THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 315 — 18 March 2019

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

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

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Abstracts of Newly Accepted Papers . . . . . . . . . . . 6
Abstracts of Newly Accepted Major Reviews . 32
Summary of Upcoming Meetings . . . . . . . . . . . . . 34

Technical Editor: Hsi-Wei Yen
hwyen@asiaa.sinica.edu.tw
Editorial Board
Joao Alves
Alan Boss
Jerome Bouvier
Lee Hartmann
Thomas Henning
Paul Ho
Jes Jorgensen
Charles J. Lada
Thijs Kouwenhoven
Michael R. Meyer
Ralph Pudritz
Luis Felipe Rodrı́guez
Ewine van Dishoeck
Hans Zinnecker
The Star Formation Newsletter is a vehicle forfast distribution of information of interest for astronomers working on star and planet formationand molecular clouds. You can submit material
for the following sections: Abstracts of recently
accepted papers (only for papers sent to refereed
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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
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Cover Picture
The image shows a small area of Cygnus X as observed by Spitzer. Cygnus X is a rich region of starformation at an approximate distance of 1.7 kpc
and containing thousands of young low-mass stars
and numerous OB stars. Blue represents light at 3.6
microns; 4.5-micron light is blue-green; 8.0-micronlight is green; and 24-micron light is red.
Image courtesy the Spitzer Space Telescope.

Submitting your abstracts
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nificant radio line. In 1968 and 1969, ammonia, water,
and formaldehyde were found, but none of these pointed
to extensive molecular clouds.

Robert Wilson
in conversation with Bo Reipurth

Q: In 1963 you moved to Bell Laboratories at Crawford
Hill in New Jersey. What did you plan to do there?

A: A big attraction at Bell Labs was the 20 foot Hornreflector and the availability of traveling wave MASER
amplifiers which were the lowest noise amplifiers which
existed then and could compensate for the small antenna.
The horn-reflector has very low back and side lobes so it
could potentially be used to measure the brightness of aregion of the sky with reference to only a lab noise reference. No other part of the sky need be referenced. In mythesis, I had used the fact that the Milky Way is very muchthinner than its diameter and ignored any residual radiation 10 degrees away from the plane. The horn-reflector
was also small enough that we could have a source in its
far field and accurately measure its gain. Thus it could
Q: What was the topic of your PhD, and who was your do two fundamental measurements which most radio telescopes could not - absolute brightness of the sky and absoadvisor?
lute flux of a discrete source. A second attraction of Bell
A: My thesis was titled ”Observations of the Galactic Labs was that I could see that if I tired of doing radio
Plane at 960 Mc/s” and my advisor was John Bolton astronomy, there were many other technical opportunities(John returned to Australia before I finished and Maarten there which I would enjoy working on.
Schmidt stood in for him at the end). I used one of the
90 foot OVRO antennas prior to their operating as an in- I joined Arno Penzias who had been at Bell Labs for more
terferometer and mapped all of the Galactic plane which than a year and we decided to do those and several otherwas visible from the Owens Valley. For most of the plane, measurements for which the horn-reflector was suitable.
I would drive the antenna to a point 10 deg. West of the It had a 4 GHz (7.5 cm) MASER on it which was madeplane and let the Earth’s rotation scan the beam across for the Telstar project and we had been promised a 21cm
the plane to 10 deg. East. The output came on chart pa- MASER which could be adapted from a cold war radar
per and I would draw a baseline with a meter stick from receiver developed by Bell Labs. Our plan was to first
the flat region on one side of the plane to the other and make accurate flux measurements of several bright radio
measure above that baseline. By comparing with other sources (such as CasA). These would be useful for radio assurveys, I determined properties of the discrete sources tronomy and for calibrating satellite Earth stations whichand divided the more general radiation into free-free and used the 4 GHz communications band as the down link forcommunications satellites. Then we would measure thesynchrotron components.
brightness of the sky away from the plane of the Galaxy.
Q: What was known about dark clouds back then?
Extrapolations from lower frequencies indicated that we
A: I don’t remember thinking much about dark clouds in should measure something close to 0K at 4 GHz. Having
those days. They were certainly known to contain ’dust’, proven our measuring system, we would measure the backbut I don’t remember any talk of molecules, or even star ground at 21cm. As most astronomers know, this control
formation. I think that even in 1970 there was little aware- measurement failed and after almost a year of trying toness of the possibility of molecular regions in interstellar find the ”problem” it lead to the discovery of the Cosmic
1
space even though Solomon & Wickramasinghe showed Microwave Radiation from the Big Bang.
−3
that dense clouds with a hydrogen density n > 100cm
Q: In 1970 you and a small group of colleagues went towould all be molecular clouds with molecular hydrogen H2 observe with the newly completed NRAO 36 foot antenna.
as the dominant constituent and very little atomic hydro- During this observing run you discovered CO. What were
gen. Interstellar CH and CN and CH+ had been known in the circumstances?
diffuse clouds from their optical absorption lines since thelate 1930s. In a talk in 1955, Charles Townes suggested A: The story starts shortly after propagation through a
1 For a more complete description of the discovery, see my Noradio astronomers should look for a number of transitions
in simple molecules, including OH, NH3 , H2 O, and CO. bel Lecture: The Cosmic Microwave Background Radiation, R. W.
In 1963 Sander Weinreb detected OH as the second sig- Wilson,Science, Vol. 205, No. 4409, pp. 866-874, August 31, 1979
https://www.cfa.harvard.edu/~ rwilson/WilsonNobelLecture.pdf

3

waveguide was demonstrated at AT&T in 1932. Calculations showed that the T E01 mode in a circular waveguide
had low loss which decreased with increasing frequency.
The Holmdel group (later Crawford Hill) was charged withimproving long distance transmission and kept this fact inmind. By the time I joined they were intensely developing
a long distance waveguide system using a 2 inch circular
waveguide to transmit 38-120 GHz for wide band, long
distance communication. Although the development of
low loss optical fiber soon caused them to switch to optical transmission, Charles Burrus had developed Schottky
barrier diodes which he incorporated into low noise millimeter wave receivers for that system.

ever, Keith and I got it all working in the control room andput the receiver at the focus. Remarkably it continued towork, so I looked at our list of sources. Orion was up, so
I asked the operator to point to the BN-KL region. The
spectrometer required frequency switching. It had a mode
where the integrators at the output of the phase detectors
on each channel operated as 2 second time constants. The
whole thing was analog and each channel had its uniquegain and offset. There was an oscilloscope display showing the 50 spectral channels. It was a cloud of points near
the zero line. I was watching it when some of the central points shifted up. I asked the operator and was toldthat the telescope had just arrived at the source. I asked
him to move off the source and the points moved down.
Thus after much work making the most sensitive receiver
we could, we discovered CO in a few seconds. This andthe follow on were truly exhilarating. 2

After the initial excitement of the CMB discovery had
settled down, Arno and I were reminded that our charter
was to do radio astronomy half time and more relevant
communications work the other half. We both took on
communications related projects, but Arno had a projectat NRAO and became aware of the 36 foot antenna andthat NRAO did not have very good millimeter wave receivers for it. Charlie Burrus offered to make a mixer for
us and we asked for observing time on the 36’. In 1968 we
took an 85 GHz receiver there and had an observing run.
The 36’ was not ready for serious observations and little
science came of that effort.

Q: After your discovery of CO in the BN-KL region, what
were your next steps?
A: The first thing I did was to explore around the BN-KL
region and discover that the source was quite extended.
After Orion set we got some much needed sleep while theplane of the Galaxy was down. The next day we found CO
in a number of other Galactic HII regions. During thatfirst run I made a careful spectrum of the BN-KL region
using two different local oscillator settings (the spectrometer was not wide enough to contain the whole line andenough baseline). That spectrum appeared in our first paper. My one regret is that we did not recognize that thewings of the line were much wider than an extension of
the core of the line. In 1976 Ben Zuckerman pointed out
the high velocity outflow from the central source.

Arno had been a student of Charles Townes and was awareof his list of molecules to look for. By the Spring of 1970
Sandy Weinreb of NRAO had offered to provide a filterbank spectrometer and a phase lock system to control
the frequency of the Klystron Local Oscillators at the 36’.
Charlie Burrus offered to make us a mixer in the 90-140
GHz band and we proposed to look for rotational transitions in simple molecules. After consulting with Phil
Solomon (who suggested CO again) and Pat Thaddeus(who reminded us that CN has a transition near CO 1-0)
we decided to look for CO, then CN and if those failed, wewould look for the recombination line H38α at a nearby
frequency. Since formaldehyde had been seen in the ISM,
I thought that of the molecules we were considering, CO
was quite likely as it would be a breakdown product of
H2 CO. We did not know if CN would be in equilibriumwith the CMB and therefore invisible. Arno invited Keith
Jefferts, an atomic physicist at Murray Hill he had worked
with, to join in on this effort.

In our next observing run we observed CN in Orion andW51 as well as preliminary measurements in Sgr A and
Sgr B. We also started observing less abundant isotopesof carbon and oxygen in CO.
Since the NRAO spectrometer could only store its integrations on magnetic tape and there was no facility toread those tapes on Kitt Peak, Keith and I put together adata capture and reduction system over the summer using
a minicomputer he had bought for lab use. This greatly
increased our efficiency. By the following spring we published strip maps of a number of sources and isotope ratiosof the CO species 12 CO, 13 CO and C18 O.

Sandy sent a 36’ receiver box and a rack of control equipment to Crawford Hill. Keith and I spent a frantic two
weeks wiring our receiver to their equipment. We had notquite finished when we had to ship it to Tucson. Sandy,
Keith and I went to the 36’ and spent several days trying
to make it all work simultaneously. It seemed that every time we fixed one thing, something else would break.
After three days Sandy had to leave for a meeting in Charlottesville and felt quite discouraged. The next day, how-

We went on to discover other molecules, isotopes and sources.
We pushed our luck with isotopes, discovering deuterated species and learning about chemical evolution of the
Galaxy.
2 A fuller description of the discovery can be found in Discovering CO and other Interstellar Molecules with the NRAO
36 Foot Antenna in ’Frontiers of Astrophysics: A Celebration of
NRAO’s 50th Anniversary’. ASP Conference Series, Vol. 395 or
https://www.cfa.harvard.edu/~ rwilson/DiscoveryCOforNRAO50.pdf

4When I look back at Phil Solomon’s 1973 paper in Physics
Today, it is clear that we and the growing community of
millimeter-wave observers had gotten a lot right in two
and a half years. By comparing the lines of moleculeswith different dipole moments and molecules with moreand less abundant isotopes, it was understood that theexcitation of the molecules was by collisions with hydrogenmolecules. From that cloud densities and therefore cloudmasses could be determined. Molecular clouds were known
to be centers of star formation, more massive than theassociated HII regions, and an important component of
the Galaxy’s mass. Dark clouds were seen to contain CO
extended over degrees. Mapping of them was beginningand was showing intense emission in spots. Isotope ratios
were seen to be near terrestrial except for deuterium, forwhich chemical fractionation was a proposed explanation.
The formation of diatomic molecules in the gas phase was
beginning to be understood.

about the universe coming from WMAP and PLANCK
observations. In millimeter wave work, ALMA allows observations we didn’t dream of in 1970.
By now, the whole electromagnetic spectrum has been explored and Gravity waves are the new unexplored source.
I don’t feel competent to predict what is next, just amazedand pleased at the experience I have had.

The 1970’s were an amazing time and I had a lot of fun.
We had many joint projects with Pat Thaddeus, Phil
Solomon, and their students. We worked hard and wereconstantly alert to equipment failures (I still jump when
I hear a Sonalert). The Bell Labs group had the only receiver above 100 GHz for several years, so we were prettymuch free to observe what we wanted to and that contributed to rapid advances. We had a lot of instant gratification with new sources, new molecules, or new insightsfrom every observing run. After a while I found that 24hours of searching for something new and not finding it
became depressing.
Q: In 1978 you received the Nobel Prize in Physics together
with Pyotr Kapitsa and Arno Penzias for the discovery of
the cosmic microwave background. Did your interests shift
to cosmology or did you continue your work on molecular
clouds?
A: By that time, we were thoroughly converted to millimeter astronomy. CMB work required very specialized
equipment which did not seem feasible at Bell Labs. We
had designed, bought and outfitted the 7-meter antenna
at Bell Labs, but it served a dual purpose, doing satellite
communication research when the weather was bad andmm-wave astronomy when it was good.
Q: You have taken part in an astonishing technical evolution in millimeter astronomy culminating with the ALMA
observatory. Where do you see the next technological frontier?
A: Yes, the advances in the technology used for astronomy
in my professional lifetime is indeed amazing. Equally important is the simultaneous advances in theoretical understanding. This is especially true of the CMB where theincrease of many orders of magnitude in sensitivity coupled with theory advances results in a page full of numbers

5Abstracts of recently accepted papers

１

Near-infrared spectroscopy of the massive stellar population of W51: evidence for multiseeded star formation
A. Bik1,2 , Th. Henning2 , S. -W. Wu2 , M. Zhang2 , W. Brandner2 , A. Pasquali3 and A. Stolte4
1

Department of Astronomy, Stockholm University, AlbaNova University Centre, 106 91 Stockholm, Sweden; 2 MaxPlanck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 3 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universitt Heidelberg, Münchhofstr. 12 - 14, 69120 Heidelberg, Germany; 4 Argelander
Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
E-mail contact: arjan.bik at astro.su.se
The interplay between the formation of stars, stellar feedback and cloud properties strongly influences the star formation history of giant molecular clouds. The formation of massive stars leads to a variety of stellar clusters, ranging fromlow stellar density OB associations to dense, gravitationally bound starburst clusters. We aimed at identifying themassive stellar content and reconstructing the star formation history of the W51 giant molecular cloud. We performednear-infrared imaging and K-band spectroscopy of the massive stars in W51. We analyzed the stellar populations using colour-magnitude and colour-colour diagrams and compared the properties of the spectroscopically identified stars
with stellar evolution models. We derived the ages of the different sub-clusters in W51 and, based on our spectroscopy
derived an age for W51 of 3 Myrs or less. The age of the P Cygni star LS1 and the presence of two still forming
proto-clusters suggests that the star formation history of W51 is more complex than a single burst. We did not findevidence for triggered star formation and we concluded that the star formation in W51 is multi seeded. We finallyconcluded that W51 is a OB association where different sub-clusters form over a time span of at least 3-5 Myrs.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1902.05460

２

Simulating the atomic and molecular content of molecular clouds using probability distributions of physical parameters
Thomas G. Bisbas1,2 , Andreas Schruba3 and Ewine van Dishoeck3,4
1

I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, Germany; 2 Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece; 3 Max-Planck-Institut für Extraterrestrische Physik,
Giessenbachstrasse 1, D-85748 Garching, Germany; 4 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300
RA Leiden, The Netherlands
E-mail contact: tbisbas at gmail.com

Modern observations of the interstellar medium (ISM) in galaxies detect a variety of atomic and molecular species.
The goal is to connect these observations to the astrochemical properties of the ISM. 3D hydro-chemical simulationsattempt this but due to extreme computational cost, they have to rely on simplified chemical networks and are boundto individual case studies. We present an alternative approach which models the ISM at larger scales by an ensembleof pre-calculated 1D thermo-chemical photodissociation region (PDR) calculations that determine the abundance andexcitation of atomic and molecular species. We adopt lognormal distributions of column density (AV -PDFs) for
which each column density is linked to a volume density as derived by hydrodynamical simulations. We consider two
lognormal AV -PDFs: a diffuse, low density medium with average visual extinction of AV = 0.75 mag and dispersionof σ = 0.5 and a denser giant molecular cloud with AV = 4 mag and σ = 0.8. We treat the UV radiation field, cosmicray ionization rate and metallicity as free parameters. We find that the low density medium remains fully Hi- andCii-dominated under all explored conditions. The denser cloud remains almost always molecular (i.e. H2 -dominated)while its carbon phase (CO, Ci and Cii) is sensitive to the above free parameters, implying that existing methods oftracing H2 -rich gas may require adjustments depending on environment. Our numerical framework can be used to6

estimate the PDR properties of large ISM regions and quantify trends with different environmental parameters as it
is fast, covers wide parameter space, and is flexible for extensions.
Accepted by MNRAS
https://arxiv.org/pdf/1901.11306

３

Formation of planetary systems by pebble accretion and migration: Growth of gas giants
Bertram Bitsch1 , Andre Izidoro2 , Anders Johansen3 , Sean N. Raymond4 , Alessandro Morbidelli5,Michiel Lambrechts3 , and Seth A. Jacobson6
1

Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 2 UNESP, Univ. Estadual Paulista- Grupo de Dinàmica Orbital Planetologia, Guaratinguetà, CEP 12.516-410, São Paulo, Brazil; 3 Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, 22100 Lund, Sweden; 4 Laboratoired’Astrophysique de Bordeaux, CNRS and Université de Bordeaux, Allée Geoffroy St. Hilaire, 33165 Pessac, France; 5
University Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, Laboratoire LAGRANGE, CS 34229, 06304
Nice cedex 4, France; 6 Northwestern University, Department of Earth and Planetary Sciences, 2145 Sheridan Road,
Evanston, IL 60208-3130, USA
E-mail contact: bitsch at mpia.de
Giant planets migrate though the protoplanetary disc as they grow. We investigate how the formation of planetarysystems depends on the radial flux of pebbles through the protoplanetary disc and on the planet migration rate. Our
N-body simulations confirm previous findings that Jupiter-like planets in orbits outside the water ice line originate
from embryos starting out at 20–40 AU when using nominal type-I and type-II migration rates and a pebble flux of
100–200 Earth masses per million years, enough to grow Jupiter within the lifetime of the solar nebula. The planetary
embryos placed up to 30 AU migrate into the inner system (r < 1 AU) and form super-Earths or hot and warm gas
giants, producing systems that are inconsistent with the configuration of the solar system, but consistent with some
exoplanetary systems. We also explore slower migration rates which allow the formation of gas giants from embryos
originating from the 5–10AU region, which are stranded exterior to 1 AU at the end of the gas-disc phase. We identify
a pebble flux threshold below which migration dominates and moves the planetary core to the inner disc, where thepebble isolation mass is too low for the planet to accrete gas efficiently. Giant planet growth requires a sufficiently-highpebble flux to enable growth to out-compete migration. Even higher pebble fluxes produce systems with multiple gas
giants. We show that planetary embryos starting interior to 5 AU do not grow into gas giants, even if migration is slow
and the pebble flux is large. Instead they grow to the mass regime of super-Earths. This stunted growth is caused by
the low pebble isolation mass in the inner disc and is independent of the pebble flux. Additionally we show that thelong term evolution of our formed planetary systems can produce systems with hot super-Earths and outer gas giants
as well as systems of giants on eccentric orbits.
Accepted by A&A
http://arxiv.org/pdf/1902.08771

４

Unveiling a cluster of protostellar disks around the massive protostar GGD27 MM1
G. Busquet1,2 , J.M. Girart1,2 , R. Estalella3 , M. Fernández-López4 , R. Galván-Madrid5 , G. Anglada6 ,C. Carrasco-González5 , N. Añez-López1,2 , S. Curiel7 , M. Osorio6 , L.F. Rodrı́guez5 and J.M. Torrelles1,21Institut de Ciències de l’Espai (ICE, CSIC), can Magrans s/n, E-08193 Cerdanyola del Vallès, Catalonia; 2 Institutd’Estudis Espacials de Catalunya (IEEC), Barcelona, Catalonia; 3 Departament de Fı́sica Quàntica i Astroff́isica,
Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Catalonia; 4 Instituto Argentino de Radioastronomı́a, CCT-La Plata (CONICET), Argentina; 5 Instituto de Radioastronomı́a y Astrofı́sica (IRyA), Morelia,México; 6 Instituto de Astrofı́sica de Andalucı́a (IAA, CSIC), Granada, Spain; 7 Instituto de Astronomı́a, Universidad
Nacional Autónoma de México (UNAM)
E-mail contact: busquet at ice.cat

Context. Most stars form in clusters, and thus it is important to characterize the protostellar disk population in dense
environments to assess whether the environment plays a role in the subsequent evolution; specifically, whether planet

7

formation is altered with respect to more isolated stars formed in dark clouds.
Aims. Investigate the properties of the protostellar disks in the GGD 27 cluster and compare them with those obtained
from disks formed in nearby regions.
Methods. We used ALMA to observe the star-forming region GGD 27 at 1.14 mm with an unprecedented angularresolution, 40 mas (∼ 56 au) and sensitivity (∼ 0.002 M⊙ ).
Results. We detected a cluster of 25 continuum sources, most of which are likely tracing disks around Class 0/I
protostars. Excluding the two most massive objects, disks masses are in the range 0.003-0.05 M⊙ . The analysis of thecluster properties indicates that GGD 27 displays moderate subclustering. This result combined with the dynamicaltimescale of the radio jet (∼ 104 years) suggests the youthfulness of the cluster. The lack of disk mass segregation
signatures may support this too. We found a clear paucity of disks with Rdisk > 100 au. The median value of theradius is 34 au, smaller than the median of 92 au for Taurus but comparable to the value found in Ophiuchus and in
the Orion Nebula Cluster. In GGD 27 there is no evidence of a distance-dependent disk mass distribution (i.e., disk
mass depletion due to external photoevaporation), most likely due to the cluster youth. There is a clear deficit ofdisks for distances < 0.02 pc. Only for distances > 0.04 pc stars can form larger and more massive disks, suggestingthat dynamical interactions far from the cluster center are weaker, although the small disks found could be the resultof disk truncation. This work demonstrates the potential to characterize disks from low-mass YSOs in distant andmassive (still deeply embedded) clustered environments.
Accepted by Astronomy & Astrophysics Letters
https://arxiv.org/pdf/1902.07581

５

Methylamine and other simple N-bearing species in the hot cores NGC 6334I MM1-3
Eva G. Bøgelund1 , Brett A. McGuire2 , Michiel R. Hogerheijde1,3 , Ewine F. van Dishoeck1,4 , and Niels
F.W. Ligterink1,5
1

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA; 3 Anton Pannekoek Institute for Astronomy,
University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands; 4 Max-Planck Institut für Extraterrestrische Physik, Giessenbachstr. 1, 85748 Garching, Germany; 5 Center for Space and Habitability (CSH),
University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
E-mail contact: bogelund at strw.leidenuniv.nl
In the search for the building blocks of life, nitrogen-bearing molecules are of particular interest since nitrogencontaining bonds are essential for the linking of amino acids and ultimately the formation of larger biological structures.
The elusive molecule methylamine (CH3 NH2 ) is thought to be a key pre-biotic species but has so far only been securely
detected in the giant molecular cloud Sgr B2. We identify CH3 NH2 and other simple nitrogen-bearing species towards
three hot cores in NGC 6334I. Column density ratios are derived in order to investigate the relevance of the individual
species as precursors of biotic molecules. Observations obtained with ALMA were used to study transitions of CH3 NH2 ,CH2 NH, NH2 CHO, and the 13 C- and 15 N-methyl cyanide (CH3 CN) isotopologues. Column densities are derived foreach species assuming LTE and excitation temperatures in the range 220–340 K for CH3 NH2 , 70–110 K for the CH3 CN
isotopologues, and 120–215 K for NH2 CHO and CH2 NH. We report the first detections of CH3 NH2 towards NGC
6334I with column density ratios with respect to CH3 OH of 5.9 × 10−3 , 1.5 × 10−3 , and 5.4 × 10−4 for the three
hot cores MM1, MM2, and MM3, respectively. These values are slightly lower than the values derived for Sgr B2
but higher by more than order of magnitude as compared with the values derived for the low-mass protostar IRAS
16293−2422B. The detections of CH3 NH2 in the hot cores of NGC 6334I hint that CH3 NH2 is generally common in theinterstellar medium, albeit high-sensitivity observations are essential for its detection. The good agreement between
model predictions of CH3 NH2 ratios and the observations towards NGC 6334I indicate a main formation pathway via
radical recombination on grain surfaces.
Accepted by A&A
http://arxiv.org/pdf/1902.07060

8

６

The central 1000 AU of a pre-stellar core revealed with ALMA. I. 1.3 mm continuum
observations
Paola Caselli1 , Jaime E. Pineda1 , Bo Zhao1 , Malcolm C. Walmsley2,3, Eric Keto4 , Mario Tafalla5 , Ana
Chacón-Tanarro1,5 , Tyler L. Bourke6 , Rachel Friesen7 , Daniele Galli2 and Marco Padovani2
1

Max-Planck-Institut für Extraterrestrische Physik, Gießenbachstrasse 1, 85741 Garching bei München, Germany;
INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 3 Dublin Institute of Advanced
Studies, Fitzwilliam Place 31, Dublin 2, Ireland; 4 Harvard-Smithsonian Center for Astrophysics, 160 Garden Street,
Cambridge, MA 02420, USA; 5 Observatorio Astronómico Nacional (OAG-IGN), Alfonso XII 3, 28014, Madrid, Spain;
6
SKA Organization, Jodrell Bank Observatory, Lower Withington, Macclesfield, Cheshire SK11 9DL, UK; 7 National
Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA
2E-mail contact: caselli at mpe.mpg.de
Stars like our Sun form in self-gravitating dense and cold structures within interstellar clouds, called pre-stellar cores.
Although much is known about the physical structure of dense clouds just before and soon after the switch-on ofa protostar, the central few thousand astronomical units (au) of pre-stellar cores are unexplored. It is within thesecentral regions that stellar systems assemble and fragmentation may take place, with the consequent formation ofbinaries and multiple systems. We present ALMA Band 6 observations (ACA and 12m array) of the dust continuum
emission of the 8 M⊙ pre-stellar core L1544, with angular resolution of 2′′ × 1.6′′ (linear resolution 270 au × 216 au).
Within the primary beam, a compact region of 0.1 M⊙ , which we call a ”kernel”, has been unveiled. The kernel iselongated, with a central flat zone with radius Rker ≃10′′ (≃1400 au). The average number density within Rker is≃1×106 cm−3 , with possible local density enhancements. The region within Rker appears to have fragmented, but
detailed analysis shows that similar substructure can be reproduced by synthetic interferometric observations of asmooth centrally concentrated dense core with a similar central flat zone. The presence of a smooth kernel withina dense core is in agreement with non-ideal magneto-hydro-dynamical simulations of a contracting cloud core witha peak number density of 1×107 cm−3 . Dense cores with lower central densities are completely filtered out whensimulated 12m-array observations are carried out. These observations demonstrate that the kernel of dynamically
evolved dense cores can be investigated at high angular resolution with ALMA.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/1902.05299

７

An in depth study of the hypercompact Hii region G24.78+0.08 A1
R. Cesaroni1 , M. T. Beltrán1 , L. Moscadelli1, Á. Sánchez-Monge2 and R. Neri3
1

INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 2 I. Physikalisches Institut,
Universität zu Köln, Zülpicher Strasse 77, 50937, Köln, Germany; 3 Institut de Radioastronomie Millimétrique (IRAM),
300 rue de la Piscine, F-38406 Saint Martin dHères, France
E-mail contact: cesa at arcetri.astro.it
The earliest phases of the evolution of a massive star are tightly related to the developement of an Hii region.
Hypercompact Hii regions are the most interesting in this respect because they are very young and hence best suited
to study the beginning of the expansion of the ionized gas inside the parental core. We aim to analyse the geometricaland physical structure of the hypercompact Hii region G24.78+0.08 A1, making use of new continuum and hydrogen
recombination line (H41α, H63α, H66α, H68α) data as well as data from the literature (H30α, H35α). We fit thecontinuum spectrum with a homogenous, isothermal shell of ionized gas at 104 K and derive the size of the Hii region
and the Lyman continuum luminosity of the ionizing star. We also fit the recombination line spectra emitted fromthe same shell with a model taking into account expansion at constant speed. The best fits to the continuum and line
spectra allow derivation of the Lyman continuum luminosity of the ionizing star, Hii region size, geometrical thicknessof the shell, and expansion velocity. Comparison between the 5 cm and 7 mm brightness temperature distributions
demonstrates that a thin layer of ionized gas of a few 1000 K at the surface of the Hii region is necessary to reproduce
the morphology of the continuum emission at both wavelengths. We confirm that the G24.78+0.08 A1 hypercompact
Hii region consists of a thin shell ionized by an O9.5 star. The shell is expanding at a speed comparable to the soundspeed in the ionized gas. The radius of the Hii region exceeds the critical value needed to trap the ionized gas by thegravitational field of the star, consistent with the observed expansion.

9

Accepted by Astronomy and Astrophysics
http://www.arcetri.astro.it/~cesa/preprints/g24hchii.pdf

８

A New Equation of State for Dense Hydrogen/Helium Mixtures
Gilles Chabrier1 , Stephane Mazevet3 and Francois Soubiran4
1

CRAL, ENS-Lyon / (2) U. Exeter, UK; 3 LUTH, Obs. Paris, France; 4 LGLTPE, ENS-Lyon, France

E-mail contact: chabrier at ens-lyon.fr
We present a new equation of state (EOS) for dense hydrogen/helium mixtures that covers a range of densities
from 10−8 to 106 g cm−3 , pressures from 10−9 to 1013 GPa, and temperatures from 102 to 108 K. The calculations
combine the EOS of Saumon, Chabrier & van Horn in the low-density, low-temperature molecular/atomic domain,
the EOS of Chabrier & Potekhin in the high-density, high-temperature fully ionized domain, the limits of which
differ for H and He, and ab initio quantum molecular dynamics calculations in the regime of intermediate density
and temperature, characteristic of pressure dissociation and ionization. The EOS for the H/He mixture is based on
the so-called additive volume law and thus does not take into account the interactions between the two species. A
major improvement of the present calculations over existing ones is that we calculate the entropy over the entiredensity-temperature domain, a necessary quantity for calculations of stellar or planetary evolution. The EOS results
are compared with existing experimental data, namely Hugoniot shock experiments for pure H and He, and with
first-principles numerical simulations for both the single elements and the mixture. This new EOS covers a wide rangeof physical and astrophysical conditions, from Jovian planets to solar-type stars, and recovers the existing relativistic
EOS at very high densities, in the domains of white dwarfs and neutron stars. All the tables are made publicly
available.
Accepted by Astrophysical Journal (2019, 872, A51)
https://arxiv.org/pdf/1902.01852.pdf

９

A VLT/FLAMES survey for massive binaries in Westerlund 1: VI. Properties of X-ray
bright massive cluster members
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: spz at strw.leidenuniv.nl
Despite the first detection of X-rays from massive stars occurring four decades ago, the physical dependence of theemission mechanism(s) on the underlying stellar and binary properties of the emitters remains uncertain. The young
massive cluster Westerlund 1 provides an ideal testbed for understanding this phenomenon, with over 50 cluster
members detected in historical X-ray observations. In the decade since these data were obtained, significant new
multi-epoch observations of the cluster have been made, allowing a fundamental reappraisal of the nature of both
X-ray bright and dark stars. A total of 45 X-ray sources within Wd1 now have precise spectral classifications. Theseobservations identify 16 candidate and confirmed massive binaries; by comparison 22 stars have X-ray properties that
imply a contribution from a wind collision zone. X-ray emission appears confined to O9–B0.5 supergiants, Wolf-Rayets
and a small group of highly luminous interacting/post-interaction binaries. Despite their presence in large numbers,
no emission is seen from earlier, less evolved O stars or later, cooler B super-/hypergiants. We suppose that the lack of
X-ray emission from O giants is due to their comparatively low bolometric luminosities if, as expected, they follow thecanonical LX /Lbol relation for hot stars. The transition away from X-ray emission for OB supergiants occurs at thelocation of the bistability jump; we speculate that below this limit, stellar wind velocities are insufficient for internal,
X-ray emitting shocks to form. Our results are consistent with recent findings that massive binaries are not uniformly
brighter than single stars of comparable luminosity and spectral type, although it is noteworthy that the brightest andhardest stellar X-ray sources within Wd1 are all either confirmed or candidate massive, interacting/post-interaction
binaries.

10

Accepted by A&A
http://arxiv.org/pdf/1902.05322

１０

A new view of the corona of classical T Tauri stars: Effects of flaring activity in circumstellar disks
S. Colombo1,2,3, S. Orlando3 , G. Peres1,3 , F. Reale1,3 , C. Argiroffi1,3 , R. Bonito3 , L. Ibgui2 , and C.
Stehlé2
1

Dipartimento di Fisica & Chimica Specola Universitaria, Universitá degli Studi di Palermo, Piazza del Parlamento 1,
90143 Palermo, Italy; 2 LERMA, Osbervatoire de Paris, Sorbonne Université, Université PSL, CNRS, Paris, France;
3
INAF-Osservatorio Astronomico di Palermo “G.S. Vaiana”, Piazza del Parlamento 1, 90134 Palermo, Italy
E-mail contact: scolombo at astropa.inaf.it
Classical T Tauri stars (CTTSs) are young low-mass stellar objects accreting mass from their circumstellar disks. They
are characterized by high levels of coronal activity as revealed by X-ray observations. This activity may affect the diskstability and the circumstellar environment. Here we investigate if an intense coronal activity due to flares occurring
close to the accretion disk may perturb the inner disk stability, disrupt the inner part of the disk and, possibly, trigger
accretion phenomena with rates comparable with those observed. We model a magnetized protostar surrounded byan accretion disk through 3D magnetohydrodinamic simulations. We explore cases characterized by a dipole plus anoctupole stellar magnetic field configuration and different density of the disk or by different levels of flaring activity.
As a result of the simulated intense flaring activity, we observe the formation of several loops that link the star to thedisk; all these loops build up a hot extended corona with an X-ray luminosity comparable with typical values observedin CTTSs. The intense flaring activity close to the disk can strongly perturb the disk stability. The flares trigger
overpressure waves which travel through the disk and modify its configuration. Accretion funnels may be triggeredby the flaring activity, thus contributing to the mass accretion rate of the star. Accretion rates synthesized from thesimulations are in a range between 10−10 and 10−9 M⊙ yr−1 The accretion columns can be perturbed by the flares
and they can interact with each other, possibly merging together in larger streams. As a result, the accretion pattern
can be rather complex: the streams are highly inhomogeneous, with a complex density structure, and clumped.
Accepted by A&A
http://arxiv.org/pdf/1902.07048

１１ ISPY - the NaCo Imaging Survey for Planets around Young stars: A young companion

candidate embedded in the R CrA cloud

G. Cugno1 , S. P. Quanz1 , R. Launhard2 , A. Musso Barcucci2 , S. S. Brems3 , A. Cheetham4 , N. Godoy5,6 ,G. M. Kennedy7,8 , T. Henning2 , A. M.2 , J. Olofsson5,6, F. Pepe4 , A. Quirrenbach3 , S. Reffert3 , E. L.
Rickman4 and D. Ségransan4
1

ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland; 2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 3 Landessternwarte, Zentrum
für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany; 4 Observatoire Astronomiquede l’Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland; 5 Instituto de Fı́sica y Astronomı́a, Facultad de Ciencas, Universidad de Valparaı́so, Av. Gran Bretaña 1111, Playa Ancha, Valparaı́so, Chile; 6 Núcleo Milenio
Formación Planetaria - NPF, Universidad de Valparaı́so, Av. Gran Bretaña 1111, Valparaı́so, Chile; 7 Department of
Physics, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK; 8 Centre for Exoplanets and Habitability,
University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK
E-mail contact: gabriele.cugno at phys.ethz.ch
Within the NaCo-ISPY exoplanet imaging program, we aim at detecting and characterizing the population of low-masscompanions at wide separations (>10AU), focusing in particular on young stars either hosting a known protoplanetary
disk or a debris disk. R CrA is one of the youngest (1-3 Myr) and most promising objects in our sample because of two
previous studies that suggested the presence of a close companion. Our aim is to directly image and characterize thecompanion for the first time. We observed R CrA twice with the NaCo instrument at VLT in the L′ filter with a one
year time baseline in between. The high-contrast imaging data were reduced and analyzed, and in both datasets the11companion candidate was detected. We used artificial negative signals to determine the position and brightness of thecompanion and the related uncertainties. The companion is detected at a separation of 196.8 ± 4.5/196.6 ± 5.9 mas(18.7 ± 1.3/18.7 ± 1.4 AU) and position angle of 134.7 ± 0.5◦ /133.7 ± 0.7◦ in the first/second epoch observation. We
measure a contrast of 7.29 ± 0.18/6.70 ± 0.15 mag with respect to the primary. Stellar proper motion study rejects the
hypothesis of the signal being a background object. The companion candidate orbits in the clockwise direction and,
if on a face-on circular orbit, its period is ∼ 43 − 47 yr. This value disagrees with the estimated orbital motion andtherefore a face-on circular orbit may be excluded. Depending on the assumed age, extinction and brightness of the
primary, the stellar companion has a mass between 0.10 ± 0.02 M⊙ and 1.03+0.20−0.18 M⊙ range, if no contribution fromcircumsecondary material is taken into account. As already hypothesized by previous studies, we have directly detected
a low-mass stellar companion orbiting the young Herbig Ae/Be star R CrA. Depending on the age assumptions, thecompanion is among the youngest forming companions imaged to date, and its presence needs to be taken into accountwhen analyzing the complex circumstellar environment of R CrA.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1902.04092

１２

Consistent dust and gas models for protoplanetary disks IV. A panchromatic view ofprotoplanetary disks
O. Dionatos1 , P. Woitke2,3 , M. Güdel1 , P. Degroote4 , A. Liebhart1 , F. Anthonioz5 , S. Antonellini6,7,
C. Baldovin-Saavedra1 , A. Carmona8 , C. Dominik9 , J. Greaves10 , J. D. Ilee11 , I. Kamp6 , F. Ménard5 ,M. Min9,12 , C. Pinte5,13,14 , C. Rab1,6 , L. Rigon2 , W. F. Thi15 , L. B. F. M. Waters9,121

University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, A-1180, Vienna, Austria; 2 SUPA Schoolof Physics & Astronomy, University of St Andrews, North Haugh, KY16 9SS, St Andrews, UK; 3 Centre for Exoplanet
Science, University of St Andrews, St Andrews, UK; 4 Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D,
3001, Leuven, Belgium; 5 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 6 Kapteyn AstronomicalInstitute, University of Groningen, Postbus 800, 9700 AV Groningen, The Netherlands; 7 Astrophysics ResearchCentre, School of Mathematics and Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN, UK; 8
IRAP, Université de Toulouse, CNRS, UPS, Toulouse, France; 9 Astronomical institute Anton Pannekoek, Universityof Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands; 10 School of Physics and Astronomy, Cardiff
University, 4 The Parade, Cardiff CF24 3AA, UK; 11 Institute of Astronomy, University of Cambridge, Madingley Road,
Cambridge CB3 0HA, UK; 12 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht,
The Netherlands; 13 UMI-FCA, CNRS/INSU France (UMI 3386), and Departamento de Astronomica, Universidad
de Chile, Santiago, Chile; 14 Monash Centre for Astrophysics (MoCA) and School of Physics and Astronomy, Monash
University, Clayton Vic 3800, Australia; 15 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1,
85748 Garching, Germany;
E-mail contact: odysseas.dionatos at univie.ac.at
Context: Consistent modeling of protoplanetary disks requires the simultaneous solution of both continuum and line
radiative transfer, heating/cooling balance between dust and gas and, of course, chemistry. Such models depend on
panchromatic observations that can provide a complete description of the physical and chemical properties and energybalance of protoplanetary systems. Along these lines we present a homogeneous, panchromatic collection of data ona sample of 85 T Tauri and Herbig Ae objects for which data cover a range from X-rays to centimeter wavelengths.
Datasets consist of photometric measurements, spectra, along with results from the data analysis such as line fluxes
from atomic and molecular transitions. Additional properties resulting from modeling of the sources such as disc massand shape parameters, dust size and PAH properties are also provided for completeness.
Aims: The purpose of this data collection is to provide a solid base that can enable consistent modeling of the propertiesof protoplanetary disks. To this end, we performed an unbiased collection of publicly available data that were combined
to homogeneous datasets adopting consistent criteria. Targets were selected based on both their properties but also
on the availability of data.
Methods: Data from more than 50 different telescopes and facilities were retrieved and combined in homogeneous
datasets directly from public data archives or after being extracted from more than 100 published articles. X-ray data
for a subset of 56 sources represent an exception as they were reduced from scratch and are presented here for the first
time.

12

Results: Compiled datasets along with a subset of continuum and emission-line models are stored in a dedicateddatabase and distributed through a publicly accessible online system. All datasets contain metadata descriptors thatallow to backtrack them to their original resources. The graphical user interface of the online system allows the user
to visually inspect individual objects but also compare between datasets and models. It also offers to the user the
possibility to download any of the stored data and metadata for further processing.
Accepted by A&A
https://arxiv.org/pdf/1902.11204

１３

Pebble accretion in self-gravitating protostellar discs
D.H. Forgan1
1

Centre for Exoplanet Science, SUPA, School of Physics & Astronomy, University of St Andrews, St Andrews KY16
9SS, UK
E-mail contact: dhf3 at st-andrews.ac.uk

Pebble accretion has become a popular component to core accretion models of planet formation, and is especiallyrelevant to the formation of compact, resonant terrestrial planetary systems. Pebbles initially form in the innerprotoplanetary disc, sweeping outwards in a radially expanding front, potentially forming planetesimals and planetarycores via migration and the streaming instability. This pebble front appears at early times, in what is typicallyassumed to be a low mass disc. We argue this picture is in conflict with the reality of young circumstellar discs,
which are massive and self-gravitating. We apply standard pebble accretion and streaming instability formulae toself-gravitating protostellar disc models. Fragments will open a gap in the pebble disc, but they will likely fail toopen a gap in the gas, and continue rapid inward migration. If this does not strongly perturb the pebble disc, ourresults show that disc fragments will accrete pebbles efficiently. We find that in general the pebble-to-gas-density ratio
fails to exceed 0.01, suggesting that the streaming instability will struggle to operate. It may be possible to activate
the instability if 10 cm grains are available, and spiral structures can effectively concentrate them in regions of low
gravito-turbulence. If this occurs, lunar mass cores might be assembled on timescales of a few thousand years, but thisis likely to be rare, and is far from proven. In any case, this work highlights the need for study of how self-gravitating
protostellar discs define the distribution and properties of solid bodies, for future planet formation by core accretion.
Accepted by MNRAS
http://arxiv.org/pdf/1902.05385

１４

Misaligned accretion disc formation via Kozai-Lidov oscillations
Alessia Franchini1 , Rebecca G. Martin1 , and Stephen H. Lubow2
1
Department of Physics and Astronomy, University of Nevada, 4505 South Maryland Parkway, Las Vegas, NV 89154,
USA; 2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

E-mail contact: alessia.franchini at unlv.edu
We investigate the formation and evolution of misaligned accretion discs around the secondary component of a binary
through mass transfer driven by Kozai-Lidov oscillations of the circumprimary disc’s eccentricity and inclination. We
perform SPH simulations to study the amount of mass transferred to the secondary star as a function of both the discand binary parameters. For the range of parameters we explore, we find that increasing the disc aspect ratio, viscosity
parameter and initial inclination as well as decreasing the binary mass ratio leads to larger amount of mass transfer,
up to a maximum of about ten per cent of the initial mass of the primary disc. The circumsecondary disc forms
with a high eccentricity and a high inclination and is also able to undergo KL oscillations. The circumsecondary discoscillations have a shorter period than those in the disc around the primary. We find that some of the material thatescapes the Roche-lobe of the two components forms a narrow misaligned circumbinary accretion disc. This study has
implications for disc evolution in young binary star systems.
Accepted by MNRAS
http://arxiv.org/pdf/1902.04090

13

１５

Identifying Variability in Deeply Embedded Protostars with ALMA and CARMA
Logan Francis1,2 , Doug Johnstone1,2 , Michael M. Dunham3,4 , Todd R. Hunter5 , Steve Mairs6
1

Department of Physics and Astronomy, University of Vic- toria, 3800 Finnerty Road, Elliot Building, Victoria,
BC, V8P 5C2, Canada; 2 NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E
2E7, Canada; 3 Department of Physics, State University of New York at Fre- donia, 280 Central Avenue, Fredonia,
NY, 14063, USA; 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 5
NRAO, 520 Edgemont Road, Charlottesville, VA 22903, USA; 6 East Asian Observatory, 660 North A’ohōkū Place,
University Park, Hilo, Hawaii 96720, USA
E-mail contact: loganfrancis3 at uvic.ca
Variability of pre-main-sequence stars observed at optical wavelengths has been attributed to fluctuations in the massaccretion rate from the circumstellar disk onto the forming star. Detailed models of accretion disks suggest that young
deeply embedded protostars should also exhibit variations in their accretion rates, and that these changes can be tracked
indirectly by monitoring the response of the dust envelope at mid-IR to millimeter wavelengths. Interferometers suchas ALMA offer the resolution and sensitivity to observe small fluctuations in brightness at the scale of the disk where
episodic accretion may be driven. In this work, we present novel methods for comparing interferometric observations
and apply them to CARMA and ALMA 1.3mm observations of deeply embedded protostars in Serpens taken 9 years
apart. We find no brightness variation above the limits of our analysis of a factor of >∼50%, due to the limited sensitivityof the CARMA observations and small number of sources common to both epochs. We further show that follow up
ALMA observations with a similar sample size and sensitivity may be able to uncover variability at the level of a few
percent, and discuss implications for future work.
Accepted by ApJ
http://arxiv.org/pdf/1902.00588

１６Magnetic braking of supermassive stars through winds
Lionel Haemmerlé1 and Georges Meynet1
1

Université de Genève, Switzerland

E-mail contact: lionel.haemmerle at unige.ch
Supermassive stars (SMSs) are candidates for being progenitors of supermassive quasars at high redshifts. However,their formation process requires strong mechanisms that would be able to extract the angular momentum of the gasthat the SMSs accrete. We investigate under which conditions the magnetic coupling between an accreting SMS
and its winds can remove enough angular momentum for accretion to proceed from a Keplerian disc. We numericallycomputed the rotational properties of accreting SMSs that rotate at the ΩΓ-limit and estimated the magnetic field thatis required to maintain the rotation velocity at this limit using prescriptions from magnetohydrodynamical simulationsof stellar winds. We find that a magnetic field of 10 kG at the stellar surface is required to satisfy the constraints
on stellar rotation from the ΩΓ-limit. Magnetic coupling between the envelope of SMSs and their winds could allow
for SMS formation by accretion from a Keplerian disc, provided the magnetic field is at the upper end of present-day
observed stellar fields. Such fields are consistent with primordial origins.
Accepted by A&A
https://arxiv.org/pdf/1903.00020

１７Magnetic topologies of young suns: The weak-line T Tauri stars TWA 6 and TWA 8A
C.A. Hill1 , C.P. Folsom1 , J.-F. Donati1 , G.J. Herczeg2 , G.A.J. Hussain3,1 , S.H.P. Alencar4 , S.G.
Gregory5 and the MaTYSSE collaboration
1

IRAP, Université de Toulouse, CNRS, UPS, CNES, 14 Avenue Edouard Belin, Toulouse, F-31400, France; 2 Kavli
Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871, China; 3
ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany; 4 Departamento de Fı́sica - ICEx-UFMG, Av. Antônio
Carlos, 6627, 30270–901 Belo Horizonte, MG, Brazil; 5 University of St Andrews, St Andrews, KY16 9SS, UK
E-mail contact: chill at irap.omp.eu
14

We present a spectropolarimetric study of two weak-line T Tauri stars (wTTSs), TWA 6 and TWA 8A, as part of the
MaTYSSE (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) program. Both stars
display significant Zeeman signatures that we have modelled using Zeeman Doppler Imaging (ZDI). The magnetic fieldof TWA 6 is split equally between poloidal and toroidal components, with the largest fraction of energy in higher-ordermodes, with a total unsigned flux of 840 G, and a poloidal component tilted 35◦ from the rotation axis. TWA 8A
has a 70 per cent poloidal field, with most of the energy in higher-order modes, with an unsigned flux of 1.4 kG(with a magnetic filling factor of 0.2), and a poloidal field tilted 20◦ from the rotation axis. Spectral fitting of thevery strong field in TWA 8A (in individual lines, simultaneously for Stokes I and V) yielded a mean magnetic fieldstrength of 6.0±0.5 kG. The higher field strengths recovered from spectral fitting suggests that a significant proportionof magnetic energy lies in small-scale fields that are unresolved by ZDI. So far, wTTSs in MaTYSSE appear to showthat the poloidal-field axisymmetry correlates with the magnetic field strength. Moreover, it appears that classical T
Tauri stars (cTTSs) and wTTSs are mostly poloidal and axisymmetric when mostly convective and cooler than ∼4300
K, with hotter stars being less axisymmetric and poloidal, regardless of internal structure.
Accepted by MNRAS
http://arxiv.org/pdf/1902.06725

１８

Initial phases of high-mass star formation: A multiwavelength study towards the extended green object G12.42+0.50
Namitha Issac1 , Anandmayee Tej1 , Tie Liu2,3 , Watson Varricatt4 , Sarita Vig1 , Ishwara Chandra C.H.5
and Mathias Schultheis6
1

Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547, Kerala, India; 2 Korea Astronomy
and Space Science Institute, 776 Daedeokdaero, Yuseong-gu, Daejeon 34055, Republic of Korea; 3 East Asian Observatory, 660 N. Aóhoku Place, Hilo, HI 96720, USA; 4 Institute for Astronomy, UKIRT Observatory, 660 N. Aóhoku place,
Hilo, HI 96720, USA; 5 National Centre for Radio Astrophysics (NCRA-TIFR), Pune, India; 6 Laboratoire Lagrange,
Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Blvd de l’Observatoire, F-06304 Nice, France
E-mail contact: namithaissac.16 at res.iist.ac.in
We present a multiwavelength study of the extended green object, G12.42+0.50 in this paper. The associated ionized,
dust, and molecular components of this source are studied in detail employing various observations at near-, mid- andfar-infrared, submillimeter and radio wavelengths. Radio continuum emission mapped at 610 and 1390 MHz, using theGiant Meterwave Radio Telescope, India, advocates for a scenario of coexistence of an UC H ii region and an ionizedthermal jet possibly powered by the massive young stellar object, IRAS 18079-1756 with an estimated spectral typeof B1 − B0.5. Shock-excited lines of H2 and [FeII], as seen in the near-infrared spectra obtained with UKIRT-UIST,
lend support to this picture. Cold dust emission shows a massive clump of mass 1375 M⊙ enveloping G12.42+0.50.
Study of the molecular gas kinematics using the MALT90 and JCMT archival data unravels the presence of both
infall activity and large-scale outflow suggesting an early stage of massive star formation in G12.42+0.50. A networkof filamentary features are also revealed merging with the massive clump mimicking a hub-filament layout. Velocity
structure along these indicate bulk inflow motion.
Accepted by MNRAS
https://arxiv.org/pdf/1902.03724

１９

The Early Stage of Molecular Cloud Formation by Compression of Two-phase Atomic
Gases
Kazunari Iwasaki1 , Kengo Tomida1 , Tsuyoshi Inoue2 and Shu-ichiro Inutsuka2
1
2

Department of Earth and Space Science, Osaka University, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan;
Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan

E-mail contact: iwasaki at astro-osaka.jp
We investigate the formation of molecular clouds from atomic gas by using three-dimensional magnetohydrodynamic
simulations, including non-equilibrium chemical reactions and heating/cooling processes. We consider super-Alfvénic
head-on colliding flows of atomic gas possessing the two-phase structure that consists of HI clouds and surrounding
15

warm diffuse gas. We examine how the formation of molecular clouds depends on the angle θ between the upstream
flow and the mean magnetic field. We find that there is a critical angle θcr above which the shock-amplified magnetic
field controls the post-shock gas dynamics. If the atomic gas is compressed almost along the mean magnetic field(θ ≪ θcr ), super-Alfvénic anisotropic turbulence is maintained by the accretion of the highly inhomogeneous upstream
atomic gas. As a result, a greatly extended turbulence-dominated post-shock layer is generated. Around θ ∼ θcr , theshock-amplified magnetic field weakens the post-shock turbulence, leading to a dense post-shock layer. For θ ≫ θcr ,the strong magnetic pressure suppresses the formation of cold dense clouds. Efficient molecular cloud formation is
expected if θ is less than a few times θcr . Developing an analytic model and performing a parameter survey, we obtainan analytic formula for the critical angle as a function of the mean density, collision speed, and field strength of the
upstream atomic gas. The critical angle is found to be less than ∼ 15◦ as long as the field strength is larger than
1 µG, indicating that the probability of occurrence of compression with θ < θcr is limited if shock waves come fromvarious directions.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1806.03824

２０

The Synthetic ALMA Multiband Analysis of the Dust Properties of the TW Hya Protoplanetary Disk
Seongjoong Kim1 , Hideko Nomura1 , Takashi Tsukagoshi2 , Ryohei Kawabe2,3,4 and Takayuki Muto5
1

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo
152-8551, Japan; 2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;
3
The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 4Department of Astronomy, School of Science, University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan; 5 Division of
Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677, Japan
E-mail contact: kim.s at eps.sci.titech.ac.jp
Analyzing multiband observations of dust continuum emission is one of the useful tools to constrain dust properties
which help us to understand the physical properties of the disks. We perform the synthetic ALMA multiband analysis
to find the best ALMA band set for constraining the dust properties of the TW Hya protoplanetary disk. We findthat the Band [10,6,3] set is the best set among the possible combinations of ALMA Band [3,4,5,6,7,8,9,10]. We alsofind two conditions for the good ALMA band sets providing narrow constraint ranges on dust properties; (1) Band
9 or 10 is included in the band set and (2) Enough frequency intervals between the bands. These are related withthe conditions which give good constraints on dust properties: the combination of optically thick and thin bands are
required, and large β (β is the power-law index of dust opacity), and low dust temperature are preferable. To examine
our synthetic analysis results, we apply the multiband analysis to ALMA archival data of the TW Hya disk at Band4, 6, 7, and 9. Band [9,6,4] set provides the dust properties close to the model profile, while Band [7,6,4] set gives thedust properties deviating from the model at all radii with too broad constraint range to specify the accurate valuesof dust temperature, optical depth, and β. Since these features are expected by the synthetic multiband analysis, we
confirm that the synthetic multiband analysis is well consistent with the results derived from real data.
Accepted by ApJ

http://arxiv.org/pdf/1902.00168

２１

Resolving the MYSO binaries PDS 27 and PDS 37 with VLTI/PIONIER
E. Koumpia1 , K. M. Ababakr10 , W. J. de Wit2 , R. D. Oudmaijer1 , A. Caratti o Garatti3 , P. Boley4,5 ,H. Linz6 , S. Kraus7 , J. S. Vink8 and J.-B Le Bouquin9
1

School of Physics and Astronomy, E.C. Stoner Building, University of Leeds, Leeds LS2 9JT, UK; 2 ESO Vitacura,
Alonso de Córdova 3107 Vitacura, Casilla 19001 Santiago de Chile, Chile; 3 Dublin Institute for Advanced Studies,
Astronomy & Astrophysics Section, 31 Fitzwilliam Place, Dublin 2, Ireland; 4 Moscow Institute of Physics andTechnology, 9 Institutski per., Dolgoprudny 141701, Russia; 5 Ural Federal University, 51 Lenin Ave., Ekaterinburg
620075, Russia; 6 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 7 University of
Exeter, School of Physics, Astrophysics Group, Stocker Road, Exeter, EX4 4QL, UK; 8 Armagh Observatory and16Planetarium, College Hill, Armagh BT61 9DG, Ireland; 9 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble,
France; 10 Erbil Polytechnic University, Kirkuk Road, Erbil, Iraq
E-mail contact: ev.koumpia at gmail.com
Binarity and multiplicity appear to be a common outcome in star formation. In particular, the binary fraction ofmassive (OB-type) stars can be very high. In many cases, the further stellar evolution of these stars is affected bybinary interactions at some stage during their lifetime. The origin of this high binarity and the binary parameters arepoorly understood because observational constraints are scarce, which is predominantly due to a dearth of known young
massive binary systems. We aim to identify and describe massive young binary systems in order to fill in the gaps of
our knowledge of primordial binarity of massive stars, which is crucial for our understanding of massive star formation.
We observed the two massive young stellar objects (MYSOs) PDS 27 and PDS 37 at the highest spatial resolution
provided by VLTI/PIONIER in the H-band (1.3 mas). We applied geometrical models to fit the observed squared
visibilities and closure phases. In addition, we performed a radial velocity analysis using published VLT/FORS2
spectropolarimetric and VLT/X-shooter spectroscopic observations. Our findings suggest binary companions for bothobjects at 12 mas (30 au) for PDS 27 and at 22-28 mas (42-54 au) for PDS 37. This means that they are among theclosest MYSO binaries resolved to date. Our data spatially resolve PDS 27 and PDS 37 for the first time, revealing
two of the closest and most massive (> 8 M⊙ ) YSO binary candidates to date. PDS 27 and PDS 37 are rare but greatlaboratories to quantitatively inform and test the theories on formation of such systems.
Accepted by Astronomy & Astrophysics
https://www.aanda.org/articles/aa/pdf/forth/aa34624-18.pdf

２２

The dynamical evolution of molecular clouds near the Galactic Centre - II. Spatial
structure and kinematics of simulated clouds
J.M.D. Kruijssen1,2 , J.E. Dale3 , S.N. Longmore4 , D.L. Walker5,6 , J.D. Henshaw2 , S.M.R. Jeffreson1 ,M.A. Petkova1 , A. Ginsburg7 , A.T. Barnes4,8,9 , C.D. Battersby10 , K. Immer11 , J.M. Jackson12 , E.R.
Keto13 , N. Krieger2 , E.A.C. Mills14, Á. Sánchez-Monge15 , A. Schmiedeke8 , S.T. Suri2,15 and Q. Zhang13
1

Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120
Heidelberg, Germany; 2 Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 3 Centre
for Astrophysics Research, University of Hertfordshire, Hatfield, AL10 9AB, UK; 4 Astrophysics Research Institute,
Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK; 5 Joint
ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile; 6 National Astronomical Observatory ofJapan, Alonso de Cordova 3788, 61B Vitacura, Santiago, Chile; 7 National Radio Astronomy Observatory, P.O. Box O
1009, Lopezville Drive, Socorro, NM 87801, USA; 8 Max-Planck Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany; 9 Argelander Institute for Astronomy, University of Bonn, Auf dem Hug̈el 71,
53121 Bonn, Germany; 10 University of Connecticut, Department of Physics, 2152 Hillside Road, U-3046, Storrs, CT
06269, USA; 11 Joint Institute for VLBI ERIC (JIVE), Postbus 2, NL-7990 AA Dwingeloo, the Netherlands; 12 Schoolof Mathematical and Physical Sciences, University of Newcastle, University Drive, Callaghan NSW 2308, Australia; 13Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 14 Physics Department,
Brandeis University, 415 South Street, Waltham, MA 02453, USA; 15 I. Physikalisches Institut, Universität zu Köln,
Zülpicher Straße 77, 50937 Köln, Germany
E-mail contact: kruijssen at uni-heidelberg.de
The evolution of molecular clouds in galactic centres is thought to differ from that in galactic discs due to a significant
influence of the external gravitational potential. We present a set of numerical simulations of molecular clouds
orbiting on the 100-pc stream of the Central Molecular Zone (the central ∼500 pc of the Galaxy) and characterise
their morphological and kinematic evolution in response to the background potential and eccentric orbital motion.
We find that the clouds are shaped by strong shear and torques, by tidal and geometric deformation, and by theirpassage through the orbital pericentre. Within our simulations, these mechanisms control cloud sizes, aspect ratios,
position angles, filamentary structure, column densities, velocity dispersions, line-of-sight velocity gradients, spin
angular momenta, and kinematic complexity. By comparing these predictions to observations of clouds on the Galactic
Centre ’dust ridge’, we find that our simulations naturally reproduce a broad range of key observed morphologicaland kinematic features, which can be explained in terms of well-understood physical mechanisms. We argue that theaccretion of gas clouds onto the central regions of galaxies, where the rotation curve turns over and the tidal field17

is fully compressive, is accompanied by transformative dynamical changes to the clouds, leading to collapse and starformation. This can generate an evolutionary progression of cloud collapse with a common starting point, which either
marks the time of accretion onto the tidally-compressive region or of the most recent pericentre passage. Together,
these processes may naturally produce the synchronised starbursts observed in numerous (extra)galactic nuclei.
Accepted by MNRAS
http://arxiv.org/pdf/1902.01860

２３

Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc
R. Lallement1 , C. Babusiaux2,1 , J.L. Vergely3 D. Katz1 , F. Arenou1 , B. Valette4 , C. Hottier1 , and L.
Capitanio1
1

GEPI, Observatoire de Paris, PSL University, CNRS, 5 Place Jules Janssen, 92190 Meudon, France; 2 Univ. Grenoble
Alpes, CNRS, IPAG, 38000 Grenoble, France; 3 ACRI-ST, Sophia-Antipolis, France; 4 ISTerre, Université Grenoble
Alpes, France
E-mail contact: rosine.lallement at obspm.fr
Gaia data are revolutionizing our knowledge of the evolutionary history of the Milky Way. 3D maps of the interstellar
dust provide complementary information and are a tool for a wide range of uses. We aimed at building 3D mapsof the dust in the Local arm and surrounding regions. To do so, Gaia DR2 photometric data were combined with
2MASS measurements to derive extinction towards stars that possess accurate photometry and relative uncertainties
on DR2 parallaxes smaller than 20%. We applied to the extinctions a new hierarchical inversion algorithm adaptedto large datasets and to a inhomogeneous target distribution. Each step associates regularized Bayesian inversions
along radial directions and a subsequent inversion in 3D of their results. Each inverted distribution serves as a priorfor the subsequent step and the spatial resolution is progressively increased. We present the resulting 3D distributionof the dust in a 6 × 6 × 0.8 kpc3 volume around the Sun. Its main features are found to be elongated along different
directions that vary from below to above the mid-plane: the outer part of Carina-Sagittarius, mainly located above
the mid-plane, the Local arm/Cygnus Rift around and above the mid-plane and the fragmented Perseus arm areoriented close to the direction of circular motion. The long spur (nicknamed the split) that extends between the Local
Arm and Carina-Sagittarius, the compact near side of Carina-Sagittarius and the Cygnus Rift below the Plane areoriented along l=40 to 55 deg. Dust density images in vertical planes reveal in some regions a wavy pattern andshow that the solar neighborhood within 500 pc remains atypical by its extent above and below the Plane. We show
several comparisons with the locations of molecular clouds, HII regions, O stars and masers. The link between the
dust concentration and these tracers is markedly different from one region to the other.
Accepted by A&A
http://arxiv.org/pdf/1902.04116

２４

Magnetized interstellar molecular clouds: II. The Large-Scale Structure and Dynamics
of Filamentary Molecular Clouds
Pak Shing Li1 and Richard I. Klein1,2
1

Astronomy Department, University of California, Berkeley, CA 94720, USA; 2 Lawrence Livermore National Laboratory,P.O.Box 808, L-23, Livermore, CA 94550, USA
E-mail contact: psli at berkeley.edu
We perform ideal MHD high resolution AMR simulations with driven turbulence and self-gravity and find that long
filamentary molecular clouds are formed at the converging locations of large-scale turbulence flows and the filaments
are bounded by gravity. The magnetic field helps shape and reinforce the long filamentary structures. The main
filamentary cloud has a length of ∼ 4.4 pc. Instead of a monolithic cylindrical structure, the main cloud is shown to
be a collection of fiber/web-like sub-structures similar to filamentary clouds such as L1495. Unless the line-of-sightis close to the mean field direction, the large-scale magnetic field and striations in the simulation are found roughly
perpendicular to the long axis of the main cloud, similar to L1495. This provides strong support for a large-scale
moderately strong magnetic field surrounding L1495. We find that the projection effect from observations can leadto incorrect interpretations of the true three-dimensional physical shape, size, and velocity structure of the clouds.
18Helical magnetic field structures found around filamentary clouds that are interpreted from Zeeman observations canbe explained by a simple bending of the magnetic field that pierces through the cloud. We demonstrate that two
dark clouds form a T-shape configuration which are strikingly similar to the Infrared dark cloud SDC13 leading to theinterpretation that SDC13 results from a collision of two long filamentary clouds. We show that a moderately strong
magnetic field (MA ∼ 1) is crucial for maintaining a long and slender filamentary cloud for a long period of time ∼ 0.5
million years.
Accepted by MNRAS
http://arxiv.org/pdf/1901.04593

２５

CLIcK: a Continuum and Line fItting Kit for circumstellar disks
Yao Liu1,2 , Ilaria Pascucci1,3,4 , and Thomas Henning1
1

Max Planck Institute for Astronomy, Königsthul 17, 69117, Heidelberg, Germany; 2 Purple Mountain Observatory,
Chinese Academy of Sciences, 2 West Beijing Road, Nanjing 210008, China; 3 Lunar and Planetary Laboratory,
University of Arizona, Tucson, AZ 85721, USA; 4 Earths in Other Solar Systems Team, NASA Nexus for Exoplanet
System ScienceE-mail contact: yliu at mpia.de
Infrared spectroscopy with medium to high spectral resolution is essential to characterize the gas content of circumstellar disks. Unfortunately, conducting continuum and line radiative transfer of thermochemical disk models is too timeconsuming to carry out large parameter studies. Simpler approaches using a slab model to fit continuum-subtracted
spectra require the identification of either the global or local continuum. Continuum subtraction, particularly when
covering a broad wavelength range, is challenging but critical in rich molecular spectra as hot (several hundreds K)
molecular emission lines can also produce a pseudo continuum. In this work, we present CLIcK, a flexible tool tosimultaneously fit the continuum and line emission. The DDN01 continuum model (Dullemond et al. 2001) and aplane-parallel slab of gas in local thermodynamic equilibrium are adopted to simulate the continuum and line emission
respectively, both of them are fast enough for homogeneous studies of large disk samples. We applied CLIcK to fit theobserved water spectrum of the AA Tau disk and obtained water vapor properties that are consistent with literature
results. We also demonstrate that CLIcK properly retrieves the input parameters used to simulate the water spectrumof a circumstellar disk. CLIcK will be a versatile tool for the interpretation of future James Webb Space Telescope
spectra.
Accepted by A&A
http://arxiv.org/pdf/1902.03891

２６Structure of a Protobinary System: An Asymmetric Circumbinary Disk and Spiral
Arms
Tomoaki Matsumoto1,2,3 , Kazuya Saigo4 and Shigehisa Takakuwa5,6
1

Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan; 2 Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA; 3 RIKEN Center for Computational
Science (R-CCS), 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan; 4 Chile Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 5 Department of Physics
and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima
890-0065, Japan; 6 Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Section 4, Roosevelt Road,
Taipei 10617, Taiwan
E-mail contact: matsu at hosei.ac.jp
We investigate the gas structures around young binary stars by using three-dimensional numerical simulations. Eachmodel exhibits circumstellar disks, spiral arms, and a circumbinary disk with an inner gap or cavity. The circumbinary
disk has an asymmetric pattern rotating at an angular velocity of approximately one-fourth of the binary orbit of themoderate-temperature models. Because of this asymmetry, the circumbinary disk has a density bump and a vortex,
both of which continue to exist until the end of our calculation. The density bump and vortex are attributed toenhanced angular momentum, which is promoted by the gravitational torque of the stars. In a hot model (c ≥ 2.0), the19asymmetry rotates considerably more slowly than in the moderate-temperature models. The cold models (c ≤ 0.02)
exhibit eccentric circumbinary disks, the precession of which is approximated by a secular motion of the ballistic
particles. The asymmetry in the circumbinary disk does not depend on the mass ratio, but it becomes less clear as the
specific angular momentum of the infalling envelope increases. The relative accretion rate onto the stars is sensitive
to the angular momentum of the infalling envelope. For envelopes with constant angular momentum, the secondary
tends to have a higher accretion rate than the primary, except in very low angular momentum cases. For envelopes
with a constant angular velocity, the primary has a higher accretion rate than the secondary because gas with low
specific angular momentum falls along the polar directions.
Accepted by ApJ
https://arxiv.org/pdf/1812.01626

２７

A new HLLD Riemann solver with Boris correction for reducing Alfvén speed
Tomoaki Matsumoto1,2,3 , Takahiro Miyoshi4 and Shinsuke Takasao5
1

Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan; 2 Department of
Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA; 3 RIKEN Center for Computational Science (R-CCS), 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan; 4 Department of
Physical Science, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima 739-8526,
Japan; 5 Department of Physics, Nagoya University, Nagoya, Aichi, 464-8602, Japan
E-mail contact: matsu at hosei.ac.jp
A new Riemann solver is presented for the ideal magnetohydrodynamics (MHD) equations with the so-called Boris
correction. The Boris correction is applied to reduce wave speeds, avoiding an extremely small timestep in MHD
simulations. The proposed Riemann solver, Boris-HLLD, is based on the HLLD solver. As done by the original HLLD
solver, (1) the Boris-HLLD solver has four intermediate states in the Riemann fan when left and right states are given,(2) it resolves the contact discontinuity, Alfvén waves, and fast waves, and (3) it satisfies all the jump conditions
across shock waves and discontinuities except for slow shock waves. The results of a shock tube problem indicatethat the scheme with the Boris-HLLD solver captures contact discontinuities sharply and shock waves without any
overshoot when using the minmod limiter. The stability tests show that the scheme is stable when |u| <∼ 0.5c for a
c),
where
u,
c,
and
V
denotethegasvelocity,
speedoflight,
andAlfvénspeed,
respectively.
low Alfvén speed (VA <A∼
For a high Alfvén speed (VA >∼ c), where the plasma beta is relatively low in many cases, the stable region is large,|u| <∼ (0.6 − 1)c. We discuss the effect of the Boris correction on physical quantities using several test problems. The
Boris-HLLD scheme can be useful for problems with supersonic flows in which regions with a very low plasma beta
appear in the computational domain.
Accepted by ApJ
https://arxiv.org/pdf/1902.02810

２８

Could 1I/Oumuamua be an Icy Fractal Aggregate?
Amaya Moro-Martı́n1
1

Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

E-mail contact: amaya at stsci.edu
1I/Oumuamua is the first interstellar interloper to be detected, and it shows a non-gravitational acceleration thatcannot be accounted for by outgassing, given the strict upper limits of outgassing evident from Spitzer observations,
unless the relative abundances of the common volatiles are very different to those in comets. As an alternative, it
has been suggested that its peculiar acceleration is due to radiation pressure, requiring a planar-sheet geometry of an
unknown natural or artificial origin. Here we assess whether or not the internal structure of 1I/Oumuamua, rather
than its geometry, could support a radiation-pressure-driven scenario. We adopt a mass fractal structure and findthat the type of aggregate that could yield the required area-to-mass ratio would have to be extraordinarily porous,
with a density ∼ 10−5 g cm−3 . Such porous aggregates can naturally arise from the collisional grow of icy dust
particles beyond the snowline of a protoplanetary disk, and we propose that 1I/Oumuamua might be a member ofthis population. This is a hypothesis worth investigating because, if this were the case, 1I/Oumuamua would have20

opened a new observation window on to the study of the building blocks of planets around other stars. This could set
unprecedented constraints on planet formation models.
Accepted by Astrophysical Journal Letters
http://arxiv.org/pdf/1902.4100

２９Formation of planetary systems by pebble accretion and migration: Growth of gas giants
Olivier Mousis1 , Thomas Ronnet1,2 , and Jonathan I. Lunine3
1
Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France; 2 Lund Observatory, Department of Astronomy andTheoretical Physics, Lund University, Box 43, 221 00 Lund, Sweden; 3 Department of Astronomy, Cornell University,
Ithaca, NY 14853, USA

E-mail contact: olivier.mousis at lam.fr
Argon, krypton, xenon, carbon, nitrogen, sulfur, and phosphorus have all been measured enriched by a quasi uniform
factor in the 2–4 range, compared to their protosolar values, in the atmosphere of Jupiter. To elucidate the originof these volatile enrichments, we investigate the possibility of inward drift of particles made of amorphous ice andadsorbed volatiles, and their ability to enrich in heavy elements the gas phase of the protosolar nebula once they crossthe amorphous-to-crystalline ice transition zone, following the original idea formulated by Monga & Desch (2015).
To do so, we use a simple accretion disk model coupled to modules depicting the radial evolution of icy particles
and vapors, assuming growth, fragmentation and crystallization of amorphous grains. We show that it is possible toaccrete supersolar gas from the nebula onto proto-Jupiter’s core to form its envelope, and allowing it to match theobserved volatile enrichments. Our calculations suggest that nebular gas with a metallicity similar to that measured
in Jupiter can be accreted by its envelope if the planet formed in the ∼0.5–2 Myr time range and in the 0.5–20 AU
distance range from the Sun, depending on the adopted viscosity parameter of the disk. These values match a wide
range of Jupiter’s formation scenarios, including in situ formation and migration/formation models.
Accepted by ApJ
http://arxiv.org/pdf/1902.08924

３０

The core and stellar mass functions in massive collapsing filaments
Evangelia Ntormousi1,2 and Patrick Hennebelle2,3
1

Foundation for Research and Technology (FORTH), Nikolaou Plastira 100, Vassilika Vouton GR - 711 10, Heraklion,
Crete, Greece; 2 Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp - CNRS - Université Paris Diderot, 91191, Gif-surYvette Cedex, France; 3 LERMA (UMR CNRS 8112), Ecole Normale Supérieure, 75231 Paris Cedex, France
E-mail contact: entorm at physics.uoc.gr
The connection between the pre-stellar core mass function (CMF) and the stellar initial mass function (IMF) lies at
the heart of all star formation theories. In this paper, we study the earliest phases of star formation with a series ofhigh-resolution numerical simulations that include the formation of sinks. In particular, we focus on the transition
from cores to sinks within a massive molecular filament. We compare the CMF and IMF between magnetized andunmagnetized simulations, and between different resolutions. We find that selecting cores based on their kinematic
virial parameter excludes collapsing objects because they host large velocity dispersions. Selecting only the thermallyunstable magnetized cores, we observe that their mass-to-flux ratio spans almost two orders of magnitude for a given
mass. We also see that, when magnetic fields are included, the CMF peaks at higher core mass values with respect
to pure hydrodynamical simulations. Nonetheless, all models produce sink mass functions with a high-mass slope
consistent with Salpeter. Finally, we examine the effects of resolution and find that, in isothermal simulations, evenmodels with very high dynamical range fail to converge in the mass function. Our main conclusion is that, although theresulting CMFs and IMFs have similar slopes in all simulations, the cores have slightly different sizes and kinematicalproperties when a magnetic field is included. However, a core selection based on the mass-to-flux ratio alone is notenough to alter the shape of the CMF, if we do not take thermal stability into account. Finally, we conclude that
extreme care should be given to resolution issues when studying sink formation with an isothermal equation of state.
Accepted by A&A
http://arxiv.org/pdf/1902.05744

21

３１

A dynamically young, gravitationally stable network of filaments in Orion B
Jan H. Orkisz1,2,3 , Nicolas Peretto4 , Jérôme Pety2,3 , Maryvonne Gerin3 , François Levrier3 , EmericBron5,6 , Sébastien Bardeau2 , Javier R. Goicoecha6 , Pierre Gratier7 , Viviana V. Guzmán8 , Annie
Hughes9 , David Languignon5 , Franck Le Petit5 , Harvey S. Liszt10 , Karin Öberg11 , Evelyne Roueff5 ,Albrecht Sievers12 and Pascal Tremblin131Univ. Grenoble Alpes, IRAM, F-38000 Grenoble, France; 2 IRAM, 300 rue de la Piscine, F-38406 Saint MartindHères, France; 3 Sorbonne Université, Observatoire de Paris, Université PSL, École normale suprieure, CNRS,LERMA, F-75005, Paris, France; 4 School of Physics and Astronomy, Cardiff University, Queens buildings, Cardiff
CF24 3AA, UK; 5 Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, F-92190, Meudon,
France; 6 Grupo de Astrofı́sica Molecular. IFF-CSIC. Calle Serrano 121-123. 28006, Madrid, Spain; 7 Laboratoired’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France; 8Instituto de Astrofı́sica, Ponticia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago,
Chile; 9 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France; 10 National Radio Astronomy
Observatory, 520 Edgemont Road, Charlottesville, VA, 22903, USA; 11 Harvard-Smithsonian Center for Astrophysics,
60 Garden Street, Cambridge, MA, 02138, USA; 12 IRAM, Avenida Divina Pastora, 7, Núcleo Central, E-18012
Granada, Spain; 13 Maison de la Simulation, CEA-CNRS-INRIA-UPS-UVSQ, USR 3441, Centre détude de Saclay,
F-91191 Gif-Sur-Yvette, France
E-mail contact: jan.orkisz at chalmers.se
Filaments are a key step on the path that leads from molecular clouds to star formation. However, their characteristics(for instance their width) are heavily debated, and the exact processes that lead to their formation and fragmentation
into dense cores still remain to be fully understood. We aim at characterising the mass, kinematics, and stability
against gravitational collapse of a statistically significant sample of filaments in the Orion B molecular cloud, whichis renown for its very low star formation efficiency. We characterise the gas column densities and kinematics overa field of 1.9 deg2 , using C18 O(J = 1 − 0) data from the IRAM-30m large programme ORION-B, at angular andspectral resolutions of 23.5′′ and 49.5 kHz, respectively. Using two different Hessian-based filters, we extract andcompare two filamentary networks, each containing over 100 filaments. Independent of the extraction method, thefilament networks have consistent characteristics. The filaments have widths of ∼ 0.12 ± 0.04 pc, and show a wide
range of linear (∼ 1 − 100 M⊙pc−1 ) and volume densities (∼ 2 × 103 − 2 × 105 cm−3 ). Compared to previous studies,the filament population is dominated by low-density, thermally sub-critical structures, suggesting that most of theidentified filaments are not collapsing to form stars. In fact, only ∼ 1% of the Orion B cloud mass covered by ourobservations can be found in super-critical, star-forming filaments, explaining the low star formation efficiency of theregion. The velocity profiles observed across the filaments show quiescence in the center, and coherency in the plane of
the sky, despite being mostly supersonic. The filaments in Orion B apparently belong to a continuum which contains
a few elements comparable to already studied star-forming filaments (e.g. in the IC 5146, Aquila or Taurus regions)as well as many lower-density, gravitationally unbound structures. This comprehensive study of the Orion B filamentsshows that the mass fraction in super-critical filaments is a key factor in determining star formation efficiency.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1902.02077

３２

The consequences of planetary migration on the minor bodies of the early Solar System
S. Pirani1 , A. Johansen1 , B. Bitsch2 , A.J. Mustill1 , and D. Turrini3
1

Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund,
Sweden; 2 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 3 Institute for Space
Astrophysics and Planetology INAF-IAPS, Via Fosso del Cavaliere 100, 00133 Rome, Italy
E-mail contact: simona at astro.lu.se
Pebble accretion is an efficient mechanism able to build up the core of the giant planets within the lifetime of the
protoplanetary disc gas-phase. The core grows via this process until the protoplanet reaches its pebble isolation massand starts to accrete gas. During the growth, the protoplanet undergoes a rapid, large-scale, inward migration due
to the interactions with the gaseous protoplanetary disc. In our work, we investigate how this early migration would
have affected the minor body populations in our solar system. In particular, we focus on the Jupiter Trojans and the22Hildas asteroids. We found that a massive and eccentric Hilda group is captured during the migration from a region
between 5 and 8 au and subsequently depleted during the late instability of the giant planets. Our simulations also
show that inward migration of the giant planets always produces a Jupiter Trojans’ leading swarm more populated
than the trailing one, with a ratio comparable to the current observed Trojan asymmetry ratio. The in situ formationof Jupiter, on the other hand, produces symmetric leading/trailing swarms. The reason for the asymmetry is therelative drift between the migrating planet and the particles in the coorbital resonance. The capture happens during
the growth of Jupiter’s core and Trojan asteroids are afterwards carried along during the giant planet’s migration totheir final orbits. The asymmetry and eccentricity of the captured Trojans correspond well to observations, but their
inclinations are near zero and their total mass is 3–4 orders of magnitude higher than the current population. Future
modelling will be needed to understand whether the dynamical evolution of the Trojans over billions of years will raise
the inclinations and deplete the masses to observed values.
Accepted by A&A
http://arxiv.org/pdf/1902.04591

３３

Organic molecules in the protoplanetary disk of DG Tau revealed by ALMA
L. Podio1 , F. Bacciotti1 , D. Fedele1 , C. Favre1 , C. Codella1,2 , K. L. J. Rygl3 , I. Kamp4 , G. Guidi5 , E.
Bianchi2 , C. Ceccarelli2 , D. Coffey6,7 , A. Garufi1 and L. Testi8,11

INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 Univ. Grenoble Alpes, IPAG,
F-38000 Grenoble, France; 3 INAFIstituto di Radioastronomia & Italian ALMA Regional Centre, via P. Gobetti 101,
40129 Bologna, Italy; 4 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands; 5 ETH Zurich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093
Zurich, Switzerland; 6 School of Physics, University College Dublin, Belfield, Dublin 4, Ireland; 7 School of Cosmic
Physics, The Dublin Institute for Advanced Studies, Dublin 2, Ireland; 8 European Southern Observatory (ESO),
Karl-Schwarzschild-Str. 2, 85748, Garching, Germany
E-mail contact: lpodio at arcetri.astro.it
Planets form in protoplanetary disks and inherit their chemical compositions. It is thus crucial to map the distribution
and investigate the formation of simple organics, such as formaldehyde and methanol, in protoplanetary disks. We
analyze ALMA observations of the nearby disk-jet system around the T Tauri star DG Tau in the o-H2 CO 31,2 − 21,1
and CH3 OH 3−2,2 − 4−1,4 E, 50,5 − 40,4 A transitions at an unprecedented resolution of ∼ 0.15”, i.e., ∼ 18 au at a
distance of 121 pc. The H2 CO emission originates from a rotating ring extending from ∼ 40 au with a peak at ∼ 62
au, i.e., at the edge of the 1.3 mm dust continuum. CH3 OH emission is not detected down to an r.m.s. of 3 mJy/beamin the 0.162 km s−1 channel. Assuming an ortho-to-para ratio of 1.8 − 2.8 the ring- and disk-height-averaged H2 COcolumn density is ∼ 0.3 − 4 × 1014 cm−2 , while that of CH3 OH is < 0.04 − 0.7 × 1014 cm−2 . In the inner 40 au noo-H2 CO emission is detected with an upper limit on its beam-averaged column density of ∼ 0.5 − 6 × 1013 cm−2 .
The H2 CO ring in the disk of DG Tau is located beyond the CO iceline (RCO ∼ 30 au). This suggests that theH2 CO abundance is enhanced in the outer disk due to formation on grain surfaces by the hydrogenation of CO ice.
The emission peak at the edge of the mm dust continuum may be due to enhanced desorption of H2 CO in the gas
phase caused by increased UV penetration and/or temperature inversion. The CH3 OH/H2 CO abundance ratio is< 1, in agreement with disk chemistry models. The inner edge of the H2 CO ring coincides with the radius where thepolarization of the dust continuum changes orientation, hinting at a tight link between the H2 CO chemistry and thedust properties in the outer disk and at the possible presence of substructures in the dust distribution.
Accepted by A&A Letters
http://arxiv.org/pdf/1902.02720

３４

The nitrogen carrier in protoplanetary disks
Klaus M. Pontoppidan1 , Colette Salyk2 , Andrea Banzatti3 , Geoffrey A. Blake4 , Catherine Walsh5 , John
H. Lacy6 , Matthew J. Richter7
1

Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 2 Vassar College Physics andAstronomy Department, 124 Raymond Avenue, Poughkeepsie, NY 12604, USA; 3 Lunar and Planetary Laboratory,

23

The University of Arizona, Tucson, AZ, 85721, USA; 4 Division of Geological and Planetary Sciences, California
Institute of Technology, MC 150-21, 1200 E California Blvd., Pasadena, CA 91125, USA; 5 School of Physics andAstronomy, University of Leeds, Leeds, LS2 9JT, UK; 6 Department of Astronomy, The University of Texas at Austin,
2515 Speedway, Stop C1400, Austin, TX 78712, USA; 7 Department of Physics, University of California Davis, 1
Shields Avenue, Davis, CA 95616, USA
E-mail contact: pontoppi at stsci.edu
The dominant reservoirs of elemental nitrogen in protoplanetary disks have not yet been observationally identified.
Likely candidates are HCN, NH3 and N2 . The relative abundances of these carriers determine the composition ofplanetesimals as a function of disk radius due to strong differences in their volatility. A significant sequestration of
nitrogen in carriers less volatile than N2 is likely required to deliver even small amounts of nitrogen to the Earth andpotentially habitable exo-planets. While HCN has been detected in small amounts in inner disks (<10 au), so far
only relatively insensitive upper limits on inner disk NH3 have been obtained. We present new Gemini-TEXES highresolution spectroscopy of the 10.75 µm band of warm NH3 , and use 2-dimensional radiative transfer modeling to
improve previous upper limits by an order of magnitude to [NH3 /Hnuc ] < 10−7 at 1 au. These NH3 abundances are
significantly lower than those typical for ices in circumstellar envelopes ([NH3 /Hnuc ] ∼ 3 × 10−6 ). We also consistently
retrieve the inner disk HCN gas abundances using archival Spitzer spectra, and derive upper limits on the HCN ice
abundance in protostellar envelopes using archival ground-based 4.7 µm spectroscopy ([HCNice ]/[H2 Oice ] < 1.5–9%).
We identify the NH3 /HCN ratio as an indicator of chemical evolution in the disk, and use this ratio to suggestthat inner disk nitrogen is efficiently converted from NH3 to N2, significantly increasing the volatility of nitrogen inplanet-forming regions.
Accepted by ApJ
http://arxiv.org/pdf/1902.03647

３５

Observing the gas component of circumplanetary disks around wide-orbit planet-masscompanions in the (sub)mm regime
Ch. Rab1 , I. Kamp1 , C. Ginski2,3 , N. Oberg1 , G. A. Muro-Arena2 , C. Dominik2 , L. B. F. M. Waters4,2 ,W.-F. Thi5 and P. Woitke6
1

Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands; 2
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam; 3 Leiden
Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 4 SRON Netherlands Institute forSpace Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands; 5 Max-Planck-Institut für extraterrestrische
Physik, Giessenbachstrasse 1, 85748 Garching, Germany; 6 SUPA, School of Physics & Astronomy, University of St.
Andrews, North Haugh, St. Andrews KY16 9SS, UK
E-mail contact: rab at astro.rug.nl
Several detections of wide-orbit planet-mass/sub-stellar companions around young solar-like stars were reported in thelast decade. The origin of those possible planets is still unclear but accretion tracers and VLT/SPHERE observations
indicate that they are surrounded by circumplanetary material or even a circumplanetary disk. We want to investigate
if the gas component of disks around wide-orbit companions is detectable with current and future (sub)mm telescopes
and what constraints such gas observations can provide on the nature of the circumplanetary material and on themass of the companion. We applied the radiation thermo-chemical disk code ProDiMo to model the dust and gas
component of passive circumplanetary disks and produced realistic synthetic observables. We considered different
companion properties, disk parameters and radiative environments and compared the resulting synthetic observables
to telescope sensitivities and to existing dust observations. The main criterion for a successful detection is the sizeof the circumplanetary disk. At a distance of about 150 pc, a circumplanetary disk with an outer radius of about
10 au is detectable with ALMA in about 6 hours in optically thick CO lines. Other aspects such as the companion’s
luminosity, disk inclination and background radiation fields are also relevant and should be considered to optimize
the observing strategy for detection experiments. For most of the known wide-orbit planet-mass companions, theirmaximum theoretical disk size of one third of the Hill radius would be sufficient to allow detection of CO lines. It istherefore feasible to detect their gas disks and constrain the mass of the companion through the kinematic signature.
Even in the case of non-detections such observations will provide stringent constraints on disk size and gas mass,information crucial for formation theories.
24

Accepted by A&A
https://arxiv.org/pdf/1902.04096

３６

A high resolution mid-infrared survey of water emission from protoplanetary disks
Colette Salyk1 , John Lacy2 , Matt Richter3 , Ke Zhang4 , Klaus Pontoppidan5 , John S. Carr6 , Joan R.
Najita7 , Geoffrey A. Blake8
1

Department of Physics and Astronomy, Vassar College, 124 Raymond Ave, Poughkeepsie, NY 12604, USA; 2 Department of Astronomy, University of Texas at Austin, Austin, TX 78712, USA; 3 Physics Department, University ofCalifornia at Davis, Davis, CA 95616, USA; 4 Department of Astronomy, University of Michigan, 311 West Hall, 1085
South University Avenue, Ann Arbor, MI 48109, USA; 5 Space Telescope Science Institute, 3700 San Martin Drive,
Baltimore, MD 21218, USA; 6 Naval Research Laboratory, Code 7213, Washington, DC 20375, USA; 7 National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719, USA; 8 Division of Geological and Planetary
Sciences, California Institute of Technology, MC 150-21, 1200 E California Blvd, Pasadena, CA 91125, USA
E-mail contact: csalyk at gmail.com
We present the largest survey of spectrally resolved mid-infrared water emission to date, with spectra for 11 disks
obtained with the Michelle and TEXES spectrographs on Gemini North. Water emission is detected in 6 of 8 disks
around classical T Tauri stars. Water emission is not detected in the transitional disks SR 24 N and SR 24 S, in
spite of SR 24 S having pre-transitional disk properties like DoAr 44, which does show water emission (Salyk et
al. 2015). With R∼100,000, the TEXES water spectra have the highest spectral resolution possible at this time,and allow for detailed lineshape analysis. We find that the mid-IR water emission lines are similar to the “narrowcomponent” in CO rovibrational emission (Banzatti & Pontoppidan 2015), consistent with disk radii of a few AU.
The emission lines are either single peaked, or consistent with a double peak. Single-peaked emission lines cannot
be produced with a Keplerian disk model, and may suggest that water participates in the disk winds proposed to
explain single-peaked CO emission lines (Bast et al. 2011, Pontoppidan et al. 2011). Double-peaked emission lines
can be used to determine the radius at which the line emission luminosity drops off. For HL Tau, the lower limit on
this measured dropoff radius is consistent with the 13 AU dark ring (ALMA partnership et al. 2015). We also reportvariable line/continuum ratios from the disks around DR Tau and RW Aur, which we attribute to continuum changes
and line flux changes, respectively. The reduction in RW Aur line flux corresponds with an observed dimming at
visible wavelengths (Rodriguez et al. 2013).
Accepted by ApJ
http://arxiv.org/pdf/1902.02708

３７

ALMA High Angular Resolution Polarization Study: An Extremely Young Class 0
Source, OMC-3/MMS 6
Satoko Takahashi1,2,3,4 , Masahiro N. Machida5 , Kohji Tomisaka3,6 , Paul T. P. Ho4,7 , Edward B. Fomalont1,8 ,Kouichiro Nakanishi3,6 and Josep Miquel Girart9,10
1

Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile; 2 NAOJ Chile Observatory, Alonsode Cordova 3788, Oficina 61B, Vitacura, Santiago, Chile; 3 Department of Astronomical Science, School of PhysicalSciences, SOKENDAI (The Graduate University for Advanced Studies); 4 Academia Sinica Institute of Astronomy
and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 5 Department of Earth and Planetary Sciences, Facultyof Sciences, Kyushu University, Fukuoka 812-8581, Japan; 6 National Astronomical Observatory of Japan, Mitaka,
Tokyo 181-8588, Japan; 7 East Asian Observatory, Hilo 96720, HI, USA; 8 National Radio Astronomy Observatory,
Charlottesville, VA 22903, USA; 9 Institut de Ciencies de l’Espai (ICE, CSIC), Can Magrans s/n, E-08193 Cerdanyola
del Valles, Catalonia, Spain; 10 Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Catalonia,
Spain
E-mail contact: satoko.takahashi at nao.ac.jp
Using the ≈16 km long baseline data obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), we
imaged the Stokes I emission and linearly polarized intensity (PI) in the 1.1 mm continuum band of a very youngintermediate-mass protostellar source, MMS 6, in the Orion Molecular Cloud-3. The achieved angular resolution,

25

0′′ 02×0′′ 03 (≈10 au), shows for the first time a wealth of data on the dust emission polarization in the central 200
au of a protostar. The PI peak is offset to the southeast (SE) by ≈20 au with respect to the Stokes I peak. Its
polarization degree is 11% with its E-vector orientation of the position angle ≈135. A partial ringlike structure with aradius of ≈80 au is detected in PI but not in the Stokes I. Northwest (NW) and SE parts of the ring are bright, witha high polarization degree of ≥10%, and their E-vector orientations are roughly orthogonal to those observed near thecenter. We also detected an armlike polarized structure, extending to 1000 au scale to the north, with the E-vectorsaligned along the minor axis of the structure. We explored possible origins of the polarized emission by comparing
them with magnetohydrodynamical simulations of the toroidal wrapping of the magnetic field. The simulations are
consistent with the PI emission in the ringlike and the extended armlike structures observed with ALMA. However, thecurrent simulations do not completely reproduce observed polarization characteristics in the central 50 au. Although
the self-scattering model can explain the polarization pattern and positional offset between the Stokes I and PI in thecentral 50 au, this model is not able to reproduce the observed high degree of polarization.
Accepted by Astrophysical Journal
http://adsabs.harvard.edu/pdf/2019ApJ...872...70T
http://arxiv.org/pdf/1812.03189

３８

Polarization of stars with debris disks: comparing observations with models
Julien Vandeportal1 , Pierre Bastien1 , Amélie Simon1 , Jean-Charles Augereau2 and Émilie Storer3
1Département de physique and Centre de recherche en astrophysique du Québec, Université de Montréal, C.P. 6128,
Succ. centre-ville, Montréal, QC H3C 3J7, Canada; 2 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France;
3
Department of Physics and Centre de recherche en astrophysique du Québec, McGill University, 3600 University St.,
Montréal, QC H3A 2T8, Canada
E-mail contact: bastien at astro.umontreal.ca
The Herschel Space telescope carried out an unprecedented survey of nearby stars for debris disks. The dust present
in these debris disks scatters and polarizes stellar light in the visible part of the spectrum. We explore what can belearned with aperture polarimetry and detailed radiative transfer modelling about stellar systems with debris disks.
We present a polarimetric survey, with measurements from the literature, of candidate stars observed by DEBRIS and
DUNES Herschel surveys. We perform a statistical analysis of the polarimetric data with the detection of far-infraredexcess by Herschel and Spitzer with a sample of 223 stars. Monte Carlo simulations were performed to determine
the effects of various model parameters on the polarization level and find the mass required for detection with current
instruments. Eighteen stars were detected with a polarization 0.01 ≤ P ≤ 0.1 per cent and ≥ 3σP , but only two ofthem have a debris disk. No statistically significant difference is found between the different groups of stars, with,without, and unknown status for far-infrared excess, and presence of polarization. The simulations show that the
integrated polarization is rather small, usually < 0.01 per cent for typical masses detected by their far-infrared excess
for hot and most warm disks. Masses observed in cold disks can produce polarization levels above 0.01 per centsince there is usually more dust in them than in closer disks. We list five factors which can explain the observed
low-polarization detection rate. Observations with high-precision polarimeters should lead to additional constraints
on models of unresolved debris disks.
Accepted by Monthly Notices of the Royal Astronomical Society (2019, Vol. 483, pp. 3510 - 3528)
http://arxiv.org/pdf/1811.04889

３９

The survivability of planetary systems in young and dense star clusters
A. van Elteren1 , S. Portegies Zwart1 , I. Pelupessy2 , Maxwell X. Cai1 , and S.L.W. McMillan3
1

Leiden Observatory, Leiden University, NL-2300RA Leiden, The Netherlands; 2 The Netherlands eScience Center,
The Netherlands; 3 Drexel University, Department of Physics, Philadelphia, PA 19104, USA

E-mail contact: spz at strw.leidenuniv.nl
We perform a simulation using the Astrophysical Multipurpose Software Environment of the Orion Trapezium starcluster in which the evolution of the stars and the dynamics of planetary systems are taken into account. The initialconditions are selected from earlier simulations in which the size and mass distributions of the observed circum-stellar26disks in this cluster are satisfactorily reproduced. Four, five or size planets per star were introduced in orbit around the
500 solar-like stars with a maximum orbital separation of 400 au. Our study focuses on the production of free-floating
planets. From a total of 2522 planets in the initial conditions of the simulation, a total of 357 become unbound.
Of these, 281 leave the cluster within the crossing time-scale of the star cluster, the others remain bound to thecluster as free-floating intra-cluster planets. Five of these free-floating intra-cluster planets are captured at a latertime by another star. The two main mechanisms by which planets are lost from their host star, ejection upon a strong
encounter with another star or internal planetary scattering, drive the evaporation independently of planet mass oforbital separation at birth. The effect of small perturbations due to slow changes in the cluster potential are important
for the evolution of planetary systems. In addition, the probability for a star losing a planet is independent of theplanet mass and independent of its initial orbital separation. As a consequence, the mass-distribution of free-floating
planets is indistinguishable from the mass distribution of planets bound to their host star.
Accepted by A&A
http://arxiv.org/pdf/1902.04652

４０

Spatial segregation of dust grains in transition disks. SPHERE observations of 2MASSJ16083070-3828268 and RXJ1852.3-3700
M. Villenave1,2 , M. Benisty1,3,4 , W. R. F. Dent5 , F. Ménard1 , A. Garufi6 , C. Ginski7 , P. Pinilla8 , C.
Pinte9,1 , J. P. Williams10, J. de Boer11 , J.-I. Morino12 , M. Fukagawa12 , C. Dominik7 , M. Flock13 , T.
Henning13 , A. Juhasz14 , M. Keppler13 , G. Muro-Arena7 , J. Olofsson15,16, L. M. Perez4 , G. van der
Plas1 , A. Zurlo17,18,19 , M. Carle19 , P. Feautrier1 , A. Pavlov13 , J. Pragt21 , J. Ramos13 , J.-F. Sauvage20,13 ,E. Stadler1 and L. Weber22
1

Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile; 3 Unidad
Mixta Internacional Franco-Chilena de Astronomia (CNRS, UMI 3386); 4 Departamento de Astronomia, Universidad
de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 5 Joint ALMA Observatory, Alonso de Cordova
3107, Vitacura 763-0355, Santiago, Chile; 6 INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125
Firenze, Italy; 7 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904,1098XH
Amsterdam, The Netherlands; 8 Department of Astronomy/Steward Observatory, The University of Arizona, 933
North Cherry Avenue, Tucson, AZ 85721, USA; 9 Monash Centre for Astrophysics (MoCA) and School of Physics
and Astronomy, Monash University, Clayton Vic 3800, Australia; 10 Institute for Astronomy, University of Hawaii,
Honolulu, Hawaii, USA; 11 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands;
12
National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo, 181-8588, Japan; 13 Max Planck
Institute for Astronomy, Koinigstuhl 17, 69117 Heidelberg, Germany; 14 Institute of Astronomy, Madingley Road,
Cambridge CB3 OHA, UK; 15 Facultad de Ciencias, Instituto de Fisica y Astronomia, Universidad de Valparaiso, Av.
Gran Bretana 1111, 5030 Casilla, Valparaiso, Chile; 16 Nucleo Milenio Formacion Planetaria - NPF, Universidad de
Valparaiso, Av. Gran Bretana 1111, Valparaiso, Chile; 17 Nucleo de Astronomia, Facultad de Ingenieria y Ciencias,
Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 18 Escuela de Ingenieria Industrial, Facultad deIngenieria y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 19 Aix Marseille Universite,
CNRS, LAM, 13388 Marseille, France; 20 DOTA, ONERA, Universite Paris Saclay, F-91123, Palaiseau France; 21
NOVA Optical Infrared Instrumentation Group, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands; 22
Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland
2

E-mail contact: marion.villenave at univ-grenoble-alpes.fr
Context. The mechanisms governing the opening of cavities in transition disks are not fully understood. Several
processes have been proposed, but their occurrence rate is still unknown.
Aims. We present spatially resolved observations of two transition disks, and aim at constraining their vertical andradial structure using multiwavelength observations that probe different regions of the disks and can help understanding
the origin of the cavities. Methods. We have obtained near-infrared scattered light observations with VLT/SPHEREof the transition disks 2MASS J16083070-3828268 (J1608) and RXJ1852.3-3700 (J1852), located in the Lupus andCorona Australis star-forming regions respectively. We complement our datasets with archival ALMA observations,and with unresolved photometric observations covering a wide range of wavelengths. We performed radiative transfer
modeling to analyze the morphology of the disks, and then compare the results with a sample of 20 other transition27

disks observed with both SPHERE and ALMA.
Results. We detect scattered light in J1608 and J1852 up to a radius of 0.54” and 0.4” respectively. The image ofJ1608 reveals a very inclined disk (i∼74deg), with two bright lobes and a large cavity. We also marginally detect the
scattering surface from the rear-facing side of the disk. J1852 shows an inner ring extending beyond the coronagraphic
radius up to 15 au, a gap and a second ring at 42au. Our radiative transfer model of J1608 indicates that themillimeter-sized grains are less extended vertically and radially than the micron-sized grains, indicating advanced
settling and radial drift. We find good agreement with the observations of J1852 with a similar model, but due to the
low inclination of the system, the model remains partly degenerate. The analysis of 22 transition disks shows that, ingeneral, the cavities observed in scattered light are smaller than the ones detected at millimeter wavelengths.
Conclusions. The analysis of a sample of transition disks indicates that the small grains, well coupled to the gas, canflow inward of the region where millimeter grains are trapped. While 15 out of the 22 cavities in our sample could
be explained by a planet of less than 13 Jupiter masses, the others either require the presence of a more massive
companion or of several low-mass planets.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1902.04612.pdf

４１

Ejection History of the IRAS 04166+2706 Molecular Jet
Liang-Yao Wang1,2 , Hsien Shang1,2 and Tzu-Yang Chiang1,2
1

Academia Sinica, Theoretical Institute for Advanced Research in Astrophysics; 2 Academia Sinica, Institute of
Astronomy and Astrophysics, Taipei, Taiwan
E-mail contact: lywang at tiara.sinica.edu.tw

The high-velocity molecular jet driven by Class 0 protostar IRAS 04166+2706 exhibits a unique saw-tooth velocity
pattern. It consists of a series of well-aligned symmetric knots with similar averaged speeds, whose speeds at peaksof emission decreases roughly linearly away from the origin. Recent ALMA observations of knots R6 and B6 reveal
kinematic behavior with expansion velocity increasing linearly from the axis to the edge. This pattern can be formed bya spherically expanding wind with axial density concentration. In this picture, the diverging velocity profile naturally
possesses an increasing expansion velocity away from the axis, resulting in a tooth-like feature on the position-velocity
diagram through projection. Such geometric picture predicts a correspondence between the slopes of the teeth andthe outflow inclination angles, and the same inclination angle of 52◦ of the IRAS 04166+2706 can generally explain
the whole pattern. Aided by numerical simulations in the framework of unified wind model by Shang et al. (2006),
the observed velocity pattern can indeed be generated. A proper geometrical distribution of the jet and wind material
is essential to the reconstruction the ejection history of the system.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1902.06038

４２

Luminosity outburst chemistry in protoplanetary discs: going beyond standard tracers
Dmitri S. Wiebe1 , Tamara S. Molyarova1 , Vitaly V. Akimkin1 , Eduard I. Vorobyov2,3 and Dmitry A.
Semenov4,51

Institute of Astronomy, Russian Academy of Sciences, Moscow, 119017, Russia; 2 Department of Astrophysics,
University of Vienna, Vienna 1180, Austria; 3 Research Institute of Physics, Southern Federal University, Stachki Ave.
194, 344090, Rostov-on-Don, Russia; 4 Chemistry Department, Ludwig Maximilian University, Butenandtstr. 5-13,
D-81377 Munich, Germany; 5 Max Planck Institute for Astronomy, Königstuhl 17, 69117, Heidelberg, Germany
E-mail contact: dwiebe at inasan.ru
The chemical influence of luminosity outbursts on the environments of young solar-type stars is explored. Species are
categorised into several types according to their response to the outburst. The first and second types imply chemicalchanges only during the outburst (with slightly different behaviours). These response types are mostly observed close
to the star and are caused by icy mantle evaporation. However, mantles recover after the outburst almost immediately.
A notable exception is benzene ice, which is accumulated on dust surfaces during and after the outburst, so that its
abundance exceeds the pre-outburst level by orders of magnitude. The third type of response is mostly seen at the disc28

periphery and implies alteration of abundances during the outburst and preservation of these ‘abnormal’ abundances
for centuries. This behaviour is typical of organic compounds, like HCOOCH3 , CH3 CN, CH2 CO. Their presence inthe dark disc regions can be a manifestation of the past outburst. CO and CO2 only trace past outbursts at the remote
disc regions. The outburst changes the C/O ratio, but it quickly returns to the pre-outburst value almost everywherein the disc. An important factor determining the sensitivity of molecular composition to the outburst is the dust size
distribution. The duration of the pre-outburst stage and of the outburst itself influence the chemical effects, if the
burst duration is shorter than 50 yr and the duration of the quiescent phase between the bursts is shorter than 100
kyr.
Accepted by MNRAS
http://arxiv.org/pdf/1902.07475

４３

External photoevaporation of protoplanetary discs in Cygnus OB2: linking discs to starformation dynamical history
Andrew J. Winter1 , Cathie J. Clarke1 and Giovanni P. Rosotti1
1

Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK

E-mail contact: ajwinter at ast.cam.ac.uk
Many stars form in regions of enhanced stellar density, wherein the influence of stellar neighbours can have a strong
influence on a protoplanetary disc (PPD) population. In particular, far ultraviolet (FUV) flux from massive stars
drives thermal winds from the outer edge of PPDs, accelerating disc destruction. In this work, we present a novel
technique for constraining the dynamical history of a star forming environment using PPD properties in a strongly
FUV irradiated environment. Applying recent models for FUV induced mass loss rates to the PPD population of
Cygnus OB2, we constrain how long ago primordial gas was expelled from the region; 0.5 Myr ago if the Shakura &Sunyaev α-viscosity parameter is α = 10−2 (corresponding to a viscous timescale of τvisc ≈ 0.5 Myr for a disc of scaleradius 40 au around a 1 M⊙ star). This value of α is effectively an upper limit, since it assumes efficient extinctionof FUV photons throughout the embedded phase. With this gas expulsion timescale we are able to produce a fulldynamical model that fits kinematic and morphological data as well as disc fractions. We suggest Cygnus OB2 wasoriginally composed of distinct massive clumps or filaments, each with a stellar mass ∼104 M⊙ . Finally we predictthat in regions of efficient FUV induced mass loss, disc mass Mdisc as a function of stellar host mass mstar follows
a power law with Mdisc ≈ mstar β , where β >∼ 2.7 (depending on disc initial conditions and FUV exposure). This is
steeper than observed correlations in regions of moderate FUV flux (1 < β < 1.9), and offers a promising diagnostic
to establish the influence of external photoevaporation in a given region.
Accepted by MNRAS
http://arxiv.org/pdf/1902.04586

４４

The Distances to Molecular Clouds at High Galactic Latitudes based on GAIA DR2
Qing-Zeng Yan1,2 , Bo Zhang2 , Ye Xu1 , Sufen Guo2,3 , J.P. Macquart4 , Zheng-Hong Tang2,3 , A.J. Walsh5
1

Purple Mountain Observatory, Nanjing 210008, China; 2 Shanghai Astronomical Observatory, Chinese Academyof Sciences, Shanghai 200030, China; 3 School of Astronomy and Space Science, University of Chinese Academyof Sciences, 19A Yuquanlu, Beijing 100049, China; 4 International Centre for Radio Astronomy Research, Curtin
University, GPO Box U1987, Perth WA 6845, Australia; 5 Department of Physics and Astronomy and MQ ResearchCentre in Astronomy, Astrophysics and Astrophotonics, Macquarie University, NSW 2109, Australia
E-mail contact: qzyan at pmo.ac.cn
We report the distances of molecular clouds at high Galactic latitudes (|b| > 10◦ ) derived from parallax and G
band extinction (AG) measurements in the second Gaia data release, Gaia DR2. Aided by Bayesian analyses, we
determined distances by identifying the breakpoint in the extinction AG towards molecular clouds and using theextinction AG of Gaia stars around molecular clouds to confirm the breakpoint. We use nearby star-forming regions,such as Orion, Taurus, Cepheus, and Perseus, whose distances are well-known to examine the reliability of our method.
By comparing with previous results, we found that the molecular cloud distances derived from this method are reliable.
The systematic error in the distances is approximately 5%. In total, 52 molecular clouds have their distances well29

determined, most of which are at high Galactic latitudes, and we provide reliable distances for 13 molecular clouds forthe first time.
Accepted by A&A
http://arxiv.org/pdf/1902.02052

４５An Ordered Envelope-disk Transition in the Massive Protostellar Source G339.88-1.26
Yichen Zhang1 , Jonathan C. Tan2,3 , Nami Sakai1 , Kei E. I. Tanaka4,5 , James M. De Buizer6 , Mengyao
Liu3 , Maria T. Beltrán7 , Kaitlin Kratter8 , Diego Mardones9 and Guido Garay9
1

Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan;
Department of Space, Earth & Environment, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden;
3
Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325, USA; 4 Department of Earthand Space Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; 5 ALMA Project, National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 6 SOFIA-USRA, NASA Ames Research Center, MS 232-12,
Moffett Field, CA 94035, USA; 7 INAF Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 8
Department of Astronomy and Steward Observatory, University of Arizona, 933 N Cherry Ave, Tucson, AZ, 85721,
USA; 9 Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile
2

E-mail contact: yczhang.astro at gmail.com
We report molecular line observations of the massive protostellar source G339.88-1.26 with the Atacama Large Millimeter/Submillimeter Array. The observations reveal a highly collimated SiO jet extending from the 1.3 mm continuum
source, which connects to a slightly wider but still highly collimated CO outflow. Rotational features perpendicular tothe outflow axis are detected in various molecular emissions, including SiO, SO2 , H2 S, CH3 OH, and H2 CO emissions.
Based on their spatial distributions and kinematics, we find that they trace different parts of the envelope-disk system.
The SiO emission traces the disk and inner envelope in addition to the jet. The CH3 OH and H2 CO emissions mostly
trace the infalling-rotating envelope, and are enhanced around the transition region between envelope and disk, i.e.,the centrifugal barrier. The SO2 and H2 S emissions are enhanced around the centrifugal barrier, and also trace theouter part of the disk. Envelope kinematics are consistent with rotating-infalling motion, while those of the disk areconsistent with Keplerian rotation. The radius and velocity of the centrifugal barrier are estimated to be about 530
au and 6 km s−1 , leading to a central mass of about 11 M⊙ , consistent with estimates based on spectral energy distribution fitting. These results indicate that an ordered transition from an infalling-rotating envelope to a Kepleriandisk through a centrifugal barrier, accompanied by changes of types of molecular line emissions, is a valid descriptionof this massive protostellar source. This implies that at least some massive stars form in a similar way as low-massstars via Core Accretion.
Accepted by ApJ
https://arxiv.org/pdf/1811.04381

４６

The Weakening Outburst of the Young Eruptive Star V582 Aur
G. Zsidi1,2 , P. Ábrahám1 , J. A. Acosta-Pulido3,4 , Á. Kóspál1,5 , M. Kun1 , Zs. M. Szabó1,2 , A. Bódi1,6 ,B. Cseh1 , N. Castro Segura4,7 , O. Hanyecz1 , B. Ignácz1,2 , Cs. Kalup1,2 , L. Kriskovics1 , L. Mészáros1 ,A. Ordasi1 , A. Pál1 , K. Sárneczky1 , B. Seli1,2 , Á. Sódor1 and R. Szakáts1
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, KonkolyThege Miklós út 15-17, Budapest, Hungary; 2 Eötvös Loránd University, Department of Astronomy, Budapest, Hungary; 3 Instituto de Astrofı́sica de Canarias, Avenida Vı́a Láctea, Tenerife, Spain; 4 Departamento de Astrofı́sica,
Universidad de La Laguna, Tenerife, Spain; 5 Max Planck Institute for Astronomy, Heidelberg, Germany; 6 MTACSFK Lendület Near-Field Cosmology Research Group, Budapest, Hungary; 7 Physics and Astronomy Department,
University of Southampton, Southampton, UK
E-mail contact: zsidi.gabriella at csfk.mta.hu

V582 Aur is a pre-main-sequence FU Orionis type eruptive star, which entered a brightness minimum in 2016 Marchdue to changes in the line-of-sight extinction. Here, we present and analyze new optical B, V , RC , and IC band
multiepoch observations and new near-infrared J, H, and KS band photometric measurements from 2018 January–30

2019 February, as well as publicly available midinfrared Wide-field Infrared Survey Explorer (WISE) data. We foundthat the source shows a significant optical–near-infrared variability, and the current brightness minimum has notcompletely finished yet. If the present dimming originates from the same orbiting dust clump that caused a similar
brightness variation in 2012, then our results suggest a viscous spreading of the dust particles along the orbit. Anotherscenario is that the current minimum is caused by a dust structure, that is entering and leaving the inner part of thesystem. The WISE measurements could be consistent with this scenario. Our long-term data, as well as an accretion
disk modeling hint at a general fading of V582 Aur, suggesting that the source will reach the quiescent level in ∼80
years.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1902.03673.pdf

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.

31

Abstracts of recently accepted major reviews

The role of magnetic field in molecular cloud formation and evolution
Patrick Hennebelle1 and Shu-ichiro Inutsuka2
1

Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp – CNRS – Université Paris Diderot, 91191 Gif-sur-Yvette Cedex,
France LERMA (UMR CNRS 8112), Ecole Normale Supérieure, 75231 Paris Cedex, France; 2 Department of Physics,
Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
E-mail contact: patrick.hennebelle at cea.fr
We review the role that magnetic field may have on the formation and evolution of molecular clouds. After a briefpresentation and main assumptions leading to ideal MHD equations, their most important correction, namely theion-neutral drift is described. The nature of the multi-phase interstellar medium (ISM) and the thermal processes thatallows this gas to become denser are presented. Then we discuss our current knowledge of compressible magnetizedturbulence, thought to play a fundamental role in the ISM. We also describe what is known regarding the correlation
between the magnetic and the density fields. Then the influence that magnetic field may have on the interstellar
filaments and the molecular clouds is discussed, notably the role it may have on the prestellar dense cores as well as
regarding the formation of stellar clusters. Finally we briefly review its possible effects on the formation of molecular
clouds themselves. We argue that given the magnetic intensities that have been measured, it is likely that magnetic
field is i) responsible of reducing the star formation rate in dense molecular cloud gas by a factor of a few, ii) strongly
shaping the interstellar gas by generating a lot of filaments and reducing the numbers of clumps, cores and stars,
although its exact influence remains to be better understood. Moreover at small scales, magnetic braking is likely adominant process that strongly modifies the outcome of the star formation process. Finally, we stress that by inducing
the formation of more massive stars, magnetic field could possibly enhance the impact of stellar feedback.
Accepted by Frontiers in Astronomy and Space Sciences
http://arxiv.org/pdf/1902.00798

Interferometric Observations of Magnetic Fields in Forming StarsCharles L. H. Hull1,2,3 and Qizhou Zhang41

National Astronomical Observatory of Japan, NAOJ Chile Observatory, Alonso de Córdova 3788, Office 61B, 7630422,
Vitacura, Santiago, Chile
2
Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
3
NAOJ Fellow
4
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
E-mail contact: chat.hull at nao.ac.jp
The magnetic field is a key ingredient in the recipe of star formation. However, the importance of the magnetic fieldin the early stages of the formation of low- and high-mass stars is still far from certain. Over the past two decades, themillimeter and submillimeter interferometers BIMA, OVRO, CARMA, SMA, and most recently ALMA have mademajor strides in unveiling the role of the magnetic field in star formation at progressively smaller spatial scales; ALMA
observations have recently achieved spatial resolutions of up to ∼ 100 au and ∼ 1,000 au in nearby low- and high-massstar-forming regions, respectively. From the kiloparsec scale of molecular clouds down to the inner few hundred au
immediately surrounding forming stars, the polarization at millimeter and submillimeter wavelengths is dominatedby polarized thermal dust emission, where the dust grains are aligned relative to the magnetic field. Interferometricstudies have focused on this dust polarization and occasionally on the polarization of spectral-line emission. We
review the current state of the field of magnetized star formation, from the first BIMA results through the latest
ALMA observations, in the context of several questions that continue to motivate the studies of high- and low-mass
32

star formation. By aggregating and analyzing the results from individual studies, we come to several conclusions:(1) Magnetic fields and outflows from low-mass protostellar cores are randomly aligned, suggesting that the magnetic
field at ∼ 1000 au scales is not the dominant factor in setting the angular momentum of embedded disks and outflows.
(2) Recent measurements of the thermal and dynamic properties in high-mass star-forming regions reveal small virial
parameters, challenging the assumption of equilibrium star formation. However, we estimate that a magnetic fieldstrength of a fraction of a mG to several mG in these objects could bring the dense gas close to a state of equilibrium.
Finally, (3) We find that the small number of sources with hourglass-shaped magnetic field morphologies at 0.01–0.1 pc
scales cannot be explained purely by projection effects, suggesting that while it does occur occasionally, magneticallydominated core collapse is not the predominant mode of low- or high-mass star formation.
Published in Frontiers in Astronomy and Space Sciences
https://www.frontiersin.org/articles/10.3389/fspas.2019.00003/full
https://arxiv.org/pdf/1903.03177

The Role of Magnetic Fields in Setting the Star Formation Rate and the Initial Mass
Function
Mark R. Krumholz1,2 and Christoph Federrath1,2
1

Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT, Australia; 2 Centreof Excellence for Astronomy in Three Dimensions (ASTRO-3D), Australia
E-mail contact: mark.krumholz at anu.edu.au

Star-forming gas clouds are strongly magnetized, and their ionization fractions are high enough to place them close to
the regime of ideal magnetohydrodyamics on all but the smallest size scales. In this review we discuss the effects ofmagnetic fields on the star formation rate (SFR) in these clouds, and on the mass spectrum of the fragments that are
the outcome of the star formation process, the stellar initial mass function (IMF). Current numerical results suggestthat magnetic fields by themselves are minor players in setting either the SFR or the IMF, changing star formation
rates and median stellar masses only by factors of ∼2–3 compared to non-magnetized flows. However, the indirect
effects of magnetic fields, via their interaction with star formation feedback in the form of jets, photoionization,
radiative heating, and supernovae, could have significantly larger effects. We explore evidence for this possibility incurrent simulations, and suggest avenues for future exploration, both in simulations and observations.
Accepted by Frontiers of Astronomy and Space Science
http://arxiv.org/pdf/1902.02557

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Summary of Upcoming Meetings

New Quests in Stellar Astrophysics IV. Astrochemistry, astrobiology and the Orign of Life
31 March - 5 April 2019, Puerto Vallarta, Mexico
http://www.inaoep.mx/puerto19
New Horizons in Planetary Systems
13 - 17 May 2019 - Victoria, Canada
http://go.nrao.edu/NewHorizons
Exploring the Infrared Universe: The Promise of SPICA
20 - 23 May 2019, Crete, Greece
http://www.spica2019.org
Workshop on Polarization in Protoplanetary Disks and Jets
20 - 24 May 2019, Sant Cugat del Vallès, Catalonia, Spain
http://sites.google.com/view/sant-cugat-forum-astrophysics/next-session
Cloudy Workshop
20 - 24 May 2019, University of Kentucky, USA
http://cloud9.pa.uky.edu/~gary/cloudy/CloudySummerSchool/
Star Clusters: from the Milky Way to the Early Universe
27 - 31 May 2019, Bologna, Italy
http://iausymp351.oas.inaf.it/
Partially Ionised Plasmas in Astrophysics
3 - 7 June 2019, Palma de Mallorca, Spain
http://solar1.uib.es/pipa2019/
Zooming in on Star Formation - A tribute to Åke Nordlund
9 - 14 June 2019, Nafplio, Greece
http://www.nbia.dk/nbia-zoomstarform-2019
From Stars to Planets II: Connecting our Understanding of Star and Planet Formation
17 - 20 June 2019, Gothenburg, Sweden
http://cosmicorigins.space/fstpii
Gaia’s View of Pre-Main Sequence Evolution. Linking the T Tauri and Herbig Ae/Be Stars
18 - 21 June 2019, Leeds, UK
https://starry-project.eu/final-conference
Gordon Conference on Origins of Solar Systems: Meteoritical, Spacecraft and Astrophysical Perspectives on the Assembly and Composition of Planets
23 - 28 June 2019https://www.grc.org/origins-of-solar-systems-conference/2019/
Astrochemistry: From nanometers to megaparsecs - A Symposium in Honour of John H. Black24 - 28 June 2019, Gothenburg, Sweden
https://www.chalmers.se/en/conference/JHBlacksymp2019/
Smoothed Particle Hydrodynamics International Workshop
25 - 27 June 2019, Exeter, UK
http://spheric2019.co.uk/
Great Barriers in Planet Formation
21 - 26 July 2019 Palm Cove, Australia
https://dustbusters.bitbucket.io/great-barriers-2019/34

Celebrating the first 40 Years of Alexander Tielens’ Contribution to Science: The Physics and Chemistry of the ISM
2 - 6 september 2019, Avignon, France https://tielens2019.sciencesconf.org
The Pleiades and friends: stellar associations in the GAIA era
9 - 13 September 2019, Coruña, Spain
http://www.laeff.cab.inta-csic.es/projects/pleiades2019/main/index.php
Crete III - Through dark lanes to new stars Celebrating the career of Prof. Charles Lada
23 - 27 September 2019 Crete, Greece
http://crete3.org
COOL STARS 21: Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
21 -26 June 2020, Toulouse, France
https://coolstars21.github.io/

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