THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 326 — 17 February 2020

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

Abstracts of Newly Accepted Major Reviews . . 39

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

Summary of Upcoming Meetings . . . . . . . . . . . . . . 41

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

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

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

Cover Picture
A hydrodynamic simulation of an M dwarf witha massive protostellar disk in which gravitational
fragmentation leads to the rapid formation of a protoplanet.
Image courtesy Dimitris Stamatellos (see Mercer &Stamatellos A&A, 633, A116, 2020)

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

John Lattanzio and I used Joe Monaghan’s first versionof his smoothed-particle hydrodynamics code to simulate
this turbulent compression and reproduce the complex supersonic spectral line shapes seen in CO.

Eric Ketoin conversation with Bo Reipurth

Q: Not long after, you published several papers on the ultracompact HII region G10.6-0.4. What is special about
G10.6-0.4?
A: The high-latitude clouds are mostly of interest becauseof their CO absorption and dust extinction and the effects
on other observations.
The first of these publications came out of my PhD thesis.
The VLA receivers at that time did not have the sensitivity to observe thermal NH3 emission at combined subarcsecond and kms−1 resolution. So Paul Ho and I used
the UCHII region as a back light to observe NH3 in absorption. The total ionization from the several stars within thecommon UCHII region creates a particularly bright radio
continuum, and their combined mass extends the radius ofhigh infall velocities to a resolvable size. Later I mapped
the accretion flow in the ionized gas using radio recombination lines. On top of all that, Paul managed to get two
more PhD theses out of G10.6-0.4. There are just a few
of these bright, massive, accreting UCHII regions in the
Galaxy. This was our first.

Q: What was your thesis about and who was your adviser?
A: My thesis with Paul Ho was titled, "Microwave spectroscopy and Gravitational Collapse". We used the VLA
and the NH3 lines at 23 GHz to map the accretion flow
onto a small group of massive stars, G10.6-0.4. The VLA
had just recently been completed and for the first time
provided arcsecond angular resolution at radio frequencies,
similar to the resolution of ground-based optical observations. Spectroscopy provided the information necessary
to estimate the structure along the line-of-sight. For example, the gas temperatures from the NH3 hyperfine line
ratios indicate the radial distance from the emission to thecentral cluster. This was the first mapping of the whirlpool
motion of a star-forming accretion flow, although feeding
several massive stars simultaneously. The journal article
received a recognition from the AAS as a significant result in astronomy in 1987. I remember when I handed thebound copies of my thesis to our department administrator, she said, "This is only 30 pages. Did your advisor
read this?" I said, "Don’t know, but he signed it."

Q: In a series of papers you have also dealt with the problem of the formation of massive stars as a competition
between gravitational attraction and thermal pressure of
the HII region. What are your main findings?
A: The main conclusion is a new understanding of HII
regions as part of the accretion process. The textbook
model of spherical expansion driven by the pressure difference between the hot gas ionized by the star and the surrounding cold neutral gas neglects the gravitational force
necessary for star formation. Although this works wellenough for giant optical HII regions that are large enoughthat the gravitational attraction is negligible at the HIIboundary, a better model for accreting stars is describedin Mestel’s 1954 paper as ionization within a Bondi accretion flow. However, lacking the double-front structure of
the HII boundary, ionization plus shock, first described by
Savedoff and Greene in the following year, Mestel’s modelis inconsistent in the subsonic part of the accretion flow. I
put the two concepts together in 2003 to describe the fullaccretion flow from subsonic to supersonic and show that
accretion is possible through an HII region with the flowtransitioning from molecular to ionized. In a 2007 study of
two-dimensional accretion, I found that the density gradient owing to rotational flattening results in accretion
along the dense mid-plane, transitioning from molecular
to ionized, simultaneously with a pressure-driven ionizedoutflow along the poles. This model captures the essential features seen in later numerical hydrodynamic simu-

Q: In 1986 you published a paper with Phil Myers with COmaps of high-latitude clouds.
A: That was my first publication in astronomy and as with
my PhD thesis was made possible by new instrumentation.
The IRAS satellite had recently discovered wide-spread IR
emission from dust in the low-density HI clouds that makeup part of the Galactic disk. In some regions, compression within these turbulent clouds creates densities highenough for CO to persist by self-shielding. We used Pat
Thaddeus’s 1m antenna on Cerro Tololo to observe thisCO.
We found that the high-latitude CO clouds are bound by
external pressure. This turns out to be the ram pressure of
the HI turbulence, a finding made possible by another new
advancement, in this case in numerical hydrodynamics.
3

lations, for example in Peters et al. 2010, and Kuiper et
al. 2019. Simultaneous accretion and outflow works wellwith the observations as seen in Thomas Peters’s paperand earlier with Kenny Wood in 2006. So we should really think of HII regions around massive protostars as anactive element in the accretion dynamics.

star formation. The least massive cores, those with masses
below their thermal Bonnor-Ebert critical mass, may end
up completely supported by thermal energy.
Q: In a recent paper with Paola Caselli and Jonathan
Rawlings you compared observed spectra of the L1544 corewith different models of gravitational collapse. What wereyour findings?

Q: You have worked with Paola Caselli on a division ofstarless cores into two classes, depending on the central A: This was our next to last paper in a series on thedensity. What is the main idea?
slow contraction of starless cores leading to star formation.
A: The two classes are sometimes referred to as "star- The problem addressed is the observational ambiguity ofless" and "pre-stellar", although both are starless since different inflow solutions. The Shu 1977, Larson-Penston
neither contain protostars. This division, and the confus- 1969, and Keto and Field 2005 models share a density
ing nomenclature, refers to an observational distinction. profile scaling as the inverse radius squared, also shared by
The "starless" starless cores are more nearly isothermal, the hydrostatic model. Discriminating between models byless dense, less massive, less chemically depleted and have the density profile alone, for example as revealed by dust
narrower line widths than the "pre-stellar" starless cores. observations, isn’t possible. However, the models predict
The latter are presumed to be on the verge of gravitational different inflow velocities in the inner and outer regions ofcollapse and star formation. Earlier, Neal Evans pointed the core. Our Herschel observations provided us with aout that cores without a protostar should be heated from spectral line profile for gas-phase, thermal water emission.
the outside by the background near-UV of the Galaxy and The critical density for thermal water emission is aboutcooled from the inside by IR emission from dust. George 108 cm−3 while the CO is nearly completely depleted fromField and I developed this idea into a more complete model the gas phase at densities above 105 . So we know that theof radiative and chemical equilibrium including cooling by two emission lines come only from inner and outer regions
molecular lines and heating by cosmic rays and infall com- of the core, respectively. We found that the model of slow
pression. The optical depth at different wavelengths from quasi-equilibrium contraction described in Keto and Field
the UV to millimeter (molecular lines) affects the radia- 2005 matches both observed lines. The supersonic COtive equilibrium and the chemical abundances. Paola and line widths and profiles predicted by the other models are
I found that the observational differences between the two not observed. In our last paper, at least so far, we foundclasses can all be explained simply by varying the central this model also matched the profile of a high frequency
density. In hydrostatic equilibrium, the central density is ammonia line observed by Herschel (Caselli et al. 2017).
a single parameter describing the overall core density and Q: You recently retired. What are your current plans?
therefore the optical depth as well. Maybe the title of thepaper should have been, "There is really only one class of A: A motivation in my shift from high-mass to low-massstar formation was the opportunity at the time to workstarless cores."with some extraordinary people. I hope I can continue.
Q: You have had an interest in the question about oscilla- Some of my co-authors have moved to different topics andtions of starless cores. What is the status of that subject? responsibilities, but George Field and I just published a
A: For the moment, finished. This topic began when paper about a new gravitational instability driven by speCharlie Lada pointed out that variations in spectral line cific entropy in molecular clouds that has relevance for
profiles across B68 require more complex motions than any fragmentation and star formation. With Avi Loeb’s help
combination of rotation and either contraction or expan- hosting me at Harvard’s Institute for Theory and Comsion. Along with Avery Broderick and Ramesh Narayan, putation, I am finding new people and new topics. We
we found that the line profiles are consistent with subsonic don’t know how our plans or we ourselves will evolve. To
turbulence described as a collection of oscillatory modes pay for college, I worked as a geologist with an oil comwith wavelengths on the order of the core size. These os- pany in New Mexico on a deep-drilling project measuring
cillations are similar to those seen in stars such as the gamma-rays from uranium deposits in sandstone. WatchSun. In contrast with the Sun, the thermal and turbu- ing the stars sweep over the southwest desert, the mechanlent energies in the starless cores are comparable, and as ical roar of the diesel drilling rig didn’t suggest that later I
shown in a paper with Avery, the turbulence contributes would be watching the same stars in the same desert a few
to the hydrostatic balance of the cores. Because the cores miles away, but listening to the weep-weep of cryogenicallyhave no internal sources of energy to replenish the tur- cooled radio receivers. It’s quieter in the astrophysics thebulent energy lost through dissipation and radiation, the ory group. Work with good people. Join them. Learn
more massive "starless" starless cores can evolve to "pre- something. Help out. Everyone can help, and the beststellar" over time and then to gravitational collapse and people accept help.
4

a factor of ≈ 5 improvement over previous estimates available when the Handbook was published.

Perspective

1

Distances to Star-forming
Regions

Kinematic Distances

Kinematic distances are determined using a cloud’s radial
velocity in combination with an adopted rotation curvefor the Galaxy. Assuming that a cloud is in purely circular rotation around the Galactic center, one can connect
the radial velocity of the cloud to a unique Galactocentric
radius R using a rotation curve. This Galactocentric radius can then be converted to a distance using geometricarguments (see Roman-Duval et al. 2009 and Figure 1).
Beyond the solar circle (R > R0 ), the radial velocity of
the cloud uniquely identifies its distance. However, inside
the solar circle (R < R0 ), a single radial velocity associated with the same Galactocentric radius can correspondto two different distances, known as the “near" and “far"kinematic distances. This distance ambiguity is difficult
to resolve, but can be narrowed down using a number ofapproaches (e.g. HI self-absorption, Galactic latitude of
the cloud in question, the size-linewidth relationship, association with masers; see e.g. Rice et al. 2016, Anderson
et al. 2012, Roman-Duval et al. 2009), with some approaches much more discriminative than others.

Catherine Zucker

Determining accurate distances to star-forming regions is
critically important for understanding the star formation
process, as distance affects the calculation of many physical properties, including mass, density, physical size, andluminosity. Until very recently, distance estimates to starforming regions – particularly within the solar neighborhood – suffered from large error bars and were obtained
The main benefit of the kinematic distance method is that
non-homogeneously on a cloud-by-cloud basis.
it is very easy to apply, as long as the cloud’s radial veThis is evident in the Star Formation Handbook (Reipurth locity is known and is expected to follow Galactic rota2008, Star Formation Handbook, vols I and II) – a com- tion. Mention of kinematic distances in the Astrophysicalpilation of the sixty most important star-forming regions Data System (ADS) dates back to the 1960s and 1970s,
within ≈ 2 − 3 kpc. Distance estimates for clouds in the and are even more readily applied today due to the adHandbook were obtained using a diversity of techniques, vent of high-resolution CO and HI surveys (e.g. COHRS,
including kinematic methods, parallax-based methods, CHIMPS, GRS, FUGIN, GALFA; Dempsey et al. 2013,and methods based on isochrone-fitting of associated stel- Rigby et al. 2015, Jackson et al. 2006, Umemoto et al.
lar clusters. On average, though, ten years ago, distance 2017, Peek et al. 2011). Errors in kinematic distances
uncertainties to the Handbook clouds were on the order of derive from uncertainties in the Galactic rotation curve,≈ 30%, with some distances uncertain by a factor of two. the inability to resolve the kinematic distance ambiguIn this Perspective article, we briefly discuss three major ity, and the presence of non-circular “peculiar" motions.
techniques for determining distances to molecular clouds. While recent BeSSeL results (The Bar And Spiral StrucTwo of these methods – the kinematic distance method ture Legacy Survey; Reid et al. 2019) calibrate the roand the parallax-based method – have a rich history in tation curve to unprecedented accuracy using distances
the literature, but have benefited from the rise of large- and velocities of high-mass star-forming regions, individscale VLBI surveys (see Reid et al. 2019; Loinard 2013) ual molecular clouds are still heavily affected by peculiar
over the past ten years. The third technique – based in 3D motions. These deviations occur due to feedback (e.g. sudust mapping – has only become possible within the last 5 pernovae) or due to streaming motions near spiral arms
years due to the advent of cheap, publicly available all-sky and the Galactic bar. The latter means that the kinematic
photometry and new statistical machinery. We discuss the distance method is considered particularly unreliable nearcurrent uncertainties associated with each method, where the Galactic center (|l| < 15◦ ). Recent numerical simthey are best applied, and key observational results. We ulations quantifying the impact of streaming motions on
conclude by presenting a uniform catalog of accurate dis- kinematic distance determinations estimate average untances to Star Formation Handbook clouds using 3D dust certainties of 1 kpc, though they can be as high as 2 kpc
mapping, with typical distance uncertainties of only ≈ 5% in some regions (Ramon-Fox & Bonnell 2018). Kinematic
nearby (< 1.5 kpc) and ≈ 10% farther away (> 1.5 kpc), distances also cannot be reliably used for local clouds with5

Galactic center. Previous kinematic distance estimatesplaced it between 2.0-2.4 kpc (Chini & Hoffmeister 2008),
while modern measurements based on Gaia astrometry
towards the M17 cluster (Kuhn et al. 2019) and 3D dust
mapping (Zucker et al. 2020) place it closer, around 15001600 pc.

2

Parallax-Based Distances

Parallax is the apparent angular shift of the position ofstars on the plane of the sky, caused by the Earth’s
orbit around the Sun. Given that the location of the
Earth relative to the Sun is known, the angular shift inthe source’s position over time can be related to a distance with trigonometry. Parallax-based approaches offer
a more direct measurement of distance compared to kineFigure 1: Illustration of the kinematic distance method, matic methods, and come with significantly smaller error
taken from Roman-Duval et al. 2009 (see their Figure 1 bars. As such, parallax is considered the “gold standard"
for full details), where l is the cloud’s longitude, R0 is the of distance determination.
Sun’s Galactocentric radius, R is the cloud’s Galactocen- Stellar parallax has traditionally been measured at optitric radius, Vr is the cloud’s radial velocity, and d is the cal wavelengths, with the first major breakthrough coming
cloud’s distance. The radial velocity, Vr , of a cloud can be in the 1990s with the Hipparcos mission (Perryman et al.
connected to its Galactocentric radius, R, via an adopted 1997). Hipparcos measured the trigonometric parallax ofrotation curve for the Galaxy. Inside the solar circle, the around 100,000 stars (most within the nearest few hunsame radial velocity can correspond to two different dis- dred parsecs) with typical uncertainties of ≈ 1 mas. The
tances – the “near" and “far" kinematic distances. The recent release of Gaia (Lindegren et al. 2018) increased
ambiguity can be resolved via a number of approaches, the stellar sample by four orders of magnitude, up to 1
including HI self-absorption.
billion stars. Gaia achieves a typical uncertainty of 0.04
mas for the brightest stars and 0.7 mas for the very faintest
small radial velocities (within the nearest ≈ 1 kpc) since stars. In the Gaia era, parallax-based distances can be dethe obtainable distance resolution is coarser than the pe- termined to molecular clouds by determining distances toyoung stars and clusters confirmed to be associated withculiar motions for objects so close to the Sun.
them based on previous X-ray, optical, and infrared studThe kinematic distance method is useful for deriving dis- ies. For example, Groβschedl et al. 2018 uses a sample oftances to clouds en masse, so the method is often ap- 700 mid-infrared selected young stellar objects with Gaia
plied to Galaxy-wide cloud catalogs derived from clever distances towards the Orion A molecular cloud to condecompositions of CO emission into a set of molecular struct a 3D map of the region, determining that Orion A isclouds (e.g. dendrograms, SCIMES; see Rice et al. 2016, actually a 90 pc long filament, with a significant distance
Colombo et al. 2018, Miville-Deschenes et al. 2017a). Due gradient along the line of sight (see also Kounkel at alto the effects described above, however, typical uncertain- 2018). Similar work was carried out by Kuhn et al. 2019,ties are on the order of ≈ 30%, though this can be much which uses a combination of infrared and X-ray surveys tolarger in certain cases. In the context of the Star Forma- identify a sample of YSOs (ages between 1-5 Myr) withtion Handbook, the kinematic distance method has been Gaia distances towards around 20 nearby stellar clusters.
used to derive distances to farther away “local" clouds (between 1-3 kpc). For instance, previous kinematic distance While Gaia provides accurate distances to 1 billion stars,
estimates for the W3 complex discussed in the Handbook it is an optical instrument, and as such cannot probe the(Megeath et al. 2008) places it around 3.5-4 kpc (Heyer densest star-forming regions due to dust extinction. To& Terebey 1998) while modern parallax-based methods do so, one needs radio observations, and recent VLBI sur(from BeSSeL; Reid et al. 2019, see §2) place it at 2 kpc veys like the BeSSeL survey (Reid et al. 2014, 2019)(Reid et al. 2019), likely due to large streaming motions and The Gould’s Belt Distances Survey (GOBELINS)
near the Perseus Arm. A similar story occurs for the star- (Loinard 2013) channel the strengths of Gaia at muchforming region M17, which suffers uncertainty in its kine- longer wavelengths. At radio wavelengths, there are twomatic distance due to its longitude of l = 15◦ , near the types of sources bright enough to be detected with VLBI

6

!"#$%&'%(')*+',-,-./$"&'$"0&)*1%2-.%#$%*'/'0*)&%'123-!"#$%&'()*+,'-

Figure 2: Left: Plots of extinction (in mag) as a function of distance (in kpc) for three different sightlines from Neckel& Klare (1980). Each black dot marks the distance and extinction measurement of an individual star. The blackline indicates the model for the distribution of dust along the line of sight. Right: Plot of extinction as a function of
distance modulus for one sightline from Zucker et al. (2020). Each red cross marks the most probable distance andextinction for individual stars. The blue line indicates the best-fit model for the distribution of dust along the line ofsight. The sharp increase in extinction in all panels indicates the existence of a dust cloud at that distance, as thecloud is being bracketed by unextinguished foreground stars and extinguished background stars.

3– masers associated with high-mass star-forming regions,and compact radio emission caused by the gyration of electrons near magnetically active, lower-mass young stars.
The BeSSeL survey has determined accurate distances toaround 200 high-mass star-forming regions to date, including about 30 in the nearest 2 kpc, with typical uncertainties < 10%. To complement the BeSSeL survey, the
GOBELINS survey has targeted low-mass star-forming regions throughout the Taurus (Galli et al. 2018), Orion(Kounkel et al. 2017), Perseus (Ortiz-Leon et al. 2018),
Serpens (Ortiz-Leon et al. 2017b), and Ophiuchus molecular clouds (Ortiz-Leon et al. 2017a), with uncertainties
to individual clumps of ≈ 1-2 pc. In clouds with enough
VLBI detections, it is possible to determine 3D structure.
For instance, Galli et al. 2018 find that Taurus is composed of multiple distance components and has significant
depth along the line of sight, with individual subregions
spread between ≈ 130 − 160 pc.

3D Dust Mapping Distances

Using stars to trace “dark nebulae" has its roots in theearly twentieth century (see Wolf 1923 and his accompanying “Wolf diagrams") but in the modern era, 3D dust
mapping is based on the principle outlined in Neckel &Klare 1980. In short, Neckel & Klare 1980 determine
the distance and extinction to stars of known spectral
type along different sightlines through nearby molecular
clouds. To do so, they needed to know three quantities
for each star: its apparent colors, its absolute magnitude,
and its (unreddened) intrinsic colors; the former can be derived from photometry while the latter two can be derived
from the star’s Morgan-Keenan (MK) spectral type, which
uniquely parameterizes a star’s luminosity. Knowing all
three allows for the determination of the star’s distancemodulus (and thus its distance) as well as the integrated
extinction between the observer and the star. Repeating
this procedure for many stars in the same region of thesky allows one to build up a model for the dust as a function of distance, because any dust cloud will appear as a“break" in extinction, bracketed between unextinguishedforeground stars and extinguished background stars. Thisis evident in the left panel of Figure 2, which shows extinction as a function of distance for three different sightlines
from Neckel & Klare 1980. A sharp rise in extinction coincident with the cloud’s distance is apparent in each panel.

While VLBI-based distances are fantastically accurate, themain limitation is that they are extremely expensive to obtain, and they can only be used in “special" places on thesky, which coincide with bright compact radio emission.
This means it will never be possible to obtain complete
coverage of entire molecular clouds, or to target clouds inthe very earliest stages of star formation, or those too diffuse to form stars (e.g. the Draco cloud; Miville-Deschenes
et al. 2017b). The initial five year phase of the BeSSeL
survey required 3,500 hours of radio observations to obtain measurements for 200 high-mass star-forming regions(Reid et al. 2019). Likewise, the GOBELINS survey required about 2000 hours of VLBI observations to map fivenearby star-forming regions (Loinard 2013).

Neckel & Klare 1980 limited their sample to 11,000 stars
with known spectral type, so only a few dozen stars wereavailable per region. Even today, however, spectroscopy
is only available for millions of stars, while photometry
is available for billions. New statistical infrastructure in7❲✆✕❲☎✕❲✖

❈②☞✁✍✏ ❳❈✌✒♣✞❡①❈❡♣✓❡✍✏✕✎❛

◆✌ t✓

▲✑✆✖✖

❆✒❡ ✐✔❛▼✑✠▲✄✝✝✕▲✄✗✗▼✑✗❙❡ ♣❡✁✏❙✓✂✕✂✆✂▲✂✄✑▼✂☛❈❛✞✐✎✌ ✁✐❛▲❛☞✌✌✁❆q✍✐✞❛ ❘✐✎t
✟✟●☎
■❈☎☎✆

▲✆✗✄

◆✟❈✠✠☛☎

❖ ✐✌✁
❈♦✆☎

◆✌ ✒❛

▼✌✁❖♦✑✟❡✒ ❖♦✑▼✌✁❘✂❈✐ ✔✐✁✍✏❆ ❛❘✌✏❡tt❡❈▼❛❱❡✞❛ ❈▼❛✡✡❛✞❡✁❛◆✟❈✂✆✠✂❘❈❲✆✝

■❈✂✄☎☎❈❛ ✐✁❛

Figure 3: Bird’s eye view of local molecular clouds, looking down on the disk of the Galaxy, with the Sun marked
via the yellow circle (from Zucker et al. 2020). Each blue point marks a piece of a molecular cloud in the Star
Formation Handbook (Reipurth 2008, Star Formation Handbook, vols I and II). An interactive version of this figure
is available at tinyurl.com/sfn-fig1. The background grayscale shows the 3D dust distribution of all material (notjust star-forming regions), produced using a similar method (see Green et al. 2019). The catalog has been shown toagree with VLBI-parallax based results to within 10% in regions of overlap, with no systematic bias out to 2.5 kpc(see Zucker et al. 2020 and Figure 4).
combination with high-performance computing now allows
for the determination of accurate distances to molecular
clouds using only photometry of stars, which is cheaply
and publicly available. While a star’s type, distance,and extinction can now be determined using photometry alone (see e.g. Green et al. 2014; Zucker & Speagle
et al. 2019), new parallax measurements from Gaia inform stellar distance estimates based on photometry whenavailable, which in turn considerably improves distances
to local molecular clouds. The right panel of Figure 2
shows a distance-extinction plot for a sightline throughthe Vela C molecular cloud, available in the new study by

Zucker et al. 2020. Thus, compared to VLBI approaches,
3D dust mapping technique can provide coverage over amuch larger sample of local molecular clouds, since it requires neither compact radio emission nor YSOs observable with Gaia in order to constrain distances. Rather, it
relies on inferring the distance and extinction to unassociated stars in front of and behind the cloud using opticaland near-infrared surveys (from Pan-STARRS1, DECaPS,
NSC, and 2MASS; see Chambers et al. 2016, Schlafly et
al. 2018, Nidever et al. 2018, Skrutskie et al. 2006).
This means that 3D dust mapping is targeting the material around cores, rather than the cores themselves, due

8

3,(/4*&+(),-./(*01.2

the requirement of being able to see stars through clouds. no systematic offsets (see Figure 4). For GOBELINS
clouds which show evidence of distance gradients, includ%!!!
ing Perseus (≈ 25 pc gradient; Ortiz-Leon et al. 2018),
3D dust mapping techniques obtain not only the same av$"!!
erage distances, but also the same distance gradients (seeZucker et al. 2018).
The main limitation of 3D dust mapping is that unlike
VLBI approaches it cannot easily target the most extinguished regions in local molecular clouds (AV > 10 mag)#"!!
or clouds > 3 kpc away in the Galactic plane. This is because the method relies on seeing stars through clouds to#!!!
constrain distances, which is difficult particularly in the
Galactic plane, when there are multiple clouds along theline of sight. However, new, deeper infrared data (from"!!
UKIDSS, VVV, GLIMPSE, and unWISE; Lucas et al.
2007, Alonso-Garcia et al. 2018, Benjamin et al. 2003,
!
!
"!!
#!!!
#"!!
$!!!
$"!!
%!!!
Schlafly et al. 2019) should produce significantly more&'()*&+(),-./(*01.2stars visible behind dense regions. These datasets are currently being integrated (Zucker et al. 2020b, in prep) and
Figure 4: Comparison of VLBI-based parallax distances cloud distance catalogs complete out to ≈ 6 kpc should
towards masers and radio-bright low mass stars (BeSSeL; become available in the coming years.
Reid et al. 2014, 2016 and GOBELINS; Loinard 2013)
versus 3D dust distances towards the same star-forming
regions (Zucker et al. 2020). The blue shaded area shows
4 Conclusions
the average uncertainties of the dust distances across thefull sample. The dust distances agree with VLBI parallaxbased distances to within 10%, without systematic biases. It is an exciting time to map distances to star-forming
regions. The rise of high-angular resolution spectral-line
Using this framework, Zucker et al. 2020 produce a uni- surveys, in combination with more precise rotation curves
form catalog of accurate distances to sixty star-forming are providing kinematic distances to thousands of clouds
regions in the Star Formation Handbook – the largest of across the Galactic disk. The release of Gaia (Lindegren etits kind – with typical uncertainties of 5 − 6% nearby and al. 2018) mapped the position of one billion stars, and the
10% further away (> 1.5 kpc).1 A bird’s eye view of the release of VLBI astrometry from GOBELINS and BeSSeL
distribution of these clouds is shown in Figure 3.2 Not provided accurate distances to star-forming regions with
only can 3D dust mapping provide coverage across a larger bright compact radio emission in the solar neighborhood
sample of clouds, but it can also reveal the 3D structure and beyond. In the midst of it all, 3D dust mapping iswithin an individual cloud, because much larger areas of providing accurate distances to regions where kinematiceach cloud can be targeted. In this vein, detailed distance distances are unreliable and that VLBI-based approaches
maps – revealing evidence of distance gradients and/or cannot target. This has enabled the creation of a catalog
multiple components – are available for a subset of twenty- of distances to sixty famous nearby star-forming regions
five of the most famous molecular clouds in the Star For- in the Star Formation Handbook, which agrees with VLBI
mation Handbook (see Figure 8 in Zucker & Speagle et parallax-derived distances to within < 10% in regions ofal. 2019; tinyurl.com/sfn-fig2). On a cloud-by-cloud overlap (Zucker et al. 2020). The incorporation of deeper
basis, comparison of these averaged 3D dust based dis- near-infrared data, in combination with enhanced statistitances with VLBI-parallax based distances (BeSSeL and cal methodology, should allow 3D dust mapping to extend
GOBELINS; see §2) shows that the dust distances agree its reach beyond local molecular clouds, towards dust enwith the VLBI distances to < 10% out to 2.5 kpc with shrouded regions deep in the Galactic plane.
$!!!

References:

1 See also Yan et al.

2019 for another catalog of distances, but
obtained using only Gaia data
2 For the curious, this catalog has enabled the discovery of a 2.7
kpc undulating filament which includes a majority of the nearby
star-forming regions and appears to be the Local Arm nearby. The
structure – termed the “Radcliffe Wave" – also contains many of
the so-called “Gould’s Belt" clouds, which challenges the notion thatthese clouds are part of a ring, disputing the Gould’s Belt model.
For details, see Alves et al. 2020: doi:10.1038/s41586-019-1874-z

Alves et al. 2020, Nature. doi:10.1038/s41586-019-1874-z
Alonso-García et al. 2018, A&A, 619, A4
Anderson et al. 2012, ApJ, 754, 62
Benjamin et al. 2003, PASP, 115, 953
Chambers et al. 2016, arXiv, arXiv:1612.05560
Chini & Hoffmeister 2008, hsf1.book, 5, 625

9Colombo et al. 2019, MNRAS, 483, 4291
Dempsey et al. 2013, ApJS, 209, 8
Galli et al. 2018, ApJ, 859, 33
Green et al. 2019, ApJ, 887, 93
Green et al. 2014, ApJ, 783, 114
Großschedl et al. 2018, A&A, 619, A106
Heyer & Tereby 1998, ApJ, 502, 265
Jackson et al. 2006, ApJS, 163, 145
Kounkel et al. 2018, AJ, 156, 84
Kounkel et al. 2017, ApJ, 834, 142
Kuhn et al. 2019, ApJ, 870, 32
Lindegren et al. 2018, A&A, 616, A2
Loinard 2013, IAUS, 289, 36
Lucas et al. 2008, MNRAS, 391, 136
Megeath et al. 2008, hsf1.book, 4, 264
Miville-Deschênes et al. 2017, A&A, 599, A109
Miville-Deschênes et al. 2017, ApJ, 834, 57
Neckel and Klare 1980, A&AS, 42, 251
Nidever et al. 2018, AJ, 156, 131
Ortiz-León et al. 2017, ApJ, 834, 141
Ortiz-León et al. 2018, ApJ, 865, 73
Ortiz-León et al. 2017, ApJ, 834, 143
Peek et al. 2011, ApJS, 194, 20
Perryman et al. 1997, A&A, 500, 501
Reid et al. 2014, ApJ, 783, 130
Reid et al. 2019, ApJ, 885, 131
Reid et al. 2014, ApJ, 796, 2
Reipurth, B. 2008, The Star Formation Handbook, Astron. Soc.
Pacific Monograph Publications, Vols. 4 and 5 Rice et al. 2016,
ApJ, 822, 52
Rigby et al. 2016, MNRAS, 456, 2885
Roman-Duval et al. 2009, ApJ, 699, 1153
Schlafly et al. 2018, ApJS, 234, 39
Schlafly et al. 2019, ApJS, 240, 30
Skrutskie et al. 2006, AJ, 131, 1163
Umemoto et al. 2017, PASJ, 69, 78
Wolf 1923, AN, 219, 109
Yan 2019, A&A, 624, A6
Zucker et al. 2018, ApJ, 869, 83
Zucker & Speagle et al. 2019, ApJ, 879, 125
Zucker et al. 2020, A&A, 633, A51

10

Abstracts of recently accepted papers

1

2MASS J15491331-3539118: a new low-mass wide companion of the GQ Lup system
J. M. Alcalá1 , F. Z. Majidi2 , S. Desidera3 , A. Frasca4 , C. F. Manara5 , E. Rigliaco3 , R. Gratton3 , M.
Bonnefoy6 , E. Covino1 , G. Chauvin6 , R. Claudi3 , V. D’Orazi3 , M. Langlois7 , C. Lazzoni3 , D. Mesa3 ,J.E. Schlieder8 and A. Vigan91

INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy; 2 Dipartimento di Fisica,dell’Universitá di Roma Sapienza, P.le A. Moro, 5, Roma I-00185, Italy; 3 INAF-Osservatorio Astronomico di Padova,
vicolo dell’Osservatorio 5, 35122 Padova, Italy; 4 INAF-Osservatorio Astrofisico di Catania, via S. Sofia, 78, 95123
Catania, Italy; 5 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen, Germany; 6 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 7 CRAL, UMR 5574, CNRS, Université deLyon, Ecole Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07, France; 8 Exoplanets and Stellar
Astrophysics Laboratory, Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA; 9 Aix Marseille
Université, CNRS, CNES, LAM, Marseille, France
E-mail contact: juan.alcala at inaf.it
Substellar companions at wide separation around stars hosting planets or brown dwarfs (BDs) yet close enough fortheir formation in the circumstellar disc are of special interest. In this letter we report the discovery of a wide
(projected separation ∼16.0 arcsec, or 2400 AU, and position angle 114.61◦) companion of the GQ Lup A-B system,
most likely gravitationally bound to it. A VLT/X-Shooter spectrum shows that this star, 2MASS J15491331-3539118,
is a bonafide low-mass (∼0.15 M⊙) young stellar object (YSO) with stellar and accretion/ejection properties typical of
Lupus YSOs of similar mass, and with kinematics consistent with that of the GQ Lup A-B system. A possible scenario
for the formation of the triple system is that GQ Lup A and 2MASS J15491331-3539118 formed by fragmentation ofa turbulent core in the Lup I filament, while GQ Lup B, the BD companion of GQ Lup A at 0.7 arcsec, formed in situ
by the fragmentation of the circumprimary disc. The recent discoveries that stars form along cloud filaments would
favour the scenario of turbulent fragmentation for the formation of GQ Lup A and 2MASS J15491331-3539118.
Accepted by Astronomy and Astrophysics Letters
https://ui.adsabs.harvard.edu/link_gateway/2020arXiv200110879A/EPRINT_PDF

2

A Galactic-scale gas wave in the Solar NeighborhoodJoão Alves1,2 , Catherine Zucker3 , Alyssa A. Goodman2,3 , Joshua S. Speagle3 , Stefan Meingast1 , Thomas
Robitaille4, Douglas P. Finkbeiner3,5 , Edward F. Schlaﬂy6 and Gregory M. Green7
1

University of Vienna, Dept. of Astrophysics, Türkenschanzstr. 17, 1180 Vienna, Austria; 2 Radcliffe Institute forAdvanced Study, Harvard University, 10 Garden Street, Cambridge, MA 02138, USA; 3 Harvard University Departmentof Astronomy - CfA, 60 Garden St. Cambridge, MA 02138, USA; 4 Aperio Software, Headingley Enterprise & Arts
Centre, Bennett Road, Leeds LS6 3HN, UK; 5 Harvard University Department of Physics, 17 Oxford Street, Cambridge,
MA 02138, USA; 6 Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA; 7 Kavli
Institute, Stanford University, 452 Lomita Mall, Stanford, CA 94305, USA
E-mail contact: joao.alves at univie.ac.at
For the past 150 years, the prevailing view of the local Interstellar Medium (ISM) was based on a peculiarity known
as the Gould’s Belt, an expanding ring of young stars, gas, and dust, tilted about 20◦ to the Galactic plane. Still, thephysical relation between local gas clouds has remained practically unknown because the distance accuracy to clouds
is of the same order or larger than their sizes. With the advent of large photometric surveys and the Gaia satellite
astrometric survey this situation has changed. Here we report the 3-D structure of all local cloud complexes. We finda narrow and coherent 2.7 kpc arrangement of dense gas in the Solar neighborhood that contains many of the clouds
thought to be associated with the Gould Belt. This finding is inconsistent with the notion that these clouds are part11

of a ring, disputing the Gould Belt model. The new structure comprises the majority of nearby star-forming regions,has an aspect ratio of about 1:20, and contains about 3 million solar masses of gas. Remarkably, the new structureappears to be undulating and its 3-D distribution is well described by a damped sinusoidal wave on the plane of the
Milky Way, with an average period of about 2 kpc and a maximum amplitude of about 160 pc. Our results represent
a first step in the revision of the local gas distribution and Galactic structure and offer a new, broader context tostudies on the transformation of molecular gas into stars.
Accepted by Nature
https://arxiv.org/pdf/2001.08748

3 The Gaia-ESO Survey: a new approach to chemically characterising young open clusters
M. Baratella1 , V. D’Orazi2,3 , G. Carraro1 , S. Desidera2 , S. Randich4 et al.
1

Dipartimento di Fisica e Astronomia Galileo Galilei, Vicolo Osservatorio 3, I-35122, Padova, Italy; 2 INAF –Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, 35122, Padova, Italy; 3 Monash Centre for Astrophysics(MoCA), Monash University, School of Physics and Astronomy, Clayton, VIC 3800, Melbourne, Australia; 4 INAF –Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy
E-mail contact: martina.baratella.1 at phd.unipd.it
Open clusters (OCs) are recognised as excellent tracers of Galactic thin-disc properties. At variance with intermediateage and old OCs, for which a significant number of studies is now available, clusters younger than 150 Myr havebeen mostly overlooked in terms of their chemical composition, with few exceptions. On the other hand, previous
investigations seem to indicate an anomalous behaviour of young clusters, which includes slightly sub-solar iron (Fe)abundances and extreme, unexpectedly high barium (Ba) enhancements. In a series of papers, we plan to expand
our understanding of this topic and investigate whether these chemical peculiarities are instead related to abundance
analysis techniques. We present a new determination of the atmospheric parameters for 23 dwarf stars observed by
the Gaia-ESO survey in five young OCs (younger than 150 Myr) and one star-forming region (NGC 2264). We exploit
a new method based on titanium (Ti) lines to derive the spectroscopic surface gravity, and most importantly, themicroturbulence parameter. A combination of Ti I and Fe I lines is used to obtain effective temperatures. We alsoinfer the abundances of Fe II, Ti II, Na I, Mg I, Al I, Si I, Ca I, Cr I and Ni I. Our findings are in fair agreement with
Gaia-ESO iDR5 results for effective temperatures and surface gravities, but suggest that for very young stars, themicroturbulence parameter is over-estimated when Fe lines are employed. This affects the derived chemical compositionand causes the metal content of very young clusters to be under-estimated. Our clusters display a metallicity [Fe/H]
between +0.04 and +0.12; they are not more metal poor than the Sun. Although based on a relatively small sample
size, our explorative study suggests that we may not need to call for ad hoc explanations to reconcile the chemicalcomposition of young OCs with Galactic chemical evolution models.
Accepted by A&A
http://arxiv.org/pdf/2001.03179

the spatial origin of complex organic molecules in young protostars with
4 Questioning
the CALYPSO survey
A. Belloche1 , A. J. Maury2,3 , S. Maret4 , S. Anderl4 , A. Bacmann4 , Ph. André2 , S. Bontemps5 , S.
Cabrit6 , C. Codella7 , M. Gaudel2 , F. Gueth8 , C. Lefèvre8 , B. Leﬂoch4 , L. Podio7 and L. Testi91

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 2 Laboratoire d’Astrophysique(AIM), CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette,
France; 3 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA; 4 Univ. Grenoble Alpes,
CNRS, IPAG, 38000 Grenoble, France; 5 Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N,
allée Geoffroy Saint-Hilaire, 33615 Pessac, France; 6 PSL Research University, Sorbonne Université, Observatoire deParis, CNRS, LERMA, 75014 Paris, France; 7 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125
Firenze, Italy; 8 Institut de Radioastronomie Millimétrique (IRAM), 38406 Saint-Martin-d’Hères, France; 9 ESO, Karl
Schwarzschild Straße 2, 85748 Garching bei München, Germany
E-mail contact: belloche at mpifr-bonn.mpg.de

12

Context. Complex organic molecules (COMs) have been detected in a few Class 0 protostars but their origin is notwell understood. While the usual picture of a hot corino explains their presence as resulting from the heating of
the inner envelope by the nascent protostar, shocks in the outflow, a disk wind, the presence of a flared disk, or
the interaction region between envelope and disk at the centrifugal barrier have also been claimed to enhance theabundance of COMs. Aims. Going beyond studies of individual objects, we want to investigate the origin of COMs
in young protostars on a statistical basis. Methods We use the CALYPSO survey performed with the Plateau deBure Interferometer of the Institut de Radioastronomie Millimétrique (IRAM) to search for COMs at high angularresolution in a sample of 26 solar-type protostars, including 22 Class 0 and four Class I objects. We derive thecolumn densities of the detected molecules under the local thermodynamic equilibrium approximation and search forcorrelations between their abundances and with various source properties. Results. Methanol is detected in 12 sources
and tentatively in one source, which represents half of the sample. Eight sources (30%) have detections of at least
three COMs. We find a strong chemical differentiation in multiple systems with five systems having one component
with at least three COMs detected but the other component devoid of COM emission. All sources with a luminosity
higher than 4 L⊙ have at least one detected COM whereas no COM emission is detected in sources with internal
luminosity lower than 2 L⊙ , likely because of a lack of sensitivity. The internal luminosity is found to be the source
parameter impacting the most the COM chemical composition of the sources, while there is no obvious correlation
between the detection of COM emission and that of a disk-like structure. A canonical hot-corino origin may explain
the COM emission in four sources, an accretion-shock origin in two or possibly three sources, and an outflow origin
in three sources. The CALYPSO sources with COM detections can be classified into three groups on the basis of
the abundances of oxygen-bearing molecules, cyanides, and CHO-bearing molecules. These chemical groups correlate
neither with the COM origin scenarii, nor with the evolutionary status of the sources if we take the ratio of envelope
mass to internal luminosity as an evolutionary tracer. We find strong correlations between molecules that are a priori
not related chemically (for instance methanol and methyl cyanide), implying that the existence of a correlation does
not imply a chemical link. Conclusions. The CALYPSO survey has revealed a chemical differentiation in multiple
systems that is markedly different from the case of the prototypical binary IRAS16293-2422. This raises the question
whether all low-mass protostars go through a phase showing COM emission. A larger sample of young protostars anda more accurate determination of their internal luminosity will be necessary to make further progress. Searching forcorrelations between the COM emission and the jet/outflow properties of the sources may also be promising.
Accepted by A&A
http://arxiv.org/pdf/2002.00592

5

13

C17 O suggests gravitational instability in the HL Tau disc

Alice S. Booth1 and John D. Ilee1
1

School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT, UK

E-mail contact: pyasb at leeds.ac.uk
We present the first detection of the 13 C17 O J=3–2 transition toward the HL Tau protoplanetary disc. We findsignificantly more gas mass (at least a factor of ten higher) than has been previously reported using C18 O emission.
This brings the observed total disc mass to 0.2 M⊙ , which we consider to be a conservative lower limit. Our analysisof the Toomre Q profile suggests that this brings the disc into the regime of gravitational instability. The radial regionof instability (50–110 au) coincides with the location of a proposed planet-carved gap in the dust disc and a spiral in
the gas. We, therefore, propose that if the origin of the gap is confirmed to be due to a forming giant planet, then it
is likely to have formed via the gravitational fragmentation of the protoplanetary disc.
Accepted by MNRAS
http://arxiv.org/pdf/2001.07550

6

Fragmentation favoured in discs around higher mass stars
James Cadman1,2 , Ken Rice1,2 , Cassandra Hall3 , Thomas J. Haworth4 and Beth Biller1,2
1

SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, Scotland, UK; 2
Centre for Exoplanet Science, University of Edinburgh, Edinburgh, UK; 3 Dept. of Physics and Astronomy, University

13

of Leicester, University Road, Leicester, LE1 7RH, UK; 4 Astronomy Unit, School of Physics and Astronomy, Queen
Mary University of London, London, E1 4NS, UK
E-mail contact: cadman at roe.ac.uk
We investigate how a protoplanetary disc’s susceptibility to gravitational instabilities and fragmentation depends onthe mass of its host star. We use 1D disc models in conjunction with 3D SPH simulations to determine the critical
disc-to-star mass ratios at which discs become unstable against fragmentation, finding that discs become increasingly
prone to the effects of self-gravity as we increase the host star mass. The actual limit for stability is sensitive to thedisc temperature, so if the disc is optically thin stellar irradiation can dramatically stabilise discs against gravitational
instability. However, even when this is the case we find that discs around 2 M⊙ stars are prone to fragmentation,
which will act to produce wide-orbit giant planets and brown dwarfs. The consequences of this work are two-fold:that low mass stars could in principle support high disc-to-star mass ratios, and that higher mass stars have discs thatare more prone to fragmentation, which is qualitatively consistent with observations that favour high-mass wide-orbit
planets around higher mass stars. We also find that the initial masses of these planets depends on the temperature in
the disc at large radii, which itself depends on the level of stellar irradiation.
Accepted by MNRAS
http://arxiv.org/pdf/2001.06224

reveals a large structured disk and nested rotating outflows in DG Tau B
7 ALMAA. de Valon , C. Dougados , S. Cabrit , F. Louvet , L. A. Zapata and D. Mardones
1

1

2,1

3

4

3

1

Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 PSL University, Sorbonne Université, Observatoirede Paris, LERMA, CNRS UMR 8112, 75014 Paris, France; 3 Departamento de Astronomia de Chile, Universidad deChile, Santiago, Chile; 4 Instituto de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, P.O.
Box 3-72, 58090, Morelia, Michoacan, Mexico
E-mail contact: alois.de-valon at univ-grenoble-alpes.fr
We present Atacama Large Millimeter Array (ALMA) Band 6 observations at 14-20 au spatial resolution of the disk
and CO(2-1) outflow around the Class I protostar DG Tau B in Taurus. The disk is very large, both in dust continuum(Reff,95% =174 au) and CO (RCO =700 au). It shows Keplerian rotation around a 1.1±0.2 M⊙ central star and two
dust emission bumps at r = 62 and 135 au. These results confirm that large structured disks can form at an earlystage where residual infall is still ongoing. The redshifted CO outflow at high velocity shows a striking hollow cone
morphology out to 3000 au with a shear-like velocity structure within the cone walls. These walls coincide with thescattered light cavity, and they appear to be rooted within < 60 au in the disk. We confirm their global averagerotation in the same sense as the disk, with a specific angular momentum ≃ 65 au km s−1 . The mass-flux rate of
1.7-2.9 × 10−7 M⊙ yr−1 is 35±10 times that in the atomic jet. We also detect a wider and slower outflow component
surrounding this inner conical flow, which also rotates in the same direction as the disk. Our ALMA observations
therefore demonstrate that the inner cone walls, and the associated scattered light cavity, do not trace the interface
with infalling material, which is shown to be confined to much wider angles (> 70◦ ). The properties of the conicalwalls are suggestive of the interaction between an episodic inner jet or wind with an outer disk wind, or of a massive
disk wind originating from 2-5 au. However, further modeling is required to establish their origin. In either case, suchmassive outflow may significantly affect the disk structure and evolution.
Accepted by Astronomy and Astrophysics (A&A)

https://arxiv.org/pdf/2001.09776.pdf

drift and planetesimal formation in protoplanetary discs with embedded planets
8 Pebble
Linn E.J. Eriksson , Anders Johansen , Beibei Liu
1

1

1

1

Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 221 00 Lund,
SwedenE-mail contact: linn at astro.lu.se
Nearly-axisymmetric gaps and rings are commonly observed in protoplanetary discs. The leading theory regarding
14

the origin of these patterns is that they are due to dust trapping at the edges of gas gaps induced by the gravitational
torques from embedded planets. If the concentration of solids at the gap edges becomes high enough, it could
potentially result in planetesimal formation by the streaming instability. We test this hypothesis by performing global
1-D simulations of dust evolution and planetesimal formation in a protoplanetary disc that is perturbed by multiple
planets. We explore different combinations of particle sizes, disc parameters, and planetary masses, and find thatplanetesimals form in all these cases. We also compare the spatial distribution of pebbles from our simulations with
protoplanetary disc observations. Planets larger than one pebble isolation mass catch drifting pebbles efficiently at theedge of their gas gaps, and depending on the efficiency of planetesimal formation at the gap edges, the protoplanetary
disc transforms within a few 100,000 years to either a transition disc with a large inner hole devoid of dust or to a discwith narrow bright rings. For simulations with planetary masses lower than the pebble isolation mass, the outcome
is a disc with a series of weak ring patterns but no strong depletion between the rings. Lowering the pebble size
artificially to 100 micrometer-sized “silt”, we find that regions between planets get depleted of their pebble mass on alonger time-scale of up to 0.5 million years. These simulations also produce fewer planetesimals than in the nominalmodel with millimeter-sized particles and always have at least two rings of pebbles still visible after 1 Myr.
Accepted by A&A
http://arxiv.org/pdf/2001.11042

9

A survey for variable young stars with small telescopes: II – Mapping a protoplanetary
disk with stable structures at 0.15 AU
Jack J. Evitts1 , Dirk Froebrich1 , Aleks Scholz2 , Jochen Eislöﬀel3, Justyn Campbell-White1,4 et al.
1

Centre for Astrophysics and Planetary Science, School of Physical Sciences, University of Kent, Canterbury CT2
7NH, UK; 2 SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16
9SS, UK; 3 Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany; 4 SUPA, School of Science andEngineering, University of Dundee, Nethergate, Dundee DD1 4HN, UK
E-mail contact: df at star.kent.ac.uk
The HOYS citizen science project conducts long term, multifilter, high cadence monitoring of large YSO samples witha wide variety of professional and amateur telescopes. We present the analysis of the light curve of V1490 Cyg in the
Pelican Nebula. We show that colour terms in the diverse photometric data can be calibrated out to achieve a medianphotometric accuracy of 0.02 mag in broadband filters, allowing detailed investigations into a variety of variability
amplitudes over timescales from hours to several years. Using GaiaDR2 we estimate the distance to the Pelican
Nebula to be 870+70−55 pc. V1490 Cyg is a quasi-periodic dipper with a period of 31.447±0.011d. The obscuring dust
has homogeneous properties, and grains larger than those typical in the ISM. Larger variability on short timescales isobserved in U and Rc –Hα, with U-amplitudes reaching 3 mag on timescales of hours, indicating the source is accreting.
The Hα equivalent width and NIR/MIR colours place V1490 Cyg between CTTS/WTTS and transition disk objects.
The material responsible for the dipping is located in a warped inner disk, about 0.15 au from the star. This mass
reservoir can be filled and emptied on time scales shorter than the period at a rate of up to 10−10 M⊙ yr−1 , consistent
with low levels of accretion in other T Tauri stars. Most likely the warp at this separation from the star is induced bya protoplanet in the inner accretion disk. However, we cannot fully rule out the possibility of an AA Tau-like warp,
or occultations by the Hill sphere around a forming planet.
Accepted by MNRAS
http://arxiv.org/pdf/2001.05570

Resolved Dust Continuum Measurements of Individual Giant Molecular Clouds
10 First
in the Andromeda Galaxy
Jan Forbrich1,2 , Charlie Lada2 , Sebastien Viaene3 and Glen Petitpas2
1

Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK; 2 Center for
Astrophysics ; 3 Harvard & Smithsonian, 60 Garden St, MS 72, Cambridge, MA 02138, USA
E-mail contact: j.forbrich at herts.ac.uk
In our local Galactic neighborhood, molecular clouds are best studied using a combination of dust measurements,
15

to determine robust masses, sizes and internal structures of the clouds, and molecular-line observations to determine
cloud kinematics and chemistry. We present here the first results of a program designed to extend such studies tonearby galaxies beyond the Magellanic Clouds. Utilizing the wideband upgrade of the Submillimeter Array (SMA)
at 230 GHz we have obtained the first continuum detections of the thermal dust emission on sub-GMC scales (∼ 15pc) within the Andromeda galaxy (M 31). These include the first resolved continuum detections of dust emission
from individual GMCs beyond the Magellanic Clouds. Utilizing a powerful capability of the SMA, we simultaneously
recorded CO(2-1) emission with identical (u, v) coverage, astrometry and calibration, enabling the first measurementsof the CO conversion factor, α CO(2−1) , toward individual GMCs across an external galaxy. Our direct measurement
yields an average CO–to–dust mass conversion factor of α′CO−dust = 0.042 ± 0.018 M⊙ (K km s−1 pc2 )−1 for theJ = 2 − 1 transition. This value does not appear to vary with galactocentric radius. Assuming a constant gas-to-dust
ratio of 136, the resulting αCO = 5.7 ± 2.4 M⊙ (K km s−1 pc2 )−1 for the 2-1 transition, is in excellent agreementwith that of Milky Way GMCs, given the uncertainties. Finally, using the same analysis techniques, we compare ourresults with observations of the local Orion molecular clouds, placed at the distance of M 31 and simulated to appear
as they would if observed by the SMA.
Accepted by ApJ
http://arxiv.org/pdf/2001.02914

11 Corona-Australis DANCe. I. Revisiting the census of stars with Gaia-DR2 data

P.A.B. Galli1 , H. Bouy1 , J. Olivares1 , N. Miret-Roig1, L. M. Sarro2 , D. Barrado3 , A. Berihuete4 and
W. Brandner5
1

Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hillaire, F-33615
Pessac, France; 2 Depto. de Inteligencia Artificial, UNED, Juan del Rosal, 16, 28040 Madrid, Spain; 3 Centro de
Astrobiología, Depto. de Astrofísica, INTA-CSIC, ESAC Campus, Camino Bajo del Castillo s/n, 28692 Villanueva
de la Cañada, Madrid, Spain; 4 Dept. Statistics and Operations Research, University of Cádiz, Campus Universitario
Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain; 5 Max Planck Institute for Astronomy, Königstuhl 17, 69117,
Heidelberg, Germany
E-mail contact: phillip.galli at u-bordeaux.fr
Context: Corona-Australis is one of the nearest regions to the Sun with recent and ongoing star formation, but thecurrent picture of its stellar (and substellar) content is not complete yet.
Aims: We take advantage of the second data release of the Gaia space mission to revisit the stellar census and search
for additional members of the young stellar association in Corona-Australis.
Methods: We applied a probabilistic method to infer membership probabilities based on a multidimensional astrometricand photometric data set over a field of 128 deg2 around the dark clouds of the region.
Results: We identify 313 high-probability candidate members to the Corona-Australis association, 262 of which had
never been reported as members before. Our sample of members covers the magnitude range between G > 5 mag and
G < 20 mag, and it reveals the existence of two kinematically and spatially distinct subgroups. There is a distributed‘off-cloud’ population of stars located in the north of the dark clouds that is twice as numerous as the historicallyknown ‘on-cloud’ population that is concentrated around the densest cores. By comparing the location of the stars inthe HR-diagram with evolutionary models, we show that these two populations are younger than 10 Myr. Based on
their infrared excess emission, we identify 28 Class II and 215 Class III stars among the sources with available infrared
photometry, and we conclude that the frequency of Class II stars (i.e. ‘disc-bearing’ stars) in the on-cloud region is
twice as large as compared to the off-cloud population. The distance derived for the Corona-Australis region basedon this updated census is d = 149.4+0.4−0.4 pc, which exceeds previous estimates by about 20 pc.
Conclusions: In this paper we provide the most complete census of stars in Corona-Australis available to date that canbe confirmed with Gaia data. Furthermore, we report on the discovery of an extended and more evolved populationof young stars beyond the region of the dark clouds, which was extensively surveyed in the past.
Accepted by A&A
http://arxiv.org/pdf/2001.05190

16

12 Angular momentum profiles of Class 0 protostellar envelopes

M. Gaudel1,2,3 , A. J. Maury1,4 , A. Belloche2 , S. Maret5 , Ph. André1 , P. Hennebelle1, M. Galametz1 ,L. Testi6 , S. Cabrit3 , P. Palmeirim7 , B. Ladjelate8 , C. Codella9 and L. Podio9

1

Laboratoire AIM, CEA Saclay/DRF/IRFU, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris
Cité, F-91191 Gif-sur-Yvette, France; 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn,
Germany; 3 LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Université
Paris 06, 75014 Paris, France; 4 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA; 5 Université
Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 6 ESO, Karl Schwarzschild Strasse 2, 85748 Garching bei
München, Germany; 7 Instituto de Astrofisica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas,
4150-762, Porto, Portugal; 8 Instituto Radioastronomia Milimétrica, Av. Divina Pastora 7, Nucleo Central, 18012,
Granada, Spain; 9 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
E-mail contact: mathilde.gaudel at obspm.fr
Understanding the initial properties of star forming material and how they affect the star formation process is a key
question. The infalling gas must redistribute most of its initial angular momentum inherited from prestellar cores
before reaching the central stellar embryo. Disk formation has been naturally considered as a possible solution to this"angular momentum problem". However, how the initial angular momentum of protostellar cores is distributed andevolves during the main accretion phase and the beginning of disk formation has largely remained unconstrained up
to now. In the framework of the IRAM CALYPSO survey, we obtained observations of the dense gas kinematics that
we used to quantify the amount and distribution of specific angular momentum at all scales in collapsing-rotating
Class 0 protostellar envelopes. We used the high dynamic range C18 O (2−1) and N2 H+ (1−0) datasets to produce
centroid velocity maps and probe the rotational motions in the sample of 12 envelopes from scales ∼50 to ∼5000 au.
We identify differential rotation motions at scales <1600 au in 11 out of the 12 protostellar envelopes of our sample
by measuring the velocity gradient along the equatorial axis, which we fit with a power-law model v ∝ rα . Thissuggests that coherent motions dominate the kinematics in the inner protostellar envelopes. The radial distributionsof specific angular momentum in the CALYPSO sample suggest the following two distinct regimes within protostellar
envelopes: the specific angular momentum decreases as j ∝ r1.6±0.2 down to ∼1600 au and then tends to become
relatively constant around ∼6 × 10−4 km s−1 pc down to ∼50 au. The values of specific angular momentum measured
in the inner Class 0 envelopes suggest that material directly involved in the star formation process (<1600 au) has a
specific angular momentum on the same order of magnitude as what is inferred in small T-Tauri disks. Thus, disk
formation appears to be a direct consequence of angular momentum conservation during the collapse. Our analysis
reveals a dispersion of the directions of velocity gradients at envelope scales >1600 au, suggesting that these gradients
may not be directly related to rotational motions of the envelopes. We conclude that the specific angular momentum
observed at these scales could find its origin in other mechanisms, such as core-forming motions (infall, turbulence),or trace an imprint of the initial conditions for the formation of protostellar cores.
Accepted by A&A
http://arxiv.org/pdf/2001.10004

13 What determines the formation and characteristics of protoplanetary discs?
Patrick Hennebelle1, Benoit Commerçon3 , Yueh-Ning Lee4,2,1 , and Sébastien Charnoz2
1

AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, F-91191 Gif-sur-Yvette,
France; 2 Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Universirté Paris Diderot, UMR 7154 CNRS,
F-75005 Paris, France; 3 Univ Lyon, Ens de Lyon, Univ Lyon1, CNRS, Centre de Recherche Astrophysique de Lyon
UMR5574, F-69007, Lyon, France; 4 Department of Earth Sciences, National Taiwan Normal University, 88, Sec. 4,
Ting-Chou Road, Taipei 11677, Taiwan
E-mail contact: patrick.hennebelle at cea.fr
Planets form in protoplanetary discs. Their masses, distribution, and orbits sensitively depend on the structure of the
protoplanetary discs. However, what sets the initial structure of the discs in terms of mass, radius and accretion rateis still unknown. We perform non-ideal MHD numerical simulations using the adaptive mesh refinement code Ramses,
of a collapsing, one solar mass, molecular core to study the disc formation and early, up to 100 kyr, evolution, paying
great attention to the impact of numerical resolution and accretion scheme. We found that while the mass of the17central object is almost independent of the numerical parameters such as the resolution and the accretion scheme onto
the sink particle, the disc mass, and to a lower extent its size, heavily depend on the accretion scheme, which we found,is itself resolution dependent. This implies that the accretion onto the star and through the disc are largely decoupled.
For a relatively large domain of initial conditions (except at low magnetisation), we found that the properties of thedisc do not change too significantly. In particular both the level of initial rotation and turbulence do not influence
the disc properties provide the core is sufficiently magnetized. After a short relaxation phase, the disc settles in astationary state. It then slowly grows in size but not in mass. The disc itself is weakly magnetized but its immediatesurrounding is on the contrary highly magnetized. Our results show that the disc properties directly depend on the
inner boundary condition, i.e. the accretion scheme onto the central object, suggesting that the disc mass is eventuallycontrolled by the small scale accretion process, possibly the star-disc interaction. Because of ambipolar diffusion andits significant resistivity, the disc diversity remains limited and except for low magnetisation, their properties are
weakly sensitive to initial conditions such as rotation and turbulence.
Accepted by A&A
http://arxiv.org/pdf/2001.00197

14 Survival of Primordial Planetary Atmospheres: Photodissociation Driven Mass Loss
Alex R. Howe1 , Fred C. Adams2,3 and Michael R. Meyer2

1

NASA Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771, USA; 2 Department of Astronomy,
University of Michigan, Ann Arbor, Michigan 48109, USA; 3 Department of Physics, University of Michigan, Ann
Arbor, Michigan 48109, USA
E-mail contact: alex.r.howe at nasa.gov
The most widely-studied mechanism of mass loss from extrasolar planets is photoevaporation via XUV ionization,
primarily in the context of highly irradiated planets. However, the lower energy regime of FUV dissociation of hydrogenmolecules can also theoretically drive atmospheric evaporation on low-mass planets because the dissociation energy ofhydrogen is an order of magnitude greater than the escape energy per proton from the gravity well of an Earth-sizedplanet. For temperate planets such as the early Earth, impact erosion is expected to dominate in the traditional
planetesimal accretion model, but it would be greatly reduced in pebble accretion scenarios, allowing other mass loss
processes to be major contributors. We apply the same prescription for photoionization to this photodissociation
mechanism and compare it to an analysis of other possible sources of mass loss in pebble accretion scenarios. We findthat energy-limited photodissociation could remove the hydrogen atmosphere of an early Earth analog over several
Gyr, though not over the shorter period of mass loss in Earth’s early history. Impact erosion could remove ∼2,300 barsof hydrogen if 1% of the planet’s mass is accreted as planetesimals, and these are dominant over all other mass loss
processes. Similar results apply to super-Earths and mini-Neptunes, which have only modestly greater escape energies.
This mechanism could also preferentially remove hydrogen from a planet’s primordial atmosphere, thereby leaving alarger abundance of primordial water compared to standard dry formation models. We discuss the implications ofthese results for models of rocky planet formation including Earth’s formation and the possible application of thisanalysis to mass loss from observed exoplanets.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/1912.08820

multi-frequency ALMA characterization of substructures in the GM Aur protoplan15 Aetary
diskJane Huang1 , Sean M. Andrews1 , Cornelis P. Dullemond2, Karin I. Öberg1 , Chunhua Qi1 et al.
1

Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, United States ofAmerica; 2 Zentrum für Astronomie, Heidelberg University, Albert Ueberle Str. 2, 69120 Heidelberg, Germany
E-mail contact: jane.huang at cfa.harvard.edu
The protoplanetary disk around the T Tauri star GM Aur was one of the first hypothesized to be in the midst of being
cleared out by a forming planet. As a result, GM Aur has had an outsized influence on our understanding of disk
structure and evolution. We present 1.1 and 2.1 mm ALMA continuum observations of the GM Aur disk at a resolution18

of ∼50 mas (∼8 au), as well as HCO+ J=3–2 observations at a resolution of ∼100 mas. The dust continuum shows at
least three rings atop faint, extended emission. Unresolved emission is detected at the center of the disk cavity at both
wavelengths, likely due to a combination of dust and free-free emission. Compared to the 1.1 mm image, the 2.1 mm
image shows a more pronounced “shoulder” near R ∼ 40 au, highlighting the utility of longer-wavelength observations
for characterizing disk substructures. The spectral index α features strong radial variations, with minima near theemission peaks and maxima near the gaps. While low spectral indices have often been ascribed to grain growth anddust trapping, the optical depth of GM Aur’s inner two emission rings renders their dust properties ambiguous. The
gaps and outer disk (R > 100 au) are optically thin at both wavelengths. Meanwhile, the HCO+ emission indicatesthat the gas cavity is more compact than the dust cavity traced by the millimeter continuum, similar to other disks
traditionally classified as “transitional.”
Accepted by ApJ
http://arxiv.org/pdf/2001.11040

16 The Evolutionary Status of Protostellar Clumps Hosting Class II Methanol Masers
B.M. Jones1 , G.A. Fuller1,2 , S.L. Breen3 , A. Avison1,2 , J.A. Green4 et al.

1

Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The School of Natural Sciences, The
University of Manchester, Manchester M13 9PL, UK; 2 UK ALMA Regional Centre Node, M13 9PL, UK; 3 Sydney
Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia; 4 CSIRO Astronomy
and Space Science, 26 Dick Perry Avenue, Kensington, WA 6151, Australia
E-mail contact: bethany.jones at manchester.ac.uk

The Methanol MultiBeam survey (MMB) provides the most complete sample of Galactic massive young stellar objects(MYSOs) hosting 6.7 GHz class II methanol masers. We characterise the properties of these maser sources using
dust emission detected by the Herschel Infrared Galactic Plane Survey (Hi-GAL) to assess their evolutionary state.
Associating 731 (73%) of MMB sources with compact emission at four Hi-GAL wavelengths, we derive clump propertiesand define the requirements of a MYSO to host a 6.7 GHz maser. The median far-infrared (FIR) mass and luminosity
are 630 M⊙ and 2500 L⊙ for sources on the near side of Galactic centre and 3200 M⊙ and 10000 L⊙ for more distantsources. The median luminosity-to-mass ratio is similar for both at ∼4.2 L⊙ M⊙ −1 . We identify an apparent minimum
70 µm luminosity required to sustain a methanol maser of a given luminosity (with L70 ≈ L6.7 0.6 ). The maser hostclumps have higher mass and higher FIR luminosities than the general Galactic population of protostellar MYSOs.
Using principal component analysis, we find 896 protostellar clumps satisfy the requirements to host a methanol
maser but lack a detection in the MMB. Finding a 70 µm flux density deficiency in these objects, we favour the
scenario in which these objects are evolved beyond the age where a luminous 6.7 GHz maser can be sustained. Finally,
segregation by association with secondary maser species identifies evolutionary differences within the population of
6.7 GHz sources.
Accepted by MNRAS
http://arxiv.org/pdf/2001.08449

17 Spiral arms and instability within the AFGL 4176 mm1 disc

K. G. Johnston1 , M. G. Hoare1 , H. Beuther2 , R. Kuiper3 , N. D. Kee4 , H. Linz2 , P. Boley5,6 , L. T.
Maud7 , A. Ahmadi2 and T. P. Robitaille8

1School of Physics & Astronomy, E.C. Stoner Building, The University of Leeds, Leeds, LS2 9JT, UK; 2 Max Planck
Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg, Germany; 3 Institute of Astronomy and Astrophysics,
Eberhard Karls University Tuebingen, Auf der Morgenstelle 10, D-72076 Tuebingen, Germany; 4 Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium; 5 Moscow Institute of Physics and Technology,
9 Institutskiy per., Dolgoprudny 141701, Russia; 6 Ural Federal University, 19 Mira st., Ekaterinburg 620075, Russia; 7 ESO Headquarters, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen, Germany; 8 Aperio Software,
Headingley Enterprise and Arts Centre, Bennett Road, Headingley, Leeds, LS6 3HN, UK
E-mail contact: k.g.johnston at leeds.ac.uk
We present high-resolution (30 mas or 130 au at 4.2 kpc) Atacama Large Millimeter/submillimeter Array observations19

at 1.2 mm of the disc around the forming O-type star AFGL 4176 mm1. The disc (AFGL 4176 mm1-main) has aradius of ∼1000 au and contains significant structure, most notably a spiral arm on its redshifted side. We fitted
the observed spiral with logarithmic and Archimedean spiral models. We find that both models can describe its
structure, but the Archimedean spiral with a varying pitch angle fits its morphology marginally better. As well as
signatures of rotation across the disc, we observe gas arcs in CH3 CN that connect to other millimetre continuum
sources in the field, supporting the picture of interactions within a small cluster around AFGL 4176 mm1-main. Using
local thermodynamic equilibrium modelling of the CH3 CN K-ladder, we determine the temperature and velocity field
across the disc, and thus produce a map of the Toomre stability parameter. Our results indicate that the outer disc isgravitationally unstable and has already fragmented or is likely to fragment in the future, possibly producing further
companions. These observations provide evidence that disc fragmentation is one possible pathway towards explaining
the high fraction of multiple systems around high-mass stars.
Accepted by Astronomy & Astrophysics Letters
https://doi.org/10.1051/0004-6361/201937154
http://arxiv.org/pdf/1911.09692

18 Photometric, kinematic and variability study in the young open cluster NGC 1960
Y.C. Joshi1 , J. Maurya1,2 , Ancy A. John1,3 , A. Panchal1 , Santosh Joshi1 , Brijesh Kumar1
1

Aryabhatta Research Institute of Observational Sciences (ARIES), Manora peak, Nainital - 263002, India; 2 School ofStudies in Physics and Astrophysics, Pandit Ravishankar Shukla University, Chattisgarh 492 010, India; 3 Pondicherry
University, R.V. Nagar, Kalapet, Puducherry - 605014, India
E-mail contact: yogesh at aries.res.in
We present a comprehensive photometric analysis of a young open cluster NGC 1960 (M36) along with the long-term
variability study of this cluster. Based on the kinematic data of Gaia DR2, the membership probabilities of 3871
stars are ascertained in the cluster field among which 262 stars are found to be cluster members. Considering thekinematic and trigonometric measurements of the cluster members, we estimate a mean cluster parallax of 0.86±0.05
mas and mean proper motions of µRA = −0.143 ± 0.008 mas yr−1 , µDec = −3.395 ± 0.008 mas yr−1 . We obtainbasic parameters of the cluster such as E(B − V ) = 0.24 ± 0.02 mag, log(Age/yr) = 7.44 ± 0.02, and distance =1.17±0.06 kpc. The mass function slope in the cluster for the stars in the mass range of 0.72–7.32 M⊙ is found to be
γ = −1.26 ± 0.19. We find that mass segregation is still taking place in the cluster which is yet to be dynamicallyrelaxed. This work also presents first high-precision variability survey in the central 13′ × 13′ among which 72 areperiodic variables. Among them, 59 are short-period (P < 1 day)and 13 are long-period (P > 1 day). The variable
stars have V magnitudes ranging between 9.1 to 19.4 mag and periods between 41 minutes to 10.74 days. On the basisof their locations in the H-R diagram, periods and characteristic light curves, the 20 periodic variables belong to thecluster. We classified them as 2 δ-Scuti, 3 γ-Dor, 2 slowly pulsating B stars, 5 rotational variables, 2 non-pulsating B
stars and 6 as miscellaneous variables.
Accepted by MNRAS
http://arxiv.org/pdf/2001.04068

19 Distortion of Magnetic Fields in Barnard 335
Ryo Kandori1 , Masao Saito2 , Motohide Tamura1,2,3 , Kohji Tomisaka2 , Tomoaki Matsumoto4 , Ryo
Tazaki5 , Tetsuya Nagata6 , Nobuhiko Kusakabe1 , Yasushi Nakajima7 , Jungmi Kwon3 , Takahiro
Nagayama8 and Ken’ichi Tatematsu2
1

Astrobiology Center of NINS, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan; 2 National Astronomical Observatoryof Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of Astronomy, The University of Tokyo,
7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan; 4 Faculty of Sustainability Studies, Hosei University, Fujimi,
Chiyoda-ku, Tokyo 102-8160; 5 Astronomical Institute, Graduate School of Science Tohoku University, 6-3 Aramaki,
Aoba-ku, Sendai 980-8578, Japan; 6 Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan;
7
Hitotsubashi University, 2-1 Naka, Kunitachi, Tokyo 186-8601, Japan; 8 Kagoshima University, 1-21-35 Korimoto,Kagoshima 890-0065, Japan20

E-mail contact: r.kandori at nao.ac.jp
In this study, the detailed magnetic field structure of the dense protostellar core Barnard 335 (B335) was revealed
based on near-infrared polarimetric observations of background stars to measure dichroically polarized light producedby magnetically aligned dust grains in the core. Magnetic fields pervading B335 were mapped using 24 stars after
subtracting unrelated ambient polarization components, for the first time revealing that they have an axisymmetricallydistorted hourglass-shaped structure toward the protostellar core. On the basis of simple two- and three-dimensional
magnetic field modeling, magnetic inclination angles in the plane-of-sky and line-of-sight directions were determined
to be 90◦ ± 7◦ and 50◦ ± 10◦, respectively. The total magnetic field strength of B335 was determined to be 30.2 ± 17.7
µG. The critical mass of B335, evaluated using both magnetic and thermal/turbulent support against collapse, wasdetermined to be Mcr = 3.37 ± 0.94 M⊙ , which is identical to the observed core mass of Mcore = 3.67 M⊙ . We thus
concluded that B335 started its contraction from a condition near equilibrium. We found a linear relationship in thepolarization versus extinction diagram, up to AV ∼ 15 mag toward the stars with the greatest obscuration, which
verified that our observations and analysis provide an accurate depiction of the core.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/2001.08542

of Irregular, Sub-mm Opaque Structures in the Orion Molecular Clouds:
20 Detection
Protostars within 10000 years of formation?
Nicole Karnath1,11 , S. T. Megeath1 , John J. Tobin2 , Ameila Stutz3,4 , Zhi-Yun Li5 , Patrick Sheehan2 ,Nick Reynolds6 , Sarah Sadavoy7 , Ian W. Stephens8 , Mayra Osorio9 , Guillem Anglada9 , Ana K. DiazRodriguez9 and Erin Cox10
1

Ritter Astrophysical Research Center, University of Toledo, 2801 W. Bancroft St, Toledo, OH 43606, USA; 2 National
Radio Astronomy Observatory, 520 Edgemont Rd Charlottesville, VA 22903, USA; 3 Departmento de Astronomia,
Facultad de Ciencias Fisicas y Mathematicas, Universidad de Concepcion, Concepcion, Chile; 4 Max-Planck-Institutefor Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany; 5 Department of Astronomy, University of Virginia, Charlottesville, VA 22903; 6 Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W.
Brooks St., Norman, OK 73019, USA; 7 Department of Physics, Engineering Physics, and Astronomy, Queen’s University, Kingston, ON K7L 3N6 Canada; 8 Harvard-Smithsonian Center for Astrophysics, 60 Garden St. Cambridge,
MA, USA; 9 Instituto de Astrofisica de Andalucia, CSIC, Glorieta de la Astronomia, s/n, 18008, Granada, Spain;
10
Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Department of Physics and Astronomy, Northwestern University, 2145 N. Sheridan Rd., Evanston, IL 60208, USA; 11 Sofia Science Center, USRA,
NASA Ames Research Center, Moffett Field, CA 94035, USA
E-mail contact: nkarnath at sofia.usra.edu
We report ALMA and VLA continuum observations that potentially identify the four youngest protostars in theOrion Molecular Clouds taken as part of the Orion VANDAM program. These are distinguished by bright, extended,
irregular emission at 0.87 and 8 mm and are optically thick at 0.87 mm. These structures are distinct from the disk orpoint-like morphologies seen toward the other Orion protostars. The 0.87 mm emission implies temperatures of 41-170
K, requiring internal heating. The bright 8 mm emission implies masses of 0.5 to 1.2 Msun assuming standard dust
opacity models. One source has a Class 0 companion, while another exhibits substructure indicating a companioncandidate. Three compact outflows are detected, two of which may be driven by companions, with dynamical times of?300 to ?1400 years. The slowest outflow may be driven by a first hydrostatic core. These protostars appear to trace
an early phase when the centers of collapsing fragments become optically thick to their own radiation and compression
raises the gas temperature. This phase is thought to accompany the formation of hydrostatic cores. A key question iswhether these structures are evolving on free fall times of ?100 years, or whether they are evolving on Kelvin-Helmholtz
times of several thousand years. The number of these sources imply a lifetime of ?6000 years, in closer agreement with
the Kelvin-Helmholtz time. In this case, rotational and/or magnetic support could be slowing the collapse.
Accepted by ApJ
https://arxiv.org/pdf/2001.04997.pdf

21

Instability and the Fragmentation of Star-Forming Clouds
21 AEricTurbulent-Entropic
Keto , George Field and Eric Blackman
1

2

3

1

Harvard University, Institute for Theory and Computation, 60 Garden St., Cambridge, MA 02138, USA; 2 Harvard University, Department of Astronomy, 60 Garden St., Cambridge, MA 02138, USA; 3 University of Rochester,
Department of Physics and Astronomy, Rochester, NY,14627-0171, USA
E-mail contact: eketo at cfa.harvard.edu
The kinetic energy of supersonic turbulence within interstellar clouds is subject to cooling by dissipation in shocks andsubsequent line radiation. The clouds are therefore susceptible to a condensation process controlled by the specificentropy. In a form analogous to the thermodynamic entropy, the entropy for supersonic turbulence is proportional to
the log of the product of the mean turbulent velocity and the size scale. We derive a dispersion relation for the growthof entropic instabilities in a spherical self-gravitating cloud and find that there is a critical maximum dissipation timescale, about equal to the crossing time, that allows for fragmentation and subsequent star formation. However, thetime scale for the loss of turbulent energy may be shorter or longer, for example with rapid thermal cooling or the
injection of mechanical energy. Differences in the time scale for energy loss in different star-forming regions may resultin differences in the outcome, for example, in the initial mass function.
Accepted by MNRAS
http://arxiv.org/pdf/2001.02678

Ionization of Planet-Opened Gaps in Protostellar Disks
22 X-RayS. Y. Kim
and N. J. Turner
1,2,3

4

1

California Institute of Technology; 2 Ohio State University; 3 University of Surrey, UK; 4 Jet Propulsion Laboratory,
California Institute of Technology
E-mail contact: neal.turner at jpl.nasa.gov
Young planets with masses approaching Jupiter’s have tides strong enough to clear gaps around their orbits in the
protostellar disk. Gas flow through the gaps regulates the planets’ further growth and governs the disks’ evolution.
Magnetic forces may drive that flow if the gas is sufficiently ionized to couple to the fields. We compute the ionizing
effects of the X-rays from the central young star, using Monte Carlo radiative transfer calculations to find the spectrumof Compton-scattered photons reaching the planet’s vicinity. The scattered X-rays ionize the gas at rates similar to or
greater than the interstellar cosmic ray rate near planets the mass of Saturn and of Jupiter, located at 5 au and at 10
au, in disks with the interstellar mass fraction of sub-micron dust and with the dust depleted a factor 100. Solving a
gas-grain recombination reaction network yields charged particle populations whose ability to carry currents is sufficient
to partly couple the magnetic fields to the gas around the planet. Most cases can undergo Hall shear instability, andsome can launch magneto-centrifugal winds. However the material on the planet’s orbit has diffusivities so large in all
the cases we examine, that magneto-rotational turbulence is prevented and the non-ideal terms govern the magnetic
field’s evolution. Thus the flow of gas in the gaps opened by the young giant planets depends crucially on the finite
conductivity.
Accepted by ApJ

https://arxiv.org/pdf/1804.04265

Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope
23 FOREST(FUGIN). VI. Dense gas and mini-starbursts in the W43 giant molecular cloud complex
Mikito Kohno1 , Kengo Tachihara1 , Kazufumi Torii2 , Shinji Fujita1 , Atsushi Nishimura1,3 , Nario
Kuno4,5 , Tomofumi Umemoto2,6 , Tetsuhiro Minamidani2,6,7, Mitsuhiro Matsuo2 , Ryosuke Kiridoshi3,
Kazuki Tokuda3,7 , Misaki Hanaoka1 , Yuya Tsuda8 , Mika Kuriki4 , Akio Ohama1 , Hidetoshi Sano1,9 ,Tetsuo Hasegawa7 , Yoshiaki Sofue10 , Asao Habe11 , Toshikazu Onishi3 and Yasuo Fukui1,91Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 4648602, Japan; 2 Nobeyama Radio Observatory, National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS), 462-2, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; 3 De-

22

partment of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku,
Sakai, Osaka 599-8531, Japan; 4 Department of Physics, Graduate School of Pure and Applied Sciences, University ofTsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8577, Japan; 5 Tomonaga Center for the History of the Universe, University of Tsukuba, Ten-nodai 1-1-1, Tsukuba, Ibaraki 305-8571, Japan; 6 Department of Astronomical Science, Schoolof Physical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1, Osawa, Mitaka, Tokyo 1818588, Japan; 7 National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS),
2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 8 Department of Physics, School of Science and Engineering, Meisei
University, 2-1-1 Hodokubo, Hino-shi, Tokyo 191-8506, Japan; 9 Institute for Advanced Research (IAR), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan; 10 Institute of Astronomy (IoA), The University of Tokyo,2-21-1, Osawa, Mitaka, Tokyo 181-0015, Japan; 11 Department of Physics, Faculty of Science, Hokkaido University,
Kita 10 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
E-mail contact: mikito at a.phys.nagoya-u.ac.jp
We performed new large-scale 12 CO, 13 CO, and C18 O J =1–0 observations of the W43 giant molecular cloud complex
in the tangential direction of the Scutum arm (l ∼ 30◦ ) as a part of the FUGIN project. The low-density gas traced
by 12 CO is distributed over 150 pc × 100 pc (l × b), and has a large velocity dispersion (20-30 km s−1 ). However, thedense gas traced by C18 O is localized in the W43 Main, G30.5, and W43 South (G29.96-0.02) high-mass star-forming
regions in the W43 GMC complex, which have clumpy structures. We found at least two clouds with a velocity
difference of ∼ 10-20 km s−1 , both of which are likely to be physically associated with these high-mass star-forming
regions based on the results of high 13 CO J = 3-2 to J = 1-0 intensity ratio and morphological correspondence with
the infrared dust emission. The velocity separation of these clouds in W43 Main, G30.5, and W43 South is too large
for each cloud to be gravitationally bound. We also revealed that the dense gas in the W43 GMC has a high local
column density, while "the current SFE" of entire the GMC is low (∼ 4%) compared with the W51 and M17 GMC.
We argue that the supersonic cloud-cloud collision hypothesis can explain the origin of the local mini-starbursts anddense gas formation in the W43 GMC complex.
Accepted by PASJ
https://arxiv.org/pdf/2001.10693

24 Dispersal of protoplanetary disks by the combination of magnetically driven and photoevaporative winds

Masanobu Kunitomo1 , Takeru K. Suzuki2 and Shu-ichiro Inutsuka3
1

Department of Physics, School of Medicine, Kurume University, 67 Asahimachi, Kurume, Fukuoka 830-0011, Japan;
School of Arts & Sciences, The University of Tokyo, 3-8-1, Komaba, Meguro, Tokyo 153-8902, Japan; 3 Departmentof Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan2

E-mail contact: kunitomo.masanobu at gmail.com
We investigate the roles of magnetically driven disk wind (MDW) and thermally driven photoevaporative wind (PEW)in the long-time evolution of protoplanetary disks. We start simulations from the early phase in which the disk mass is0.118 M⊙ around a 1 M⊙ star and track the evolution until the disk is completely dispersed. We incorporate the massloss by PEW and the mass loss and magnetic braking (wind torque) by MDW, in addition to the viscous accretion,
viscous heating, and stellar irradiation. We find that MDW and PEW respectively have different roles: magneticallydriven wind ejects materials from an inner disk in the early phase, whereas photoevaporation has a dominant role in
the late phase in the outer (>∼1au) disk. The disk lifetime, which depends on the combination of MDW, PEW, andviscous accretion, shows a large variation of ∼1–20Myr; the gas is dispersed mainly by the MDW and the PEW in
the cases with a low viscosity and the lifetime is sensitive to the mass-loss rate and torque of the MDW, whereas the
lifetime is insensitive to these parameters when the viscosity is high. Even in disks with very weak turbulence, thecooperation of MDW and PEW enables the disk dispersal within a few Myr.
Accepted by MNRAS
http://arxiv.org/pdf/2001.03949

23

25 The Herschel view of the dense core population in the Ophiuchus molecular cloudBilal Ladjelate1,2 , Philippe André2 , Vera Könyves2,3 , Derek Ward-Thompson3 , Alexander
Men’shchikov2 , Andrea Bracco4 , Pedro Palmeirim5 , Arabindo Roy2 , Yoshito Shimajiri6,7 , Jason M.
Kirk3 , Doris Arzoumanian5 , Milena Benedettini8 , James Di Francesco9 , Eleonora Fiorellino12,13,14,
Nicola Schneider10,11 and Stefano Pezzuto7
1Instituto de Radioastronomía Milimétrica, IRAM, Avenida Divina Pastora 7, Local 20, 18012, Granada, Spain; 2Laboratoire d’Astrophysique (AIM), CEA/DRF, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne
Paris Cité, 91191 Gif-sur-Yvette, France; 3 Jeremiah Horrocks Institute, University of Central Lancashire, Preston,
Lancashire, PR1 2HE, UK; 4 Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS,
Sorbonne Université, Université de Paris, Paris, France; 5 Instituto de Astrofísica e Ciências do Espaço, Universidade
do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal; 6 Department of Physics and Astronomy, Graduate
School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan;
7
National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan; 8 INAF - Istituto di
Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, I-00133 Roma, Italy; 9 National Research Councilof Canada, Herzberg Astronomy & Astrophysics Research Centre, 5071 West Saanich Road Victoria, BC V9E 2E7,
Canada; 10 I. Physik. Institut, University of Cologne, 50937, Cologne, Germany; 11 Laboratoire d’Astrophysique de
Bordeaux, CNRS/INSU, Université de Bordeaux, UMR, 5804, France; 12 Dipartimento di Fisica, Universit di Roma‘Tor Vergata’ Via della Ricerca Scientifica 1, 00133, Roma, Italy; 13 INAF-Osservatorio Astronomico di Roma, via
di Frascati 33, 00078, Monte Porzio Catone, Italy; 14 European Southern Observatory, Karl-Schwarzschild-Strasse 2,85748 Garching bei München, Germany
E-mail contact: ladjelate at iram.es
Context. Herschel observations of nearby clouds in the Gould Belt support a paradigm for low-mass star formation,
starting with the generation of molecular filaments, followed by filament fragmentation, and the concentration of massinto self-gravitating prestellar cores.
In the case of the Ophiuchus molecular complex, a rich star formation activity has been documented for many years
inside the clumps of L1688, the main and densest cloud of the complex, and in the more quiescent twin cloud L1689
thanks to extensive surveys at infrared and other wavelengths.
Aims. With the unique far-infrared and submillimeter continuum imaging capabilities of the Herschel Space observatory, the closeby (d = 139 pc) Ophiuchus cloud was extensively mapped at five wavelengths from 70 µm to 500 µm
with the aim of providing a complete census of dense cores in this region, including unbound starless cores, boundprestellar cores, and protostellar cores.
Methods. Taking full advantage of the high dynamic range and multi-wavelength nature of the Herschel data, we used
the multi-scale decomposition algorithms getsources and getfilaments to identify an essentially complete sample ofdense cores and filaments in the cloud and study their properties.
Results. The densest clouds of the Ophiuchus complex, L1688 and L1689, which thus far are only indirectly describedas filamentary regions owing to the spatial distribution of their young stellar objects (YSOs), are now confirmed to be
dominated by filamentary structures. The tight correlation observed between prestellar cores and filamentary structures in L1688 and L1689 supports the view that solar-type star formation occurs primarily in dense filaments.
While the sub clouds of the complex show some disparities, L1689 being apparently less efficient than L1688 at forming stars when considering their total mass budgets, both sub clouds share almost the same prestellar core formation
efficiency in dense molecular gas. We also find evidence in the Herschel data for a remarkable concentric geometricalconfiguration in L1688 which is dominated by up to three arc-like compression fronts and presumably created byshockwave events emanating from the Sco OB2 association, including the neighboring massive (O9V) star σ Sco.
Conclusions. Our Herschel study of the well-documented Ophiuchus region has allowed us to further analyze theinfluence of several early-type (OB) stars surrounding the complex, thus providing positive feedback and enhancing
star formation activity in the dense central part of the region, L1688.
Accepted by A&A
https://arxiv.org/pdf/2001.11036.pdf

24

26 Physical and chemical modeling of a starless core: L1512
Sheng-Jun Lin1 , Laurent Pagani2 , Shih-Ping Lai1 , Charlène Lefèvre3 and François Lique4
1

Institute of Astronomy, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu 30013, Taiwan; 2
LERMA & UMR8112 du CNRS, Observatoire de Paris, PSL University, Sorbonne Universités, CNRS, F-75014 Paris,
France; 3 Institut de Radioastronomie Millimétrique (IRAM), 300 rue de la Piscine, 38400 Saint-Martin d’Hères,France; 4 LOMC - UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, 76063, Le Havre, France
E-mail contact: sj.lin at gapp.nthu.edu.tw
The deuterium fractionation in starless cores gives us a clue to estimate their lifetime scales, thus allowing us todistinguish between different dynamical theories of core formation. Cores also seem to be subject to a differential
N2 and CO depletion which was not expected from models. We aim to make a survey of 10 cores to estimate their
lifetime scales and depletion profiles in detail. After L183, in Serpens, we present the second cloud of the series, L1512
in Auriga. To constrain the lifetime scale, we perform chemical modeling of the deuteration profiles across L1512
based on dust extinction measurements from near-infrared observations and non-local thermal equilibrium radiativetransfer with multiple line observations of N2 H+ , N2 D+ , DCO+ , C18 O, and 13 CO, plus H2 D+ (110 –111 ). We finda peak density of 1.1×105 cm−3 and a central temperature of 7.5±1 K, which are respectively higher and lower+2
compared with previous dust emission studies. The depletion factors of N2 H+ and N2 D+ are 27+17−13 and 4−1 in L1512,
intermediate between the two other more advanced and denser starless core cases, L183 and L1544. These factors also
indicate a similar freeze-out of N2 in L1512, compared to the two others despite a peak density one to two orders ofmagnitude lower. Retrieving CO and N2 abundance profiles with the chemical model, we find that CO has a depletion
factor of ∼430–870 and the N2 profile is similar to that of CO unlike towards L183. Therefore, L1512 has probably
been living long enough so that N2 chemistry has reached steady state. N2 H+ modeling remains compulsory to assess
the precise physical conditions in the center of cold starless cores, rather than dust emission. L1512 is presumably older
than 1.4 Myr. Therefore, the dominating core formation mechanism should be ambipolar diffusion for this source.
Accepted by A&A
https://arxiv.org/pdf/2002.01346.pdf

27 VVV-WIT-01: highly obscured classical nova or protostellar collision?

P. W. Lucas1 , D. Minniti2,3,4 , A. Kamble5 , D. L. Kaplan6 , N. Cross7 , I. Dekany8 , V. D. Ivanov9 , R.
Kurtev2,10 , R.K. Saito11 , L.C. Smith12 , M. Catelan2,13 , N. Masetti14,3 , I. Toledo15 , M. Hempel3, M.A.
Thompson1 , C. Contreras Peña16 , J. Forbrich1 , M. Krause1 , J. Dale1 , J. Borissova2,10 and J. Emerson17

1

Centre for Astrophysics, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK; 2 Millennium Instituteof Astrophysics, Av. Vicuna Mackenna 4860, 782-0436, Macul, Santiago, Chile; 3 Departamento de Ciencias Físicas,
Universidad Andrés Bello, Fernández Concha 700, Las Condes, Santiago, Chile; 4 Vatican Observatory, V00120 Vatican
City State, Italy; 5 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA; 6 Center
for Gravitation, Cosmology and Astrophysics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201,
USA; 7 Wide-Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford
Hill, Edinburgh EH9 3HJ, UK; 8 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg,
Mönchhofstr. 12-14, D-69120 Heidelberg, Germany; 9 European Southern Observatory, Karl-Schwarszchild-Str 2, D85748 Garching bei Muenchen, Germany; 10 Instituto de Física y Astronomía, Universidad de Valparaíso, ave. Gran
Bretaña, 1111, Casilla 5030, Valparaíso, Chile; 11 Departamento de Física, Universidade Federal de Santa Catarina,
Trindade 88040-900, Florianopolis, SC, Brazil; 12 Institute of Astronomy, University of Cambridge, Madingley Road,
Cambridge, CB3 0HA, UK; 13 Instituto de Astrofisica, Pontificia Universidad Catolica de Chile, Av. Vicuna Mackenna
4860, 7820436 Macul, Santiago, Chile; 14 INAF - Osservatorio di Astrofisica e Scienza dello Spazio, via Gobetti 93/3, I40129 Bologna, Italy; 15 ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile; 16 School of Physics,
University of Exeter, Stocker Road, Exeter, EX4 4QL, UK; 17 Astronomy Unit, School of Physics and Astronomy,
Queen Mary University of London, Mile End Road, London, E1 4NS, UK
E-mail contact: p.w.lucas at herts.ac.uk
A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally
red transient VVV-WIT-01 (H − Ks = 5.2). It peaked before March 2010, then faded by ∼9.5 mag over the following
two years. The 1.6–22 µm spectral energy distribution in March 2010 was well fit by a highly obscured black body25

with T ∼ 1000 K and AKs ∼ 6.6 mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC
G331.062−0.294. The chance projection probability is small for any single event (p ≈ 0.01 to 0.02) which suggests
a physical association, e.g. a collision between low mass protostars. However, black body emission at T ∼ 1000 K
is common in classical novae (especially CO novae) at the infrared peak in the light curve, due to condensationof dust ∼30–60 days after the explosion. Radio follow up with the Australia Telescope Compact Array (ATCA)
detected a fading continuum source with properties consistent with a classical nova but probably inconsistent withcolliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises
the probability of a chance association to p = 0.13 to 0.24. After weighing several options, it appears likely that
VVV-WIT-01 was a classical nova event located behind an IRDC.
Accepted by MNRAS
https://arxiv.org/pdf/2001.05536.pdf

ALMA-PILS survey: Inventory of complex organic molecules towards IRAS
28 The16293−2422 A
S. Manigand1 , J.K. Jørgensen1 , H. Calcutt2 , H.S.P. Müller3 , N.F.W. Ligterink4 et al.
1

Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen, Ø]ster Voldgade 5–7, DK1350 Copenhagen K., Denmark; 2 Department of Space, Earth and Environment, Chalmers University of Technology,
41296, Gothenburg, Sweden; 3 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany;
4
Center for Space and Habitability (CSH), University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
E-mail contact: sebastien at nbi.ku.dk
Complex organic molecules (COM) are detected in many sources in the warm inner regions of envelopes surrounding
deeply embedded protostars. Exactly how these COM form remains an open question. This study aims to constrain
the formation of complex organic molecules through comparisons of their abundances towards the Class 0 protostellar
binary IRAS 16293−2422 (IRAS16293). We utilised observations from the ALMA Protostellar Interferometric Line
Survey of IRAS16293. The species identification and the rotational temperature and column density estimation were
derived by fitting the extracted spectra towards IRAS16293 A and IRAS16293 B with synthetic spectra. The majorityof the work in this paper pertains to the analysis of IRAS16293 A for a comparison with the results from the other binary
component, which have already been published. We detect 15 different COM, as well as 16 isotopologues towards themost luminous companion protostar IRAS16293 A. Tentative detections of an additional 11 isotopologues are reported.
We also searched for and report on the first detections of CH3 OCH2 OH and t-C2 H5 OCH3 towards IRAS16293 B andthe follow-up detection of CH2 DCHO and CH3 CDO. Twenty-four lines of CHD2 OH are also identified. The comparison
between the two protostars of the binary system shows significant differences in abundance for some of the species,
which are partially correlated to their spatial distribution. The spatial distribution is consistent with the sublimation
temperature of the species; those with higher expected sublimation temperatures are located in the most compact
region of the hot corino towards IRAS16293 A. This spatial differentiation is not resolved in IRAS16293 B and will
require observations at a higher angular resolution. In parallel, the list of identified CHD2 OH lines shows the need ofaccurate spectroscopic data including their line strength.
Accepted by A&A
http://arxiv.org/pdf/2001.06400

for kinematic evidence of Keplerian disks around Class 0 protostars with
29 Searching
CALYPSO
S. Maret1 , A. J. Maury2 , A. Belloche3 , M. Gaudel2 , Ph. André2 , S. Cabrit4 , C. Codella1,5, C. Lefèvre6 ,L. Podio5 , S. Anderl1 , F. Gueth6 and P. Hennebelle2
1

Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France; 3 Max-Planck-Institut für Radioastronomie, Auf
dem Hügel 69, 53121 Bonn; 4 LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université,
UPMC Université Paris 06, 75014 Paris, France; 5 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125
Firenze, Italy; 6 Institut de Radioastronomie Millimétrique (IRAM), 38406 Saint-Martin-d’Hères, France26

E-mail contact: sebastien.maret at univ-grenoble-alpes.fr
The formation of protoplanetary disks is not well understood. To understand how and when these disks are formed,
it is crucial to characterize the kinematics of the youngest protostars at a high angular resolution. Here we study asample of 16 Class 0 protostars to measure their rotation profile at scales from 50 to 500 au and search for Keplerianrotation. We used high-angular-resolution line observations obtained with the Plateau de Bure Interferometer as partof the CALYPSO large program. From 13 CO (J = 2 − 1), C18 O (J = 2 − 1) and SO (Nj = 56 − 45 ) moment maps, wefind that seven sources show rotation about the jet axis at a few hundred au scales: SerpS-MM18, L1448-C, L1448-NB,
L1527, NGC1333- IRAS2A, NGC1333-IRAS4B, and SVS13-B. We analyzed the kinematics of these sources in the uv
plane to derive the rotation profiles down to 50 au scales. We find evidence for Keplerian rotation in only two sources,
L1527 and L1448-C. Overall, this suggests that Keplerian disks larger than 50 au are uncommon around Class 0
protostars. However, in some of the sources, the line emission could be optically thick and dominated by the envelope
emission. Due to the optical thickness of these envelopes, some of the disks could have remained undetected in ourobservations.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2001.06355

for the onset of self-gravitation and star formation in molecular gas governed
30 Abymodel
galactic forces: II. the bottleneck to collapse set by cloud-environment decoupling
Sharon E. Meidt1,2 , Simon C.O. Glover3 , J.M. Diederik Kruijssen4 , Adam K. Leroy5 , Erik Rosolowsky6
et al.
1

Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 2 Sterrenkundig Observatorium,
Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium; 3 Institut für theoretische Astrophysik, Zentrum fürAstronomie der Universität Heidelberg, Albert-Ueberle Str. 2, D-69120 Hei- delberg, Germany; 4 Astronomisches
Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany; 5 Department of Astronomy, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210, USA; 6
Department of Physics, University of Alberta, Edmonton, AB, Canada
E-mail contact: shmeidt at gmail.com
In Meidt et al. (2018), we showed that gas kinematics on the scale of individual molecular clouds are not dominatedby self-gravity but also track a component that originates with orbital motion in the potential of the host galaxy.
This agrees with observed cloud line widths, which show systematic variations from virial motions with environment,
pointing at the influence of the galaxy potential. In this paper, we hypothesize that these motions act to slow down
the collapse of gas and so help regulate star formation. Extending the results of Meidt et al. (2018), we derive adynamical collapse timescale that approaches the free-fall time only once the gas has fully decoupled from the galactic
potential. Using this timescale we make predictions for how the fraction of free-falling, strongly self-gravitating gas
varies throughout the disks of star-forming galaxies. We also use this collapse timescale to predict variations in themolecular gas star formation efficiency, which is lowered from a maximum, feedback-regulated level in the presence ofstrong coupling to the galactic potential. Our model implies that gas can only decouple from the galaxy to collapse
and efficiently form stars deep within clouds. We show that this naturally explains the observed drop in star formation
rate per unit gas mass in the Milky Way’s CMZ and other galaxy centers. The model for a galactic bottleneck tostar formation also agrees well with resolved observations of dense gas and star formation in galaxy disks and theproperties of local clouds.
Accepted by ApJ
http://arxiv.org/pdf/2001.07459

formation around M dwarfs via disc instability
31 Planet
Anthony Mercer and Dimitris Stamatellos
111

Jeremiah Horrocks Institute for Mathematics, Physics & Astronomy, University of Central Lancashire, Preston, PR1
2HE, UK
E-mail contact: dstamatellos at uclan.ac.uk
27

Context: Around 30 per cent of the observed exoplanets that orbit M dwarf stars are gas giants that are more massive
than Jupiter. These planets are prime candidates for formation by disc instability.
Aims: We want to determine the conditions for disc fragmentation around M dwarfs and the properties of the planetsthat are formed by disc instability.
Methods: We performed hydrodynamic simulations of M dwarf protostellar discs in order to determine the minimum
disc mass required for gravitational fragmentation to occur. Different stellar masses, disc radii, and metallicities wereconsidered. The mass of each protostellar disc was steadily increased until the disc fragmented and a protoplanet wasformed.
Results: We find that a disc-to-star mass ratio between ∼ 0.3 and ∼ 0.6 is required for fragmentation to happen. The
minimum mass at which a disc fragments increases with the stellar mass and the disc size. Metallicity does not significantly affect the minimum disc fragmentation mass but high metallicity may suppress fragmentation. Protoplanets
form quickly (within a few thousand years) at distances around ∼ 50 AU from the host star, and they are initiallyvery hot; their centres have temperatures similar to the ones expected at the accretion shocks around planets formedby core accretion (up to 12,000 K). The final properties of these planets (e.g. mass and orbital radius) are determinedthrough long-term disc-planet or planet-planet interactions.
Conclusions: Disc instability is a plausible way to form gas giant planets around M dwarfs provided that discs haveat least 30% the mass of their host stars during the initial stages of their formation. Future observations of massive
M dwarf discs or planets around very young M dwarfs are required to establish the importance of disc instability forplanet formation around low-mass stars.
Accepted by Astronomy & Astrophysics
https://www.aanda.org/articles/aa/pdf/2020/01/aa36954-19.pdf
http://arxiv.org/pdf/2001.10062

hybrid radiative transfer method for massive star formation
32 AR. new
Mignon-Risse , M. González , B. Commerçon , and J. Rosdahl
1

1

2

3

1

AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, F-91191 Gif-sur-Yvette,
France; 2 Centre de Recherche Astrophysique de Lyon UMR5574, ENS de Lyon, Univ. Lyon1, CNRS, Université deLyon, 69007 Lyon, France; 3 Univ Lyon, Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique deLyon UMR5574, F-69230, Saint-Genis- Laval, France
E-mail contact: raphael.mignon-risse at cea.fr
Frequency-dependent/hybrid approaches for stellar irradiation are of primary importance in numerical simulations ofmassive star formation. We seek to compare outflow and accretion mechanisms in star formation simulations. We
investigate the accuracy of a hybrid radiative transfer method using the gray M1 closure relation for proto-stellar
irradiation and gray flux-limited diffusion (FLD) for photons emitted everywhere else. We have coupled the FLD
module of the adaptive-mesh refinement code Ramses with Ramses-RT, which is based on the M1 closure relation.
Our hybrid (M1+FLD) method takes an average opacity at the stellar temperature for the M1 module, instead of thelocal environmental radiation field. We have tested this approach in radiative transfer tests of disks irradiated by astar for three levels of optical thickness and compared the temperature structure with RADMC-3D and MCFOST. We
applied it to a radiation-hydrodynamical simulation of massive star formation. Our tests validate our hybrid approachfor determining the temperature structure of an irradiated disk in the optically-thin and moderately optically-thickregimes and the most optically-thick test shows the limitation of our approach. The optically-thick setups highlightthe ability of the hybrid method to partially capture the self-shielding in the disk while the FLD cannot. The radiative
acceleration is 100 times greater with the hybrid method. It consistently leads to about +50% more extended andwider-angle radiative outflows in the massive star formation simulation. We obtain a 17.6 M⊙ at t ≈ 0.7τrmf f , while
the accretion phase is ongoing. Finally, despite the use of refinement to resolve the radiative cavities, no RayleighTaylor instability appears in our simulations, and we justify their absence by physical arguments based on the entropy
gradient.
Accepted by A&A
http://arxiv.org/pdf/2001.10886

28

33 APEX observations of ortho-H D towards dense cores in the Orion B9 filament
2+

Oskari Miettinen1
1

Academy of Finland, Hakaniemenranta 6, P.O. Box 131, FI-00531 Helsinki, FinlandE-mail contact: oskari.miettinen at aka.fi
Context. Initial conditions and very early stages of star formation can be probed through spectroscopic observationsof deuterated molecular species.
Aims. We aim to determine the ortho-H2 D+ properties (e.g. column density and fractional abundance with respect toH2 ) in a sample of dense cores in the Orion B9 star-forming filament, and to compare those with the previously determined source characteristics, in particular with the gas kinetic temperature, [N2 D+ ]/[N2 H+ ] deuterium fractionation,and level of CO depletion.
Methods. We used the Atacama Pathfinder EXperiment (APEX) telescope to observe the 372 GHz o-H2 D+ (JKa , Kc =11, 0 − 11, 1 ) line towards three prestellar cores and three protostellar cores in Orion B9. We also employed our previous
APEX observations of C17 O, C18 O, N2 H+ , and N2 D+ line emission, and 870 µm dust continuum emission towards
the target sources.
Results. The o-H2 D+ (11, 0 ?11, 1 ) line was detected in all three prestellar cores, but in only one of the protostellar
cores. The corresponding o-H2 D+ abundances were derived to be ∼ (12 − 30) × 10?11 and ∼ 6 × 10?11 . Two additional
spectral lines, DCO+ (5 − 4) and N2 H+ (4 − 3), were detected in the observed frequency bands with high detection ratesof 100% and 83%, respectively. We did not find any significant correlations among the explored parameters, although
our results are mostly consistent with theoretical expectations. Also, the Orion B9 cores were found to be consistent
with the relationship between the o-H2 D+ abundance and gas temperature obeyed by other low-mass dense cores.
The o-H2 D+ abundance was found to decrease as the core evolves.
Conclusions. The o-H2 D+ abundances in the Orion B9 cores are in line with those found in other low-mass dense
cores and larger than derived for high-mass star-forming regions. The higher o-H2 D+ abundance in prestellar corescompared to that in cores hosting protostars is to be expected from chemical reactions where higher concentrationsof gas-phase CO and elevated gas temperature accelerate the destruction of H2 D+ . The validity of using the [oH2 D+ ]/[N2 D+ ] abundance ratio as an evolutionary indicator, which has been proposed for massive clumps, remains
to be determined when applied to these target cores. Similarly, the behaviour of the [o-H2 D+ ]/[DCO+ ] ratio as thesource evolves was found to be ambiguous. Still larger samples and observations of additional deuterated species areneeded to explore these potential evolutionary indicators further. The low radial velocity of the line emission from oneof the targeted prestellar cores, SMM 7 (∼ 3.6 km s−1 versus the systemic Orion B9 velocity of ∼ 9 km s−1 ), suggeststhat it is a chance superposition seen towards Orion B9. Overall, as located in a dynamic environment of the Orion
B molecular cloud, the Orion B9 filament provides an interesting target system to investigate the deuterium-based
chemistry, and further observations of species like para-H2 D+ and D2 H+ would be of particular interest.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2001.04075.pdf

34 COBRaS: The e-MERLIN 21 cm Legacy survey of Cygnus OB2

J.C. Morford1 , D.M. Fenech2 , R.K. Prinja1 , R. Blomme3 , J.A. Yates1 et al.

1

Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK; 2 Astrophysics Group, Cavendish Laboratory, University of Cambridge, UK; 3 Royal Observatory of Belgium, Ringlaan 3,1180 Brussel, Belgium
E-mail contact: dmfd2 at cam.ac.uk
The role of massive stars is central to an understanding of galactic ecology. It is important to establish the detailsof how massive stars provide radiative, chemical, and mechanical feedback in galaxies. Central to these issues is anunderstanding of the evolution of massive stars, and the critical role of mass loss via strongly structured winds andstellar binarity. Ultimately, massive stellar clusters shape the structure and energetics of galaxies. We aim to conduct
high-resolution, deep field mapping at 21 cm of the core of the massive Cygnus OB2 association and to characterise
the properties of the massive stars and colliding winds at this waveband. We used seven stations of the e-MERLIN
radio facility, with its upgraded bandwidth and enhanced sensitivity to conduct a 21 cm census of Cygnus OB2. Based29

on 42 hours of observations, seven overlapping pointings were employed over multiple epochs during 2014 resulting
in 1σ sensitivities down to ∼21 µJy and a resolution of ∼180 mas. A total of 61 sources are detected at 21cm overa ∼0.48◦ × 0.48◦ region centred on the heart of the Cyg OB2 association. Of these 61 sources, 33 are detected forthe first time. We detect a number of previously identified sources including four massive stellar binary systems,
two YSOs, and several known X-ray and radio sources. We also detect the LBV candidate (possible binary system)
and blue hypergiant (BHG) star of Cyg OB2 #12. The 21cm observations secured in the COBRaS Legacy projectprovide data to constrain conditions in the outer wind regions of massive stars; determine the non-thermal propertiesof massive interacting binaries; examine evidence for transient sources, including those associated with young stellar
objects; and provide unidentified sources that merit follow-up observations. The 21cm data are of lasting value andwill serve in combination with other key surveys of Cyg OB2.
Accepted by A&A
http://arxiv.org/pdf/2001.06363

localised deviations from Keplerian rotation in the DSHARP circumstellar disks:
35 NineKinematic evidence for protoplanets carving the gaps
C. Pinte1,2 , D.J. Price1 , F. Ménard2 , G. Duchêne3,2 , V. Christiaens1 et al.
1

School of Physics and Astronomy, Monash University, Clayton Vic 3800, Australia; 2 Univ. Grenoble Alpes, CNRS,
IPAG, F-38000 Grenoble, France. 3 Astronomy Department, University of California, Berkeley, CA 94720-3411, USA
E-mail contact: christophe.pinte at monash.edu
We present evidence for localised deviations from Keplerian rotation, i.e., velocity “kinks”, in 8 of 18 circumstellar
disks observed by the DSHARP program: DoAr 25, Elias 2-27, GW Lup, HD 143006, HD 163296, IM Lup, Sz 129
and WaOph 6. Most of the kinks are detected over a small range in both radial extent and velocity, suggesting aplanetary origin, but for some of them foreground contamination prevents us from measuring their spatial and velocity
extent. Because of the DSHARP limited spectral resolution and signal-to-noise in the 12 CO J=2–1 line, as well as
cloud contamination, the kinks are usually detected in only one spectral channel, and will require confirmation. The
strongest circumstantial evidence for protoplanets in the absence of higher spectral resolution data and additional
tracers is that, upon deprojection, we find that all of the candidate planets lie within a gap and/or at the end ofa spiral detected in dust continuum emission. This suggests that a significant fraction of the dust gaps and spirals
observed by ALMA in disks are caused by embedded protoplanets.
Accepted by ApJL
http://arxiv.org/pdf/2001.07720

36 M

dust –M⋆ Relation Hints at the Origin of Particle Traps in Protoplanetary Disks

Paola Pinilla1 , Ilaria Pascucci2,3 , and Sebastian Marino1
1

Max-Planck-Institut für Astronomie, Königstuhl 17, 69117, Heidelberg, Germany; 2 Lunar and Planetary Laboratory,
The University of Arizona, Tucson, AZ 85721, USA; 3 Earths in Other Solar Systems Team, NASA Nexus for Exoplanet
System ScienceE-mail contact: pinilla at mpia.de
Demographic surveys of protoplanetary disks, mainly with ALMA, have provided access to a large range of disk dust
masses (Mdust ) around stars with different stellar types and for different star-forming regions. These surveys found a
linear relation in logarithmic scale between Mdust and M⋆ that steepens with time, but that is flatter for transition
disks (TDs). We perform dust evolution models and include perturbations to the gas surface density with different
amplitudes to investigate the effect of particle trapping on the Mdust –M⋆ relation. These perturbations aim to mimicpressure bumps originated by planets. We focus on the effect caused by different stellar and disk masses because
exoplanet statistics show a dependence of planet mass with stellar mass and metallicity. We find that models of
dust evolution can reproduced the observed Mdust –M⋆ relation in different star-forming regions when strong pressure
bumps are included and when the disk mass scales with stellar mass (case of Mdust = 0.05 M⋆ in our models). This
result arises from dust trapping and dust growth beyond centimeter-size grains inside pressure bumps. However, theflatter relation of Mdust –M⋆ for TDs and disks with substructures cannot be reproduced by the models, unless the30formation of boulders is inhibited inside pressure bumps. In the context of planets originating pressure bumps, ourresults agree with the current exoplanet statistics about giant planet occurrence increasing with stellar mass, but wecannot conclude about the type of planets needed in the case of low mass stars. This is because for M⋆ < 1 M⊙ , theobserved Mdust obtained from models is very low due to the efficient growth of dust particles beyond centimeter sizes(boulders) inside pressure bumps.
Accepted by A&A
http://arxiv.org/pdf/2001.11045

of feedback of massive stars in the fragmentation, distribution, and kinematics of
37 Effect
the gas in two star forming regions in the Carina NebulaDavid Rebolledo1,2, Andrés E. Guzmán3 , Yanett Contreras4 , Guido Garay5 , S.-N.X. Medina6 et al.
1

Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 2 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA; 3 National Astronomical Observatory of Japan, National
Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 Leiden Observatory, Leiden University,
PO Box 9513, NL-2300 RA Leiden, the Netherlands; 5 Departamento de Astronomía, Universidad de Chile, Santiago,
Chile 6 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
E-mail contact: david.rebolledo at alma.cl
We present ALMA high spatial resolution observations towards two star forming regions located in one of the mostextreme zones of star formation in the Galaxy, the Carina Nebula. One region is located at the center of the nebulaand is severally affected by the stellar feedback from high-mass stars, while the other region is located further south
and is less disturbed by the massive star clusters. We found that the region at the center of the nebula is forming lessbut more massive cores than the region located in the south, suggesting that the level of stellar feedback effectively
influence the fragmentation process in clumps. Lines such as HCN, HCO+ and SiO show abundant and complex gas
distributions in both regions, confirming the presence of ionization and shock fronts. Jeans analysis suggests thatthe observed core masses in the region less affected by the massive stars are consistent with thermal fragmentation,
but turbulent Jeans fragmentation might explain the high masses of the cores identified in the region in the center ofCarina. Consistently, two different analyses in the HCO+ line provided evidence for a higher level of turbulence in thegas more affected by the stellar feedback. The gas column density probability functions, N-PDFs, show log-normal
shapes with clear transitions to power law regimes. We observed a wider N-PDF in the region at the center of thenebula, which provides further evidence for a higher level of turbulence in the material with a higher level of massive
stellar feedback.
Accepted by ApJ
http://arxiv.org/pdf/2001.06969

38 Detectability of embedded protoplanets from hydrodynamical simulations
E. Sanchis1,2 , G. Picogna2 , B. Ercolano2,3 , L. Testi1,3,4 and G. Rosotti5,61European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany; 2
Universitäts-Sternwarte, Ludwig-Maximilians-Universität München, Scheinerstrasse 1, D-81679 München, Germany;
3
Excellence Cluster Origins, Boltzmannstrasse 2, D-85748 Garching bei München, Germany; 4 INAF/Osservatorio
Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy; 5 Institute of Astronomy, University of Cambridge,
Madingley Road, Cambridge, UK; 6 Leiden Observatory, Leiden University, P.O. Box 9531, NL-2300 RA Leiden, theNetherlands
E-mail contact: esanchis at eso.org
We predict magnitudes for young planets embedded in transition discs, still affected by extinction due to material in
the disc. We focus on Jupiter-size planets at a late stage of their formation, when the planet has carved a deep gap
in the gas and dust distributions and the disc starts being transparent to the planet flux in the infrared (IR). Column
densities are estimated by means of three-dimensional hydrodynamical models, performed for several planet masses.
Expected magnitudes are obtained by using typical extinction properties of the disc material and evolutionary models
of giant planets. For the simulated cases located at 5.2 AU in a disc with local unperturbed surface density of 127
31

g cm−2 , a 1 MJ planet is highly extincted in J-, H- and K-bands, with predicted absolute magnitudes ≥50 mag. In
L- and M-bands extinction decreases, with planet magnitudes between 25 and 35 mag. In the N-band, due to thesilicate feature on the dust opacities, the expected magnitude increases to 40 mag. For a 2 MJ planet, the magnitudes
in J-, H- and K-bands are above 22 mag, while for L-, M- and N-bands the planet magnitudes are between 15 and20 mag. For the 5 MJ planet, extinction does not play a role in any IR band, due to its ability to open deep gaps.
Contrast curves are derived for the transition discs in CQ Tau, PDS70, HL Tau, TW Hya and HD163296. Planet
mass upper-limits are estimated for the known gaps in the last two systems.
Accepted by MNRAS
http://arxiv.org/pdf/2001.03565

SILCC-Zoom: H and CO-dark gas in molecular clouds - the impact of feedback and39 magnetic
fields2

D. Seifried1 , S. Haid1 , S. Walch1 , E. M. A. Borchert1 and T. G. Bisbas1,2,3
1

Universität zu Köln, I. Physikalisches Institut,; 2 Department of Physics, Aristotle University of Thessaloniki; 3
National Observatory of Athens, Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing
E-mail contact: seifried at ph1.uni-koeln.de
We analyse the CO-dark molecular gas content of simulated molecular clouds from the SILCC-Zoom project. The
simulations reach a resolution of 0.1 pc and include H2 and CO formation, radiative stellar feedback and magnetic
fields. CO-dark gas is found in regions with local visual extinctions AV,3D ∼ 0.2 - 1.5, number densities of 10 103 cm−3 and gas temperatures of few 10 K - 100 K. CO-bright gas is found at number densities above 300 cm−3 andtemperatures below 50 K. The CO-dark gas fractions range from 40% to 95% and scale inversely with the amount ofwell-shielded gas (AV,3D > 1.5), which is smaller in magnetised molecular clouds. We show that the density, chemical
abundances and AV,3D along a given line-of-sight cannot be properly determined from projected quantities. As an
example, pixels with a projected visual extinction of AV,2D ≃ 2.5 - 5 can be both, CO-bright or CO-dark, which can be
attributed to the presence or absence of strong density enhancements along the line-of-sight. By producing synthetic
CO(1-0) emission maps of the simulations with RADMC-3D, we show that about 15 - 65% of the H2 is in regionswith intensities below the detection limit. Our clouds have XCO -factors around 1.5 × 1020 cm−2 (K km s−1 )−1 witha spread of up to a factor ≃ 4, implying a similar uncertainty in the derived total H2 masses and even worse forindividual pixels. Based on our results, we suggest a new approach to determine the H2 mass, which relies on theavailability of CO(1-0) emission and AV,2D maps. It reduces the uncertainty of the clouds’ overall H2 mass to a factorof < 1.8 and for individual pixels, i.e. on sub-pc scales, to a factor of < 3.
Accepted by MNRAS
https://arxiv.org/pdf/1906.01015

40 Variable stars in the Sh 2-170 HII region

Tirthendu Sinha1,4 , Saurabh Sharma1 , A.K. Pandey1 , R.K. Yadav2 , K. Ogura3 et al.

1

Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263 002, India; 2 National
Astronomical Research Institute of Thailand, Chiang Mai 50200, Thailand; 3 Kokugakuin University, Higashi, Shibuyaku, Tokyo 150-8440, Japan; 4 Department of Physics, SSJ Campus, Kumaun University, Nainital 263 002, India
E-mail contact: tirthendu at aries.res.in

We present multi-epoch deep (∼20 mag) Ic band photometric monitoring of the Sh 2-170 star-forming region tounderstand the variability properties of pre-main-sequence (PMS) stars. We report identification of 47 periodic and
24 non-periodic variable stars with periods and amplitudes ranging from ∼4 hrs to 18 days and from ∼0.1 to 2.0 mag,respectively. We have further classified 49 variables as PMS stars (17 Class ii and 32 Class iii) and 17 as main-sequence(MS)/field star variables. A larger fraction of MS/field variables (88%) show periodic variability as compared to the
PMS variables (59%). The ages and masses of the PMS variable stars are found to be comparable with those of
T-Tauri stars. Their variability amplitudes show an increasing trend with the near-IR/mid-IR excess. The period
distribution of the PMS variables shows two peaks, one near ∼1.5 days and the other near ∼4.5 days. It is foundthat the younger stars with thicker discs and envelopes seem to rotate slower than their older counterparts. These32

properties of the PMS variables support the disc-locking mechanism. Both the period and amplitude of PMS stars
show decrease with increasing mass probably due to the effective dispersal of circumstellar discs in massive stars. Our
results favour the notion that cool spots on weak line T-Tauri stars are responsible for most of their variations, while
hot spots on classical T-Tauri stars resulting from variable mass accretion from an inner disc contribute to their larger
amplitudes and irregular behaviours.
Accepted by MNRAS
http://arxiv.org/pdf/2001.08892

and Radio Continuum Study of Elephant Trunks: The Pillars of Creation in
41 CO-Line
M16
Yoshiaki Sofue1
1Institute of Astronomy, The University of Tokyo, Mitaka, Tokyo 181-0015

E-mail contact: sofue at ioa.s.u-tokyo.ac.jp
Molecular-line and radio continuum properties of the elephant trunks (ET, pillars of creation) in M16 are investigatedby analyzing the 12 CO (J =1–0), 13 CO (J=1–0) and C18 O (J=1–0)-line survey data with the Nobeyama 45-m telescope
and the Galactic plane radio survey at 20 and 90 cm with the Very Large Array. The head clump of Pillar West I isfound to be the brightest radio source in M16, showing thermal spectrum and property of a compact HII region with
the nearest O5 star in NGC 6611 being the heating source. The radio pillars have cometary structure concave to themolecular trunk head, and the surface brightness distribution obeys a simple illumination law by a remote excitation
source. The molecular density in the pillar head is estimated to be several 104 H2 cm−3 and molecular mass ∼13–
40 M⊙ . CO-line kinematics reveals random rotation of the clumps in the pillar tail at ∼1–2 km s−1 , comparable tothe velocity dispersion and estimated Alfven velocity. It is suggested that the random directions of velocity gradientswould manifest a torsional magnetic oscillation of the clumps around the pillar axis.
Accepted by MNRAS
http://arxiv.org/pdf/2001.05623

VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Proto42 Thestars. A Statistical Characterization of Class 0 and I Protostellar DisksJohn J. Tobin1 , Patrick D. Sheehan1 , S. Thomas Megeath2 , Ana Karla Díaz-Rodríguez3 , Stella S.R.
Oﬀner4 et al.
1
National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA; 2 Department of
Physics and Astronomy, University of Toledo, Toledo, OH 43560; 3 Instituto de Astrofísica de Andalucía, CSIC,
Glorieta de la Astronomía s/n, E-18008 Granada, Spain; 4 The University of Texas at Austin, 2500 Speedway, Austin,
TX USAE-mail contact: jjtobin at gmail.com
We have conducted a survey of 328 protostars in the Orion molecular clouds with ALMA at 0.87 mm at a resolutionof ∼0.′′ 1 (40 au), including observations with the VLA at 9 mm toward 148 protostars at a resolution of ∼0.′′ 08 (32au). This is the largest multi-wavelength survey of protostars at this resolution by an order of magnitude. We use thedust continuum emission at 0.87 mm and 9 mm to measure the dust disk radii and masses toward the Class 0, ClassI, and Flat Spectrum protostars, characterizing the evolution of these disk properties in the protostellar phase. The
+4.9
+3.7
mean dust disk radii for the Class 0, Class I, and Flat Spectrum protostars are 44.9+5.8−3.4 , 37.0−3.0 , and 28.5−2.3 au,
+3.8
+3.5
respectively, and the mean protostellar dust disk masses are 25.9+7.7−4.0 , 14.9−2.2 , 11.6−1.9 Earth masses, respectively.
The decrease in dust disk masses is expected from disk evolution and accretion, but the decrease in disk radii may
point to the initial conditions of star formation not leading to the systematic growth of disk radii or that radial drift is
keeping the dust disk sizes small. At least 146 protostellar disks (35% out of 379 detected 0.87 mm continuum sources
plus 42 non-detections) have disk radii greater than 50 au in our sample. These properties are not found to varysignificantly between different regions within Orion. The protostellar dust disk mass distributions are systematicallylarger than that of Class II disks by a factor of >4, providing evidence that the cores of giant planets may need to at33

least begin their formation during the protostellar phase.
Accepted by ApJ
http://arxiv.org/pdf/2001.04468

43 An Eclipsing Substellar Binary in a Young Triple System discovered by SPECULOOS

Amaury H.M.J. Triaud1 , Adam J. Burgasser2 , Artem Burdanov3 , Vedad Kunovac Hodzić1 . Roi Alonso4
et al.
1

School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom; 2Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, Mail Code 0424,
La Jolla, CA 92093, USA; 3 Astrobiology Research Unit, Universit’e de Liège, Allée du 6 août 19, Sart Tilman, 4000,
Liège 1, Belgium; 4 Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
E-mail contact: shmeidt at gmail.com
Mass, radius, and age are three of the most fundamental parameters for celestial objects, enabling studies of theevolution and internal physics of stars, brown dwarfs, and planets. Brown dwarfs are hydrogen-rich objects that are
unable to sustain core fusion reactions but are supported from collapse by electron degeneracy pressure. As theyage, brown dwarfs cool, reducing their radius and luminosity. Young exoplanets follow a similar behaviour. Brown
dwarf evolutionary models are relied upon to infer the masses, radii and ages of these objects. Similar models areused to infer the mass and radius of directly imaged exoplanets. Unfortunately, only sparse empirical mass, radius
and age measurements are currently available, and the models remain mostly unvalidated. Double-line eclipsingbinaries provide the most direct route for the absolute determination of the masses and radii of stars. Here, we report
the SPECULOOS discovery of 2M1510A, a nearby, eclipsing, double-line brown dwarf binary, with a widely-separated
tertiary brown dwarf companion. We also find that the system is a member of the 45±5 Myr-old moving group, Argus.
The system’s age matches those of currently known directly-imaged exoplanets. 2M1510A provides an opportunity tobenchmark evolutionary models of brown dwarfs and young planets. We find that widely-used evolutionary models
do reproduce the mass, radius and age of the binary components remarkably well, but overestimate the luminosity by
up to 0.65 magnitudes, which could result in underestimated photometric masses for directly-imaged exoplanets andyoung field brown dwarfs by 20 to 35%.
Accepted by Nature Astronomy
http://arxiv.org/pdf/2001.07175

44 Constraining planet formation around 6 M –8 M stars⊙⊙

Dimitri Veras1,2 , Pier-Emmanuel Tremblay1 , J.J. Hermes3 , Catriona H. McDonald1,2 , Grant M.
Kennedy1,2 et al.
1

Centre for Exoplanets and Habitability, University of Warwick, Coventry CV4 7AL, UK; 2 Department of Physics,
University of Warwick, Coventry CV4 7AL, UK; 3 Department of Astronomy, Boston University, 725 CommonwealthAve., Boston, MA 02215, USA
E-mail contact: d.veras at warwick.ac.uk
Identifying planets around O-type and B-type stars is inherently difficult; the most massive known planet host has amass of only about 3 M⊙ . However, planetary systems which survive the transformation of their host stars into whitedwarfs can be detected via photospheric trace metals, circumstellar dusty and gaseous discs, and transits of planetarydebris crossing our line-of-sight. These signatures offer the potential to explore the efficiency of planet formation
for host stars with masses up to the core-collapse boundary at ≈8 M⊙ , a mass regime rarely investigated in planet
formation theory. Here, we establish limits on where both major and minor planets must reside around ≈6 M⊙ –8 M⊙stars in order to survive into the white dwarf phase. For this mass range, we find that intact terrestrial or giant
planets need to leave the main sequence beyond approximate minimum star-planet separations of respectively about
3 and 6 au. In these systems, rubble pile minor planets of radii 10, 1.0, and 0.1 km would have been shorn apart by
giant branch radiative YORP spin-up if they formed and remained within, respectively, tens, hundreds and thousandsof au. These boundary values would help distinguish the nature of the progenitor of metal-pollution in white dwarf
atmospheres. We find that planet formation around the highest mass white dwarf progenitors may be feasible, and34

hence encourage both dedicated planet formation investigations for these systems and spectroscopic analyses of thehighest mass white dwarfs.
Accepted by MNRAS
http://arxiv.org/pdf/2001.08757

45 The origin of tail-like structures around protoplanetary disks

Eduard Vorobyov1,2 , Alexandr Skliarevskii2 , Vardan Elbakyan2,3 , Michihiro Takami4 , Hauyu Baobab
Liu4 , Sheng-Yuan Liu4 and Eiji Akiyama5

1

Department of Astrophysics, University of Vienna, Vienna, Austria; 2 Institute of Physics, Southern Federal University, Rostov-on-Don, Russia; 3 Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University,
22100 Lund, Sweden; 4 Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan, R.O.C.; 5
Institute for the Advancement of Higher Education, Hokkaido University, Sapporo, 060-0817, Japan
E-mail contact: eduard.vorobiev at univie.ac.at
We study the origin of tail-like structures recently detected around the disk of SU Aurigae and several FU Orionis-typestars.
Dynamic protostellar disks featuring ejections of gaseous clumps and quiescent protoplanetary disks experiencing aclose encounter with an intruder star were modeled using the numerical hydrodynamics code FEOSAD. Both the gas
and dust dynamics were taken into account, including dust growth and mutual friction between the gas and dust
components. Only plane-of-the-disk encounters were considered.
Ejected clumps produce a unique type of tail that is characterized by a bow-shock shape. Such tails originate from thesupersonic motion of ejected clumps through the dense envelope that often surrounds young gravitationally unstable
protostellar disks. The ejected clumps either sit at the head of the tail-like structure or disperse if their mass is insufficient to withstand the head wind of the envelope. On the other hand, close encounters with quiescent protoplanetarydisks produce three types of the tail-like structure; we define these as pre-collisional, post-collisional, and spiral tails.
These tails can in principle be distinguished from one another by particular features of the gas and dust flow in andaround them. We find that the brown-dwarf-mass intruders do not capture circumintruder disks during the encounter,
while the subsolar-mass intruders can acquire appreciable circumintruder disks with elevated dust-to-gas ratios, which
can ease their observational detection. However, this is true only for prograde collisions; the retrograde intruders fail
to collect appreciable amounts of gas or dust from the disk of the target. The mass of gas in the tail varies in therange 0.85–11.8 MJup , while the total mass of dust lies in the 1.75–30.1 M⊕ range, with the spiral tails featuring thehighest masses. The predicted mass of dust in the model tail-like structures is therefore higher than what was inferred
for similar structures in SU Aur, FU Ori, and Z CMa, making their observational detection feasible.
Tail-like structures around protostellar and protoplanetary disks can be used to infer interesting phenomena such as
clump ejection or close encounters. In particular, the bow-shock morphology of the tails could point to clump ejections
as a possible formation mechanism. Further numerical and observational studies are needed to better understand thedetectability and properties of the tails.
Accepted by Astronomy & Astrophysics

HI/OH/Recombination line survey of the inner Milky Way (THOR): data release46 The2 and HI overview
Y. Wang1 , H. Beuther1 , M. R. Rugel2 , J. D. Soler1 , J. M. Stil3 , J. Ott4 , S. Bihr1 , N. M. McClureGriﬃths5 , L. D. Anderson6,7,8 , R. S. Klessen9,10 , P. F. Goldsmith11 , N. Roy12 , S. C. O. Glover9 , J. S.
Urquhart13 , M. Heyer14 , H. Linz1 , R. J. Smith15 , F. Bigiel16, J. Dempsey5 and T. Henning1
1

Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 3 Department of Physics and Astronomy, The Universityof Calgary, 2500 University Drive NW, Calgary AB T2N 1N4, Canada; 4 National Radio Astronomy Observatory,
P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801, USA; 5 Research School of Astronomy and Astrophysics, The
Australian National University, Canberra, ACT, Australia; 6 Department of Physics and Astronomy, West Virginia
University, Morgantown, WV 26506, USA; 7 Adjunct Astronomer at the Green Bank Observatory, P.O. Box 2, GreenBank WV 24944, USA; 8 Center for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge
35

Research Building, Morgantown, WV 26505, USA; 9 Universität Heidelberg, Zentrum für Astronomie, Institut fürTheoretische Astrophysik, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 10 Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, INF 205, 69120, Heidelberg, Germany; 11 Jet Propulsion Laboratory,
California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA; 12 Department of Physics, Indian
Institute of Science, Bengaluru 560012, India; 13 School of Physical Sciences, University of Kent, Ingram Building,Canterbury, Kent CT2 7NH, UK; 14 Department of Astronomy, University of Massachusetts, Amherst, MA01003,
USA; 15 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester,
Oxford Road, Manchester, M13 9PL, UK; 16 Argelander Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn,
Germany
E-mail contact: wang at mpia.de
The Galactic plane has been observed extensively by a large number of Galactic plane surveys from infrared to radio
wavelengths at an angular resolution below 40 arcsec. However, a 21 cm line and continuum survey with comparable
spatial resolution is lacking.
The first half of THOR data (l = 14.0◦ − 37.9◦ , and l = 47.1◦ − 51.2◦, |b|≤ 1.25◦ ) has been published in our data
release 1 paper. With this data release 2 paper, we publish all the remaining spectral line data and Stokes I continuum
data with high angular resolution (10 arcsec–40 arcsec), including a new HI dataset for the whole THOR survey region(l = 14.0 − 67.4◦ and |b| ≤ 1.25◦ ). As we published the results of OH lines and continuum emission elsewhere, weconcentrate on the HI analysis in this paper.
With the Karl G. Jansky Very Large Array (VLA) in C-configuration, we observed a large portion of the first Galactic
quadrant, achieving an angular resolution of ≤ 40 arcsec. At L Band, the WIDAR correlator at the VLA was set tocover the 21 cm HI line, four OH transitions, a series of Hnα radio recombination lines (RRLs; n = 151 to 186), andeight 128 MHz-wide continuum spectral windows (SPWs), simultaneously.
We publish all OH and RRL data from the C-configuration observations, and a new HI dataset combining VLA
C+D+GBT (VLA D-configuration and GBT data are from the VLA Galactic Plane Survey) for the whole survey.
The HI emission shows clear filamentary substructures at negative velocities with low velocity crowding. The emission
at positive velocities is more smeared-out, likely due to higher spatial and velocity crowding of structures at the positive
velocities. Compared to the spiral arm model of the Milky Way, the atomic gas follows the Sagittarius and Perseus Arm
well, but with significant material in the inter-arm regions. With the C-configuration-only HI+continuum data, we
produced a HI optical depth map of the THOR areal coverage from 228 absorption spectra with the nearest-neighbormethod. With this τ map, we corrected the HI emission for optical depth, and the derived column density is 38%
higher than the column density with optically thin assumption. The total HI mass with optical depth correction in thesurvey region is 4.7×108 M⊙ , 31% more than the mass derived assuming the emission is optically thin. If we applied
this 31% correction to the whole Milky Way, the total atomic gas mass would be 9.4–10.5×109 M⊙ . Comparing theHI with existing CO data, we find a significant increase in the atomic-to-molecular gas ratio from the spiral arms to
the inter-arm regions.
The high-sensitivity and resolution THOR HI dataset provides an important new window on the physical and kinematic
properties of gas in the inner Galaxy. Although the optical depth we derive is a lower limit, our study shows that the
optical depth correction is significant for HI column density and mass estimation. Together with the OH, RRL andcontinuum emission from the THOR survey, these new HI data provide the basis for high-angular-resolution studiesof the interstellar medium (ISM) in different phases.
Accepted by A&A
https://arxiv.org/pdf/1912.08223

formation in the atomic and molecular phase: HI self absorption (HISA) towards
47 Clouda Giant Molecular Filament
Y. Wang1 , S. Bihr1 , H. Beuther1 , M. R. Rugel1,2 , J. D. Soler1 , J. Ott3 , J. Kainulainen4 , N. Schneider5 ,R. S. Klessen6,7, S. C. O. Glover6 , N. M. McClure-Griﬃths8 , P. F. Goldsmith9 , K. G. Johnston10 , K.
M. Menten2 , S. Ragan11 , L. D. Anderson12,13,14 , J. S. Urquhart15 , H. Linz1 , N. Roy16 , R. J. Smith17 , F.
Bigiel18, T. Henning1 and S. N. Longmore19
1

Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 3 National Radio Astronomy Observatory, P.O. Box O,
1003 Lopezville Road, Socorro, NM 87801, USA; 4 Chalmers University of Technology, Department of Space, Earth36

and Environment, SE-412 93 Gothenburg, Sweden; 5 I. Physik. Institut, University of Cologne, Zülpicher Str.77,
50937 Cologne, Germany; 6 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik,
Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 7 Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, INF 205, 69120, Heidelberg, Germany; 8 Research School of Astronomy and Astrophysics,
The Australian National University, Canberra, ACT, Australia; 9 Jet Propulsion Laboratory, California Institute ofTechnology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA; 10 School of Physics and Astronomy, University ofLeeds, Leeds LS2 9JT, UK; 11 School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade,
Cardiff, CF24 3AA, UK; 12 Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506,
USA; 13 Adjunct Astronomer at the Green Bank Observatory, P.O. Box 2, Green Bank WV 24944, USA; 14 Center
for Gravitational Waves and Cosmology, West Virginia University, Chestnut Ridge Research Building, Morgantown,
WV 26505, USA; 15 School of Physical Sciences, University of Kent, Ingram Building, Canterbury, Kent CT2 7NH,
UK; 16 Department of Physics, Indian Institute of Science, Bengaluru 560012, India; 17 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK;
18
Argelander Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany; 19 Astrophysics Research Institute,
Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF, UK
E-mail contact: wang at mpia.de
Molecular clouds form from the atomic phase of the interstellar medium. However, characterizing the transition
between the atomic and the molecular interstellar medium (ISM) is a difficult observational task. Here we address cloudformation processes by combining HI self absorption (HISA) with molecular line data. Column density probability
density functions (N-PDFs) are a common tool to examine molecular clouds. One scenario proposed by numericalsimulations is that the N-PDF evolves from a log-normal shape at early times to a power-law-like shape at latertimes. To date, investigations of N-PDFs are mostly limited to the molecular component of the cloud. In this paper,
we study the cold atomic component of the giant molecular filament GMF38.1-32.4a (GMF38a, distance=3.4 kpc,
length∼ 230 pc), calculate its N-PDFs and study its kinematics. We identify an extended HISA feature, which ispartly correlated with the 13 CO emission. The peak velocities of the HISA and 13 CO observations agree well on theeastern side of the filament, whereas a velocity offset of approximately 4 km s−1 is found on the western side. The sonic
Mach number we derive from the linewidth measurements shows that a large fraction of the HISA, which is ascribedto the cold neutral medium (CNM), is at subsonic and transonic velocities. The column density of the CNM part is on
the order of 1020 to 1021 cm−2 . The column density of molecular hydrogen, traced by 13 CO, is an order of magnitude
higher. The N-PDFs from HISA (CNM), HI emission (the warm and cold neutral medium), and 13 CO (molecularcomponent) are well described by log-normal functions, which is in agreement with turbulent motions being the main
driver of cloud dynamics. The N-PDF of the molecular component also shows a power law in the high column-density
region, indicating self-gravity. We suggest that we are witnessing two different evolutionary stages within the filament.
The eastern subregion seems to be forming a molecular cloud out of the atomic gas, whereas the western subregion
already shows high column density peaks, active star formation and evidence of related feedback processes.
Accepted by A&A
https://arxiv.org/pdf/2001.00953

48 The accretion rates and mechanisms of Herbig Ae/Be stars

C. Wichittanakom1,2 , R.D. Oudmaijer2 , J.R. Fairlamb3 , I. Mendigutía4 , M. Vioque2 and K.M. Ababakr5

1

Department of Physics, Faculty of Science and Technology, Thammasat University, Rangsit Campus, Pathum Thani
12120, Thailand; 2 School of Physics and Astronomy, EC Stoner Building, University of Leeds, Leeds LS2 9JT,
UK; 3 Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA; 4 Centro de
Astrobiología (CSIC-INTA), Departamento de Astrofísica, ESA-ESAC Campus, PO Box 78, 28691 Villanueva de laCañada, Madrid, Spain; 5 Erbil Polytechnic University, Kirkuk Road, Erbil, Iraq
E-mail contact: pycw at leeds.ac.uk
This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30
objects. Stellar parameters such as temperature, reddening, mass, luminosity and age are homogeneously determined.
Mass accretion rates are determined from Hα emission line measurements. Our data is complemented with the XShooter sample from previous studies and we update results using Gaia DR2 parallaxes giving a total of 78 objects
with homogeneously determined stellar parameters and mass accretion rates. In addition, mass accretion rates of37

an additional 85 HAeBes are determined. We confirm previous findings that the mass accretion rate increases asa function of stellar mass, and the existence of a different slope for lower and higher mass stars respectively. The
mass where the slope changes is determined to be 3.98+1.37−0.94 M⊙ . We discuss this break in the context of different
modes of disk accretion for low- and high mass stars. Because of their similarities with T Tauri stars, we identify
the accretion mechanism for the late-type Herbig stars with the Magnetospheric Accretion. The possibilities for theearlier-type stars are still open, we suggest the Boundary Layer accretion model may be a viable alternative. Finally,
we investigated the mass accretion - age relationship. Even using the superior Gaia based data, it proved hard toselect a large enough sub-sample to remove the mass dependency in this relationship. Yet, it would appear that themass accretion does decline with age as expected from basic theoretical considerations.
Accepted by MNRAS
http://arxiv.org/pdf/2001.05971

49 Turbulence in a self-gravitating molecular cloud core
Siyao Xu1,2 , Alex Lazarian1

1

Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706, USA; 2 Hubble
Fellow
E-mail contact: sxu93 at wisc.edu

Externally driven interstellar turbulence plays an important role in shaping the density structure in molecular clouds.
Here we study the dynamical role of internally driven turbulence in a self-gravitating molecular cloud core. Dependingon the initial conditions and evolutionary stages, we find that a self-gravitating core in the presence of gravity-driven
turbulence can undergo constant, decelerated, and accelerated infall, and thus has various radial velocity profiles. In
the gravity-dominated central region, a higher level of turbulence results in a lower infall velocity, a higher density,and a lower mass accretion rate. As an important implication of this study, efficient reconnection diffusion of magnetic
fields against the gravitational drag naturally occurs due to the gravity-driven turbulence, without invoking externallydriven turbulence.
Accepted by ApJ
http://arxiv.org/pdf/2001.07721

compendium of distances to molecular clouds in the Star Formation Handbook
50 ACatherine
Zucker , Joshua Speagle , Edward Schlaﬂy , Gregory Green , Douglas Finkbeiner , Alyssa
1Goodman

1,5

and João Alves

1

2

3

1

4,5

1

Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA; 2 Lawrence Berkeley
National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA; 3 Kavli Institute for Particle Astrophysics andCosmology, Physics and Astrophysics Building, 452 Lomita Mall, Stanford, CA 94305, USA; 4 University of Vienna,
Department of Astrophysics, Türkenschanzstraße 17, 1180 Vienna, Austria; 5 Radcliffe Institute for Advanced Study,
Harvard University, 10 Garden St, Cambridge, MA 02138
E-mail contact: catherine.zucker at cfa.harvard.edu
Accurate distances to local molecular clouds are critical for understanding the star and planet formation process, yetdistance measurements are often obtained inhomogeneously on a cloud-by-cloud basis. We have recently developed amethod which combines stellar photometric data with Gaia DR2 parallax measurements in a Bayesian framework toinfer the distances of nearby dust clouds to a typical accuracy of ∼ 5%. After refining the technique to target lower
latitudes and incorporating deep optical data from DECam in the southern Galactic plane, we have derived a catalog
of distances to molecular clouds in Reipurth (2008, Star Formation Handbook, vols I and II) which contains a large
fraction of the molecular material in the solar neighborhood. Comparison with distances derived from maser parallax
measurements towards the same clouds shows our method produces consistent distances with <∼10% scatter for clouds
across our entire distance spectrum (150 pc − 2.5 kpc). We hope this catalog of homogeneous distances will serve asa baseline for future work.
Accepted by A&A
https://arxiv.org/pdf/2001.00591
38

Abstracts of recently accepted major reviews

Observations of Protoplanetary Disk Structures
Sean M. Andrews1
1

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

E-mail contact: sandrews at cfa.harvard.edu
The disks that orbit young stars are the essential conduits and reservoirs of material for star and planet formation.
Their structures, meaning the spatial variations of the disk physical conditions, reflect the underlying mechanismsthat drive those formation processes. Observations of the solids and gas in these disks, particularly at high resolution,
provide fundamental insights on their mass distributions, dynamical states, and evolutionary behaviors. Over the
past decade, rapid developments in these areas have largely been driven by observations with the Atacama Large
Millimeter/submillimeter Array (ALMA). This review highlights the state of observational research on disk structures,emphasizing three key conclusions that reflect the main branches of the field: (1) Relationships among disk structure
properties are also linked to the masses, environments, and evolutionary states of their stellar hosts; (2) There is clear,
qualitative evidence for the growth and migration of disk solids, although the implied evolutionary timescales suggest
the classical assumption of a smooth gas disk is inappropriate; and (3) Small-scale substructures with a variety ofmorphologies, locations, scales, and amplitudes – presumably tracing local gas pressure maxima – broadly influence
the physical and observational properties of disks. The last point especially is reshaping the field, with the recognition
that these disk substructures likely trace active sites of planetesimal growth or are the hallmarks of planetary systems
at their formation epoch.
Accepted by Annual Reviews of Astronomy and Astrophysics
https://ui.adsabs.harvard.edu/pdf/2020arXiv200105007A/abstract
http://arxiv.org/pdf/2001.05007

39

Meetings

IMPRS Summer School 2020: Planet Formation in Protoplanetary DisksIMPRS Heidelberg invites early-career scientists to its 15th summer school.
The school will focus on the most relevant aspects of planet formation, including the physics of radiation transfer,hydrodynamics and planet-disk interactions, observations of protoplanetary disks ranging from the near-infrared toradio wavelengths and recent achievements in exoplanet astronomy.
Five distinguished invited lecturers, along with an assortment of local experts, will provide an introduction to thefield. In addition to the formal lectures, there will be hands-on sessions to perform simulations on hydrodynamic andradiation transfer. We will provide career discussions, and a variety of social activities.
Topics that are covered include: planet formation models, Monte Carlo radiation transfer, ALMA observations,hydrodynamics using the FARGO3D and PLUTO codes and models of Exoplanets atmospheres.
Scientific organizing committee: Bertram Bitsch, Mario Flock, Paola Pinilla (all at MPIA)
School lecturers: Pablo Benítez Llambay (Niels Bohr Institute, University of Copenhagen), Cornelis P. Dullemond(ITA, University of Heidelberg), Michiel Lambrecths (Lund Observatory), Yamila Miguel (Leiden Observatory), andCatherine Walsh (Leeds University, TBC)
More information at: https://www.imprs-hd.mpg.de/Summer-School

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.

40Summary of Upcoming Meetings

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

41

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

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.

42