
observational data to discriminate between models. The profiles of N2 H+ and HCO+ show qualitative differences
between supercritical and subcritical models on scales of 0.01 pc, which may allow the two cases to be distinguished.
However, this requires knowledge of the hydrogen column density, which is not directly measureable, and predicted
line intensity profiles from radiative transfer modelling are similar for these molecules. Other commonly observed
18species, such as HCN and CH3 OH, have line intensity profiles which differ more strongly between models, and so are
more promising as tracers of the mechanism of cloud collapse.
Accepted by MNRAS
http://arxiv.org/pdf/1907.02736

30

31

Probing CO and N2

The Massive Star-Forming Regions Omnibus X-Ray Catalog, Third Installment

32 Leisa K. Townsley1, Patrick S. Broos1, Gordon P. Garmire2 and Matthew S. Povich3
1

Pennsylvania State University, Department of Astronomy & Astrophysics, 525 Davey Laboratory, University Park,PA 16802, USA; 2 Huntingdon Institute for X-ray Astronomy, LLC, 10677 Franks Road, Huntingdon, PA 16652, USA;3
California State Polytechnic University, Department of Physics & Astronomy, 3801 West Temple Avenue, Pomona,
CA 91768, USA
E-mail contact: townsley at astro.psu.edu
We offer to the star formation community the third installment of the Massive Star-forming Regions (MSFRs) Omnibus
X-ray Catalog (MOXC3), a compilation of X-ray point sources detected in 50 archival Chandra/ACIS observations of
14 Galactic MSFRs and surrounding fields. The MOXC3 MSFRs are NGC 2264, NGC 6193, RCW 108-IR, Aur OB1,
DR15, NGC 6231, Berkeley 87, NGC 6357, AFGL 4029, h Per (NGC 869), NGC 281, Onsala 2S, G305, and RCW
49 (Wd 2); they have distances of 0.7 kpc to 4.2 kpc. Most exhibit clumped or clustered young stellar populations;several contain at least two distinct massive young stellar clusters. The total MOXC3 catalog includes 27,923 X-ray
point sources. We take great care to identify even the faintest X-ray point sources across these fields. This allows us toremove this point source light, revealing diffuse X-ray structures that pervade and surround MSFRs, often generated
by hot plasmas from massive star feedback. As we found in MOXC1 and MOXC2, diffuse X-ray emission is traceable
in all MOXC3 MSFRs; here we perform spectral fitting to investigate the origins of selected diffuse regions. Onceagain, MOXC3 shows the value of high spatial resolution X-ray studies of MSFRs enabled by Chandra.
Accepted by ApJ Supplements
https://arxiv.org/pdf/1907.13126

WISE Discovery of Mid-infrared Variability in Massive Young Stellar Objects

33 Mizuho Uchiyama1 and Kohei Ichikawa2,3
1

National Astronomical Observatory of Japan,2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 Frontier ResearchInstitute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan; 3 Astronomical Institute, Graduate
School of Science Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai 980-8578, Japan
E-mail contact: mizuho.uchiyama at nao.ac.jp
We systematically investigate the mid-infrared (MIR; λ > 3 µm) time variability of uniformly selected ∼ 800 massive
young stellar objects (MYSOs) from the Red MSX Source (RMS) survey. Out of the 806 sources, we obtain reliable9-year-long MIR magnitude variability data of 331 sources at the 3.4 µm (W1) and 4.6 µm (W2) bands by crossmatching the MYSO positions with ALLWISE and NEOWISE catalogs. After applying the variability selections
using ALLWISE data, we identify 5 MIR-variable candidates. The light curves show various classes, with the periodic,
plateau-like, and dipper features. Out of the obtained two color-magnitude diagram of W1 and W1−W2, one shows“bluer when brighter and redder when fainter” trends in variability, suggesting change in extinction or accretion rate.
Finally, our results show that G335.9960−00.8532 (hereafter, G335) has a periodic light curve, with a ≈ 690-day
cycle. Spectral energy density model fitting results indicate that G335 is a relatively evolved MYSO; thus, we may
be witnessing the very early stages of a hyper- or ultra-compact HII region, a key source for understanding MYSO
evolution.
Accepted by ApJ
https://arxiv.org/pdf/1907.13244

Thermal Infrared Imaging of MWC 758 with the Large Binocular Telescope: Planetary

34 Driven Spiral Arms?

Kevin Wagner1,2 , Jordan M. Stone1,3 , Eckhart Spalding1 , Daniel Apai1,2,4 , Ruobing Dong5 , Steve
Ertel6,1 , Jarron Leisenring1 , & Ryan Webster1
1
Steward Observatory, University of Arizona; 2 NASA NExSS Earths in Other Solar Systems Team; 3 NASA Hubble
Postdoctoral Fellow; 4 Lunar and Planetary Laboratory, University of Arizona; 5 University of Victoria, British
Columbia, Canada; 6 Large Binocular Telescope Observatory, University of Arizona20

E-mail contact: kwagner at as.arizona.edu
Theoretical studies suggest that a giant planet around the young star MWC 758 could be responsible for driving thespiral features in its circumstellar disk. Here, we present a deep imaging campaign with the Large Binocular Telescopewith the primary goal of imaging the predicted planet. We present images of the disk in two epochs in the L′ filter(3.8 µm) and a third epoch in the M ′ filter (4.8 µm). The two prominent spiral arms are detected in each observation,
which constitute the first images of the disk at M ′ , and the deepest yet in L′ (∆L′ = 12.1 exterior to the disk at 5σ
significance). We report the detection of a S/N∼3.9 source near the end of the Sourthern arm, and, from the source’s
detection at a consistent position and brightness during multiple epochs, we establish a ∼90% confidence-level thatthe source is of astrophysical origin. We discuss the possibilities that this feature may be a) an unresolved disk feature,and b) a giant planet responsible for the spiral arms, with several arguments pointing in favor of the latter scenario.
We present additional detection limits on companions exterior to the spiral arms, which suggest that a <∼4 MJup planet
exterior to the spiral arms could have escaped detection. Finally, we do not detect the companion candidate interior
to the spiral arms reported recently by Reggiani et al. (2018), although forward modelling suggests that such a source
would have likely been detected.
Accepted by ApJ
http://arxiv.org/pdf/1907.06655

Orbital Evolution of a Circumbinary Planet in a Gaseous Disk

35 Akihiro Yamanaka1 , Takanori Sasaki1
1

Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake- cho, Sakyo-ku, Kyoto, 606-8502, Japan

E-mail contact: akihiro at kusastro.kyoto-u.ac.jp
Sub-Jupiter classed circumbinary planets discovered in close-in binary systems have orbits just beyond the dynamicallyunstable region, which is determined by the eccentricity and mass ratio of the host binary stars. These planets are
assumed to have formed beyond the snow line and migrated to the current orbits rather than forming in situ. We
propose a scenario in which a planet formed beyond the snow line and migrated to the inner edge of the circumbinary
disk, which was within the unstable area, and then moved to the current orbit through outward transportation.
This outward transportation is driven by the balance of orbital excitation of the central stars inside the gravitationallyunstable region and damping by the gas-drag force. We carried out N-body simulations with a dissipating circumbinary
protoplanetary disk for binary systems with different eccentricities and mass ratios. Planets are more likely to achievea stable orbit just beyond the unstable region in less eccentric binary systems. This result is not as sensitive to mass
ratio as it is to eccentricity. These dependencies are consistent with the data from observed binary systems hosting
circumbinary planets. We find CBPs’ orbits close to the instability boundaries are explained by our orbital evolution
scenario.
Accepted by Earth, Planets and Space
http://arxiv.org/pdf/1907.09793

36

Northern Galactic Molecular Cloud Clumps in Hi-GAL: Clump and Star Formation
within Clouds
Erika Zetterlund1 , Jason Glenn1 , Erik Rosolowsky2
1

CASA, Department of Astrophysical and Planetary Sciences, University of Colorado 389-UCB, Boulder, CO 80309,
USA; 2 Department of Physics, University of Alberta, Edmonton, Alberta, Canada

E-mail contact: erika.zetterlund at colorado.edu
We investigate how the properties of Galactic giant molecular clouds (GMCs) and their denser substructures (clumps)
correlate with the local star formation rate. We trace clouds using the 12 CO (3–2) transition, as observed by the COHigh Resolution Survey (COHRS). We identify their constituent clumps using thermal dust emission, as observed by
the Herschel infrared GALactic plane survey (Hi-GAL). We estimate star formation rates in these clouds using 70µm emission. In total, we match 3,674 clumps to 473 clouds in position-position-velocity space spanning the Galactic
longitude range 10◦ < ℓ < 56◦ . We find that more massive clouds produce more clumps and more massive clumps.

21

These clumps have average number densities an order of magnitude greater than their host clouds. We find a mean
clump mass fraction of 0.20+0.13−0.10 . This mass fraction weakly varies with mass and mass surface density of clouds, andshows no clear dependence on the virial parameter and line width of the clouds. The average clump mass fraction is
only weakly dependent upon Galactocentric radius. Although the scatter in our measured properties is significant,the star formation rate for clouds is independent of clump mass fraction. However, there is a positive correlation
between the depletion times for clouds and clump mass fraction. We find a star formation efficiency per free fall timeof ǫff = 0.15% for GMCs but ǫff = 0.37% for clumps.
Accepted by ApJ
http://arxiv.org/pdf/1907.00150

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send the editor your new address. If the Newsletterbounces back from an address for three consecutive
months, the address is deleted from the mailing list.

22

Dissertation Abstracts

The physics and chemistry of envelopes and disks around young
protostars
Elizabeth Artur de la Villarmois

Thesis work conducted at: Centre for Star and Planet Formation, Niels Bohr Institute, University of Copenhagen
Current address: Øster Voldgade 5–7, DK-1350, Copenhagen K, Denmark
Electronic mail: elizabeth.artur@nbi.ku.dk
Ph.D dissertation directed by: Jes K. Jørgensen and Lars E. Kristensen
Ph.D degree awarded: June 2019

Important clues about the formation of our own Solar System are revealed by studying other young sources that are
currently forming. The study of low-mass protostars in different evolutionary stages is, therefore, essential to link
their physical and chemical evolution to what we know about the Solar System. In particular, low-mass protostars
are associated with disks, where planets form. Very little is known about the initial physical and chemical conditions
for planet formation and the relationship between the physical and chemical structures of embedded disks. Therefore,
the study of the physics and chemistry at small scales may provide important clues about how the material falls
from the envelope to the disk and accretes from the disk into the protostar and what is the physico-chemical link
between deeply embedded stages and the onset of planet formation. The goal of this thesis is to study the physics
and chemistry at play at small scales (disk scales) towards low-mass protostars in order to constrain the mass flow
and identify the physical and chemical processes that dominate at these scales. The study of the formation andevolution of disks is challenging since they are embedded in the parental cloud and are relatively small in size (≤700AU), requiring observations with high sensitivity and angular resolution. For this, we observe a sample of Class I
protostars using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Submillimeter Array (SMA)
to characterise their physical and chemical structures. Class I sources have been chosen since disks are expected
to have been formed at this stage and because they serve as a link between the deeply embedded Class 0 sources
and the emergence of protoplanetary disks. The results from these studies are presented in three papers (publishedin international journals). We find an empirical linear correlation between the bolometric luminosity and the massaccretion rate, suggesting that more massive protostars accrete material with a higher accretion rate. The mean massaccretion estimated for a sample of 13 Class I sources is 2.4 × 10−7 M⊙ yr−1 . This value is lower than the expected
if the accretion is constant in time and rather points to a scenario of accretion occurring in bursts. In addition, thislow mass accretion rate provides observational evidence that a typical protostar will spend most of its lifetime in aquiescent state of accretion. The formation and evolution of the disk are reflected on the chemical structure of theenvelope, from large to small scales. The disk shields material beyond its extent where cold temperature tracers are23

detected, such as DCO+ . Furthermore, the non detection of CH3 OH suggests that material from the inner envelope
follows the flattened structure of the disk and, since less material is exposed to high temperatures, desorption ofcomplex-organic molecules is not efficient. In addition, compact emission and large line widths of warm SO2 emission
are consistent with the presence of accretion shocks produced at the interface between the inner envelope and thedisk surface. Class I sources show a physical and chemical link between deeply embedded Class 0 sources and more
evolved Class II sources. The gas column density decreases as the system evolves, which is reflected in the emissionof high-density tracers such as CO isotopologues. The formation and evolution of the disk, together with the increaseof the outflow-opening angle as the system evolves, allow the UV radiation from the central protostar to reach thesurface layers of the disk, promoting the photodissociation of molecules and enhancing the abundance of others, forexample, CN. On the other hand, the chemistry of Class 0 sources can be preserved, to some extent, in Class II sources
mainly towards the disk midplane and beyond its extension, where the shielding is efficient.

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.

24New Jobs

Applications Now Accepted for 51 Pegasi b Fellowships(with U. Michigan as a potential Host Institution)
Now is a great time to study exoplanets at the University of Michigan! We are pleased to announce that the Universityof Michigan is an approved Host Institution for the 51 Pegasi b Fellowship Program, sponsored by the Heising-Simons
Foundation. Applications are due September 20, 2019. More information can be found at:https://www.hsfoundation.org/programs/science/51-pegasi-b-fellowship/
The University of Michigan is home to several research groups focused on planet formation, exoplanet science, andsolar system exploration, utilizing theoretical, numerical, and observational methods, including the development ofnovel instrumentation. Potential faculty hosts include Fred Adams, Ted Bergin, Nuria Calvet, Lia Corrales, Elena
Gallo, Lee Hartmann, Michael Meyer, John Monnier, Emily Rauscher, as well as others. We also anticipate that
additional post-doctoral research positions in the areas of planet formation and exoplanets will be advertised this fall.
The University of Michigan hosts a vibrant astrophysics research community within the Departments of Astronomy andPhysics, as well as significant expertise in planetary sciences within the Earth & Environmental Sciences and Climate& Space Sciences Departments. We have a particular strength in the interrelated study of stars, planets, and theirformation. Postdoctoral researchers in our department can apply as PI to any of our telescope facility partnerships,
currently including the Magellan Telescopes in Chile, the MDM Observatory in Arizona, the CHARA Interferometer,
the SWIFT space telescope, and the NOEMA mm array. Significant computing resources are available throughthe Department and through the University of Michigan. The Michigan Institute for Research in Astrophysics funds
cross-disciplinary efforts, including a series of intellectually stimulating conferences, and conversations on inclusion andequity, while the Michigan Institute for Data Science advances cross-cutting data science methodology and applications
relevant to solving fundamental research problems in planetary science.
The University of Michigan is recognized as a top academic employer and Ann Arbor, Michigan is routinely celebrated
for its high quality of life. We are a department that values diversity, equity, and inclusion as essential to scientificexcellence and encourage applications from those with identities underrepresented in astronomy.
Please share this information with potentially interested persons, and do not hesitate to contact individual members of the scientific staff to learn more about research opportunities in planetary science or visit our website athttps://lsa.umich.edu/astro.

51 Pegasi Fellowship Opportunities at Cornell University
The Department of Astronomy at Cornell University encourages early career researchers in astronomy and planetarysciences to apply to the 51 Pegasi b Fellowship. Cornell University is among the fourteen host institutions for thisplanetary astronomy focused postdoctoral fellowship. Deadline: September 20th
Diversity and inclusion are a part of Cornell University’s heritage. We particularly welcome applications from individuals who belong to groups that have been historically underrepresented in planetary sciences and astronomy suchas women, persons with disabilities, racial and ethnic minorities, gender and sexual minorities, and others who may
contribute to diversification of the field. Our inclusive community of scholars, students, and staff impart an uncommon
sense of larger purpose, and contribute creative ideas to further the university’s mission of teaching, discovery, andengagement.
For more information, please contact Nikole Lewis (nkl35@cornell.edu)
https://www.hsfoundation.org/programs/science/51-pegasi-b-fellowship/25

Meetings

NAOJ Science Workshop II: Planet Formation Workshop 2019
November 25th-28th, 2019, Tokyo, Japan
In the last few years, our field has been dramatically developing especially achieved by ALMA and other fascinating
telescopes. This workshop aims at sharing and discussing the latest understandings of planet formation and protoplanetary disks as well as numerical and theoretical developments in this field. We especially expect active participationfrom the East Asia for learning this excitingly developing field and finding a new network in geographically close
collaborators, while participation from any countries and regions are welcome. In addition, we encourage early-stage
researchers such as master and Ph.D. students and postdocs to join this workshop.
INVITED SPEAKERS:
Chris Ormel (University of Amsterdam → Tsinghua Univ., China)
Gregory J. Herczeg (KIAA, China)
Kenji Furuya (Tsukuba Univ., Japan)
Min-Kai Lin (ASIAA, Taiwan)
Satoshi Okuzumi (Tokyo Tech., Japan)
Woojin Kwon (KASI, Korea)
Xue-Ning Bai (Tsinghua Univ., China)
Ya-Wen Tang (ASIAA, Taiwan)
TOPICS:
Formation of protoplanetary disks
Evolution of protoplanetary disks
Disk observations
Evolution of solids in disks
Formation of planetary system
Debris disks
IMPORTANT DATES:
Registration open: currently open
Abstract submission deadline: September 1st, 2019
Announcement of program: mid of September, 2019
Registration deadline: October 25th, 2019
Workshop dates: November 25th-28th, 2019
Contact: planet-formation-workshop2019@th.nao.ac.jp
Organizers: Akimasa Kataoka (Chair), Takahiro Ueda (Co-Chair), Hideko Nomura, Shinsuke Takasao, Takashi Tsukagoshi, Misako Tatsuuma
http://th.nao.ac.jp/meeting/planet-formation-workshop2019/26

Summary of Upcoming Meetings

Orion Uncovered
26 - 30 August 2019 Leiden, The Netherlands
https://sites.google.com/view/OrionLeiden2019
Understanding the Nearby Star-forming Universe with JWST
26 - 30 Aug 2019 Courmayeur, Italy
http://www.stsci.edu/institute/conference/unsfjwst2019
Celebrating the first 40 Years of Alexander Tielens’ Contribution to Science: The Physics and Chemistry of the ISM
2 - 6 september 2019, Avignon, France https://tielens2019.sciencesconf.org
From Gas to Stars: The Links between Massive Star and Star Cluster Formation
16-20 September 2019 York, UK
https://starformmapper.org/final-conference/
Crete III - Through dark lanes to new stars - Celebrating the career of Prof. Charles Lada
23 - 27 September 2019 Crete, Greece
http://crete3.org
The UX Ori type stars and related topics
30 September - 4 October 2019 St. Petersburg, Russia
http://uxors-2019.craocrimea.ru
First Stars VI
1 - 6 March 2020 Concepcion, Chile
http://www.astro.udec.cl/FirstStarsVI/
Linking Dust, Ice, and Gas in Space19 - 24 April 2020, Capri, Italy
http://frcongressi.net/ecla2020.meet
COOL STARS 21: Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
22 -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, France
https://cral.univ-lyon1.fr
Planet Formation Workshop 201925 - 28 November Tokyo, Japan
http://th.nao.ac.jp/meeting/planet-formation-workshop2019/27