THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 321 — 16 September 2019

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

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

Abstracts of Newly Accepted Papers . . . . . . . . . . . 3
Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 41
New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

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

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

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

Passings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Summary of Upcoming Meetings . . . . . . . . . . . . . 44

Editorial Board
Joao Alves
Alan Boss
Jerome Bouvier
Lee Hartmann
Thomas Henning
Paul Ho
Jes Jorgensen
Charles J. Lada
Thijs Kouwenhoven
Michael R. Meyer
Ralph Pudritz
Luis Felipe 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.

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

Cover Picture
The Musca cloud filament is located at an approximate distance of 150 pc and has a projected lengthof about 6.5 pc. The filament is quiescent, withmagnetic field lines perpendicular to the long axis,
along which background material may be accreting.
Star formation has yet to start in this filament.
Image courtesy Marco Lorenzi
https://www.glitteringlights.com/

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Abstracts of recently accepted papers

1

HST spectra reveal accretion in MY Lupi
J.M. Alcalá1 , C.F. Manara2 , K. France3 , C.P. Schneider4 , N. Arulanantham3 , A. Miotello2, H.M.
Günther5 and A. Brown6
1

INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy; 2 European Southern
Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen, Germany; 3 Laboratory for Atmospheric andSpace Physics, University of Colorado, 392 UCB, Boulder, CO 80303, USA; 4 Hamburger Sternwarte, Gojenbergsweg
112, D-21029 Hamburg, Germany; 5 MIT, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts
Avenue, Cambridge, MA 02139, USA; 6 Center for Astrophysics and Space Astronomy, University of Colorado,
Boulder, CO 80309-0389, USA
E-mail contact: juan.alcala at inaf.it
The mass accretion rate is a crucial parameter for the study of the evolution of accretion discs around young low-massstellar and substellar objects (YSOs). We revisit the case of MY Lup, an object where VLT/X-Shooter data suggested
a negligible mass accretion rate, and show it to be accreting on a level similar to other Class II YSOs in Lupus
based on Hubble Space Telescope (HST) observations. In our HST-Cosmic Origins Spectrograph (HST-COS) and-Space Telescope Imaging Spectrograph (HST-STIS) spectra, we find many emission lines, as well as substantial farultraviolet (FUV) continuum excess emission, which can be ascribed to active accretion. The total luminosity of the
C iv λ1549 Å doublet is 4.1×10−4 L⊙ . Using scalings between accretion luminosity, Lacc , and C iv luminosity from theliterature, we derive Lacc ∼2×10−1L⊙ , which is more than an order of magnitude higher than the upper limit estimatedfrom the X-Shooter observations. We discuss possible reasons for the X-Shooter-HST discrepancy, the most plausible
being that the low contrast between the continuum excess emission and the photospheric+chromospheric emission
at optical wavelengths in MY Lup hampered detection of excess emission. The luminosity of the FUV continuumand C iv lines, strong H2 fluorescence, and a ”1600 A Bump” place MY Lup in the class of accreting objects withgas-rich discs. So far, MY Lup is the only peculiar case in which a significant difference between the HST and XShooter Ṁacc estimates exists that is not ascribable to variability. The mass accretion rate inferred from the revisited−8
Lacc estimate is Ṁacc ∼ 1(+1.5M⊙ yr−1 . This value is consistent with the typical value derived for accreting−0.5 )×10
YSOs of similar mass in Lupus and points to less clearing of the inner disc than indicated by near- and mid-infraredobservations. This is confirmed by Atacama Large Millimeter Array (ALMA) data, which show that the gaps andrings seen in the sub-millimetre are relatively shallow.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1908.10647

2

Gaia DR2 distances to Collinder 419 and NGC 2264 and new astrometric orbits for HD
193 322 Aa,Ab and 15 Mon Aa,Ab
J. Maı́z Apellániz1
1

Centro de Astrobiologı́a, CSIC-INTA. Campus ESAC. C. bajo del castillo s/n. E-28 692 Villanueva de la Cañada,
Madrid, Spain
E-mail contact: jmaiz at cab.inta-csic.es
Context. Gaia DR2 has opened a trove of astrometric and photometric data for Galactic clusters close to the Sun.
Lucky imaging has been an operational technique to measure the positions of visual binary systems for a decade anda half, enough to apply its results to the calculation of orbits of some massive multiple systems within ∼1 kpc of theSun.
Aims. We are measuring distances to Galactic stellar groups containing O stars and I start with two of them: Collinder
419 in Cygnus and NGC 2264 in Monoceros. I also aim to derive new astrometric orbits for the Aa,Ab components
3for the main ionizing sources for both clusters: HD 193 322 and 15 Mon, respectively.
Methods. I present a method that uses Gaia DR2 photometry, positions, proper motions, and parallaxes to obtain themembership and distance of a stellar group and apply it to Collinder 419 and NGC 2264. Second, I present a newcode that calculates astrometric orbits by searching the whole 7-parameter orbit space and apply it to HD 193 322
Aa,Ab and 15 Mon Aa,Ab using as input literature data from the Washington Double Star Catalog (WDS) and the
AstraLux measurements recently presented by Maz Apellniz et al. (2019).
Results. I obtain Gaia DR2 distances of 1006+37−34 pc for Collinder 419 and 719±16 pc for NGC 2264, with the main
contribution to the uncertainties coming from the spatial covariance of the parallaxes. The two NGC 2264 subclusters
are at the same distance (within the uncertainties) and they show a significant relative proper motion. The distances
are shown to be robust. HD 193 322 Aa,Ab follows an eccentric (e = 0.58+0.03−0.04 ) orbit with a period of 44±1 a andthe three stars it contains have a total mass of 76.1+9.9
M
.
The
orbit
of
15 Mon Aa,Ab is even more eccentric⊙−7.4+0.023+3.6(e = 0.770−0.030 ), with a period of 108±12 a and a total mass of 45.1−3.3 M⊙ for its two stars.
Accepted by A&A
http://arxiv.org/pdf/1908.02040

3

Inner rocky super-Earth formation: distinguishing the formation pathways in viscously
heated and passive discs
Bertram Bitsch1
1

Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

E-mail contact: bitsch at mpia.de
The formation of super-Earths is strongly linked to the structure of the protoplanetary disc, which determines growthand migration. In the pebble accretion scenario, planets grow to the pebble isolation mass, at which the planet carvesa small gap in the gas disc halting the pebble flux and thus its growth. The pebble isolation mass scales with the disc’s
aspect ratio, which directly depends on the disc structure. I compare the growth of super-Earths in viscously heateddiscs and discs purely heated by the central star with super-Earth observations. This allows two formation pathways ofsuper-Earths to be distinguished in the inner systems. Planets growing within 1 Myr in the viscously heated inner discreach pebble isolation masses that correspond directly to the inferred masses of the Kepler observations for systems
that feature planets in resonance or not in resonance. However, to explain the period ratio distribution of Kepler
planets — where most Kepler planet pairs are not in mean motion resonance configurations — a fraction of theseresonant chains has to be broken. In case the planets are born early in a viscously heated disc, these resonant chains
thus have to be broken without planetary mergers. If super-Earths form either late or in purely passive discs, thepebble isolation mass is too small to explain the Kepler observations, implying that planetary mergers are important
for the final system architecture. Resonant planetary systems thus have to experience mergers already during the gas
disc phase, so the planets can get trapped in resonance after reaching 5–10 Earth masses. In case instabilities are
dominating the system architecture, the systems should not be flat with mutually inclined orbits. This implies that
future observations of planetary systems with RV and transits could distinguish between these two formation channels
of super-Earth.
Accepted by A&A
http://arxiv.org/pdf/1908.08710

4

The First Detection of 13 C17 O in a Protoplanetary Disk: a Robust Tracer of Disk Gas
Mass
Alice S. Booth1 , Catherine Walsh1 , John D. Ilee1 , Shota Notsu2,3 , Chunhua Qi4 , Hideko Nomura5,6 ,and Eiji Akiyama7
1

School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK; 2 Department of Astronomy, Graduate
School of Science, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan; 3 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA, Leiden, the Netherlands; 4 Harvard-Smithsonian Center for
Astrophysics, Cambridge, MA 02138, USA; 5 Department of Earth and Planetary Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551, Japan; 6 National Astronomical Observatory Japan (NAOJ),

4

Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 7 Institute for the Advancement of Higher Education, Hokkaido University, Kita 17, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0817, Japan
E-mail contact: pyasb at leeds.ac.uk
Measurements of the gas mass are necessary to determine the planet formation potential of protoplanetary disks.
Observations of rare CO isotopologues are typically used to determine disk gas masses; however, if the line emission
is optically thick this will result in an underestimated disk mass. With ALMA we have detected the rarest stable
CO isotopologue, 13 C17 O, in a protoplanetary disk for the first time. We compare our observations with the existing
detections of 12 CO, 13 CO, C18 O and C17 O in the HD163296 disk. Radiative transfer modelling using a previously
benchmarked model, and assuming interstellar isotopic abundances, significantly underestimates the integrated intensity of the 13 C17 O J=3–2 line. Reconciliation between the observations and the model requires a global increase in
CO gas mass by a factor of 3.5. This is a factor of 2–6 larger than previous gas mass estimates using C18 O. We findthat C18 O emission is optically thick within the CO snow line, while the 13 C17 O emission is optically thin and is thus
a robust tracer of the bulk disk CO gas mass.
Accepted by ApJL
http://arxiv.org/pdf/1908.05045

5

The fulcrum wavelength of young stellar objects – the case of LRLL 31
Geoffrey R. Bryan1 , Sarah T. Maddison1 , and Kurt Liffman1
1

Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3018, Australia
E-mail contact: gbryan at swin.edu.au
A small subset of young stellar objects (YSOs) exhibit “see-saw” temporal variations in their mid-infrared SED; as
the flux short-ward of a fulcrum wavelength (λf ) increases the flux long-wards of this wavelength decreases (and viceversa) over timescales of weeks to years. While previous studies have shown that an opaque, axisymmetric occulter ofvariable height can cause this behaviour in the SED of these objects, the conditions under which a single λf occurs
have not previously been determined, nor the factors determining its value. Using radiative transfer modelling, we
conduct a parametric study of the exemplar of this class, LRLL 31 to explore this phenomenon, and confirm that thecause of this flux variation is likely due to the change in height of the optically thick inner rim of the accretion disc at
the dust sublimation radius, or some other phenomenon which results in a similar appearance. We also determine thata fulcrum wavelength only occurs for high inclinations, where the line of sight intersects the accretion disc. Acceptingthat the disc of LRLL 31 is highly inclined, the inner rim radius, radial and vertical density profiles are independently
varied to gauge what effect this had on λf and its position relative to the silicate feature near 10 µm. While λf is afunction of each of these parameters, it is found to be most strongly dependent on the vertical density exponent β.
All other factors being held constant, only for flatter discs (β < 1.2) did we find a λf beyond the silicate feature.
Accepted by MNRAS
http://arxiv.org/pdf/1908.08703

6

Radial Drift and Concurrent Ablation of Boulder-Sized Objects
Remo Burn1 , Ulysse Marboeuf1 , Yann Alibert1 and Willy Benz1
1

Physikalisches Institut & Center for Space and Habitability, Universität Bern, CH-3012 Bern, Switzerland

E-mail contact: remo.burn at space.unibe.chContext. The composition of a protoplanetary disk at a given location does not only depend on temperature andpressure but also on the time dependent transport of matter, such as radial drift of solid bodies, which could releasewater and other volatile species before disintegration or accretion onto a larger body with potentially considerable
implications for the composition of planets.
Aims. We perform a parameter study focused on the water depletion of different sized bodies able to cross the water
snowline by gas induced radial drift.
Methods. Either the analytical Hertz-Knudsen-Langmuir sublimation formula assuming equilibrium temperature
5

within the body or a more involved, numerical model for the internal thermal evolution is coupled with an α-disk
model. Different properties of the disk and the embedded body are explored.
Results. Bodies with radii up to 100 meter drift faster towards the central star than the water snowline, hence, crossit. The region that can be reached before complete disintegration — and is therefore polluted with H2 O ice — extends
to 10 percent closer to the star than the snowline location. The extent of this polluted region could be multiple times
larger in the presence of a dust mantle, which is, however, unlikely to form due to frequent collisions with smaller-thancentimeter sized objects.
Conclusions. Given a significant abundance of meter sized boulders in protoplanetary disks, the transport of waterby radial drift of these bodies towards regions closer to the star than the snowline is not negligible and this flux ofvolatiles can be estimated for a given distribution of solid body sizes and compositions. A simple expression for surface
sublimation is applicable for a homogeneous body consisting of only dust and water ice without a dust mantle.
Accepted by A&A
http://arxiv.org/pdf/1908.02513

7

The Structure of Dark Molecular Gas in the Galaxy – II. Physical State of “CO-Dark”
Gas in the Perseus Arm
Michael P. Busch1 , Ronald J. Allen2,1 , Philip D. Engelke1 , David E. Hogg3 , David A. Neufeld1 , MarkG. Wolfire4
1

Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD
21218, USA; 2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 3 National
Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA; 4 Department of Astronomy,
University of Maryland, College Park, MD 20742, USA
E-mail contact: mpbusch at jhu.edu
We report the results from a new, highly sensitive (∆Tmb ∼ 3mK) survey for thermal OH emission at 1665 and 1667
MHz over a dense, 9 × 9-pixel grid covering a 1◦ × 1◦ patch of sky in the direction of l = 105◦, b = +2.◦ 50 towards the
Perseus spiral arm of our Galaxy. We compare our Green Bank Telescope (GBT) 1667 MHz OH results with archival
CO J=1–0 observations from the Five College Radio Astronomy Observatory (FCRAO) Outer Galaxy Survey within
the velocity range of the Perseus Arm at these galactic coordinates. Out of the 81 statistically-independent pointingsin our survey area, 86% show detectable OH emission at 1667 MHz, and 19% of them show detectable CO emission.
We explore the possible physical conditions of the observed features using a set of diffuse molecular cloud models.
In the context of these models, both OH and CO disappear at current sensitivity limits below an AV of 0.2, but
the CO emission does not appear until the volume density exceeds 100–200 cm−3 . These results demonstrate that a
combination of low column density AV and low volume density nH can explain the lack of CO emission along sight lines
exhibiting OH emission. The 18-cm OH main lines, with their low critical density of n∗ ∼ 1 cm−3 , are collisionallyexcited over a large fraction of the quiescent galactic environment and, for observations of sufficient sensitivity, provide
an optically-thin radio tracer for diffuse H2 .
Accepted by ApJ
http://arxiv.org/pdf/1908.04829

8

Stars and brown dwarfs in the sigma Orionis cluster. IV. IDS/INT and OSIRIS/GTC
spectroscopy and Gaia DR2 astrometry
J.A. Caballero1 , A. de Burgos2,1 , F.J. Alonso-Floriano3,4, A. Cabrera-Lavers5,6,7 , D. Garcı́a-Álvarez5,6,7 ,D. Montes4
1

Centro de Astrobiologı́a (CSIC-INTA), ESAC, camino bajo del castillo s/n, 28691 Villanueva de la Cañada, Madrid,
Spain; 2 Isaac Newton Group of Telescopes, Apartado de correos 321, 38700 Santa Cruz de La Palma, La Palma,
Spain; 3 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, 2300 RA Leiden, The Netherlands; 4Departamento de Fı́sica de la Tierra y Astrofı́sica & IPARCOS-UCM (Instituto de Fı́sica de Partı́culas y del Cosmos
de la UCM), Facultad de Ciencias Fı́sicas, Universidad Complutense de Madrid, 28040 Madrid, Spain; 5 Institutode Astrofı́sica de Canarias, Avenida Vı́a Láctea, 38205 La Laguna, Tenerife, Spain; 6 Grantecan S. A., Centro de
Astrofı́sica de La Palma, Cuesta de San José, 38712 Breña Baja, La Palma, Spain; 7 Departamento de Astrofı́sica,
Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain6E-mail contact: caballero at cab.inta-csic.es
Context. Only a few open clusters are as important for the study of stellar and substellar objects, and their formationand evolution, as the young σ Orionis cluster. However, a complete spectroscopic characterisation of its whole stellar
population is still missing.
Aims. We filled most of that gap with a large spectroscopic and astrometric survey of targets towards σ Orionis.
Eventually, it will be one of the open clusters with the lowest proportion of interlopers and the largest proportion ofconfirmed cluster members with known uncontrovertible youth features.
Methods. We acquired 317 low-resolution optical spectra with the Intermediate Dispersion Spectrograph (IDS) at the
2.5 m Isaac Newton Telescope (INT) and the Optical System for Imaging and low Resolution Integrated Spectroscopy(OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). We measured equivalent widths of Li i, Hα, and otherkey lines from these spectra, and determined spectral types. We complemented this information with Gaia DR2
astrometric data and other features of youth (mid-infrared excess, X-ray emission) compiled with Virtual Observatory
tools and from the literature.
Results. Of the 168 observed targets, we determined for the first time spectral types of 39 stars and equivalent widths′′of Li i and Hα of 34 and 12 stars, respectively. We identified 11 close (ρ <∼ 3 ) binaries resolved by Gaia, of which
three are new, 14 strong accretors, of which four are new and another four have Hα emission shifted by over 120 km
s−1 , two juvenile star candidates in the sparse population of the Ori OB1b association, and one spectroscopic binary
candidate. Remarkably, we found 51 non-cluster-members, 35 of which were previously considered as sigma Orionis
members and taken into account in high-impact works on, for example, disc frequency and initial mass function.
Accepted by A&A
http://arxiv.org/pdf/1908.10340

9

Dust accretion in binary systems: implications for planets and transition discs
Yayaati Chachan1,2,3 , Richard A. Booth2 , Amaury H.M.J. Triaud2,4 , Cathie Clarke2
1

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA; 2 Instituteof Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 3 St John’s College, Cambridge,
CB2 1TP, UK; 4 School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
E-mail contact: ychachan at caltech.edu
The presence of planets in binary systems poses interesting problems for planet formation theories, both in cases
where planets must have formed in very compact discs around the individual stars and where they are located near
the edge of the stable circumbinary region, where in situ formation is challenging. Dust dynamics is expected toplay an important role in such systems, since dust trapping at the inner edge of circumbinary discs could aid in situ
formation, but would simultaneously starve the circumstellar discs of the solid material needed to form planets. Here
we investigate the dynamics of dust in binary systems using Smooth Particle Hydrodynamics. We find that all our
simulations tend towards dust trapping in the circumbinary disc, but the timescale on which trapping begins depends
on binary mass ratio (q) and eccentricity as well as the angular momentum of the infalling material. For q >∼ 0.1, wefind that dust can initially accrete onto the circumstellar discs, but as the circumbinary cavity grows in radius, dust
eventually becomes trapped in the circumbinary disc. For q = 0.01, we find that increasing the binary eccentricity
increases the time required for dust trapping to begin. However, even this longer timescale is likely to be shorter thanthe planet formation timescale in the inner disc and is insufficient to explain the observed pre-transitional discs. This
indicates that increase in companion eccentricity alone is not enough to allow significant transfer of solids from theouter to the inner disc.
Accepted by MNRAS
http://arxiv.org/pdf/1908.11377

How do velocity structure functions trace gas dynamics in simulated molecular clouds?

10 R.-A. Chira1 , J.C. Ibáñez-Mejı́a2,3, M.-M. Mac Low4,5,6, and Th. Henning1
1

Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 2 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany; 3 Max-Planck-Institut für Extraterrestrische Physik,
Giessenbachstrasse 1, 85748 Garching, Germany; 4 Dept. of Astrophysics, American Museum of Natural History,

7

79th St. at Central Park West, New York, NY 10024, USA; 5 Zentrum für Astronomie, Institut für Theoretische
Astrophysik, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 6 Center for Computational
Astrophysics, Flatiron Institute, 162 Fifth Ave, New York, NY 10010, USA
E-mail contact: roxana-adela.chira at alumni.uni-heidelberg.deContext. Supersonic disordered flows accompany the formation and evolution of MCs. It has been argued that turbulence can support against gravitational collapse and form hierarchical sub-structures.
Aims. We study the time evolution of simulated MCs to investigate: What physical process dominates the driving of
turbulent flows? How can these flows be characterised? Do the simulated flows agree with observations?
Methods. We analyse three MCs that have formed self-consistently within kpc-scale numerical simulations of the ISM.
The simulated ISM evolves under the influence of physical processes including self-gravity, stratification, magnetic
fields, supernova-driven turbulence, and radiative heating and cooling. We characterise the flows using VSFs with/out
density weighting or a density cutoff, and computed in one or three dimensions.
Results. In regions with sufficient resolution, the density-weighted VSFs initially appear to follow the expectations
for uniform turbulence consistent with Larson’s size-velocity relationship. SN blast wave impacts produce short-lived
coherent motions at large scales, increasing the scaling exponents for a crossing time. Gravitational contraction drives
small-scale motions, producing scaling coefficients that drop or even turn negative as small scales become dominant.
Conclusions. We conclude that two different effects coincidentally reproduce Larson’s size velocity relationship. Initially, uniform turbulence dominates, so the energy cascade produces VSFs consistent with Larson’s relationship.
Later, contraction dominates, the density-weighted VSFs become much shallower or even inverted, but the relationship of the global average velocity dispersion of the MCs to their radius follows Larson’s relationship, reflecting virial
equilibrium or free-fall collapse. The injection of energy by shocks is visible in the VSFs, but decays within a crossing
time.
Accepted by A&A
http://arxiv.org/pdf/1908.03951

A VLT/FLAMES survey for massive binaries in Westerlund 1: VII. Cluster census

11 J.S. Clark1 , B.W. Ritchie1,2, and I. Negueruela3
1

School of physical sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom; 2
Lockheed Martin Integrated Systems, Building 1500, Langstone, Hampshire, PO9 1SA, UK; 3 Departamento de Fı́sica
Aplicada, Facultad de Ciencias, Universidad de Alicante, Carretera San Vicente del Raspeig s/n, E03690, San Vicentedel Raspeig, Spain
E-mail contact: s.clark at open.ac.uk
The formation, properties, and evolution of massive stars remain subject to considerable uncertainty; impacting onfields as diverse as galactic feedback and the nature of the progenitors of both electromagnetic and gravitational wave
transients. The clusters many such stars reside within provide a unique laboratory for addressing these issues, and in
this work we provide a comprehensive stellar census of Westerlund 1 to underpin such efforts. 69 new members wereidentified via I-band spectroscopy, yielding a total cluster population of 166 stars with initial masses of ∼25M⊙ to∼50M⊙, with more massive stars already lost to supernova. The stellar population follows a smooth and continuous
morphological sequence from late-O giant through to OB supergiant. Subsequently, the progression bifurcates, with
one branch yielding mid- to late-B hypergiants and cool super-/hypergiants, and the other massive blue stragglers,prior to a diverse population of H-depleted Wolf-Rayets. A substantial population of O-type stars with anomalously
broad Paschen series lines are seen, a property which we attribute to binarity. Binary interaction is clearly required
to yield the uniquely rich cohort of hypergiants, which includes both mass-stripped primaries and rejuvenated secondaries/stellar mergers. As a consequence future observations of Wd1 and similar stellar aggregates hold out theprospect of characterising both single- and binary- evolutionary channels for massive stars and determining theirrelative contributions. This in turn will permit the physical properties of such objects at the point of core-collapse
to be predicted; of direct relevance for understanding the formation of relativistic remnants such as the magnetars
associated with Wd1 and other young massive clusters.
Accepted by A&A
http://arxiv.org/pdf/1908.05616

8

The case of Trappist-1
12 Pebbles versus 1Planetesimals:
1
1
G.A.L. Colemanz , A. Leleuz , and Y. Alibert, W. Benz
1

Physikalisches Institut, Universität Bern, Gesellschaftsstr. 6, 3012 Bern, Switzerland

E-mail contact: gavin.coleman at space.unibe.ch
We present a study on the formation of planetary systems around low mass stars similar to Trappist-1, through theaccretion of either planetesimals or pebbles. The aim is to determine if the currently observed systems around low
mass stars favour one scenario over the other. We ran numerous N-body simulations, coupled to a thermally evolving
viscous disc model, including prescriptions for planet migration and photoevaporation. We examine the differences
between the pebble and planetesimal accretion scenarios, but also look at the influences of disc mass, planetesimalsize, and the percentage of solids locked up within pebbles. When comparing the resulting planetary systems to
Trappist-1, we find that a wide range of initial conditions for both accretion scenarios can form planetary systems
similar to Trappist-1, in terms of planet mass, periods, and resonant configurations. Typically these planets formed
exterior to the water iceline and migrated in resonant convoys to close to the central star. When comparing theplanetary systems formed from pebbles to those formed from planetesimals, we find a large number of similarities,
including average planet masses, eccentricities, inclinations and period ratios. One major difference was that of thewater content of the planets. When including the effects of ablation and full recycling of the planets envelope with thedisc, planets formed from pebbles were extremely dry, whilst those formed from planetesimals were extremely wet. If
the water content is not fully recycled and instead falls to the planets core, or if ablation of the water is neglected,
then the planets formed from pebbles are extremely wet, similar to those formed from planetesimals. Should thewater content of the Trappist-1 planets be determined accurately, this could point to a preferred formation pathway
for planetary systems, or to specific physics that may be at play.
Accepted by A&A
http://arxiv.org/pdf/1908.04166

13

Effects of Radiation in Accretion Regions of Classical T Tauri Stars: Pre-heating ofaccretion column in non-LTE regime
S. Colombo1,2,3, L. Ibgui2 , S. Orlando3 , R. Rodriguez5 , G. Espinosa5 , M. González4 , C. Stehlé2 , L. de
Sá2 , C. Argiroffi1,3 , R. Bonito3 , and G. Peres1,3
1

Università degli Studi di Palermo, Dipartimento di Fisica e Chimica, via Archirafi 36, Palermo, Italy; 2 LERMA,
Observatoire de Paris, Sorbonne Université, Université de Cergy-Pontoise, CNRS, Paris, France; 3 INAF - Osservatorio
Astronomico di Palermo, Piazza del Parlamento 1, Palermo, Italy; 4 Université Paris Diderot, Sorbonne Paris Cité,AIM, UMR7158, CEA, CNRS, F-91191 Gif-sur-Yvette, France; 5 Universidad de Las Palmas de Gran Canaria, Gran
Canaria, Spain
E-mail contact: salvatore.colombo at inaf.it
Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regionsat the base of accretion columns, in which optically thin and thick plasma components coexist. Thus an accurate
description of these impacts requires to account for the effects of absorption and emission of radiation. We study theeffects of radiation emerging from shock-heated plasma in impact regions on the structure of the pre-shock downfallingmaterial. We investigate if a significant absorption of radiation occurs and if it leads to a pre-shock heating of theaccreting gas. We developed a radiation hydrodynamics model describing an accretion column impacting onto thesurface of a Classical T Tauri Star. The model takes into account the stellar gravity, the thermal conduction, andthe effects of both radiative losses and absorption of radiation by matter in the non local thermodynamic equilibrium
regime. After the impact, a hot slab of post-shock plasma develops at the base of the accretion column. Part ofradiation emerging from the slab is absorbed by the pre-shock accreting material. As a result, the pre-shock accretion
column gradually heats up to temperatures of 105 K, forming a radiative precursor of the shock. The precursor hasa thermal structure with the hottest part at T ≈ 105 K, with size comparable to that of the hot slab, above thepost-shock region. At larger distances the temperature gradually decreases to T ≈ 104 K.
Accepted by A&A
http://arxiv.org/pdf/1908.06799

9

14Interstellar Plunging Waves: ALMA resolves the physical structure of non-stationary
MHD shocks
Giuliana Cosentino1,2 , Izaskun Jimnez-Serra3,4 , Paola Caselli5, Jonathan D. Henshaw6 , Ashley T.
Barnes7 , Jonathan C. Tan8,9 , Serena Viti1 , Francesco Fontani10 and Benjamin Wu11
1

Department of Physics and Astronomy, University College London, Gower St, London, WC1E6BT, UK; 2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany; 3 Departamento de Astrofisica,Centro de Astrobiologia, 28850 Torrejon de Ardoz, Madrid, Spain; 4 School of Physics & Astronomy, Queen Mary
University of London, Mile End Road, E1 4NS, London, UK; 5 Max-Planck Institute for Extraterrestrial Physics,
Giessenbachstrasse 2, 85748 Garching, Germany; 6 Max-Planck Instiutute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany; 7 Argelander-Institut für Astronomie Auf dem Hugel 71, D-53121 Bonn, Germany; 8 Space, Earthand Environment Department, Chalmers University of Technology, Chalmersplatsen 4, 41296 Goteborg, Sweden; 9
Department of Astronomy, University of Virginia, Charlottesville, Virginia, USA; 10 INAF-Osservatorio Astrofisico
di Arcetri, Largo E. Fermi 2, I-50125 Firenze, Italy; 11 National Astronomical Observatory of Japan, Yubinbango
181-8588 Tokio, Mitaka, Osawa 2-21-1, Japan
E-mail contact: giuliana.cosentino.15 at ucl.ac.uk
Magneto-hydrodynamic (MHD) shocks are violent events that inject large amounts of energy in the interstellar medium(ISM) dramatically modifying its physical properties and chemical composition. Indirect evidence for the presenceof such shocks has been reported from the especial chemistry detected toward a variety of astrophysical shocked
environments. However, the internal physical structure of these shocks remains unresolved since their expected spatial
scales are too small to be measured with current instrumentation. Here we report the first detection of a fully
spatially resolved, MHD shock toward the Infrared Dark Cloud (IRDC) G034.77-00.55. The shock, probed by Silicon
Monoxide (SiO) and observed with the Atacama Large Millimetre/sub-millimetre Array (ALMA), is associated withthe collision between the dense molecular gas of the cloud and a molecular gas flow pushed toward the IRDC by
the nearby supernova remnant (SNR) W44. The interaction is occurring on sub-parsec spatial scales thanks to theenhanced magnetic field of the SNR, making the dissipation region of the MHD shock large enough to be resolved with
ALMA. Our observations suggest that molecular flow- flow collisions can be triggered by stellar feedback, inducing
shocked molecular gas densities compatible with those required for massive star formation.
Accepted by The Astrophysical Journal Letters
https://iopscience.iop.org/article/10.3847/2041-8213/ab38c5; https://arxiv.org/pdf/1908.09743.pdf

15

Resolved ALMA continuum image of the circumbinary ring and circumstellar disks inthe L1551 IRS 5 system
Fernando Cruz-Sáenz de Miera1 , Ágnes Kóspal1,2 , Péter Ábrahám1 , Hauyu Baobab Liu3 and Michihiro
Takami3
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences,
Hungarian Academy of Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary; 2 Max Planck Institute for
Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 3 Institute of Astronomy and Astrophysics, Academia Sinica,
11F of Astronomy-Mathematics Building, AS/NTU, No.1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan, R.O.C.
E-mail contact: cruzsaenz.fernando at csfk.mta.hu
L1551 IRS 5 is a FUor-like object located in the Taurus star forming region. We present ALMA 1.3 mm continuum
observations using a wide range of baselines. The observations recovered the two circumstellar disks composing thesystem and, for the first time, resolved the circumbinary ring. We determined the geometry and estimated lower
mass limits for the circumstellar disks using simple models. We calculated lower limits for the total mass of both
circumstellar disks. After subtracting the two circumstellar disk models from the image, the residuals show a clearly
resolved circumbinary ring. Using a radiative transfer model, we show that geometrical effects can explain some of
the brightness asymmetries found in the ring. The remaining features are interpreted as enhancements in the dust
density.
Accepted by The Astrophysical Journal Letters
https://arxiv.org/pdf/1908.04649

10

16

Onset of planet formation in the warm inner disk – Colliding dust aggregates at hightemperatures
Tunahan Demirci1 , Corinna Krause1 , Jens Teiser1 , and Gerhard Wurm1
1

University of Duisburg-Essen, Faculty of Physics, Lotharstr. 1-21, D-47057 Duisburg, Germany

E-mail contact: tunahan.demirci at uni-due.de
Collisional growth of dust occurs in all regions of protoplanetary disks with certain materials dominating between
various condensation lines. The sticking properties of the prevalent dust species depend on the specific temperatures.
The inner disk is the realm of silicates spanning a wide range of temperatures from room temperature up to sublimation
beyond 1500 K. For the first time, we carried out laboratory collision experiments with hot levitated basalt dust
aggregates of 1 mm in size. The aggregates are compact with a filling factor of 0.37±0.06. The constituent grains
have a wide size distribution that peaks at about 0.6 µm. Temperatures in the experiments are varied between
approximately 600 K and 1100 K. Collisions are slow with velocities between 0.002 m s−1 and 0.15 m s−1 , i.e., relevant
for protoplanetary disks. Aside from variations of the coefficients of restitution due to varying collision velocities,
the experiments show low sticking probability below 900 K and an increasing sticking probability starting at 900 K.
This implies that dust can grow to larger size in hot regions, which might change planet formation. One scenario isan enhanced probability for local planetesimal formation. Another scenario is a reduction of planetesimal formation
as larger grains are more readily removed as a consequence of radial drift. However, the increased growth at hightemperatures likely changes planetesimal formation one way or the other.
Accepted by A&A
http://arxiv.org/pdf/1908.11657

17

Cluster-forming site AFGL 5157: colliding filamentary clouds and star formation
L. K. Dewangan1
1

Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, India

E-mail contact: lokeshd at prl.res.in
We observationally investigate star formation (SF) process occurring in AFGL 5157 (area ∼13.5 pc × 13.5 pc) using
a multi-wavelength approach. Embedded filaments are seen in the Herschel column density map, and one of them is
identified as an elongated filamentary feature (FF) (length ∼8.3 pc; mass ∼1170 M⊙ ). Five Herschel clumps (Mclump∼45–300 M⊙ ) are traced in the central part of FF, where an extended temperature structure (Td ∼13.5–26.5 K) is
observed. In the direction of the central part of FF, the warmer region at Td ∼20–26.5 K spatially coincides witha mid-infrared (MIR) shell surrounding a previously known evolved infrared cluster. Diffuse Hα emission is traced
inside the infrared shell, suggesting the presence of massive stars in the evolved cluster. Based on the surface density
analysis of young stellar objects (YSOs), embedded clusters of YSOs are traced toward the central part of FF, andare distributed around the infrared shell. Previously detected H2 O masers, H2 knots, massive protostar candidates,and H ii region are also seen toward the embedded clusters. Using the 12 CO and 13 CO line data, the central part of
FF is observed at the overlapping zones of two filamentary molecular clouds (length ∼12.5 pc) around −20 and −17
km s−1 , which are also connected in velocity. Our observational results suggest that the formation of massive stars
appears to be triggered by a collision of two filamentary molecular clouds, which might have also influenced the birthof YSOs in AFGL 5157.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1909.01298

18

Star formation activity and the spatial distribution and mass segregation of dense coresin the early phases of star formation
Sami Dib1,2 and Thomas Henning2
1

Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615,
Pessac, France; 2 Max Planck Institute for Astronomy, Königstuhl 17, D-69117, Heidelberg, Germany
E-mail contact: sami.dib at gmail.com

11

We examine the spatial distribution and mass segregation of dense molecular cloud cores in a number of nearby
star forming regions (the region L1495 in Taurus, Aquila, Corona Australis, and W43) that span about four ordersof magnitude in star formation activity. We used an approach based on the calculation of the minimum spanningtree, and for each region, we calculated the structure parameter Q and the mass segregation ratio ΛMSR measured
for various numbers of the most massive cores. Our results indicate that the distribution of dense cores in youngstar forming regions is very substructured and that it is very likely that this substructure will be imprinted onto thenascent clusters that will emerge out of these clouds. With the exception of Taurus in which there is nearly no masssegregation, we observe mild-to-significant levels of mass segregation for the ensemble of the 6, 10, and 14 most massive
cores in Aquila, Corona Australis, and W43, respectively. Our results suggest that the clouds’ star formation activity
are linked to their structure, as traced by their population of dense cores. We also find that the fraction of massive
cores that are the most mass segregated in each region correlates with the surface density of star formation in theclouds. The Taurus region with low star forming activity is associated with a highly hierarchical spatial distribution of
the cores (low Q value) and the cores show no sign of being mass segregated. On the other extreme, the mini-starburst
region W43-MM1 has a higher Q that is suggestive of a more centrally condensed structure. Additionally, it possesses
a higher fraction of massive cores that are segregated by mass. While some limited evolutionary effects might bepresent, we largely attribute the correlation between the star formation activity of the clouds and their structure to adependence on the physical conditions that have been imprinted on them by the large scale environment at the timethey started to assemble
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1808.07057

19

Measuring the ionisation fraction in a jet from a massive protostar
R. Fedriani1,2 , A. Caratti o Garatti1,2 , S. J. D. Purser1 , A. Sanna3 , J. C. Tan4,5 , R. Garcia-Lopez1 ,T. P. Ray1 , D. Coffey2,1 , B. Stecklum6 & M. Hoare7
1

Dublin Institute for Advanced Studies, School of Cosmic Physics, Astronomy & Astrophysics Section, 31 Fitzwilliam
Place, Dublin 2, Ireland; 2 University College Dublin, School of Physics, Belfield, Dublin 4, Ireland; 3 Max-PlanckInstitut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 4 Dept. of Space, Earth & Environment,
Chalmers University of Technology, SE-412 93 Gothenburg, Sweden; 5 Dept. of Astronomy, University of Virginia,
530 McCormick Road, Charlottesville, VA 22904-4325, USA; 6 Thüringer Landessternwarte Tautenburg, Sternwarte
5, 07778 Tautenburg, Germany; 7 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK.
E-mail contact: fedriani at cp.dias.ie
It is important to determine if massive stars form via disc accretion, like their low-mass counterparts. Theory andobservation indicate that protostellar jets are a natural consequence of accretion discs and are likely to be crucial
for removing angular momentum during the collapse. However, massive protostars are typically rarer, more distantand more dust enshrouded, making observational studies of their jets more challenging. A fundamental question iswhether the degree of ionisation in jets is similar across the mass spectrum. Here we determine an ionisation fractionof ∼ 5 − 12% in the jet from the massive protostar G35.20-0.74N, based on spatially coincident infrared and radio
emission. This is similar to the values found in jets from lower-mass young stars, implying a unified mechanism ofshock ionisation applies in jets across most of the protostellar mass spectrum, up to at least ∼ 10 solar masses.
Published by Nature Communications
https://www.nature.com/articles/s41467-019-11595-x
https://arxiv.org/pdf/1908.05346

20

Measuring the magnetic field of young stars using iSHELL observations: BP Tau andV347 Aur
Christian Flores1 , Michael S. Connelley1 , Bo Reipurth1 and Adwin Boogert2
1

Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI 96720, USA; 2 Institute for
Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
E-mail contact: caflores at hawaii.edu

While it has been suggested that there is a connection between the magnetic properties and the internal structure of12young stars, there have not been enough magnetic measurements to firmly establish such a correlation at the earliest
ages. Here, we contribute to this endeavor by presenting stellar parameters and magnetic field strength measurementsof BP Tau and V347 Aur, both stars observed with the near-infrared spectrograph iSHELL. We first test the accuracyof our method by fitting synthetic stellar spectra to a sample of nine main and post-main-sequence stars. We report
uncertainties of σTeff = 91 K in temperature and σlog(g) = 0.14 in gravity. We then apply the modeling technique to
BP Tau and measure a surface magnetic field strength of hBi = 2.5+0.15−0.16 kG, confirming literature results. For thisstar, however, we obtain a much lower temperature value than previous optical studies (∆T ∼ 400 K) and interpret
this significant temperature difference as due to the relatively higher impact of starspots at near-infrared wavelengths
than at optical wavelengths. We further apply this technique to the class I protostellar source V347 Aur and measure+0.14
for the first time its magnetic field strength hBi = 1.36+0.06−0.05 kG and its surface gravity log(g) = 3.25−0.14 . Lastly, we
combine our measurements with pre-main-sequence stellar evolutionary models and illustrate the effects produced bystarspots on the retrieved masses and ages of young stars.
Accepted by ApJ
https://arxiv.org/pdf/1908.08583.pdf

21

Origin of the PN molecule in star-forming regions: the enlarged sample
F. Fontani1 , V.M. Rivilla1 , F.F.S. van der Tak2,3 , C. Mininni1,4, M.T. Beltrán1 , and P. Caselli51INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Florence, Italy; 2 SRON Netherlands Institutefor Space Research, Landleven 12, 9747 AD Groningen, The Netherlands; 3 Kapteyn Astronomical Institute, Universityof Groningen, The Netherlands; 4 Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze, I-50125 Florence, Italy; 5 Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse
1, 85748 Garching, Germany
E-mail contact: fontani at arcetri.astro.it

Phosphorus nitride (PN) is the P-bearing species with the highest number of detections in star-forming regions. Multiline studies of the molecule have shown that the excitation temperature of PN is usually lower than the gas kinetic
temperature, suggesting that PN is likely in conditions of sub-thermal excitation. We present an analysis of PN whichtakes the possible sub-thermal excitation conditions into account in a sample of 24 massive star-forming regions. We
observed PN (2–1), (3–2), (4–3), and (6–5) with the IRAM-30m and APEX telescopes and detected PN lines in 15of them. Together with 9 similar sources detected in PN in previous works, we have analysed the largest sample ofstar-forming regions to date, made of 33 sources with 24 detections in total (among which 13 are new detections).
Hence, we have increased the number of star-forming regions detected in PN by more than a factor 2. Our analysis
indicates that the PN lines are indeed sub-thermally excited, but well described by a single excitation temperature.
We have compared line profiles and fractional abundances of PN and SiO, a typical shock tracer, and found that
almost all objects detected in PN have high-velocity SiO wings. Moreover, the SiO and PN abundances with respect
to H2 are correlated over several orders of magnitude, and uncorrelated with gas temperature. This clearly shows thatthe production of PN is strongly linked to the presence of shocked gas, and rules out alternative scenarios based onthermal evaporation from iced grain mantles.
Accepted by MNRAS
http://arxiv.org/pdf/1908.11280

22

H2 ortho-para spin conversion on inhomogeneous grain surfaces
Kenji Furuya1 , Yuri Aikawa2 , Tetsuya Hama3 and Naoki Watanabe3
1

Center for Computer Sciences, University of Tsukuba, 305-8577 Tsukuba, Japan; 2 Department of Astronomy, The
University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan; 3 Institute of Low Temperature Science, Hokkaido University,
Sapporo, Hokkaido 0600819, Japan
E-mail contact: furuya at ccs.tsukuba.ac.jp
We investigate the evolution of the ortho-to-para ratio of overall (gas + ice) H2 via the nuclear spin conversion on
grain surfaces coated with water ice under physical conditions that are relevant to star- and planet-forming regions.

13

We utilize the rate equation model that considers adsorption of gaseous H2 on grain surfaces which have a variety ofbinding sites with a different potential energy depth, thermal hopping, desorption, and the nuclear spin conversion ofadsorbed H2 . It is found that the spin conversion efficiency depends on the H2 gas density and the surface temperature.
As a general trend, enhanced H2 gas density reduces the efficiency, while the temperature dependence is not monotonic;
there is a critical surface temperature at which the efficiency is the maximum. At low temperatures, the exchange ofgaseous and icy H2 is inefficient (i.e., adsorbed H2 does not desorb and hinders another gaseous H2 to be adsorbed),
while at warm temperatures, the residence time of H2 on surfaces is too short for the spin conversion. Additionally, thespin conversion becomes more efficient with lowering the activation barriers for thermal hopping. We discuss whether
the spin conversion on surfaces can dominate over that in the gas-phase in star- and planet-forming regions. Finally,
we establish a simple but accurate way to implement the H2 spin conversion on grain surfaces in existing astrochemical
models.
Accepted by ApJ
https://arxiv.org/pdf/1908.01966.pdf

23Structure and kinematics of the Taurus star-forming region from Gaia-DR2 and VLBI
astrometry
P.A.B. Galli1 , L. Loinard2,3 , H. Bouy1 , L. M. Sarro4 , G.N. Ortiz-León5 , S.A. Dzib5 , J. Olivares1 ,M. Heyer6 , J. Hernandez7 , C. Román-Zúñiga7, M. Kounkel8 and K. Covey8
1

Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615
Pessac, France; 2 Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, Apartado
Postal 3-72, Morelia 58089, México; 3 Instituto de Astronomı́a, Universidad Nacional Autónoma de México, Apartado
Postal 70-264, 04510 Ciudad de México, México; 4 Depto. de Inteligencia Artificial , UNED, Juan del Rosal, 16,28040 Madrid, Spain; 5 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121, Bonn, Germany;
6
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA; 7 Instituto de Astronomı́a,
Universidad Nacional Autónoma de México, Unidad Académica en Ensenada, Ensenada 22860, México; 8 Departmentof Physics and Astronomy, Western Washington University, 516 High St, Bellingham, WA 98225, USA.
E-mail contact: phillip.galli at u-bordeaux.fr
Aims: We take advantage of the second data release of the Gaia space mission and the state-of-the-art astrometry
delivered from very long baseline interferometry observations to revisit the structure and kinematics of the nearby
Taurus star-forming region.
Methods: We apply a hierarchical clustering algorithm for partitioning the stars in our sample into groups (i.e.,clusters) that are associated with the various molecular clouds of the complex, and derive the distance and spatial
velocity of individual stars and their corresponding molecular clouds.
Results: We show that the molecular clouds are located at different distances and confirm the existence of important
depth effects in this region reported in previous studies. For example, we find that the L 1495 molecular cloud is located+1.2
at d = 129.9+0.4−0.3 pc, while the filamentary structure connected to it (in the plane of the sky) is at d = 160.0−1.2 pc.
+1.6
+2.5
We report B 215 and L 1558 as the closest (d = 128.5−1.6 pc) and most remote (d = 198.1−2.5 pc) substructures of
the complex, respectively. The median inter-cloud distance is 25 pc and the relative motion of the subgroups is on
the order of a few km/s. We find no clear evidence for expansion (or contraction) of the Taurus complex, but signs of
the potential effects of a global rotation. Finally, we compare the radial velocity of the stars with the velocity of theunderlying 13 CO molecular gas and report a mean difference of 0.04 ± 0.12 km/s (with r.m.s. of 0.63 km/s) confirmingthat the stars and the gas are tightly coupled.
Accepted by A&A

24

Linking planetesimal and dust content in protoplanetary disks via a local toy model
Konstantin Gerbig1,2 , Christian T. Lenz1 , and Hubert Klahr1
1

Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Department of Astronomy andAstrophysics, University of California, Santa Cruz, CA 95064, USA14

E-mail contact: gerbig at mpia.de
If planetesimal formation is an efficient process, as suggested by several models involving gravitational collapse of
pebble clouds, then, before long, a significant part of the primordial dust mass should be absorbed in many km
sized objects. A good understanding of the total amount of solids in the disk around a young star is crucial for planet
formation theory. But as the mass of particles above the mm size cannot be assessed observationally, one must ask how
much mass is hidden in bigger objects. We perform 0-d local simulations to study how the planetesimal to dust andpebble ratio is evolving in time and to develop an understanding of the potentially existing mass in planetesimals for acertain amount of dust and pebbles at a given disk age. We perform a parameter study based on a model considering
dust growth, planetesimal formation and collisional fragmentation of planetesimals, while neglecting radial transport
processes. While at early times, dust is the dominant solid particle species, there is a phase during which planetesimals
make up a significant portion of the total mass starting at approximately 104 –106 yr. The time of this phase and the
maximal total planetesimal mass strongly depend on the distance to the star R, the initial disk mass, and the efficiencyof planetesimal formation ǫ. After approximately 106 yr, our model predicts planetesimal collisions to dominate, which
resupplies small particles. In our model, planetesimals form fast and everywhere in the disk. For a given ǫ, we wereable to relate the dust content and mass of a given disk to its planetesimal content, providing us with some helpful
basic intuition about mass distribution of solids and its dependence on underlying physical processes.
Accepted by A&A
http://arxiv.org/pdf/1908.02608

25

Chondrule Formation by the Jovian Sweeping Secular Resonance
Munan Gong1 , Xiaochen Zheng2 , Douglas N.C. Lin2,3,4 , Kedron Silsbee1, Clement Baruteau5 , Shude
Mao2
1

Max-Planck Institute for Extraterrestrial Physics, Garching by Munich, 85748, Germany; 2 Department of Astronomy
and Center for Astrophysics, Tsinghua University, Beijing 10086, China; 3 Institute for Advanced Studies, Tsinghua
University, Beijing 10086, China; 4 Department of Astronomy and Astrophysics, University of California Santa Cruz,
Santa Cruz, CA 95064, USA; 5 Institut de Recherche en Astrophysique et Planétologie (IRAP) 14 avenue Edouard
Belin, 31400 Toulouse, France
E-mail contact: munan at mpe.mpg.de
Chondrules are silicate spheroids found in meteorites, serving as important fossil records of the early solar system.
In order to form chondrules, chondrule precursors must be heated to temperatures much higher than the typicalconditions in the current asteroid belt. One proposed mechanism for chondrule heating is the passage through bow
shocks of highly eccentric planetesimals in the protoplanetary disk in the early solar system. However, it is difficultfor planetesimals to gain and maintain such high eccentricities. In this paper, we present a new scenario in whichplanetesimals in the asteroid belt region are excited to high eccentricities by the Jovian sweeping secular resonance ina depleting disk, leading to efficient formation of chondrules. We study the orbital evolution of planetesimals in thedisk using semi-analytic models and numerical simulations. We investigate the dependence of eccentricity excitationon the planetesimal’s size as well as the physical environment, and calculate the probability for chondrule formation.
We find that 50–2000 km planetesimals can obtain eccentricities larger than 0.6 and cause effective chondrule heating.
Most chondrules form in high velocity shocks, in low density gas, and in the inner disk. The fraction of chondrule
precursors which become chondrules is about 4–9% between 1.5–3 au. Our model implies that the disk depletion
timescale is τdep ≈ 1 Myr, comparable to the age spread of chondrules; and that Jupiter formed before chondrules, nomore than 0.7 Myr after the formation of the CAIs.
Accepted by ApJ
http://arxiv.org/pdf/1908.09840

26

Close-in giant-planet formation via in-situ gas accretion and their natal disk properties
Yasuhiro Hasegawa1 , Tze Yeung Mathew Yu2 , and Bradley M. S. Hansen2
1

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA; 2 Department of Physics& Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA15

E-mail contact: yasuhiro.hasegawa at jpl.nasa.gov
The origin of close-in Jovian planets is still elusive. We examine the in-situ gas accretion scenario as a formation
mechanism of these planets. We reconstruct natal disk properties from the occurrence rate distribution of close-in
giant planets, under the assumption that the occurrence rate may reflect the gas accretion efficiency onto cores of theseplanets. We find that the resulting gas surface density profile becomes an increasing function of the distance from thecentral star with some structure at r ≃ 0.1 au. This profile is quite different from the standard minimum-mass solar
nebula model, while our profile leads to better reproduction of the population of observed close-in super-Earths basedon previous studies. We compute the resulting magnetic field profiles and find that our profiles can be fitted by stellar
dipole fields (∝ r−3 ) in the vicinity of the central star and large-scale fields (∝ r−2 ) at the inner disk regions, either if
the isothermal assumption breaks down or if non-ideal MHD effects become important. For both cases, the transition
between these two profiles occurs at r ≃ 0.1 au, which corresponds to the period valley of giant exoplanets. Our work
provides an opportunity to test the in-situ gas accretion scenario against disk quantities, which may constrain the gas
distribution of the minimum-mass extra solar nebula.
Accepted by A&A Letters
http://arxiv.org/pdf/1908.00647

How first hydrostatic cores, tidal forces and gravo-turbulent fluctuations set the char-

27 acteristic mass of stars

Patrick Hennebelle1, Yueh-Ning Lee2 and Gilles Chabrier3,4
1

Laboratoire AIM, Paris-Saclay CEA/IRFU/SAp – CNRS – Université Paris Diderot, 91191 Gif-sur-Yvette Cedex,
France; 2 Institut de Physique du Globe de Paris Sorbonne Paris Cité, Universrté Paris Diderot UMR 7154 CNRS,
F-75005 Paris, France; 3 École normale supérieure de Lyon CRAL, UMR CNRS 5574, 69364, Lyon Cedex 07, France;
4
School of Physics University of Exeter, Exeter, EX4 4QL, UK
E-mail contact: patrick.hennebelle at cea.fr
The stellar initial mass function (IMF) is playing a critical role in the history of our universe. We propose a theory thatis based solely on local processes, namely the dust opacity limit, the tidal forces and the properties of the collapsing gas
envelope. The idea is that the final mass of the central object is determined by the location of the nearest fragments,
which accrete the gas located further away, preventing it to fall onto the central object. To estimate the relevant
statistics in the neighbourhood of an accreting protostar, we perform high resolution numerical simulations. We also
use these simulations to further test the idea that fragmentation in the vicinity of an existing protostar is determinant
in setting the peak of the stellar mass spectrum. We develop an analytical model, which is based on a statisticalcounting of the turbulent density fluctuations, generated during the collapse, that are at least equal to the mass ofthe first hydrostatic core, and sufficiently important to supersede tidal and pressure forces to be self-gravitating. The
analytical mass function presents a peak located at roughly 10 times the mass of the first hydrostatic core in good
agreement with the numerical simulations. Since the physical processes involved are all local, i.e. occurs at scales of afew 100 AU or below, and do not depend on the gas distribution at large scale and global properties such as the mean
Jeans mass, the mass spectrum is expected to be relatively universal.
Accepted by ApJ
http://arxiv.org/pdf/1908.07250

28

First sub-arcsecond submillimeter-wave [C I] image of 49 Ceti with ALMA
Aya E. Higuchi1 , Kazuya Saigo1 , Hiroshi Kobayashi2 , Kazunari Iwasaki1 , Munetake Momos3 , Kang
Lou Soon3 , Nami Sakai4 , Masanobu Kunitomo5, Daisuke Ishihara6 and Satoshi Yamamoto7
1

National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 Department of Physics,
Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan; 3 College of Science, Ibaraki University,
Bunkyo 2-1-1, Mito 310-8512, Japan; 4 RIKEN Cluster for Pioneering Research, 2-1, Hirosawa, Wako-shi, Saitama 3510198, Japan; 5 Department of Physics, School of Medicine, Kurume University, 67 Asahi-machi, Kurume, Fukuoka 8300011, Japan; 6 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai,
Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan; 7 Department of Physics, The University of Tokyo, Hongo, Bunkyo-

16

ku, Tokyo 113-0033, Japan
E-mail contact: aya.higuchi at nao.ac.jp
We present the first sub-arcsecond images of 49 Ceti in the [C I] 3 P1 –3 P0 emission and the 614 µm dust continuum
emission observed with ALMA, as well as that in the CO(J=3–2) emission prepared by using the ALMA archival
data. The spatial distribution of the 614 µm dust continuum emission is found to have a broad-ring structure with aradius of about 100 au around the central star. A substantial amount of gas is also associated with 49 Ceti. The [C I]
emission map shows two peaks inside the dust ring, and its overall extent is comparable to that of the dust continuum
emission and the CO emission. We find that the [C I]/CO(J=3–2) intensity ratio significantly varies along the majoraxis. The ratio takes the minimum value of 1.8 around the dust peak position, and increases inwards and outwards.
The enhanced ratio around the central star (∼3) likely originates from the stellar UV radiation, while that in theouter disk (∼10) from the interstellar UV radiation. Such complex distributions of the [C I] and CO(J=3–2) emission
will be a key to understand the origin of the gas in 49 Ceti, and will also provide a stringent constraint on physicaland chemical models of gaseous debris disks.
Accepted by ApJ
https://arxiv.org/pdf/1908.07032

29

L1495 Revisited: A PPMAP View of a Star-Forming Filament
A.D.P. Howard1 , A.P. Whitworth1 , K.A. Marsh2 , S.D. Clarke3 , M.J. Griffin1 , M.W.L. Smith1 and O.D.
Lomax41

School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, CF24 3AA, UK; 2 IPAC, Caltech, 1200E
California Boulevard, Pasadena, CA 91125, USA; 3 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77,
D-50937 Köln, Germany; 4 ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, Netherlands
E-mail contact: alexander.howard at astro.cf.ac.uk

We have analysed the Herschel and SCUBA-2 dust continuum observations of the main filament in the Taurus L1495
star forming region, using the Bayesian fitting procedure ppmap. (i) If we construct an average profile along the whole
length of the filament, it has fwhm ≃ 0.087 ± 0.003 pc; , but the closeness to previous estimates is coincidental. (ii) If
we analyse small local sections of the filament, the column-density profile approximates well to the form predicted forhydrostatic equilibrium of an isothermal cylinder. (iii) The ability of ppmap to distinguish dust emitting at different
temperatures, and thereby to discriminate between the warm outer layers of the filament and the cold inner layers
near the spine, leads to a significant reduction in the surface-density, Σ, and hence in the line-density, µ. If we adopt
the canonical value for the critical line-density at a gas-kinetic temperature of 10 K, µCRIT ≃ 16 M⊙ pc−1 , the filamentis on average trans-critical, with µ̄ ∼ µCRIT ; local sections where µ > µCRIT tend to lie close to pre-stellar cores. (iv)
The ability of ppmap to distinguish different types of dust, i.e. dust characterised by different values of the emissivity
index, β, reveals that the dust in the filament has a lower emissivity index, β ≤ 1.5, than the dust outside the filament,β ≥ 1.7, implying that the physical conditions in the filament have effected a change in the properties of the dust.
Accepted by MNRAS
https://arxiv.org/pdf/1908.02295

30

Nobeyama 45 m Mapping Observations toward Orion A. II. Classification of cloud
structures and variation of the 13 CO/C18 O abundance ratio due to far-UV Radiation
Shun Ishii1,2 , Fumitaka Nakamura1,3,4 , Yoshito Shimajiri1,5,6 , Ryohei Kawabe1,3,4 , Takashi Tsukagoshi1 ,Kazuhito Dobashi7 , Tomomi Shimoikura7,8
1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 Joint ALMA Observatory, Alonso de Córdova 3107 Vitacura, Santiago, Chile; 3 The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 4 The University of Tokyo, 7-3-1 Hongo Bunkyo, 113-0033
Tokyo, Japan; 5 Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/Service d’Astrophysique, CEA
Saclay, 91191 Gif-sur-Yvette, France; 6 Department of Physics and Astronomy, Graduate School of Science andEngineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan; 7 Department of
Astronomy and Earth Sciences, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501, Japan; 817

Otsuma Womens University Faculty of Social Information Studies Chiyoda-ku, Tokyo 102-8357, Japan
E-mail contact: shun.ishii at nao.ac.jp
We present results of the classification of cloud structures toward the Orion A Giant Molecular Cloud based on widefield 12 CO (J = 1–0), 13 CO (J = 1-0), and C18 O (J = 1-0) observations using the Nobeyama 45 m radio telescope. We
identified 78 clouds toward Orion A by applying Spectral Clustering for Interstellar Molecular Emission Segmentation(SCIMES) to the data cube of the column density of 13 CO. Well-known subregions such as OMC-1, OMC-2/3, OMC-4,
OMC-5, NGC 1977, L1641-N, and the dark lane south filament (DLSF) are naturally identified as distinct structuresin Orion A. These clouds can also be classified into three groups: the integral-shaped filament, the southern regionsof Orion A, and the other filamentary structures in the outer parts of Orion A and the DLSF. These groups show
differences in scaling relations between the physical properties of the clouds. We derived the abundance ratio between
13
CO and C18 O, X13 CO /XC18 O , which ranges from 5.6 to 17.4 on median over the individual clouds. The significant
variation of X13 CO /XC18 O , is also seen within a cloud in both of the spatial and velocity directions and the ratio tends
to be high at the edge of the cloud. The values of X13 CO /XC18 O , decrease from 17 to 10 with the median of the column
15−2>
densities of the clouds at the column density of NC18 O >∼ 1 × 10 cm or visual extinction of AV ∼ 3 mag under the3strong far-ultraviolet (FUV) environment of G0 > 10 , whereas it is almost independent of the column density in the
weak FUV radiation field. These results are explained if the selective photodissociation of C18O is enhanced under astrong FUV environment and it is suppressed in the dense part of the clouds.
Accepted by PASJ
http://arxiv.org/pdf/1908.11800

31

New evidence for weak magnetic fields in Herbig Ae/Be stars
S.P. Järvinen1 , T.A. Carroll1 , S. Hubrig1 , I. Ilyin1 and M. Schöller2
1

Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany; 2 European
Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
E-mail contact: sjarvinen at aip.de
In recent years Herbig Ae/Be stars receive considerable attention as their disks are believed to be the sites of on-goingplanet formation. Confirming the presence of magnetic fields in these stars is critical for understanding the transportof angular momentum during the protostellar phase. Furthermore, magnetic fields set the conditions for strongly
anisotropic accretion. In this study we present the results of our recent observing campaigns of a sample of Herbig
Ae/Be stars aimed at measurements of their magnetic fields applying the Singular Value Decomposition method tohigh resolution spectropolarimetric observations. The strongest longitudinal magnetic field of 209 G is detected in the
Herbig Be star HD 58647, whereas the weakest field of 17 G is measured in the Herbig Ae star HD 190073. A change ofpolarity is detected for HD 58647 and in the Herbig Be star HD 98922. The obtained results provide further evidence
that Herbig Ae/Be stars possess much weaker magnetic fields than their lower mass counterpart T Tauri stars withmagnetic fields of kG order.
Accepted by MNRAS
http://arxiv.org/pdf/1908.02093

32

Dynamical Gaseous Rings in Global Simulations of Protoplanetary Disk Formation
Kundan Kadam1 , Eduard Vorobyov2,3 , Zsolt Regály1 , Ágnes Kóspál1,4 and Péter Ábrahám1
1

Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences, KonkolyThege Miklós út 15-17, 1121 Budapest, Hungary; 2 Research Institute of Physics, Southern Federal University, Stachki
Ave. 194, 344090 Rostov-on-Don, Russia; 3 Department of Astrophysics, The University of Vienna, A-1180 Vienna,
Austria; 4 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
E-mail contact: kundan.kadam at csfk.mta.hu

Global numerical simulations of protoplanetary disk formation and evolution were conducted in thin-disk limit, where
the model included magnetically layered disk structure, a self-consistent treatment for the infall from cloud core aswell as the smallest possible inner computational boundary. We compared the evolution of a layered disk with a fully
18

magnetically active disk. We also studied how the evolution depends on the parameters of the layered disk model —the MRI triggering temperature and active layer thickness — as well as the mass of the prestellar cloud core. With thecanonical values of parameters a dead zone formed within the inner ≈ 15 au region of the magnetically layered disk.
The dead zone was not a uniform structure and long-lived, axisymmetric, gaseous rings ubiquitously formed within
this region due to the action of viscous torques. The rings showed a remarkable contrast in the disk environment ascompared to a fully magnetically active disk and were characterized by high surface density and low effective viscosity.
Multiple gaseous rings could form simultaneously in the dead zone region which were highly dynamical and showed
complex, time-dependent behavior such as inward migration, vortices, gravitational instability and large-scale spiralwaves. An increase in MRI triggering temperature had only marginal effects, while changes in active layer thickness
as well as the initial cloud core mass had significant effects on the structure and evolution of the inner disk. Dust withlarge fragmentation barrier could be trapped in the rings, which may play a key role in planet formation.
Accepted by ApJ
http://arxiv.org/pdf/1908.02515

33

Abundant refractory sulfur in protoplanetary disks
Mihkel Kama1 , Oliver Shorttle1 , Adam S. Jermyn1,2 , Colin P. Folsom3, Kenji Furuya4 , Edwin A.
Bergin5 , Catherine Walsh6 , and Lindsay Keller7
1

Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 2 Kavli Institute for
Theoretical Physics, University of California at Santa Barbara, Santa Barbara, CA 93106, USA; 3 IRAP, Université deToulouse, CNRS, UPS, CNES, 31400, Toulouse, France; 4 Center for Computational Sciences, University of Tsukuba,
1-1-1 Tennoudai, 305-8577, Tsukuba, Japan; 5 Department of Astronomy, University of Michigan, 1085 S. University
Avenue, Ann Arbor, MI 48109, USA; 6 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK;
7
ARES, Code XI3, NASA/JSC, Houston, TX 77058, USA
E-mail contact: mkama at ast.cam.ac.uk
Sulfur is one of the most abundant elements in the Universe, with important roles in astro-, geo-, and biochemistry.
Its main reservoirs in planet-forming disks have previously eluded detection: gaseous molecules only account for <1%of total elemental sulfur, with the rest likely in either ices or refractory minerals. Mechanisms such as giant planets
can filter out dust from gas accreting onto disk-hosting stars. For stars above 1.4 solar masses, this leaves a chemicalsignature on the stellar photosphere that can be used to determine the fraction of each element that is locked in dust.
Here, we present an application of this method to sulfur, zinc, and sodium. We analyse the accretion-contaminatedphotospheres of a sample of young stars and find (89±8)% of elemental sulfur is in refractory form in their disks. The
main carrier is much more refractory than water ice, consistent with sulfide minerals such as FeS.
Accepted by ApJ

http://arxiv.org/pdf/1908.05169

34

Constraining the detectability of water ice in debris disks
Minjae Kim1 , Sebastian Wolf1 , Alexey Potapov2 , Harald Mutschke3 and C. Jäger2
1

Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 15, 24118
Kiel, Germany; 2 Laborastrophysikgruppe des Max-Planck-Instituts für Astronomie am Institut für Festkörperphysik,Friedrich-Schiller-Universität Jena, Helmholtzweg 3, 07743 Jena, Germany; 3 Astrophysikalisches Institut und Universitäts-Sternwarte, Friedrich-Schiller-Universität Jena, Schillergäßchen 2-3, 07745 Jena, Germany
E-mail contact: mkim at astrophysik.uni-kiel.de
Water ice is important for the evolution and preservation of life. Identifying the distribution of water ice in debris disks
is therefore of great interest in the field of astrobiology. Furthermore, icy dust grains are expected to play importantroles throughout the entire planet formation process. However, currently available observations only allow deriving
weak conclusions about the existence of water ice in debris disks. We investigate whether it is feasible to detect water
ice in typical debris disk systems. We take the following ice destruction mechanisms into account: sublimation ofice, dust production through planetesimal collisions, and photosputtering by UV-bright central stars. We consider
icy dust mixture particles with various shapes consisting of amorphous ice, crystalline ice, astrosilicate, and vacuum
19inclusions (i.e., porous ice grains). We calculated optical properties of inhomogeneous icy dust mixtures using effective
medium theories, that is, Maxwell-Garnett rules. Subsequently, we generated synthetic debris disk observables, suchas spectral energy distributions and spatially resolved thermal reemission and scattered light intensity and polarization
maps with our code DMS. We find that the prominent ∼ 3 µm and 44 µm water ice features can be potentially detectedin future observations of debris disks with the James Webb Space Telescope (JWST) and the Space Infrared telescope
for Cosmology and Astrophysics (SPICA). We show that the sublimation of ice, collisions between planetesimals, andphotosputtering caused by UV sources clearly affect the observational appearance of debris disk systems. In addition,highly porous ice (or ice-rich aggregates) tends to produce highly polarized radiation at around 3 µm. Finally, thelocation of the ice survival line is determined by various dust properties such as a fractional ratio of ice versus dust,
physical states of ice (amorphous or crystalline), and the porosity of icy grains.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/1908.07354

Molecular envelope around the HII region RCW 120

35 M. S. Kirsanova1 , Ya. N. Pavlyuchenkov1 , D. S. Wiebe1, P. A. Boley2,3, S. V. Salii3, S. V. Kalenskii4,
A. M. Sobolev3 and L. D. Anderson5,6,7
1

Institute of Astronomy, Russian Academy of Sciences, 119017, 48 Pyatnitskaya Str., Moscow, Russia; 2 Moscow
Institute of Physics and Technology, 141701, 9 Institutskiy per., Dolgoprudny, Moscow Region, Russia; 3 Ural Federal
University, 620075, 19 Mira Str., Ekaterinburg, Russia; 4 Astro Space Center, Lebedev Physical Institute, Russian
Academy of Sciences, 117997, 84/32 Profsoyuznaya Str., Moscow, Russia; 5 Department of Physics and Astronomy,West Virginia University, Morgantown WV 26506, USA; 6 Adjunct Astronomer at the Green Bank Observatory, P.O.
Box 2, Green Bank WV 24944, USA; 7 Center for Gravitational Waves and Cosmology, West Virginia University,
Chestnut Ridge Research Building, Morgantown, WV 26505, USA
E-mail contact: kirsanova at inasan.ru
The HII region RCW 120 is a well-known object, which is often considered as a target to verify theoretical models
of gas and dust dynamics in the interstellar medium. However, the exact geometry of RCW 120 is still a matter of
debate. In this work, we analyse observational data on molecular emission in RCW 120 and show that 13 CO(2–1) and
C18 O(2–1) lines are fitted by a 2D model representing a ring-like face-on structure. The changing of the C18 O(3–2)
line profile from double-peaked to single-peaked from the dense molecular Condensation 1 might be a signature ofstalled expansion in this direction. In order to explain a self-absorption dip of the 13 CO(2–1) and 13 CO(3–2) lines,
we suggest that RCW 120 is surrounded by a diffuse molecular cloud, and find confirmation of this cloud on a map ofinterstellar extinction. Optically thick 13 CO(2–1) emission and the infrared 8 µm PAH band form a neutral envelopeof the HII region resembling a ring, while the envelope breaks into separate clumps on images made with opticallythin C18 O(2–1) line and far-infrared dust emission.
Accepted by MNRAS, 488, 5641, 2019https://arxiv.org/pdf/1908.05394

A Comparison of the X-ray Properties of FU Ori-type Stars to Generic Young Stellar

36 Objects

Michael A. Kuhn1 and Lynne A. Hillenbrand1
1

Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA

E-mail contact: mkuhn at astro.caltech.edu
Like other young stellar objects (YSOs), FU Ori-type stars have been detected as strong X-ray emitters. However,
little is known about how the outbursts of these stars affect their X-ray properties. We assemble available X-ray
data from XMM Newton and Chandra observations of 16 FU Ori stars, including a new XMM Newton observation ofGaia 17bpi during its optical rise phase. Of these stars, six were detected at least once, while 10 were non-detections,for which we calculate upper limits on intrinsic X-ray luminosity (LX ) as a function of plasma temperature (kT ) andcolumn density (NH ). The detected FU Ori stars tend to be more X-ray luminous than typical for non-outbursting
YSOs, based on comparison to a sample of low-mass stars in the Orion Nebula Cluster. FU Ori stars with high LX
20

have been observed both at the onset of their outbursts and decades later. We use the Kaplan-Meier estimator toinvestigate whether the higher X-ray luminosities for FU Ori stars is characteristic or a result of selection effects, andwe find the difference to be statistically significant (p < 0.01) even when non-detections are taken into account. The
additional X-ray luminosity of FU Ori stars relative to non-outbursting YSOs cannot be explained by accretion shocks,
given the high observed plasma temperatures. This suggests that, for many FU Ori stars, either 1) the outburst leads
to a restructuring of the magnetosphere in a way that enhances X-ray emission, or 2) FU Ori outbursts are more likely
to occur among YSOs with the highest quiescent X-ray luminosity.
Accepted by ApJ
https://arxiv.org/pdf/1907.03325

37

Disk Formation in Magnetized Dense Cores with Turbulence and Ambipolar Diffusion
Ka Ho Lam1 , Zhi-Yun Li1 , Che-Yu Chen1 , Kengo Tomida2,3 and Bo Zhao4
1

Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 2 Department of Earth andSpace Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; 3 Department of Astrophysical Sciences, Princeton
University, Princeton, NJ 08544, USA; 4 Max-Planck-Institut für extraterrestrische Physik (MPE), Garching D-85748,
Germany
E-mail contact: kl4sf at virginia.edu
Disks are essential to the formation of both stars and planets, but how they form in magnetized molecular cloud
cores remains debated. This work focuses on how the disk formation is affected by turbulence and ambipolar diffusion(AD), both separately and in combination, with an emphasis on the protostellar mass accretion phase of star formation.
We find that a relatively strong, sonic turbulence on the core scale strongly warps but does not completely disrupt
the well-known magnetically-induced flattened pseudodisk that dominates the inner protostellar accretion flow in thelaminar case, in agreement with previous work. The turbulence enables the formation of a relatively large disk atearly times with or without ambipolar diffusion, but such a disk remains strongly magnetized and does not persist
to the end of our simulation unless a relatively strong ambipolar diffusion is also present. The AD-enabled disks inlaminar simulations tend to fragment gravitationally. The disk fragmentation is suppressed by initial turbulence. The
ambipolar diffusion facilitates the disk formation and survival by reducing the field strength in the circumstellar region
through magnetic flux redistribution and by making the field lines there less pinched azimuthally, especially at latetimes. We conclude that turbulence and ambipolar diffusion complement each other in promoting disk formation. The
disks formed in our simulations inherit a rather strong magnetic field from its parental core, with a typical plasma-βof order a few tens or smaller, which is 2-3 orders of magnitude lower than the values commonly adopted in MHD
simulations of protoplanetary disks. To resolve this potential tension, longer-term simulations of disk formation andevolution with increasingly more realistic physics are needed.
Accepted by MNRAS
https://arxiv.org/pdf/1908.11806

38

Evaluation of nearby young moving groups based on unsupervised machine learning
Jinhee Lee1 and Inseok Song1
1

Department of Physics and Astronomy, The University of Georgia, Athens, GA 30602

E-mail contact: jinhee at uga.edu
Nearby young stellar moving groups have been identified by many research groups with different methods and criteria
giving rise to cautions on the reality of some groups. We aim to utilise moving groups in an unbiased way to createa list of unambiguously recognisable moving groups and their members. For the analysis, two unsupervised machinelearning algorithms (K-means and Agglomerative Clustering) are applied to previously known bona fide members ofnine moving groups from our previous study. As a result of this study, we recovered six previously known groups(AB Doradus, Argus, β-Pic, Carina, TWA, and Volans-Carina). Three the other known groups are recognised as well;
however, they are combined into two new separate groups (ThOr+Columba and TucHor+Columba).
Accepted by MNRAS
http://arxiv.org/pdf/1908.05922

21

39

Characterizing Magnetic Field Morphologies in Three Serpens Protostellar Cores with
ALMA
Valentin J. M. Le Gouellec1,2 , Charles L. H. Hull3,4 , Analle J. Maury2,5 , Josep M. Girart6,7 , Lukasz
Tychoniec8 , Lars E. Kristensen9 , Zhi-Yun Li10 , Fabien Louvet11 , Paulo C. Cortes4,12 and Ramprasad
Rao13
1

European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 2 AIM, CEA, CNRS, Universit
Paris-Saclay, Universit Paris Diderot, Sorbonne Paris Cite, F-91191 Gif-sur-Yvette, France; 3 National Astronomical
Observatory of Japan, NAOJ Chile, Alonso de Córdova 3788, Office 61B, 7630422, Vitacura, Santiago, Chile; 4Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 5 Harvard-Smithsonian Center for
Astrophysics, Cambridge, MA 02138, USA; 6 Institut de Cincies de l’Espai (ICE-CSIC), Campus UAB, Carrer de
Can Magrans S/N, E-08193 Cerdanyola del Valls, Catalonia; 7 Institut d’Estudis Espacials de Catalunya, E-08030
Barcelona, Catalonia; 8 Leiden Observatory, Leiden University, PO Box 9513, 23000RA, Leiden, The Netherlands;
9
Centre for Star and Planet Formation, Niels Bohr Institute and Natural History Museum of Denmark, Universityof Copenhagen, ster Voldgade 5-7, DK-1350 Copenhagen K, Denmark; 10 Department of Astronomy, University ofVirginia, 530 McCormick Road, Charlottesville, VA 22904, USA; 11 Departamento de Astronoma, Universidad deChile, Camino el Observatorio 1515, Las Condes, Santiago, Chile; 12 National Radio Astronomy Observatory, 520
Edgemont Road, Charlottesville, VA 22903, USA; 13 Submillimeter Array, Academia Sinica Institute of Astronomy
and Astrophysics, 645 N. Aohoku Place, Hilo, HI 96720, USA
E-mail contact: Valentin.LeGouellec at eso.org
With the aim of characterizing the dynamical processes involved in the formation of young protostars, we present highangular resolution ALMA dust polarization observations of the Class 0 protostellar cores Serpens SMM1, Emb 8(N),and Emb 8. With spatial resolutions ranging from 150 to 40 au at 870 µm, we find unexpectedly high values of thepolarization fraction along the outflow cavity walls in Serpens Emb8(N). We use 3 mm and 1 mm molecular tracers toinvestigate outflow and dense gas properties and their correlation with the polarization. These observations allow us
to investigate the physical processes involved in the Radiative Alignment Torques (RATs) acting on dust grains along
the outflow cavity walls, which experience irradiation from accretion processes and outflow shocks. The inner core of
SMM1-a presents a polarization pattern with a poloidal magnetic field at the bases of the two lobes of the bipolar
outflow. To the south of SMM1-a we see two polarized filaments, one of which seems to trace the redshifted outflow
cavity wall. The other may be an accretion streamer of material infalling onto the central protostar. We propose thatthe polarized emission we see at millimeter wavelengths along the irradiated cavity walls can be reconciled with the
expectations of RAT theory if the aligned grains present at ¡ 500 au scales in Class 0 envelopes have grown larger thanthe 0.1 µm size of ISM dust grains. Our observations allow us to constrain the star-forming sources magnetic fieldmorphologies within the central cores, along the outflow cavity walls, and in possible accretion streamers.
Accepted by APJ
https://arxiv.org/pdf/1909.00046

40

Diagnosing 0.1–10 au scale morphology of the FU Ori disk using ALMA and VLTI/GRAVITY
Hauyu Baobab Liu1 , Antoine Mérand2 , Joel D. Green3 , Sebastián Pérez4 , Antonio S. Hales5 , YaoLun Yang6 , Michael M. Dunham7 , Yasuhiro Hasegawa8 , Thomas Henning9 , Roberto Galván-Madrid10 ,Ágnes Kóspál11,9 , Michihiro Takami1 , Eduard I. Vorobyov12,13 , Zhaohuan Zhu14
1

Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan; 2 European
Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748, Garching, Germany; 3 Space Telescope Science Institute, Baltimore, MD 21218, USA ; Department of Astronomy, The University of Texas at Austin, Austin, TX 78712,
USA; 4 Universidad de Santiago de Chile, Av. Libertador Bernardo O’Higgins 3363, Estación Central, Santiago, Chile;
5
Joint ALMA Observatory, Avenida Alonso de CÃşrdova 3107, Vitacura 7630355, Santiago, Chile; National Radio
Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, USA; 6 The University of Texas atAustin, Department of Astronomy, 2515 Speedway, Stop C1400, Austin, TX 78712, USA; 7 Department of Physics,
State University of New York at Fredonia, 280 Central Avenue, Fredonia, NY 14063, USA; 8 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA; 9 Max Planck Institute for Astronomy (MPIA),
Königstuhl 17, 69117 Heidelberg, Germany; 10 Instituto de Radioastronomı́a y Astrofı́sica (IRyA), UNAM, Apdo.
Postal 72-3 (Xangari), Morelia, Michoacn 58089, Mexico; 11 Konkoly Observatory, Research Centre for Astronomy
22and Earth Sciences, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary; 12
Department of Astrophysics, University of Vienna, Vienna, 1180, Austria; 13 Research Institute of Physics, Southern
Federal University, Rostov-on-Don, 344090 Russia; 14 Department of Physics and Astronomy, University of Nevada,
Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154, USA E-mail contact: hyliu at asiaa.sinica.edu.tw
We report new Atacama Large Millimeter/submillimeter Array Band 3 (86–100 GHz; ∼80 mas angular resolution)
and Band 4 (146–160 GHz; ∼50 mas angular resolution) observations of the dust continuum emission towards thearchetypal and ongoing accretion burst young stellar object FU Ori, which simultaneously covered its companion, FU
Ori S. In addition, we present near-infrared (2–2.45 µm) observations of FU Ori taken with the General Relativity
Analysis via VLT InTerferometrY (GRAVITY; ∼1 mas angular resolution) instrument on the Very Large TelescopeInterferometer (VLTI). We find that the emission in both FU Ori and FU Ori S at (sub)millimeter and near infrared
bands is dominated by structures inward of ∼10 au radii. We detected closure phases close to zero from FU Ori
with VLTI/GRAVITY, which indicate the source is approximately centrally symmetric and therefore is likely viewed
nearly face-on. Our simple model to fit the GRAVITY data shows that the inner 0.4 au radii of the FU Ori disk has atriangular spectral shape at 2–2.45 µm, which is consistent with the H2 O and CO absorption features in a Ṁ ∼ 10−4M⊙ yr−1 , viscously heated accretion disk. At larger (∼0.4–10 au) radii, our analysis shows that viscous heating may
also explain the observed (sub)millimeter and centimeter spectral energy distribution when we assume a constant,∼ 10−4 M⊙ yr−1 mass inflow rate in this region. This explains how the inner 0.4 au disk is replenished with mass
at a modest rate, such that it neither depletes nor accumulates significant masses over its short dynamic timescale.
Finally, we tentatively detect evidence of vertical dust settling in the inner 10 au of the FU Ori disk, but confirmation
requires more complete spectral sampling in the centimeter bands.
Accepted by ApJ
http://arxiv.org/pdf/1908.02981

41

Constraining the Formation of the Four Terrestrial Planets in the Solar System
Patryk Sofia Lykawka1 and Takashi Ito2
1

School of Interdisciplinary Social and Human Sciences, Kindai University, Shinkamikosaka 228-3, Higashiosaka,
Osaka, 577-0813, Japan; 2 National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo, 181-8588,
JapanE-mail contact: patryksan at gmail.com
To reproduce the orbits and masses of the terrestrial planets (analogs) of the solar system, most studies scrutinize
simulations for success as a batch. However, there is insufficient discussion in the literature on the likelihood of
forming planet analogs simultaneously in the same system (analog system). To address this issue, we performed 540
N-body simulations of protoplanetary disks representative of typical models in the literature. We identified a totalof 194 analog systems containing at least three analogs, but only 17 systems simultaneously contained analogs ofthe four terrestrial planets. From an analysis of our analog systems, we found that, compared to the real planets,
truncated disks based on typical outcomes of the Grand Tack model produced analogs of Mercury and Mars that were
too dynamically cold and located too close to the Venus and Earth analogs. Additionally, all the Mercury analogs
were too massive, while most of the Mars analogs were more massive than Mars. Furthermore, the timing of theMoon-forming impact was too early in these systems, and the amount of additional mass accreted after the event
was too great. Therefore, such truncated disks cannot explain the formation of the terrestrial planets. Our results
suggest that forming the four terrestrial planets requires disks with the following properties: 1) Mass concentrated
in narrow core regions between ∼0.7–0.9 and ∼1.0–1.2 au; 2) an inner region component starting at ∼0.3–0.4 au; 3)a less massive component beginning at ∼1.0–1.2 au; 4) embryos rather than planetesimals carrying most of the disk
mass; and 5) Jupiter and Saturn placed on eccentric orbits.
Accepted by ApJ
http://arxiv.org/pdf/1908.04934

23

42

Runaway Young Stars in the Orion Nebula
Aidan McBride1 and Marina Kounkel1
1

Department of Physics and Astronomy, Western Washington University, 516 High St, Bellingham, WA 98225

E-mail contact: mcbrida5 at wwu.edu
The star forming region of the Orion Nebula (ONC) is ideal to study the stellar dynamics of young stars in a clusteredenvironment. Using Gaia DR2 we search for the pre-main sequence stars with unusually high proper motions that may
be representative of a dynamical ejection from unstable young triple systems or other close three-body encounters.
We identify twenty-six candidate stars that are likely to have had such an encounter in the last 1 Myr. Nine of thesestars could be traced back to the densest central-most region of the ONC, the Trapezium, while five others have likelyinteractions with other OB-type stars in the cluster. Seven stars originate from other nearby populations within theOrion Complex that coincidentally scattered towards the ONC. A definitive point of origin cannot be identified forthe remaining sources. These observations shed light on the frequency of the ejection events in young clusters.
Accepted by ApJ
http://arxiv.org/pdf/1908.07550

43

The physical and chemical structure of Sagittarius B2 – V. Non-thermal emission in theenvelope of Sgr B2
F. Meng1 , Á. Sánchez-Monge1 , P. Schilke1 , M. Padovani2 , A. Marcowith3 , A. Ginsburg4 , A. Schmiedeke5 ,A. Schwörer1 , C. DePree6 , V. S. Veena1 , and Th. Möller1
1

I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany; 2 INAF-Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 3 Laboratoire Univers et Particules de Montpellier,UMR 5299 du CNRS, Universit de Montpellier, place E. Bataillon, cc072, 34095 Montpellier, France; 4 Jansky Fellowof the National Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801, USA; 5 Max Planck Institutefor Extraterrestrial Physics, Giessenbachstrasse 1, D-85748 Garching, Germany; 6 Agnes Scott College, 141 E. College
Ave., Decatur, GA 30030, USA
E-mail contact: meng at ph1.uni-koeln.de
The giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most massive region with ongoing high-mass starformation in the Galaxy. In the southern region of the 40-pc large envelope of SgrB2, we encounter the SgrB2(DS)region which hosts more than 60 high-mass protostellar cores distributed in an arc shape around an extended HII
region. We use the Very Large Array in its CnB and D configurations, and in the frequency bands C (4–8 GHz) andX (8–12 GHz) to observe the whole SgrB2 complex. Continuum and radio recombination line maps are obtained. We
detect radio continuum emission in SgrB2(DS) in a bubble-shaped structure. From 4 to 12 GHz, we derive a spectral
index between −1.2 and −0.4, indicating the presence of non-thermal emission. We decompose the contribution fromthermal and non-thermal emission, and find that the thermal component is clumpy and more concentrated, while thenon-thermal component is more extended and diffuse. The radio recombination lines in the region are found to be notin local thermodynamic equilibrium (LTE) but stimulated by the non-thermal emission. The thermal free-free emission
is likely tracing an HII region ionized by an O7 star, while the non-thermal emission can be generated by relativistic
electrons created through first-order Fermi acceleration. We have developed a simple model of the SgrB2(DS) region
and found that first-order Fermi acceleration can reproduce the observed flux density and spectral index.
Accepted by A&A
http://arxiv.org/pdf/1908.07237

44

The chemical structure of the very young starless core L1521E
Z. Nagy1 , S. Spezzano1 , P. Caselli1, A. Vasyunin2,3 , M. Tafalla4 , L. Bizzocchi1 , D. Prudenzano1 and E.
Redaelli1
1
Centre for Astrochemical Studies, Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748
Garching, Germany; 2 Ural Federal University, Ekaterinburg 620002, Russia; 3 Visiting Leading Researcher, Engineering Research Institute, ’Ventspils International Radio Astronomy Centre’ of Ventspils University of Applied Sciences,

24

Inzenieru 101, VentspilsLV-3601, Latvia; 4 Observatorio Astronómico Nacional (IGN), Calle Alfonso XII, 3 Madrid,Spain
E-mail contact: znagy at mpe.mpg.de
L1521E is a dense starless core in Taurus that was found to have relatively low molecular depletion by earlier studies,
thus suggesting a recent formation.
We aim to characterize the chemical structure of L1521E and compare it to the more evolved L1544 pre-stellar core.
We have obtained ∼2.5×2.5 arcminute maps toward L1521E using the IRAM-30m telescope in transitions of various
species, including C17 O, CH3 OH, c-C3 H2 , CN, SO, H2 CS, and CH3 CCH. We derived abundances for the observed
species and compared them to those obtained toward L1544. We estimated CO depletion factors using the C17 O
IRAM-30m map, an N (H2 ) map derived from Herschel /SPIRE data and a 1.2 mm dust continuum emission map
obtained with the IRAM-30m telescope.
Similarly to L1544, c-C3 H2 and CH3 OH peak at different positions. Most species peak toward the c-C3 H2 peakincluding C2 S, C3 S, HCS+ , HC3 N, H2 CS, CH3 CCH, and C34 S. C17 O and SO peak close to both the c-C3 H2 and theCH3 OH peaks. CN and N2 H+ peak close to the Herschel dust peak. We found evidence of CO depletion toward
L1521E. The lower limit of the CO depletion factor derived toward the Herschel dust peak is 4.3±1.6, which is abouta factor of three lower than toward L1544. We derived abundances for several species toward the dust peaks of L1521E
and L1544. The abundances of most sulfur-bearing molecules such as C2 S, HCS+ , C34 S, C33 S, and HCS+ are higher
toward L1521E than toward L1544 by factors of ∼2-20, compared to the abundance of A-CH3 OH. The abundance of
methanol is very similar toward the two cores.
The fact that the abundances of sulfur-bearing species toward L1521E are higher than toward L1544 suggests thatsignificant sulfur depletion takes place during the dynamical evolution of dense cores, from the starless to pre-stellar
stage. The CO depletion factor measured toward L1521E suggests that CO is more depleted than previously found.
Similar CH3 OH abundances between L1521E and L1544 hint that methanol is forming at specific physical conditions
22−2
in the Taurus Molecular Cloud Complex, characterized by densities of a few ×104 cm−3 and N (H2 ) >∼ 10 cm , when
CO starts to catastrophically freeze-out, while water can still be significantly photodissociated, so that the surfaces ofdust grains become rich in solid CO and CH3 OH, as already found toward L1544. Methanol can thus provide selective
crucial information about the transition region between dense cores and the surrounding parent cloud.
Accepted by A&A
https://arxiv.org/pdf/1904.01136

45First clear detection of the CCS Zeeman splitting toward the pre-stellar core, Taurus
Molecular Cloud-1
Fumitaka Nakamura1 , Seiji Kameno2 , Takayoshi Kusune3 , Izumi Mizuno4 , Kazuhito Dobashi5 , Tomomi
Shimoikura5,6 and Kotomi Taniguchi7
1

NAOJ, Sokendai, Univ. of Tokyo; 2 NAOJ, JAO; 3 NAOJ; 4 EAO; 5 Tokyo Gakugei University; 6 Otsuma Women
University; 7 University of Virginia
E-mail contact: fumitaka.nakamura at nao.ac.jp
We report a first clear detection of the Zeeman splitting of a CCS emission line at 45 GHz toward a nearby prestellar
dense filament, Taurus Molecular Cloud-1. We observed HC3 N non-Zeeman line simultaneously as the CCS line,
and did not detect any significant splitting of HC3 N line. Thus, we conclude that our detection of the CCS Zeeman
splitting is robust. The derived line-of-sight magnetic field strength is about 117 ± 21 µG, which corresponds to thenormalized mass-to-magnetic flux ratio of 2.2 if we adopt the inclination angle of 45◦ . Thus, we conclude that the
TMC-1 filament is magnetically supercritical. Recent radiative transfer calculations of CCS and HC3 N lines along theline of sight suggest that the filament is collapsing with a speed of ∼ 0.6 km s−1 , which is comparable to three times theisothermal sound speed. This infall velocity appears to be consistent with the evolution of a gravitationally-infallingcore.
Accepted by PASJ
http://arxiv.org/pdf/1908.07708

25

46

Variability of Hα emission in young stellar objects in the cluster IC 348
Elena Nikoghosyan1 and Naira Azatyan1
1

Byurakan Astrophysical observatory, 0213, Byurakan vil., Aragatsotn reg., Armenia

E-mail contact: elena at bao.sci.am
Hα emission is one of the most prominent features of young stellar objects in the optical range, and importantly, theequivalent width of Hα emission (EW(Hα )) is used to characterize an evolutionary stage of young stars.
The aim of this work is to identify and study the stellar objects with variable EW(Hα ) in the young stellar cluster
IC 348. We performed photometric and slit-less observations at several epochs in order to reveal the variable objects.
Significant variability of EW(Hα ) was found in 90 out of 127 examined stars. From all epochs of observations, 32
objects were classified as CTT (classical T Tauri) and 69 as WTT (weak-line T Tauri) objects. The fraction of thevariables in these samples is about 60%. We also identified 20 stellar objects, which showed not only a significant
variability of the equivalent width, but which also change their apparent evolutionary stage (CTT ⇐⇒ WTT). For 6stars, Hα line was observed both in emission and in absorption.
The analysis of data obtained over a wide wavelength range (from X-ray to mid-infrared) has shown that Hα activity
and the measure of its variability are in good agreement with the activity of stellar objects measured with its otherparameters, such as X-ray radiation and the mass accretion rate. The EW(Hα ) differs not only between objects at
different evolutionary stages, but also between variable and non-variable objects. The variables in the CTT and WTT
samples are more active than non-variables although they have almost the same evolutionary age. Another distinct
difference between these variables and non-variables is their average masses. The variables from both CTT and
WTT samples are noticeably more massive than non-variables. Our data confirm the assumption made for other starformation regions, that the decay of accretion activity occurs more slowly for more massive CTT objects. Apparently,
a similar trend is also present in WTT objects, which are at a later stage of evolution. The variability of the stellar
objects, which change their evolutionary classes (CTT ⇐⇒ WTT), at least in a fraction of them, is due to the factthat they are close binaries, which affects and modulates their Hα emission activity.
Accepted by PASA
http://arxiv.org/pdf/1908.07987

47

Impact of Cosmic-Ray Feedback on Accretion and Chemistry in Circumstellar Disks
Stella S.R. Offner1 , Brandt A.L. Gaches2,3 , and Jonathan R. Holdship4
1

Department of Astronomy, The University of Texas at Austin, TX 78712, USA; 2 Department of Astronomy,
University of Massachusetts, Amherst, MA 01003, USA; 3 I. Physikalisches Institut, Universität zu Köln, Zülpicher
Str. 77, Germany; 4 Dept. of Physics and Astronomy, University College London, WC1E 6BT, London, UK

E-mail contact: soffner at astro.as.utexas.edu
We use the gas-grain chemistry code UCLCHEM to explore the impact of cosmic-ray feedback on the chemistry ofcircumstellar disks. We model the attenuation and energy losses of the cosmic-rays as they propagate outwards fromthe star and also consider ionization due to stellar radiation and radionuclides. For accretion rates typical of youngstars, Ṁ∗ ∼ 10−9 –10−6 M⊙ yr−1 , we show that cosmic rays accelerated by the stellar accretion shock produce a
cosmic-ray ionization rate at the disk surface ζ ≥ 10−15 s−1 , at least an order of magnitude higher than the ionization
rate associated with the Galactic cosmic-ray background. The incident cosmic-ray flux enhances the disk ionization
at intermediate to high surface densities (Σ > 10 g cm−2 ) particularly within 10 au of the star. We find the dominant−2
ions are C+ , S+ and Mg+ in the disk surface layers, while the H+.
3 ion dominates at surface densities above 1.0 g cm
We predict the radii and column densities at which the magneto-rotational instability (MRI) is active in T Tauri disks
and show that ionization by cosmic-ray feedback extends the MRI-active region towards the disk mid-plane. However,the MRI is only active at the mid-plane of a minimum mass solar nebula disk if cosmic-rays propagate diffusively(ζ ∝ r−1 ) away from the star. The relationship between accretion, which accelerates cosmic rays, the dense accretion
columns, which attenuate cosmic rays, and the MRI, which facilitates accretion, create a cosmic-ray feedback loopthat mediates accretion and may produce luminosity variability.
Accepted by ApJ
http://arxiv.org/pdf/1908.08061

26

48

Non-thermal emission from cosmic rays accelerated in Hii regions
Marco Padovani1 , Alexandre Marcowith2 , Álvaro Sánchez-Monge3 , Fanyi Meng3 and Peter Schilke3
1

INAF-Osservatorio Astrofisico di Arcetri, Italy; 2 LUPM-Université de Montpellier, France; 3 I. Physikalisches
Institut, Universität zu Köln, Germany
E-mail contact: padovani at arcetri.astro.it

Radio observations at metre-centimetre wavelengths shed light on the nature of the emission of Hii regions. Usually thiscategory of objects is dominated by thermal radiation produced by ionised hydrogen, namely protons and electrons.
However, a number of observational studies have revealed the existence of Hii regions with a mixture of thermal
and non-thermal radiation. The latter represents a clue as to the presence of relativistic electrons. However, neither
the interstellar cosmic-ray electron flux nor the flux of secondary electrons, produced by primary cosmic rays throughionisation processes, is high enough to explain the observed flux densities. We investigate the possibility of accelerating
local thermal electrons up to relativistic energies in Hii region shocks. We assumed that relativistic electrons can be
accelerated through the first-order Fermi acceleration mechanism and we estimated the emerging electron fluxes, thecorresponding flux densities, and the spectral indexes. We find flux densities of the same order of magnitude of thoseobserved. In particular, we applied our model to the ‘deep south’ (DS) region of Sagittarius B2 and we succeeded in
reproducing the observed flux densities with an accuracy of less than 20% as well as the spectral indexes. The model
also gives constraints on magnetic field strength (0.3 − 4 mG), density (1 − 9 × 104 cm−3 ), and flow velocity in theshock reference frame (33 − 50 km s−1 ) expected in DS. We suggest a mechanism able to accelerate thermal electrons
inside HII regions through the first-order Fermi acceleration. The existence of a local source of relativistic electrons
can explain the origin of both the observed non-thermal emission and the corresponding spectral indexes.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1908.07246

49

Hα emission-line stars in molecular clouds
Bertil Pettersson1 and Bo Reipurth2
1

Observational Astronomy, Division of Astronomy and Space Physics, Department of Physics and Astronomy,
Uppsala University, Box 516, SE-751 20 Uppsala, Sweden ; 2 Institute for Astronomy, University of Hawaii at Manoa,
640 North Aohoku Place, Hilo, HI 96720, USA
E-mail contact: bertil.pettersson@physics.uu.se
A deep objective-prism survey for Hα emission stars towards the Canis Major star forming clouds has been performed.
A total of 398 Hα emitters were detected, 353 of which are new detections. There is a strong concentration of these Hαemitters towards the molecular clouds surrounding the CMa OB1 association, and it is likely that these stars are youngstellar objects recently born in the clouds. An additional population of Hα emitters is scattered all across the region,and probably includes unrelated foreground dMe stars and background Be stars. About 90% of the Hα emitters aredetected by WISE, 75 % with usable photometry. When plotted in a WISE colour-colour diagram it appears that the
majority are Class II YSOs. Coordinates and finding charts are provided for all the new stars, and coordinates for all
detections. We searched the Gaia-DR2 catalogue and from 334 Hα emission stars with useful parallaxes, we selecteda subset of 98 stars which have parallax errors less than 20% and nominal distances in the interval 1050 to 1350 pc
that surrounds a strong peak at 1185 pc in the distance distribution. Similarly, Gaia distances were obtained for 51
OB-stars located towards Canis Major and selected with the same parallax errors as the Hα stars. We find a median
distance for the OB stars of 1182 pc, in excellent correspondence with the distance from the Hα stars. Two known
runaway stars are confirmed as members of the association. Finally, two new Herbig-Haro objects are identified.
Accepted by Astron. & Astrophys.
http://arxiv.org/pdf/1908.11446

50

Dusty clumps in circumbinary discs
Pedro P. Poblete1,2 , Nicolás Cuello1,2, and Jorge Cuadra1,2
1

Instituto de Astrofı́sica, Pontificia Universidad Católica de Chile, Santiago, Chile; 2 Núcleo Milenio de Formación27Planetaria (NPF), Chile
E-mail contact: pppoblete at uc.cl
Recent observations have revealed that protoplanetary discs often exhibit cavities and azimuthal asymmetries such as
dust traps and clumps. The presence of a stellar binary system in the inner disc regions has been proposed to explain
the formation of these structures. Here, we study the dust and gas dynamics in circumbinary discs around eccentricand inclined binaries. This is done through two-fluid simulations of circumbinary discs, considering different valuesof the binary eccentricity and inclination. We find that two kinds of dust structures can form in the disc: a single
horseshoe-shaped clump, on top of a similar gaseous over-density; or numerous clumps, distributed along the innerdisc rim. The latter features form through the complex interplay between the dust particles and the gaseous spirals
caused by the binary. All these clumps survive between one and several tens of orbital periods at the feature location.
We show that their evolution strongly depends on the gas-dust coupling and the binary parameters. Interestingly,
these asymmetric features could in principle be used to infer or constrain the orbital parameters of a stellar companion— potentially unseen — inside the inner disc cavity. Finally, we apply our findings to the disc around AB Aurigae.
Accepted by MNRAS
http://arxiv.org/pdf/1908.05784

51

Infrared and sub-mm observations of outbursting young stars with Herschel and Spitzer
Andreas Postel1 , Marc Audard1 , Eduard Vorobyov2,3 , Odysseas Dionatos2 , Christian Rab4 and ManuelGüdel2
1

University of Geneva, Department of Astronomy, Chemin d’Ecogia 16, 1290 Versoix, Switzerland; 2 Universityof Vienna, Department of Astrophysics, Türkenschanzstrasse 17, Vienna, Austria; 3 Research Institute of Physics,
Southern Federal University, Stachki 194, Rostov-on-Don, 344090 Russia; 4 Kapteyn Astronomical Institute, Universityof Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands
E-mail contact: andreas.postel at unige.ch
Episodic accretion plays an important role in the evolution of young stars. Although it has been under investigation
for a long time, the origin of such episodic accretion events is not yet understood. We investigate the dust and gas
emission of a sample of young outbursting sources in the infrared to get a better understanding of their properties andcircumstellar material, and we use the results in a further work to model the objects. We used Herschel data, fromour PI program of 12 objects and complemented with archival observations to obtain the spectral energy distributions(SEDs) and spectra of our targets. We report here the main characteristics of our sample, focussing on the SED
properties and on the gas emission lines detected in the PACS and SPIRE spectra. The SEDs of our sample show
the diversity of the outbursting sources, with several targets showing strong emission in the far-infrared from theembedded objects. Most of our targets reside in a complex environment, which we discuss in detail. We detected
several atomic and molecular lines, in particular rotational CO emission from several transitions from J=38-37 to J=43. We constructed rotational diagrams for the CO lines, and derived in three domains of assumed local thermodynamic
equilibrium (LTE) temperatures and column densities, ranging mainly between 0-100 K and 400-500 K. We confirm
correlation in our sample between intense CO J=16-15 emission and the column density of the warm domain of CO,
N(warm). We notice a strong increase in luminosity of HH 381 IRS and a weaker increase for PP 13 S, which shows
the beginning of an outburst.
Accepted by A&A
https://arxiv.org/pdf/1909.00722

52

Flares of accretion activity of the 20 Myr old UXOR RZ Psc
I.S. Potravnov1 , V.P. Grinin2,3 and N.A. Serebriakova4
1

Institute of Solar-Terrestrial Physics, Siberian branch of Russian Academy of Sciences, Lermontov Str. 126A, 664033,
Irkutsk, Russia; 2 Pulkovo Astronomical Observatory, Russian Academy of Sciences, 196140, Pulkovo, St.Petersburg,
Russia; 3 V.V.Sobolev Astronomical Institute, Saint-Petersburg State University, Universitetski pr. 28, 198504,
St.Petersburg, Russia; 4 Kazan Federal University, Kremlyovskaya Str. 18, 420008, Kazan, Russia

28

E-mail contact: ilya.astro at gmail.com
We discuss a revision of accretion activity and kinematics of the enigmatic isolated UX Ori type star RZ Psc. Previously,
RZ Psc was known to possess only spectroscopic signatures of outflow in the low-excitation lines of alkali metals. The
archival high-resolution spectra reveal a short-lived episode of magnetospheric accretion in the system observed via
inverse P Cyg profiles at the Hα and CaII 8542Å lines. The simultaneous presence of accretion and outflow signaturesat CaII 8542Å is suggestive of an accretion-driven origin of the RZ Psc wind. We argue that RZ Psc experiences
matter ejection via the magnetic propeller mechanism but variable accretion episodes allow it to sometimes movein the magnetospheric accretion regime. The presence of the weak accretion in the system is also supported by theradiation of the hot accretion spot on the stellar surface observed spectroscopically at the deep photometric minimumof the star. The Galactic motion of RZ Psc calculated with new GAIA DR2 astrometric data suggests possible
membership in Cas-Tau OB association with an age of t = 20+3
−5 Myr.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1908.08673

53

Not so different after all: Properties and Spatial Structure of Column Density Peaks in
the Pipe and Orion A Clouds
Carlos G. Román-Zúñiga1, Emilio Alfaro2 , Aina Palau3 , Birgit Hasenberger4 , João F. Alves4 , Marco
Lombardi5 , and G. Paloma S. Sánchez3
1Instituto de Astronomı́a en Ensenada, Universidad Nacional Autónoma de México, Km 107 Carr. Tijuana-Ensenada,
Ensenada BC 22860, Mexico; 2 Instituto de Astrofı́sica de Andalucı́a, (CSIC), Granada, 18008, Spain; 3 Instituto deRadioastronomı́a y Astrofı́sica, UNAM, Morelia, Mexico; 4 Department for Astrophysics, University of Vienna, Vienna
1180, Austria; 5 Dipartimento di Fisica, Università di Milano, Milan, Italy
E-mail contact: croman at astro.unam.mx

We present a comparative study of the physical properties and the spatial distribution of column density peaks in
two Giant Molecular Clouds (GMC), the Pipe Nebula and Orion A, which exemplify opposite cases of star cluster
formation stages. The density peaks were extracted from dust extinction maps constructed from Herschel/SPIRE
farinfrared images. We compare the distribution functions for dust temperature, mass, equivalent radius and mean
volume density of peaks in both clouds, and made a more fair comparison by isolating the less active Tail region inOrion A and by convolving the Pipe Nebula map to simulate placing it at a distance similar to that of the Orion
Complex. The peak mass distributions for Orion A, the Tail, and the convolved Pipe, have similar ranges, sharing amaximum near 5 M⊙ , and a similar power law drop above 10 M⊙ . Despite the clearly distinct evolutive stage of theclouds, there are very important similarities in the physical and spatial distribution properties of the column density
peaks, pointing to a scenario where they form as a result of uniform fragmentation of filamentary structures acrossthe various scales of the cloud, with density being the parameter leading the fragmentation, and with clustering beinga direct result of thermal fragmentation at different spatial scales. Our work strongly supports the idea that theformation of clusters in GMC could be the result of the primordial organization of pre-stellar material.
Accepted by MNRAS
http://arxiv.org/pdf/1908.08148

54

Effect of nucleation on icy pebble growth in protoplanetary discs
Katrin Ros1 , Anders Johansen1 , Ilona Riipinen2,3,4 and Daniel Schlesinger2,31Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund,
Sweden; 2 Department of Environmental Science and Analytical Chemistry, Stockholm University, 106 91 Stockholm,
Sweden; 3 Bolin Centre for Climate Research, 106 91 Stockholm, Sweden; 4 Aerosol Physics, Faculty of Science,
Tampere University of Technology, Tampere, FinlandE-mail contact: katrin.ros at astro.lu.se
Solid particles in protoplanetary discs can grow by direct vapour deposition outside of ice lines. The presence of
microscopic silicate particles may nevertheless hinder growth into large pebbles, since the available vapour is deposited

29

predominantly on the small grains that dominate the total surface area. Experiments on heterogeneous ice nucleation,
performed to understand ice clouds in the Martian atmosphere, show that the formation of a new ice layer on a silicate
surface requires a substantially higher water vapour pressure than the deposition of water vapour on an existing ice
surface. In this paper, we investigate how the difference in partial vapour pressure needed for deposition of vapour
on water ice versus heterogeneous ice nucleation on silicate grains influences particle growth close to the water ice
line. We developed and tested a dynamical 1D deposition and sublimation model, where we include radial drift,
sedimentation, and diffusion in a turbulent protoplanetary disc. We find that vapour is deposited predominantly on
already ice-covered particles, since the vapour pressure exterior of the ice line is too low for heterogeneous nucleation
on bare silicate grains. Icy particles can thus grow to centimetre-sized pebbles in a narrow region around the ice line,
whereas silicate particles stay dust-sized and diffuse out over the disc. The inhibition of heterogeneous ice nucleation
results in a preferential region for growth into planetesimals close to the ice line where we find large icy pebbles. The
suppression of heterogeneous ice nucleation on silicate grains may also be the mechanism behind some of the observed
dark rings around ice lines in protoplanetary discs, as the presence of large ice pebbles outside ice lines leads to adecrease in the opacity there.
Accepted by A&A
https://arxiv.org/pdf/1907.08471

55

Influence of the Disk Wind on the Intrinsic Polarization of Young Stars
S. G. Shulman1 and V. P. Grinin1,2
1

St. Petersburg State University, Universitetskii pr. 28, St. Petersburg, 198504 Russia; 2 Pulkovo Astronomical
Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, St. Petersburg, 196140 Russia
E-mail contact: sgshulman at gmail.com
The behavior of the linear polarization parameters of UX Ori stars during their eclipses by circumstellar dust clouds
is studied. A circumstellar disk with a disk wind creating a puffing in the dust sublimation zone is considered. We
show that the disk puffing can strongly affect the degree of polarization and color index of the star during its eclipse.
A strong wind can change the orientation of the plane of linear polarization. The scattered radiation from a thin disk
is polarized perpendicularly to its plane, but the radiation from a disk with a strong wind can be polarized along thedisk plane. A situation where the disk-scattered radiation is not polarized in a certain spectral band is possible owing
to the disk puffing. There can be different orientations of the linear polarization of the disk radiation in different
spectral bands.
Accepted by Astronomy Letters

https://link.springer.com/article/10.1134/S1063773719060057

56

The CARMA-NRO Orion Survey: Core Emergence and Kinematics in the Orion A
Cloud
Kong Shuo1,2 , Héctor G. Arce1 , Anneila I. Sargent3 , Steve Mairs4 , Ralf S. Klessen5,6, John Bally7 ,Paolo Padoan8,9 , Rowan J. Smith10 , Marı́a José Maureira1,19 , John M. Carpenter11 , Adam Ginsburg12 ,Amelia M. Stutz13,14 , Paul Goldsmith15, Stefan Meingast16 , Peregrine McGehee17 , Álvaro SánchezMonge18 , Sümeyye Suri18 , Jaime E. Pineda19 , João Alves16,20 , Jesse R. Feddersen1 , Jens Kauffmann21
and Peter Schilke18
1

Yale University, 52 Hillhouse Ave, New Haven, CT 06511, USA; 2 University of Arizona, 933 N Cherry Ave, Tucson,
AZ 85719, USA; 3 California Institute of Technology, 249-17, Pasadena, CA 91125, USA; 4 East Asian Observatory,
660 N. A’ohoku Place, Hilo, HI 96720, USA; 5 Universität Heidelberg, Zentrum für Astronomie, Albert-Ueberle-Str. 2,
D-69120 Heidelberg, Germany; 6 Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen,
INF 205, D-69120 Heidelberg, Germany; 7 University of Colorado, Boulder, CO, USA; 8 Universitat de Barcelona,
IEEC-UB, Marté i Franquès 1, E08028 Barcelona, Spain; 9 ICREA, Pg. Lluı́s Companys 23, E-08010 Barcelona,
Spain; 10 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford
Road, Manchester M13 9PL, UK; 11 Joint ALMA Observatory, Alonso de Córdova 3107 Vitacura, Santiago, Chile;
12
National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, NM 87801, USA; 13 Departmento de30

Astronomı́a, Facultad de Ciencias Fı́sicas y Matemáticas, Universidad de Concepción, Concepción, Chile; 14 MaxPlanck-Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 15 California Institute of Technology,
4800 Oak Grove Drive, Pasadena, CA 91109, USA; 16 University of Vienna, Türkenschanzstrasse 17, A-1180 Wien,
Austria; 17 Department of Earth and Space Sciences, College of the Canyons, Santa Clarita, CA 91355, USA; 18
I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany; 19 Max-Planck-Institutfür extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching, Germany; 20 Radcliffe Institute for Advanced
Study, Harvard University, 10 Garden Street, Cambridge, MA 02138, USA; 21 Haystack Observatory, Massachusetts
Institute of Technology, 99 Millstone Road, Westford, MA 01886, USA
E-mail contact: shuo.kong at yale.edu
We have investigated the formation and kinematics of sub-mm continuum cores in the Orion A molecular cloud. A
comparison between sub-mm continuum and near infrared extinction shows a continuum core detection threshold of
AV ∼ 5-10 mag. The threshold is similar to the star formation extinction threshold of AV ∼ 7 mag proposed by recent
work, suggesting a universal star formation extinction threshold among clouds within 500 pc to the Sun. A comparison
between the Orion A cloud and a massive infrared dark cloud G28.37+0.07 indicates that Orion A produces more
dense gas within the extinction range 15 mag < AV < 60 mag. Using data from the CARMA-NRO Orion Survey, we
find that dense cores in the integral-shaped filament (ISF) show sub-sonic core-to-envelope velocity dispersion that issignificantly less than the local envelope line dispersion, similar to what has been found in nearby clouds. Dynamical
analysis indicates that the cores are bound to the ISF. An oscillatory core-to-envelope motion is detected along the
ISF. Its origin is to be further explored.
Accepted by ApJ
https://arxiv.org/pdf/1908.04488

57

Masses and Implications for Ages of Low-Mass PMS Stars in Taurus and Ophiuchus
M. Simon1,2 , S. Guilloteau3 , Tracy L. Beck4 , E. Chapillon3,7, E. Di Folco3 , A. Dutrey3 , Gregory A.
Feiden5 , N. Grosso6 , V. Pietu7 , L. Prato8 and Gail H. Schaefer91

Dept of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA; 2 Dept. of Astrophysics,
American Museum of Natural History, New York, NY 10024, USA; 3 Laboratoire d’Astrophysique de Bordeaux, Univ.
Bordeaux, CNRS B18N, allee Geoffrey Saint-Hilaire, 33615 Pessac, Francs; 4 Space Telescope Science Institute, 3700
San Mateo Dr., Baltimore, MD 20218, USA; 5 Dept.of Physics and Astronomy, Univ. of North Georgia, Dahlonega,GA, 30597. USA; 6 Aix Marseille University, CNRS, CNES, LAM, Marseille, France; 7 IRAM, 300 rue de la Piscine,
F-38406 Saint Martin d’Heres, France; 8 Lowell Obs. 1400 West Mars Hill Rd., Flagstaff, AZ, 86001, USA; 9 The
CHARA Array of Georgia State Univ., Mount Wilson Obs., Mount Wilson, CA 91023, USA
E-mail contact: michal.simon at stonybrook.edu
The accuracy of masses of pre-main sequence (PMS) stars derived from their locations on the Hertzsprung-Russell
Diagram (HRD) can be tested by comparison with accurate and precise masses determined independently. We present
29 single stars in the Taurus star-forming region (SFR) and 3 in the Ophiuchus SFR with masses measured dynamicallyto a precision of at least 10%. Our results include 9 updated mass determinations and 3 that have not had theirdynamical masses published before. This list of stars with fundamental, dynamical masses, Mdyn , is drawn from alarger list of 39 targets in the Taurus SFR and 6 in the Ophiuchus SFR. Placing the stars with accurate and precise
dynamical masses on HRDs that do not include internal magnetic fields underestimates the mass compared to Mdyn
by about 30%. Placing them on an HRD that does include magnetic fields yields mass estimates in much better
agreement with Mdyn , with an average difference between Mdyn and the estimated track mass of 0.01 ± 0.02 M⊙ .
The ages of the stars, 3–10 MY on tracks that include magnetic fields, is older than the 1–3 MY indicated by thenon-magnetic models. The older ages of T Tauri stars predicted by the magnetic models increase the time available
for evolution of their disks and formation of the giant gas exoplanets. The agreement between our Mdyn values andthe masses on the magnetic field tracks provides indirect support for these older ages.
Accepted by ApJ
http://arxiv.org/pdf/1908.10952

31

58

The origin of R CrA variability: A complex triple system hosting a disk
E. Sissa1 , R. Gratton1 , J.M.Alcalá2 , S. Desidera1 , S. Messina3 , D. Mesa1 , V. D’Orazi1 and E. Rigliaco11INAF-Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, I-35122, Padova, Italy; 2 INAF-Osservatorio
Astronomico di Capodimonte, Salita Moiariello 16, I-80131, Napoli, Italy; 3 INAF-Osservatorio Astrofisico di Catania,
Via S.Sofia 78, I-95123, Catania, Italy
E-mail contact: raffaele.gratton at inaf.it
R CrA is the brightest member of the Coronet star forming region and it is the closest Herbig AeBe star with aspectrum dominated by emission lines. Its luminosity has been monitored since the end of the 19th century, but theorigin of its variability, which shows a stable period of 65.767 ± 0.007 days, is still unknown. We studied photometricand spectroscopic data for this star to investigate the nature of the variability of R CrA. We exploited the fact that nearinfrared luminosity of the Herbig AeBe stars is roughly proportional to the total luminosity of the stars to derive theabsorption, and then mass and age of R CrA. In addition, we model the periodic modulation of the light curve as due
to partial attenuation of a central binary by a circumbinary disk. This model reproduces very well the observations.
We found that the central object in R CrA is a very young (1.5 ± 1.5 Myr), highly absorbed (AV = 5.47 ± 0.4 mag)binary; we obtain masses of MA = 3.02 ± 0.43 M⊙ and MB = 2.32 ± 0.35 M⊙ for the two components. We proposethat the secular decrease of the R CrA apparent luminosity is due to a progressive increase of the disk absorption.
This might be related to precession of a slightly inclined disk caused by the recently discovered M-dwarf companion.
Thus, R CrA may be a triple system hosting a disk.
Accepted by Astronomy and Astrophysics

https://arxiv.org/pdf/1908.07256.pdf

59First Sub-pc Sale Mapping of Magnetic Fields in the Vicinity of a Very Low Luminosity
Object, L1521F-IRS
Archana Soam1,2 , Chang Won Lee2,3 , B-G Andersson1 , Maheswar G.4 , Mika Juvela5 , Tie Liu6,2,7 ,Gwanjeong Kim8 , Ramprasad Rao9 , Eun Jung Chung2 , Woojin Kwon2,3 and Ekta S.4
1

SOFIA Science Centre, USRA, NASA Ames Research Centre, MS-12, N232, Moffett Field, CA 94035, USA; 2 Korea
Astronomy and Space Science Institute (KASI), 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; 3
University of Science and Technology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea;
4
Indian Institute of Astrophysics, Kormangala (IIA), Bangalore 560034, India; 5 Department of Physics, P.O.Box
64, FI-00014, University of Helsinki; 6 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 NandanRoad, Shanghai 200030, China; 7 East Asian Observatory, 660 N. A’ohoku Place, University Park, Hilo, HI 96720,
USA; 8 Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural
Sciences, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; 9 Academia Sinica Institute of Astronomy
and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan
E-mail contact: archanasoam.bhu at gmail.com
L1521F is found to be forming multiple cores and it is cited as an example of the densest core with an embedded
VeLLO in a highly dynamical environment. We present the core-scale magnetic fields (B-fields) in the near vicinityof the VeLLO L1521F-IRS using submm polarization measurements at 850 µm using JCMT POL-2. This is thefirst attempt to use high-sensitivity observations to map the sub-parsec scale B-fields in a core with a VeLLO. The
B-fields are ordered and very well connected to the parsec-scale field geometry seen in our earlier optical polarization
observations and the large-scale structure seen in Planck dust polarization. The core scale B-field strength estimatedusing Davis-Chandrasekhar-Fermi relation is 330±100 µG which is more than ten times of the value we obtained in
the envelope (envelope in this paper is “core envelope”). This indicates that B-fields are getting stronger on smallerscales. The magnetic energies are found to be 1 to 2 orders of magnitude higher than non-thermal kinetic energies
in the envelope and core. This suggests that magnetic fields are more important than turbulence in the energy
budget of L1521F. The mass-to-flux ratio of 2.3±0.7 suggests that the core is magnetically-supercritical. The degreeof polarization is steadily decreasing towards the denser part of the core with a power law slope of −0.86.
Accepted by ApJ
http://arxiv.org/pdf/1908.01018

32

60

Magnetic fields in the infrared dark cloud G34.43+0.24
Archana Soam1,2 , Tie Liu3,2,4 , B-G Andersson1 , Chang Won Lee2,5 , Junhao Liu6,7,8 , Mika Juvela9 ,Pak Shing Li1 0, Paul F. Goldsmith11, Qizhou Zhang8 , Patrick M. Koch12 , Kee-Tae Kim2 , Keping
Qiu6,7 , Neal J. Evans II2,13,14 , Doug Johnstone15,16 , Mark Thompson17 , Derek Ward-Thompson18 , JamesDi Francesco15,16 , Ya-Wen Tang12 , Julien Montillaud19 , Gwanjeong Kim20 , Steve Mairs21 , Patricio
Sanhueza22 , Shinyoung Kim2,5 , David Berry21 , Michael S. Gordon1 , Ken’ichi Tatematsu22 , Sheng-Yuan
Liu12 , Kate Pattle23 , David Eden24 , Peregrine M. McGehee25 , Ke Wang26 , I. Ristorcelli27, Sarah F.
Graves21 , Dana Alina28 , Kevin M. Lacaille29,30 , Ludovic Montier27 , Geumsook Park2 , Woojin Kwon2,5 ,Eun Jung Chung2 , Veli-Matti Pelkonen9,31 , Elisabetta R. Micelotta9 , Mika Saajasto9 , and Gary Fuller32
1

SOFIA Science Centre, USRA, NASA Ames Research Centre, MS-12, N232, Moffett Field, CA 94035, USA; 2
Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea;
3
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China; 4East Asian Observatory, 660 N. Aohoku Place, Hilo, HI 96720, USA; 5 University of Science and Technology, Korea(UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea; 6 School of Astronomy and Space Science,
Nanjing University, 163 Xianlin Avenue, Nanjing 210023, Peoples Republic of China; 7 Key Laboratory of Modern
Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210023, Peoples Republic of China;
8
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 9 Department of
Physics, P.O.Box 64, FI-00014, University of Helsinki, Finland; 10 University of California, Berkeley, United States;
11
Jet Propulsion Laboratory, National Aeronautics and Space Administration, United States; 12 Academia Sinica
Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan; 13 Department of Astronomy, The
University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, Texas 78712-1205, USA; 14 Humanitas College,
Global Campus, Kyung Hee University, Yongin-shi 17104, Korea; 15 NRC Herzberg Astronomy and Astrophysics, 5071
West Saanich Road, Victoria, BC V9E 2E7, Canada; 16 Department of Physics and Astronomy, University of Victoria,
Victoria, BC V8P 1A1, Canada; 17 University of Hertfordshire (Centre for Astrophysics Research), United Kingdom;
18
Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK; 19 Institut UTINAM UMR 6213 - CNRS - Univ Bourgogne Franche Comte, OSU THETA, 41bis avenue de l’Observatoire, 25000 Besançon,
France; 20 Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural
Sciences, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; 21 East Asian Observatory, 660 N. A‘ohōkū
Place, University Park, Hilo, HI 96720, USA; 22 National Astronomical Observatory of Japan, National Institutesof Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 23 Institute of Astronomy and Department of
Physics, National Tsing Hua University, Hsinchu 30013, Taiwan; 24 Astrophysics Research Institute, Liverpool John
Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK; 25 College of the Canyons,
United States; 26 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian
District, Beijing 100871, China; 27 Institut pour la Recherche en Astrophysique et Plantologie, France; 28 Nazarbayev
University (Department of Physics), Kazakhstan; 29 Department of Physics and Astronomy, McMaster University,
Hamilton, ON L8S 4M1 Canada; 30 Department of Physics and Atmospheric Science, Dalhousie University, Halifax
B3H 4R2, Canada; 31 Institut de Cincies del Cosmos, Universitat de Barcelona, IEEC-UB, Mart Franqus 1, E08028
Barcelona; 32 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester,
Oxford Road, Manchester, M139PL, UK
E-mail contact: asoam at usra.edu
We present the B-fields mapped in IRDC G34.43+0.24 using 850 µm polarized dust emission observed with the POL-2
instrument at JCMT. We examine the magnetic field geometries and strengths in the northern, central, and southern
regions of the filament. The overall field geometry is ordered and aligned closely perpendicular to the filament’s
main axis, particularly in regions containing the central clumps MM1 and MM2, whereas MM3 in the north has
field orientations aligned with its major axis. The overall field orientations are uniform at large (POL-2 at 14′′ andSHARP at 10′′ ) to small scales (TADPOL at 2.5′′ and SMA at 1.5′′ ) in the MM1 and MM2 regions. SHARP/CSO
observations in MM3 at 350 µm from Tang et al. show a similar trend as seen in our POL-2 observations. TADPOL
observations demonstrate a well-defined field geometry in MM1/MM2 consistent with MHD simulations of accretingfilaments. We obtained a plane-of-sky magnetic field strength of 470±190 µG, 100±40 µG, and 60±34 µG in thecentral, northern and southern regions of G34, respectively, using the updated Davis-Chandrasekhar-Fermi relation.
The estimated value of field strength, combined with column density and velocity dispersion values available in theliterature, suggests G34 to be marginally critical with criticality parameter λ values 0.8±0.4, 1.1±0.8, and 0.9±0.5
in the central, northern, and southern regions, respectively. The turbulent motions in G34 are sub-Alfvénic with33

Alfvénic Mach numbers of 0.34±0.13, 0.53±0.30, and 0.49±0.26 in the three regions. The observed aligned B-fields
in G34.43+0.24 are consistent with theoretical models suggesting that B-fields play an important role in guiding thecontraction of the cloud driven by gravity.
Accepted by ApJ
http://arxiv.org/pdf/1908.03624

61

A study of accretion and disk diagnostics in the NGC 2264 cluster
Alana P. Sousa1,2 , Silvia H. P. Alencar1 , Luisa M. Rebull3 , Catherine C. Espaillat4 , Nuria Calvet5 , andPaula S. Teixeira6
1

Departamento de Fı́sica-Icex-UFMG Antônio Carlos, 6627, 31270-901. Belo Horizonte, MG, Brazil; 2 UniversitéGrenoble Alpes, IPAG, F-38000 Grenoble, France; 3 Infrared Science Archive (IRSA), IPAC, 1200 E. California Blvd.,
California Institute of Technology, Pasadena, CA 91125, USA; 4 Department of Astronomy, Boston University, 725
Commonwealth Avenue, Boston, MA 02215, USA; 5 Department of Astronomy, University of Michigan, 830 Dennison
Building, 500 Church Street, Ann Arbor, MI 48109, USA; 6 Scottish Universities Physics Alliance (SUPA), School ofPhysics and Astronomy, University of St. Andrews, North Haugh, Fife, KY16 9SS, St. Andrews, UK
E-mail contact: alana at fisica.ufmg.br
Understanding disk dissipation is essential for studying how planets form. Disk gaps and holes, which almost correspond to dust-free regions, are inferred from infrared observations of T Tauri stars (TTS), indicating the existence ofa transitional phase between thick accreting disks and debris disks. Transition disks are usually referred to as candidates for newly formed planets. We searched for transition disk candidates belonging to NGC 2264. We characterizedaccretion, disk, and stellar properties of transition disk candidates and compared them to systems with a full disk anddiskless stars. We modeled the spectral energy distribution (SED) of a sample of 401 TTS, with Hyperion SED fittingcode using photometric data from the U band to the MIPS band. We used the SED modeling to distinguish transition
disk candidates, full disk systems, and diskless stars. We classified 52% of the sample as full disk systems, 41% as
diskless stars, and 7% of the systems as transition disk candidates, among which seven systems are new transition disk
candidates belonging to the NGC 2264 cluster. The sample of transition disk candidates present dust in the inner disk
similar to anemic disks, according to the αIRAC classification, which shows that anemic disk systems can be candidate
transition disks. We show that the presence of a dust hole in the inner disk does not stop the accretion process since
82% of transition disk candidates accrete and show Hα, UV excess, and mass accretion rates at the same level as fulldisk systems. We estimate the inner hole sizes, ranging from 0.1 to 78AU, for the sample of transition disk candidates.
In only 18% of the transition disk candidates, the hole size could be explained by X-ray photoevaporation from stellar
radiation.
Accepted by A&A
http://arxiv.org/pdf/1908.03487

62

Near-Infrared Imaging Polarimetry toward M17 SWex
Koji Sugitani1 , Fumitaka Nakamura2 , Tomomi Shimoikura3 , Kazuhito Dobashi4 , Quang Nguyen-Luong5 ,Takayoshi Kusune2 , Takahiro Nagayama6 , Makoto Watanabe7 , Shogo Nishiyama8 and Motohide Tamura9
1

Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya 467-8501, Japan; 2 National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan; 3 Otsuma Women University, Department of Astronomy and
Earth Science, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan; 4 Department of Astronomy and Earth
Science, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan; 5 IBM Canada, 120 Bloor Street East, Toronto,
ON, M4Y 1B7, Canada; 6 Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan; 7 Department ofApplied Physics, Okayama University of Science, 1-1 Ridai-cho, Kita-ku, Okayama 700-0005, Japan; 8 Miyagi University of Education, 149 Aramaki-aza-Aoba, Aobaku, Sendai, Miyagi 980-0845, Japan; 9 Department of Astronomy,
The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
E-mail contact: sugitani at nsc.nagoya-cu.ac.jp
We conducted near-infrared (JHKs) imaging polarimetry toward the infrared dark cloud (IRDC) M17 SWex, including
almost all of the IRDC filaments as well as its outskirts, with the polarimeter SIRPOL on the IRSF 1.4 m telescope.
34

We revealed the magnetic fields of M17 SWex with our polarization-detected sources that were selected by some criteria
based on their near-IR colors and the column densities toward them, which were derived from the Herschel data. The
selected sources indicate not only that the ordered magnetic field is perpendicular to the cloud elongation as a whole,
but also that at both ends of the elongated cloud the magnetic field appears to bent toward its central part, i.e.,large-scale hourglass-shaped magnetic field perpendicular to the cloud elongation. In addition to this general trend,
the elongations of the filamentary subregions within the dense parts of the cloud appear to be mostly perpendicular totheir local magnetic fields, while the magnetic fields of the outskirts appear to follow the thin filaments that protrude
from the dense parts. The magnetic strengths were estimated to be ∼ 70−300 µG in the subregions, of which lengths
and average number densities are ∼3–9 pc and ∼2–7×103 cm−3 , respectively, by the Davis-Chandrasekhar-Fermi
method with the angular dispersion of our polarization data and the velocity dispersion derived from the C18 O (J =1–0) data obtained by the Nobeyama 45 m telescope. These field configurations and our magnetic stability analysisof the subregions imply that the magnetic field have controlled the formation/evolution of the M17 SWex cloud.
Accepted by PASJ
http://arxiv.org/pdf/1906.12138

S and VV Corona Australis: Spectroscopic Variability in Two Young Binary Star Sys-

63 tems

Kendall Sullivan1,2 , L. Prato2 , Suzan Edwards3 , Ian Avilez2 , and Gail H. Schaefer4
1

University of Texas at Austin, Austin TX 78712, USA; 2 Lowell Observatory, Flagstaff AZ 86001, USA; 3 Smith
College, Northampton MA 01063, USA; 4 The CHARA Array of Georgia State University, Mount Wilson Observatory,
Mount Wilson CA 91023, USA
E-mail contact: kendallsullivan at utexas.edu
We used high-resolution near-infrared spectroscopy from the NIRSPEC instrument on the Keck II telescope, takenover multiple epochs spanning five years, to examine two young binary T Tauri star systems, S Corona Australis
and VV Corona Australis. The stars in these 1′′ –2′′ separation systems have optically thick circumstellar disks andhigh extinctions at optical and near-infrared wavelengths. Using a combination of new and archival data, we havedetermined the spectral types of all the stars in these two systems for the first time, examined the variable NIR veiling,measured the emission line equivalent widths, and created spectral energy distributions. They have similar spectral
types (K7–M1) and are at approximately the same evolutionary stage, allowing comparison of the four stars in thetwo systems. We conclude that S CrA and VV CrA are young binary systems of stars bridging the Class I and ClassII evolutionary stages, characterized by high accretion luminosities and variable emission lines.
Accepted by ApJ
http://arxiv.org/pdf/1908.06135

ALMA observations of fragmentation, sub-structure, and protostars in high-mass star-

64 less clump candidates

Brian E. Svoboda1,2 , Yancy L. Shirley2 , Alessio Traficante3,4 , Cara Battersby5,6 , Gary A. Fuller4 , Qizhou
Zhang6 , Henrik Beuther7 , Nicolas Peretto8 , Crystal Brogan9 , Todd Hunter9
1

National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA; 2 Steward Observatory,
University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 USA; 3 IAPS-INAF, via Fosso del Cavaliere, 100,
I-00133, Roma Italy; 4 Jodrell Bank Centre for Astrophysics, The School of Physics and Astronomy, The Universityof Manchester, Oxford Road, Manchester M13 9PL UK; 5 Department of Physics, University of Connecticut, 2152
Hillside Road, Storrs, CT 06269 USA; 6 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge,
MA 02138 USA; 7 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg Germany; 8 School ofPhysics & Astronomy, Cardiff University, Queen?s building, The parade, Cardiff, CF24 3AA UK; 9 National Radio
Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 USA
E-mail contact: bsvoboda at nrao.edu
The initial physical conditions of high-mass stars and protoclusters remain poorly characterized. To this end we present
the first targeted ALMA 1.3 mm continuum and spectral line survey towards high-mass starless clump candidates,
35

selecting a sample of 12 of the most massive candidates (400– 4000 M⊙ ) within 5 kpc. The joint 12+7 m array maps
have a high spatial resolution of ∼3000 au (∼0.8′′ ) and have point source mass-completeness down to ∼0.3 M⊙ at 6σ (or1σ column density sensitivity of 1.1 × 1022 cm−2 ). We discover previously undetected signposts of low-luminosity starformation from CO (2–1) and SiO (5–4) bipolar outflows and other signatures towards 11 out of 12 clumps, showingthat current MIR/FIR Galactic Plane surveys are incomplete to low- and intermediate-mass protostars (<∼50 L⊙ ).
We compare a subset of the observed cores with a suite of radiative transfer models of starless cores. We find a highmass starless core candidate with a model-derived mass consistent with 29+52−15 M⊙ when integrated over size scalesof 2 × 104 au. Unresolved cores are poorly fit by starless core models, supporting the interpretation that they areprotostellar even without detection of outflows. Substantial fragmentation is observed towards 10 out of 12 clumps.
We extract sources from the maps using a dendrogram to study the characteristic fragmentation length scale. Nearest
neighbor separations when corrected for projection are consistent with being equal to the clump average thermal Jeans
length. Our findings support a hierarchical fragmentation process, where the highest density regions are not strongly
supported against thermal gravitational fragmentation by turbulence or magnetic fields.
Accepted by ApJ
http://arxiv.org/pdf/1908.10374

65

Investigation of 13 C Isotopic Fractionation of CCH in Two Starless Cores: L1521B andL134N
Kotomi Taniguchi1,2 , Eric Herbst1,2 , Hiroyuki Ozeki3 and Masao Saito4
1

Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 2 Department of Chemistry,
University of Virginia, Charlottesville, VA 22903, USA; 3 Department of Environmental Science, Faculty of Science,
Toho University, Miyama, Funabashi, Chiba 274-8510, Japan; 4 National Astronomical Observatory of Japan (NAOJ),
Osawa, Mitaka, Tokyo 181-8588, Japan
E-mail contact: kotomi.taniguchi at gakushuin.ac.jp
We have carried out observations of CCH and its two 13 C isotopologues, 13 CCH and C13 CH, in the 84 – 88 GHz band
toward two starless cores, L1521B and L134N (L183), using the Nobeyama 45 m radio telescope. We have detected
C13 CH with a signal-to-noise (S/N) ratio of 4, whereas no line of 13 CCH was detected in either the dark clouds. The
column densities of the normal species were derived to be (1.66 ± 0.18)×1014 cm−2 and (7.3 ± 0.9)×1013 cm−2 (1σ)
in L1521B and L134N, respectively. The column density ratios of N (C13 CH)/N (13 CCH) were calculated to be > 1.1
and > 1.4 in L1521B and L134N, respectively. The characteristic that 13 CCH is less abundant than C13 CH is likely
common for dark clouds. Moreover, we find that the 12 C/13 C ratios of CCH are much higher than those of HC3 N in
L1521B by more than a factor of 2, as well as in Taurus Molecular Cloud-1 (TMC-1). In L134N, the differences in the12
C/13 C ratios between CCH and HC3 N seem to be smaller than those in L1521B and TMC-1. We discuss the originsof the 13 C isotopic fractionation of CCH and investigate possible routes that cause the significantly high 12 C/13 C ratioof CCH especially in young dark clouds, with the help of chemical simulations. The high 12 C/13 C ratios of CCH seemto be caused by reactions between hydrocarbons (e.g., CCH, C2 H2 , l, c-C3 H) and C+ .
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1908.09983

66

Multi-wavelength observations of protoplanetary discs as a proxy for the gas disc mass
B. Veronesi1,3 , G. Lodato1,3 , G. Dipierro2 , E. Ragusa2 , C. Hall2,3 , and D.J. Price3
1

Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria, 16, Milano, I-20133, Italy; 2 Departmentof Physics and Astronomy, University of Leicester, Leicester, United Kingdom; 3 School of Physics and Astronomy,
Monash University, VIC 3800, Australia
E-mail contact: benedetta.veronesi at unimi.it
Recent observations of protoplanetary discs reveal disc substructures potentially caused by embedded planets. We
investigate how the gas surface density in discs changes the observed morphology in scattered light and dust continuum
emission. Assuming that disc substructures are due to embedded protoplanets, we combine hydrodynamical modellingwith radiative transfer simulations of dusty protoplanetary discs hosting planets. The response of different dust species
to the gravitational perturbation induced by a planet depends on the drag stopping time — a function of the generally36

unknown local gas density. Small dust grains, being stuck to the gas, show spirals. Larger grains decouple, showing
progressively more axisymmetric (ring-like) substructure as decoupling increases with grain size or with the inverseof the gas disc mass. We show that simultaneous modelling of scattered light and dust continuum emission is able toconstrain the Stokes number, St. Hence, if the dust properties are known, this constrains the local gas surface density,Σgas , at the location of the structure, and hence the total gas mass. In particular, we found that observing ring-like−2
structures in mm-emitting grains requires St >∼ 0.4 g cm . We apply this idea to observed∼0.4 and therefore Σgas <protoplanetary discs showing substructures both in scattered light and in the dust continuum.
Accepted by MNRAS
http://arxiv.org/pdf/1908.08865

67

Gravitoviscous protoplanetary disks with a dust component. II. Spatial distribution
and growth of dust in a clumpy disk
Eduard Vorobyov1,2 and Vardan Elbakyan2
1

Department of Astrophysics, University of Vienna, Vienna, Austria; 2 Institute of Physics, Southern Federal University, Rostov-on-Don, Russia
E-mail contact: eduard.vorobiev at univie.ac.at
Spatial distribution and growth of dust in a clumpy protoplanetary disk subject to vigorous gravitational instability
and fragmentation is studied numerically with sub-au resolution using the FEOSAD code.
Hydrodynamics equations describing the evolution of self-gravitating and viscous protoplanetary disks in the thin-disk
limit were modified to include a dust component consisting of two parts: sub-micron-sized dust and grown dust witha variable maximum radius. The conversion of small to grown dust, dust growth, friction of dust with gas, and dust
self-gravity were also considered.
We found that the disk appearance is notably time-variable with spiral arms, dusty rings, and clumps, constantly forming, evolving, and decaying. As a consequence, the total dust-to-gas mass ratio is highly non-homogeneous throughout
the disk extent, showing order-of-magnitude local deviations from the canonical 1:100 value. Gravitationally boundclumps formed through gravitational fragmentation have a velocity pattern that deviates notably from the Keplerianrotation. Small dust is efficiently converted into grown dust in the clump interiors, reaching a maximum radius ofseveral decimeters. Concurrently, grown dust drifts towards the clump center forming a massive compact central condensation (70–100 M⊕ ). We argue that protoplanets may form in the interiors of inward-migrating clumps before theydisperse through the action of tidal torques. We foresee the formation of protoplanets at orbital distances of several
tens of au with initial masses of gas and dust in the protoplanetary seed in the (0.25–1.6) MJup and (1.0–5.5) M⊕
limits, respectively. The final masses of gas and dust in the protoplanets may however be much higher due to accretionfrom surrounding massive metal-rich disks/envelopes.
Dusty rings formed through tidal dispersal of inward-migrating clumps may have a connection to ring-like structures
found in youngest and massive protoplanetary disks. Numerical disk models with a dust component that can follow
the evolution of gravitationally bound clumps through their collapse phase to the formation of protoplanets are needed
to make firm conclusions on the characteristics of planets forming through gravitational fragmentation.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/1908.10589

68

Modeling Time Dependent Water Chemistry Due to Powerful X-ray Flares from T-Tauri
Stars
Abygail R. Waggoner1 and L. Ilsedore Cleeves1,2
1

Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA; 2 Department of Astronomy,
University of Virginia, Charlottesville, VA 22904, USA
E-mail contact: arw6qz at virginia.edu
Young stars emit strong flares of X-ray radiation that penetrate the surface layers of their associated protoplanetarydisks. It is still an open question as to whether flares create significant changes in disk chemical composition. We
present models of the time-evolving chemistry of gas-phase water during X-ray flaring events. The chemistry is modeledat point locations in the disk between 1 and 50 au at vertical heights ranging from the mid-plane to the surface. We
37

find that strong, rare flares, i.e., those that increase the unattenuated X-ray ionization rate by a factor of 100 every
few years, can temporarily increase the gas-phase water abundance relative to H can by more than a factor of ∼3–5
along the disk surface (Z/R ≥ 0.3). We report that a “typical” flare, i.e., those that increase the unattenuated X-ray
ionization rate by a factor of a few every few weeks, will not lead to significant, observable changes. Dissociative
recombination of H3 O+ , water adsorption and desorption onto dust grains, and ultraviolet photolysis of water andrelated species are found to be the three dominant processes regulating the gas-phase water abundance. While thechanges are found to be significant, we find that the effect on gas phase water abundances throughout the disk isshort-lived (days). Even though we do not see a substantial increase in long term water (gas and ice) production,
the flares’ large effects may be detectable as time varying inner disk water ‘bursts’ at radii between 5 and 30 au with
future far infrared observations.
Accepted by ApJ
http://arxiv.org/pdf/1908.08048

69

Planetesimals to Terrestrial Planets: collisional evolution amidst a dissipating gas disk
Kevin J. Walsh1 and Harold F. Levison1
1Southwest Research Institute, 1050 Walnut St. Suite 300, Boulder, CO 80302, USA

E-mail contact: kwalsh at boulder.swri.edu
We present numerical simulations of terrestrial planet formation that examine the growth continuously from planetesimals to planets in the inner Solar System. Previous studies show that the growth will be inside-out, but it isstill common practice to assume that the entire inner disk will eventually reach a bi-modal distribution of embryos
and planetesimals. For the combinations of disk mass, initial planetesimal radius and gas disk lifetime explored inthis work the entire disk never reaches a simple bi-modal mass distribution. We find that the inside-out growth isamplified by the combined effects of collisional evolution of solid bodies and interactions with a dissipating gas disk.
This leads to oligarchic growth never being achieved in different places of the disk at the same time, where in somecases the disk can simultaneoulsy support chaotic growth and giant impacts inside 1 au and runaway growth beyond
2 au. The planetesimal population is efficiently depleted in the inner disk where embryo growth primarily advancesin the presence of a significant gas disk. Further out in the disk growth is slower relative to the gas disk dissipation,
resulting in more excited planetesimals at the same stage of growth and less efficient accretion. This same effect drives
mass loss due to collisional grinding strongly altering the surface density of the accreted planets relative to the initial
mass distribution. This effect decreases the Mars-to-Earth mass ratios compared to previous works with no collisional
grinding. Similar to some previous findings utilizing vastly different growth scenarios these simulations produce a first
generation of planetary embryos that are stable for 10–20 Myr, or 5–10 e-folding times of the gas dissipation timescale,
before having an instability and entering the chaotic growth stage.
Accepted by Icarus
http://arxiv.org/pdf/1908.00897

70

Kinematic signatures of cluster formation from cool collapse in the Lagoon Nebulacluster NGC 6530
Nicholas J. Wright1 and Richard J. Parker2
1

Astrophysics Group, Keele University, Keele, ST5 5BG, UK; 2 Department of Physics & Astronomy, The Universityof Sheffield, Hicks Building, Sheffield, S3 7RH, UK
E-mail contact: n.j.wright at keele.ac.uk
We examine the mass-dependence of the velocity dispersion of stars in the young cluster NGC 6530 to better understandhow it formed. Using a large sample of members we find that the proper motion velocity dispersion increases withstellar mass. While this trend is the opposite to that predicted if the cluster were developing energy equipartition, it
is in agreement with recent N-body simulations that find such a trend develops because of the Spitzer instability. In
these simulations the massive stars sink to the centre of the cluster and form a self-gravitating system with a higher
velocity dispersion. If the cluster has formed by the cool collapse of an initially substructured distribution then thisoccurs within 1-2 Myr, in agreement with our observations of NGC 6530. We therefore conclude that NGC 6530
formed from much more extended initial conditions and has since collapsed to form the cluster we see now. This38

cluster formation model is inconsistent with the idea that all stars form in dense, compact clusters and provides thefirst dynamical evidence that star clusters can form by hierarchical mergers between subclusters.
Accepted by MNRAS
https://arxiv.org/pdf/1908.11398

71

There is no magnetic braking catastrophe: Low-mass star cluster and protostellar discformation with non-ideal magnetohydrodynamics
James Wurster1 , Matthew R. Bate1 and Daniel J. Price2
1

School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter EX4 4QL, UK; 2 School of Physics andAstronomy, Monash University, VIC 3800, Australia
E-mail contact: j.wurster at exeter.ac.uk
We present results from the first radiation non-ideal magnetohydrodynamics (MHD) simulations of low-mass starcluster formation that resolve the fragmentation process down to the opacity limit. We model 50 M⊙ turbulent clouds
initially threaded by a uniform magnetic field with strengths of 3, 5 10 and 20 times the critical mass-to-magnetic flux
ratio, and at each strength, we model both an ideal and non-ideal (including Ohmic resistivity, ambipolar diffusion andthe Hall effect) MHD cloud. Turbulence and magnetic fields shape the large-scale structure of the cloud, and similar
11−3
structures form regardless of whether ideal or non-ideal MHD is employed. At high densities (106 <∼ 10 cm ), all∼ nH <
models have a similar magnetic field strength versus density relation, suggesting that the field strength in dense coresis independent of the large-scale environment. Albeit with limited statistics, we find no evidence for the dependence of
the initial mass function on the initial magnetic field strength, however, the star formation rate decreases for models
with increasing initial field strengths; the exception is the strongest field case where collapse occurs primarily along
field lines. Protostellar discs with radii >∼20 au form in all models, suggesting that disc formation is dependent on thegas turbulence rather than on magnetic field strength. We find no evidence for the magnetic braking catastrophe, andfind that magnetic fields do not hinder the formation of protostellar discs.
Accepted by MNRAS
https://arxiv.org/pdf/1908.03241

72

Properties of Density and Velocity Gaps Induced by a Planet in a Protoplanetary Disk
Han Gyeol Yun1 , Woong-Tae Kim1,2 , Jaehan Bae3 , and Cheongho Han4
1

Department of Physics & Astronomy, Seoul National University, Seoul 08826, Korea; 2 Center for Theoretical Physics(CTP), Seoul National University, Seoul 08826, Korea; 3 Department of Terrestrial Magnetism, Carnegie Institution
for Science, 5241 Broad Branch Road NW, Washington, DC 20015, USA; 4 Department of Physics, Chungbuk National
University, Cheongju 28644, Korea
E-mail contact: hangyeol at snu.ac.kr
Gravitational interactions between a protoplanetary disk and its embedded planet is one of the formation mechanismsof gaps and rings found in recent ALMA observations. To quantify the gap properties measured in not only surface
density but also rotational velocity profiles, we run two-dimensional hydrodynamic simulations of protoplanetary disks
by varying three parameters: the mass ratio q of a planet to a central star, the ratio of the disk scale height hp tothe orbital radius rp of the planet, and the viscosity parameter α. We find the gap depth δΣ in the gas surface
density depends on a single dimensionless parameter K ≡ q 2 (hp /rp )−5 α−1 as δΣ = (1+0.046K)−1, consistent
with the previous results of Kanagawa et al. (2015a). The gap depth ?V in the rotational velocity is given by
δV = 0.007(hp /rp )K 1.38 /(1 + 0.06K 1.03). The gap width, in both surface density and rotational velocity, has aminimum of about 4.7hp when the planet mass Mp is around the disk thermal mass Mth , while it increases in a
power-law fashion as Mp /Mth increases or decrease from unity. Such a minimum in the gap width arises because
spirals from sub-thermal planets have to propagate before they shock the disk gas and open a gap. We compare ourrelations for the gap depth and width with the previous results, and discuss their applicability to observations.
Accepted by ApJ
http://arxiv.org/pdf/1908.11065

39

73

Systematic Variations of CO Gas Abundance with Radius in Gas-rich Protoplanetary
Disks
Ke Zhang1 , Edwin A. Bergin1 , Kamber R. Schwarz2 , Sebastiaan Krijt3 , Fred Ciesla4
1

Department of Astronomy, University of Michigan, 323 West Hall, 1085 S. University Ave, Ann Arbor, MI 48109,
USA; 2 Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721, USA; 3
Department of Astronomy/Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ
85721, USA; 4 Department of the Geophysical Sciences, The University of Chicago, 5734 South Ellis Avenue, Chicago,
IL 60637, USA E-mail contact: kezhang at umich.edu
CO is the most widely used gas tracer of protoplanetary disks. Its abundance is usually assumed to be an interstellar
ratio throughout the warm molecular layer of the disk. But recent observations of low CO gas abundance in many
protoplanetary disks challenge our understanding of physical and chemical evolutions in disks. Here we investigate
the CO abundance structures in four well-studied disks and compare their structures with predictions of chemical
processing of CO and transport of CO ice-coated dust grains in disks. We use spatially resolved CO isotopologue line
observations and detailed thermo-chemical models to derive CO abundance structures. We find that the CO abundance
varies with radius by an order of magnitude in these disks. We show that although chemical processes can efficiently
reduce the total column of CO gas within 1 Myr under an ISM level of cosmic-ray ionization rate, the depletion mostly
occurs at the deep region of a disk. Without sufficient vertical mixing, the surface layer is not depleted enough to
reproduce weak CO emissions observed. The radial profiles of CO depletion in three disks are qualitatively consistent
with predictions of pebble formation, settling, and drifting in disks. But the dust evolution alone cannot fully explain
the high depletion observed in some disks. These results suggest that dust evolution may play a significant role intransporting volatile materials and a coupled chemical-dynamical study is necessary to understand what raw materials
are available for planet formation at different distances from the central star.
Accepted by ApJ
http://arxiv.org/pdf/1908.03267

74

An Episodic Wide-angle Outflow in HH 46/47
Yichen Zhang1 , Héctor G. Arce2 , Diego Mardones3,4 , Sylvie Cabrit5,6 , Michael M. Dunham7 , Guido
Garay3 , Alberto Noriega-Crespo8 , Stella S. R. Offner9 , Alejandro C. Raga10 , and Stuartt A. Corder111Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan;
Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520, USA; 3 Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile; 4 Centre for Astrochemical Studies, Max-PlanckInstitute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748, Garching, Germany; 5 LERMA, Observatoire deParis, UMR 8112 du CNRS, ENS, UPMC, UCP, 61 Av. de l’Observatoire, F-75014 Paris, France; 6 Institut dePlanétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, 38041, France; 7 Department of Physics,
State University of New York at Fredonia, 280 Central Avenue, Fredonia, NY 14063, USA; 8 Space Telescope Science
Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA; 9 Department of Astronomy, The University of Texas atAustin, Austin, TX 78712, USA; 10 Instituto de Ciencias Nucleares, UNAM, Ap. 70-543, 04510 D.F., Mexico; 11 Joint
ALMA Observatory, Av. Alonso de Córdova 3107, Vitacura, Santiago, Chile E-mail contact: yichen.zhang at riken.jp
2

During star formation, the accretion disk drives fast MHD winds which usually contain two components, a collimatedjet and a radially distributed wide-angle wind. These winds entrain the surrounding ambient gas producing molecular
outflows. We report recent observation of 12 CO (2–1) emission of the HH 46/47 molecular outflow by the Atacama
Large Millimeter/sub-millimeter Array, in which we identify multiple wide-angle outflowing shell structures in boththe blue and red-shifted outflow lobes. These shells are highly coherent in position-position-velocity space, extending
−1
4
to >
∼ 40–50 km s in velocity and 10 au in space with well defined morphology and kinematics. We suggest theseoutflowing shells are the result of the entrainment of ambient gas by a series of outbursts from an intermittent wideangle wind. Episodic outbursts in collimated jets are commonly observed, yet detection of a similar behavior inwide-angle winds has been elusive. Here we show clear evidence that the wide-angle component of the HH 46/47
protostellar outflows experiences similar variability seen in the collimated component.
Accepted by ApJ
http://arxiv.org/pdf/1908.00689

40

Dissertation Abstracts

Complex organic chemistry in high-mass star-forming regions
Mélisse Bonfand

Max-Planck-Institut für Radioastronomie, Bonn, Germany
Address as of July 2019: Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux B18N, Pessac, FranceElectronic mail: melisse.bonfand-caldeira at u-bordeaux.fr
Ph.D dissertation directed by: Prof. Dr. Karl M. Menten
Ph.D degree awarded: June 2019
The quest for interstellar complex organic molecules (COMs) lies at the heart of astrochemistry. One basic motivation
is to figure out how the rich inventory of COMs found in meteorites and comets is connected to interstellar chemistry.
While the number of COMs detected in the interstellar medium increases, we wish to understand whether chemicalcomplexity is a natural outcome of interstellar chemistry, which degree of complexity can be reached, and when,
where and under which conditions these molecules form and how their occurence evolves from interstellar clouds toplanetary systems. Most interstellar COMs were first detected toward the dense and warm parts of high-mass starforming regions, called hot molecular cores. In particular, Sagittarius B2 (Sgr B2), one of the most active star-forming
regions in our Galaxy, is an excellent target to study the production of COMs under extreme physical conditions(high densities, strong radiation field, high cosmic-ray flux). In this thesis we take advantage of the high sensitivityof a new type of imaging spectral line survey made possible by the Atacama Large Millimeter/submillimeter Array(ALMA). It affords studies of the spatial structure and chemical content of active star-forming regions in Sgr B2 in
unprecedented detail. We report the detection of three new hot cores in Sgr B2(N), one of Sgr B2’s main star-forming
sites. In a detailed comparative study, we determine their chemical composition, density, mass, temperature, andspatial structure. We check for association with maser sources and ultra-compact HII regions, signposts of recent
high-mass star formation, as well as outfows, to evaluate the evolutionary stage of the hot cores. In the second partof the thesis we analyze their physical evolution from the cold pre-stellar phase to the present time. We use results ofprevious radiation-magnetohydrodynamical simulations of high-mass star formation and stellar structure calculations
combined with a radiative transfer model to derive the thermal history of the sources. We compute time-dependentchemical abundances using the astrochemical code MAGICKAL, focusing especially on selected COMs to investigate indetail the chemical reactions and processes involved in their formation under the extreme conditions that characterize
Sgr B2(N). We compare the chemical model results to the abundances derived from the observations toward the hot
cores and find that a cosmic-ray ionization rate 50 times higher than the solar neighborhood value best characterizes
Sgr B2(N)’s environmental conditions. We are also able to constrain the range of dust temperatures reached during
the earlier pre-stellar phase at which COMs form on dust-grain surfaces. We show that COMs still form efficiently
with minimum dust temperatures as high as 15 K, but the current chemical composition of the hot cores excludes
minimum temperatures higher than 25 K.
41

New Jobs

Postdoctoral position at IPAG, Grenoble, on exoplanetary atmosphere
evaporation models.
A 3yr postdoctoral position is offered at IPAG, Grenoble, starting January 1st, 2020, to develop and/or adapt modelsof planetary atmosphere evaporation around young stars and predict the observable signatures of such processes.
Previous experience in planetary evaporation models will be most valuable. The work will take place at IPAG in
the framework of the ERC-funded project SPIDI (http://www.spidi-eu.org), and will involve collaborations with
Alain Lecavelier des Etangs (IAP, Paris) and Vincent Bourrier (Obs. Geneve). Applications are to be sent toJerome.Bouvier@univ-grenoble-alpes.fr by November 15, 2019.

Postdoctoral Positions in Star and Planet Formation
National Institute of Science Education and Research (NISER)
Bhubaneswar, India
Looking for hiring highly motivated and bright postdoctoral candidates interested in different areas of Astrochemistry
and Radio/Sub-millimeter/Infrared Astronomy to address the physics of star and planet formation.
The candidate will also have access to the IRAM-30m, ALMA Cycle 6 and 7, SOFIA Cycle 7 data as well as NASA’s
JWST-MIRI guaranteed time observations and will be involved to prepare science case for SKA’s Cradle of Life
Consortium (Band 6).
PhDs with Astronomy & Astrophysics/Space Science/Planetary Science or relevant background may apply. Candidates
with good scientific programming and astronomical data analysis skills are highly encouraged.
Please contact Dr. Liton Majumdar (Assistant Professor, NISER, Bhubaneswar, India & Visiting Researcher, NASA JPL, Pasadena, USA) at liton@niser.ac.in with your CV, research interest and statement
addressing the scientific objective.

42

Meetings

Protostars & Planets VII
Kyoto, April 1 (Thu) - 7 (Wed), 2021
We are planning to organize an international conference, Protostars & Planets VII (PP7), at Kyoto in April 2021, which
will be the first conference of the series held in Asia. This series of conference has provided important opportunity forthe scientists working on the formation of stars and planets. We would like to have a series of review talks summarizing
the development in our field in recent years. As in the previous Protostars & Planets Series, we will publish thosereviews as a new volume, PROTOSTARS AND PLANETS VII, in the Space Science Series of University of Arizona
Press. The information of the meeting is the following:
Meeting Name: Protostars & Planets VII (PP7)Venue: Kyoto International Conference Center, Kyoto, Japan
Date: April 1 (Thu) - 7 (Wed), 2021
Website: http://www.ppvii.org
Call for Chapter Proposals: Winter of 2019
List of Editors:
Shu-ichiro Inutsuka (Nagoya University), Motohide Tamura (University of Tokyo), Yuri Aikawa (University of Tokyo),
Takayuki Muto (Kogakuin University), and Kengo Tomida (Osaka University)
Scientific Advisory Committee:
Joao Alves (Austria), Philippe Andre (France), Isabelle Baraffe (UK), John Carpenter (Chile), Paola Caselli (Germany), Weng-Ping Chen (Taiwan), Kees Dullemond (Germany), Tristan Guillot (France), Alyssa Goodman (USA),
Lynne Hillenbrand (USA), Thomas Henning (Germany), Shigeru Ida (Japan), Doug Johnstone (Canada), Inga Kamp
(Netherlands), Mark Krumholz (Australia), Jeong-Eun Lee (Korea), Victoria Meadows (USA), Michael Meyer (USA),
Richard Nelson (UK), Toshikazu Onishi (Japan), Eve Ostriker (USA), Ilaria Pascucci (USA), Yasuhito Sekine (Japan),
Shogo Tachibana (Japan), Mario Tafalla (Spain), Ewine van Dishoeck (Netherland), and Jonathan Williams (USA)43Summary of Upcoming Meetings

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
Planet Formation Workshop 201925 - 28 November Tokyo, Japan
http://th.nao.ac.jp/meeting/planet-formation-workshop2019/
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
http://staratlyon.univ-lyon1.fr/en
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org

44

Passings

Alfred E. Glassgold
20 July 1929 - 4 January 2019
Alfred Glassgold, an atomic and nuclear physicist who became an astrophysicist and astrochemist, died in San Francisco
on 4 January 2019. His work progressed from atomic nuclei and superfluidity, to interstellar clouds and circumstellar
envelopes, to winds from young stars and the birthplaces of planets, illuminating our understanding of these regionsof the cosmos. A versatile physicist who was active in teaching and research well into his 80s, he was also a treasured
colleague and mentor.
Born 20 July 1929 and raised in Philadelphia, Al was an accomplished clarinetist, who initially considered a careerin music but ultimately chose physics as his lifelong pursuit. As an undergraduate, he majored in Physics at the
University of Pennsylvania. He later studied theoretical nuclear physics with Victor Weisskopf’s group, obtaining his
PhD from MIT in 1954. For his postdoctoral studies, Al moved to UC Berkeley, where he worked on problems instatistical mechanics with applications to atomic physics, superfluidity, and nuclear physics. For a few years, he taught
with Edward Teller, physics courses to UC students.
In 1963, Al moved with his wife and two children to New York, where he joined the physics faculty at NYU. He was an45

integral member of the University for 36 years, serving as head of the academic senate as well as chair of the Physics
Department during an important period when the department was growing rapidly and its new building was plannedand constructed.
Although his initial background was in atomic and nuclear physics, Al’s research interests turned to astrophysics in theearly 1970s, as a result of the detection of interstellar molecules made by the Charles Townes group using microwave
techniques as well as UV observations of interstellar molecules made from space. Simple interstellar molecules had
been detected in absorption as early as 1937. However, the detection of molecular emission and the discovery ofpolyatomic molecules (e.g., ammonia, water) opened up many new avenues of study.
Inspired to use his knowledge of atomic physics to understand the physical conditions in the interstellar medium, Al
went to UC Berkeley for a summer to work with Townes, who shared his interest in this topic. It was the beginning of his
career as an astrophysicist and an astrochemist. Throughout the 1970s and 1980s, Al and his collaborators, students,
and postdocs studied the thermal, chemical, and ionization structure of interstellar clouds and the circumstellar
envelopes of late-type stars.
In 1990, Al spent a sabbatical year at UC Berkeley, and his research interests changed direction once again. At thetime, Berkeley was a lively focal point for studies on the origins of stars and planets. Al’s astrochemistry expertisecomplemented the theoretical and observational interests of the star and planet formation group, and he began longterm collaborations with Frank Shu and others. His insights contributed to our understanding of the important role
atomic winds play in driving molecular outflows and solving a star’s “angular momentum problem,” i.e., understanding
how stars remove enough angular momentum to allow their assembly to proceed.
Al’s work on winds also led to studies of protoplanetary disks, the rotationally supported structures around young stars
that are the birthplaces of planets. Over the past two decades, he led fundamental work on the ionization structure ofdisks as well as the molecular and atomic diagnostics that are used to understand their chemical and dynamical nature.
These studies demonstrated that stellar X-rays, not cosmic rays, are primarily responsible for disk ionization. The
ionization structure of disks governs how they interact with magnetic fields and how they evolve dynamically. Further
studies on disk chemistry illustrated how water and other simple molecules can be synthesized in disk atmospheres,and how atmospheres can be heated enough to produce observable emission features, i.e., the signposts that provide
clues to their nature.
Much of this later work was carried out after 2000, when Al retired from NYU and joined the UC Berkeley Astronomy
faculty. He continued to teach and advise students and postdocs until just a few years ago. Throughout his life, Al
read widely on all subjects and enjoyed music, art, and food. Since moving to San Francisco, he had also been closely
involved in the political life of the city.
Al is remembered not only for his research accomplishments but also as a treasured mentor and colleague. Unfailingly
polite and with a playful sense of humor, he welcomed and encouraged colleagues of diverse backgrounds, including
many women astronomers. He is survived by his wife Irene and children, Judith and Eric Glassgold. He is much
missed.
Joan R. Najita
National Optical Astronomy Observatory
Tucson, Arizona
najita@noao.edu
This obituary previously appeared online in Physics Today:
https://physicstoday.scitation.org/do/10.1063/PT.6.4o.20190730a/full/
For an interview with Al Glassgold, see Star Formation Newsletter No. 264

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Short Announcements

New book ”Host Stars and their Effects on Exoplanet Atmospheres”
I would like to bring to the attention of the exoplanet community my new book ”Host Stars and their Effects on
Exoplanet Atmospheres” published in June 2019 by Springer. I will send the Table of Contents for the book to people
who send me an email. The book should be a useful textbook or reference for classes on exoplanets.
Jeff Linsky
University of Colorado at Boulder
jlinsky@jila.colorado.edu

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

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.

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