THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 325 — 15 January 2020

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

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

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Abstracts of Newly Accepted Papers . . . . . . . . . . . 9
Abstracts of Newly Accepted Major Reviews . . 30

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

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 31

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

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Summary of Upcoming Meetings . . . . . . . . . . . . . . 36

Editorial Board
Joao Alves
Alan Boss
Jerome Bouvier
Lee Hartmann
Thomas Henning
Paul Ho
Jes Jorgensen
Charles J. Lada
Thijs Kouwenhoven
Michael R. Meyer
Ralph Pudritz
Luis Felipe Rodríguez
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

Cover Picture
The L1622 cloud in Orion is a ﬁne case of a brightrimmed cometary cloud. It is located just outside ofBarnard’s Loop, and points towards the OB stars in
the Orion Nebula Cluster. The bright nebulous star
near the center of the image is the young multiple
system HBC 515.
Subaru 8m image by Bo Reipurth
Processing by Robert Gendler.

Submitting your abstracts
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submitting
abstractsand dissertation abstracts (by e-mail toreipurth@ifa.hawaii.edu)
areappendedtoeach Call for Abstracts.
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Perspective
Protostellar accretion and its
impact on the pre-main
sequence evolution
Emanuele Tognelli

1

Introduction

The detailed computation of what happens to a star at the
beginning of its life, the phases that lead to the formationof a star (protostellar evolution) and the subsequent premain sequence evolution (PMS) has been a hard task formany years. Starting from the pioneering work by Larson(1969), which analysed the protostellar evolution from thegravitational collapse of the parental cloud to the PMS
phase, recently such an evolution has been revised thanks
to the improvements in both the input physics and computational power. A particularly interesting result is thateven if the ﬁrst collapsing phases are diﬃcult to follow, thesimulations predict the formation of a hydrostatic core:
the characteristics of such a hydrostatic core (2nd Larsoncore) such as its mass, radius, temperature and density,
appear to be very robust.
The ideal approach would be to follow the whole protostellar and then stellar evolution in hydrodynamical simulation, to treat simultaneously and in detail the structureand evolution of both the protostar and the surrounding
material that falls on it. However, such an approach is at
the moment extremely diﬃcult and not feasible. To overcome this problem, some simpliﬁcations can be adopted.
A common approach consists in starting the protostellar evolution after the formation of the 2nd Larson core,when the central protostar is assumed to be hydrostatic.
The matter surrounding the star can be treated both as aspherical structure that radially falls on the star (sphericalaccretion, e.g. Stahler et al. 1980) or a disc like structure that provides accreting matter via accretion streams(disc accretion, e.g. Hartmann et al. 1997). In this shortreview, I will present some of the main characteristics ofaccreting models in these two geometries (spherical or discaccretion) and some related problems, focusing on the formation of low-mass (M < 1 M⊙ ) solar metallicity stars.
More details can be found in the review by Larson (2003)
and Hartmann et al. (2016).

3

Cloud collapse and protostellar accretion

Stars form in a region (cloud) that contracts and gives
birth to denser cores that eventually form the protostar
and then the star. In this process, the mass of a protostar
progressively increases as the matter in the cloud falls onto
a central denser object. The cloud collapse is a complexhydrodynamical problem, a challenging task in the stellar
formation ﬁeld. Depending on the characteristics of thecloud and on the conﬁguration assumed in the computations (chemical composition, magnetic ﬁelds, rotation,geometry...) the collapse occurs faster or slower, but thegeneral evolution can be summarised as outlined below(for more details see Larson 1969, 1972 and the review by
Larson 2003):• Isothermal collapse: during the ﬁrst collapse, thecloud does not warm up as it contracts. This istrue until a central density of about 10−13 g cm−3 isreached. When this occurs, the matter in the inner
region of the cloud is dense enough to partially trap
radiation.
• Formation of the first Larson core: the energy is partially trapped inside the denser region of the cloud
preventing a further collapse of this region. A ﬁrst
temporarily hydrostatic core forms (with a mass ofabout 0.01 M⊙ and a radius of several AU). Outsideof it the matter is still falling on the core. There isa transition region (shock front) close to the surfaceof the core where the matter settles and passes fromsupersonic to subsonic.
• Second collapse: the hydrostatic core contracts because it can partially radiate energy at the surface.
So, although its mass is increasing due to accretionof mass, its radius shrinks. The contraction of thecore leads to a temperature rise, until T ∼ 2000 K
is reached, and molecular hydrogen dissociates. The
contraction energy does not warm the core but it isused to dissociate H2 . The density and pressure of
the core increase.
• Formation of the 2nd Larson core: after the total
dissociation of H2 and the increase of density andpressure, the s occurta5111(c)-1.3r aD(i).34903()0.673904(e)-1x

protostellar evolution cannot be easily checked with obser- mainly concerns the geometry of the accreting protostarvations, as the protostellar evolution in these ﬁrst phases envelope system:
occurs within the cloud and the central core cannot be• Spherical accretion (see e.g. Stahler et al. 1980,
directly observed.
Stahler 1988, Stahler & Palla 1991, 1992, 1993).
The star is supposed to be deeply embedded into
the parental cloud and the matter falls on it almost
4 Protostellar accretion in hydroradially. The whole stellar surface is subjected tostatic stellar evolution codes
the accretion and as such in this case the energy
radiated from the star can be reabsorbed by the enThe hydrodynamical evolution of accreting stars is stillvelope. The whole protostellar accretion occurs as aa challenging task from the computational point of view.
radial infall, from a cloud that has mass enough to
For only a few cases has it been possible to follow a portion
generate the star, at a ﬁxed value of the accretionof the evolution for PMS stars. However, for what conrate.
cerns the central protostar, it is not necessary to employ a• Disc accretion (Hartmann et al. 1997, Siess et al.
hydrodynamical code, as the protostar itself is hydrostatic1997). The matter falls from a boundary layer ofif the accretion phase after the formation of the 2nd Lara disc and reaches the star via accretion streams.
son core is considered. In this approximation, the central
Most of the stellar surface is not subjected by theobject can be described using a mono dimensional hydroaccretion and the star is free to radiate its energy,
static stellar evolutionary code (e.g. Siess et al. 1997,
most of which is lost in space. The disc structure is
Stahler et al. 1980).
assumed to be totally decoupled from the that of the
The problem resides in the characteristics of the envelope
central star and it is not treated in the stellar evosurrounding the protostar, which does not satisfy the hylution code (nor its evolution neither its structure).
drostatic conditions. It is important to remember that the
The parameters that deﬁne the accretion (accretion
structure of the envelope of matter surrounding the starrate, disk lifetime, accretion energy) consequently
provides the characteristics of the accretion ﬂow. In moreare considered as external free parameters which candetail, it gives information about the following quantities:
be taken from detailed accretion disc evolution codes(e.g. Vorobyov & Basu 2010, Baraﬀe et al. 2012).
• The accretion rate. The accretion rate (ṁ) deﬁnes
the rate at which the star changes its mass in time. The spherical accretion scenario is likely to describe the
The value of ṁ can vary of order of magnitude dur- ﬁrst stages of the formation of the protostar when the staring the accretion phase, passing from ṁ< 10−6 - is still embedded within the cloud that retains an approx10−7 M⊙ /yr (quiescent accretion) to rapid and in- imate spherical geometry. However, observations suggest
tense episodes of accretion of matter (bursts, ṁ∼ that at some stage of protostellar evolution, the cloud col10−4 -10−3 M⊙ /yr, e.g. FU Ori stars, Hartmann & lapses to a disc, and it is during the disc accretion that
Kenyon 1996).
the star gains most of its ﬁnal mass. So, both scenarios are interesting and describe a part of the protostellar
accretion.

• The energy in the accreted matter. The matter that
falls on the star before reaching the stellar surface
has a kinetic energy. However, when it settles on thestellar surface, the kinetic energy is equal to zero.
So, energy conservation states that the kinetic energy has been converted into another form of energy. Depending on the characteristic of the accretion ﬂow, such an energy can be thermal energy (theaccreted matter is hot), or the energy can be radiated (photons) before the matter reaches the stellar
surface (at the shock front), or part of the energy canbe retained by the matter and part radiated. The
fraction of energy accreted can also depend on theaccretion rate (e.g. Baraﬀe et al. 2012).

The most important diﬀerence between spherical and discaccretion, which deeply aﬀects the protostellar evolution,is the amount of energy retained in the accreted matter.
Indeed, while in the simpliﬁed spherical accretion it is possible to estimate the amount of energy retained by theaccreted matter, in disc accretion this quantity is deﬁned
by a free parameter (αacc ). The impact of this on theevolution is discussed in the next sections.

5

Spherical and disc protostellar accretion

The diﬃculty in treating simultaneously the protostar andthe envelope evolution requires some simpliﬁcation, which The spherical accretion scenario applies to a star that isdeeply embedded in a cloud of gas. In this case, the evo5

10−6 to 10−3 M⊙ /yr), adopting a spherical protostellar
accretion code similar to that used by Stahler and Palla.
They showed that increasing ṁ, the birthline moves towards larger luminosities and radii, thus still in full agreement with the observations.
It is also interesting to note that spherical accretion models produce low-mass stars (on the birthline) in a region
that corresponds to the top of the Hayashi track of standard stellar models (see Figure 3). So, diﬀerences between standard and spherical accreting models in low-massstars are negligible, and consequently standard evolutionary tracks/isochrones can be safely used to infer the characteristic of young stellar populations (at least for ages
above 1 Myr).
However, as anticipated, it is commonly accepted thatstars do not accrete spherically during their whole protostellar phase. They gain most of their mass from anaccretion disc, thus motivating the detailed study of proFigure 3: Comparison between standard tracks (solid tostellar accretion in this geometry.
lines) and the birthline (dotted line) obtained by Palla Diﬀerently from the spherical accretion, in the disc geome& Stahler (1993). Dots represents T Tauri and Herbig try, most of the star is free to radiate its energy into space
Ae/Be stars. Figure adapted from Palla & Stahler (1993). and the accretion streams cover only a very limited partof the stellar surface (few percent, see e.g. Hartmann etal. 1997). All the parameters that deﬁnes the accretion
lution of the star and of the envelope have to be treated(i.e. accretion rate, energy inside the accreted matter) are
simultaneously. This allows to have a consistent evaluatreated as external parameters.
tion of the amount of thermal energy that the accretionﬂows brings inside the star. Qualitatively, the energy emit- In the disc accretion geometry, it is possible to follow also
ted from the stellar surface is not free to escape into space an analytic approach to analyse the main characteristics
since it has to cross the matter around the star, thus such of the protostellar accretion on a forming star. Following
an energy is partially reabsorbed by the matter in the en- the formalism developed by Hartmann et al. (1997), it
velope, and it eventually reaches the star. The eﬀect of is possible to write a simple equation for the temporal
this process is that the star has a kind of external energy evolution of the accreting star radius as follows,source that warms up the stellar surface. The injection
1 GM 2 ṁ
7 RṘinto the star of thermal energy from the accreted mass
(1)
β
−
L
+
α
−
=
D
ph
acc
R
3 GM 27
R M
forces the star to expand or at least to compensate for theradius decrease caused by injection of mass.
where M and R are the stellar mass and radius, βD exThe impact of spherical accretion on the formation of PMS presses the luminosity due to the deuterium burning (Dstars has been largely analysed in the pioneering work by burning), Lph is the luminosity at the stellar surface, ṁStahler and Palla, and recently also by Hosokawa and col- is the mass accretion rate and αacc represents the fraclaborators. One of the main result of such a spherical tion of the accretion energy actually deposed into the staraccretion scenario is that stars during the accretion phase (thermal energy in the accreted matter).
remain bright and extended. Using a mild and constantEquation (1) contains three terms: the ﬁrst and the second
accretion rate of 10−5 M⊙ /yr, Palla & Stahler (1993),
are the normal terms that deﬁnes the evolution of the star
showed that it is possible to produce an accreting sequencewith a surface radiative loss (Lph ) plus D-burning energy
in a region of the HR diagram that corresponds to thegeneration βD , while the last term is that responsible forupper envelope of the locus where young PMS stars are
the accretion, being proportional to ṁ. This term contains
located (see Figure 3). The authors deﬁned this sequencealso the dependency on the thermal energy carried into theas the birthline, which is the locus of stars with diﬀerstar by the accretion (αacc ). Such a parameter has to be
ent masses where the stars become visible when accretion
speciﬁed as an external free parameter that moves in theends.
range [0, 1] (or in case of thin disc [0, 1/2], see e.g. Siess etMore recently, Hosokawa et al. (2009) computed a set of al. 1997). From the same equation, it is also evident thatbirthlines for diﬀerent values of the accretion rate (from αacc = 1/7 ≡ αacc,cr deﬁnes a critical value, meaning that6

for αacc < αacc,cr the third term is negative, and would
contribute to a radius decrease, while for αacc > αacc,cr
the last term produces a radius expansion. It is common
to refer to the case αacc ∼ 0 (or αacc ≪ αacc,cr) as the cold
disc accretion and αacc > αacc,cr as the hot disc accretion.
Looking at eq. (1) it is clear that a radius expansion requires a positive value of the right side of equation, which
can be obtained both having 1) an eﬃcient deuterium
burning (large βD ) or 2) an eﬃcient accretion energy transport into the protostar (αacc < αacc,cr ). These two cases
are discussed separately in the next two sections.

6

D-burning during protostellar accretion

First, it is convenient to analyse if it is possible to produce an extended protostar using only the D-burning. To
do this, let’s assume αacc = 0. From eq. (1), to produce
a radius increase, D-burning has to supply the star withenergy to counterbalance the radiative loss at the stellar
surface plus the gravitational energy decrease caused by
the mass ingestion. If this condition is not satisﬁed, theprotostar contracts and the resulting model at the endof the protostellar phase has a radius much smaller thanthat expected in standard (or spherical accretion) cases.
The dependency of the radius on deuterium abundance(usunetccoeclthedotrAbstracts of recently accepted papers

1

On the mass segregation of cores and stars
Hayley L. Alcock1 and Richard J. Parker1
1

Department of Physics and Astronomy, The University of Sheﬃeld, Hicks Building, Hounsﬁeld Road, Sheﬃeld S3
7RH, UK
E-mail contact: R.Parker at sheﬃeld.ac.uk
Observations of pre- and proto-stellar cores in young star-forming regions show them to be mass segregated, i.e. themost massive cores are centrally concentrated, whereas pre-main sequence stars in the same star-forming regions (andolder regions) are not. We test whether this apparent contradiction can be explained by the massive cores fragmenting
into stars of much lower mass, thereby washing out any signature of mass segregation in pre-main sequence stars.
Whilst our fragmentation model can reproduce the stellar initial mass function, we ﬁnd that the resultant distributionof pre-main sequence stars is mass segregated to an even higher degree than that of the cores, because massive coresstill produce massive stars if the number of fragments is reasonably low (between one and ﬁve). We therefore suggestthat the reason cores are observed to be mass segregated and stars are not is likely due to dynamical evolution of thestars, which can move signiﬁcant distances in star-forming regions after their formation.
Accepted by MNRAS

https://arxiv.org/pdf/1909.07982

2

Exploring the formation pathways of formamide near young O-type stars
V. Allen1,2,3 , F.F.S. van der Tak2,3 , A. López-Sepulcre4,5 , Á. Sánchez-Monge6 , V.M. Rivilla7, and R.
Cesaroni7
1

NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA; 2 Kapteyn AstronomicalInstitute, University of Groningen, Landleven 12, 9747 AD Groningen, the Netherlands; 3 SRON, Landleven 12, 9747
AD Groningen, the Netherlands; 4 CNRS, IPAG, Univ. Grenoble Alpes, F-38000 Grenoble, France; 5 IRAM, 300 rue
de la Piscine, 38406 Saint-Martin d’ Hères, France; 6 I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße77, 50937 Köln, Germany; 7 INAF, Osservatorio Astroﬁsico di Arcetri, Largo Enrico Fermi 5, I-50125 Florence, Italy
E-mail contact: veronica.a.allen at nasa.gov
Context. As a building block for amino acids, formamide (NH2 CHO) is an important molecule in astrobiology andastrochemistry, but its formation path in the interstellar medium is not understood well.
Aims. We aim to ﬁnd empirical evidence to support the chemical relationships of formamide to HNCO and H2 CO.
Methods. We examine high angular resolution (∼0.′′ 2) Atacama Large Millimeter/submillimeter Array (ALMA) mapsof six sources in three high-mass star-forming regions and compare the spatial extent, integrated emission peak position,and velocity structure of HNCO and H2 CO line emission with that of NH2 CHO by using moment maps. Throughspectral modeling, we compare the abundances of these three species.
Results. In these sources, the emission peak separation and velocity dispersion of formamide emission is most often
similar to HNCO emission, while the velocity structure is generally just as similar to H2 CO and HNCO (within errors).
From the spectral modeling, we see that the abundances between all three of our focus species are correlated, and therelationship between NH2 CHO and HNCO reproduces the previously demonstrated abundance relationship.
Conclusions. In this ﬁrst interferometric study, which compares two potential parent species to NH2 CHO, we ﬁndthat all moment maps for HNCO are more similar to NH2 CHO than H2 CO in one of our six sources (G24 A1). For
the other ﬁve sources, the relationship between NH2 CHO, HNCO, and H2 CO is unclear as the diﬀerent moment maps
for each source are not consistently more similar to one species as opposed to the other.
Accepted by A&A
http://arxiv.org/pdf/1912.11883
9

Inner Disc Misalignments Common? ALMA Reveals an Isotropic Outer Disc In3 Are
clination Distribution for Young Dipper Stars
M. Ansdell1,2,3, E. Gaidos4 , C. Hedges5 , M. Tazzari6 , A.L. Kraus7 et al.
1

Center for Integrative Planetary Science, University of California at Berkeley, Berkeley, CA 94720, USA; 2 Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720, USA; 3 Flatiron Institute, Simons
Foundation, 162 Fifth Ave, New York, NY 10010, USA; 4 Department of Earth Sciences, University of Hawai’i atMan̄oa, Honolulu, HI, USA; 5 NASA Ames Research Center, Moﬀett Blvd, Mountain View, CA 94035, USA; 6 Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA, Cambridge, UK; 7 Department of Astronomy,
The University of Texas at Austin, Austin, TX 78712, USA
E-mail contact: mansdell at ﬂatironinstitute.org
Dippers are a common class of young variable star exhibiting day-long dimmings with depths of up to several tensof percent. A standard explanation is that dippers host nearly edge-on (70◦ ) protoplanetary discs that allow close-in(<1 au) dust lifted slightly out of the midplane to partially occult the star. The identiﬁcation of a face-on dipper discand growing evidence of inner disc misalignments brings this scenario into question. Thus we uniformly (re)derive
the inclinations of 24 dipper discs resolved with (sub-)mm interferometry from ALMA. We ﬁnd that dipper disc
inclinations are consistent with an isotropic distribution over 0◦ –75◦ , above which the occurrence rate declines (likely
an observational selection eﬀect due to optically thick disc midplanes blocking their host stars). These ﬁndings
indicate that the dipper phenomenon is unrelated to the outer (>10 au) disc resolved by ALMA and that inner discmisalignments may be common during the protoplanetary phase. More than one mechanism may contribute to thedipper phenomenon, including accretion-driven warps and "broken" discs caused by inclined (sub-)stellar or planetarycompanions.
Accepted by MNRAS
http://arxiv.org/pdf/1912.01610

4

The Orion Protostellar Explosion and Runaway Stars Revisited:
Stellar Masses, Disk Retention, and an Outflow from BN
John Bally1 , Adam Ginsburg2 , Jan Forbrich3 , and Jaime Vargas-González3
1

Center for Astrophysics and Space Astronomy, Astrophysical and Planetary Sciences Department, University ofColorado, UCB 389 Boulder, Colorado 80309, USA; 2 Department of Astronomy, University of Florida, Bryant Space
Science Center, Stadium Road, Gainesville, FL 32611; 3 Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, Hertfordshire University, College Lane, Hatﬁeld, AL10 9AB, UK
E-mail contact: john.bally@colorado.edu

The proper motions of the three stars ejected from Orion’s OMC1 cloud core are combined with the requirement that
their center of mass is gravitationally bound to OMC1 to show that radio source I (Src I) is likely to have a massaround 15 M⊙ consistent with recent measurements. Src I, the star with the smallest proper motion, is suspected tobe either an AU-scale binary or a protostellar merger remnant produced by a dynamic interaction ∼550 years ago.
Near-infrared 2.2 µm images spanning ∼21 years conﬁrm the ∼55 km/s motion of ‘source x’ (Src x) away from thesite of stellar ejection and point of origin of the explosive OMC1 protostellar outﬂow. The radial velocities and massesof the Becklin-Neugebauer (BN) object and Src I constrain the radial velocity of Src x to be VLSR = −28 ± 10 km/s.
Several high proper-motion radio sources near BN, including Zapata 11 ([ZRK2004] 11) and a diﬀuse source nearIRc 23, may trace a slow bipolar outﬂow from BN. The massive disk around Src I is likely the surviving portion ofa disk that existed prior to the stellar ejection. Though highly perturbed, shocked, and re-oriented by the N-bodyinteraction, enough time has elapsed to allow the disk to relax with its spin axis roughly orthogonal to the propermotion.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2001.00899

10

5

ALMA observations reveal no preferred outflow–filament and outflow–magnetic fieldorientations
T. Baug1 , Ke Wang1 , Tie Liu2 , Mengyao Tang3 , Qizhou Zhang4 , Di Li5,6 , Eswaraiah Chakali5,7 , ShengYuan Liu8 , Anandmayee Tej9 , Paul F. Goldsmith10, Leonardo Bronfman11 , Sheng-Li Qin3 , Viktor L.
Toth12 , Pak-Shing Li13 and Kee-Tae Kim14
1

Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing
100871, China; 2 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai
200030, China; 3 Department of Astronomy, Yunnan University, Kunming, 650091, China; 4 Harvard-Smithsonian
Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 5 CAS Key Laboratory of FAST, National
Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China; 6 University of Chinese Academyof Sciences, Beijing 100049, China; 7 National Astronomical Observatories, Chinese Academy of Science, A20 Datun
Road, Chaoyang District, Beijing 100012, China; 8 Academia Sinica, Institute of Astronomy and Astrophysics, P.O.
Box 23-141, Taipei 106, Taiwan; 9 Indian Institute of Space Science and Technology, Thiruvananthapuram 695 547,
Kerala, India; 10 Jet Propulsion Laboratory, National Aeronautics and Space Administration, United States; 11 Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile; 12 Eövös Loránd University, Departmentof Astronomy, Pázmány Péter sétány 1/A, H-1117, Budapest, Hungary; 13 University of California, Berkeley, UnitedStates; 14 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of
Korea
E-mail contact: tapas.polo at gmail.com
We present a statistical study on the orientation of outﬂows with respect to large-scale ﬁlaments and the magnetic
ﬁelds. Although ﬁlaments are widely observed toward Galactic star-forming regions, the exact role of ﬁlaments
in star formation is unclear. Studies toward low-mass star-forming regions revealed both preferred and randomorientation of outﬂows respective to the ﬁlament long-axes, while outﬂows in massive star-forming regions mostly
oriented perpendicular to the host ﬁlaments, and parallel to the magnetic ﬁelds at similar physical scales. Here, we
explore outﬂows in a sample of 11 protoclusters in HII regions, a more evolved stage compared to IRDCs, using ALMA
CO (3–2) line observations. We identify a total of 105 outﬂow lobes in these protoclusters. Among the 11 targets, 7
are embedded within parsec-scale ﬁlamentary structures detected in 13 CO line and 870 µm continuum emissions. The
angles between outﬂow axes and corresponding ﬁlaments (γFil ) do not show any hint of preferred orientations (i.e.,
orthogonal or parallel as inferred in numerical models) with respect to the position angle of the ﬁlaments. Identiﬁed
outﬂow lobes are also not correlated with the magnetic ﬁelds and Galactic plane position angles. Outﬂows associatedwith ﬁlaments aligned along the large-scale magnetic ﬁelds are also randomly orientated. Our study presents theﬁrst statistical results of outﬂow orientation respective to large-scale ﬁlaments and magnetic ﬁelds in evolved massive
star-forming regions. The random distribution suggests a lack of alignment of outﬂows with ﬁlaments, which may be
a result of the evolutionary stage of the clusters.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1912.13240

6

The Young Suns Exoplanet Survey: Detection of a wide orbit planetary mass companion
to a solar-type Sco-Cen member
A.J. Bohn1 , M.A. Kenworthy1 , C. Ginski2 , C.F. Manara3 , M.J. Pecaut4 et al.
1

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 Sterrenkundig Instituut
Anton Pannekoek, Science Park 904, 1098 XH Amsterdam, The Netherlands; 3 European Southern Observatory, KarlSchwarzschild-Strasse 2, 85748 Garching bei München, Germany; 4 Rockhurst University, Department of Physics, 1100
Rockhurst Road, Kansas City, MO 64110, USA
E-mail contact: bohn at strw.leidenuniv.nl
The Young Suns Exoplanet Survey (YSES) consists of a homogeneous sample of 70 young, solar-mass stars locatedin the Lower Centaurus-Crux subgroup of the Scorpius-Centaurus association with an average age of 15±3 Myr. We
report the detection of a co-moving companion around the K3IV star TYC 8998-760-1 (2MASSJ13251211-6456207)
that is located at a distance of 94.6±0.3 pc using SPHERE/IRDIS on the VLT. Spectroscopic observations with
VLT/X-SHOOTER constrain the mass of the star to 1.00±0.02 M⊙ and an age of 16.7±1.4 Myr. The companion
11

TYC 8998-760-1 b is detected at a projected separation of 1.′′ 71, which implies a projected physical separation of
162 au. Photometric measurements ranging from Y to M band provide a mass estimate of 14±3 Mjup by comparison
to BT-Settl and AMES-dusty isochrones, corresponding to a mass ratio of q = 0.013 ± 0.003 with respect to theprimary. We rule out additional companions to TYC 8998-760-1 that are more massive than 12 Mjup and farther
than 12 au away from the host. Future polarimetric and spectroscopic observations of this system with ground andspace based observatories will facilitate testing of formation and evolution scenarios shaping the architecture of thecircumstellar environment around this ‘young Sun’.
Accepted by MNRAS
http://arxiv.org/pdf/1912.04284

7

USco1621 B and USco1556 B: Two wide companions at the deuterium-burning mass
limit in Upper Scorpius
Patricia Chinchilla1,2 , Víctor J.S. Béjar1,2 , Nicolas Lodieu1,2 , Bartosz Gauza3,4 , Maria Rosa Zapatero
Osorio5 et al.
1

Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain; 2 Departamentode Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Tenerife, Spain; 3 Departamento de Astronomía,
Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile; 4 Janusz Gil Institute of Astronomy,
University of Zielona Góra, Lubuska 2, 65-265 Zielona Góra, Poland; 5 Centro de Astrobiología (CSIC-INTA), Ctra.
de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
E-mail contact: pcg at iac.es
Our aim is to identify analogues of gas giant planets, as companions at wide separations of very young stars. To identify
these objects, we cross correlated the Visible and Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey(VHS) and the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Clusters Survey (UKIDSS GCS)
catalogues to search for common proper motion companions to 1195 already known members of Upper Scorpius (USco;age ∼5–10 Myr, distance ∼145 pc). We present the discovery and spectroscopic characterisation of two very wide
substellar companions of two early-M stars in Upper Scorpius: USco1621 B and USco1556 B. We obtained opticaland near-infrared low-resolution spectroscopy of the candidates to characterise their spectral energy distribution andconﬁrm their membership to the association. We also acquired adaptive optics images of the primaries and secondaries
to search for signs of binarity and close companions. We determined a spectral type of M8.5 in the optical for bothcompanions, along with L0 and L0.5 in the near-infrared for USco1621 B and USco1556 B, respectively. The spectraof the two companions show evident markers of youth. The comparison with theoretical evolutionary models gives
estimated masses of 0.015±0.002 and 0.014±0.002 M⊙ , with temperatures of 2270±90 and 2240±100 K, respectively.
The physical separations between the components of both systems are 2880±20 and 3500±40 AU for USco1621 andUSco1556 systems, respectively. We did not ﬁnd any additional close companion in the adaptive optics images. The
probability that the two secondaries are physically bound to their respective primaries, and not chance alignments of
USco members, is 86%, and the probability that none of them are physically related is 1.0%.
Accepted by A&A
http://arxiv.org/pdf/1912.04150

8

Seeds of Life in Space (SOLIS) V. Methanol and acetaldehyde in the protostellar jetdriven shocks L1157-B0 and B1
C. Codella1,2 , C. Ceccarelli2,1 , E. Bianchi2 , N. Balucani3,2,1 , L. Podio1 , P. Caselli4, S. Feng5,6,7 , B.
Lefloch2 , A. López-Sepulcre2,8 , R. Neri8 , S. Spezzano4 and M. De Simone2
1

INAF, Osservatorio Astroﬁsico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 Univ. Grenoble Alpes, CNRS,
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), 38000 Grenoble, France; 3 Dipartimento di Chimica,
Biologia e Biotecnologie, Via Elce di Sotto 8, 06123 Perugia, Italy; 4 Max-Planck-Institut für extraterrestrische Physik(MPE), Giessenbachstrasse 1, 85748 Garching, Germany; 5 National Astronomical Observatory of China, Datun Road
20, Chaoyang, Beijing, 100012, P. R. China; 6 CAS Key Laboratory of FAST, NAOC, Chinese Academy of Sciences,
P. R. China; 7 National Astronomical Observatory of Japan, 2 Chome-21-1 Osawa, Mitaka-shi, Tokyo-to 181-0015,

12

Japan; 8 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, Domaine Universitaire de Grenoble, 38406,
Saint-Martin d’Hères, France
E-mail contact: codella at arcetri.astro.it
Context: It is nowadays clear that a rich organic chemistry takes place in protostellar regions. However, the processes
responsible for it, i.e. the dominant formation routes to interstellar complex organic molecules, are still source of
debate. Two paradigms have been evoked: the formation of these molecules on the interstellar dust mantles or/and
their formation in the gas-phase from simpler species previously synthetised on the dust mantles.
Aims: In the past, observations of protostellar shocks have been able to set constraints on the formation route offormamide (NH2 CHO), exploiting its observed spatial distribution and comparison with astrochemical model predictions. In this work, we follow the same strategy to study the case of acetaldehyde (CH3 CHO).
Methods: To this end, we used the data obtained with the IRAM NOEMA interferometer in the framework of theLarge Program SOLIS to image the B0 and B1 shocks along the L1157 blueshifted outﬂow methanol (CH3 OH) andacetaldehyde line emission.
Results: We imaged six CH3 OH and eight CH3 CHO lines which cover upper level energies up to ∼ 30 K. Both species
trace the B0 molecular cavity as well as the northern B1 portion, i.e. the regions where the youngest shocks (∼ 1000yr) occurred. The CH3 OH and CH3 CHO emission peaks towards the B1b clump, where we measured the following
column densities and relative abundances: 1.3 × 1016 cm−2 and 6.5 × 10−6 (methanol), and 7 × 1013 cm−2 and 3.5
× 10−8 (acetaldehyde). We carried out a non-LTE LVG analysis of the observed CH3 OH line: the average kinetic
temperature and density of the emitting gas are Tkin ∼ 90 K and nH2 ∼ 4 × 105 cm−3 , respectively. The CH3 OH andCH3 CHO abundance ratio towards B1b is 190, varying by less than a factor 3 throughout the whole B0–B1 structure.
Conclusions: The comparison of astrochemical model predictions with the observed methanol and acetaldehyde spatial distribution does not allow to distinguish whether acetaldehyde is formed on the grain mantles or rather on thegas-phase, as its gas-phase formation, dominated by the reaction of ethyl radical (CH3 CH2 ) with atomic oxygen, isvery fast. Observations of acetaldehyde in younger shocks, e.g. ∼ 102 yr old, or/and of the ethyl radical, whose
frequencies are not presently available, are necessary to settle the issue.
Accepted by A&A
http://arxiv.org/pdf/2001.00217

9

Catastrophic events in protoplanetary disks and their observational manifestations
Tatiana V. Demidova1 and Vladimir P. Grinin2
1

Crimean Astrophysical Observatory, Nauchny, Crimea, Russia; 2 Pulkovo Observatory of the Russian Academy of
Sciences, St. Petersburg, Russia
E-mail contact: proxima1 at list.ru
Observations of protoplanetary disks with high angular resolution using an ALMA interferometer showed that ringshaped structures are often visible in their images, indicating strong disturbances in the disks. The mechanisms of
their formation are vividly discussed in the literature. This article shows that the formation of such structures can be
the result of destructive collisions of large bodies (planetesimals and planetary embryos) accompanied by the formationof a large number of dust particles, and the subsequent evolution of a cloud of dust formed in this way.
Accepted by Astrophysical Journal Letters
https://arxiv.org/pdf/1912.12328

10 Astrochemical Bistability: Autocatalysis in Oxygen Chemistry
Gwenaelle Dufour1,2,3 and Steven Charnley1

1
Astrochemistry Laboratory, Code 691, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; 2 Department of Physics, Catholic University of America, Washington, DC 20064, USA; 3 Leiden Observatory, Leiden
University, Leiden, The Netherlands

E-mail contact: gwenaelle.c.dufour at nasa.gov
The origin of bistable solutions in the kinetic equations describing the chemistry of dense interstellar clouds is explained13

as being due to the autocatalysis and feedback of oxygen nuclei from the oxygen dimer (O2 ). We identify four
autocatalytic processes that can operate in dense molecular clouds, driven respectively by reactions of H+ , He+ , C+
and S+ with O2 . We show that these processes can produce the bistable solutions found in previous studies, aswell as the dependence on various model parameters such as the helium ionization rate, the sulfur depletion and theH+
3 electron recombination rate. We also show that ion-grain neutralizations are unlikely to aﬀect the occurrenceof bistability in dense clouds. It is pointed out that many chemical models of astronomical sources should have thepotential to show bistable solutions.
Accepted by ApJ
https://doi.org/10.3847/1538-4357/ab4e9c

11 Thermal instability revisited
Samuel Falle1 , Christopher Wareing2 and J.M. Pittard2
1

School of Mathematics, University of Leeds, Leeds, LS2 9JT, UK; 2 School of Physics and Astronomy, University ofLeeds, Leeds, LS2 9JT, UK
E-mail contact: S.A.E.G.Falle at leeds.ac.uk

Field’s linear analysis of thermal instability is repeated using methods related to Whitham’s theory of wave hierarchies,
which brings out the physically relevant parameters in a much clearer way than in the original analysis. It is also used
for the stability of non-equilibrium states and we show that for gas cooling behind a shock, the usual analysis is only
quantitatively valid for shocks that are just able to trigger a transition to the cold phase. A magnetic ﬁeld can readily
be included and we show that this does not change the stability criteria. By considering steady shock solutions, weshow that almost all plausible initial conditions lead to a magnetically dominated state on the unstable part of theequilibrium curve. These results are used to analyse numerical calculations of perturbed steady shock solutions andof shocks interacting with a warm cloud.
Accepted by MNRAS
https://arxiv.org/pdf/2001.01092

12 Mirror, mirror on the outflow cavity wall. Near-infrared CO overtone disc emission of
the high-mass YSO IRAS 11101-5829

R. Fedriani1,2 , A. Caratti o Garatti1,2 , M. Koutoulaki1,2 , R. Garcia-Lopez1,2 A. Natta1 R. Cesaroni3 R.
Oudmaijer4 D. Coffey2,1 T. Ray1 B. Stecklum5
1

Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2, Ireland; 2 University
College Dublin, School of Physics, Belﬁeld, Dublin 4, Ireland; 3 INAF, Osservatorio Astroﬁsico di Arcetri, Largo E.
Fermi 5, 50125 Firenze, Italy 4 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK 5 Thüringer
Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
E-mail contact: fedriani at cp.dias.ie
Aims: The inner regions of high-mass protostars are often invisible in the near-infrared, obscured by thick envelopes
and discs. We aim to investigate the inner gaseous disc of IRAS 11101-5829 through scattered light from the outﬂow
cavity walls.
Methods: We observed the immediate environment of the high-mass young stellar object IRAS 11101-5829 and theclosest knots of its jet, HH135-136, with the integral ﬁeld unit VLT/SINFONI. We also retrieved archival data fromthe high-resolution long-slit spectrograph VLT/X-shooter. We analysed imaging and spectroscopic observations todiscern the nature of the near-infrared CO emission.
Results: We detect the ﬁrst three bandheads of the υ = 2 − 0 CO vibrational emission for the ﬁrst time in thisobject. It is coincident with continuum and Brγ emission and extends up to ∼ 10 000 au to the north-east and∼ 10 000 au to the south-west. The line proﬁles have been modelled as a Keplerian rotating disc assuming a single
ring in local thermodynamic equilibrium. The model output gives a temperature of ∼ 3000 K, a CO column densityof ∼ 1 × 1022 cm−2 , and a projected Keplerian velocity vK sin idisc ∼ 25 km s−1 , which is consistent with previous
modelling in other high-mass protostars. In particular, the low value of vK sin idisc suggests that the disc is observed
14

almost face-on, whereas the well-constrained geometry of the jet imposes that the disc must be close to edge-on. Thisapparent discrepancy is interpreted as the CO seen reﬂected i! n the mirror of the outﬂow cavity wall.
Conclusions: From both jet geometry and disc modelling, we conclude that all the CO emission is seen throughreﬂection by the cavity walls and not directly. This result implies that in the case of highly embedded objects, as formany high-mass protostars, line proﬁle modelling alone might be deceptive and the observed emission could aﬀect thederived physical and geometrical properties; in particular the inclination of the system can be incorrectly interpreted.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2001.00369.pdf

Resolved Dust Continuum Measurements of Individual Giant Molecular Clouds
13 First
in the Andromeda Galaxy
Jan Forbrich1,2 , Charles J. Lada2 , Sébastien Viaene3,1 and Glen Petitpas2
1

Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatﬁeld AL10 9AB, UK; 2 Center
for Astrophysics | Harvard & Smithsonian, 60 Garden St, MS 72, Cambridge, MA 02138, USA; 3 Sterrenkundig
Observatorium, Universiteit Gent, Krijgslaan 281, 9000, Gent, Belgium
E-mail contact: j.forbrich at herts.ac.uk
In our local Galactic neighborhood, molecular clouds are best studied using a combination of dust measurements,
to determine robust masses, sizes and internal structures of the clouds, and molecular-line observations to determine
cloud kinematics and chemistry. We present here the ﬁrst results of a program designed to extend such studies tonearby galaxies beyond the Magellanic Clouds. Utilizing the wideband upgrade of the Submillimeter Array (SMA)
at 230 GHz we have obtained the ﬁrst continuum detections of the thermal dust emission on sub-GMC scales (∼ 15pc) within the Andromeda galaxy (M 31). These include the ﬁrst resolved continuum detections of dust emission
from individual GMCs beyond the Magellanic Clouds. Utilizing a powerful capability of the SMA, we simultaneously
recorded CO(2-1) emission with identical (u, v) coverage, astrometry and calibration, enabling the ﬁrst measurementsof the CO conversion factor, α CO(2−1) , toward individual GMCs across an external galaxy. Our direct measurement
yields an average CO–to–dust mass conversion factor of α′CO−dust = 0.042 ± 0.018 M⊙ (K km s−1 pc2 )−1 for theJ = 2 − 1 transition. This value does not appear to vary with galactocentric radius. Assuming a constant gas-to-dust
ratio of 136, the resulting αCO = 5.7 ± 2.4 M⊙ (K km s−1 pc2 )−1 for the 2-1 transition is in excellent agreementwith that of Milky Way GMCs, given the uncertainties. Finally, using the same analysis techniques, we compare ourresults with observations of the local Orion molecular clouds, placed at the distance of M 31 and simulated to appear
as they would if observed by the SMA.
Accepted by ApJ
https://arxiv.org/pdf/2001.02914

H II Regions are Complicated: Considering Perturbations from Winds, Radiation
14 WhenPressure, and Other Effects
Sam Geen1,2 , Eric Pellegrini1 , Rebekka Bieri3 and Ralf Klessen1,4
1

Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2,69120 Heidelberg, Germany; 2 Anton Pannekoek Institute for Astronomy, Universiteit van Amsterdam, Science Park
904, 1098 XH Amsterdam, The Netherlands; 3 Max-Planck-Institute for Astrophysics, Karl-Schwartzschild-Strasse 1,
Garching, Germany; 4 Universität Heidelberg, Interdisziplinäres Zentrum fur Wissenschaftliches Rechnen, INF 205,
69120, Heidelberg, Germany
E-mail contact: s.t.geen at uva.nl
We explore to what extent simple algebraic models can be used to describe HII regions when winds, radiation pressure,gravity and photon breakout are included. We a) develop algebraic models to describe the expansion of photoionised
HII regions under the inﬂuence of gravity and accretion in power-law density ﬁelds with ρ ∝ r−w , b) determine
when terms describing winds, radiation pressure, gravity and photon breakout become signiﬁcant enough to aﬀect the
dynamics of the HII region where w = 2, and c) solve these expressions for a set of physically-motivated conditions.

15

We ﬁnd that photoionisation feedback from massive stars is the principal mode of feedback on molecular cloud scales,
driving accelerating outﬂows from molecular clouds in cases where the peaked density structure around young massive
stars is considered at radii between ∼0.1 and 10-100 pc. Under a large range of conditions the eﬀect of winds andradiation on the dynamics of HII regions is around 10% of the contribution from photoionisation. The eﬀect of winds
and radiation pressure are most important at high densities, either close to the star or in very dense clouds such as
those in the Central Molecular Zone of the Milky Way. Out to ∼0.1 pc they are the principal drivers of the HII region.
Lower metallicities make the relative eﬀect of photoionisation even stronger as the ionised gas temperature is higher.
Accepted by MNRAS
https://arxiv.org/pdf/1906.05649

15

A HARPS RV search for planets around young nearby stars
A. Grandjean1 , A.-M. Lagrange1 , M. Keppler2 , N. Meunier1 , L. Mignon1 et al.
1

Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 Max Planck Institute for Astronomy, Königstuhl
17, D-69117 Heidelberg, Germany
E-mail contact: Antoine.Grandjean1 at univ-grenoble-alpes.fr
Young nearby stars are good candidates in the search for planets with both radial velocity (RV) and direct imaging
techniques. This, in turn, allows for the computation of the giant planet occurrence rates at all separations. The
RV search around young stars is a challenge as they are generally faster rotators than older stars of similar spectral
types and they exhibit signatures of magnetic activity (spots) or pulsation in their RV time series. Speciﬁc analyses
are necessary to characterize, and possibly correct for, this activity. Our aim is to search for planets around young
nearby stars and to estimate the giant planet (GP) occurrence rates for periods up to 1000 days. We used the HARPS
spectrograph on the 3.6m telescope at La Silla Observatory to observe 89 A–M young (<600 Myr) stars. We used
our SAFIR (Spectroscopic data via Analysis of the Fourier Interspectrum Radial velocities ) software to compute the
RV and other spectroscopic observables. Then, we computed the companion occurrence rates on this sample. We
conﬁrm the binary nature of HD177171, HD181321 and HD186704. We report the detection of a close low mass stellar
companion for HIP36985. No planetary companion was detected. We obtain upper limits on the GP (<13 MJup ) andBD (13–80 MJup ) occurrence rates based on 83 young stars for periods less than 1000 days, which are set, 2+3−2 % and
1+3%.
−1
Accepted by A&A
http://arxiv.org/pdf/1912.02741

16 Tracing shock type with chemical diagnostics: an application to L1157
T.A. James1 , S. Viti1 , J. Holdship1 , and I. Jimenez-Serra2
1

Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK; 2 Centrode Astrobiologia (CSIC, INTA), Ctra. de Ajalvir, km. 4, Torrejón de Ardoz, 28850 Madrid, Spain
E-mail contact: tjames at star.ucl.ac.uk
Aims. The physical structure of a shock wave may take a form unique to its shock type, implying that the chemistryof each shock type is unique as well. We aim to investigate the diﬀerent chemistries of J-type and C-type shocks inorder to identify unique molecular tracers of both shock types. We apply these diagnostics to the protostellar outﬂow
L1157 to establish whether the B2 clump could host shocks exhibiting type-speciﬁc behaviour. Of particular interestis the L1157-B2 clump, which has been shown to exhibit bright emission in S-bearing species and HNCO.
Methods. We simulate, using a parameterised approach, a planar, steady-state J-type shock wave using UCLCHEM.
We compute a grid of models using both C-type and J-type shock models to determine the chemical abundance ofshock-tracing species as a function of distance through the shock and apply it to the L1157 outﬂow. We focus on
known shock-tracing molecules such as H2 O, HCN, and CH3 OH.
Results. We ﬁnd that a range of molecules including H2 O and HCN have unique behaviour speciﬁc to a J-type shock,but that such diﬀerences in behaviour are only evident at low vs and low nH . We ﬁnd that CH3 OH is enhancedby shocks and is a reliable probe of the pre-shock gas density. However, we ﬁnd no diﬀerence between its gas-phase16

abundance in C-type and J-type shocks. Finally, from our application to L1157, we ﬁnd that the fractional abundances
within the B2 region are consistent with both C-type and J-type shock emission.
Accepted by A&A
http://arxiv.org/pdf/1912.03721

17 Mass constraints for 15 protoplanetary disks from HD 1–0
M. Kama1,2 , L. Trapman3 , D. Fedele4 , S. Bruderer5 , M.R. Hogerheijde2,6 et al.
1

Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 2 Tartu Observatory,
Observatooriumi 1, Tõravere 61602, Tartu, Estonia; 3 Leiden Observatory, Leiden University, Niels Bohrweg 2, NL2333 CA Leiden, The Netherlands; 4 INAF–Osservatorio Astroﬁsico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy;
5
Max-Planck-institute für extraterrestrische Physic, Giessenbachstraße, D-85748 Garching bei München, Germany;
6
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1090 GE Amsterdam, The
Netherlands
E-mail contact: mkama at ast.cam.ac.uk
Hydrogen deuteride (HD) rotational line emission can provide reliable protoplanetary disk gas mass measurements,
but it is diﬃcult to observe and detections have been limited to three T-Tauri disks. No new data have been available
since the Herschel Space Observatory mission ended in 2013. We set out to obtain new disk gas mass constraints byanalysing upper limits on HD 1–0 emission in Herschel /PACS archival data from the DIGIT key programme. Witha focus on the Herbig Ae/Be disks, whose stars are more luminous than T Tauris, we determine upper limits for
HD in data previously analysed for its line detections. Their signiﬁcance is studied with a grid of models run with
the DALI physical-chemical code, customised to include deuterium chemistry. Nearly all the disks are constrained to
Mgas ≤ 0.1 M⊙ , ruling out global gravitational instability. A strong constraint is obtained for the HD 163296 disk mass,
Mgas ≤ 0.067 M⊙ , implying ∆g/d ≤ 100. This HD-based mass limit is towards the low end of CO-based mass estimates
for the disk, highlighting the large uncertainty in using only CO and suggesting that gas-phase CO depletion in HD
163296 is at most a factor of a few. The Mgas limits for HD 163296 and HD 100546, both bright disks with massive
candidate protoplanetary systems, suggest disk-to-planet mass conversion eﬃciencies of Mp /(Mgas + Mp ) ≈ 10 to 40%
for present-day values. Near-future observations with SOFIA/HIRMES will be able to detect HD in the brightest
Herbig Ae/Be disks within 150 pc with ≈10h integration time.
Accepted by A&A
http://arxiv.org/pdf/1912.11883

18 Distortion of Magnetic Fields in a Starless Core VI: Application of Flux Freezing Model
and Core Formation of FeSt 1-457

Ryo Kandori1 , Kohji Tomisaka2 , Masao Saito2 , Motohide Tamura1,2,3 , Tomoaki Matsumoto4 , Ryo
Tazaki5 , Tetsuya Nagata6 , Nobuhiko Kusakabe1 , Yasushi Nakajima7 , Jungmi Kwon3 , Takahiro Nagayama8
and Ken’ichi Tatematsu2
1

Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatoryof Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of Astronomy, The University of Tokyo,
7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 4 Faculty of Sustainability Studies, Hosei University, Fujimi,
Chiyoda-ku, Tokyo 102-8160; 5 Astronomical Institute, Graduate School of Science Tohoku University, 6-3 Aramaki,
Aoba-ku, Sendai 980-8578, Japan; 6 Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;
7
Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601, Japan; 8 Kagoshima University, 1-21-35 Korimoto,Kagoshima 890-0065, Japan
E-mail contact: r.kandori at nao.ac.jp
Observational data for the hourglass-like magnetic ﬁeld toward the starless dense core FeSt 1-457 were compared with
a ﬂux freezing magnetic ﬁeld model (Myers et al. 2018). Fitting of the observed plane-of-sky magnetic ﬁeld using theﬂux freezing model gave a residual angle dispersion comparable with the results based on a simple three-dimensional
parabolic model. The best-ﬁt parameters for the ﬂux freezing model were a line-of-sight magnetic inclination angleof γmag = 35◦ ± 15◦ and a core center to ambient (background) density contrast of ρc /ρbkg = 75. The initial density
17

for core formation (ρ0 ) was estimated to be ρc /75 = 4670 cm−3 , which is about one order of magnitude higher thanthe expected density (∼ 300 cm−3 ) for the inter-clump medium of the Pipe Nebula. FeSt 1-457 is likely to have been
formed from the accumulation of relatively dense gas, and the relatively dense background column density of AV ≃ 5
mag supports this scenario. The initial radius (core formation radius) R0 and the initial magnetic ﬁeld strength B0
were obtained to be 0.15 pc (1.64R) and 10.8 − 14.6 µG, respectively. We found that the initial density ρ0 is consistent
with the mean density of the nearly critical magnetized ﬁlament with magnetic ﬁeld strength B0 and radius R0 .
The relatively dense initial condition for core formation can be naturally understood if the origin of the core is thefragmentation of magnetized ﬁlaments.
Accepted by ApJ
https://arxiv.org/pdf/1912.02935

19 Distortion of Magnetic Fields in the Dense Core CB81 (L1774, Pipe 42) in the Pipe
NebulaRyo Kandori1 , Motohide Tamura1,2,3 , Masao Saito3 , Kohji Tomisaka3 , Tomoaki Matsumoto4 , Ryo
Tazaki5 , Tetsuya Nagata6 , Nobuhiko Kusakabe1 , Yasushi Nakajima7 , Jungmi Kwon2 , Takahiro Nagayama8
and Ken’ichi Tatematsu3
1

Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 Department of Astronomy, The
University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 3 National Astronomical Observatory ofJapan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 Faculty of Sustainability Studies, Hosei University, Fujimi,
Chiyoda-ku, Tokyo 102-8160; 5 Astronomical Institute, Graduate School of Science, Tohoku University, 6-3 Aramaki,
Aoba-ku, Sendai 980-8578, Japan; 6 Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;
7
Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601, Japan; 8 Kagoshima University, 1-21-35 Korimoto,Kagoshima 890-0065, Japan
E-mail contact: r.kandori at nao.ac.jp

The detailed magnetic ﬁeld structure of the starless dense core CB81 (L1774, Pipe 42) in the Pipe Nebula wasdetermined based on near-infrared polarimetric observations of background stars to measure dichroically polarized
light produced by magnetically aligned dust grains in the core. The magnetic ﬁelds pervading CB81 were mappedusing 147 stars and axisymmetrically distorted hourglass-like ﬁelds were identiﬁed. On the basis of simple 2D and
3D magnetic ﬁeld modeling, the magnetic inclination angles in the plane-of-sky and line-of-sight directions were
determined to be 4◦ ± 8◦ and 20◦ ± 20◦ , respectively. The total magnetic ﬁeld strength of CB81 was found to be
7.2 ± 2.3 µG. Taking into account the eﬀects of thermal/turbulent pressure and magnetic ﬁelds, the critical mass of
CB81 was calculated to be Mcr = 4.03 ± 0.40 M⊙ , which is close to the observed core mass of Mcore = 3.37 ± 0.51 M⊙ .
We thus conclude that CB81 is in a condition close to the critical state. In addition, a spatial oﬀset of 92′′ was foundbetween the center of magnetic ﬁeld geometry and the dust extinction distribution; this oﬀset structure could not havebeen produced by self-gravity. The data also indicate a linear relationship between polarization and extinction up to
AV ∼ 30 mag going toward the core center. This result conﬁrms that near-infrared polarization can accurately trace
the overall magnetic ﬁeld structure of the core.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/1912.10029

and NACO observations towards the young exoring transit system J1407 (V1400
20 ALMA
Cen)
Matthew Kenworthy1 , Pamela Klaassen2 , Michiel Min3 , Nienke van der Marel4,5 , Alexander Bohn1 ,Mihkel Kama6 , Amaury Triaud7 , Antonio Hales8,9 , Jacqueline Monkiewicz10 , Erin Scott11 and Eric
Mamajek12,13
1

Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands; 2 UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK; 3 SRON Netherlands Institutefor Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands; 4 Herzberg Astronomy & Astrophysics Programs, National Research Council of Canada Herzberg, 5071 West Saanich Rd, Victoria, BC, V9E 2E7, Canada; 518

Department of Physics & Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada; 6 Institute of Astronomy,
University of Cambridge, Madingley Road, Cambridge, CB3 OHA, UK; 7 School of Physics & Astronomy, University ofBirmingham, Edgbaston, Birmingham B15 2TT, UK; 8 National Radio Astronomy Observatory, 520 Edgemont Road,
Charlottesville, VA 22903-2475.; 9 Atacama Large Millimeter/Submillimeter Array, Joint ALMA Observatory, Alonsode Cordova 3107, Vitacura 763-0355, Santiago; 10 School of Earth and Space Exploration, Arizona State University,
Tempe, AZ 85287, USA; 11 Chinese Academy of Sciences, 52 Sanlihe Road, Xicheng District, 100864 Beijing, China;
12
Jet Propulsion Laboratory, California Institute of Technology, M/S 321-100, 4800 Oak Grove Drive, Pasadena, CA
91109, USA; 13 Department of Physics & Astronomy, University of Rochester, Rochester, NY 14627, USA
E-mail contact: kenworthy at strw.leidenuniv.nl
Our aim was to directly detect the thermal emission of the putative exoring system responsible for the complex deeptransits observed in the light curve for the young Sco-Cen star 1SWASP J140747.93-394542.6 (V1400 Cen, hereafter
J1407), conﬁrming it as the occulter seen in May 2007, and to determine its orbital parameters with respect to the star.
We used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the ﬁeld centred on J1407 in the 340
GHz (Band 7) continuum in order to determine the ﬂux and astrometric location of the ring system relative to the star.
We used the VLT/NACO camera to observe the J1407 system in March 2019 and to search for the central planetary
mass object at thermal infrared wavelengths. We detect no point source at the expected location of J1407, and derive
an upper limit 3σ level of 57.6 µJy. There is a point source detected at an angular separation consistent with the
expected location for a free-ﬂoating ring system that occulted J1407 in May 2007, with a ﬂux of 89 µJy consistent
with optically thin dust surrounding a massive substellar companion. At 3.8 microns with the NACO camera, wedetect the star J1407 but no other additional point sources within 1.3 arcseconds of the star, with a lower boundon the sensitivity of 6MJup at the location of the ALMA source, and down to 4MJup in the sky background limit.
The ALMA upper limit at the location of J1407 implies that a hypothesised bound ring system is composed of dust
smaller than 1 mm in size, implying a young ring structure. The detected ALMA source has multiple interpretations,
including: (i) it is an unbound substellar object surrounded by warm dust in Sco-Cen with an upper mass limit of
6MJup , or (ii) it is a background galaxy.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/1912.03314

21 V346 Nor: the post-outburst life of a peculiar young eruptive star
Á. Kóspál1,2 , Zs. M. Szabó1,3 , P. Ábrahám1 , S. Kraus4 , M. Takami5 , P. W. Lucas6 , C. Contreras Peña4and A. Udalski7
1

Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly-Thege M. út 15-17, 1121 Budapest, Hungary; 2 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 3 Eötvös
Loránd University, Department of Astronomy, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary; 4 School ofPhysics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK; 5 Institute of Astronomy and Astrophysics,
Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Rd, Taipei 10617,
Taiwan, R.O.C.; 6 Centre for Astrophysics, University of Hertfordshire, College Lane, Hatﬁeld AL10 9AB, UK; 7
Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
E-mail contact: kospal at konkoly.hu
FU Orionis-type objects (FUors) are young low-mass stars undergoing powerful accretion outbursts. The increased
accretion is often accompanied by collimated jets and energetic, large-scale molecular outﬂows. The extra heating
during the outburst may also induce detectable geometrical, chemical, and mineralogical changes in the circumstellar
material, aﬀecting possible planet formation around these objects. V346 Nor is a southern FUor with peculiar spectral
characteristics. Decades after the beginning of its outburst, it unexpectedly underwent a fading event around 2010
due to a decrease in the mass accretion rate onto the star by at least two orders of magnitude. Here we present
optical and near-infrared photometry and spectroscopy obtained after the minimum. Our light curves show a gradualre-brightening of V346 Nor, with its Ks -band brightness only 1.5 mag below the outburst brightness level. Our
VLT/XSHOOTER spectroscopic observations display several strong forbidden emission lines towards the source fromvarious metals and molecular hydrogen, suggesting the launch of a new jet. Our N -band spectrum obtained with
VLT/VISIR outlines a deeper silicate absorption feature than before, indicating that the geometry of the circumstellar
medium has changed in the post-outburst period compared to peak brightness.
19

Accepted by Astrophysical Journal
https://arxiv.org/pdf/1912.03753.pdf

22 Ring Morphology with Dust Coagulation in Protoplanetary Disks
J.T. Laune1 , Hui Li1 , Shengtai Li1 , Ya-Ping Li1 , Levi G. Walls2 et al.
1

Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA; 2 School of Physics andAstronomy, University of Minnesota, 116 Church Street, Minneapolis, MN 55455, USA
E-mail contact: jl3929 at cornell.edu
Tidal interactions between the embedded planets and their surrounding protoplanetary disks are often postulated to
produce the observed complex dust substructures, including rings, gaps, and asymmetries. In this Letter, we explore
the consequences of dust coagulation on the dust dynamics and ring morphology. Coagulation of dust grains leads todust size growth which, under typical disk conditions, produces faster radial drifts, potentially threatening the dust
ring formation. Utilizing 2D hydrodynamical simulations of protoplanetary disks which include a full treatment of
dust coagulation, we ﬁnd that if the planet does not open a gap quickly enough, the formation of an inner ring isimpeded due to dust coagulation and subsequent radial drift. Furthermore, we ﬁnd that a “buildup” of sub-mm sizedgrains often appears in the dust emission at the outer edge of the dust disk.
Accepted by ApJL
http://arxiv.org/pdf/1912.11178

of the Milky Way with SOFIA: II. M 17
23 Surveying 1the Giant HII Regions
1
1
Wanggi Lim , James M. De Buizer and James T. Radomski
1

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

E-mail contact: wlim at usra.edu
We present our second set of results from our mid-infrared imaging survey of Milky Way Giant HII regions. We used
the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy to obtain 20 and 37 µm imagesof the central ∼10′ ×10′ area of M 17. We investigate the small- and large-scale properties of M 17 using our datain conjunction with previous multi-wavelength observations. The spectral energy distributions of individual compact
sources were constructed with Spitzer-IRAC, SOFIA-FORCAST, and Herschel-PACS photometry data and ﬁtted
with massive young stellar object (MYSO) models. Seven sources were found to match the criteria for being MYSO
candidates, four of which are identiﬁed here for the ﬁrst time, and the stellar mass of the most massive object, UC 1,
is determined to be 64 M⊙ . We resolve the extended mid-infrared emission from the KW Object, and suggest thatthe angle of this extended emission is inﬂuenced by outﬂow. IRS 5 is shown to decrease in brightness as a function of
wavelength from the mid- to far-infrared, and has several other indicators that point to it being an intermediate massClass II object and not a MYSO. We ﬁnd that the large-scale appearance of emission in M 17 at 20 µm is signiﬁcantly
aﬀected by contamination from the [SIII] emission line from the ionized gas of the Giant HII region. Finally, a numberof potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M 17 is likely younger
than the northern bar.
Accepted by ApJ
https://arxiv.org/pdf/1912.02855

24 The Column Density Structure of Orion A Depicted by N-PDF
Yuehui Ma1,2 , Hongchi Wang1 , Chong Li1,2 and Ji Yang1

1

Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua
Road, Nanjing 210033, China; 2 University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District,
Beijing 100049, China
E-mail contact: mayh at pmo.ac.cn

20We have conducted a large-ﬁeld simultaneous survey of 12 CO, 13 CO, and C18 O J = 1 − 0 emission toward the Orion A
giant molecular cloud (GMC) with a sky coverage of ∼ 4.4 deg2 using the PMO-13.7 m millimeter-wavelength telescope.
We use the probability distribution function of the column density (N-PDF) to investigate the distribution of molecularhydrogen in the Orion A GMC. The H2 column density, derived from the 13 CO emission, of the GMC is dominatedby log-normal distribution in the range from ∼4×1021 to ∼1.5×1023 cm−2 with excesses both at the low-density andhigh-density ends. The excess of the low-density end is possibly caused by an extended and low-temperature (∼10K) component with velocities in the range of 5−8 km s−1 . Compared with the northern sub-regions, the southern
sub-regions of the Orion A GMC contain less gas with column density in NH2 > 1.25 × 1022 cm−2 . The dispersionsof the N-PDFs of the sub-regions are found to correlate with the evolutionary stages of the clouds across the Orion
A GMC. The structure hierarchy of Orion A GMC is explored with the DENDROGRAM algorithm, and it is foundthat the GMC is composed of two branches. All structures except one in the tree have virial parameters less than 2,
indicating self-gravity is important on the spatial scales from ∼0.3 to ∼4 pc. Although power-laws and departuresfrom log-normal distributions are found at the high-density end of N-PDFs of active star-forming regions, the N-PDFs
of structures in the Orion A GMC are predominantly log-normal on scales from R∼0.4 to 4 pc.
Accepted by Research in Astronomy and Astrophysics
http://arxiv.org/pdf/1912.06984

of age-benchmark low-mass stars and brown dwarfs
25 Spectral library
1,2
3,4
3,4
5
E. Manjavacas, N. Lodieu, V.J.S. Béjar, M.R. Zapatero-Osorio , S. Boudreault6 , M. Bonnefoy7

1

W.M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela, HI 96743, USA; 2 Department of Astronomy/Steward
Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ, 85721, USA; 3 Instituto de Astrofísica
de Canarias, C/ Vía Láctea, s/n, E38205, La Laguna (Tenerife), Spain; 4 Dpt. de Astrofísica, Univ. de La Laguna,Avda. Astrofísico Francisco Sánchez s/n, 38206, La Laguna (Tenerife), Spain; 5 Centro de Astrobiología (CSIC-INTA),
Crta. Ajalvir km 4, E-28850 Torrejón de Ardoz, Madrid, Spain; 6 Max-Planck-Institut für Sonnensystemforschung,
Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany; 7 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble,
FranceE-mail contact: emanjavacas at keck.hawaii.edu
In the past years, some extremely red brown dwarfs were found. They were believed to have low surface gravity,
but many of their spectral characteristics were similar to those of high surface gravity brown dwarfs, showing thatyouth (or low surface gravity) spectral characteristics are poorly understood. We aim to test surface gravity indicatorsin late-M and early-L brown dwarf spectra using data obtained with the X-shooter spectrograph at the Very Large
Telescope. We selected a benchmark sample of brown dwarfs members of Chamaeleon I (∼2 Myr), Upper Scorpius(5–10 Myr), Pleiades (132±27 Myr), and Praesepe (590–790 Myr) with well-constrained ages, and similar metallicities.
We provided a consistent spectral classiﬁcation of the sample in the optical and in the near-infrared. We measured theequivalent widths of their alkali lines, ﬁnding that they have a moderate correlation with age, especially for objects
with spectral types M8 and later. We used spectral indices deﬁned in the literature to estimate surface gravity, ﬁndingthat their gravity assignment is accurate for 75% of our sample. We investigated the correlation between red colours
and age, ﬁnding that after ∼10 Myr, the colour does not change signiﬁcantly for our sample with spectral types M6.0–
L3.0. In this case, red colours might be associated with circumstellar disks, ring structures, extinction, or viewing
angle. Finally, we calculated the bolometric luminosity, and J and K bolometric corrections for our sample. We foundthat six objects are overluminous compared to other members of the same association. Those objects are also ﬂagged
as binary candidates by the Gaia survey.
Accepted by MNRAS
http://arxiv.org/pdf/1912.02806

26 Long-term multi-frequency maser observations of the intermediate-mass young stellar
object G107.298+5.639

Mateusz Olech1 , Marian Szymczak1 , Pawel Wolak1 , Eric Gérard2 and Anna Bartkiewicz1
1

Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka21

5, 87-100 Torun, Poland; 2 GEPI, UMR 8111, CNRS and Observatoire de Paris, 5 Place J.Janssen, 92195 Meudon
Cedex, France
E-mail contact: olech at astro.umk.pl
Periodic ﬂares of maser emission are thought to be induced either by variations of the seed photon ﬂux in young
binary systems or the pump rate regulated by stellar and accretion luminosities. We seek to study the variability offour maser transitions of three diﬀerent species in G107.298+5.639 to constrain the dominant mechanism of periodic
ﬂares. Light curves of the 6.7 GHz methanol and 22.2 GHz water vapour maser were obtained with the Torun 32m
radio telescope over 39 and 34 cycles, respectively. The target was also monitored at the 1.6 GHz hydroxyl transitions
with the NanŊay radio telescope over 13 cycles. All these maser lines were imaged using VLBI arrays. The study
conﬁrms alternating ﬂares of the methanol and water masers with a period of 34.4d and reveals the synchronised
behaviour of the methanol and hydroxyl masers in this source. The observed spatial distribution of the methanol
maser cloudlets and the measured time delays of the ﬂares of individual features imply a ring-like structure of radius
240au and thickness 30au. Internal proper motions indicate that the velocity of methanol cloudlets is dominated by adisc-wind component of about 5km/s. The methanol emission detected during only one VLBI observation is locatedin a region about 550au from a central star, which also exhibits OH maser ﬂares. The erratic appearance of methanolfeatures can be related to a powering object of relatively low luminosity which, during some variability cycles, canexcite molecules only in the nearest part of the disc. A careful analysis of the maser and infrared light curves reveala strong correlation between the 6.7 GHz line and the infrared ﬂux densities supporting a radiative pumping of themaser. The synchronised behaviour of the hydroxyl and methanol transitions indicates a common pumping mechanism
for the periodic ﬂares of G107.298+5.639.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2001.01625

27 Large scale star formation in Auriga region
A.K. Pandey1 , Saurabh Sharma1 , N. Kobayashi2,3 , Y. Sarugaku3 and K. Ogura4
1

Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263 002, India; 2 Instituteof Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 Kiso Observatory, School of
Science, University of Tokyo, Mitake-mura, Kiso-gun, Nagano 397-0101, Japan; 4 Kokugakuin University, Higashi,
Shibuya-ku, Tokyo 150-8440, Japan
E-mail contact: pandey at aries.res.in

New observations in the VI bands along with archival data from the 2MASS and WISE surveys have been used togenerate a catalog of young stellar objects (YSOs) covering an area of about 6◦ × 6◦ in the Auriga region centered
at l ∼ 173◦ and b ∼ 1.◦ 5. The nature of the identiﬁed YSOs and their spatial distribution are used to study thestar formation in the region. The distribution of YSOs along with that of the ionized and molecular gas reveals tworing-like structures stretching over an area of a few degrees each in extent. We name these structures as Auriga
Bubbles 1 and 2. The center of the Bubbles appears to be above the Galactic mid-plane. The majority of Class i YSOs
are associated with the Bubbles, whereas the relatively older population, i.e., Class ii objects are rather randomly
distributed. Using the minimum spanning tree analysis, we found 26 probable sub-clusters having 5 or more members.
The sub-clusters are between ∼0.5 pc – ∼3 pc in size and are somewhat elongated. The star formation eﬃciency inmost of the sub-cluster region varies between 5% – 20% indicating that the sub-clusters could be bound regions. The
radii of these sub-clusters also support it.
Accepted by MNRAS
http://arxiv.org/pdf/1912.11789

28 Probing the early phases of high mass star formation with 6.7 GHz methanol masers
Sonu Tabitha Paulson1 , Jagadheep D. Pandian1
1

Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram
695547, Kerala, India

22

E-mail contact: sonutabitha.15 at res.iist.ac.in
Methanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards
massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive
star formation. We present here a study of the spectral energy distributions of 320 6.7 GHz methanol masers chosenfrom the MMB catalogue, which fall in the Hi-GAL range (|l| ≤ 60◦ , |b| ≤ 1◦ ). The spectral energy distributions areconstructed from 870–70 µm using data from the ATLASGAL and Hi-GAL surveys. The emission from cold dust
is modelled by a single grey body component ﬁt. We estimate the clump properties such as mass, FIR luminosityand column density using the best ﬁt parameters of the SED ﬁts. Considering the Kauﬀman criteria for massive starformation, we ﬁnd that all but a few maser hosts have the potential to harbour at least one high mass star. The
physical properties of the methanol maser hosts are also discussed. The evolutionary stages of 6.7 GHz maser sources,
explored using the mass luminosity diagram, suggests that they are predominantly associated with high mass stars
with the majority being in the accretion phase. However, we observe a small number of sources that could possibly
be related to intermediate or low-mass stars.
Accepted by MNRAS
http://arxiv.org/pdf/1912.06973

29 Formation of moon systems around giant planets: Capture and ablation of planetesimals
as foundation for a pebble accretion scenario
T. Ronnet1 and A. Johansen1
1

Department of Astronomy and Theoretical Physics, Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden

E-mail contact: thomas.ronnet at astro.lu.se
The four major satellites of Jupiter, known as the Galilean moons, and Saturn’s most massive satellite, Titan, arebelieved to have formed in a predominantly gaseous circum-planetary disk, during the last stages of formation of theirparent planet. Pebbles from the protoplanetary disk are blocked from ﬂowing into the circumplanetary disk by the
positive pressure gradient at the outer edge of the planetary gap, so the gas drag assisted capture of planetesimals
should be the main contributor to the delivery of solids onto circum-planetary disks. However, a consistent framework
for the subsequent accretion of the moons remains to be built. Here we use numerical integrations to show that mostplanetesimals being captured within a circum-planetary disk are strongly ablated due to the frictional heating theyexperience, thus supplying the disk with small dust grains, whereas only a small fraction ‘survives’ their capture. We
then construct a simple model of a circum-planetary disk supplied by ablation, where the ﬂux of solids through the disk
is at equilibrium with the ablation supply rate, and investigate the formation of moons in such disks. We show that thegrowth of satellites is driven mainly by accretion of the pebbles that coagulate from the ablated material. The pebbleaccreting protosatellites rapidly migrate inward and pile up in resonant chains at the inner edge of the circum-planetary
disk. We propose that dynamical instabilities in these resonant chains are at the origin of the diﬀerent architectures ofJupiter’s and Saturn’s moon systems. The assembly of moon systems through pebble accretion can therefore be seen
as a down-scaled manifestation of the same process that forms systems of super-Earths and terrestrial-mass planets
around solar-type stars and M-dwarfs.
Accepted by A&A
http://arxiv.org/pdf/1912.04765

30 The molecular outflow from R Mon

Goran Sandell1 , W. Vacca2 , L. Bouscasse3 and R. Güsten3
1

University of Hawaii, Institute for Astronomy - Hilo, 640 N. Aohoku Place, Hilo, HI 96720, USA; 2 SOFIA Science
Center, NASA Ames Research Center, USRA, MS 232-12, Building N232, PO Box 1, Moﬀett Field, CA 94035-0001,
USA; 3 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
E-mail contact: gsandell at hawaii.edu
We have mapped the young Herbig Be star R Mon in CO(3–2) and 13 CO(3–2) with APEX in Chile and analyzed
unpublished Herschel images. We ﬁnd that R Mon is embedded in a small cloud with a gas temperature of ∼ 20 K

23and a total mass of ∼ 70 M⊙ . We conﬁrm that R Mon drives a bipolar molecular outﬂow, which is blue-shifted northof R Mon. The blue-shifted outﬂow has excavated the molecular cloud north of R Mon, creating the reﬂection nebula
NGC 2261 and ﬁlling it with high-velocity gas. At “high’ velocities the orientation of the outﬂow is approximatelyn-s, which agrees with the optical jet, suggesting that the accretion disk is e-w. The outﬂow velocities are modest,± 9 km/s. The outﬂow is rather massive, ∼ 0.56 M⊙ in the blue-shifted outﬂow lobe. The outﬂow is completely
optically thick in CO(3–2) towards R Mon, indicating that it’s envelope is <∼ 2,000 au. The mass of the accretion disk
and surrounding envelope determined from an isothermal graybody ﬁt is ∼ 0.34 M⊙ . We estimate a mass loss rateof ∼ (1 - 3) × 10−5 M⊙ yr−1 , corresponding to an accretion rate of (1 - 9) × 10−6 M⊙ yr−1 . We ﬁnd that R Mon
has bolometric luminosity of < 1000 L⊙ . R Mon is still in an active accretion phase, contributing to the observed
luminosity. Hence R Mon cannot be a B0 star. It must be a late B star or even an early A star.
Accepted by The Astrophysical Journal

31 Laboratory Experiments on the Motion of Dense Dust Clouds
Niclas Schneider1 and Gerhard Wurm1
1

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

E-mail contact: niclas.schneider at uni-due.de
In laboratory experiments, we study the motion of levitated, sedimenting clouds of sub-mm grains at low ambientpressure and at high solid-to-gas ratios ǫ. The experiments show a collective behavior of particles, i.e. grains in clouds
settle faster than an isolated grain. In collective particle clouds, the sedimentation velocity linearly depends on ǫ andlinearly depends on the particle closeness C. However, collective behavior only sets in at a critical value ǫcrit which
linearly increases with the experiment Stokes number St. For St < 0.003 particles always behave collectively. For
large Stokes numbers, large solid-to-gas ratios are needed to trigger collective behavior, e.g. ǫcrit = 0.04 at St = 0.01.
Applied to protoplanetary disks, particles in dense environments will settle faster. In balance with upward gas motions(turbulent diﬀusion, convection) the thickness of the midplane particle layer will be smaller than calculated based on
individual grains, especially for dust. For pebbles, large solid-to-gas ratios are needed to trigger instabilities based on
back-reaction.
Accepted by ApJL
http://arxiv.org/pdf/1912.01714

32 The evolution of dust in discs influenced by external photoevaporation
Andrew D. Sellek1 , Richard A. Booth1 and Cathie J. Clarke1
1

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

E-mail contact: ads79 at cam.ac.uk
Protoplanetary discs form and evolve in a wide variety of stellar environments and are accordingly exposed to a wide
range of ambient far ultraviolet (FUV) ﬁeld strengths. Strong FUV ﬁelds are known to drive vigorous gaseous ﬂows
from the outer disc. In this paper we conduct the ﬁrst systematic exploration of the evolution of the solid componentof discs subject to external photoevaporation. We ﬁnd that the main eﬀect of photoevaporation is to reduce thereservoir of dust at large radii and this leads to more eﬃcient subsequent depletion of the disc dust due to radial drift.
Eﬃcient radial drift means that photoevaporation causes no signiﬁcant increase of the dust to gas ratio in the disc.
We show that the disc lifetime in both dust and gas is strongly dependent on the level of the FUV background andthat the relationship between these two lifetimes just depends on the Shakura-Sunyaev α parameter, with the similar
lifetimes observed for gas and dust in discs pointing to higher α values (∼ 10−2 ). On the other hand the distributionof observed discs in the plane of disc size versus ﬂux at 850 µm is better reproduced by lower α (∼ 10−3 ). We ﬁnd thatphotoevaporation does not assist rocky planet formation but need not inhibit mechanisms (such as pebble accretionat the water snow line) which can be eﬀective suﬃciently early in the disc’s lifetime (i.e. well within a Myr).
Accepted by MNRAS
https://arxiv.org/pdf/1912.06154

24

33 Characterising the i-band variability of YSOs over six orders of magnitude in timescale
Darryl J. Sergison1 , Tim Naylor1 , S.P. Littlefair1,2 , Cameron P.M. Bell1,3 and C.D.H. Williams1
1

School of Physics, University of Exeter, Exeter EX4 4QL; 2 Department of Physics & Astronomy, University ofSheﬃeld, Sheﬃeld S3 7RH; 3 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam,
Germany
E-mail contact: timn at astro.ex.ac.uk
We present an i-band photometric study of over 800 young stellar objects in the OB association Cep OB3b, whichsamples timescales from 1 minute to ten years. Using structure functions we show that on all timescales (τ ) there isa monotonic decrease in variability from Class I to Class II through the transition disc (TD) systems to Class III, i.e.
the more evolved systems are less variable. The Class Is show an approximately power-law increase (τ 0.8 ) in variability
from timescales of a few minutes to ten years. The Class II, TDs and Class III systems show a qualitatively diﬀerent
behaviour with most showing a power-law increase in variability up to a timescale corresponding to the rotational
period of the star, with little additional variability beyond that timescale. However, about a third of the Class IIs
show lower overall variability, but their variability is still increasing at 10 years. This behaviour can be explained if all
Class IIs have two primary components to their variability. The ﬁrst is an underlying roughly power-law variability
spectrum, which evidence from the infrared suggests is driven by accretion rate changes. The second component isapproximately sinusoidal and results from the rotation of the star. We suggest that the systems with dominant longertimescale variability have a smaller rotational modulation either because they are seen at low inclinations or havemore complex magnetic ﬁeld geometries. We derive a new way of calculating structure functions for large simulated
datasets (the “fast structure function”), based on fast Fourier transforms.
Accepted by MNRAS
http://arxiv.org/pdf/1912.01615

34 Effects of photoevaporation on protoplanetary disc ‘isochrones’
Alice Somigliana1 , Claudia Toci2 , Giuseppe Lodato1,2 , Giovanni Rosotti3 and Carlo F. Manara4
1

Dipartimento di Fisica, Universitá degli Studi di Milano, Via Giovanni Celoria 16, I-20133 Milano, Italy; 2 INAF Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milan, Italy; 3 Leiden Observatory, Leiden University, P.O.
Box 9531, NL-2300 RA Leiden, the Netherlands; 4 European Southern Observatory, Karl-Schwarzschild-Strasse 2,85748 Garching bei München, Germany
E-mail contact: alice.somigliana at studenti.unimi.it
Protoplanetary discs are the site of star and planet formation, and their evolution and consequent dispersal deeply
aﬀect the formation of planetary systems. In the standard scenario they evolve on timescales ∼Myr due to the viscoustransport of angular momentum. The analytical self-similar solution for their evolution predicts also speciﬁc discisochrones in the accretion rate – disc mass plane. However, photoevaporation by radiation emitted by the central
star is likely to dominate the gas disc dispersal of the innermost region, introducing another (shorter) timescale forthis process. In this paper, we include the eﬀect of internal (X and EUV) photoevaporation on the disc evolution,ﬁnding numerical solutions for a population of protoplanetary discs. Our models naturally reproduce the expected
quick dispersal of the inner region of discs when their accretion rates match the rate of photoevaporative mass loss, inline with previous studies. We ﬁnd that photoevaporation preferentially removes the lightest discs in the sample. The
net result is that, counter-intuitively, photoevaporation increases the average disc mass in the sample, by dispersing
the lightest discs. At the same time, photoevaporation also reduces the mass accretion rate by cutting the supply ofmaterial from the outer to the inner disc. In a purely viscous framework, this would be interpreted as the result of alonger viscous evolution, leading to an overestimate of the disc age. Our results thus show that photoevaporation isa necessary ingredient to include when interpreting observations of large disc samples with measured mass accretion
rates and disc masses. Photoevaporation leaves a characteristic imprint on the shape of the isochrone. Accurate datain the accretion rate – disc mass plane in the low disc mass region therefore give clues on the typical photoevaporation
rate.
Accepted by MNRAS
http://arxiv.org/pdf/1912.05623

25

Assembly of Stellar Systems and Their Evolution with the SMA (MASSES) Full
35 Mass
Data Release
Ian W. Stephens1 , Tyler L. Bourke2,1 , Michael M. Dunham3,1 , Philip C. Myers1 , Riwaj Pokhrel4 , John
J. Tobin5 , Héctor G. Arce6 , Sarah I. Sadavoy1 , Eduard I. Vorobyov7,8 , Jaime E. Pineda9 , Stella S. R.
Offner10 , Katherine I. Lee1 , Lars E. Kristensen11 , Jes K. Jørgensen11 , Mark A. Gurwell1 and Alyssa A.
Goodman1
1

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; 2 SKA Organization,
Jodrell Bank, Lower Withington, Macclesﬁeld, Cheshire SK11 9FT, UK; 336

at the northern part of NGC2264-D. Possible interpretations of the I(HC3 N)/I(CH3 OH) ratio are discussed. We havealso observed molecular emission lines from CCS and N2 H+ toward ﬁve positions in each clump. We investigate theN (N2 H+ )/N (CCS) and N (N2 H+ )/N (HC3 N) column density ratios among the ten positions in order to test whether
they can be used as chemical evolutionary indicators in these clumps. The N (N2 H+ )/N (CCS) ratio shows a very highvalue toward a bright embedded IR source (IRS1), whereas the N (N2 H+ )/N (HC3 N) ratio at IRS1 is comparable withthose at the other positions. These results suggest that UV radiation aﬀects the chemistry around IRS1. We ﬁndthat there are positive correlations between these column density ratios and the excitation temperatures of N2 H+ ,which implies the chemical evolution of clumps. These chemical evolutionary indicators likely reﬂect the combinationof evolution along the ﬁlamentary structure and evolution of each clump.
Accepted by The Monthly Notices of the Royal Astronomical Society
https://arxiv.org/pdf/1912.10766

dynamics in star-forming regions: the interplay between gravity and turbu37 Multi-scale
lence
A. Traficante1,2 , G.A. Fuller2 , A. Duarte-Cabral3 , D. Elia1 , M.H. Heyer4 , S. Molinari1 , N. Peretto3 , E.
Schisano1
1

IAPS - INAF, via Fosso del Cavaliere, 100, I-00133 Roma, Italy; 2 Jodrell Bank Centre for Astrophysics, Departmentof Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL, UK; 3 School ofPhysics and Astronomy, Cardiﬀ University, Queens Buildings, The Parade, Cardiﬀ CF24 3AA, UK; 4 Department of
Astronomy, University of Massachusetts, Amherst, MA 01003, USA
E-mail contact: alessio.traﬁcante at iaps.inaf.it
In this work we investigate the interplay between gravity and turbulence at diﬀerent spatial scales and in diﬀerent
density regimes. We analyze a sample of 70 µm quiet clumps that are divided into three surface density bins and wecompare the dynamics of each group with the dynamics of their respective ﬁlaments. The densest clumps form within
the densest ﬁlaments on average, and they have the highest value of the velocity dispersion. The kinetic energy istransferred from the ﬁlaments down to the clumps most likely through a turbulent cascade, but we identify a criticalvalue of the surface density, Σ ≈ 0.1 g cm2 , above which the dynamics changes from being mostly turbulent-driven
to mostly gravity-driven. The scenario we obtain from our data is a continuous interplay between turbulence andgravity, where the former creates structures at all scales and the latter takes the lead when the critical surface density
threshold is reached. In the densest ﬁlaments this transition can occur at the parsec, or even larger scales, leading toa global collapse of the whole region and most likely to the formation of the massive objects.
Accepted by MNRAS
http://arxiv.org/pdf/1912.00031

38 Self-Induced Dust Traps Around Snow Lines in Protoplanetary Discs
Arnaud Vericel1 , Jean François Gonzalez1
1Univ Lyon, Univ Claude Bernard Lyon 1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon
UMR5574, F-69230, Saint-Genis-Laval, France
E-mail contact: arnaud.vericel at univ-lyon1.fr
Dust particles need to grow eﬃciently from micrometre sizes to thousands of kilometres to form planets. With thegrowth of millimetre to meter sizes being hindered by a number of barriers, the recent discovery that dust evolution
is able to create ‘self-induced’ dust traps shows promises. The condensation and sublimation of volatile species atcertain locations, called snow lines, is also thought to be an important part of planet formation scenarios. Given that
dust sticking properties change across a snow line, this raises the question: how do snow lines aﬀect the self-induced
dust trap formation mechanism? The question is particularly relevant with the multiple observations of the carbon
monoxide (CO) snow line in protoplanetary discs, since its eﬀect on dust growth and dynamics is yet to be understood.
In this paper, we present the eﬀects of snow lines in general on the formation of self-induced dust traps in a parameter
study, then focus on the CO snow line. We ﬁnd that for a range of parameters, a dust trap forms at the snow line
where the dust accumulates and slowly grows, as found for the water snow line in previous work. We also ﬁnd that,27depending on the grains sticking properties on either side of the CO snow line, it could either be a starting or braking
point for dust growth and drift. This could provide clues to understand the link between dust distributions and snowlines in protoplanetary disc observations.
Accepted by MNRAS
http://arxiv.org/pdf/1912.02464

39 Observations of Orion Source I Disk and Outflow Interface
Melvyn Wright1 , Richard Plambeck1 , Tomoya Hirota2 , Adam Ginsburg3 , Brett McGuire3 et al.
1

Radio Astronomy Lab, University of California, 501 Campbell Hall, Berkeley CA 94720-3441, USA; 2 Mizusawa
VLBI Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 3
National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
E-mail contact: bmcguire at nrao.edu
We imaged the continuum and molecular line emission from Orion Source I (SrcI) with up to 30 mas (12 AU) resolution
at 43, 99, 223, and 340 GHz in an attempt to probe the structure and chemistry of the circumstellar disk and bipolar
outﬂow associated with this high mass protostar. The continuum spectral index ranges from ∼2 along the midplaneof the disk to ∼3 along the edges, consistent with dust that is optically thick in the midplane but becomes opticallythin at the periphery. Salt (NaCl) emission is visible where the dust is optically thin; it provides a unique tracer ofthe velocity ﬁeld within the disk. All other molecules that we have mapped — H2 O, AlO, SiO, SiS, SO, and SO2 —appear to originate primarily in the bipolar outﬂow. The base of the outﬂow is corotating with the disk. SiS shows aﬁlamentary structure that is most prominent along the edges of the outﬂow. The molecular distributions suggest that
Si and Al released from dust grains in the disk react with oxygen derived from H2 O to form SiO and AlO, and with
SO and SO2 to form SiS.
Accepted by ApJ
http://arxiv.org/pdf/1912.08862

40 High-Resolution Near-Infrared Polarimetry and Sub-Millimeter Imaging of FS Tau A:
Possible Streamers in Misaligned Circumbinary Disk System

Yi Yang1,2 , Eiji Akiyama3 , Thayne Currie4 , Ruobing Dong5 , Jun Hashimoto1,2 et al.
1
Astrobiology Center, NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatoryof Japan (NAOJ), National Institutes of Natural Sciences (NINS), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3Institute for the Advancement of Higher Education, Hokkaido University, Kita 17, Nishi 8, Kita-ku, Sapporo, Hokkaido,
060-0817, Japan; 4 Subaru Telescope, NAOJ, NINS, 650 North A’ohoku Place, Hilo, HI 96720, USA; 5 Department of
Physics & Astronomy, University of Victoria, Victoria BC V8P 1A1, Canada

E-mail contact: yi.yang at nao.ac.jp
We analyzed the young (2.8-Myr-old) binary system FS Tau A using near-infrared (H-band) high-contrast polarimetry
data from Subaru/HiCIAO and sub-millimeter CO (J=2–1) line emission data from ALMA. Both the near-infraredand sub-millimeter observations reveal several clear structures extending to ∼240 AU from the stars. Based on theseobservations at diﬀerent wavelengths, we report the following discoveries. One arm-like structure detected in the nearinfrared band initially extends from the south of the binary with a subsequent turn to the northeast, corresponding to
two bar-like structures detected in ALMA observations with an LSRK velocity of 1.19–5.64 km s−1 . Another featuredetected in the near-infrared band extends initially from the north of the binary, relating to an arm-like structure
detected in ALMA observations with an LSRK velocity of 8.17–16.43 km s−1 . From their shapes and velocities, wesuggest that these structures can mostly be explained by two streamers that connect the outer circumbinary disk andthe central binary components. These discoveries will be helpful for understanding the evolution of streamers andcircumstellar disks in young binary systems.
Accepted by ApJ
http://arxiv.org/pdf/1912.11301

28

41 The widest Hα survey of accreting protoplanets around nearby transition disksA. Zurlo1,2 , G. Cugno3 , M. Montesinos4,5,6, S. Perez7 , H. Canovas8
1

Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago,
Chile; 2 Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito
441, Santiago, Chile; 3 ETH Zürich, Institute for Particle Physics and Astrophysics, Wolfgang-Pauli-Str. 27, 8093
Zürich, Switzerland; 4 Núcleo Milenio de Formación Planetaria (NPF), Chile; 5 Instituto de Física y Astronomía,
Universidad de Valparaíso, Valparaíso, Chile; 6 Chinese Academy of Sciences South America Center for Astronomy,
National Astronomical Observatories, CAS, Beijing, China; 7 Universidad de Santiago de Chile, Av. Libertador
Bernardo O’Higgins 3363, Estacion Central, Santiago, Chile; 8 European Space Astronomy Centre (ESA/ESAC),
Operations Department, Villanueva de la Cañada, Madrid, Spain
E-mail contact: alice.zurlo at mail.udp.cl

The mechanisms of planet formation are still under debate. We know little about how planets form, even if morethan 4000 exoplanets have been detected to date. Recent investigations target the cot of newly born planets: theprotoplanetary disk. At the ﬁrst stages of their life, exoplanets still accrete material from the gas-rich disk in which
they are embedded. Transitional disks are indeed disks that show peculiarities, such as gaps, spiral arms, and rings,
which can be connected to the presence of substellar companions. To investigate what is responsible for these features,
we selected all the known transitional disks in the solar neighborhood (<200 pc) that are visible from the southernhemisphere. We conducted a survey of 11 transitional disks (TDs) with the SPHERE instrument at the VLT. Thisis the largest Hα survey that has been conducted so far to look for protoplanets. The observations were performed
with the Halpha ﬁlter of ZIMPOL in order to target protoplanets that are still in the accretion stage. All the selected
targets are very young stars, less than 20 Myr, and show low extinction in the visible. We reduced the ZIMPOL
pupil stabilized data by applying the method of the angular spectral diﬀerential imaging (ASDI), which combines
both techniques. The datacubes are composed of the Cnt_Hα and the narrow band ﬁlter Hα, which are taken
simultaneously to permit the suppression of the speckle pattern. The principal component analysis (PCA) method
was employed for the reduction of the data. For each dataset, we derived the 5σ contrast limit and converted it
in upper limits on the accretion luminosity. We do not detect any new accreting substellar companions around thetargeted transition disks down to an average contrast of 12 magnitudes at 0.′′ 2 from the central star (continues in the
manuscript).
Accepted by A&A
http://arxiv.org/pdf/1912.04911

29

Abstracts of recently accepted major reviews

The Dawn of Dust Astronomy
Eberhard Grün1,2 , Harald Krüger3 , and Ralf Srama4
1

Max-Planck-Institut für Kernphysik, Heidelberg, Germany; 2 LASP, University of Colorado, Boulder, CO, USA; 3
Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany; 4 Institut für Raumfahrtsysteme Universität
Stuttgart, Germany
E-mail contact: harald.krueger at mps.mpg.de
We review the development of dust science from the ﬁrst ground-based astronomical observations of dust in space tocompositional analysis of individual dust particles and their source objects. A multitude of observational techniques
is available for the scientiﬁc study of space dust: from meteors and interplanetary dust particles collected in theupper atmosphere to dust analyzed in situ or returned to Earth. In situ dust detectors have been developed from
simple dust impact detectors determining the dust hazard in Earth orbit to dust telescopes capable of providing
compositional analysis and accurate trajectory determination of individual dust particles in space. The concept ofDust Astronomy has been developed, recognizing that dust particles, like photons, carry information from remotesites in space and time. From knowledge of the dust particles’ birthplace and their bulk properties, we learn about
the remote environment out of which the particles were formed. Dust Observatory missions like Cassini, Stardust,
and Rosetta study Saturn’s satellites and rings and the dust environments of comet Wild 2 and comet ChuryumovGerasimenko, respectively. Supplemented by simulations of dusty processes in the laboratory we are beginning tounderstand the dusty environments in space.
Accepted by ISSI book Cosmic Dust from the Laboratory to the Stars

http://arxiv.org/pdf/1912.00707

The Role of Magnetic Fields in Protostellar Outflows and Star Formation
Ralph E. Pudritz1 and Tom P. Ray2
1

Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada; 2 School of Cosmic
Physics, Dublin Institute for Advanced Studies, Ireland
The role of outﬂows in the formation of stars and the protostellar disks that generate them is a central question inastrophysics. Outﬂows are associated with star formation across the entire stellar mass spectrum. In this review,
we describe the observational, theoretical, and computational advances on magnetized outﬂows, and their role in theformation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks
by magnetized winds to eﬃciently extract and transport disk angular momentum was developed in early theoreticalmodels and conﬁrmed by a variety of numerical simulations. The recent high resolution ALMA observations of disks
and outﬂows now conﬁrm several key aspects of these ideas, e.g. that jets rotate and originate from large regionsof their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI)
turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk
angular momentum. This has major consequences for star formation, as well as planet formation. Outﬂows also play
an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being
almost certainly fundamental to their production and focusing, magnetic ﬁelds in outﬂows in protostellar systems, andeven in the disks, are notoriously diﬃcult to measure. Most methods are indirect and lack precision, as for example,
when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore
what is known about magnetic ﬁelds from observations, and take a forward look to the time when facilities such as
SPIRou and the SKA are in routine operation.
Accepted by Frontiers in Astronomy and Space Sciences
http://arxiv.org/pdf/1912.05605
30

Dissertation Abstracts

New Dimensions in the Observational Analysis of Molecular Clouds
Birgit Hasenberger
Department for Astrophysics, University of Vienna
Türkenschanzstraße 17, 1180 Vienna, Austria
Electronic mail: birgit.hasenberger at univie.ac.at
Ph.D dissertation directed by: João Alves
Ph.D degree awarded: October 2019

Stars are formed in molecular clouds via a complex process that involves a variety of physical and chemical mechanisms. Characterising the inﬂuence of these mechanisms represents a crucial, yet challenging task for observational
astronomers. This thesis explores new techniques that reveal the properties of molecular clouds and their populationof dense cores by studying dust-emission observations towards a nearby (d ∼ 130 pc) molecular cloud, the Pipe nebula.
Dust-emission observations provide information on the dust column density and the eﬀective dust temperature. While
the former is employed frequently to study the structure of molecular clouds, the latter is rarely used due to possible
systematic eﬀects in its derivation. However, this work demonstrates that the eﬀective dust temperature can aid
in locating regions of high volume density within the cloud and in identifying the mechanisms that dominate thethermodynamics of cores.
In many cases, the process of observation reduces the number of spatial dimensions with respect to the physical object.
For instance, molecular clouds and dense cores are inherently three-dimensional objects, while observations capture
only two spatial dimensions. This fundamental diﬀerence in dimensionality represents an obstacle for the derivation ofphysical quantities from observational data. A novel technique to overcome this obstacle is presented in this thesis: The
AVIATOR algorithm represents a new, robust method to estimate three-dimensional density distributions from their
two-dimensional projections. To this end, the algorithm employs a set of intuitive assumptions about the line-of-sightdensity distribution.
By reconstructing the three-dimensional density and temperature distribution of the Pipe nebula region with the AVIATOR algorithm, new insights on the physical properties of structures within the cloud are gained. The gravitational
potential and acceleration arising from the density distribution provide a new way to assess the gravitational inﬂuenceand energy budget of structures. In particular, the gravitational potential, in conjunction with the distribution ofthermal energy, forms the basis of a scheme to deﬁne core boundaries in a physically motivated fashion. The resulting
population of dense cores in the Pipe nebula exhibits properties markedly diﬀerent from those reported in the literature, including a high degree of gravitational binding and a comparably shallow high-mass slope of the core mass
distribution.
The methods introduced in this thesis enable a new view on molecular clouds and dense cores that exploits theinformation provided by dust-emission observations and considers the inherently three-dimensional structure of theseobjects. The core properties found here are in conﬂict with the literature, demonstrating the need for a thoroughevaluation of techniques that are used frequently to deﬁne core boundaries and determine their energy budget. Withthe tools presented in this thesis, additional dimensions of the available observational data are utilised, leading towards
a deeper understanding of the physical processes relevant at the early stages of star formation.

31

New Jobs

Postdoctoral Position in Star Formation & Observational Astrophysics
Center for Astrophysics and Space Astronomy (CASA)
Astrophysical and Planetary Sciences Department (APS)
University of Colorado, Boulder
Boulder, Colorado, USA
Applications are invited for a two-year postdoctoral position at the University of Colorado Boulder starting between
May and August 2020, to work with Prof. John Bally on observations and theory of star-formation.
The successful applicant will contribute to a research program using multi-wavelength imaging and spectroscopy from
Apache Point Observatory, Subaru, ALMA, the JVLA, and other facilities. Familiarity with data reduction methods
and tools is essential. Candidates familiar with numerical simulations such as N-body, SPH, or other codes used toinvestigate the physics of outﬂows, their interactions with the surrounding ISM, protostellar dynamic interactions andmergers among protostars will also be considered.
Speciﬁc program goals are: [1] Complete the analysis and publication of existing data on the Orion OMC1 outﬂow,
ejected stars, and environment. [2] Observe other Galactic explosive outﬂow candidates to constrain their event rates,
properties, and impacts. [3] Continue near-IR monitoring of nearby star-forming galaxies to determine if N-bodyprotostellar interactions are responsible for some extra-galactic IR transients detected by Spitzer. [4] Explore the useof 6.7 GHz (methanol) and 22 GHz (water) maser outbursts as alerts for protostellar mergers or major accretionpowered IR-transients. [5] Model circumstellar disk & envelope behavior in interactions using public-domain SPH and
N-body codes.
Who We Are:
The Center for Astrophysics and Space Astronomy (CASA) is dedicated to advancing our understanding of the Universe
in which we live through observations, theory, and the development of ground-based and space-borne instrumentation.
Founded in 1985, CASA is an aﬃliated unit within the structure of the Astrophysical and Planetary Sciences (APS)
Department at the University of Colorado, Boulder.
What Your Key Responsibilities Will Be: The successful applicant will contribute to the research program by generating new observing proposals, reducing and analyzing data, and writing-up results. Speciﬁc goals of this program are:(1) Measure the momentum and energy injection rates of various feedback mechanisms such as protostellar outﬂows,
stellar winds, and radiation by measuring proper motions, radial velocities, and densities on multi-epoch narrow-bandvisual and near-IR images and spectra. (2) Assist in the analysis of ALMA and other interferometer data tracing
molecular gas in clouds and outﬂows from forming stars. (3) Assist in the preparation of new observing proposals.
What We Oﬀer: The appointment will be for an initial period of two years, with renewal for a third year contingent
upon satisfactory progress and availability of funds. The position includes a competitive salary, research/travel funds,
and access to CU’s computing resources and partnership in the Apache Point Observatory and Sloan Digital Sky
Survey.
Beneﬁts: The University of Colorado oﬀers excellent beneﬁts, including medical, dental, retirement, paid time oﬀ,
tuition beneﬁt and ECO Pass. The University of Colorado Boulder is one of the largest employers in Boulder County
and oﬀers an inspiring higher education environment. Learn more about the University of Colorado Boulder.
Be Adaptable. Be Imaginative. Be Boulder.
What We Require: Applicants must have a PhD in astronomy or physics on arrival.
What We Would Like You To Have: Experience with visual, infrared, and radio data reduction and analysis methods.
Familiarity with numerical simulation of star-forming environments would be welcome.
Special Instructions: To apply, please submit the following materials by April 15 , 2020:32

• Resume/CV (including a list of publications)• Cover letter• Transcripts/Proof of Degree• Statement of research philosophy - Brief (up to 3 pages) research statement of your scientiﬁc interests and how you
would speciﬁcally contribute to the research program described above.
• Three letters of recommendation to be emailed as PDFs
Application materials are accepted electronically via CU Boulder Jobs. Please send copies of application material via
e-mail to john.bally@colorado.edu. Full consideration will be given to applications that are completed by April 15 ,2020.
Posting Contact Information:
https://jobs.colorado.edu/jobs/JobDetail/?jobId=23016
Posting Contact Name: Boulder Campus Human Resources
Posting Contact Email: Recruiting@colorado.edu
The University of Colorado Boulder is committed to building a culturally diverse community of faculty, staﬀ, andstudents dedicated to contributing to an inclusive campus environment. We are an Equal Opportunity employer,
including veterans and individuals with disabilities.

ERC-funded postdoc position in star formation at
Konkoly Observatory, Budapest
The “Structured Accretion Disks” ERC-funded research group invites applicants to a postdoc position at Konkoly
Observatory (Budapest, Hungary) on the topic of structure, composition, and chemistry of circumstellar disks aroundyoung eruptive stars. The ERC Starting Grant is awarded to Dr Ágnes Kóspál, and its aim is to provide realistic initialconditions for the planet formation process. The position is for two years, available immediately, with a possibility ofa shorter extension until 2022 June. Applicants must have a PhD in astrophysics (or related discipline).

Multiple PhD positions in star/planet formation and exoplanet research
The University of Exeter is inviting applications for several fully funded PhD studentships to start in the fall of 2020.
The Exeter Astrophysics group is one of the leading, and largest, groups in the UK for studying star formation andextra-solar planets.
(1) Breaking the stellar activity barrier to determining robust masses of small exoplanets. In this PhD Project, thestudent will use a variety of solar observations to develop models of intrinsic RV variations. They will identify andstudy velocity ﬂows and small-scale magnetic features seen in spatially resolved observations of the Sun, notably fromthe Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory (SDO/HMI). This will allow themto develop models of intrinsic RV variations, which they will test against observations of the Sun seen as a distant,point-like star with the High-Accuracy Radial-velocity Planet Searcher in the Northern hemisphere (HARPS-N). The
student will apply their models to other stars to determine robust planet masses by participating in the HARPS-N
RV follow-up of TESS planet candidates. They will have opportunities to work with international collaborators in the
United States and Europe. This project will be supervised by Dr. Raphaëlle Haywood, who is joining the Universityof Exeter in the summer of 2020. To apply, visit https://jobregister.aas.org/ad/1b442f2a(2) Simulations of protoplanetary discs, dust coagulation, and planetesimal formation. The theme of this PhD projectis simulating the beginnings of planet formation inside gas-rich protoplanetary discs. The student will (f72.057(m)]TJ266.52117.67145

Meetings

Call for Review Proposal: Deadline April 1, 2020
Protostars & Planets VII (PP7)
1 - 7 April 2021, Kyoto, JapanThe Protostars & Planets series has served the community for more than three decades with state-of-the-art compilations of the current knowledge in the ﬁelds of star and planet formation. The previous volume PPVI was publishedin 2014. Since then, the ﬁeld of Protostars & Planets has advanced signiﬁcantly. The next Protostars & Planets
conference will take place in Kyoto, Japan, April 1-7, 2021. For more details about the schedule and location, please
visit the conference website: http://ppvii.org.
A primary outcome of the conference will be a book of review articles as “Protostars and Planets VII”. This announcement is a call for proposals for review chapters in the book and associated talks. The organizers have defined rulesin the submission of proposals, such as “one proposal per person” rule. Please refer to the website.
Since the organizers would like to have suﬃcient time to evaluate the proposals, we ask you to submit proposals byApril 1, 2020. The respective deadlines and dates are the following:
Dec. 13, 2019 (this announcement): Call for review chapters and talk proposals
Apr. 1, 2020 (15:00JST): Deadline for the submission of proposals
Oct. 1, 2020: Decision on review chapters and talks
Oct. 1, 2020: Start of registration
Dec. 1, 2020: End of early registration
Feb. 1, 2021: Submission of extended skeleton papers
Mar. 1, 2021: Submission of the ﬁnal review article
Apr. 1, 2021: Start of PP7 meeting
Scientiﬁc Advisory Committee (SAC):
Joao Alves (Austria), Philippe Andre (France), Isabelle Baraﬀe (UK), John Carpenter (Chile), Paola Caselli (Germany), Wen-Ping Chen (Taiwan), Kees Dullemond (Germany), Tristan Guillot (France), Alyssa Goodman (USA),
Lynne Hillenbrand (USA), Thomas Henning (Germany), Shigeru Ida (Japan), Doug Johnstone (Canada), Inga Kamp
(Netherlands), Mark Krumholz (Australia), Jeong-Eun Lee (Korea), Victoria Meadows (USA), Michael Meyer (USA),
Richard Nelson (UK), Toshikazu Onishi (Japan), Eve Ostriker (USA), Ilaria Pascucci (USA), Yasuhito Sekine (Japan),
Shogo Tachibana (Japan), Mario Tafalla (Spain), Ewine van Dishoeck (Netherland), and Jonathan Williams (USA)PP7 Editors:
Shu-ichiro Inutsuka (Nagoya University), Motohide Tamura (University of Tokyo), Yuri Aikawa (University of Tokyo),
Takayuki Muto (Kogakuin University), and Kengo Tomida (Osaka University)

35Summary of Upcoming Meetings

First Stars VI
1 - 6 March 2020 Concepcion, Chile
http://www.astro.udec.cl/FirstStarsVI/
Interstellar Shocks School
22 - 27 March 2020, Les Houches, France
https://www.sciencesconf.org/browse/conference/?confid=8899
Linking Dust, Ice, and Gas in Space19 - 24 April 2020, Capri Islands, Italy
http://www.frcongressi.it/ecla2020/
AIP Thinkshop on Protoplanetary Disk Chemodynamics
11 - 15 May 2020, Leibnitz Institute for Astrophysics Potsdam, Germany
https://meetings.aip.de/event/1
Planet Formation: From Dust Coagulation to Final Orbital Assembly
1 - 26 June 2020, Munich, Germany
http://www.munich-iapp.de/planetformation
Cool Stars, Stellar Systems, and the Sun 21
21 - 26 June 2020, Toulouse, France
https://coolstars21.github.io/
The Physics of Star Formation: From Stellar Cores to Galactic Scales; 29 June - 3 July 2020, Lyon,
Francehttp:/staratlyon.univ-lyon1.fr/en
Illuminating the Dusty Universe: A Tribute to the Work of Bruce Draine
6 - 10 July 2020, Florence, Italy
https://web.astro.princeton.edu/IlluminatingTheDusty Universe
The Early Phase of Star Formation
12 - 17 July 2020, Ringberg, Germany
http://www.mpia.de/homes/stein/EPoS/2020/2020.php
Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann
17 - 20 August 2020, Malahide, Ireland
https://www.dias.ie/cloudstodiscs/
Star Formation in Different Environments 202024 - 28 August 2020, Quy Nhon, Vietnam
http://icisequynhon.com/conferences/sfde/
Planetary Science: The Young Solar System
6 - 12 September 2020, Quy Nhon, Vietnam
http://www.icisequynhon.com/conferences/planetary_science/
Wheel of Star Formation: A conference dedicated to Prof. Jan Palouš
14 - 18 September 2020, Prague, Czech Republic
https://janfest2020.asu.cas.cz
Conditions and Impact of Star Formation - Across Times and Scales
28 September - 2 October 2020, Chile
https://astro.uni-koeln.de/symposium-star-formation-2020.html

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From Clouds to Planets II: The Astrochemical Link
28 September - 2 October 2020, Berlin, Germany
https://events.mpe.mpg.de/event/12/
The Aftermath of a Revolution: Planet Formation Five Years after HL Tau
7 - 11 December 2020, Chile
https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org

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