THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 322 — 17 October 2019

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

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

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Abstracts of Newly Accepted Papers . . . . . . . . . . 11

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

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 55

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

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Editorial Board

New Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

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

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

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Summary of Upcoming Meetings . . . . . . . . . . . . . 59

Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 62

Cover Picture
ALMA observations of the embedded protostellar
binary [BHB2007]-11 in B59, with a projected separation of 28 AU, shows highly contorted circumbinary material, revealing a highly dynamical andshort-lived configuration. For details, see the abstract by Alves et al. in this issue.
Image Credit ALMA (ESO/NAOJ/NRAO)

Submitting your abstracts
Latex
macrosfor
submitting
abstractsand dissertation abstracts (by e-mail toreipurth@ifa.hawaii.edu)
areappendedtoeach Call for Abstracts.
You can also
submitvia
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http://www2.ifa.hawaii.edu/starformation/index.cfm

Q: Another highly cited paper from 1977 dealt with the distribution of mass in the planetary system and solar nebula.

Stuart Weidenschillingin conversation with Bo Reipurth

A: That might be my most-cited paper, and the least useful. It was based on the concept that planets accreted frommaterial in local ’feeding zones’ at their present heliocentric distances, which was generally taken for granted atthat time. Their masses were consistent with a –3/2 powerlaw nebular surface density, which seemed plausible. However, it has become apparent that planets migrate rather
than accrete in situ, rendering the conclusion meaningless.
That paper is now of historical interest only, and serves as
an example of how our understanding of planetary formation has changed over the last four decades.
Q: In 1980 you published a paper on the way dust settles
towards the midplane of a solar nebula and the subsequent
formation of planetesimals. What were the key results?
A: The drag-induced particle drift velocities are size-dependent. This leads to collisions in any ensemble of particles
with a range of sizes. I modeled numerically the rate at
which bodies would grow and the resulting size distribution, using simple rules for collisional outcomes (sticking,erosion, shattering) as functions of size and impact velocity. Settling and particle growth have a positive feedback;larger particles settle more rapidly, while the higher density of particles near the nebular midplane increases theircollision frequency. If sticking occurs, km-sized planetesimals can grow rapidly, on the order of 1000 orbital periods.
When particles settle into a dense layer, they drag the local gas with them at nearly the Kepler velocity, faster thanthe pressure-supported gas. I showed by dimensional arguments that this shear flow was unstable and would become turbulent. This shear-generated turbulence would
limit the density of the particle layer, inhibiting gravitational instability.

Q: In 1977 you published a very influential paper on aerodynamics of solid bodies in the solar nebula. For 20 years
this paper lived in a dormant state, with a handful of citations per year. But then gradually the paper became
more recognized, and in 2018 alone garnered 100 citations.
What were your key conclusions, and what accounts forthis belated recognition?
A: The chief point of that paper was that the nebular gas
is partially supported by a radial pressure gradient, andmust rotate a bit slower than the Kepler velocity. Solidbodies lack this support, and must move relative to thegas. The drag force causes them to spiral inward. Thiswas first stated by Fred Whipple in 1972 in an obscure conference proceeding, where he gave results for radial velocities in the limiting cases of large and small bodies. WhenI read his paper, I was intrigued by it (perhaps because
my undergraduate degree was in aeronautical engineering), and I derived equations of motion valid for bodies
of all sizes and various drag laws. Among my conclusions
were that for a typical nebular model the peak radial velocity occurred for roughly m-sized bodies, decreasing at
smaller and larger sizes. The peak rate was tens of m/s,or ∼1 AU/century. Bodies would be lost into the Sun unless they could rapidly grow through the meter size range;
this places a strong constraint on any mechanism of planetesimal formation. The interaction of solid particles withdrag of nebular gas is a fundamental process that must be
taken into account by all current models of planetesimalformation, including collisional coagulation, gravitational
collapse, streaming instability, or the currently popular
pebble accretion. Presumably this is the reason for theincreasing number of citations. Various implications ofparticle-gas interactions led me to do many follow-up papers over the next three decades. My career would havebeen very different if I had not encountered that paper by
Whipple!

Q: A few years later you explored how solid grains in aturbulent solar nebula lead to aggregates which, however,
have difficulty growing to larger bodies because of collisions. How have these models held up with time?
A: Particle growth depends on the nebular properties (pressure gradient, turbulent velocities), which determine impact velocities vs. size, but also on the mechanical properties of the grain aggregates (stickiness and impact strength).
That inspired a lot of experimental work on particle collisions, notably by J. Blum and coworkers in Germany.
They found that for aggregates of silica grains, there isa size/velocity threshold at which sticking gives way tobouncing, effectively halting further growth at ∼ cm size.
However, if grains in the solar nebula were stickier thanpure silicates, e. g., if they included organic matter or ices,larger bodies could have grown. Impact velocities still increase up to m-sized bodies, so growth in that size range

3

could stall due to erosion or shattering, unless aggregatesare sufficiently strong. That result has inspired theories
in which turbulent concentration or streaming instability
forms massive clumps of cm- to decimeter-sized aggregates, which then collapse directly to form large planetesimals without growing through intermediate sizes. Thosemight be viable growth mechanisms, but collisional coagulation would probably be quicker if grain aggregates
could stick through the cm - m size range. We still don’tknow the material properties of primordial aggregates wellenough to decide how planetesimals formed.

distribution deviates from a self-similar power law, withbumps produced by transition between regimes governedby random velocities and Keplerian shear. The placementof those bumps depends on the initial planetesimal size.
The simulation with small primary bodies of size ∼100 m
yielded a much better match to the observed size distribution of asteroids than for the usually assumed km-sizedplanetesimals. That result is consistent with formation ofplanetesimals by drag-driven coagulation.
Q: In a 1996 study in Nature you suggested that exoplanetswith high eccentricities could be the result of gravitational
scattering, which could also lead to ejection of planets.

Q: In 1997 you carried out simulations of cometary formation based on drag-induced collisions and gravitational
accretion. Do recent close-up studies of comets from spacecraft support this scenario?

A: ’Hot Jupiters’ could be brought into close circular orbits by tidal interactions with a circumstellar disk, butsome exoplanets were found to have eccentric orbits. I
and my coauthor Francesco Marzari proposed that in systems in which three or more gas giants formed, their massgain during gas accretion could destabilize their orbits.
We performed orbital integrations that showed the usualoutcome was ejection of one planet, leaving two in eccentric but stable orbits. Somewhat later we referred to thisas the ’jumping Jupiters’ model.

A: In that paper I pointed out that if bodies can grow pastmeter size, drag becomes less effective. Relative velocities
decrease with increasing size; growth slows, and mass piles
up at larger sizes, until the largest bodies are controlled
more by their gravity than by gas drag. The minimum
relative velocity occurs when the drag-induced velocities
are comparable to the escape velocity, at sizes ∼100m inthat simulation. Further growth would be dominated bygravitational accretion, starting from primary planetesimals of that size. It is not obvious that structure on thatscale would be preserved through later growth. In any
case, that scenario was not supported by Rosetta’s observations of 67P, which showed a variety of landforms on
many scales, with no obvious preferred size of components.
That comet’s history is complex, with a surface that has
evolved over many perihelion passages. Ultima Thule ispristine, and shows hints of hierarchical structure, but was
imaged at a resolution too low to constrain the mechanismof its formation.

Q: What are your current interests?

A: Recently I have been studying the formation of the asteroids. Thermal histories derived from meteorites imply
that the onset of accretion was delayed for ∼1 Myr, andextended over a comparable interval, or they would havebeen melted by radiogenic heating. This conflicts with dynamical models that suggest asteroid-sized bodies would
have accreted rapidly from smaller primary planetesimals.
I have been trying to reconcile this contradiction by modeling the evolution of the size distribution during accretion.
Although asteroid-sized bodies can melt, a significant fraction of material can be preserved in bodies too small to
Q: You also used numerical simulations to model growth be heated. This material can be added as a veneer on theof large bodies from planetesimals.
larger bodies, possibly accounting for the less processed
A: Those used another code that treated accretion of bod- types of meteorites. There is also a significant stochastic
ies using Keplerian dynamics, i.e., large enough that grav- variation in accretion histories, so thermal evolution is notitational forces were dominant, with gas drag only a minor a simple function of asteroid size.
perturbation. The swarm of small bodies was modeled asa statistical continuum in a series of radial zones of semimajor axis. The largest objects were treated individuallywith their own orbital parameters; they could interact bygravitational perturbations and collisions. I used various
versions of the code to study problems such as how large
protoplanetary embryos emerged from a swarm of planetesimals, their mass distribution and orbital spacing. In
a 1997 paper I showed that rapid runaway growth in theterrestrial region produced lunar- to Mars-sized embryos
on short timescales, less than 1 Myr. Perhaps the mostinteresting application was to accretion in the asteroid region. In 2011 I published a study of accretion startingwith various initial sizes of planetesimals. The final size
4

The spectra of FU Ori stars were long controversial, since
they resemble those of rapidly rotating supergiant stars. It
is now broadly accepted that their spectra are dominatedby contributions from a self-luminous accretion disk. In
contrast, the spectra of normal accreting T Tauri stars
have contributions from both the star and an accretion
disk, modified by accretion processes, with the relative
contributions from each varying with wavelength.

Perspective
Accretion Outbursts in
Low-Mass Protostars
Will Fischer

An FU Ori outburst is thought to begin when gravitationalor magnetorotational instabilities in the disk cause it tofragment, and the accretion rate rapidly spikes as fragments accrete onto the central star (e.g., Zhu et al. 2012;
Vorobyov & Basu 2015; Kratter & Lodato 2016). This
leads to a range of photometric and spectroscopic behavior. Photometric evidence includes a brightening at all
wavelengths. The spectroscopic characteristics of FU Ori
stars in the optical and near-infrared were outlined by Herbig (1977) and Connelley & Reipurth (2018), respectively.
Comprehensive overviews of the outburst phenomenon include those by Hartmann & Kenyon (1996), Reipurth &Aspin (2010), Audard et al. (2014), and sections of Hartmann et al. (2016).

1

By 1990, FU Ori, V1057 Cyg, and V1515 Cyg were theknown FU Ori stars. With the advent of large-scale IRsky surveys, deeply embedded outbursts have been detected with increasing frequency. In many cases, the stars
are too deeply embedded for optical and IR spectroscopy,
so efforts have focused on the interpretation of their photometric behavior. It is not clear whether all of the major
protostellar brightenings that have been observed can beconsidered part of a homogeneous FU Ori class, so I referto them more generally as bursts.

Introduction

In the winter of 1936–1937, A. A. Wachmann watched thestar FU Orionis become about six magnitudes brighter inthe B band. In 2014, University of Toledo undergraduate
Emily Safron, who was working with me and with Tom
Megeath on her senior thesis, discovered in archival Spitzer
images that the protostar HOPS 383 had become brighterby a factor of 35 at 24 µm. Here in the ninth decadeof the study of outbursting young stellar objects, we are One question that can be addressed through photometric
beginning to establish the importance of this phenomenon studies is what fraction of a star’s ultimate main-sequencemass is accreted in bursts as opposed to quiescent forms
for the process of stellar mass assembly.
of accretion. This can be written schematically as
The number of outbursting young stellar objects is difficult to state precisely because of disagreements about the
fb = Ṁb × ∆tb × Nb ,number of types of outburst, how to classify each source as
one of these types, what distinguishes outbursts from rou- where Ṁb is the typical accretion rate during bursts, ∆tb
tine variability, and whether to count objects that have is the typical length of a burst, and Nb is the number ofsome characteristics of outbursts but were not directly bursts a protostar experiences during its formation period.
observed to burst. Audard et al. (2014) list 41 in their I will review our understanding of these parameters during“non-exhaustive list of eruptive young stars.” Of these, the protostellar phase, when an infalling envelope is still
ten are listed as FU Ori outbursts, the most dramatic and present. After the protostellar phase, typical accretion
longest-lasting type. Sixteen are classified as FU Ori-like, rates of order 10−8 to 10−7 M⊙ yr−1 persist for a period
which are spectroscopically similar to FU Ori outbursts of a few million years, confirming that relatively little ofbut have not been directly observed to erupt. The other the star’s mass is accumulated after the envelope is gone.
15 are listed as known or possible EX Lup objects, whichfeature less dramatic outbursts that last for months to
Bursts in the Orion Protostars
years and may repeat in a given star. While other lists 2
vary in the details, the numbers are similar and growing
with time. Hartmann et al. (2016) note that about one The Herschel Orion Protostar Survey (HOPS) obtained
new outburst is discovered per year.
photometry and spectroscopy of protostars in Orion that5

were identified in the Spitzer survey of Orion (Megeath
et al. 2012). While HOPS efforts were centered on theanalysis of far-IR data from Herschel, we also included
near-IR to submillimeter photometry, spectroscopy, andimaging. Furlan et al. (2016) concluded that 319 of the373 HOPS targets were bonafide protostars. The other 54
were a mixture of Class II (post-protostellar) young stellar
objects, extragalactic contaminants, and non-detections.
While FU Ori itself lies within the boundaries of the Orion
constellation, it is well to the north of the Orion molecular
clouds. Among the Orion protostars, five bursts have beenreported. They are discussed below.
• V883 Ori. No precise estimate exists for the onsetof this outburst, but Strom & Strom (1993) concluded from a report by Pickering (1890) that it has
been bright since at least the late nineteenth century.
• Reipurth 50. It began its outburst between 1955
and 1979 (Strom & Strom 1993), and it has shown
recent variability that has been interpreted as variable dust obscuration, not a change in its accretion
rate (Chiang et al. 2015).
• V1647 Ori. Just before the beginning of Spitzer ’sscientific operations in late 2003, this star began an
outburst that illuminated McNeil’s Nebula in Lynds
1630. It peaked in both 2003 and 2008 (Reipurth &Aspin 2004; Aspin 2011).
• HOPS 223. This burst was discovered in near-IR
imaging by Caratti o Garatti et al. (2011). Also
known as V2775 Ori, it is a flat-spectrum protostar(one with a relatively weak envelope) that brightened from 4.5 to 51 L⊙ between 2005 and 2007 andsubsequently faded to 28 L⊙ (Fischer et al. 2012).
• HOPS 383. This burst was discovered and firstreported by Safron et al. (2015). It lies about 2′ eastof the northern end of the integral-shaped filament(Johnstone & Bally 1999). It is a deeply embedded
Class 0 protostar that brightened by a factor of 35 at
24 µm between 2004 and 2008, reaching a luminosityof 7.5 L⊙ .
Another two Orion protostars, Haro 5a/6a and NGC 2071
MM3, are reported by Connelley & Reipurth (2018) as FU
Ori-like objects. They have near-IR spectra typical of theclass but no observed outbursts.
HOPS 223 and HOPS 383 have been the subject of detailed multiwavelength investigations by the HOPS team.
Figure 1 shows mid-IR images of HOPS 223 before andafter its outburst as well as the evolution of its SED, discussed above. Figure 2 shows how it has the characteristic spectrum of an FU Ori outburst, differing sharply

3

Measuring Burst Parameters

3.1

The Accretion Rate in Bursts

It is challenging to measure the accretion rates of outbursting protostars. The two usual methods for T Tauri stars
are to directly measure the excess accretion emission in theultraviolet or to measure the luminosities of optical andnear-IR emission lines as proxies. The UV is extinguishedby dust in embedded protostars. The copious emission
lines seen in accreting young stars, which typically become stronger as accretion speeds up, ironically disappear
or go into absorption in FU Ori-like spectra (Figure 2).
The spectrum changes because the way in which gas accretes onto the star changes. In normal accretors, the accretion disk is truncated a few stellar radii from the surfaceof the star by the star’s magnetic field, and optically thingas flows from the disk to the star along magnetic fieldlines (magnetospheric accretion). In FU Ori stars, the disk
reaches the surface of the star, and the accretion zone is
optically thick. Another challenge in measuring accretion
rates is that we need stellar masses and radii to convert
accretion luminosities into accretion rates, and these havehistorically been difficult to obtain for outbursts because
the central star is faint compared to the disk.
The largest accretion rates measured from emission lines
are those of the EX Lup outbursts mentioned above. Theiraccretion rates are of order 10−6 M⊙ yr−1 . Lacking emission lines, we assume that the accretion luminosity of an
FU Ori burst is roughly equal to its total luminosity; i.e.,any contribution from the star itself is minimal. Assuming L is roughly equal to GM⊙ Ṁ /R⊙ , where deviationsof the M∗ /R∗ ratio from solar and the details of the accretion process may affect the result by a factor of a few,
10 L⊙ corresponds to about 10−5 M⊙ yr−1 , and 100 L⊙
corresponds to about 10−4 M⊙ yr−1 .
The classical FU Ori outbursts have luminosities of a few
hundred L⊙ , and the recently discovered outbursts HOPS
223 and HOPS 383 have luminosities of 28 L⊙ and 10 L⊙ ,respectively. Baraffe et al. (2012) showed that the transition from typical magnetospheric accretion to outburst
accretion takes place around 10−5 M⊙ yr−1 . This suggests that HOPS 223, with its FU Ori-like spectrum, may
revert to a typical emission-line spectrum if it fades significantly. While the first FU Ori stars to be discovered
have become less bright over time, such a reversion to atypical spectrum has not yet been observed.

3.2

The Interval between Bursts

Comparing sky surveys across multiple epochs is useful instatistically constraining the frequency of bursts. Scholz

3.3

The Durations of Bursts

this should become clear with future study of more distantlarge regions.

With no space-based far-IR telescopes expected to launch
for at least a decade, the Stratospheric Observatory for
Infrared Astronomy (SOFIA) is crucial for monitoring thedurations of protostellar bursts that are not accessible tooptical and near-IR facilities. We observed HOPS 223
with SOFIA’s FORCAST instrument in November 2015,
and we observed it again alongside HOPS 383 in February
2016. In both cases, the protostars had mid-IR fluxes
consistent with their 2008 Spitzer and 2010 WISE fluxes,
showing that the bursts had persisted for nearly a decade.

3.4

In addition to the luminosity, the chemical signatures ofa protostar are also affected by outbursts. Poteet et al.
(2011) found evidence for crystalline silicates in HOPS
68, which could be explained by a relatively recent period
of intense heating. Molecular tracers in the protostellar
environment can also serve as archaeological evidence forbursts (Visser et al. 2015; Frimann et al. 2017; Hsieh et al.
2019). These chemical signatures of a burst can persist inspectra for 105 yr, which is long compared to some of therecurrence timescales that have recently been derived. In
this case, most protostars should show evidence for a past
burst.

Implications for Mass Assembly

If most protostars do not show evidence for past bursts,
it may be the case that only a subset of protostars areprone to bursting. Their bursts would recur on timescales
shorter than derived if we assume that all protostars undergo such events. They may, for example, have massive
disks that drive recurrent major luminosity spikes due toenhanced accretion, while most protostars are more quiescent. There may be an additional dependence on themass of the central object or on the evolutionary state.
Most studies so far have considered all protostars together,but perhaps Class 0 protostars burst more frequently thanClass I protostars (Hsieh et al. 2019). Far-IR monitoringof larger samples than studied to date will enable substantial progress on these matters.

The HOPS 223 outburst features a luminosity that is afactor of 15 above its quiescent state, and this state has
persisted for more than 10 yr. The fractional change
in luminosity is expected to be similar to the fractionalchange in accretion rate. If protostars have an accretion
rate 15× above their quiescent rate for 20 out of every
1000 yr, or 2% of the time, this suggests that roughly(0.02×15)/(0.02×15+0.98) = 23% of the mass of the staris accumulated in times of outburst. The parameters that
go into this estimate still feature large uncertainties, and
it is unlikely that a similar situation prevails for every protostar. Nonetheless, a range of inputs would be consistent
with outbursts being responsible for an important fractionof each star’s main-sequence mass. This schematic calculation is consistent with the estimate of Offner & McKee(2011) that the mass fraction accumulated in outbursts isapproximately 25%.

4

Further study of HOPS 383 should be fruitful in understanding bursts of the youngest protostars. Initially, thissource was virtually invisible in Spitzer images. Its estimated luminosity of only 0.2 L⊙ was consistent with thatof a very low-mass star. It then brightened over at mostfour years to reach a luminosity typical of Class 0 protostars. Perhaps the central star is currently undergoing its
first major growth episode as it evolves toward the main
sequence.

Outlook and Conclusions

If a protostar typically bursts every 1000 yr, then in theOrion sample of 319 protostars, one should burst every 3
to 3.5 yr, on average. The outburst of McNeil’s protostar began just before our Spitzer to WISE comparison,in 2003. Perhaps the two protostars shown by Connelley & Reipurth (2018) to have FU Ori-like spectra, but
for which no burst was observed, were the previous two
sources to erupt. Fischer et al. (2017) reported a surplus
of intermediate-luminosity protostars across Orion; these
may be bursts from the last few centuries that have notcompletely returned to their pre-outburst states. Orion
has been a particular focus of our statistical studies because it contains hundreds of protostars at a distance where
they can, for the most part, be individually resolved by themost recent generation of IR space telescopes. It is notclear whether the star-forming environment affects outburst rates or the properties of individual outbursts, andAs we approach the 83rd anniversary of the first detected
accretion outburst, we have observed bursts across protostellar evolution, from Class 0 protostars detected mostly
beyond 24 µm to pre-main-sequence stars that retain little
envelope mass. Evidence from a variety of angles showsthat bursts are more frequent in the earlier stages. To
make further progress in understanding how accretion outbursts shape the assembly of low-mass stars, planned missions such as the Space Infrared Telescope for Cosmology
and Astrophysics (SPICA) and proposed missions such as
the Origins Space Telescope will be necessary. These will
enable far-IR photometry and spectroscopy of large samples of bursting protostars across the full range of stellar
masses and evolutionary states. The data will constrain
occurrence rates and durations and reveal the chemicaland physical properties of bursts.
9

I close by noting that countless advances in the study ofaccretion outbursts have been due to the careful work ofamateur astronomers, and I thank them for their contributions to the field.
References:
Aspin, C. 2011, AJ, 142, 135
Audard, M., Ábrahám, P., Dunham, M.M., et al. 2014, PPVI, 387
Baraffe, I., Vorobyov, E., & Chabrier, G. 2012, ApJ, 756, 118
Caratti o Garatti, A., Garcia Lopez, R., Scholz, A., et al. 2011,
A&A, 526, L1
Chiang, H., Reipurth, B., Walawender, J., et al. 2015, ApJ, 805, 54
Connelley, M.S., & Reipurth, B. 2018, ApJ, 861, 145
Contreras Peña, C., Naylor, T., & Morrell, S. 2019, MNRAS, 486,
4590
Fischer, W.J., Megeath, S.T., Furlan, E., et al. 2017, ApJ, 840, 69
Fischer, W.J., Megeath, S.T., Tobin, J.J., et al. 2012, ApJ, 756, 99
Fischer, W.J., Safron, E., & Megeath, S.T. 2019, ApJ, 872, 183
Frimann, S., Jørgensen, J.K., Dunham, M.M., et al. 2017, A&A,
602, A120
Furlan, E., Fischer, W.J., Ali, B., et al. 2016, ApJS, 224, 5Hartmann, L., Herczeg, G., & Calvet, N. 2016, ARA&A, 54, 135
Hartmann, L., & Kenyon, S.J. 1996, ARA&A, 34, 207
Herbig, G.H. 1977, ApJ, 217, 693
Hsieh, T.-H., Murillo, N.M., Belloche, A., et al. 2019, ApJ, in press
Johnstone, D., & Bally, J. 1999, ApJ, 510, L49
Kratter, K., & Lodato, G. 2016, ARA&A, 54, 271
Megeath, S.T., Gutermuth, R., Muzerolle, J., et al. 2012, AJ, 144,
192
Offner, S.S.R., & McKee, C.F. 2011, ApJ, 736, 53
Pickering E.C. 1890, Ann. Harvard College Obs., 18, 113
Poteet, C.A., Megeath, S.T., Watson, D.M., et al. 2011, ApJ, 733,
L32
Reipurth, B., & Aspin, C. 2004, ApJ, 606, L119
Reipurth, B., & Aspin, C. 2010, in Evolution of Cosmic Objects
through their Physical Activity, 19
Reipurth, B., Aspin, C., & Herbig, G.H. 2012, ApJ, 748, L5
Safron, E.J., Fischer, W.J., Megeath, S.T., et al. 2015, ApJ, 800, L5
Scholz, A., Froebrich, D., & Wood, K. 2013, MNRAS, 430, 2910
Strom, K.M., & Strom, S.E. 1993, ApJ, 412, L63
Visser, R., Bergin, E.A., & Jørgensen, J.K. 2015, A&A, 577, A102
Vorobyov, E.I., & Basu, S. 2015, ApJ, 805, 115
Zhu, Z., Hartmann, L., Nelson, R.P., & Gammie, C.F. 2012, ApJ,
746, 11010

Abstracts of recently accepted papers

Abstracts of recently accepted papers
１

Disk Kinematics and Stability in High-Mass Star Formation: Linking Simulations andObservations
Aida Ahmadi1 , Rolf Kuiper2,1 and Henrik Beuther1
1

Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany; 2 Institute of Astronomy andAstrophysics, University of Tuebingen, Auf der Morgenstelle 10, 72076, Tuebingen, Germany
E-mail contact: ahmadi at mpia.de
In the disk-mediated accretion scenario for the formation of the most massive stars, high densities and accretion
rates could induce gravitational instabilities in the disk, forcing it to fragment and produce companion objects. We
investigate the effects of inclination and spatial resolution on observable kinematics and stability of disks in high-massstar formation. We study a high-resolution 3D radiation-hydrodynamic simulation that leads to the fragmentation ofa massive disk. Using RADMC-3D we produce 1.3 mm continuum and CH3 CN line cubes at different inclinations.
The model is set to different distances and synthetic observations are created for ALMA at ∼80 mas resolution and
NOEMA at ∼0.3”. The synthetic ALMA observations resolve all fragments and their kinematics well. The synthetic
NOEMA observations at 800 pc with linear resolution of ∼300 au are able to resolve the fragments, while at 2000 pc
with linear resolution of ∼800 au only a single structure slightly elongated towards the brightest fragment is observed.
The position-velocity (PV) plots show the differential rotation of material best in the edge-on views. A discontinuity
is seen at a radius of ∼250 au, corresponding to the position of the centrifugal barrier. As the observations becomeless resolved, the inner high-velocity components of the disk become blended with the envelope and the PV plots
resemble rigid-body-like rotation. Protostellar mass estimates from PV plots of poorly resolved observations are
therefore overestimated. We fit the emission of CH3 CN lines and produce maps of gas temperature with values in
the range of 100–300 K. Studying the Toomre stability of the disks, we find low Q values below the critical value forstability against gravitational collapse at the positions of the fragments and in the arms connecting the fragments
for the resolved observations. For the poorly resolved observations we find low Q values in the outskirts of the disk.
Therefore, despite not resolving any of the fragments, we are able to predict that the disk is unstable and fragmenting.
This conclusion is true regardless of knowledge about the inclination of the disk. These synthetic observations reveal
the potential and limitations to study disks in high-mass star formation with current (mm) interferometers. While theextremely high spatial resolution of ALMA reveals extraordinary details, rotational structures and instabilities within
accretion disks can also be identified in poorly resolved observations.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1909.04051

2

Gas flow and accretion via spiral streamers and circumstellar disks in a young binary
protostar
Felipe O. Alves1 , Paola Caselli1 , Josep M. Girart2,3 , Dominique Segura-Cox1 , Gabriel A. P. Franco4 ,Anika Schmiedeke1 and Bo Zhao1
1

Max-Planck-Institut für extraterrestrische Physik, Garching, 85748, Germany; 2 Institut de Ciències de l'Espai, Consejo Superior de Investigaciones Cientı́ficas, Cerdanyola del Vallès, E-08193, Catalunya, Spain.; 3 Institut d'Estudis
Espacials de Catalunya, Barcelona, E-08034, Spain; 4 Departamento de Fı́sica, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, 30.123-970, Brazil.
11E-mail contact: falves at mpe.mpg.de
The majority of stars are part of gravitationally bound stellar systems, such as binaries. Observations of protobinary systems constrain the conditions that lead to stellar multiplicity and subsequent orbital evolution. We reporthigh−angular resolution observations of the circumbinary disk around [BHB2007] 11, a young binary protostar system.
The two protostars are embedded in circumstellar disks that have radii of 2 to 3 astronomical units and probably
contain a few Jupiter masses. These systems are surrounded by a complex structure of filaments connecting to thelarger circumbinary disk. We also observe accretion and radio jets associated with the protobinary system. The
accretion is preferentially onto the lower−mass protostar, consistent with theoretical predictions.
Accepted by Science
http://arxiv.org/pdf/1910.01141

3

A Radio Census of the Massive Stellar Cluster Westerlund 1
H. Andrews1 , D. Fenech2 , R.K. Prinja1 , J.S. Clark3 , and L. Hindson4
1

University College London, Gower St, Bloomsbury, London WC1E 6BT; 2 Cavendish Laboratory, JJ Thomson
Avenue, Cambridge CB3 0HE; 3 Open University, Walton Hall, Kents Hill, Milton Keynes MK7 6AA; 4 University of
Hertfordshire, Hatfield, Hertfordshire, AL10 9AB
E-mail contact: holly.andrews.16 at ucl.ac.uk
Context. Massive stars and their stellar winds are important for a number of feedback processes. The mass lost in thestellar wind can help determine the end-point of the star as a NS or a BH. However, the impact of mass-loss on the
post-Main Sequence evolutionary stage of massive stars is not well understood. Westerlund 1 is an ideal astrophysicallaboratory in which to study massive stars and their winds in great detail over a large range of different evolutionary
phases.
Aims. We aim to study the radio emission from Westerlund 1, in order to measure radio fluxes from the populationof massive stars, and determine mass-loss rates and spectral indices where possible.
Methods. Observations were carried out in 2015 and 2016 with the Australia telescope compact array (ATCA) at 5.5
and 9 GHz using multiple configurations, with maximum baselines ranging from 750 m to 6 km.
Results. 30 stars were detected in the radio from the fully concatenated dataset, 10 of which were WRs (predominantly
late type WN stars), 5 YHGs, 4 RSGs, 1 LBV star, the sgB[e] star W9, and several O and B supergiants. New source
detections in the radio were found for 5 WR stars, and 5 OB supergiants. These detections have led to evidence for 3
new OB supergiant binary candidates, inferred from derived spectral index limits.
Conclusions. Spectral indices and index limits were determined for massive stars in Westerlund 1. For cluster
members found to have partially optically thick emission, mass-loss rates were calculated. Under the approximation ofa thermally emitting stellar wind and a steady mass-loss rate, clumping ratios were then estimated for 8 WRs. Diffuse
radio emission was detected throughout the cluster. Detections of knots of radio emission with no known stellar
counterparts indicate the highly clumped structure of this intra-cluster medium, likely shaped by a dense cluster wind.
Accepted by A&A

http://arxiv.org/pdf/1909.04339

4

An Ideal Testbed for Planet-disk Interaction: Two Giant Protoplanets in ResonanceShaping the PDS 70 Protoplanetary Disk
Jaehan Bae1,2 , Zhaohuan Zhu3 , Clément Baruteau4 , Myriam Benisty5,6,7 , Cornelis P. Dullemond8,
Stefano Facchini9 , Andrea Isella10 , Miriam Keppler11 , Laura M. Pérez5 , and Richard Teague12,13
1

Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington,
DC 20015, USA; 2 NHFP Sagan Fellow; 3 Department of Physics and Astronomy, University of Nevada, Las Vegas,
4505 South Maryland Parkway, Las Vegas, NV 89154, USA; 4 IRAP, Université de Toulouse, CNRS, UPS, F-31400
Toulouse, France; 5 Departamento de Astronomı́a, Universidad de Chile, Camino El Observatorio 1515, Las Condes,
Santiago, Chile; 6 Unidad Mixta Internacional Franco-Chilena de Astronomı́a, CNRS, UMI 3386; 7 Univ. Grenoble
Alpes, CNRS, IPAG, 38000 Grenoble, France; 8 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2,69120 Heidelberg, Germany; 9 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany;

12

10

Department of Physics and Astronomy, Rice University, 6100 Main Street, MS-108, Houston, TX 77005, USA;Max Planck Institute for Astronomy, Königstuhl 17, 69117, Heidelberg, Germany; 12 Department of Astronomy,
University of Michigan, 311 West Hall, 1085 S. University Ave, Ann Arbor, MI 48109, USA; 13 Harvard-Smithsonian
Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
11E-mail contact: jbae at carnegiescience.edu
While numerical simulations have been playing a key role in the studies of planet-disk interaction, testing numericalresults against observations has been limited so far. With the two directly imaged protoplanets embedded in its
circumstellar disk, PDS 70 offers an ideal testbed for planet-disk interaction studies. Using two-dimensional hydrodynamic simulations we show that the observed features can be well explained with the two planets in formation,
providing strong evidence that previously proposed theories of planet-disk interaction are in action, including resonantmigration, particle trapping, size segregation, and filtration. Our simulations suggest that the two planets are likely
in 2:1 mean motion resonance and can remain dynamically stable over million-year timescales. The growth of theplanets at 10−8 –10−7 MJup yr−1 , rates comparable to the estimates from Hα observations, does not destabilize theresonant configuration. Large grains are filtered at the gap edge and only small, (sub-)µm grains can flow to thecircumplanetary disks and the inner circumstellar disk. With the sub-millimeter continuum ring observed outward of
the two directly imaged planets, PDS 70 provides the first observational evidence of particle filtration by gap-opening
planets. The observed sub-millimeter continuum emission at the vicinity of the planets can be reproduced when(sub-)µm grains survive over multiple circumplanetary disk gas viscous timescales and accumulate therein. One suchpossibility is if (sub-)µm grains grow in size and remain trapped in pressure bumps, similar to what we find happening
in circumstellar disks. We discuss potential implications to planet formation in the solar system and mature extrasolar
planetary systems.
Accepted by ApJL
http://arxiv.org/pdf/1909.09476

5

What is the physics behind the Larson mass-size relation?
J. Ballesteros-Paredes1 , C. Román-Zúñiga2, Q. Salomé1 , M. Zamora-Avilés3 and M.J. Jiménez-Donaire4
1

Instituto de Radioastronomı́a y Astrofı́sica, UNAM, campus Morelia. PO Box 3-72. 58090. Morelia, Michoacán,México; 2 Instituto de Astronomı́a, UNAM, campus Ensenada. Ensenada, Baja California. 22860. México; 3
CONACYT-Instituto Nacional de Astrofı́sica, Óptica y Electrónica, Luis E. Erro 1, 72840 Tonantzintla, Puebla,
Mı́exico; 4 Harvard-Smithsonian Center for Astrophysics, 60 GardenStreet, Cambridge, MA 02138, USA
E-mail contact: j.ballesteros at irya.unam.mx
Different studies have reported a power-law mass-size relation M ∝ Rq for ensembles of molecular clouds. In the caseof nearby clouds, the index of the power-law q is close to 2. However, for clouds spread all over the Galaxy, indexes
larger than 2 are reported. We show that indexes larger than 2 could be the result of line-of-sight superposition ofemission that does not belong to the cloud itself. We found that a random factor of gas contamination, between
0.001% and 10% of the line-of-sight, allows to reproduce the mass-size relation with q ∼ 2.2–2.3 observed in Galactic
CO surveys. Furthermore, for dense cores within a single cloud, or molecular clouds within a single galaxy, we argue
that, even in these cases, there is observational and theoretical evidence that some degree of superposition may beoccurring. However, additional effects may be present in each case, and are briefly discussed. We also argue thatdefining the fractal dimension of clouds via the mass-size relation is not adequate, since the mass is not necessarily
a proxy to the area, and the size reported in M –R relations is typically obtained from the square root of the area,rather than from an estimation of the size independent from the area. Finally, we argue that the statistical analysis
of finding clouds satisfying the Larson’s relations does not mean that each individual cloud is in virial equilibrium.
Accepted by MNRAS
http://arxiv.org/pdf/1909.03175

6

Influence of Wolf–Rayet stars on surrounding star-forming molecular clouds
T. Baug1 , Richard de Grijs2,3,4 , L. K. Dewangan5 , Gregory J. Herczeg1 , D. K. Ojha6 , Ke Wang1 , Licai
Deng7 and B. C. Bhatt8

13

1Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, People’s Republic of China;
Department of Physics and Astronomy, Macquarie University, Balaclava Road, Sydney, NSW 2109, Australia; 3Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Balaclava Road, Sydney,
NSW 2109, Australia; 4 International Space Science Institute–Beijing, 1 Nanertiao, Zhongguancun, Hai Dian District,
Beijing 100190, People’s Republic of China; 5 Physical Research Laboratory, Navrangpura, Ahmedabad 380 009, India;
6
Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai
400 005, India; 7 Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academyof Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, People’s Republic of China; 8 Indian Institute of
Astrophysics, II Block, Koramangala, Bangalore 560 034, India
2

E-mail contact: tapas.polo at gmail.com
We investigate the influence of Wolf–Rayet (W–R) stars on their surrounding star-forming molecular clouds. We study
five regions containing W–R stars in the inner Galactic plane (l ∼[14◦ –52◦]), using multi-wavelength data from nearinfrared to radio wavelengths. Analysis of 13 CO line data reveals that these W–R stars have developed gas-deficient
cavities in addition to molecular shells with expansion velocities of a few km s−1 . The pressure owing to stellar
winds primarily drives these expanding shells and sweeps up the surrounding matter to distances of a few pc. The
column densities of shells are enhanced by a minimum of 14% for one region to a maximum of 88% for another region
with respect to the column densities within their central cavities. No active star formation — including molecularcondensations, protostars, or ionized gas — is found inside the cavities, whereas such features are observed around themolecular shells. Although the expansion of ionized gas is considered an effective mechanism to trigger star formation,
the dynamical ages of the H ii regions in our sample are generally not sufficiently long to do so efficiently. Overall, ourresults hint at the possible importance of negative W–R wind-driven feedback on the gas-deficient cavities, where starformation is quenched as a consequence. In addition, the presence of active star formation around the molecular shells
indicates that W–R stars may also assist in accumulating molecular gas, and that they could initiate star formation
around those shells.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1909.01996

7

A Search for Spatially Resolved Infrared Ro-Vibrational Molecular Hydrogen Emission
from the Disks of Young Stars
Tracy L. Beck1 and Jeﬀrey S. Bary2
1

Space Telescope Science Institute; 2 Colgate University

E-mail contact: tbeck at stsci.edu
We present results from a survey searching for spatially resolved near-infrared line emission from molecular hydrogengas in the circumstellar environments of nine young stars: AA Tau, AB Aur, DoAr 21, GG Tau, GM Aur, LkCa 15,
LkHα 264, UY Aur, and V773 Tau. Prior high-resolution spectra of these stars showed the presence of ro-vibrational
H2 line emission at 2.12µm with characteristics more typical of gas located in proto-planetary disks rather thanoutflows. In this study, we spatially resolve the H2 emission in the eight stars where it is detected. LkCa 15 is the only
target that exhibits no appreciable H2 despite a prior detection. We find an anti-correlation between H2 and X-ray
luminosities, likely indicating that the X-ray ionization process is not the dominant H2 excitation mechanism in thesesystems. AA Tau, UY Aur, and V773 Tau show discrete knots of H2 , as typically associated with shocks in outflowinggas. UY Aur and V773 Tau exhibit spatially resolved velocity structures, while the other systems have spectrally
unresolved emission consistent with systemic velocities. V773 Tau exhibits a complex line morphology indicating thepresence of multiple excitation mechanisms, including red and blue-shifted bipolar knots of shock-excited outflowinggas. AB Aur, GM Aur, and LkHα 264 have centralized, yet spatially resolved H2 emission consistent with a disk origin.
The H2 images of AB Aur reveal spiral structures within the disk, matching those observed in ALMA CO maps. Thissurvey reveals new insights into the structure and excitation of warm gas in the circumstellar environments of theseyoung stars.
Accepted by ApJ
https://arxiv.org/pdf/1909.04730

14

8

ALMA resolves the hourglass magnetic field in G31.41+0.31
M. T. Beltrán1 , M. Padovani1 , J. M. Girart2,3 , D. Galli1 , R. Cesaroni1 , R. Paladino4 , G. Anglada5 , R.
Estalella6 , M. Osorio5 , R. Rao7 , Á. Sánchez-Monge8 , Q. Zhang91

INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 2 Institut de Ciències de l’Espai(ICE, CSIC), Can Magrans s/n, E-08193 Cerdanyola del Vallès, Catalonia, Spain; 3 Institut d’Estudis Espacials dede Catalunya (IEEC), E-08034 Barcelona, Catalonia, Spain; 4 INAF-Istituto di Radioastronomia, via P. Gobetti
101, I-40129 Bologna, Italy; 5 Instituto de Astrofı́sica de Andalucı́a, CSIC, Glorieta de la Astronomı́a, s/n, E-18008,
Granada, Spain; 6 Departament de Fı́sica Quàntica i Astrofı́sica, Institut de Ciències del Cosmos, Universitat deBarcelona, IEEC-UB, Martı́ i Franquès 1, E-08028 Barcelona, Spain; 7 Institute of Astronomy and Astrophysics,
Academia Sinica 645 North Aohoku Place, Hilo, Hawaii 96720, USA; 8 I. Physikalisches Institut, Universität zu Köln,
Zülpicher Str. 77, D-50937 Köln, Germany; 9 Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street,
Cambridge, MA 02138, USA
E-mail contact: mbeltran at arcetri.astro.it
Context. Submillimeter Array (SMA) 870 µm polarization observations of the hot molecular core G31.41+0.31 revealed
one of the clearest examples up to date of an hourglass-shaped magnetic field morphology in a high-mass star-forming
region.
Aims. To better establish the role that the magnetic field plays in the collapse of G31.41+0.31, we carried out Atacama
Large Millimeter/submillimeter Array (ALMA) observations of the polarized dust continuum emission at 1.3 mm withan angular resolution four times higher than that of the previous (sub)millimeter observations to achieve an unprecedented image of the magnetic field morphology.
Methods. We used ALMA to perform full polarization observations at 233 GHz (Band 6). The resulting synthesized
beam is 0.28” × 0.20” which, at the distance of the source, corresponds to a spatial resolution of ∼875 au.
Results. The observations resolve the structure of the magnetic field in G31.41+0.31 and allow us to study the fieldin detail. The polarized emission in the Main core of G31.41+0.41 is successfully fit with a semi-analytical magnetostatic model of a toroid supported by magnetic fields. The best fit model suggests that the magnetic field is well
represented by a poloidal field with a possible contribution of a toroidal component of ∼10% of the poloidal component, oriented southeast to northwest at ∼ −44◦ and with an inclination of ∼ −45◦ . The magnetic field is oriented
perpendicular to the northeast to southwest velocity gradient detected in this core on scales from 103 –104 au. This
supports the hypothesis that the velocity gradient is due to rotation of the core and suggests that such a rotation has
little effect on the magnetic field. The strength of the magnetic field estimated in the central region of the core with
the Davis-Chandrasekhar-Fermi method is ∼8–13 mG and implies that the mass-to-flux ratio in this region is slightly
supercritical (λ=1.4–2.2).
Conclusions. The magnetic field in G31.41+0.31 maintains an hourglass-shaped morphology down to scales of<1000 au. Despite the magnetic field being important in G31.41+0.31, it is not enough to prevent fragmentationand collapse of the core, as demonstrated by the presence of at least four sources embedded in the center of the core.
Accepted by A&A
https://www.aanda.org/articles/aa/pdf/2019/10/aa35701-19.pdf

9Kinematics around the B335 protostar down to au scales
Per Bjerkeli1 , Jon P. Ramsey2,4 , Daniel Harsono3 , Hannah Calcutt1 , Lars E. Kristensen4 , Matthijs H.
D. van der Wiel5, Jes K. Jørgensen4 , Sébastien Muller1 and Magnus V. Persson1
1

Department of Space, Earth, and Environment, Chalmers University of Technology, Onsala Space Observatory,
439 92 Onsala, Sweden; 2 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 3
Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands; 4 Niels Bohr Instituteand Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 57, DK-1350 Copenhagen K,
Denmark; 5 ASTRON, the Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo,
The Netherlands
E-mail contact: per.bjerkeli at chalmers.se
The relationship between outflow launching and the formation of accretion disks around young stellar objects isstill not entirely understood, which is why spectrally and spatially resolved observations are needed. Recently, the15

Atacama Large Millimetre/sub-millimetre Array (ALMA) carried out long-baseline observations towards a handfulof young sources, revealing connections between outflows and the inner regions of disks. Here we aim to determine
the small-scale kinematical and morphological properties of the outflow from the isolated protostar B335 for which no
Keplerian disk has, so far, been observed on scales down to 10 au. We used ALMA in its longest-baseline configuration
to observe emission from CO isotopologues, SiO, SO2 , and CH3 OH. The proximity of B335 provides a resolution of∼3 au (0.03′′ ). We also combined our long-baseline data with archival observations to produce a high-fidelity image
covering scales up to 700 au (7′′ ). 12 CO has an X-shaped morphology with arms ∼50 au in width that we associatewith the walls of an outflow cavity, similar to what is observed on larger scales. Long-baseline continuum emission is
confined to <7 au from the protostar, while short-baseline continuum emission follows the 12 CO outflow and cavity
walls. Methanol is detected within ∼30 au of the protostar. SiO is also detected in the vicinity of the protostar, but
extended along the outflow. The 12 CO outflow does not show any clear signs of rotation at distances >∼30 au fromthe protostar. SiO traces the protostellar jet on small scales, but without obvious rotation. CH3 OH and SO2 trace aregion <16 au in diameter, centred on the continuum peak, which is clearly rotating. Using episodic, high-velocity,
12
CO features, we estimate the launching radius of the outflow to be <0.1 au and dynamical timescales of the orderof a few years.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1909.05178

10

Probing planet formation and disk substructures in the inner disk of Herbig Ae stars
with CO rovibrational emission
Arthur D. Bosman1 , Andrea Banzatti2,3 , Simon Bruderer4 , Alexander G.G.M. Tielens1 , Geoﬀrey A.
Blake5 , and Ewine F. van Dishoeck1,4
1

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 Department of Physics,
Texas State University, 749 N Comanche Street, San Marcos, TX 78666, USA; 3 Department of Planetary Sciences,
University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, USA; 4 Max-Planck-Institut für Extraterrestrische Physik, Gießenbachstrasse 1, 85748 Garching, Germany; 5 Division of Geological & Planetary Sciences,
California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125
E-mail contact: bosman at strw.leidenuniv.nl
CO rovibrational lines are efficient probes of warm molecular gas and can give unique insights into the inner 10 AU of
proto-planetary disks. Recent studies have found a relation between the ratio of lines originating from the second andfirst vibrationally excited state, denoted as ν2/ν1, and the emitting radius of CO. In disks around Herbig Ae stars thevibrational excitation is low when CO lines come from close to the star, and high when lines only probe gas at large
radii (more than 5 AU). We aim to find explanations for the observed trends between CO vibrational ratio, emitting
radii, and NIR excess, and identify their implications in terms of the physical and chemical structure of inner disks
around Herbig stars. Slab models and full disk thermo chemical models are calculated. Simulated observations fromthe models are directly compared to the data. Broad CO lines with low vibrational ratios are best explained by awarm (400–1300 K) inner disk surface with gas-to-dust ratios below 1000; no CO is detected within/at the inner dust
rim, due to dissociation at high temperatures. In contrast, explaining the narrow lines with high vibrational ratios
requires an inner cavity of a least 5 AU in both dust and gas, followed by a cool (100–300 K) molecular gas reservoir
with gas-to-dust ratios greater than 10000 at the cavity wall. In all cases the CO gas must be close to thermalization
with the dust. The high gas-to-dust ratios needed to explain high ν2/ν1 in narrow CO lines for a subset of group I
disks can naturally be interpreted as due to the dust traps that have been proposed to explain millimeter dust cavities.
The broad lines seen in most group II objects indicate a very flat disk in addition to inner disk substructures within
10 AU that can be related to the substructures recently observed with ALMA.
Accepted by A&A
http://arxiv.org/pdf/1909.02031

11

Signatures of an eccentric disc cavity: Dust and gas in IRS 48
Josh Calcino1 , Daniel J. Price2 , Christophe Pinte2,3 , Nienke van der Marel 4 , Enrico Ragusa5 , Giovanni
Dipierro5 , Nicolás Cuello6,7, Valentin Christiaens2
16

1School of Mathematics and Physics, The University of Queensland, QLD 4072, Australia; 2 Monash Centre for Astrophysics (MoCA) and School of Physics and Astronomy, Monash University, Clayton Vic 3800, Australia; 3 Univ.
Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 4 Herzberg Astronomy & Astrophysics Programs, National
Research Council of Canada, 5071 West Saanich Road, Victoria BC V9E 2E7, Canada; 5 Department of Physics
and Astronomy, University of Leicester, Leicester, United Kingdom; 6 Instituto de Astrofı́sica, Pontificia Universidad
Católica de Chile, Santiago, Chile; 7 Núcleo Milenio de Formación Planetaria (NPF), Chile
E-mail contact: j.calcino at uq.edu.au
We test the hypothesis that the disc cavity in the ‘transition disc’ Oph IRS 48 is carved by an unseen binary companion.
We use 3D dust-gas smoothed-particle hydrodynamics simulations to demonstrate that marginally coupled dust grains
concentrate in the gas over-density that forms in the cavity around a low binary mass ratio binary. This produceshigh contrast ratio dust asymmetries at the cavity edge similar to those observed in the disc around IRS 48 and othertransition discs. This structure was previously assumed to be a vortex. However, we show that the observed velocity
map of IRS 48 displays a peculiar asymmetry that is not predicted by the vortex hypothesis. We show the unusual
kinematics are naturally explained by the non-Keplerian flow of gas in an eccentric circumbinary cavity. We further
show that perturbations observed in the isovelocity curves of IRS 48 may be explained as the product of the dynamicalinteraction between the companion and the disc. The presence of a ∼0.4 M⊙ companion at a ∼10 au separation canqualitatively explain these observations. High spatial resolution line and continuum imaging should be able to confirm
this hypothesis.
Accepted by MNRAS
http://arxiv.org/pdf/1910.00161

12

The ALMA-PILS survey: propyne (CH3CCH) in IRAS 16293−2422
H. Calcutt1 , E. R. Willis2, J. K. Jørgensen3 , P. Bjerkeli1 , N. F. W. Ligterink4 , A. Coutens5 , H. S. P.
Müller6, R. T. Garrod2 , S. F. Wampﬂer4 and M. N. Drozdovskaya4
1

Department of Space, Earth and Environment, Chalmers University of Technology, 41296, Gothenburg, Sweden;
Departments of Chemistry and Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 3 Niels Bohr
Institute, University of Copenhagen, Øster Voldgade 5−7, DK-1350 Copenhagen K., Denmark; 4 Center for Space andHabitability, University of Bern, Gesellschaftsstrasse 6, CH-3012 Bern, Switzerland; 5 Laboratoire d’Astrophysiquede Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France; 6 I. Physikalisches
Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
2

E-mail contact: hannah.calcutt at chalmers.se
Context. Propyne (CH3 CCH), also known as methyl acetylene, has been detected in a variety of environments, from
Galactic star-forming regions to extragalactic sources. Such molecules are excellent tracers of the physical conditions
in star-forming regions, allowing the temperature and density conditions surrounding a forming star to be determined.
Aims. This study explores the emission of CH3 CCH in the low-mass protostellar binary, IRAS 16293−2422, examining
the spatial scales traced by this molecule, as well as its formation and destruction pathways.
Methods. Atacama Large Millimeter/submillimeter Array (ALMA) observations from the Protostellar InterferometricLine Survey (PILS) are used to determine the abundances and excitation temperatures of CH3 CCH towards bothprotostars. This data allows us to explore spatial scales from 70 to 2400 au. This data is also compared with thethree-phase chemical kinetics model MAGICKAL, to explore the chemical reactions of this molecule.
Results. CH3 CCH is detected towards both IRAS 16293A and IRAS 16293B and is found to trace the hot corino
component around each source in the PILS dataset. Eighteen transitions above 3σ are detected, enabling robust
excitation temperatures and column densities to be determined in each source. In IRAS 16293A, an excitation
temperature of 90 K and a column density of 7.8×1015 cm−2 best fits the spectra. In IRAS 16293B, an excitation
temperature of 100 K and 6.8×1015 cm−2 best fits the spectra. The chemical modelling finds that in order toreproduce the observed abundances, both gas-phase and grain-surface reactions are needed. The gas-phase reactions
are particularly sensitive to the temperature at which CH4 desorbs from the grains.
Conclusions. CH3 CCH is a molecule whose brightness and abundance in many different regions can be utilised toprovide a benchmark of molecular variation with the physical properties of star-forming regions. It is essential when17

making such comparisons, that the abundances are determined with a good understanding of the spatial scale of theemitting region, to ensure that accurate abundances are derived.
Accepted by A&A
https://arxiv.org/pdf/1909.13329

13

The mass of dusty clumps with temperature and density structure
Riccardo Cesaroni1
1

INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy

E-mail contact: cesa at arcetri.inaf.it
We consider a dusty clump in the two cases of spherical and cylindrical symmetry to investigate the effect of temperature and density gradients on the observed flux density. Conversely, we evaluate how the presence of such gradientsaffects the calculation of the clump mass from the observed flux. We provide the reader with approximate expressions
relating flux density and mass in the optically thick and thin limits, in the Rayleigh-Jeans regime, and discuss thereliability of these expressions by comparing them to the outcome of a numerical code. Finally, we present an application of our calculations to three examples taken from the literature, which shows how the correction introduced after
taking into account temperature and density gradients may affect our conclusions on the stability of the clumps.
Accepted by Astronomy and Astrophysics
http://arxiv.org/pdf/1909.07259

14

Dust accretion in binary systems: implications for planets and transition discs
Yayaati Chachan1,2,3 , Richard A. Booth2 , Amaury H. M. J. Triaud4 and Cathie Clarke2
1

Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA; 2
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 3 St John’s College,
University of Cambridge, Cambridge, CB2 1TP, UK; 4 School of Physics and Astronomy, University of Birmingham,
Edgbaston, Birmingham B15 2TT, UK
E-mail contact: ychachan at caltech.edu

The presence of planets in binary systems poses interesting problems for planet formation theories, both in cases
where planets must have formed in very compact discs around the individual stars and where they are located near
the edge of the stable circumbinary region, where in situ formation is challenging. Dust dynamics is expected toplay an important role in such systems, since dust trapping at the inner edge of circumbinary discs could aid in situ
formation, but would simultaneously starve the circumstellar discs of the solid material needed to form planets. Here
we investigate the dynamics of dust in binary systems using Smooth Particle Hydrodynamics. We find that all our
simulations tend towards dust trapping in the circumbinary disc, but the timescale on which trapping begins depends
on binary mass ratio (q) and eccentricity as well as the angular momentum of the infalling material. For q >∼ 0.1, wefind that dust can initially accrete onto the circumstellar discs, but as the circumbinary cavity grows in radius, dust
eventually becomes trapped in the circumbinary disc. For q = 0.01, we find that increasing the binary eccentricity
increases the time required for dust trapping to begin. However, even this longer timescale is likely to be shorter thanthe planet formation timescale in the inner disc and is insufficient to explain the observed pre-transitional discs. This
indicates that increase in companion eccentricity alone is not enough to allow significant transfer of solids from theouter to the inner disc.
Accepted by MNRAS
https://arxiv.org/pdf/1908.11377

15

VLA cm-wave survey of young stellar objects in the Oph A cluster: constraining extreme
UV- and X-ray-driven disk photo-evaporation – A pathfinder for Square Kilometre
Array studies
A. Coutens1 , H. B. Liu2 , I. Jiménez-Serra3 , T. L. Bourke4 , J. Forbrich5 , M. Hoare6 , L. Loinard7,8 ,18

L. Testi2,9 , M. Audard10,11 , P. Caselli12 , A. Chacón-Tanarro13 , C. Codella9,14 , J. Di Francesco15,16 ,F. Fontani9 , M. Hogerheijde17,18, A. Johansen19 , D. Johnstone15,16 , S. Maddison20 , O. Panić6 , L. M.
Pérez21 , L. Podio9 , A. Punanova22 , J. M. C. Rawlings23 , D. Semenov24,25 , M. Tazzari26 , J. J. Tobin27 ,M. H. D. van der Wiel28 , H. J. van Langevelde29,16 , W. Vlemmings30, C. Walsh6 and D. Wilner31
1

LAB, France; 2 ESO, Germany; 3 QMUL, UK; 4 SKA, UK; 5 University of Hertfordshire, UK; 6 University of Leeds,
UK; 7 IRyA, UNAM, México; 8 IA, UNAM, México; 9 INAF, Italy; 10 University of Geneva, Switzerland; 11 Universityof Geneva, Switzerland; 12 MPE, Germany; 13 OAN, Spain; 14 IPAG, France; 15 NRS-HAA, Canada; 16 Universityof Victoria, Canada; 17 Leiden University, The Netherlands; 18 API, The Netherlands; 19 Lund Observatory, Sweden;
20
CAS, Australia; 21 Universidad de Chile; 22 Ural Federal University, Russia; 23 UCL, UK; 24 Ludwig Maximilian
University, Germany; 25 MPIA, Germany; 26 University of Cambridge, UK; 27 NRAO, USA; 28 ASTRON, The
Netherlands; 29 JIVE, The Netherlands; 30 Chalmers University of Technology, Sweden; 31 CfA, USA
E-mail contact: acoutens at gmail.com
Observations of young stellar objects (YSOs) in centimeter bands can probe the continuum emission from growing dust
grains, ionized winds, and magnetospheric activity, which are intimately connected to the evolution of protoplanetarydisks and the formation of planets. We have carried out sensitive continuum observations toward the Ophiuchus A
star-forming region using the Karl G. Jansky Very Large Array (VLA) at 10 GHz over a field-of-view of 6′ with aspatial resolution of θmaj × θmin ∼ 0.4′′ × 0.2′′ . We achieved a 5 µJy beam−1 root-mean-square noise level at thecenter of our mosaic field of view. Among the eighteen sources we detected, sixteen are YSOs (three Class 0, five
Class I, six Class II, and two Class III) and two are extragalactic candidates. We find that thermal dust emission
generally contributes less that 30% of the emission at 10 GHz. The radio emission is dominated by other types ofemission such as gyro-synchrotron radiation from active magnetospheres, free-free emission from thermal jets, free-freeemission from the outflowing photo-evaporated disk material, and/or synchrotron emission from accelerated cosmicrays in jet or protostellar surface shocks. These different types of emission could not be clearly disentangled. Our
non-detections towards Class II/III disks suggest that extreme UV-driven photoevaporation is insufficient to explain
the disk dispersal, assuming that the contribution of UV photoevaporating stellar winds to radio flux does not evolvewith time. The sensitivity of our data cannot exclude photoevaporation due to X-ray photons as an efficient mechanism
for disk dispersal. Deeper surveys with the Square Kilometre Array will be able to provide strong constraints on disk
photoevaporation.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/1909.03515

16

Sub-stellar companions of the young weak-line TTauri Star DoAr21
Salvador Curiel1 , Gisela N. Ortiz-León2 , Amy J. Mioduszewski3, and Rosa M. Torres4
1

Instituto de Astronomı́a, Universidad Nacional Autónoma de México (UNAM), Apdo Postal 70-264, México, D.F.,
México; 2 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 3 National Radio
Astronomy Observatory, Domenici Science Operations Center, 1003 Lopezville Road, Socorro, NM 87801, USA; 4
Centro Universitario de Tonalá, Universidad de Guadalajara, Avenida Nuevo Periférico No. 555, Ejido San José
Tatepozco, C.P. 48525, Tonalá, Jalisco, México
E-mail contact: scuriel at astro.unam.mx
The compact, non-thermal emission in DoAr21 has been studied with the VLBA to investigate the possibility thatthe residuals of the astrometry fitting are due to the reflex motion induced by a possible companion. We find thatthe fitting of VLBA astrometric observations of DoAr21 improves significantly by adding the orbital motions of threecompanions. We obtain an improved distance to the source of 134.6±1.0 pc, and estimate that the central star,
DoAr21, has a mass of about 2.04±0.70 M⊙ . We suggest that DoAr21 represents a unique case where two sub-stellar
companions, DoAr21b and DoAr21c (mb ∼ 35.6 ± 27.2 Mjup and mc ∼ 44.0 ± 13.6 Mjup, respectively), have beenfound associated to a relatively low mass, pre-main sequence star. In addition, we find that this WTTau star is anastrometric double system, having a low-mass star companion, DoAr21B (mB ∼ 0.35 ± 0.12 M⊙ ), in a relatively
eccentric orbit. The orbit of this low-mass stellar companion is compact, while the Brown Dwarfs are located inexternal orbits. DoAr21c has the strongest astrometric signature in the periodogram, while DoAr21B has a weak but
significant signature. On the other hand, the astrometric signature of DoAr21b does not appear in the periodogram,19

however, this Brown Dwarf was directly detected in some of the VLBA observations. The estimated orbital periods of
DoAr21B, DoAr21b and DoAr21c are PB ∼ 92.92 ± 0.02, Pb ∼ 450.9 ± 3.8 and Pc ∼ 1013.5 ± 25.3 days, respectively.
Since the estimated age of this young star is about 0.4–0.8 Myrs, the detected Brown Dwarf companion is among theyoungest companions observed to date.
Accepted by ApJ
http://arxiv.org/pdf/1909.02870

17

A Search for Intermediate Separation Low Mass Binaries in the Orion Nebula Cluster
Matthew De Furio1 , Megan Reiter2 , Michael Meyer1 , Alexandra Greenbaum1 , Trent Dupuy3 and Adam
Kraus41

Department of Astronomy, University of Michigan, Ann Arbor, MI, USA; 2 UK Astronomy Technology Centre,
Edinburgh, United Kingdom; 3 Gemini Observatory, Hilo, HI, USA; 4 Department of Astronomy, University of Texas- Austin, Austin, TX, USA
E-mail contact: defurio at umich.edu
We present the results of a binary population study in the Orion Nebula Cluster (ONC) using archival Hubble Space
Telescope (HST) data obtained with the Advanced Camera for Surveys (ACS) in Johnson V filter (HST Proposal
10246, PI M. Robberto). Young clusters and associations hold clues to the origin and properties of multiple starsystems. Binaries with separations <∼ 100 AU are useful as tracers of the initial binary population since they are notas likely to be destroyed through dynamical interactions. Low mass, low stellar density star-forming regions such as
Taurus-Auriga, reveal an excess of multiples compared to the Galactic Field. Studying the binary population of higher
mass, higher stellar density star-forming regions like the ONC provides useful information concerning the origin of the
Galactic Field star population. In this survey, we characterize the previously unexplored (and incomplete) separation
parameter space of binaries in the ONC (15 - 160 AU) by fitting a double-PSF model built from empirical PSFs. We
identified 14 candidate binaries (11 new detections) and find that 8+4%
−2% of our observed sample are in binary systems,
complete over mass ratios and separations of 0.6 < q < 1.0 and 30 < a < 160 AU. This is consistent with the Galactic
Field M-dwarf population over the same parameter ranges, 6.5% ± 3%. Therefore, high mass star forming regions likethe ONC would not require further dynamical evolution for their binary population to resemble the Galactic Field, assome models have hypothesized for young clusters.
Accepted by The Astrophysical Journal

http://arxiv.org/pdf/1910.02092

18

Including Dust Coagulation in Hydrodynamic Models of Protoplanetary Disks: Dust
Evolution in the Vicinity of a Jupiter-mass Planet
Joanna Draz̧k̇owska1 , Shengtai Li2 , Til Birnstiel1 , Sebastian M. Stammler1 and Hui Li2
1

University Observatory, Ludwig Maximilian University of Munich, Scheinerstr. 1, 81673 Munich, Germany; 2Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
E-mail contact: joanna.drazkowska at lmu.de

Dust growth is often neglected when building models of protoplanetary disks due to its complexity and computational
expense. However, it does play a major role in shaping the evolution of protoplanetary dust and planet formation. In
this paper, we present a numerical model coupling 2-D hydrodynamic evolution of a protoplanetary disk, including
a Jupiter-mass planet, and dust coagulation. This is obtained by including multiple dust fluids in a single gridbased hydrodynamic simulation and solving the Smoluchowski equation for dust coagulation on top of solving for thehydrodynamic evolution. We find that fragmentation of dust aggregates trapped in a pressure bump outside of theplanetary gap leads to an enhancement in density of small grains. We compare the results obtained from the fullcoagulation treatment to the commonly used, fixed dust size approach and to previously applied, less computationallyintensive methods for including dust coagulation. We find that the full coagulation results cannot be reproduced using
the fixed-size treatment, but some can be mimicked using a relatively simple method for estimating the characteristic
dust size in every grid cell.

20

Accepted by ApJ
http://arxiv.org/pdf/1909.10526

19

Ingredients for Solar-like Systems:
protostar IRAS 16293-2422 B versus comet 67P/Churyumov–Gerasimenko
Maria N. Drozdovskaya1 , Ewine F. van Dishoeck2,3 , Martin Rubin4 , Jes K. Jørgensen5 and Kathrin
Altwegg4
1

Center for Space and Habitability, Universität Bern, Sidlerstrasse 5, 3012 Bern, Switzerland; 2 Leiden Observatory,
Leiden University, P.O. Box 9513, 2300 RA, Leiden, The Netherlands; 3 Max-Planck-Institut für Extraterrestrische
Physik, Giessenbachstrasse 1, 85748 Garching, Germany; 4 Physikalisches Institut, Universität Bern, Sidlerstrasse 5,3012 Bern, Switzerland; 5 Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen,Øster Voldgade 57, 1350 Copenhagen K., DenmarkE-mail contact: maria.drozdovskaya at csh.unibe.ch
Our modern day Solar System has 4.6 × 109 yrs of evolution behind it with just a few relics of its birth conditions

20

21

The chemical structure of young high-mass star-forming clumps: (I) Deuteration
S. Feng1,2 , P. Caselli3, K. Wang4 , Y. Lin5 , H. Beuther6 and O. Sipilä31National Astronomical Observatory of China, Datun Road 20, Chaoyang, Beijing, 100012, P. R. China; 2 National Astronomical Observatory of Japan, 2 Chome-21-1 Osawa, Mitaka-shi, Tokyo-to 181-8588, Japan; 3 Max-Planck-Institutfür Extraterrestrische Physik, Gießenbachstraße 1, D-85748, Garching bei München, Germany; 4 Kavli Institute for
Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, China; 5 Max
Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany; 6 Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg, Germany
E-mail contact: siyi.s.feng at

22

than the previous ALMA observations in this region. The high resolution allowed us to resolve highly filamentary CO
distributions with typical width of ∼0.1 pc (full width half maximum) and line mass of a few × 100 M⊙ pc−1 . The
filaments (more than ten in number) show outstanding hub-filament structure emanating from the Nebular center
toward the north. We identified for the first time two massive protostellar outflows of ∼104 yr dynamical age along
one of the most massive filaments. The observations also revealed several pillar-like CO features around the Nebula.
The H ii region and the pillars show complementary spatial distribution and the column density of the pillars is anorder of magnitude higher than that of the pillars in the Eagle nebula (M16) in the Galaxy, suggesting an early stageof pillar formation with an age younger than ∼105 yrs. We suggest that a cloud-cloud collision triggered the formationof the filaments and protostar within the last ∼2 Myr. It is possible that the collision is more recent since part of the
kpc-scale H i flows come from the tidal interaction resulting from the close encounter between the LMC and SMC∼200 Myr ago as suggested for R136 by Fukui et al. (2017).
Accepted by ApJ
https://arxiv.org/pdf/1811.00812

23

GIARPS High-resolution Observations of T Tauri stars (GHOsT).
I: Jet line emission
T. Giannini1 , B. Nisini1, S. Antoniucci1 , K.Biazzo1,2 , J. Alcalá3 , F. Bacciotti4 , D. Fedele4 , A. Frasca2 ,A. Harutyunyan5 , U. Munari6 , E. Rigliaco6 and F. Vitali1
1

INAF - Osservatorio Astronomico di Roma - Via Frascati 33, 00078, Monte Porzio Catone, Italy; 2 INAF - Osservatorio Astrofisico di Catania - Via S.Sofia 78, 95123, Catania, Italy; 3 INAF - Osservatorio Astronomico di Capodimonte- Salita Moiariello 16, 80131, Napoli, Italy; 4 INAF - Osservatorio Astrofisico di Arcetri - Largo Enrico Fermi 5, 50125,
Firenze, Italy; 5 Fundación Galileo Galilei INAF - Telescopio Nazionale Galileo, 38700, Breña Baja, Santa Cruz deTenerife, Spain; 6 INAF - Osservatorio Astronomico di Padova - Via dell’ Osservatorio 8, 36012, Asiago (VI), Italy
E-mail contact: teresa.giannini at inaf.it
The mechanism for jet formation in the disks of T Tauri stars remains poorly understood. Observational benchmarks
to launching models can be provided by tracing the physical properties of the kinematic components of the wind andjet in the inner 100 au of the disk surface. In the framework of the GHOsT (GIARPS High-resolution Observationsof T Tauri stars) project, we aim to perform a multi-line analysis of the velocity components of the gas in the jet
acceleration zone. We analyzed the GIARPS-TNG spectra of six objects in the Taurus-Auriga complex (RY Tau, DG
Tau, DL Tau, HN Tau, DO Tau, RW Aur A). Thanks to the combined high-spectral resolution (ℜ =5̇0 000−115 000)
and wide spectral coverage (∼ 400−2400 nm) we observed several O, S+, N, N+, Fe+, forbidden lines spanning a large
range of excitation and ionization conditions. In four objects (DG Tau, HN Tau, DO Tau, RW Aur A), temperature(Te ), electron and total density (ne , nH ), and fractional ionization (xe ) were derived as a function of velocity throughan excitation and ionization model. The abundance of gaseous iron, X(Fe), a probe of the dust content in the jet,
was derived in selected velocity channels. The physical parameters vary smoothly with velocity, suggesting a common
origin for the different kinematic components. In DG Tau and HN Tau, Te , xe , and X(Fe) increase with velocity(roughly from 6000 K, 0.05, 10%X(Fe)⊙ to 15 000 K, 0.6, 90%X(Fe)⊙ ). This trend is in agreement with disk–windmodels in which the jet is launched from regions of the disk at different radii. In DO Tau and RW Aur A, we infer xe << X(Fe) at all velocities. These findings are tentatively explained by the formation
0.1, nH ∼ 106−7 cm−3 , and X(Fe) ∼⊙of these jets from dense regions inside the inner, gaseous disk, or as a consequence of their high degree of collimation.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1909.10392

24

First detection of CS masers around a high-mass young stellar object, W51 e2eAdam Ginsburg1,2 and Ciriaco Goddi3,4
1

Department of Astronomy, University of Florida, PO Box 112055, USA; 2 Jansky fellow of the National Radio
Astronomy Observatory, Socorro, NM 87801 USA; 3 ALLEGRO/Leiden Observatory, Leiden University, PO Box
9513, 2300 RA Leiden, the Netherlands; 4 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO
Box 9010, 6500 GL Nijmegen, the Netherlands

23E-mail contact: adam.g.ginsburg at gmail.com
We report the discovery of maser emission in the two lowest rotational transitions of CS toward the high-mass
protostar W51 e2e with ALMA and the JVLA. The masers from CS J=1–0 and J=2–1 are neither spatially nor
spectrally coincident (they are separated by ∼150 AU and ∼30 km s−1 ), but both appear to come from the base of
the blueshifted outflow from this source. These CS masers join a growing list of rarely-detected maser transitions that
may trace a unique phase in the formation of high-mass protostars.
Accepted by AJ
http://arxiv.org/pdf/1909.11089

25

Gas velocity structure of the Orion A Integral Shaped Filament
Valentina González Lobos1 and Amelia M. Stutz1,2
1

Departmento de Astronomı́a, Facultad de Ciencias Fı́sicas y Matemáticas, Universidad de Concepción, Concepción,Chile; 2 Max-Planck-Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
E-mail contact: vgonzalezl at udec.cl
We present analysis of the gas kinematics of the Integral Shaped Filament (ISF) in Orion A using four different
molecular lines, 12 CO (1-0), 13 CO (1-0), NH3 (1,1), and N2 H+ (1-0). We describe our method to visualize the positionvelocity (PV) structure using the intensity-weighted line velocity centroid, which enables us to identify structures thatwere previously muddled or invisible. We observe a north to south velocity gradient in all tracers that terminates in avelocity peak near the center of the Orion Nebula Cluster (ONC), consistent with the previously reported ”wave-like”
properties of the ISF. We extract the velocity dispersion profiles and compare the non-thermal line widths to the gas
gravitational potential. We find supersonic Mach number profiles, yet the line widths are consistent with the gas
being deeply gravitationally bound. We report the presence of two 12 CO velocity components along the northernhalf of the ISF; if interpreted as circular rotation, the angular velocity is ω = 1.4 Myr−1 . On small scales we report
the detection of N2 H+ and NH3 ”twisting and turning” structures, with short associated timescales that give theimpression of a torsional wave. Neither the nature of these structures nor their relation to the larger scale wave ispresently understood.
Accepted by MNRAS
https://arxiv.org/pdf/1909.02589

26

Gaia 19ajj: A Young Star Brightening Due toEnhanced Accretion + Reduced Extinction
3
Lynne A. Hillenbrand1 , Bo Reipurth2 , Michael Connelley2 , Roc M. Cutri
att /R7020779(
u
tand
et
C)-1
Howard.66516(n)]TJ -302.
Isaacson4 -11.8801 T /R5.22707(l)-6.21462(e)-2.97988

and PV Cep, both of which similarly experience bright phases that recur on long timescales, with large-amplitude
photometric variations and emission-dominated spectra. We interpret the behavior of Gaia 19ajj as caused by cycles
of enhanced disk accretion accompanied by reduced extinction.
Accepted by Astronomical Journal (AJ)
http://arxiv.org/pdf/1910.05790

27

The New EXor Outburst of ESO-Hα 99 observed by Gaia ATLAS and TESS
Klaus W. Hodapp1 , Bo Reipurth1 , Bertil Pettersson2 , John Tonry3 , Larry Denneau3 , Patrick J. Vallely4 ,Benjamin J. Shappee3 , James D. Armstrong5 , Michael S. Connelley1 , C. S. Kochanek4 , MichaelFausnaugh6 , Rolf Chini7 , Martin Haas7 and Catalina Sobrino Figaredo7
1

University of Hawaii, Institute for Astronomy, 640 N. Aohoku Place, Hilo, HI 96720, USA; 2 Department of Physics
and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; 3 University of Hawaii, Institute for
Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; 4 Department of Astronomy, The Ohio State University,
140 West 18th Avenue, Columbus Ohio, 43210-1173, USA; 5 University of Hawaii, Institute for Astronomy, 34 Ohia Ku
St., Pukalani, HI 96768, USA; 6 MIT Kavli Institute for Space and Astrophysics Research, 77 Massachusetts Avenue,
37-241, Cambridge, MA 02139, USA; 7 Astronomisches Institut, Ruhr-Universität Bochum, Universitätsstraße 150,
44801 Bochum, Germany
E-mail contact: hodapp at hawaii.edu
We report photometry and spectroscopy of the outburst of the young stellar object ESO-Hα 99. The outburst was
first noticed in Gaia alert Gaia18dvc and later by ATLAS. We have established the outburst light curve with archival
ATLAS “Orange” filter photometry, Gaia data, new V -band photometry, and J, H, and Ks photometry from IRIS
and UKIRT. The brightness has fluctuated several times near the light curve maximum. The TESS satellite observed
ESO-Hα 99 with high cadence during one of these minor minima and found brightness fluctuations on timescales ofdays and hours. Imaging with UKIRT shows the outline of an outflow cavity, and we find one knot of H2 1 − 0 S(1)emission, now named MHO 1520, on the symmetry axis of this nebula, indicating recent collimated outflow activity
from ESO-Hα 99. Its pre-outburst SED shows a flat FIR spectrum, confirming its early evolutionary state and its
similarity to other deeply embedded objects in the broader EXor class. The pre-outburst luminosity is 34 L⊙ , amuch higher luminosity than typical EXors, indicating that ESO-Hα 99 may be a star of intermediate mass. Infraredand optical spectroscopy show a rich emission line spectrum, including HI lines, strong red CaII emission, as well as
infrared CO bandhead emission, all characteristic EXors in the broadest sense. Comparison of the present spectrawith an optical spectrum obtained in 1993, presumably in the quiescent state of the object, shows that during thepresent outburst the continuum component of the spectrum has increased notably more than the emission lines. The
Hα equivalent width during the outburst is down to one half of its 1993 level, and shock-excited emission lines aremuch less prominent.
Accepted by The Astronomical Journal

28

Chronology of Episodic Accretion in Protostars - an ALMA survey of the CO and H2Osnowlines
Tien-Hao Hsieh1 , Nadia M. Murillo2, Arnaud Belloche3 , Naomi Hirano1 , Catherine Walsh4 , Ewine F.
van Dishoeck2,5 , Jes K. Jørgensen6 and Shih-Ping Lai7
1

Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan; 2 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA, Leiden, the Netherlands; 3 Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69, 53121 Bonn, Germany; 4 School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT,
UK; 5 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße 1, 85748, Garching bei München, Germany; 6 Niels Bohr Institute, University of Copenhagen, Øster Voldgade 57, DK 1350 Copenhagen K., Denmark; 7Institute of Astronomy, National Tsing Hua University (NTHU), Hsinchu 30013, Taiwan
E-mail contact: shawinchone at gmail.com
Episodic accretion has been used to explain the wide range of protostellar luminosities, but its origin and influence on
the star forming process are not yet fully understood. We present an ALMA survey of N2 H+ (1 − 0) and HCO+ (3 − 2)25

toward 39 Class 0 and Class I sources in the Perseus molecular cloud. N2 H+ and HCO+ are destroyed via gas-phasereactions with CO and H2 O, respectively, thus tracing the CO and H2 O snowline locations. A snowline location ata much larger radius than that expected from the current luminosity suggests that an accretion burst has occurredin the past which has shifted the snowline outward. We identified 18/18 Class 0 and 9/10 Class I post-burst sourcesfrom N2 H+ , and 7/17 Class 0 and 1/8 Class I post-burst sources from HCO+ . The accretion luminosities during thepast bursts are found to be ∼ 10 − 100 L⊙ . This result can be interpreted as either evolution of burst frequency or
disk evolution. In the former case, assuming that refreeze-out timescales are 1000 yr for H2 O and 10,000 yr for CO,
we found that the intervals between bursts increases from 2400 yr in the Class 0 to 8000 yr in the Class I stage. Thisdecrease in the burst frequency may reflect that fragmentation is more likely to occur at an earlier evolutionary stage
when the young stellar object is more prone to instability.
Accepted by ApJ
https://arxiv.org/pdf/1909.02706

29

Understanding the origin of the magnetic field morphology in the wide-binary protostellar system BHR 71
Charles L. H. Hull1,2,11 Valentin J. M. Le Gouellec3,4 Josep M. Girart5,6 John J. Tobin7,8,9 Tyler L.
Bourke101

National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Córdova 3788, Office 61B, 7630422, Vitacura,Santiago, Chile; 2 Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 3 European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 4 AIM, CEA, CNRS, Université Paris-Saclay,
Université Paris Diderot, Sorbonne Paris Cité, F-91191 Gif-sur-Yvette; 5 Institut de Ciències de l’Espai (ICE-CSIC),
Campus UAB, Carrer de Can Magrans S/N, E-08193 Cerdanyola del Vallès, Catalonia; 6 Institut d’Estudis Espacials
de Catalunya, E-08030 Barcelona, Catalonia; 7 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22903, USA; 8 Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma,
440 W. Brooks Street, Norman, OK 73019, USA; 9 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300RA
Leiden, The Netherlands; 10 Square Kilometre Array Organization, Jodrell Bank Observatory, Lower Withington,
Macclesfield, Cheshire SK11 9DL, UK; 11 NAOJ Fellow

E-mail contact: chat.hull at nao.ac.jp
We present 1.3 mm ALMA observations of polarized dust emission toward the wide-binary protostellar system BHR
71 IRS1 and IRS2. IRS1 features what appears to be a natal, hourglass-shaped magnetic field. In contrast, IRS2
exhibits a magnetic field that has been affected by its bipolar outflow. Toward IRS2, the polarization is confined
mainly to the outflow cavity walls. Along the northern edge of the redshifted outflow cavity of IRS2, the polarized
emission is sandwiched between the outflow and a filament of cold, dense gas traced by N2 D+ , toward which no dust
polarization is detected. This suggests that the origin of the enhanced polarization in IRS2 is the irradiation of theoutflow cavity walls, which enables the alignment of dust grains with respect to the magnetic field—but only to adepth of ∼ 300 au, beyond which the dust is cold and unpolarized. However, in order to align grains deep enough inthe cavity walls, and to produce the high polarization fraction seen in IRS2, the aligning photons are likely to be in themid- to far-infrared range, which suggests a degree of grain growth beyond what is typically expected in very young,Class 0 sources. Finally, toward IRS1 we see a narrow, linear feature with a high (10–20%) polarization fraction anda well ordered magnetic field that is not associated with the bipolar outflow cavity. We speculate that this feature
may be a magnetized accretion streamer; however, this has yet to be confirmed by kinematic observations of dense-gas
tracers.
Accepted for publication in the Astrophysical Journal
http://arxiv.org/abs/1910.07290

30

On the origin of wide-orbit ALMA planets: giant protoplanets disrupted by their cores
J. Humphries1 & S. Nayakshin1
1

Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK

E-mail contact: rjh73 at le.ac.uk

26

Recent ALMA observations may indicate a surprising abundance of sub-Jovian planets on very wide orbits in protoplanetary discs that are only a few million years old. These planets are too young and distant to have been formed via
the Core Accretion (CA) scenario, and are much less massive than the gas clumps born in the classical Gravitational
Instability (GI) theory. It was recently suggested that such planets may form by the partial destruction of GI protoplanets: energy output due to the growth of a massive core may unbind all or most of the surrounding pre-collapse
protoplanet. Here we present the first 3D global disc simulations that simultaneously resolve grain dynamics in the discand within the protoplanet. We confirm that massive GI protoplanets may self-destruct at arbitrarily large separations
from the host star provided that solid cores of mass around 10–20 Earth masses are able to grow inside them during
their pre-collapse phase. In addition, we find that the heating force recently analysed by Masset and Velasco Romero(2017) perturbs these cores away from the centre of their gaseous protoplanets. This leads to very complicated dust
dynamics in the protoplanet centre, potentially resulting in the formation of multiple cores, planetary satellites, andother debris such as planetesimals within the same protoplanet. A unique prediction of this planet formation scenario
is the presence of sub-Jovian planets at wide orbits in Class 0/I protoplanetary discs.
Accepted by MNRAS
http://arxiv.org/pdf/1909.04395

31

New four-color optical photometry of the young stars V521 Cyg and FHO 27
Sunay Ibryamov1 and Evgeni Semkov2
1

Department of Physics and Astronomy, Faculty of Natural Sciences, University of Shumen, 115, Universitetska Str.,
9700 Shumen, Bulgaria; 2 Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of
Sciences, 72, Tsarigradsko Shose Blvd., 1784 Sofia, Bulgaria
E-mail contact: sibryamov at shu.bg
Results from new BVRI photometric observations of the pre-MS stars V521 Cyg and FHO 27 collected during theperiod from February 2015 to July 2019 are presented. These stars are embedded in the LDN 935, dubbed “The Gulf
of Mexico” in the active star-forming complex NGC 7000/IC 5070. Previous studies revealed them as variables withlarge amplitude brightness variations. Our new observations show that the stars continue to exhibit strong photometricvariability and fading events in the brightness. On the basis of the new data received and the data available in theliterature, we were able to specify the periodicity in the brightness variations of V521 Cyg. In the case of FHO 27, wefound a significant peak in its periodogram corresponding to 893 days period.
Accepted by Bulgarian Astronomical Journal
http://arxiv.org/pdf/1909.01458

32

ALMA observations of water deuteration: A physical diagnostic of the formation of
protostars
S. S. Jensen1 , J. K. Jørgensen1 , L. E. Kristensen1 , K. Furuya2 , A. Coutens3 , E. F. van Dishoeck4,5 , D.
Harsono4 and M. V. Persson6
1

Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 5-7, DK1350 Copenhagen K, Denmark; 2 Center for Computational Sciences, University of Tsukuba, Japan; 3 Laboratoired’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, alle Geoffroy Saint-Hilaire, 33615 Pessac, France; 4Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 5 Max–Planck Institute für
extraterrestrische Physik (MPE), Giessenbachstrasse, 85748 Garching, Germany; 6 Department of Space, Earth andEnvironment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
E-mail contact: sigurd.jensen at nbi.ku.dk
How water is delivered to planetary systems is a central question in astrochemistry. The deuterium fractionation ofwater can serve as a tracer for the chemical and physical evolution of water during star formation and can constrain
the origin of water in Solar System bodies.
The aim is to determine the HDO/H2 O ratio in the inner warm gas toward three low-mass Class 0 protostars selected
to be in isolated cores, i.e., not associated with any cloud complexes. Previous sources for which the HDO/H2 O

27

ratio have been established were all part of larger star-forming complexes. Determining the HDO/H2 O ratio toward
three isolated protostars allows comparison of the water chemistry in isolated and clustered regions to determine theinfluence of local cloud environment.
We present ALMA Band 6 observations of the HDO 31,2 –22,1 and 21,1 –21,2 transitions at 225.897 GHz and 241.562 GHz
along with the first ALMA Band 5 observations of the H18
2 O 31,3 –22,0 transition at 203.407 GHz. The high angularresolution observations (0.3′′ -1.3′′ ) allow the study of the inner warm envelope gas. Model-independent estimates for
the HDO/H2 O ratios are obtained and compared with previous determinations of the HDO/H2 O ratio in the warm gas
toward low-mass protostars. We successfully detect the targeted water transitions toward the three sources with S/N ¿5. We determine the HDO/H2 O ratio toward L483, B335 and BHR71–IRS1 to be (2.2 ± 0.4)×10−3, (1.7 ± 0.3)×10−3,
and (1.8 ± 0.4)×10−3, respectively, assuming Tex = 124 K. The degree of water deuteration of these isolated protostars
are a factor of 2–4 higher relative to Class 0 protostars that are members of known nearby clustered star-forming
regions.
The results indicate that the water deuterium fractionation is influenced by the local cloud environment. This effectcan be explained by variations in either collapse timescales or temperatures, which depends on local cloud dynamics
and could provide a new method to decipher the history of young stars.
Accepted by A&A
https://arxiv.org/pdf/1909.10533

33

A stellar relic filament in the Orion star forming region
Tereza Jerabkova1,2,3 , Henri M.J. Boﬃn1 , Giacomo Beccari1 , and Richard I. Anderson1,4
1

European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany; 2 Helmholtz
Institut für Strahlen und Kernphysik, Universität Bonn, Nussallee 14-16, 53115 Bonn, Germany; 3 AstronomicalInstitute, Charles University in Prague, V Holesovickach 2, CZ-180 00 Praha 8, Czech Republic; 4 Départementd’Astronomie, Université de Genève, 51 Ch des Maillettes, 1290 Sauverny, Switzerland
E-mail contact: tjerabkova at gmail.com
We report the discovery of the oldest stellar substructure in the Orion star forming region (OSFR), the Orion relicfilament. The relic filament is physically associated with the OSFR as demonstrated by Gaia DR2 photometry andastrometry, as well as targeted radial velocity follow-up observations of a bright sub-sample of proper-motion selectedcandidate members. Gaia DR2 parallaxes place the Orion relic filament in the more distant part of the OSFR, ≈430pc from the Sun. Given its age, velocity dispersion, spatial extent, and shape, it is not possible for the Orion relicfilament to have formed as a single stellar cluster, even taking into account residual gas expulsion. The relic filament isalso too young to be a tidal stream, since Galactic tides act on much longer time scales of order 100 Myr. It therefore
appears likely that the structure formed from a molecular cloud filament similar to Orion A in the OSFR and retained
its morphology despite decoupling from its natal gas. Hence, the Orion relic filament bears witness to the short-lived
evolutionary phase between gas removal and dispersion due to shears and tides, and provides crucial new insights into
how stars are formed in molecular clouds.
Accepted by MNRAS

http://arxiv.org/pdf/1909.04056

34

Exploring the conditions for forming cold gas giants through planetesimal accretion
Anders Johansen1 and Bertram Bitsch2
1

Lund Observatory; 2 Max Planck Institute for Astronomy

E-mail contact: anders at astro.lu.se
The formation of cold gas giants similar to Jupiter and Saturn in orbit and mass is a great challenge for planetesimaldriven core accretion models because the core growth rates far from the star are low. Here we model the growth andmigration of single protoplanets that accrete planetesimals and gas. We integrated the core growth rate using fits inthe literature to N -body simulations, which provide the efficiency of accreting the planetesimals that a protoplanet
migrates through. We take into account three constraints from the solar system and from protoplanetary discs: (1)28the masses of the terrestrial planets and the comet reservoirs in Neptune’s scattered disc and the Oort cloud areconsistent with a primordial planetesimal population of afew Earth masses per AU, (2) evidence from the asteroid
belt and the Kuiper belt indicates that the characteristic planetesimal diameter is 100 km, and (3) observationsof protoplanetary discs indicate that the dust is stirred by weak turbulence; this gas turbulence also excites theinclinations of planetesimals. Our nominal model built on these constraints results in maximum protoplanet masses of
0.1 Earth masses. Ignoring constraint (1) above, we show that even a planetesimal population of 1,000 Earth masses,
corresponding to 50 Earth masses per AU, fails to produce cold gas giants (although it successfully forms hot andwarm gas giants). We conclude that a massive planetesimal reservoir is in itself insufficient to produce cold gas giants.
The formation of cold gas giants by planetesimal accretion additionally requires that planetesimals are small and thatthe turbulent stirring is very weak, thereby violating all three above constraints.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/1909.10429

35

Origin of hydrogen fluoride emission in the Orion Bar: An excellent tracer for CO-dark
H2 gas clouds
Umit Kavak1,2 , F.F.S. van der Tak2,1 , A.G.G.M. Tielens3 and R.F. Shipman2,11

Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands;
SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands; 3 Leiden
Observatory, Leiden University, PO Box 9513, NL-2300RA, Leiden, the Netherlands
2E-mail contact: kavak at astro.rug.nl
The hydrogen fluoride (HF) molecule is seen in absorption in the interstellar medium (ISM) along many lines of sight.
Surprisingly, it is observed in emission toward the Orion Bar, which is an interface between the ionized region aroundthe Orion Trapezium stars and the Orion molecular cloud. We aim to understand the origin of HF emission in theOrion Bar by comparing its spatial distribution with other tracers. We examine three mechanisms to explain the HF
emission: thermal excitation, radiative dust pumping, and chemical pumping. We used a Herschel /HIFI strip map of
the HF J = 1 → 0 line, covering 0.5′ by 1.5′ that is oriented perpendicular to the Orion Bar. We used the RADEX
non-local thermodynamic equilibrium (non-LTE) code to construct the HF column density map. We use the Meudon
PDR code to explain the morphology of HF. The bulk of the HF emission at 10 km s−1 emerges from the CO-darkmolecular gas that separates the ionization front from the molecular gas that is deeper in the Orion Bar. The excitationof HF is caused mainly by collisions with H2 at a density of 105 cm−3 together with a small contribution of electrons
in the interclump gas of the Orion Bar. Infrared pumping and chemical pumping are not important. We conclude
that the HF J = 1 → 0 line traces CO-dark molecular gas. Similarly, bright photodissociation regions associated withmassive star formation may be responsible for the HF emission observed toward active galactic nuclei.
Accepted by Astronomy and Astrophysics (A&A) on September 23, 2019.
http://arxiv.org/pdf/1910.00707

36

Resolving Linear Polarization due to Emission and Extinction of Aligned Dust Grainson NGC1333 IRAS4A with JVLA and ALMA
Chia-Lin Ko1,2 , Hauyu Baobab Liu2,3 , Shih-Ping Lai1 , Tao-Chung Ching4,5 , Ramprasad Rao2 and Josep
Miquel Girart6,7
1

Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan; 2
Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan; 3 European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, 85748, Garching, Germany; 4 National Astronomical Observatories,
Chinese Academy of Sciences, Beijing 100012, People’s Republic of China; 5 CAS Key Laboratory of FAST, National
Astronomical Observatories, Chinese Academy of Sciences, People’s Republic of China; 6 Institut de Ciències de l’Espai(ICE, CSIC), Can Magrans, s/n, 08193, Cerdanyola del Vallès, Catalonia, Spain; 7 Institut d’Estudis Espacials deCatalunya (IEEC), 08034, Barcelona, Catalonia, Spain
E-mail contact: chialinko at gapp.nthu.edu.tw
We report high angular resolution observations of linearly polarized dust emission towards the Class 0 young stellar
29object (YSO) NGC1333 IRAS4A (hereafter, IRAS4A) using the Karl G. Jansky Very Large Array (JVLA) at K (11.5–
16.7 mm), Ka (8.1–10.3 mm), and Q bands (6.3–7.9 mm), and using the Atacama Large Millimeter Array (ALMA) at
Band 6 (1.2 mm) and Band 7 (0.85–0.89 mm). On 100-1000 AU scales, all of these observations consistently trace thehourglass shaped magnetic field topology as shown in the previous studies. In the innermost 100 AU region of IRAS4A1,
the polarization position angles (E-field) detected at 6.3–16.7 mm are consistent, however, are nearly 90 degrees offset
from those detected at 1.2 mm and 0.85–0.89 mm. Such a 90 degree offset may be explained by that the inner ∼100 AU
area is optically thick at wavelengths shorter than ∼1.5 mm, whereby the observations probe the absorption of aligned
dust against the weakly or unpolarized warm dust emission from the innermost region. This can also consistently
explain why the highest angular resolution ALMA images at Band 7 show that the polarization percentage increases
with dust brightness temperature in the inner ∼100 AU region of IRAS4A1. Following this interpretation and assumingthat the dust grains are aligned with the magnetic fields, the inferred magnetic field position angle based on the 90◦
rotated at 6.3–7.9 mm in the central peak of IRAS4A1 is ∼ −22◦ , which is approximately consistent with the outflow
direction ∼ −9◦ .
Accepted by ApJ
https://arxiv.org/pdf/1909.09628

37

Characterising the surface magnetic fields of T Tauri stars with high-resolution nearinfrared spectroscopy
A. Lavail1,2 , O. Kochukhov1 , and G.A.J. Hussain2
1

Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; 2 European
Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany
E-mail contact: alexis.lavail at physics.uu.se
We aim to characterise the surface magnetic fields of a sample of 8 T Tauri stars from high-resolution near-IR
spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetricstudies. Our goals are 1) to apply Zeeman broadening modelling to T Tauri stars with high-resolution data, 2) toexpand the sample of stars with measured surface magnetic field strengths, 3) to investigate possible rotational or
long-term magnetic variability by comparing spectral time series of given targets, and 4) to compare the magnetic
field modulus <B> tracing small-scale magnetic fields to those of large-scale magnetic fields derived by Stokes V
Zeeman Doppler Imaging. We modelled the Zeeman broadening of magnetically sensitive spectral lines in the near-IR
K-band from high-resolution spectra by using magnetic spectrum synthesis based on realistic model atmospheres andby using different descriptions of the surface magnetic field. We developped a Bayesian framework that selects thecomplexity of the magnetic field prescription based on the information contained in the data. We obtain individual
magnetic field measurements for each star in our sample using four different models. We find that the Bayesian Model
4 performs best in the range of magnetic fields measured on the sample (from 1.5 kG to 4.4 kG). We do not detecta strong rotational variation of <B> with a mean peak-to-peak variation of 0.3 kG. Our confidence intervals are of
the same order of magnitude, which suggests that the Zeeman broadening is produced by a small-scale magnetic field
homogeneously distributed over stellar surfaces. A comparison of our results with mean large-scale magnetic fieldmeasurements from Stokes V ZDI show different fractions of mean field strength being recovered, from 25–42% forrelatively simple poloidal axisymmetric field topologies to 2–11% for more complex fields.
Accepted by A&A
http://arxiv.org/pdf/1909.04965

38

Spiral Structures in an Embedded Protostellar Disk Driven by Envelope Accretion
Chin-Fei Lee1,2 , Zhi-Yun Li3 , & Neal J. Turner4
1

Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 2 Graduate Instituteof Astronomy and Astrophysics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan; 3Astronomy Department, University of Virginia, Charlottesville, VA 22904, USA 4 Jet Propulsion Laboratory, California
Institute of Technology, Pasadena, CA 91109, USA
E-mail contact: cflee at asiaa.sinica.edu.tw30

Hydrodynamical simulations show that a pair of spiral arms can form in the disk around a rapidly-growing young starand that the arms are crucial in transporting angular momentum as the disk accretes material from the surrounding
envelope. Here we report the detection of a pair of symmetric spiral structures in a protostellar disk, supporting theformation of spiral arms in the disk around a forming star. The HH 111 VLA 1 source is a young Class I source
embedded in a massive infalling protostellar envelope and is actively accreting, driving the prominent HH 111 jet.
Previous observations showed a ring of shock emission around the disk’s outer edge, indicating accretion of the envelopematerial onto the disk at a high rate. Now with ALMA observations of thermal emission from dust particles, we detecta pair of spiral arms extending from the inner region to the disk’s outer edge, similar to that seen in many simulations.
Additionally, the disk is massive, with Toomre’s Q parameter near unity in the outer parts where the spiral structures
are detected, supporting the notion that envelope accretion is driving the outer disk gravitationally unstable. In ourobservations, another source, HH 111 VLA 2, is spatially resolved for the first time, showing a disk-like structure witha diameter of ∼26 au and an orientation nearly orthogonal to that of the HH 111 VLA 1 disk.
Accepted by
http://arxiv.org/pdf/1909.02812

39

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

Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China;
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; 3 University of Chinese Academy of
Sciences, 19A Yuquanlu, Beijing 100049, China; 4 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences,
210008, Nanjing, China; 5 Department of Astronomy and Steward Observatory, University of Arizona, 933 N Cherry
Avenue., Tucson, AZ 85721, USA; 6 Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh, EH9
3HJ, UK; 7 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany; 8 Astronomy
Department, University of Science and Technology, Chinese Academy of Sciences, Hefei 210008, China; 9 School ofPhysics and Astronomy, Queen Mary University of London, Mile End Road, E1 4NS London, UK
2E-mail contact: shanghuo.li at gmail.com
We performed a survey in the J = 5 → 4 line toward a sample of 199 Galactic massive star-forming regions at different
evolutionary stages with the Submillimeter Telescope (SMT) 10 m and Caltech Submillimeter Observatory (CSO)
10.4 m telescopes. The sample consists of 44 infrared dark clouds (IRDCs), 86 protostellar candidates, and 69 young
H II regions. We detected J = 5 → 4 line emission in 102 sources, with a detection rate of 57%, 37%, and 65% for
IRDCs, protostellar candidates, and young H II regions, respectively. We find both broad line emission with full widths
at zero power (FWZP) > 20 km s−1 and narrow line emissions of SiO in objects at various evolutionary stages, likely
associated with high-velocity shocks and low-velocity shocks, respectively. The SiO luminosities do not show apparent
differences among various evolutionary stages in our sample. We find no correlation between the SiO abundance andthe luminosity-to-mass ratio, indicating that the SiO abundance does not vary significantly in regions at different
evolutionary stages of star formation.
Accepted by ApJ
https://arxiv.org/pdf/1905.08395

40

Formation of Massive Protostellar Clusters – Observations of Massive 70 µm Dark
Molecular Clouds
Shanghuo Li1,2,3 , Qizhou Zhang2 , Thushara Pilla4 , Ian W. Stephens2 , Junzhi Wang1,5 and Fei Li1,3
1

Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China;
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; 3 University of Chinese Academyof Sciences, 19A Yuquanlu, Beijing 100049, China; 4 Institute for Astrophysical Research, Boston University, 725
Commonwealth Ave, Boston, MA 02215, USA; 5 Key Laboratory of Radio Astronomy, Chinese Academy of Sciences,
210008, Nanjing, China
2E-mail contact: shanghuo.li at gmail.com

31

We present Submillimeter Array (SMA) observations of seven massive molecular clumps which are dark in the farinfrared for wavelengths up to 70 µm. Our 1.3 mm continuum images reveal 44 dense cores, with gas masses ranging
from 1.4 to 77.1 M⊙ . Twenty-nine dense cores have masses greater than 8 M⊙ and the other fifteen dense cores havemasses between 1.4 and 7.5 M⊙ . Assuming the core density follows a power-law in radius ρ ∝ r−b , the index b is foundto be between 0.6 and 2.1 with a mean value of 1.3. The virial analysis reveals that the dense cores are not in virial
equilibrium. CO outflow emission was detected toward 6 out of 7 molecular clumps and associated with 17 dense cores.
For five of these cores, CO emissions appear to have line-wings at velocities of greater than 30 km s−1 with respect
to the source systemic velocity, which indicates that most of the clumps harbor protostars and thus are not quiescentin star formation. The estimated outflow timescale increase with core mass, which likely indicates that massive cores
have longer accretion timescale than that of the less massive ones. The fragmentation analysis shows that the massof low-mass and massive cores are roughly consistent with thermal and turbulent Jeans masses, respectively.
Accepted by ApJ
https://arxiv.org/pdf/1909.08916

41

A Gaia view of the two OB associations Cygnus OB2 and Carina OB1: The signatureof their formation process
Beomdu Lim1,2,3 , Yaël Nazé2 , Eric Gosset2 , and Gregor Rauw2
1

School of Space Research, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104,
Republic of Korea; 2 Space sciences, Technologies and Astrophysics Research Institute, Université de Liège, Quartier
Agora, Allée du 6 Août 19c, Bât. B5c, 4000, Liège, Belgium; 3 Department of Astronomy and Space Science, Sejong
University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Republic of Korea
E-mail contact: blim at khu.ac.kr
OB associations are the prime star forming sites in galaxies. However the detailed formation process of such stellar
systems still remains a mystery. In this context, identifying the presence of substructures may help tracing thefootprints of their formation process. Here, we present a kinematic study of the two massive OB associations Cygnus
OB2 and Carina OB1 using the precise astrometry from the Gaia Data Release 2 and radial velocities. From theparallaxes of stars, these OB associations are confirmed to be genuine stellar systems. Both Cygnus OB2 and Carina
OB1 are composed of a few dense clusters and a halo which have different kinematic properties: the clusters occupy
regions of 5–8 parsecs in diameter and display small dispersions in proper motion, while the halos spread over tensof parsecs with a 2–3 times larger dispersions in proper motion. This is reminiscent of the so-called “line42

http://arxi/99809

model shows that 1) the characteristic mass of super-Earth is set by the pebble isolation mass. Super-Earth masses
increase linearly with the mass of its stellar host, corresponding to one Earth mass around a late M-dwarf star and
20 M⊕ around a solar-mass star. 2) The low-mass planets up to 20 M⊕ can form around stars with a wide range ofmetallicities, while massive gas giant planets are preferred to grow around metal-rich stars. 3) Super-Earth planetsthat are mainly composed of silicates, with relatively low water fractions can form from protoplanetary embryos at thewater ice line in weakly turbulent disks where outward migration is suppressed. However, if the embryos are formed
over a wide range of radial distances, the super-Earths would end up having a distinctive, bimodal composition inwater mass. Our model succeeds in quantitatively reproducing several important observed properties of exoplanetsand correlations with their stellar hosts.
Accepted by A&A
http://arxiv.org/pdf/1909.00759

43

Interstellar formamide (NH2 CHO): A key prebiotic precursor
Ana López-Sepulcre1,2 , Nadia Balucani3 , Cecilia Ceccarelli1 , Claudio Codella4,1, François Dulieu5 andPatrice Theulé6
1

Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France; 2 Institut de Radioastronomie Millimétrique (IRAM), 300
rue de la piscine, F-38406 Saint-Martin dHères, France; 3 Dipartimento di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, I-06123 Perugia, Italy; 4 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125,
Firenze, Italy; 5 Université de Cergy-Pontoise, Observatoire de Paris, PSL University, Sorbonne Université, CNRS,LERMA, F-95000, Cergy-Pontoise, France; 6 Aix-Marseille Université, PIIM UMR-CNRS 7345, 13397 Marseille,
FranceE-mail contact: lopez at iram.fr
Formamide (NH2 CHO) has been identified as a potential precursor of a wide variety of organic compounds essential
to life, and many biochemical studies propose it likely played a crucial role in the context of the origin of life on ourplanet. The detection of formamide in comets, which are believed to have –at least partially– inherited their current
chemical composition during the birth of the Solar System, raises the question whether a non-negligible amount offormamide may have been exogenously delivered onto a very young Earth about four billion years ago. A crucial partof the effort to answer this question involves searching for formamide in regions where stars and planets are forming
today in our Galaxy, as this can shed light on its formation, survival, and chemical re-processing along the different
evolutionary phases leading to a star and planetary system like our own. The present review primarily addresses
the chemistry of formamide in the interstellar medium, from the point of view of (i) astronomical observations, (ii)experiments, and (iii) theoretical calculations. While focusing on just one molecule, this review also more generally
reflects the importance of joining efforts across multiple scientific disciplines in order to make progress in the highlyinterdisciplinary science of astrochemistry.
Accepted by ACS Earth and Space Chemistry
http:///arxiv.org/pdf/1909.11770

44

A Census of Early Phase High-Mass Star Formation in the Central Molecular Zone
Xing Lu1 , Elisabeth A. C. Mills2, Adam Ginsburg3 , Daniel Walker4,1 , Ashley Barnes5 , Natalie Butterﬁeld6 ,Jonathan Henshaw7 , Cara Battersby8 , J. M. Diederik Kruijssen9 , Steven N. Longmore10 , Qizhou
Zhang11 , John Bally12 , Jens Kauﬀmann13 , Jürgen Ott3 , Matthew Rickert14,3 and Ke Wang15
1

National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan; 2 Physics Department,
Brandeis University, 415 South Street, Waltham, MA 02453, USA; 3 National Radio Astronomy Observatory, 1003
Lopezville Rd., Socorro, NM 87801, USA; 4 Joint ALMA Observatory, Alonso de Crdova 3107, Vitacura 763 0355,
Santiago, Chile; 5 Argelander-Institut für Astronomie, Universität Bonn, Auf dem Huügel 71, D-53121 Bonn, Germany;
6
Green Bank Observatory, 155 Observatory Rd, P.O. Box 2, Green Bank, WV 24944, USA; 7 Max-Planck-Institut für
Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 8 University of Connecticut, Department of Physics, 2152
Hillside Road, Storrs, CT 06269, USA; 9 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität
Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg, Germany; 10 Astrophysics Research Institute, Liverpool John

33

Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK; 11 Center for Astrophysics Harvard & Smithsonian,
60 Garden Street, Cambridge, MA 02138, USA; 12 Department of Astrophysical and Planetary Sciences, Universityof Colorado, 389 UCB, Boulder, CO 80309, USA; 13 Haystack Observatory, Massachusetts Institute of Technology,
Westford, MA 01886, USA; 14 CIERA and Department of Physics and Astronomy, Northwestern University, 2145
Sheridan Rd, Evanston, IL 60208-3112, USA; 15 Kavli Institute for Astronomy and Astrophysics, Peking University,
5 Yiheyuan Road, Haidian District, Beijing 100871, P. R. China
E-mail contact: xinglv.nju at gmail.com
We present new observations of C-band continuum emission and masers to assess high-mass (>8 M⊙ ) star formation
at early evolutionary phases in the inner 200 pc of the Central Molecular Zone (CMZ) of the Galaxy. The continuum
observation is complete to free-free emission from stars above 10–11 M⊙ in 91% of the covered area. We identify
104 compact sources in the continuum emission, among which five are confirmed ultracompact H II regions, 12 are
candidates of ultra-compact H II regions, and the remaining 87 sources are mostly massive stars in clusters, fieldstars, evolved stars, pulsars, extragalactic sources, or of unknown nature that is to be investigated. We detect class
II CH3 OH masers at 23 positions, among which six are new detections. We confirm six known H2 CO masers in two
high-mass star forming regions, and detect two new H2 CO masers toward the Sgr C cloud, making it the ninth region
in the Galaxy that contains masers of this type. In spite of these detections, we find that current high-mass starformation in the inner CMZ is only taking place in seven isolated clouds. The results suggest that star formation at
early evolutionary phases in the CMZ is about 10 times less efficient than expected by the dense gas star formation
relation, which is in line with previous studies that focus on more evolved phases of star formation. This means that
if there will be any impending, next burst of star formation in the CMZ, it has not yet begun.
Accepted by ApJS
https://arxiv.org/pdf/1909.02338

45

Detection of new methanol maser transitions associated with G358.93-0.03
G. C. MacLeod1,2 , K. Sugiyama3 , T. R. Hunter4 , J. Quick2 , W. Baan5 , S. L. Breen6 , C. L. Brogan4 , R.
A. Burns3,7 , A. Caratti o Garatti8 , X. Chen9,10 , J. O. Chibueze11,12 , M. Houde1 , J. F. Kaczmarek13 , H.
Linz14 , F. Rajabi15,16 , Y. Saito17 , S. Schmidl18 , A. M. Sobolev19 , B. Stecklum18 , S. P. van den Heever2
and Y. Yonekura17
1

The University of Western Ontario, 1151 Richmond Street, London, ON N6A 3K7, Canada; 2 Hartebeesthoek
Radio Astronomy Observatory, PO Box 443, Krugersdorp, 1741, South Africa; 3 Mizusawa VLBI Observatory, National Astronomical Observatory of Japan (NAOJ), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 National Radio Astronomy Observatory (NRAO), 520 Edgemont Rd, Charlottesville, VA, 22903, USA; 5 Netherlands Institutefor Radio Astronomy, ASTRON, 7991 PD, Dwingeloo, The Netherlands; 6 Sydney Institute for Astronomy (SIfA),
School of Physics, University of Sydney, NSW 2006, Australia; 7 Korea Astronomy and Space Science Institute, 776
Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea; 8 Dublin Institute for Advanced Studies, Astronomy &Astrophysics Section, 31 Fitzwilliam Place, D02 XF86, Dublin 2, Ireland; 9 Center for Astrophysics, GuangZhou University, Guangzhou 510006, China; 10 Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 NandanRoad, Shanghai, 200030, China; 11 Space Research Unit, Physics Department, North West University, Potchefstroom
2520, South Africa; 12 Department of Physics and Astronomy, Faculty of Physical Sciences, University of Nigeria,
Carver Building, 1 University Road, 410001, Nsukka, Nigeria; 13 CSIRO Astronomy and Space Science, CSIRO
Parkes Observatory, PO Box 276 Parkes NSW 2870, Australia; 14 Max Planck Institute for Astronomy, Königstuhl
17, 69117 Heidelberg, Germany; 15 Institute for Quantum Computing and Department of Physics and Astronomy,
The University of Waterloo, 200 University Ave. West, Waterloo, Ontario N2L 3G1, Canada; 16 Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5, Canada; 17 Center for Astronomy, Ibaraki University, 2-1-1
Bunkyo, Mito, Ibaraki 310-8512, Japan; 18 Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany;
19
Astronomical Observatory, Institute for Natural Sciences and Mathematics, Ural Federal University, 19 Mira street,
Ekaterinburg, 620002, Russia
E-mail contact: gord at hartrao.ac.za
We report the detection of new 12.178, 12.229, 20.347, and 23.121 GHz methanol masers in the massive star-forming
region G358.93-0.03, which are flaring on similarly short timescales (days) as the 6.668 GHz methanol masers also
associated with this source. The brightest 12.178 GHz channel increased by a factor of over 700 in just 50 days.
34

The masers found in the 12.229 and 20.347 GHz methanol transitions are the first ever reported and this is only the
fourth object to exhibit associated 23.121 GHz methanol masers. The 12.178 GHz methanol maser emission appears
to have a higher flux density than that of the 6.668 GHz emission, which is unusual. No associated near infrared flarecounterpart was found, suggesting that the energy source of the flare is deeply embedded.
Accepted by MNRAS
http://arxiv.org/pdf/1910.00685

46

Constraining disk evolution prescriptions of planet population synthesis models withobserved disk masses and accretion rates
C.F. Manara1 , C. Mordasini2 , L. Testi1,3 , J.P. Williams4, A. Miotello1, G. Lodato5 and A. Emsenhuber6,21European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 2 Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6 CH 3012 Bern, Switzerland; 3 INAF - Osservatorio Astrofisico
di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy; 4 Institute for Astronomy, University of Hawaii at Mnoa, Honolulu,
HI, USA; 5 Dipartimento di Fisica, Universit Degli Studi di Milano, Via Celoria, 16, 20133 Milano, Italy; 6 Lunar andPlanetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA

E-mail contact: cmanara at eso.org
While planets are commonly discovered around main-sequence stars, the processes leading to their formation are still
far from being understood. Current planet population synthesis models, which aim at describing the planet formation
process from the protoplanetary disk phase to the time exoplanets are observed, rely on prescriptions for the underlying
properties of protoplanetary disks where planets form and evolve. The recent development in measuring disk masses
and disk-star interaction properties, i.e. mass accretion rates, in large samples of young stellar objects demand a more
careful comparison between the models and the data. Here we perform a first critical assessment of the assumptions
made by planet synthesis population models by looking at the relation between mass accretion rates and disk masses
in the models and in the currently available data. We find that the currently used disk models predict mass accretion
rate in line with what is measured, but with a much lower spread of values than observed. This difference is mainly
due to the fact that the models have a smaller spread of viscous timescales than what is needed to reproduce theobservations. We also find an overabundance of weakly accreting disks in the models where giant planets have formed
with respect to observations of typical disks. We suggest that either fewer giant planets have formed in the reality orthat the prescription for planet accretion predicts too high accretion on the planets. Finally, the comparison of theproperties of transition disks with large cavities confirms that in many of these objects the observed accretion rates
are higher than those predicted by the models. On the other hand, PDS70, a transition disk with two detected giant
planets in the cavity, shows mass accretion rates well in line with model predictions.
Accepted by Astronomy & Astrophysics Letters
https://arxiv.org/pdf/1909.08485

47

Runaway Young Stars in the Orion Nebula
Aidan McBride1 and Marina Kounkel1
1

Department of Physics and Astronomy, Western Washington University, 516 High St, Bellingham, WA 98225

E-mail contact: mkounkel at umich.edu
The star forming region of the Orion Nebula (ONC) is ideal to study the stellar dynamics of young stars in a clusteredenvironment. Using Gaia DR2 we search for the pre-main sequence stars with unusually high proper motions that may
be representative of a dynamical ejection from unstable young triple systems or other close three-body encounters.
We identify twenty-six candidate stars that are likely to have had such an encounter in the last 1 Myr. Nine of thesestars could be traced back to the densest central-most region of the ONC, the Trapezium, while five others have likelyinteractions with other OB-type stars in the cluster. Seven stars originate from other nearby populations within theOrion Complex that coincidentally scattered towards the ONC. A definitive point of origin cannot be identified forthe remaining sources. These observations shed light on the frequency of the ejection events in young clusters.
Accepted by ApJ
https://arxiv.org/pdf/1908.07550.pdf

35

48

Bright C2 H emission in protoplanetary disks in Lupus: high volatile C/O>1 ratios
A. Miotello1, S. Facchini1 , E.F. van Dishoeck2,3 , P. Cazzoletti3 , L. Testi1 , J.P. Williams4, M. Ansdell5,6
and S. van Terwisga2 , and N. van der Marel7
1

European Southern Observatory, Karl-Schwarzschild-Str 2, D-85748 Garching, Germany; 2 Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden, The Netherlands; 3 Max-Planck-institute für extraterrestrische
Physik, Giessenbachstraße, D-85748 Garching, Germany; 4 Institute for Astronomy, University of Hawaii, 2680 Woodlawn dr., 96822 Honolulu HI, USA; 5 Center for Integrative Planetary Science, University of California at Berkeley,
Berkeley, CA 94720, USA; 6 Center for Computational Mathematics & Center for Computational Astrophysics, Flatiron Institute,162 Fifth Ave New York, NY 10010, USA; 7 Herzberg Astronomy & Astrophysics Programs, National
Research Council of Canada, 5071 West Saanich Road, Victoria BC V9E 2E7, Canada
E-mail contact: amiotell at eso.org
ALMA surveys have shown that CO emission in protoplanetary disks is much fainter than expected. Accordingly, CObased gas masses and gas/dust ratios are orders of magnitude lower than previously thought. This may be explained
either as fast gas dispersal, or as chemical evolution and locking up of volatiles in larger bodies leading to the low
observed CO fluxes. The latter processes lead to enhanced C/O ratios in the gas, which may be reflected in enhanced
abundances of molecules like C2 H. The goal of this work is to employ C2 H observations to understand whether low
CO fluxes are caused by volatile depletion, or by fast gas dissipation. We present ALMA Cycle 4 C2 H observationsof a subsample of nine sources in Lupus. The integrated C2 H emission is determined and compared to previous CO
observations and model predictions. Seven out of nine disks are detected in C2 H, whose line emission is almost as
bright as 13 CO. All detections are significantly brighter than the typical sensitivity of the observations, hinting at abimodal distribution of the C2 H line intensities. When compared with DALI models, the observed C2 H fluxes can be
reproduced only if some level of volatile carbon and oxygen depletion is allowed and C/O>1 in the gas. Models with
reduced gas/dust ratios fail instead to reproduce the observations. A steeper than linear correlation between C2 H
and CN emission line is found. This is linked to the fact that C2 H emission lines are affected more strongly by C/Ovariations than CN lines. Ring-like structures are detected both in C2 H and in continuum emission but, as for CN,
they do not seem to be connected. Sz 71 shows ring shaped emission in both C2 H and CN with the location of thepeak intensity coinciding. Our new ALMA C2 H observations favour volatile carbon and oxygen depletion rather thanfast gas dispersal to explain the faint CO observations for most of the disks.
Accepted by A&A
http://arxiv.org/pdf/1909.04477

49

Protostellar Outflows at the EarliesT Stages (POETS). III. H2 O masers tracing diskwinds and jets near luminous YSOs
L. Moscadelli1, A. Sanna2 , C. Goddi3,4 , V. Krishnan1,5 , F. Massi1 , and F. Bacciotti11INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 3 Leiden Observatory, Leiden University, PO Box 9513, 2300
RA Leiden, The Netherlands; 4 Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL,
Nijmegen, The Netherlands; 5 South African Radio Astronomy Observatory (SARAO), 2 Fir street, Black River Park,
Observatory, Cape Town, 7925, South Africa
E-mail contact: mosca at arcetri.astro.it
The goal of the Protostellar Outflows at the EarliesT Stages (POETS) survey is to image the disk-outflow interface onscales of 10–100 au in a statistically significant sample (36) of luminous young stellar objects (YSO), targeting both themolecular and ionized components of the outflows. The outflow kinematics is studied at milliarcsecond scales through
VLBI observations of the 22 GHz water masers. We employed the JVLA at 6, 13, and 22 GHz in the A- and B-Arrayconfigurations to determine the spatial structure and the spectral index of the radio continuum emission. In about
half of the targets, the water masers observed at separation ≤1000 au from the YSOs trace either or both of thesekinematic structures: 1) a spatially elongated distribution oriented at close angle with the direction of collimation of
the maser proper motions (PM), and 2) a linear LSR velocity (VLSR ) gradient across the YSO position. The kinematic
structure (1) is readily interpreted in terms of a protostellar jet, as confirmed in some targets via the comparison withindependent observations of the YSO jets, in thermal (continuum and line) emissions, reported in the literature. The

36

kinematic structure (2) is interpreted in terms of a disk-wind (DW) seen almost edge-on on the basis of several piecesof evidence: first, it is invariably directed perpendicular to the YSO jet; second, it agrees in orientation and polarity
with the VLSR gradient in thermal emissions (when reported in the literature) identifying the YSO disk at scales of≤1000 au; third, the PMs of the masers delineating the VLSR gradients hint at flow motions at a speed of 10–20 km
s−1 directed at large angles with the disk midplane. In the remaining targets, the maser PMs are not collimated but
rather tend to align along two almost perpendicular directions, and could originate in DW-jet systems slightly inclined(≤30◦ ) with respect to edge-on.
Accepted by A&A
http://arxiv.org/pdf/1909.08374

50

The Properties of Planetesimal Collisions under Jupiter’s Perturbation and the Application to Chondrule Formation via Impact Jetting
Shoichi Oshino1,2 , Yasuhiro Hasegawa3 , Shigeru Wakita1,4 , and Yuji Matsumoto1,5,6
1

Center for Computational Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588,
Japan; 2 Institute for Cosmic Ray Research, University of Tokyo, Hida, Gifu 506-1205, Japan; 3 Jet Propulsion
Laboratory, California Institute of Technology, Pasadena, CA 91109, USA; 4 Earth-Life Science Institute, Tokyo
Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan; 5 Planetary Exploration Research Center, Chiba Instituteof Technology, Narashino, Chiba 275-0016, Japan; 6 Institute of Astronomy and Astrophysics, Academia Sinica, Taipei
10617, Taiwan
E-mail contact: oshino at icrr.u-tokyo.ac.jp
Understanding chondrule formation provides invaluable clues about the origin of the solar system. Recent studies
suggest that planetesimal collisions and the resulting impact melts are promising for forming chondrules. Given thatthe dynamics of planetesimals is a key in impact-based chondrule formation scenarios, we here perform direct Nbody simulations to examine how the presence of Jupiter affects the properties of chondrule-forming collisions. Our
results show that the absence/presence of Jupiter considerably changes the properties of high velocity collisions whose
impact velocities are higher than 2.5 km s−1 ; high velocity collisions occur due to impacts between protoplanets andplanetesimals for the case without Jupiter; for the case with Jupiter, eccentricities of planetesimals are pumped up by
the secular and resonant perturbations from Jupiter. We also categorize the resulting planetesimal collisions and findthat most of high velocity collisions are classified as grazing ones for both cases. To examine the effect of Jupiter onchondrule formation directly, we adopt the impact jetting scenario and compute the resulting abundance of chondrules.
Our results show that for the case without Jupiter, chondrule formation proceeds in the inside-out manner, following
the growth of protoplanets. If Jupiter is present, the location and timing of chondrule formation are determined by
Jupiter’s eccentricity, which is treated as a free parameter in our simulations. Thus, the existence of Jupiter is the
key parameter for specifying when and where chondrule formation occurs for impact-based scenarios.
Accepted by ApJ
http://arxiv.org/pdf/1909.03655

51

Molecules in the CepE-mm jet: evidence for shock-driven photochemistry ?
J. Ospina-Zamudio1 , B. Leﬂoch1 , C. Favre1 , A. López-Sepulcre1,2 , E. Bianchi1 , C. Ceccarelli1 , M. De
Simone1 , M. Bouvier1 and C. Kahane1
1

CNRS, IPAG, Univ. Grenoble Alpes, F-38000 Grenoble, France; 2 Institut de Radioastronomie Millimétrique(IRAM), 38406 Saint Martin d’Hères, France
E-mail contact: juan-david.ospina-zamudio at univ-grenoble-alpes.fr
The chemical composition of protostellar jets and its origin are still badly understood. More observational constraints
are needed to make progress. With that objective, we have carried out a systematic search for molecular species in
the jet of Cep E-mm, a template for intermediate-mass Class 0 protostars, associated with a luminous, high-velocity
outflow. We made use of an unbiased spectral line survey in the range 72-350 GHz obtained with the IRAM 30m
telescope, complementary observations of the CO J=3–2 transition with the JCMT, and observations at 1” angularresolution of the CO J=2–1 transition with the IRAM Plateau de Bure interferometer. In addition to CO, we
37

have detected rotational transitions from SiO, SO, H2 CO, CS, HCO+ and HCN. A strong chemical differentiation isobserved in the southern and northern lobes of the jet. Radiative transfer analysis in the Large Velocity Gradientapproximation yields typical molecular abundances of the order of 10−8 for all molecular species other than CO. Overall,
the jets exhibit an unusual chemical composition, as CS, SO and H2 CO are found to be the most abundant species,
with a typical abundance of (3–4)×10−8. The transverse size of the CO jet emission estimated from interferometricobservations is about 1000 au, suggesting that we are detecting emission from a turbulent layer of gas entrained by
the jet in its propagation and not the jet itself. We propose that some molecular species could be the signatures ofthe specific photochemistry driven by the UV radiation field generated in the turbulent envelope.
Accepted by MNRAS
https://arxiv.org/pdf/1909.12002

52

Jupiter’s composition suggests its core assembled exterior to the N2 snowline
Karin I Öberg1 , Robin Wordsworth2,3
1

Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA; 2 Harvard Paulson Schoolof Engineering and Applied Sciences, Harvard University, Cambridge, MA 02140, USA; 3 Department of Earth andPlanetary Sciences, Harvard University, Cambridge, MA 02140, USA
E-mail contact: koberg at cfa.harvard.edu

Jupiter’s atmosphere is enriched in C, N, S, P, Ar, Kr and Xe with respect to solar abundances by a factor of ∼3. Gas
Giant envelopes are mainly enriched through the dissolution of solids in the atmosphere, and this constant enrichment
factor is puzzling since several of the above elements are not expected to have been in the solid phase in Jupiter’s
feeding zone; most seriously, Ar and the main carrier of N, N2 , only condense at the very low temperatures, 21–26
K, associated with the outer solar nebula. We propose that a plausible solution to the enigma of Jupiter’s uniform
enrichment pattern is that Jupiter’s core formed exterior to the N2 and Ar snowlines, beyond 30 au, resulting in a Solarcomposition core in all volatiles heavier than Ne. During envelope accretion and planetesimal bombardment, some of
the core mixed in with the envelope causing the observed enrichment pattern. We show that this scenario naturally
produces the observed atmosphere composition, even with substantial pollution from N-poor pebble and planetesimalaccretion in Jupiter’s final feeding zone. We note that giant core formation at large nebular radii is consistent withrecent models of gas giant core formation through pebble accretion, which requires the core to form exterior to Jupiter’scurrent location to counter rapid inward migration during the core and envelope formation process. If this scenario
is common, gas giant core formation may account for many of the gaps observed in protoplanetary disks between 10s
and 100 au.
Accepted by ApJ
http://arxiv.org/pdf/1909.11246

53

Dusty clumps in circumbinary discs
Pedro Poblete1,2 , Nicolas Cuello1,2 and Jorge Cuadra1,2
1

Instituto de Astrofisica, Pontificia Universidad Catolica de Chile, Vicua Mackenna 4860, 8970117 Santiago, Chile; 2
Nucleo Milenio de Formacion Planetaria (NPF), Valparaiso 2340000, Chile
E-mail contact: pppoblete at uc.cl

Recent observations have revealed that protoplanetary discs often exhibit cavities and azimuthal asymmetries such as
dust traps and clumps. The presence of a stellar binary system in the inner disc regions has been proposed to explain
the formation of these structures. Here, we study the dust and gas dynamics in circumbinary discs around eccentricand inclined binaries. This is done through two-fluid simulations of circumbinary discs, considering different valuesof the binary eccentricity and inclination. We find that two kinds of dust structures can form in the disc: a single
horseshoe-shaped clump, on top of a similar gaseous over-density; or numerous clumps, distributed along the innerdisc rim. The latter features form through the complex interplay between the dust particles and the gaseous spirals
caused by the binary. All these clumps survive between one and several tens of orbital periods at the feature location.
We show that their evolution strongly depends on the gas–dust coupling and the binary parameters. Interestingly,
these asymmetric features could in principle be used to infer or constrain the orbital parameters of a stellar companion38

— potentially unseen — inside the inner disc cavity. Finally, we apply our findings to the disc around AB Aurigae.
Accepted by MNRAS
https://arxiv.org/pdf/1908.05784.pdf

54

Runaway O-star Bow Shocks as Particle Accelerators? The Case of AE Aur revisited
Blagoy Rangelov1 , Thierry Montmerle2 , S. R. Federman3 , Patrick Boissé2 and Stefano Gabici4
1

Department of Physics, Texas State University, 601 University Drive, San Marcos, TX 78666, USA; 2 Sorbonne
Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98bis, Bd Arago, 75014 Paris, France; 3 Departmentof Physics & Astronomy, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA; 4 APC,
Université Paris Diderot, CNRS/IN2P3, CEA/IRFU, Observatoire de Paris, Sorbonne Paris Cité, F-75013 Paris,
FranceE-mail contact: rangelov at txstate.edu
We present results of our Chandra/ACIS observations of the field centered on the fast, runaway O star AE Aur andits bow shock. Previous XMM-Newton observations revealed an X-ray “blob” near the IR arc tracing the bow shock,possibly a nonthermal source consistent with models of Inverse Compton scattering of dust IR photons by electrons
accelerated at the shock. The new, subarcsecond resolution Chandra data, while confirming the presence of the XMMNewton source, clearly indicate that the latter is neither extended nor coincident with the IR arc and strongly suggest
it is a background AGN. Motivated by results published for the bow shock of BD+43◦ 3654, we extended our study to
the radio domain, by analyzing archival EVLA data. We find no radio emission from the AE Aur bow shock either.
The corresponding upper limits for the absorbed (unabsorbed) X-ray flux of 5.9(7.8) × 10−15 erg cm−2 s−1 (3σ) and,in the radio range, of 2 mJy (1.4 GHz), and 0.4 mJy (5.0 GHz), are used to put constraints on model predictions forparticle acceleration within the bow shock. In the “classical” framework of Diffusive Shock Acceleration, we find thatthe predicted X-ray and radio emission by the bow shock is at least two orders of magnitude below the current upper
limits, consistent with the systematic non-detections of up to 60 stellar bow shocks. The only exception so far remainsthat of BD+43◦ 3654, probably the result of its very large mass-loss rate among runaway O stars.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1909.01424

55

Supernova Shocks in Molecular Clouds: Velocity Distribution of Molecular Hydrogen
William T. Reach1 , Le Ngoc Tram1 , Matthew Richter2 , Antoine Gusdorf3 , Curtis DeWitt1
1
Universities Space Research Association, MS 232-11, Moffett Field, CA 94035, USA; 2 University of California,
Davis, CA USA; 3 Observatoire de Paris, École normale supérieure, Sorbonne Université, CNRS, LERMA, 75005
Paris, France

E-mail contact: wreach at sofia.usra.edu
Supernovae from core-collapse of massive stars drive shocks into the molecular clouds from which the stars formed.
Such shocks affect future star formation from the molecular clouds, and the fast-moving, dense gas with compressedmagnetic fields is associated with enhanced cosmic rays. This paper presents new theoretical modeling, using the ParisDurham shock model, and new observations, using the Stratospheric Observatory for Infrared Astronomy (SOFIA),of the H2 S(5) pure rotational line from molecular shocks in the supernova remnant IC443. We generate MHD models
for non-steady-state shocks driven by the pressure of the IC443 blast wave into gas of densities 103 to 105 cm−3 . We
present the first detailed derivation of the shape of the velocity profile for emission from H2 lines behind such shocks,
taking into account the shock age, preshock density, and magnetic field. For preshock densities 103 –105 cm−3 , the thepredicted shifts of line centers, and the line widths, of the H2 lines range from 20–2, and 30–4 km s−1 , respectively.
The a priori models are compared to the observed line profiles, showing that clumps C and G can be explained byshocks into gas with density 103 to 2 × 104 cm−3 and strong magnetic fields. For clump B2 (a fainter region nearclump B), the H2 spectrum requires a J-type shock into moderate density (∼100 cm−3 ) with the gas accelerated to
100 km s−1 from its pre-shock location. Clump B1 requires both a magnetic-dominated C-type shock (like for clumps
C and G) and a J-type shock (like for clump B1) to explain the highest observed velocities. The J-type shocks that
produce high-velocity molecules may be locations where the magnetic field is nearly parallel to the shock velocity,
39

which makes it impossible for a C-type shock (with ions and neutrals separated) to form.
Accepted by ApJ
http://arxiv.org/pdf/1909.02079

56

Illuminating the Tadpole’s metamorphosis I: MUSE observations of a small globule ina sea of ionizing photons
Megan Reiter1 , Anna F. McLeod2,3 , Pamela D. Klaassen1 , Andrés E. Guzmán4 , J.E. Dale5 , Joseph C.
Mottram6 and Guido Garay7
1

UK Astronomy Technology Centre, ROE, Blackford Hill, Edinburgh, EH9 3HJ, UK; 2 Department of Astronomy,
University of California Berkeley, Berkeley, CA 94720, USA; 3 Department of Physics and Astronomy, Texas Tech
University, PO Box 41051, Lubbock, TX 79409, USA; 4 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 5 Centre for Astrophysics Research, University of Hertfordshire, College Lane,
Hatfield, AL10 9AB, UK; 6 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 7
Departamento de Astronoma, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile
E-mail contact: megan.reiter at stfc.ac.uk
We present new MUSE/VLT observations of a small globule in the Carina H ii region that hosts the HH 900 jet+outflow
system. Data were obtained with the GALACSI ground-layer adaptive optics system in wide-field mode, providing
spatially-resolved maps of diagnostic emission lines. These allow us to measure the variation of the physical properties
in the globule and jet+outflow system. We find high temperatures (Te ≈ 104 K), modest extinction (AV ≈ 2.5 mag),and modest electron densities (ne ≈ 200 cm−3 ) in the ionized gas. Higher excitation lines trace the ionized outflow;
both the excitation and ionization in the outflow increase with distance from the opaque globule. In contrast, lower
4−3
excitation lines that are collisionally de-excited at densities >∼10 cm trace the highly collimated protostellar jet.
Assuming the globule is an isothermal sphere confined by the pressure of the ionization front, we compute a BonnorEbert mass of ∼ 3.7 M⊙ . This is two orders of magnitude higher than previous mass estimates, calling into question
whether small globules like the Tadpole contribute to the bottom of the IMF. Derived globule properties are consistent
with a cloud that has been and/or will be compressed by the ionization front on its surface. At the estimated globule
photoevaporation rate of ∼ 5 × 10−7 M⊙ yr−1 , the globule will be completely ablated in ∼ 7 Myr. Stars that form inglobules like the Tadpole will emerge into the H ii later and may help resolve some of the temporal tension between
disk survival and enrichment.
Accepted by MNRAS
https://arxiv.org/pdf/1909.12666

57

Laser experiment for the study of accretion dynamics of Young Stellar Objects: designand scaling
G. Revet1,2 , B. Khiar3 , J. Béard4 , R. Bonito5 , S. Orlando5 , M.V. Starodubtsev2 , A. Ciardi6 and J.
Fuchs1,2,7
1

LULI - CNRS, École Polytechnique, CEA: Université Paris-Saclay; UPMC Univ Paris 06: Sorbonne Universités- F-91128 Palaiseau cedex, France; 2 Institute of Applied Physics, 46 Ulyanov Street, 603950 Nizhny Novgorod,
Russia; 3 Flash Center for Computational Science, Department of Astronomy & Astrophysics, The University of
Chicago, IL, United States; 4 LNCMI, UPR 3228, CNRS-UGA-UPS-INSA, 31400 Toulouse, France; 5 INAF (Istituto
Nazionale di Astrofisica) - Osservatorio Astronomico di Palermo, Palermo, Italy; 6 LERMA, Observatoire de Paris,
PSL Research University, CNRS, Sorbonne University, UPMC Univ. Paris 06, F-75005, Paris, France; 7 ELI-NP,“Horia Hulubei” National Institute for Physics and Nuclear Engineering, 30 Reactorului Street, RO-077125, BucharestMagurele, Romania
E-mail contact: guilhem.revet at u-bordeaux.fr
A new experimental set-up designed to investigate the accretion dynamics in newly born stars is presented. It takes
advantage of a magnetically collimated stream produced by coupling a laser-generated expanding plasma to a 2×105 G(20 T ) externally applied magnetic field. The stream is used as the accretio

reported in Revet et al. (2017). Here, the characteristics of the stream are detailed and a link between the experimental
plasma expansion and a 1D adiabatic expansion model is presented. Dimensionless numbers are also calculated inorder to characterize the experimental flow and its closeness to the ideal MHD regime. We build a bridge between our
experimental plasma dynamics and the one taking place in the Classical T Tauri Stars (CTTSs), and we find that our
set-up is representative of a high plasma β CTTS accretion case.
Accepted by High Energy Density Phys.
http://arxiv.org/pdf/1909.00730

58

CHIMPS: Physical properties of molecular clumps across the inner Galaxy
Andrew J. Rigby1,2 , Toby J. T. Moore2 , David J. Eden2 , James S. Urquhart3 , Sarah E. Ragan1 , Nicolas
Peretto1 , Rene Plume4 , Mark A. Thompson5 , Malcolm J. Currie6 and Geumsook Park7
1School of Physics & Astronomy, Cardiff University, Queens Building, The Parade, Cardiff, CF24 3AA, UK; 2
Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill,
Liverpool; 3 Centre for Astrophysics and Planetary Science, The University of Kent, Canterbury, Kent CT2 7NH, UK;
4
Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4,
Canada; 5 Centre for Astrophysics Research, Science & Technology Research Institute, University of Hertfordshire,College Lane, Hatfield, Herts AL10 9AB, UK; 6 RAL Space, Rutherford Appleton Laboratory, Harwell Oxford, Didcot,
Oxfordshire OX11 0QX, UK; 7 Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon
34055, Republic of Korea
E-mail contact: rigbya at cardiff.ac.uk
The latest generation of high-angular-resolution unbiased Galactic plane surveys in molecular-gas tracers are enabling
the interiors of molecular clouds to be studied across a range of environments. The CO Heterodyne Inner Milky Way
Plane Survey (CHIMPS) simultaneously mapped a sector of the inner Galactic plane, within 27.8◦ ≤ ℓ ≤ 46.2◦ and|b| ≤ 0.5◦ , in 13 CO (3–2) and C18 O (3–2) at an angular resolution of 15 arcsec. The combination of the CHIMPS datawith 12 CO (3–2) data from the CO High Resolution Survey (COHRS) has enabled us to perform a voxel-by-voxel
local-thermodynamic-equilibrium (LTE) analysis, determining the excitation temperature, optical depth, and column
density of 13 CO at each ℓ, b, v position. Distances to discrete sources identified by FellWalker in the 13 CO (3–2)
emission maps were determined, allowing the calculation of numerous physical properties of the sources, and we present
the first source catalogues in this paper. We find that, in terms of size and density, the CHIMPS sources represent
an intermediate population between large-scale molecular clouds identified by CO and dense clumps seen in thermal
dust continuum emission, and therefore represent the bulk transition from the diffuse to the dense phase of moleculargas. We do not find any significant systematic variations in the masses, column densities, virial parameters, mean
excitation temperature, or the turbulent pressure over the range of Galactocentric distance probed, but we do find ashallow increase in the mean volume density with increasing Galactocentric distance. We find that inter-arm clumps
have significantly narrower linewidths, and lower virial parameters and excitation temperatures than clumps locatedin spiral arms. When considering the most reliable distance-limited subsamples, the largest variations occur on theclump-to-clump scale, echoing similar recent studies that suggest that the star-forming process is largely insensitive
to the Galactic-scale environment, at least within the inner disc.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1909.04714

59

Investigating the nature of the extended structure around the Herbig star RCrA using
integral field and high-resolution spectroscopy
Elisabetta Rigliaco1 , R. Gratton1 , D. Mesa1 , V. D’orazi1 , M. Bonnefoy2 , J. M. Alcala’3 , S. Antoniucci4 ,F. Bacciotti5 , M .Dima1 , B. Nisini4 , L. Podio5 , M., Barbieri6 , R. Claudi1 , S. Desidera1 , A. Garuﬁ5 ,E. Hugot7 , M. Janson8,9 , M. Langlois10 , E.L. Rickman11 , E. Sissa1 , M. Ubeira Gabellini12 , G. van der
Plas2 , A. Zurlo13,14,18 , Y. Magnard15 , D. Perret16 , R. Roelfsema17 and L. Weber18
1

INAF/Osservatorio Astronomico di Padova, Vicolo dell’osservatorio 5, 35122 Padova; 2 Univ. Grenoble Alpes,
CNRS, IPAG, 38000 Grenoble, France; 3 INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16,4180131 Napoli, Italy; 4 INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00078 Monte Porzio Catone,
Italy; 5 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125, Firenze, Italy; 6 INCT, Universidad
De Atacama, calle Copayapu 485, Copiapo’, Atacama, Chile; 7 Aix Marseille Univ, CNRS, CNES LAM, Marseille,
France; 8 Max-Planck-Institut fuur Astronomie, Konigstuhl 17, 69117, Heidelberg, Germany; 9 AlbaNova University
Center, Stockholm University, Stockholm, Sweden;60

bolometric luminosity of ionized jets from low and high-mass stars are extremely well-correlated. Our data improveupon previous studies by providing further evidence of a common origin for jets independently of luminosity.
Accepted by ApJ
https://arxiv.org/pdf/1905.12089

61

Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. III. Survey
Overview
Sarah Sadavoy1,2 , Ian Stephens1 , Philip Myers1 , Leslie Looney3 , John Tobin4 , Woojin Kwon5,6 , Benoit
Commercon7 , Dominique Segura-Cox8 , Thomas Henning9 and Patrick Hennebelle10,11
1

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138, USA; 2 Department for
Physics, Engineering Physics and Astrophysics, Queen’s University, Kingston, ON, K7L 3N6, Canada; 3 Departmentof Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL, 61801, USA; 4 National Radio Astron3
N-433.637(RS5.88993(n),6..671215)957.2292(a)16.48541(o)-5.89192(aomy Observatory, Charlottesville, VA 22903, USA; 5 Korea Astronomy
and Space Science Institute62

nascent discs is only accessible in simulations. Such simulations are constrained in their approach of computing theformation of gas giants by dimensionality, resolution, consideration of self-gravity, energy treatment and the adopted
opacity law. Our study explores how a number of these parameters affect that measured accretion rate of a Saturnmass planet. We present a global 3D radiative hydrodynamics framework using the FARGOCA-code. The planet isrepresented by a gravitational potential with a smoothing length at the location of the planet. No mass or energy
sink is used, instead luminosity and gas accretion rates are self-consistently computed. We find that the gravitationalsmoothing length must be resolved by at least 10 grid cells to obtain converged measurements of the gas accretion
rates. Secondly, we find gas accretion rates into planetary envelopes compatible with previous studies, and continue
to explain those via the structure of our planetary envelopes and their luminosities. Our measured gas accretion rates
are formally in the stage of Kelvin-Helmholtz contraction due to the modest entropy loss that can be obtained over thesimulation time-scale, but our accretion rates are compatible with those expected during late run-away accretion. Ourdetailed simulations of the gas flow into the envelope of a Saturn-mass planet provides a framework for understanding
the general problem of gas accretion during planet formation and highlights circulation features that develop inside theplanetary envelopes. Those circulation features feedback into the envelope energetics and can have further implications
for transporting dust into the inner regions of the envelope.
Accepted by A&A
http://arxiv.org/pdf/1909.08359

Complex Organic Molecules in Star-Forming Regions of the Magellanic Clouds
63

Marta Sewilo1,2 , Steven B. Charnley3 , Peter Schilke4 , Vianney Taquet5 , Joana M. Oliveira6 , Takashi
Shimonishi7,8, Eva Wirstrom9 , Remy Indebetouw10,11 , Jacob L. Ward12 , Jacco Th. van Loon6 , Jennifer
Wiseman3 , Sarolta Zahorecz13,14 , Toshikazu Onishi13 , Akiko Kawamura15 , C.-H. Rosie Chen16 , Yasuo
Fukui17 and Roya Hamedani Golshan4
1

CRESST II and NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; 2 Department of Astronomy,
University of Maryland, College Park, MD 20742, USA; 3 NASA Goddard Space Flight Center, Greenbelt, MD
20771, USA; 4 I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, 50937, Köln, Germany; 5 INAF,
Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 6 Lennard-Jones Laboratories, Keele University, ST5 5BG, UK; 7 Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578,
Japan; 8 Astronomical Institute, Tohoku University, Aramakiazaaoba 6-3, Aoba-ku, Sendai, Miyagi, 980-8578, Japan;
9
Chalmers University of Technology, Onsala Space Observatory, 43992, Onsala, Sweden; 10 Department of Astronomy,
University of Virginia, PO Box 400325, Charlottesville, VA 22904, USA; 11 National Radio Astronomy Observatory,
520 Edgemont Rd, Charlottesville, VA 22903, USA; 12 Astronomisches Rechen-Institut, Zentrum für Astronomie derUniversität Heidelberg, 69120 Heidelberg Germany; 13 Department of Physical Science, Graduate School of Science,
Osaka Prefecture University, Osaka 599-8531, Japan; 14 Chile Observatory, NAOJ, National Institutes of Natural
Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 15 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 16 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69 D-53121 Bonn,
Germany; 17 Nagoya University, School of Science, Furo-cho, Chikusa-ku, Nagoya, JP 464-8602

E-mail contact: marta.m.sewilo at nasa.gov
The Large and Small Magellanic Clouds (LMC and SMC), gas-rich dwarf companions of the Milky Way, are the nearest
laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) under metal poor
conditions. To date, only methanol, methyl formate, and dimethyl ether have been detected in these galaxies – allthree toward two hot cores in the N113 star-forming region in the LMC, the only extragalactic sources exhibiting
complex hot core chemistry. We describe a small and diverse sample of the LMC and SMC sources associated with
COMs or hot core chemistry, and compare the observations to theoretical model predictions. Theoretical models
accounting for the physical conditions and metallicity of hot molecular cores in the Magellanic Clouds have been able
to broadly account for the existing observations, but fail to reproduce the dimethyl ether abundance by more than anorder of magnitude. We discuss future prospects for research in the field of complex chemistry in the low-metallicity
environment. The detection of COMs in the Magellanic Clouds has important implications for astrobiology. The
metallicity of the Magellanic Clouds is similar to galaxies in the earlier epochs of the Universe, thus the presenceof COMs in the LMC and SMC indicates that a similar prebiotic chemistry leading to the emergence of life, as it
happened on Earth, is possible in low-metallicity systems in the earlier Universe.

44Accepted by ACS Earth and Space Chemistry
https://arxiv.org/pdf/1909.06843

64

Modeling deuterium chemistry in starless cores: full scrambling versus proton hop
O. Sipilä1 , P. Caselli1 , and J. Harju2,1
1

Max-Planck-Institute for Extraterrestrial Physics (MPE), Giessenbachstr. 1, 85748 Garching, Germany; 2 Department of Physics, P.O. Box 64, 00014 University of Helsinki, FinlandE-mail contact: osipila at mpe.mpg.de
We constructed two new models for deuterium and spin-state chemistry for the purpose of modeling the low-temperatureenvironment prevailing in starless and pre-stellar cores. The fundamental difference between the two models is in thetreatment of ion-molecule proton-donation reactions of the form XH+ + Y → X + YH+ , which are allowed to proceed
either via full scrambling or via direct proton hop, i.e., disregarding proton exchange. The choice of the reaction
mechanism affects both deuterium and spin-state chemistry, and in this work our main interest is on the effect on
deuterated ammonia. We applied the new models to the starless core H-MM1, where several deuterated forms ofammonia have been observed. Our investigation slightly favors the proton hop mechanism over full scrambling because the ammonia D/H ratios are better fit by the former model, although neither model can reproduce the observed
NH2 D ortho-to-para ratio of 3 (the models predict a value of ∼2). Extending the proton hop scenario to hydrogen
atom abstraction reactions yields a good agreement for the spin-state abundance ratios, but greatly overestimates thedeuterium fractions of ammonia. However, one can find a reasonably good agreement with the observations with thismodel by increasing the cosmic-ray ionization rate over the commonly-adopted value of ∼10−17 s−1 . We also find thatthe deuterium fractions of several other species, such as H2 CO, H2 O, and CH3 , are sensitive to the adopted protondonation reaction mechanism. Whether the full scrambling or proton hop mechanism dominates may be dependent on
the reacting system, and new laboratory and theoretical studies for various reacting systems are needed to constrainchemical models.
Accepted by A&A
http://arxiv.org/pdf/1909.04341

65

Using Herschel and Planck observations to delineate the role of magnetic fields in molecular cloud structure
Juan D. Soler1
1

Max Planck Institute for Astronomy

E-mail contact: soler at mpia.de
We present a study of the relative orientation between the magnetic field projected onto the plane of sky (B⊥ ) on scales
down to 0.4 pc, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, andthe distribution of gas column density (NH ) structures on scales down to 0.026 pc, derived from the observations by
Herschel in submillimeter wavelengths, toward ten nearby (d<450 pc) molecular clouds. Using the histogram of relativeorientation technique in combination with tools from circular statistics, we found that the mean relative orientation
between NH and B⊥ toward these regions increases progressively from 0◦ , where the NH structures lie mostly parallelto B⊥ , with increasing NH , in many cases reaching 90◦ , where the NH structures lie mostly perpendicular to B⊥ . We
also compared the relative orientation between NH and B⊥ and the distribution of NH , which is characterized by theslope of the tail of the NH probability density functions (PDFs). We found that the slopes of the NH PDF tail are
steepest in regions where NH and B⊥ are close to perpendicular. This coupling between the NH distribution and themagnetic field suggests that the magnetic fields play a significant role in structuring the interstellar medium in andaround molecular clouds. However, we found no evident correlation between the star formation rates, estimated fromthe counts of young stellar objects, and the relative orientation between NH and B⊥ in these regions.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/1909.04862

45

Investigating the gas-to-dust ratio in the protoplanetary disk of HD 142527
66

Kang-Lou Soon1 , Munetake Momose1, Takayuki Muto2 , Takashi Tsukagoshi3 , Akimasa Kataoka3 , Tomoyuki Hanawa4 , Misato Fukagawa3 , Kazuya Saigo3 and Hiroshi Shibai5
1

College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan; 2 Division of Liberal Arts,
Kogakuin University, 1-24-2 Nishi-Shinjyuku, Shinjyuku-ku, Tokyo 163-8677, Japan; 3 National Astronomical Observatory Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 4 Center for Frontier Science, Chiba University, 1-33
Yayoi-cho, Inage-ku, Chiba, Chiba 263-8522, Japan; 5 Department of Earth and Space Science, Graduate School of
Science, Osaka University, 1-1, Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
E-mail contact: kanglou.soon at gmail.com
We present ALMA observations of the 98.5 GHz dust continuum and the 13 CO J = 1 − 0 and C18 O J = 1 − 0 line
emissions of the protoplanetary disk associated with HD 142527. The 98.5 GHz continuum shows a strong azimuthalasymmetric distribution similar to that of the previously reported 336 GHz continuum, with a peak emission in dust
concentrated region in the north. The disk is optically thin in both the 98.5 GHz dust continuum and the C18 O J = 1−0emissions. We derive the distributions of gas and dust surface densities, Σg and Σd , and the dust spectral opacity
index, β, in the disk from ALMA Band 3 and Band 7 data. In the analyses, we assume the local thermodynamic
equilibrium and the disk temperature to be equal to the peak brightness temperature of 13 CO J = 3 − 2 with acontinuum emission. The gas-to-dust ratio, G/D, varies azimuthally with a relation G/D ∝ Σd−0.53 , and β is derived
to be ≈ 1 and ≈ 1.7 in the northern and southern regions of the disk, respectively. These results are consistent withthe accumulation of larger dust grains in a higher pressure region. In addition, our results show that the peak Σd islocated ahead of the peak Σg . If the latter corresponds to a vortex of high gas pressure, the results indicate that the
dust is trapped ahead of the vortex, as predicted by some theoretical studies.
Accepted by PASJ
https://arxiv.org/pdf/1909.06745

67

The DSHARP Rings: Evidence of Ongoing Planetesimal Formation?
Sebastian M. Stammler1 , Joanna Dra̧żkowska1 , Til Birnstiel1 , Hubert Klahr2 , Cornelis P. Dullemond3,
and Sean M. Andrews4
1

University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität München, Scheinerstraße 1, D-81679
Munich, Germany; 2 Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 3 Zentrum für
Astronomie, Heidelberg University, Albert-Ueberle-Straße 2, D-69120 Heidelberg, Germany; 4 Center for Astrophysics— Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
E-mail contact: stammler at usm.lmu.de
Recent high-resolution interferometric observations of protoplanetary disks at (sub-)millimeter wavelengths reveal omnipresent substructures, such as rings, spirals, and asymmetries. A detailed investigation of eight rings detected infive disks by the DSHARP survey came to the conclusion that all rings are just marginally optically thick with opticaldepths between 0.2 and 0.5 at a wavelength of 1.25 mm. This surprising result could either be coincidental or indicatethat the optical depth in all of the rings is regulated by the same process.
We investigated if ongoing planetesimal formation could explain the “fine-tuned” optical depths in the DSHARP rings
by removing dust and transforming it into “invisible” planetesimals. We performed a one-dimensional simulation ofdust evolution in the second dust ring of the protoplanetary disk around HD 163296, including radial transport of gas
and dust, dust growth and fragmentation, and planetesimal formation via gravitational collapse of sufficiently dense
pebble concentrations.
We show that planetesimal formation can naturally explain the observed optical depths if streaming instability regulates the midplane dust-to-gas ratio to unity. Furthermore, our simple monodisperse analytical model supports the
hypothesis that planetesimal formation in dust rings should universally limit their optical depth to the observed range.
Accepted by ApJL
http://arxiv.org/pdf/1909.04674

46

The Infall Motion in the Low-Mass Protostellar Binary NGC 1333 IRAS 4A1/4A2
68

Yu-Nung Su1 , Sheng-Yuan Liu1 , Zhi-Yun Li2 , Chin-Fei Lee1 , Naomi Hirano1 , Shigehisa Takakuwa1,3
and I-Ta Hsieh1
1Institute of Astronomy and Astrophysics, Academia Sinica, 11F of ASMAB, AS/NTU No.1, Sec. 4, Roosevelt
Road, Taipei 10617, Taiwan; 2 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 3
Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35
Korimoto, Kagoshima 890-0065, Japan
E-mail contact: ynsu at asiaa.sinica.edu.tw
We report ALMA observations of NGC 1333 IRAS 4A, a young low-mass protostellar binary, referred as 4A1 and
4A2. With multiple H2 CO transitions and HNC (4–3) observed at a resolution of 0.′′ 25 (∼70 au), we investigate thegas kinematics of 4A1 and 4A2. Our results show that, on the large angular scale (∼10′′ ), 4A1 and 4A2 each display
a well-collimated outflow along the N-S direction, and an S-shaped morphology is discerned in the outflow poweredby 4A2. On the small scale (∼0.′′ 3), 4A1 and 4A2 exhibit distinct spectral features toward the continuum centroid,with 4A1 showing simple symmetric profiles predominantly in absorption and 4A2 demonstrating rather complicatedprofiles in emission as well as in absorption. Based on radiative transfer modeling exercises, we find that the physicalparameters inferred from earlier low-resolution observations cannot be directly extrapolated down to the 4A1 inner
region. Possible reasons for the discrepancies between the observed and modelled profiles are discussed. We constrain
the mass infall rate in 4A1 to be at most around 3 × 10−5 M⊙ yr−1 at the layer of 75 au. For the kinematics of the 4A2
inner envelope, the absorbing dips in the H2 CO spectra are skewed toward the redshifted side and likely signaturesof inward motion. These absorbing dips are relatively narrow. This is, like the case for 4A1, significantly slower than
the anticipated inflow speed. We estimate a mass infall rate of 3.1–6.2 × 10−5 M⊙ yr−1 at the layer of 100 au in 4A2.
Accepted by ApJ
http://arxiv.org/pdf/1909.12443

69

An ALMA Study of the FU-Ori Type Object V900 Mon: Implications for the Progenitor
Michihiro Takami1 , Tsu-Sheng Chen1 , Hauyu Baobab Liu1 , Naomi Hirano1 , Ágnes Kóspál2,3 , Péter
Ábrahám2 , Eduard I. Vorobyov4,5 , Fernando Cruz-Sáenz de Miera2 , Timea Csengeri6 , Joel Green7 ,Michiel Hogerheijde8, Tien-Hao Hsieh1 , Jennifer L. Karr1 , Ruobing Dong9,1 , Alfonso Trejo1 and Lei
Chen2
1

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.; 2 Konkoly Observatory, Research Centre for Astronomy
and Earth Sciences, Hungarian Academy of Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary; 3
Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany; 4 Research Institute of Physics,
Southern Federal University, Roston-on-Don 344090, Russia; 5 Department of Astrophysics, University of Vienna,
Vienna 1080, Austria; 6 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 7Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA; 8 Leiden Observatory, Leiden
University & Anton Pannekoek Institute for Astronomy, University of Amsterdam, PO Box 9513, 2300 RA, Leiden,
The Netherlands; 9 Department of Physics & Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada
E-mail contact: hiro at asiaa.sinica.edu.tw
We present ALMA observations of 12 CO, 13 CO, and C18 O J=2–1 lines and the 230 GHz continuum for the FU Oritype object (FUor) V900 Mon (d∼1.5 kpc), for which the accretion burst was triggered between 1953 and 2009. We
identified CO emission associated with a molecular bipolar outflow extending up to a ∼104 au scale and a rotating
molecular envelope extending over >104 au. The interaction with the hot energetic FUor wind, which was observed
using optical spectroscopy, appears limited to a region within ∼400 au of the star. The envelope mass and thecollimation of the extended CO outflow suggest that the progenitor of this FUor is a low-mass Class I young stellar
object (YSO). These parameters for V900 Mon, another FUor, and a few FUor-like stars are consistent with theidea that FUor outbursts are associated with normal YSOs. The continuum emission is marginally resolved in ourobservations with a 0”.2×0”.15 (∼300×225 au) beam, and a Gaussian model provides a deconvolved FWHM of ∼90
au. The emission is presumably associated with a dusty circumstellar disk, plus a possible contribution from a windor a wind cavity close to the star. The warm compact nature of the disk continuum emission could be explained with47

viscous heating of the disk, while gravitational fragmentation in the outer disk and/or a combination of grain growth
and their inward drift may also contribute to its compact nature.
Accepted by Astrophysical Journal
http://arxiv.org/pdf/1909.05520

70

Magnetospheric Accretion as a Source of Hα Emission from Proto-planets around PDS
70Thanawuth Thanathibodee1 , Nuria Calvet1 , Jaehan Bae2 , James Muzerolle3 , and Ramiro Franco
Hernández4
1

Department of Astronomy, University of Michigan, 323 West Hall, 1085 South University Avenue, Ann Arbor, MI
48109, USA; 2 Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW,
Washington, DC 20015, USA; 3 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218,
USA; 4 Instituto de Astronomı́a y Meteorologı́a, Universidad de Guadalajara, Avenida Vallarta No. 2602, Col. Arcos
Vallarta, CP 44130, Guadalajara, Jalisco, México
E-mail contact: thanathi at umich.edu
Advances in high-resolution imaging have revealed Hα emission separated from the host star. It is generally believedthat the emission is associated with forming planets in protoplanetary disks. However, the nature of this emission
is still not fully understood. Here we report a modeling effort of Hα emission from the planets around the youngstar PDS 70. Using standard magnetospheric accretion models previously applied to accreting young stars, we findthat the observed line fluxes can be reproduced using a range of parameters relevant to PDS 70b and c, with themean mass accretion rate of log(Ṁ ) = −8.0 ± 0.6 MJup yr−1 and −8.1 ± 0.6 MJup yr−1 for PDS 70b and PDS 70c,
respectively. Our results suggest that Hα emission from young planets can originate in the magnetospheric accretionof mass from the circumplanetary disk. We find that empirical relationships between mass accretion rate and Hαline properties frequently used in T Tauri stars are not applicable in the planetary mass regime. In particular, thecorrelations between line flux and mass accretion rate underpredict the accretion rate by about an order of magnitude,
and the width at the 10% height of the line is insensitive to the accretion rate at Ṁ < 10−8 MJup yr−1 .
Accepted by ApJ
http://arxiv.org/pdf/1909.06450

71

The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars I. Identifying and Characterizing the Protostellar Content of the OMC2-FIR4 andOMC2-FIR3 Regions
John Tobin1 , S. Thomas Megeath2 , Merel van ’t Hoﬀ3 , Ana Karla Diaz-Rodriguez4 , Nickalas Reynolds20 ,Mayra Osorio4, Guillem Anglada4 , Elise Furlan5 , Nicole Karnath2 , Stella S. R. Oﬀner6 , Patrick Sheehan1 ,Sarah I. Sadavoy7 , Amelia M. Stutz8 , William J. Fischer9 , Mihkel Kama10 , Magnus Persson11 , James Di
Francesco12 , Leslie W. Looney13 , Dan M. Watson14 , Zhi-Yun Li15 , Ian Stephens7 , Claire J. Chandler1 ,Erin Cox16 , Michanel M. Dunham17 , Kaitlin Kratter18 , Marina Kounkel19 , Brian Mazur2 , Nadia M.
Murillo3, Lisa Patel20 , Laura Perez21 , Dominique Segura-Cox22 , Rajeeb Sharma20 , Lukasz Tychoniec3
and Friedrich Wyrowski23
1

National Radio Astronomy Observatory; 2 University of Toledo; 3 Leiden Observatory; 4 Instituto de Astrofisica
de Andalucia; 5 Infrared Processing and Analysis Center; 6 University of Texas; 7 Harvard-Smithsonian Center for
Astrophysics; 8 University of Concepcion; 9 Space Telescope Science Insititute; 10 Cambridge University; 11 Chalmers
University; 12 NRC-Herzberg; 13 University of Illinois; 14 University of Rochester; 15 University of Virginia; 16 Northwestern University; 17 SUNY-Fredonia; 18 University of Arizona; 19 University of Western Washington; 20 Universityof Oklahoma; 21 University of Chile; 22 Max Planck Institute for Extraterrestrial Physics; 23 Max Planck Institute forRadio Astronomy
E-mail contact: jtobin at nrao.edu
We present ALMA (0.87 mm) and VLA (9 mm) observations toward OMC2-FIR4 and OMC2-FIR3 within the Orion
integral-shaped filament that are thought to be the nearest regions of intermediate mass star formation. We charac48

terize the continuum sources within these regions on ∼40 AU (0.1 arcsec) scales and associated molecular line emission
at a factor of ∼30 better resolution than previous observations at similar wavelengths. We identify six compact continuum sources within OMC2-FIR4, four in OMC2-FIR3, and one additional source just outside OMC2-FIR4. This
continuum emission is tracing the inner envelope and/or disk emission on less than 100 AU scales. HOPS-108 is the
only protostar in OMC2-FIR4 that exhibits emission from high-excitation transitions of complex organic molecules(e.g., methanol and other lines) coincident with the continuum emission. HOPS-370 in OMC2-FIR3 with L ∼ 360 L⊙ ,also exhibits emission from high-excitation methanol and other lines. The methanol emission toward these two protostars is indicative of temperatures high enough to thermally evaporate methanol from icy dust grains; overall these
protostars have characteristics similar to hot corinos. We do not identify a clear outflow from HOPS-108 in 12 CO,
but find evidence of interaction between the outflow/jet from HOPS-370 and the OMC2-FIR4 region. The multitude
of observational constraints indicate that HOPS-108 is likely a low to intermediate-mass protostar in its main massaccretion phase and it is the most luminous protostar in OMC2-FIR4. The high resolution data presented here are
essential for disentangling the embedded protostars from their surrounding dusty environments and characterizingthem.
Accepted by ApJ
http://arxiv.org/pdf/1910.00605

72

Binary stars in Upper Scorpius
Andrei Tokovinin1 , Cesar Briceño1
1

Cerro Tololo Inter-American Observatory, Casilla 603, La Serena, Chile

E-mail contact: atokovinin at ctio.noao.edu
To address the statistics of binary stars in the 8-Myr old Upper Scorpius star formation region, we conducted speckleinterferometric survey of 614 association members more massive than 0.4 M⊙ (spectral types earlier than M3V) basedon the list of Luhman et al. (2018). We resolved 187 pairs, 55 of those are new discoveries. Using also the publisheddata and the Gaia DR2, a catalog of 250 physical binaries is produced. We carefully estimated detection limits foreach target and studied binary statistics in the separation range from 0.′′ 06 to 20′′ (9 to 2800 au), as well as clustering
at larger separations. The frequency of companions with mass ratios q > 0.3 closer than 50 au reaches 0.2 per decadeof separation (1.4× more than for the field solar-type stars) and does not depend on the mass. At wider separations
from 100 to 104 au, the separation distribution and companion fraction resemble those of solar-type stars in the field.
However, unlike in the field, we found a deficit of binaries with q > 0.7 at separations of ∼500 au, compared to smaller
and larger separations. The distribution of q clearly depends on the separation, with a preference of larger q and alarger fraction of twins with q > 0.95 at smaller separations. The binary population of Upper Scorpius differs frombinaries in the field in several ways, proving that binary statistics is not universal.
Accepted by AJ
http://arxiv.org/pdf/1909.12700

73

An ALMA view of molecular filaments in the Large Magellanic Cloud II: An early stageof high-mass star formation embedded at colliding clouds in N159W-South
Kazuki Tokuda1,2 , Yasuo Fukui3,4 , Ryohei Harada1 , Kazuya Saigo2 , Kengo Tachihara3 , Kisetsu Tsuge3 ,Tsuyoshi Inoue3 , Kazufumi Torii5 , Atsushi Nishimura1 , Sarolta Zahorecz1,2 , Omnarayani Nayak6 , Margaret Meixner6,7 , Tetsuhiro Minamidani2 , Akiko Kawamura2 , Norikazu Mizuno2,8 , Remy Indebetouw9,10 ,Marta Sewilo11,12 , Suzanne Madden13 , Maud Galametz13 , Vianney Lebouteiller13 , C.-H. Rosie Chen14
and Toshikazu Onishi1
1

Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,
Sakai, Osaka 599-8531, Japan; 2 National Astronomical Observatory of Japan, National Institutes of Natural Science,
2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of Physics, Nagoya University, Chikusa-ku, Nagoya 4648602, Japan; 4 Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan;
5
Nobeyama Radio Observatory, 462-2 Nobeyama Minamimaki-mura, Minamisaku-gun, Nagano 384-1305, Japan; 6Department of Physics & Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA;49

7

Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 8 Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033, Japan; 9 Department of
Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904, USA; 10 National Radio Astronomy
Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA; 11 CRESST II and Exoplanets and Stellar Astrophysics Laboratory, NASA, Goddard Space Flight Center, Greenbelt, MD 20771, USA; 12 Department of Astronomy,
University of Maryland, College Park, MD 20742, USA; 13 AIM, CEA, CNRS, Université Paris-Saclay, Université
Paris Diderot, Sorbonne Paris Cité, F-91191 Gif-sur-Yvette, France; 14 Max Planck Institute for Radio Astronomy,
Auf dem Huegel 69, D-53121 Bonn, Germany
E-mail contact: tokuda at p.s.osakafu-u.ac.jp
We have conducted ALMA CO isotopes and 1.3 mm continuum observations toward filamentary molecular clouds of
the N159W-South region in the Large Magellanic Cloud with an angular resolution of ∼0.′′ 25 (∼0.07 pc). Although
the previous lower resolution (∼1′′ ) ALMA observations revealed that there is a high-mass protostellar object at
an intersection of two linear-shaped filaments in 13 CO with the length scale of ∼10 pc (Fukui et al. 2015), thespatially resolved observations, in particular, toward the highest column density part traced by the 1.3 mm continuum
emission, the N159W-South clump, show complicated hub-filamentary structures. We also discovered that there are
multiple protostellar sources with bipolar outflows along the massive filament. The redshifted/blueshifted componentsof the 13 CO emission around the massive filaments/protostars show complementary distribution to each other, whichis considered to be a possible piece of evidence for a cloud-cloud collision. We propose a new scenario that thesupersonically colliding gas flow triggered the formation of both the massive filament and protostars. This is a
modification of the earlier scenario of cloud-cloud collision which postulated the two filamentary clouds prior to thehigh-mass star formation by Fukui et al. (2015). A recent theoretical study of the shock compression in colliding
molecular flows by Inoue et al. (2018) demonstrates that the formation of filaments with hub-structure is a usualoutcome of the collision, lending support for the present scenario. In the theory the filaments are formed as denseparts in a shock compressed sheet-like layer, which resembles “an umbrella with pokes”.
Accepted by ApJ
https://arxiv.org/pdf/1811.04400

74

X-shooter spectroscopy of young stars with disks. The TW Hydrae association as aprobe of the final stages of disk accretion
L. Venuti1,2,3 , B. Stelzer1,4 , J. M. Alcalá5 , C. F. Manara6 , A. Frasca7 , R. Jayawardhana2 , S. Antoniucci8 ,C. Argiroﬃ9,4 , A. Natta10 , B. Nisini8, S. Randich11 and A. Scholz121Eberhard Karls Universität, Institut für Astronomie und Astrophysik, Sand 1, 72076 Tübingen, Germany; 2 Department of Astronomy, Cornell University, Space Sciences Building, Ithaca, NY 14853, USA; 3 NASA Ames ResearchCenter, Moffett Blvd, Mountain View, CA 94035, USA; 4 INAF – Osservatorio Astronomico di Palermo, Piazza delParlamento 1, 90134 Palermo, Italy; 5 INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131
Napoli, Italy; 6 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany; 7 INAF – Osservatorio Astrofisico di Catania, via S. Sofia, 78, 95123 Catania, Italy; 8 INAF – Osservatorio
Astronomico di Roma, via di Frascati 33, 00078 Monte Porzio Catone, Italy; 9 Dipartimento di Fisica e Chimica,
Università degli Studi di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy; 10 Dublin Institute for Advanced
Studies, 31 Fitzwilliam Place, Dublin 2, Ireland; 11 INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5,50125 Florence, Italy; 12 SUPA, School of Physics & Astronomy, University of St Andrews, North Haugh, St Andrews
KY169SS, UK
E-mail contact: laura.venuti at nasa.gov
Measurements of the fraction of disk-bearing stars in clusters as a function of age indicate protoplanetary disk lifetimes< 10 Myr. However, our knowledge of the time evolution of mass accretion in young stars over the disk lifespans∼
is subject to many uncertainties, especially at the lowest stellar masses (M⋆ ). We investigate ongoing accretion
activity in young stars in the TW Hydrae association (TWA). The age of the association (∼8–10 Myr) renders it
an ideal target to probe the final stages of disk accretion, and its proximity (∼50 pc) enables a detailed assessmentof stellar and accretion properties down to brown dwarf masses. Our sample comprises eleven TWA members with
infrared excess, amounting to 85% of the total TWA population with disks. Our targets span spectral types between
M0 and M9, and masses between 0.58 and 0.02 M⊙ . We employed homogeneous spectroscopic data from 300 to50

2500 nm, obtained synoptically with the X-shooter spectrograph, to derive individual extinction, stellar parameters,
and accretion parameters for each object simultaneously. We then examined the luminosity of Balmer lines andforbidden emission lines to probe the physics of the star–disk interaction environment. Disk-bearing stars represent
around 24% of the total TWA population. We detected signatures of ongoing accretion for 70% of our TWA targets
for which accurate measurements of the stellar parameters could be derived. This implies a fraction of accretors of
13–17% across the entire TWA (accounting for the disk-bearing, potentially accreting members not included in our
survey). The spectral emission associated with these stars reveals a more evolved stage of these accretors compared toyounger PMS populations studied with the same instrument and analysis techniques (e.g., Lupus): (i) a large fraction(∼50%) exhibit nearly symmetric, narrow Hα line profiles; (ii) over 80% of them exhibit Balmer decrements consistent
with moderate accretion activity and optically thin emission; (iii) less than a third exhibit forbidden line emission in[O I] 6300Å, indicative of winds and outflows activity; (iv) only one sixth exhibit signatures of collimated jets. However,the distribution in accretion rates (Ṁacc ) derived for the TWA sample follows closely that of younger regions (Lupus,
Chamaeleon I, σ Orionis) over the mass range of overlap (M⋆ ∼ 0.1–0.3 M⊙ ). An overall correlation between Ṁacc
and M⋆ is detected, best reproduced by the function Ṁacc ∝ M⋆2.1±0.5 . At least in the lowest M⋆ regimes, stars thatstill retain a disk at ages ∼8–10 Myr are found to exhibit statistically similar, albeit moderate, accretion levels as
those measured around younger objects. This “slow” Ṁacc evolution apparent at the lowest masses may be associatedwith longer evolutionary timescales of disks around low-mass stars, suggested by the mass-dependent disk fractions
reported in the literature within individual clusters.
Accepted by A&A
https://arxiv.org/pdf/1909.06699

75

A solution to the proplyd lifetime problem
Andrew J. Winter1,2 , Cathie J. Clarke2 , Giovanni P. Rosotti3, Alvaro Hacar3 , Richard Alexander1
1

Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK; 2 Institute of Astronomy,
University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK; 3 Leiden Observatory, Leiden University, P.O.
Box 9513, 2300-RA Leiden, The Netherlands
E-mail contact: a.j.winter at le.ac.uk
Protoplanetary discs (PPDs) in the Orion Nebula Cluster (ONC) are irradiated by UV fields from the massive star
θ1 C. This drives thermal winds, inducing mass loss rates of up to Ṁwind ∼ 10−7 M⊙ yr−1 in the ‘proplyds’ (ionised
PPDs) close to the centre. For the mean age of the ONC and reasonable initial PPD masses, such mass loss rates imply
that discs should have been dispersed. However, ∼80% of stars still exhibit a NIR excess, suggesting that significant
circumstellar mass remains. This ‘proplyd lifetime problem’ has persisted since the discovery of photoevaporating
discs in the core of the ONC by O’Dell & Wen (1994). In this work, we demonstrate how an extended period ofstar formation can solve this problem. Coupling N-body calculations and a viscous disc evolution model, we obtainhigh disc fractions at the present day. This is partly due to the migration of older stars outwards, and younger stars
inwards such that the most strongly irradiated PPDs are also the youngest. We show how the disc mass distribution
can be used to test the recent claims in the literature for multiple stellar populations in the ONC. Our model also
explains the recent finding that host mass and PPD mass are only weakly correlated, in contrast with other regions ofsimilar age. We conclude that the status of the ONC as the archetype for understanding the influence of environment
on planet formation is undeserved; the complex star formation history (involving star formation episodes within ∼0.8
Myr of the present day) results in confusing signatures in the PPD population.
Accepted by MNRAS
http://arxiv.org/pdf/1909.04093

76

Molecular cloud distances based on the MWISP CO survey and Gaia DR2
Qing-Zeng Yan1 , Ji Yang1 , Yan Sun1 , Yang Su1 and Ye Xu1
1

Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing
210034, Peoples Republic of China
E-mail contact: jiyang at pmo.ac.cn

51

We present a new method of calculating distances of molecular clouds in the Galactic plane, using CO observations
and the Gaia DR2 parallax and G-band extinction (AG ) measurements. Due to the complexity of dust environmentsin the Galactic plane, AG contains irregular variations, which is difficult to model. To overcome this difficulty, we
propose that the AG of off-cloud stars (Gaia stars around molecular clouds) can be used as a baseline to calibrate theAG of on-cloud stars (Gaia stars toward molecular clouds), which removes the AG components that are unrelated tomolecular clouds. The distance is subsequently inferred from the jump point in on-cloud AG with Bayesian analysis
and Markov chain Monte Carlo (MCMC) sampling. We applied this baseline subtraction method to a 100 square
degree region (209.◦ 75 ≤ l ≤ 219.◦ 75 and |b| ≤ 5◦ ) in the third Galactic quadrant, which was mapped as part of the
Milky Way Imaging Scroll Painting (MWISP) project, covering three CO isotopologue lines, and derived distances andmasses for 11 molecular clouds, including the Maddalena molecular cloud and Sh 2-287. The results indicate that the
distance of the Perseus Arm in this region is about 2.4 kpc and molecular clouds are present in the interarm regions.
Accepted by ApJ
http://arxiv.org/pdf/1909.07590

77

Possible progression of mass flow processes around young intermediate-mass stars basedon high-resolution near-infrared spectroscopy. I. Taurus
Chikako Yasui1 , Satoshi Hamano1 , Kei Fukue2 , Sohei Kondo2 , Hiroaki Sameshima2 , Keiichi Takenaka2 ,Noriyuki Matsunaga3 , Yuji Ikeda4 , Hideyo Kawakita2 , Shogo Otsubo2 , Ayaka Watase2 , Daisuke Taniguchi3 ,Misaki Mizumoto5 , Natsuko Izumi1 and Naoto Kobayashi61National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan, 2-21-1 Osawa, Mitaka,
Tokyo 181-8588, Japan; 2 Laboratory of Infrared High-resolution spectroscopy (LIH), Koyama Astronomical Observatory, Kyoto Sangyo University, Mo-toyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan; 3 Department of Astronomy,
Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; 4 Photocoding,460-102 Iwakura-Nakamachi, Sakyo-ku, Kyoto,606-0025, Japan; 5 Centre for Extragalactic Astronomy, Department of
Physics, University of Durham, South Road, Durham DH1 3LE, UK; 6 Institute of Astronomy, University of Tokyo,2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan
E-mail contact: ck.yasui at nao.ac.jp
We used the WINERED spectrograph to perform near-infrared high-resolution spectroscopy (resolving power R =28,000) of 13 young intermediate-mass stars in the Taurus star-forming region. Based on the presence of near- andmid-infrared continuum emission, young intermediate-mass stars can be classified into three different evolutionary
stages: Phases I, II, and III in the order of evolution. Our obtained spectra (λ = 0.91–1.35 µm) depict He i λ10830
and Pβ lines that are sensitive to magnetospheric accretion and winds. We also investigate five sources each forPβ and He i lines that were obtained from previous studies along with our targets. We observe that the Pβ profile
morphologies in Phases I and II corresponded to an extensive variety of emission features; however, these features
are not detected in Phase III. We also observe that the He I profile morphologies are mostly broad subcontinuum
absorption lines in Phase I, narrow subcontinuum absorption lines in Phase II, and centered subcontinuum absorption
features in Phase III. Our results indicate that the profile morphologies exhibit a progression of the dominant mass
flow processes: stellar wind and probably magnetospheric accretion in the very early stage, magnetospheric accretionand disk wind in the subsequent stage, and no activities in the final stage. These interpretations further suggestthat opacity in protoplanetary disks plays an important role in mass flow processes. Results also indicate that He i
absorption features in Phase III sources, associated with chromospheric activities even in such young phases, arecharacteristics of intermediate-mass stars.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/1909.09850.pdf

78

Near-equilibrium isotope fractionation during planetesimal evaporation
E.D. Young1 , A. Shahar2 , F. Nimmo3, H.E. Schlichting1 , E.A. Schauble1 , H. Tang1 , J. Labidi1
1

Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA, USA; 2 Geophysical Laboratory,
Carnegie Institution for Science, Washington DC, USA; 3 Department of Earth and Planetary Sciences, University of52

California Santa Cruz, Santa Cruz CA, USA
E-mail contact: eyoung at epss.ucla.edu
Silicon and Mg in differentiated rocky bodies exhibit heavy isotope enrichments that have been attributed to evaporation of partially or entirely molten planetesimals. We evaluate the mechanisms of planetesimal evaporation in the earlysolar system and the conditions that controlled attendant isotope fractionations. Energy balance at the surface of abody accreted within ∼1 Myr of CAI formation and heated from within by 26 Al decay results in internal temperatures
exceeding the silicate solidus, producing a transient magma ocean with a thin surface boundary layer of order <1meter that would be subject to foundering. Bodies that are massive enough to form magma oceans by radioisotope
decay (≥0.1%) can retain hot rock vapor even in the absence of ambient nebular gas. We find that a steady-state rockvapor forms within minutes to hours and results from a balance between rates of magma evaporation and atmosphericescape. Vapor pressure buildup adjacent to the surfaces of the evaporating magmas would have inevitably led to an
approach to equilibrium isotope partitioning between the vapor phase and the silicate melt. Numerical simulationsof this near-equilibrium evaporation process for a body with a radius of ∼700 km yield a steady-state far-field vapor
pressure corresponding to 95% saturation. Approaches to equilibrium isotope fractionation between vapor and melt
should have been the norm during planet formation due to the formation of steady-state rock vapor atmospheres
and/or the presence of protostellar gas. We model the Si and Mg isotopic composition of bulk Earth and show thatthe best fit is for a carbonaceous chondrite-like source material with about 12% loss of Mg and 15% loss of Si resulting
from near-equilibrium evaporation into the solar protostellar disk of hydrogen gas on timescales of 10,000 to 100,000
years.
Accepted by Icarus
http://arxiv.org/pdf/1909.05978

79

The young massive star cluster Westerlund 2 observed with MUSE. II. MUSEpack – a
Python package to analyze the kinematics of young star clusters
Peter Zeidler1,2 , Antonella Nota2,3 , Elena Sabbi2 , Peter Luljak4,2 , Anna F. McLeod5,6 , Eva K. Grebel7 ,Anna Pasquali7 , Monica Tosi81

Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA; 2 Space Telescope
Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 3 ESA, SRE Operations Devision, Spain; 4Harvey Mudd College, 301 Platt Boulevard, Claremont, CA 91711, USA; 5 Department of Astronomy, University ofCalifornia Berkeley, Berkeley, CA 94720, USA; 6 Department of Physics and Astronomy, Texas Tech University, PO
Box 41051, Lubbock, TX 79409, USA; 7 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität
Heidelberg, Mönchhofstraße 12–14, D-68120 Heidelberg, Germany; 8 INAF–Osservatorio di Astrofisica e Scienza dello
Spazio di Bologna, Via Gobetti 93/3, I-40129 Bologna, Italy
E-mail contact: zeidler at stsci.edu
We mapped the Galactic young massive star cluster Westerlund 2 (Wd2) with the integral field spectrograph MUSE
(spatial resolution: 0.′′ 2 px−1 , spectral resolution: ∆λ = 1.25 Å, wavelength range 4600–9350 Å) mounted on the VLT,
as part of an on-going study to measure the stellar and gas kinematics of the cluster region. In this paper we present
the fully reduced dataset and introduce our new Python package “MUSEpack”, which we developed to measure stellar
radial velocities with an absolute precision of 1–2 km s−1 without the necessity of a spectral template library. This
novel method uses the two-dimensional spectra and an atomic transition line library to create templates around strong
absorption lines for each individual star. The code runs fully automatically on multi-core machines, which makes it
possible to efficiently determine stellar radial velocities of a large number of stars with the necessary precision tomeasure the velocity dispersion of young star clusters. MUSEpack also provides an enhanced method for removing
telluric lines in crowded fields without sky exposures and a Python wrapper for ESO’s data reduction pipeline. We
observed Wd2 with a total of 11 short and 5 long exposures to cover the bright nebular emission and OB stars, aswell as the fainter pre-main sequence stars down to ∼1 M⊙ . The survey covers an area of ∼11 arcmin2 (15.8 pc2 ).
In total, we extracted 1,725 stellar spectra with a mean S/N>5 per pixel. A typical radial velocity (RV) uncertainty
of 4.78 km s−1 , 2.92 km s−1 , and 1.1 km s−1 is reached for stars with a mean S/N>10, S/N>20, S/N>50 per pixel,
respectively. Depending on the number of spectral lines used to measure the RVs, it is possible to reach RV accuraciesof 0.9 km s−1 , 1.3 km s−1 , and 2.2 km s−1 with ≥5, 3–4, and 1–2 spectral lines, respectively. The combined statisticaluncertainty on the radial velocity measurements is 1.10 km s−1 .
53Accepted by AJ
http://arxiv.org/pdf/1909.08143

80

The Nearby, Young, χ1 For Cluster: Membership, Age, and an Extraordinary Ensembleof Dusty Debris Disks
B. Zuckerman1 , Beth Klein1 and Joel Kastner2
1

Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1562, USA; 2 Chester F.
Carlson Center for Imaging Science, School of Physics and Astronomy, & Laboratory for Multiwavelength Astrophysics,
Rochester Institute of Technology, Rochester, NY 14623, USA
E-mail contact: ben at astro.ucla.edu

Only four star clusters are known within ∼100 pc of Earth. Of these, the χ1 For cluster has barely been studied.
We use the Gaia DR2 catalog and other published data to establish the cluster membership, structure, and age. The
age of and distance to the cluster are ∼40 Myr and 104 pc, respectively. A remarkable, unprecedented, aspect of
the cluster is the large percentage of M-type stars with warm excess infrared emission due to orbiting dust grains —these stars lie in an annulus that straddles the tidal radius of the cluster. The χ1 For cluster appears to be closely
related to two extensive, previously known, groups of co-moving, coeval stars (the Tucana-Horologium and Columba
Associations) that are spread over much of the southern sky. While Tuc-Hor and χ1 For are comoving and coeval, thedifference in the frequency of their warm dusty debris disks at M-type stars could hardly be more dramatic.
Accepted by ApJ
http://arxiv.org/pdf/1909.08764

54

Dissertation Abstracts
On Dust, Carbon Monoxide, and Molecular Hydrogen in the Census ofHigh and Medium-Mass Protostars
Rebecca Pitts

University of Florida, Bryant Space Science Center, Stadium Rd, Gainesville, FL 32611, USA
The Niels Bohr Institute, University of Copenhagen, Geologisk Museum, Øster Voldgade 5 - 7, 1350 København,
Denmark
Electronic mail: rebecca.pitts at nbi.ku.dk
Ph.D dissertation directed by: Peter J. Barnes
Ph.D degree awarded: July 2019
I used FIR and submillimeter continuum data from Herschel and APEX to fit pixel-by-pixel modified Planck SEDs toprestellar and protostellar clumps in the Census of High- and Medium-mass Protostars (CHaMP) (280◦ < ℓ < 300◦ ,−4◦ < b < +2◦ ). I present maps of dust temperature (Td ) and H2 column density (NH2 ) for molecular clumps
throughout the CHaMP survey, with detailed study of the Carina Nebula complex (Regions 9–11) and surrounding
RCW 64 (Region 26). I find that Td minima coincide with NH2 , maxima ∼ 86% of the time, implying that coolingand density enhancement must be simultaneous steps in prestellar clump evolution.
I compared the column densities of CO and H2 to chart local variations in their correspondence, and derive maps of
CO abundance. The CO abundance varies by an order of magnitude or more across each region, and the distribution
across each clump correlates in both form and magnitude with environmental conditions, especially Td . The COabundance has a Td dependence that is parabolic in the log for the aggregated CHaMP data. Combined with thepower law of Barnes et al. 2018, however, this temperature-abundance relation is unsuitable for NH2 ≤ 1025.5 m−2 .
H2 column densities from SED-fitting of dust, which is optically thin, allowed me to compute the XCO -factor( NH2 I12 CO −1 ) directly for the entire CHaMP sample (> 80, 000 pixels). It is not constant: XCO is a broken
power law with a broad transition, and exponents of -0.49 and 1.3 for low and high values of I12 CO , respectively.
These values agree well with simulations. For the greatest and smallest I12 CO , a constant XCO underpredicts NH2 by
up to 60%.
Finally, I present multi-wavelength data on the globally collapsing molecular cloud/protostellar cluster BYF 73,
revealing eight protostellar objects, of which only two had detectable far-infrared counterparts. MIR 2 is the most
massive at ∼ 240 M⊙ , more massive than all the others combined by up to tenfold, and may have a dynamical age as
small as 7000 years.
Altogether, a portrait emerges of molecular gas clumps as physically and chemically distinct entities with long latency
periods spent cooling and contracting before star-formation can begin. Despite the sensitivity of gas-phase COabundance to local conditions, comparison with dust emission reveals surprisingly simple methods of compensation,with broad implications for measured H2 mass budgets in the Milky Way and beyond.
55

The Transition Points in Young Stars and Young Star Clusters
Nicole Karnath

University of Toledo
Electronic mail: nicole.karnath at rockets.utoledo.edu
Ph.D dissertation directed by: S. T. Megeath
Ph.D degree awarded: August 2019

To study transitions of embedded clusters into open clusters, we present visible light spectroscopic observations of
190 young stars in the Cepheus OB3b young cluster. These observations have enabled us to constrain the fate of
Cep OB3b, the nearest example of a large young cluster in the late stages of gas dispersal. The Gaia DR2 data has
resolved previous ambiguities in the distance to Cep OB3b with a distance of 819 pc. The cluster contains two distinct
sub-clusters; the proper motions show the two sub-clusters are moving away from one another. Based on the velocity
dispersion measured with the visible spectra, each sub-cluster will form a bound cluster of 300 stars each.
To study the transition point between protostars and pre-main sequence stars, the 66 near-IR high resolution spectroscopy of Orion HOPS protostars is paving the way to observationally constrain the temperatures, luminosities, andradii of a large sample of late stage protostars at a common distance without the need to use theoretical models.
We identify temperature sensitive features in the HOPS spectra spectral typing each target with a suite of spectral
typing standards, simultaneously, lines without temperature sensitivity will be used to measure veiling. In parallel
effort outside of this dissertation, hydrogen lines are currently being fit to measure the accretion luminosity in each
HOPS protostar. The hydrogen line fits will be used to correct the intrinsic luminosity from the total luminosity. The
luminosities and effective temperatures from spectral types will be used to determine the radii of the protostars andcan be combined with masses from model tracks, as well as direct measurements of masses using the Keplerian disk
motions resolved in future ALMA data. The combination of radii and masses for dozens of flat spectrum protostars
will independently provide the starting point of contraction without need for theoretical models that assume an initial
mass and radius.
To measure the transition from a collapsing gas fragment to protostar with the high spatial resolution of ALMA
and VLA, we present 0.87 and 8 mm continuum images of the theoretically predicted optically thick phase of starformation that has eluded observation for decades. The mm continuum observations resolve the youngest protostars
in the Orion Molecular Clouds. Specifically, four irregularly shaped protostars have properties that constrain their age
to be younger than 10,000 years. The four detections out of 328 protostars also suggest lifetimes of a few thousand
years. The four irregular protostars are optically thick at 0.87 mm and given their masses, radii, and luminosities,
appear to be collapsing slowly on Kelvin-Helmholtz timescales, which is also a few thousand years; in comparison
free fall times are a few hundred years. The slow contraction is in contradiction with virial arguments, which showthat thermal energies at the observed temperatures are much too low to support the inner envelopes against collapse.
Other sources of energy, rotation, turbulence and/or magnetic fields, are needed. Future observations are required
to constrain the dust law and measure the turbulent and/or rotational motions of the inner envelopes to determine
whether they are sufficient to support the envelopes against collapse.
https://etd.ohiolink.edu/!etd.send_file?accession=toledo1564763305735395&disposition=inline
56

New Jobs

Rice University: Tenure-track faculty position in Astronomy in thegeneral field of galactic star formation and planet formation, including
exoplanet characterization
The Department of Physics and Astronomy at Rice University invites applications for a tenure-track faculty positionin Astronomy in the general field of galactic star formation and planet formation, including exoplanet characterization.
We seek an outstanding theoretical, observational, or computational astronomer whose research will complement andextend existing activities in these areas within the department. In addition to developing an independent and vigorous
research program, the successful applicant will be expected to teach, on average, one undergraduate or graduate course
each semester, and contribute to the service missions of the department and university. The department expects tomake the appointment at the assistant professor level. A Ph.D. in astronomy/astrophysics or related field is required.
See: https://physics.rice.edu/open-positions

Postdoctoral position in computational star and planet formation
Applications are invited for a 2-year Postdoctoral Research Fellow to work with Dr. Benoı̂t Commerçon and Dr. Guillaume Laibe at the Centre de Recherche Astrophysique de Lyon (http://cral.univ-lyon1.fr) in the AstroENS
team based at Ecole Normale Supérieure de Lyon on computational star and planet formation.
This includes any of the following aspects:• Formation and evolution of protostellar disks• Evolution of dust grains from the diffuse interstellar medium up to protoplanetary disks• Modelling of dusty turbulence• Modelling of multi-fluid flows dynamics.

The successful candidate should have a Ph.D. in Astrophysics, Physics or Applied mathematics in relation with hydrodynamics with experience computational star or planet formation.
By November 15th 2019, enthusiastic candidates should submit on the web platform at this address
https://emploi.cnrs.fr/Offres/CDD/UMR5574-BENCOM-002/Default.aspxi) a CV including a publication list, ii) a brief statement of research interests and iii) arrange for three letters of reference to be provided separately (sent to benoit.commercon@ens-lyon.fr and guillaume.laibe@ens-lyon.fr). Applications
which will not be submitted on the web platform will not be considered.
E-mail contact: benoit.commercon@ens-lyon.fr ; guillaume.laibe@ens-lyon.fr

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Meetings

Science with the Atacama Pathfinder Experiment (APEX2020)
Schloss Ringberg, Tegernsee, Germany, February 25, 2020
The Atacama Pathfinder Experiment (APEX) 12 m submillimeter telescope has significantly contributed to a wide
variety of astronomy science areas, ranging from the discoveries of new molecules to large-scale and deep imaging of
the submillimeter sky.
Since 2012, every other year, the Ringberg APEX workshops bring together APEX users and other interested scientists
working on a wide range of exciting results covering the Solar System to distant galaxies in the early Universe.
APEX2020 aims at presenting new science results and to looking into new science opportunities for the next years.
In the last two years, APEX has been significantly improved by upgrades of the antenna itself as well as by thecommissioning of new instruments, including new large cameras for wide-field continuum imaging and new heterodyne
instruments highly complementary to ALMA.
While ALMA operation is in full swing, APEX is strengthening its role not only as a pathfinder for studying large
source samples and probing larger spatial scales to prepare detailed high angular resolution ALMA follow ups, butalso as a fast response instrument to complement new results from ALMA. Furthermore, APEX ensures southernhemisphere access for submillimeter projects complementing archival Herschel research as well as new SOFIA science.
The conference venue, Ringberg Castle, provides a unique setting for in depth discussions on current and futurescience with APEX. In particular, sessions on new scientific results, on synergies with other observatories and on the
exploitation of the upcoming new APEX capabilities are envisioned.
Registration at the workshop website is now open:
https://events.mpifr-bonn.mpg.de/indico/event/134/

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Summary of Upcoming Meetings

Planet Formation Workshop 201925 - 28 November 2019, Tokyo, Japan
http://th.nao.ac.jp/meeting/planet-formation-workshop2019/
First Stars VI
1 - 6 March 2020 Concepcion, Chile
http://www.astro.udec.cl/FirstStarsVI/
Linking Dust, Ice, and Gas in Space19 - 24 April 2020, Capri, Italy
http://frcongressi.net/ecla2020.meet
COOL STARS 21: Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
22 -26 June 2020, Toulouse, France
https://coolstars21.github.io/
The Physics of Star Formation: From Stellar Cores to Galactic Scales
29 June - 3 July 2020, Lyon, France
http://staratlyon.univ-lyon1.fr/en
Interstellar Shocks School
22 - 27 March 2020, Les Houches, France
https://www.sciencesconf.org/browse/conference/?confid=8899
Linking Dust, Ice, and Gas in Space; 19 - 24 April 2020, Capri Islands, Italy
http://www.frcongressi.it/ecla2020/
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, France
http:/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
Planetary Science: The Young Solar System
6 - 12 September 2020, Quy Nhon, Vietnam
http://www.icisequynhon.com/conferences/planetary_science/
Conditions and Impact of Star Formation - Across Times and Scales
21 September - 2 October 2020, Chile
https://www.sfb965.de/science/overview
The Aftermath of a Revolution: Planet Formation Five Years after HL Tau
7 - 11 December 2020, Chile59https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org

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

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

60

New Books

Star Formation
Mark R. Krumholz1
1Research School of Astronomy and Astrophysics, Mt. Stromlo Observatory, Cotter Rd., Weston Creek ACT 2612,
Australia

This book covers the basics of star formation, ending at the transition to planet formation. The first two chapters,
comprising part I, begin with a discussion of observational techniques, and the basic phenomenology they reveal. The
goal is to familiarize students with the techniques that will be used throughout, and to provide a common vocabulary
for the rest of the book. The next five chapters form part II, and provide a similar review of the basic physical processes
that are important for star formation. Part III includes all the remaining chapters. These discuss star formation overa variety of scales, starting with the galactic scale and working down to the scales of individual stars and their disks,with slight deviations to discuss the particular problems of the formation of massive stars and of the first stars. The
book concludes with the clearing of disks and the transition to planet formation.
The book includes the following chapters:
1. Observing the Cold Interstellar Medium
2. Observing Young Stars
3. Chemistry and Thermodynamics
4. Gas Flows and Turbulence
5. Magnetic Fields and Magnetized Turbulence
6. Gravitational Instability and Collapse
7. Stellar Feedback
8. Giant Molecular Clouds
9. The Star Formation Rate at Galactic Scales: Observations
10. The Star Formation Rate at Galactic Scales: Theory
11. Stellar Clustering
12. The Initial Mass Function: Observations
13. The Initial Mass Function: Theory
14. Protostellar Disks and Outflows: Observations
15. Protostellar Disks and Outflows: Theory
16. Protostar Formation
17. Protostellar Evolution
6118. Massive Star Formation
19. The First Stars
20. Late-Stage Stars and Disks
21. The Transition To Planet Formation
In addition, the book includes five problem sets with solutions.
World Scientific Publishing, hardcover $128, softcover $88, ebook $70
Paper copies are available from Amazon and other retailers, a free version (compiled PDF or latex source) can also be
obtained from the URL here:
http://www.mso.anu.edu.au/~krumholz/publications.html

Short Announcements

Fizeau exchange visitors program - call for applications
Dear colleagues!
The Fizeau exchange visitors program in optical interferometry funds (travel and accommodation) visits of researchers
to an institute of his/her choice (within the European Community) to perform collaborative work and training on one of
the active topics of the European Interferometry Initiative. The visits will typically last for one month, and strengthen
the network of astronomers engaged in technical, scientific and training work on optical/infrared interferometry. The
program is open for all levels of astronomers (Ph.D. students to tenured staff), with priority given to PhD students
and young postdocs. non-EU based missions will only be funded if considered essential by the Fizeau Committee.
Applicants are strongly encouraged to seek also partial support from their home or host institutions.
The deadline for applications is November 15. Fellowships can be awarded for missions to be carried out between mid
January 2020 and July 2020!
Note: the next call will be issued in May 2020!
Further informations and application forms can be found at www.european-interferometry.eu
The program is funded by OPTICON/H2020.
Please distribute this message also to potentially interested colleagues outside of your community!
Looking forward to your applications,Josef Hron & Péter Ábrahám(for the European Interferometry Initiative)

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