THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 314 — 17 February 2019

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

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

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
My Favorite Object . . . . . . . . . . . . . . . . . . . . . . . . . . . X
Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XX

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

Abstracts of Newly Accepted Papers . . . . . . . . . XX

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

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . XX

Editorial Board

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XX

Joao Alves
Alan Boss
Jerome Bouvier
Lee Hartmann
Thomas Henning
Paul Ho
Jes Jorgensen
Charles J. Lada
Thijs Kouwenhoven
Michael R. Meyer
Ralph Pudritz
Luis Felipe Rodrı́guez
Ewine van Dishoeck
Hans Zinnecker
The Star Formation Newsletter is a vehicle forfast distribution of information of interest for astronomers working on star and planet formationand molecular clouds. You can submit material
for the following sections: Abstracts of recently
accepted papers (only for papers sent to refereed
journals), Abstracts of recently accepted major reviews (not standard conference contributions), Dissertation Abstracts (presenting abstracts of new
Ph.D dissertations), Meetings (announcing meetings broadly of interest to the star and planet formation and early solar system community), New
Jobs (advertising jobs specifically aimed towards
persons within the areas of the Newsletter), andShort Announcements (where you can inform or request information from the community). Additionally, the Newsletter brings short overview articles
on objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

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

Abstracts of Newly Accepted Major Reviews

XX

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XX

Summary of Upcoming Meetings . . . . . . . . . . . . XX
New Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XX
Short Announcements . . . . . . . . . . . . . . . . . . . . . . . XX

Cover Picture
Messier 16 is the bright HII region excited by themassive OB stars in the NGC 6611 cluster. The distance to M16 is about 1.7-1.8 kpc and the cluster isabout 2-3 Myr old. Embedded in the HII region are
the large elephant trunks seen in the now famous
HST images of the region.
Image courtesy ESO.

Submitting your abstracts
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areappendedtoeach Call for Abstracts.
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submitvia
theNewsletterwebinterfaceat
http://www2.ifa.hawaii.edu/starformation/index.cfm

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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Bo Reipurth3profiles, a somewhat bothersome result! If one looks atother HH objects, this result appears to be a general feature of HH objects, and is one of the important remaining
problems in their interpretation.

Alex Ragain conversation with Bo Reipurth

Q: For the past 30 years, you have published prolificallywith your colleague Jorge Cantó. How did that start?
A: In 1987 I attended a star formation conference in British
Columbia, in which I met a group of most pleasant Mexican astronomers, including L. F. Rodrı́guez, M. Tapia
and A. López. Alberto López asked me if I had met Jorge
Cantó, which I had not, even though I had read most of his
papers, and given my negative reply Alberto said that hewould organize a workshop in Ensenada, Mexico so that
we would meet, he thought that this would be an event ofmajor importance in the lives of Jorge Cantó and I, because we would be friends and collaborators for the restof our lives. I thought that this was a somewhat curious“premonition”, but when the following year Alberto did
organize the workshop I gladly participated.

Q: What was the subject of your PhD and who was youradviser?

The second day of the workshop Jorge and I had alreadybecome good friends - we shared the “black/white worldview” of descendants of Catalan anarchists! - and before
the end of the workshop we had advanced on what would
be our first paper together - out of a current number of 112
refereed joint papers. Some years later, in 1995, I moved
to Mexico to work with Jorge at the UNAM, and here I
have remained.

A: My thesis work, from 1982 to 1985, was about bow
shock models of Herbig-Haro objects. These objects were
one of the interests of Karl-Heinz Böhm, my advisor at the
University of Washington. His first paper on HH objects
dates back to 1955, only a few years after their discovery.
Karl-Heinz Böhm, who died 5 years ago, was a major influence in my life and, I suspect, in the life of many ofhis students. He provided a strong example of how to ap- Q: In 1990 you and your collaborators published a highly
proach research, and also life in general, which within my cited paper on Herbig-Haro jets with intrinsically variable
sources. What were the key points?
limited abilities I have tried to emulate.

Q: After your PhD you continued to work closely with A: The work for this paper was mostly carried out during
Karl-Heinz Böhm, particularly related to the bright HH 1/2 a 2-week workshop in Mérida in Venezuela organized by
Nuria Calvet, now at the Univ. of Michigan, and all of theobjects. What were the main results?
A: During my first postdoc, with Karl-Heinz, we explored co-authors were participants of the workshop. The idea istime-dependent bow shock models. These models showed that a time-dependent ejection with a velocity variability
that one naturally produces the “broken-up bow shocks” of supersonic amplitude leads to the formation of twoobserved in HH 1 and 2. I then helped Karl-Heinz, with shock “internal working surfaces” or “heads” that travel
J. Solf, A. Noriega-Crespo and other collaborators, on the down the jet beam. I think that we were quite lucky atinterpretation of spatially-resolved optical and UV spec- the time, because - as is so often the case - clearly othertroscopy, mainly of HH 1/2, but also of other HH objects. researchers were aiming in the same direction (the names
This work, as well as contemporary work of P. Hartigan, J. of Reipurth and Hartigan come to mind!). In this first
Raymond and their collaborators, showed that it is rela- paper, we realized that a variability with two “modes” tively straightforward to explain the observed spatially- for example a short period mode and a long period mode or
resolved emission line profiles with gasdynamical mod- a sudden “turning on” - produced structures that looked
els of different degrees of sophistication, basically “1.5- like the HH 34 jet. Interpreting this beautiful object had
dimensional” models calculated with a superposition of been in our minds for quite a few years. Also, the model
oblique shocks and fully axisymmetric or 3D gasdynami- produced in a direct way the proper motions of the chainof knots of this object (which were published later, but had
cal models.
already been reported in conferences by Eislöffel, Mundt
The other, less satisfying, result is that it is more difficult & Ray and by Heathcote & Reipurth).
to model the observed line ratios. In order to model the
spatially resolved line ratios of HH 1/2 one needs lower We later realized that Martin Rees had published a paper
flow velocities than the ones implied by the observed line back in 1978 pointing out that internal shocks in extra4

galactic jets could be produced by “velocity irregularities”,
and that Mike Wilson in 1984 had studied this problem
numerically. However, the idea of variable ejections really
took off in the mid-1990’s in the field of HH jets when highresolution HST images of HH 34 and HH 111, among others, showed that many of the knots along the jets looked
like “small bow shocks” as expected for internal working
surfaces produced by ejection velocity variabilities. This
has now become the standard interpretation of HH jets.

tions. Learning from this code, I wrote a simpler 2D code(“coral” - named for the relatively puny american relative of the cobra snake), with which I played for a decade.
When a decade later I started to do 3D simulations I decided to write a new 2/3D code with a different concept
for the adaptive grid (actually, more similar to the cobra
code of Falle and Giddings). We called this code “yguazú”,
which means “big water” in the South American Guaranı́
language.

An interesting feature of this interpretation is that HH
jets therefore are a kind of “archaeological record” of thepast ejection time-variability. This record, however, becomes more confused for the material ejected in the moredistant past (which is now seen at larger distances fromthe source) because of the distortion (braking) resulting
from the interaction of the outflow with the surrounding
environment. Also, substantial “gaps” in the “archaeological jet record” appear because of the fact that material
ejected over relatively extended periods merges to produce
single internal working surfaces. These effects probably
have analogues in “real archaeology”.

Some versions of the “coral” and the “yguazú” codes arestill being used today, because they included a number offeatures which work quite well, and a considerable amountof work is required to introduce them in more modern
codes. Some of these features are a treatment of a many
species non-equilibrium ionization/cooling network, and of
the multi-wavelength radiative transfer of the direct stellar
and the diffuse photoionizing radiation field. This latterfeature has only been partially incorporated into our more
modern codes!

Over the years I have worked on this problem with Sylvie
Cabrit and Jorge Cantó (I would like to note that the
papers with Sylvie are among my best papers, a resultof Sylvie’s intelligence and higher standards). During thepast year I have worked with Benoit Tabone, Sylvie Cabritand Guillaume Pineau des Forêts on new entrainment models, devised for interpreting ALMA observations of thesource regions of molecular outflows. The new observations of these regions with ALMA offer a fascinating possibility of making clear progress on understanding the process of entrainment of molecular material in HH flows.

one is the effect of the orbital motion which, because of
the time-dependent direction of the orbital velocity, produces periodic deviations in the ejection direction with a
jet and counterjet “mirror symmetry”. The presence ofa binary companion can also produce a precession in theaccretion disk which produces or collimates the outflow,
and hence in the outflow itself. This results in deviationsof the ejection direction with “point symmetry” between
jet and counterjet. In principle, these two effects should
be visible in an outflow system from a source in a binary
system.

The other positive result of the “yguazú” code is that ageneration of young students and postdocs at the UNAM,
Q: You have for a long time been interested in the rela- among them Pablo Velázquez, Fabio De Colle, Verónica
tion between jets and molecular outflows, a topic you have Lora, Alejandro Esquivel and Ary Rodrı́guez, used it toworked closely on with Sylvie Cabrit.
learn how to develop gasdynamic codes. These people,
A: The relation between HH jets and molecular outflows is and their students, have developed a new generation ofa very interesting problem, with little theoretical progress fixed and adaptive grid codes - appropriate for parallel
being obtained over the last ∼ 3 decades. This relative machines - which are now the workhorses that we use forlack of progress is due to the fact that the process of en- computing astrophysical gasdynamic simulations.
trainment into a coherent flow is very complicated. This Q: You have written a number of papers on jets with timeprocess has defied researchers in fluid dynamics for more dependent ejection directions and their relation to binarity
than a century. In HH jets, the presence of “internal work- of the sources. What are your main conclusions?
ing surfaces”, resulting from an ejection variability, further A: The ejection of a jet from a stellar source in a bicomplicates the entrainment process.
nary system shows two main effects. The “inevitable”

Q: About 20 years ago you developed a new 3D adaptive
grid code, yguazú-a, to deal with gasdynamical problems,
and you have used it extensively on a variety of problems.
What were the new features of this code and key results?

Precession-like, point-symmetric direction deviations areseen in a number of “giant” parsec scale HH outflows.
Also, subtle mirror symmetric deviations are seen in the
inner regions of some HH outflows. A simple, ballistic
A: Around 1990-1991 I was a postdoc of Sam Falle at the motion model can be used to derive the orbital paramUniversity of Leeds in the UK. At that time, Sam Falle and eters from the observed curvature of the jet/counterjet,
Jack Giddings had developed a quite pioneering adaptive which in the known examples give most reasonable stelgrid code (“cobra”) for scientific and commercial applica- lar/substellar masses for the companion star. A panoply5

of observed shapes for the jet/counterjet can be obtained
considering different orbital motion/precession combinations, non-circular binary orbits and motions of the outflow source in a multiple system. As far as I am aware,jets from multiple stars have still not been modeled.

clouds.
With the relatively recent availability of multi-epoch HST
observations of a number of HH outflows, we started totry to have “automatic” proper motion determinations.
By “automatic” I mean an algorithm which determines
proper motions from two or more epochs without having
to choose by hand which regions have to be compared in
the successive images. Such selection was an undesirable
feature of the favoured “cross correlation method”, firstused in HH objects by Heathcote & Reipurth. We first
tried covering the images with “cross correlation boxes”(or “tiles”), but found that this introduces a series of complications. The next idea was to convolve the frames witha wavelet function of a chosen size, and to then find corresponding peaks in the successive degraded resolution,
convolved images.

Another interesting point is whether an elliptic (or more
complex) orbital motion of an outflow source (in a binary
or multiple system) can drive an ejection velocity/density
variability in the jet. In your paper from 2000 you suggested that close passages of stellar companions of thesource might lead to strong “outflow events” in the jet
and counterjet system. Simulations of outflow systems inwhich such events take place have been calculated, but
as far as I am aware the outflow ejection with perturbations from a stellar companion has still not been studied
theoretically. This is probably not surprising given thecontinuing doubts that remain about the detailed nature The referee of our first paper on this method pointedly of the HH jet production mechanism.
and correctly - said that degrading the resolution of the
Q: A rather different topic is your study of analytic solu- images and then finding peaks was not an impressively
tions to wind-driven HII regions and Strömgren spheres. innovative method for calculating proper motions. HowA: My current interest in expanding (and non-expanding) ever, I am personally very happy with the (Python) softHII regions began because I am writing a book on the ISM. ware that I have been working on, with which one can find
I tend to get bored writing chapters describing well known proper motions from sets of images in an extremely rapid
work, so then I begin to play around with variations (lead- way, without having to go through the previous choice “bying to at least partially new results). One of the things I hand” of boxes containing coherent structures that appear
tried was obtaining analytic solutions for the HII/HI tran- in the successive frames. With the current “wavelet proper
sition at the outer edge of a stationary HII region. This is motion” method, one only chooses a size for the wavelet,
the problem of Strömgren, who in an absolutely beautiful and there it goes!
paper from 1939 published two approximate analytic solutions for the transition. We found that it is possible toobtain better - though of course more complex - analytic
solutions, and wrote a few papers on this ultra-traditional
subject.

Q: What are you currently working on?
A: The past few years I have put a considerable amountof effort into analyzing new HST images of HH objects
together with my collaborators. I have come to realizethat with HST observations one enters a Faustian pact inwhich in order to obtain scientific progress (i.e., the HST
images) one trades away one’s soul (i.e., one dedicates acouple of years’ work to them). I think that the resultsthat we have obtained have been worth it! I am currently
working on a similar Faustian pact with the interpretationof ALMA observations together with Sylvie Cabrit and anumber of other collaborators, and I am steeling myself
for life with the sword of Damocles (i.e., JWST) which isstarting to hang above our heads.

Looking at analytic solutions for an expanding HII region, I found a way to include in an approximate way
the strong to weak transition of the outer shock, which
is driven by the expansion. It is also possible to include
the strong/weak shock transition in analytic solutions ofa wind-driven HII region, and of an expanding supernova
remnant. Jorge Cantó and I were quite excited in finding
an approximate (analytic) version of the Sedov-Taylor expansion with a transition to the weak shock regime! Luckily, this paper did not raise interest in its military applications (retrospectively not surprising given the present easeof carrying out numerical simulations).
Q: Recently you have pioneered the use of wavelets in the
study of outflows. What are the benefits of this approach?
A: Years after interacting with Dick Henriksen, who was
the pioneer of using wavelet transforms in astrophysicalapplications, I started using wavelets for analyzing thestructures of HH outflows. This was a natural extension ofHenriksen’s work on the observed structures of molecular6

Abstracts of recently accepted papers

Revealing the dust grain size in the inner envelope of the Class I protostar Per-emb-50

1 C. Agurto-Gangas , J.E. Pineda , L. Szucs , L. Testi
1

6

1

7

Dunham , I.W. Stephens and T.L. Bourke

1

2,3,4

, M. Tazzari5 , A. Miotello2, P. Caselli1 , M.

81

Max-Planck-Institute for Extraterrestrial Physics (MPE), Giessenbachstr. 1, D-85748 Garching, Germany; 2 ESO,
Karl Schwarzschild str. 2, D-85748 Garching, Germany; 3 INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi
5, Firenze, 50125, Italy; 4 Excellence Cluster Universe, Boltzmannstr. 2, D-85748 Garching, Germany; 5 Institute of
Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK; 6 Department of Physics, State
University of New York at Fredonia, 280 Central Ave, Fredonia, NY 14063, USA; 7 Harvard-Smithsonian Center
for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 8 SKA Organisation, Jodrell Bank Observatory,
Cheshire SK11 9DL, UK
E-mail contact: cagurto at mpe.mpg.de

A good constraint of when the growth of dust grains from sub-micrometer to millimeter sizes occurs, is crucial for planet
formation models. This provides the first step towards the production of pebbles and planetesimals in protoplanetarydisks. Currently, it is well established that Class II objects have large dust grains. However, it is not clear when in
the star formation process this grain growth occurs. We use multi-wavelength millimeter observations of a Class I
protostar to obtain the spectral index of the observed flux densities αmm of the unresolved disk and the surrounding
envelope. Our goal is to compare our observational results with visibility modeling at both wavelengths simultaneously.
We present data from NOEMA at 2.7 mm and SMA at 1.3 mm of the Class I protostar, Per-emb-50. We model thedust emission with a variety of parametric and radiative transfer models to deduce the grain size from the observed
emission spectral index. We find a spectral index in the envelope of Per-emb-50 of αenv =3.3±0.3, similar to the typical
ISM values. The radiative transfer modeling of the source confirms this value of αenv with the presence of dust witha amax ≤100 µm. Additionally, we explore the backwarming effect, where we find that the envelope structure affects
the millimeter emission of the disk. Our results reveal grains with a maximum size no larger than 100 µm in the innerenvelope of the Class I protostar Per-emb-50, providing an interesting case to test the universality of millimeter grain
growth expected in these sources.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1901.05021.pdf

2Resolved young binary systems and their disks
Rachel L. Akeson1 , Eric L. N. Jensen2 , John Carpenter3 , Luca Ricci4 , Stefan Laos5 , Natasha F.
Nogueira2 and Emma M. Suen-Lewis2
1

IPAC-NExScI, Caltech, Pasadena, CA 91125, USA; 2 Swarthmore College, Dept. of Physics & Astronomy, 500 College
Ave., Swarthmore, PA 19081-1390, USA; 3 Joint ALMA Observatory, Avenida Alonso 3107 Vitacura, Santiago, Chile;4
Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge,
CA 91330, USA; 5 Physics and Astronomy Department, Vanderbilt University, 6301 Stevenson Center Nashville, TN37235, USA
E-mail contact: rla at ipac.caltech.edu
We have conducted a survey of young single and multiple systems in the Taurus-Auriga star-forming region with the
Atacama Large Millimeter Array (ALMA), substantially improving both the spatial resolution and sensitivity withwhich individual protoplanetary disks in these systems have been observed. These ALMA observations can resolve
binary separations as small as 25–30 AU and have an average 3σ detection level of 0.35 mJy, equivalent to a disk massof 4 × 10−5 M⊙ for an M3 star. Our sample was constructed from stars that have an infrared excess and/or signs ofaccretion and have been classified as Class II. For the binary and higher order multiple systems observed, we detect7λ = 1.3 mm continuum emission from one or more stars in all of our target systems. Combined with previous surveys
of Taurus, our 21 new detections increase the fraction of millimeter-detected disks to over 75% in all categories ofstars (singles, primaries, and companions) earlier than spectral type M6 in the Class II sample. Given the wealth ofother information available for these stars, this has allowed us to study the impact of multiplicity with a much larger
sample. While millimeter flux and disk mass are related to stellar mass as seen in previous studies, we find that bothprimary and secondary stars in binary systems with separations of 30 to 4200 AU have lower values of millimeter flux
as a function of stellar mass than single stars. We also find that for these systems, the circumstellar disk around theprimary star does not dominate the total disk mass in the system and contains on average 62% of the total mass.
Accepted by Astrophysical Journal
https://lanl.arxiv.org/pdf/1901.05029

3

The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation,
Sample, Calibration, and Overview
Sean Andrews1 , Jane Huang1 , Laura Pérez2 , Andrea Isella3 , Cornelis Dullemond4, Nicolás Kurtovic2 ,Viviana Guzmán5,6 , John Carpenter5 , David Wilner1 , Shangjia Zhang7 , Zhaohuan Zhu7 , Tilman Birnstiel8 ,Xue-Ning Bai9 , Myriam Benisty10,11 , Meredith Hughes12 , Karin Öberg1 and Luca Ricci13
1

Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA; 2 Departamento de Astronomı́a, Universidad
de Chile, Santiago, Chile; 3 Department of Physics & Astronomy, Rice University, Houston, TX, USA; 4 Zentrum für
Astronomie, Heidelberg University, Heidelberg, Germany; 5 Joint ALMA Observatory, Santiago, Chile; 6 Instituto de
Astrofı́sica, Pontificia Universidad Católica de Chile, Santiago, Chile; 7 Department of Physics & Astronomy, University of Nevada - Las Vegas, Las Vegas, NV, USA; 8 University Observatory, Faculty of Physics, Ludwig-MaximiliansUniversität München, Munich, Germany; 9 Institute for Advanced Study and Tsinghua Center for Astrophysics,
Tsinghua University, Beijing, China; 10 Unidad Mixta Internacional Franco-Chilena de Astronomı́a, CNRS/INSU,
Departamento de Astronomı́a, Universidad de Chile, Santiago, Chile; 11 Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France; 12 Department of Astronomy, Van Vleck Observatory, Wesleyan University, Middletown, CT, USA; 13
Department of Physics & Astronomy, California State University Northridge, Northridge, CA, USA
E-mail contact: sandrews@cfa.harvard.edu
We introduce the Disk Substructures at High Angular Resolution Project (DSHARP), one of the initial Large Programs
conducted with the Atacama Large Millimeter/submillimeter Array (ALMA). The primary goal of DSHARP is to findand characterize substructures in the spatial distributions of solid particles for a sample of 20 nearby protoplanetarydisks, using very high resolution (∼0.035 arcseconds, or 5 au, FWHM) observations of their 240 GHz (1.25 mm)
continuum emission. These data provide a first homogeneous look at the small-scale features in disks that are directly
relevant to the planet formation process, quantifying their prevalence, morphologies, spatial scales, spacings, symmetry,
and amplitudes, for targets with a variety of disk and stellar host properties. We find that these substructures are
ubiquitous in this sample of large, bright disks. They are most frequently manifested as concentric, narrow emission
rings and depleted gaps, although large-scale spiral patterns and small arc-shaped azimuthal asymmetries are alsopresent in some cases. These substructures are found at a wide range of disk radii (from a few astronomical units tomore than 100 au), are usually compact (≤10 au), and show a wide range of amplitudes (brightness contrasts). Here we
discuss the motivation for the project, describe the survey design and the sample properties, detail the observations
and data calibration, highlight some basic results, and provide a general overview of the key conclusions that arepresented in more detail in a series of accompanying articles. The DSHARP data — including visibilities, images,
calibration scripts, and more – are released for community use at https://almascience.org/alma-data/lp/DSHARP
Accepted by Astrophysical Journal Letters (869, L41, 2018https://arxiv.org/pdf/1812.04040.pdf

4Magnetic Field Structure of Dense Cores using Spectroscopic Methods
Sayantan Auddy1,2 , Philip C. Myers1 , Shantanu Basu2 , Jorma Harju3,4 , Jaime E. Pineda3 and Rachel
K. Friesen51Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 2 Department of
Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7, Canada; 3 Max-Planck-Institutefor Extraterrestrial Physics (MPE), Giessenbachstr. 1, 85748 Garching, Germany; 4 Department of Physics, P.O. Box
864, 00014 University of Helsinki, Finland; 5 National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
E-mail contact: sauddy3 at uwo.ca
We develop a new “core field structure” (CFS) model to predict the magnetic field strength and magnetic field
fluctuation profile of dense cores using gas kinematics. We use spatially resolved observations of the nonthermalvelocity dispersion from the Green Bank Ammonia survey along with column density maps from SCUBA-2 to estimate
the magnetic field strength across seven dense cores located in the L1688 region of Ophiuchus. The CFS model predicts
the profile of the relative field fluctuation, which is related to the observable dispersion in direction of the polarization
vectors. Within the context of our model we find that all the cores have a transcritical mass-to-flux ratio.
Accepted by ApJ
https://arxiv.org/pdf/1901.09537

5

The statistical properties of stars and their dependence on metallicity
Matthew R. Bate1
1

School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, United Kingdom

E-mail contact: mbate at astro.ex.ac.uk
We report the statistical properties of stars and brown dwarfs obtained from four radiation hydrodynamical simulationsof star cluster formation, the metallicities of which span a range from 1/100 to 3 times the solar value. Unlike previous
similar investigations of the effects of metallicity on stellar properties, these new calculations treat dust and gas
temperatures separately and include a thermochemical model of the diffuse interstellar medium. The more advanced
treatment of the interstellar medium gives rise to very different gas and dust temperature distributions in the four
calculations, with lower metallicities generally resulting in higher temperatures and a delay in the onset of starformation. Despite this, once star formation begins, all four calculations produce stars at similar rates and manyof the statistical properties of their stellar populations are difficult to distinguish from each other and from those ofobserved stellar systems. We do find, however, that the greater cooling rates at high gas densities due to the lower
opacities at low metallicities increase the fragmentation on small spatial scales (disc, filament, and core fragmentation).
This produces an anti-correlation between the close binary fraction of low-mass stars and metallicity similar to thatwhich is observed, and an increase in the fraction of protostellar mergers at low metallicities. There are also indications
that at lower metallicity close binaries may have lower mass ratios and the abundance of brown dwarfs to stars may
increase slightly. However, these latter two effects are quite weak and need to be confirmed with larger samples.
Accepted by MNRASPreprint at: https://arxiv.org/pdf/1901.03713
Animations available at: http://www.astro.ex.ac.uk/people/mbate/Animations/

6

Disentangling the spatial substructure of Cygnus OB2 from Gaia DR2
S.R. Berlanas1,2 , N.J. Wright3 , A. Herrero1,2 , J.E. Drew4 and D.J. Lennon5,1
1

Instituto de Astrofı́sica de Canarias, 38200 La Laguna, Tenerife, Spain; 2 Departamento de Astrofı́sica, Universidad
de La Laguna, 38205 La Laguna, Tenerife, Spain; 3 Astrophysics Group, Keele University, Keele, ST5 5BG, UK; 4
School of Physics, Astronomy & Mathematics, University of Hertfordshire, Hatfield AL10 9AB, UK; 5 ESA, European
Space Astronomy Centre, Apdo. de Correos 78, E-28691 Villanueva de la Cañada, Madrid, Spain
E-mail contact: srberlan at iac.es
For the first time, we have explored the spatial substructure of the Cygnus OB2 association using parallaxes fromthe recent second Gaia data release. We find significant line-of-sight substructure within the association, which wequantify using a parameterised model that reproduces the observed parallax distribution. This inference approach isnecessary due to the non-linearity of the parallax-distance transformation and the asymmetry of the resulting probability distribution. By using a Markov Chain Monte Carlo ensemble sampler and an unbinned maximum likelihood
test we identify two different stellar groups superposed on the association. We find the main Cygnus OB2 group at∼1760 pc, further away than recent estimates have envisaged, and a foreground group at ∼1350 pc. We also calculate
individual membership probabilities and identify outliers as possible non-members of the association.
9

Accepted by MNRAS
http://arxiv.org/pdf/1901.02959

7

The Disk Substructures at High Angular Resolution Project (DSHARP):
V. Interpreting ALMA maps of protoplanetary disks in terms of a dust model
Tilman Birnstiel1 , Cornelis P. Dullemond2 , Zhaohuan Zhu3 , Sean M. Andrews4 , Xue-Ning Bai5 , David
J. Wilner4 , John M. Carpenter6 , Jane Huang4 , Andrea Isella7 , Myriam Benisty8,9 , Laura M. Pérez10
and Shangjia Zhang3
1

University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 Munich,Germany; 2 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany; 3
Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV
89154, USA; 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 5
Institute for Advanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China;
6
Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile; 7 Department of Physics
and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA; 8 Unidad Mixta Internacional FrancoChilena de Astronomı́a, CNRS/INSU UMI 3386, Departamento de Astronomı́a, Universidad de Chile, Camino El
Observatorio 1515, Las Condes, Santiago, Chile; 9 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 10
Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile
E-mail contact: til.birnstiel at lmu.de

The Disk Substructures at High Angular Resolution Project (DSHARP) is the largest homogeneous high-resolution(∼0.”035, or ∼ 5 au) disk continuum imaging survey with ALMA so far. In the coming years, many more disks will
be mapped with ALMA at similar resolution. Interpreting the results in terms of the properties and quantities ofthe emitting dusty material is, however, a very non-trivial task. This is in part due to the uncertainty in the dust
opacities, an uncertainty which is not likely to be resolved any time soon. It is also partly due to the fact that, as the
DSHARP survey has shown, these disk often contain regions of intermediate to high optical depth, even at millimeter
wavelengths and at relatively large radius in the disk. This makes the interpretation challenging, in particular if thegrains are large and have a large albedo. On the other hand, the highly structured features seen in the DSHARP
survey, of which strong indications were already seen in earlier observations, provide a unique opportunity to study thedust growth and dynamics. To provide continuity within the DSHARP project, its follow-up projects, and projects
by other teams interested in these data, we present here the methods and opacity choices used within the DSHARP
collaboration to link the measured intensity Iν to dust surface density Σd .
Accepted by ApJL
https://arxiv.org/pdf/1812.04043

8 Stellar Clustering

The Spatial Evolution of Young Massive Clusters I. A New Tool to Quantitatively Trace
Anne S.M. Buckner1 , Zeinab Khorrami2 , Pouria Khalaj3 , Stuart L. Lumsden1 , Isabelle Joncour3,5 ,Estelle Moraux3 , Paul Clark2 , René D. Oudmaijer1 , José Manuel Blanco4 , Ignacio de la Calle4 , José
M. Herrera-Fernandez4 , Frédérique Motte3 , Jesús J. Salgado4 and Luis Valero-Martı́n4
1

School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, U.K.; 2 School of Physics and Astronomy,
Cardiff University, The Parade, CF24 3AA, U.K.; 3 Universit Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France;
4
Quasar Science Resources, S.L., Edificio Ceudas, Ctra. de La Coruña, Km 22.300, 28232, Las Rozas de Madrid,
Madrid, Spain; 5 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
E-mail contact: a.s.m.buckner at leeds.ac.uk
Aims. To present the new novel statistical clustering tool ‘INDICATE’ which assesses and quantifies the degree of
spatial clustering of each object in a dataset, discuss its applications as a tracer of morphological stellar features instar forming regions, and to look for these features in the Carina Nebula (NGC 3372).
Results. We successfully recover known stellar structure of the Carina Nebula, including the 5 young star clusters
in this region. Four sub-clusters contain no, or very few, stars with a degree of association above random which

10suggests they may be fluctuations in the field rather than real clusters. In addition we find: (1) Stars in the NW
and SE regions have significantly different clustering tendencies, which is reflective of differences in the apparent starformation activity in these regions. Further study is required to ascertain the physical origin of the difference; (2) The
different clustering properties between these two regions are even more pronounced for OB stars; (3) There are no
signatures of classical mass segregation present in the SE region — massive stars here are not spatially concentrated
together above random; (4) Stellar concentrations are more frequent around massive stars than typical for the general
population, particularly in the Tr14 cluster; (5) There is a relation between the concentration of OB stars and theconcentration of (lower mass) stars around OB stars in the centrally concentrated Tr14 and Tr15, but no such relation
exists in Tr16. We conclude this is due to the highly sub-structured nature of Tr16.
Conclusions. INDICATE is a powerful new tool employing a novel approach to quantify the clustering tendencies ofindividual objects in a dataset within a user-defined parameter space. As such it can be used in a wide array of data
analysis applications.
Accepted by A&A
http://arxiv.org/pdf/1901.02371

9

Surveys of Clumps, Cores, and Condensations in Cygnus X: I. a New Catalog of 0.1
pc Massive Dense Cores
Yue Cao1,2 , Keping Qiu1,2 , Qizhou Zhang3 , Yuwei Wang1,2 , Bo Hu1,2 and Junhao Liu1,2
1School of Astronomy and Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing 210023, P.R.China; 2 KeyLaboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210023,
P.R.China; 3 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 42, Cambridge, MA 02138 USA
E-mail contact: mg1626002 at smail.nju.edu.cn
Using infrared to (sub)millimeter data from Spitzer, Herschel, the James Clerk Maxwell Telescope, and the IRAM
30-m telescope, we conducted an unbiased survey of the massive dense cores (MDCs) in the Cygnus X molecular cloudcomplex, aimed at characterizing the physical conditions of high-mass star formation (HMSF) at ∼0.1 pc scales. We
created 5◦ ×6◦ images of the 70–1200 µm dust continuum, gas column density, and dust temperature of Cygnus X. A
spatial relation between the dense regions (Av ≥ 15) and the developed H II regions was found, indicating the impactof the latter on the global structures of Cygnus X. With a 35-M⊙ mass threshold implied by HMSF signposts, we
identified 151 MDCs with sizes of ∼0.1 pc, masses of 35–1762 M⊙ , and temperatures of 8–35 K. Our MDC sample
is statistically complete in Cygnus X and is three times larger than that in Motte et al. (2007). The MDCs wereclassified into IR-bright/IR-quiet ones based on their mid-infrared fluxes and a large “IR-quiet” proportion (90%) was
found in our sample. Two possible scenarios were proposed to interpret this: accelerated HMSF and the incapabilityof HMSF of the IR-quiet MDCs. We also found 26 starless MDCs by their lack of compact emissions at 21–70 µm
wavelengths, of which the most massive ones are probably the best candidates of initial HMSF sites in Cygnus X.
Accepted by ApJS
https://arxiv.org/pdf/1901.06475.pdf

Orion Region: Evidence of enhanced cosmic-ray density in a stellar wind forward
10 Theshock interaction with a high density shell
M. Cardillo1 , N. Marchili1 , G. Piano1 , A. Giuliani5 , M. Tavani1,2,3,4 , and S. Molinari1
1

INAF-IAPS, Via del Fosso del Cavaliere 100 - 00133 Roma, Italy; 2 Dip. di Fisica, Univ. Tor Vergata, Via della
Ricerca Scientifica 1, I-00133 Roma, Italy; 3 Gran Sasso Science Institute, viale Francesco Crispi 7, I-67100 L’Aquila,
Italy; 4 Astronomia, Accademia Nazionale dei Lincei, Via della Lungara 10, I-00165 Roma, Italy; 5 INAF - IASF
Milano, Via E. Bassini 15, I-20133, Milano, Italy
E-mail contact: martina.cardillo at inaf.it
Context. In recent years, an in-depth γ-ray analysis of the Orion region has been carried out by the AGILE and FermiLAT (Large Area Telescope) teams with the aim of estimating the H2 –CO conversion factor, XCO . The comparison of
the data from both satellites with models of diffuse γ-ray Galactic emission unveiled an excess at (l,b)=[213.9, -19.5],
in a region at a short angular distance from the OB star κ-Ori. Possible explanations of this excess are scatteringof the so-called “dark gas”, non-linearity in the H2 -CO relation, or Cosmic-Ray (CR) energization at the κ-Ori wind11

shock.
Aims. Concerning this last hypothesis, we want to verify whether cosmic-ray acceleration or re-acceleration could betriggered at the κ-Ori forward shock, which we suppose to be interacting with a star-forming shell detected in several
wavebands and probably triggered by high energy particles.
Methods. Starting from the AGILE spectrum of the detected γ-ray excess, showed here for the first time, we developed
a valid physical model for cosmic-ray energization, taking into account re-acceleration, acceleration, energy losses, andsecondary electron contribution.
Results. Despite the characteristic low velocity of an OB star forward shock during its “snowplow” expansion phase,
we find that the Orion γ-ray excess could be explained by re-acceleration of pre-existing cosmic rays in the interaction
between the forward shock of κ-Ori and the CO-detected, star-forming shell swept-up by the star expansion. According
to our calculations, a possible contribution from freshly accelerated particles is sub-dominant with respect the reacceleration contribution. However, a simple adiabatic compression of the shell could also explain the detected γ-ray
emission. Futher GeV and TeV observations of this region are highly recommended in order to correctly identify thereal physical scenario.
Accepted by A&A
http://arxiv.org/pdf/1901.01764

11

Upper limits on CH3 OH in the HD 163296 protoplanetary disk: evidence for a low
gas-phase CH3 OH/H2 CO ratio
M.T. Carney1 , M.R. Hogerheijde1 , V.V. Guzmán2,3 , C. Walsh4 , K.I. Öberg5 , E.C. Fayolle6 , L.I.
Cleeves7 , J.M. Carpenter2 , C. Qi5
1Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, The Netherlands; 2 Joint ALMA Observatory (JAO),
Alonso de Cordova 3107, Vitacura, Santiago de Chile, Chile; 3 Instituto de Astrofı́sica, Ponticia Universidad Católicade Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile; 4 School of Physics and Astronomy, Universityof Leeds, Leeds LS2 9JT, UK; 5 Department of Astronomy, Harvard University, Cambridge, MA 02138, USA; 6 Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA; 7
University of Virginia, Charlottesville, VA 22904, USA
E-mail contact: masoncarney at strw.leidenuniv.nl
Methanol (CH3 OH) is at the root of organic ice chemistry in protoplanetary disks. However, its weak emission has
made detections difficult. To date, gas-phase CH3 OH has been detected in only one Class II disk, TW Hya. We use the
Atacama Large Millimeter/submillimeter Array (ALMA) to search for a total of four CH3 OH emission lines in bands
6 and 7 toward the disk around the young Herbig Ae star HD 163296. The disk-averaged column density of methanol
and its related species formaldehyde (H2 CO) are estimated assuming optically thin emission in local thermodynamic
equilibrium. We compare these results to the gas-phase column densities of the TW Hya disk. No targeted methanollines were detected individually nor after line stacking. The 3σ disk-integrated intensity upper limits are <51 mJy km
s−1 for the band 6 lines and <26 mJy km s−1 for the band 7 lines. The band 7 lines provide the strictest 3σ upper limit
on disk-averaged column density with Navg < 5.0 × 1011 cm−2 . The methanol-to-formaldehyde ratio is CH3 OH/H2 CO<0.24 in the HD 163296 disk compared to a ratio of 1.27 in the TW Hya disk. Differences in the stellar irradiationof Herbig disks compared to T Tauri disks likely influence the gaseous methanol and formaldehyde content. Possible
reasons for the lower HD 163296 methanol-to-formaldehyde ratio include: a higher than expected gas-phase formationof H2 CO in the HD 163296 disk, uncertainties in the grain surface formation efficiency of CH3 OH and H2 CO, anddifferences in the disk structure and/or CH3 OH and H2 CO desorption processes that release the molecules from ice
mantles back into the gas phase. These results provide observational evidence that the gas-phase chemical complexity
found in disks may be strongly influenced by the spectral type of the host star.
Accepted by A&A
http://arxiv.org/pdf/1901.02371

12

Determining the presence of characteristic fragmentation length-scales in filaments
S. D. Clarke1 , G. M. Williams2, J. C. Ibanez-Mejia1 and S. Walch1,3
1

I. Physikalisches Institut, University of Cologne, D-50937 Cologne, Germany; 2 Centre for Astrophysics Research,

12

School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield, Al10 9AB, UK;
3
Cologne Centre for Data and Simulation Science, University of Cologne, Cologne, Germany
E-mail contact: clarke at ph1.uni-koeln.de
Theories suggest that filament fragmentation should occur on a characteristic fragmentation length-scale. This fragmentation length-scale can be related to filament properties, such as the width and the dynamical state of the filament.
Here we present a study of a number of fragmentation analysis techniques applied to filaments, and their sensitivity tocharacteristic fragmentation length-scales. We test the sensitivity to both single-tier and two-tier fragmentation, i.e.
when the fragmentation can be characterised with one or two fragmentation length-scales respectively. The nearest
neighbour separation, minimum spanning tree separation and two-point correlation function are all able to robustly
detect characteristic fragmentation length-scales. The Fourier power spectrum and the Nth nearest neighbour technique are both poor techniques, and require very little scatter in the core spacings for the characteristic length-scale
to be successfully determined. We develop a null hypothesis test to compare the results of the nearest neighbour andminimum spanning tree separation distribution with randomly placed cores. We show that a larger number of coresis necessary to successfully reject the null hypothesis if the underlying fragmentation is two-tier, N > 20. Once thenull is rejected we show how one may decide if the observed fragmentation is best described by single-tier or two-tierfragmentation, using either Akaike’s information criterion or the Bayes factor. The analysis techniques, null hypothesis
tests, and model selection approaches are all included in a new open-source Python/C library called FragMent.
Accepted by MNRAS
http://adsabs.harvard.edu/pdf/2019arXiv190106205C

13

A distant OB association around RAFGL 5475
F. Comerón1 , A.A. Djupvik2 , J. Torra3 , N. Schneider4,5 and A. Pasquali6
1

European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 2 Nordic Optical Telescope,
Apdo 474, E-38700 Santa Cruz de La Palma, Spain; 3 Institut de Ciències del Cosmos (ICCUB-IEEC), Barcelona,
E-08028, Spain; 4 I. Physik Institut University of Cologne, D-50937 Cologne, Germany; 5 OASU/LAB-UMR5804,
CNRS, Université Bordeaux 1, F-33270 Floirac, France; 6 Astronomisches Rechen-Institut, Zentrum für Astronomie
der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg, Germany
E-mail contact: fcomeron at eso.org
Context: Observations of the galactic disk at mid-infrared and longer wavelengths reveal a wealth of structuresindicating the existence of complexes of recent massive star formation. However, little or nothing is known about thestellar component of those complexes.
Aims: We have carried out observations aiming at the identification of early-type stars in the direction of thebright infrared source RAFGL 5475, around which several interstellar medium structures usually associated with thepresence of massive stars have been identified. Our observations have the potential of revealing the suspected but thus
far unknown stellar component of the region around RAFGL 5475.
Methods: We have carried out near-infrared imaging observations (JHKS bands) designed to reveal the presenceof early-type stars based on their positions in color-color and color-magnitude diagrams centered on the location of
RAFGL 5475. We took into account the possibility that candidates found might belong to a foreground population
physically related either to M16 or M17, two giant HII regions lying midway between the Sun and RAFGL 5475.
Results: The near-infrared color-color diagram shows clear evidence for the presence of a moderately obscured
population of early-type stars in the region imaged. By studying the distribution of extinction in their direction andbasic characteristics of the interstellar medium we show that these new early-type stars are most likely associated withRAFGL 5475.
Conclusions: By investigating the possible existence of massive early-type stars in the direction of RAFGL 5475 wehave discovered the existence of a new OB association. A very preliminary assessment of its contents suggests thepresence of several O-type stars, some of them likely to be associated with structures in the interstellar medium. The
new association is located at 4 kpc from the Sun in the Scutum-Centaurus arm.
Accepted by Astronomy and Astrophysics
http://www.eso.org/~fcomeron/RAFGL5475.pdf

13

14

Physics of Planet Trapping with Applications to HL Tau
A.J. Cridland1,2 , Ralph E. Pudritz2,3 , & Matthew Alessi2
1

Leiden Observatory, Leiden University, 2300 RA Leiden, the Netherlands; 2 Department of Physics and Astronomy,
McMaster University, Hamilton, Ontario, Canada, L8S 4E8; 3 Origins Institute, McMaster University, Hamilton,
Ontario, Canada, L8S 4E8
E-mail contact: cridland at strw.leidenuniv.nl
We explore planet formation in the HL Tau disk and possible origins of the prominent gaps and rings observed by
ALMA. We investigate whether dust gaps are caused by dynamically trapped planetary embryos at the ice lines ofabundant volatiles. The global properties of the HL Tau disk (total mass, size) at its current age are used to constrain
an evolving analytic disk model describing its temperature and density profiles. By performing a detailed analysisof the planet-disk interaction for a planet near the water ice line including a rigorous treatment of the dust opacity,
we confirm that water is sufficiently abundant (1.5 × 10−4 molecules per H) to trap planets at its ice line due toan opacity transition. When the abundance of water is reduced by 50% planet trapping disappears. We extend ouranalysis to other planet traps: the heat transition, dead zone edge, and the CO2 ice line and find similar trapping.
The formation of planets via planetesimal accretion is computed for dynamically trapped embryos at the water ice
line, dead zone, and heat transition. The end products orbit in the inner disk (R < 3 AU), unresolved by ALMA, with
masses that range between sub-Earth to 5 Jupiter masses. While we find that the dust gaps correspond well with theradial positions of the CO2 , CH4 , and CO ice lines, the planetesimal accretion rates at these radii are too small tobuild large embryos within 1 Myr.
Accepted by MNRAS
http://arxiv.org/pdf/1901.00778

Age Determination in Upper Scorpius with Eclipsing Binaries

J. David , Lynne A. Hillenbrand , Edward Gillen , Ann Marie Cody , Steve B. Howell ,15 Trevor
Howard T. Isaacson and John H. Livingston
1,2

2

6

3

4

5

7

1

Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;
Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA; 3 Astrophysics Group,
Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK; 4 NASA Ames Research Center, Moffet
Field, CA 94035, USA; 5 NASA Ames Research Center, Moffett Field, CA 94035, USA; 6 Astronomy Department,
University of California, Berkeley, CA 94720, USA; 7 Department of Astronomy, University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113-0033, Japan2

E-mail contact: trevor.j.david at jpl.nasa.gov
The Upper Scorpius OB association is the nearest region of recent massive star formation and thus an importantbenchmark for investigations concerning stellar evolution and planet formation timescales. We present nine eclipsingbinaries (EBs) in Upper Scorpius, three of which are newly reported here and all of which were discovered from K2
photometry. Joint fitting of the eclipse photometry and radial velocities from newly acquired Keck-I/HIRES spectra
yields precise masses and radii for those systems that are spectroscopically double-lined. The binary orbital periods
in our sample range from 0.6–100 days, with total masses ranging from 0.2–8 M⊙ . At least 33% of the EBs residein hierarchical multiples, including two triples and one quadruple. We use these EBs to develop an empirical mass–
radius relation for pre-main-sequence stars, and to evaluate the predictions of widely-used stellar evolutionary models.
We report evidence for an age of 5–7 Myr which is self-consistent in the mass range of 0.3–5 M⊙ and based on
the fundamentally-determined masses and radii of EBs. Evolutionary models including the effects of magnetic fields
imply an age of 9–10 Myr. Our results are consistent with previous studies that indicate many models systematicallyunderestimate the masses of low-mass stars by 20–60% based on H–R diagram analyses. We also consider the dynamical
states of several binaries and compare with expectations from tidal dissipation theories. Finally, we identify RIK 72
b as a long-period transiting brown dwarf (M = 59.2 ± 6.8 MJup , R = 3.10 ± 0.31 RJup , P ≈ 97.8 days) and an ideal
benchmark for brown dwarf cooling models at 5–10 Myr.
Accepted by ApJ
http://arxiv.org/pdf/1901.05532

14

16

Star-disc (mis-)alignment in Rho Oph and Upper Sco: insights from spatially resolved
disc systems with K2 rotation periods
Claire L Davies1
1

Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK

E-mail contact: cdavies at astro.ex.ac.uk
The discovery of close in, giant planets (hot Jupiters) with orbital angular momentum vectors misaligned with respect
to the rotation axis of their host stars presents problems for planet formation theories in which planets form in discs withangular momentum vectors aligned with that of the star. Violent, high eccentricity migration mechanisms purported
to elevate planetary orbits above the natal disc plane predict populations of proto-hot Jupiters which have not been
observed with Kepler. Alternative theories invoking primordial star-disc misalignments have recently received more
attention. Here, the relative alignment between stars and their protoplanetary discs is assessed for the first time for asample of 20 pre-main sequence stars. Recently published rotation periods derived from high quality, long duration,high cadence K2 light curves for members of the Rho Ophiuchus and Upper Scorpius star forming regions are matchedwith high angular resolution observations of spatially resolved discs and projected rotational velocities to determine
stellar rotation axis inclination angles which are then compared to the disc inclinations. Ten of the fifteen systems
for which the stellar inclination could be estimated are consistent with star-disc alignment while five systems indicate
potential misalignments between the star and its disc. The potential for chance misalignment of aligned systems due
to projection effects and characteristic measurement uncertainties is also investigated. While the observed frequency ofapparent star-disc misalignments could be reproduced by a simulated test population in which 100 percent of systems
are truly aligned, the distribution of the scale of inferred misalignment angles could not.
Accepted by Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/1901.01929

17

Simulations of the dynamics of the debris disks in the systems Kepler-16, Kepler-34,
and Kepler-35
Tatiana Demidova1 and Ivan Shevchenko1
1

Pulkovo Astronomial Observatory of the Russian Academy of Sciences

E-mail contact: proxima1 at list.ru
The long-term dynamics of planetesimals in debris discs in models with parameters of binary star systems Kepler-16,
Kepler-34 and Kepler-35 with planets is investigated. Our calculations have shown the formation of a stable coorbitalwith the planet ring is possible for Kepler-16 and Kepler-35 systems. In Kepler-34 system, significant eccentricities ofthe orbits of the binary and planets can to prevent the formation of such a structure. Detection circumbinary annularstructures in observations of systems binary stars can be evidence of the existence of planets, retaining coorbital rings
from dust and planetesimals.
Accepted by Astronomy Letters (2018, Vol. 44, No. 2, pp. 119-125)
https://arxiv.org/pdf/1901.07390

18

The Disk Substructures at High Angular Resolution Project (DSHARP)
VI: Dust trapping in thin-ringed protoplanetary disks
Cornelis P. Dullemond1 , Tilman Birnstiel2 , Jane Huang3 , Nicolás T. Kurtovic4 , Sean M. Andrews3 ,Viviana V. Guzmán5,11 , Laura M. Pérez4 , Andrea Isella6 , Zhaohuan Zhu7 , Myriam Benisty8 , David
J. Wilner3 , Xue-Ning Bai9 , John M. Carpenter5 , Shangjia Zhang7 , and Luca Ricci10
1

Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany; 2 University
Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 Munich, Germany;3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 4 Departamentode Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 5 Joint ALMA
Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile; 6 Department of Physics and Astronomy,
Rice University 6100 Main Street, MS-108, Houston, TX 77005, USA; 7 Department of Physics and Astronomy,
15

University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV, 89154, USA; 8 Unidad Mixta Internacional
Franco-Chilena de Astronomı́a, CNRS/INSU UMI 3386, Departamento de Astronomı́a, Universidad de Chile, Camino
El Observatorio 1515, Las Condes, Santiago, Chile; Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 9Institute for Advanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China; 10
Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge,
CA 91130, USA; 11 Instituto de Astrofı́sica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860,
7820436 Macul, Santiago, Chile
E-mail contact: dullemond@uni-heidelberg.de
A large fraction of the protoplanetary disks observed with ALMA display multiple well-defined and nearly perfectly
circular rings in the continuum, in many cases with substantial peak-to-valley contrast. The DSHARP campaign
shows that several of these rings are very narrow in radial extent. In this paper we test the hypothesis that thesedust rings are caused by dust trapping in radial pressure bumps, and if confirmed, put constraints on the physics ofthe dust trapping mechanism. We model this process analytically in 1D, assuming axisymmetry. By comparing thismodel to the data, we find that all rings are consistent with dust trapping. Based on a plausible model of the dust
temperature we find that several rings are narrower than the pressure scale height, providing strong evidence for dust
trapping. The rings have peak absorption optical depth in the range between 0.2 and 0.5. The dust masses stored ineach of these rings is of the order of tens of Earth masses, though much ambiguity remains due to the uncertainty ofthe dust opacities. The dust rings are dense enough to potentially trigger the streaming instability, but our analysis
cannot give proof of this mechanism actually operating. Our results show, however, that the combination of very low
αturb ≪ 5 × 10−4 and very large grains agrain ≫ 0.1 cm can be excluded by the data for all the rings studied in thispaper.
Accepted by ApJL (869:L46, 2018)https://arxiv.org/pdf/1812.04044

19

Hints for a Turnover at the Snow Line in the Giant Planet Occurrence Rate
Rachel B. Fernandes1,2 , Gijs D. Mulders3,2 , Ilaria Pascucci1,2 , Christoph Mordasini4 and Alexandre
Emsenhuber1,41Lunar and Planetary Laboratory, The University of Arizona, 1629 E University Blvd, Tucson, AZ 85721, USA; 2
Earths in Other Solar Systems Team, NASA Nexus for Exoplanet System Science; 3 Department of the GeophysicalSciences, The University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA; 4 Physikalisches Institut,
Universität Bern, Gesellschaftsstrasse 6, CH-3012 Bern, Switzerland
E-mail contact: rachelbf at lpl.arizona.edu
The orbital distribution of giant planets is crucial for understanding how terrestrial planets form and predicting yields
of exoplanet surveys. Here, we derive giant planets occurrence rates as a function of orbital period by taking into
account the detection efficiency of the Kepler and radial velocity (RV) surveys. The giant planet occurrence rates for
Kepler and RV show the same rising trend with increasing distance from the star. We identify a break in the RV giant
planet distribution between ∼2-3 au — close to the location of the snow line in the Solar System — after which theoccurrence rate decreases with distance from the star. Extrapolating a broken power-law distribution to larger semimajor axes, we find good agreement with the ∼ 1% planet occurrence rates from direct imaging surveys. Assuming
a symmetric power law, we also estimate that the occurrence of giant planets between 0.1−100 au is 26.6+7.5−5.4 % forplanets with masses 0.1-20 MJ and decreases to 6.2+1.5%
forplanetsmore
massivethanJupiter.
This
impliesthat only−1.2
a fraction of the structures detected in disks around young stars can be attributed to giant planets. Various planet
population synthesis models show good agreement with the observed distribution, and we show how a quantitative
comparison between model and data can be used to constrain planet formation and migration mechanisms.
Accepted by ApJ
https://arxiv.org/pdf/1812.05569

16

20 M. Figueira , C. López-Calderón , L. Bronfman , A. Zavagno , C. Hervı́as-Caimapo , N. Duronea
Multiwavelength study of the G345.5+1.5 region
1,2

and L-Å. Nyman

3

4

1

5

6

3,7

1

Aix Marseille Univ, CNRS, LAM, Laboratoire d'Astrophysique de Marseille, Marseille, France; 2 National Centre
for Nuclear Research, ul. Hoża 69, 00-681, Warszawa, Poland; 3 Joint ALMA Observatory (JAO), Alonso de Córdova
3107, Vitacura, Santiago, Chile; 4 Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile;
5
Jodrell Bank Centre for Astrophysics, School of Physics & Astronomy, University of Manchester, Oxford Road,
Manchester M139PL, U.K.; 6 Instituto Argentino de Radioastronomı́a, CONICET, CCT-La Plata. C.C.5., 1894 Villa
Elisa, Argentina; 7 European Southern Observatory, Alonso de Crdova 3107, Vitacura, Santiago, Chile
E-mail contact: Miguel.Figueira at ncbj.gov.pl
The star formation process requires the dust and gas present in the Milky Way to self-assemble into dense reservoirs ofneutral material where the new generation of stars will emerge. Star forming regions are usually studied in the context
of Galactic surveys but dedicated observations are sometimes needed when to go beyond them. A better understandingof the star formation process in the Galaxy goes through the study of several regions. This allows to increase thesample of objects (clumps, cores, stars) for further statistical works and deeper follow-up studies can be undertaken.
Here, we studied the G345.5+1.5 region located slightly above the Galactic plane to understand its star formation
properties. We combine LABOCA and 12 CO(4−3) transition line (NANTEN2) observations complemented with the
Hi-GAL and Spitzer-GLIMPSE surveys to study the star formation towards this region. We used the Clumpfind
algorithm to extract the clumps from the 870 µm and the 12 CO(4−3) data. Radio emission at 36 cm is used toestimate the number of H ii regions and to remove the contamination from the free-free emission at 870 µm. We
employed color-color diagrams and spectral energy distribution (SED) slopes to distinguish between prestellar andprotostellar clumps. We studied the boundness of the clumps through the virial parameter. Finally, we estimated thestar formation efficiency (SFE) and star formation rate (SFR) of the region and used the Schmidt-Kennicutt diagram
to compare its ability to form stars with other regions of the Galactic plane. Among the 13 radio sources found using
the MGPS-2 catalog, 7 of them are found to be associated with H ii regions corresponding to late B/early O stars.
We found 45 870 µm-clumps with diameters between 0.4 and 1.2 pc and masses between 43 M⊙ and 3923 M⊙ , and
107 12 CO clumps having diameters between 0.4 pc and 1.3 pc and masses between 28 M⊙ and 9433 M⊙ . More than
50% of the clumps are protostellar and bounded and are able to host (massive) star formation. An high SFR andSFR density (ΣSF R ) values are associated to the region with a star formation efficiency (SFE) of a few percent. Withsubmillimeter, CO transition and short wavelength infrared observations, our study reveals a population of massive
stars, protostellar and bound starless clumps towards G345.5+1.5. This region is therefore actively forming stars andits location in the starburst quadrant of Schmidt-Kennicutt diagram is comparable to other star-forming regions foundwithin the Galactic plane.
Accepted by A&A
http://arxiv.org/pdf/1901.10905

21

Constraining the Rate of Protostellar Accretion Outbursts in the Orion Molecular
CloudsWilliam J. Fischer1 , Emily Safron2 and S. Thomas Megeath3
1

Space Telescope Science Institute, Baltimore, MD, USA; 2 Department of Physics and Astronomy, Louisiana State
University, Baton Rouge, LA, USA; 3 Department of Physics and Astronomy, University of Toledo, Toledo, OH, USA
E-mail contact: wfischer at stsci.edu
Outbursts due to dramatic increases in the mass accretion rate are the most extreme type of variability in young stellar
objects. We searched for outbursts among 319 protostars in the Orion molecular clouds by comparing 3.6, 4.5, and24 µm photometry from the Spitzer Space Telescope to 3.4, 4.6, and 22 µm photometry from the Wide-field Infrared
Survey Explorer (WISE ) obtained ∼ 6.5 yr apart. Sources that brightened by more than two standard deviations
above the mean variability at all three wavelengths were marked as burst candidates, and they were inspected visually
to check for false positives due primarily to the reduced angular resolution of WISE compared to Spitzer. We recovered
the known burst V2775 Ori (HOPS 223) as well as a previously unknown burst, HOPS 383, which we announced inan earlier paper. No other outbursts were found. With observations over 6.5 yr, we estimate an interval of about171000 yr between bursts with a 90% confidence interval of 690 to 40,300 yr. The most likely burst interval is shorter
than those found in studies of optically revealed young stellar objects, suggesting that outbursts are more frequent inprotostars than in pre-main-sequence stars that lack substantial envelopes.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/1901.08062

22

Orion Source I’s disk is salty
Adam Ginsburg,1 Brett McGuire,2 ,3 , Richard Plambeck,4 John Bally,5 Ciriaco Goddi,6 ,7 and Melvyn
Wright4
1

Jansky fellow of the National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA; 2 National Radio Astronomy Observatory, Charlottesville, VA 22903 USA; 3 Harvard-Smithsonian Center for Astrophysics,
Cambridge, MA 02138 USA; 4 Radio Astronomy Laboratory, University of California, Berkeley, CA 94720; 5 CASA,
University of Colorado, 389-UCB, Boulder, CO 80309; 6 ALLEGRO/Leiden Observatory, Leiden University, PO Box
9513, 2300 RA Leiden, the Netherlands; 7 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO
Box 9010, 6500 GL Nijmegen, the Netherlands
E-mail contact: adam.g.ginsburg@gmail.com
We report the detection of NaCl, KCl, and their 37 Cl and 41 K isotopologues toward the disk around Orion Source I.
About 60 transitions of these molecules were identified. This is the first detection of these molecules in the interstellar
medium not associated with the ejecta of evolved stars. It is also the first ever detection of the vibrationally excitedstates of these lines in the ISM above v = 1, with firm detections up to v = 6. The salt emission traces theregion just above the continuum disk, possibly forming the base of the outflow. The emission from the vibrationallyexcited transitions is inconsistent with a single temperature, implying the lines are not in LTE. We examine several
possible explanations of the observed high excitation lines, concluding that the vibrational states are most likely to beradiatively excited via rovibrational transitions in the 25-35 µm (NaCl) and 35-45 µm (KCl) range. We suggest thatthe molecules are produced by destruction of dust particles. Because these molecules are so rare, they are potentiallyunique tools for identifying high-mass protostellar disks and measuring the radiation environment around accreting
young stars.
Accepted by ApJ
https://arxiv.org/pdf/1901.04489

23

Distributed star formation throughout the Galactic Center cloud Sgr B2Adam Ginsburg1 , John Bally8 , Ashley Barnes16 , Nate Bastian 16 , Cara Battersby24,26 , Henrik Beuther18 ,Crystal Brogan3 , Yanett Contreras6 , Joanna Corby3,25 , Jeremy Darling8 , Chris De Pree19 , Roberto
Galván-Madrid10 , Guido Garay20 , Jonathan Henshaw18 , Todd Hunter3 , J. M. Diederik Kruijssen7 ,Steven Longmore16 , Xing Lu29 , Fanyi Meng17 , Elisabeth A.C. Mills 11,23 , Juergen Ott2 , Jaime E.
Pineda22 , Álvaro Sánchez-Monge17 , Peter Schilke17 , Anika Schmiedeke17,22 , Daniel Walker16,27,28 , David
Wilner24
1

Jansky fellow of the National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA ; 2 National
Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA ; 3 National Radio Astronomy Observatory, 520 Edgemont Rd, Charlottesville, VA 22903, USA ; 4 European Southern Observatory, Karl-SchwarzschildStraße 2, D-85748 Garching bei München, Germany ; 5 Department of Astrophysics/IMAPP, Radboud University
Nijmegen, PO Box 9010, 6500 GL Nijmegen, the Netherlands; 6 ALLEGRO/Leiden Observatory, Leiden University,
PO Box 9513, 2300 RA Leiden, the Netherlands; 7 Astronomisches Rechen-Institut, Zentrum für Astronomie derUniversität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany; 8 CASA, University of Colorado, 389UCB, Boulder, CO 80309; 9 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University ofManchester, Oxford Road, Manchester M13 9PL, UK; 10 Instituto de Radioastronomı́a y Astrofı́sica, UNAM, A.P.
3-72, Xangari, Morelia, 58089, Mexico; 11 San Jose State University, One Washington Square, San Jose, CA 95192;
12
Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK; 13 Dept. ofPhysics, University of Alberta, Edmonton, Alberta, Canada; 14 INAF-Osservatorio Astrofisico di Arcetri, Largo E.

18

Fermi 5, I-50125, Florence, Italy ; 15 Excellence Cluster Universe, Boltzman str. 2, D-85748 Garching bei München,
Germany ; 16 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3
5RF, UK ; 17 I. Physikalisches Institut, Universiät zu Köln, Zülpicher Str. 77, 50937 Köln, Germany; 18 Max-PlanckInstitute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany; 19 Agnes Scott College, 141 E. College Ave.,
Decatur, GA 30030; 20 Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile; 21 Leiden
Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands ; 22 Max-Planck-Institut für
extraterrestrische Physik, D-85748 Garching, Germany; 23 Boston University Astronomy Department, 725 Commonwealth Avenue, Boston, MA 02215, USA; 24 Harvard-Smithsonian Center for Astrophysics, 60 Garden St. Cambridge,
MA 02138; 25 University of South Florida, Physics Department, 4202 East Fowler Ave, ISA 2019 Tampa, FL 33620; 26
University of Connecticut, Department of Physics, 2152 Hillside Rd., Storrs, CT 06269; 27 Joint ALMA Observatory,
Alonso de Crdova 3107, Vitacura, Santiago, Chile; 28 National Astronomical Observatory of Japan, Alonso de Crdova
3788, 61B Vitacura, Santiago, Chile; 29 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka,Tokyo,
181-8588, Japan
E-mail contact: adam.g.ginsburg@gmail.com
We report ALMA observations with resolution ≈ 0.5 arcsec at 3 mm of the extended Sgr B2 cloud in the Central
Molecular Zone (CMZ). We detect 271 compact sources, most of which are smaller than 5000 AU. By ruling out
alternative possibilities, we conclude that these sources consist of a mix of hypercompact H IIregions and young stellar
objects (YSOs). Most of the newly detected sources are YSOs with gas envelopes that, based on their luminosities,
must contain objects with stellar masses M∗ >∼ 8 M⊙ . Their spatial distribution spread over a ∼ 12 × 3 pc region
demonstrates that Sgr B2 is experiencing an extended star formation event, not just an isolated ‘starburst’ within the
protocluster regions. Using this new sample, we examine star formation thresholds and surface density relations in
23−2
Sgr B2. While all of the YSOs reside in regions of high column density (N (H2 ) >∼ 2 × 10 cm ), not all regions ofhigh column density contain YSOs. The observed column density threshold for star formation is substantially higher
than that in solar vicinity clouds, implying either that high-mass star formation requires a higher column density orthat any star formation threshold in the CMZ must be higher than in nearby clouds. The relation between the surface
density of gas and stars is incompatible with extrapolations from local clouds, and instead stellar densities in Sgr B2
follow a linear Σ∗ − Σgas relation, shallower than that observed in local clouds. Together, these points suggest that ahigher volume density threshold is required to explain star formation in CMZ clouds.
Accepted by ApJ (853,171,2018)
http://adsabs.harvard.edu/pdf/2018ApJ...853..171G
http://arxiv.org/pdf/1801.04941

24

A high cluster formation efficiency in the Sagittarius B2 complex
Adam Ginsburg1 , J. M. Diederik Kruijssen2
1

Jansky fellow of the National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA ; 2
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120
Heidelberg, Germany
E-mail contact: adam.g.ginsburg@gmail.com
The fraction of stars forming in compact, gravitationally bound clusters (the ‘cluster formation efficiency’ or CFE) is
an important quantity for deriving the spatial clustering of stellar feedback and for tracing star formation using stellar
clusters across the Universe. Observations of clusters in nearby galaxies have revealed a strong dependence of the CFE
on the local gas density, indicating that more stars form in star clusters when the star formation rate surface density
is higher. Previously, it has not been possible to test this relation at very young ages and in clusters with individual
stars resolved due to the universally-low densities in the cluster-forming regions in the Local Group. This has evenled to the suggestion that the CFE increases with distance from the Sun, which would suggest an observational bias.
However, the Central Molecular Zone of the Milky Way hosts clouds with densities that are orders of magnitude
higher than anywhere else in the Local Group. We report a measurement of the CFE in the highest-density region
in the Galaxy, Sgr B2, based on ALMA observations of high-mass young stellar objects. We find that over a thirdof the stars (37 ± 7%) in Sgr B2 are forming in bound clusters. This value is consistent with the predictions ofenvironmentally-dependent models for the CFE and is inconsistent with a constant CFE in the Galaxy.

19

Accepted by ApJ (864,17,2018)
http://adsabs.harvard.edu/pdf/2018ApJ...864L..17G and http://arxiv.org/pdf/1808.06616

A Keplerian disk around Orion Source I, a ∼ 15 M⊙ YSO

25 Adam Ginsburg, John Bally, Ciriaco Goddi, , Richard Plambeck, and Melvyn Wright
1

3

4 5

2

2

1

Jansky fellow of the National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA; 2
Radio Astronomy Laboratory, University of California, Berkeley, CA 94720; 3 CASA, University of Colorado, 389UCB, Boulder, CO 80309; 4 ALLEGRO/Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, theNetherlands 5 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen,the Netherlands;
E-mail contact: adam.g.ginsburg@gmail.com
We report ALMA long-baseline observations of Orion Source I with resolution 0.03-0.06 arcsec (12-24 AU) at 1.3 and3.2 mm. We detect both continuum and spectral line emission from Source I’s disk. We also detect a central weakly
resolved source that we interpret as a hot spot in the inner disk, which may indicate the presence of a binary system.
The high angular resolution and sensitivity of these observations allow us to measure the outer envelope of the rotation
curve of the H2 O 55,0 − 64,3 line, which gives a mass MI ≈ 15 ± 2 M⊙ . We detected several other lines that moreclosely trace the disk, but were unable to identify their parent species. Using centroid-of-channel methods on theseother lines, we infer a similar mass. These measurements solidify Source I as a genuine high-mass protostar systemand support the theory that Source I and the Becklin Neugebauer Object were ejected from the dynamical decay of amultiple star system ∼500 years ago, an event that also launched the explosive molecular outflow in Orion.
Accepted by ApJ (860,119,2018)

http://adsabs.harvard.edu/pdf/2018ApJ...860..119G and http://arxiv.org/pdf/1804.10622

Fundamental properties of the pre-main sequence eclipsing stars of MML 53 and themass of the tertiary

26 Y. Gómez Maqueo Chew , L. Hebb , H.C. Stempels , A. Paat , K.G. Stassun , F. Faedi , R.A.
1

9

10

2

3

11

Street , G. Rohn , C. Hellier , and D.R. Anderson

4

5,6

7,8

11

1

Instituto de Astronomı́a, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Ciudad de México,México; 2 Department of Physics, Hobart and William Smith Colleges, Geneva, New York, 14456, USA; 3 Departmentof Physics & Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden; 4 National Optical Astronomy
Observatory, 950 N. Cherry Ave, Tucson, Arizona 85719, USA; 5 Department of Physics, Vanderbilt University,
Nashville, TN, USA; 6 Department of Physics, Fisk University, Nashville, TN, USA; 7 INAF-Osservatorio Astrofisico
di Catania, , Via S. Sofia 78, I-95123 Catania, Italy; 8 University of Warwick, Department of Physics, Gibbet Hill
Road, Coventry, CV4 7AL, UK; 9 Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr. Suite 102,
Goleta, CA 93117, USA; 10 Physics Department, State University of New York at Cortland, Cortland, New York
13045, USA; 11 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK
E-mail contact: ygmc at astro.unam.mx
We present the most comprehensive analysis to date of the Upper Centaurus Lupus eclipsing binary MML 53 (2.097892d), and for the first time, confirm the bound-nature of the third star (∼9 yr orbit). Our analysis uses new andarchival spectra and time-series photometry. We determined the temperature of the primary star to be 4880±100
K. The study of the close binary incorporated treatment of spots and dilution by the tertiary in the light curves,allowing for the robust measurement of the masses of the eclipsing components within 1% (M1 = 1.0400 ± 0.0067
and M2 = 0.8907 ± 0.0058 M⊙ ), their radii within 4.5% (R1 = 1.283 ± 0.043 and R2 = 1.107 ± 0.049 R⊙ ), and thesecondary temperature (4379±100 K). From the analysis of the eclipse timings, and the change in systemic velocity ofthe eclipsing binary and the radial velocities of the third star, we measured the mass of the outer companion to be 0.7
M⊙ within 20%. The age we derived from the evolution of the temperature ratio between the eclipsing components
is fully consistent with previous estimates of the age of UCL (16±2 Myr). At this age, the tightening of the MML
53 eclipsing binary has already occurred, thus supporting close-binary formation mechanisms that act early in theirevolution. The eclipsing stars roughly follow the same theoretical isochrone, but appear to be inflated in radius (by20

20% for the primary and 10% for the secondary). However, our primary radius measurement of is in full agreementwith the independent measurement of the secondary of NP Per which has the same mass and a similar age. The
eclipsing stars of MML 53 are found to be larger but not cooler than predicted by non-magnetic models, it is not clear
what is the mechanism that is causing the radius inflation given that activity, spots and/or magnetic fields slowing
their contraction, require the inflated stars to be cooler to remain in thermal equilibrium.
Accepted by A&A
http://arxiv.org/pdf/1901.10611

27

Blobs, spiral arms, and a possible planet around HD 169142
R. Gratton1 , R. Ligi2 , E. Sissa1 , S. Desidera1 , D. Mesa1 , M. Bonnefoy3 , G. Chauvin3,4 , A. Cheetham5 ,M. Feldt6 , A.M. Lagrange3 , M. Langlois7,8 , M. Meyer9,10 , A. Vigan7 , A. Boccaletti11 , M. Janson6,12 , C.
Lazzoni1 , A. Zurlo7,13 , J. De Boer14 , T. Henning6 , V. D’Orazi1 , L. Gluck3 , F. Madec7 , M. Jaquet7 , P.
Baudoz11 , D. Fantinel1 , A. Pavlov6 , and F. Wildi5
1

Osservatorio Astronomico di Padova - INAF; 2 Osservatorio Astronomico di Brera - INAF; 3 Univ. Grenoble Alpes,
CNRS, IPAG, F-38000 Grenoble, France; 4 Unidad Mixta Internacional Franco-Chilena de Astronomı́a, CNRS/INSU
UMI 3386 and Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile; 5 Geneva Observatory, University of Geneva, Chemin des Mailettes 51, 1290 Versoix, Switzerland; 6 Max Planck Institute for
Astronomy, Konigstuhl 17, D-69117 Heidelberg, Germany; 7 Aix Marseille Université, CNRS, LAM (Laboratoired’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France; 8 CRAL, UMR 5574, CNRS, Université de Lyon,
Ecole Normale Superieure de Lyon, 46 Alle d’Italie, F-69364 Lyon Cedex 07, France; 9 Institute for Astronomy, ETH
Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland; 10 Department of Astronomy, University of Michigan,
Ann Arbor, MI 48109, US; 11 LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universite,
UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cit, 5 place Jules Janssen, 92195 Meudon, France; 12
Department of Astronomy, Stockholm University, SE-106 91 Stockholm, Sweden; 13 Núcleo de Astronoma, Facultad deIngenierı́a, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile; 14 Leiden Observatory, Universiteit Leiden
E-mail contact: raffaele.gratton at inaf.it
Young planets are expected to cause perturbations in protostellar disks that may be used to infer their presence. Clear
detection of still-forming planets embedded within gas-rich disks is rare. HD 169142 is a very young Herbig Ae-Be
star surrounded by a pre-transitional disk, composed of at least three rings. While claims of sub-stellar objects aroundthis star have been made previously, follow-up studies remain inconclusive. We used SPHERE at ESO VLT to obtaina sequence of high-contrast images of the immediate surroundings of this star over about three years. This enables
a photometric and astrometric analysis of the structures in the disk. While we were unable to definitively confirm
the previous claims of a massive sub-stellar object at 0.′′ 1–0.′′ 15 from the star, we found both spirals and blobs within
the disk. The spiral pattern may be explained as due to the presence of a primary, a secondary, and a tertiary arm
excited by a planet of a few Jupiter masses lying along the primary arm, likely in the cavities between the rings. The
blobs orbit the star consistently with Keplerian motion, allowing a dynamical determination of the mass of the star.
While most of these blobs are located within the rings, we found that one of them lies in the cavity between the rings,
along the primary arm of the spiral design. This blob might be due to a planet that might also be responsible for the
spiral pattern observed within the rings and for the cavity between the two rings. The planet itself is not detected atshort wavelengths, where we only see a dust cloud illuminated by stellar light, but the planetary photosphere might
be responsible for the emission observed in the K band. The mass of this putative planet may be constrained using
photometric and dynamical arguments; it should be between 1 and 4 Jupiter masses. The brightest blobs are foundat the 1:2 resonance with this putative planet
Accepted by A&A
http://arxiv.org/pdf/1901.06555

The Disk Substructures at High Angular Resolution Program (DSHARP). VIII. The
Rich Ringed Substructures in the AS 209 Disk

28 Viviana V. Guzmán , Jane Huang , Sean M. Andrews , Andrea Isella , Laura M. Pérez , John M.
1,2

3

3

4

5

Carpenter1 , Cornelis P. Dullemond6 , Luca Ricci7 , Tilman Birnstiel8 , Shangjia Zhang9 , Zhaohuan Zhu9 ,Xue-Ning Bai10 , Myriam Benisty11,12 , Karin I. Öberg3 and David J. Wilner321

1

Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile; 2 Instituto de Astrofı́sica,
Ponticia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile; 3 HarvardSmithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 4 Department of Physics andAstronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA; 5 Departamento de Astronomı́a, Universidad
de Chile, Casilla 36-D, Santiago, Chile; 6 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, D69120 Heidelberg, Germany; 7 Department of Physics and Astronomy, California State University Northridge, 18111
Nordhoff Street, Northridge, CA 91130, USA; 8 University Observatory, Faculty of Physics, Ludwig-MaximiliansUniversität München, Scheinerstr. 1, D-81679 Munich, Germany; 9 Department of Physics and Astronomy, Universityof Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154, USA; 10 Institute for Advanced Study andTsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, People?s Republic of China; 11 Unidad Mixta
Internacional Franco-Chilena de Astronomı́a, CNRS/INSU UMI 3386, Departamento de Astronoma, Universidad deChile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 12 Univ. Grenoble Alpes, CNRS, IPAG, F-38000
Grenoble, France
E-mail contact: vguzman at astro.puc.cl
We present a detailed analysis of the high angular resolution (0.′′ 037, corresponding to 5 au) observations of the 1.25
mm continuum and 12 CO 2–1 emission from the disk around the T Tauri star AS 209. AS 209 hosts one of the mostunusual disks from the Disk Substructures at High Angular Resolution Project sample, the first high angular resolution
Atacama Large Millimeter Array survey of disks, as nearly all of the emission can be explained with concentric Gaussian
rings. In particular, the dust emission consists of a series of narrow and closely spaced rings in the inner ∼60 au, twowell-separated bright rings in the outer disk, centered at 74 and 120 au, and at least two fainter emission featuresat 90 and 130 au. We model the visibilities with a parametric representation of the radial surface brightness profile,consisting of a central core and seven concentric Gaussian rings. Recent hydrodynamical simulations of low-viscosity
disks show that super-Earth planets can produce the multiple gaps seen in AS 209 millimeter continuum emission. The
12
CO line emission is centrally peaked and extends out to ∼300 au, much farther than the millimeter dust emission.
We find axisymmetric, localized deficits of CO emission around four distinct radii, near 45, 75, 120, and 210 au. The
outermost gap is located well beyond the edge of the millimeter dust emission, and therefore cannot be due to dust
opacity and must be caused by a genuine CO surface density reduction, due either to chemical effects or depletion of
the overall gas content.
Accepted by ApJ Letters
http://adsabs.harvard.edu/pdf/2018ApJ...869L..48G

29

PTF 14jg: The Remarkable Outburst and Post-Burst Evolution of a Previously Anonymous Galactic Star
Lynne A. Hillenbrand1 , Adam A. Miller1,2 , John M. Carpenter1,3 , Mansi M. Kasliwal1 , Howard Isaacson4 ,Sumin Tang1,5 , Vishal Joshi6 , D.P.K. Banerjee7 and Roc M. Cutri8
1

Department of Astronomy, California Institute of Technology, Pasadena CA 91125, USA; 2 Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, 2145 Sheridan Road, Evanston,
IL 60208, USA; 3 Joint ALMA Observatory, Avenida Alonso de Crdova 3107, Vitacura, Santiago, Chile; 4 University of California at Berkeley, Berkeley, CA, USA; 5 Kavli Institute for Theoretical Physics, University of California,
Santa Barbara, CA 93106, USA; 6 Astronomy and Astrophysics Division, Physical Research Laboratory, Navrangpura, Ahmedabad, Gujarat 380 009, India; 7 Astronomy and Astrophysics Division, Physical Research Laboratory,
Navrangpura, Ahmedabad, Gujarat 380 009, India; 8 Infrared Processing and Analysis Center, California Institute ofTechnology, Pasadena CA 91125, USA
E-mail contact: lah at astro.caltech.edu
We report the outbursting source iPTF 14jg, which prior to the onset of its late 2013 eruption, was a faint, unstudied,and virtually uncatalogued star. The salient features of the iPTF 14jg outburst are: (i) projected location near theW4 H II region and radial velocity consistent with physical association; (ii) a lightcurve that underwent a ∼6-7 mag
optical (R-band) through mid-infrared (L-band) brightening on a few month time scale, that peaked and then faded
by ?3 mag, but plateaued still >3.5 mag above quiescence by ∼8 months post-peak, lasting to at least four years after
eruption; (iii) strong outflow signatures, with velocities reaching ∼530 km/s; (iv) a low gravity and broad (∼100-150
km/s FWHM) optical absorption line spectrum that systematically changes its spectral type with wavelength; (v)22lithium; and (vi) ultraviolet and infrared excess. We tentatively identify the outburst as exhibiting characteristics ofa young star FU Ori event. However, the burst would be unusually hot, with an absorption spectrum exhibiting highexcitation (∼11,00015,000 K) lines in the optical, and no evidence of CO in the near-infrared, in addition to exhibiting
an unusual lightcurve. We thus also consider alternative scenarios including various forms of novae, nuclear burning
instabilities, massive star events, and mergers - finding them all inferior to the atypically hot FU Ori star classification.
The source eventually may be interpreted as a new category of young star outburst with larger amplitude and shorter
rise time than most FU Ori-like events. Continued monitoring of the lightcurve and the spectral evolution will reveal
its true nature.
Accepted by ApJ
http://arxiv.org/pdf/1901.10693

Nonlinear outcome of gravitational instability in an irradiated protoplanetary disc

Hirose and Ji-Ming Shi
30 Shigenobu
Department of Mathematical Science and Advanced Technology, JAMSTEC, Yokohama 236-0001, Japan; Depart1

2

1

2

ment of Astrophysical Sciences, Princeton University, 4 Ivy Ln, Princeton, NJ 08544
E-mail contact: hirose.shigenobu at gmail.com
Using local three dimensional radiation hydrodynamics simulations, the nonlinear outcome of gravitational instability
in an irradiated protoplanetary disc is investigated in a parameter space of the surface density Σ and the radiusr. Starting from laminar flow, axisymmetric self-gravitating density waves grow first. Their self-gravitating degree
becomes larger when Σ is larger or the cooling time is shorter at larger radii. The density waves eventually collapse
owing to non-axisymmetric instability, which results in either fragmentation or gravito-turbulence after a transientphase. The boundaries between the two are found at r ∼ 75 AU as well as at the Σ that corresponds to the initial
Toomre’s parameter of ∼0.2. The former boundary corresponds to the radius where the cooling time becomes short,approximating unity. Even when gravito-turbulence is established around the boundary radius, such a short coolingtime inevitably makes the fluctuation of Σ large enough to trigger fragmentation. On the other hand, when Σ isbeyond the latter boundary (i.e. the initial Toomre’s parameter is less than ∼0.2), the initial laminar flow is so
unstable against self-gravity that it evolves into fragmentation regardless of the radius or, equivalently, the coolingtime. Runaway collapse follows fragmentation when the mass concentration at the centre of a bound object is highenough that the temperature exceeds the H2 dissociation temperature.
Accepted by MNRAS
http://arxiv.org/pdf/1901.04082

The Disk Substructures at High Angular Resolution Project (DSHARP). II. Characteristics of Annular Substructures

31 Jane Huang , Sean M. Andrews , Cornelis P. Dullemond , Andrea Isella , Laura M. Pérez , Viviana V.
1

5,6

1

1

7

2

3

7

8

4

Guzmán , Karin I. , Zhaohuan Zhu , Shangjia Zhang , Xue-Ning Bai , Myriam Benisty9,10 , Tilman
Birnstiel11 , John M. Carpenter5 , A. Meredith Hughes12 , Luca Ricci13 , Erik Weaver3 and David J.
Wilner1
1

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, United States of America;
Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany; 3 Departmentof Physics and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, United States of America; 4 Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 5 Joint
ALMA Observatory, Avenida Alonso de C’ordova 3107, Vitacura, Santiago, Chile; 6 Instituto de Astrofı́sica, Pontificia
Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile; 7 Department of Physics
and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV, 89154, USA; 8 Institute forAdvanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China; 9 Unidad Mixta
Internacional Franco-Chilena de Astronomı́a, CNRS/INSU UMI 3386, Departamento de Astronomı́a, Universidad deChile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 10 Univ. Grenoble Alpes, CNRS, IPAG, 38000
Grenoble, France; 11 University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Schein2

23

erstr. 1, 81679 Munich, Germany; 12 Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96
Foss Hill Drive, Middletown, CT 06459, USA; 13 Department of Physics and Astronomy, California State University
Northridge, 18111 Nordhoff Street, Northridge, CA 91130, USA
E-mail contact: jane.huang at cfa.harvard.edu
The Disk Substructures at High Angular Resolution Project used ALMA to map the 1.25 millimeter continuum of
protoplanetary disks at a spatial resolution of ? 5 au. We present a systematic analysis of annular substructures in the
18 single-disk systems targeted in this survey. No dominant architecture emerges from this sample; instead, remarkably
diverse morphologies are observed. Annular substructures can occur at virtually any radius where millimeter continuum
emission is detected and range in widths from a few au to tens of au. Intensity ratios between gaps and adjacentrings range from near-unity to just a few percent. In a minority of cases, annular substructures co-exist with othertypes of substructures, including spiral arms (3/18) and crescent-like azimuthal asymmetries (2/18). No clear trend
is observed between the positions of the substructures and stellar host properties. In particular, the absence of an
obvious association with stellar host luminosity (and hence the disk thermal structure) suggests that substructures do
not occur preferentially near major molecular snowlines. Annular substructures like those observed in DSHARP havelong been hypothesized to be due to planet-disk interactions. A few disks exhibit characteristics particularly suggestiveof this scenario, including substructures in possible mean-motion resonance and double gap features reminiscent ofhydrodynamical simulations of multiple gaps opened by a planet in a low-viscosity disk.
Accepted by ApJL
https://arxiv.org/pdf/1812.04041

32

The Disk Substructures at High Angular Resolution Project (DSHARP). III. Spiral
Structures in the Millimeter Continuum of the Elias 27, IM Lup, and WaOph 6 Disks
Jane Huang1 , Sean M. Andrews1 , Laura M. Pérez2 , Zhaohuan Zhu3 , Cornelis P. Dullemond4 , Andrea Isella5 , Myriam Benisty6,7 , Xue-Ning Bai8 , Tilman Birnstiel9 , John M. Carpenter10 , Viviana V.
Guzmán10,11 , A. Meredith Hughes12 , Karin I. 1 , Luca Ricci13 , David J. Wilner1 and Shangjia Zhang3
1

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, United States of America;
Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 3
Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV,
89154, USA; 4 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany;
5
Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005, United Statesof America; 6 Unidad Mixta Internacional Franco-Chilena de Astronomı́a, CNRS/INSU UMI 3386, Departamento de
Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 7 Univ. Grenoble Alpes,
CNRS, IPAG, 38000 Grenoble, France; 8 Institute for Advanced Study and Tsinghua Center for Astrophysics, Tsinghua
University, Beijing 100084, China; 9 University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität
München, Scheinerstr. 1, 81679 Munich, Germany; 10 Joint ALMA Observatory, Avenida Alonso de Córdova 3107,
Vitacura, Santiago, Chile; 11 Instituto de Astrofı́sica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna
4860, 7820436 Macul, Santiago, Chile; 12 Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96
Foss Hill Drive, Middletown, CT 06459, USA; 13 Department of Physics and Astronomy, California State University
Northridge, 18111 Nordhoff Street, Northridge, CA 91130, USA
2E-mail contact: jane.huang at cfa.harvard.edu
We present an analysis of ALMA 1.25 millimeter continuum observations of spiral structures in three protoplanetarydisks from the Disk Substructures at High Angular Resolution Project. The disks around Elias 27, IM Lup, and
WaOph 6 were observed at a resolution of ∼40−60 mas (∼6−7 au). All three disks feature m = 2 spiral patterns inconjunction with annular substructures. Gas kinematics established by 12 CO J = 2 − 1 observations indicate that thecontinuum spiral arms are trailing. The arm-interarm intensity contrasts are modest, typically less than 3. The Elias
27 spiral pattern extends throughout much of the disk, and the arms intersect the gap at R∼69 au. The spiral patternin the IM Lup disk is particularly complex-it extends about halfway radially through the disk, exhibiting pitch angle
variations with radius and interarm features that may be part of ring substructures or spiral arm branches. Spiralarms also extend most of the way through the WaOph 6 disk, but the source overall is much more compact than theother two disks. We discuss possible origins for the spiral structures, including gravitational instability and density
waves induced by a stellar or planetary companion. Unlike the millimeter continuum counterparts of many of the disks24with spiral arms detected in scattered light, these three sources do not feature high-contrast crescent-like asymmetries
or large (R >20 au) emission cavities. This difference may point to multiple spiral formation mechanisms operating
in disks.
Accepted by ApJL
https://arxiv.org/pdf/1812.04193

33 R.V. Ibañez Bustos , A.P. Buccino , M. Flores , C.I. Martinez , D. Maizel , Sergio Messina , andFirst long-term activity study of AU Microscopii: a possible chromospheric cycle
1

P.J.D. Mauas

1,2

3,4

3

1

5

1,2

1

Instituto de Astronomı́a y Fı́sica del Espacio (CONICET-UBA), C.C. 67 Sucursal 28, C1428EHA-Buenos Aires,
Argentina; 2 Departamento de Fı́sica. FCEyN-Universidad de Buenos Aires, Buenos, Argentina; 3 Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE-CONICET), San Juan, Argentina—; 4 Facultad de Ciencias
Exactas, Fı́sicas y Naturales, Universidad Nacional de San Juan, San Juan, Argentina; 5 INAF-Catania AstrophysicalObservatory, via S. Sofia 78, 95123, Catania, Italy
E-mail contact: abuccino at iafe.uba.ar
M stars are ideal targets to search for Earth-like planets. However, they usually have high levels of magnetic activity,
which could affect their habitability and make difficult the detection of exoplanets orbiting around them. Unfortunately,
long-term variability of dM stars has not been extensively studied, due to their low intrinsic brightness. For this reason,in 1999 we started the HKα project, which systematically observes the spectra of a large number of stars, in particulardM stars, at the Complejo Astronomico El Leoncito (CASLEO). In this work, we study the long-term activity of
the young active dM1 star AU Microscopii. We analyze the Mount Wilson index S derived from CASLEO spectra
obtained between 2004 and 2016, which we complement with the S-index derived from HARPS, FEROS and UVES
public spectra. We also analyze the simultaneous photometric counterpart provided by the ASAS public databasefor this star between 2000 and 2009, and our own photometry. In both totally independent time series, we detect apossible activity cycle of period around 5 years. We also derived a precise rotation period for this star Prot = 4.85
days, consistent with the literature. This activity cycle reflects that an αΩ dynamo could be operating in this star.
Accepted by MNRAS
http://arxiv.org/pdf/1901.01433

34 Shigeru Ida , Takeru Yamamura and Satoshi Okuzumi

Water delivery by pebble accretion to rocky planets in habitable zones in evolving disks
1

2

2

1
Earth-Life Science Institute, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan; 2 Department ofEarth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551, Japan

E-mail contact: ida at elsi.jp
The Earth’s ocean mass is only 2.3 × 10−4 of the whole planet mass. Even including water in the interior, it would
be at most 10−3 –10−2 . Ancient Mars may have had a similar or slightly smaller water fraction. It is important toclarify the water delivery mechanism to rocky planets in habitable zones in exoplanetary systems, as well as that tothe Earth and Mars. Here, we consider water delivery to planets by icy pebbles after the snowline inwardly passes
the planetary orbits and derive the water mass fraction (fwater ) of the final planet as a function of disk parametersand discuss the parameters that reproduce fwater comparable to that inferred for the Earth and ancient Mars. We
calculate the growth of icy pebbles and their radial drift with a 1D model, and accretion of icy pebbles onto planets,
by simultaneously solving the snowline migration and the disk dissipation, to evaluate fwater of the planets. We findthat fwater is regulated by the total mass (Mres ) of icy dust materials preserved in the outer disk regions at the timing(t = tsnow ) of the snowline passage of the planetary orbit. Because Mres decays rapidly after the pebble formation
front reaches the disk outer edge (at t = tpff ), fwater is sensitive to the ratio tsnow /tpff , which is determined by the disk
parameters. We find tsnow /tpff < 10 or > 10 is important. Deriving an analytical formula for fwater that reproduces
the numerical results, we find that fwater of a rocky planet near 1 au is ∼ 10−4 –10−2 , in the disks with initial disk size
∼30–50 au and the initial disk mass accretion rate ∼ (10−8 –10−7 ) M⊙ yr−1 . Because these disks may be median orslightly compact/massive disks, the water fraction of rocky planets in habitable zones may be often similar to that of25

the Earth, if the icy pebble accretion is responsible for the water delivery.
Accepted by A&A
http://arxiv.org/pdf/1901.04611

35

The Disk Substructures at High Angular Resolution Project (DSHARP). IX. A Highdefinition Study of the HD 163296 Planet-forming Disk
Andrea Isella1 , Jane Huang2 , Sean M. Andrews2 , Cornelis P. Dullemond3 , Tilman Birnstiel4 , Shangjia
Zhang5 , Zhaohuan Zhu5 , Viviana V. Guzmán6,7 , Laura M. Pérez8 , Xue-Ning Bai9 , Myriam Benisty10,11 ,John M. Carpenter6 , Luca Ricci12 and David J. Wilner2
1

Department of Physics and Astronomy, Rice University, 6100 Main Street, MS-108, Houston, TX 77005, USA;
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 3 Zentrum fr Astronomie, Heidelberg University, Albert Ueberle Str. 2, D-69120 Heidelberg, Germany; 4 University Observatory,
Faculty of Physics, Ludwig-Maximilians-Universitt Mnchen, Scheinerstr. 1, D-81679 Munich, Germany; 5 Departmentof Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154,
USA; 6 Joint ALMA Observatory, Avenida Alonso de Crdova 3107, Vitacura, Santiago, Chile; 7 Instituto de Astrofsica,
Pontificia Universidad Catlica de Chile, Av. Vicua Mackenna 4860, 7820436 Macul, Santiago, Chile; 8 Departamentode Astronoma, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 9 Institute for Advanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, Peoples Republic of China;
10
Unidad Mixta Internacional Franco-Chilena de Astronoma, CNRS/INSU UMI 3386, Departamento de Astronoma,
Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 11 Univ. Grenoble Alpes, CNRS,
IPAG, F-38000 Grenoble, France; 12 Department of Physics and Astronomy, California State University Northridge,
18111 Nordhoff Street, Northridge, CA 91130, USA
2E-mail contact: isella at rice.edu
The Atacama Large Millimeter/submillimeter Array observations of protoplanetary disks acquired by the Disk Substructure at High Angular Resolution Project resolve the dust and gas emission on angular scales as small as 3
astronomical units, offering an unprecedented detailed view of the environment where planets form. In this Letter, we
present and discuss observations of the HD 163296 protoplanetary disk that imaged the 1.25 mm dust continuum and
12CO J = 2-1 rotational line emission at a spatial resolution of 4 and 10 au, respectively. The continuum observations
resolve and allow us to characterize the previously discovered dust rings at radii of 68 and 100. They also reveal new
small-scale structures, such as a dark gap at 10 au, a bright ring at 15 au, a dust crescent at a radius of 55 au, andseveral fainter azimuthal asymmetries. The observations of the CO and dust emission provide information about thevertical structure of the disk and allow us to directly constrain the dust extinction optical depth at the dust rings.
Furthermore, the observed asymmetries in the dust continuum emission corroborate the hypothesis that the complex
structure of the HD 163296 disk is the result of the gravitational interaction with yet-unseen planets.
Accepted by ApJL
https://arxiv.org/pdf/1812.04047

36

How planetary growth outperforms migration
Anders Johansen1 , Shigeru Ida2 and Ramon Brasser2
1

Lund Observatory, Lund University, Sweden; 2 ELSI, Tokyo Institute of Technology, Japan

E-mail contact: anders at astro.lu.se
Planetary migration is a major challenge for planet-formation theories. The speed of type-I migration is proportional
to the mass of a protoplanet, while the final decade of growth of a pebble-accreting planetary core takes place at a ratethat scales with the mass to the two-thirds power. This results in planetary growth tracks (i.e., the evolution of themass of a protoplanet versus its distance from the star) that become increasingly horizontal (migration-dominated)with the rising mass of the protoplanet. It has been shown recently that the migration torque on a protoplanet is
reduced proportional to the relative height of the gas gap carved by the growing planet. Here we show from 1D
simulations of planet–disc interaction that the mass at which a planet carves a 50% gap is approximately 2.3 times
the pebble isolation mass. Our measurements of the pebble isolation mass from 1D simulations match published 3D26

results relatively well, except at very low viscosities (α < 10−3 ) where the 3D pebble isolation mass is significantly
higher, possibly due to gap edge instabilities that are not captured in 1D. The pebble isolation mass demarks thetransition from pebble accretion to gas accretion. Gas accretion to form gas-giant planets therefore takes place overa few astronomical units of migration after reaching first the pebble isolation mass and, shortly after, the 50% gap
mass. Our results demonstrate how planetary growth can outperform migration both during core accretion and during
gas accretion, even when the Stokes number of the pebbles is small, St ∼ 0.01, and the pebble-to-gas flux ratio in
the protoplanetary disc is in the nominal range of 0.01–0.02. We find that planetary growth is very rapid in the firstmillion years of the protoplanetary disc and that the probability for forming gas-giant planets increases with the initialsize of the protoplanetary disc and with decreasing turbulent diffusion.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1811.00523

37 Venu M. KalariClassical T-Tauri stars with VPHAS+: II: NGC 6383 in Sh 2-012
1,2

1Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile; 2 Gemini-CONICYT,
Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D Santiago, Chile
E-mail contact: venukalari at gmail.com
This paper presents optical (ugriHα)–infrared (JHKs,3.6–8.0µm) photometry, and Gaia astrometry of 55 Classical TTauri stars (CTTS) in the star-forming region Sh 2-012, and its central cluster NGC 6383. The sample was identified
based on photometric Hα emission line widths, and has a median age of 2.8±1.6 Myr, with a mass range between
0.3–1 M⊙ . 94% of CTTS with near-infrared cross-matches fall on the near-infrared T-Tauri locus, with all stars
having mid-infrared photometry exhibiting evidence for accreting circumstellar discs. CTTS are found concentrated
around the central cluster NGC 6383, and towards the bright rims located at the edges of Sh 2-012. Stars across theregion have similar ages, suggestive of a single burst of star formation. Mass accretion rates (Ṁacc ) estimated via Hαand u-band line intensities show a scatter (0.3 dex) similar to spectroscopic studies, indicating the suitability of Hαphotometry to estimate Ṁacc . Examining the variation of Ṁacc with stellar mass (M∗ ), we find a smaller intercept in
the Ṁacc -M∗ relation than oft-quoted in the literature, providing evidence to discriminate between competing theories
of protoplanetary disc evolution.
Accepted by MNRAS
https://arxiv.org/pdf/1901.07511

38 IV. Characterizing substructures and interactions in disks around multiple star systems.
The Disk Substructures at High Angular Resolution Project (DSHARP):

Nicolás T. Kurtovic1 , Laura M. Pérez1 , Myriam Benisty1,2,3 , Zhaohuan Zhu4 , Shangjia Zhang4 , Jane
Huang5 , Sean M. Andrews5 , Cornelis P. Dullemond6, Andrea Isella7 , Xue-Ning Bai8 , John M. Carpenter9 ,Viviana V. Guzmán9,10 , Luca Ricci11 and David J. Wilner5 .
1

Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile.;
Unidad Mixta Internacional Franco-Chilena de Astronomı́a, CNRS/INSU UMI 3386.; 3 Univ. Grenoble Alpes,
CNRS, IPAG, 38000 Grenoble, France.; 4 Department of Physics and Astronomy, University of Nevada, Las Vegas,
4505 S. Maryland Pkwy, Las Vegas, NV, 89154, USA. 5 Harvard-Smithsonian Center for Astrophysics, 60 Garden
Street, Cambridge, MA 02138, USA. 6 Zentrum fr̈ Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120
Heidelberg, Germany. 7 Department of Physics and Astronomy, Rice University 6100 Main Street, MS-108, Houston,
TX 77005, USA. 8 Institute for Advanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing
100084, China. 9 Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile. 1 0 Institutode Astrofı́sica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile.
1
1 Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge,
CA 91130, USA.
2

E-mail contact: nicokurtovic@gmail.com
To characterize the substructures induced in protoplanetary disks by the interaction between stars in multiple systems,
27

we study the 1.25 mm continuum and the 12 CO(J = 2 − 1) spectral line emission of the triple systems HT Lup andAS 205, at scales of ≈ 5 au, as part of the “Disk Substructures at High Angular Resolution Project” (DSHARP). In
the continuum emission, we find two symmetric spiral arms in the disk around AS 205 N, with pitch angle of 14◦ , while
the southern component AS 205 S, itself a spectroscopic binary, is surrounded by a compact inner disk and a brightring at a radius of 34 au. The 12 CO line exhibits clear signatures of tidal interactions, with spiral arms, extended
arc-like emission, and high velocity gas, possible evidence of a recent close encounter between the disks in the AS 205
system, as these features are predicted by hydrodynamic simulations of fly-by encounters. In the HT Lup system, we
detect continuum emission from all three components. The primary disk, HT Lup A, also shows two-armed symmetricspiral structure with a pitch angle of 4◦ , while HT Lup B and C, located at 25 and 434 au in projected separation fromHT Lup A, are barely resolved with ∼ 5 and ∼ 10 au in diameter, respectively. The gas kinematics for the closest pair
indicates a different sense of rotation for each disk, which could be explained by either a counter rotation of the two
disks in different, close to parallel, planes, or by a projection effect of these disks with a close to 90◦ misalignment
between them.
Accepted by ApJL
https://arxiv.org/pdf/1812.04536

Extremely high excitation SiO lines in disk-outflow system in Orion Source I

39 Mi Kyoung Kim , Tomoya Hirota , Masahiro N. Machida , Yuko Matsushita , Kazuhito Motogi ,1,2

Naoko Matsumoto

3,7

3,4

5

5

6

1,8

& Mareki Honma

1

Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Hoshigaoka 2-12, Mizusawa-ku, Oshu,
Iwate 023-0861, Japan; 2 Korea Astronomy and Space Science Institute, Hwaam-dong 61-1, Yuseong-gu, Daejeon, 305348, Republic of Korea; 3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1,
Mitaka, Tokyo 181-8588, Japan; 4 Department of Astronomical Sciences, SOKENDAI (The Graduate University for
Advanced Studies), Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 5 Department of Earth and Planetary Sciences,
Faculty of Sciences, Kyushu University, Motooka 744, Nishi-ku, Fukuoka, Fukuoka 819-0395, Japan; 6 Graduate Schoolof Science and Engineering, Yamaguchi University, Yoshida 1677-1, Yamaguchi, Yamaguchi 753-8511, Japan; 7 The
Research Institute for Time Studies, Yamaguchi University, Yoshida 1677-1, Yamaguchi, Yamaguchi 753-8511, Japan; 8Department of Astronomical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hoshigaoka2-12,
Mizusawa-ku, Oshu, Iwate 023-0861, Japan
E-mail contact: mikyoung.kim at nao.ac.jp
We present high-resolution images of the submillimeter SiO line emissions of a massive young stellar object Orion
Source I using the Atacama Large Millimeter/ Submillimeter Array (ALMA) at band 8. We detected the 464 GHz
SiO v=4 J=11–10 line in Source I, which is the first detection of the SiO v=4 line in star-forming regions, together
with the 465 GHz 29 SiO v=2 J=11–10 and the 428 GHz SiO v=2 J=10–9 lines with a resolution of 50 AU. The 29 SiO
v=2 J=11–10 and SiO v=4 J=11–10 lines have compact structures with the diameter of <80 AU. The spatial andvelocity distribution suggest that the line emissions are associated with the base of the outflow and the surface of theedge-on disk. In contrast, SiO v=2 J=10–9 emission shows a bipolar structure in the direction of northeast-southwest
low-velocity outflow with ∼200 AU scale. The emission line exhibits a velocity gradient along the direction of the disk
elongation. With the assumption of the ring structure with Keplerian rotation, we estimated the lower limit of thecentral mass to be 7 solar mass and the radius of 12 AU< r <26 AU.
Accepted by ApJ
http://arxiv.org/pdf/1901.07208

40

The potential of combining MATISSE and ALMA observations: Constraining the structure of the innermost region in protoplanetary discs
Julia Kobus1 , Sebastian Wolf1 and Robert Brunngräber1
1

Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 15, 24118
Kiel, Germany
E-mail contact: jkobus at astrophysik.uni-kiel.de28

In order to study the initial conditions of planet formation, it is crucial to obtain spatially resolved multi-wavelength
observations of the innermost region of protoplanetary discs. We evaluate the advantage of combining observations
with MATISSE/VLTI and ALMA to constrain the radial and vertical structure of the dust in the innermost regionof circumstellar discs in nearby star-forming regions. Based on a disc model with a parameterized dust density
distribution, we apply 3D radiative-transfer simulations to obtain ideal intensity maps. These are used to derive thecorresponding wavelength-dependent visibilities we would obtain with MATISSE as well as ALMA maps simulatedwith CASA.
Within the considered parameter space, we find that constraining the dust density structure in the innermost 5 auaround the central star is challenging with MATISSE alone, whereas ALMA observations with reasonable integration
times allow us to derive significant constraints on the disc surface density. However, we find that the estimationof the different disc parameters can be considerably improved by combining MATISSE and ALMA observations.
For example, combining a 30-minute ALMA observation (at 310 GHz with an angular resolution of 0.03 arcsec) for
MATISSE observations in the L and M bands (with visibility accuracies of about 3 %) allows the radial density slope
and the dust surface density profile to be constrained to within ∆α = 0.3 and ∆(α − β) = 0.15, respectively. For an
accuracy of ∼ 1 % even the disc flaring can be constrained to within ∆β = 0.1. To constrain the scale height to within
5 au, M band accuracies of 0.8 % are required. While ALMA is sensitive to the number of large dust grains settled
to the disc midplane we find that the impact of the surface density distribution of the large grains on the observed
quantities is small.
Accepted by A&A
https://arxiv.org/pdf/1901.04342

Gas flow around a planet embedded in a protoplanetary disc: the dependence on theplanetary mass

41 Ayumu Kuwahara , Hiroyuki Kurokawa , and Shigeru Ida
1

2

2

1

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, 1528551, Japan; 2 Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo, 152-8550,
Japan
E-mail contact: kuwahara.a.aa at m.titech.ac.jp
The three-dimensional structure of the gas flow around a planet is thought to influence the accretion of both gas andsolid materials. In particular, the outflow in the mid-plane region may prevent the accretion of the solid materials
and delay the formation of super-Earths’ cores. However, it is not yet understood how the nature of the flow field andoutflow speed change as a function of the planetary mass. In this study, we investigate the dependence of gas flow
around a planet embedded in a protoplanetary disc on the planetary mass. Assuming an isothermal, inviscid gas disc,we perform three-dimensional hydrodynamical simulations on the spherical polar grid, which has a planet located at
its centre. We find that gas enters the Bondi or Hill sphere at high latitudes and exits through the mid-plane regionof the disc regardless of the assumed dimensionless planetary mass m = RBondi /H, where RBondi and H are theBondi radius of the planet and disc scale height, respectively. The altitude from where gasp
predominantly enters theenvelope varies
withtheplanetarymass.
The
outflow
speed
can
be
expressedas|u|=
3/2mcs (RBondi ≤ RHill )outpor |uout | = 3/2(m/3)1/3 cs (RBondi ≥ RHill ), where cs is the isothermal sound speed and RHill is the√Hill radius. The
outflow around a planet may reduce the accretion of dust and pebbles onto the planet when m >∼ St, where St is
the Stokes number. Our results suggest that the flow around proto-cores of super-Earths may delay their growth and,
consequently, help them to avoid runaway gas accretion within the lifetime of the gas disc.
Accepted by A&A
http://arxiv.org/pdf/1901.08253

Surveying the Giant HII Regions of the Milky Way with SOFIA: I. W 51 A

42 Wanggi Lim and James M. De Buizer
1

1

1

SOFIA-USRA, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035, USA29

E-mail contact: wlim at usra.edu
We discuss the first results from our mid-infrared imaging survey of Milky Way Giant HII regions with our detailed
analysis of W 51 A, which is one of the largest GHII regions in our Galaxy. We used the FORCAST instrument on
SOFIA to obtain 20 and 37 µm images of the central 10′ × 20′ area, which encompasses both of the G49.5-0.4 andG49.4-0.3 sub-regions. Based on these new data, and in conjunction with previous multi-wavelength observations,
we conjecture on the physical nature of several individual sources and sub-components within W 51 A. We find thatextinction seems to play an important role in the observed structures we see in the near- to mid-infrared, both globallyand locally. We used the SOFIA photometry combined with Spitzer -IRAC and Herschel -PACS photometry data toconstruct spectral energy distributions (SEDs) of sub-components and point sources detected in the SOFIA images.
We fit those SEDs with young stellar object models, and found 41 sources that are likely to be massive young stellar
objects, many of which are identified as such in this work for the first time. Close to half of the massive young stellar
objects do not have detectable radio continuum emission at cm wavelengths, implying a very young state of formation.
We derived luminosity-to-mass ratio and virial parameters of the extended radio sub-regions of W 51 A to estimate
their relative ages.
Accepted by ApJ
https://arxiv.org/pdf/1901.07561

43 of Filamentary Molecular Clouds

Magnetized interstellar molecular clouds: II. The Large-Scale Structure and Dynamics

Pak Shing Li1 , and Richard I. Klein1,2
1

Astronomy Department, University of California, Berkeley, CA 94720, USA; 2 Lawrence Livermore National Laboratory,P.O.Box 808, L-23, Livermore, CA 94550, USA
E-mail contact: psli at berkeley.edu
Ideal MHD high resolution AMR simulations with driven turbulence and self-gravity have been performed that demonstrate the formation of long filamentary molecular clouds at the converging location of large-scale turbulence flow,bounded by gravity, and the magnetic field helps shaping and reinforcing the long filamentary appearance. The main
filamentary cloud has a length of ∼4.4 pc. Instead of a monolithic cylindrical structure, the main cloud is shown to
be a collection of fiber/web-like sub-structures similar to filamentary clouds such as L1495. Unless the line-of-sightis close to the mean field direction, the large-scale magnetic field and striations in the simulation are found roughly
perpendicular to the long axis of the main cloud, similar to 1495. This provides strong support for a large-scale
moderately strong magnetic field surrounding L1495. We find that the projection effect from observations can leadto incorrect interpretations of the true three-dimensional physical shape, size, and velocity structure of the clouds.
Helical magnetic field structures found around filamentary clouds that are interpreted from Zeeman observations canbe explained by a simple bending of the magnetic field that pierces through the cloud. We demonstrate that two
dark clouds form a T-shape configuration which are strikingly similar to the Infrared dark cloud SDC13 leading to theinterpretation that SDC13 results from a collision of two long filamentary clouds. We show that a moderately strong
magnetic field (MA ∼ 1) is crucial for maintaining a long and slender filamentary cloud for a long period of time ∼0.5
million years.
Accepted by MNRAS
http://arxiv.org/pdf/1901.04593

Magma ascent in planetesimals: control by grain size

44 Tim Lichtenberg , Tobias Keller , Richard F. Katz , Gregor J. Golabek and Taras V. Gerya
1,∗

2

3

1

4

1

Institute of Geophysics, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland; 2 Department of Geophysics,
Stanford University, Stanford, CA 94305, United States; 3 Department of Earth Sciences, University of Oxford,
Oxford OX1 3AN, United Kingdom 3 Bayerisches Geoinstitut, University of Bayreuth, Universitätsstrasse 30, 95440
Bayreuth, Germany ∗ Current address: Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Rd,
Oxford OX1 3PU, United Kingdom
E-mail contact: tim.lichtenberg at physics.ox.ac.uk
30

Rocky planetesimals in the early solar system melted internally and evolved chemically due to radiogenic heatingfrom 26 Al. Here we quantify the parametric controls on magma genesis and transport using a coupled petrologicaland fluid mechanical model of reactive two-phase flow. We find the mean grain size of silicate minerals to be a key
control on magma ascent. For grain sizes larger than ≈ 1 mm, melt segregation produces distinct radial structure andchemical stratification. This stratification is most pronounced for bodies formed at around 1 Myr after formation of
Ca,Al-rich inclusions. These findings suggest a link between the time and orbital location of planetesimal formationand their subsequent structural and chemical evolution. According to our models, the evolution of partially molten
planetesimal interiors falls into two categories. In the magma ocean scenario, the whole interior of a planetesimal
experiences nearly complete melting, which would result in turbulent convection and core-mantle differentiation by
the rainfall mechanism. In the magma sill scenario, segregating melts gradually deplete the deep interior of theradiogenic heat source. In this case, magma may form melt-rich layers beneath a cool and stable lid, while coreformation would proceed by percolation. Our findings suggest that grain sizes prevalent during the internal heatingstage governed magma ascent in planetesimals. Regardless of whether evolution progresses toward a magma ocean
or magma sill structure, our models predict that temperature inversions due to rapid 26 Al redistribution are limited
to bodies formed earlier than ≈ 1 Myr after CAIs. We find that if grain size was smaller than ≈ 1 mm during peakinternal melting, only elevated solid–melt density contrasts (such as found for the reducing conditions in enstatitechondrite compositions) would allow substantial melt segregation to occur.
Accepted by Earth and Planetary Science Letters
https://doi.org/10.1016/j.epsl.2018.11.034
https://arxiv.org/pdf/1802.02157
blog post: http://bit.ly/2GZZ0e9

45 Tim Lichtenberg , Gregor J. Golabek , Remo Burn , Michael R. Meyer , Yann Alibert , Taras V.
A water budget dichotomy of rocky protoplanets from 26 Al-heating
1,∗

1

Gerya , Christoph Mordasini

2

3

4

3,5

3,5

1

Institute of Geophysics, ETH Zürich, Zürich, Switzerland; 2 Bayerisches Geoinstitut, University of Bayreuth,
Bayreuth, Germany; 3 Physikalisches Institut, University of Bern, Bern, Switzerland 4 Department of Astronomy,
University of Michigan, Ann Arbor, MI, USA 5 Center for Space and Habitability, University of Bern, Bern, Switzerland ∗ Present address: Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
E-mail contact: tim.lichtenberg at physics.ox.ac.uk
In contrast to the water-poor planets of the inner Solar System, stochasticity during planetary formation and orderof-magnitude deviations in exoplanet volatile contents suggest that rocky worlds engulfed in thick volatile ice layers
are the dominant family of terrestrial analogues among the extrasolar planet population. However, the distributionof compositionally Earth-like planets remains insufficiently constrained, and it is not clear whether the Solar System
is a statistical outlier or can be explained by more general planetary formation processes. Here we use numericalmodels of planet formation, evolution and interior structure to show that a planets bulk water fraction and radius
are anti-correlated with initial 26 Al levels in the planetesimal-based accretion framework. The heat generated by thisshort-lived radionuclide rapidly dehydrates planetesimals before their accretion onto larger protoplanets and yields asystem-wide correlation of planetary bulk water abundances, which, for instance, can explain the lack of a clear orbital
trend in the water budgets of the TRAPPIST-1 planets. Qualitatively, our models suggest two main scenarios for theformation of planetary systems: high-26 Al systems, like our Solar System, form small, water-depleted planets, whereas
those devoid of 26 Al predominantly form ocean worlds. For planets of similar mass, the mean planetary transit radiiof the ocean planet population can be up to about 10% larger than for planets from the 26 Al-rich formation scenario.
Accepted by Nature Astronomy Letters
https://doi.org/10.1038/s41550-018-0688-5
arXiv: https://arxiv.org/pdf/1902.04026
blog post: https://go.nature.com/2QEYth5

31

46 Xing Lu , Qizhou Zhang , Jens Kauffmann , Thushara Pillai , Adam Ginsburg , Elisabeth A. C. Mills ,Star Formation Rates of Massive Molecular Clouds in the Central Molecular Zone
1

2

3

7

4

8

5

6

9

J. M. Diederik Kruijssen , Steven N. Longmore , Cara Battersby , Hauyu Baobab Liu
Gu11

10

and Qiusheng

1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan; 2 Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; 3 Haystack Observatory, Massachusetts Institute of Technology, 99 Millstone Road, Westford, MA 01886, USA; 4 Boston University Astronomy
Department, 725 Commonwealth Avenue, Boston, MA 02215, USA; 5 National Radio Astronomy Observatory, 1003
Lopezville Rd., Socorro, NM 87801, USA; 6 Physics Department, Brandeis University, 415 South Street, Waltham, MA
02453, USA; 7 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße
12-14, D-69120 Heidelberg, Germany; 8 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK; 9 University of Connecticut, Department of Physics, 2152 Hillside Road, Storrs, CT
06269, USA; 10 European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei München, Germany; 11 School of Astronomy and Space Science, Nanjing University, Nanjing, Jiangsu 210093, China
E-mail contact: xinglv.nju at gmail.com
We investigate star formation at very early evolutionary phases in five massive clouds in the inner 500 pc of the Galaxy,
the Central Molecular Zone. Using interferometer observations of H2O masers and ultra-compact H II regions, we
5−3find evidence of ongoing star formation embedded in cores of 0.2 pc scales and >densities. Among the∼10 cmfive clouds, Sgr C possesses a high (9%) fraction of gas mass in gravitationally bound and/or protostellar cores, and4−3follows the dense (>∼10 cm ) gas star formation relation that is extrapolated from nearby clouds. The other four
clouds have less than 1% of their cloud masses in gravitationally bound and/or protostellar cores, and star formation
rates 10 times lower than predicted by the dense gas star formation relation. At the spatial scale of these cores, thestar formation efficiency is comparable to that in Galactic disk sources. We suggest that the overall inactive starformation in these Central Molecular Zone clouds could be because there is much less gas confined in gravitationallybound cores, which may be a result of the strong turbulence in this region and/or the very early evolutionary stage ofthe clouds when collapse has only recently started.
Accepted by ApJ
https://arxiv.org/pdf/1901.07779

gap in HD 92945’s broad planetesimal disc revealed by ALMA
47 AS. Marino, B. Yelverton , M. Booth , V. Faramaz , G.M. Kennedy , L. Matrá and M.C. Wyatt
1,2

1

3

4

5,6

7

1

1

Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 2 Max Planck Institutefor Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 3 Astrophysikalisches Institut und Universitätssternwarte,Friedrich-Schiller-Universität Jena, Schillergäßchen 2-3, 07745 Jena, Germany; 4 Jet Propulsion Laboratory, California
Institute of Technology, 4800 Oak Grove drive, Pasadena CA 91109, USA; 5 Department of Physics, Universityof Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK; 6 Centre for Exoplanets and Habitability, University of
Warwick, Gibbet Hill Road, Coventry, CV4 7AL, UK; 7 Harvard-Smithsonian Center for Astrophysics, 60 Garden
Street, Cambridge, MA 02138, USA
E-mail contact: sebastian.marino.estay at gmail.com
In the last few years, multiwavelength observations have revealed the ubiquity of gaps/rings in circumstellar discs.
Here we report the first ALMA observations of HD 92945 at 0.86 mm, that reveal a gap at about 73±3 au within abroad disc of planetesimals that extends from 50 to 140 au. We find that the gap is 20+10−8 au wide. If cleared by aplanet in situ, this planet must be less massive than 0.6 MJup , or even lower if the gap was cleared by a planet thatformed early in the protoplanetary disc and prevented planetesimal formation at that radius. By comparing opposite
sides of the disc we also find that the disc could be asymmetric. Motivated by the asymmetry and the fact thatplanets might be more frequent closer to the star in exoplanetary systems, we show that the gap and asymmetry could
be produced by two planets interior to the disc through secular resonances. These planets excite the eccentricity ofbodies at specific disc locations, opening radial gaps in the planetesimal distribution. New observations are necessary
to confirm if the disc is truly asymmetric, thus favouring the secular resonance model, or if the apparent asymmetryis due to a background galaxy, favouring the in-situ planet scenario. Finally, we also report the non-detection of CO32

and HCN gas confirming that no primordial gas is present. The CO and HCN non-detections are consistent with thedestruction of volatile-rich Solar System-like comets.
Accepted by MNRAS
http://arxiv.org/pdf/1901.01406

On the physical nature of accretion disc viscosity

48 R.G. Martin , C.J. Nixon , J.E. Pringle , M. Livio
1,2

2

2,3

1

1

Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas,
NV 89154, USA; 2 Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK; 3 Instituteof Astronomy, Madingley Road, Cambridge, CB3 0HA, UK
E-mail contact: rebecca.martin at unlv.edu
We use well-established observational evidence to draw conclusions about the fundamental nature of the viscosity inaccretion discs. To do this, we first summarise the observational evidence for the value of the dimensionless accretion
disc viscosity parameter α, defined by Shakura & Sunyaev (1973, 1976). We find that, for fully ionized discs, thevalue of ? is readily amenable to reliable estimation and that the observations are consistent with the hypothesis thatα ∼ 0.2–0.3. In contrast in discs that are not fully ionized, estimates of the value of α are generally less direct andthe values obtained are generally <0.01 and often ≪0.01. We conclude that this gives us crucial information about
the nature of viscosity in accretion discs. First, in fully ionized discs the strength of the turbulence is always limited
by being at most trans-sonic. This implies that it is necessary that credible models of the turbulence reflect thisfact. Second, the smaller values of α found for less ionized, and therefore less strongly conducting, discs imply thatmagnetism plays a dominant role. This provides important observational support for the concept of magneto-rotational
instability (MRI) driven hydromagnetic turbulence.
Accepted by New Astronomy
http://arxiv.org/pdf/1901.01580

49

On the Ubiquity and Stellar Luminosity Dependence of Exocometary CO Gas: Detection around M Dwarf TWA 7
L. Matrá1 , K.I. Öberg1 , D.J. Wilner1 , J. Olofsson2,3 , and A. Bayo2,31

Department of Astrophysical Sciences, Princeton University, Princetion, NJ 08544; 2 Institute for Advanced Study,
Tsinghua University, Beijing 100084, China; 3 Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084,
China; 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA, 02138; 5 Department of
Physics, Purdue University, 525 Northwestern Ave., West Lafayette, IN 47907, USA
E-mail contact: luca.matra at cfa.harvard.edu

Millimeter observations of CO gas in planetesimal belts show a high detection rate around A stars, but few detections
for later type stars. We present the first CO detection in a planetesimal belt around an M star, TWA 7. The opticallythin CO (J=3-2) emission is co-located with previously identified dust emission from the belt, and the emission
velocity structure is consistent with Keplerian rotation around the central star. The detected CO is not well shieldedagainst photodissociation, and must thus be continuously replenished by gas release from exocomets within the belt.
We analyze in detail the process of exocometary gas release and destruction around young M dwarfs and how thisprocess compares to earlier type stars. Taking these differences into account, we find that CO generation throughexocometary gas release naturally explains the increasing CO detection rates with stellar luminosity, mostly because
the CO production rate from the collisional cascade is directly proportional to stellar luminosity. More luminousstars will therefore on average host more massive (and hence more easily detectable) exocometary CO disks, leading
to the higher detection rates observed. The current CO detection rates are consistent with a ubiquitous release of
exocometary gas in planetesimal belts, independent of spectral type.
Accepted by AJ
http://arxiv.org/pdf/1901.05004

33

50

Thermal balance and comparison of gas and dust properties of dense clumps in the
Hi-GAL survey
Manuel Merello1,2, Sergio Molinari1 , Kazi L. J. Rygl3 , Neal J. Evans II4,5,6 , Davide Elia1 , Eugenio
Schisano1 , Alessio Traficante1 , Yancy Shirley7 , Brian Svoboda7 and Paul F. Goldsmith8
1

INAF-Istituto di Astrofisica e Planetologia Spaziale, Via Fosso del Cavaliere 100, I-00133 Roma, Italy; 2 Universidade
de São Paulo, IAG Rua do Matão, 1226, Cidade Universitária, 05508-090, São Paulo, Brazil; 3 Italian ALMA Regional
Centre, INAF-IRA, Via P. Gobetti 101, 40129 Bologna, Italy; 4 Department of Astronomy, The University of Texas atAustin, 2515 Speedway, Stop C1400, Austin, Texas 78712-1205, USA; 5 Korea Astronomy and Space Science Institute,
776 Daedeokdaero, Daejeon 305-348, Korea; 6 Humanitas College, Global Campus, Kyung Hee University, Yongin-shi
17104, Korea; 7 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 8
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA 91109, USA
E-mail contact: manuel.merello at usp.br
We present a comparative study of physical properties derived from gas and dust emission in a sample of 1068
dense Galactic clumps. The sources are selected from the crossmatch of the Hi-GAL survey with 16 catalogues of
NH3 line emission in its lowest inversion (1,1) and (2,2) transitions. The sample covers a large range in masses
and bolometric luminosities, with surface densities above Σ = 0.1 g cm−2 and with low virial parameters α < 1.
The comparison between dust and gas properties shows an overall agreement between Tkin and Tdust at volumetricdensities n ≥ 1.2 × 104 cm−3 , and a median fractional abundance χ(NH3 )= 1.46 × 10−8. While the protostellar clumps
in the sample have small differences between Tkin and Tdust , prestellar clumps have a median ratio Tkin /Tdust = 1.24,
suggesting that these sources are thermally decoupled. A correlation is found between the evolutionary tracer L/M
and the parameters Tkin /Tdust and χ(NH3 ) in prestellar sources and protostellar clumps with L/M < 1 L⊙ M⊙ −1 .
In addition, a weak correlation is found between non-thermal velocity dispersion and the L/M parameter, possibly
indicating an increase of turbulence with protostellar evolution in the interior of clumps. Finally, different processes
are discussed to explain the differences between gas and dust temperatures in prestellar candidates, and the origin of
non-thermal motions observed in the clumps.
Accepted by MNRAS
https://arxiv.org/pdf/1812.06134

51 Rotational Braking

The Rotation-Disk Connection in Young Brown Dwarfs: Strong Evidence for Early

Keavin Moore1,2 , Aleks Scholz3 and Ray Jayawardhana1,41Faculty of Science, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada; 2 Department of Earth &Planetary Sciences, McGill University, 3450 rue University, Montreal, QC H3A 0E8, Canada; 3 SUPA, School of Physics& Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, United Kingdom; 4 Department of
Astronomy, Cornell University, Ithaca, NY 14853, USA
E-mail contact: keavin.moore at mail.mcgill.ca
We use Kepler/K2 lightcurves to measure rotation periods of brown dwarfs and very low mass stars in the Upper
Scorpius star-forming region. Our sample comprises a total of 104 periods. Depending on the assumed age of Upper
Scorpius, about a third of them are for brown dwarfs. The median period is 1.28 d for the full sample and 0.84 dfor the probable brown dwarfs. With this period sample, we find compelling evidence for early rotational braking inbrown dwarfs, caused by the interaction between the central object and the disk. The median period for objects withdisks is at least 50% longer than for those without. Two brown dwarfs show direct signs of ’disk-locking’ in theirlightcurves, in the form of dips that recur on a timescale similar to the rotation period. Comparing the period samples
for brown dwarfs at different ages, there is a clear need to include rotational braking into period evolution tracks
between 1 and 10 Myr. A locked period over several Myr followed by spin-up due to contraction fits the observational
data. We conclude that young brown dwarfs are affected by the same rotational regulation as stars, though they start
off with significantly faster rotation, presumably set by initial conditions.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1901.05523

34

52

Temperature Structure in the Inner Regions of Protoplanetary Disks: Inefficient Accretion Heating by Energy Dissipation Profile of Nonideal Magnetohydrodynamics
Shoji Mori1 , Xue-Ning Bai2 and Satoshi Okuzumi3
1

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8551, Japan;
Institute for Advanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China; 3Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo, 152-8551, Japan2

E-mail contact: mori.s at geo.titech.ac.jp
Gas temperature in protoplanetary disks (PPDs) is determined by a combination of irradiation heating and accretion
heating, with the latter conventionally attributed to turbulent dissipation. However, recent studies have suggested
that the inner disk (a few AU) is largely laminar with accretion primarily driven by magnetized disk winds, as aresult of non-ideal magnetohydrodynamic (MHD) effects from weakly ionized gas, suggesting an alternative heating
mechanism by Joule dissipation. We perform local stratified MHD simulations including all three non-ideal MHD
effects (Ohmic, Hall, and ambipolar diffusion), and investigate the role of Joule heating and the resulting disk verticaltemperature profiles. We find that in the inner disk, as Ohmic and ambipolar diffusion strongly suppress electricalcurrent around the midplane, Joule heating primarily occurs at several scale heights above the midplane, making
midplane temperature much lower than that with the conventional viscous heating model. Including the Hall effect,
Joule heating is enhanced/reduced when magnetic fields threading the disks are aligned/anti-aligned with the disk
rotation, but is overall ineffective. Our results further suggest that the midplane temperature in inner PPDs is almost
entirely determined by irradiation heating, unless viscous heating can trigger thermal ionization in the disk innermost
region to self-sustain MRI turbulence.
Accepted by ApJ
http://arxiv.org/pdf/1901.06921

A 10-M⊙ YSO with a Keplerian disk and a nonthermal radio jet

53 L. Moscadelli , A. Sanna , R. Cesaroni , V.M. Rivilla , C. Goddi , and K.L.J. Rygl
1

2

1

1

3,4

5

1

INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 MPIfR, Auf dem Hügel 69,
53121, Bonn, Germany; 3 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands;
4
Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL, Nijmegen, The Netherlands; 5INAF - Istituto di Radioastronomia & Italian ALMA Regional Centre, Via P. Gobetti 101, 40129, Bologna, Italy
E-mail contact: mosca at arcetri.astro.it
We previously observed the star-forming region G16.59−0.05 through interferometric observations of both thermal
and maser lines, and identified a high-mass young stellar object (YSO) which is surrounded by an accretion disk anddrives a nonthermal radio jet. We performed high-angular-resolution (beam FWHM ∼0.′′ 15) 1.2-mm continuum andline observations towards G16.59−0.05 with the Atacama Large Millimeter Array (ALMA). The main dust clump,with size ∼104 au, is resolved into four relatively compact (diameter ∼2000 au) millimeter (mm) sources. The source
harboring the high-mass YSO is the most prominent in molecular emission. By fitting the emission profiles of several
unblended and optically thin transitions of CH3 OCH3 and CH3 OH, we derived gas temperatures inside the mmsources in the range 42–131 K, and calculated masses of 1–5 M⊙ . A well-defined Local Standard of Rest velocity(VLSR ) gradient is detected in most of the high-density molecular tracers at the position of the high-mass YSO,
pinpointed by compact 22-GHz free-free emission. This gradient is oriented along a direction forming a large (∼70
degree) angle with the radio jet, traced by elongated 13-GHz continuum emission. The butterfly-like shapes of theP-V plots and the linear pattern of the emission peaks of the molecular lines at high velocity confirm that this VLSR
gradient is due to rotation of the gas in the disk surrounding the high-mass YSO. The disk radius is ∼500 au, and the
VLSR distribution along the major axis of the disk is well reproduced by a Keplerian profile around a central mass of′′
10±2 M⊙ . The position of the YSO is offset by >∼0. 1 from the axis of the radio jet and the dust emission peak. To
explain this displacement we argue that the high-mass YSO could have moved from the center of the parental mm
source owing to dynamical interaction with one or more companions.
Accepted by A&A
http://arxiv.org/pdf/1901.02713

35

54

55

Disruption of the Orion Molecular Core 1 by the stellar wind of the massive star Θ1 Ori
C
C. Pabst1 , R. Higgins2,J.R. Goicoechea3 ,D. Teyssier4 , O. Berne5 , E. Chambers6 , M. Wolfire7 , S. Suri2 ,R. Guesten8 , J. Stutzki2 , U.U. Graf2 , C. Risacher8,9 , A.G.G.M. Tielens1
1

Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333CA Leiden, The Netherlands; 2 I. Physikalisches
Institut der Universität zu Köln, Zlpicher Strasse 77, 50937 Koln, Germany; 3 Instituto de Fsica Fundamental (CSIC),
Calle Serrano 121, 28006 Madrid, Spain; 4 Telespazio Vega UK Ltd for ESA/ESAC, Camino bajo del Castillo, s/n,
Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, E-28692 Madrid, Spain; 5 IRAP, Universit de Toulouse,
CNRS, CNES, Université Paul Sabatier, (Toulouse), France; 6 USRA/SOFIA, NASA Ames Research Center, Mail
Stop 232-12, BuildingN232, PO Box 1, Moffett Field, CA94035-0001, USA; 7 Department of Astronomy, Universityof Maryland, College Park, MD 20742, USA; 8 Max-Planck-Institut für Radioastronomie, Auf dem Hugel 69, 53121
Bonn, Germany; 9 IRAM, 300 rue de la Piscine, 38406, St. Martin d’Hères, France
E-mail contact: olivier.berne at gmail.com
Massive stars inject mechanical and radiative energy into the surrounding environment, which stirs it up, heats thegas, produces cloud and intercloud phases in the interstellar medium, and disrupts molecular clouds (the birth sites of
new stars). Stellar winds, supernova explosions and ionization by ultraviolet photons control the lifetimes of molecular
clouds. Theoretical studies predict that momentum injection by radiation should dominate that by stellar winds, but
this has been difficult to assess observationally. Velocity-resolved large-scale images in the fine-structure line of ionizedcarbon ([C II]) provide an observational diagnostic for the radiative energy input and the dynamics of the interstellar
medium around massive stars. Here we report observations of a one-square-degree region (about 7 pc in diameter)of Orion molecular core — the region nearest to Earth that exhibits massive-star formation — at a resolution of
16′′ (0.03 pc) in the [C II] line at 1.9 THz (158 µm). The results reveal that the stellar wind originating from themassive star Θ1 Orionis C has swept up the surrounding material to create a bubble roughly four pc in diameter witha 2,600-solar-mass shell, which is expanding at 13 km s−1 . This finding demonstrates that the mechanical energy fromthe stellar wind is converted very efficiently into kinetic energy of the shell and causes more disruption of the Orion
molecular core 1 than do photo-ionization and evaporation or future supernova explosions.
Accepted by Nature
http://arxiv.org/pdf/1901.04221

Understanding formation of young, distributed low-mass stars and clusters in the W4
cloud complex
Neelam Panwar1, 3, Manash R. Samal2 , A.K. Pandey1 , H.P. Singh3 , Saurabh Sharma1
1

Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital - 263001, India; 2 Physical ResearchLaboratory, Navrangpura, Ahmedabad - 380009, India; 3 Department of Physics & Astrophysics, University of Delhi,
Delhi-110007, India
E-mail contact: neelam 1110 at yahoo.co.in
It is well known that most of the stars form in rich clusters. However, recent Spitzer observations have shown thata significant number of stars also form in distributed mode, origin of which is not well understood. In this work, we
aim to investigate clustered and distributed mode of star formation in the W4 complex. To do so, we identified andcharacterized the young stellar population associated with the region using homogeneous infra-red data-sets obtained
from 2MASS, GLIMPSE, MIPS and WISE surveys. We make stellar surface density and minimum spanning treemaps to identify young clusters, and use Spitzer images to identify irradiated structures, such as elephant trunk-likestructures (ETLSs) and pillars in the region. The surface density distribution of the young stellar objects (YSOs)
reveals three new clusterings and ∼50% distributed protostars in the Hii region. The clusters are of low-mass nature
but significantly younger than the central cluster IC 1805. We identified ∼38 ETLSs in the region, a majority of which
consist of one or a few stars at their tips. We find these stars are low-mass (< 2 M⊙ ) YSOs, located at the outskirts(> 17 pc) of the cluster IC 1805 and are part of scattered distributed population. We argued that the star formationin the ETLSs of W4 is going on possibly due to triggering effect of expanding W4 bubble. Although high-resolution
photometric and spectroscopic data would be required to confirm the scenario, nonetheless, we discuss the implicationsof this scenario for our understanding of distributed low-mass star formation in cloud complexes as opposed to other36

mechanisms such as turbulent fragmentation and dynamical ejection.
Accepted by AJ
http://arxiv.org/pdf/1901.00888

56

The Disk Substructures at High Angular Resolution Project (DSHARP): X. Multiple
rings, a misaligned inner disk, and a bright arc in the disk around the T Tauri star
HD 143006
Laura M. Pérez1 , Myriam Benisty1,2,3 , Sean M. Andrews4 , Andrea Isella5 , Cornelis P. Dullemond6 , Jane
Huang4 , Nicolás T. Kurtovic1 , Viviana V. Guzmán7,8 , Zhaohuan Zhu9 , Tilman Birnstiel10, Shangjia
Zhang9 , John M. Carpenter7 , David J. Wilner4 , Luca Ricci1 1, Xue-Ning Bai1 2, Erik Weaver5 , andKarin I. Öberg4
1

Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile;
Unidad Mixta Internacional Franco-Chilena de Astronomı́a, CNRS/INSU UMI 3386, France; 3 Univ. Grenoble
Alpes, CNRS, IPAG, 38000 Grenoble, France; 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
Cambridge, MA 02138, USA; 5 Department of Physics and Astronomy, Rice University 6100 Main Street, MS-108,
Houston, TX 77005, USA; 6 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg,
Germany; 7 Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile; 8 Instituto de
Astrofı́sica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile; 9
Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV,
89154, USA; 1 0 University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstr.
1, 81679 Munich, Germany; 1 1 Department of Physics and Astronomy, California State University Northridge, 18111
Nordhoff Street, Northridge, CA 91130, USA; 1 2 Institute for Advanced Study and Tsinghua Center for Astrophysics,
Tsinghua University, Beijing 100084, China E-mail contact: lperez at das.uchile.cl2

We present a detailed analysis of new ALMA observations of the disk around the T-Tauri star HD 143006, whichat 46 mas (7.6 au) resolution reveal new substructures in the 1.25 mm continuum emission. The disk resolves into
a series of concentric rings and gaps together with a bright arc exterior to the rings that resembles hydrodynamics
simulations of a vortex, and a bridge-like feature connecting the two innermost rings. Although our 12 CO observations
at similar spatial resolution do not show obvious substructure, they reveal an inner disk depleted of CO emission. Fromthe continuum emission and the CO velocity field we find that the innermost ring has a higher inclination than theoutermost rings and the arc. This is evidence for either a small (∼ 8◦ ) or moderate (∼ 41◦ ) misalignment between the
inner and outer disk, depending on the specific orientation of the near/far sides of the inner/outer disk. We compare
the observed substructures in the ALMA observations with recent scattered light data from VLT/SPHERE of thisobject. In particular, the location of narrow shadow lanes in the SPHERE image combined with pressure scale height
estimates, favor a large misalignment of about 41◦ . We discuss our findings in the context of a dust-trapping vortex,
planet-carved gaps, and a misaligned inner disk due to the presence of an inclined companion to HD 143006.
Accepted by ApJ Letters
https://doi.org/10.3847/2041-8213/aaf745

57

Infrared imaging of high-mass young stellar objects: Evidence of multiple shocks andof a new proto-star/star eclipsing system
Paolo Persi1 and Mauricio Tapia2
1

NAF-Istituto Astrofisica e Planetologia Spaziale, Via Fosso del Cavaliere 100, Roma, 00133, Italy; 2 Instituto de
Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada, B. C., 22860, Mexico
E-mail contact: mt at astro.unam.mx
We present deep near- and mid-infrared images of six high-mass young stellar objects (YSOs) in order to help understand the physical mechanisms of their formation. We have searched for shocked H2 emission around such massive
protostars. All but one of these regions exhibit series of molecular hydrogen emission knots, either in perfect alignment
or in more complex configurations. In the case of the Class I object Mol 7, the protostars driving a couple of highly
bipolar collimated outflows appear to be members of a binary or multiple system. A similar scenario appears to apply

37

to Mol 143. The protostar Mol 12 drives a large low-collimated bipolar outflow with a number of H2 emission nebulosities. In two other methanol cores studied here, we also found shocked molecular hydrogen knots driven by highly
embedded YSOs, some of them in clusters. From their near-IR to millimetre-wavelength spectral energy distributions,
we derived stellar masses and temperatures, extinctions, luminosities, disk masses, and accretion rates. We provide
photometric evidence that the dense dust core housing Mol 12, a Class I YSO, has eclipsed the light of an early-type
main-sequence star. The latter is probably a physical companion to the proto-star, as indicated by both having nearly
identical coordinates and parallaxes as measured by Gaia (DR2) in the case of the star and by VLBI techniques in thecase of the of the water maser associated to the YSO. This eclipse lasted about 15 years (1985-2000) and amounted
to ∆AV ≃ 22. Since the year 2002, no further significant variations have been recorded.
Accepted by MNRAS

ftp://ftp.astrosen.unam.mx/iauname/mt/preprints/persiandtapiawappdx.pdf

58

Massive and low-mass protostars in massive “starless” cores
Thushara Pillai1,2 , Jens Kauffmann1,3 , Qizhou Zhang4 , Patricio Sanhueza5 , Silvia Leurini1,6 , Ke Wang7 ,T.K. Sridharan4 , Carsten König1
1

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 2 Institute for Astrophysical Research, 725 Commonwealth Ave, Boston University, Boston, MA 02215, USA; 3 Haystack Observatory, Massachusetts Institute of Technology, 99 Millstone Road, Westford, MA 01886, USA; 4 Harvard-Smithsonian Center for
Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 5 National Astronomical Observatory of Japan, National
Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 6 INAF - Osservatorio Astronomico di
Cagliari, via della Scienza 5, 09047, Selargius (CA), Italy; 7 European Southern Observatory, Karl-Schwarzschild-Str.
2, D-85748 Garching bei München, Germany
E-mail contact: tpillai.astro at gmail.com
The infrared dark clouds (IRDCs) G11.11−0.12 and G28.34+0.06 are two of the best-studied IRDCs in our Galaxy.
These two clouds host clumps at different stages of evolution, including a massive dense clump in both clouds thatis dark even at 70 and 100 µm. Such seemingly quiescent massive dense clumps have been speculated to harborcores that are precursors of high-mass stars and clusters. We observed these two “prestellar” regions at 1 mm with
the Submillimeter Array (SMA) with the aim of characterizing the nature of such cores. We show that the clumps
fragment into several low- to high-mass cores within the filamentary structure of the enveloping cloud. However, while
the overall physical properties of the clump may indicate a starless phase, we find that both regions host multiple
outflows. The most massive core though 70 µm dark in both clumps is clearly associated with compact outflows.
Such low-luminosity, massive cores are potentially the earliest stage in the evolution of a massive protostar. We also
identify several outflow features distributed in the large environment around the most massive core. We infer thatthese outflows are being powered by young, low-mass protostars whose core mass is below our detection limit. Thesefindings suggest that low-mass protostars have already formed or are coevally formed at the earliest phase of high-massstar formation.
Accepted by A&A
http://arxiv.org/pdf/1901.07582

A deep X-ray view of the Class I YSO Elias 29 with XMM-Newton and NuSTAR

59 I. Pillitteri , S. Sciortino , F. Reale , G. Micela , C. Argiroffi , E. Flaccomio , and B. Stelzer
1,2

1

1,3

1

3

1

4,1

1

INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy; 2 Harvard-Smithsonian
Center for Astrophysics, 60 Garden St., 02138 Cambridge MA, USA; 3 Università degli Studi di Palermo, Piazza delParlamento 1, 90134 Palermo, Italy; 4 Eberhard Karls Universität, Institut für Astronomie und Astrophysik, Sand 1,
72076 Tübingen, Germany
E-mail contact: ignazio.pillitteri at inaf.it
We investigated the X-ray characteristics of the Class I YSO Elias 29 with joint XMM-Newton and NuSTAR observations of 300 ks and 450 ks, respectively. These are the first observations of a very young (<1 Myr) stellar object
in a band encompassing simultaneously both soft and hard X-rays. In addition to the hot Fe complex at 6.7 keV, we38

observed fluorescent emission from Fe at ∼6.4 keV, confirming the previous findings. The line at 6.4 keV is detectedduring quiescent and flaring states and its flux is variable. The equivalent width is found varying in the ≈0.15–0.5
keV range. These values make unrealistic a simple model with a centrally illuminated disk and suggest a role of thecavity containing Elias 29 and possibly reverberation processes that could occur in it. We observed two flares, withduration of 20 ks and 50 ks, respectively. We systematically observed an increase of NH during the flares of a factor
five. This behavior has been observed during flares previously detected in Elias 29 with XMM-Newton and ASCA. The
phenomenon hints that the flaring regions could be buried under the accretion streams and at high stellar latitudes,
as the X-rays from flares pass through gas denser than the gas along the line of sight of the quiescent corona. In adifferent scenario, a contribution from scattered soft photons to the primary coronal emission could mimic a shallower
NH in the quiescent spectrum. In the spectrum of the full NuSTAR exposure, we detect hard X-ray emission in
the band ≈20–80 keV in excess with respect to the thermal emission. The hard X-ray emission could be due to a
population of energetic electrons accelerated by the magnetic field along the accretion streams. These particles could
concur to pumping up the Fe fluorescence of cold Fe of the disk along with X-ray photons with E > 7.11 keV.
Accepted by A&A
http://arxiv.org/pdf/1901.07814

60

A pilot survey of the binarity of Massive Young Stellar Objects with K band adaptive
opticsRobert Pomohaci1 , René D. Oudmaijer1 , Simon P. Goodwin2
1

School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK; 2 Department of
Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK
E-mail contact: rob.pomohaci at gmail.com
We present the first search for binary companions of Massive Young Stellar Objects (MYSOs) using AO-assisted Kband observations, with NaCo at the VLT. We have surveyed 32 MYSOs from the RMS catalogue, probing the widest
companions, with a physical separation range of 400–46,000 au, within the predictions of models and observations for
multiplicity of MYSOs. Statistical methods are employed to discern whether these companions are physical rather
than visual binaries. We find 18 physical companions around 10 target objects, amounting to a multiplicity fraction of
31±8% and a companion fraction of 53±9%. For similar separation and mass ratio ranges, MYSOs seem to have morecompanions than T Tauri or O stars, respectively. This suggests that multiplicity increases with mass and decreases
with evolutionary stage. We compute very rough estimates for the mass ratios from the K band magnitudes, and theseappear to be generally larger than 0.5. This is inconsistent with randomly sampling the IMF, as predicted by thebinary capture formation theory. Finally, we find that MYSOs with binaries do not show any different characteristics
to the average MYSO in terms of luminosity, distance, outflow or disc presence.
Accepted by MNRAS
http://arxiv.org/pdf/1901.04716

61

The Gaia-ESO Survey: age spread in the star forming region NGC 6530 from the HR
diagram and gravity indicators
L. Prisinzano1 , F. Damiani1 , V. Kalari2,3 , R. Jeffries4 , R. Bonito1 , G. Micela1 , N. J. Wright4 , R.
J. Jackson4 , E. Tognelli5, M. G. Guarcello1 , J. S. Vink3 , A. Klutsch6 , F. M. Jiménez-Esteban7 , V.
Roccatagliata5,8,9 , G. Tautvaisienė10 , G. Gilmore11 , S. Randich8 , E. J. Alfaro12 , E. Flaccomio1 , S.
Koposov11 , A. Lanzafame13 , E. Pancino8 , M. Bergemann14 , G. Carraro15 , E. Franciosini8 , A. Frasca6 ,A. Gonneau11 , A. Hourihane11 , P. Jofré16 , J. Lewis11 , L. Magrini8 , L. Monaco16 , L. Morbidelli8, G. G.
Sacco8 , C.C. Worley11 and S. Zaggia17
1
INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134, Palermo, Italy; 2 Departamento de
Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile; 3 Armagh Observatory and Planetarium, College Hill,
Armagh, BT61 9DG, UK; 4 Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, United Kingdom;
5
Department of Physics ‘E. Fermi’, University of Pisa, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy; 6 INAF Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123, Catania, Italy; 7 Departmento de Astrofı́sica, Centro de
Astrobiologı́a (INTA-CSIC), ESAC Campus, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid,39

Spain; 8 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Florence, Italy; 9 INFN, Sezione di Pisa,
Largo Pontecorvo 3, 56127 Pisa, Italy; 10 Astronomical Observatory, Institute of Theoretical Physics and Astronomy,
Vilnius University; 11 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United
Kingdom; 12 Instituto de Astrofı́sica de Andalucı́a-CSIC, Apdo. 3004, 18080 Granada, Spain; 13 Dipartimento di Fisica
e Astronomia, Universit di Catania, via S. Sofia 78, 95123, Catania, Italy; 14 Max Planck Institute for Astronomy,
Koenigstuhl 17, 69117 Heidelberg, Germany; 15 Dipartimento di Fisica e Astronomia Galileo Galilei, Università di
Padova, Vicolo Osservatorio 3, I-35122, Padova, Italy; 16 Departamento de Ciencias Fisicas, Universidad Andres Bello,
Republica 220, Santiago, Chile; 17 INAF - Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
E-mail contact: loredana.prisinzano at inaf.it
In very young clusters, the stellar age distribution is the empirical proof of the duration of star cluster formation andthus it gives indications of the physical mechanisms involved in the star formation process. Determining the amountof interstellar extinction and the correct reddening law are crucial steps to derive fundamental stellar parameters andin particular accurate ages from the HR diagram. In this context, we derived accurate stellar ages for NGC 6530, theyoung cluster associated with the Lagoon Nebula to infer the star formation history of this region. We use the GaiaESO survey observations of the Lagoon Nebula, together with photometric literature data and Gaia DR2 kinematics,
to derive cluster membership and fundamental stellar parameters. Using spectroscopic effective temperatures, weanalyze the reddening properties of all objects and derive accurate stellar ages for cluster members. We identified 652
confirmed and 9 probable members. The reddening inferred for members and non-members allows us to distinguishforeground objects, mainly main-sequence (MS) stars, and background objects, mainly giants. This classification is inagreement with the distances inferred from Gaia DR2 parallaxes for these objects. The foreground and backgroundstars show a spatial pattern that allows us to trace the three-dimensional structure of the nebular dust component.
Finally, we derive stellar ages for 382 confirmed cluster members for which we obtained the individual reddening values.
In addition, we find that the gravity-sensitive γ index distribution for the M-type stars is correlated with stellar age.
For all members with Teff < 5500 K, the mean logarithmic age is 5.84 (units of years) with a dispersion of 0.36 dex.
The age distribution of stars with accretion and/or disk (CTTSe) is similar to that of stars without accretion andwithout disk (WTTSp). We interpret this dispersion as evidence of a real age spread since the total uncertainties onage determinations, derived from Monte Carlo simulations, are significantly smaller than the observed spread. Thisconclusion is supported by the evidence of a decreasing of the gravity-sensitive γ index as a function of stellar ages.
The presence of a small age spread is also supported by the spatial distribution and the kinematics of old and young
members. In particular, members with accretion and/or disk, formed in the last 1 Myr, show evidence of subclustering
around the cluster center, in the Hourglass Nebula and in the M8-E region, suggesting a possible triggering of starformation events by the O-type star ionization fronts.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1901.09589

62

The HH34 jet/counterjet system at 1.5 and 4.5 µm
A. C. Raga1 , B. Reipurth2 , A. Noriega-Crespo3
1

Instituto de Ciencias Nucleares, UNAM, Mexico; 2 Institute for Astronomy, Univ. of Hawaii, USA; 3 Space Telescope
Science Institute, USA
E-mail contact: raga at nucleares.unam.mx

We present a (previously unpublished) 1.5 µm archival HST image of the HH 34 Herbig-Haro jet, in which the northerncounterjet is seen at an unprecedented angular resolution of ∼ 0.1′′ (this counterjet had only been imaged previously at
lower resolution with Spitzer). The jet/counterjet structure observed in this image shows evidence of low-amplitude,
point-symmetric deviations from the outflow axis, indicating the presence of a precession in the ejection direction. We
use the ratios between the 1.5 and 4.5 µm intensities of the emitting knots (from the HST image and from a previously
published 4.5 µm Spitzer image) to obtain an estimate of the spatial dependence of the optical extinction to the HH 34
jet/counterjet system. We find evidence for extinction from a central, dense core surrounding the outflow source andfrom a more extended region in the foreground of the HH 34 counterjet.
Accepted by RMxAA
http://bigbang.nucleares.unam.mx/astroplasmas/

40

63

MHD simulations of the formation and propagation of protostellar jets to observational
length scales
Jon P. Ramsey1,3 and David A. Clarke2
1

Centre for Star and Planet Formation, Natural History Museum of Denmark and the Niels Bohr Institute, Universityof Copenhagen, Copenhagen, Denmark; 2 Department of Astronomy & Physics, Saint Mary’s University, Halifax, Nova
Scotia; 3 Department of Astronomy, University of Virginia, Charlottesville, Virginia, USA
E-mail contact: jpramsey at virginia.edu
We present 2.5-D global, ideal MHD simulations of magnetically and rotationally driven protostellar jets from Keplerianaccretion discs, wherein only the initial magnetic field strength at the inner radius of the disc, Bi , is varied. Using the
AMR-MHD code AZEuS, we self-consistently follow the jet evolution into the observational regime (> 103 AU) with aspatial dynamic range of ∼ 6.5 × 105 . The simulations reveal a three-component outflow: 1) A hot, dense, super-fastand highly magnetised ‘jet core’; 2) a cold, rarefied, trans-fast and highly magnetised ‘sheath’ surrounding the jetcore and extending to a tangential discontinuity; and 3) a warm, dense, trans-slow and weakly magnetised shocked
ambient medium entrained by the advancing bow shock. The simulations reveal power-law relationships between Bi
and the jet advance speed, vjet , the average jet rotation speed, hvϕ i, as well as fluxes of mass, momentum, and kinetic
energy. Quantities that do not depend on Bi include the plasma-β of the transported material which, in all cases,
seems to asymptote to order unity. Jets are launched by a combination of the ‘magnetic tower’ and ‘bead-on-a-wire’
mechanisms, with the former accounting for most of the jet acceleration—even for strong fields—and continuing wellbeyond the fast magnetosonic point. At no time does the leading bow shock leave the domain and, as such, thesesimulations generate large-scale jets that reproduce many of the observed properties of protostellar jets including theircharacteristic speeds and transported fluxes.
Accepted by MNRAS
https://arxiv.org/pdf/1901.02845

The G332 molecular cloud ring: I. Morphology and physical characteristics

64 Domenico Romano , Michael G. Burton , Michael C.B. Ashley , Sergio Molinari , David Rebolledo ,
1,2
1

1,3

Catherine Braiding and Eugenio Schisano

1

2

4,5

2,6

1

School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia; 2 Instituto Nazionale diAstrofisica, INAF, Roma Tor Vergata, Via Fosso del Cavaliere 100, I-00133 Roma, Italy; 3 Armagh Observatory andPlanetarium, College Hill, Armagh BT61 9DG, UK; 4 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura,Santiago, Chile; 5 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA; 6
Inaf - Istituto di RadioAstronomia and Italian ALMA Regional Centre, Via Gobetto 101, I-40129 Bologna, Italy
E-mail contact: domenico.romano at student.unsw.edu.au
We present a morphological and physical analysis of a Giant Molecular Cloud (GMC) using the carbon monoxide
isotopologues (12 CO, 13 CO, C18 O 3 P2 → 3 P1 ) survey of the Galactic Plane (Mopra CO Southern Galactic Plane
Survey), supplemented with neutral carbon maps from the HEAT telescope in Antarctica. The giant molecular cloud
structure (hereinafter the ring) covers the sky region 332◦ < l < 333◦ and b = ±0.◦ 5 (hereinafter the G332 region). The
mass of the ring and its distance are determined to be respectively ∼ 2 × 105 M⊙ and ∼3.7 kpc from Sun. The darkmolecular gas fraction, estimated from the 13 CO and [CI] lines, is ∼17% for a CO Tex between [10, 20 K]. Comparing809
the [CI] integrated intensity and N (H2 ) traced by 13 CO and 12 CO, we define an XCIfactor, analogous to the usual
809
21
−2
−1
−1
XCO , through the [CI] line. XCI ranges between [1.8, 2.0] × 10 cm K km s. We examined local variation in
XCO and Tex across the cloud, and find in regions where the star formation activity is not in an advanced state, anincrease in the mean and dispersion of the XCO factor as the excitation temperature decreases. We present a catalogueof C18 O clumps within the cloud. The star formation (SF) activity ongoing in the cloud shows a correlation with Tex ,[CI] and CO emissions, and anti-correlation with XCO , suggesting a North-South spatial gradient in the SF activity.
We propose a method to disentangle dust emission across the Galaxy, using HI and 13 CO data. We describe Virtual
Reality (VR) and Augmented Reality (AR) data visualisation techniques for the analysis of radio astronomy data.
Accepted by MNRAS
http://arxiv.org/pdf/1901.05961

41

The SOMA Radio Survey. I. Comprehensive SEDs Of High-Mass Protostars From
Infrared To Radio And The Emergence Of Ionization Feedback

65 V. Rosero

1,5,9, K. E. I. Tanaka2,3,9 , J. C. Tan4,5 , J. Marvil1 , M. Liu5,9 , Y. Zhang6 , J. M. De Buizer7 and
M. T. Beltrán8
1

National Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801, USA; 2 Department of Earthand Space Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; 3 Chile Observatory, National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 4 Dept. of Space, Earth and Environment, Chalmers University,
SE-412 96 Gothenburg, Sweden; 5 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA;
6
Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 3510198, Japan;
7
SOFIA–USRA, NASA Ames Research Center, MS 23212, Moffett Field, CA 94035, USA; 8 INAF, Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 9 Department of Astronomy, University of Florida,
Gainesville, FL 32611, USA
E-mail contact: viviana.a.rosero at gmail.com
We study centimeter continuum emission of eight high- and intermediate-mass protostars that are part of the SOFIA
Massive (SOMA) Star Formation Survey, thus building extended spectral energy distributions (SEDs) from the radio
to the infrared. We discuss the morphology seen in the centimeter continuum images, which are mostly derived fromarchival VLA data, and the relation to infrared morphology. We use the SEDs to test new models of high-mass starformation including radiative and disk-wind feedback and associated free-free and dust continuum emission (Tanaka,Tan, & Zhang 2016). We show that interferometric data of the centimeter continuum flux densities provide additional,
stringent tests of the models by constraining the ionizing luminosity of the source and help to break degeneracies
encountered when modeling the infrared-only SEDs, especially for the protostellar mass. Our derived parameters are
consistent with physical parameters estimated by other methods such as dynamical protostellar masses. We find a few
examples of additional stellar sources in the vicinity of the high-mass protostars, which may be low-mass young stellar
objects. However, the stellar multiplicity of the regions, at least as traced by radio continuum emission, appears to berelatively low.
Accepted by ApJ
https://arxiv.org/pdf/1809.01264

66

Implications of a hot atmosphere/corino from ALMA observations towards NGC1333
IRAS 4A1
Dipen Sahu1 , Sheng-Yuan Liu2 , Yu-Nung Su2 , Zhi-Yun Li3 , Chin-Fei Lee2 , Naomi Hirano2 and Shigehisa
Takakuwa4,2
1

Indian Institute of Astrophysics, Sarjapur Main Road, 2nd Block, Koramangala,Bangalore-560034, India; 2 Academia
Sinica Institute of Astronomy and Astrophysics, 11F of AS/NTU Astronomy-Mathematics Building, No.1, Sec. 4,
Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.; 3 Astronomy Department, University of Virginia, Charlottesville, VA
22904, USA; 4 Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima
University, 1-21-35 Korimoto, Kagoshima 890-0065
E-mail contact: dipenthink at gmail.com

We report high angular resolution observations of NGC1333 IRAS4A, a protostellar binary including A1 and A2, at
0.84 mm with the Atacama Large Millimeter/submillimeter Array. From the continuum observations, we suggest thatthe dust emission from the A1 core is optically thick, and A2 is predominantly optically thin. The A2 core, exhibiting
a forest of spectral lines including complex molecules, is a well known hot corino as suggested by previous works.
More importantly, we report, for the first time, the solid evidence of complex organic molecules (COMs), including
CH3 OH, 13 CH3 OH, CH2 DOH, CH3 CHO associated with the A1 core seen in absorption. The absorption features
mostly arise from a compact region around the continuum peak position of the A1 core. Rather than originating froma larger common envelope surrounding the protobinary, the COM features are associated with individual cores A1 andA2. Considering the signatures observed in both continuum and spectral lines, we propose two possible scenarios for
IRAS 4A1 — the COM absorption lines may arise from a hot-corino-like atmosphere at the surface of an opticallythick circumstellar disk around A1, or the absorption may arise from different layers of a temperature-stratified denseenvelope.

42

Accepted by ApJ
http://arxiv.org/pdf/1901.05424

Discovery of a sub-Keplerian disk with jet around a 20 M⊙ young star. ALMA observations of G023.01-00.41

67 A. Sanna , A. Koelligan , L. Moscadelli , R. Kuiper , R. Cesaroni , T. Pillai , K.M. Menten , Q.
1

4

2

3

5

2

6

7

3

1

1

8

Zhang , A. Caratti o Garatti , C. Goddi , S. Leurini and C. Carrasco-Gonzalez
1

Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany; 2 Institute of Astronomy andAstrophysics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany; 3 INAF, Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 4 Harvard-Smithsonian Center for Astrophysics, 60
Garden Street, Cambridge, MA 02138, USA; 5 Dublin Institute for Advanced Studies, Astronomy & Astrophysics
Section, 31 Fitzwilliam Place, Dublin 2, Ireland; 6 Department of Astrophysics/IMAPP, Radboud University Nijmegen,
PO Box 9010, NL-6500 GL Nijmegen, the Netherlands; 7 INAF, Osservatorio Astronomico di Cagliari, via della Scienza
5, 09047 Selargius (CA), Italy; 8 Instituto de Radioastronomı́a y Astrofı́sica UNAM, Apartado Postal 3-72 (Xangari),
58089 Morelia, Michoacán, México
E-mail contact: asanna at mpifr-bonn.mpg.de
It is well established that Solar-mass stars gain mass via disk accretion, until the mass reservoir of the disk is exhausted
and dispersed, or condenses into planetesimals. Accretion disks are intimately coupled with mass ejection via polar
cavities, in the form of jets and less collimated winds, which allow mass accretion through the disk by removing asubstantial fraction of its angular momentum. Whether disk accretion is the mechanism leading to the formation ofstars with much higher masses is still unclear. Here, we are able to build a comprehensive picture for the formationof an O-type star, by directly imaging a molecular disk which rotates and undergoes infall around the central star,and drives a molecular jet which arises from the inner disk regions. The accretion disk is truncated between 2000–
3000 au, it has a mass of about a tenth of the central star mass, and is infalling towards the central star at a highrate (6 × 10−4 M⊙ yr−1 ), as to build up a very massive object. These findings, obtained with the Atacama Large
Millimeter/submillimeter Array at 700 au resolution, provide observational proof that young massive stars can form
via disk accretion much like Solar-mass stars.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1805.09842v2

68

Protostellar Outflows at the EarliesT Stages (POETS). II. A possible radio synchrotron
jet associated with the EGO G035.02+0.35
A. Sanna1 , L. Moscadelli2 , C. Goddi3 , M. Beltrán2 , C.L. Brogan4 , A. Caratti o Garatti5 , C. CarrascoGonzález6 , T.R. Hunter4 , F. Massi2 and M. Padovani2
1

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 2 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 3 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, NL-6500 GL Nijmegen, the Netherlands; 4 NRAO, 520 Edgemont Road, Charlottesville,
VA 22903, USA; 5 Dublin Institute for Advanced Studies, Astronomy & Astrophysics Section, 31 Fitzwilliam Place,
Dublin 2, Ireland; 6 Instituto de Radioastronomı́a y Astrofı́sica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México
E-mail contact: asanna at mpifr-bonn.mpg.de
Centimeter continuum observations of protostellar jets have revealed the presence of knots of shocked gas where theflux density decreases with frequency. This spectrum is characteristic of nonthermal synchrotron radiation and implies
the presence of both magnetic fields and relativistic electrons in protostellar jets. Here, we report on one of the few
detections of nonthermal jet driven by a young massive star in the star-forming region G035.02+0.35. We made useof the NSF’s Karl G. Jansky Very Large Array (VLA) to observe this region at C, Ku, and K bands with the Aand B-array configurations, and obtained sensitive radio continuum maps down to a rms of 10 µJy beam−1 . Theseobservations allow for a detailed spectral index analysis of the radio continuum emission in the region, which weinterpret as a protostellar jet with a number of knots aligned with extended 4.5 µm emission. Two knots clearly43emit nonthermal radiation and are found at similar distances, of approximately 10,000 au, each side of the central
young star, from which they expand at velocities of hundreds km s−1 . We estimate both the mechanical force and themagnetic field associated with the radio jet, and infer a lower limit of 0.4 × 10−4 M⊙ yr−1 km s−1 and values in therange 0.7–1.3 mG, respectively.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1901.08611

69

Clumpy dust rings around non-accreting young stars
Aleks Scholz1 , Antonella Natta2 , Inna Bozhinova1 , Maya Petkova1,4 , Howard Relles1 and Jochen
Eislöffel3
1

SUPA, School of Physics & Astronomy, North Haugh, University of St Andrews, St Andrews, KY16 9SS, UK; 2
Dublin Institute of Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland; 3 Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany; 4 Astronomisches Recheninstitut, Zentrum für Astronomie derUniversität Heidelberg, Mönchhofstrasse 12-14, 69120 Heidelberg, Germany
E-mail contact: as110 at st-andrews.ac.uk

We investigate four young, but non-accreting, very low mass stars in Orion, which show irregular eclipses by circumstellar dust. The eclipses are not recurring periodically, are variable in depth, lack a flat bottom, and their durationis comparable to the typical timescale between eclipses. The dimming is associated with reddening consistent withdust extinction. Taken together this implies the presence of rings around these four stars, with radii ranging from 0.01
to 40 AU, comprised of optically thin dust clouds. The stars also show IR excess indicating the presence of evolved
circumstellar disks, with orders of magnitude more material than needed for the eclipses. However, the rings need tocover an opening angle of about 20 degrees to explain how common these variable stars are in the coeval populationin the same region, which is more extended than a typical disk. Thus, we propose that the rings may not be part ofthe disks, but instead separate structures with larger scale heights. To be sustained over years, the rings need to be
replenished by dust from the disk or gravitationally bound to an object (e.g., planets or planetesimals). These fourstars belong to a growing and diverse class of post-T Tauri stars with dips or eclipses in their lightcurves. Dusty rings
with scale heights exceeding those of disks may be a common phenomenon at stellar ages between 5 and 10 Myr, inthe transition from accretion disks to debris disks. These structures could be caused by migrating planets and may
be signposts for the presence of young planetary systems.
Accepted by MNRAS
https://arxiv.org/pdf/1901.10386

Is Molecular Cloud Turbulence Driven by External Supernova Explosions?

70 D. Seifried , S. Walch , S. Haid , P. Girichidis and T. Naab
1

1

1

2,3

4

1

University of Cologne, I. Physical Institute,Germany; 2 Leibniz-Institut für Astrophysik Potsdam,Germany; 3 Heidelberg Institute for Theoretical Studies, Germany; 4 Max-Planck-Institut für Astrophysik, Germany
E-mail contact: seifried at ph1.uni-koeln.de
We present high-resolution (∼ 0.1 pc), hydrodynamical and magneto-hydrodynamical simulations to investigate
whether the observed level of molecular cloud (MC) turbulence can be generated and maintained by external supernova (SN) explosions. The MCs are formed self-consistently within their large-scale galactic environment following
the non-equilibrium formation of H2 and CO including (self-) shielding and important heating and cooling processes.
The MCs inherit their initial level of turbulence from the diffuse ISM, where turbulence is injected by SN explosions.
However, by systematically exploring the effect of individual SNe going off outside the clouds, we show that at laterstages the importance of SN driven turbulence is decreased significantly. This holds for different MC masses as well
as MCs with and without magnetic fields. The SN impact also decreases rapidly with larger distances. Nearby SNe(d ∼ 25 pc) boost the turbulent velocity dispersions of the MC by up to 70 per cent (up to a few km s−1 ). For d > 50
pc, however, their impact decreases fast with increasing d and is almost negligible. For all probed distances the gain
in velocity dispersion decays rapidly within a few 100 kyr. This is significantly shorter than the average timescale fora MC to be hit by a nearby SN under solar neighbourhood conditions (∼ 2 Myr). Hence, at these conditions SNe are44not able to sustain the observed level of MC turbulence. However, in environments with high gas surface densities
and SN rates like the Central Molecular Zone, observed elevated MC dispersions could be triggered by external SNe.
Accepted by ApJ
http://adsabs.harvard.edu/pdf/2018ApJ...855...81S

71 D. Seifried , S. Walch , S. Reissl and J. C. Ibanez-Mejia

72

SILCC-Zoom: Polarization and depolarization in molecular clouds
1

1

2

1

1

University of Cologne, I. Physical Institute, germany; 2 University of Heidelberg, Institute for Theoretical Astrophysics, Germany
E-mail contact: seifried at ph1.uni-koeln.de
We present synthetic dust polarisation maps of 3D magneto-hydrodynamical simulations of molecular clouds before
the onset of stellar feedback. The clouds are modelled within the SILCC-Zoom project and are embedded in theirgalactic environment. The radiative transfer is carried out with POLARIS for wavelengths from 70 µm to 3 mm at aresolution of 0.12 pc, and includes self-consistently calculated alignment efficiencies for radiative torque alignment. We
explore the reason of the observed depolarisation in the center of molecular clouds: We find that dust grains remain
well aligned even at high densities (n > 103 cm−3 ) and visual extinctions (AV > 1). The depolarisation is rather
caused by strong variations of the magnetic field direction along the LOS due to turbulent motions. The observed
magnetic field structure thus resembles best the mass-weighted, line-of-sight averaged field structure. Furthermore,
it differs by only a few 1◦ for different wavelengths and is little affected by the spatial resolution of the synthetic
observations. Noise effects can be reduced by convolving the image. Doing so, for λ ≥ 160 µm the observed magnetic
field traces reliably the underlying field in regions with intensities I ≥ 2 times the noise level and column densities
above 1 M⊙ pc−2 . Here, typical deviations are ≤ 10◦ . The observed structure is less reliable in regions with low
polarisation degrees and possibly in regions with large column density gradients. Finally, we show that a simplified
and widely used method without self-consistent dust alignment efficiencies can provide a good representation of theobservable polarisation structure with deviations below 5◦ .
Accepted by MNRAS
http://adsabs.harvard.edu/pdf/2019MNRAS.482.2697S
http://arxiv.org/pdf/1804.10157

Multicomponent kinematics in a massive filamentary IRDC
Vlas Sokolov1 , Ke Wang2,3 , Jaime E. Pineda1 , Paola Caselli1, Jonathan D. Henshaw4 , Ashley T.
Barnes5 , Jonathan C. Tan6,7 , Francesco Fontani8 and Izaskun Jimenez-Serra9
1

Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching bei Munchen, Germany;
European Southern Observatory (ESO) Headquarters, Karl-Schwarzschild-Str. 2, 85748 Garching bei Munchen,
Germany; 3 Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District,
Beijing 100871, China; 4 Max Planck Institute for Astronomy, Konigstuhl 17, D-69117 Heidelberg, Germany; 5
Argelander Institute for Astronomy, University of Bonn, Auf dem Hugel 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 Astrobiologia (CSIC/INTA), Ctra de Torrejon a Ajalvir, km 4, 28850 Torrejon 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 long tailextending 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 same45

73

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 The Astrophysical Journal
https://arxiv.org/pdf/1812.09581

Histogram of oriented gradients: a technique for the study of molecular cloud formation
J.D. Soler1 , H. Beuther1 , M. Rugel1 , Y. Wang1 , P.C. Clark2 , S.C.O. Glover3 , P.F. Goldsmith4, M.
Heyer5 , L.D. Anderson6 , A. Goodman7 , Th. Henning1 , J. Kainulainen8 , R.S. Klessen3,9 , S.N. Longmore10 ,N.M. McClure-Griffiths11 , K.M. Menten12 , J.C. Mottram1 , J. Ott13 , S.E. Ragan2 , R.J. Smith14 , J.S.
Urquhart15 , F. Bigiel16,3, P. Hennebelle17, N. Roy18 and P. Schilke19
1

Max Planck Institute for Astronomy, Königstuhl 17, 69117, Heidelberg, Germany; 2 School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff, CF24 3AA, UK; 3 Universität Heidelberg, Zentrum
für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, 69120, Heidelberg, Germany; 4 Jet
Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena CA, 91109, USA; 5 Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305, USA; 6 Department of Physics andAstronomy, West Virginia University, Morgantown, WV 26506, USA; 7 Harvard-Smithsonian Center for Astrophysics,
60 Garden Street, MS 42, Cambridge, MA 02138, USA; 8 Dept. of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden; 9 Universität Heidelberg, Interdiszipliäres
Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer Feld 205, 69120 Heidelberg, Germany; 10 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK; 11 Research School of
Astronomy and Astrophysics, The Australian National University, Canberra, ACT, Australia; 12 Max Planck Institutefor Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany; 13 National Radio Astronomy Observatory, PO Box
O, 1003 Lopezville Road, Socorro, NM 87801, USA; 14 Jodrell Bank Centre for Astrophysics, School of Physics andAstronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK; 15 Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK; 16 Argelander-Institut für Astronomie, Universität Bonn,
Auf dem Hügel 71, 53121 Bonn, Germany; 17 Laboratoire AIM, Paris-Saclay, CEA/IRFU/SAp - CNRS - Université
Paris Diderot, 91191, Gif-sur-Yvette Cedex, France; 18 Department of Physics, Indian Institute of Science, 560012
Bangalore, India; 19 Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
E-mail contact: soler at mpia.de
We introduce the histogram of oriented gradients (HOG), a tool developed for machine vision that we propose as
a new metric for the systematic characterization of spectral line observations of atomic and molecular gas and thestudy of molecular cloud formation models. In essence, the HOG technique takes as input extended spectral-line
observations from two tracers and provides an estimate of their spatial correlation across velocity channels. We
characterized HOG using synthetic observations of Hi and 13 CO (J = 1 → 0) emission from numerical simulations ofmagnetohydrodynamic (MHD) turbulence leading to the formation of molecular gas after the collision of two atomic
clouds. We found a significant spatial correlation between the two tracers in velocity channels where vHI ≈ v13CO ,almost independent of the orientation of the collision with respect to the line of sight. Subsequently, we used HOG
to investigate the spatial correlation of the Hi, from The Hi/OH/recombination line survey of the inner Milky Way(THOR), and the 13 CO (J = 1 → 0) emission from the Galactic Ring Survey (GRS), toward the portion of the Galactic
plane 33◦ 7. 5 ≤ l ≤ 35◦ 2. 5 and |b| ≤ 1◦ 2. 5. We found a significant spatial correlation between the two tracers in extended
portions of the studied region. Although some of the regions with high spatial correlation are associated with Hi selfabsorption (HISA) features, suggesting that it is produced by the cold atomic gas, the correlation is not exclusive to thiskind of region. The HOG results derived for the observational data indicate significant differences between individual
regions: some show spatial correlation in channels around vHI ≈ v13CO while others present spatial correlations invelocity channels separated by a few kilometers per second. We associate these velocity offsets to the effect of feedback
and to the presence of physical conditions that are not included in the atomic-cloud-collision simulations, such as moregeneral magnetic field configurations, shear, and global gas infall.

46

Accepted by Astronomy & Astrophysics
http://adsabs.harvard.edu/pdf/2018arXiv180908338S

Pebble accretion in class 0/I YSOs as a possible pathway for early planet formation

74 Yuki A. Tanaka and Yusuke Tsukamoto
1,2

2

1

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551, Japan; 2
Graduate School of Science and Engineering, Kagoshima University, 1-21-40, Korimoto, Kagoshima, 890-0065, Japan
E-mail contact: tanaka.y.cn at m.titech.ac.jp
Recent theoretical works suggest that the pebble accretion process is important for planet formation in protoplanetarydisks, because it accelerates the growth of planetary cores. While several observations reveal axisymmetric sharp gaps
in very young disks, which may be indicative of the existence of planets. We investigate the possibility of planet
formation via pebble accretion in much earlier phases, the gravitationally unstable disks of class 0/I young stellar
objects. We find that under the conditions of the class 0/I disks, the pebble accretion timescales can be shortercompared to the typical protoplanetary disks due to larger gas and dust accretion rate, but also find that the accretion
timescale is not always a decreasing function of the gas accretion rate. By using estimated accretion timescales, wegive a required initial mass to form cores of gas giants within the lifetime of class 0/I phases under several parameters,such as radial distances from the host star, gas accretion rates, and dust-to-gas mass ratio. In the most optimistic
case, for example the dust-to-gas mass ratio is f = 3fsolar , ∼ 10−4 M⊕ objects at 10 au can grow to 10 M⊕ cores
during the typical lifetime of the class 0/I phases, 0.5 Myr.
Accepted by MNRAS
http://arxiv.org/pdf/1901.01714

75

Survey Observations to Study Chemical Evolution from High-Mass Starless Cores toHigh-Mass Protostellar Objects II. HC3 N and N2 H+
Kotomi Taniguchi1 , Masao Saito2,4 , T. K. Sridharan3 and Tetsuhiro Minamidani2,41

Departments of Astronomy and Chemistry, University of Virginia, Charlottesville, VA 22904, USA; 2 National
Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), Osawa, Mitaka, Tokyo
181-8588, Japan; 3 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 78, Cambridge, MA 02138,
USA; 4 Department of Astronomical Science, School of Physical Science, SOKENDAI (The Graduate University for
Advanced Studies), Osawa, Mitaka, Tokyo 181-8588, Japan
E-mail contact: kt8pm at virginia.edu
We have carried out survey observations of molecular emission lines from HC3 N, N2 H+ , CCS, and cyclic-C3 H2 in
the 81−94 GHz band toward 17 high-mass starless cores (HMSCs) and 28 high-mass protostellar objects (HMPOs)
with the Nobeyama 45-m radio telescope. We have detected N2 H+ in all of the target sources except one andHC3 N in 14 HMSCs and in 26 HMPOs. We investigate the N (N2 H+ )/N (HC3 N) column density ratio as a chemical
evolutionary indicator of massive cores. Using the Kolmogorov-Smirnov (K-S) test and Welch’s t test, we confirm that
the N (N2 H+ )/N (HC3 N) ratio decreases from HMSCs to HMPOs. This tendency in high-mass star-forming regions
is opposite to that in low-mass star-forming regions. Furthermore, we found that the detection rates of carbon-chain
species (HC3 N, HC5 N, and CCS) in HMPOs are different from those in low-mass protostars. The detection rates of
cyanopolyynes (HC3 N and HC5 N) are higher and that of CCS is lower in high-mass protostars, compared to low-mass
protostars. We discuss a possible interpretation for these differences.
Accepted by ApJ
https://arxiv.org/pdf/1901.06446

76 J.S. Urquhart , C. Figura , F. Wyrowski , A. Giannetti , W.-J. Kim , M. Wienen , S. Leurini , T.
ATLASGAL — Molecular fingerprints of a sample of massive star forming clumps
1,2

2

3

2

2

1

4,2

2

2

6

Pillai , T. Csengeri , S.J. Gibson , K. Menten , T.J.T. Moore , M.A. Thompson

47

2

7

5,2

1

Centre for Astrophysics and Planetary Science, University of Kent, Canterbury, CT2 7NH, UK; 2 Max-Planck-Institutfür Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 3 Wartburg College, Waverly, IA, 50677, USA; 4
INAF - Istituto di Radioastronomia & Italian ALMA Regional Centre, Via P. Gobetti 101, I-40129 Bologna, Italy;5
INAF - Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047, Selargius (CA), Italy; 6 Astrophysics
Research Institute, Liverpool John Moores University, Liverpool Science Park, 146 Brownlow Hill, Liverpool, L3 5RF,
UK; 7 Science and Technology Research Institute, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK
E-mail contact: j.s.urquhart at gmail.com
We have conducted a 3-mm molecular-line survey towards 570 high-mass star-forming clumps, using the Mopra telescope. The sample is selected from the 10,000 clumps identified by the ATLASGAL survey and includes all of themost important embedded evolutionary stages associated with massive star formation, classified into five distinct categories (quiescent, protostellar, young stellar objects, Hii regions and photo-dominated regions). The observations were
performed in broadband mode with frequency coverage of 85.2 to 93.4 GHz and a velocity resolution of ∼0.9 km s−1 ,detecting emission from 26 different transitions. We find significant evolutionary trends in the detection rates, integrated line intensities, and abundances of many of the transitions and also identify a couple of molecules that appear
to be invariant to changes in the dust temperature and evolutionary stage (N2 H+ (1–0) and HN13 C (1–0)). We use theK-ladders for CH3 C2 H (5–4) and CH3 CH (5–4) to calculate the rotation temperatures and find ∼1/3 of the quiescentclumps have rotation temperatures that suggest the presence of an internal heating source. These sources may constitute a population of very young protostellar objects that are still dark at 70 µm and suggest that the fraction of truly
quiescent clumps may only be a few per cent. We also identify a number of line ratios that show a strong correlation
with the evolutionary stage of the embedded objects and discuss their utility as diagnostic probes of evolution.
Accepted by MNRAS
http://arxiv.org/pdf/1901.03759

77

Protoplanetary disk rings and gaps across ages and luminosities
Nienke van der Marel1 , Ruobing Dong2 , James di Francesco1,2 , Jonathan Williams3 and John Tobin4
1

Herzberg Astronomy & Astrophysics Programs, National Research Council of Canada, 5071 West Saanich Road,
Victoria BC V9E 2E7, Canada; 2 Physics & Astronomy Department, University of Victoria, 3800 Finnerty Road,
Victoria, BC, V8P 5C2, Canada; 3 Institute for Astronomy, University of Hawaii, 2680 Woodlawn dr., 96822 Honolulu
HI, USA; 4 NRAO, 520 Edgemont Road Charlottesville, VA 22903-2475 USA
E-mail contact: astro at nienkevandermarel.com
Since the discovery of the multi-ring structure of the HL Tau disk, ALMA data suggest that the dust continuum
emission of many, if not all, protoplanetary disks consists of rings and gaps, no matter their spectral type or age. The
origin of these gaps so far remains unclear. We present a sample study of 16 disks with multiple ring-like structures in
the continuum, using published ALMA archival data, to compare their morphologies and gap locations in a systematicway. The 16 targets range from early to late type stars, from <0.5 Myr to >10 Myr, from ∼0.2 to 40 L⊙ and include
both full and transitional disks with cleared inner dust cavities. Stellar ages are revised using new Gaia distances.
Gap locations are derived using a simple radial fit to the intensity profiles. Using a radiative transfer model, thetemperature profiles are computed. The gap radii generally do not correspond to the orbital radii of snow lines of themost common molecules. A snow line model can likely be discarded as a common origin of multi-ring systems. In
addition, there are no systematic trends in the gap locations that could be related to resonances of planets. Finally,
the outer radius of the disks decreases for the oldest disks in the sample, indicating that if multi-ring disks evolve ina similar way, outer dust rings either dissipate with the gas or grow into planetesimal belts.
Accepted by ApJ
http://arxiv.org/pdf/1901.03680

ALMA study of the HD 100453 AB system and the tidal interaction of the companion
with the disk

78 G. van der Plas , F. Ménard , J.-F. Gonzalez , S. Perez , L. Rodet , C. Pinte , L. Cieza , S.
1

Casassus

3,4

1

2

3,4

1,4

and M. Benisty

48

1

1,5

6

1

Univ. Grenoble Alpes, CNRS, IPAG (UMR 5274), F-38000 Grenoble, France; 2 Univ Lyon, Univ Lyon1, Ens de
Lyon, CNRS, Centre de Recherche Astrophysique de Lyon UMR5574, F-69230, Saint-Genis-Laval, France; 3 Millenium
Nucleus Protoplanetary Disks in ALMA Early Science, Universidad de Chile, Casilla 36-D, Santiago, Chile; 4 Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile; 5 Monash Centre for Astrophysics (MoCA)
and School of Physics and Astronomy, Monash University, Clayton Vic 3800, Australia; 6 Departamento de Ciencias
Fisicas, Facultad de Ciencias Exactas, Universidad Andres Bello. Av. Fernandez Concha 700, Las Condes, Santiago,
Chile; 7 Nucleo de Astronomia, Facultad de Ingenieria, Universidad Diego Portales, Av Ejercito 441, Santiago, Chile
E-mail contact: info at gerritvanderplas.com
Context: The complex system HD 100453 AB with a ring-like circumprimary disk and two spiral arms, one of whichis pointing to the secondary, is a good laboratory to test spiral formation theories.
Aims: To resolve the dust and gas distribution in the disk around HD 100453 A and to quantify the interaction of
HD 100453 B with the circumprimary disk.
Methods: Using ALMA band 6 dust continuum and CO isotopologue observations we study the HD 100453 AB systemwith a spatial resolution of 0.09” × 0.17” at 234 GHz. We use SPH simulations and orbital fitting to investigate thetidal influence of the companion on the disk.
Results: We resolve the continuum emission around HD 100453 A into a disk between 0.22” and 0.40” with aninclination of 29.5 degrees and a position angle of 151.0 degrees, an unresolved inner disk, and excess mm emission
cospatial with the northern spiral arm which was previously detected using scattered light observations. We also
detect CO emission from 7 au (well within the disk cavity) out to 1.10”, i.e., overlapping with HD 100453 B at leastin projection. The outer CO disk PA and inclination differ by up to 10 degrees from the values found for the inner
CO disk and the dust continuum emission, which we interpret as due to gravitational interaction with HD 100453 B.
Both the spatial extent of the CO disk and the detection of mm emission at the same location as the northern spiralarm are in disagreement with the previously proposed near co-planar orbit of HD 100453 B.
Conclusions: We conclude that HD 100453 B has an orbit that is significantly misaligned with the circumprimary
disk. Because it is unclear whether such an orbit can explain the observed system geometry we highlight an alternative
scenario that explains all detected disk features where another, (yet) undetected, low mass close companion within
the disk cavity, shepherds a misaligned inner disk whose slowly precessing shadows excite the spiral arms.
Accepted by Astronomy & Astrophysics.
https://arxiv.org/pdf/1902.00720

Imaging the disc rim and a moving close-in companion candidate in the pre-transitional
disc of V1247 Orionis

79 Matthew Willson , Stefan Kraus , Jacques Kluska , John D. Monnier , Michel Cure , Mike Sitko ,
1

3

1

7

1,2

8

3

1

4

5,6

1

Alicia Aarnio , Michael J. Ireland , Aaron Rizzuto , Edward Hone , Alexander Kreplin , Sean Andrews9 ,Nuria Calvet3 , Catherine Espaillat10 , Misato Fukagawa11 , Tim J. Harries1 , Sasha Hinkley1 , Samer
Kanaan4 , Takayuki Muto12 and David J. Wilner91

University of Exeter, Astrophysics Group, School of Physics, Stocker Road, Exeter EX4 4QL, UK; 2 Instituut voor
Sterrenkunde (IvS), KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium; 3 Department of Astronomy, Universityof Michigan, 311 West Hall, 1085 South University Ave, Ann Arbor, MI 48109, USA; 4 Instituto de Fsica y Astronoma,
Universidad de Valparaso, Av. Gran Bretana 1111, Valparaso, Chile; 5 Department of Physics, University of Cincinnati, Cincinnati, OH 45221, USA; 6 Space Science Institute, 475 Walnut St., Suite 205, Boulder, CO 80301, USA; 7
Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia; 8Department of Astronomy, The University of Texas at Austin, Austin, TX 78712, USA; 9 HarvardSmithsonian Center
for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 10 Department of Astronomy, Boston University,
725 Commonwealth Avenue, Boston, MA 02215, USA; 11 National Astronomical Observatory of Japan, 2-21-1 Osawa,
Mitaka, Tokyo 181-8588, Japan; 12 Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinijuku-ku,
Tokyo 163-8677, Japan
E-mail contact: mwillson at astro.gsu.edu
V1247 Orionis harbours a pre-transitional disc with a partially cleared gap. Earlier interferometric and polarimetricobservations revealed strong asymmetries both in the gap region and in the outer disc. The presence of a companion
was inferred to explain these asymmetric structures and the ongoing disc clearing. Using an extensive set of multi49

wavelength and multi-epoch observations we aimed to identify the origin of the previously detected asymmetries. We
have observed V1247 Ori at three epochs spanning ∼ 678 days using sparse aperture masking interferometry with
Keck/NIRC2 and VLT/NACO. In addition, we search for signs of accretion through VLT/SPHERE-ZIMPOL spectral
differential imaging in Hα and R-band continuum. Our SMA sub-millimetre interferometry in 880 µm continuum andin the CO(3-2) line allows us to constrain the orientation and direction of rotation of the outer disc. We find theL’-band emission to be dominated by static features which trace forward-scattered dust emission from the inner edgeof the outer disc located to the north-east. In H- and K-band, we see evidence for a companion candidate that moved
systematically by 45◦ within the first ∼345 days. The separation of the companion candidate is not well constrained,
but the observed position angle change is consistent with Keplerian motion of a body located on a 6 au orbit. From the
SMA CO moment map, the location of the disc rim, and the detected orbital motion, we deduced the three-dimensional
orientation of the disc. We see no indication of accretion in Hα and set upper limits for an accreting companion. The
measured contrast of the companion candidate in H and K is consistent with an actively accreting protoplanet. Hence,
we identify V1247 Ori as a unique laboratory for studying companion-disc interactions and disc clearing.
Accepted by Astronomy and Astrophysics
https://www.aanda.org/articles/aa/pdf/2019/01/aa30215-16/aa30215-16.html

80Chemical network reduction in protoplanetary disks
Rui Xu1 , Xue-Ning Bai2,3 , Karin Öberg4 , Hao Zhang5
1

Department of Astrophysical Sciences, Princeton University, Princetion, NJ 08544; 2 Institute for Advanced Study,
Tsinghua University, Beijing 100084, China; 3 Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084,
China; 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA, 02138; 5 Department of
Physics, Purdue University, 525 Northwestern Ave., West Lafayette, IN 47907
E-mail contact: ruix at princeton.edu
Protoplanetary disks (PPDs) are characterized by different kinds of gas dynamics and chemistry, which are coupled
via ionization, heating and cooling processes, as well as advective and turbulent transport. However, directly couplinggas dynamics with time-dependent chemistry is prohibitively computationally expensive when using comprehensive
chemical reaction networks. In this paper, we evaluate the utility of a species-based network reduction method in
different disk environments to produce small chemical networks that reproduce the abundances of major species foundin large gas-phase chemistry networks. We find that the method works very well in disk midplane and surfaces regions,where approximately 20–30 gas phase species, connected by ∼50–60 gas phase reactions, are sufficient to reproduce thetargeted ionization fraction and chemical abundances. Most species of the reduced networks, including major carriersof oxygen, carbon and nitrogen, also have similar abundances in the reduced and complete network models. Our results
may serve as an initial effort for future hydrodynamic/magnetohydrodynamic simulations of PPDs incorporating timedependent chemistry in appropriate regions. Accurately modeling the abundances of major species at intermediate
disk heights, however, will require much more extended network incorporating gas-grain chemistry and are left for
future studies.
Accepted by ApJ
http://arxiv.org/pdf/1901.04888

81

Signs of outflow feedback from a nearby young stellar object on the protostellar envelope
around HL Tau
Hsi-Wei Yen1,2 , Shigehisa Takakuwa3,2 , Pin-Gao Gu2 , Naomi Hirano2 , Chin-Fei Lee2 , Hauyu Baobab
Liu1,2 , Sheng-Yuan Liu2 and Chun-Ju Wu4,2
1

European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany; 2 Academia Sinica
Institute of Astronomy and Astrophysics, 11F of Astro-Math Bldg, 1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan; 3
Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35
Korimoto, Kagoshima, Kagoshima 890-0065, Japan; 4 Department of Physics, National Taiwan University, No. 1, Sec.
4, Roosevelt Road, Taipei 106, Taiwan
E-mail contact: hwyen at asiaa.sinica.edu.tw

50

Aims. HL Tau is a Class I–II protostar embedded in an infalling and rotating envelope and possibly associated witha planet forming disk, and it is co-located in a 0.1 pc molecular cloud with two nearby young stellar objects withprojected distance of ∼20 arcsec–30 arcsec (2800–4200 au) to HL Tau. Our observations with the Atacama Large
Millimeter/Submillimeter Array (ALMA) revealed two arc-like structures on a 1000 au scale connected to the disk,
and their kinematics could not be explained with any conventional model of infalling and rotational motions. In thiswork, we investigate the nature of these arc-like structures connected to the HL Tau disk.
Methods. We conducted new observations in the 13 CO and C18 O (3–2; 2–1) lines with the James Clerk Maxwell
Telescope and the IRAM 30m telescope, and obtained the data with the 7-m array of the Atacama Compact Array(ACA). With the single-dish, ACA, and ALMA data, we analyzed the gas motions on both 0.1 pc and 1000 au
scales in the HL Tau region. We constructed new kinematical models of an infalling and rotating envelope with theconsideration of relative motion between HL Tau and the envelope.
Results. By including the relative motion between HL Tau and its protostellar envelope, our kinematical model can
explain the observed velocity features in the arc-like structures. The morphologies of the arc-like structures can also
be explained with an asymmetric initial density distribution in our model envelope. In addition, our single-dish results
support that HL Tau is located at the edge of a large-scale (0.1 pc) expanding shell driven by the wind or outflow fromXZ Tau, as suggested in the literature. The estimated expanding velocity of the shell is comparable to the relative
velocity between HL Tau and its envelope in our kinematical model. These results hints that the large-scale expanding
motion likely impacts the protostellar envelope around HL Tau and affects its gas kinematics. We found that the mass
infalling rate from the envelope onto the HL Tau disk can be decreased by a factor of two due to this impact by thelarge-scale expanding shell.
Accepted by A&A
https://arxiv.org/pdf/1901.03452

An unbiased spectral line survey observation toward the low-mass star-forming region
L1527

Kento Yoshida , Nami Sakai , Yuri Nishimura, Tomoya Tokudome , Yoshimasa Watanabe ,82 Takeshi
Sakai , Shuro Takano and Satoshi Yamamoto
1,2

7

2

1,3,4

8

1

5,6

1,9

1

Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; 2 Star andPlanet Formation Laboratory, RIKEN Cluster for Pioneering Research (CPR), 2-1, Hirosawa, Wako, Saitama 3510198, Japan; 3 Institute of Astronomy, The University of Tokyo, 2-21-1, Osawa, Mitaka, Tokyo 181-0015, Japan; 4Chile Observatory, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 5Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan;
6
Tomonaga Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan; 7Department of Communication Engineering and Informatics, Graduate School of Informatics and Engineering, The
University of Electro-Communications, Chofugaoka, Chofu, Tokyo 182-8585, Japan; 8 Department of Physics, General
Studies, College of Engineering, Nihon University, 1, Nakagawara, Tokusada, Tamuramachi, Koriyama, Fukushima
963-8642, Japan; 9 Research Center for the Early Universe, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo
113-0033, Japan
E-mail contact: yoshida at taurus.phys.s.u-tokyo.ac.jp
An unbiased spectral line survey toward a solar-type Class 0/I protostar, IRAS 04368+2557, in L1527 has been carriedout in the 3 mm band with the Nobeyama 45 m telescope. L1527 is known as a warm carbon-chain chemistry (WCCC)
source, which harbors abundant unsaturated organic species such as Cn H (n = 3, 4, 5, . . .) in a warm and dense region
near the protostar. The observation covers the frequency range from 80 to 116 GHz. A supplementary observation
has also been conducted in the 70 GHz band to observe fundamental transitions of deuterated species. In total, 69
molecular species are identified, among which 27 species are carbon-chain species and their isomers, including theirminor isotopologues. This spectral line survey provides us with a good template of the chemical composition of the
WCCC source.
Accepted by PASJ
https://doi.org/10.1093/pasj/psy136
https://arxiv.org/pdf/1901.06546

51

83

First detection of the pre-biotic molecule glycolonitrile (HOCH2CN) in the interstellar
medium
S. Zeng1 , D. Quénard1 , I. Jiménez-Serra2 , J. Martı́n-Pintado2 , V. M. Rivilla3 , L. Testi3,4,5 and R.
Martı́n-Doménech6
1

School of Physics and Astronomy, Queen Mary University of London, Mile End Road, E1 4NS London, United
Kingdom; 2 Centro de Astrobiologı́a (CSIC, INTA), Ctra. de Ajalvir, km. 4, Torrejón de Ardoz, 28850 Madrid,
Spain; 3 INAF-Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125, Florence, Italy; 4 Excellence Cluster”Universe”, Boltzmann str. 2, D-85748 Garching bei Muenchen, Germany; 5 ESO/European Southern Observatory,
Karl Schwarzschild str. 2, D-85748, Garching, Germany; 6 Harvard-Smithsonian Center for Astrophysics, 60 Garden
Street, Cambridge, MA 02138, USA
E-mail contact: s.zeng at qmul.ac.uk
Theories of a pre-RNA world suggest that glycolonitrile (HOCH2 CN) is a key species in the process of ribonucleotide
assembly, which is considered as a molecular precursor of nucleic acids. In this Letter, we report the first detectionof this pre-biotic molecule in the interstellar medium (ISM) by using ALMA data obtained at frequencies between
86.5 GHz and 266.5 GHz toward the Solar-type protostar IRAS16293-2422 B. A total of 15 unblended transitions of
HOCH2 CN were identified. Our analysis indicates the presence of a cold (Tex =24±8 K) and a warm (Tex =158±38 K)
component meaning that this molecule is present in both the inner hot corino and the outer cold envelope of IRAS16293
B. The relative abundance with respect to H2 is (6.5±0.6)×10−11 and ≥(6±2)×10−10 for the warm and cold components respectively. Our chemical modelling seems to underproduce the observed abundance for both the warm andcold component under various values of the cosmic-ray ionisation rate (ζ). Key gas phase routes for the formation ofthis molecule might be missing in our chemical network.
Accepted by MNRAS Letters

https://arxiv.org/pdf/1901.02576

The Disk Substructures at High Angular Resolution Project (DSHARP). VII. The
84 PlanetDisk
Interactions Interpretation
Shangjia Zhang1 , Zhaohuan Zhu1 , Jane Huang2 , Viviana V. Guzmán3,4 , Sean M. Andrews2 , Tilman
Birnstiel5, Cornelis P. Dullemond6 , John M. Carpenter7 , Andrea Isella8 , Laura M. Pérez9 , Myriam
Benisty10,11 , David J. Wilner2 , Clément Baruteau12 , Xue-Ning Bai13 and Luca Ricci14
1

Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Parkway, Las Vegas, NV
89154, USA; 2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 00000001-6947-6072; 3 Joint ALMA Observatory, Avenida Alonso de Crdova 3107, Vitacura, Santiago, Chile; 4 Institutode Astrofsica, Pontificia Universidad Catlica de Chile, Av. Vicua Mackenna 4860, 7820436 Macul, Santiago, Chile; 5
University Observatory, Faculty of Physics, Ludwig-Maximilians-Universitt Mnchen, Scheinerstr. 1, D-81679 Munich,Germany; 6 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, D-69120 Heidelberg, Germany; 7Joint ALMA Observatory, Avenida Alonso de Crdova 3107, Vitacura, Santiago, Chile; 8 Department of Physics andAstronomy, Rice University, 6100 Main Street, Houston, TX 77005, USA; 9 Departamento de Astronoma, Universidad
de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 10 Unidad Mixta Internacional Franco-Chilenade Astronoma (CNRS, UMI 3386), Departamento de Astronoma, Universidad de Chile, Camino El Observatorio 1515,
Las Condes, Santiago, Chile; 11 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 12 CNRS/Institut
de Recherche en Astrophysique et Plantologie, 14 avenue Edouard Belin, F-31400 Toulouse, France; 13 Institute forAdvanced Study and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, Peoples Republic ofChina; 14 Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street,
Northridge, CA
E-mail contact: zhaohuan.zhu at unlv.edu
The Disk Substructures at High Angular Resolution Project (DSHARP) provides a large sample of protoplanetarydisks with substructures that could be induced by young forming planets. To explore the properties of planets that
may be responsible for these substructures, we systematically carry out a grid of 2D hydrodynamical simulations,
including both gas and dust components. We present the resulting gas structures, including the relationship between
the planet mass, as well as (1) the gaseous gap depth/width and (2) the sub/super-Keplerian motion across the gap.

52

We then compute dust continuum intensity maps at the frequency of the DSHARP observations. We provide therelationship between the planet mass, as well as (1) the depth/width of the gaps at millimeter intensity maps, (2)the gap edge ellipticity and asymmetry, and (3) the position of secondary gaps induced by the planet. With these
relationships, we lay out the procedure to constrain the planet mass using gap properties, and study the potential
planets in the DSHARP disks. We highlight the excellent agreement between observations and simulations for AS
209 and the detectability of the young solar system analog. Finally, under the assumption that the detected gaps are
induced by young planets, we characterize the young planet population in the planet masssemimajor axis diagram.
We find that the occurrence rate for >5 MJ planets beyond 5-10 au is consistent with direct imaging constraints. Disk
substructures allow us to probe a wide-orbit planet population (Neptune to Jupiter mass planets beyond 10 au) thatis not accessible to other planet searching techniques.
Accepted by The Astrophysical Journal Letters
http://adsabs.harvard.edu/pdf/2018ApJ...869L..47Z
http://arxiv.org/pdf/1812.04045

Anchoring Magnetic Fields in Turbulent Molecular Clouds II - from 0.1 to 0.01 parsec

85

Y. Zhang1 , Z. Guo1 , H.H. Wang1 & H-b Li1
1

Department of Physics, The Chinese University of Hong Kong, Shatin, New Territory, Hong Kong, China

E-mail contact: hbli at cuhk.edu.hk
We (Li et al. 2009; Paper-I) compared the magnetic field directions inferred from polarimetry data obtained from
100-pc scale inter-cloud media (ICM) and from sub-pc scale molecular cloud cores. The highly correlated result led
us to conclude that cloud turbulence must be sub-Alfvenic. Here we extend the study with 0.01-pc cores observed byinterferometers. The inferred field directions at this scale significantly deviate from that of the surrounding ICM. An
obvious question to ask is whether this high-resolution result contradicts the sub-Alfvenic picture concluded earlier.
We performed MHD simulations of a slightly super-critical (magnetic criticality = 2) clouds with Alfvenic Mach
number MA=0.63, which can reproduce the Paper-I results, and observed the development towards smaller scales.
Interestingly, all subregions hosting cores with nH2 > 105 cc−1 (the typical density observed by interferometers) possess
MA=2–3. Not too surprisingly, these slightly super-Alfvenic cores result in B-field orientation offsets comparable tothe interferometer observations. The result suggests that gravity can concentrate (and maybe also contribute to,which takes more study to confirm) turbulent energy and create slightly super-Alfvenic cores out from sub-Alfvenic
clouds. The results of our simulations also agree with the observed velocity-scale (Kauffmann et al. 2013), mass-scale(Lombardi et al. 2010) and field strength-density (Li et al. 2015; Crutcher et al. 2010) relations.
Accepted by ApJ
http://arxiv.org/pdf/1901.03964

86

Inclined massive planets in a protoplanetary disc: gap opening, disc breaking, andobservational 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 3D hydrodynamical simulations to study planet-disc interactions for inclined high-mass planets, focusing
on the disc’s secular evolution induced by the planet. We find that, when the planet is massive enough and theinduced gap is deep enough, the disc inside the planet’s orbit breaks from the outer disc. The inner and outer discs
precess around the system’s total angular momentum vector independently at different precession rates, which causes
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 simulated
broken discs. Both disc shadowing in near-infrared images and gas kinematics probed by molecular lines [e.g. from53

the Atacama Large Millimeter/submillimeter Array (ALMA)] can reveal the misaligned inner disc. The relationshipbetween the rotation rate of the disc shadow and the precession rate of the inner disc is also provided. Using ourdisc breaking condition, we conclude that the disc shadowing due to misaligned discs should be accompanied by deepgaseous 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, and HD 143006) and these systems should be the prime targets
for searching young massive planets (>MJ ) in discs.
Accepted by MNRAS
http://adsabs.harvard.edu/pdf/2019MNRAS.483.4221Z
http://arxiv.org/pdf/1812.01262

87

The VMC Survey - XXXII. Pre-main-sequence populations in the Large Magellanic
Cloud
Viktor Zivkov1,2 , Joana M. Oliveira1 , Monika G. Petr-Gotzens2 , Maria-Rosa L. Cioni3 , Stefano Rubele4,5 ,Jacco Th. van Loon1 , Kenji Bekki6 , Felice Cusano7 , Richard de Grijs8,9,10 , Valentin D. Ivanov2 , Marcella
Marconi11 , Florian Niederhofer3 , Vincenzo Ripepi11 and Ning-Chen Sun12
1

Lennard-Jones Laboratories, School of Chemical and Physical Sciences, Keele University, ST5 5BG, UK; 2 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany; 3 Leibniz-Institut für
Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany; 4 Dipartimento di Fisica e Astronomia,
Università di Padova, Vicolo dellOsservatorio 2, I-35122 Padova, Italy; 5 Osservatorio Astronomico di Padova INAF,
Vicolo dellOsservatorio 5, I-35122 Padova, Italy; 6 ICRAR, M468, University of Western Australia, 35 Stirling Hwy,
6009 Crawley, Western Australia, Australia; 7 INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via
P. Gobetti 93/3, I-40129 Bologna, Italy; 8 Department of Physics and Astronomy, Macquarie University, Balaclava
Road, Sydney, NSW 2109, Australia; 9 Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie
University, Balaclava Road, Sydney, NSW 2109, Australia; 10 International Space Science Institute–Beijing, 1 Nanertiao, Zhongguancun, Hai Dian District, Beijing 100190, China; 11 INAF-Osservatorio Astronomico di Capodimonte,
via Moiariello 16, 80131, Naples, Italy; 12 Kavli Institute for Astronomy & Astrophysics and Department of Astronomy,
Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871, China
E-mail contact: v.zivkov at keele.ac.uk
Detailed studies of intermediate- and low-mass pre-main-sequence (PMS) stars outside the Galaxy have so far been
conducted only for small targeted regions harbouring known star formation complexes. The VISTA Survey of the
Magellanic Clouds (VMC) provides an opportunity to study PMS populations down to solar masses on a galaxy-wide
scale. Our goal is to use near-infrared data from the VMC survey to identify and characterise PMS populations
down to ∼1 M⊙ across the Magellanic Clouds. We present our colour−magnitude diagram method, and apply it to a
∼ 1.5 deg2 pilot field located in the Large Magellanic Cloud. The pilot field is divided into equal-size grid elements. We
compare the stellar population in every element with the population in nearby control fields by creating Ks /(Y − Ks )Hess diagrams; the observed density excesses over the local field population are used to classify the stellar populations.
Our analysis recovers all known star formation complexes in this pilot field (N 44, N 51, N 148, and N 138) and forthe first time reveals their true spatial extent. In total, around 2260 PMS candidates with ages <∼10 Myr are foundin the pilot field. PMS structures, identified as areas with a significant density excess of PMS candidates, display a
power-law distribution of the number of members with a slope of −0.86 ± 0.12. We find a clustering of the youngstellar populations along ridges and filaments where dust emission in the far-infrared (FIR) (70 µm – 500 µm) is bright.
Regions with young populations lacking massive stars show a lower degree of clustering and are usually located in
the outskirts of the star formation complexes. At short FIR wavelengths (70 µm, 100 µm) we report a strong dust
emission increase in regions hosting young massive stars, which is less pronounced in regions populated only by lessmassive (<∼4 M⊙ ) PMS stars.
Accepted by Astronomy & Astrophysics

https://arxiv.org/pdf/1810.03917.pdf

54

Dissertation Abstracts

Thermal Evolution of Forming Planets
Isotope Enrichment, Differentiation & Volatile Retention
Tim Lichtenberg

Institute of Geophysics & Institute for Astronomy, ETH Zürich, Switzerland
Current address: Atmospheric, Oceanic and Planetary Physics, University of Oxford, United Kingdom
Electronic mail: tim.lichtenberg@physics.ox.ac.uk
Ph.D dissertation directed by: Taras V. Gerya & Michael R. Meyer
Ph.D degree awarded: October 2018
Discoveries of extrasolar planets in the last decades raise the question of how common Earth-like worlds with clement
surface environments are within the galaxy. Because astronomical observations are ultimately limited in providing acomplete picture of the planetary census, a comprehensive understanding of planetary systems’ formation and evolution
can deliver valuable insights into key physical and chemical properties that cannot be probed by remote sensing alone.
In order to understand how terrestrial worlds are formed and distributed, I investigate in this thesis the early evolutionof planetary systems and the interior dynamics and volatile retention of rocky protoplanets.
To place the solar system in the context of the extrasolar planet population, I model the enrichment of protoplanetarydisks with short-lived radionuclides, namely 26 Al and 60 Fe, in typical star-forming environments. I find their distribution to be dichotomous: many planetary systems with zero or negligible abundances, and fewer systems with levels
comparable to the early solar system. Further, I quantify the parametric controls on interior evolution and volatile lossof planetesimals that accrete to form terrestrial planets. I derive the primary thermochemical regimes for the build-up
of internal magma oceans, core segregation, chemical differentiation, and volatile retention. Matching planetesimal
interior evolution with meteoritic evidence, I constrain the accretion dynamics and reprocessing of planetary materials
in the early solar system, in order to gain a better understanding of planetary assembly. Finally, by extrapolating thederived mechanisms to the exoplanet population, I demonstrate the primary influence of short-lived radionuclides on
the efficiency of volatile delivery to terrestrial planets: enriched systems with solar-like or higher levels tend to form
water-depleted planets, while not- or barely-enriched systems dominantly form ocean worlds.
My findings provide a direct link between the star-forming birth environment of planetary systems and the compositional make-up and long-term evolution of rocky planets that form in them. The system-to-system deviations in
the abundance of short-lived radionuclides across young star-forming regions qualitatively distinguish planetary systems’ formation and evolution, and control the distribution and prevalence of terrestrial planets with Earth-like bulk
compositions.
Thesis link: https://doi.org/10.3929/ethz-b-000298059
55

New Jobs

Tenure track position at Lund University in observations andcharacterisation of exoplanets
Lund Observatory at Lund University is recruiting a person into a tenure-track faculty position in observational
studies of exoplanets. The Associate Senior Lecturer will conduct research on the detection of exoplanets, in studies
of exoplanet atmospheres or in the characterization of exoplanet host stars, with the purpose of understanding theplanetary system.
The new Associate Senior Lecturer will join a vibrant scientific environment at Lund Observatory. Research work at
Lund Observatory has as a common focus the formation and evolution of the Milky Way and its constituents. Our
work combines theory with observations and science support for space missions. Data from ESA’s Gaia satellite gives
information about the Milky Way and will find some several thousand exoplanetary systems. Astronomers in Lund
are involved in programmes for processing and exploitation of Gaia data, and for the acquisition of complementary
data from ground-based telescopes (e.g., Gaia-ESO Survey). Theoretical work concerns the formation and dynamics
of exoplanetary systems, the growth of black holes, and the progenitors of the brightest explosions in the Universe(supernovae and gamma-ray bursts). Observational as well as theoretical work benefits from our participation indevelopment and preparation of next generation instrumentation (e.g., 4MOST and PLATO).
All employees in Sweden and at Lund University enjoy full access to the national health care system. The position
includes 5 weeks paid annual leave. For employees with small children there are extra possibilities of leave and there
are state provided daycare facilities.
Last day of applying: 28 February 2019
Full job announcement (apply here):
http://www.astro.lu.se/Staff/staff_vacancies.html
Information about Lund Observatory:
http://www.astro.lu.se/
http://www.astro.lu.se/Research/
Inquiries about position: Professor Anders Johansen (anders@astro.lu.se)

PhD and Postdoc Positions in Observational Astrochemistry, Niels
Bohr Institute, Copenhagen, Denmark
The Niels Bohr Institute, University of Copenhagen, Denmark, offers two positions, a PhD and a postdoc position, invarious aspects of observational astrochemistry.
The candidates will join the group of Lars Kristensen in the Section of Astrophysics and Planetary Sciences at the Niels
Bohr Institute. The group focuses on understanding the chemistry and physics of star-forming regions, specificallyby observing such regions at millimeter and sub-millimeter wavelengths with telescopes such as the Atacama Large
Millimeter/sub-millimeter Array (ALMA), and the SubMillimeter Array (SMA). These observations are coupled withradiative-transfer models to further understand and constrain the chemistry taking place in these regions.
More information is available here:
PhD position: https://jobportal.ku.dk/phd/?show=148817
Postdoc position: https://jobportal.ku.dk/videnskabelige-stillinger/?show=148815
The deadline for both positions is Feb 28th, 2019.
56

Lecturer / Senior Lecturer / Reader in Mathematics and Physics(Astrophysics)
We are seeking to recruit an experienced academic to a joint position between Mathematics and Physics within the
School of Science and Engineering at the University of Dundee. This is a full time permanent Teaching & Research
position and depending on experience the appointment will be on the level of Lecturer, Senior Lecturer, or Reader(approximately equivalent to the assistant professor to professor range). We are looking for a highly motivated,
enthusiastic and collegiate individual with a PhD in Astrophysics, Physics or Mathematics and an excellent researchrecord who maintains, or develops, a vigorous, independent, theoretical or computational research programme. Bothdisciplines contribute to an active research cluster in Astrophysics within the School and we would particularly welcome
applications from individuals who complement our existing research strengths in star formation, exoplanet systems,
solar magnetohydrodynamics and scientific computing. We will also consider exceptional applications from otherrelated Mathematical Physics research fields and encourage applications from holders of personal fellowships.
We deliver BSci and MSci degrees in Physics with Astrophysics, Mathematics and Astrophysics, Mathematics, andPhysics. The successful candidate will be expected to contribute with high-quality teaching to these programmes.
Full details of the required criteria for the position can be found in the Further Particulars posted on
https://www.dundee.ac.uk/hr/uodrecruitmen/jobvacancies/
Please submit with your completed application form your full CV, a five year research plan, and a statement on yourapproach to teaching. More information about the post may be obtained by contacting both Professor Gunnar Hornig(g.hornig@dundee.ac.uk) and Professor David Keeble (d.j.keeble@dundee.ac.uk).
We welcome applications from everyone irrespective of gender or ethnic group. As women and members of ethnic
minorities are currently under-represented in posts at this level we particularly encourage applications from membersof these groups. As a global University, we are interested in attracting candidates working in all parts of the world
and can offer relocation support.
Closing date for receipt of applications: Wednesday 20 March 2019

PhD position in numerical studies of protostellar disks
Applications are invited for a PhD position in numerical studies of protostellar disks in the Astrophysics group of Prof.
Manuel Guedel at the Institute of Astrophysics, University of Vienna, Vienna. The position is funded by the FWF
grant ”The chemodynamical evolution of circumstellar disks with non-solar metallicities”. The successful candidate
will study the chemical evolution of young protostellar disks using sophisticated thermochemical codes (ProDIMO,
ANDES) in tight collaboration with chemodynamical studies of protostellar disks led by Dr. Eduard Vorobyov. The
project is focused 1) on the implications of low metal content for the chemical and dynamical evolution of young
circumstellar disks, 2) on the role of gravitational instability and fragmentation in sub-solar and low-metallicity disks,
3) on the character of protostellar accretion at non-solar metallicities, and 4) on making predictions for observational
campaigns of low-metallicity star-forming regions.
The successful applicant should have a background in astrophysics and/or astrochemistry, and also basic knowledgeof Fortran, IDL, and Python is desirable. Her/his tasks will involve modification and improvement of astrochemical
codes, as well as performance and analysis of chemical and chemodynamical simulations of circumstellar disks. The
candidate should hold a MSc. degree in physics, astronomy or a related field. The appointment will be for three
years. The salary is based on the Austrian scale for PhD students (75% employment, gross annual salary 37,680).
The University of Vienna is an equal opportunity employer in accordance with Austrian laws.
Closing date for application is February 18, 2019, but search will continue until the position is filled. Applicants should
send a single PDF file containing a short resume, educational record, and a statement of research interests. Please,also arrange for two letters of recommendation to be sent to Dr. Eduard Vorobyov. The preferable starting date isJune-July 2019. For further questions, please, contact Dr. Eduard Vorobyov at eduard.vorobiev(at)univie.ac.at57

Postdoctoral Fellow Position: Time-domain and/or
Exoplanetary/Substellar Astronomy
Prof. Stanimir Metchev at the University of Western Ontario (UWO) and Centre for Planetary Science and Exploration(CPSX), Canada, invites applications for a Postdoctoral Fellow. Two areas of expertise are sought, and applicantswith qualifications in either or both areas are invited to apply.
The first area of expertise is time-domain astronomy and automation of telescopic observations. The successful
applicant will be expected to aid with the commissioning and operations of an array of three 0.5m robotic telescopes
equipped with rapid-imaging cameras for detecting stellar occultations by Kuiper Belt Objects or transiting extrasolar
planets. Strong computer programming expertise is required. Background in systems automation, data management,
or image analysis would be advantageous.
The second area of expertise is exoplanetary or brown dwarf astrophysics. The successful applicant will be expected tolead aspects of on-going programs with the Spitzer Space Telescope and TESS. Background in precision photometry,
spectroscopy, or time series analysis would be advantageous.
The candidate will be expected to actively pursue additional ground-based observations in support of one or both of
the above programs. Depending on interest, additional opportunities for collaboration with Metchev’s group exist in
the fields of brown dwarfs, exoplanets, circumstellar debris disks, or solar system astronomy.
UWO has access to all Canadian national telescopes, including Gemini, the CHFT, ALMA, and a slew of 1-2 metreclass telescopes. Metchev’s team also regularly uses other facilities, including Spitzer, TESS, Hubble, Magellan, NOAO
telescopes, NASA/IRTF, and McDonald Observatory.
Candidates must have a doctoral degree in Astronomy or a related field. The start date is flexible, but preferably
no later than September 1, 2019. Candidates should submit a curriculum vitae, a 2-3-page statement of researchexperience and interests, and the names and contacts of three references directly to Prof. Metchev. The position is
open until filled. For full consideration, complete applications should be received by March 1, 2019.
For further information, please contact Prof. Metchev (smetchev@uwo.ca).

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.

58

Meetings

Second Announcement

Workshop on Polarization in Protoplanetary Disks and Jets
Abstract submission by 28th February 2019
May 20-24, 2019 - Sant Cugat del Vallès, Catalonia Spain
https://sites.google.com/view/sant-cugat-forum-astrophysics/next-session
The study of the formation and evolution of protoplanetary disks around young stars saw a tremendous boost by theadvent of ALMA and the development of new capabilities in the infrared and radio telescopes, thanks to the huge
combined improvement in sensitivity, angular resolution, and image fidelity. However, the role of magnetic fields in theformation and evolution of disks around young stars is still a poorly understood topic. Are protoplanetary disks andprotostellar jets magnetized? Polarimetric observations are the primary means to obtain information regarding themagnetic fields. However, this technique can be hampered by other polarization mechanisms such as dust selfscattering,radiation alignment of aspherical grains or anisotropic resonant scattering of linear polarization of molecular lines. The
main goal of this focused meeting is to bring together observers and theoreticians interested in the study of magnetic
fields in protoplanetary disks and protostellar jets as well as polarization mechanisms to review the current state of
the research and explore effective means to probe magnetic fields.
Confirmed Invited Speakers: Carlos Carrasco-González, Benoı̂t Comenrçon, Paulo Cortes, Christian Fendt, Martin
Houde, Akimasa Kataoka, Ana´’elle Maury, Ya-Wen Tang, Zhaohuan Zhu
Important Dates:
Close Abstract submission: February 28, 2019
Close Early Registration and payment: April 30, 2019
The number of participants is limited to about 70
The Scientific Organizing Committee: Maria Teresa Beltran, Gemma Busquet, Jean Francois Donati, Josep Miquel
Girart, Shih-Ping Lai, Aina Palau, Mayra Osorio, Wouter Vlemmings, Qizhou Zhang

Cloudy workshop 2019
Registration is now open for the Cloudy workshop to be held from 2019 May 20 to May 24 at the University of Kentucky.
Cloudy is a large-scale code that simulates the microphysics of matter exposed to ionizing radiation. It calculates theatomic physics, chemistry, radiation transport, and dynamics problems simultaneously and self-consistently, building
from a foundation of individual atomic and molecular processes. The result is a prediction of the conditions in thematerial and its observed spectrum. The workshop will cover observations, theory, and application of Cloudy to awide variety of astronomical environments. This includes the theory of diffuse matter and quantitative spectroscopy,
the science of using spectra to make physical measurements. We will use Cloudy to simulate such objects as AGB
stars, Active Galactic Nuclei, Starburst galaxies, and the intergalactic medium. The sessions will consist of a mix of
textbook study, using Osterbrock & Ferland, ’Astrophysics of Gaseous Nebulae and Active Galactic Nuclei’, applicationof Cloudy to a variety of astrophysical problems, and projects organized by the participants. No prior experience with
Cloudy is assumed although some knowledge of spectroscopy and the physics of the interstellar medium is useful.
To register please visit http://cloud9.pa.uky.edu/~gary/cloudy/CloudySummerSchool/
59

Smoothed Particle Hydrodynamics International Workshop
June 25 - 27, 2019 - Exeter, UK
Dear colleagues:
It is for me a pleasure to invite you to the 2019 edition of the SPHERIC international workshop, devoted to thepromotion and development of the Smoothed Particle Hydrodynamics method, that will take place in Exeter (UK)from the 25th to the 27th of June 2019.
The SPHERIC Workshop is the definitive global meeting focussed on the Smoothed Particle Hydrodynamics (SPH)
computational method and related meshless particle approaches. Some examples of the research topics that will becovered during the workshop will be:* Interaction with solids and complex structures * Free surface flows and moving boundaries * Multi-phase flows
and multiple continua * Viscosity and turbulence modelling * Incompressible flows * Astrophysics * Maritime andnaval architecture applications * Hydraulic applications * Microfluidics * Disaster simulations * Solids and Fracture
Mechanics
Before the main workshop, the optional training day on the 24th of June will provide an intensive theoretical andhands-on introduction to state-of-the-art SPH. This is ideal for students beginning their work in the field, but will also
be of interest to seasoned researchers who want to explore specific themes in depth, or experience latest developments
in SPH software.
The registration process and call for abstract submission is now open. The deadline for abstract submission is the
18th of February. Contributions from all areas and applications of the SPH method are extremely welcome. All the
relevant deadlines and detailed information can be found at the conference webpage:
http://spheric2019.co.uk/
Please, feel free to circulate this email amongst your colleagues and do not hesitate to contact me if you have any
doubt. Thanks a lot for your time and looking forward to see you in Exeter.
Kind regards,
Pablo Loren-Aguilar
Chair of the 2019 SPHERIC international workshop on Smoothed Particle Hydrodynamics

Partially Ionised Plasmas in Astrophysics - PIPA2019
3 - 7 June 2019, Palma de Mallorca, Spain
http://solar1.uib.es/pipa2019/
The Partially Ionised Plasmas in Astrophysics meetings are a series of conferences whose core subject is the study ofpartial ionisation effects in any Astrophysical context.
PIPA2019, the 3rd meeting of the series, will be organised in Palma de Mallorca (Spain) in the period 03 07 June
2019. The meeting is hosted by the Solar Physics group of the University of the Balearic Islands, Spain.
The meeting aims to broaden and strengthen the collaboration of scientists working in partially ionised plasmas inspace (e.g., solar chromosphere, interstellar medium, protostellar discs, planetary magnetospheres and ionospheres,etc.) and to develop common scientific interests that could enhance cross-collaborations between scientists working inthis field.
The meeting will focus on (but is not limited to) the following topics:
Partially ionised plasmas in the solar atmosphere - Electrodynamics of planetary magnetospheres - Astrophysicalpartially ionised plasmas
The format of this edition will be similar to that of the previous ones: a 5-day informal-style meeting with significant
time for discussions. The meeting will take place in the hotel Amic Miraflores, located 6.5 km from Palma de Mallorcas
airport and 8 km from downtown Palma.
60Second Announcement
Gaia’s view of pre-Main Sequence evolution. Linking the T Tauri and
Herbig Ae/Be stars
Leeds, UK 18-21 June 2019
Abstract Submission 15 April 2019
The Herbig Ae/Be stars bridge the gap in mass between the lower mass T Tauri stars and the higher mass Massive
Young Stellar Objects. By linking the low and high mass stars, the Herbig Ae/Be stars are crucial in finding similarities
and differences between the formation processes in both regimes. The time is ripe for experts to come together anddiscuss their latest results on star formation. The time is also ripe to probe the links between the T Tauri stars andHerbig Ae/Be stars in more detail and a major aim of the workshop is to bring the respective communities together
to compare and contrast the properties, appearance and formation mechanisms of both types of object
The registration is now open at https://starry-project.eu/final-conference/
Topics include:
Pre-Main sequence evolution models and observations
T Tauri stars, Herbig Ae/Be stars, related objects and their links
Evolution of the circumstellar disks
Accretion, theory, observations, episodic accretion
Magnetic fields
The circumstellar environment, disks, outflows, planets
Clusters and multiplicity
Gaia and other modern facilities
Confirmed invited speakers are:
Evelyne Alecian, France
Allessandro Bressan, Italy
Sean Brittain, USA
Jerome Bouvier, France
Nuria Calvet, USA
Antonio Garufi, Italy
Lee Hartmann, USA
Lynne Hillenbrand, USA
Alcione Mora, Spain
James Muzerolle, USA
Antonella Natta, Ireland
Christian Schneider, Germany
The SOC consists of René Oudmaijer, UK (chair); Ricardo Pérez Martinez, Spain; Deborah Baines, Spain; Ignacio
Mendiguta, Spain; Willem-Jan de Wit, ESO Chile; John Fairlamb, USA; Gaitee Hussain, ESO Germany
More information is to be found on the conference web-site https://starry-project.eu/final-conference/61

Exploring the Infrared Universe: The Promise of SPICA
Crete, Greece, 20-23 May 2019http://www.spica2019.org/
Science rationale:
The infrared wavelength range is key to understand the origin and evolution of galaxies, stars and planetary systems,
which are obscured by dust during a large part of their life cycles. With a large cold mirror and a sensitive suite of
instruments, SPICA, in 2018 selected as a candidate for ESAs Cosmic Visions program, stands poised to revolutionize
these fields by providing ultra-deep spectroscopy in the 12-230 µm range, as well as imaging (17–37 µm and 100–350µm) and polarimetry (100–350 µm). With launch planned for 2030, SPICA will provide a huge leap in capabilities
over previous infrared space missions, and complement current and upcoming facilities, filling the spectral gap between
JWST and ALMA. We would like to invite the international astronomical community to participate in the conference,
Exploring the Infrared Universe: The Promise of SPICA, which will take place on the island of Crete on 20–23
May 2019. At this conference, participants will learn about the capabilities and current design of SPICA, which
includes a significant Guest Observer program, while discussing the exciting scientific promise of the mission. Up todate information about the SPICA mission and its instruments can be found at http://www.spica-mission.org, inaddition to links to a set of whitepapers recently published in the journal PASA, that focus on some of the scienceenabled by SPICA.
Topics to be addressed:• Galaxy evolution• Metals and dust across cosmic time
• Star formation and the baryon cycle in galaxies• Galactic star formation• Formation of habitable planets• Debris disks, planetary systems, and the Solar system
Confirmed invited speakers:
Susanne Aalto, Michihiro Takami, Françoise Combes, Bill Dent, Edith Falgarone, Davide Fedele, Andrea Ferrara,
Javier Goicoechea, Masateru Ishiguro, Patrick Koch, Leon Koopmans, Diane Cormier, Roberto Maiolino, Margaret
Meixner, Thomas Müller, Tohru Nagao, Klaus Pontoppidan, Alexandra Pope, Peter Roelfsema
Scientific organizing committee:
Lee Armus, Martin Giard, Sue Madden, Marc Audard, Matt Griffin, Mikako Matsuura, Vassilis Charmandaris, Doug
Johnstone, Stefanie Milam, Carlotta Gruppioni, Inga Kamp, Paco Najarro, Yasuo Doi , Hidehiro Kaneda, Takashi
Onaka, Eiichi Egami, Ciska Kemper, Luigi Spinoglio, David Elbaz, Kotaro Kohno, Floris van der Tak (chair) Jan
TauberLocal organizing committee:
Margaret Balothiari, Vassilis Charmandaris (chair), Evangelia Ntormousi, Raphael Skalidis, Kostas Tassis

62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
New Quests in Stellar Astrophysics IV. Astrochemistry, astrobiology and the Orign of Life
31 March - 5 April 2019, Puerto Vallarta, Mexico
http://www.inaoep.mx/puerto19
New Horizons in Planetary Systems
13 - 17 May 2019 - Victoria, Canada
http://go.nrao.edu/NewHorizons
Exploring the Infrared Universe: The Promise of SPICA
20 - 23 May 2019, Crete, Greece
http://www.spica2019.org
Workshop on Polarization in Protoplanetary Disks and Jets
20 - 24 May 2019, Sant Cugat del Vallès, Catalonia, Spain
http://sites.google.com/view/sant-cugat-forum-astrophysics/next-session
Cloudy Workshop
20 - 24 May 2019, University of Kentucky, USA
http://cloud9.pa.uky.edu/~gary/cloudy/CloudySummerSchool/
Star Clusters: from the Milky Way to the Early Universe
27 - 31 May 2019, Bologna, Italy
http://iausymp351.oas.inaf.it/
Partially Ionised Plasmas in Astrophysics
3 - 7 June 2019, Palma de Mallorca, Spain
http://solar1.uib.es/pipa2019/
Zooming in on Star Formation - A tribute to Åke Nordlund
9 - 14 June 2019, Nafplio, Greece
http://www.nbia.dk/nbia-zoomstarform-2019
From Stars to Planets II: Connecting our Understanding of Star and Planet Formation
17 - 20 June 2019, Gothenburg, Sweden
http://cosmicorigins.space/fstpii
Gaia’s View of Pre-Main Sequence Evolution. Linking the T Tauri and Herbig Ae/Be Stars
18 - 21 June 2019, Leeds, UK
https://starry-project.eu/final-conference
Gordon Conference on Origins of Solar Systems: Meteoritical, Spacecraft and Astrophysical Perspectives on the Assembly and Composition of Planets
23 - 28 June 2019https://www.grc.org/origins-of-solar-systems-conference/2019/63

Astrochemistry: From nanometers to megaparsecs - A Symposium in Honour of John H. Black24 - 28 June 2019, Gothenburg, Sweden
https://www.chalmers.se/en/conference/JHBlacksymp2019/
Smoothed Particle Hydrodynamics International Workshop
25 - 27 June 2019, Exeter, UK
http://spheric2019.co.uk/
Great Barriers in Planet Formation
21 - 26 July 2019 Palm Cove, Australia
https://dustbusters.bitbucket.io/great-barriers-2019/
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/

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

64