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Shun ISHII ,1,2 ,∗ Fumitaka NAKAMURA ,1,3 ,4 Yoshito SHIMAJIRI ,1,5,6
Ryohei KAWABE ,1,3 ,4 Takashi TSUKAGOSHI ,1 Kazuhito DOBASHI ,7
and Tomomi SHIMOIKURA 7 ,81

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
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,
K F
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 (and Engineering, 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
8
Otsuma Women’s University Faculty of Social Information Studies Chiyoda-ku, Tokyo 102-8357, Japan
2

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Nobeyama 45 m mapping observations toward
Orion A. II. Classification of cloud structures andvariation of the 13 CO/C18 O abundance ratio due
to far-UV radiation

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filamentS(DLSF) are naturally identified as distinct structures in Orion A. These clouds can∗taE-mail: shun.ishii@nao.ac.jp

Received 2018 December 5; Accepted 2019 May 17

12

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also be classified into three groups: the integral-shaped filament, the southern regions ofOrion 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

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Shun ISHII ,1,2 ,∗ Fumitaka NAKAMURA ,1,3 ,4 Yoshito SHIMAJIRI ,1,5,6
Ryohei KAWABE ,1,3 ,4 Takashi TSUKAGOSHI ,1 Kazuhito DOBASHI ,7
and Tomomi SHIMOIKURA 7 ,8

Ø
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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
4The 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 and Engineering, 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
8
Otsuma Women’s University Faculty of Social Information Studies Chiyoda-ku, Tokyo 102-8357, Japan

Ø

∗

v

E-mail: shun.ishii@nao.ac.jp

Received 2018 December 5; Accepted 2019 May 17

Abstract
We present results of the classification of cloud structures toward the Orion A Giant
Molecular Cloud based on wide-field 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 Segmenta&tion (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 structures in Orion A. These clouds canalso be classified into three groups: the integral-shaped filament, the southern regions ofOrion 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

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Nobeyama 45 m mapping observations toward
Orion A. II. Classification of cloud structures andvariation of the 13 CO/C18 O abundance ratio due
to far-UV radiation

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Advance Access publication 2019 August 8

New evidence for weak magnetic fields in Herbig Ae/Be stars
S. P. Järvinen ,1‹ T. A. Carroll,1 S. Hubrig,1 I. Ilyin1 and M. Schöller2
2 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany

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1 I N T RO D U C T I O N
Herbig Ae/Be stars are pre-main-sequence objects with pronounced
emission-line features and an infrared excess indicative of dustin their circumstellar discs. It was previously assumed that thesestars are intermediate-mass analogues of T Tauri stars, but withconvectively stable envelopes that do not support the dynamo action
found in the fully convective T Tauri stars. A number of magnetic
studies have been attempted in the last years, indicating that aboutstars with relatively low v sin i values confirm the results of thisstudy, revealing the presence of weak, frequently just of the order ofa few tens of Gauss, magnetic fields measured with an uncertainty
of only a few Gauss (Hubrig et al. 2015; Järvinen et al. 2015,2018).
In this work, we discuss the results of our recent observing
campaigns of a sample of Herbig Ae/Be stars using the HighAccuracy Radial velocity Planet Searcher polarimeter (HARPSpol;
Snik et al. 2008).

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Downloaded from https://academic.oup.com/mnras/article-abstract/489/1/886/5545215 by Institute of Statistical Sci

1 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany) ,~hAdvance Access publication 2019 August 8

New evidence for weak magnetic fields in Herbig Ae/Be stars
S. P. Järvinen ,

1‹

1

1

1

T. A. Carroll, S. Hubrig, I. Ilyin and M. Schöller2a2 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany

24
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Accepted 2019 July 31. Received 2019 July 30; in original form 2019 June 25

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ABSTRACTIn recent years Herbig Ae/Be stars receive considerable attention as their discs are believed
to be the sites of on-going planet formation. Confirming the presence of magnetic fields
in these stars is critical for understanding the transport of angular momentum during theprotostellar 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 (SVD) method to high 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 thantheir lower mass counterpart T Tauri stars with magnetic fields of kG order.

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Downloaded from https://academic.oup.com/mnras/article-abstract/489/1/886/5545215 by Institute of Statistical Sci

1 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany

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convectively stable envelopes that do not support the dynamo action
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campaigns of a sample of Herbig Ae/Be stars using the HighAccuracy Radial velocity Planet Searcher polarimeter (HARPSpol;
Snik et al. 2008).

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CHARACTERIZING MAGNETIC FIELD MORPHOLOGIES IN THREE
SERPENS PROTOSTELLAR CORES WITH ALMA
Valentin J. M. Le Gouellec1,2 , Charles L. H. Hull3,4⇤ , Anaëlle J. Maury2,5 , Josep M. Girart6,7 , Łukasz
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, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, F-91191 Gif-sur-Yvette, France
3 National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Córdova 3788, Oﬃce 61B, 7630422, Vitacura, Santiago, Chile
4 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
5 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
6 Institut de Ciències de l’Espai (ICE-CSIC), Campus UAB, Carrer de Can Magrans S/N, E-08193 Cerdanyola del Vallès, Catalonia[astro-ph.GA] 30 Aug 2019Ø ecg
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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, University of Copenhagen, Øster

Voldgade 5-7, DK-1350 Copenhagen K, Denmark

10 Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA

11 Departamento de Astronomía, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile
12 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA and

13 Submillimeter Array, Academia Sinica Institute of Astronomy and Astrophysics, 645 N. A’ohoku Place, Hilo, HI 96720, USA

Accepted for publication in ApJ on 29 August 2019

ABSTRACT
dblpg With the aim of characterizing the dynamical processes involved in the formation of young protostars,
Lr we present high angular 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 valuesof the polarization fraction along the outflow cavity walls in,,%,,)tracers%to investigate outflow and dense gas,, ) - Serpens Emb8(N). We use 3 mm andØ 1 mm molecular
nlpg
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These observations allow
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mpdo
8 7 18seems to trace the redshifted outflow cavity wall. The other may be an accretion streamer of material

CHARACTERIZING MAGNETIC FIELD MORPHOLOGIES IN THREE
SERPENS PROTOSTELLAR CORES WITH ALMA
Valentin J. M. Le Gouellec1,2 , Charles L. H. Hull3,4⇤ , Anaëlle J. Maury2,5 , Josep M. Girart6,7 , Łukasz
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, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, F-91191 Gif-sur-Yvette, France
3 National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Córdova 3788, Oﬃce 61B, 7630422, Vitacura, Santiago, Chile
4 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
5 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
6 Institut de Ciències de l’Espai (ICE-CSIC), Campus UAB, Carrer de Can Magrans S/N, E-08193 Cerdanyola del Vallès, Catalonia[astro-ph.GA] 30 Aug 2019

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7 Institut d’Estudis Espacials de Catalunya, E-08030 Barcelona, Catalonia
à
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8 Leiden Observatory, Leiden University, PO Box 9513, 23000RA, Leiden, The Netherlands
9 Centre for Star and Planet Formation, Niels BohrH InstituteVReand H
S University of Copenhagen, ØsterNatural History Museum of Denmark,Voldgade
5-7, DK-1350 Copenhagen K, Denmark
ØeSH
10 Department of Astronomy,
University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA
11 Departamento de Astronomía, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile
à
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12
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA and

13 Submillimeter Array, Academia Sinica Institute of Astronomy and Astrophysics, 645 N. A’ohoku Place, Hilo, HI 96720, USA

Accepted for publication in ApJ on 29 August 2019ØABSTRACTyH
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4 protostars,
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With the aim of characterizing the dynamical
processes involved
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observations of (the Class 0 protostellar
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870 µm, we find unexpectedly high values of the polarization
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0 4

properties and their correlation with the polarization. These observations allow us to investigate thephysical processes involved in the RadiativeØAlignment
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Abundant refractory sulfur in protoplanetary disks
Mihkel Kama,1 Oliver Shorttle,1 Adam S. Jermyn,1, 2 Colin P. Folsom,3 Kenji Furuya,4 Edwin A. Bergin,5Catherine Walsh,6 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 de Toulouse, 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(Received; Revised; Accepted)

Submitted to ApJ
ABSTRACT
Sulfur is one of the most abundant elements in the Universe, with important roles in astro-, geo-, andbiochemistry. 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 refractoryminerals. Mechanisms such as giant planets can filter out dust from gas accreting onto disk-hostingstars. For stars above 1.4 solar masses, this leaves a chemical signature on the stellar photospherethat 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 intheir disks. The main carrier is much more refractory than water ice, consistent with sulfide mineralssuch as FeS.
Keywords: astrochemistry, chemical abundances — protoplanetary disks — Herbig Ae/Be stars" !     

Constraining the detectability of water ice in debris disks
M. Kim1 , S. Wolf1 , A. Potapov2 , H. Mutschke3 , and C. Jäger2
1

Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 15, 24118 Kiel, Germany
e-mail: mkim@astrophysik.uni-kiel.de
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

ABSTRACT
Context. Water ice is important for the evolution and preservation of life. Identifying the distribution of water ice in debris disks istherefore of great interest in the field of astrobiology. Furthermore, icy dust grains are expected to play important roles throughout theentire planet formation process. However, currently available observations only allow deriving weak conclusions about the existenceof water ice in debris disks.
Aims. 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 of ice, dust production through planetesimal collisions, and photosputtering by UV-brightcentral stars. We consider icy dust mixture particles with various shapes consisting of amorphous ice, crystalline ice, astrosilicate, andvacuum inclusions (i.e., porous ice grains).
Methods. We calculated optical properties of inhomogeneous icy dust mixtures using e↵ective medium theories, that is, MaxwellGarnett rules. Subsequently, we generated synthetic debris disk observables, such as spectral energy distributions and spatially resolved thermal reemission and scattered light intensity and polarization maps with our code DMS.
Results. We find that the prominent ⇠ 3 µm and 44 µm water ice features can be potentially detected in 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, and photosputtering caused by UV sources clearly a↵ect
the observational appearance of debris disk systems. In addition, highly porous ice (or ice-rich aggregates) tends to produce highlypolarized radiation at around 3 µm. Finally, the location of the ice survival line is determined by various dust properties such as afractional ratio of ice versus dust, physical states of ice (amorphous or crystalline), and the porosity of icy grains.
Key words. circumstellar matter – planetary systems – methods : numerical

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Dynamical Gaseous Rings in Global Simulations of Protoplanetary Disk Formation
Kundan Kadam,1 Eduard Vorobyov,2, 3 Zsolt Regály,1 Ágnes Kóspál,1, 4 and Péter Ábrahám1
1 Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly-Thege 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(Received 2019 March 27; Revised 2019 July 24; Accepted 2019 July 30)

ABSTRACT
Global numerical simulations of protoplanetary disk formation and evolution were conducted in thindisk limit, where the model included magnetically layered disk structure, a self–consistent treatment
for the infall from cloud core as well as the smallest possible inner computational boundary. We
compared the evolution of a layered disk with a fully 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 the canonical values of parameters a dead zone formed within the inner ⇡15 au region of themagnetically 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 as compared to a fully magnetically active disk
and were characterized by high surface density and low e↵ective 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
spiral waves. An increase in MRI triggering temperature had only marginal e↵ects, while changes in
active layer thickness as well as the initial cloud core mass had significant e↵ects on the structure andevolution of the inner disk. Dust with large fragmentation barrier could be trapped in the rings, which
may play a key role in planet formation.
Keywords: protoplanetary disks — stars: formation — stars: variables: T Tauri — hydrodynamics —&#-5 !,&5*6
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+-8 ("'<$. 3/59Molecular envelope around the HII region RCW 120

d 2019 July 23; in original form12019 May 10

M. S. Kirsanova , Ya. N. Pavlyuchenkov,1 D. S. Wiebe ,1 P. A. Boley,2,3
S. V. Salii,3 S. V. Kalenskii,4 A. M. Sobolev3 and L. D. Anderson5,6 †1 Institute of Astronomy, Russian Academy of Sciences, 48 Pyatnitskaya Str., 119017 Moscow, Russia

ABSTRACT

3 Institute of Natural Sciences and Mathematics, Ural Federal University, 19 Mira Str., 620075 Ekaterinburg, Russia

Downloaded from https://academic.oup.com/mnras/article-abstract/488/4/5641/5538853 by Academia Sinica user on 24

2 Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, 141701 Moscow Region, Russia

The H II region RCW 120 is a well-known object, which is often considered as a target toverify theoretical models of gas and dust dynamics in the interstellar medium. However, theexact geometry of RCW 120 is still a matter of debate. In this work, we analyse observational
Accepted
2019 molecular
July 23. Received 2019
July 23; in originalform 2019120
May 10and show that 13 CO(2–1) and C18 O(2–1) lines aredata onemissionin RCW
fitted by a 2D model representing a ring-like face-on structure. The changing of the C18 O(3–2)
ABSTRACTline profile from double-peaked
to single-peaked from the dense molecular Condensation 1
The H II region RCW 120 is a well-known object, which is often considered as a target tomight be a signature ofverify
stalledexpansionorder
to explain
self-absorption
theoreticalmodels ofin
gasthisand direction.
dust dynamics In
in theinterstellar
medium. aHowever,
the
13
13
exact
geometry
of
RCW
120
is
still
a
matterofdebate.
In
this
work,
we
analyseobservational
dip of the CO(2–1) and CO(3–2) lines, we suggest that13RCW 120 18is surrounded by adata on molecular emission in RCW 120 and show that CO(2–1) and C O(2–1) lines are
diffuse molecular cloud,andconfirmationof thisface-on
cloudstructure.
on a mapof interstellar
extinction.
fittedby afind
2D modelrepresenting a ring-like
The changing
of the C18 O(3–2)
13
line
profilefromdouble-peakedtosingle-peaked
from
the
dense
molecular
Condensation
1
Optically thick CO(2–1) emission and the infrared 8 µm PAH band form a neutral envelope
might be a signature of stalled expansion in this direction. In order to explain a self-absorptionof the H II region resemblingwhile
envelope
intoRCW
separateclumps byona images
CO(2–1)
and 13theCO(3–2)lines, webreaks
suggest that
120 is surrounded
dip of thea13ring,18
diffusecloud,
find confirmationof thiscloudemission.
on a map of interstellar extinction.
made with optically thin
C molecularO(2–1)
lineandandfar-infrared
dust
13

4 Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences, 84/32 Profsoyuznaya Str., 117997 Moscow, Russia
5 Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA

6 Center for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USA

Optically thick CO(2–1) emission and the infrared 8 µm PAH band form a neutral envelopeof the H II region resembling a ring, while the envelope breaks into separate clumps on images
stars: formation – stars: massive– dust, extinction – H ii regions – ISM: kinematmade with optically thin C18 O(2–1) line and far-infrared dust emission.

Key words:
ics and, dynamics. C

1 I N T RO D U C T I O N

8

W S H
C

C
3 O
C

Key words: stars: formation – stars: massive – dust, extinction – H ii regions – ISM: kinematics and dynamics.

RM

shed light onshed
thelight
detailed
structure
distribution
on the detailed
structureofof mattermatter distribution
in star- in starC
10
forming
regions,ontheinteractionofmassive
stars
with
their
forming regions, on the interaction of massive stars withparent
their parent

Spitzer and WISE maps of the Milky Way Galaxy have revealed

molecular clouds, on the dust evolution in the vicinity of massive

he Milky
Galaxyrevealed
onon thedust evolution
the vicinityof massive
moreWay
than five
thousandhave
ring-likestructures, which aremolecularcommonly clouds,
stars, andthe possibility
and extent ofin
triggeredstar formation.
IIregions
excitedbyreferredtoasinfrared(IR)
bubbles,aroundH
ButtheproblemoftheactualgeometryofIR
ring
nebulaeisg-like structures, which are commonlystars, and on the possibility and extent of triggered star still
formation.
young massive stars (e.g. Churchwell et al. 2006, 2007; Deharveng
far from being solved.
II regions
excitedubbles, etaroundBut
thethe actualof performed
IR ring by
nebulaeal. 2010;HAndersonet al. 2011,2014; by
Simpson et al.
2012,
andproblem
An ofimportantstudy ofgeometry
this issue was
Beau- is still
also
recentstudiesbyTopchieva
et
al.
2017;
Topchieva,
Wiebe
&
mont
&
Williams(2010).
They
utilized
observationsofCO(3–2)
urchwell et al. 2006, 2007; Deharveng
far from being solved.
+

aded from https://academic.oup.com/mnras/article-abstract/488/4/5641/5538853 by Academia Sinica user

MNRAS
488, 5641–5650(2019)
doi:10.1093/mnras/stz2048
ronomy, West
Virginia
University,
Morgantown, WV 26506, USA
Advance Access publication 2019 July 25s and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown, WV 26505, USA

2 I

HTypeset using LATEX twocolumn style in AASTeX62

A Comparison of the X-ray Properties of FU Ori-type Stars to Generic Young Stellar Objects
Michael A. Kuhn1 and Lynne A. Hillenbrand1
1 Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA(Received May 10, 2019; Revised July 31, 2019; Accepted August 9, 2019)

Submitted to ApJ
ABSTRACT
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 a↵ect 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 of Gaia 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 ) and column 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 withhigh LX have been observed both at the onset of their outbursts and decades later. We use the KaplanMeier estimator to investigate whether the higher X-ray luminosities for FU Ori stars is characteristic
or a result of selection e↵ects, and we find the di↵erence to be statistically significant (p < 0.01) evenwhen 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 restructuringof 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.
Keywords: accretion disks, stars: formation, stars: individual (Gaia 17bpi), stars: variables: T Tauri,

O

F
O

O
S
O
1

U
6

Zhi-Yun Li, Che-Yu Chen, Kengo Tomida,
MNRAS 000, 1–24 (2019)

Preprint 2 September 2019

and Bo Zhao

Compiled using MNRAS L TEX style file v3.0

y, University of Virginia, Charlottesville, VA 22904, USASpace Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
cal Sciences,
University,
NJ 08544,
USA Cores with
DiskPrinceton
Formation
in Princeton,
Magnetized
Dense
xtraterrestrische Physik (MPE), Garching D-85748, Germany

Turbulence and Ambipolar Di↵usion

1? Zhi-Yun Li,1 Che-Yu Chen,1 Kengo Tomida,2,3 and Bo Zhao4
YY; in Ka
original
form ZZZ
Ho Lam,1 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA

2 Department of Earth and Space Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
3 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA

Xiv:1908.11806v1 [astro-ph.SR] 30 Aug 2019

4 Max-Planck-Institut für extraterrestrische Physik (MPE), Garching D-85748, Germany

ABSTRACTDisks are essential to the formation of both stars and planets, but how they form inmagnetized molecular cloud cores remains debated. This work focuses on how the disk
formation is a↵ected by turbulence and ambipolar di↵usion (AD), both separately
and in combination,ABSTRACT
with an emphasis on the protostellar mass accretion phase of star
Disks are essential to the formation of both stars and planets, but how they form information. We find thata relatively
strong,sonicdebated.
turbulence
onfocuses
the oncore
magnetizedmolecular cloud
cores remains
This workhowscalethe diskstrongly
formationisa↵ectedbyturbulenceandambipolardi↵usion(AD),
bothseparately
warps but does not andcompletely
disrupt the well-known magnetically-induced flattenedin combination, with an emphasis on the protostellar mass accretion phase of starpseudodisk that dominates
theprotostellar
accretion
case,formation. We
findinnerthat a relatively
strong, sonicturbulence flowon the incorethescale laminarstrongly
warps
but
does
not
completely
disrupt
thewell-known
magnetically-induced
flattenedin agreement with previous work. The turbulence enables the formation of a relatively
pseudodisk that dominates the inner protostellar accretion flow in the laminar case,large disk at early times
withwithor previous
without
ambipolardi↵usion,but suchdisk remains
in agreement
work.
The turbulenceenables the formationof aarelatively
diskdoesat earlynot
timespersist
with or without
ambipolardi↵usion,such a disk remains
strongly magnetizedlarge
andto theend ofour but
simulation
unless a relstrongly magnetized and does not persist to the end of our simulation unless a relatively strong ambipolardi↵usionis di↵usion
also present.
TheTheAD-enableddisks
in laminar
atively strong
ambipolar
is also present.
AD-enabled disks
in laminarto fragment gravitationally.
The diskfragmentation is suppressedbysimulations tend to simulations
fragmenttend
gravitationally.
The diskfragmentation
is suppressedbyinitial turbulence. The ambipolar di↵usion facilitates the disk formation and survival
initial turbulence. The
ambipolar
facilitates
disk
formation
andre-survival
by reducing
the field di↵usion
strength in thecircumstellarthe
regionthroughmagnetic flux
distribution
and bythe field lines thereregion
less pinchedazimuthally,
especially flux reby reducing the fieldstrength
in makingthe circumstellar
throughmagnetic
at late times. We conclude that turbulence and ambipolar di↵usion complement each
distribution and byothermakingthe field lines there less pinched azimuthally, especiallyin promoting disk formation. The disks formed in our simulations inherit a rather
at late times. We conclude
thatfield
turbulence
andcore,ambipolardi↵usioncomplement
each
strong magnetic
from its parental
with a typicalplasma- oforder a few
tensor
smaller,
which
is
2-3
ordersofmagnitude
lower
than
the
valuescommonly
other in promoting disk
formation. The disks formed in our simulations inherit a rather
adopted in MHD simulations of protoplanetary disks. To resolve this potential tenstrong magnetic field
its parental
core,with aandtypicalof ordersion,fromlonger-term
simulations of
disk formation
evolutionplasmawith increasingly
more a few
realistic
physics
areneeded.
tens or smaller, which is 2-3 orders of magnitude lower than the values commonly
Key words: di↵usion– magnetic fields – magnetohydrodynamics
adopted in MHD simulationsof protoplanetarydisks. To resolve(MHD)
this– methods:
potential tennumerical – protoplanetary discs – stars: formation – turbulencesion, longer-term simulations of disk formation and evolution with increasingly more
realistic physics are needed.

Accepted XXX. Received YYY; in original form ZZZ

1INTRODUCTION
and star-forming cloud cores in particular(for recentKeywords: di↵usion – magnetic fields 2015)– magnetohydrodynamics(MHD)– methods:

D

A

A

MNRAS 000, 1–10 (2019)

Preprint 19 August 2019

Compiled using MNRAS LATEX style file v3.0

seok Song,1d Astronomy, The University of Georgia, Athens, GA 30602

Evaluation of nearby young moving groups based on
unsupervised machine learning

1? Inseok Song,1
YY; in original
Jinheeform
Lee,ZZZ

iv:1908.05922v1 [astro-ph.SR] 16 Aug 2019

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

ABSTRACT
Accepted XXX. Received YYY; in original form ZZZNearby young stellar moving groups have been identified by many research groups withdi↵erent methods and criteria giving rise to cautions on the reality of some groups. We
aim to utilise moving ABSTRACT
groups in an unbiased way to create a list of unambiguously recogNearby young stellar moving groups have been identified by many research groups withnisable moving groups
and methods
their members.
Forrisetheto analysis,
twounsupervisedmachinedi↵erent
and criteria giving
cautions on therealityof some groups. Weaimtoutilisemovinggroupsinanunbiasedwaytocreatealistofunambiguously
recoglearning algorithms (K-means
and Agglomerative Clustering) are applied to previously
nisable moving groups and their members. For the analysis, two unsupervised machine
known bona fide membersof nine (K-means
movingandgroupsfrom Clustering)
our previous
study.
As a result
learning algorithms
Agglomerative
are applied
to previously
known
bona
fide
membersofninemovinggroupsfrom
ourprevious
study.
Asaresult -Pic,of this study, we recovered six previously known groups (AB Doradus, Argus,of this study, we recovered six previously known groups (AB Doradus, Argus, -Pic,
Carina, TWA, and Volans-Carina).
Three theThree
other
known
groupsarerecognisedasCarina, TWA, and Volans-Carina).
the otherknowngroups arerecognisedaswell;
however,they
arecombined
into
two
new
separategroups(ThOr+Columba
andwell; however, they are combined into two new separate groups (ThOr+Columba andTucHor+Columba).
TucHor+Columba).
Key words: methods: data analysis – (Galaxy:) open clusters and associations:general – (Galaxy:) solar neighbourhood

Key words: methods: data analysis – (Galaxy:) open clusters and associations:general – (Galaxy:) solar neighbourhood
1

INTRODUCTION

A
-

a
C

A

later redefined or disappeared. Tucana association (Zuckerman & Webb 2000) and Horologium association (TorNearby young stellar moving groups (NYMGs, hereafter)
res et al. 2000) were merged as a single group by Zuckare gravitationally unbound loose stellar associations, and in
erman (2001) [Tucana Horologium Association (TucHor)].
this paper we focus primarily on NYMGs that areyoungerlater
redefinedor disappeared.
TucanaLiu (2015)
points out that several
movingassociationgroups may be (Zuckthan 100 Myr and have mean distances smaller than 100
merged,rejected,ornewgroupscanbediscovered.
pc of the Sun. The first NYMG, the TW Hya erman
association& Webb 2000) and Horologium association (TorIn this study, we re-evaluate the well-known nineving groups(NYMGs,hereafter)(TWA), wasdiscovered inlate 1990 (Kastner etresal. 1997).
et al. 2000)
asprevious
a singlegroup
by ZuckNYMGs were
without merged
relying on any
knowledge.
For this
new associations,
NYMGs were identified
nd looseThen,stellarand inby discoveries of cotask,
theclusteranalysis
would
be
an
ideal
technique.
The
erman
groups of stars in a small region of space(within (2001) [Tucana Horologium Association (TucHor)].
cluster analysis is a branch of unsupervised machine learning
arily onmoving
NYMGs
that
are
youngerfew tens of pc) with signs of similar ages. Even
Liuthough(2015) thatpointsout thatgroupsfinds groups
withinseveral
a dataset moving
without priorreferencemay be
NYMGs have smallera relativelythan
short history
mean distances
100 (about 20 years),
to the outcome. For identifying a star belonging to a cermerged,
NYMGs (N ⇠10) and their members (N >2000)
have rejected, or new groups can be discovered.
tain NYMG, the required information is Galactic position
NYMG,many
the
TW
Hya
association
been discovered (e.g., Zuckerman et al. 2001; Zuckerman
In & this(XYstudy,
wevelocity
re-evaluate
well-known
nineZ), Galactic(UVW), and theage. Stars
occupyingn late 1990
etal.al.
Song (Kastner
2004; Torres et2008;1997).
Mamajek 2007; Malo et al.

KA