THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 313 — 17 January 2019

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

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

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Abstracts of Newly Accepted Papers . . . . . . . . . . . 9
Abstracts of Newly Accepted Major Reviews . 39

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

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

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

Summary of Upcoming Meetings . . . . . . . . . . . . . 46

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

Editorial Board
Joao Alves
Alan Boss
Jerome Bouvier
Lee Hartmann
Thomas Henning
Paul Ho
Jes Jorgensen
Charles J. Lada
Thijs Kouwenhoven
Michael R. Meyer
Ralph Pudritz
Luis Felipe Rodrı́guez
Ewine van Dishoeck
Hans Zinnecker
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Cover Picture
HD 97300 is an intermediate mass young star in
the Chamaeleon I star forming complex. It is a
B9V star which is transitioning from Herbig Ae/Be
type to a zero-age main sequence star. The star isilluminating the IC 2631 = Cederblad 112 reflection
nebula. HD 97300 is an 0.8 arcsecond binary, where
the lower-mass companion is about 3 magnitudes
fainter at K, and thus likely a T Tauri star.
Image courtesy ESO.

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The Star Formation Newsletter seeks a WEBMASTER
Are you one of those people with too much time on your hands and too muchmoney in your pocket? Then go on reading.
The Star Formation Newsletter is a volunteer effort that I have invested timeand energy in for the past 26 years, in recent years with the capable help
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The Newsletter website, however, has not changed in all these years, and is
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Bo Reipurth3high-mass stars.
The study of Herbig Ae/Be stars is active and for recent reviews on the class, I refer the reader to the Topical Collection on Herbig Ae/Be stars published in 2015by Astrophysics and Space Science1 . It includes reviewsby Kraus (2015) on interferometric results, Grady et al.
(2015), Quanz (2015), and Wyatt et al. (2015) who review (proto-planetary) disks, Brittain et al. (2015) on
spectroscopy, Vink (2015, spectropolarimetry), Duchêne(2015, binarity) and Beltran (2015) for the earlier phasesin their formation. A dedicated workshop on the topic willtake place in June 20192.

Perspective
Herbig Ae/Be stars
René Oudmaijer

2

Introduction

Stars come in many sizes and masses, and traditionallyastronomers study either high- or low-mass objects. Star
formation has been no exception. In a way, this is quite
understandable as there are large disparities in our understanding of the formation of low- and high-mass stars. For
1 Summary
example, we can readily identify two issues that indicatethat the formation of a massive star differs from that of a
Here I describe the pre-Main Sequence Herbig Ae/Be stars lower mass star.
and highlight their role in studies of star formation. TheyFirstly, it has long been a recognized problem that thewere discovered by George Herbig in 1960, at a time whenintense brightness of massive stars (the luminosity on thethe solar mass T Tauri stars had only just been identiMain Sequence goes roughly as M 3.3 ) can halt the accrefied to be in the pre-Main Sequence phase of evolution.
tion of matter onto the stellar surface because of the inLooking for more massive analogues, and by focussing his
creased radiation pressure on the infalling material. The
search on objects with A and B spectral types, Herbig
upper limit to the maximum possible mass has been estifound a few dozen such stars, which later came to bemated to be of order 10-30 M⊙ (e.g. Wolfire & Cassinelli
known as Herbig Ae/Be stars. They have masses between
1987; Zinnecker & Yorke 2007), implying stars more masthose of T Tauri stars and Massive Young Stellar Objects.
sive than that cannot be formed. However, such stars are
The latter group of stars are optically invisible as they arecommonplace, so another mechanism for the formation ofstill embedded in their native clouds (e.g. Lumsden et al.
massive stars needs to be explored.
2013). The intermediate-mass Herbig Ae/Be stars play aparticularly important part in understanding the differ- After intense debate over the last couple of decades, oneences in the formation of, and accretion of matter onto, of the more popular theories put forward to explain highmass star formation, the merging of two lower mass stars
low- and high-mass stars, respectively.
(Bonnell et al. 1998), lost support for being the sole
As Herbig Ae/Be stars are bright and have relatively large
such mechanism due to the exceptionally high densities ofdisks, they are ideal targets for high spatial resolution obstars needed to make this happen (Baumgardt & Klessen
servations (e.g. Garufi et al. 2018), and they have become2011). The theories that are nowadays put forward can beprime targets to study planet formation in their circumroughly divided into two groups. On the one hand, a mechstellar disks as well. Indeed, as of now, several systems
anism similar to the low-mass star formation paradigm ishave been observed to not only be actively accreting mainvoked. In this case a star forms through the monolithic
terial but are also orbited by planets (see e.g. the review
collapse of a molecular cloud and is fed through an acby Quanz 2015), although sometimes the evidence is amcretion disk (McKee & Tan 2003; Krumholz et al. 2009).
biguous (e.g. Mendigutia et al. 2018).
Its main competing scenario requires the presence of clusAs the proto-planetary disk aspect has been discussed in ters. In this scenario, a large number of stars form simulearlier Perspectives in the SF Newsletter (e.g. Nienke van taneously through the gravitational collapse of a cloud.
der Marel in SF 308), I will focus on the stars’ impor1 http://link.springer.com/journal/volumesAndIssues10509?tabtance for understanding star formation with emphasis on Name=topicalCollections
2 https://starry-project.eu/final-conference/
identifying differences and similarities between low- and
4

The most massive of the fragments steal material fromthe other objects and grow more rapidly and to larger final masses. This process has been coined “competitive
accretion” (Bonnell et al. 2001; 2004). A nice overview ofmassive star formation is provided by Jonathan Tan in the
Perspectives of a recent issue of the SF Newsletter (306).
What is relevant here is that both theories require thepresence of an accretion disk through which material isconcentrated in the equatorial plane so that it may overcome the strong ionising radiation of the central object
and be efficiently accreted (e.g. Kuiper et al., 2010; 2011).
Much effort has been devoted to finding and characterizing
the accretion disks.
This brings us to the second major difference in the formation of low- and high-mass stars. Magnetic fields are
known to play an important role in the accretion of material onto lower mass stars. Material flows from an accretion disk onto the stars along magnetic field lines andcrashes onto the young, growing and unsuspecting, object,giving rise to huge shocks that are visible in X-rays andUltraviolet excess emission. This process is called magnetically controlled accretion (MA) and has stood the testof time thus far. A useful reference is for example Bouvier et al. (2007), where evidence for the MA paradigm isoutlined.

Figure 1: The derived mass accretion rate as function of mass for
the Herbig Ae/Be stars with good Gaia DR2 parallaxes by Fairlamb
et al. (2015) and Wichittanakom et al. (2019, in prep.). The massdependency of the accretion rate is different for stars with mass lowerand higher than 3 M⊙ , respectively.

subject to scrutiny. It now appears that Herbig Ae stars
are more akin to T Tauri stars than to Herbig Be stars.
Among the earliest such reports are that the linear spectropolarimetric signatures across the Hα emission line observed in both T Tauri and Herbig Ae stars are very similar
to each other, while those observed for higher mass Herbig
Be stars are not (Vink et al. 2002; 2003). As the features
towards the T Tauri stars can be explained with accretion
hot spots due to magnetically channeled accreting material (Vink et al. 2005; Mottram et al. 2007), it would thenfollow that Herbig Ae stars may form in the same manner
as T Tauri stars.

The more massive objects are non-magnetic. Because
their envelopes are radiative, no magnetic field is generated as this usually happens in stars by convection. Indeed, magnetic fields have hardly, if at all, been detected
towards those (e.g. Alecian et al. 2013). As a result MA
is not expected to apply in the case of the most massive
objects, requiring another accretion mechanism. However,
how the material arrives at the stellar surface in the absence of magnetic fields is still unclear.

Similar findings have been published since. Magnetic fields
were reported to be present in some Herbig Ae/Be stars bysome (Wade et al 2005; Hubrig et al. 2004; Alecian et al.
2013). Others reported differences in properties between
Herbig Ae and Be stars but similarities between the Herbig
Ae and T Tauri stars (Mendigutia et al. 2012). Grady
et al. (2010) deduce that the accretion shock regions in
3 From Herbig Ae to Herbig Be
a Herbig Ae star are comparable in size and location to
those in the lower mass magnetic objects. Scholler et al.
It is in the mass range spanned by the Herbig Ae/Be (2016) interpret the spectroscopic variability observed in
objects that the acting star forming mechanism switches the spectrum of a Herbig Ae star as evidence that it isfrom magnetically controlled accretion from disks with in- currently undergoing magnetically-controlled accretion in
ner holes to an as yet unknown mechanism. They play the same manner as the T Tauri stars. On the other hand,
therefore an important role in understanding star formaiton dedicated modeling indicated that, if present at all, themagnetosphere in a particular Herbig Be star with spectral
at higher masses.
Traditionally, this transition was thought to occur at com- type B9IV must be small (Kurosawa et al. 2016) while forparatively low stellar temperatures, at the G/F to A spec- other Herbig Be stars MA may not be necessary at all
tral type boundary, where the envelopes become radiative. to explain the observations (Patel et al. 2017). It would
However, since the start of this century, this view has been appear that there is a break at around late B spectral typewhere the MA star formation mechanism ceases to operate
In the following I highlight several studies of large samplesof objects from an observational point of view to see towhat extent the MA scenario may or may not apply toobjects more massive than T Tauri stars.

5and another mechanism takes over.
6

Depolarization

Number of Objects

In addition to these specific studies mentioning the modes
Line polarization
McLeanof accretion, various studies have shown differences beComplex
tween low- and high-mass Herbig Ae/Be stars (e.g. Fuente
4
et al. 1998 on mm emission; Testi et al. 1999 on clustering; Baines et al. 2006 on binarity; Millan-Gabet et al.
2007 on near-infrared sizes; Mendigutia et al. 2011a on
2
spectroscopic variability). Using spectroscopy, Cauley &Johns-Krull (2014; 2015) infer that Herbig Ae stars are
more likely to have red-shifted absorption than Herbig Be
B0 B1 B2 B3 B6 B7 B8 B9 A0 A1 A2 A3 A5 A7 A8 F2 F7 F8 G2 G3 G5 K2 K3 K5 K7stars, indicating a different infall geometry. However, theSpectral Type
precise mass where the lower mass objects deviate fromhigher mass objects is not well defined in the above stud- Figure 2: The occurrence of the various line effects observed inies.
the linear spectropolarimetry as a function of spectral type. The“line de-polarization” across Hα probes disks reaching close to thestar and is mostly found for the more massive Herbig Be stars. In
contrast, the “line polarization” traces line emission scattering off acircumstellar disk. This is predominately present towards the lower
mass, Herbig Ae and T Tauri stars. It appears that the change
occurs roughly around spectral type B7-B8. Figure adapted from
Ababakr et al. (2017).

To address this question, one needs large samples of objects, and below I discuss three recent studies that havethe potential of settling this issue.

3.1

Spectroscopic accretion diagnostics

Fairlamb et al. (2015) presented X-Shooter spectra for
91 Herbig Ae/Be objects, the largest such sample to havebeen investigated spectroscopically. From these data, they
determined the stellar parameters such as temperatureand gravity of these stars in a homogeneous fashion byfitting the spectra with stellar atmospheric models, andderived the accretion rates from the UV excess following the methodology of Muzerolle et al. (2004), Donehew& Brittain (2011) and extending the work of Mendigutia
et al. (2011b) for all these objects. An interesting byproduct of the study was already discussed by Mendigutia
et al. (2011b); all emission lines ranging from hydrogen
recombination lines at various wavelengths to atomic permitted and forbidden lines have luminosities that correlate
well with the accretion luminosity as measured by the UV
excess. They therefore also correlate with accretion rate
(Fairlamb et al. 2017). Although it is not clear whether
this correlation is intrinsically due to accretion or someother effect (Mendigutia et al. 2015), they do provide anobservationally cheap manner to derive the accretion rateof an object without having to resort to the rather delicate
and time-consuming process of measuring the UV excess
in Herbig Ae/Be stars, stars which have, contrary to thecooler T Tauri stars, a significant amount of intrinsic UV
radiation already.

are available for most of the stars in the Fairlamb andWichittanakom samples, the distances to the objects canbe determined to the highest accuracy hitherto possible.
Armed with this information, the luminosities and masses,
and hence the accretion rates, could be re-determined anddetermined, respectively. Restricting the sample to objects that were flagged as having good Gaia DR2 parallaxes (see discussion in Vioque et al.) results in a sampleof 97 objects containing many of the Thé et al. Table 1
objects which are the best Herbig Ae/Be candidate stars
known. Figure 1 shows the mass accretion rates as function of mass, and represents the best such data available.
It can be seen that the slope is steeper at the low mass
end than at the high mass end, while the spread in values
is also increased. The break at which the slope changes
is determined to be ∼ 3 M⊙ . In addition, Fairlamb et al.
(2015) found that Herbig Ae stars can be explained by
MA, but that the earliest Herbig Be stars have too large
UV-excesses to be explained by the usual accretion shock
scenario.

3.2

Probing the disks - linear spectropolarimetry

Linear spectropolarimetry across Hα has been long known
to reveal the presence of very small-scale circumstellar
disks (Oudmaijer & Drew 1999). Subsequent studies of
Herbig Ae/Be stars showed that spectropolarimetric effects across the Hα emission fall into a small number ofcategories (e.g. Ababakr, Oudmaijer & Vink, 2016). In
particular, Vink et al. (2002, 2003) found that intrinsic
Using the new Gaia DR2 data (Vioque et al. 2018) thatline polarization of Hα predominately occurs for T Tauri
To extend the sample to the northern hemisphere, Wichittanakom (2019, in prep.) obtained spectra for 30 objects
using the Isaac Newton Telescope and determined theirstellar parameters in the same manner as Fairlamb et al.
(2015). This led to a large, combined, sample of Herbig
Ae/Be stars that were analyzed in a homogeneous manner.

6and Herbig Ae stars and can be explained by compact Hαemission scattered off a circumstellar disk, while the Herbig Be stars typically display a line de-polarization thatcan be explained with a disk reaching onto the stellar surface (Vink, Harries & Drew 2005).
With 56 objects, Ababakr, Oudmaijer & Vink (2017) presented the largest linear spectropolarimetric study of Herbig Ae/Be stars. They found a break in the spectropolarimetric, and possibly accretion, properties of high- andlow-mass objects to occur around the B7-B8 spectral type.
This is found in both the detection statistics and, especially, the nature of the line-effect (see Fig. 2). Intriguingly, the B7-B8 spectral type boundary corresponds to∼3 M⊙ , just like the break in accretion properties above.
The similarities in the spectropolarimetric properties be- Figure 3: Herbig Ae/Be stars placed in the HR-diagam using
tween T Tauri stars - which are known to undergo mag- Gaia DR2 parallaxes. Figure adapted from Vioque et al. (2018).
netospheric accretion - and the late-type Herbig Be andHerbig Ae stars suggest this mechanism also acts on these
Hα emission line profiles (collated from the literature) isintermediate-mass stars (cf. Vink et al. 2002).
significantly higher in the variable sample than in the nonAn accretion scenario for the more massive stars is notvariable sample. As doubly-peaked emission is expected
well established. A promising contestant is the so-called
to originate from edge-on disk configurations. The edge“Boundary Layer” accretion. In this model, the circum- on (Hα lines), dusty (infrared excess) disk scenario for thestellar disk reaches onto the stellar surface, and the thin
UXOR phenomenon has now gained, strong, additional
layer in which the Keplerian rotating material loses its
observational support.
angular momentum and kinetic energy gives rise to excess
UV emission (e.g. Blondel & Tjin a Djie 2006; Cauley & Let us now return to the differences between high- andJohns-Krull 2015). As of yet, details have to be worked low-mass Herbig Ae/Be stars. The photometric variability
out for the case of higher mass pre-Main Sequence stars. and infrared excess are found to be present for low-massstars, but not for higher mass stars. With masses obtained using the Gaia derived HR diagram, Vioque et al.
3.3 The new frontier : Gaia
(2018) find that the break occurs at 7 M⊙ . This is a higher
mass than the 3 M⊙ where both the accretion rates deterFinally, a Gaia study of Herbig Ae/Be stars was recently mined from spectroscopy as well as the nature of the accompleted by Vioque et al. (2018). After selecting on cretion as probed by spectropolarimetry change. This aphigh-quality parallaxes, they were able to put more than parent contradiction can be understood when we consider
200 objects in the HR diagram (see Figure 3). In addition, the spatial scales involved; whereas the spectroscopy andthey derived the photometric variability of the objects us- spectropolarimetry trace the ionized material very close to
ing the data provided in the Gaia catalogue and identified the star, the infrared emission traces the dusty material
43 strongly variable objects. It turns out that most of much further out. The former is therefore more likely tothese variable objects have strong infrared excesses due be associated with the accretion process, while the latterto circumstellar dust, while the least variable objects ap- is more likely associated with dust dispersal mechanisms:
pear to be surrounded by less dust. It suggests that the the higher radiation pressure from the hotter and brighter
dust may be responsible for the extinction, and, indeed, objects will result in faster clearing of the dusty disks (e.g.
most known UXOR variables are included in the highly Gorti et al. 2009).
variable sample. The UXORs are hypothesized to be surrounded by inhomogeneous, dusty, edge-on disks, whose
orbital motions induce variable, but not necessarily peri- 4
Final remarks and Outlook
odic, extinction. The best observational evidence thus far
for this scenario is the fact that during periods of high
The main take away messages from this short overview are
extinction, the linear polarization - tracing scattered lightthat:- peaks (e.g. Grinin 2000).
New support for this scenario now comes from the fact that i) Herbig Ae/Be stars bridge the gap between low- andVioque et al. find that the occurrence of doubly-peaked high-mass young stars and cover the mass where a changein accretion mechanism occurs.
7ii) From both mass accretion rates and Hα line spectropolarimetry, there appears to be a change in properties, andtherefore perhaps accretion mode, at around 3 M⊙ (corresponding to mid- to late B spectral type).
iii) Using Gaia DR2 data and auxiliary information, alarge sample of Herbig Ae/Be stars has been placed in the
HR diagram. A change in infrared and photometric properties is found to occur at higher masses, 7 M⊙ , which is
identified with dust dispersal being faster and more efficient in the vicinity of hotter, luminous Herbig Be stars.

Fairlamb, J. R. et al. 2017, MNRAS, 464, 4721
Fuente, A., Martin-Pintado, J., Bachiller, R., Neri, R., & Palla, F.
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The latter study had been carried out in the context of
the EU-funded STARRY project. It served as the firststep in characterizing the known Herbig Ae/Be stars. We
are currently using Gaia to expand the set of known Herbig Ae/Be stars from the Gaia database using machinelearning techniques to improve on the statistical findingspresented here. In addition, following the initial work by
Testi, Palla & Natta (1999), we aim to establish the presence or absence of clusters around these objects to study
their clustering properties as function of mass.

Krumholz, M. R., Klein, R. I., McKee, C. F., Offner, S. S. R., &Cunningham, A. J. 2009, Science, 323, 754
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Acknowledgements:

Mendigutı́a, I., Eiroa, C., Montesinos, B., et al. 2011a, A&A, 529,
A34

It is a pleasure to thank Ignacio Mendigutı́a, Miguel Vioque
and John Fairlamb for fruitful discussions and their feed- Mendigutı́a, I., Calvet, N., Montesinos, B., et al. 2011b, A&A, 535,
A99
back on an earlier version of this manuscript. I thank
Chumpon Wichittanakom for kindly providing Figure 1 Mendigutı́a, I., Mora, A., Montesinos, B., et al. 2012, A&A, 543,
A59
prior to publication. The STARRY project receives fundMendigutı́a I., Oudmaijer R. D., Rigliaco E., Fairlamb J. R., Calvet
ing from the European Union’s Horizon 2020 Marie
N., Muzerolle J., Cunningham N., Lumsden S. L., 2015, MNRAS,
Sklodowska Curie Actions (MSCA) programme under Grant 452, 2837
Agreement No 676036.
Mendigutı́a I., Oudmaijer R. D. Schneider P. C. Huélamo N., Baines,
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Abstracts of recently accepted papers

1 Steven C. Adams , Máté Ádámkovics , John S. Carr , Joan R. Najita and Sean D. Brittain
Water and OH Emission from the inner disk of a Herbig Ae/Be star
1

1

2

3

1,3

1

Department of Physics and Astronomy, 118 Kinard Laboratory, Clemson University, Clemson, SC 29634-0978, USA;
Naval Research Laboratory, Code 7211, Washington, D.C. 20375, USA; 3 National Optical Astronomy Observatory,
950 North Cherry Avenue, Tucson, AZ 85719, USA
2E-mail contact: scadams at clemson.edu
We report the detection of hot H2 O and OH emission from the Herbig Ae/Be star HD 101412 using the Cryogenic
Infrared Echelle Spectrograph on the Very Large Telescope. Previous studies of Herbig Ae/Be stars have shown thepresence of OH around some of these sources, but H2 O has proven more elusive. While marginal water emission has
been reported in the mid-infrared, and a few Herbig Ae/Be stars show water emission in the far-infrared, water emission
near 2.9 µm has not been previously detected. We apply slab models to the ro-vibrational OH, H2 O, and CO spectraof this source and show that the molecules are consistent with being cospatial. We discuss the possibility that thedetection of the CO overtone bandhead emission, detection of water emission, and the large line to continuum contrastof the OH lines may be connected to its high inclination and the λ Boö nature of this star. If the low abundance ofrefractories results from the selective accretion of gas relative to dust, the inner disk of HD 101412 should be strongly
dust-depleted allowing us to probe deeper columns of molecular gas in the disk, enhancing its molecular emission. Ourdetection of C- and O-bearing molecules from the inner disk of HD 101412 is consistent with the expected presence inthis scenario of abundant volatiles in the accreting gas.
Accepted by ApJ
https://arxiv.org/pdf/1812.07094.pdf

2 Hossam Aly , Giuseppe Lodato , and Paolo Cazzoletti

On The Secular Evolution of GG Tau A Circumbinary Disc: A Msialigned Disc Scenario
1

1

2

1

Universit degli Studi di Milano, Via Giovanni Celoria 16, 20133 Milano, Italy; 2 Max-Planck-Institut für Extraterrestrische Physik, Gießenbachstraße, 85741 Garching bei München, Germany
E-mail contact: hossam.aly at unimi.it
The binary system GG Tau A is observed to have a circumbinary disc with a dust ring located further out than
expected, assuming a co-planar disc and a corresponding semi-major axis of 34 AU. Given the binary separation,
this large cavity can be explained by relaxing the assumption of a co-planar disc and instead fit the observations
with a mis-aligned circumbinary disc around an eccentric binary with a wider semi-major axis of 60 AU, consistent
with fitting the proper motion data for the system. We run SPH simulations to check this possibility and indeed wefind that a misalignment angle of 30 degrees and a binary eccentricity of 0.45 fit both the astrometric data and thedisc cavity. However, such configuration could in principle be unstable to polar, rather that planar alignment. We
investigate the secular evolution of this configuration and show that it is indeed stable throughout the disc lifetime.
Accepted by MNRAS
http://arxiv.org/pdf/1809.06383

3

Methyl cyanide (CH3 CN) and propyne (CH3 CCH) in the low mass protostar IRAS
16293−2422
Ines Andron1 , Pierre Gratier1 , Liton Majumdar2 , Thomas H.G. Vidal1 , Audrey Coutens1 , JeanChristophe Loison3,4 , and Valentine Wakelam1
1

Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac,
9France; 2 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109,
USA; 3 Univ. Bordeaux, ISM, UMR 5255, F-33400, Talence, France; 4 CNRS, ISM, UMR 5255, F-33400, Talence,FranceE-mail contact: valentine.wakelam at u-bordeaux.fr
Methyl cyanide (CH3 CN) and propyne (CH3 CCH) are two molecules commonly used as gas thermometers for interstellar gas. They are detected in several astrophysical environments and in particular towards protostars. Using dataof the low-mass protostar IRAS 16293−2422 obtained with the IRAM 30m single-dish telescope, we constrained theorigin of these two molecules in the envelope of the source. The line shape comparison and the results of a radiativetransfer analysis both indicate that the emission of CH3 CN arises from a warmer and inner region of the envelope
than the CH3 CCH emission. We compare the observational results with the predictions of a gas-grain chemical model.
Our model predicts a peak abundance of CH3 CCH in the gas-phase in the outer part of the envelope, at around 2000
au from the central star, which is relatively close to the emission size derived from the observations. The predicted
CH3 CN abundance only rises at the radius where the grain mantle ices evaporate, with an abundance similar to theone derived from the observations.
Accepted by MNRAS
http://arxiv.org/pdf/1812.05416

4

A method to analyse velocity structure
Becky Arnold1 and Simon Goodwin1
1

University of Sheffield, UK

E-mail contact: rjarnold1 at sheffield.ac.uk
We present a new method of analysing and quantifying velocity structure in star forming regions suitable for the
rapidly increasing quantity and quality of stellar position-velocity data. The method can be applied to data in any
number of dimensions, does not require the centre or characteristic size (e.g. radius) of the region to be determined,
and can be applied to regions with any underlying density and velocity structure. We test the method on a variety
of example datasets and show it is robust with realistic observational uncertainties and selection effects. This method
identifies velocity structures/scales in a region, and allows a direct comparison to be made between regions.
Accepted by MNRAS
https://arxiv.org/pdf/1812.05628

5

Investigation of the stellar content in the IRAS 05168+3634 star-forming region
N. M. Azatyan1
1

Byurakan Astrophysical Observatory, Armenia

E-mail contact: nayazatyan at gmail.com
We present the investigation results of structure and stellar content of a molecular cloud surrounding the five IRAS
sources: 05168+3634, 05184+3635, 05177+3636, 05162+3639, and IRAS 05156+3643. Using multi-color criteria, we
identified a rich population of embedded YSO candidates with infrared excess (Class 0/I and Class II) and theircharacteristics in a quite large molecular cloud which is located in the region of 24 arcmin radius. The molecular
cloud includes 240 candidates of YSOs within the radii of sub-regions around 5 IRAS sources. The color-magnitude
diagrams of the sub-regions suggest a very young stellar population. We construct the K luminosity function (KLF)of the sub-regions and according to the values of the slopes of KLFs, the age of the sub-regions can be estimatedbetween 0.1-3 Myr. The SEDs are constructed for 45 Class I and 75 Class II evolutionary stages YSOs and thereceived parameters of those YSOs are well correlated with the results obtained by other methods.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1812.06808.pdf

106Creating retrogradely orbiting planets by prograde stellar fly-bys
Andreas Breslau1 and Susanne Pfalzner1,2
1Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 2 Jülich Supercomputing
Center, Forschungszentrum Jülich, 52428 Jülich, Germany
E-mail contact: abreslau at mpifr.de
Several planets have been found that orbit their host star on retrograde orbits (spin-orbit angle ϕ > 90◦ ). Currently,
the largest measured projected angle between the orbital angular momentum axis of a planet and the rotation axis of its
host star has been found for HAT-P-14b to be ≈ 171◦ . One possible mechanism for the formation of such misalignments
is through long-term interactions between the planet and other planetary or stellar companions. However, with thisprocess, it has been found to be difficult to achieve retrogradely orbiting planets, especially planets that almost
exactly counter-orbit their host star (ϕ ≈ 180◦ ) such as HAT-P-14b. By contrast, orbital misalignment can beproduced efficiently by perturbations of planetary systems that are passed by stars. Here we demonstrate that
not only retrograde fly-bys, but surprisingly, even prograde fly-bys can induce retrograde orbits. Our simulations
show that depending on the mass ratio of the involved stars, there are significant ranges of planetary pre-encounterparameters for which counter-orbiting planets are the natural consequence. We find that the highest probability to
produce counter-orbiting planets (≈ 20%) is achieved with close prograde, coplanar fly-bys of an equal-mass perturberwith a pericentre distance of one-third of the initial orbital radius of the planet. For fly-bys where the pericentre
distance equals the initial orbital radius of the planet, we still find a probability to produce retrograde planets of≈ 10 % for high-mass perturbers on inclined (60◦ < i < 120◦) orbits. As usually more distant fly-bys are morecommon in star clusters, this means that inclined fly-bys probably lead to more retrograde planets than those withinclinations < 60◦ . Such close fly-bys are in general relatively rare in most types of stellar clusters, and only in very
dense clusters will this mechanism play a significant role. The total production rate of retrograde planets depends
then on the cluster environment. Finally, we briefly discuss the application of our results to the retrograde minor
bodies in the solar system and to the formation of retrograde moons during the planet-planet scattering phase.
Accepted by A&A
http://arxiv.org/pdf/1812.04104

7

The CIDA Variability Survey of Orion OB1. II: demographics of the young, low-massstellar populations
César Briceño1 , Nuria Calvet2 , Jesús Hernández3 , A. Katherina Vivas1 , Cecilia Mateu4,6 , Juan José
Downes5,6 , Jaqueline Loerincs7 , Alice Pérez8 , Perry Berlind9 , Catherine Espaillat10 , Lori Allen11 , Lee
Hartmann2 , Mario Mateo2 and John I. Bailey III12
1

Cerro Tololo Inter-American Observatory, National Optical Astronomical Observatory, Casilla 603, La Serena, Chile;
Dept. of Astronomy, University of Michigan, 311 West Hall, 1085 S University Av, Ann Arbor, MI 48109, USA; 3
Instituto de Astronomı́a, UNAM, Unidad Académica en Ensenada, Ensenada, 22860, México; 4 Depto de Astronomı́a,Instituto de Fı́sica, Univ. de la República, Iguá 4225, CP 11400 Montevideo, Uruguay; 5 PDU Ciencias Fı́sicas, Centro
Universitario Regional del Este (CURE), Univ. de la República, 27000 Rocha, Uruguay; 6 Centro de Investigaciones deAstronomı́a (CIDA), Apdo. Postal 264, Mérida 5101-A, Venezuela; 7 School of Mines, University of Colorado, Boulder,
CO, USA; 8 University of Leeds, School of Physics and Astronomy, LS29JT, Leeds, UK.; 9 Harvard-Smithsonian Center
for Astrophysics, 60 Cambridge, MA 02138, USA; 10 Boston University, Astronomy Department, 725 CommonwealthAvenue, Boston, MA 02215, USA; 11 National Optical Astronomical Observatory, 950 North Cherry Avenue, Tucson,
AZ 85719, USA; 12 Leiden University, Niels Bohrweg 2, 2333 CA Leiden, Netherlands
2E-mail contact: cbriceno at ctio.noao.edu
We present results of our large scale, optical, multi-epoch photometric survey across ∼ 180 square degrees in the Orion
OB1 association, complemented with extensive follow up spectroscopy. Our focus is mapping and characterizing theoff-cloud, low-mass, pre-main sequence populations. We report 2062 K and M-type confirmed T Tauri members; 59%
are located in the OB1a subassociation, 27% in the OB1b subassociation, and the remaining 14% in the A and B
molecular clouds. We characterize two new clusterings of T Tauri stars, the HD 35762 and HR 1833 groups, both
located in OB1a not far from the 25 Ori cluster. We also identify two stellar overdensities in OB1b, containing 231
PMS stars, and find that the OB1b region is composed of two populations at different distances, possibly due to the11OB1a subassociation overlapping on front of OB1b. A ∼ 2 deg wide halo of young stars surrounds the Orion Nebula
Cluster, corresponding in part to the low-mass populations of NGC 1977 and NGC 1980.
We use the strength of Hα in emission, combined with IR excess and optical variability, to define a new type of T
Tauri star, the C/W class, stars we propose may be nearing the end of their accretion phase, in an evolutionary state
between Classical and Weak-lined T Tauri stars. The evolution of the ensemble-wide equivalent width of Li I λ6707
indicates a Li depletion timescale of ∼ 8.5 Myr. Disk accretion declines with an e-folding timescale of ∼ 2 Myr,
consistent with previous studies.
Accepted by The Astronomical Journal
https://arxiv.org/pdf/1805.01008

8

Spectroscopic study of the extremely young O-type triple system Herschel 36 A in the
Hourglass Nebula. I. Orbital properties
Abdo R. Campillay1 , Julia I. Arias1 , Rodolfo H. Barbá1 , Nidia I. Morrell2 , Roberto C. Gamen3 , JesúsMaı́z Apellániz4
1

Departamento de Fı́sica y Astronomı́a, Universidad de La Serena, Av. Juan Cisternas 1200 Norte, La Serena, Chile;
Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena, Chile; 3 Instituto de Astrofı́sica de La
Plata, CONICET–UNLP, and Facultad de Ciencias Astronómicas y Geofı́sicas, UNLP. Paseo del Bosque s/n, La Plata,
Argentina; 4 Centro de Astrobiologı́a, CSIC-INTA, Campus ESAC Camino bajo del castillo s/n, 28 692 Villanueva dela Cañada, Spain
2

E-mail contact: acampillay at dfuls.cl
We present a detailed spectroscopic study of Herschel 36 A (H36A), the main stellar component of the massive multiple
system Herschel 36 in the Hourglass Nebula, based on high-resolution optical spectra obtained along an 11 years span.
The three stellar components present in the spectrum of H36A are separated by means of a spectral disentangling
technique. Individual spectral classifications are improved, and high precision orbital solutions for the inner andthe outer orbits are calculated. H36A is confirmed to be a hierarchical triple system composed of a close massive
binary (Ab1+Ab2, O9.5 V+B0.7 V) in wide orbit around a third O-type star (Aa, O7.5 Vz). The inner-pair orbit
is characterized by a period of 1.54157±0.00006 days, and semi-amplitudes of 181.2±0.7 and 295.4±1.7 km/s. The
outer orbit has a period of 492.81±0.69 days, and semi-amplitudes of 62.0±0.6 and 42.4±0.8 km/s. Inner and outerorbits are not coplanar, having a relative inclination of at least 20 degrees. Dynamical minimum masses of 20.6±0.8
M⊙ , 18.7±1.1 M⊙ , and 11.5±1.1 M⊙ are derived for the Aa, Ab1, and Ab2 components, respectively, in reasonableagreement with the theoretical calibrations.
Accepted by MNRAS
http://arxiv.org/pdf/1812.10861

9

The early instability scenario: terrestrial planet formation during the giant planet instability, and the effect of collisional fragmentation
Matthew S. Clement1 , Nathan A. Kaib1 , Sean N. Raymond2 , John E. Chambers3 , & Kevin J. Walsh4
1

HL Dodge Department of Physics Astronomy, University of Oklahoma, Norman, OK 73019, USA; 2 LaboratoiredAstrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, alle Geoffroy Saint-Hilaire, 33615 Pessac, France; 3
Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington,
DC 20015, USA; 4 Southwest Research Institute, 1050 Walnut St. Suite 300, Boulder, CO 80302, USA
E-mail contact: matt.clement at ou.edu
The solar system’s dynamical state can be explained by an orbital instability among the giant planets. A recent model
has proposed that the giant planet instability happened during terrestrial planet formation. This scenario has beenshown to match the inner solar system by stunting Mars’ growth and preventing planet formation in the asteroid belt.
Here we present a large sample of new simulations of the “Early Instability” scenario. We use an N-body integration
scheme that accounts for collisional fragmentation, and also perform a large set of control simulations that do notinclude an early giant planet instability. Since the total particle number decreases slower when collisional fragmentationis accounted for, the growing planets’ orbits are damped more strongly via dynamical friction and encounters with small
12bodies that dissipate angular momentum (eg: hit-and-run impacts). Compared with simulations without collisional
fragmentation, our fully evolved systems provide better matches to the solar system’s terrestrial planets in terms of
their compact mass distribution and dynamically cold orbits. Collisional processes also tend to lengthen the dynamicalaccretion timescales of Earth analogs, and shorten those of Mars analogs. This yields systems with relative growthtimescales more consistent with those inferred from isotopic dating. Accounting for fragmentation is thus supremely
important for any successful evolutionary model of the inner solar system.
Accepted by Icarus
http://arxiv.org/pdf/1812.07590

Flybys in protoplanetary discs: I. Gas and dust dynamics

10 Nicolás Cuello , Giovanni Dipierro , Daniel Mentiplay , Daniel J. Price , Christophe Pinte , Jorge
1,7

1,6,7

Cuadra2

4

3

5, Guillaume Laibe , François Ménard , Pedro P. Poblete

3

1,6,7

3

and Matı́as Montesinos7,8,9

1

Instituto de Astrofı́sica, Pontificia Universidad Católica de Chile, Santiago, Chile; 2 Department of Physics andAstronomy, University of Leicester, Leicester, LE1 7RH, United Kingdom; 3 Monash Centre for Astrophysics (MoCA)
and School of Physics and Astronomy, Monash University, Clayton, Vic 3800, Australia; 4 Univ Lyon, Univ Lyon1, Ens
de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, France; 5 Univ.
Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 6 Millennium Nucleus “Protoplanetary Disks”, Santiago,
Chile; 7 Núcleo Milenio de Formación Planetaria (NPF), Chile; 8 Instituto de Fı́sica y Astronomı́a, Universidad
de Valparaı́so, Chile; 9 Chinese Academy of Sciences South America Center for Astronomy, National Astronomical
Observatories, CAS, Beijing 100012, China
E-mail contact: ncuello at astro.puc.cl
We present 3D smoothed particle hydrodynamics simulations of protoplanetary discs undergoing a flyby by a stellar
perturber on a parabolic orbit lying in a plane inclined relative to the disc mid-plane. We model the disc as a mixtureof gas and dust, with grains ranging from 1 µm to 10 cm in size. Exploring different orbital inclinations, periastron
distances and mass ratios, we investigate the disc dynamical response during and after the flyby. We find that flybys
induce evolving spiral structure in both gas and dust which can persist for thousands of years after periastron. Gas
and dust structures induced by the flyby differ because of drag-induced effects on the dust grains. Variations in theaccretion rate by up to an order of magnitude occur over a time-scale of order 10 years or less, inducing FU Orionis-likeoutbursts. The remnant discs are truncated and warped. The dust disc is left more compact than the gas disc, bothbecause of disc truncation and accelerated radial drift of grains induced by the flyby.
Accepted by MNRAS
http://arxiv.org/pdf/1812.00961

11

A search for accreting young companions embedded in circumstellar disks:
High-contrast Hα imaging with VLT/SPHERE
G. Cugno1 , S. P. Quanz1,2 , S. Hunziker1 , T. Stolker1 , H. M. Schmid1 , H. Avenhaus3 , P. Baudoz4 , A.
J. Bohn5 , M. Bonnefoy6 , E. Buenzli1 , G. Chauvin6,7 , A. Cheetham8 , S. Desidera9 , C. Dominik10 , P.
Feautrier6 , M. Feldt3 , C. Ginski5 , J. H. Girard11,6 , R. Gratton9 , J. Hagelberg1 , E. Hugot12 , M. Janson13 ,A.-M. Lagrange6 , M. Langlois12,14 , Y. Magnard6 , A.-L. Maire3 , F. Menard6,15 , M. Meyer16,1 , J. Milli17,
C. Mordasini18 , C. Pinte19,6 , J. Pragt20 , R. Roelfsema20, F. Rigal20 , J. Szulágyi21 , R. van Boekel3 , G.
van der Plas6 , A. Vigan12 , Z. Wahhaj17 and A. Zurlo12,22,23
1

ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland; 2 National Center of Competence in Research ”PlanetS”; 3 Max-Planck-Institut für Astronomie, Königstuhl
17, 69117 Heidelberg, Germany; 4 LESIA, CNRS, Observatoire de Paris, Université Paris Diderot, UPMC, 5 place J.
Janssen, 92190 Meud; 5 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands;
6
Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 7 Unidad Mixta International Franco-Chilena de
Astronomia, CNRS/INSU UMI 3386 and Departemento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago,
Chile; 8 Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland; 9 INAF Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy; 10 Anton Pannekoek Astronom-13

ical Institute, University of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands; 11 Space Telescope
Science Institute, Baltimore 21218, MD, USA; 12 Aix Marseille Université, CNRS, CNES, LAM, Marseille, France; 13
Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden; 14 Centre
de Recherche Astrophysique de Lyon, CNRS/ENSL Universit Lyon 1, 9 av. Ch. Andr, 69561 Saint-Genis-Laval,
France; 15 CNRS, IPAG, 38000 Grenoble, France; 16 The University of Michigan, Ann Arbor, Mi 48109, USA; 17 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001 Vitacura, Santiago 19, Chile; 18 Physikalisches
Institut, Universität Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland; 19 Monash Centre for Astrophysics (MoCa)
and School of Physics and Astronomy, Monash University, Clayton Vic 3800, Australia; 20 NOVA Optical Infrared
Instrumentation Group at ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands; 21 Institutefor Computational Science, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland; 22 Núcleo deAstronomı́a, Facultad de Ingenierı́a y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 23
Escuela de Ingenierı́a Industrial, Facultad de Ingenierı́a y Ciencias, Universidad Diego Portales, Av. Ejercito 441,
Santiago, Chile
E-mail contact: gabriele.cugno at phys.ethz.ch
In recent years, our understanding of giant planet formation progressed substantially. Even the detections of a few
young protoplanet candidates still embedded in the circumstellar disks of their host stars have been made. The exact
physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk
and eventually onto the young, forming planet is still an open question.We want to detect and quantify observables
related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming
planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the resultof interactions with planets. We analyzed observations of 6 young stars (age 3.5 − 10 Myr) and their surrounding
environments with the SPHERE/ZIMPOL instrument on the VLT in the Hα filter (656 nm) and a nearby continuum
filter (644.9 nm). We applied several PSF subtraction techniques to reach the highest possible contrast near the
primary star, specifically investigating regions where forming companions were claimed or have been suggested basedon observed disk morphology. We re-detect the known accreting M-star companion HD142527 B with the highest+2.1
published signal to noise to date in both Hα and the continuum. We derive new astrometry (r = 62.8−2.7
mas and+0.2+0.3◦
P A = (98.7 ± 1.8) ) and photometry (∆N Ha=6.3−0.3 mag, ∆B Ha=6.7 ± 0.2 mag and ∆Cnt Ha=7.3−0.2 mag) forthe companion in agreement with previous studies, and estimate its mass accretion rate (Ṁ ≈ 1 − 2 × 10−10 M⊙ yr−1 ).
A faint point-like source around HD135344 B (SAO206462) is also investigated, but a second deeper observation isrequired to reveal its nature. No other companions are detected. In the framework of our assumptions we estimate
detection limits at the locations of companion candidates around HD100546, HD169142 and MWC 758 and calculate2that processes involving Hα fluxes larger than ∼ 8 × 10−14 − 10−15 erg/s/cm (Ṁ > 10−10 − 10−12 M⊙ yr −1 ) can be
excluded. Furthermore, flux upper limits of ∼ 10−14 − 10−15 erg/s/cm2 (Ṁ < 10−11 − 10−12 M⊙ yr−1 ) are estimatedwithin the gaps identified in the disks surrounding HD135344 B and TW Hya. The derived luminosity limits exclude
Hα signatures at levels similar to those previously detected for the accreting planet candidate LkCa15 b.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1812.06993

12

A 3D Hydrodynamics Study of Gravitational Instabilities in a Young Circumbinary
Disc
Karna M. Desai1 , Thomas Y. Steiman-Cameron1 , Scott Michael1 , Kai Cai2 , Richard H. Durisen1
1

Department of Astronomy, Indiana University Bloomington, 727 East 3rd Street, Swain West 318, Bloomington, IN
47405, USA; 2 Pine Manor College, 400 Heath Street, Chestnut Hill, MA 02467, USA
E-mail contact: kardesai at iu.edu
We present a 3D hydrodynamics study of gravitational instabilities (GIs) in a 0.14 M⊙ circumbinary protoplanetary
disc orbiting a 1 M⊙ star and a 0.02 M⊙ brown dwarf companion. We examine the thermodynamical state of thedisc and determine the strengths of GI-induced density waves, nonaxisymmetric density structures, mass inflow andoutflow, and gravitational torques. Results are compared with a parallel simulation of a protoplanetary disc without
the brown dwarf binary companion. Simulations are performed using CHYMERA, a radiative 3D hydrodynamics code.
The onset of GIs in the circumbinary disc is much more violent due to the stimulation of a strong one-armed density

14

wave by the brown dwarf. Despite this early difference, detailed analyses show that both discs relax to a very similar
quasi-steady phase by 2,500 years after the beginning of the simulations. Similarities include the thermodynamics
of the quasi-steady phase, the final surface density distribution, radial mass influx, and nonaxisymmetric power andtorques for spiral arm multiplicities of two or more. Effects of binarity in the disc are evident in gravitational torqueprofiles, temperature profiles in the inner discs, and radial mass transport. After 3,800 years, the semimajor axis of
the binary decreases by about one percentage and the eccentricity roughly doubles. The mass transport in the outercircumbinary disc associated with the one-armed wave may influence planet formation.
Accepted by MNRAS
http://arxiv.org/pdf/1812.10763

A Model-Independent Mass and Moderate Eccentricity for β Pic b

13 Trent J. Dupuy , Timothy D. Brandt , Kaitlin M. Kratter and Brendan P. Bowler
1

2

3

4

1

Gemini Observatory, Northern Operations Center, 670 N. A’ohoku Place, Hilo, HI 96720, USA; 2 Department of
Physics, University of California, Santa Barbara, Santa Barbara, CA 93106, USA; 3 Department of Astronomy and
Steward Observatory, University of Arizona, Tucson, AZ 85721, USA; 4 The University of Texas at Austin, Departmentof Astronomy, 2515 Speedway C1400, Austin, TX 78712, USA
E-mail contact: tdupuy at gmail.com
We use a cross-calibration of Hipparcos and Gaia DR2 astrometry for β Pic to measure the mass of the giant planet
β Pic b (13 ± 3 MJup ) in a comprehensive joint orbit analysis that includes published relative astrometry and radial
velocities. Our mass uncertainty is somewhat higher than previous work because our astrometry from the Hipparcos–
Gaia Catalog of Accelerations accounts for the error inflation and systematic terms that are required to bring the twodata sets onto a common astrometric reference frame, and because we fit freely for the host-star mass (1.84 ± 0.05 M⊙ ).
This first model-independent mass for a directly imaged planet is inconsistent with cold-start models given the age ofthe β Pic moving group (22 ± 6 Myr) but consistent with hot- and warm-start models, concordant with past work. We
find a higher eccentricity (0.24±0.06) for β Pic b compared to previous orbital fits. If confirmed by future observations,this eccentricity may help explain inner edge, scale height, and brightness asymmetry of β Pic’s disk. It could also
potentially signal that β Pic b has migrated inward to its current location, acquiring its eccentricity from interaction
with the 3:1 outer Lindblad resonance in the disk.
Accepted by ApJ Letters
https://arxiv.org/pdf/1812.11530

Episodic excursions of low-mass protostars on the Hertzsprung-Russell diagram

14 Vardan G. Elbakyan , Eduard I. Vorobyov , Christian Rab , D. M.-A. Meyer , Manuel Güdel ,1

5

Takashi Hosokawa and Harold Yorke

1,2

3

4

2

6

1

Research Institute of Physics, Southern Federal University, Roston-on-Don, 344090, Russia; 2 University of Vienna,
Department of Astrophysics, Vienna, 1180, Austria; 3 Kapteyn Astronomical Institute, University of Groningen, PO
Box 800, 9700 AV Groningen, The Netherlands; 4 Astrophysics Group, School of Physics and Astronomy, Universityof Exeter, Exeter EX4 4QL, United Kingdom; 5 Department of Physics, Kyoto University, Sakyo, Kyoto 606-8502,
Japan; 6 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
E-mail contact: vgelbakyan at sfedu.ru
Following our recent work devoted to the effect of accretion on the pre-main-sequence evolution of low-mass stars, we
perform a detailed analysis of episodic excursions of low-mass protostars in the Hertzsprung-Russell (H-R) diagram
triggered by strong mass accretion bursts typical of FU Orionis-type objects (FUors). These excursions reveal themselves as sharp increases in the stellar total luminosity and/or effective temperature of the protostar and can last fromhundreds to a few thousands of years, depending on the burst strength and characteristics of the protostar. During
the excursions, low-mass protostars occupy the same part of the H-R diagram as young intermediate-mass protostars
in the quiescent phase of accretion. Moreover, the time spent by low-mass protostars in these regions is on average afactor of several longer than that spent by the intermediate-mass stars in quiescence. During the excursions, low-mass
protostars pass close to the position of most known FUors in the H-R diagram, but owing to intrinsic ambiguity the15model stellar evolutionary tracks are unreliable in determining the FUor properties. We find that the photosphericluminosity in the outburst state may dominate the accretion luminosity already after a few years after the onset ofthe outburst, meaning that the mass accretion rates of known FUors inferred from the bolometric luminosity may besystematically overestimated, especially in the fading phase.
Accepted by MNRAS
https://arxiv.org/pdf/1812.10982.pdf

15 Juan P. Farias , Jonathan C. Tan and Sourav ChatterjeeStar Cluster Formation from Turbulent Clumps. II. Gradual Star Cluster Formation
1

1,2

3

1

Dept. of Space, Earth & Environment, Chalmers University of Technology, Gothenburg, Sweden; 2 Dept. of
Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 3 Tata Institute of Fundamental Research, Homi
Bhabha Road, Mumbai 400005, India
E-mail contact: juan.farias at chalmers.se
We investigate the dynamical evolution of star clusters during their formation, assuming that they are born from aturbulent starless clump of a given mass that is embedded within a parent self-gravitating molecular cloud characterized
by a particular mass surface density. In contrast to the standard practice of most N -body studies, we do not assume
that all stars are formed at once. Rather, we explore the effects of different star formation rates on the global
structure and evolution of young embedded star clusters, also considering various primordial binary fractions and masssegregation levels. Our fiducial clumps studied in this paper have initial masses of Mcl = 3000 M⊙, are embedded
in ambient cloud environments of Σcloud = 0.1 and 1 g cm−2 , and gradually form stars with an overall efficiency of
50% until the gas is exhausted. We investigate star formation efficiencies per free-fall time in the range ǫff = 0.01 to
1, and also compare to the instantaneous case (ǫff = ∞) of Paper I. We show that most of the interesting dynamical
processes that determine the future of the cluster, happen during the early formation phase. In particular, the ejected
stellar population is sensitive to the duration of star cluster formation: for example, clusters with longer formation
times produce more runaway stars, since these clusters remain in a dense state for longer, thus favouring occurrence ofdynamical ejections. We also show that the presence of radial age gradients in star clusters depends sensitively on thestar formation efficiency per free fall time, with observed values being matched best by our slowest forming clusters
with ǫff <∼ 0.03.
Accepted by MNRAS
https://arxiv.org/pdf/1809.04607

Gas density perturbations induced by forming planet(s) in the AS 209 protoplanetary
disk as seen with ALMA

16 Cécile Favre , Davide Fedele , Luke Maud , Richard Booth , Marco Tazzari , Anna Miotello , Leonardo
1

Testi

5,6,1

1

7,8

, Dmitry Semenov

2

3

3

4

9

and Simon Bruderer

1

INAF-Osservatorio Astrofisico di Arcetri,Largo E. Fermi 5, I-50125, Florence, Italy; 2 Leiden Observatory, Leiden
University, PO Box 9513, 2300 RA Leiden, The Netherlands; 3 Institute of Astronomy, University of Cambridge,
Madingley Road, Cambridge CB3 0HA, UK; 4 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 5 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany; 6
Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany; 7 Max Planck Institute for Astronomy,
Knigstuhl 17, 69117 Heidelberg, Germany; 8 Department of Chemistry, Ludwig Maximilian University, Butenandtstr.
5-13, D-81377 Munich, Germany; 9 Max Planck Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748
Garching, Germany
E-mail contact: cfavre at arcetri.astro.it
The formation of planets occurs within protoplanetary disks surrounding young stars, resulting in perturbation of
the gas and dust surface densities. Here, we report the first evidence of spatially resolved gas surface density (Σg )perturbation towards the AS 209 protoplanetary disk from the optically thin C18 O (J = 2 − 1) emission. The
observations were carried out at 1.3 mm with ALMA at a spatial resolution of about 0.3′′ × 0.2′′ (corresponding to∼ 38 × 25 au). The C18 O emission shows a compact (≤60 au), centrally peaked emission and an outer ring peaking
16

at 140 au, consistent with that observed in the continuum emission and, its azimuthally averaged radial intensity
profile presents a deficit that is spatially coincident with the previously reported dust map. This deficit can only be
reproduced with our physico-thermochemical disk model by lowering Σgas by nearly an order of magnitude in the
dust gaps. Another salient result is that contrary to C18 O, the DCO+ (J = 3 − 2) emission peaks between the twodust gaps. We infer that the best scenario to explain our observations (C18 O deficit and DCO+ enhancement) is agas perturbation due to forming-planet(s), that is commensurate with previous continuum observations of the source
along with hydrodynamical simulations. Our findings confirm that the previously observed dust gaps are very likely
due to perturbation of the gas surface density that is induced by a planet of at least 0.2 MJupiter in formation. Finally,
our observations also show the potential of using CO isotopologues to probe the presence of saturn mass planet(s).
Accepted by ApJ
https://arxiv.org/pdf/1812.04062

17

The Planet Formation Potential Around a 45 Myr old Accreting M Dwarf
Kevin Flaherty1,2 , A. Meredith Hughes2 , Eric E. Mamajek3,4 and Simon J. Murphy5
1

Department of Astronomy and Department of Physics, Williams College, Williamstown, MA 01267 USA; 2 Van
Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 USA;3
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 USA;
4
Department of Physics and Astronomy, University of Rochester, 500 Wilson Blvd., Rochester, NY 14627 USA; 5
School of Physical, Environment and Mathematical Sciences, University of New South Wales Canberra, ACT 2600,
Australia
E-mail contact: kmf4 at williams.edu
Debris disk detections around M dwarfs are rare, and so far no gas emission has been detected from an M dwarf debris
disk. This makes the 45 Myr old M dwarf WISEJ080822.18-644357.3 a bit of a curiosity; it has a strong infraredexcess at an age beyond the lifetime of a typical planet-forming disk, and also exhibits broad Hα emission consistent
with active accretion from a gaseous disk. To better understand the cold gas and dust properties of this system, we
obtained ALMA observations of the 1.3mm continuum and the CO/13 CO/C18 O J=2-1 emission lines. No cold CO
gas is detected from this system, ruling out a gas-rich protoplanetary disk. Unresolved dust continuum emission isdetected at a flux of 198±15 µJy, consistent with 0.057±0.006 M⊕ worth of optically thin dust, and consistent withbeing generated through a collisional cascade induced by large bodies at radii <16 au. With a sufficiently strong
stellar wind, dust grains released in the outer disk can migrate inwards via PR drag, potentially serving as a sourceof grains for the strong infrared excess.
Accepted by ApJ
https://arxiv.org/pdf/1812.04124.pdf

18

A 1000 AU Scale Molecular Outflow Driven by a Protostar with an age of lesssim4000
Years
Ray S. Furuya1 , Yoshimi Kitamura2 and Hiroko Shinnaga3
1

Institute of Liberal Arts and Sciences, Tokushima University, Minami Jousanjima-Machi 1-1, Tokushima, Tokushima
770-8502, Japan; 2 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai
3-1-1, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan; 3 Department of Physics, Faculty of Science, Kogoshima
University, Korimoto 1-21-35, Kagoshima, Kogoshima 890-0065, Japan
E-mail contact: rsf at tokushima-u.ac.jp
To shed light on the early phase of a low-mass protostar formation process, we conducted interferometric observations
towards a protostar GF 9-2 using the CARMA and SMA. The observations have been carried out in the 12 CO J = 3−2line and in the continuum emission at the wavelengths of 3.3 mm, 1.1 mm and 850 µm with a spatial resolution of≈ 400 AU. All the continuum images detected a single point-like source with a beam-deconvolved effective radius of
250±80 AU at the center of the previously known 1.1 – 4.5 M⊙ molecular cloud core. A compact emission is detected
towards the object at the Spitzer MIPS and IRAC bands as well as the four bands at the WISE. Our spectroscopic
imaging of the CO line revealed that the continuum source is driving a 1000 AU scale molecular outflow, including a17

pair of lobes where a collimated “higher” velocity (∼ 10 km s−1 with respect to the velocity of the cloud) red lobe
exists inside a poorly collimated “lower” velocity (∼ 5 km s−1 ) red lobe. These lobes are rather young (dynamical
time scales of ∼ 500 – 2000 yrs) and the least powerful (momentum rates of ∼ 10−8 − 10−6 M⊙ km s−1 yr−1 ) ones
so far detected. A protostellar mass of M∗ <∼ 0.06 M⊙ was estimated using an upper limit of the protostellar age of
3
τ∗ <
(4
±
1)
×
10
yrs
and
an
inferred
non-sphericalsteady mass accretion rate of ∼ 1 × 10−5 M⊙ yr−1 . Together with∼results from an SED analysis, we discuss that the outflow system is driven by a protostar whose surface temperatureof ∼ 3, 000 K, and that the natal cloud core is being dispersed by the outflow.
Accepted by ApJ
https://arxiv.org/pdf/1812.07806

ALMA Observations of the massive molecular outflow G331.512−0.103 II: physical properties, kinematics, and geometry modeling

19 Carlos Hervı́as-Caimapo , Manuel Merello , Leonardo Bronfman , Lars Åke-Nyman , Guido Garay ,
1,2

3

1

4

1

Nadia Lo1 , Neal J. Evans II5,6 , Cristian López-Calderón4 , and Edgar Mendoza3
1

Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile; 2 Jodrell Bank Centre for
Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK;
3
Universidade de São Paulo, IAG Rua do Matão, 1226, Cidade Universitária, 05508-090, São Paulo, Brazil; 4 Joint
ALMA Observatory (JAO), Alonso de Córdova 3107, Vitacura, Santiago, Chile; 5 Department of Astronomy, The
University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA; 6 Korea Astronomy andSpace Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon, 34055, Republic of Korea
E-mail contact: aconcagua.chc at gmail.com
We present observations and analysis of the massive molecular outflow G331.512−0.103, obtained with ALMA band
7, continuing the work from Merello et al. (2013). Several lines were identified in the observed bandwidth, consistingof two groups: lines with narrow profiles, tracing the emission from the core ambient medium; and lines with broad
velocity wings, tracing the outflow and shocked gas emission. The physical and chemical conditions, such as density,
temperature, and fractional abundances are calculated. The ambient medium, or core, has a mean density of ∼5 ×
106 cm−3 and a temperature of ∼70 K. The SiO and SO2 emission trace the very dense and hot part of the shocked
outflow, with values of nH2 ∼ 109 cm−3 and T ∼ 160–200 K. The interpretation of the molecular emission suggests
an expanding cavity geometry powered by stellar winds from a new-born UCHII region, alongside a massive andhigh-velocity molecular outflow. This scenario, along with the estimated physical conditions, is modeled using the 3D
geometry radiative transfer code MOLLIE for the SiO(J=8–7) molecular line. The main features of the outflow andthe expanding shell are reproduced by the model.
Accepted by ApJ
http://arxiv.org/pdf/1812.09779

20

Gaia 17bpi: An FU Ori Type Outburst
Lynne A. Hillenbrand1 , Carlos Contreras Peña2 , Sam Morrell2 , Tim Naylor2 , Michael A. Kuhn1 , Roc
M. Cutri3 , Luisa M. Rebull3 , Simon Hodgkin4 , Dirk Froebrich5 and Amy K. Mainzer6
1

Department of Astronomy, California Institute of Technology, Pasadena CA 91125, USA; 2 School of Physics,
University of Exeter, Stocker Road Exeter, Devon, EX4 4QL; 3 IPAC, California Institute of Technology, Pasadena
CA 91125, USA; 4 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 5
Centre for Astrophysics & Planetary Science, The University of Kent, Canterbury, Kent CT2 7NH, UK; 6 JPL, 4800
Oak Grove Dr. Pasadena 91109, USA
E-mail contact: lah at astro.caltech.edu
We report on the source Gaia 17bpi and identify it as a new, ongoing FU Ori type outburst, associated with a youngstellar object. The optical lightcurve from Gaia exhibited a 3.5 mag rise with the source appearing to plateau in
mid/late 2018. Mid-infrared observations from NEOWISE also show a >3 mag rise that occurred in two stages, withthe second one coincident with the optical brightening, and the first one preceeding the optical brightening by ∼1.5

18

years. We model the outburst as having started between October and December of 2014. This wavelength-dependent
aspect of young star accretion-driven outbursts has never been documented before. Both the mid-infrared and theoptical colors of the object become bluer as the outburst proceeds. Optical spectroscopic characteristics in the outburst
phase include: a GK-type absorption spectrum, strong wind/outflow in e.g. Mgb, NaD, Hα, KI, OI, and CaII profiles,and detection of LiI 6707 Å. The infrared spectrum in the outburst phase is similar to that of an M-type spectrum,
notably exhibiting prominent H2 O and 12 CO (2-0) bandhead absorption in the K-band, and likely HeI wind in the
Y-band. The new FU Ori source Gaia 17bpi is associated with a little-studied dark cloud in the galactic plane, locatedat a distance of 1.27 kpc.
Accepted by ApJ (20 December, 2018 issue)
http://arxiv.org/pdf/1812.06640

On the resolution requirements for modelling molecular gas formation in solar neighbourhood conditions

21 P. R. Joshi , S. Walch , D. Seifried , S. C. O. Glover and M. Weis
1

1

1

2

1

1

Universität zu Köln, I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany; 2 Zentrum für Astronomie
der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
E-mail contact: joshi at ph1.uni-koeln.de

The formation of molecular hydrogen (H2 ) and carbon monoxide (CO) is sensitive to the volume and column density
distribution of the turbulent interstellar medium. In this paper, we study H2 and CO formation in a large set ofhydrodynamical simulations of periodic boxes with driven supersonic turbulence, as well as in colliding flows with
the Flash code. The simulations include a non-equilibrium chemistry network, gas self-gravity, and diffuse radiativetransfer. We investigate the spatial resolution required to obtain a converged H2 and CO mass fraction and formation
history. From the numerical tests we find that H2 converges at a spatial resolution of <∼ 0.2 pc, while the required
resolution for CO convergence is <
0.04
pc
in
gas
with
solar
metallicity
whichis
subject
to a solar neighbourhood∼interstellar radiation field. We derive two critical conditions from our numerical results: the simulation has to at least
resolve the densities at which (1) the molecule formation time in each cell in the computational domain is equal tothe dissociation time, and (2) the formation time is equal to the the typical cell crossing time. For both H2 and CO,
the second criterion is more restrictive. The formulae we derive can be used to check whether molecule formation isconverged in any given simulation.
Accepted by MNRAS
https://arxiv.org/pdf/1812.03725

22

CO Outflow Survey of 68 Very Low Luminosity Objects: a Search for Proto-Brown
Dwarf Candidates
Gwanjeong Kim1,2,3,7 , Chang Won Lee2,3 , Gopinathan Maheswar4 , Mi-Ryang Kim2 , Archana Soam2,9 ,Masao Saito5 , Kazuhiro Kiyokane5,6 and Sungeun Kim8
1

Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences,
Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; 2 Korea Astronomy and Space Science Institute, 776
Daedeokdae-ro, Yuseong-gu, Daejeon, 34055, Republic of Korea; 3 Department of Astronomy and Space Science,
University of Science & Technology, 217, Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea; 4 Indian
Institute of Astrophysics, II Block, Koramangala, Bengaluru 560 034, INDIA; 5 National Astronomical Observatoryof Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 6 Department of
Astronomy, The University of Tokyo, 7 Chome-3-1 Hongo, Bunky?, Tokyo 113-8654, Japan; 7 Department of Physics
and Astronomy, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul, 05006, Republic of Korea; 8 Department of
Astronomy and Space Science, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul, 05006, Republic of Korea;
9
SOFIA Science Centre, USRA, NASA Ames Research Centre, MS N232-12 Moffett Field, CA 94035, USA
E-mail contact: gj.kim at nao.ac.jp
We present the results of a systematic search for molecular outflows in 68 Very Low Luminosity Objects (VeLLOs)
from single-dish observations in CO isotopologues which find 16 VeLLOs showing clear outflow signatures in the19CO maps. With additional three VeLLOs from the literature, we analyzed the outflow properties for 19 VeLLOs,
identifying 15 VeLLOs as proto-Brown Dwarf (BD) candidates and four VeLLOs as likely faint protostar candidates.
The proto-BD candidates are found to have a mass accretion rate (∼ 10−8 − 10−7 M⊙ yr−1 ) lower than that of the−6
protostar candidates (>M⊙ yr−1 ). Their accretion luminosities are similar to or smaller than their internal∼10luminosities, implying that many proto-BD candidates might have had either small accretion activity in a quiescentmanner throughout their lifetime, or be currently exhibiting a relatively higher (or episodic) mass accretion than thepast. There are strong trends that outflows of many proto-BDs are less active if they are fainter or have less massive
envelopes. The outflow forces and internal luminosities for more than half of the proto-BD candidates seem to follow
an evolutionary track of a protostar with its initial envelope mass of ∼0.08 M⊙ , indicating that some BDs may formin less massive dense cores in a way similar to normal stars. But, because there also exists a significant fraction (about40%) of proto-BDs with much weaker outflow force than expected by the relations for protostars, we should not ruleout the possibility of other formation mechanism for the BDs.
Accepted by ApJS
https://arxiv.org/pdf/1812.08275

Dependence of Hall Coefficient on Grain Size and Cosmic Ray Rate and Implication for
Circumstellar Disk Formation

23 Shunta Koga , Yusuke Tsukamoto , Satoshi Okuzumi and Masahiro N. Machida
1

2

3

1

1

Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 819-0395, Japan;
Department of Earth and Space Science, Graduate Schools of Science and Engineering, Kagoshima University,
Kagoshima, Japan; 3 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan2

E-mail contact: s.koga.098 at s.kyushu-u.ac.jp
The Hall effect plays a significant role in star formation because it induces rotation in the infalling envelope, which inturn affects the formation and evolution of the circumstellar disk. The importance of the Hall effect varies with theHall coefficient, and this coefficient is determined by the fractional abundances of charged species. These abundancevalues are primarily based on the size and quantity of dust grains as well as the cosmic ray intensity, which respectively
absorb and create charged species. Thus, the Hall coefficient varies with both the properties of dust grains and thecosmic ray rate (or ionization source). In this study, we explore the dependence of the Hall coefficient on the grain sizeand cosmic ray ionization rate using a simplified chemical network model. Following this, using an analytic model,
we estimate the typical size of a circumstellar disk induced solely by the Hall effect. The results show that the disk
grows during the main accretion phase to a size of ∼ 3 - 100 au, with the actual size depending on the parameters.
These findings suggest that the Hall effect greatly affects circumstellar disk formation, especially in the case that the
dust grains have a typical size of ∼ 0.025 µm - 0.075 µm.
Accepted by MNRAS
https://arxiv.org/pdf/1812.07131

24

The outbursting protostar 2MASS 22352345+7517076 and its environment
M. Kun1 , P. Ábrahám1 , J. A. Acosta Pulido2 , A. Moór1 and T. Prusti3
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121
Budapest, Konkoly Thege út 15–17, Hungary; 2 Instituto de Astrofı́sica de Canarias, Avenida Vı́a Láctea, 38205 La
Laguna, Tenerife, Spain; 3 Directorate of Science, ESTEC–ESA, PO Box 299, 2200 AG, Noordwijk, The Netherlands
E-mail contact: kun at konkoly.hu
We studied the Class I protostar 2MASS 22352345+7517076 whose dramatic brightening between the IRAS , Akari,and WISE surveys was reported by Onozato et al. (2015). 2MASS 22352345+7517076 is a member of a small groupof low-mass young stellar objects, associated with IRAS 22343+7501 in the molecular cloud Lynds 1251. The IRAS ,ISO , Spitzer , Akari, Herschel , and WISE missions observed different stages of its outburst. Supplemented these datawith archival and our own near-infrared observations, and considering the contributions of neighbouring sources to the
mid-infrared fluxes we studied the nature and environment of the outbursting object, and its photometric variations
from 1983 to 2017. The low-state bolometric luminosity Lbol ≈ 32 L⊙ is indicative of a 1.6–1.8M⊙, 1–2×105 years
20old protostar. Its 2-µm brightness started rising between 1993 and 1998, reached a peak in 2009–2011, and started
declining in 2015. Changes in the spectral energy distribution suggest that the outburst was preceded by a decadelong, slow brightening in the near-infrared. The actual accretion burst occurred between 2004 and 2007. We fitted
the spectral energy distribution in the bright phases with simple accretion disc models. The modelling suggested anincrease of the disc accretion rate from ∼ 3.5 × 10−7 M⊙ yr−1 to ∼ 1.1 × 10−4 M⊙ yr−1 . The central star accreted
nearly 10−3 M⊙ , about a Jupiter mass during the ten years of the outburst. We observed H2 emission lines in the
K -band spectrum during the fading phase in 2017. The associated optical nebulosity RNO 144 and the Herbig–Haroobject HH 149 have not exhibited significant variation in shape and brightness during the outburst.
Accepted by MNRAS
https://arxiv.org/pdf/1812.06137.pdf

Characterising the high-mass star forming filament G351.776–0.527 with Herschel and
APEX dust continuum and gas observations

25 S. Leurini , E. Schisano , T. Pillai , A. Giannetti , J. Urquhart , T. Csengeri , S. Casu , M.
1

2,3

7

2

4,5

7

3,4

4

6,4

2

8

Cunningham , D. Elia , P. A. Jones , C. K. , S. Molinari , T. Stanke , L. Testi
K. M. Menten4

4

8,9,101, F. Wyrowski4 and

1

INAF - Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy; 2 Istituto di
Astrofisica e Planetologia Spaziali - INAF, Via Fosso del Cavaliere 100, I-00133 Roma, Italy; 3 INAF - Istituto diRadioastronomia, and Italian ALMA Regional Centre, via P. Gobetti 101, I-40129, Bologna, Italy; 4 Max-PlanckInstitut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 5 Institute for Astrophysical Research,
Boston University, 725 Commonwealth Ave, Boston, MA, 02215, USA; 6 Centre for Astrophysics and Planetary
Science, University of Kent, Canterbury CT2 7NH, UK; 7 School of Physics, University of New South Wales, Sydney,
NSW 2052, Australia; 8 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748, Garching bei Mnchen,
Germany; 9 INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy; 10 Excellence Cluster
Universe, Boltzmannstr. 2, 85748, Garching bei Mnchen, Germany
E-mail contact: silvia.leurini at inaf.it
G351.776-0.527 is among the most massive, closest, and youngest filaments in the inner Galactic plane and therefore
it is an ideal laboratory to study the kinematics of dense gas and mass replenishment on a large scale. In this paper,
we present far-infrared (FIR) and submillimetre wavelength continuum observations combined with spectroscopic
C18 O (2–1) data of the entire region to study its temperature, mass distribution, and kinematics. The structure iscomposed of a main elongated region with an aspect ratio of ∼ 23, which is associated with a network of filamentary
structures. The main filament has a remarkably constant width of 0.2 pc. The total mass of the network (including themain filament) is ≥ 2600 M⊙ , while we estimate a mass of ∼ 2000 M⊙ for the main structure. Therefore, the network
harbours a large reservoir of gas and dust that could still be accreted onto the main structure. From the analysis of
the gas kinematics, we detect two velocity components in the northern part of the main filament. The data also reveal
velocity oscillations in C18 O along the spine in the main filament and in at least one of the branches. Considering theregion as a single structure, we find that it is globally close to virial equilibrium indicating that the entire structure isapproximately in a stable state.
Accepted by A&A
http://arxiv.org/pdf/1812.01035

26

Catalogue of High Protostellar Surface Density Regions in Nearby Embedded Clusters
Juan Li1,2 , Philip C. Myers3 , Helen Kirk4,5 , Robert A. Gutermuth6 , Michael M. Dunham7,3 , Riwaj
Pokhrel6,3
1

Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan RD, Shanghai 200030, China; 2 Keylaboratory for Radio Astronomy, Chinese Academy of Science, 2 West Beijing Road, Nanjing, JiangSu 210008, China;
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 4 Department of
Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC, Canada V8P 5C2; 5 Departmentof Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada; 6 Department of Astronomy,
University of Massachusetts, Amherst, MA 01003, USA; 7 Department of Physics, State University of New York at
21

Fredonia, 280 Central Ave, Fredonia, NY 14063, USA
E-mail contact: lijuan at shao.ac.cn
We analyze high-quality stellar catalogs for 24 young and nearby (within 1 kpc) embedded clusters and present a
catalogue of 32 groups which have a high concentration of protostars. The median effective radius of these groups
is 0.17 pc. The median protostellar and pre-main sequence star surface densities are 46 M⊙ pc−2 and 11 M⊙ pc−2 ,respectively. We estimate the age of these groups using a model of constant birthrate and random accretion stoppingand find a median value of 0.25 Myr. Some groups in Aquila and Serpens, Corona Australia and Ophichus L1688
show high protostellar surface density and high molecular gas surface density, which seem to be undergoing vigorousstar formation. These groups provide an excellent opportunity to study initial conditions of clustered star formation.
Comparison of protostellar and pre-main-sequence stellar surface densities reveal continuous low-mass star formationof these groups over several Myr in some clouds. For groups with typical protostellar separations of less than 0.4 pc,
we find that these separations agree well with the thermal Jeans fragmentation scale. On the other hand, for groups
with typical protostellar separations larger than 0.4 pc, these separations are always larger than the associated Jeans
length.
Accepted by ApJ
http://arxiv.org/pdf/1812.00556

Evolutionary models of cold and low-mass planets: Cooling curves, magnitudes, anddetectability

27 Esther F. Linder , Christoph Mordasini , Paul Mollière , Gabriel-Dominique Marleau , Matej Malik ,
1

1

5

2

3

4

6

Sascha P. Quanz and Michael R. Meyer
1

Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland; 2 Sterrewacht Leiden,
Huygens Laboratory, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands; 3 Institut für Astronomie und Astrophysik,
Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany; 4 Center for Space andHabitability, University of Bern, Gesellschaftsstrasse 6, CH-3012, Bern, Switzerland; 5 Institute for Particle Physics
and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland; 6 Department of Astronomy,
University of Michigan, 1085 S. University, Ann Arbor MI 48109, USA
E-mail contact: esther.linder at space.unibe.ch
Future instruments like NIRCam and MIRI on JWST or METIS at the ELT will be able to image exoplanets thatare too faint (because of a low mass, and hence a small size or low effective temperature) for current direct imaging
instruments. On the theoretical side, core accretion formation models predict a significant population of low-mass
and/or cool planets at orbital distances of ∼ 10–100 au. Evolutionary models predicting the planetary intrinsic
luminosity as a function of time have traditionally concentrated on gas-dominated giant planets. We extend these
cooling curves to Saturnian and Neptunian planets.We simulate the cooling of isolated core-dominated and gas giant
planets with masses of 5 Earth masses to 2 Jupiter masses. The planets consist of a core made of iron, silicates,
and ices, surrounded by a H/He envelope, similar to the ice giants in the solar system. The luminosity includes thecontribution from the cooling and contraction of the core and of the H/He envelope, as well as radiogenic decay. For
the atmosphere we use grey, AMES-Cond, petitCODE, and HELIOS models. We consider solar and non-solar metallicities
as well as cloud-free and cloudy atmospheres. The most important initial conditions, namely the core-to-envelope ratio
and the initial (i.e., post formation) luminosity are taken from planet formation simulations based on the core accretion
paradigm.We first compare our cooling curves for Uranus, Neptune, Jupiter, Saturn, GJ 436b, and a 5 Earth masses
planet with a 1% H/He envelope with other evolutionary models. We then present the temporal evolution of planetswith masses between 5 Earth masses and 2 Jupiter masses in terms of their luminosity, effective temperature, radius,and entropy. We discuss the impact of different post formation entropies. For the different atmosphere types andinitial conditions magnitudes in various filter bands between 0.9 and 30 micrometer wavelength are provided. Using
black body fluxes and non-grey spectra, we estimate the detectability of such planets with JWST. It is found thata 20 (100) Earth masses planet can be detected with JWST in the background limit up to an age of about 10 (100)Myr with NIRCam and MIRI, respectively.
Accepted by Astronomy & Astrophyscis
https://arxiv.org/pdf/1812.02027

22

ALMA Detection of Extended Millimeter Halos in the HD 32297 and HD 61005 Debris
Disks

28 Meredith A. MacGregor , Alycia J. Weinberger , A. Meredith Hughes , D.J. Wilner , Thayne Currie ,
1,2

6

1

3

1

3

7

4

5

8

John H. Debes , Jessica K. Donaldson , Seth Redﬁeld , Aki Roberge , Glenn Schneider
1

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 Department of Astronomy, Wesleyan
University, Van Vleck Observatory, 96 Foss Hill Drive, Middletown, CT 06457, 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 ALMA 1.3 mm (230 GHz) observations of the HD 32297 and HD 61005 debris disks, two of the most
iconic debris disks due to their dramatic swept-back wings seen in scattered light images. These observations achievesensitivities of 14 and 13 µJy beam−1 for HD 32297 and HD 61005, respectively, and provide the highest resolution
images of these two systems at millimeter wavelengths to date. By adopting a MCMC modeling approach, we determinethat both disks are best described by a two-component model consisting of a broad (∆R/R > 0.4) planetesimal beltwith a rising surface density gradient, and a steeply falling outer halo aligned with the scattered light disk. The innerand outer edges of the planetesimal belt are located at 78.5±8.1 AU and 122±3 AU for HD 32297, and 41.9±0.9
AU and 67.0±0.5 AU for HD 61005. The halos extend to 440±32 AU and 188±8 AU, respectively. We also detect
12
CO J=2–1 gas emission from HD 32297 co-located with the dust continuum. These new ALMA images provide
observational evidence that larger, millimeter-sized grains may also populate the extended halos of these two disks
previously thought to only be composed of small, micron-sized grains. We discuss the implications of these results forpotential shaping and sculpting mechanisms of asymmetric debris disks.
Accepted by ApJ
http://arxiv.org/pdf/1812.05610

The JCMT Transient Survey: An Extraordinary Submillimetre Flare in the T Tauri
29 Binary
System JW 566
Steve Mairs1 , Bhavana Lalchand2 , Geoﬀrey C. Bower3 , Jan Forbrich4 , Graham S. Bell1 , Gregory J.
Herczeg5 , Doug Johnstone6 , Wen-Ping Chen2 , Jeong-Eun Lee7 and Alvaro Hacar8
1

East Asian Observatory, 660 N. A’ohoku Pl. Hilo, Hawaii, 96720, USA; 2 Graduate Institute of Astronomy, National
Central University, 300 Jhongda Road, Zhongli, Taoyuan 32001, Taiwan; 3 Academia Sinica Institute of Astronomy
and Astrophysics, 645 N A’ohoku Place, Hilo, HI, 96720, USA; 4 Centre for Astrophysics Research, School of Physics,
Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK; 5 Kavli Institutefor Astronomy and Astrophysics, Peking University, Yiheyuan Lu 5, Haidian Qu, 100871 Beijing, People??s Republicof China; 6 NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd, Victoria, BC, V9E 2E7, Canada; 7
School of Space Research, Kyung Hee University, 1732, Deogyeong-Daero, Giheung-gu Yongin-shi, Gyunggi-do 17104,
Korea; 8 Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands
E-mail contact: s.mairs at eaobservatory.org
The binary T Tauri system JW 566 in the Orion Molecular Cloud underwent an energetic, short-lived flare observedat submillimetre wavelengths by the SCUBA-2 instrument on 26 November 2016 (UT). The emission faded by nearly
50% during the 31 minute integration. The simultaneous source fluxes averaged over the observation are 500 +/- 107
mJy/beam at 450 microns and 466 +/- 47 mJy/beam at 850 microns. The 850 micron flux corresponds to a radio
luminosity of Lν = 8 × 1019 erg/s/Hz, approximately one order of magnitude brighter (in terms of νLν ) than that ofa flare of the young star GMR-A, detected in Orion in 2003 at 3mm. The event may be the most luminous known
flare associated with a young stellar object and is also the first coronal flare discovered at sub-mm wavelengths. The
spectral index between 450 microns and 850 microns of α = 0.11 is broadly consistent with non-thermal emission.
The brightness temperature was in excess of 6 × 104 K. We interpret this event to be a magnetic reconnection that23

energised charged particles to emit gyrosynchrotron/synchrotron radiation.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/1812.00016

30Structure of a protobinary system: an asymmetric circumbinary disk and spiral arms
Tomoaki Matsumoto1,2,3 , Kazuya Saigo4 , and ShigehisaTakakuwa5,6
1

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

On the episodic excursions of massive protostars in the Hertzsprung-Russell diagram

31 D. M.-A. Meyer , L. Haemmerle and E.I. Vorobyov
1

2

3,4

1

Astrophysics Group, School of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom;
Observatoire de Genve, Universit de Genve, chemin des Maillettes 51, CH-1290 Sauverny, Switzerland; 3 ResearchInstitute of Physics, Southern Federal University, Stachki 194, Rostov-on-Don, 344090, Russia; 4 Department of
Astrophysics, The University of Vienna, Vienna, A-1180, Austria

2E-mail contact: dmameyer.astro at gmail.com
Massive protostars grow and evolve under the effect of rapid accretion of circumstellar gas and dust, falling at high rates(≥ 10−4 -10−3 M⊙ yr−1 ). This mass infall has been shown, both numerically and observationally, to be episodicallyinterspersed by accretion of dense gaseous clumps migrating through the circumstellar disc to the protostellar surface,causing sudden accretion and luminous bursts. Using numerical gravito-radiation-hydrodynamics and stellar evolution
calculations, we demonstrate that, in addition to the known bloating of massive protostars, variable episodic accretion
further influences their evolutionary tracks of massive young stellar objects (MYSOs). For each accretion-driven
flare, they experience rapid excursions toward more luminous, but colder regions of the Hertzsprung-Russell diagram.
During these excursions, which can occur up to the end of the pre-main-sequence evolution, the photosphere of
massive protostars can episodically release much less energetic photons and MYSOs surreptitiously adopt the same
spectral type as evolved massive (supergiants) stars. Each of these evolutionary loop brings the young high-mass stars
close to the forbidden Hayashi region and might make their surrounding H iiregions occasionally fainter, before they24

recover their quiescent, pre-burst surface properties. We interpret such cold, intermittent pre-main-sequence stellar
evolutionary excursions and the dipping variability of HII regions as the signature of the presence of a fragmenting
circumstellar accretion disc surrounding the MYSOs. We conjecture that this mechanism might equivalently affectyoung stars in the intermediate-mass regime.
Accepted by MNRAS
https://arxiv.org/pdf/1812.10762

The Zeeman Effect in the 44 GHz Class I Methanol (CH3 OH) Maser Line Toward
DR21W

32 E. Momjian and A.P. Sarma121

National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA; 2 Physics Department, DePaul
University, 2219 N. Kenmore Ave., Chicago, IL 60614, USA
E-mail contact: emomjian at nrao.edu
We report the detection of the Zeeman effect in the 44 GHz Class I methanol maser line toward the high mass star
forming region DR21W. There are two prominent maser spots in DR21W at the ends of a northwest-southeast linear
arrangement. For the maser at the northwestern end (maser A), we fit three Gaussian components. In the strongest
component, we obtain a significant Zeeman detection, with zBlos = −23.4 ± 3.2 Hz. If we use z = −0.920 Hz mG−1
for the F = 5 → 4 hyperfine transition, this corresponds to a magnetic field |Blos | = 25.4 mG; Blos would be higher if
a different hyperfine was responsible for the 44 GHz maser, but our results also rule out some hyperfines, since fields inthese regions cannot be hundreds of mG. Class I methanol masers form in outflows where shocks compress magnetic
fields in proportion to gas density. Designating our detected Blos = 25 mG as the magnetic field in the post-shock gas,
we find that Blos in the pre-shock gas should be 0.1–0.8 mG. Although there are no thermal-line Zeeman detections
toward DR21W, such values are in good agreement with Zeeman measurements in the CN thermal line of 0.36 and 0.71
mG about 3.′ 5 away in DR21(OH) in gas of comparable density to the pre-shock gas density in DR21W. Comparisonof our derived magnetic energy density to the kinetic energy density in DR21W indicates that magnetic fields likely
play a significant role in shaping the dynamics of the post-shocked gas in DR21W.
Accepted by ApJ
http://arxiv.org/pdf/1812.09977

Shock-Generating Planetesimals Perturbed by a Giant Planet in a Gas Disk

33 M. Nagasawa , K.K. Tanaka , H. Tanaka , H. Nomura , T. Nakamoto , and H. Miura
1

2

2

3

3

4

1

Department of Physics, Kurume University School of Medicine, 67 Asahi-machi, Kurume-city, Fukuoka 830-0011,
Japan; 2 Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku Sendai, Miyagi 980-8578, Japan; 3 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8551,
Japan; 4 Graduate School of Natural Sciences, Nagoya City University, Yamanohata 1, Mizuho-cho, Mizuho-ku,
Nagoya 467-8501
E-mail contact: nagasawa makiko at med.kurume-u.ac.jp
We examined the excitations of planetesimals caused by the resonances of a giant planet in a protoplanetary gas
disk. The highly excited planetesimals generate bow shocks, the mechanism of which results in chondrule formation,
crystallization of silicate dust, and evaporation of icy planetesimals. The planetesimals beyond 2:1 resonance migrateowing to the gas drag and obtain the maximum eccentricity around 3:1 resonance, which is located at approximately
half the planetary distance. The eccentricity depends on the parameters of the planetesimals and the Jovian planet,such as size and location, and gas density of the disk. The maximum relative velocity of a 100-km-sized planetesimalwith respect to the gas disk reaches up to ∼12 km s−1 in the case of Jupiter owing to secular resonance, which occurs
because of the disk’s gravity. We find that if a Jovian mass planet is located within 10 au, the planetesimals larger
than 100 km gain sufficient velocity to cause the melting of chondrule precursors and crystallization of the silicate.
The maximum velocity is higher for large planetesimals and eccentric planets. Planetesimals are trapped temporarily
in the resonances and continue to have high speed over >1 Myr after the formation of a Jovian planet. This durationfits into the timescale of chondrule formation suggested by the isotopic data. The evaporation of icy planetesimals
25

occurs when a Jovian planet is located within 15 au. This mechanism can be a new indicator of planet formation in
exosystems if some molecules ejected from icy planetesimals are detected.
Accepted by ApJ
http://arxiv.org/pdf/1812.05250

34 Gisela N. Ortiz-León , Laurent Loinard , Sergio A. Dzib , Marina Kounkel , Phillip A.B. Galli , John
Gaia-DR2 confirms VLBA parallaxes in Ophiuchus, Serpens and Aquila
1

6,7

2,3

8

1

9

4

2

5

10

J. Tobin , Neal J. Evans II , Lee Hartmann , Luis F. Rodrı́guez , Cesar Briceño , Rosa M. Torres11
and Amy J. Mioduszewski12
1

Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 2 Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de Mexico, Morelia 58089, Mexico; 3 Instituto de Astronomı́a,
Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510 Ciudad de México, México; 4 Departmentof Physics and Astronomy, Western Washington University, 516 High St, Bellingham, WA 98225, USA; 5 Laboratoired’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hillaire, 33615 Pessac, France; 6Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK
73019, USA; 7 Leiden Observatory, PO Box 9513, NL-2300 RA, Leiden, The Netherlands; 8 Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205, USA; 9 Departmentof Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48105, USA; 10 Cerro Tololo Interamerican Observatory, Casilla 603, La Serena, Chile; 11 Centro Universitario de Tonalá, Universidad de Guadalajara,
Avenida Nuevo Periférico No. 555, Ejido San José Tatepozco, C.P. 48525, Tonalá, Jalisco, México; 12 National Radio
Astronomy Observatory, Domenici Science Operations Center, 1003 Lopezville Road, Socorro, NM 87801, USA
E-mail contact: gortiz at mpifr-bonn.mpg.de
We present Gaia-DR2 astrometry of a sample of YSO candidates in Ophiuchus, Serpens Main and Serpens South/W40
in the Aquila Rift, which had been mainly identified by their infrared excess with Spitzer. We compare the GaiaDR2 parallaxes against published and new parallaxes obtained from our Very Long Baseline Array (VLBA) program
GOBELINS. We obtain consistent results between Gaia and the VLBA for the mean parallaxes in each of the regions
analyzed here. We see small offsets, when comparing mean values, of a few tens of micro-arcseconds in the parallaxes,
which are either introduced by the Gaia zero-point error or due to a selection effect by Gaia toward the brightest, lessobscured stars. Gaia-DR2 data alone conclusively places Serpens Main and Serpens South at the same distance, as wefirst inferred from VLBA data alone in a previous publication. Thus, Serpens Main, Serpens South and W40 are allpart of the same complex of molecular clouds, located at a mean distance of 436±9 pc. In Ophiuchus, both Gaia and
VLBA suggest a small parallax gradient across the cloud, and the distance changes from 144.2±1.3 pc to 138.4±2.6
pc when going from L1689 to L1688.
Accepted by ApJL
http://arxiv.org/pdf/1812.02360

35

ALMA Observations of Ethyl Formate toward Orion KL
Yaping Peng1,2 , V. M. Rivilla3, Li Zhang1 , J. X. Ge4 and Bing Zhou1,2
1Department of Astronomy, Yunnan University, and Key Laboratory of Astroparticle Physics of Yunnan Province,
Kunming, 650091, China; 2 College of Science, Yunnan Agricultural University, Kunming, 650201, China; 3 INAFOsservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125, Firenze, Italia; 4 Departamento de Astronomı́a,
Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile
E-mail contact: pyp893 at 163.com
Orion KL is one of the prime templates of astrochemical and prebiotic chemical studies. We wish to explore moreorganic molecules with increasing complexity in this region. In particular, we have searched for one of the mostcomplex organic molecules detected in space so far, ethyl formate (C2 H5 OCHO). This species is the next step inchemical complexity after the simplest member of esters (methyl formate, CH3 OCHO). The mechanisms leading to its
formation are still poorly known. We have used high angular resolution (∼ 1.′′ 5) ALMA observations covering a large
bandwidth from 214 to 247 GHz. We have detected 82 unblended lines of C2 H5 OCHO (49 and 33 of the trans and26

gauche conformers, respectively). The line images showed that C2 H5 OCHO arises mainly from the compact ridge andthe hot core-southwest regions. The derived rotational temperatures and column densities are 122 ± 34 K, (0.9 ± 0.3)
× 1016 cm−2 for the hot core-SW, and 103 ± 13 K, (0.6 ± 0.3) × 1016 cm−2 for the compact ridge. The comparisonof spatial distribution and abundance ratios with chemically related molecules (methyl formate, ethanol and formicacid) indicates that C2 H5 OCHO is likely formed on the surface of dust grains by addition of CH3 to functional-groupradicals (CH2 OCHO) derived from methyl formate (CH3 OCHO)
Accepted by ApJ
http://arxiv.org/pdf/1812.03700

Unveiling the nature of candidate high-mass young stellar objects in the Magellanic
36 Clouds
with near-IR spectroscopy
Megan Reiter1,2 , Omnarayani Nayak3 , Margaret Meixner3,4 and Olivia Jones2
1

University of Michigan, USA; 2 UK Astronomy Technology Centre, UK; 3 Johns Hopkins University, USA; 4 STScI,USA
E-mail contact: megan.reiter at stfc.ac.uk

As nearby neighbors to the Milky Way, the Large and Small Magellanic Clouds (LMC and SMC) provide a unique
opportunity to study star formation in the context of their galactic ecosystems. Thousands of young stellar objects(YSOs) have been characterized with large-scale Spitzer and Herschel surveys. In this paper, we present new near-IR
spectroscopy of five high-mass YSOs in the LMC and one in the SMC. We detect multiple hydrogen recombinationlines, as well as He i 2.058 µm, H2 , [Fe ii], and [S iii] in these highly excited sources. We estimate the internal extinctionof each source and find that it is highest for sources with the youngest evolutionary classifications. Using line ratios,
we assess the dominant excitation mechanism in the three sources where we detect both H2 2.12 µm and [Fe ii] 1.64
µm. In each case, photoexcitation dominates over shock excitation. Finally, we detect CO bandhead absorption in oneof our LMC sources. While this feature is often associated with evolved stars, this object is likely young with strong
PAH and fine-structure emission lines tracing an H ii region detected at longer wavelengths. Compared to high-mass
YSOs in the Galaxy, our sources have higher bolometric and line luminosities, consistent with their selection as someof the brightest sources in the LMC and SMC.
Accepted by MNRAS
https://arxiv.org/pdf/1811.12451

GHz methanol maser survey of the central molecular zone
37 AM.6.7
Rickert , F. Yusef-Zadeh and, J. Ott
1

1

2

1
Department of Physics and Astronomy, Northwestern University, Evanston, Il. 60208, USA; 2 National Radio
Astronomy Observatory, Socorro, NM 87801, USA

E-mail contact: matthewrickert2017@u.northwestern.edu
The Central Molecular Zone (CMZ) spans the inner ∼450 pc (∼3deg) of our Galaxy. This region is defined by
its enhanced molecular emission and contains 5% of the entire Galaxy’s molecular gas mass. However, the numberof detected star forming sites towards the CMZ may be low for the amount of molecular gas that is present, andimproved surveys of star formation indicators can help clarify this. With the Karl G Jansky Very Large Array (VLA),
we conducted a blind survey of 6.7 GHz methanol masers spanning the inner 3deg × 40arcmin (450 pc × 100 pc) of
the Galaxy. We detected 43 methanol masers towards 28 locations, 16 of which are new detections. The velocities
of most of these masers are consistent with being located within the CMZ. A majority of the detected methanol
masers are distributed towards positive Galactic longitudes, similar to 2/3 of the molecular gas mass distributed at
positive Galactic longitudes. The 6.7 GHz methanol maser is an excellent indicator of high mass (> 8 solar mass) starformation, with new detections indicating sites of massive star formation in the CMZ.
Accepted by MNRAS (482, 5349, 2019)http://arxiv/pdf/1812.05730

27

Flat Spectrum Radio Continuum Emission Associated with ǫ Eridani

38 Luis F. Rodrı́guez , Susana Lizano , Laurent Loinard , Miguel Chávez-Dagostino , Timothy S.
1,2

1

5

1,3

4

5

Bastian and Anthony J. Beasley1

Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México,, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México; 2 Mesoamerican Center for Theoretical Physics, Universidad Autónoma
de Chiapas, Carretera Emiliano Zapata Km.4, Real del Bosque (Terán). 29050 Tuxtla Gutiérrez, Chiapas, México;3
Instituto de Astronomı́a, Universidad Nacional Autónoma de México, Apartado Postal 70-264, CdMx, CP 04510,
México; 4 Instituto Nacional de Astrofı́sica, Optica y Electrónica, Luis Enrique Erro #1, CP 72840, Tonantzintla,
Puebla, México; 5 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
E-mail contact: l.rodriguez at irya.unam.mx
We present Very Large Array observations at 33.0 GHz that detect emission coincident with ǫ Eridani to within
0.′′ 07 (0.2 AU at the distance of this star), with a positional accuracy of 0.′′ 05. This result strongly supports thesuggestion of previous authors that the quiescent centimeter emission comes from the star and not from a proposed
giant exoplanet with a semi-major axis of ∼ 1.′′ 0 (3.4 AU). The centimeter emission is remarkably flat and is consistent
with optically thin free-free emission. In particular, it can be modeled as a stellar wind with a mass loss rate of theorder of 6.6 × 10−11 M⊙ yr−1 , which is 3,300 times the solar value, exceeding other estimates of this star’s wind.
However, interpretation of the emission in terms of other thermal mechanisms like coronal free-free and gyroresonanceemission cannot be discarded.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/1901.00903

of Hubble wedges in episodic protostellar outflows
39 Evolution
P. F. Rohde , S. Walch , D. Seifried , A. P. Whitworth , S. D. Clarke and D. A. Hubber
1

1

1

2

1

3

1

Universität zu Köln, I. Physikalisches Institut, Zülpicher Str. 77, D-50937 Koeln, Germany
School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK
3
Universiẗats-Sternwarte München, Scheinerstrasse, 1, D-81679 München, Germany
2

E-mail contact: rohde at ph1.uni-koeln.de
Young low-mass protostars undergo short phases of high accretion and outburst activity leading to lumpy outflows.
Recent observations have shown that the position-velocity and mass-velocity diagrams of such outflows exhibit individual bullet-like features; some of these bullets subscribe to a ‘Hubble Law’ velocity relation, and others are manifest
as ‘Hubble wedges’. In order to explore the origin of these features, we have developed a new episodic outflow modelfor the SPH code gandalf, which mimics the accretion and ejection behaviour of FU Ori type stars. We apply
this model to simulations of star formation, invoking two types of initial conditions: spherically symmetric cores insolid-body rotation with ρ ∝ r−2 , and spherically symmetric turbulent cores with density proportional to the densityof a Bonnor-Ebert sphere. For a wide range of model parameters, we find that episodic outflows lead to self-regulationof the ejected mass and momentum, and we achieve acceptable results, even with relatively low resolution. Using thismodel, we find that recently ejected outflow bullets produce a ‘Hubble wedge’ in the position-velocity relation. However, once such a bullet hits the leading shock front, it decelerates and aligns with older bullets to form a ‘Hubble-law’.
−1.5
Bullets can be identified as bumps in the mass-velocity relation, which can be fit with a power-law, dM/dυRAD ∝ υRAD.
Accepted by MNRAS
http://arxiv.org/pdf/1811.03611

40

Evidence of Hubble flow-like motion of young stellar populations away from the Perseus
arm
Carlos Román-Zúñiga1,3, Alexandre Roman-Lopes2,3 , Mauricio Tapia1,3 , Jesús Hernández1 and Valeria
Ramı́rez Preciado1
1

Instituto de Astronomı́a, Universidad Nacional Autónoma de México, Unidad Académica en Ensenada; 2 Departamento de Fı́sica y Astronomı́a, Universidad La Serena, Chile; 3 Programa de Estancias de Investigación (PREI),28

DGAPA UNAM, Mexico
E-mail contact: croman at astro.unam.mx
In this letter we present evidence of coherent outward motion of a sample of young stars (t <30 Myr) in the Perseus
Arm, whose apparent origin is located in the vicinity of the W3/W4/W5 complex. Using astrometric and photometricdata from the Gaia DR2 catalog of an 8◦ radius field centered near W4, we selected a sample of young, intermediate
to high-mass star candidates. The sample is limited to sources with parallax uncertainties below 20% and Bayesian
distance estimates within 1800 and 3100 pc. The selection includes embedded stellar populations as well as young
open clusters. Projected velocities derived from perspective-corrected proper motions clearly suggest that the youngstar population emerge from the Perseus arm, with a possible convergence zone near W3/W4/W5 region, tracing afront that expands away at a rate of about 15 km s−1 kpc−1 .
Accepted by Astrophysical Journal Letters
https://arxiv.org/pdf/1812.11102

Identifying Young Stellar Objects in the Outer Galaxy: l = 224◦ Region in Canis Major

41 Marta Sewilo , Barbara A. Whitney , Bosco H. K. Yung , Thomas P. Robitaille , Davide Elia ,
1,2

3,4

9,10

5,6

8,11

5

7

12

8

13

Remy Indebetouw , Eugenio Schisano , Ryszard Szczerba , Agata Karska , Jennifer Wiseman ,Brian Babler4 , Martha Boyer14 , William J. Fischer14 , Marilyn Meade4 , Luca Olmi15, Deborah Padgett16
and Natasza Siódmiak5
1

Department of Astronomy, University of Maryland, College Park, MD 20742, USA; 2 CRESST II and Exoplanets
and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; 3 Space
Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301, USA; 4 Department of Astronomy, University of
Wisconsin – Madison, 475 North Charter St., Madison, WI 53706, USA; 5 N. Copernicus Astronomical Centre, PAS,
Rabiańska 8, 87-100 Toruń, Poland; 6 Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30-244
Kraków, Poland; 7 Freelance Consultant, Headingley Enterprise and Arts Centre, Bennett Road Headingley, Leeds
LS6 3HN, United Kingdom; 8 Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100,
I-00133 Roma, Italy; 9 Department of Astronomy, University of Virginia, PO Box 3818, Charlottesville, VA 22903,
USA; 10 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA; 11 Istituto diRadio Astronomia, INAF-IRA, Via Pietro Gobetti 101, 40126, Bologna, Italy; 12 Centre for Astronomy, Faculty ofPhysics, Astronomy and Informatics, Nicolaus Copernicus University, Grudzikadzka 5, 87-100 Toruń, Poland; 13 NASA
Goddard Space Flight Center, Greenbelt, MD 20771, USA; 14 Space Telescope Science Institute, 3700 San Martin Dr.,
Baltimore, MD 21218, USA; 15 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 16
NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA
E-mail contact: marta.m.sewilo at nasa.gov
We study a very young star-forming region in the outer Galaxy that is the most concentrated source of outflows in
the Spitzer Space Telescope GLIMPSE360 survey. This region, dubbed CMa–l224, is located in the Canis Major OB1
association. CMa–l224 is relatively faint in the mid-infrared, but it shines brightly at the far-infrared wavelengths
as revealed by the Herschel Space Observatory data from the Hi-GAL survey. Using the 3.6 and 4.5 µm data fromthe Spitzer/GLIMPSE360 survey, combined with the JHKs 2MASS and the 70–500 µm Herschel/Hi-GAL data, wedevelop a young stellar object (YSO) selection criteria based on color-color cuts and fitting of the YSO candidates’
spectral energy distributions with YSO 2D radiative transfer models. We identify 293 YSO candidates and estimate
physical parameters for 210 sources well-fit with YSO models. We select an additional 47 sources with GLIMPSE360only photometry as ‘possible YSO candidates’. The vast majority of these sources are associated with high H2
column density regions and are good targets for follow-up studies. The distribution of YSO candidates at different
evolutionary stages with respect to Herschel filaments supports the idea that stars are formed in the filaments andbecome more dispersed with time. Both the supernova-induced and spontaneous star formation scenarios are plausible
in the environmental context of CMa–l224. However, our results indicate that a spontaneous gravitational collapse offilaments is a more likely scenario. The methods developed for CMa–l224 can be used for larger regions in the Galactic
plane where the same set of photometry is available.
Accepted by Astrophysical Journal Supplement Series
https://arxiv.org/pdf/1811.12122

29

IRAM and Gaia views of multi-episodic star formation in IC1396A: The origin anddynamics of the Class 0 protostar at the edge of an HII region

42 Aurora Sicilia-Aguilar , Nimesh Patel , Min Fang , Veronica Roccatagliata , Konstantin Getman and

43

1Paul Goldsmith

2

3

4

5

6

1

SUPA, School of Science and Engineering, University of Dundee, Nethergate, Dundee DD1 4HN, UK; 2 HarvardSmithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 3 Department of Astronomy,
University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 4 ipartimento di Fisica “Enrico Fermi”,
Università di Pisa, Largo Pontecorvo 3, 56127 Pisa , Italy; 5 Department of Astronomy & Astrophysics, 525 Davey
Laboratory, Pennsylvania State University, University Park PA 16802, USA; 6 Jet Propulsion Laboratory, M/S 180703, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
E-mail contact: asiciliaaguilar at dundee.ac.uk
IC 1396A is a cometary globule that contains the Class 0 source IC1396A-PACS-1, discovered with Herschel.
We use IRAM 30m telescope and Gaia DR2 data to explore the star-formation history of IC 1396A and investigate
the possibilities of triggered star formation.
IRAM and Herschel continuum data are used to obtain dust temperature and column density maps. Heterodyne data
reveal the velocity structure of the gas. Gaia DR2 proper motions for the stars complete the kinematics of the region.
IC1396A-PACS-1 presents molecular emission similar to a hot corino with warm carbon chain chemistry due to the
UV irradiation. The source is embedded in a dense clump surrounded by gas at velocities significantly different fromthe velocities of the Tr 37 cluster. CN emission reveals photoevaporation, while continuum data and high density
tracers (C18 O, HCO+ , DCO+ , N2 D+ ) reveal distinct gaseous structures with a range of densities and masses.
Combining the velocity, column density, and temperature information and Gaia DR2 kinematics, we confirm thatthe globule has suffered various episodes of star formation. IC1396A-PACS-1 is probably the last intermediate-mass
protostar that will form within IC 1396A, showing evidence of triggering by radiative driven implosion. Chemicalsignatures such as CCS place IC1396A-PACS-1 among the youngest protostars known. Gaia DR2 data reveal velocities
in the plane of the sky ∼4 km/s for IC 1396A with respect to Tr 37. The total velocity difference (8 km/s) between
the Tr 37 cluster and IC 1396A is too small for IC 1396A to have undergone substantial rocket acceleration, which
imposes constraints on the distance to the ionizing source in time and the possibilities of triggered star formation.
The three stellar populations in the globule reveal that objects located within relatively close distances (<0.5 pc) can
be formed in various star-forming episodes within ∼1-2 Myr period. Once the remaining cloud disperses, we expect
substantial differences in evolutionary stage and initial conditions for the resulting objects and their protoplanetarydisks, which may affect their evolution. Finally, evidence for short-range feedback from the embedded protostars and,in particular, the A-type star V390 Cep is also observed.
Accepted by A&A
https://arxiv.org/pdf/1812.07282.pdf

Chandra Observations of the Massive Star-Forming Region Onsala 2
Stephen L. Skinner1 , Kimberly R. Sokal2 and Manuel Guedel3
1

Center for Astrophysics and Space Astron. (CASA), Univ. of Colorado, Boulder, CO 80309, USA; 2 Dept. of
Astronomy, Univ. of Texas, Austin, TX 78712, USA; 3 Dept. of Astrophysics, Univ. of Vienna, A-1180 Vienna,
AustriaE-mail contact: stephen.skinner at colorado.edu
Previous radio and infrared observations have revealed an obscured region of high-mass star formation in Cygnus
known as Onsala 2 (ON 2). Within this region lies the optically-revealed young stellar cluster Berkeley 87 whichcontains several OB stars and the rare oxygen-type Wolf-Rayet star WR 142. Previous radio studies of ON 2 havealso discovered masers and several H II regions excited by embedded OB stars. Radio and GAIA parallaxes have now
shown that the H II regions are more distant than Berkeley 87. We summarize two Chandra X-ray observations of ON
2 which detected more than 300 X-ray sources. Several optically-identified stars in Berkeley 87 were detected including
massive OB stars and WR 142, the latter being a faint hard source whose X-ray emission likely arises in hot thermal
plasma. Intense X-ray emission was detected near the compact H II regions G75.77+0.34 and G75.84+0.40 consistingof numerous point sources and diffuse emission. Heavily-absorbed X-ray sources and their near-IR counterparts that30

may be associated with the exciting OB stars of the H II regions are identified. Shocked winds from embedded
massive stars offer a plausible explanation of the diffuse emission. Young stellar object candidates in the ON 2 region
are identified using near-IR colors, but surprisingly few counterparts of X-ray sources have near-IR excesses typical ofclassical T Tauri stars.
Accepted by ApJ
https://arxiv.org/pdf/1812.02210

Multicomponent kinematics in a massive filamentary IRDC

Vlas Sokolov , Ke Wang , Jaime E. Pineda , Paola Caselli , Jonathan D. Henshaw , Ashley T.
44 Barnes, Jonathan C. Tan , Francesco Fontani and Izaskun Jiménez-Serra
1

5

2,3

1

6,7

8

1

4

9

1

Max Planck Institute for Extraterrestrial Physics, Gießenbachstraßse 1, D-85748 Garching bei München, Germany;
European Southern Observatory (ESO) Headquarters, Karl-Schwarzschild-Str. 2, 85748 Garching bei München,
Germany; 3 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District,
Beijing 100871, China; 4 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 5
Argelander Institute for Astronomy, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany; 6 Departmentof Astronomy, University of Florida, Gainesville, FL, 32611, USA; 7 Department of Physics, University of Florida,
Gainesville, FL, 32611, USA; 8 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 9Centro de Astrobiologı́a (CSIC/INTA), Ctra de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Spain
2

E-mail contact: vlas.sokolov at mpg-alumni.de
To probe the initial conditions for high-mass star and cluster formation, we investigate the properties of dense filaments
within the infrared dark cloud G035.39−00.33 (IRDC G035.39) in a combined Very Large Array (VLA) and the GreenBank Telescope (GBT) mosaic tracing the NH3 (1,1) and (2,2) emission down to 0.08 pc scales. Using agglomerative
hierarchical clustering on multiple line-of-sight velocity component fitting results, we identify seven extended velocitycoherent components in our data, likely representing spatially coherent physical structures, some exhibiting complex
gas motions. The velocity gradient magnitude distribution peaks at its mode of 0.35 km s−1 pc−1 and has a longtail extending into higher values of 1.5–2 km s−1 pc−1 , and is generally consistent with those found toward the samecloud in other molecular tracers and with the values found towards nearby low-mass dense cloud cores at the same
scales. Contrary to observational and theoretical expectations, we find the non-thermal ammonia line widths to besystematically narrower (by about 20%) than those of N2 H+ (1–0) line transition observed with similar resolution.
If the observed ordered velocity gradients represent the core envelope solid-body rotation, we estimate the specificangular momentum to be about 2 × 1021 cm2 s−1 , similar to the low-mass star-forming cores. Together with theprevious finding of subsonic motions in G035.39, our results demonstrate high levels of similarity between kinematics
of a high-mass star-forming IRDC and the low-mass star formation regime.
Accepted by ApJ
http://arxiv.org/pdf/1812.09581

On the Gravitational Instabilities of Protoplanetary Disks

45 Ning Sui , Ping He
1,2

1,3,4

, and Min Li5

1

College of Physics, Jilin University, Changchun, Jilin 130012, China; 2 Max-Planck-Institut für Astronomie, Königstuhl
17, 69117 Heidelberg, Germany; 3 NAOCUKZN Computational Astrophysics Centre (NUCAC), University of KwaZuluNatal, Durban 4000, South Africa; 4 Center for High Energy Physics, Peking University, Beijing 100871, China; 5Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154, USA
E-mail contact: min.li at unlv.edu
The gravitational instabilities are important to the evolution of the disks and the planet formation in the disks. We
calculate the evolution of the disks which form from the collapse of the molecular cloud cores. By changing theproperties of the cloud cores and the hydrodynamical viscosity parameters, we explore their effects on the propertiesof the gravitational instabilities. We find that the disk is unstable when the angular velocity of the molecular cloudcore is larger than a critical value. The time duration of the instability increases as the angular velocity of the core
increases. The increase of the hydrodynamical viscosity parameter hardly affects the stability of the disk, but decreases
31the time duration of the critical state of the gravitational instability in the disk. The instability of the disks can happen
at very early time of evolution of the disk, which is consistent with the observations.
Accepted by PASP
http://arxiv.org/pdf/1812.02826

46

The CARMA-NRO Orion Survey: The filamentary structure as seen in C18 O emission
S. T. Suri1 , A. Sanchez-Monge1 , P. Schilke1 , S. D. Clarke1 , R. J. Smith2 , V. Ossenkopf-Okada1 , R.
Klessen3, P. Padoan4,5 , P. Goldsmith6, H. G. Arce7 , J. Bally8 , J. M. Carpenter9 , A. Ginsburg10 , D.
Johnstone11,12 , J. Kauﬀmann13 , S. Kong7 , D. C. Lis14,15 , S. Mairs16 , T. Pillai17 , J. E. Pineda18 and A.
Duarte-Cabral19
1

I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany; 2 Jodrell Bank Centre for
Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK;
3
Universität Heidelberg, Zentrum für Astronomie, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 4 Institut deCiències del Cosmos, Universitat de Barcelona, IEEC-UB, Martı́ i Franquès 1, E08028 Barcelona, Spain; 5 ICREA, Pg.
Lluı́s Companys 23, 08010 Barcelona, Spain; 6 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak
Grove Drive, Pasadena, CA 91109, USA; 7 Department of Astronomy, Yale University, New Haven, Connecticut 06511,
USA; 8 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado, USA; 9 Joint
ALMA Observatory, Alonso de Córdova 3107 Vitacura, Santiago, Chile; 10 National Radio Astronomy Observatory,
1003 Lopezville road, Socorro NM, 87801; 11 NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Rd,
Victoria, BC, V9E 2E7, Canada; 12 Department of Physics and Astronomy, University of Victoria, BC, V8P 5C2,
Canada; 13 Haystack Observatory, Massachusetts Institute of Technology, 99 Millstone Road, Westford, MA 01886,
USA; 14 Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, LERMA, F-75014, Paris, France; 15 Cahill
Center for Astronomy and Astrophysics 301-17, California Institute of Technology, Pasadena, CA 91125, USA; 16 East
Asian Observatory, 660 N. A’ohoku Place, Hilo, Hawaii, 96720, USA; 17 Max–Planck–Institut für Radioastronomie,
Auf dem Hügel 69, D–53121 Bonn; 18 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748
Garching; 19 School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, UK
E-mail contact: suri at mpia.de
We present an initial overview of the filamentary structure in the Orion A molecular cloud utilizing a high angular andvelocity resolution C18 O(1-0) emission map that was recently produced as part of the CARMA-NRO Orion Survey.
The main goal of this study is to build a credible method to study varying widths of filaments which has previously
been linked to star formation in molecular clouds. Due to the diverse star forming activities taking place throughout
its ?20 pc length, together with its proximity of 388 pc, the Orion A molecular cloud provides an excellent laboratory
for such an experiment to be carried out with high resolution and high sensitivity. Using the widely-known structure
identification algorithm, DisPerSE, on a 3-dimensional (PPV) C18 O cube, we identified 625 relatively short (the longest
being 1.74 pc) filaments over the entire cloud. We study the distribution of filament widths using FilChaP, a python
package that we have developed and made publicly available. We find that the filaments identified in a 2 square degree
PPV cube do not overlap spatially, except for the complex OMC-4 region that shows distinct velocity components
along the line of sight. The filament widths vary between 0.02 and 0.3 pc depending on the amount of substructurethat a filament possesses. The more substructure a filament has, the larger is its width. We also find that despite
this variation, the filament width shows no anticorrelation with the central column density which is in agreement withprevious Herschel observations.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1901.00176.pdf

The formation of rings and gaps in wind-launching non-ideal MHD disks: three-dimensional
simulations

47 Scott S. Suriano , Zhi-Yun Li , Ruben Krasnopolsky , Takeru K. Suzuki and Hsien Shang
1,2

2

3

1

1

3

School of Arts & Sciences, University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902, Japan; 2 Department of
Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 3 Academia Sinica, Institute of Astronomy and32

Astrophysics, Taipei 10617, Taiwan
E-mail contact: suriano at ea.c.u-tokyo.ac.jp
Previous axisymmetric investigations in two dimensions (2D) have shown that rings and gaps develop naturally in
non-ideal magnetohydrodynamic (MHD) disk-wind systems, especially in the presence of ambipolar diffusion (AD).
Here we extend these 2D simulations to three dimensions (3D) and find that rings and gaps are still formed in thepresence of a moderately strong ambipolar diffusion. The rings and gaps form from the same basic mechanism that was
identified in the 2D simulations, namely, the redistribution of the poloidal magnetic flux relative to the disk material
as a result of the reconnection of a sharply pinched poloidal magnetic field lines. Thus, the less dense gaps are morestrongly magnetized with a large poloidal magnetic field compared to the less magnetized (dense) rings. The ringsand gaps start out rather smoothly in 3D simulations that have axisymmetric initial conditions. Non-axisymmetricvariations arise spontaneously at later times, but they do not grow to such an extent as to disrupt the rings and gaps.
These disk substructures persist to the end of the simulations, lasting up to 3000 orbital periods at the inner edgeof the simulated disk. The longevity of the perturbed yet still coherent rings make them attractive sites for trapping
large grains that would otherwise be lost to rapid radial migration due to gas drag. As the ambipolar diffusivity
decreases, both the disk and the wind become increasingly turbulent, driven by the magnetorotational instability,with tightly-wound spiral arms becoming more prominent in the disk.
Accepted by MNRAS
https://arxiv.org/pdf/1810.02234

48

The young star population of L1188
E. Szegedi-Elek1 , M. Kun1 , A. Moór1 , G. Marton1 and B. Reipurth2
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121
Budapest, Konkoly Thege út 15–17, Hungary; 2 Institute for Astronomy, University of Hawaii at Manoa, 640 N.
Aohoku Place, Hilo, HI 96720, USA
E-mail contact: elek.elza at csfk.mta.hu
We present new results on the young star population of the Lynds 1188 molecular cloud, associated with the Cepheus
Bubble, a giant interstellar shell around the association Cep OB 2. In order to reveal the star-forming scenario of themolecular cloud located on the supershell, and understand the history of star formation in the region, we identified
and characterized young star candidates based on an Hα emission survey and various published photometric datasets.
Using Gaia DR2 astrometry we studied the spatial distribution of the young star candidates and isolated three groups
based on their distances. We constructed spectral energy distributions of our target stars, based on Pan-STARRS,
2MASS, Spitzer and WISE photometric data, estimating their spectral types, extinctions, and luminosities. We
estimated masses by means of pre-main-sequence evolutionary models, and derived accretion rates from the equivalent
width of the Hα line. We studied the structure of the cloud by constructing a new extinction map, based on PanSTARRS data. Our results show that the distribution of low-mass young stars in L1188 is well correlated with that ofthe dust and molecular gas. We identified two small, compact clusters and a loose aggregate of young stars. We foundthat star formation in L1188 started about 5 million years ago. The apparent age gradient of young stars across thecloud and the ammonia cores located to the east of the optically visible young stellar groups support the scenario ofstar formation propagating away from the centre of the Cepheus Bubble.
Accepted by MNRAS
http://arxiv.org/pdf/1812.06251

49

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

Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 2 NAOJ Chile Observatory, Alonsode Córdova 3788, Oficina 61B, Vitacura, Santiago, Chile; 3 Department of Astronomical Science, School of PhysicalSciences, SOKENDAI (The Graduate University for Advanced Studies), Mitaka, Tokyo 181-8588, Japan; 4 Academia
33

Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 5 Department of Earth andPlanetary Sciences, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan; 6 National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 7 East Asian Observatory, Hilo 96720, HI, USA; 8 National Radio
Astronomy Observatory, Charlottesville, VA 22903, USA; 9 Institut de Ciéncies de lEspai (ICE, CSIC), Can Magranss/n, E-08193 Cerdanyola del Vallés, Catalonia, Spain; 10 Institut dEstudis Espacials de de Catalunya (IEEC), E-08034
Barcelona, Catalonia, Spain
E-mail contact: satoko.takahashi at nao.ac.jp
Using the ≈15 km ALMA long baselines, we imaged the Stokes I emission and linearly polarized intensity (PI) in
the 1.1-mm continuum band of a very young intermediate-mass protostellar source, MMS 6, in the Orion Molecular
Cloud-3. The achieved angular resolution, 0.′′ 02 × 0.′′ 03 (≈10 AU), shows for the first time a wealth of data on the
dust emission polarization in the central 200 AU of a protostar. The PI peak is offset to the south-west (SW) by ≈20
AU with respect to the Stokes I peak. Its polarization degree is 11% with its E-vector orientation of P.A.≈135◦ . A
partial ring-like structure with a radius of ≈80 AU is detected in PI but not in the Stokes I. NW (north-west) andSE (south-east) parts of the ring are bright with a high polarization degree of >∼10%, and their E-vector orientations
are roughly orthogonal to those observed near the center. We also detected arm-like polarized structures, extending
to 1000 AU scale to the north, with the E-vectors aligned along the minor axis of the structures. We exploredpossible origins of the polarized emission comparing with magnetohydrodynamical (MHD) simulations of the toroidal
wrapping of the magnetic field. The simulations are consistent with the PI emission in the ring-like and the extended
arm-like structures observed with ALMA. However, the current simulations do not completely reproduce observed
polarization characteristics in the central 50 AU. Although the self-scattering model can explain the polarization
pattern and positional offset between the Stokes I and PI, this model is not able to reproduce the observed high degreeof polarization.
Accepted by ApJ
http://arxiv.org/pdf/1812.03189

50

Time Evolution of 3D Disk Formation with Misaligned Magnetic Field and Rotation
Axes
Miikka S. Väisälä1,2 , Hsien Shang1,2 , Ruben Krasnopolsky1,2 , Sheng-Yuan Liu1,2 , Ka Ho Lam2,3 andZhi-Yun Li3
1

Academia Sinica, Theoretical Institute for Advanced Research in Astrophysics, Taipei, Taiwan; 2 Academia Sinica,
Institute of Astronomy and Astrophysics, Taipei, Taiwan; 3 Astronomy Department, University of Virginia, Charlottesville, VA 22904, USA
E-mail contact: mvaisala at asiaa.sinica.edu.tw
Distinguishing diagnostic observational signatures produced by MHD models is essential in understanding the physics
for the formation of protostellar disks in the ALMA era. Developing suitable tools along with time evolution will
facilitate better identification of diagnostic features. With a ray-tracing based radiative transfer code Perspective,
we explore time evolution of MHD models carried out in Li, Krasnopolsky & Shang (2013) — most of which have90◦ misalignment between the rotational axis and the magnetic field. Four visible object types can be characterized,
origins of which are dependent on the initial conditions. Our results show complex spiraling density, velocity andpolarization structures. The systems are under constant change, but many of those distinctive features are present
already early on, and they grow more visible in time, but most could not be identified from the data without examining
their change in time. The results suggest that spiraling pseudodisk structures could function as an effective observation
signature of the formation process, and we witness accretion in the disk with eccentric orbits which appear as spiral-like
perturbation from simple circular Keplerian orbits. Magnetically aligned polarization appears purely azimuthal in thedisk and magnetic field can lead to precession of the disk.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/1812.11471

34

51

Modeling carbon-chain species formation in lukewarm corinos with new multiphasemodelsYao Wang1,2 , Qiang Chang3 and Hongchi Wang1
1

Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 8 Yuanhua
Road, Nanjing 210034, China; 2 University of Science and Technology of China, 96 Jinzhai Road, Hefei 230026, China;
3
Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi 830011, China
E-mail contact: wangyao at pmo.ac.cn
Context. Abundant carbon-chain species have been observed towards lukewarm corinos L1527, B228, and L483. These
carbon-chain species are believed to be synthesized in the gas phase after CH4 desorbs from the dust grain surface atthe temperature around 30 K.
Aims. We investigate carbon-chain species formation in lukewarm corinos using a more rigorous numerical method
and advanced surface chemical models. We also pay attention to the significance of the finite size effect.
Methods. We use the macroscopic Monte Carlo method in simulations. In addition to the two-phase model, the basic
multiphase model and the new multiphase models are used for modeling surface chemistry on dust grains. All volatile
species can sublime at their sublimation temperatures in the two-phase model while most volatile species are frozen
in the ice mantle before water ice sublimes in the basic and the new multiphase models. The new multiphase models
allow more volatile species to sublime at their sublimation temperatures than the basic multiphase model does.
Results. The significance of the finite size effect is dependent on the duration of the cold phase. The discrepancies
between the rate equation approach and the Monte Carlo method decrease as the duration of the cold phase increases.
When T ∼ 30 K, the abundances of gaseous CH4 and CO in the two-phase model are the highest while the basic
multiphase model predicts the lowest CO and CH4 abundances among all models. The abundances of carbon-chain
species in the basic and the new multiphase models are lower than that in the two-phase model when T ∼ 30 K because
CH4 is crucial for the synthesis of carbon-chain species. However, because the abundance of electrons increases as theabundance of H3 O+ decreases, some carbon-chain species abundances predicted by the basic multiphase model may
not be lower than that in the new multiphase models. The two-phase model performs the best to predict carbon-chain
species abundances to fit observations while the basic multiphase model works the worst. The abundances of carbonchain species predicted by the new multiphase models agree reasonably well with observations.
Conclusions. The amount of CH4 that can diffuse inside the ice mantle, thus sublime upon warm-up plays a crucialrole in the synthesis of carbon-chain species in the gas phase. The carbon-chain species observed in lukewarm corinos
may be able to gauge surface chemical models.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1901.01032.pdf

The role of magnetic fields in the formation of protostellar discs

52 James Wurster and Zhi-Yun Li
1

2

1

School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter EX4 4QL, UK; 2 Astronomy Department,
University of Virginia, Charlottesville, USA
E-mail contact: j.wurster at exeter.ac.uk
The formation of a protostellar disc is a natural outcome during the star formation process. As gas in a molecular
cloud core collapses under self-gravity, the angular momentum of the gas will slow its collapse on small scales andpromote the formation of a protostellar disc. Although the angular momenta of dense star-forming cores remain to be
fully characterized observationally, existing data indicates that typical cores have enough angular momenta to form
relatively large, rotationally supported discs. However, molecular clouds are observed to be permeated by magnetic
fields, which can strongly affect the evolution of angular momentum through magnetic braking. Indeed, in the ideal
MHD limit, magnetic braking has been shown to be so efficient as to remove essentially all of the angular momentumof the material close to the forming star such that disc formation is suppressed. This is known as the magnetic braking
catastrophe. The catastrophe must be averted in order for the all-important rotationally supported discs to appear,
but when and how this happens remains debated. We review the resolutions proposed to date, with emphasis on
misalignment, turbulence and especially non-ideal effects. The dissipative non-ideal effects weaken the magnetic field,
and the dispersive term redirects it to promote or hinder disc formation. When self-consistently applying non-ideal

35

processes, rotationally supported discs of at least tens of au form, thus preventing the magnetic braking catastrophe.
The non-ideal processes are sensitive to the magnetic field strength, cosmic ray ionization rate, and gas and dust grainproperties, thus a complete understanding of the host molecular cloud is required. Therefore, the properties of thehost molecular cloud – and especially its magnetic field – cannot be ignored when numerically modelling the formationand evolution of protostellar discs.
Accepted by Frontiers in Astronomy and Space Science
http://arxiv.org/pdf/1812.06728

53

IN-SYNC. VIII. Primordial Disk Frequencies in NGC 1333, IC 348, and the Orion A
Molecular CloudYuhan Yao1 , Michael R. Meyer2 , Kevin R. Covey3 , Jonathan C. Tan4,5 and Nicola Da Rio5
1

Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA; 2 Department of
Astronomy, University of Michigan, Ann Arbor, MI 48109, USA; 3 Department of Physics & Astronomy, Western
Washington University, Bellingham, WA 98225, USA; 4 Department of Space, Earth and Environment, Chalmers
University of Technology, Gothenburg, Sweden; 5 Department of Astronomy, University of Virginia, Charlottesville,
Virginia 22904, USA
E-mail contact: yyao at caltech.edu
In this paper, we address two issues related to primordial disk evolution in three clusters (NGC 1333, IC 348, and OrionA) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged
over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC 348 andOrion A is that primordial disks around intermediate-mass stars (2–5 Msun) evolve faster than those around loss-massstars (0.1–1 Msun), which is consistent with previous results. However, considering only low-mass stars, we do notfind a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories ongas giant planet formation timescales. Second, in the Orion A molecular cloud, in the mass range of 0.35–0.7Msun, we
provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By
using surface gravity as an age indicator and employing 4.5 micron excess as a primordial disk diagnostic, we observea trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC 1333 and IC
348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1-sigma effect.
Accepted by ApJ
http://arxiv.org/pdf/1810.06088

54

JCMT POL-2 and ALMA polarimetric observations of 6000–100 au scales in the protostar B335: linking magnetic field and gas kinematics in observations and MHD simulations
Hsi-Wei Yen1,2 , Bo Zhao3 , I-Ta Hsieh1 , Patrick Koch1 , Ruben Krasnopolsky1 , Chin-Fei Lee1 , Zhi-Yun
Li4 , Sheng-Yuan Liu1 , Nagayoshi Ohashi5 , Shigehisa Takakuwa6,1 and Ya-Wen Tang1
1

Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan; 2 European
Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany; 3 Max-Planck-Institut für
extraterrestrische Physik (MPE), Garching, Germany, 85748; 4 Astronomy Department, University of Virginia, Charlottesville, VA 22904, USA; 5 Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku
Place, Hilo, HI, 96720, USA; 6 Department of Physics and Astronomy, Graduate School of Science and Engineering,Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan
E-mail contact: hwyen at asiaa.sinica.edu.tw
We present our analysis of the magnetic field structures from 6000 au to 100 au scales in the Class 0 protostar B335
inferred from our JCMT POL-2 observations and the ALMA archival polarimetric data. To interpret the observational
results, we perform a series of (non-)ideal MHD simulations of the collapse of a rotating non-turbulent dense core,
whose initial conditions are adopted to be the same as observed in B335, and generate synthetic polarization maps.
The comparison of our JCMT and simulation results suggests that the magnetic field on a 6000 au scale in B335
is pinched and well aligned with the bipolar outflow along the east–west direction. Among all our simulations, the36

ALMA polarimetric results are best explained with weak magnetic field models having an initial mass-to-flux ratio of
9.6. However, we find that with the weak magnetic field, the rotational velocity on a 100 au scale and the disk size inour simulations are larger than the observational estimates by a factor of several. An independent comparison of oursimulations and the gas kinematics in B335 observed with the SMA and ALMA favors strong magnetic field models
with an initial mass-to-flux ratio smaller than 4.8. We discuss two possibilities resulting in the different magnetic fieldstrengths inferred from the polarimetric and molecular-line observations, (1) overestimated rotational-to-gravitationalenergy in B335 and (2) additional contributions in the polarized intensity due to scattering on a 100 au scale.
Accepted by ApJ
https://arxiv.org/pdf/1901.00242

An Asymmetric Keplerian Disk Surrounding an O-type Protostar

A. Zapata , Guido Garay , Aina Palau , Luis F. Rodrıǵuez , Manuel Fernández-López , Robert
55 LuisEstalella , Andres Guzmán
1

4

2

1

1

3

5

1

Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090,
Morelia, Michoacán, México; 2 Departamento de Astronomı́a, Universidad de Chile, Camino el Observatorio 1515,
Santiago, Chile; 3 Instituto Argentino de Radioastronomı́a (CCT-La Plata, CONICET; CICPBA), C.C. No. 5,1894, Villa Elisa, Buenos Aires, Argentina; 4 Dep. de Fı́sica Quàntica i Astrofı́sica, Institut de Ciencies del Cosmos,
Universitat de Barcelona, IEEC-UB, Marti i Franques 1, 08028 Barcelona, Spain; 5 National Astronomical Observatoryof Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
E-mail contact: lzapata@irya.unam.mx
During the last decades, a great interest has emerged to know if even the most massive stars in our galaxy (namely
the spectral O-type stars) are formed in a similar manner as the low- and intermediate-mass stars, that is, throughthe presence of accreting disks and powerful outflows. Here, using sensitive observations of the Atacama Large
Millimeter/Submillimeter Array (ALMA), we report a resolved Keplerian disk (with fifteen synthesized beams across its
major axis) surrounding the deeply embedded O-type protostar IRAS16547−4247. The disk shows some asymmetries
that could arise because of the disk is unstable and fragmenting or maybe because of different excitation conditions
within the disk. The enclosed mass estimated from the disk Keplerian radial velocities is 25±3 M⊙ . The molecular
disk is at the base of an ionized thermal radio jet and is approximately perpendicular to the jet axis orientation. We
additionally find the existence of a binary system of compact dusty objects at the center of the accreting disk, whichindicates the possible formation of an O-type star and a companion of lower mass. This is not surprising due to thehigh binary fraction reported in massive stars. Subtracting the contribution of the dusty disk plus the envelope andthe companion, we estimated a mass of 20 M⊙ for the central star.
Accepted by The Astrophysical Journal
http://adsabs.harvard.edu/pdf/2019arXiv190104896Z

Inclined Massive Planets in a Protoplanetary Disc: Gap Opening, Disc Breaking, and
56 Observational
Signatures
Zhaohuan Zhu1
1

Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV,
89154, USA
E-mail contact: zhaohuan.zhu at unlv.edu
We carry out three-dimensional hydrodynamical simulations to study planet-disc interactions for inclined high massplanets, focusing on the disc’s secular evolution induced by the planet. We find that, when the planet is massive enoughand the induced gap is deep enough, the disc inside the planet’s orbit breaks from the outer disc. The inner and outerdiscs precess around the system’s total angular momentum vector independently at different precession rates, whichcauses significant disc misalignment. We derive the analytical formulae, which are also verified numerically, for: 1)
the relationship between the planet mass and the depth/width of the induced gap, 2) the migration and inclination
damping rates for massive inclined planets, and 3) the condition under which the inner and outer discs can breakand undergo differential precession. Then, we carry out Monte-Carlo radiative transfer calculations for the simulated37

broken discs. Both disc shadowing in near-IR images and gas kinematics probed by molecular lines (e.g. from ALMA)
can reveal the misaligned inner disc. The relationship between the rotation rate of the disc shadow and the precession
rate of the inner disc is also provided. Using our disc breaking condition, we conclude that the disc shadowing due tomisaligned discs should be accompanied by deep gaseous gaps (e.g. in Pre/Transitional discs). This scenario naturally
explains both the disc shadowing and deep gaps in several systems (e.g. HD 100453, DoAr 44, AA Tau, HD 143006)
and these systems should be the prime targets for searching young massive planets (>MJ ) in discs.
Accepted by MNRAS
http://arxiv.org/pdf/1812.01262

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

38

Abstracts of recently accepted major reviews

Star Clusters Across Cosmic TimeMark R. Krumholz1,2 , Christopher F. McKee3 , and Joss Bland-Hawthorn2,4,5
1

Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia;
Centre of Excellence for All Sky Astrophysics in Three Dimensions (ASTRO-3D), Australia; 3 Departments ofAstronomy and of Physics, University of California, Berkeley, CA 94720, USA; 4 Sydney Institute for Astronomy,
School of Physics A28, University of Sydney, NSW 2006, Australia; 5 Miller Professor, Miller Institute, University ofCalifornia, Berkeley, CA 94720, USA
2E-mail contact: mark.krumholz at anu.edu.auStar clusters stand at the intersection of much of modern astrophysics: the interstellar medium, gravitational dynamics,
stellar evolution, and cosmology. Here we review observations and theoretical models for the formation, evolution,and eventual disruption of star clusters. Current literature suggests a picture of this life cycle with several phases:(1) Clusters form in hierarchically-structured, accreting molecular clouds that convert gas into stars at a low rate per
dynamical time until feedback disperses the gas. (2) The densest parts of the hierarchy resist gas removal long enoughto reach high star formation efficiency, becoming dynamically-relaxed and well-mixed. These remain bound aftergas removal. (3) In the first ∼100 Myr after gas removal, clusters disperse moderately fast, through a combinationof mass loss and tidal shocks by dense molecular structures in the star-forming environment. (4) After ∼100 Myr,clusters lose mass via two-body relaxation and shocks by giant molecular clouds, processes that preferentially affectlow-mass clusters and cause a turnover in the cluster mass function to appear on ∼1–10 Gyr timescales. (5) Even
after dispersal, some clusters remain coherent and thus detectable in chemical or action space for multiple galactic
orbits. In the next decade a new generation of space- and AO-assisted ground-based telescopes will enable us to test
and refine this picture.
Accepted by ARAA
http://arxiv.org/pdf/1812.01615

Solar System formation in the context of extra-solar planets
Sean N. Raymond1 , Andre Izidoro2 and Alessandro Morbidelli3
1

Laboratoire d’Astrophysique de Bordeaux, CNRS and Université de Bordeaux, Allée Geoffroy St. Hilaire, 33165
Pessac, France; 2 UNESP, Univ. Estadual Paulista - Grupo de Dinâmica Orbital Planetologia, Guaratinguetá, CEP
12.516-410, São Paulo, Brazil; 3 Laboratoire Lagrange, UMR 7293, Université de Nice Sophia-Antipolis, CNRS,
Observatoire de la Côte d’Azur, Boulevard de l’Observatoire, 06304 Nice Cedex 4, France
E-mail contact: rayray.sean at gmail.com
Exoplanet surveys have confirmed one of humanity’s (and all teenagers’) worst fears: we are weird. If our Solar Systemwere observed with present-day Earth technology – to put our system and exoplanets on the same footing – Jupiteris the only planet that would be detectable. The statistics of exo-Jupiters indicate that the Solar System is unusual
at the ∼1% level among Sun-like stars (or ∼0.1% among all main sequence stars). But why are we different?
This review focuses on global models of planetary system formation. Successful formation models for both the Solar
System and exoplanet systems rely on two key processes: orbital migration and dynamical instability. Systems ofclose-in ‘super-Earths’ or ‘sub-Neptunes’ cannot have formed in-situ, but instead require substantial radial inward
motion of solids either as drifting mm- to cm-sized pebbles or migrating Earth-mass or larger planetary embryos.
We argue that, regardless of their formation mode, the late evolution of super-Earth systems involves migration into
chains of mean motion resonances anchored at the inner edge of the protoplanetary disk. The vast majority of resonant
chains go unstable when the disk dissipates. The eccentricity distribution of giant exoplanets suggests that migration
followed by instability is also ubiquitous in giant planet systems. We present three different models for inner Solar
39

System formation – the low-mass asteroid belt, Grand Tack, and Early Instability models – each of which invokes a
combination of migration and instability. We discuss how each model may be falsified.
We argue that most Earth-sized habitable zone exoplanets are likely to form much faster than Earth, with most of
their growth complete within the disk lifetime. Their water contents should span a wide range, from dry rock-ironplanets to water-rich worlds with tens of percent water. Jupiter-like planets on exterior orbits may play a central rolein the formation of planets with small but non-zero, Earth-like water contents. Water loss during giant impacts andheating from short-lived radioisotopes like 26 Al may also play an important role in setting the final water budgets ofhabitable zone planets.
Finally, we identify the key bifurcation points in planetary system formation. We present a series of events that can
explain why our Solar System is so weird. Jupiter’s core must have formed fast enough to quench the growth of Earth’s
building blocks by blocking the flux of pebbles drifting inward through the gaseous disk. The large Jupiter/Saturn
mass ratio is rare among giant exoplanets but may be required to maintain Jupiter’s wide orbit. The giant planets’
instability must have been gentle, with no close encounters between Jupiter and Saturn, also unusual in the larger(exoplanet) context. Our Solar System system is thus the outcome of multiple unusual, but not unheard of, events.
Accepted by Planetary Astrobiology (Eds Meadows, Arney, Des Marais, Schmidt)
https://arxiv.org/pdf/1812.01033

The Role of Magnetic Fields in the Formation of Protostellar Discs
James Wurster1 and Zhi-Yun Li2
1

School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom,; 2 Astronomy Department, University of Virginia, Charlottesville, VA, United States
E-mail contact: j.wurster at exeter.ac.uk
The formation of a protostellar disc is a natural outcome during the star formation process. As gas in a molecular
cloud core collapses under self-gravity, the angular momentum of the gas will slow its collapse on small scales andpromote the formation of a protostellar disc. Although the angular momenta of dense star-forming cores remain to be
fully characterized observationally, existing data indicates that typical cores have enough angular momenta to form
relatively large, 100 au-scale, rotationally supported discs, as illustrated by hydrodynamic simulations. However, themolecular clouds are observed to be permeated by magnetic fields, which can in principle strongly affect the evolutionof angular momentum during the core collapse through magnetic braking. Indeed, in the ideal magnetohydrodynamic(MHD) limit, magnetic braking has been shown to be so efficient as to remove essentially all of the angular momentumof the material close to the forming star such that disc formation is suppressed. This failure to produce discs inidealized cores is known as the magnetic braking catastrophe. The catastrophe must be averted in order for the
all-important rotationally supported discs to appear, but when and how this happens remains debated. We review theresolutions proposed to date, with emphasis on misalignment, turbulence and especially non-ideal effects. Non-ideal
MHD accounts for charged and neutral species, making it a natural extension to the ideal MHD approximation, sincemolecular clouds are only weakly ionized. The dissipative non-ideal effects diffuse the magnetic field to weaken it, andthe dispersive term redirects the magnetic field to promote or hinder disc formation, dependent upon the magnetic
geometry. When self-consistently applying non-ideal processes, rotationally supported discs of at least tens of au form,
thus preventing the magnetic braking catastrophe. The non-ideal processes are sensitive to the magnetic field strength,
cosmic ray ionization rate, and gas and dust grain properties, thus a complete understanding of the host molecular
cloud is required. Therefore, the properties of the host molecular cloudand especially its magnetic fieldcannot beignored when numerically modeling the formation and evolution of protostellar discs.
Accepted by Frontiers in Astronomy and Space Sciences

https://www.frontiersin.org/articles/10.3389/fspas.2018.00039/full
http://arxiv.org/pdf/1812.06728

40

New Jobs

Postdoctoral position in theoretical and numerical star formation
Applications are invited for a three-year Post-Doctoral Research Associate (PDRA) position in The School of Physics
and Astronomy at Cardiff University, to work with Professor Anthony Whitworth, on theoretical and numerical starformation. This PDRA position is funded by a Consolidated Grant from the UK’s Science and Engineering ResearchCouncil (Ref. ST/S00033X/1). The project is focused on exploring the formation and fragmentation of filaments andcores, the properties of the stars and star-systems they spawn, the roles of radiative and mechanical feedback, and theconstraints that can be inferred from dust continuum and molecular line observations of filaments and cores.
The Astrophysics, Gravitational Waves, and Astronomical Instrumentation Groups in Cardiff comprise 32 faculty, 19
postdoctoral fellows and research associates, and 50 PhD students. We have a broad range of research programmes instar and planet formation, galaxies, cosmology gravitational wave sources, and in building the instruments needed todetect and observe these objects, particularly at far-infrared and sub-millimetre wavelengths. The School of Physics
and Astronomy was ranked sixth in the most recent UK Research Excellence Framework evaluation, and provides a
stimulating and well-resourced environment in which to pursue research, with very good computing facilities.
Applicants must have a PhD in astrophysics or a closely related discipline, or expect to be awarded their PhD before
the start of the position. They must have expertise in numerical hydrodynamics and/or radiation transport, preferably
in the context of star formation.

The closing date for applications is 18 February 2019.
Applications should be made electronically via http://www.cardiff.ac.uk/jobs, ‘Academic Vacancies’, Ref. 8156BR.
With your completed application, please submit your full CV, a list of publications, and a brief statement of researchexperience, research interests and career goals.
Informal enquiries about the role can be made to Professor Whitworth by email [ant@astro.cf.ac.uk] or telephone[+4429-20874798]. Informal enquiries about working at Cardiff University can be made to Glesni Lloyd by email[LloydGW@cardiff.ac.uk].
The position is fixed term until 31st March 2022.
Salary: £33199 to £39609 (Grade 6), depending on experience.
Interviews will be held, and offers made, by 1st March 2019.

Cardiff University and the School of Physics and Astronomy are committed to supporting and promoting equalityand diversity. Our inclusive environment welcomes applications from talented people from diverse backgrounds. We
strongly encourage female applicants and those from any ethnic minority group. The School of Physics & Astronomy
has a Juno Practitioner accreditation that recognises good employment practice and a commitment to develop the
careers of women working in science. The University sustains a positive working environment for all staff to flourish
and achieve. The University has developed a flexible and responsive framework of procedures to support staff inmanaging their work and personal commitments.

41

Two Tenure-Track Faculty Positions in the Department of Astronomy
at the University of Florida
The Department of Astronomy at the University of Florida invites applications for two full-time, nine-month, tenuretrack faculty positions at the level of Assistant Professor to begin on August 16, 2019. We invite applications fromobservers, theorists, and instrumentalists. We are conducting two parallel searches. The first search focuses on thearea of star formation in the Milky Way and nearby galaxies, including (but not limited to) molecular cloud physics,
interstellar medium, young stellar objects, and circumstellar disks. The second search focuses on the areas of stars
and stellar systems, including (but not limited to) the solar system, stellar physics, multiple star systems, stellar
populations, extrasolar planets (e.g., detection, characterization or demographics). The Department of Astronomy isespecially interested in qualified candidates who can contribute, through their research, teaching, and service, to thediversity and excellence of the academic community at the University of Florida.
These searches are part of a continuing effort by the University of Florida to expand in the area of Astronomy andAstrophysics and follow three tenure-track faculty hires in the Department of Astronomy and two astrophysics-relatedtenure-track faculty hires in the Department of Physics last year. The University of Florida has access to several worldclass research facilities and telescopes. In addition, the university is home to HiPerGator, the third most powerfulcomputer at a US public university. We welcome applicants who can benefit from access to these resources whiledeveloping high impact research programs using other major observational national and international astronomical
facilities, and publicly-available large datasets. The Department of Astronomy has built numerous state-of-the-art
instruments for some of the best observatories on Earth, and is currently involved in several major international
projects, including the Illustris collaboration and the Dark Energy Spectroscopic Instrument. Information about the
Department of Astronomy can be found at www.astro.ufl.edu.
Candidates should already have a strong established research program that complements ongoing research in the
Department of Astronomy, a compelling plan for future research, and the ability to supervise both graduate andundergraduate research projects. A Ph.D. degree in Astronomy, Astrophysics, Physics, or a closely related field is
required. The salary is competitive and commensurate with qualifications and experience, and includes a full benefits
package.
Applications must be submitted online. Candidates may be considered for both positions through the submission of two
independent applications. The link to each position is http://apply.interfolio.com/55767 and http://apply.interfolio.com/55777. All applications must include: (1) a cover letter, (2) a complete curriculum vitae, (3) a list of publications, (4) aresearch statement summarizing the applicants qualifications, past research, and future research plans, (5) a statementof teaching experience and interest, and (6) three confidential letters of recommendation. For full consideration, applications should be submitted by December 17, 2018, at which time the committee will begin reviewing applications.
Applications received after this date may be considered at the discretion of the committee until the two positions arefilled.
The successful candidates will be required to provide an official transcript to the hiring department upon hire. A transcript will not be considered official if a designation of Issued to Student is visible. Degrees earned from an educational
institution outside of the United States require evaluation by a professional credentialing service provider approved by
the National Association of Credential Evaluation Services (NACES), which can be found at http://www.naces.org/ .
The University of Florida is an equal opportunity institution dedicated to building a broadly diverse and inclusive
faculty and staff and strongly encourages applications from female and minority candidates. Searches are conductedin accordance with Florida’s Sunshine Law. If an accommodation due to disability is needed to apply for this position,please call (352) 392-2477 or the Florida Relay System at (800) 955-8771 (TDD). The Department of Astronomy iscommitted to creating an environment that affirms diversity across a variety of dimensions, including ability, class,ethnicity/race, gender identity and expression. We particularly welcome applicants who can contribute to such anenvironment through their scholarship, teaching, mentoring, and professional service. The university and greater
Gainesville community enjoy a diversity of cultural events, restaurants, year-round outdoor recreational activities, andsocial opportunities.
Questions may be addressed to the Search Committee Chair, Professor Rafael Guzman at guzman@astro.ufl.edu .

42

Two positions in Astrophysics at the University of Exeter
The University of Exeter has two positions available in Astrophysics to expand current research performed in the Astrophysics group (theoretical, observational, computational, instrumentation). The group is particularly active in thefields of exoplanets, star formation and computational stellar astrophysics and engages in cutting-edge instrumentation
projects. Candidates in areas related or complementary to existing Exeter strengths will be considered.
More information can be found at the links below- Tenure Lecturer/Senior Lecturer/Associate Professor position: https://jobregister.aas.org/ad/1d3bcf7c- Lecturer/Senior Lecturer position on a fixed term basis of up to 5 years: https://jobregister.aas.org/ad/922d3faa
The application deadline for both positions is January 31 2019.

Abstract submission deadline
The deadline for submitting abstracts and othersubmissions is the first day of the month.

43

Meetings

Second Announcement

From Stars to Planets II
Abstract Submission by 28th Feb. 2019
From Stars to Planets II - Connecting our understanding of star and planet formation
Mon. 17th - Thur. 20th June 2019
Chalmers University, Gothenburg, Sweden
http://cosmicorigins.space/fstpii/
Star formation, planet formation, astrochemistry and exoplanet studies are undergoing rapid, revolutionary advances
and this conference aims to bring together researchers in these fields, especially to explore and develop new connections.
The scientific scope of the meeting will include:- Molecular Clouds and Star Formation in the Milky Way- Star Cluster Formation and Evolution- Pre-stellar and Protostellar Cores- Protostellar and Protoplanetary Disks- Planet Formation- Astrochemistry of Star and Planet Forming Regions and Exoplanets- Exoplanet Properties and Evolution- Formation and Evolution of the Solar System
Meeting schedule and preliminary logistics:
Sunday 16th June 2019, 6pm Welcome reception
Monday 17th - Thur. 20th June 2019, 3.5 days of science sessions, 0.5 day excursion
Friday 21st June 2019, Midsummer celebration (optional post-conference activity)
Confirmed Invited Speakers:- Viviana Guzman- Anders Johansen- Christoph Mordasini- Gijs Mulders- Richard Nelson- David Nesvorny- Stella Offner- Nami Sakai- Leonardo Testi- Ewine van Dishoeck- Catherine Walsh- Zhaohuan Zhu
SOC: Jonathan Tan (Chair, Chalmers/UVa), Ilse Cleeves (UVa), Maria Drozdovskaya (Bern), Eric Herbst (UVa),
Jouni Kainulainen (Chalmers), Zhi-Yun Li (UVa), Yamila Miguel (Leiden), Darin Ragozinne (BYU), John Tobin(NRAO), Jonathan Williams (UH), Andrew Youdin (UA)44

LOC Contact: Jonathan Tan ( jonathan.tan@chalmers.se )ABSTRACT SUBMISSION:
If you are interested in attending the conference, please submit an abstract by 28th February 2019 via the link fromthis page: http://cosmicorigins.space/fstpii/
We expect decisions on abstracts to be made by mid March. Note, it is possible that we will receive more submissions
than can be accepted given the size of the venue. Registration and logistics information, including hotel room blocks,
for attendees will be sent out by the end of March.

The Pleiades and friends: stellar associations in the GAIA era
A Coruña, Spain, 9-13 September 2019
Stellar clusters play a crucial role in astrophysics, because they provide homogeneous samples of stars of the sameage and metallicity. In fact, they can be considered as astrophysical laboratories, because they provide snap shotsat different times. That is, any particular association allows study of dependencies with stellar mass, whereas thecomparison of stars of the same mass but belonging to different associations allows one to derive how any property
depends on age.
Gaia has forced us to revisit many of our assumptions: better proper motions yield new membership lists, improved
distances translate into different age estimates. The results from DR2 are starting to be digested, but a huge effort
to truly understand the implications from Gaia in many diverse areas is needed. In addition, new large photometricand spectroscopic surveys are providing an amazing amount of data concerning open clusters (Gaia-ESO, Vista, K2,
TESS, and so on). This wealth of data has to be put in context within the new Gaia framework.
In this realm, the Pleiades cluster has a very significant role, due to its age and proximity. Thousands of papers havebeen devoted to this amazing cluster. It is truly a stepping stone to understand key stellar properties such as rotation,
activity, internal mixing, etc. In a wider context, the Pleiades together with younger and older siblings may allow us
to put planetary formation in better context.
This conference is devoted to the Gaia DR2 exploitation in the context of the stellar (and substellar) members ofstellar clusters and associations. The goal is to provide a venue to present the most up-to-date results and to foster
new collaborations, keeping in mind that future Gaia DR will provide new waves of amazing data and surprising
results which will shape our astrophysical knowledge. We plan to have special session devoted to Big Data and newtools and techniques.
Webpage: http://www.laeff.cab.inta-csic.es/projects/pleiades2019/main/index.php

45

Summary of Upcoming Meetings

Planet Formation and Evolution
27 February - 1 March 2019, Rostock, Germany
http://pfe2019.stat.physik.uni-rostock.de
Dusting the Universe
4 - 8 March 2019, Tucson, USA
http://www.noao.edu/meetings/dust2019/

Chemical Abundances in Gaseous Nebulae
11 - 14 March 2019, São José Dos Campos, Brazil
https://www.univap.br/universidade/instituto-de-pesquisa/agenda-e-eventos/chemical-abundances-in-gaseous-neb
Star Clusters: from the Milky Way to the Early Universe
27 - 31 May 2019, Bologna, Italy
http://iausymp351.oas.inaf.it/
New Quests in Stellar Astrophysics IV. Astrochemistry, astrobiology and the Orign of Life
31 March - 5 April 2019, Puerto Vallarta, mexico
http://www.inaoep.mx/puerto19
New Horizons in Planetary Systems
13 - 17 May 2019 - Victoria, Canada
http://go.nrao.edu/NewHorizons
Exploring the Infrared Universe: The Promise of SPICA
20 - 23 May 2019, Crete, Greece
http://www.spica2019.org
Workshop on Polarization in Protoplanetary Disks and Jets
20 - 24 May 2019, Sant Cugat del Vallès, Catalonia, Spain
http://sites.google.com/view/sant-cugat-forum-astrophysics/next-session
Zooming in on Star Formation - A tribute to Åke Nordlund
9 - 14 June 2019, Nafplio, Greece
http://www.nbia.dk/nbia-zoomstarform-2019
From Stars to Planets II: Connecting our Understanding of Star and Planet Formation
17 - 20 June 2019, Gothenburg, Sweden
http://cosmicorigins.space/fstpii
Gaia’s View of Pre-Main Sequence Evolution. Linking the T Tauri and Herbig Ae/Be Stars
18 - 21 June 2019, Leeds, UK
https://starry-project.eu/final-conference
Gordon Conference on Origins of Solar Systems: Meteoritical, Spacecraft and Astrophysical Perspectives on the Assembly and Composition of Planets
23 - 28 June 2019https://www.grc.org/origins-of-solar-systems-conference/2019/
Astrochemistry: From nanometers to megaparsecs - A Symposium in Honour of John H. Black24 - 28 June 2019, Gothenburg, Sweden
https://www.chalmers.se/en/conference/JHBlacksymp2019/
Great Barriers in Planet Formation
21 - 26 July 2019 Palm Cove, Australia
https://dustbusters.bitbucket.io/great-barriers-2019/46

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

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