THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 318 — 18 June 2019

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

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

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
My Favorite Object . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Abstracts of Newly Accepted Papers . . . . . . . . . . 10

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

Abstracts of Newly Accepted Major Reviews . 48

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

Summary of Upcoming Meetings . . . . . . . . . . . . . 52

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

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
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on objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

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Cover Picture
IC 417 - aka Sh2-234 - is located almost exactly inthe opposite direction from the galactic cente. The
young cluster Stock 8, seen towards the top of theimage, is associated with IC 417. It is at a distanceof about 2 kpc and forms part of the OB association
Aur OB2. The cover ﬁgure shows an infrared image
from Spitzer. 2MASS data at 1.2 microns is shownin blue. The Spitzer wavelengths of 3.6 and 4.5
microns are green and red, respectively. Extensive
star formation is seen in the lower half of the imahe.
Courtesy NASA/IPAC

Submitting your abstracts
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facilities available at that time to study millimeter wavelength molecular lines and we had almost unlimited accessto observing time. The MWO was already being used formany thesis studies, however no one was using the MWO
to study dark clouds, and Paul suggested that this would
be a good thesis project. Receiver sensitivity was muchpoorer back then, and to obtain a reasonable detection of
the weak 12 CO emission in these dark clouds took at leastten minutes of integration. I selected nine dark clouds forstudy, eight not known to be forming stars and one withknown star formation (L1551 - a fortuitous choice). Largemaps (at least for the time) were made of 12 CO and 13 CO
in each cloud requiring hundreds of hours of observing. In
addition smaller maps were made of dense gas tracers in
the cores. The temperatures, densities, masses, sizes andmolecular abundances were derived for each cloud and theradial dependence of the density and temperature weremodeled. Line widths were also explored and an early
form of the size-line width relation was found.

Ronald Snellin conversation with Bo Reipurth

Q: Back in 1977 you published a paper on self-reversing
CO profiles in collapsing molecular clouds. How did yourinterest in the study of molecular lines originate?

In these early days of millimeter wavelength astronomy
almost any observation could produce new and exciting
results. So it was impossible to resist pursuing researchbeyond my thesis work. I worked with fellow graduate
student Al Wootten on a number of projects. One area ofparticular interest involved deuterated molecules and wemade the ﬁrst detection of DNC. Also with Michel Guélin
and Bill Langer we investigated the fractionation process
and how this could be used to set an upper limit on theelectron density in cloud cores.

A: When I began graduate school at the University ofTexas my interest was theoretical astrophysics and my ﬁrst
research project was with Craig Wheeler. At the sametime I was funded though a research assistantship withDavid Lambert studying stellar spectra. David suggested
that I might work one summer with Paul Vanden Boutand thus by chance I began studies of molecular lines.
Paul had a copy of a code, I think from Nick Scoville,
to compute the molecular line emission from clouds andgave me the task of making it work. Instead I decided it
was easier to write a new code from scratch. Bob Loren,
who had just completed his Ph.D., suggested we apply
this code to collapsing clouds with an in-fall velocity proportional to r−1/2 . Such a velocity law has two positions
along a given line of sight with the same radial velocity
and thus can lead to self-absorption. In clouds where thedensity and temperature decreased outward (producing an
excitation gradient), we found that optically thick lines,
such as CO, would have slightly redshifted self-absorption
features. Thus the CO line proﬁles were double-peakedwith the blue-peak stronger than the red-peak. Our models matched well the line proﬁles in four clouds showing
self-absorption features and we suggested that this was evidence of non-homologous collapse. Although the application to these clouds may have been incorrect, the conceptof what one should observe in non-homologous collapse
was sound. This concept was reﬁned later by many researchers using more detailed collapse models to ﬁt the line
proﬁles of thick and thin lines in collapsing cloud cores.

Q: In 1980 you wrote a paper with Robert Loren and Richard
Plambeck on a bipolar outflow in the L1551 cloud which
has had an enormous impact on star formation studies.
What were the circumstances of this discovery?

A: The only cloud in my thesis sample known to formingstars was L1551. The earlier studies of Gillian Knapp andher colleagues had shown that this cloud had a broad secondary velocity feature oﬀset to the south-west of the infrared source IRS-5 and displaced to lower velocity. Theyinterpreted this broad secondary velocity component as
possibly due to collapse. Bob Loren was helping with the
CO mapping of this source, as he was now in residence
at the MWO. As we extended the map outwards fromthe center we were surprised to ﬁnd both red-shifted andblue-shifted broad CO velocity features that arose froma well-deﬁned double-lobed structure centered on the infrared source IRS-5. We later came across a paper by Paul
Nachman that made a passing remark about the presenceof velocity features at higher velocity. With the help of
Q: You finished your thesis in 1979, what was that project Dick Plambeck, we used his receiver on the MWO to observe the J=2-1 line from this region. Although the idea
about, and who was your adviser?
of outﬂows from young stars had already been suggested
A: After that summer, I changed research areas and began to explain the broad line wings in Orion, this was the ﬁrst
working with Paul Vanden Bout. The Millimeter Wave source to show such clear bipolar structure. We interObservatory (MWO) in West Texas was one of the few
3preted the high velocity gas to be the result of collimatedand oppositely directed winds from IRS-5. Associatedwith the blueshifted outﬂow lobe were several Herbig-Haro
objects, and Richard Schwartz had suggested earlier that
H-H-objects might be shocked regions produced by winds
from young stars. Kyle Cudworth and George Herbig had
just measured the proper motions of the H-H objects in
L1551. They found large transverse velocities for these HH objects and suggested several options for their origin, including that they were accelerated away from IRS-5. Thus
the presence of these Herbig-Haro objects ﬁt well with amodel in which IRS-5 was producing oppositely directedcollimated winds. These winds we believed were responsible for accelerating ambient molecular gas producing thebipolar molecular outﬂow and producing the shocks responsible for the H-H objects. We were fortunate that
this ﬁrst source was one of the better examples of a bipolar molecular outﬂow.

Q: You have written a series of papers on water in molecular clouds. What have you learnt?
A: I was one of the co-investigators on the Submillimeter
Wave Astronomy Satellite (SWAS), a NASA Small Explorer mission led by Gary Melnick. The primary science goals were to observe water and molecular oxygen inmolecular clouds. When we proposed this mission we expected that SWAS, using the water abundance predicted
at that time, would be able to detect the water line from
GMC cores in a matter of seconds. The sensitivity of
SWAS in orbit was as planned, however it took hours tomake a good detection of water, reﬂecting the lower than
expected gas-phase abundance of water. In 2000 we wrote
a series of papers presenting SWAS results. We foundthat in GMC cores the water abundance was several orders of magnitude lower than chemical models at that time
predicted and, although we were unable to detect waterin dark cloud cores, the upper limits also established apaucity of gas-phase water in these cores. We concluded
that gaseous water was not an important reservoir of elemental oxygen in cloud cores. We also speculated thatmuch of elemental oxygen was frozen on dust grains in
the form of molecular ices. Subsequent modeling by Dave
Hollenbach and colleagues predicted that gaseous water
should be present primarily toward the outer layers ofclouds where photodesorption can maintain water in thegas phase. Our analysis in 2011, based on the SWAS water maps of Orion, showed that most of gas-phase water
was located near the cloud surface, in agreement with thismodel.

Q: A few years later you summarized your studies of anumber of molecular outflows. What were your findings?
A: After ﬁnishing my Ph.D., I moved on to the University of Massachusetts and began a post-doc with the Five
College Radio Astronomy Observatory. There I teamed
up with Suzan Edwards to search for further connections
between molecular outﬂows and H-H objects using the recently ﬁnished FCRAO 14-m telescope. One of our ﬁrst
detections was the bipolar outﬂow in NGC 1333 associated with HH 7-11. Like L1551, the H-H objects were associated with the blueshifted outﬂowing gas and this wasanother example of a well delineated bipolar outﬂow. Our
searches continued yielding a number of outﬂows associated with H-H objects and we could make a convincing
case that high-velocity gas and H-H objects had a common origin in the interaction of stellar winds with thesurrounding ambient molecular cloud.

Q: What have you been doing more recently?
A: For the past 5 years I, along with co-authors Jon Marrand Stan Kurtz, have been writing a textbook on radio
astronomy. The text book, entitled Fundamentals of Radio Astronomy, is in two volumes. The ﬁrst volume (Observational Methods) describes how radio telescopes, interferometers, and radio detectors function as well as how
observations are made. The second volume (Astrophysics)
describes the production of radio continuum and spectralline emission and speciﬁcally how observations at radio
wavelengths can be used to determine the properties of
HII regions, stars, pulsars, the ISM in the Milky Way
and other galaxies, AGNS and the CMB. The ﬁrst volume was published in 2016 and the second volume wasjust published in May of this year. Now that this projectis ﬁnished I have more time for science. The SEQUOIA
receiver, which was used for many years on the 14-m telescope, is now installed on the Large Millimeter Telescopeand I have a number of projects in the works to continue
my studies of the molecular interstellar medium.

Q: In the latter half of the 1980s you wrote a number of
papers on the structure and kinematics of molecular outflows.
A: To better understand the structure of molecular outﬂows, it was important to obtain high signal to noise andhigh angular resolution observations. To improve the angular resolution of the 14-m telescope, Peter Schloerb andI observed L1551 during a lunar occultation. Later with
graduate student Gerald Moriarty-Schieven, we obtained aheavily oversampled map of L1551 that was reconstructedusing a maximum entropy algorithm. Based on these data
we suggested a model for the L1551 outﬂow in which theoutﬂowing molecular gas was located in a thin expanding shell which was accelerating away from IRS 5. With
Gerald we also obtained high angular resolution images ofboth the B335 and NGC2071 outﬂows and suggested they
had similar shell structures as L1551.

4referred to as the east and west sub-clusters. Each subcluster is surrounded by a lower density halo of stars. A
large number of stars in Cep OB3b are optically visible(Fig. 1, upper panel) indicating that some degree of gas
clearing has already occurred in the region.

My Favorite Object
Cepheus OB3b: A Story of Two
Expanding Sub-Clusters
Nicole Karnath1

Introduction

Our very own Sun likely formed in a cluster that dispersed
its stars and natal gas into the disk of the Milky Way(Adams et al. 2001). In fact, Lada & Lada (2003) foundthat only ∼ 7-10% of young, embedded star clusters survive to form bound, open clusters, while most clusters will
self-destruct within a few Myr by expelling their gas, andthus stellar components, into the disk of the Galaxy therefore drastically lowering the gravitational potential of thecluster. The natal gas is presumably expelled via stellar feedback, i.e., ultraviolet radiation and massive stellar
winds from OB stars and/or supernovae, the ensuing dynamical evolution will determine whether the cluster - inwhole or in part - will form a bound open cluster or disperse into the galactic disk. At a distance of ∼ 820 pc(Karnath et al. 2019, hereafter: K19), Cepheus OB3b is aunique cluster to observationally constrain the brief stageof a cluster undergoing gas dispersal, which is thought tobe the main mechanism for unbinding stars from a cluster.
Analyses of Cep OB3b give a snapshot of cluster evolution toward the end of gas dispersal and at a later stageof evolution than, for example, the Orion Nebula Cluster(ONC), which is of comparable size and membership.

Figure 1: Top: A visible light image of Cep OB3b fromthe 0.9-m on Kitt peak. The four ﬁlters used were blue,
visual (cyan), near infrared (orange), and an emission lineof hydrogen (red). Image credit: NOAO. Bottom: The
Cepheus OB3 cloud including the Cep A, B, C, D, and E
at 3.6, 5.8, and 24 µm via Spitzer. The blue circles correspond to the locations of the east and west sub-clusters.

The ﬁrst study of Cepheus OB3b, (Cep OB3b, see Fig.
1), came from Blaauw et al. (1959), ﬁnding one O star
(O7V, HD 217086) and several B stars throughout theentire cluster. Sargent (1977) and Heyer et al. (1996)
followed up ﬁnding two distinct molecular clumps of gas
within the larger Cep OB3 molecular cloud. The approximate locations of the two gas clumps are shown as blue
circles in Fig 1. These also correspond to what appear
to be two distinct sub-clusters in Cep OB3b, henceforth

Pozzo et al. (2003) pointed out that there was evidence ofa supernova remnant in the east sub-cluster, possibly explaining the structural diﬀerences of the two sub-clusters.
Getman et al. (2009) used Spitzer and Chandra to identify, ∼ 600 mid-infrared sources and IR-excess low-massmembers in Cep OB3b. It was proposed that the O7 staris creating a radiative driven implosion (RDI) in the rim of
the associated molecular clump resulting in continued starformation along the edge of the east sub-cluster. More re5

cently, Allen et al. (2012) carried out a census of the youngstellar objects (YSOs) in Cep OB3b employing Spitzer
data, a combination of new and archival Chandra data,
and visible light photometry from the literature to identify
stars on the Cep OB3b isochrone.
Cluster ages have been reported in the literature ranging
from 3−5 Myr (Nayler et al. 2001; Pozzo et al. 2003; Littlefair et al. 2010; Allen et al. 2012). Pozzo et al. (2003)
speculated that most of the molecular material shielded
the low mass stars from losing their disks via ionizing
radiation from the OB stars and that the material has
only recently been removed. Additionally, rotation periods have been obtained for 475 pre-main sequence stars
in Cep OB3b (Littlefair et al. 2010) ﬁnding that the lowmass stars are rotating much more slowly compared tostars in NGC 2362 that is a similar age. This may be apotential link between star-forming environment and rotation properties calling into question models of stellar
angular momentum evolution in young star clusters (Littlefair et al. 2010).
Gaia DR2 data measured the parallaxes with a clear peakat a distance of 819±16 pc in K19 in agreement with theGaia DR2 distance measured in Kuhn et al. (2019). The
Gaia distance resolves an inconsistency in the distance estimates and places the cluster at the upper end of therange of previous estimates.

2

The Sizes and Structures of the
Cep OB3b Sub-Clusters

In total there are ∼ 3000 members of Cep OB3b, consisting of primarily low-mass (<1 M⊙ ) stars (Allen et al.
2012). The entire population of identiﬁed young stars isfound in a ∼ 7 pc × 10 pc region, and the young stars areconcentrated in the east and west sub-clusters surroundedby an extended halo of these objects (Allen et al. 2012).
The east sub-cluster has ∼ 2.5× more pre-main sequencestars than the west and the disk fractions are diﬀerent in
the two sub-clusters: 32% for the east and 50% for thewest (Allen et al. 2012). The diﬀerence of disk fractions is
attributed to the diﬀerence in the ages of the sub-clusters,with the east being older.
In K19, we constrained the sizes, structures, and densitiesof the sub-clusters (see Table 1) using the analytic model
developed by King (1962) for globular clusters. The central coordinates of the sub-clusters were adopted from themethod of Gutermuth et al. (2009) that ﬁnds local surface density enhancements. The King model is not appropriate for the elongated and irregular structure of moredeeply embedded clusters such as the ONC (Gutermuth
et al. 2009; Kuhn et al. 2014; Megeath et al. 2016), but

the more circular symmetry of the two Cep OB3b subclusters motivates the use of this model. The Spitzer andChandra data were used for the King model ﬁts parameterized by a core radius, an outer radius, and a central
peak density (see Figure 2). The core radii are 1.4 pc(east) and 0.5 pc (west) with outer radii of 2.32 pc (east)and 3.1 pc (west). K19 found the west deviates signiﬁcantly from circular symmetry and it is signiﬁcantly elongated. In comparison, the east appears circularly symmetric with a relatively smooth distribution of stars, is richer
in members than the west and has a larger core radius.
The east also has the lone O star in the cluster vs thewest that has several B stars scattered throughout. The
west is characterized by elongation, a core radius that isless than half of that for the east, and has fewer members.
These properties support the idea that the east has undergone expansion due to gas dispersal in contrast to thewest, which is more compact. Cep OB3b is comparable insize and membership to the ONC (Carpenter et al. 2000
& Allen et al. 2007). The peak densities can be comparedto the ONC. Both sub-clusters have peak densities thatare much lower than in the ONC (Hillenbrand et al. 1998
& Megeath et al. 2016) suggesting they have undergone
expansion.

3

An RV Survey of Cep OB3b

K19 carried out a radial velocity (RV) survey of the two
sub-clusters using Hectoschelle on the Multi Mirror Telescope on Mount Hopkins, AZ. Hectoschelle is a ﬁber-fed
echelle spectrograph with resolving power of ∼ 32,000. A
total of 561 spectra over ﬁve epochs were taken of 499 distinct stars, 190 of which were identiﬁed as members (Figure 3). Sources showing signatures of multiplicity were
removed from the analysis, as stars in a binary or multiple will have RV motions measured due to the orbital
motions of the system instead of the kinetic energy of thecluster itself. The average RV of the sub-clusters are similar, -12.09 ±0.56 km s−1 for the east and -10.86 ±0.54 km
s−1 for the west.
To constrain the velocity dispersions of the sub-clusters, aBayesian parameter estimation was implemented for each
sub-cluster (K19) using a Monte-Carlo likelihood function comparison. Unresolved binaries were accounted for
adopting the approach of Cottaar et al. (2012) to add
the eﬀect of orbital motions. Three binary fractions were
tested to probe the eﬀect of binary fraction on the resulting dispersion: 0, 0.5, and 1.0 as seen in Figure 4.
Accounting for unresolved binaries is an important stepwhen probing an accurate kinematical survey of young
clusters, since for all but the youngest, most compact clusters, the motions of the binaries dominate the observed velocity dispersion. This is due to the eﬀect of the gas masson the cluster motions. As the gas is dispersed and thecluster expands, binaries will begin to dominate the observed distribution if the cluster remains near virial equilibrium while expanding.

3.1

The Kinetic and Potential Energies of
the Sub-Clusters

The probability distribution functions (PDF) (Figure 4) of
the sub-cluster velocity dispersions were adopted to derive
the kinetic energies of the sub-clusters. Here we assumed
a symmetric three dimensional velocity dispersion withthe values for the two directions in the plane of the sky
equal to that in the radial direction. These are combinedwith potential energy (PE) derived from the King models
to determine a ﬁnal PDF, which is close to the expected
fraction, of log(T/|U|) (Figure 5). Adopting a binary fraction of 0.5 in the east, log(T/|U|) has a mean value at 0.3
and a value at the peak of the distribution of 0.6. Thisimplies that the east sub-cluster is unbound and in a stateof expansion, which is consistent with the proper motion
analysis of Kuhn et al. (2019). If no stars are binaries
then log(T/|U|) > 0, also implying an unbound, expanding state. With all the stars being binaries the mean value
is in a subvirial, bound state with a probability of 61% of4.3

A Double Cluster?

Table 1: Main Parameters of Cep OB3b in K19
Parameter
East
West# of Members
∼ 800
∼ 450
A (pc−2 )541±202258±42
Rcore (pc)1.36±0.30
0.52±0.11
Router (pc)2.32±0.19
3.1±1.0
AAPmeas1.155
1.724
Gas Mass (M⊙ )136
697
RV (km s−1 )-12.09±0.563 -10.86±0.538
Velocity Dispersion (km s−1 )1.9+0.5
1.10+0.30
−0.4
−0.44
log(T/U)
0.3-0.16

The Gaia DR2 catalog was cross matched with Cep OB3b
members with youth indicators using their 2MASS IDs,
to determine the proper motion of both sub-clusters and a
distance to Cep OB3b (K19). The total cluster has propermotion components of 0.69±0.02 (µ∗α ) and -2.44±0.02 (µδ )mas yr−1 ; this translates to a diﬀerence of ∼ 2 km s−1 ofthe sub-clusters. The sub-clusters are moving away fromeach other and will continue to increase in separation. The
anticipated result will be the formation of two bound clusters of ∼ 300 stars each. This seems exceptional in thelight that ∼ 7% of embedded clusters form open clusters(Lada & Lada 2003). This might be due to unusual environmental conditions in the Cep OB3b cluster. Alternatively, there might be other factors that contribute to
the dissipation of clusters and the two sub-clusters will,in the end, disperse. For example, additional dynamical
eﬀects come into play in simulations when binaries and arealistic range of masses are used (Moeckel et al. 2012).
Finally, the tidal forces between the sub-clusters, and between the sub-clusters and molecular clouds may disrupt
the clusters or strip members. It should also be noted thatthe large uncertainties in the velocity dispersions translate
into large uncertainties in the dynamical outcomes in K19.

Hillenbrand & Hartmann (1998) ApJ, 492, 540
Karnath et al. (2019) ApJ, 871, 46
King (1962) AJ, 67, 471
Kuhn et al. (2014) ApJ, 787, 107
Kuhn et al. (2019) ApJ, 870, 32
Lada & Lada (2003) ARA&A, 41, 57
Littlefair et al. (2010) MNRAS, 403, 545
Megeath et al. (2016) AJ, 151, 5
Moeckel & Bate (2010) MNRAS, 404, 721
Moeckel et al. (2012) MNRAS 425, 450
Nayler et al. (2001), in Montmerle T., Andre, P., eds, ASP Conf.
Ser. 243, From Darkness to Light. Astron. Soc. Pac., San Francisco, p. 705
Parmentier & Pfalzner (2013) A&A, 549, A132
Pozzo et al. (2003) MNRAS, 341, 805
Raghavan et al. (2010) ApJS, 190, 1
Sargent (1977) ApJ, 218, 736

If both sub-clusters do in fact form bound clusters as predicted by some simulations, Cep OB3b will become a rare
double cluster, with each cluster drifting away in time. It
will also be a rare laboratory for establishing the conditions and environmental factors that produce bound clusters.
Future spectroscopic RV data of higher resolution canprobe the diﬀerences between the east and west sub-clusters
and aid in a better understanding of the age and initial
mass function of Cep OB3b. The rich data set of Cep
OB3b continues to grow and its comparable size with the
ONC, but during disk dissipation and gas dispersal, increases our understanding of cluster evolution. Further
observations with Gaia and other telescopes will provide
more detailed studies of Cep OB3b in addition to othercluster regions to understand the evolution of young clusters from formation to dispersal.
References:
Adams (2000) ApJ, 542, 964
Adams et al. (2001) AJ, 121, 2053
Allen et al. (2007) AAS, 211, 8919
Allen et al. (2012) ApJ, 750, 125
Baumgardt & Kroupa (2007) MNRAS, 380, 1589
Blaauw et al. (1959) ApJ, 130, 69
Carpenter (2000) AJ, 120, 3139
Cottaar et al. (2012) A&A, 547, A35
Farias et al. (2018) MNRAS, 476, 5341
Gutermuth et al. (2005) ApJ, 632, 397
Gutermuth et al. (2009) ApJS, 184, 18
Gutermuth et al. (2011) AAS, 21725819
Heyer et al. (1996) ApJ, 463, 630

9

Abstracts of recently accepted papers

1First grids of low-mass stellar models and isochrones with self-consistent treatment ofrotation : From 0.2 to 1.5 M⊙ at 7 metallicities from PMS to TAMS
L. Amard1,2,3 , A. Palacios2 , C. Charbonnel1,4 , F. Gallet5,1 , C. Georgy1 , N. Lagarde6 , and L. Siess7
1

Department of Astronomy - University of Geneva - Chemin des Maillettes, 51 - CH-1290 Versoix, Switzerland; 2
LUPM UMR 5299 CNRS/UM, Université de Montpellier, CC 72, 34095 Montpellier Cedex 05, France; 3 University of
Exeter, Department of Physics & Astronomy, Stoker Road, Devon, Exeter, EX4 4QL, UK; 4 IRAP, UMR 5277 CNRS
and Université de Toulouse, 14 Av. E. Belin, F-31400 Toulouse, France; 5 Univ. Grenoble Alpes, CNRS, IPAG, 38000
Grenoble, France; 6 Institut UTINAM, CNRS UMR 6213, Univ. Bourgogne Franche-Comté, OSU THETA FrancheComté-Bourgogne, Observatoire de Besançon, BP 1615, 25010, Besançon Cedex, France; 7 Institut d’Astronomie etd’Astrophysique, Université Libre de Bruxelles (ULB), CP226, Boulevard du Triomphe, B-1050 Brussels, Belgium
E-mail contact: l.amard at exeter.ac.uk
We present an extended grid of state-of-the art stellar models for low-mass stars including updated physics (nuclear
reaction rates, surface boundary condition, mass-loss rate, angular momentum transport, torque and rotation-induced
mixing prescriptions). We aim at evaluating the impact of wind braking, realistic atmospheric treatment, rotation androtation-induced mixing on the structural and rotational evolution from the pre-main sequence to the turn-oﬀ. Using
the STAREVOL code, we provide an updated PMS grid. We compute stellar models for 7 diﬀerent metallicities,
from [Fe/H] = −1 dex to [Fe/H] = +0.3 dex with a solar composition corresponding to Z=0.0134. The initialstellar mass ranges from 0.2 to 1.5 M⊙ with extra grid reﬁnement around one solar mass. We also provide rotating
models for three diﬀerent initial rotation rates (slow, median and fast) with prescriptions for the wind braking anddisc-coupling timescale calibrated on observed properties of young open clusters. The rotational mixing includes an
up-to-date description of the turbulence anisotropy in stably stratiﬁed regions. The overall behaviour of our models
at solar metallicity – and its constitutive physics – is validated through a detailed comparison with a variety of
distributed evolutionary tracks. The main diﬀerences arise from the choice of surface boundary conditions and initialsolar composition. The models including rotation with our prescription for angular momentum extraction and selfconsistent formalism for angular momentum transport are able to reproduce the rotation period distribution observedin young open clusters over a broad mass-range. These models are publicly available and may be used to analyse data
coming from present and forthcoming asteroseismic and spectroscopic surveys such as Gaia, TESS and PLATO.
Accepted by A&A
http://arxiv.org/pdf/1905.08516

2

Planet-forming material in a protoplanetary disc: the interplay between chemical evolution and pebble drift
R.A. Booth1 and J.D. Ilee2
1

Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK; 2 School of Physics & Astronomy, Universityof Leeds, Leeds LS2 9JT, UK
E-mail contact: rab200 at ast.cam.ac.uk
The composition of gas and solids in protoplanetary discs sets the composition of planets that form out of them.
Recent chemical models have shown that the composition of gas and dust in discs evolves on Myr time-scales, withvolatile species disappearing from the gas phase. However, discs evolve due to gas accretion and radial drift of duston time-scales similar to these chemical time-scales. Here we present the ﬁrst model coupling the chemical evolution
in the disc mid-planes with the evolution of discs due to accretion and radial drift of dust. Our models show thattransport will always overcome the depletion of CO2 from the gas phase, and can also overcome the depletion of CO−3−17
and CH4 unless both transport is slow (viscous α <∼ 10 ) and the ionization rate is high (ζ ≈ 10 ). Including10

radial drift further enhances the abundances of volatile species because they are carried in on the surface of grains
before evaporating left at their ice lines. Due to large diﬀerences in the abundances within 10 au for models withand without eﬃcient radial drift, we argue that composition can be used to constrain models of planet formation via
pebble accretion.
Accepted by MNRAS
http://arxiv.org/pdf/1905.12639

3

IRAS 23385+6053: An embedded massive cluster in the making
R. Cesaroni1 , H. Beuther2 , A. Ahmadi2 , M. T. Beltrán1 , T. Csengeri3 , R. Galván-Madrid4 , C. Gieser2 ,T. Henning2 , K. G. Johnston5 , P. D. Klaassen6 , R. Kuiper7 , S. Leurini8 , H. Linz2 , S. Longmore9 ,S. L. Lumsden5 , L. T. Maud10 , L. Moscadelli1, J. C. Mottram2 , A. Palau4 , T. Peters11 , R. E. Pudritz12 ,Á. Sánchez-Monge13 , P. Schilke13 , D. Semenov2,14 , S. Suri2 , J. S. Urquhart15 , J. M. Winters16 , Q. Zhang17
and H. Zinnecker18,19
1

INAF, Osservatorio Astroﬁsico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 2 Max Planck Institute for
Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel
69, D-53121 Bonn, Germany; 4 Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México,
PO Box 3-72, 58090 Morelia, Michoacán, México; 5 School of Physics and Astronomy, University of Leeds, Leeds LS2
9JT, United Kingdom; 6 UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh,
EH9 3HJ, UK; 7 Institute of Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, 72076,
Tübingen, Germany; 8 INAF, Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047, Selargius (CA),
Italy; 9 Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF, UK; 10 European
Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany; 11 Max-Planck-Institutfür Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching, Germany; 12 Department of Physics and Astronomy,
McMaster University, 1280 Main St. W, Hamilton, ON L8S 4M1, Canada; 13 I. Physikalisches Institut, Universitätzu Köln, Zülpicher Strasse 77, 50937, Köln, Germany; 14 Department of Chemistry, Ludwig Maximilian University,
Butenandtstr. 5-13, 81377 Munich, Germany; 15 Centre for Astrophysics and Planetary Science, University of Kent,
Canterbury CT2 7NH, UK; 16 Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, F-38406
Saint Martin d’Hères, France; 17 Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA
02138, USA; 18 Deutsches SOFIA Institut, Pfaﬀenwaldring 29, Universität Stuttgart, 70569 Stuttgart, Germany; 19
Universidad Autonoma de Chile, Av. Pedro Valdivia 425, Santiago de Chile, Chile
E-mail contact: cesa at arcetri.astro.it
This study is part of the CORE project, an IRAM/NOEMA large program consisting of observations of the millimeter
continuum and molecular line emission towards 20 selected high-mass star-forming regions. The goal of the programis to search for circumstellar accretion disks, study the fragmentation process of molecular clumps, and investigate
the chemical composition of the gas in these regions. We focus on IRAS 23385+6053, which is believed to be theleast-evolved source of the CORE sample. This object is characterized by a compact molecular clump that is IR-dark
shortward of 24 µm and is surrounded by a stellar cluster detected in the near-IR. Our aim is to study the structure
and velocity ﬁeld of the clump. Observations were performed at ∼1.4 mm and employed three conﬁgurations of
NOEMA and additional single-dish maps, merged with the interferometric data to recover the extended emission. Our
correlator setup covered a number of lines from well-known hot core tracers and a few outﬂow tracers. The angular(∼0.45–0.9 arcsec) and spectral (0.5 km/sec) resolutions were suﬃcient to resolve the clump in IRAS 23385+6053 andinvestigate the existence of large-scale motions due to rotation, infall, or expansion. We ﬁnd that the clump splits into
six distinct cores when observed at sub-arcsecond resolution. These are identiﬁed through their 1.4 mm continuum andmolecular line emission. We produce maps of the velocity, line width, and rotational temperature from the methanol
and methyl cyanide lines, which allow us to investigate the cores and reveal a velocity and temperature gradient in themost massive core. We also ﬁnd evidence of a bipolar outﬂow, possibly powered by a low-mass star. We present thetentative detection of a circumstellar self-gravitating disk lying in the most massive core and powering a large-scale
outﬂow previously known in the literature. In our scenario, the star powering the ﬂow is responsible for most of
the luminosity of IRAS 23385+6053 (∼3000 L⊙ ). The other cores, albeit with masses below the corresponding virial
masses, appear to be accreting material from their molecular surroundings and are possibly collapsing or on the vergeof collapse. We conclude that we are observing a sample of star-forming cores that is bound to turn into a cluster of11massive stars.
Accepted by Astronomy and Astrophysics
http://arxiv.org/pdf/1905.11257

4

Emerging trends in metallicity and lithium properties of debris disc stars
C. Chavero1 , R. de la Reza2 , L. Ghezzi2,6 , F. Llorente de Andrés,3 , C. B. Pereira2 , C. Giuppone4 and
G. Pinzón5
1

Universidad Nacional de Córdoba, Observatorio Astronómico, Laprida 854, 5000 Córdoba, CONICET, Argentina; 2Observatório Nacional, Rua General José Cristino, 77, 20921-400, São Cristóvão, Rio de Janeiro, RJ, Brazil; 3 Ateneo
de Almagro (Secc. Ciencia & Tecnologı́a)- 13270 Almagro, Spain; 4 Universidad Nacional de Córdoba, Observatorio Astronómico, IATE, Laprida 854, 5000 Córdoba, Argentina; 5 Universidad Nacional de Colombia, Colombia; 6
Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antônio 43, Rio de Janeiro, RJ
20080-090
E-mail contact: carolina at oac.unc.edu.ar
Dwarf stars with debris discs and planets appear to be excellent laboratories to study the core accretion theory ofplanets formation. These systems are however, insuﬃciently studied. In this paper we present the main metallicity
and lithium abundance properties of these stars together with stars with only debris discs and stars with only planets.
Stars without detected planets nor discs are also considered. The analysed sample is formed by main-sequence FGK
ﬁeld single stars. Apart from the basic stellar parameters, we include the use of dusty discs masses. The main results
show for the ﬁrst time that the dust mass of debris disc stars with planets correlate with metallicity. We conﬁrm thatthese disc dust masses are related to their central stellar masses.
Separately, the masses of stars and those of planets also correlate with metallicity. We conclude that two conditions
are necessary to form giant planets: to have a suﬃcient metallicity and also a suﬃcient protoplanetary mass of gas
and dust. The debris discs masses of stars without giant planets do not correlate with metallicity, because they do
not fulﬁl these two conditions. Concerning lithium, by adopting a stellar model for lithium depletion based on astrong interaction between the star and a protoplanetary disc, we found that in agreement with the model predictions,observations indicate that the main lithium depletion occurs during this initial protoplanetary evolution stage. We
show that the ultimately lithium depletion is independent of the presence or absence of planets and appears to be only
age dependent.
Accepted by MNRAS

http://arxiv.org/pdf/1905.12066

5

Evidence for a circumplanetary disc around protoplanet PDS 70 b
Valentin Christiaens1 , Faustine Cantalloube2 , Simon Casassus3 , Daniel J. Price1 , Olivier Absil4 , Christophe
Pinte1 , Julien Girard5 , Matias Montesinos6,7,8
1

School of Physics and Astronomy, Monash University, VIC 3800, Australia; 2 MPIA, Heidelberg, Germany; 3
Departamento de Astronomia, Universidad de Chile, Santiago, Chile; 4 STAR institute, Université de Liège, Liège,
Belgium; 5 Space Telescope Science Institute, Baltimore, USA; 6 Instituto de Fı́sica y Astronomı́a, Universidad de
Valparaı́so, Chile; 7 CASSACA, National Astronomical Observatories, Beijing, China; 8 Nućleo Milenio de FormaciónPlanetaria, Chile
E-mail contact: valentin.christiaens at monash.edu
We present the ﬁrst observational evidence for a circumplanetary disc around the protoplanet PDS 70 b, based ona new spectrum in the K band acquired with VLT/SINFONI. We tested three hypotheses to explain the spectrum:
Atmospheric emission from the planet with either (1) a single value of extinction or (2) variable extinction, and (3) acombined atmospheric and circumplanetary disc model. Goodness-of-ﬁt indicators favour the third option, suggesting
circumplanetary material contributing excess thermal emission — most prominent at λ >∼ 2.3 µm. Inferred accretion
rates (∼10−7.8–10−7.3 MJ yr−1 ) are compatible with observational constraints based on the Hα and Brγ lines. For
the planet, we derive an eﬀective temperature of 1500–1600 K, surface gravity log(g) ∼ 4.0, radius ∼1.6 RJ , mass12

∼10 MJ , and possible thick clouds. Models with variable extinction lead to slightly worse ﬁts. However, the amplitude<(∆AV >∼ 3 mag) and timescale of variation (∼years) required for the extinction would also suggest circumplanetary
material.
Accepted by ApJL
http://arxiv.org/pdf/1905.06370

Separating extended disc features from the protoplanet in PDS 70 using VLT/SINFONI

6

V. Christiaens1,2,3 , S. Casassus1 , O. Absil2 , F. Cantalloube4 , C. Gomez Gonzalez5 , J. Girard6 , R.
Ramı́rez1 , B. Pairet7 , V. Salinas8 , D.J. Price3 , C. Pinte3,5 , S.P. Quanz9 , A. Jordán10 , D. Mawet11,12 andZ. Wahhaj13
1

Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile; 2 Space sciences, Technologies& Astrophysics Research (STAR) Institute, Université de Liège, Allée du Six Aout̂ 19c, B-4000 Sart Tilman, Belgium; 3 Monash Centre for Astrophysics (MoCA) and School of Physics and Astronomy, Monash University, Clayton
Vic 3800, Australia; 4 Max Planck Institute for Astronomy, Germany; 5 Université Grenoble Alpes, IPAG, F-38000
Grenoble, France; 6 Space Telescope Science Institute, 3700 San Martin Dr. Baltimore, MD 21218, USA; 7 ISPGroup,
ELEN/ICTEAM, UCLouvain, Belgium; 8 Department of Physics and Astronomy, Graduate School of Science andEngineering, Kagoshima University, Japan; 9 Eidgenossische Technische Hochschule Zurich Departement Physik, Institute for Particle Physics and Astrophysics, Zurich, Switzerland; 10 Instituto de Astrofı́sica, Pontiﬁcia Universidad
Católica de Chile, Vicunã Mackenna 4860, 7820436 Macul, Santiago, Chile; 11 Department of Astronomy, California
Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA; 12 Jet Propulsion Laboratory, 4800
Oak Grove Dr., Pasadena, CA 91109, USA; 13 European Southern Observatory, Alonso de Córdova 3107, Vitacura,Santiago, Chile
E-mail contact: Valentin.Christiaens at monash.edu
Transition discs are prime targets to look for protoplanets and study planet-disc interactions. We present VLT/SINFONI
observations of PDS 70, a transition disc with a recently claimed embedded protoplanet. We take advantage of theangular and spectral diversity present in our data for an optimal PSF modeling and subtraction using principal component analysis (PCA). We report the redetection of PDS 70 b, both the front and far side of the outer disc edge, andthe detection of several extended features in the annular gap. We compare spectral diﬀerential imaging applied before(PCA-SADI), and after (PCA-ASDI) angular diﬀerential imaging. Our tests suggest that PCA-SADI better recovers
extended features, while PCA-ASDI is more sensitive to point sources. We adapted the negative fake companion(NEGFC) technique to infer the astrometry of the companion, and derived r = 193.5 ± 4.9 mas and PA = 158.7 ± 3.0
deg. We used both NEGFC and ANDROMEDA to infer the K-band spectro-photometry of the protoplanet, andfound results consistent with recent VLT/SPHERE observations, except for their 2018/02 epoch measurement in the
5 MbK2 ﬁlter. Finally, we derived an upper limit of Ṁb < 1.26 × 10−7 [ MJup][ RRJup] MJup yr−1 for the accretion rate ofb
the companion based on an adaptation of PCA-SADI/PCA-ASDI around the Brγ line.
Accepted by MNRAS
http://arxiv.org/pdf/1905.01860

7Time variability in the bipolar scattered light nebula of L1527 IRS: A possible warped
inner disk
Brian T. Cook1 , John J. Tobin2 , Michael F. Skrutskie3 and Matthew J. Nelson3
1

Leiden Observatory, 2333 CA Leiden, Netherlands; 2 National Radio Astronomy Observatory Charlottesville, VA,
22903, USA; 3 Astronomy Department, University of Virginia Charlottesville, VA, 22901, USA
E-mail contact: cook at strw.leidenuniv.nl
Context. The bipolar outﬂows associated with low-mass protostars create cavities in the infalling envelope. These
cavities are illuminated by the central protostar and inner disk, creating a bipolar scattered light nebula at near-infraredand mid-infrared wavelengths. The variability of the scattered light nebula in both total intensity and intensity as
a function of position in the scattered light nebula can provide important insights into the structure of the inner13

disk that cannot be spatially resolved. Aims. We aim to determine the likelihood that a warped inner disk is theorigin of the surface brightness variability in the bipolar scattered light nebula associated with L1527 IRS. Methods.
We present results from near-IR imaging conducted over the course of seven years, with periods of monthly cadence
monitoring. We used Monte Carlo radiative transfer models to interpret the observations. Results. We ﬁnd a timevarying, asymmetrical brightness in the scattered light nebulae within the outﬂow cavities of the protostar. Starting in
2007, the surface brightnesses of the eastern and western outﬂow cavities were roughly symmetric. Then, in 2009, thesurface brightnesses of the cavities were found to be asymmetric, with a substantial increase in surface brightness anda larger increase in the eastern outﬂow cavity. More regular monitoring was conducted from 2011 to 2014, revealinga rotating pattern of surface brightness variability in addition to a slow change of the eastern and western outﬂow
cavities toward symmetry, but still not as symmetric as observed in 2007. We ﬁnd that an inner disk warp is a feasible
mechanism to produce the rotating pattern of surface brightness variability.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1905.04134.pdf

8

ALMA reveals the magnetic field evolution in the high-mass star forming complex
G9.62+0.19
D. Dall’Olio1, W.H.T. Vlemmings1, M.V. Persson1 , F.O. Alves2 , H. Beuther3 , J.M. Girart4,5 , G. Surcis6 ,J.M. Torrelles4,5 , and H.J. Van Langevelde7,8
1

Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, Observatorievägen 90, 43992 Onsala, Sweden; 2 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstr. 1,
D-85748 Garching, Germany; 3 Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 4Institut de Ciències de l’Espai (ICE, CSIC), Can Magrans, s/n, E-08193 Cerdanyola del Vallès, Catalonia; 5 Institut d’Estudis Espacials de Catalunya (IEEC), E-08034, Barcelona, Catalonia; 6 INAF–Osservatorio Astronomico di
Cagliari, Via della Scienza 5, 09047 Selargius, Italy; 7 Joint Institute for VLBI ERIC, Oude Hoogeveensedijk 4, 7991
PD Dwingeloo, The Netherlands; 8 Sterrewacht Leiden, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The
Netherlands
E-mail contact: daria.dallolio at chalmers.se
Context. The role of magnetic ﬁelds during the formation of high-mass stars is not yet fully understood, and theprocesses related to the early fragmentation and collapse are largely unexplored today. The high-mass star forming
region G9.62+0.19 is a well known source, presenting several cores at diﬀerent evolutionary stages.
Aims. We determine the magnetic ﬁeld morphology and strength in the high-mass star forming region G9.62+0.19,
to investigate its relation to the evolutionary sequence of the cores.
Methods. We use Band 7 ALMA observations in full polarisation mode and we analyse the polarised dust emission.
We estimate the magnetic ﬁeld strength via the Davis-Chandrasekhar-Fermi and the Structure Function methods.
Results. We resolve several protostellar cores embedded in a bright and dusty ﬁlamentary structure. The polarisedemission is clearly detected in six regions. Moreover the magnetic ﬁeld is oriented along the ﬁlament and appears
perpendicular to the direction of the outﬂows. We suggest an evolutionary sequence of the magnetic ﬁeld, and theless evolved hot core exhibits a magnetic ﬁeld stronger than the more evolved one. We detect linear polarisation fromthermal line emission and we tentatively compared linear polarisation vectors from our observations with previous
linearly polarised OH masers observations. We also compute the spectral index, the column density and the mass forsome of the cores.
Conclusions. The high magnetic ﬁeld strength and the smooth polarised emission indicate that the magnetic ﬁeld
could play an important role for the fragmentation and the collapse process in the star forming region G9.62+019 andthat the evolution of the cores can be magnetically regulated. On average, the magnetic ﬁeld derived by the linear
polarised emission from dust, thermal lines and masers is pointing in the same direction and has consistent strength.
Accepted by A&A
http://arxiv.org/pdf/1905.00415

14

9Interaction between Northern Coal Sack in the Cyg OB 7 cloud complex and the multiple super nova remnants including HB 21
Kazuhito Dobashi1 , Tomomi Shimoikura1 , Nobuhiro Endo1 , Chisato Takagi1 , Fumitaka Nakamura2,3 ,Yoshito Shimajiri4 and Jean-Philippe Bernard5
1

Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan; 2National Astronomical Observatory, Miktaka, Tokyo 181-85588, Japan; 3 Department of Astronomical Science, Schoolof Physical Science, SOKENDAI (The Graduate University for Advanced Studies), Osawa, Mitaka, Tokyo 181-85588,
Japan; 4 Laboratoire AIM, CEA/DSM-CNRS-Universit Paris Diderot, IRFU/Service dAstrophysique, CEA Saclay,
91191, Gif-sur-Yvette, France; 5 Universit de Toulouse, Institut de Recherche en Astrophysique et Plantologie, F-31028,
Toulouse cedex 4, France
E-mail contact: dobashi at u-gakugei.ac.jp
We report possible interaction between multiple super nova remnants (SNRs) and Northern Coal Sack (NCS) which isa massive clump (∼ 1000 Mo ) in the Cyg OB 7 cloud complex and is forming a massive Class 0 object. We performed
molecular observations of the 12 CO(J = 1 − 0), 13 CO(J = 1 − 0), and C18 O(J = 1 − 0) emission lines using the
45m telescope at the Nobeyama Radio Observatory, and we found that there are mainly four velocity components
at VLSR ≃ −20, −6, −4, and 10 kms. The −6 and −4 kms components correspond to the systemic velocities of
NCS and the Cygnus OB 7 complex, respectively, and the other velocity components originate from distinct smaller
clouds. Interestingly, there are apparent correlations and anti-correlations among the spatial distributions of the four
components, suggesting that they are physically interacting with one another. On a larger scale, we ﬁnd that a groupof small clouds belonging to the −20 and 10 kms components are located along two diﬀerent arcs around some SNRs
including HB 21 which has been suggested to be interacting with the Cyg OB 7 cloud complex, and we also ﬁnd that
NCS is located right at the interface of the arcs. The small clouds are likely to be the gas swept up by the stellar windof the massive stars which created the SNRs. We suggest that the small clouds aligned along the two arcs recently
encountered NCS and the massive star formation in NCS was triggered by the strong interaction with the small clouds.
Accepted by Publications of the Astronomical Society of Japan
https://arxiv.org/pdf/1905.07395

Cloud-cloud collision in the DR 21 cloud as a trigger of massive star formation

10 Kazuhito Dobashi1, Tomomi Shimoikura1, Shou Katakura1 , Fumitaka Nakamura2,3 and Yoshito Shimajiri4
1

Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan; 2National Astronomical Observatory, Miktaka, Tokyo 181-85588, Japan; 3 Department of Astronomical Science, Schoolof Physical Science, SOKENDAI (The Graduate University for Advanced Studies), Osawa, Mitaka, Tokyo 181-85588,
Japan; 4 Laboratoire AIM, CEA/DSM-CNRS-Universit Paris Diderot, IRFU/Service dAstrophysique, CEA Saclay,
91191, Gif-sur-Yvette, France
E-mail contact: dobashi at u-gakugei.ac.jp

Accepted by Publications of the Astronomical Society of Japan
https://arxiv.org/pdf/1905.07467

11

Discovery of CCS Velocity-Coherent Substructures in the Taurus Molecular Cloud 1
Kazuhito Dobashi1 , Tomomi Shimoikura1,2 , Tetsu Ochiai1 , Fumitaka Nakamura3,4 , Seiji Kameno5 , Izumi
Mizuno6,7,8 and Kotomi Taniguchi4,6,9,10
1

Department of Astronomy and Earth Sciences, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan; 2 Otsuma
Women’s University, Chiyoda-ku, Tokyo, 102-8357, Japan; 3 National Astronomical Observatory of Japan, Mitaka,
Tokyo 181-8588, Japan; 4 The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo
181-0015, Japan; 5 Joint ALMA Observatory, Alonso de Córdova 3107 Vitacura, Santiago, Chilie; 6 Nobeyama Radio
Observatory, National Astronomical Observatory of Japan 462-2 Nobeyama, Minamisaku, Nagano 384-1305, Japan; 7Department of Physics, Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065,
Japan; 8 East Asian Observatory, 660 N. A’ohōkū Place, University Park, Hilo, HI 96720, USA; 9 Virginia Initiativeon Cosmic Origins Fellow; 10 Departments of Astronomy and Chemistry, University of Virginia, Charlottesville, VA
22904, USA
E-mail contact: dobashi at u-gakugei.ac.jp
We present the results of mapping observations toward a nearby starless ﬁlamentary cloud, the Taurus Molecular
Cloud 1 (TMC-1), in the CCS(JN = 43 − 32 , 45.379033 GHz) emission line, using the Nobeyama 45-m telescope. The
map shows that the TMC-1 ﬁlament has a diameter of ∼ 0.1 pc and a length of ∼ 0.5 pc at a distance of 140 pc. The
position-velocity diagrams of CCS clearly indicate the existence of velocity-coherent substructures in the ﬁlament. We
identify 21 substructures that are coherent in the position-position-velocity space by eye. Most of the substructures areelongated along the major axis of the TMC-1 ﬁlament. The line densities of the subﬁlaments are close to the criticalline density for the equilibrium (∼ 17 M⊙ pc−1 for the excitation temperature of 10 K), suggesting that self-gravity
should play an important role in the dynamics of the subﬁlaments.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/1905.12773

12

Revealing the Star-Disk-Jet Connection in GM Aur using Multiwavelength Variability
C. C. Espaillat1 , E. Macı́as1 , J. Hernández2 and C. Robinson1
1

Department of Astronomy & Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue,
Boston, MA 02215, USA; 2 Instituto de Astronomı́a, Universidad Autónoma Nacional de México, Campus Ensenada;MXE-mail contact: cce at bu.edu
Here we analyze the ﬁrst simultaneous X-ray, ultraviolet, optical, infrared, and centimeter observations of a T Tauri
star (TTS). We present three epochs of simultaneous Spitzer and VLA data of GM Aur separated by ∼1 wk. These
data are compared to previously published HST and Chandra observations from which mass accretion rates (Ṁ ) and
X-ray luminosities, respectively, were measured. The mid-infrared emission increases along with Ṁ , and we conclude
that this is due to an increase in the mass in the inner disk. The cm emission, which probes the jet, also appears
to increase as Ṁ increases, and the changes in the cm ﬂux are consistent with the variability in Ṁ assuming the
mass-loss rate is ∼ 10% Ṁ . The 3 cm emission morphology also appears changed compared with observations taken
three years previously, suggesting that for the ﬁrst time, we may be tracking changes in the jet morphology of a TTS.
The X-ray luminosity is constant throughout the three epochs, ruling out variable high-energy stellar radiation as thecause for the increases in the mid-infrared or cm emission. Tying together the multiwavelength variability observed,
we conclude that an increase in the surface density in the inner disk resulted in more mass loading onto the star andtherefore a higher Ṁ , which led to a higher mass-loss rate in the jet. These results stress the importance of coordinatedmultiwavelength work to better understand the star-disk-jet connection.
Accepted by ApJL
https://arxiv.org/pdf/1905.12789

16

Analysis and test of the central-blue-spot infall hallmark

13

R. Estalella1 , G. Anglada2 , A. K. Dı́az-Rodrı́guez2 and J. M. Mayen-Gijon2
1

Departament de Fı́sica Quàntica i Astrofı́sica, Institut de Ciències del Cosmos, Universitat de Barcelona, IEECUB, Martı́ i Franquès, 1, E-08028 Barcelona, Spain.; 2 Instituto de Astrofı́sica de Andalucı́a, CSIC, Glorieta de la
Astronomı́a, s/n, E-18008 Granada, Spain.
E-mail contact: robert.estalella at ub.edu
The infall of material onto a protostar, in the case of optically thick line emission, produces an asymmetry in the blueand red-wing line emissions. For an angularly resolved emission, this translates in a blue central spot in the ﬁrst-ordermoment (intensity weighted velocity) map. An analytical expression for the ﬁrst-order moment intensity as a functionof the projected distance was derived, for the cases of inﬁnite and ﬁnite infall radius. The eﬀect of a ﬁnite angularresolution, which requires the numerical convolution with the beam, was also studied. This method was applied toexisting data of several star-forming regions, namely G31.41+0.31 HMC, B335, and LDN 1287, obtaining good ﬁts tothe ﬁrst-order moment intensity maps, and deriving values of the central masses onto which the infall is taking place(G31.41+0.31 HMC: 70–120 M⊙ ; B335: 0.1 M⊙ ; Guitar Core of LDN 1287: 4.8 M⊙ ). The central-blue-spot infall
hallmark appears to be a robust and reliable indicator of infall.
Accepted by Astronomy and Astrophysics
http://arxiv.org/pdf/1904.10737

14High gas/dust size ratio indicating efficient radial drift in the mm-faint CX Tau disk
S. Facchini1 , E. F. van Dishoeck2,3 , C. F. Manara1 , M. Tazzari4 , L. Maud1,3 , P. Cazzoletti2 , G. Rosotti3 ,N. van der Marel5 , P. Pinilla6 and C. J. Clarke4
1

European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany; 2 Max-Planck-Institut für
Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany; 3 Leiden Observatory, Leiden University,
Niels Bohrweg 2, NL-2333 CA Leiden, The Netherlands; 4 Institute of Astronomy, Madingley Road, Cambridge,
CB3 OHA, UK; 5 National Research Council of Canada Herzberg Astronomy and Astrophysics Programs, 5071 West
Saanich Road, Victoria, BC, V9E2E7, Canada; 6 Department of Astronomy/Steward Observatory, The University of
Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
E-mail contact: stefano.facchini at eso.org
The large majority of protoplanetary disks have very compact continuum emission (<∼15 AU) at millimeter wavelengths.
However, high angular resolution observations that resolve these small disks are still lacking, due to their intrinsically
fainter emission compared with large bright disks. In this letter we present 1.3 mm ALMA data of the faint disk(∼ 10 mJy) orbiting the TTauri star CX Tau at a resolution of ∼ 40 mas, ∼ 5 AU in diameter. The millimeter dust
disk is compact, with a 68% enclosing ﬂux radius of 14 AU, and the intensity proﬁle exhibits a sharp drop between 10
and 20 AU, and a shallow tail between 20 and 40 AU. No clear signatures of substructure in the dust continuum areobserved, down to the same sensitivity level of the DSHARP large program. However, the angular resolution does notallow us to detect substructures on the scale of the disk aspect ratio in the inner regions. The radial intensity proﬁleclosely resembles the inner regions of more extended disks imaged at the same resolution in DSHARP, but with norings present in the outer disk. No inner cavity is detected, even though the disk has been classiﬁed as a transition
disk from the spectral energy distribution in the near-infrared. The emission of 12 CO is much more extended, with a
68% enclosing ﬂux radius of 75 AU. The large diﬀerence of the millimeter dust and gas extents (> 5) strongly points
to radial drift, and closely matches the predictions of theoretical models.
Accepted by A&A Letters
https://arxiv.org/pdf/1905.09204

15

Runaways and shells around the CMa OB1 association
B. Fernandes1 , T. Montmerle2 , T. Santos-Silva1 and J. Gregorio-Hetem1
1

Universidade de São Paulo, IAG, Departamento de Astronomia, São Paulo, 05508-090, Brazil; 2 Institut d’Astrophysiquede Paris, 75014, Paris, France
E-mail contact: beatriz.fernandes at iag.usp.br
17

The origin of the arc-shaped Sh 2-296 nebula is still unclear. Mainly due to its morphology, the nebula has beensuggested to be a 0.5 Myr-old supernova remnant (SNR) that could be inducing star formation in the CMa OB1
association. Therefore, this region can be an excellent laboratory for the investigation of the inﬂuence of massive stars
on their surroundings. We aim to show, for the ﬁrst time, that the nebula is part of a large, shell-like structure, which
we have designated the “CMa shell”, enclosing a bubble created by successive supernova (SN) explosions. We identiﬁed
three runaway stars, associated with bow-shock structures, in the direction of the CMa shell and we investigate thepossibility that they have originated in the center of the shell. By analyzing images of the CMa OB1 association
at several wavelengths, we clearly see that the Sh 2-296 nebula is in fact part of a large structure, which can beapproximated by a large (with a diameter of ∼ 60 pc) elliptical shell. Using the recent Gaia-DR2 astrometric data,
we trace back the path of the three runaway stars, in order to ﬁnd their original position in the past, with relation
to the CMa shell. We also revise the heating and ionization of the Sh 2-296 nebula, by comparing the photon budget
provided by the O stars in the region with results from radio observations. We ﬁnd that the runaway stars have likely
been ejected from a Trapezium-like progenitor cluster on three successive SN explosions having taken place ∼ 6, ∼2 and ∼ 1 Myr ago. We also show that the few late-type O stars in the region cannot explain the ionization of theSh 2-296 nebula and other mechanisms need to be at work. We argue that, though we now have evidence for several
SNe events in the CMa OB1 association, the SNe probably played a minor role in triggering star formation in theseclouds. In contrast, the CMa OB1 association, as it is now, likely testiﬁes to the last stages of a star-forming region.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/1906.00113

16

The Astrochemical Impact of Cosmic Rays in Protoclusters I: Molecular Cloud Chemistry
Brandt A. L. Gaches1 , Stella S. R. Offner2 and Thomas G. Bisbas3,4
1

Department of Astronomy, University of Massachusetts - Amherst, Amherst, MA 01003, USA; 2 Department of
Astronomy, The University of Texas at Austin, Austin, TX 78712, USA; 3 I. Physikalisches Institut, Universitat
zu Koln, Zulpicher Strae 77, Germany; 4 Department of Physics, Aristotle University of Thessaloniki, GR-54124
Thessaloniki, Greece
E-mail contact: gaches at gmail.com
We present astrochemical photo-dissociation region models in which cosmic ray attenuation has been fully coupled
to the chemical evolution of the gas. We model the astrochemical impact of cosmic rays, including those accelerated
by protostellar accretion shocks, on molecular clouds hosting protoclusters. Our models with embedded protostars
reproduce observed ionization rates. We study the imprint of cosmic ray attenuation on ions for models with diﬀerent
surface cosmic ray spectra and diﬀerent star formation eﬃciencies. We ﬁnd that abundances, particularly ions, aresensitive to the treatment of cosmic rays. We show the column densities of ions are under predicted by the ‘classic’treatment of cosmic rays by an order of magnitude. We also test two common chemistry approximations used toinfer ionization rates. We conclude that the approximation based on the H+
3 abundance under predicts the ionization
rate except in regions where the cosmic rays dominate the chemistry. Our models suggest the chemistry in dense gas
will be signiﬁcantly impacted by the increased ionization rates, leading to a reduction in molecules such as NH3 andcausing H2 -rich gas to become [C II] bright.
Accepted by ApJ
https://arxiv.org/pdf/1905.02232

17

Star-planet tidal interaction and the limits of gyrochronology
Florian Gallet1 and Philippe Delorme1
1

Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

E-mail contact: ﬂorian.gallet1 at univ-grenoble-alpes.fr
Age estimation techniques such as gyrochronology and magnetochronology cannot be applied to stars that haveexchanged angular momentum with their close environments. This is especially true for a massive close-in planetarycompanion (with a period of a few days or less) that could have been strongly impacted by the rotational evolution of18

the host star, throughout the stellar evolution, through the star-planet tidal interaction.
We show that the interaction of a close-in massive planet with its host star can strongly modify the surface rotation
rate of this latter, in most of the cases associated with a planetary engulfment. In such cases, a gyrochronology
analysis of the star would incorrectly make it appear as rejuvenated, thus preventing us from using this method with
conﬁdence. To try overcome this issue, we proposed the proof of concept of a new age determination technique that
we call the tidal-chronology method, which is based on the observed pair Prot,⋆ -Porb of a given star-planet system.
The gyrochronology technique can only be applied to isolated stars or star-planet systems outside a speciﬁc range ofProt,⋆ -Porb . This region tends to expand for increasing stellar and planetary mass. In that forbidden region, or if any
planetary engulfment is suspected, gyrochronology should be used with extreme caution, while tidal-chronology could
be considered. This technique does not provide a precise age for the system yet; however, it is already an extension of
gyrochronology and could be helpful to determine a more precise range of possible ages for planetary systems composedof a star between 0.3 and 1.2 M⊙ and a planet more massive than 1 Mjup initially located at a few hundredths of aufrom the host star.
Accepted by A&A
https://arxiv.org/pdf/1905.06070

18

Gaia Stellar Kinematics in the Head of the Orion A Cloud: Runaway Stellar Groups
and Gravitational Infall
K. V. Getman1 , E. D. Feigelson1, M. A. Kuhn2 and G. P. Garmire3
1

Pennsylvania State University, University Park, PA 16802, USA; 2 California Institute of Technology, Pasadena, CA
91125, USA; 3 Huntingdon Institute for X-ray Astronomy, Huntingdon, PA 16652, USA
E-mail contact: gkosta at astro.psu.edu
This work extends previous kinematic studies of young stars in the Head of the Orion A cloud (OMC-1/2/3/4/5). It
is based on large samples of infrared, optical, and X-ray selected pre-main sequence stars with reliable radial velocities
and Gaia-derived parallaxes and proper motions. Stellar kinematic groups are identiﬁed assuming they mimic the
motion of their parental gas. Several groups are found to have peculiar kinematics: the NGC 1977 cluster and twostellar groups in the Extended Orion Nebula (EON) cavity are caught in the act of departing their birthplaces. The
abnormal motion of NGC 1977 may have been caused by a global hierarchical cloud collapse, feedback by massive
Ori OB1ab stars, supersonic turbulence, cloud-cloud collision, and/or slingshot eﬀect; the former two models arefavored by us. EON groups might have inherited anomalous motions of their parental cloudlets due to small-scale‘rocket eﬀects’ from nearby OB stars. We also identify sparse stellar groups to the east and west of Orion A that are
drifting from the central region, possibly a slowly expanding halo of the Orion Nebula Cluster. We conﬁrm previously
reported ﬁndings of varying line-of-sight distances to diﬀerent parts of the cloud’s Head with associated diﬀerencesin gas velocity. Three-dimensional movies of star kinematics show contraction of the groups of stars in OMC-1 andglobal contraction of OMC-123 stars. Overall, the Head of Orion A region exhibits complex motions consistent withtheoretical models involving hierarchical gravitational collapse in (possibly turbulent) clouds with OB stellar feedback.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/1905.10251

19

Modelling the Spatial Distribution and Origin of CO Gas in Debris Disks
A.S. Hales1,2 , Uma Gorti3,4 , John M. Carpenter1,2 , Meredith Hughes5 , and Kevin Flaherty6,5
1
Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura 7630355, Santiago, Chile; 2 National Radio
Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475, United States of America; 3 NASA
Ames Research Center, MS 245-3, Moﬀett Field, CA 94035-1000; 4 SETI Institute, Mountain View, CA 94043; 5Wesleyan University, Van Vleck Observatory, 96 Foss Hill Dr, Middletown, CT 06459; 6 Department of Astronomy
and Department of Physics Williams College, Williamstown, MA 01267 USA

E-mail contact: ahales at alma.cl

planetary phase, or released by the collision of secondary bodies. In this paper we analyze ALMA observations at
1′′ –1.′′ 5 resolution of three debris disks where the 12 CO (2–1) rotational line was detected: HD131835, HD138813, andHD156623. We apply the iterative Lucy-Richardson deconvolution technique to the problem of circumstellar disks
to derive disk geometries and surface brightness distributions of the gas. The derived disk parameters are used as
input for thermochemical models to test both primordial and cometary scenarios for the origin of the gas. We favor asecondary origin for the gas in these disks and ﬁnd that the CO gas masses (∼3 × 10−3 M⊕ ) require production rates(∼5 × 10−7 M⊕ yr−1 ) similar to those estimated for the bona-ﬁde gas rich debris disk β Pic.
Accepted by ApJ
http://arxiv.org/pdf/1905.03844

20

Dust Polarization in Four Protoplanetary Disks at 3 mm: Further Evidence of Multiple
Origins
Rachel E. Harrison1 , Leslie W. Looney1 , Ian W. Stephens2 , Zhi-Yun Li3 , Haifeng Yang3,4 , Akimasa
Kataoka5 , Robert J. Harris1,6 , Woojin Kwon7,8 , Takayuki Muto9 and Munetake Momose10
1Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W. Green St., Urbana, IL 61801,
USA; 2 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA; 3 Departmentof Astronomy, University of Virginia, Charlottesville, VA 22903, USA; 4 Institute for Advanced Study, Tsinghua
University, Beijing, 100084, Peoples Republic of China; 5 7

21

(AJ >∼ 0.3 mag), which may indicate dust evolution eﬀect. If we apply this nonlinear relation to the NH model (i.e.,
NH ≈ τ353 1/1.2 ) allowing arbitrary τHI , the model curve reproduces well the WHI –τ353 scatter correlation, suggesting
optically thick HI (τHI ∼ 1.3) extended around the molecular clouds. Based on the correlations between the CO
integrated intensity and the NH model, we have then derived the CO-to-H2 conversion factor (XCO ) on ∼1.5◦ scales(corresponding to ∼4 persec) and found spatial variations of XCO ∼ (0.5–3) × 1020 cm−2 K−1 km−1 s across the cloudcomplex, possibly depending on the radiation ﬁeld inside or surrounding the molecular clouds. These gas properties
found in the Chamaeleon region are discussed through a comparison with other local molecular cloud complexes.
Accepted by ApJ
http://arxiv.org/pdf/1905.04184

22

APEX Millimeter Observations of Methanol Emission Toward High-Mass Star-Forming
Cores
Vicente Hernández-Hernández1 , Stan Kurtz1 , Sergei Kalenskii2, Polina Golysheva2 , Guido Garay3 ,Luis Zapata1 and Per Bergman4
1

Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, Apdo. Postal 372 (Xangari),
58090 Morelia, Michoacán, México; 2 Astro Space Center, Lebedev Physical Institute, Russian Academy of Sciences;3
Departamento de Astronomı́a, Universidad de Chile, Camino del Observatorio 1515, Las Condes, Santiago, Chile; 4
Dept of Space, Earth and Environment, Chalmers Univ. of Technology, Onsala Space Observatory, SE-43992 Onsala,SwedenE-mail contact: s.kurtz at irya.unam.mx
We present 247-GHz molecular line observations of methanol (CH3 OH) toward sixteen massive star-forming regions,using the APEX telescope with an angular resolution of 25′′ . The sample covers a range of evolutionary states,
including warm molecular cores, hot molecular cores, and ultracompact HII regions. The hot cores, all of which
include UC HII regions, show rich molecular line spectra, although the strength of diﬀerent species and transitions
varies from source to source. In contrast, the warm cores do not show signiﬁcant molecular line emission. Multiple
methanol transitions are detected toward nine of the hot cores; eight of these had enough transitions to use the rotation
diagram method to estimate rotational temperatures and column densities. The temperatures lie in the range 104–168
K and column densities from 3 × 1016 to 7 × 1018 cm−2 . Using the average methanol line parameters, we estimate
virial masses, which fall in the range from 145 to 720 M⊙ and proved to be signiﬁcantly higher than the measured
gas masses. We discuss possible scenarios to explain the chemical diﬀerences between hot cores and warm molecularcores. One of the observed methanol lines, 42 –51 A+ at 247.228 GHz, is predicted to show class II maser emission,
similar in intensity to previously reported J0 –J−1 E masers at 157 GHz. We did not ﬁnd any clear evidence for maser
emission among the observed sources; however, a weak maser in this line may exist in G345.01+1.79.
Accepted by AJ
http://arxiv.org/pdf/1905.03230

23

Investigating the Efficiency of Explosion Chemistry as a Source of Complex Organic
Molecules in TMC-1
Jonathan Holdship1, Jonathan Rawlings1 , Serena Viti1 , Nadia Balucani2 , Dimitrios Skouteris3 , andDavid Williams1
1

Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT; 2 Dipartimento
di Chimica, Universita‘ di Perugia, Via Elce di Sotto, 8 I-06123 Perugia, Italy; 3 Scuola Normale Superiore, Piazza
dei Cavalieri 7, I-56126 Pisa, Italy
E-mail contact: jrh at star.ucl.ac.uk
Many species of complex organic molecules (COMs) have been observed in several astrophysical environments but it
is not clear how they are produced, particularly in cold, quiescent regions. One process that has been proposed as ameans to enhance the chemical complexity of the gas phase in such regions is the explosion of the ice mantles of dust
grains. In this process, a build up of chemical energy in the ice is released, sublimating the ices and producing a short
lived phase of high density, high temperature gas. The gas-grain chemical code UCLCHEM has been modiﬁed to treat
21

these explosions in order to model the observed abundances of COMs towards the TMC-1 region. It is found that,based on our current understanding of the explosion mechanism and chemical pathways, the inclusion of explosions
in chemical models is not warranted at this time. Explosions are not shown to improve the model’s match to theobserved abundances of simple species in TMC-1. Further, neither the inclusion of surface diﬀusion chemistry, nor
explosions, results in the production of COMs with observationally inferred abundances.
Accepted by ApJ
http://arxiv.org/pdf/1905.01901

24

Nobeyama 45-m Mapping Observations toward Orion A. II. Classification of Cloud
Structures and Variation of the 13 CO/C18 O Abundance Ratio due to far-UV Radiation
Shun Ishii1 , Fumitaka Nakamura1,2,3 , Yoshito Shimajiri4 , Ryohei Kawabe1,2,3 , Takashi Tsukagoshi1 ,Kazuhito Dobashi5 and Tomomi Shimoikura5
1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 The Graduate
University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 The Universityof Tokyo, 7-3-1 Hongo Bunkyo, 113-0033 Tokyo, Japan; 4 Laboratoire AIM, CEA/DSM-CNRS-Universite? Paris
Diderot, IRFU/Service d Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France; 5 Department of Astronomy and
Earth Sciences, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501, Japan
E-mail contact: shun.ishii at nao.ac.jp
We present results of classiﬁcation of cloud structures toward Orion A Giant Molecular Cloud based on wide-ﬁeld 12 CO(J = 1–0), 13 CO (J = 1–0), and C18 O (J = 1–0) observations using the Nobeyama 45 m radio telescope. We identiﬁed
78 clouds toward Orion A applying Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES)
to the data cube of the column density of 13 CO. Well-known subregions such as OMC-1, OMC-2/3, OMC-4, OMC-5,
NGC1977, L1641-N, and Dark lane south ﬁlament (DLSF) are naturally identiﬁed as distinct structures in Orion A.
These clouds also can be classiﬁed into 3 groups: the integral-shaped ﬁlament, the southern regions of Orion A, andthe other ﬁlamentary structures in the outer parts of Orion A and DLSF. These groups show diﬀerences in scaling
relations between the physical properties of the clouds. We derived the abundance ratio between 13 CO and C18 O,
X13 mathrmCO /XmathrmC 18 mathrmO , which ranges from 5.6 to 17.4 on median over the individual clouds. The signiﬁcantvariation of X13 mathrmCO /XmathrmC 18 mathrmO is also seen within a cloud in both of the spatial and velocity directions
and the ratio tends to be high at the edge of the cloud. The values of X13 mathrmCO /XmathrmC 18 mathrmO decrease from17 to 10 with the median of the column densities of the clouds at the column density of NmathrmC 18 O gtrsim1times1015
cm−2 or visual extinction of AV gtrsim3 mag under strong FUV environment of G0 > 103 , whereas it is almost
independent of the column density in the weak FUV radiation ﬁeld. textcolorredThese results are explained if theselective photodissociation of C18 O is enhanced under strong FUV environment and it is suppressed in the dense partof the clouds.
Accepted by PASJ

25

The Milky Way Project Second Data Release: Bubbles and Bow Shocks
Tharindu Jayasinghe1 , Don Dixon2 , Matthew S. Povich3 , Breanna Binder3 , Jose Velasco3 , Denise M.
Lepore3 , Duo Xu4 , Stella Offner4 , Henry A. Kobulnicky5 , Loren D. Anderson6 , Sarah Kendrew7 andRobert J. Simpson8
1

Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USA; 2
Vanderbilt University, Department of Physics and Astronomy, 6301 Stevenson centre Lane, Nashville TN, 37235,
USA; 3 Department of Physics and Astronomy, California State Polytechnic University Pomona, 3801 West Temple
Avenue, Pomona CA 91768, USA; 4 Department of Astronomy, The University of Texas at Austin, Austin, TX 78712,
USA; 5 Department of Physics & Astronomy, University of Wyoming, Dept 3905, Laramie, WY 82070-1000, USA; 6
Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506, USA; 7 European Space
Agency, Space efound through automated processes. The Milky Way Project (MWP), a citizen science initiative on the Zooniverse
platform, presents internet users with infrared (IR) images from Spitzer Space Telescope Galactic plane surveys. MWP
volunteers make classiﬁcation drawings on the images to identify targeted classes of astronomical objects. We present
the MWP second data release (DR2) and an updated data reduction pipeline written in Python. We aggregate ∼3
million classiﬁcations made by MWP volunteers during the years 2012–2017 to produce the DR2 catalogue, whichcontains 2600 IR bubbles and 599 candidate bow-shock driving stars. The reliability of bubble identiﬁcations, asassessed by comparison to visual identiﬁcations by trained experts and scoring by a machine-learning algorithm,
is found to be a signiﬁcant improvement over DR1. We assess the reliability of IR bow shocks via comparison toexpert identiﬁcations and the colours of candidate bow-shock driving stars in the 2MASS point-source catalogue.
We hence identify highly-reliable subsets of 1394 DR2 bubbles and 453 bow-shock driving stars. Uncertainties onobject coordinates and bubble size/shape parameters are included in the DR2 catalog. Compared with DR1, the DR2
bubbles catalogue provides more accurate shapes and sizes. The DR2 catalogue identiﬁes 311 new bow shock driving
star candidates, including three associated with the giant H ii regions NGC 3603 and RCW 49.
Accepted by MNRAS
https://arxiv.org/pdf/1905.12625

26

When the tale comes true: multiple populations and wide binaries in the Orion Nebula
Cluster
Tereza Jerabkova1,2,3 , Giacomo Beccari1 , Henri M.J. Boffin1 , Monika G. Petr-Gotzens1 , Carlo F.
Manara1 , Pier Giorgio Prada Moroni4,5 , Emanuele Tognelli4,5 , and Scilla Degl’Innocenti4,51European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München; 2 Helmholtz Institutfür Strahlen und Kernphysik, Universität Bonn, Nussallee 14–16, 53115 Bonn, Germany; 3 Astronomical Institute,Charles University in Prague, V Holesovickách 2, CZ-180 00 Praha 8, Czech Republic; 4 Department of Physics “E.
Fermi”, University of Pisa, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy; 5 INFN, Sezione di Pisa, Largo Bruno
Pontecorvo 3, I-56127 Pisa, Italy
E-mail contact: tjerabkova at gmail.com
The high-quality OmegaCAM photometry of the 3×3 deg around the Orion Nebula Cluster (ONC) in r, and i ﬁlters
by Beccari et al. (2017) revealed three well-separated pre-main sequences in the color-magnitude diagram (CMD).
The objects belonging to the individual sequences are concentrated towards the center of the ONC. The authors
concluded that there are two competitive scenarios: a population of unresolved binaries and triples with an exotic
mass ratio distribution, or three stellar populations with diﬀerent ages. We use Gaia DR2 in combination with thephotometric OmegaCAM catalog to test and conﬁrm the presence of the putative three stellar populations. We also
study multiple stellar systems in the ONC for the ﬁrst time using Gaia DR2. We conﬁrm that the second and third
sequence members are more centrally concentrated towards the center of the ONC. In addition we ﬁnd an indicationthat the parallax and proper motion distributions are diﬀerent among the members of the stellar sequences. The age
diﬀerence among stellar populations is estimated to be 1–2 Myr. We use Gaia measurements to identify and remove as
many unresolved multiple system candidates as possible. Nevertheless we are still able to recover two well-separated
sequences with evidence for the third one, supporting the existence of the three stellar populations. We were able toidentify a substantial number of wide binary objects (separation between 1000–3000 au). This challenges previously
inferred values that suggested no wide binary stars exist in the ONC. Our inferred wide-binary fraction is ≈ 5%.
We conﬁrm the three populations correspond to three separated episodes of star formation. Based on this result, weconclude that star formation is not happening in a single burst in this region.
Accepted by A&A
http://arxiv.org/pdf/1905.06974

27

The two magnetic components in the Herbig Ae SB2 system HD 104237
S.P. Järvinen1 , T.A. Carroll1 , S. Hubrig1 , I. Ilyin1 , M. Schöller2 , N.A. Drake3,4 and M.A. Pogodin5
1

Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany; 2 European Southern Observatory, Karl-Schwarzschild-Str 2, 85748 Garching, Germany; 3 Laboratory of Observational Astrophysics,
Saint Petersburg State University, Universitetsky pr. 28, 198504 Saint Petersburg, Russia; 4 Laboriteório Nacionalde Astrofsica /MCTIC, Rua Estados Unidos, 154, CEP 37504-364, Itajubá, MG, Brazil; 5 Central Astronomical
23

Observatory at Pulkovo, Pulkovskoye chaussee 65, 196140 Saint Petersburg, Russia
E-mail contact: sjarvinen at aip.de
We present longitudinal magnetic ﬁeld measurements <Bz> for the Herbig Ae primary and the T Tauri secondary in
the SB2 system HD 104237. These measurements were carried out using high spectral resolution observations obtainedwith the High Accuracy Radial velocity Planet Searcher in polarimetric mode, installed at the ESO La Silla 3.6 m
telescope. In agreement with previous studies of Herbig Ae stars, the longitudinal magnetic ﬁeld in the primary israther weak, ranging from 47 to 72 G. The secondary component possesses a variable, much stronger magnetic ﬁeld,
up to 600 G, as expected for a magnetically active T Tauri star. We estimated the rotation period of the primary,Prot = 4.33717±0.00316 d (=104± 0.08 h), from metal line equivalent width variations.
Accepted by MNRAS
https://arxiv.org/pdf/1905.05586.pdf

28

ALMA Observations of the rho Ophiuchus B2 Region: I. Molecular Outflows and Their
Driving Sources
Takeshi Kamazaki1 , Fumitaka Nakamura1,2,3 , Ryohei Kawabe1,2,3 , Chihomi Hara3 , Shigehisa Takakuwa4 ,Naomi Hirano5 , James Di Francesco6 , Rachel Friesen7 and Motohide Tamura3
1

National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan; 2 The Graduate University for Advanced
Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 Department of Astronomy, Graduate Schoolof Science, The University of Tokyo, Tokyo 113-0033, Japan; 4 Department of Physics and Astronomy, Graduate
School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan;
5
Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 6 NRC Herzberg
Inst of Astrophysics, 5071 W Saanich Rd, Victoria BC V9E 2E7, British Columbia, Canada; 7 Dunlap Institute for
Astronomy and Astrophysics, the University of Toronto, 50 St George St, Toronto ON M5S 3H4, Canada
E-mail contact: kamazaki.takeshi at nao.ac.jp
We present the results of ALMA mosaic observations of dust continuum and 12 CO (J = 2 − 1), 13 CO (J = 2 − 1) and
C18 O (J = 2 − 1) molecular lines toward the rho Ophiuchus B2 region. The 1.3-mm dust-continuum image made fromthe combined 12-m and 7-m Array data reveals not only the dense cores identiﬁed by past single-dish observations, butalso their detailed internal substructures. The 12 CO (J = 2 − 1) images show very complex structures of protostellar
outﬂows. They suggest that the gigantic outﬂow lobes in Oph B2 are presumably driven at least by two protostars,
EL 32 and EL 33. We do not detect clear high velocity components associated with the Class I protostar SST c2d
J162730.9-242733 and the Flat Spectrum object SSTc2d J162721.8-242727. In addition, we ﬁnd interesting striations
with 15arcsec (approx 2000 au) separations in both the 12 CO and 13 CO channel maps. The CO striations appear to
be roughly parallel to the magnetic ﬁeld direction, and we speculate that the directions of the striations may follow
the magnetic ﬁeld in the envelope of Oph B2.
Accepted by ApJ

29

Extremely Dense Cores Associated with Chandra Sources in Ophiuchus A: Forming
Brown Dwarfs Unveiled?
Ryohei Kawabe1 , Chihomi Hara2 , Fumitaka Nakamura1 , Kazuya Saigo1 , Takeshi Kamazaki1 , Yoshito
Shimajiri3 , Kengo Tomida4 , Shigehisa Takayuwa5 , Yohko Tsuboi6 , Masahiro N Machida7 , James Di
Francesco8 , Rachel Friesen9 , Naomi Hirano10 , Yumiko Oasa11 , Motohide Tamura2 , Yoichi Tamura12 ,Takashi Tsukagoshi1 and David Wilner13
1

National Astronomical Observatory, Mitaka, Tokyo 181-8588, Japan; 2 Department of Astronomy, School of Science,
University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan; 3 Laboratoire AIM, CEA/DSM-CNRS-Universit Paris Diderot,
IRFU/Service d’Astrophysique, CEA, Saclay, F-91191 Gif-sur-Yvette, France; 4 Department of Earth and Space
Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; 5 Department of Physics and Astronomy, Graduate
School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan;
6
Department of Physics, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 1128551, Japan; 7 Department of Earth and Planetary Science, Faculty of Science, Kyushu University, Hakozaki 6-10-1,

24

Higashi-ku, Fukuoka, 812-8581, Japan; 8 NRC Herzberg Inst of Astrophysics, 5071 W Saanich Road, Victoria, BC V9E
2E7, British Columbia, Canada; 9 North American ALMA Science Center, National Radio Astronomy Observatory,
520 Edgemont Road, Charlottesville, VA 22903; 10 Academia Sinica Institute of Astronomy and Astrophysics, P.O.
Box 23-141, Tapei 10617, Taiwan; 11 Faculty of Education, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama
338-8570, Japan; 12 Division of Particle and Astrophysical Science, Graduate School of Science, Nagoya University,
Aichi 464-8602, Japan; 13 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138,
USA
E-mail contact: ryo.kawabe at nao.ac.jp
On the basis of various data such as ALMA, JVLA, Chandra, it Herschel, and it Spitzer, we conﬁrmed that two
protostellar candidates in Oph-A are bona ﬁde protostars or proto-brown dwarfs (proto-BDs) in extremely early
evolutionary stages. Both objects are barely visible across infrared (IR, i.e., near-IR to far-IR) bands. The physicalnature of the cores is very similar to that expected in ﬁrst hydrostatic cores (FHSCs), objects theoretically predictedin the evolutionary phase prior to stellar core formation with gas densities of sim 1011−12 cm−3 . This suggests thatthe evolutionary stage is close to the FHSC formation phase. The two objects are associated with faint X-ray sources,
suggesting that they are in very early phase of stellar core formation with magnetic activity. In addition, we found the
CO outﬂow components around both sources which may originate from the young outﬂows driven by these sources.
The masses of these objects are calculated to be sim0.01 − 0.03 Modot from the dust continuum emission. Their
physical properties are consistent with that expected from the numerical model of forming brown dwarfs. These facts(the X-ray detection, CO outﬂow association, and FHSC-like spectral energy distributions) strongly indicate that thetwo objects are proto-BDs or will be in the very early phase of protostars which will evolve more massive protostars
if they gain enough mass from the surroundings. The ages of these two objects are likely to be within sim103 years
after the protostellar core (or second core) formation, taking into account the outﬂow dynamical times (lesssim 500
yrs).
Accepted by ApJ
http://arxiv.org/pdf/1810.00573

30

Streaming Instability for Particle-Size Distributions
Leonardo Krapp1 , Pablo Benı́tez-Llambay1 , Oliver Gressel1,2 , Martin E. Pessah1
1

Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark; 2
Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
E-mail contact: krapp at nbi.ku.dk
The streaming instability is thought to play a central role in the early stages of planet formation by enabling theeﬃcient bypass of a number of barriers hindering the formation of planetesimals. We present the ﬁrst study exploring
the eﬃciency of the linear streaming instability when a particle-size distribution is considered. We ﬁnd that, for a given
dust-to-gas mass ratio, the multi-species streaming instability grows on timescales much longer than those expected
when only one dust species is involved. In particular, distributions that contain close-to-order-unity dust-to-gas mass
ratios lead to unstable modes that can grow on timescales comparable, or larger, with those of secular instabilities.
We anticipate that processes leading to particle segregation and/or concentration can create favourable conditions
for the instability to grow fast. Our ﬁndings may have important implications for a large number of processes inprotoplanetary disks that rely on the streaming instability as usually envisioned for a unique dust species. Our results
suggest that the growth rates of other resonant-drag-instabilities may also decrease considerably when multiple species
are considered.
Accepted by ApJL
http://arxiv.org/pdf/1905.13104

31

Magnetic activity of the young solar analogue V1358 Ori
L. Kriskovics1 , Zs. Kövári1 , K. Vida1 , K. Oláh1 , T.A. Carroll2 , and T. Granzer2
1

Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Budapest, Hungary; 2 Leibniz Institutefor Astrophysics (AIP), Potsdam, Germany
25E-mail contact: kriskovics.levente at csfk.mta.hu
Young, fast rotating single stars can show dramatically diﬀerent magnetic signatures and levels of magnetic activity
as compared with the Sun. While losing angular momentum due to magnetic breaking and mass loss through stellar
winds, the stars gradually spin down resulting in decreasing levels of activity. Studying magnetic activity on such solar
analogues plays a key role in understanding the evolution of solar-like stars and allows a glimpse into the past of the Sun
as well. In order to widen our knowledge of the magnetic evolution of the Sun and solar-like stars, magnetic activity of
the young solar analogue V1358 Ori is investigated. Fourier analysis of long-term photometric data is used to derive
rotational period and activity cycle length, while spectral synthesis is applied on high resolution spectroscopic data inorder to derive precise astrophysical parameters. Doppler imaging is performed to recover surface temperature maps
for two subsequent intervals. Cross-correlation of the consecutive Doppler maps is used to derive surface diﬀerential
rotation. The rotational modulation of the chromospheric activity indicators is also investigated. An activity cycleof ≈1600 days is detected for V1358 Ori. Doppler imaging revealed a surface temperature distribution dominatedby a large polar cap with a few weaker features around the equator. This spot conﬁguration is similar to othermaps of young solar analogues from the literature, and supports recent model predictions. We detected solar-likesurface diﬀerential rotation with a surface shear parameter of α = 0.016 ± 0.010 which ﬁts pretty well to our recently
proposed empirical relation between rotation and diﬀerential rotation. The chromospheric activity indicators showeda rotational modulation.
Accepted by A&A
http://arxiv.org/pdf/1905.08259

32

Magnetic field structure in Serpens South
Takayoshi Kusune1 , Fumitaka Nakamura1,2,3 , Koji Sugitani4 , Shuji Sato5 , Motohide Tamura3 , Jungmi
Kwon6 , Kazuhito Dobashi7 , Tomomi Shimoikura7 and Benjamin Wu1
1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 The Graduate
University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of
Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; 4 Graduate School of Natural
Sciences, Nagoya City University, Mizuho-ku, Nagoya, Aichi 467-8501, Japan; 5 Department of Astrophysics, Nagoya
University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; 6 Institute of Space and Astronautical Science, Japan
Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan; 7 Departmentof Astronomy and Earth Science, Tokyo Gakugei University, Koganei, Tokyo 184-8501, Japan
E-mail contact: takayoshi.kusune at nao.ac.jp
We made near-infrared polarimetric observations toward Serpens South. This region contains three dense ﬁlamentsthat are roughly parallel to one another. Using the histogram of relative orientations, the three ﬁlaments are foundto be roughly perpendicular to the global magnetic ﬁeld. The morphology of the plane-of-sky (POS) magnetic ﬁeld
and molecular gas suggests that the magnetic ﬁeld plays an important role in the ﬁlament formation and evolution.
Applying the Davis-Chandrasekhar-Fermi method, the POS magnetic ﬁeld strengths are estimated to be 30–140 >muG. The estimated magnetic ﬁeld strengths indicate that the ﬁlaments are close to magnetically critical. Since
pretellar and protostellar cores already formed along the ﬁlaments, the magnetic diﬀusion such as a ambipolar diﬀusion
and turbulence reconnection is likely to play an important role in the formation of dense cores. We speculate that theﬁlaments are formed by fragmentation of a sheet-like cloud that was created through the gravitational contraction ofa magnetized, turbulent cloud.
Accepted by PASJ33

A SiO J = 5→4 Survey Toward Massive Star Formation Regions
Shanghuo Li1,2,3 , Junzhi Wang1,4 , Min Fang5 , Qizhou Zhang2 , Fei Li1,3 , Zhi-Yu Zhang6,7 , Juan Li1 ,Qingfeng Zhu8 , and Shaoshan Zeng91

Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China; 2Center for Astrophysics — Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; 3 University ofChinese Academy of Sciences, 19A Yuquanlu, Beijing 100049, China; 4 Key Laboratory of Radio Astronomy, Chinese

26

Academy of Sciences, 210008, Nanjing, China; 5 Department of Astronomy and Steward Observatory, University of
Arizona, 933 N Cherry Ave., Tucson, AZ 85721, USA; 6 Institute for Astronomy, University of Edinburgh, Blackford
Hill, Edinburgh, EH9 3HJ, UK; 7 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching,
Germany; 8 Astronomy Department, University of Science and Technology, Chinese Academy of Sciences, Hefei 210008,
China; 9 School of Physics and Astronomy, Queen Mary University of London, Mile End Road, E1 4NS London, UK
E-mail contact: shanghuo.li at gmail.com
We performed a survey in the SiO J = 5→4 line toward a sample of 199 Galactic massive star-forming regions at
diﬀerent evolutionary stages with the SMT 10 m and CSO 10.4 m telescopes. The sample consists of 44 infrared darkclouds (IRDCs), 86 protostellar candidates, and 69 young Hii regions. We detected SiO J = 5→4 line emission in
102 sources, with a detection rate of 57%, 37%, and 65% for IRDCs, protostellar candidates, and young Hii regions,
respectively. We ﬁnd both broad line with Full Widths at Zero Power (FWZP) > 20 km s−1 and narrow line emissonsof SiO in objects at various evolutionary stages, likely associated with high-velocity shocks and low-velocity shocks,
respectively. The SiO luminosities do not show apparent diﬀerences among various evolutionary stages in our sample.
We ﬁnd no correlation between the SiO abundance and the luminosity-to-mass ratio, indicating that the SiO abundance
does not vary signiﬁcantly in regions at diﬀerent evolutionary stages of star formation.
Accepted by ApJ
http://arxiv.org/pdf/1905.08359

34

CO Outflow Candidates Toward the W3/4/5 Complex I: The Sample and its Spatial
Distribution
Yingjie Li1,2 , Ye Xu1 , Yan Sun1 , Qing-Zeng Yan1 , Yuehui Ma1,3 and Ji Yang1
1

Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China; 2 University of Science andTechnology of China, Chinese Academy of Sciences, Hefei, Anhui 230026, China; 3 University of the Chinese Academyof Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, Peoples Republic of China
E-mail contact: xuye at pmo.ac.cn
Using the Purple Mountain Observatory Delingha 13.7 m telescope, we conducted a large-scale 12 CO (J = 1–0)
outﬂow survey (over ∼110 deg2 ) toward the W3/4/5 complex and its surroundings. In total, 459 outﬂow candidates
were identiﬁed. Approximately 62% (284) were located in the Perseus arm, including W3/4/5 complex and its
surroundings, while ∼35% (162) were located in the Local arm, ∼1% (5) in the Outer arm, and ∼2% (8) in two
interarm regions. This result indicated that star formation was concentrated in the Galactic spiral arms. The detailed
spatial distribution of the outﬂow candidates showed that the Perseus arm presented the most active star formation
among the study regions. The W3/4/5 complex is a great region to research massive star formation in a triggered
environment. A key region, which has been well-studied by other researches, is in the eastern high-density W3 complex
that neighbors the W4 complex. Two shell-like structures in the Local arm contain candidates that can be used to
study the impact on star formation imposed by massive or intermediate-mass stars in relatively isolated systems. The
majority of outﬂow candidates in the two interarm regions and the Outer arm are located in ﬁlamentary structures.
Accepted by ApJS
http://arxiv.org/pdf/1905.02018

35

The anomalously low (sub)millimeter spectral indices of some protoplanetary disks may
be explained by dust self-scattering
Hauyu Baobab Liu1
1

Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan

E-mail contact: hyliu at asiaa.sinica.edu.tw
Previous (sub)millimeter observations have found that the spectral indices of dust emission from some young stellar
objects are lower than that of the black body emission in the Rayleigh-Jeans limit (i.e., 2.0). In particular, the recent
Atacama Large Millimeter Array observations have spatially resolved that the innermost regions of the protoplanetarydisks TW Hya and HD 163296 present anomalously low (i.e., <2.0) millimeter spectral indices. In some previous works,
27

such anomalously low millimeter spectral indices were considered unphysical and were attributed to measurement
errors. The present work clariﬁes that if the albedo is high and is increasing with frequency, it is possible to reproduce
such anomalously low spectral indices when the emission source is optically thick. In addition, to yield lower than
2.0 spectral index at (sub)millimeter bands, the required dust maximum grain size amax is on the order of 10-100µm, which is well-consistent with the previously derived amax values based on multi-wavelength dust polarimetricobservations. In light of this, measuring Stokes I spectral index may also serve as an auxiliary approach for assessing
whether the observed dust polarization is mainly due to dust scattering or is due to the aligned dust grains.
Accepted by ApJ Letter
http://adsabs.harvard.edu/pdf/2019arXiv190400333L

36

Large-scale periodic velocity oscillation in the filamentary cloud G350.54+0.69
Hong-Li Liu1,2,3 , Amelia Stutz3,4 and Jing-Hua Yuan5
137

Chinese Academy of Sciences South America Center for Astronomy, China-Chile Joint Center for Astronomy, Camino

Accepted by ApJ
http://arxiv.org/pdf/1905.10193

Multiple Rings of Millimeter Dust Emission in the HD 15115 Debris Disk

38 Meredith A. MacGregor1,2 , Alycia J. Weinberger1, Erika R. Nesvold1, A. Meredith Hughes3, D.J.
Wilner4 , Thayne Currie5 , John H. Debes6 , Jessica K. Donaldson1 , Seth Redfield3 , Aki Roberge7 ,Glenn Schneider81

Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington,
DC 20015, USA; 2 NSF Astronomy and Astrophysics Postdoctoral Fellow; 3 Astronomy Department and Van Vleck
Observatory, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459, USA; 4 Harvard-Smithsonian Center
for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA; 5 National Astronomical Observatory of Japan, Subaru
Telescope, National Institutes of Natural Sciences, Hilo, HI 96720, USA; 6 Space Telescope Science Institute, 3700 San
Martin Drive, Baltimore, MD, 21218, USA; 7 Exoplanets and Stellar Astrophysics Lab, NASA Goddard Space Flight
Center, Greenbelt, MD 20771, USA; 8 Steward Observatory, The University of Arizona, 933 North Cherry Avenue,
Tucson, AZ 85721, USA
E-mail contact: mmacgregor at carnegiescience.edu

We present observations of the HD 15115 debris disk from ALMA at 1.3 mm that capture this intriguing system withthe highest resolution (0.′′ 6 or 29 AU) at millimeter wavelengths to date. This new ALMA image shows evidence fortwo rings in the disk separated by a cleared gap. By ﬁtting models directly to the observed visibilities within a MCMC
framework, we are able to characterize the millimeter continuum emission and place robust constraints on the disk
structure and geometry. In the best-ﬁt model of a power law disk with a Gaussian gap, the disk inner and outer edges
are at 43.9±5.8 AU (0.′′ 89±0.′′ 12) and 92.2±2.4 AU (1.′′ 88±0.′′49), respectively, with a gap located at 58.9±4.5 AU(1.′′ 2±0.′′ 10) with a fractional depth of 0.88±0.10 and a width of 13.8±5.6 AU (0.′′ 28±0.′′ 11). Since we do not see any
evidence at millimeter wavelengths for the dramatic east-west asymmetry seen in scattered light, we conclude that
this feature most likely results from a mechanism that only aﬀects small grains. Using dynamical modeling and ourconstraints on the gap properties, we are able to estimate a mass for the possible planet sculpting the gap to be
0.16±0.06 MJup .
Accepted by ApJL
http://arxiv.org/pdf/1905.08258

Identification of Young Stellar Object candidates in the Gaia DR2 x AllWISE catalogue

39 with machine learning methods

G. Marton1 , P. Ábrahám1 , E. Szegedi-Elek1 , J. Varga1 , M. Kun1 , Á Kóspál1,2 , E. Varga-Verebélyi1 , S.
Hodgkin3 , L. Szabados1 , R. Beck4,1 , Cs. Kiss1
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly
Thege Miklós út 15-17, H-1121 Budapest, Hungary; 2 Max Planck Institute for Astronomy, Königstuhl 17, D-69117
Heidelberg, Germany; 3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA,
UK; 4 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA

E-mail contact: marton.gabor at csfk.mta.hu
The second Gaia Data Release (DR2) contains astrometric and photometric data for more than 1.6 billion objects
with mean Gaia G magnitude <20.7, including many Young Stellar Objects (YSOs) in diﬀerent evolutionary stages.
In order to explore the YSO population of the Milky Way, we combined the Gaia DR2 database with WISE and
Planck measurements and made an all-sky probabilistic catalogue of YSOs using machine learning techniques, such as
Support Vector Machines, Random Forests, or Neural Networks. Our input catalogue contains 103 million objects fromthe DR2xAllWISE cross-match table. We classiﬁed each object into four main classes: YSOs, extragalactic objects,
main-sequence stars and evolved stars. At a 90% probability threshold we identiﬁed 1,129,295 YSO candidates. To
demonstrate the quality and potential of our YSO catalogue, here we present two applications of it. (1) We explore
the 3D structure of the Orion A star forming complex and show that the spatial distribution of the YSOs classiﬁed byour procedure is in agreement with recent results from the literature. (2) We use our catalogue to classify published29

Gaia Science Alerts. As Gaia measures the sources at multiple epochs, it can eﬃciently discover transient events,
including sudden brightness changes of YSOs caused by dynamic processes of their circumstellar disk. However, inmany cases the physical nature of the published alert sources are not known. A cross-check with our new catalogue
shows that about 30% more of the published Gaia alerts can most likely be attributed to YSO activity. The catalogue
can be also useful to identify YSOs among future Gaia alerts.
Accepted by MNRAS
http://arxiv.org/pdf/1905.03063

40

Near-Infrared Variability of Low Mass Stars in IC 1396A and TR 37
Huan Y. A. Meng1 , George H. Rieke1 , Jinyoung Serena Kim1 , Aurora Sicilia-Aguilar2 , N. J. G. Cross3 ,Taran Esplin1 , Luisa M. Rebull4 and Klaus W. Hodapp5
1

Steward Observatory, Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ
85721; 2 SUPA, School of Science and Engineering, University of Dundee, Nethergate, Dundee DD1 4HN, UK; 3
Wide-Field Astronomy Unit, Institute for Astronomy, School of Physics and Astronomy, University of Edinburgh,
Royal Obser- vatory, Blackford Hill, Edinburgh EH9 3HJ, UK; 4 Spitzer Science Center, Infrared Processing andAnalysis Cen- ter, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125; 5 Institute for
Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720, USA
E-mail contact: serena00 at email.arizona.edu
We have monitored nearly a square degree in IC 1396A/Tr 37 over 21 epochs extending over 2014 - 2016 for sources
variable in the JHK bands. In our data, 65 ± 8 % of previously identiﬁed cluster members show variations, comparedwith < 0.3% of ﬁeld stars. We identify 119 members of Tr 37 on the basis of variability, forming an unbiased sample
down to the brown dwarf regime. The K-band luminosity function in Tr 37 is similar to that of IC 348 but shiftedto somewhat brighter values, implying that the K- and M-type members of Tr 37 are younger than those in IC 348.
We introduce methods to classify the causes of variability, based on behavior in the color-color and color-magnitude
diagrams. Accretion hot spots cause larger variations at J than at K with substantial scatter in the diagrams; there
are at least a dozen, with the most active resembling EXors. Eleven sources are probably dominated by intervention ofdust clumps in their circumstellar disks with color behavior indicating the presence of grains larger than for interstellar
dust, presumably due to grain growth in their disks. Thirteen sources have larger variations at K than at J or H. For
11 of them, the temperature ﬁtted to the variable component is very close to 2000K, suggesting that the changes in
output are caused by turbulence at the inner rim of the circumstellar disk exposing previously protected populationsof grains.
Accepted by Astrophysical Journal

https://arxiv.org/pdf/1905.01246.pdf

41

On the ALMA observability of nascent massive multiple systems
D. M.-A. Meyer1,2 , A. Kreplin1 , S. Kraus1 , E.I. Vorobyov3,4 , L. Haemmerle5 and J. Eisloeffel6
1

Astrophysics Group, School of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom;Institute of Physics and Astronomy, University of Potsdam, D-14476, Potsdam, Germany; 3 Research Institute ofPhysics, Southern Federal University, Stachki 194, Rostov-on-Don, 344090, Russia; 4 Department of Astrophysics, The
University of Vienna, Vienna, A-1180, Austria; 5 Observatoire de Genève, Université de Genève, chemin des Maillettes
51, CH-1290 Sauverny, Switzerland; 6 Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg,
Germany
2E-mail contact: dmameyer.astro at gmail.com
Massive young stellar object (MYSOs) form during the collapse of high-mass pre-stellar cores, where infalling molecularmaterial is accreted through a centrifugally-balanced accretion disc that is subject to eﬃcient gravitational instabilities. In the resulting fragmented accretion disc of the MYSO, gaseous clumps and low-mass stellar companions canform, which will inﬂuence the future evolution of massive protostars in the Hertzsprung-Russell diagram. We perform dust continuum radiative transfer calculations and compute synthetic images of disc structures modelled by thegravito-radiation-hydrodynamics simulation of a forming MYSO, in order to investigate the Atacama Large Millime30

ter/submillimeter Array (alma) observability of circumstellar gaseous clumps and forming multiple systems. Bothspiral arms and gaseous clumps located at ≃ a few 100 au from the protostar can be resolved by interferometric alma
Cycle 7 C43-8 and C43-10 observations at band 6 (1.2 mm), using a maximal 0.015′′ beam angular resolution and at
least 10-30 min exposure time for sources at distances of 1-2 kpc. Our study shows that substructures are observable
regardless of their viewing geometry or can be inferred in the case of an edge-viewed disc. The observation probabilityof the clumps increases with the gradually increasing eﬃciency of gravitational instability at work as the disc evolves.
As a consequence, large discs around MYSOs close to the zero-age-main-sequence line exhibit more substructures thanat the end of the gravitational collapse. Our results motivate further observational campaigns devoted to the close
surroundings of the massive protostars S255IR-NIRS3 and NGC 6334I-MM1, whose recent outbursts are a probablesignature of disc fragmentation and accretion variability.
Accepted by MNRAS
https://arxiv.org/pdf/1906.02015

42

Variable Stars in Young Open Cluster NGC 2244
G. Michalska1
1

Instytut Astronomiczny, Uniwersytet Wrocawski, Kopernika 11, 51-622 Wroclaw, Poland

E-mail contact: jordan.molet at u-bordeaux.fr
We present results of a U BV Ic variability survey in the young open cluster NGC 2244. In total, we found 245 variable
stars. Most of them, 211 stars, are variables with irregular variations. Furthermore, 23 periodic variables were found.
We also detected four candidates for δ Scuti stars and 7 eclipsing binaries. Based on the mid-infrared Spitzer and
WISE photometry and near infrared JHKs 2MASS photometry we classiﬁed 104 young stellar sources among ourvariables: 1 Class I object, 1 Class I/ﬂat spectrum object, 4 ﬂat spectrum objects, 91 Class II objects and 7 transition
disk objects. This classiﬁcation, together with r′ i′ Hα IPHAS photometry and JHK UKIDSS photometry, were used
for identiﬁcation of pre-main sequence stars among irregular and periodic variables. In this way, 97 CTTS candidates(96 irregular and one periodic variable), 68 WTTS candidates (54 irregular and 14 periodic variables) and 6 Herbig
Ae/Be stars were found. For 223 variable stars we calculated membership probability based on proper motions from
Gaia DR2 catalogue. Majority of them, 143 stars, are cluster members with probability greater than 70 percent. For
only 36 variable stars the membership probability is smaller than 20 percent.
Accepted by MNRAS
http://arxiv.org/pdf/1905.12557

43

On the planetary interpretation of multiple gaps and rings in protoplanetary disks seen
by ALMA
Ryan Miranda1 and Roman R. Rafikov1,21Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540; 2 Centre for Mathematical Sciences, Department
of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA,UK
E-mail contact: miranda at ias.edu
It has been recently suggested that the multiple concentric rings and gaps discovered by ALMA in many protoplanetarydisks may be produced by a single planet, as a result of the complex propagation and dissipation of the multiple
spiral density waves it excites in the disk. Numerical eﬀorts to verify this idea have largely utilized the so-called
locally isothermal approximation with a prescribed disk temperature proﬁle. However, in protoplanetary disks thisapproximation does not provide an accurate description of the density wave dynamics on scales of tens of au. Moreover,
we show that locally isothermal simulations tend to overestimate the contrast of ring and gap features, as well as
misrepresent their positions, when compared to simulations in which the energy equation is evolved explicitly. Thisoutcome is caused by the non-conservation of the angular momentum ﬂux of linear perturbations in locally isothermal
disks. We demonstrate this eﬀect using simulations of locally isothermal and adiabatic disks (with essentially identicaltemperature proﬁles) and show how the dust distributions, probed by mm wavelength observations, diﬀer between thetwo cases. Locally isothermal simulations may thus underestimate the masses of planets responsible for the formation31

of multiple gaps and rings on scales of tens of au observed by ALMA. We suggest that caution should be exercisedin using the locally isothermal simulations to explore planet-disk interaction, as well as in other studies of wave-likephenomena in astrophysical disks.
Accepted by ApJL
http://arxiv.org/pdf/1905.08259

44

An Origin for the Angular Momentum of Molecular Cloud Cores: a Prediction from
Filament Fragmentation
Yoshiaki Misugi1, Shu-ichiro Inutsuka1 and Doris Arzoumanian1,2
1

Department of Physics, Graduate School of Science, Nagoya University, 464-8602 Nagoya, Japan; 2 Centro de
Astroﬁsica da Universidade do Porto, Rua das estrelas, 4150-762 Porto, Portugal
E-mail contact: misugi.yoshiaki at b.mbox.nagoya-u.ac.jp
The angular momentum of a molecular cloud core plays a key role in star formation, since it is directly related to theoutﬂow and the jet emanating from the new-born star and it eventually results in the formation of the protoplanetary
disk. However, the origin of the core rotation and its time evolution are not well understood. Recent observations
reveal that molecular clouds exhibit a ubiquity of ﬁlamentary structures and that star forming cores are associatedwith the densest ﬁlaments. Since these results suggest that dense cores form primarily in ﬁlaments, the mechanism ofcore formation from ﬁlament fragmentation should explain the distribution of the angular momentum of these cores.
In this paper we analyze the relation between velocity ﬂuctuations along the ﬁlament close to equilibrium and theangular momentum of the cores formed along its crest. We ﬁrst ﬁnd that an isotropic velocity ﬂuctuation that follows
the three-dimensional Kolmogorov spectrum does not reproduce the observed angular momentum of molecular cloud
cores. We then identify the need for a large power at small scales and study the eﬀect of three power spectrum
models. We show that the one-dimensional Kolmogorov power spectrum with a slope −5/3 and an anisotropic modelwith reasonable parameters are compatible with the observations. Our results stress the importance of more detailed
and systematic observations of both the velocity structure along ﬁlaments and the angular momentum distribution ofmolecular cloud cores to determine the validity of the mechanism of core formation from ﬁlamentary molecular clouds.
Accepted by the Astrophysical Journal

http://arxiv.org/pdf/1905.08071

45

Molecular analysis of a high-mass prestellar core candidate in W43-MM1
J. Molet1 , N. Brouillet1 , T. Nony2 , A. Gusdorf3,4 , F. Motte2,5 , D. Despois1 , F. Louvet6 , S. Bontemps1 ,and F. Herpin1
1
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoﬀroy Saint-Hilaire, 33615 Pessac, France; 2 Université Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique de Grenoble, F-38000
Grenoble, France; 3 Laboratoire de Physique de l’École normale supérieure, ENS, Université PSL, CNRS, Sorbonne
Université, Université Paris-Diderot, Sorbonne Paris Cité, Paris, France; 4 LERMA, Observatoire de Paris, PSL
Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, 75231 Paris, France; 5 AIM Paris-SaclayDépartement d’Astrophysique, CEA, CNRS, Univ. Paris Diderot, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex, France;
6
Departamento de Astronomia de Chile, Universidad de Chile, Santiago, Chile

E-mail contact: jordan.molet at u-bordeaux.fr
High-mass analogues of low-mass prestellar cores are searched for to constrain the models of high-mass star formation.
Several high-mass cores, at various evolutionary stages, have been recently identiﬁed towards the massive star-forming
region W43-MM1 and amongst them a high-mass prestellar core candidate. We aim to characterise the chemistry
in this high-mass prestellar core candidate, referred to as W43-MM1 core #6, and its environment. Using ALMA
high-spatial resolution data of W43-MM1, we have studied the molecular content of core #6 and a neighbouringhigh-mass protostellar core, referred to as #3, which is similar in size and mass to core #6. We ﬁrst subtracted thecontinuum emission using a method based on the density distribution of the intensities on each pixel. Then, fromthe distribution of detected molecules, we identiﬁed the molecules centred on the prestellar core candidate (core #6)
and those associated to shocks related to outﬂows and ﬁlament formation. Then we constrained the column densities
32

and temperatures of the molecules detected towards the two cores. While core #3 appears to contain a hot corewith a temperature of about 190 K, core #6 seems to have a lower temperature in the range from 20 K to 90 K
from a rotational diagram analysis. We have considered diﬀerent source sizes for core #6 and the comparison of theabundances of the detected molecules towards the core with various interstellar sources shows that it is compatible
with a core of size 1000 au with T = 20–90 K or a core of size 500 au with T ∼ 80 K. Core #6 of W43-MM1 remains
one of the best high-mass prestellar core candidates even if we cannot exclude that it is at the very beginning of the
protostellar phase of high-mass star formation.
Accepted by A&A
http://arxiv.org/pdf/1905.12463

46

Opening the Treasure Chest in Carina
B. Mookerjea1 , G. Sandell2 , R. Guesten3 , D. Riquelme3 , H. Wiesemeyer3 and E. Chambers4
1

Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai, India; 2 Institute for Astronomy, Universityof Hawaii, 640 N. Aohoku Place, Hilo, HI 96720, USA; 3 Max Planck Institut für Radioastronomie, Auf dem Hügel
69, 53121 Bonn, Germany; 4 USRA/SOFIA, NASA Ames Research Center, Mail Stop 232-12, Building N232, P.O.
Box 1, Moﬀett Field, CA 94035-0001, USA
E-mail contact: bhaswati at tifr.res.in
Pillars and globules are the best examples of the impact of the radiation and wind from massive stars on the surrounding
interstellar medium. We mapped the G287.84-0.82 cometary globule (with the Treasure Chest cluster embedded init) in the South Pillars region of Carina (i) in [C ii], 63 µm [O i], and CO(11–10) using the heterodyne receiver array
upGREAT on SOFIA and (ii) in J=2–1 transitions of CO, 13 CO, C18 O, and J=3–2 transitions of H2 CO using the
APEX telescope in Chile. We used these data to probe the morphology, kinematics, and physical conditions of themolecular gas and the photon-dominated regions (PDRs) in G287.84-0.82. The velocity-resolved observations of [C ii]
and [O i] suggest that the overall structure of the pillar (with red-shifted photoevaporating tails) is consistent withthe eﬀect of FUV radiation and winds from η Car and O stars in Trumpler 16. The gas in the head of the pillar isstrongly inﬂuenced by the embedded cluster, whose brightest member is an O9.5 V star, CPD -59◦ 2661. The emissionof the [C ii] and [O i] lines peak at a position close to the embedded star, while all the other tracers peak at anotherposition lying to the northeast consistent with gas being compressed by the expanding PDR created by the embeddedcluster. The molecular gas inside the globule was probed with the J=2–1 transitions of CO and isotopologs as wellas H2 CO, and analyzed using a non-local thermodynamic equilibrium model (escape-probability approach), while weused PDR models to derive the physical conditions of the PDR. We identify at least two PDR gas components; thediﬀuse part (∼104 cm−3 ) is traced by [C ii], while the dense (n ∼2–8 105 cm−3 ) part is traced by [C ii], [O i], andCO(11–10). Using the F =2–1 transition of [13CII] detected at 50 positions in the region, we derived optical depths(0.9–5), excitation temperatures of [C ii] (80–255 K), and N (C+ ) of 0.3–1×1019 cm−2 . The total mass of the globuleis ∼ 1,000 M⊙ , about half of which is traced by [C ii]. The dense PDR gas has a thermal pressure of 107 –108 K cm−3 ,which is similar to the values observed in other regions.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1905.03161

47

Two epoch spectro-imagery of FS Tau B outflow system
T.A. Movsessian1 , T.Yu. Magakian1 and A.N. Burenkov2
1
Byurakan Astrophysical Observatory NAS Armenia, Byurakan, Aragatsotn prov., 0213, Armenia; 2 Special Astrophysical Observatory, N.Arkhyz, Karachaevo-Cherkesia, 369167 Russia

E-mail contact: tigmov at web.am
Herbig-Haro (HH) ﬂows exhibit a large variety of morphological and kinematical structures such as bow shocks, Machdisks, and deﬂection shocks. Both proper motion (PM) and radial velocity investigations are essential to understandthe physical nature of such structures.
We investigate the kinematics and PM of spectrally separated structures in the FS Tau B HH ﬂow. Collating thesedata makes it possible to understand the origin of these structures and to explain the unusual behavior of the jet. On
33

the other hand, the study of emission proﬁles in the associated reﬂection nebulae allows us to consider the source ofthe outﬂow both from edge-on and pole-on points of view.
We present the observational results obtained with the 6 m telescope at the Special Astrophysical Observatory of theRussian Academy of Sciences using the SCORPIO multimode focal reducer with a scanning Fabry-Perot interferometer.
Two epochs of the observations of the FS Tau B region in Hα emission (2001 and 2012) allowed us to measure thePM of the spectrally separated inner structures of the jet.
In addition to already known emission structures in the FS Tau B system, we discover new features in the extended
part of the jet and in the counter-jet. Moreover, we reveal a new HH knot in the HH 276 independent outﬂow
system and point out its presumable source. In the terminal working surface of the jet, structures with diﬀerent radial
velocities have PMs of the same value. This result can be interpreted as the direct observation of bow-shock and Machdisk regions. A bar-like structure, located southwest from the source demonstrates zero PM and can be considered as
one more example of deﬂection shock. An analysis of Hα proﬁles in the reﬂection nebulae R1 and R3 indicates theuniqueness of this object, which can be studied in pole-on and edge-on directions simultaneously.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1906.01016

48

Nobeyama 45-m Mapping Observations toward Nearby Molecular Clouds, Orion A,
Aquila Rift, and M17: Project overview
Fumitaka Nakamura1,2,3 , Shun Ishii1 , Kazuhito Dobashi4 , Tomomi Shimoikura4 , Yoshito Shimajiri5 ,Ryohei Kawabe1,2,3 , Yoshihiro Tanabe6 , Asha Hirose4 , Shuri Oyamada7 , Yumiko Urasawa8 , Hideaki
Takemura1,2 , Takashi Tsukagoshi6 , Munetake Momose6, Koji Sugitani9 , Ryoichi Nishi8 , Sachiko Okumura7 ,Patricio Sanhueza1 , Quang Nygen-Luong10 and Takayoshi Kusune1
1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 The Graduate
University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 Department of
Astronomy, The University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo 113-0033, Japan; 4 Department of Astronomy and
Earth Sciences, Tokyo Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501, Japan; 5 Laboratoire AIM,
CEA/DSM-CN115(r)-61(S)0.928763(-)-4.2603(U)3.21467(n)0.928763(iv)2110062(e)-1.66516(r)-6.48419(s)-3.4847(it)2.55961’s e Par

Nobeyama 45-m Mapping Observations toward Orion A. III. Multi-Line Observations

49 toward an Outflow-shocked Region, OMC-2 FIR 4

Fumitaka Nakamura1,2,3 , Shuri Oyamada4 , Sachiko Okumura4 , Shun Ishii1 , Yoshito Shimajiri5 , Yoshihiro Tanabe6 , Takashi Tsukagoshi1 , Ryohei Kawabe1,2,3 , Mumetake Momose7, Yumiko Urasawa8 , Ryoichi Nishi8 , Sheng-Jun Lin9 , Shih-Ping Lai9 , Kazuhito Dobashi10 , Tomomi Shimoikura10 and Koji
Sugitani11
1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 2 The Graduate
University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 Department of
Astronomy, The University of Tokyo, 7-3-1 Hongo Bunkyo, Tokyo 113-0033, Japan; 4 Faculty of Science, Departmentof Mathematical and Physical Sciences, Japan Women’s University, 2-8-1 Mejirodai, Bunkyo-ku, Tokyo 112-8681,
Japan; 5 Laboratoire AIM, CEA/DSM-CNRS-Universit’ e Paris Diderot, IRFU/Service d’Astrophysique, CEA Saclay,
F-91191 Gif-sur-Yvette, France; 6 College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan;
7
College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan; 8 Department of Physics,
Niigata University, 8050 Ikarashi-2, Niigata 950-2181, Japan; 9 Institute of Astronomy and Department of Physics,
National Tsing Hua University, Hsinchu 30013, Taiwan; 10 Department of Astronomy and Earth Sciences, Tokyo
Gakugei University, 4-1-1 Nukuikitamachi, Koganei, Tokyo 184-8501, Japan; 11 Graduate School of Natural Sciences,
Nagoya City University, Mizuho-ku, Nagoya, Aichi
E-mail contact: fumitaka.nakamura at nao.ac.jp
We present the results of mapping observations toward an outﬂow-shocked region, OMC-2 FIR 4 using the Nobeyama
45-m telescope. We observed the area in 13 CO (J = 1 − 0), C18 O (J = 1 − 0), N2 H+ (J = 1 − 0), CCS (JN = 87 − 76 ),HCO+ (J = 1 − 0), H13 CO+ (J = 1 − 0), HN13 C (J = 1 − 0), H13 CN (J = 1 − 0), DNC (J = 1 − 0), N2 D+ (J = 1 − 0),and DC3 N (J = 9 − 8). We detected a dense molecular clump that contains FIR 4/5. We also detected in 13 CO
blueshifted and redshifted components driven presumably by protostellar outﬂows in this region. The axes of the
FIR 3 and VLA 13 outﬂows, projected on the plane of the sky, appear to point toward the FIR 4 clump, suggestingthat the clump may be compressed by protostellar outﬂows from Class I sources, FIR 3 and VLA 13. Applying thehyperﬁne ﬁt of N2 H+ lines, we estimated the excitation temperature to be sim 20 K. The high excitation temperature
is consistent with the fact that the clump contains protostars. The CCS emission was detected in this region for theﬁrst time. Its abundance is estimated to be a few times10−12, indicating that the region is chemically evolved at
sim105 years, which is comparable to the typical lifetime of the Class I protostars. This timescale is consistent withthe scenario that star formation in FIR 4 is triggered by dynamical compression of the protostellar outﬂows. The[HNC]/[HCN] ratio is evaluated to be sim0.5 in the dense clump and the outﬂow lobes, whereas it is somewhat larger
in the envelope of the dense clump. The small [HNC]/[HCN] ratio indicates that the HNC formation was prevented
due to high temperatures. Such high temperatures seem to be consistent with the scenario that either protostellar
radiation or outﬂow compression, or both, aﬀected the thermal properties of this region.
Accepted by PASJ

Gaia-DR2 distance to the W3 Complex in the Perseus Arm

50 Felipe Navarete1 , Phillip A.B. Galli2 and Augusto Damineli1
1

Universidade de São Paulo, Instituto de Astronomia, Geofı́sica e Ciências Atmosféricas, Rua do Matão, 1226, 05508090, Brazil; 2 Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoﬀroy Saint-Hillaire,
33615 Pessac, France
E-mail contact: navarete at usp.br
The Perseus Arm is the closest Galactic spiral arm from the Sun, oﬀering an excellent opportunity to study indetail its stellar population. However, its distance has been controversial with discrepancies by a factor of two.
Kinematic distances are in the range 3.9–4.2 kpc as compared to 1.9–2.3 kpc from spectrophotometric and trigonometricparallaxes, reinforcing previous claims that this arm exhibits peculiar velocities. We used the astrometric informationof a sample of 31 OB stars from the star-forming W3 Complex to identify another 37 W3 members and to derive
its distance from their Gaia-DR2 parallaxes with improved accuracy. The Gaia-DR2 distance to the W3 Complex,
2.14+0.08−0.07 kpc, coincides with the previous stellar distances of ∼2 kpc. The Gaia-DR2 parallaxes tentatively show
diﬀerential distances for diﬀerent parts of the W3 Complex: W3 Main, located to the NE direction, is at 2.30+0.19
−0.16

35

+0.29kpc, the W3 Cluster (IC 1795), in the central region of the complex, is at 2.17+0.12−0.11 kpc, and W3(OH) is at 2.00−0.23
kpc to the SW direction. The W3 Cluster is the oldest region, indicating that it triggered the formation of the othertwo star-forming regions located at the edges of an expanding shell around the cluster.

Accepted by MNRAS
http://arxiv.org/pdf/1905.08593

51

ALMA observations require slower Core Accretion runaway growth
S. Nayakshin1 , G. Dipierro1 and J. Szulágyi2
1

Department of Physics and Astronomy, University of Leicester, University Road, LE1 7RH Leicester, United Kingdom; 2 Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zürich,
Winterthurerstrasse 190, CH-8057 Switzerland
E-mail contact: sn85 at astro.le.ac.uk
Thanks to recent high resolution ALMA observations, there is an accumulating evidence for presence of giant planetswith masses from ∼0.01 Jupiter mass to a few Jupiter mass with separations up to 100 AU in the annular structures
observed in young protoplanetary discs. We point out that these observations set unique “live” constraints on theprocess of gas accretion onto sub-Jovian planets that were not previously available. Accordingly, we use a population
synthesis approach in a new way: we build time-resolved models and compare the properties of the synthetic planetswith the ALMA data at the same age. Applying the widely used gas accretion formulae leads to a deﬁcit of sub-Jovian
planets and an over-abundance of a few Jupiter mass planets compared to observations. We ﬁnd that gas accretion rate
onto planets needs to be suppressed by about an order of magnitude to match the observed planet mass function. Thisslower gas giant growth predicts that the planet mass should correlate positively with the age of the protoplanetary
disc, albeit with a large scatter. This eﬀect is not clearly present in the ALMA data but may be conﬁrmed in the near
future with more observations.
Accepted by MNRAS Letters
http://arxiv.org/pdf/1905.13104

52

SOFIA/EXES observations of warm H2 at high spectral resolution: witnessing para-toortho conversion behind a molecular shock wave in HH7David A. Neufeld1 , Curtis DeWitt2 , Pierre Lesaffre3,4 , Sylvie Cabrit4 , Antoine Gusdorf3,4 , Le Ngoc
Tram2,5 , and Matthew Richter6
1
Department of Physics & Astronomy, Johns Hopkins Univ., Baltimore, MD 21218, USA; 2 SOFIA Science Center, NASA Ames Research Center, Moﬀett Field, CA 94035, USA; 3 Laboratoire de Physique de l’Ećole normale
supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, France; 4 Observatoire de Paris,
PSL University, Sorbonne Université, LERMA, 75014 Paris, France; 5 University of Science and Technology of Hanoi(USTH), Hanoi, Vietnam; 6 Universiy of California, Davis, CA 95616, USA

E-mail contact: neufeld at pha.jhu.edu
Spectrally-resolved observations of three pure rotational lines of H2 , conducted with the EXES instrument on SOFIA
toward the classic bow shock HH7, reveal systematic velocity shifts between the S(5) line of ortho-H2 and the twopara-H2 lines [S(4) and S(6)] lying immediately above and below it on the rotational ladder. These shifts, reported
here for the ﬁrst time, imply that we are witnessing the conversion of para-H2 to ortho-H2 within a shock wave driven
by an outﬂow from a young stellar object. The observations are in good agreement with the predictions of models fornon-dissociative, C-type molecular shocks. They provide a clear demonstration of the chemical changes wrought byinterstellar shock waves, in this case the conversion of para-H2 to ortho-H2 in reactive collisions with atomic hydrogen,and provide among the most compelling evidence yet obtained for C-type shocks in which the ﬂow velocity changes
continuously.
Accepted by ApJL
http://arxiv.org/pdf/1905.10381

36

53

Evidence for disc regulation in the lowest-mass stars of the young stellar cluster NGC
2264
Santiago Orcajo1,2 , Lucas A. Cieza3 , Roberto Gamen1,2 , Dawn Peterson4
1

Facultad de Ciencias Astronómicas y Geofı́sicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900
La Plata, Argentina; 2 Instituto de Astrofı́sica de La Plata, CCT La Plata, CONICETUNLP, Argentina; 3 Núcleo
de Astronomı́a, Facultad de Ingenierı́a y Ciencias, Universidad Diego Portales, Av Ejército 441, Santiago, Chile; 64Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301, USA
E-mail contact: santi at fcaglp.unlp.edu.ar
In the pre-main-sequence stage, star-disc interactions have been shown to remove stellar angular momentum andregulate the rotation periods of stars with M2 and earlier spectral types. Whether disc regulation also extends to stars
with later spectral types still remains a matter of debate. Here we present a star-disc interaction study in a sampleof over 180 stars with spectral types M3 and later (corresponding to stellar masses ≤0.3 M⊙ ) in young stellar cluster
NGC 2264. Combining rotation periods from the literature, new and literature spectral types, and newly presented
deep Spitzer observations, we show that stars with masses below 0.3 M⊙ with discs also rotate slower than stars
without a disc in the same mass regime. Our results demonstrate that disc-regulation still operates in these low-massstars, although the eﬃciency of this process might be lower than in higher-mass objects. We conﬁrm that stars with
spectral types earlier and later than M2 have distinct period distributions and that stars with spectral types M5 andlater rotate even faster M3 and M4-type stars.
Accepted by MNRAS
http://arxiv.org/pdf/1905.10312

54

A Simple Non-equilibrium Feedback Model for Galaxy-Scale Star Formation: Delayed
Feedback and SFR Scatter
Matthew E. Orr1 , Christopher C. Hayward2 and Philip F. Hopkins1
1

TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125, USA; 2 Center for Computational
Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA
E-mail contact: meorr at caltech.edu
We explore a class of simple non-equilibrium star formation models within the framework of a feedback-regulated modelof the ISM, applicable to kiloparsec-scale resolved star formation relations (e.g. Kennicutt-Schmidt). Combining a
Toomre-Q-dependent local star formation eﬃciency per free-fall time with a model for delayed feedback, we are able
to match the normalization and scatter of resolved star formation scaling relations. In particular, this simple model
suggests that large (∼dex) variations in star formation rates (SFRs) on kiloparsec scales may be due to the fact thatsupernova feedback is not instantaneous following star formation. The scatter in SFRs at constant gas surface density
in a galaxy then depends on the properties of feedback and when we observe its star-forming regions at various points
throughout their collapse/star formation “cycles”. This has the following important observational consequences: (1)the scatter and normalization of the Kennicutt-Schmidt relation are relatively insensitive to the local (small-scale) starformation eﬃciency, (2) but gas depletion times and velocity dispersions are; (3) the scatter in and normalization of theKennicutt-Schmidt relation is a sensitive probe of the feedback timescale and strength; (4) even in a model where Q̃gas
deterministically dictates star formation locally, time evolution, variation in local conditions (e.g., gas fractions anddynamical times), and variations between galaxies can destroy much of the observable correlation between SFR andQ̃gas in resolved galaxy surveys. Additionally, this model exhibits large scatter in SFRs at low gas surface densities,
in agreement with observations of ﬂat outer HI disk velocity dispersion proﬁles.
Accepted by MNRAS
https://arxiv.org/pdf/1810.09460

55

Do star clusters form in a completely mass-segregated way?
Vaclav Pavlik1,2 , Pavel Kroupa3 and Ladislav Subr1
1

Astronomical Institute of Charles University, Prague, Czech Republic; 2 Observatory and Planetarium of Prague,37

Prague, Czech Republic; 3 Helmholtz-Institut fur Strahlen- und Kernphysik (HISKP), Universitt Bonn, Bonn, Germany
E-mail contact: pavlik at sirrah.troja.mﬀ.cuni.cz
ALMA observations of the Serpens South star-forming region suggest that stellar protoclusters may be completely
mass segregated at birth. Independent observations also suggest that embedded clusters form segregated by mass. As
the primordial mass segregation seems to be lost over time, we aim to study on which timescale an initially perfectly
mass-segregated star cluster becomes indistinguishable from an initially not mass-segregated cluster. As an example,
the Orion Nebula Cluster (ONC) is also discussed. We used N -body simulations of star clusters with various masses
and two diﬀerent degrees of primordial mass segregation. We analysed their energy redistribution through two-bodyrelaxation to quantify the time when the models agree in terms of mass segregation, which sets in only dynamically inthe models that are primordially not mass segregated. A comprehensive cross-matched catalogue combining optical,
infrared, and X-ray surveys of ONC members was also compiled and made available. The models evolve to a similarradial distribution of high-mass stars after the core collapse (about half a median two-body relaxation time, trh ) andbecome observationally indistinguishable from the point of view of mass segregation at time τv ≈ 3.3 trh . In the caseof the ONC, using the distribution of high-mass stars, we may not rule out either evolutionary scenario (regardless ofwhether they are initially mass segregated). When we account for extinction and elongation of the ONC, as reported
elsewhere, an initially perfectly mass-segregated state seems to be more consistent with the observed cluster.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1905.09289

An Inner Disk in the Large Gap of the Transition Disk SR 24S

56 Paola Pinilla1,2, Myriam Benisty3,4, Paolo Cazzoletti5 , Daniel Harsono6, Laura M. Pérez7 and Marco
Tazzari8
1

Department of Astronomy/Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson,
AZ 85721, USA; 2 Hubble Fellow; 3 Unidad Mixta Internacional Franco-Chilena de Astronomı́a (CNRS, UMI 3386),
Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 4
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 5 Max-Planck-Institute for Extraterrestrial Physics(MPE), Giessen- bachstr. 1, 85748, Garching, Germany; 6 Leiden Observatory, Leiden University, P.O. Box 9513,
2300 RA Leiden, The Netherlands; 7 Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio
1515, Las Condes, Santiago, Chile; 8 nstitute of Astronomy, University of Cambridge, Madingley Road, Cambridge
CB3 0HA, UK
E-mail contact: pinilla at email.arizona.edu
We report new Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 3 observations at 2.75 mm of the
TD around SR 24S with an angular resolution of ∼0.11 × 0.09 arcsec and a peak signal-to-noise ratio of ∼ 24. We
detect an inner disk and a mostly symmetric ring-like structure that peaks at ∼0.32 arcsec, that is ∼37 au at a
distance of ∼114.4 pc. The full width at half maximum of this ring is ∼28 au. We analyze the observed structures
by ﬁtting the dust continuum visibilities using diﬀerent models for the intensity proﬁle, and compare with previous
ALMA observations of the same disk at 0.45 mm and 1.30 mm. We qualitatively compare the results of these ﬁts withtheoretical predictions of diﬀerent scenarios for the formation of a cavity or large gap. The comparison of the dust
continuum structure between diﬀerent ALMA bands indicates that photoevaporation and dead zone can be excluded
as leading mechanisms for the cavity formation in SR 24S disk, leaving the planet scenario (single or multiple planets)
as the most plausible mechanism. We compared the 2.75 mm emission with published (sub-)centimeter data and ﬁndthat the inner disk is likely tracing dust thermal emission. This implies that any companion in the system should
allow dust to move inwards throughout the gap and replenish the inner disk. In the case of one single planet, thisputs strong constraints on the mass of the potential planet inside the cavity and the disk viscosity of about <∼5 MJupand α ∼ 10−4 − 10−3 , respectively.
Accepted by ApJ

http://arxiv.org/pdf/1904.11517

38

57

Modeling the Protoplanetary Disks of Two Brown Dwarfs in the Taurus Molecular
Cloud
Anneliese M. Rilinger1, Catherine C. Espaillat1 and Enrique Macias1
1

Department of Astronomy and Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue,
Boston, MA
E-mail contact: amr5 at bu.edu
Measuring the properties of protoplanetary disks around brown dwarfs is central to understanding the formation ofbrown dwarfs and their planetary companions. We present modeling of CFHT Tau 4 and 2M0444, two brown dwarfs
with protoplanetary disks in the Taurus Molecular Cloud. By combining modeling of the spectral energy distributions
and ALMA images, we obtain disk radii and masses for these objects; these parameters can be used to constrain browndwarf formation and planet formation, respectively. We ﬁnd that the disk around CFHT Tau 4 has a total mass of
0.42 MJup and a radius of 80 au; we ﬁnd 2M0444’s disk to have a mass of 2.05 MJup and a radius of 100 au. Theseradii are more consistent with those predicted by theoretical simulations of brown dwarf formation via undisturbed
condensation from a mass reservoir than those predicted by ejection from the formation region. Furthermore, the disk
mass of 2M0444 suggests that planet formation may be possible in this disk, although the disk of CFHT Tau 4 is likely
not massive enough to form planets. The disk properties measured here provide constraints to theoretical models ofbrown dwarf formation and the formation of their planetary companions.
Accepted by ApJ

https://arxiv.org/pdf/1905.05829.pdf

58

The time evolution of dusty protoplanetary disc radii: observed and physical radii differ
Giovanni P. Rosotti1,2 , Marco Tazzari1 , Richard A. Booth1 , Leonardo Testi3 , Giuseppe Lodato4 andCathie Clarke1
1

Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK; 2 Leiden Observatory, Leiden University, P.O.
Box 9531, NL-2300 RA Leiden, the Netherlands; 3 European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748
Garching, Germany; 4 Universitá degli Studi di Milano, Via Giovanni Celoria 16, I-20133 Milano, Italy
E-mail contact: rosotti at ast.cam.ac.uk
Proto-planetary disc surveys conducted with ALMA are measuring disc radii in multiple star forming regions. The
disc radius is a fundamental quantity to diagnose whether discs undergo viscous spreading, discriminating between
viscosity or angular momentum removal by winds as drivers of disc evolution. Observationally, however, the sub-mm
continuum emission is dominated by the dust, which also drifts inwards, complicating the picture. In this paper
we investigate, using theoretical models of dust grain growth and radial drift, how the radii of dusty viscous protoplanetary discs evolve with time. Despite the existence of a sharp outer edge in the dust distribution, we ﬁnd thatthe radius enclosing most of the dust mass increases with time, closely following the evolution of the gas radius. Thisbehaviour arises because, although dust initially grows and drifts rapidly onto the star, the residual dust retained on
Myr timescales is relatively well coupled to the gas. Observing the expansion of the dust disc requires using deﬁnitions
based on high fractions of the disc ﬂux (e.g. 95 per cent) and very long integrations with ALMA, because the dust
grains in the outer part of the disc are small and have a low sub-mm opacity. We show that existing surveys lack thesensitivity to detect viscous spreading. The disc radii they measure do not trace the mass radius or the sharp outeredge in the dust distribution, but the outer limit of where the grains have signiﬁcant sub-mm opacity. We predictthat these observed radii should shrink with time.
Accepted by MNRAS
http://arxiv.org/pdf/1905.00019

59

On the millimetre continuum flux-radius correlation of proto-planetary discs
Giovanni P. Rosotti1,2, Richard A. Booth1 , Marco Tazzari1 , Cathie Clarke1 , Giuseppe Lodato3 , Leonardo
Testi41

Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK; 2 Leiden Observatory, Leiden University, P.O.
39

Box 9531, NL-2300 RA Leiden, the Netherlands; 3 Universitá degli Studi di Milano, Via Giovanni Celoria 16, I-20133
Milano, Italy; 4 European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching, Germany
E-mail contact: rosotti at ast.cam.ac.uk
A correlation between proto-planetary disc radii and sub-mm ﬂuxes has been recently reported. In this Letter weshow that the correlation is a sensitive probe of grain growth processes. Using models of grain growth and drift, wehave shown in a companion paper that the observed disc radii trace where the dust grains are large enough to havea signiﬁcant sub-mm opacity. We show that the observed correlation emerges naturally if the maximum grain size isset by radial drift, implying relatively low values of the viscous α parameter <∼0.001. In this case the relation has analmost universal normalisation, while if the grain size is set by fragmentation the ﬂux at a given radius depends on the
dust-to-gas ratio. We highlight two observational consequences of the fact that radial drift limits the grain size. The
ﬁrst is that the dust masses measured from the sub-mm could be overestimated by a factor of a few. The second isthat the correlation should be present also at longer wavelengths (e.g. 3 mm), with a normalisation factor that scales
as the square of the observing frequency as in the optically thick case.
Accepted by MNRAS Letters
http://arxiv.org/pdf/1905.00021

60

Carbon radio recombination lines from gigahertz to megahertz frequencies towards
Orion A
P. Salas1 , J.B.R. Oonk1,2 , K.L. Emig1 , C. Pabst1 , M.C. Toribio1 , H.J.A. Röttgering1 , and A.G.G.M.
Tielens1
1

Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands; 2 Netherlands Institutefor Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo, The Netherlands
E-mail contact: psalas at strw.leidenuniv.nl
Context. The combined use of carbon radio recombination lines (CRRLs) and the 158 µm-[CII] line is a powerful tool
for the study of the energetics and physical conditions (e.g., temperature and density) of photodissociation regions(PDRs). However, there are few observational studies that exploit this synergy.
Aims. Here we explore the relation between CRRLs and the 158 µm-[CII] line in light of new observations and models.
Methods. We present new and existing observations of CRRLs in the frequency range 0.15–230 GHz with ALMA,
VLA, the GBT, Eﬀelsberg 100m, and LOFAR towards Orion A (M42). We complement these observations with
SOFIA observations of the 158 µm-[CII] line. We studied two PDRs: the foreground atomic gas, known as the Veil,and the dense PDR between the HII region and the background molecular cloud.
Results. In the Veil we are able to determine the gas temperature and electron density, which we use to measure theionization parameter and the photoelectric heating eﬃciency. In the dense PDR, we are able to identify a layered PDR
structure at the surface of the molecular cloud to the south of the Trapezium cluster. There we ﬁnd that the radiolines trace the colder portion of the ionized carbon layer, the C+ /C/CO interface. By modeling the emission of the
158 µm-[CII] line and CRRLs as arising from a PDR we derive a thermal pressure >5 × 107 K cm−3 and a radiationﬁeld G0 ≈ 105 close to the Trapezium.
Conclusions. This work provides additional observational support for the use of CRRLs and the 158 µm-[CII] line
as complementary tools to study dense and diﬀuse PDRs, and highlights the usefulness of CRRLs as probes of the
C+ /C/CO interface.
Accepted by A&A
http://arxiv.org/pdf/1905.02799

61

Dynamical evolution of star-forming regions: III. Unbound stars and predictions for
Gaia
Christina Schoettler1,2 , Richard J. Parker1 , Becky Arnold1 , Liam P. Grimmett1 , Jos de Bruijne2 ,Nicholas J. Wright3
1

Department of Physics and Astronomy, The University of Sheﬃeld, Hicks Building, Hounsﬁeld Road, Sheﬃeld
S3 7RH, UK; 2 Science Support Oﬃce, Directorate of Science, European Space Research and Technology Centre
40

(ESA/ESTEC), Keplerlaan 1, NL-2201 AZ Noordwijk, the Netherlands; 3 Astrophysics Group, Keele University,
Keele ST5 5BG, UK
E-mail contact: cschoettler1 at sheﬃeld.ac.uk
We use N-body simulations to probe the early phases of the dynamical evolution of star-forming regions and focus
on mass and velocity distributions of unbound stars. In this parameter space study, we vary the initial virial ratio
and degree of spatial and kinematic substructure and analyse the fraction of stars that become unbound in two
diﬀerent mass classes (above and below 8 M⊙ ). We ﬁnd that the fraction of unbound stars diﬀers depending on theinitial conditions. After 10 Myr, in initially highly subvirial, substructured simulations, the high-mass and lowermass unbound fractions are similar at ∼23 per cent. In initially virialised, substructured simulations, we ﬁnd only
∼16 per cent of all high-mass stars are unbound, whereas ∼37 per cent of all lower-mass stars are. The velocity
distributions of unbound stars only show diﬀerences for extremely diﬀerent initial conditions. The distributions are
dominated by large numbers of lower-mass stars becoming unbound just above the escape velocity of ∼3 km s−1 withunbound high-mass stars moving faster on average than lower-mass unbound stars. We see no high-mass runaway
stars (velocity > 30 km s−1 ) from any of our initial conditions and only an occasional lower-mass runaway star frominitially subvirial/substructured simulations. In our simulations, we ﬁnd a small number of lower-mass walkaway stars(with velocity 5–30 km s−1 ) from all of our initial conditions. These walkaway stars should be observable around many
nearby star-forming regions with Gaia.
Accepted by MNRAS
http://arxiv.org/pdf/1905.10317

62

A survey of molecular cores in M17 SWex
Tomomi Shimoikura1,2 , Kazuhito Dobashi1 , Asha Hirose1 , Fumitaka Nakamura3 , Yoshito Shimajiri4
and Koji Sugitani5
1

Tokyo Gakugei University, Japan; 2 Otsuma Women’s University, Japan; 3 National Astronomical Observatory ofJapan; 4 Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, France; 5 Graduate School of Natural Sciences,
Nagoya City University, Japan
E-mail contact: ikura at otsuma.ac.jp
A survey of molecular cores covering the infrared dark cloud known as the M17 southwest extension (M17 SWex) has
been carried out with the 45 m Nobeyama Radio Telescope. Based on the N2 H+ (J=1-0) data obtained, we haveidentiﬁed 46 individual cores whose masses are in the range 43 to 3026 M o. We examined the relationship between
the physical parameters of the cores and those of young stellar objects (YSOs) associated with the cores found in theliterature. The comparison of the virial mass and the core mass indicates that most of the cores can be gravitationallystable if we assume a large external pressure. Among the 46 cores, we found four massive cores with YSOs. They
have large mass of >1000M o and line width of > 2.5 km s−1 which are similar to those of clumps forming high mass
stars. However, previous studies have shown that there is no active massive star formation in this region. Recent
measurements of near-infrared polarization infer that the magnetic ﬁeld around M17 SWex is likely to be strong
enough to support the cores against self-gravity. We therefore suggest that the magnetic ﬁeld may prevent the coresfrom collapsing, causing the low-level of massive star formation in M17 SWex.
Accepted by PASJ
http://arxiv.org/pdf/1905.07950

63

Why does ammonia not freeze out in the center of pre-stellar cores?
O. Sipilä1 , P. Caselli1 , E. Redaelli1 , M. Juvela2 and L. Bizzocchi1
1

Max-Planck-Institute for Extraterrestrial Physics (MPE), Giessenbachstr. 1, 85748 Garching, Germany; 2 Department of Physics, P.O.Box 64, FI-00014, University of Helsinki, FinlandE-mail contact: osipila at mpe.mpg.de
We carried out a parameter-space exploration of the ammonia abundance in the pre-stellar core L1544, where it has
been observed to increase toward the center of the core with no signs of freeze-out onto grain surfaces. We considered
static and dynamical physical models coupled with elaborate chemical and radiative transfer calculations, and explored41

the eﬀects of varying model parameters on the (ortho+para) ammonia abundance proﬁle. None of our models areable to reproduce the inward-increasing tendency in the observed proﬁle; ammonia depletion always occurs in thecenter of the core. In particular, our study shows that including the chemical desorption process, where exothermic
association reactions on the grain surface can result in the immediate desorption of the product molecule, leads toammonia abundances that are over an order of magnitude above the observed level in the innermost 15000 au of
the core – at least when one employs a constant eﬃciency for the chemical desorption process irrespective of the icecomposition. Our results seemingly constrain the chemical desorption eﬃciency of ammonia on water ice to below
1%. It is increasingly evident that time-dependent eﬀects must be considered so that the results of chemical models
can be reconciled with observations.
Accepted by MNRAS; arXiv:1905.02384

64

Sticking Properties of Silicates in Planetesimal Formation Revisited
Tobias Steinpilz1 , Jens Teiser1 , and Gerhard Wurm1
1

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

E-mail contact: tobias.steinpilz at uni-due.deIn the past, laboratory experiments and theoretical calculations showed a mismatch in derived sticking properties ofsilicates in the context of planetesimal formation. It has been proposed by Kimura et al. (2015) that this mismatchis due to the value of the surface energy assumed, supposedly correlated to the presence or lack of water layers of
diﬀerent thickness on a grain’s surface. We present tensile strength measurements of dust aggregates with diﬀerent
water content here. The results are in support of the suggestion by Kimura et al. (2015). Dry samples show increased
strengths by a factor of up to 10 over wet samples. A high value of γ = 0.2 J m−2 likely applies to the dry low pressure
conditions of protoplanetary disks and should be used in the future.
Accepted by ApJL
http://arxiv.org/pdf/1905.11864

65

A Radial Velocity Survey of Embedded Sources in the Rho Ophiuchi Cluster
Timothy Sullivan1 , Bruce A. Wilking1 , Thomas P. Greene2 , Lindsey Lisalda1 , Erika L. Gibb1 andChemeda Ejeta1
1

University of Missouri-St. Louis, USA; 2 NASA Ames Research Center, USA

E-mail contact: bwilking at umsl.edu
We present the results of a radial velocity survey of young stellar objects in early stages of evolution in the core of
the L 1688 molecular cloud. New and archival spectra obtained with four high resolution infrared spectrographs wereanalysed using Markov Chain Monte Carlo techniques that simultaneously ﬁt for the radial velocity, Tef f , vsini, andveiling by comparison with synthetic spectra. The radial velocity distribution for 32 objects, most with Class I or
Flat-spectrum spectral energy distributions, is marginally gaussian, with a higher dispersion relative to optical surveys
at the 2σ level. When comparing the results from both proper motion and radial velocity surveys in L 1688, there isa trend for the 1-D dispersions to be higher for samples of Class I/Flat-spectrum young stellar objects that reside in
the cloud core compared to Class II/III dominated samples which are located in the lower extinction periphery. In
addition, there is a velocity gradient along the major axis of the cloud core that appears more pronounced than thatderived from optically visible objects at the cloud edges. If these higher dispersions for Class I/Flat-spectrum objects
are conﬁrmed by future surveys, this could imply a supervirial state for the less evolved objects in the cloud core andbe a signature of the initial collapse and rebound of the cluster as suggested by recent simulations of cluster evolution.
Accepted by The Astronomical Journal

66

Discovery of an au-scale excess in millimeter emission of TW Hya
Takashi Tsukagoshi1 , Takayuki Muto2 , Hideko Nomura1,3 , Ryohei Kawabe1,4,5 , Kazuhiro D. Kanagawa6 ,Satoshi Okuzumi3 , Shigeru Ida7 , Catherine Walsh8 , Tom J. Millar9 , Sanemichi Z. Takahashi1,2 , Jun
Hashimoto10 , Taichi Uyama5 and Motohide Tamura5,10
1

Division of Radio Astronomy, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-42

8588, Japan; 2 Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo, 163-8677,
Japan; 3 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro,
Tokyo, 152-8551, Japan; 4 SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka,
Tokyo 181-8588, Japan; 5 Department of Astronomy, School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033,
Japan; 6 Research Center for the Early Universe, Graduate School of Science, University of Tokyo, Bunkyo, Tokyo
113-0033, Japan; 7 Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 1528550, Japan; 8 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK; 9 Astrophysics ResearchCentre, School of Mathematics and Physics, Queens University Belfast, University Road, Belfast BT7 1NN, UK; 10
Astrobiology Center, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
E-mail contact: takashi.tsukagoshi at nao.ac.jp
We report the detection of an excess in dust continuum emission at 233 GHz (1.3 mm in wavelength) in the protoplanetary disk around TW Hya revealed through high-sensitivity observations at ∼3 au resolution with the Atacama
Large Millimeter/submillimeter Array (ALMA). The sensitivity of the 233 GHz image has been improved by a factorof 3 with regard to that of our previous cycle 3 observations. The overall structure is mostly axisymmetric, and there
are apparent gaps at 25 and 41 au as previously reported. The most remarkable new ﬁnding is a few au-scale excess
emission in the south-west part of the protoplanetary disk. The excess emission is located at 52 au from the disk
center and is 1.5 times brighter than the surrounding protoplanetary disk at a signiﬁcance of 12σ. We performed avisibility ﬁtting to the extracted emission after subtracting the axisymmetric protoplanetary disk emission and foundthat the inferred size and the total ﬂux density of the excess emission are 4.4×1.0 au and 250 µJy, respectively. The
dust mass of the excess emission corresponds to 0.03 M⊕ if a dust temperature of 18 K is assumed. Since the excess
emission can also be marginally identiﬁed in the Band 7 image at almost the same position, the feature is unlikely
to be a background source. The excess emission can be explained by a dust clump accumulated in a small elongatedvortex or a massive circumplanetary disk around a Neptune mass forming-planet.
Accepted by Astrophysical Journal Letters
https://arxiv.org/pdf/1905.07891

67

Disk masses in the Orion Molecular Cloud-2: distinguishing time and environment
S.E. van Terwisga1 , A. Hacar1 , and E.F. van Dishoeck1,2
1

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 Max-Planck-Institut für
Extraterrestrische Physik, Gießenbachstraße, D-85741 Garching bei München, Germany
E-mail contact: terwisga at strw.leidenuniv.nl
The mass evolution of protoplanetary disks is driven by both internal processes and external factors, such as photoevaporation. Disentangling these two eﬀects, however, has remained diﬃcult. We measure the dust masses of a sample
of 132 disks in the Orion Molecular Cloud (OMC)-2 region, and compare them to (i) externally photoevaporated disks
in the Trapezium cluster, and (ii) disks in nearby low-mass star forming regions (SFRs). This allows us to test if
initial disk properties are the same in high- and low-mass SFRs, and enables a direct measurement of the eﬀect ofexternal photoevaporation on disks. A ∼20′ × 4′ mosaic of 3 mm continuum observations from the Atacama Large
Millimeter/submillimeter Array (ALMA) was used to measure the ﬂuxes of 132 disks and 35 protostars >0.5 pc awayfrom the Trapezium. We identify and characterize a sample of 34 point sources not included in the Spitzer catalog on
which the sample is based. Of the disks, 37 (28%) are detected, with masses ranging from 7–270 M⊕ . The detection
rate for protostars is higher at 69%. Disks near the Trapezium are found to be less massive by a factor 0.18+0.18−0.11 ,
implying a mass loss rate of 8 × 10−8 M⊙ yr−1 . Our observations allow us to distinguish the impact of time andenvironment on disk evolution in a single SFR. The disk mass distribution in OMC-2 is statistically indistinguishable
from that in nearby low-mass SFRs, like Lupus and Taurus. We conclude that age is the main factor determining theevolution of these disks. This result is robust with respect to assumptions of dust temperature, sample incompletenessand biases. The diﬀerence between the OMC-2 and Trapezium cluster samples is consistent with mass loss driven by
far-ultraviolet radiation near the Trapezium. Together, this implies that in isolation, disk formation and evolution
proceed similarly, regardless of cloud mass.
Accepted by A&A
http://arxiv.org/pdf/1905.09804

43constraints on the initial parameters of low-mass star formation from chemical
68 Newmodeling
Thomas H.G. Vidal1 , Pierre Gratier1 , Neil Vaytet2 , Audrey Coutens1 , and Valentine Wakelam1
1

Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoﬀroy Saint-Hilaire, 33615 Pessac,
France; 2 Data Management and Software Centre, the European Spallation Source ERIC, Ole Maales Vej 3, 2200,
Copenhagen, DenmarkE-mail contact: thomas.vidal at u-bordeaux.fr
The complexity of physico-chemical models of star formation is increasing, with models that take into account newprocesses and more realistic setups. These models allow astrochemists to compute the evolution of chemical species
throughout star formation. Hence, comparing the outputs of such models to observations allows to bring new constraints on star formation. The work presented in this paper is based on the recent public release of a database ofradiation hydrodynamical low-mass star formation models. We used this database as physical parameters to computethe time dependent chemical composition of collapsing cores with a 3-phase gas-grain model. The results are analyzed
to ﬁnd chemical tracers of the initial physical parameters of collapse such as the mass, radius, temperature, density,and free-fall time. They are also compared to observed molecular abundances of Class 0 protostars. We ﬁnd numerous
tracers of the initial parameters of collapse, except for the initial mass. More particularly, we ﬁnd that gas phase
CH3 CN, NS and OCS trace the initial temperature, while H2 CS trace the initial density and free-fall time of theparent cloud. The comparison of our results with a sample of 12 Class 0 low mass protostars allows us to constrain theinitial parameters of collapse of low-mass prestellar cores. We ﬁnd that low-mass protostars are preferentially formed
within large cores with radii greater than 20000 au, masses between 2 and 4 M⊙ , temperatures lower or equal to 15
K, and densities between 6 × 104 and 2.5 × 105 cm−3 , corresponding to free-fall times between 100 and 200 kyrs.
Accepted by MNRAS
http://arxiv.org/pdf/1905.05592

69

Global evolution of a gravitoviscous protoplanetary disk. I. The importance of the inner
sub-au region
Eduard Vorobyov1,2 , Aleksandr Skliarevskii2 , Vardan Elbakyan2 , Yaroslav Pavlyuchenkov3 , Vitaly
Akimkin3 and Manuel Guedel1
1
Department of Astrophysics, University of Vienna, Vienna, Austria; 2 Institute of Physics, Southern Federal University, Rostov-on-Don, Russia; 3 Institute of Astronomy, Russian Academy of Sciences, Moscow, Russia

E-mail contact: eduard.vorobiev at univie.ac.at
The central region of a circumstellar disk is diﬃcult to resolve in global numerical simulations of collapsing cloud cores,
but its eﬀect on the evolution of the entire disk can be signiﬁcant. We use numerical hydrodynamics simulations tomodel the long-term evolution of self-gravitating and viscous circumstellar disks in the thin-disk limit. Simulations
start from the gravitational collapse of prestellar cores of 0.5–1.0 M⊙ and both gaseous and dusty subsystems wereconsidered, including a model for dust growth. The inner unresolved 1.0 au of the disk is replaced with a central“smart” cell (CSC) – a simpliﬁed model that simulates physical processes that may occur in this region. We foundthat the mass transport rate through the CSC has an appreciable eﬀect on the evolution of the entire disk. Models withslow mass transport form more massive and warmer disks and they are more susceptible to gravitational instability
and fragmentation, including a newly identiﬁed episodic mode of disk fragmentation in the T Tauri phase of disk
evolution. Models with slow mass transport through the CSC feature episodic accretion and luminosity bursts inthe early evolution, while models with fast transport are characterized by a steadily declining accretion rate with
low-amplitude ﬂickering. Dust grows to a larger, decimeter size in the slow transport models and eﬃciently drifts in
the CSC, where it accumulates reaching the limit when streaming instability becomes operational. We argue thatgravitational instability, together with streaming instability likely operating in the inner disk regions, constitute two
concurrent planet-forming mechanisms, which may explain the observed diversity of exoplanetary orbits. We conclude
that sophisticated models of the inner unresolved disk regions should be used when modeling the formation andevolution of gaseous and dusty protoplanetary disks.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/1905.11335
44effects of ionization feedback on star formation: A case study of the M16 HII region
70 TheJin-Long Xu1,6 , Annie Zavagno2 , Naiping Yu1 , Xiao-Lan Liu1 , Ye Xu3,7 , Jinghua Yuan1 , Chuan-Peng
Zhang1 , Si-Ju Zhang2 , Guo-Yin Zhang1 , Chang-Chun Ning4 , and Bing-Gang Ju5,7
1

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China; 2 Aix Marseille Univ,
CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France; 3 Purple Mountain Observatory, Chinese
Academy of Sciences, Nanjing 210008, China; 4 Tibet University, Lhasa, Tibet 850000, China; 5 Purple Mountain
Observatory, Qinghai Station,Delingha 817000, China; 6 CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China; 7 Key Laboratory of Radio Astronomy, Chinese
Academy of Sciences, China
E-mail contact: xujl at bao.ac.cn
We aim to investigate the impact of the ionized radiation from the M16 HII region on the surrounding molecular cloudand on its hosted star formation. To present comprehensive multi-wavelength observations towards the M16 HII region,
we used new CO data and existing infrared, optical, and submillimeter data. The 12 CO J=1–0, 13 CO J=1–0, and C18 O
J=1–0 data were obtained with the Purple Mountain Observatory (PMO) 13.7m radio telescope. To trace massive
clumps and extract young stellar objects (YSOs) associated with the M16 HII region, we used the ATLASGAL and
GLIMPSE I catalogs, respectively. From CO data, we discern a large-scale ﬁlament with three velocity components.
Because these three components overlap with each other in both velocity and space, the ﬁlament may be made of threelayers. The M16 ionized gas interacts with the large-scale ﬁlament and has reshaped its structure. In the large-scaleﬁlament, we ﬁnd 51 compact cores from the ATLASGAL catalog, 20 of them being quiescent. The mean excitation
temperature of these cores is 22.5 K, while this is 22.2 K for the quiescent cores. This high temperature observed forthe quiescent cores suggests that the cores may be heated by M16 and do not experience internal heating from sourcesin the cores. Through the relationship between the mass and radius of these cores, we obtain that 45% of all the coresare massive enough to potentially form massive stars. Compared with the thermal motion, the turbulence created by
the nonthermal motion is responsible for the core formation. For the pillars observed towards M16, the H II region
may give rise to the strong turbulence.
Accepted by A&A

http://arxiv.org/pdf/1905.08030

On the formation of density filaments in the turbulent interstellar medium

71 Siyao Xu1,2, Suoqing Ji3, A. Lazarian1
1

Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706, USA; 2 Hubble
Fellow; 3 TAPIR & Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA
91125, USA; Sherman Fairchild Fellow
E-mail contact: sxu93 at wisc.edu

This study is motivated by recent observations on ubiquitous interstellar density ﬁlaments and guided by modern
theories of compressible magnetohydrodynamic (MHD) turbulence. The interstellar turbulence shapes the observed
density structures. As the fundamental dynamics of compressible MHD turbulence, perpendicular turbulent mixingof density ﬂuctuations entails elongated density structures aligned with the local magnetic ﬁeld, accounting for lowdensity parallel ﬁlaments seen in diﬀuse atomic and molecular gas. The elongation of low-density parallel ﬁlaments
depends on the turbulence anisotropy. When taking into account the partial ionization, we ﬁnd that the minimum
width of parallel ﬁlaments in the cold neutral medium and molecular clouds is determined by the neutral-ion decouplingscale perpendicular to magnetic ﬁeld. In highly supersonic MHD turbulence in molecular clouds, both low-density
parallel ﬁlaments due to anisotropic turbulent mixing and high-density ﬁlaments due to shock compression exist.
Accepted by ApJ
http://arxiv.org/pdf/1905.06341

45

72

ALMA Observations of Layered Structures due to CO Selective Dissociation in the ρ
Ophiuchi A Plane-parallel PDR
M. Yamagishi1 , C. Hara2 , R. Kawabe3 , F. Nakamura3 , T. Kamazaki3 , T. Takekoshi4 , Y. Shimajiri5 , H.
Nomura6 , S. Takakuwa7 and J. Di Francesco8
1

Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Chuo-ku, Sagamihara, Kanagawa
252-5210, Japan; 2 Graduate School of Science, The University of Tokyo, Bunkyo-ku, 113-0033, Tokyo, Japan; 3 National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan; 4 Institute of Astronomy, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 5 Laboratoire AIM, CEA/DSM-CNRS-Universit Paris Diderot, IRFU/Service dAstrophysique, CEA Saclay, F-91191 Gifsur-Yvette, France; 6 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama,
Meguro, Tokyo, 152-8551, Japan; 7 Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan; 8 NRC Herzberg Astronomy
and Astrophysics Research Centre, 5071 W Saanich Road, Victoria BC V9E 2E7, British Columbia, Canada
E-mail contact: yamagish at ir.isas.jaxa.jp
We analyze 12 CO(J=2–1), 13 CO(J=2–1), C18 O (J=2–1), and 1.3 mm continuum maps of the ρ Ophiuchi A photodissociation region (PDR) obtained with ALMA. Layered structures of the three CO isotopologues with an angularseparation of 10” = 6.6×10−3 pc = 1400 au are clearly detected around the Be star, S1 (i.e., each front of emission shifts
from the near to far side in order of 12 CO, 13 CO, and C18 O). We estimate the spatial variations of X(13 CO)/X(C18 O)
abundance ratios, and ﬁnd that the abundance ratio is as high as 40 near the emission front, and decreases to thetypical value in the solar system of 5.5 in a small angular scale of 4” = 2.6×10−3 pc = 560 au. We also ﬁnd that theI(12 CO(2–1))/I(13 CO(2–1)) intensity ratio is very high (>21) in the ﬂat-spectrum young stellar object, GY-51, locatedin the PDR. The enhancement of the ratios indicates that the UV radiation signiﬁcantly aﬀects the CO isotopologues
via selective dissociation in the overall ρ Ophiuchi A PDR, and that the ρ Ophiuchi A PDR has a plane-parallel
structure.
Accepted by ApJ

https://arxiv.org/pdf/1903.02192

73

Synthetic molecular line observations of the first hydrostatic core from chemical calculations
Alison K. Young1 , Matthew R. Bate1 , Tim J. Harries1 and David M. Acreman1
1

Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK

E-mail contact: ayoung at astro.ex.ac.uk
The ﬁrst stable object to develop in the low–mass star formation process has long been predicted to be the ﬁrst
hydrostatic core (FHSC). Despite much eﬀort, it has still yet to be deﬁnitively observed in nature. More speciﬁc
observational signatures are required to enable observers to distinguish the FHSC from young, faint, but more evolved
protostars. Here we present synthetic spectral line observations for CO, SO, CS and HCO+ that were calculated fromradiation (magneto)hydrodynamical models, chemical modelling and Monte Carlo radiative transfer. HCO+ (1 − 0)
and SO (87 −76 ) spectra of the FHSC show variations for observations at a low inclination which may allow a candidate
FHSC to be distinguished from a more evolved object. We ﬁnd that the FHSC outﬂow is unlikely to be detectablewith ALMA, which would discount the observed sources with slow outﬂows that are currently identiﬁed as candidate
FHSCs. We compare the results of simulated ALMA observations with observed candidate FHSCs and recommend
Oph A SM1N and N6-mm as the most promising candidates to follow up.
Accepted by MNRAS
https://arxiv.org/pdf/1906.01324

74

Sequential Star Formation in the filamentary structures of the Planck Galactic cold
clump G181.84+0.31
Lixia Yuan1,2,3 , Ming Zhu1,3 , Tie Liu4,5 , Jinghua Yuan1 , Yuefang Wu6 , Kee-Tae Kim4 , Ke Wang7,8 ,Chenlin Zhou1,2,3 , Ken’ichi Tatematsu9 and Nario Kuno10,1146

1

National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing
100101, China; 2 University of Chinese Academy of Sciences, 100049, Beijing, China; 3 Key Laboratory of FAST,
NAOC, Chinese Academy of Sciences, Beijing 100012, China; 4 Korea Astronomy and Space Science Institute, 776
Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; 5 East Asian Observatory, 660 N. A’ohoku Place, Hilo,
HI 96720, USA; 6 Department of Astronomy, Peking University, 100871, Beijing China; 7 Kavli Institute for Astronomy
and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, China; 8 European Southern
Observatory (ESO) Headquarters, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany; 9 National
Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 10 Tomonaga Center for theHistory of the Universe, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan; 11 Departmentof Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Ten-nodai, tsukuba, Ibaraki
305-8577, Japan
E-mail contact: lxyuan at bao.ac.cn
We present a multi-wavelength study of the Planck cold clump G181.84+0.31, which is located at the northern end of
the extended ﬁlamentary structure S242. We have extracted 9 compact dense cores from the SCUBA-2 850 um map,
and we have identiﬁed 18 young stellar objects (YSOs, 4 Class I and 14 Class II) based on their Spitzer, Wide-ﬁeld
Infrared Survey Explorer (WISE) and Two-Micron All-Sky Survey (2MASS) near- and mid-infrared colours. The dense
cores and YSOs are mainly distributed along the ﬁlamentary structures of G181.84 and are well traced by HCO+ (1-0)
and N2 H+ (1-0) spectral-line emission. We ﬁnd signatures of sequential star formation activities in G181.84: dense
cores and YSOs located in the northern and southern sub-structures are younger than those in the central region. We
also detect global velocity gradients of about 0.8±0.05 km s−1 pc−1 and 1.0±0.05 km s−1 pc−1 along the northern andsouthern sub-structures, respectively, and local velocity gradients of 1.2±0.1 km s−1 pc−1 in the central substructure.
These results may be due to the fact that the global collapse of the extended ﬁlamentary structure S242 is driven by
an edge eﬀect, for which the ﬁlament edges collapse ﬁrst and then further trigger star formation activities inward. We
identify three substructures in G181.84 and estimate their critical masses per unit length, which are ∼ 101±15 M⊙
pc−1 , 56±8 M⊙ pc−1 and 28±4 M⊙ pc−1 , respectively. These values are all lower than the observed values (∼ 200
M⊙ pc−1 ), suggesting that these sub-structures are gravitationally unstable.
Accepted by MNRAS
https://arxiv.org/pdf/1905.12258

75

One Solution to the Mass Budget Problem for Planet Formation: Optically Thick Disks
with Dust Scattering
Zhaohuan Zhu1 , Shangjia Zhang1 , Yan-Fei Jiang2 , Akimasa Kataoka3 , Tilman Birnstiel4 , Cornelis P.
Dullemond5, Sean M. Andrews6 , Jane Huang6 , Laura M. Pérez7 , John M. Carpenter8 , Xue-Ning Bai9 ,David J. Wilner6 and Luca Ricci10
1

Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas,
NV 89154, USA; 2 Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA, USA; 3
National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 4 University Observatory,
Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 Munich, Germany; 5 Zentrum für
Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany; 6 Harvard-Smithsonian Center
for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 7 Departamento de Astronomı́a, Universidad deChile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 8 Joint ALMA Observatory, Avenida Alonso deCórdova 3107, Vitacura, Santiago, Chile; 9 Institute for Advanced Study and Tsinghua Center for Astrophysics,
Tsinghua University, Beijing 100084, China; 10 Department of Physics and Astronomy, California State University
Northridge, 18111 Nordhoﬀ Street, Northridge, CA 91130, USA
E-mail contact: zhaohuan.zhu at unlv.edu
ALMA surveys have suggested that the dust in Class II disks may not be enough to explain the averaged solid massin exoplanets, under the assumption that the mm disk continuum emission is optically thin. This optically thinassumption seems to be supported by recent DSHARP observations where the measured optical depths of spatiallyresolved disks are mostly less than one. However, we point out that dust scattering can considerably reduce the emission
from an optically thick region. If that scattering is ignored, the optical depth will be considerably underestimated.
An optically thick disk with scattering can be misidentiﬁed as an optically thin disk. Dust scattering in more inclined47

disks can reduce the intensity even further, making the disk look even fainter. The measured optical depth of ∼0.6 inseveral DSHARP disks can be naturally explained by optically thick dust with an albedo of ∼0.9 at 1.25 mm. Using
the DSHARP opacity, this albedo corresponds to a dust population with the maximum grain size (smax ) of 0.1-1 mm.
For optically thick scattering disks, the measured spectral index α can be either larger or smaller than 2 depending
on if the dust albedo increases or decreases with wavelength. Using the DSHARP opacity, α < 2 corresponds tosmax of 0.03-0.3 mm. We describe how this optically thick scattering scenario could explain the observed scaling
between submm continuum sizes and luminosities, and might help ease the tension between the dust size constraints
from polarization and dust continuum measurements. We suggest that a signiﬁcant amount of disk mass can be
hidden from ALMA observations at short millimeter wavelengths. For compact disks smaller than 30 au, we can easily
underestimate the dust mass by more than a factor of 10. Longer wavelength observations (e.g. VLA or SKA) aredesired to probe the dust mass in disks.
Accepted by ApJL
https://arxiv.org/pdf/1904.02127

Abstracts of recently accepted major reviews

Probing the cold magnetized Universe with SPICA-POL (B-BOP)
Ph. André1 , A. Hughes2 , V. Guillet3,4, F. Boulanger3,5 , A. Bracco1,5,6 , E. Ntormousi1,7, D. Arzoumanian1,8 ,A.J. Maury1,9 , J.-Ph. Bernard2 , S. Bontemps10 , I. Ristorcelli2, J.M. Girart11 , F. Motte12,1 , K. Tassis7 ,E. Pantin1 , T. Montmerle13 , D. Johnstone14 , S. Gabici15 , A. Efstathiou16 , S. Basu17 , M. Béthermin18 ,H. Beuther19 , J. Braine10 , J. Di Francesco14 , E. Falgarone5 , K. Ferrière2 , A. Fletcher20 , M. Galametz1 ,M. Giard2 , P. Hennebelle1, A. Jones3 , A.A. Kepley21 , J. Kwon22 , G. Lagache18 , P. Lesaffre5 , F. Levrier5 ,D. Li23 , Z.-Y. Li24 , S.A. Mao25 , T. Nakagawa22 , T. Onaka26 , R. Paladino27 , N. Peretto28 A. Poglitsch1,29 ,V. Revéret1 , L. Rodriguez1 , M. Sauvage1 , J.D. Soler1,19 , L. Spinoglio30 , F. Tabatabaei31 , A. Tritsis32 ,F. van der Tak33 , D. Ward-Thompson34 , H. Wiesemeyer25 , N. Ysard3 , and H. Zhang35
1

Laboratoire d’Astrophysique (AIM), CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris
Cité, 91191 Gif-sur-Yvette, France; 2 Institut de Recherche en Astrophysique et Planétologie (IRAP), CNRS, 9 Av.
Colonel Roche, BP 44346, 31028 Toulouse, France; 3 Institut d’Astrophysique Spatiale (IAS), CNRS (UMR 8617)
Université Paris-Sud 11, Bâtiment 121, 91400 Orsay, France; 4 Laboratoire Univers et Particules de Montpellier, Université de Montpellier, CNRS/IN2P3, CC 72, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France;
5
LERMA/LRA - ENS Paris - UMR 8112 du CNRS, 24 rue Lhomond, 75231, Paris Cedex 05, France; 6 Nordita, KTH
Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm, Sweden; 7 Department of Physics and ITCP, University of Crete, Voutes, GR-71003 Heraklion, Greece; 8 Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan; 9 Harvard-Smithsonian
Center for Astrophysics, Cambridge, MA02138, USA; 10 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux,
CNRS, B18N, Allée Geoﬀroy Saint-Hilaire, 33615 Pessac, France; 11 Institut de Ciències de l’Espai (ICE, CSIC),Can Magrans s/n, 08193 Cerdanyola del Vallès, Catalonia, Spain; Institut d’Estudis Espacials de Catalunya (IEEC),
E-08034, Barcelona, Catalonia, Spain; 12 Univ. Grenoble Alpes, CNRS, Institut de Planétologie et d’Astrophysique deGrenoble, 38000 Grenoble, France; 13 Institut d’Astrophysique de Paris (IAP), 98bis Bd Arago, 75014 Paris, France;
14
NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada; Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada; 15 APC, AstroParticule et
Cosmologie, Université Paris Diderot, CNRS, CEA, Observatoire de Paris, Sorbonne Paris, 75205 Paris, France; 16
School of Sciences, European University Cyprus, 1516 Nicosia, Cyprus; 17 Department of Physics and Astronomy, The
48

University of Western Ontario, London, ON N6A 3K7, Canada; 18 Aix-Marseille Univ., CNRS, LAM, Laboratoired’Astrophysique de Marseille, 13013, Marseille, France; 19 Max Planck Institute for Astronomy, Königstuhl 17, 69117
Heidelberg, Germany; 20 School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne,
NE1 7RU, UK; 21 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475,
USA; 22 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa 252-5210,
Japan; 23 National Optical Astronomy Observatory, 950 N. Cherry Ave., Tucson, AZ 85726, USA; 24 Department of
Astronomy, University of Virginia, Charlottesville, VA 22901, USA; 25 Max Planck Institute for Radioastronomy, Auf
dem Hügel 69, 53111 Bonn, Germany; 26 Department of Astronomy, Graduate School of Science, University of Tokyo,
Tokyo, Japan; 27 INAF-Istituto di Radioastronomia, via P. Gobetti, 101, 40129, Bologna, Italy; 28 School of Physics& Astronomy, Cardiﬀ University, Queen’s Buildings, The Parade, Cardiﬀ, CF24 3AA, UK; 29 Max-Planck-Institutfür extraterrestrische Physik, Garching, Germany; 30 Istituto di Astroﬁsica e Planetologia Spaziali, INAF, Via Fosso
del Cavaliere 100, I-00133 Roma, Italy; 31 School of Astronomy, Institute for Research in Fundamental Sciences, P.O.
Box 19395-5531, Tehran, Iran; 32 Research School of Astronomy and Astrophysics, Australian National University,
Canberra, ACT 2611, Australia; 33 SRON Netherlands Institute for Space Research, Groningen, The Netherlands;
Kapteyn Astronomical Institute, University of Groningen, The Netherlands; 34 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK; 35 Department of Astronomy, University of Florida, Gainesville,
FL 32611, USA
E-mail contact: pandre at cea.fr
SPICA, the cryogenic infrared space telescope recently pre-selected for a “Phase A” concept study as one of the threeremaining candidates for ESA’s ﬁfth medium class (M5) mission, is foreseen to include a far-infrared polarimetricimager (SPICA-POL, now called B-BOP), which would oﬀer a unique opportunity to resolve major issues in our
understanding of the nearby, cold magnetized Universe. This paper presents an overview of the main science drivers
for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our
Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-ﬁeld 100–350 µm images oflinearly polarized dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity andspatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I).
The B-BOP 200 µm images will also have a factor ∼ 30 higher resolution than Planck polarization data. This will make
B-BOP a unique tool for characterizing the statistical properties of the magnetized interstellar medium and probing
the role of magnetic ﬁelds in the formation and evolution of the interstellar web of dusty molecular ﬁlaments giving
birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby
galaxies and testing galactic dynamo models, constraining the physics of dust grain alignment, informing the problemof the interaction of cosmic rays with molecular clouds, tracing magnetic ﬁelds in the inner layers of protoplanetarydisks, and monitoring accretion bursts in embedded protostars.
Accepted by Publications of the Astronomical Society of Australia (PASA)
http://arxiv.org/pdf/1905.03520

49

Meetings

Whispers special session: Massive data processing and analysis inradioastronomy, Amsterdam, September 26, 2019
First announcement and call for oral contributions and posters, deadline: Friday June 28th in the evening.
Datasets produced by the current and future generations of radio telescopes are becoming extremely large, due tothe increase in sensitivity, instantaneous bandpass per pixel and number of pixels per receiver. This is true for the(sub)millimeter domain where the main instruments (IRAM-30m, NOEMA, ALMA, APEX, LMT, etc) now routinely
process several tens of GHz with spectral resolutions of the order of 100 kHz (implying the measurements of about
500,000 frequencies simultaneously), as well as for the centimeter domain (VLA, FAST, LOFAR) and the foreseen
SKA that will again represent a revolution in data rate. Data processing and analysis of these large volumes require
the development of innovative methods based on the most recent advances in signal processing.
To get the best out of such powerful telescopes, and answer key questions on a wide range of astrophysical topics(from the origin of stars and planets, to cosmic dawn), requires to build bridges between the astronomy community
and the applied mathematics / signal processing communities. The proposed one-day session during the Whispers(Workshop on Hyperspectral Image and Signal Processing: Evolutions in Remote Sensing) workshop in Amsterdam
aims at presenting the challenges encountered by the radio-astronomy community and the on-going activities to solve
them. This event will be organized in 3 to 4 sessions of four to ﬁve 20-minutes contributed talks introduced by two
invited presentations to set the ﬁeld by• Anna Scaife (Manchester, UK ): Radioastronomy challenges in cosmology and galaxy evolution studies• Susan Clark (Princeton, USA): Atomic and molecular line imaging as diagnostics for ISM and star formation
Posters will be presented during a ﬂash session. The day will end with a round table to deﬁne directions for futurecollaborations. This table will be animated by Cyril Tasse (Obs. de Paris, France), Yves Wiaux (Heriot-Watt, UK,
TBC), and the SOC members.
The themes of the workshop include• Single dish and interferometer data processing• Filtering of artifacts and denoising• Structure identiﬁcation with or without velocity information• Clustering• Identiﬁcation and quantiﬁcation of temporal variations• Data - model comparisons
The astrophysics focus is put on the topics beneﬁting from advanced radioastronomy observations:• The relationship between interstellar medium properties and star formation, from the local universe to distantgalaxies.
• Observational constraints on Cosmic dawn and the epoch of reionization.

50

Registration is mandatory, with a reduced fee (190 euros) for the one day special session. The fee includes lunch andcoﬀee breaks. Participants are invited to register and submit either an abstract, an already published paper, or an
original paper for publication in IEEE.
Key dates:
Submission deadline 28 June 2019 (This is the actual deadline for this special session. Please disregard the website
deadline.)
Final program 15 July 2019.
End of registration 10 September 2019.
Special session 26 September 2019.
SOC:
Jérôme Bobin (CEA Saclay - IRFU/CosmoStat, France), Chiara Ferrari (Observatoire de la Cte d’Azur, France),
Maryvonne Gerin (Observatoire de Paris, France), Ralf Klessen (Heidelberg University, Germany), Joshua E. G. Peek
(Space Telescope Science Institute & Johns Hopkins University, USA), Jérôme Pety (IRAM & Observatoire de Paris,
France)All information can be found here
http://www.ieee-whispers.com
The submission facility is available here
http://www.ieee-whispers.com/paper-submission/
You have to create a loggin account and then submit an abstract. Please select the right session: ”Massive dataprocessing and analysis in radioastronomy”.

Mission to the Universe From Earth to Planets, Stars & Galaxies-The 2019 Annual Meeting of the German Astronomical Society
16-20 September 2019 in Stuttgart, Germany
will take placethe 2019 Annual Meeting of the German Astronomical Society.
This year, it’s titled:
Mission to the Universe
From Earth to Planets, Stars & Galaxies”It’s a German version of AAS meeting”,
with diﬀerent plenary talks and splinter sessions;plus this year Stratospheric Observatory for Infrared Astronomy (SOFIA) will visit us,
and tours for the participants will be provided.
please check the conference website:
https://conference.dsi.uni-stuttgart.de/e/ag2019
and hopefully, see you in Stuttgart!

51

Summary of Upcoming Meetings

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/
Summer School Protoplanetary Disks and Planet Formation
5 - 9 August 2019 Copenhagen, Denmark
http://nbia.nbi.ku.dk/nbia-school-2019
Orion Uncovered
26 - 30 August 2019 Leiden, The Netherlands
https://sites.google.com/view/OrionLeiden2019
Understanding the Nearby Star-forming Universe with JWST
26 - 30 Aug 2019 Courmayeur, Italy
http://www.stsci.edu/institute/conference/unsfjwst2019
Celebrating the first 40 Years of Alexander Tielens’ Contribution to Science: The Physics and Chemistry of the ISM
2 - 6 september 2019, Avignon, France https://tielens2019.sciencesconf.org
From Gas to Stars: The Links between Massive Star and Star Cluster Formation
16-20 September 2019 York, UK
https://starformmapper.org/final-conference/
Crete III - Through dark lanes to new stars Celebrating the career of Prof. Charles Lada
23 - 27 September 2019 Crete, Greece
http://crete3.org
The UX Ori type stars and related topics
30 September - 4 October 2019 St. Petersburg, Russia
http://uxors-2019.craocrimea.ru
First Stars VI
1 - 6 March 2020 Concepcion, Chile
http://www.astro.udec.cl/FirstStarsVI/
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Linking Dust, Ice, and Gas in Space19 - 24 April 2020, Capri, Italy
http://frcongressi.net/ecla2020.meet
COOL STARS 21: Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
21 -26 June 2020, Toulouse, France
https://coolstars21.github.io/
The Physics of Star Formation: From Stellar Cores to Galactic Scales
29 June - 3 July 2020 Lyon, France https://cral.univ-lyon1.fr

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

Abstract submission deadline
The deadline for submitting abstracts and othersubmissions is the ﬁrst day of the month. Abstracts
submitted after the deadline will appear in the following month’s issue.

53