THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 333 — 14 September 2020

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

List of Contents
The Star Formation Newsletter
Editor: Bo Reipurthreipurth@ifa.hawaii.edu
Associate Editor: Anna McLeod
anna.mcleod@berkeley.edu
Technical Editor: Hsi-Wei Yen
hwyen@asiaa.sinica.edu.tw
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

Editorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Editorial
After 28 years and 333 issues of the Star Formation Newsletter, I have decided that the time has come for me to step
down as Editor of the Newsletter. While it has been wonderful to interact with our community and I am thankful forthe many expressions of appreciation I have received over the years, it has also been a challenge every month to findthe time to prepare an issue, no matter what other things I was doing, or where I was.
Technology inexorably advances, and new means of communication appear. 28 years ago the world looked very
different, as we were only at the beginning of the information age, and it may be difficult for young people today tounderstand that information was not so easy to get hold of as it is now. Back then many institutes still issued preprints
and mailed them to other institutes. The process of publishing a paper was much slower, and people actually went to
the library and (gasp) read the journals as they came in.
It was in that environment that the Star Formation Newsletter was launched as the first electronic newsletter inastronomy, offering rapid dissemination not only of abstracts, but also of news about meetings, jobs, dissertations,and new books. This soon led to more such newsletters being circulated in other fields of astronomy, most of which
unfortunately had short lives, although some still exist. About 8 years ago I expanded the Newsletter to also include
interviews with leading researchers, and short articles meant to give quick overviews about particular subjects or
specially interesting objects.
Although I step down as Editor, it does not mean that the Newsletter ceases to exist. I am very happy to announce
that João Alves at the University of Vienna, Austria, has agreed to take the helm. Joao will gradually introducechanges to the Newsletter, and in next month’s issue he will lay out his vision.
I will continue to prepare interviews for the Newsletter, since they have been universally welcomed by readers. I havecome to realize that, subsequent to publication, the interviews have been buried in the archives on the webpage for
the Newsletter, and while still accessible it is a major effort to find any specific one. Hence, I have decided to make acompilation of all 77 interviews so far,. This facilitates finding particular ones, but - perhaps more importantly - allows
young researchers to see more globally how star formation has developed into its present state. The compilation, which
will be augmented yearly, is further described in the section on New Books in this issue, and it can be downloaded
from this URL:
http://www.ifa.hawaii.edu/SP2/77interviews.pdf
It has always been a puzzle to me that I only receive about 50% of the abstracts of relevant papers. Given that weall publish to be read, it seems logical that, after spending many months to prepare research results for publication,
one should also spend 5 minutes to circulate an abstract to potential readers. I therefore urge readers to submit theirabstracts to João in the spirit of a shared community. If we all do this, we all can benefit from a near-complete
monthly compilation. The Newsletter is a creation of the star formation community for the star formation community.
So please support João in his future efforts on behalf of our community.
In closing, I would like to thank all the readers who have submitted their abstracts and announcements to theNewsletter. I would like to extend special thanks to my Associate Editors Hsi-Wei Yen and Anna McLeod who havebeen steadfast in their support of the Newsletter.
Finally, on a practical note, please continue to submit your abstracts to the Newsletter website at its current location
until further notice.
Bo Reipurth3replace George Coyne on my Ph.D. Committee as Charlie
was transitioning to become an Assistant Professor at University of Arizona (Coyne had left to become the Directorof the Vatican Observatory).

Bruce Wilking
in conversation with Bo Reipurth

Q: Your PhD from 1981 focused on star formation in theρ Ophiuchi cloud. How did you choose that subject?
A: I was fortunate that Charlie Lada arrived at the University of Arizona as a Bok Fellow in 1978. He wanted to
do infrared surveys of molecular clouds and I assisted him
with infrared observations of Barnard 35 at the Mt. Lemmon 28-inch telescope. In return, he offered to take meobserving at the Millimeter Wave Observatory (MWO) in
West Texas. We had done some near-infrared polarization measurements of stars toward the ρ Oph cloud and I
thought I was seeing two cloud components. So I beganobserving 12 C16 O emission in the direction of these stars
and found the line profiles to be very complex and very
optically thick. So Charlie suggested tuning to 13 C16 O,
Q: While you were still a student you led a study on the but we found these too looked optically thick. So right
12 18
wavelength dependence of interstellar linear polarization. before we were to return to Tucson, we tuned to C O
This has remained a highly cited paper for 40 years, what and found a single strong emission line. On subsequent
trips we started mapping the cloud in 12 C18 O only to findaccounts for this longevity?
that the resident astronomer, Bob Loren, was already doA: As near-infrared polarization data of stars were becom- ing so. When Bob found out I was hoping to make thising more available, a more versatile functional form for part of my dissertation, he graciously stepped aside andthe wavelength dependence of polarization was needed. gave me the project.
George and Marcia Rieke had already measured a large
12 18
sample of field stars with one of the first near-infrared po- Once we had done a higher resolution C O map of thelarimeters, built by James Kemp, and I joined the effort. L1688 cloud with the NRAO 12-meter telescope, I carriedWith the help of Peter Martin, who was visiting the Uni- out a near-infrared survey of the highest column density
versity of Arizona at the time, we added an additional region using George and Marcia’s InSb detector at the 61free parameter to the lognormal Serkowski Law and pro- inch telescope on Mt. Bigelow. This multi-wavelength
posed some physical significance to this addition. Kristof approach to studying star formation was relatively new. I
Serkowski was also at the University of Arizona and was surveyed a 10’ x 10’ region by raster scanning with a single
supportive of us tinkering with his “Law". The relation- detector across the region over 4 nights.
ship we proposed in 1980, and in a follow-up study of Back when I was a student, observational astronomy wassources with more extreme values of λmax , was confirmed very hands-on. There were no telescope operators at MWO
by subsequent studies and became a standard marker for or Mt. Bigelow. At MWO, you had to tune the klystroninterstellar dust in the Galaxy. The narrowing of the nor- and microwave cavities to the desired frequency and at Mt.
malized polarization curve with λmax has been the target Bigelow all of the observations were done in the dome withof studies modeling how the wavelength dependence of po- the telescope and instrument. Fortunately, summer nights
larization varies with grain shape, alignment mechanisms, in the Catalinas were warm and relatively short and oband composition. It is used to compare Milky Way inter- serving time was easy to get with the “monsoons" lurking
stellar dust with that in diverse environments including to the south. Things got much easier when infrared camother galaxies.
eras became available. Tom Greene made the first infrared
I was in the Planetary Science Department and approached camera survey of the entire L1688 region with a 128x128
George about doing an observational planetary project. HgCdTe array. I told him that he could have done my surGeorge’s office and the Infrared lab where he worked were vey in about 6 minutes but he pointed out that his datain the same building as Planetary Science, the Lunar and reduction was much more involved.
Planetary Lab. He suggested a project unrelated to planets (polarimetry) and ultimately on the emerging field ofstar formation. My department was supportive of this for
my dissertation research. After all, star formation is related to planet formation. They even let Charlie Lada

Q: The ρ Ophiuchi region has become a lifelong passion foryou, and at the latest count you have written or co-written
27 refereed papers on this region. Please tell about key
points in these many studies and how our view of ρ Oph4

line, that it was “an instrument to detect heat radiationfrom young stars", was usually met with blank stares. Of
course this would never happen today given the increased
scrutiny of airport security not to mention the size of current infrared detector systems.

has developed over the last 40 years.
A: There was always more to learn about this region since,over 40 years, we have seen the emergence of infrared cameras, infrared astronomical satellites, multi-object spectrographs, and large aperture ground-based telescopes. There
are some properties of ρ Oph that make it unique - thehigh visual extinctions and its proximity to us and to the
Sco-Cen association. But of course it is now just one ofmany young clusters that have been studied in detail.

Q: Another region you have focused on is the R CrA cloud.
What are the similarities and differences with ρ Ophiuchi?
A: I find the two regions very similar. They both are
nearby low-mass star forming regions with centrally condensed molecular cores. The near-infrared image of theCoronet cluster is strikingly beautiful. I was never able toidentify as many YSOs or any young brown dwarfs in thisregion, partly since I used mostly northern hemisphere
telescopes, and thus I never attempted a mass function.
But this will be done, with help from the Gaia databaseto get a more complete census of cluster members andmulti-object spectrographs. It will be interesting to see
how the mass functions compare particularly in the substellar range.

As one of the closest star-forming regions, the ρ Oph cluster presented an opportunity to get a complete census
of the young population with which to investigate global
properties such as timescales for pre-main sequence evolution, disk frequency, cluster dynamics, and the massfunction. This required a multi-wavelength approach to
catch all stages of PMS evolution. IRAS was a real breakthrough. With Charlie and Erick Young, we were able tolocate the young stars associated with the IRAS sources inρ Oph and start building and classifying spectral energy
distributions which have become a proxy for the evolutionary states. Starting about 20 years ago, I began focusing more on spectroscopy, both optical and infrared,
for a more direct comparison with PMS models. This began with a 1999 grism study of water bands in low mass
objects with Tom Greene and Michael Meyer and the identification of young brown dwarfs in ρ Oph. Optical spectra
were obtained using the multi-object spectrographs Hydrain both the northern and southern hemispheres resulting
in over a hundred YSOs with spectral classifications. We
made our best attempt at a mass function in a 2011 paperwith Ph.D. student Kryss Erikson, Tom, and Michael, andfound it to be consistent with the Initial Mass Function
with a possible deficit of brown dwarfs. With a bit morework one may be able to fill in the substellar piece of themass function.

Q: You joined the faculty at the University of Missouri-St.
Louis in 1984 and worked with Dick Schwartz on several
projects.
A: Dick was a great colleague and mentor. I had worked
with him and Martin Cohen as they were guest observers
with Paul’s instrument on the KAO. His specialty was
Herbig-Haro objects/protostellar jets and we collaborated
on several projects including a survey of Hα emission line
objects and Herbig-Haro objects in ρ Oph and shocked
molecular hydrogen emission associated with Herbig-Haro
objects and their exciting stars. The latter observations
were made at CTIO in April 1987 and were memorable
since we had the opportunity to see and observe SN1987A.
Q: You have also studied the mm emission from cold IRAS
sources. This was back in 1989/1990 when molecular outflows were intensely studied. What did you learn?

Q: You spent your postdoc at the University of Texas working in Paul Harvey’s infrared group with experiments on A: The initial survey of cold IRAS sources with Lee Mundy
the Kuiper Airborne Observatory.
was a follow-up to our interferometric mapping of IRAS
A: This was a great experience and I have great respect 16293, one of the first “Class 0" sources. We were hopingfor groups that not only build instruments, but know the that this sample of objects would reveal similar objects
astrophysical questions to apply them to, and publish the and spur some follow-up observations. As it was a fluxresults. I was involved with the first far-infrared detection limited survey, many of the sources were more luminousof a quasar (3C 345) and the detection of the debris disk objects in more distant star-forming regions and the surof Vega. I was part of the KAO’s second southern hemi- vey did not reveal any sources analogous to IRAS 16293.
sphere deployment in 1983 and took the opportunity to However, as we were hoping, a larger fraction were associmap the R CrA cloud at 50 and 100 µm. The flight series ated with high velocity gas compared to visible YSOs. We
were exhausting and the flight schedules always chang- did follow-up observations of several of these sources ining. When flying to NASA Ames we used to take our cluding mapping some of the outflows. Other groups haveinfrared photometer, which was a gold dewar with electri- continued to study some of the higher mass protostars likecal feedthroughs and a bracket with gears and motors for IRAS 20126+4104 and IRAS 21391+5802.
the filter wheels, through airport security and place it on Q: In addition to the ρ Oph cluster, you have also exthe floor in front of our seat in coach. The security people plored the mass functions in the NGC 1333 and Serpens
were often skeptical about letting us on the plane. Our clusters.
5

A: Following our identification of young brown dwarfs inρ Oph, we did a similar study in NGC 1333 with thegrism at the IRTF and with the Hubble Space Telescope.
We were able to identify 21 young brown dwarfs. Subsequent studies have doubled this number and identifying
young brown dwarfs, “rogue" planets, and the end of themass function will be the target of a JWST program withNIRISS. Using a multi-object spectrograph, Kryss Erickson and I attempted a study in the Serpens cluster similar
to that in ρ Oph and found working in the Galactic planevery challenging. Plus, during the course of our observations, the distance to the Serpens cluster doubled thanks
to VLBI, which explained why we saw no stars at or below
the hydrogen-burning limit.
Q: Over the years you and your collaborators have studied
water maser emission from young low-mass stars, including a recent study of the T Tauri binary Haro 6-10.Whatis the information you can extract from such masers?
A: When Mark Claussen and I did our water maser surveyof ρ Oph in 1986, few outflows had been discovered inthis region due in part to the high visual extinctions andsource confusion. Using the VLA to observe water maser
emission, these selection effects could be overcome. We
then expanded our survey to monthly monitoring of 45
low-mass YSOs with the Haystack telescope. Prior to thissurvey, water maser emission was mainly associated withmassive stars. While weaker and highly variable, we foundwater masers were common among low-mass young stars
and were collisionally pumped by their winds.

The monitoring of these low mass stars was then used totrigger VLBI observations during periods of high activity.
Multi-epoch observations could measure the proper motions of these shock excited clumps, get the 3-D geometryof the outflows, and trace the outflow’s formation and acceleration within 10s .0821(w)-0.65699(u)1.34903(l)0.672679(0.6.)]TJ0.74(U)1.36.0115(w)-482.44(g)-6.0149(u)1.34903(1(u)9-3.13(e)jebivrre eogatcl1.349071(r)-5.91443(e)-350.656(c)-1.33311(o)-6.01493(1)-6.0149(0)-1.33311lti-oaiyataccs

and multiples see for instance Dûchene & Kraus 2013 andReipurth et al. 2014). For these systems we are able todirectly measure the 3-dimensional orbits and dynamicalmasses of the perturbing bodies and can image how thedisk responds to the perturbation.

My Favorite Object
GW Orionis:
A pre-main-sequence triple with awarped disk and a torn-apart ring
Stefan Kraus

One system that has the potential to serve as such a“rosetta stone” for hydrodynamic studies, is the PMS triple
GW Orionis. This system is one of the brightest and beststudied T Tauri multiple systems. It is located in the
λ Orionis star-forming region (388 pc; Kounkel et al. 2017)and has an age of ∼ 1 million years (Calvet et al. 2004).
With orbital periods of ∼ 9 months and 11 years, the orbital periods and separations are just in the right range toenable a full orbit characterisation, while expecting at thesame time strong interactions between the disk and thestars.

The triple star system
GW Ori is long known to be a single-lined spectroscopic
binary with a 242 day period (Mathieu et al. 1991). Prato
et al. (2018) reported the detection of lines associated withthe secondary. Observations with the IOTA infrared interferometer resolved the inner binary and discovered a third
component (Berger et al. 2011). Building on the workby Mathieu and coworkers, Czekala et al. presented in2017 an impressive set of spectra that were obtained over
35 years with the Fred L. Whipple Observatory and Oak
Ridge Observatory and that provide radial velocities forthe primary and secondary. Using these radial velocities
and the IOTA astrometry, Czekala and colleagues derived
first orbit solutions for all 3 stars. These orbit solutions indicated a 11.5 year orbit period for the tertiary and hinted
at a signficant misalignment between the stellar orbits andthe disk, although the small orbital arc covered by the
IOTA astrometry resulted in degeneracies in the orbit fits.
Between 2008 and 2019, the VLT Interferometer and theCHARA array were used to monitor the astrometric orbitof the inner binary and the tertiary (Kraus et al. 2020a).
The resulting orbits are shown in Figure 1 and correspondto a near-circular (e = 0.069 ± 0.009), 241.62 ± 0.05 day orbit for the inner binary and a 4216.8 ± 4.6 day orbit for thetertiary with significant eccentricity (e = 0.379 ± 0.003),
where the mutual inclination between the orbital planes is13.9 ± 1.1◦ .

Pre-main-sequence multiples as benchmark
for disk hydrodynamics
Understanding how bodies interact with each other andwith disk material holds the key to understanding thearchitecture of stellar systems and of planetary systems.
While the interactions between point sources can be described by simple gravity, interactions with disk material
require further knowledge about viscosity and gas+dust
microphysics that need to be included when simulating
disk-body interactions. As a result of our limited knowledge in these areas it is, for instance, still difficult to estimate the mass of a gap-opening planet from the morphology of a gap observed in a protoplanetary disk, or, to derive with certainty whether a gap is opened by a planet instead of by other processes. Furthermore, numerical simulations continue to unveil new dynamical processes thatmight shape protoplanetary disk structures and affect theplanet populations forming from these disks. One example
is disk tearing that might occur in the disks around multiple stars whose orbital angular momentum vectors are
misaligned with respect to the rotation axis of the disk.
Based on computer simulations it has been proposed in2012 that the resulting gravitational torques could tearthe disk apart and cause rings to separate from the disk
and to precess independently around the central objects(Nixon et al. 2012, 2013, Facchini et al. 2013, 2018). In
order to test such theories and to calibrate the fundamental parameters involved in hydrodynamic simulations, premain-sequence (PMS) multiple systems provide us with aunique laboratory (for general reviews on PMS binaries

The precise masses of the components in the GW Ori system has long been a matter of debate. Mathieu et al.
(1995) estimated the mass using evolutionary tracks, yielding 2.5 M⊙ and 0.5 M⊙ for the primary and secondary,respectively. Other workers estimated the mass from the
H-band flux ratio and derived more equal mass ratios (e.g.
3.2 M⊙ and 2.7 M⊙ ; Prato et al. 2018). These discrepancies can likely be explained by the non-negligle & time7

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2011.02005.92005.02018.1
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Figure 3: Top-left: Overlay of the ALMA continuum image (blue) and the SPHERE scattered light image (red; credit:
ESO/Exeter/Kraus et al.). Top-right: SPHERE H-band polarimetric image and model image. Bottom: Sketch of the
3-dimensional disk geometry of GW Ori. From Kraus et al. 2020a.

yields an eccentricity e = 0.3 and a semi-major axis surface that is facing away from Earth and that appearsof 43 au radius for ring R3 and that the ring is seen bright in scattered light due to the direct illumination fromunder inclination of 155◦ (Fig. 3; Kraus et al. 2020a). the stars. Arc A4 corresponds to the side facing towards
us, where we see only the self-shadowed outer side of thewarped surface (Fig. 3). The shadows from the misaligned
Broken & warped disk geometry
ring are cast onto this warped surface and appear as shadows S1 and S2, while the broad shadows S3 and S4 corShadows have been observed in several protoplanetary disks,
respond to the regions where the break orbit crosses thebut GW Ori is (to my knowledge) the first case where the plane of the outer disk, which coincides with the direction
ring casting the shadow has been spatially resolved. Thisin the warp with the highest radial column density.
enables tight constraints on the shape and 3-dimensional
orientation of the misaligned ring as well as the curvature of the warped disk surface inside of the middle ring Origin of the disk misalignments
R2 (r <
∼ 182 au). The scattered-light morphology showsa strong East-West asymmetry, where the bright Eastern To determine the origin of the extreme disk misalignments
arc A3 and the fainter Western arc A4 form together an observed in GW Ori, two teams recently presented smoothed
apparent ellipse with semi-major axis of 90 au and high particle hydrodynamic simulations. Bi et al. conductedeccentricity (e = 0.65; Fig. 4). Kraus et al. (2020a) iden- SPH simulations using the ’phantom’ code and concluded
tifies this ellipse as the point where the disk breaks due that the gravitational torque of the stars alone cannot exto the gravitational torque from the central triple system. plain the observed large misalignment between the dust
The bright arc A3 constitutes the side of the warped disk ring. Instead, they propose that an undiscovered compan10

Artist!impression(adopting!derived!3D!geometry)

SPHERE!(H−band)

Figure 4: Artist impression of the 3-dimensional geometry of the GW Ori disk (left) and comparison with the SPHERE
image (right). Credit: ESO/Calçada, Exeter/Kraus et al.

ion located between the inner and middle ring that might
have broken the disk and induced the misalignments.

OutlookOver the last few decades several exciting pre-main-sequencemultiple systems have been found and extensively studied, including GG Tau, HD142527, HD98800, and T Tauri.
GW Ori stands out with respect to the tight constraints
on the full 3-dimensional orbits for all components in thesystem, the dynamical masses, and our knowledge on the
3-dimensional geometry of the strongly distorted disk (fora visualization of the deduced disk geometry & orbits,
see the interactive 3-dimensional model in Fig. 6). Dueto this unique information, the system could serve as avaluable benchmark for calibrating hydrodynamic models and fundamental parameters under well-defined conditions. This could provide the validation & refinement thatis needed before applying the models to the much less-wellBoth simulations adopt similar Shakura-Sunyaev viscosi- constrained planet formation case, where the masses andties (αSS = 0.008 − 0.013 for Bi et al.; 0.01-0.02 for Kraus orbits of the gap-opening bodies are not known in general.
et al.). Therefore, it appears more likely that the different
The disk-tearing effect that we might witness in GW Ori inoutcomes might be related to the setup of the simulation.
action, constitutes an important new mechanism for movThere are differences concerning the number of stars ining disk material onto highly oblique or retrograde orbits,
cluded in the simulation (2 stars in Bi et al. simulation;even at very wide separations from the star. At the same
3 stars in Kraus et al. simulation) and the orbit solution
time, the observed torn ring seems to be sufficiently masthat is adopted for the simulation (Czekala et al. 2017
sive and might be sufficiently stable for planet formation
solution and Kraus et al. 2020a solution, respectively).
to occur, potentially giving rise to an yet-undiscovered
population of circum-multiple planets on highly oblique,long-period orbits.

The ’sphNG’ simulation presented in Kraus et al. (2020a),on the other hand, shows the disk tearing effect, where thegravitational torque of the three stars tears the disk apartinto distinct rings that precess independently around thecentral objects. After letting the dust distribution evolvefor a few thousand years, a ring breaks out of the disk
plane, whose radius (∼ 40 au), eccentricity (e ∼ 0.2), andextreme misalignment agree well with the observed properties of ring R3. Also, the disk breaks and a warp forms
just beyond the break radius, whose dimension, geometry,and low column density agree reasonably well with theproperties of the warp derived from the GW Ori observations (Fig. 5).

11

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log!(density!/!g!cm )Figure 5: SPH model, computed with the sphNG code developed by Matthew Bate and collaborators. The simulation
adopts the triple star orbits shown in Fig. 1 and an initial disk orientation that corresponds to the outer ALMA rings
R1+R2. The snapshot shows the gas density after 9500 years. Panel (A) shows the column density along the line-ofsight seen from Earth; in (B) and (C) the z-axis indicates the direction towards the observer.

An important open question concerns the origin of the outermost ring in GW Ori. The high submillimeter brightnessof the inner and middle ring can likely be explained by disk
tearing and dust filtration processes near the disk warp region. It is unclear whether the outer-most ring can also be
explained by the dynamical interplay between the central
triple system and the disk, or whether dust trapping neara planet-induced density gap might be required to explain
the high submillimeter surface brightness in this region.
But what caused the misalignment between the disk andthe orbits in the first place? Possibilities include turbulent
disk fragmentation (Offner et al. 2010), perturbation byother stars in a stellar cluster (Clarke & Pringle 1993), thecapture of disk material during a stellar flyby (Clarke &Pringle 1991), or the infall of material with a different angular momentum vector from that of the gas that formed
the stars initially (Bate et al. 2010, Bate 2018). To answer
this question, statistical information will be of essence,both on the disk-orbit misalignment in pre-main-sequencemultiples and on the orbital architecture and spin-orbitalignment in main-sequence systems. Obtaining such constraints on a large sample of stars is a key science objective for the proposed VLTI instrument BIFROST (Kraus
et al. 2019, 2020b) and could offer important new insights
on both the star- and planet-formation processes.

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Prato, L., et al. 2018, ApJ 852, 38
Reipurth, B. et al. 2014, Protostars and Planets V, p. 267
Shevchenko, V.S., et al. 1992, IBVS 3746, 1

Acknowledgement:
I would like to thank my collaborators on our recent paper on GW Ori
and the members of the team around Jiaqing Bi for delightful discussions on this fascinating object. Also I acknowledge support froman ERC Starting Grant (Grant Agreement No. 639889).

12Figure 6: Interactive 3-dimensional model of the disk geometry in GW Ori, as derived in Kraus et al. 2020a. Openwith Adobe Acrobat Reader, click on the graphics, and select ’trust this document’ at the top of the window.
Then click & drag with the mouse to change the viewing angle. You can use the toolbar elements or mouse/trackpad
gestures (e.g. pinch gesture on trackpad; or shift key and swipe up/down) to zoom into the graphics and to display
the triple star orbits.

13

retical evolutionary models did not agree and there was noagreed upon conversion scale for observed spectral types
to Tef f .

Perspective

The Prologue: In the late 1990’s Lisa Prato (LowellObs.), Gail Schaefer (CHARA, GSU), and I set out tomeasure Mdyn of spectroscopic and visual binaries (SBand VB) in the Taurus and the Ophiuchus SFRs. We
knew that at the average distances of these regions, VBs
and SBs whose parameters would be measurable in a reasonable amount of time (for us, and hopefully not exceeding the patience of TACs and funding agencies), would
have separations of a few tens of milli-arc seconds andtheir components would orbit at few to 10s of km/s. This
meant that the observations would have to be made at very
high angular and spectral resolutions. These requirements
eventually led us to competing for the share of observing
time funded by NASA at the Keck Observatory. Schaefer
et al. (2020) describes results of this work applied to the
T Tau triple system. We were able to measure the Mdyn
T Tau Sa and Sb and estimate the mass of T Tau N.

Masses and Ages of Pre-Main
Sequence Stars
Michal Simon

1

The Past is Prologue

I take the liberty of writing this Perspective as a personal
history. In a long, productive, and fun collaboration withwonderful colleagues I have pursued dynamical mass measurements of PMS stars for more than a quarter of a century.
The Past: Why dynamical? Dynamical masses, Mdyn ,depend only on gravity and are the gold standard of massmeasurement. Usually they have been determined by theorbital parameters of binaries. A star’s mass is an intrinsic property. It determines everything about its evolution
from formation to end. A large sample of masses in a star
forming region (SFR) such as Taurus provides information about its distribution of masses, the IMF. But there’s
more to our work than mass: Age also matters. By placing a PMS star with well-determined Tef f and luminosity
on an HR diagram (HRD) with evolutionary tracks andisochrones, we can estimate its age and learn about its
history and the formation of its associated exoplanets.

An approach to measuring Mdyn , that could be applied
to single stars, resulted from my good fortune to spend
the last half of 1998 on sabbatical leave at Observatoirede Grenoble. Stéphane Guilloteau and Anne Dutrey had
just shown that using a 12 CO J=1 to 0 line interferometric image of the circumstellar disk associated with the single star DM Tau, they could extract the disk’s rotation
velocity, inclination, and other parameters (Guilloteau &Dutrey, 1998). Since the disk mass is small compared tothat of the central star, the rotation is Keplerian and determines DM Tau’s mass dynamically. On a memorable
walk to lunch, Stéphane and I decided to embark on Mdyn
measurements of the PMS stars with disks in the Taurus
SFR.

Dynamical mass determined by the circumstellar disk technique can be obtained in a single observation while the SB
and VB techniques require many observations distributed
over the orbital period of the binary, usually several years.
Measurement of Mdyn by disk rotation can therefore proceed more rapidly than by observation of binaries. The
techniques are complementary because the disk technique
is limited to Class II T Tauri stars while the VB and SB
techniques may be applied to both Class II and III T Tauri
The HRD-fitting approach works reliably when applied to stars. This turned out to be important because we slowly
main-sequence stars because the accuracy of theoretical learned from experience that very low mass PMS stars
models of their properties has been well tested and cali- (M < 0.4M⊙ ) with disks extensive and massive enoughbrated by dynamical measurements of their masses. Un- for measurement of their rotation are rare (Schaefer et al.
fortunately, when we applied the HRD-fitting approach to 2009, Simon et al. 2019).
PMS stars, we quickly found that we were standing on
Using data from IRAM’s Plateau de Bure interferomequicksand. In addition to the expected problems associter, by 1999 we had measured Mdyn for 7 singles in Tauated with observing PMS stars, principally their variabilAur. With values of Mdyn in hand, the next step wasity, extinction, veiling, and spectral energy distributions,to place them on HRDs showing the evolutionary tracks
we faced two other obstacles: the several available theoand isochrones of four available theoretical evolutionary
14

3

12

MESA
BHAC15F16
2

8

Disk Rotation

6

Rphot/Rsun

Number of Stars

10

VBSB2
VBSB2

1.0

1

Astrom

4

1.4

0.2

0.5

2
0.1 M(msun)

Eclipsing Binaries
0
0.0

0.5

1.0
Mass (Msun)

1.5

0
6.0

2.0

6.5

7.0
Log Age(yr)

7.5

8.0

Figure 1: Mdyn good to 5% that had been measured by Figure 2: Photospheric radius vs log Age for the MESA,
BHAC15, and non-magnetic F16 models.
mid-2019 (G. Schaefer, priv. comm.)

models (Simon et al 2000). This paper shows vividly thequicksand we were walking in. We found differences aslarge as 0.2 M⊙ between the Mdyn and Mhrd . For a given
star the models indicate ages discrepant by as much as 3
MY.

• Discrepancies among the evolutionary models needed tobe resolved.

• Given that PMS stars are very variable, probably owing to active regions driven by their convective interiors
and episodic accretion, we needed at least a conservative
Hillenbrand & White (2004) confirmed and quantified these estimate of the uncertainty of the measured luminosity.
discrepancies. Using 27 Mdyn for PMS stars in the north- • The Taurus SFR spans about ∼ 50 × 50 pc in RA andern and southern hemispheres and the available evolution- Dec; its depth probably extends ∼ 50 pc as well. To avoid
ary models they found that Mhrd underestimated Mdyn by an uncertainty as large as ∼ 60% attributable to unknown
10 − 30% for Mdyn in the range 0.3 to 1.2 M⊙ in all age distance we needed precise distances to individual stars.
ranges considered. The mass and age discrepancies meantthat we could not trust the theoretical models to provide
The wheels of progress turn slowly, but through the efforts
estimates of the masses and ages of PMS stars and thatof theorists and observers they did turn. Fig. 1 shows
our understanding of the earliest years of star and planet
G. Schaefer’s compilation of 67 PMS Mdyn measured toformation were very uncertain.
precision ≤ 5.0%. The compilation includes stars in themass range 0.1 to 2.0 M⊙ . It is complete to mid-2019.
Three of the Mdyn measured by disk rotation are from
2 The Devil is in the Details Sheehan et al. (2019); the others are drawn from Simon
et al. (2019) and references therein.
Beating Back the Devil
Spectral Type to Tef f conversions are now in good agreeThe way forward was clear but achieving clarity took two ment down to the Tef f of the late M SpTy PMS stars
decades. To accomplish our over-all goals, we needed:(Luhman (2003); Pecaut and Mamajek (2013); Herczeg• A large database of PMS Mdyn distributed over a range and Hillenbrand (2014)).

of spectral types.

• The majority of known PMS stars in Taurus are M spectral type stars. Unfortunately the SpTy to Tef f conversion for M stars differed among the look-up tables available in the early 2000s and most did not extend to SpTy
M9 (understandably because on the main sequence M9’s
were brown dwarfs.) We needed a reliable SpTy to Tef flook-up table for PMS stars.

Agreement among recent models of PMS evolution that do
not include magnetic fields is now much improved (Fig. 2).
For M > 0.5 M⊙ and age > 1 MY, the models of Baraffe
et al. (2015, BHAC15), MESA (Paxton et al. 2015 andChoi et al. 2016), and the non-magnetic models of Feiden(2016), the models are in excellent agreement (Simon &Toraskar 2017). Moreover, models that included the effectof magnetic fields on the convection in low mass stars andtheir public availability (Feiden 2016) would enable their15

application to PMS stars (Richert et al. 2018; Simon etal. 2019).
Gaia DR2 in 2018 meant that precision distances became
available. The time was ripe to apply the advances of thefirst two decades of this millenium to the stars for which
we had measured Mdyn .

3

Putting It All Together

By 2019 we had measured Mdyn by disk rotation for 45
stars in Taurus. The stars are singles and components ofbinaries that are sufficiently wide that the disk rotation of
one component can be measured without confusion fromthe other. The sample includes 33 stars with previously
published dynamical masses and 12 stars for which we obtained new dynamical masses using archival ALMA data.
Of the 12 stars, 5 did not have dynamical masses published previously. Our sample consisted of well known T
Tauri stars, all Class II objects. By Gaia standards all arebright and distances with precisions better than ±2 pc areavailable for nearly all (Bailer-Jones et al. 2018). We selected 29 stars with dynamical mass precisions better than
10% for analysis.
We placed the stars on two HRDs, one using evolutionarymodels of Baraffe et al. 2015 and the other Feiden’s (2016)
magnetic models. We derived Mhrd for both and comparedthem to the Mdyn . Figures 3 (left and right) show theresults. Fig. 3 right provided the Eureka! moment.
Figure 3: Top: (Mdyn − Mhrd ) vs Mdyn for Mhrd derived
Fig. 3 (top) shows that track masses derived using the from an HRD using Baraffe et al.’s (2015) evolutionary
non-magnetic, “standard”, model of Baraffe et al. (2015) models. Bottom: Same as (a) but for Mhrd derived fromare smaller than most of the dynamical masses. The av- Feiden (2016)’s magnetic evolutionary models (see Fig. 4).
erage difference (Mdyn - Mhrd ) is 0.19 ± 0.02 M⊙ . In the All masses are in units of M⊙ .
Mdyn mass range 0.4 to 1.0 M⊙ , the normalized difference(Mdyn - Mhrd )/Mdyn is about 0.3. Our finding that masses
derived from an HRD that uses a standard evolutionary star at log (T ) = 3.58 and log (L/L ) = -0.30. Itsef f⊙model tend to underestimate the Mdyn is completely con- mass and age measured with respect to the non-magnetic
sistent with Hillenbrand and White’s (2004) result.
model would be ∼ 0.5M and ∼ 2 MY while relative to⊙On the other hand, the Mhrd evaluated using an HRD
with Feiden’s magnetic evolutionary tracks and isochrones(Fig. 4) provide values much closer to the Mdyn , Fig. 3
bottom. The average difference (Mdyn - Mhrd ) is 0.01 ±0.02 M⊙ . The magnetic models provide mass estimatesthat are more consistent with actual masses of the stars.
Fig. 4 also shows that the stars appear older (roughly 3 to
10 MY) than the 1 to 3 MY usually quoted for the Taurus
SFR based on standard models. The average age of thestars evaluated with respect to Feiden’s magnetic models
is 5.8 ± 0.8 MY (Simon and Prato, 2019).

the magnetic model its mass and age would be greater,∼ 0.7 M⊙ , and older, ∼ 3 MY. The older age is theresult of the star’s slower contraction owing to additional
magnetic pressure. It takes longer for the star to collapse
to the photospheric radius determined by its luminosityand effective temperature. Further, in the presence of the
combined gas and magnetic pressures, a stronger gravitational field than in the standard model is necessary tosupport the star at the given photospheric radius.

CI Tau, a Classic T Tauri star in our sample with mass
0.90 ± 0.02 M⊙ and age 7.8+6.8−4.0 MY hosts a well-studied
Fig. 5 illustrates why magnetic models represent the mass hot Jupiter (Flagg et al., 2019). The fact that the exof a PMS star better than non-magnetic models and also oplanet is bright enough that Flagg et al. were able toproduce an older age. The blue dot represents a PMS unravel the exoplanet’s K-band emission from that of the16

Figure 4: Mdyn on an HRD using Feiden’s (2016) mag- Figure 5: Comparison of Feiden’s standard and magnetic
netic evolutionary models. The luminosities and Tef f are models on the HRD.
derived from Herczeg & Hillenbrand (2014).

host star rules out a “cold start” model for its formation.
Apparently a “hot start” did it. This illustrates the potential of age determination to inform planet formation
scenarios.
The material in this section is described in more detail in
Simon et al. (2019).

ity of the magnetic models with measured Mdyn smaller
than 0.4 M⊙ . My colleagues and I are working on this.
The pressure of internal magnetic fields increases the star’s
photospheric radius over that predicted by the non-magnetic
models. The acid test will come from measurements of thediameters of the T Tauri stars. This measurement may bepossible soon with the next generation of O/IR interferometers.
References:

4

C. A. L., Rybizki, J., Fouesneau, M., et al. 2018, AJ,“It’s Tough to Make Predictions Bailer-Jones,
156, 58
Baraffe, I.; Homeier, D., Allard, F. & Chabrier, G., 2015, A&A, 577,
- Especially about the Future”,
42
Choi, J., Dotter, A., Conroy, C., Cantiello, M. Paxton, B., Johnson,
Yogi Berra

Where do we stand today? The work I have described
points the way out of the quicksand. We have learned thatwhen ages and masses of low mass PMS stars are needed
and dynamical masses are not available, magnetic models of stellar evolution will provide trust-worthy results
for masses > 0.4 M⊙ . Simon and Prato (2019) placed 9Class III stars, stars without disks in the Taurus SFR andfound their age, 5.4 ± 0.4 MY, is indistinguishable fromthat of the Class II stars. Obviously, the same procedurecan be applied to other SFRs whose PMS stars have welldetermined luminosities and Tef f .

B. 2016, ApJ, 823, 102
Feiden, G. A. 2016, A&A, 593, A99
Flagg, L., Johns-Krull, C. M., Nofi, L., et al. 2019, ApJL, 878, L37
Luhman, K.L.; Stauffer, J.R., Muench, A.A.; et al. 2003, ApJ, 593,
1093
Herczeg, Gregory J.; Hillenbrand, Lynne A. 2014, ApJ, 786, 97
Hillenbrand, Lynne A.; White, Russel J. 2004, ApJ, 604, 741
Paxton, B.; Marchant,P.; Schwab, J. et al. 2015, ApJS, 220, 15
Pecaut, M. J.& Mamajek, E. E., 2013, ApJS, 208, 9
Schaefer, G.H.; Dutrey, A.; Guilloteau, S. et al. 2008, ApJ, 701, 698
Schaefer, G.H.; Beck, Tracy L., Prato, L. & Simon, M. 2020, AJ,
160, 35
Simon, M.; Dutrey, A. & Guilloteau 2000, ApJ, 545, 1034
Simon. M.; Toraskar, J. 2017, ApJ, 841, 95
Simon, M., Guilloteau, S., Beck, T. L., et al. 2019, ApJ, 884, 42
Simon, M. & Prato, L. 2019, RNAAS, 3, 168.

Two advances are necessary. We need to test the reliabil17

Abstracts of recently accepted papers

1.

A Novel Survey for Young Substellar Objects with the W-band Filter. I. Filter Design
and New Discoveries in Ophiuchus and Perseus
K.N. Allers1,2 and Michael C. Liu3
Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837, USA; 2 Visiting Astronomer at
the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the
National Aeronautics and Space Administration; 3 Institute for Astronomy, University of Hawai’i, 2680 Woodlawn
Drive, Honolulu, HI 96822, USA
1E-mail contact: mliu at ifa.hawaii.edu
We present the design and implementation of a medium-band near-IR filter tailored for detecting low-mass stars andbrown dwarfs from the summit of Maunakea. The W-band filter is centered at 1.45 µm with a bandpass width of 6%,
designed to measure the depth of the H2 O water absorption prominent in objects with spectral types of M6 and later.
When combined with standard J- and H-band photometry, the W-band filter is designed to determine spectral types
to ≈1.4 subtypes for late-M and L dwarfs, largely independent of surface gravity and reddening. This filter’s primary
application is completing the census of young substellar objects in star-forming regions, using W-band selection to
greatly reduce contamination by reddened background stars that impede broad-band imaging surveys. We deployed
the filter on the UH 88-inch telescope to survey ≈3 sq. deg. of the NGC 1333, IC 348, and rho Ophiuchus star-forming
regions. Our spectroscopic followup of W-band selected candidates resulted in the confirmation of 48 ultracool dwarfs
with a success rate of 89%, demonstrating the efficacy of this new filter and selection method.
Accepted by PASP
http://arxiv.org/pdf/2008.00010

2.

Selected aspects of the analysis of molecular line observation of edge-on circumbinary
disks
Roman Avramenko1 , Sebastian Wolf1 , Tobias F. Illenseer1 and Stig Rehberg1
1

University of Kiel, Institute of Theoretical Physics and Astrophysics, Leibnizstrasse 15, 24118 Kiel, Germany

E-mail contact: ravramenko at astrophysik.uni-kiel.deContext: Inner cavities, accretion arms and density waves are characteristic structures in the density distribution of
circumbinary disks. They are the result of the tidal interaction of the non-axisymmetric gravitational forces of thecentral binary with the surrounding disk and are most prominent in the inner region, where the asymmetry is mostpronounced.
Aims: The goal of this study is to test the feasibility of reconstructing the gas density distribution and quantifying
properties of structures in the inner regions of edge-on circumbinary disks using multiple molecular line observations.
Methods: The density distribution in circumbinary disks is calculated with two-dimensional hydrodynamic simulations.
Subsequently, molecular line emission maps are generated with 3D radiative transfer simulations. Based on these, weinvestigate the observability of characteristic circumbinary structures located in the innermost region for spatiallyresolved and unresolved disks.
Results: We find that it is possible to reconstruct the inner cavity, accretion arms and density waves from spatiallyresolved multi- wavelength molecular line observation of circumbinary disks seen edge-on. For the spatially unresolved
observation only an estimate for the density gradient in the transition area from cavity to inner disk rim can bederived.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2008.10499
18

3. On the Nature of the T Tauri Triple System
Tracy L. Beck1 , G. H. Schaefer2 , S. Guilloteau3 , M. Simon4 , A. Dutrey3 , E. Di Folco3 and E. Chapillon3,5
The Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA; 2 The CHARA Array ofGeorgia State University, Mount Wilson Observatory, Mount Wilson, CA 91023, USA; 3 Laboratoire dAstrophysiquede Bordeaux, Universit de Bordeaux, CNRS, B18N, Alle Geoffroy Saint-Hilaire, 33615 Pessac, France; 4 Departmentof Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA; 5 IRAM, 300 Rue de la Piscine,
38406 Saint Martin dHres Cedex, France
1

E-mail contact: tbeck at stsci.edu
We present a multi-wavelength analysis to reveal the nature of the enigmatic T Tauri triple star system. New opticaland infrared measurements are coupled with archival X-ray, UV and mm datasets to show morphologies of disk
material and outflow kinematics. A dark lane of obscuring material is seen in silhouette in several emission lines andin model-subtracted ALMA mm continuum dust residuals near the position of T Tau Sa+Sb, revealing the attenuating
circumbinary ring around T Tau S. The flux variability of T Tau S is linked in part to the binary orbit; T Tau Sb
brightens near orbital apastron as it emerges from behind circumbinary material. Outflow diagnostics confirm thatT Tau N powers the blue-shifted western outflow, and the T Tau S binary drives the northwest-southeastern flow.
Analysis of the southern outflow shows periodic arcs ejected from the T Tau system. Correlation of these arc locations
and tangential kinematics with the orbit timing suggests that launch of the last four southern outflow ejections iscontemporaneous with, and perhaps triggered by, the T Tau Sa+Sb binary periastron passage. We present a geometryof the T Tau triple that has the southern components foreground to T Tau N, obscured by a circumbinary ring, with misaligned disks and interacting outflows. Particularly, a wind from T Tauri Sa that is perpendicular to its circumstellar
disk might interact with the circumbinary material, which may explain conflicting high contrast measurements of thesystem outflows in the literature. T Tauri is an important laboratory to understand early dynamical processes inyoung multiple systems. We discuss the historical and future characteristics of the system in this context.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2009.03861

4.

Spectroscopic characterization of the known O-star population in Cygnus OB2. Evidence of multiple star-forming bursts
S.R. Berlanas1,2,3 , A. Herrero2,3 , F. Comerón4 , S. Simón-Díaz2,3 , D.J. Lennon2 et al.
Departamento de Física Aplicada, Universidad de Alicante, 03690 San Vicente del Raspeig, Alicante, Spain; 2
Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain; 3 Departamento de Astrofísica, Universidad
de La Laguna, Tenerife, Spain; 4 ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
1E-mail contact: sara.rb at ua.es
Cygnus OB2 provides a unique insight into the high-mass stellar content in one of the largest groups of young massive
stars in our Galaxy. Although several studies of its massive population have been carried out over the last decades, anextensive spectroscopic study of the whole known O-star population in the association is still lacking. In this work, wecreated the most complete spectroscopic census of O stars carried out so far in Cygnus OB2 using already existing andnew spectroscopy. We present the spectra for 78 O-type stars, from which we identify new binary systems, obtain the
distribution of rotational velocities, and determine the main stellar parameters for all the stars in the region that havenot been detected as double-line spectroscopic binaries. We also derive radii, luminosities, and masses for those stars
with reliable Gaia astrometry, in addition to creating the Hertzsprung-Russell Diagram to interpret the evolutionary
status of the association. This work has shown the improvement reached when using accurate spectroscopic parameters
and astrometry for the interpretation of the evolutionary status of a population, revealing, in the case of Cygnus OB2,
at least two star-forming bursts at ∼3 and ∼5 Myr. We find an apparent deficit of very fast rotators in the distributionof rotational velocities. The inspection of the dynamical distribution of the sample has allowed us to identify nine O
stars with peculiar proper motions and discuss a possible dynamical ejection scenario or past supernova explosions in
the region.
Accepted by A&A
http://arxiv.org/pdf/2008.09917

19

5. Dense gas formation in the Musca filament due to the dissipation of a supersonic con-verging flow
L. Bonne1 , N. Schneider2 , S. Bontemps1 , S. D. Clarke2 , A. Gusdorf3,4 , A. Lehmann3 , M. Steinke2 , T.
Csengeri1,5 , S. Kabanovic2 , R. Simon2 , C. Buchbender2 and R. Guesten5
Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, alle Geoffrey Saint-Hilaire, 33615
Pessac, France; 2 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany; 3 Laboratoirede Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS Sorbonne Université de Paris, Paris, France;
4
Observatoire de Paris, PSL University, Sorbonne Université, LERMA, 75014 Paris, France; 5 Max-Planck-Institut
für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
1E-mail contact: lars.bonne at u-bordeaux.fr
Observations with the Herschel Space Telescope have established that most star forming gas is organised in filaments, afinding that is supported by numerical simulations of the supersonic interstellar medium (ISM) where dense filamentary
structures are ubiquitous. We aim to understand the formation of these dense structures by performing observations
covering the 12 CO(4→3), 12 CO(3→2), and various CO(2-1) isotopologue lines of the Musca filament, using the APEX
telescope. The observed CO intensities and line ratios cannot be explained by PDR (photodissociation region) emission
because of the low ambient far-UV field that is strongly constrained by the non-detections of the [CII] line at 158 µm
and the [OI] line at 63 µm, observed with the upGREAT receiver on SOFIA, as well as a weak [CI] 609 µm line detectedwith APEX. We propose that the observations are consistent with a scenario in which shock excitation gives rise towarm and dense gas close to the highest column density regions in the Musca filament. Using shock models, we findthat the CO observations can be consistent with excitation by J-type low-velocity shocks. A qualitative comparisonof the observed CO spectra with synthetic observations of dynamic filament formation simulations shows a good
agreement with the signature of a filament accretion shock that forms a cold and dense filament from a converging
flow. The Musca filament is thus found to be dense molecular post-shock gas. Filament accretion shocks that dissipate
the supersonic kinetic energy of converging flows in the ISM may thus play a prominent role in the evolution of coldand dense filamentary structures.
Accepted by A&A
https://www.aanda.org/articles/aa/pdf/2020/09/aa37104-19.pdf

6. A High Angular Resolution Survey of Massive Stars in Cygnus OB2: JHK Adaptive

Optics Results from the Gemini Near-InfraRed Imager
S.M. Caballero-Nieves1 , D.R. Gies2 , E.K. Baines3 , A.H. Bouchez4,5 , R.G. Dekany6 et al.
Department of Physics and Space Sciences, Florida Institute of Technology 150 University Blvd, Melbourne, FL
32901, USA; 2 Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State
University, P. O. Box 5060, Atlanta, GA 30302-5060, USA; 3 Remote Sensing Division, Naval Research Laboratory,
4555 Overlook Avenue SW, Washington, DC 20375, USA 4GMTO Corporation, 251 South Lake Avenue, Pasadena,
CA 91101,USA; 5 Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA
91101, USA; 6 California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA
1E-mail contact: scaballero at fit.edu
We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we
conducted with the NIRI camera and ALTAIR adaptive optics system of the Gemini North telescope. We observed 74
O- and early B-type stars in Cyg OB2 in the JHK infrared bands in order to detect binary and multiple companions.
The observations are sensitive to equal-brightness pairs at separations as small as 0.′′ 08, and progressively faintercompanions are detectable out to ∆K = 9 mag at a separation of 2′′ . This faint contrast limit due to readnoisecontinues out to 10′′ near the edge of the detector. We assigned a simple probability of chance alignment to eachcompanion based upon its separation and magnitude difference from the central target star and upon areal star counts
for the general star field of Cyg OB2. Companion stars with a field membership probability of less than 1% areassumed to be physical companions. This assessment indicates that 47% of the targets have at least one resolved
companion that is probably gravitationally bound. Including known spectroscopic binaries, our sample includes 27
binary, 12 triple, and 9 systems with four or more components. These results confirm studies of high mass stars inother environments that find that massive stars are born with a high multiplicity fraction. The results are important
20

for the placement of the stars in the H-R diagram, the interpretation of their spectroscopic analyses, and for future
mass determinations through measurement of orbital motion.
Accepted by AJ
http://arxiv.org/pdf/2008.00064

7. The observational impact of dust trapping in self-gravitating discs
James Cadman1,2 , Cassandra Hall3,4,5 , Ken Rice1,2 , Tim J. Harries6 and Pamela D. Klaassen7
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 Department of Physics and Astronomy,
University of Leicester, University Road, Leicester, LE1 7RH, UK; 4 Department of Physics and Astronomy, The
University of Georgia, Athens, GA 30602, USA; 5 Center for Simulational Physics, The University of Georgia, Athens,
GA 30602, USA; 6 Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK;7
UK Astronomy Technology Center, Royal Observatory Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ, UK
1E-mail contact: cadman at roe.ac.uk
We present a 3D semi-analytic model of self-gravitating discs, and include a prescription for dust trapping in the discspiral arms. Using Monte-Carlo radiative transfer we produce synthetic ALMA observations of these discs. In doing so
we demonstrate that our model is capable of producing observational predictions, and able to model real image data ofpotentially self-gravitating discs. For a disc to generate spiral structure that would be observable with ALMA requiresthat the disc’s dust mass budget is dominated by millimetre and centimetre-sized grains. Discs in which grains havegrown to the grain fragmentation threshold may satisfy this criterion, thus we predict that signatures of gravitational
instability may be detectable in discs of lower mass than has previously been suggested. For example, we find thatdiscs with disc-to-star mass ratios as low as 0.10 are capable of driving observable spiral arms. Substructure becomeschallenging to detect in discs where no grain growth has occurred or in which grain growth has proceeded well beyond
the grain fragmentation threshold. We demonstrate how we can use our model to retrieve information about dust
trapping and grain growth through multi-wavelength observations of discs, and using estimates of the opacity spectral
index. Applying our disc model to the Elias 27, WaOph 6 and IM Lup systems we find gravitational instability to bea plausible explanation for the observed substructure in all 3 discs, if sufficient grain growth has indeed occurred.
Accepted by MNRAS
http://arxiv.org/pdf/2008.09826

8.

Colliding in the shadows of giants: Planetesimal collisions during the growth and migration of gas giants
Philip J. Carter1 and Sarah T. Stewart1
Department of Earth and Planetary Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616,
USA
1

E-mail contact: pjcarter at ucdavis.edu
Giant planet migration is an important phenomenon in the evolution of planetary systems. Recent works have shownthat giant planet growth and migration can shape the asteroid belt, but these works have not considered interactions
between planetesimals. We have calculated the evolution of planetesimal disks, including planetesimal-planetesimalcollisions, during gas giant growth and migration. The numbers, locations, and impact velocities of these collisions
depend on the specific growth and migration path. We find that giant planet growth alone has little effect on impact
velocities, and most of the planetesimals scattered by growing giants do not undergo collisions with each other during
the growth period. In contrast, we find that giant planet migration induces large numbers of high velocity collisions
between planetesimals. These impacts have sufficient velocities to cause shock-induced vaporization for both water ice
and silicate components of planetesimals, and to cause catastrophic disruption of the bodies. New bodies may form
from impact debris. Collisional evolution reduces the efficiency of planetesimal implantation into the asteroid belt
via giant planet growth and migration. A small fraction of the largest planetesimals implanted into the asteroid belt
would have been processed via collisions. We identify important consequences of planetesimal collisions that have notbeen considered in planet accretion models. The prevalence of high velocity collisions during giant planet migration,
21

and their potential links to the properties of meteorites, and the formation of chondrules, makes impact vaporizationa critically important phenomenon. The consequences of vaporizing planetesimal constituents require further detailed
study. New collision outcome models for impacts within the nebula, and models for new planetesimal formation areneeded.
Accepted by The Planetary Science Journal
http://arxiv.org/pdf/2008.05549

9. The GAPS Programme at TNG XXVII. Reassessment of a young planetary systemwith HARPS-N: is the hot Jupiter V830 Tau b really there?
M. Damasso1 , A.F. Lanza2 , S. Benatti3 , V.M. Rajpaul4 , M. Mallonn5 et al.
INAF — Osservatorio Astrofisico di Torino, Via Osservatorio 20, I-10025, Pino Torinese (TO), Italy; 2 INAF —Osservatorio Astrofisico di Catania, Via S. Sofia,78 - 95123 Catania, Italy; 3 INAF — Osservatorio Astronomico diPalermo, Piazza del Parlamento 1, I-90134, Palermo, Italy; 4 Astrophysics Group, Cavendish Laboratory, JJ Thomson
Avenue, CB3 0HE Cambridge, UK; 5 Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam,
Germany
1E-mail contact: mario.damasso at inaf.it
Detecting and characterising exoworlds around very young stars (age <10 Myr) are key aspects of exoplanet demographic studies, especially for understanding the mechanisms and timescales of planet formation and migration.
However, detection using the radial velocity method alone can be very challenging, since the amplitude of the signals due to magnetic activity of such stars can be orders of magnitude larger than those induced even by massive
planets. We observed the very young (∼2 Myr) and very active star V830 Tau with the HARPS-N spectrographto independently confirm and characterise the previously reported hot Jupiter V830 Tau b (Kb = 68 ± 11 m s−1 ;mb sin ib = 0.57 ± 0.10 Mjup; Pb = 4.927 ± 0.008 d). Due to the observed ∼1 km s−1 radial velocity scatter clearly
attributable to V830 Tau’s magnetic activity, we analysed radial velocities extracted with different pipelines and modelled them using several state-of-the-art tools. We devised injection-recovery simulations to support our results andcharacterise our detection limits. The analysis of the radial velocities was aided by using simultaneous photometricand spectroscopic diagnostics. Despite the high quality of our HARPS-N data and the diversity of tests we performed,
we could not detect the planet V830 Tau b in our data and confirm its existence. Our simulations show that astatistically-significant detection of the claimed planetary Doppler signal is very challenging. Much as it is important
to continue Doppler searches for planets around young stars, utmost care must be taken in the attempt to overcome
the technical difficulties to be faced in order to achieve their detection and characterisation. This point must be
kept in mind when assessing their occurrence rate, formation mechanisms and migration pathways, especially without
evidence of their existence from photometric transits.
Accepted by A&A
http://arxiv.org/pdf/2008.09445

10.

Inferring (Sub)millimeter Dust Opacities and Temperature Structure in Edge-on Protostellar Disks From Resolved Multi-Wavelength Continuum Observations: The Caseof the HH 212 Disk
Zhe-Yu Daniel Lin1,2,3 , Chin-Fei Lee2,4 , Zhi-Yun Li1 , John Tobin5 and Neal Turner6
Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 2 Academia Sinica Institute of
Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan; 3 Department of Physics, National Chung Cheng
University, No.168, Sec. 1, University Rd., Minhsiung, Chiayi 62102, Taiwan; 4 Graduate Institute of Astronomy
and Astrophysics, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan; 5 National Radio
Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA; 6 Jet Propulsion Laboratory, California
Institute of Technology, Pasadena, California 91109, USA
1E-mail contact: zdl3gk at virginia.edu(Sub)millimeter dust opacities are required for converting the observable dust continuum emission to the mass, but
their values have long been uncertain, especially in disks around young stellar objects. We propose a method to22constrain the opacity κν in edge-on disks from a characteristic optical depth τ0 , ν, the density ρ0 and radius R0 at thedisk outer edge through κν = τ0,ν /(ρ0 R0 ) where τ0,ν is inferred from the shape of the observed flux along the majoraxis, ρ0 from gravitational stability considerations, and R0 from direct imaging. We applied the 1D semi-analyticalmodel to the embedded, Class 0, HH 212 disk, which has high-resolution data in ALMA Band 9, 7, 6, and 3 andVLA Ka band (λ=0.43, 0.85, 1.3, 2.9, and 9.1 mm). The modeling of the HH 212 disk is extended to 2D through
RADMC-3D radiative transfer calculations. We find a dust opacity of κν ≈ 1.9 × 10−2 , 1.3 × 10−2 , and 4.9 × 10−3
cm2 g−1 of gas and dust for ALMA Bands 7, 6, and 3, respectively with uncertainties dependent on the adopted
stellar mass. The inferred opacities lend support to the widely used prescription κλ = 2.3 × 10−2 (1.3 mm/λ) cm2 g−1
advocated by Beckwith et al. (1990). We inferred a temperature of ∼45 K at the disk outer edge which increases
radially inward. It is well above the sublimation temperatures of ices such as CO and N2 , which supports the notionthat the disk chemistry cannot be completely inherited from the protostellar envelope.
Accepted by MNRAS
http://arxiv.org/pdf/2008.08627

11. Making massive stars in the Galactic Centre via accretion onto low-mass stars within

an accretion disc
Melvyn B. Davies1 & Doug N. C. Lin2
Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, Lund, Sweden; 2 UCO/Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA
1E-mail contact: mbd at astro.lu.se
The origin of the population of very massive stars observed within ∼0.4 pc of the supermassive black hole in the
Galactic Centre is a mystery. Tidal forces from the black hole would likely inhibit in situ star formation whilst theyouth of the massive stars would seem to exclude formation elsewhere followed by transportation (somehow) into the
Galactic centre. Here we consider a third way to produce these massive stars from the lower-mass stars contained in
the nuclear stellar cluster which surrounds the supermassive black hole. A passing gas cloud can be tidally shreddedby the supermassive black hole forming an accretion disc around the black hole. Stars embedded within this accretion
disc will accrete gas from the disc via Bondi-Hoyle accretion, where the accretion rate onto a star, Ṁ⋆ ∝ M⋆ 2 . This
super-exponential growth of accretion can lead to a steep increase in stellar masses, reaching the required 40–50 M⊙
in some cases. The mass growth rate depends sensitively on the stellar orbital eccentricities and their inclinations.
The evolution of the orbital inclinations and/or their eccentricities as stars are trapped by the disc, and their orbits
are circularised, will increase the number of massive stars produced. Thus accretion onto low-mass stars can lead toa top heavy stellar mass function in the Galactic Centre and other galactic nuclei. The massive stars produced will
pollute the environment via supernova explosions and potentially produce compact binaries whose mergers may be
detectable by the LIGO-VIRGO gravitational waves observatories.
Accepted by MNRAS
http://arxiv.org/pdf/2008.10033

12.

Tidal tails of open star clusters as probes to early gas expulsion II: Predictions for Gaia
František Dinnbier1 and Pavel Kroupa2,3
I.Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln, Germany; 2 Helmholtz-Institut fürStrahlen- und Kernphysik, University of Bonn, Nussallee 14-16, 53115 Bonn, Germany; 3 Charles University in Prague,
Faculty of Mathematics and Physics, Astronomical Institute, V Holesovickách 2, 180 00 Praha 8, Czech Republic
1

E-mail contact: dinnbier at ph1.uni-koeln.de
We study the formation and evolution of the tidal tail released from a young star Pleiades-like cluster, due to expulsionof primordial gas in a realistic gravitational field of the Galaxy. The tidal tails (as well as clusters) are integrated fromtheir embedded phase for 300 Myr. We vary star formation efficiencies (SFEs) from 33% to 100% and the timescalesof gas expulsion as free parameters, and provide predictions for the morphology and kinematics of the evolved tail foreach of the models. The resulting tail properties are intended for comparison with anticipated Gaia observations inorder to constrain the poorly understood early conditions during the gas phase and gas expulsion. The simulations are23

performed with the code nbody6 including the gravitational potential of the Galaxy, and an analytical approximation
for the natal gaseous potential. Assuming that the Pleiades formed with rapid gas expulsion and an SFE of ≈ 30 %,the current Pleiades are surrounded by a rich tail extending from ≈ 150 to ≈ 350 pc from the cluster and containing
0.7× to 2.7× the number of stars in the present-day cluster. If the Pleiades formed with an SFE close to 100%, then
the tail is shorter (<∼90 pc) and substantially poorer with only ≈ 0.02× the number of present-day cluster stars. If the
Pleiades formed with an SFE of ≈ 30 %, but the gas expulsion was adiabatic, the tail signatures are indistinguishable
from the case of the model with 100% SFE. The mass function of the tail stars is close to that of the canonical massfunction for the clusters including primordial gas, but it is slightly depleted of stars more massive than ≈ 1 M⊙ forthe cluster with 100% SFE, a difference that is not likely to be observed. The model takes into account the estimatedcontamination due to the field stars and the Hyades-Pleiades stream, which constitutes a more limiting factor than
the accuracy of the Gaia measurements.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2007.00036

13. How fast do young star clusters expel their natal gas?: Estimating the upper limit of

the gas expulsion time-scale
František Dinnbier1,2 and Stefanie Walch1,3
I.Physikalisches Institut, Mathematisch-Naturwissenschaftliche Fakultät, Universität zu Köln, Zülpicher Strasse 77,
D-50937 Köln, Germany; 2 Charles University in Prague, Faculty of Mathematics and Physics, Astronomical Institute,
V Holesovickách 2, 180 00 Praha 8, Czech Republic; 3 Center for Data and Simulation Science, University of Cologne,
Germany
1E-mail contact: dinnbier at ph1.uni-koeln.de
Formation of massive stars within embedded star clusters starts a complex interplay between their feedback, inflowing
gas and stellar dynamics, which often includes close stellar encounters. Hydrodynamical simulations usually resort tosubstantial simplifications to model embedded clusters. Here, we address the simplification which approximates thewhole star cluster by a single sink particle, which completely neglects the internal stellar dynamics. In order to model
the internal stellar dynamics, we implement a Hermite predictor-corrector integration scheme to the hydrodynamic
code flash. As we illustrate by a suite of tests, this integrator significantly outperforms the current leap-frog scheme,
and it is able to follow the dynamics of small compact stellar systems without the necessity to soften the gravitational
potential. We find that resolving individual massive stars instead of representing the whole cluster by a single energetic
source has a profound influence on the gas component: for clusters of mass less than ≈ 3 × 103 M⊙ , it slows gas
expulsion by a factor of ≈ 5 to ≈ 1 Myr, and it results in substantially more complex gas structures. With increasingcluster mass (up to ≈ 3 × 103 M⊙ ), the gas expulsion time-scale slightly decreases. However, more massive clusters
3(>∼5 × 10 M⊙ ) are unable to clear their natal gas with photoionising radiation and stellar winds only if they form witha star formation efficiency (SFE) of 1/3. This implies that the more massive clusters are either cleared with anotherfeedback mechanism or they form with a SFE higher than 1/3
Accepted by MNRAS
https://arxiv.org/pdf/2008.08602

14. Strong H-alpha emission and signs of accretion in a circumbinary planetary mass com-panion from MUSE

Simon C. Eriksson1 , Rubén Asensio Torres2 , Markus Janson1 , Yuhiko Aoyama3,4 , Gabriel-DominiqueMarleau5,6,2 , Mickael Bonnefoy7 and Simon Petrus7
Institutionen för astronomi, Stockholms universitet, AlbaNova universitetscentrum, 106 91 Stockholm, Sweden; 2
MPIA, Königstuhl 17, 69117 Heidelberg, Germany; 3 Institute for Advanced Study, Tsinghua University, Beijing
100084, PR China; 4 Dept of Astronomy, Tsinghua University, Beijing 100084, PR China; 5 Institut für Astronomie
und Astrophysik, Auf der Morgenstelle 10, 72076 Tübingen, Germany; 6 Physikalisches Institut, Universität Bern,
Gesellschaftsstr. 6, 3012 Bern, Switzerland; 7 Univ. Grenoble Alpes, IPAG, Grenoble, France

1

E-mail contact: simon.eriksson at astro.su.se
24

Context: Intrinsic Hα emission can be advantageously used to detect substellar companions because it improves
contrasts in direct imaging. Characterising this emission from accreting exoplanets allows for the testing of planet
formation theories.
Aims: We characterise the young circumbinary planetary mass companion 2MASS J01033563-5515561 (AB)b (Delorme
1 (AB)b) through medium-resolution spectroscopy.
Methods: We used the new narrow-field mode for the MUSE integral-field spectrograph, located on the ESO Very
Large Telescope, during science verification time to obtain optical spectra of Delorme 1 (AB)b.
Results: We report the discovery of very strong Hα and Hβ emission, accompanied by He I emission. This is consistent
with an active accretion scenario. We provide accretion rate estimates obtained from several independent methods
and find a likely mass of 12?15 MJup for Delorme 1 (AB)b. This is also consistent with previous estimates.
Conclusions: Signs of active accretion in the Delorme 1 system might indicate a younger age than the ∼ 30 − 40
Myr expected from a likely membership in Tucana-Horologium (THA). Previous works have also shown the central
binary to be overluminous, which gives further indication of a younger age. However, recent discoveries of active discs
in relatively old (∼40 Myr), very low-mass systems suggests that ongoing accretion in Delorme 1 (AB)b might notrequire in and of itself that the system is younger than the age implied by its THA membership.
Accepted by Astronomy & Astrophysics
https://doi.org/10.1051/0004-6361/202038131

star-forming clumps: (II) parsec-scale CO
15. The chemical structure of young high-mass+
depletion and deuterium fraction of HCO

S. Feng1,2,3 , D. Li1,4 , P. Caselli5 , F. Du6,7 , Y. Lin8 et al.
National Astronomical Observatories, Chinese Academy of Science, Beijing 100101, People’s Republic of China;
ASIAA, No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, Republic of China; 3 NAOJ, National Institutes of
Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 NAOC-UKZN Computational Astrophysics Centre, University of KwaZulu-Natal, Durban 4000, South Africa; 5 Max-Planck-Institut für Extraterrestrische Physik,
Gießenbachstraße 1, Garching bei München, Germany; 6 Purple Mountain Observatory and Key Laboratory of Radio
Astronomy, Chinese Academy of Sciences, Nanjing 210023, People’s Republic of China; 7 School of Astronomy andSpace Science, University of Science and Technology of China, Hefei 230026, People’s Republic of China; 8 Max Planck
Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn, Germany

1

2

E-mail contact: siyi.s.feng at gmail.com
The physical and chemical properties of cold and dense molecular clouds are key to understanding how stars form.
Using the IRAM 30 m and NRO 45 m telescopes, we carried out a Multiwavelength line-Imaging survey of the 70 µmdArk and bright clOuds (MIAO). At a linear resolution of 0.1–0.5 pc, this work presents a detailed study of pc-scale COdepletion and HCO+ deuterium (D-) fractionation toward four sources (G11.38+0.81, G15.21−0.43, G14.49−0.13, andG34.74−0.12) included in our full sample. In each source with T < 20 K and nH ∼ 104 –105 cm−3 , we compared pairsof neighboring 70 µm bright and dark clumps and find that: (1) The H2 column density and dust temperature of eachsource show strong spatial anti-correlation; (2) The spatial distribution of CO isotopologue lines and dense gas tracers
such as 1–0 lines of H13 CO+ and DCO+ are anti-correlated; (3) The abundance ratio between C18 O and DCO+ showsa strong correlation with the source temperature; (4) Both the C18 O depletion factor and D-fraction of HCO+ showrobust decrease from younger clumps to more evolved clumps by a factor of more than 3; (5) Preliminary chemical
modeling indicates chemical ages of our sources are ∼8×104 yr, which is comparable to their free-fall timescales andsmaller than their contraction timescales, indicating that our sources are likely dynamically and chemically young.
Accepted by ApJ
http://arxiv.org/pdf/2008.03531

16. GIARPS High-resolution Observations of T Tauri stars (GHOsT)II. Connecting atomic and molecular winds in protoplanetary disks
M. Gangi1 , B. Nisini1, S. Antoniucci1 , T. Giannini1 , K;. Biazzo1 , J.M. Alcalà2 , A. Frasca3 , U. Munari4 ,A.A. Arkharov5 , A. Harutyunyan6 , C.F. Manara7 , E. Rigliaco8 and F. Vitali1
1

INAF - Osservatorio Astronomico di Roma - Via Frascati 33, 00078 Monte Porzio Catone, Italy; 2 INAF - Osservatorio
25

Astronomico di Capodimonte - Salita Moiariello 16, 80131 Napoli, Italy; 3 INAF - Osservatorio Astrofisico di Catania- Via S. Sofia 78, 95123 Catania, Italy; 4 INAF - Osservatorio Astronomico di Padova, via dell’Osservatorio 8, 36012
Asiago (VI), Italy; 5 Central Astronomical Observatory of Pulkovo, Pulkovskoe shosse 65, 196140 St. Petersburg,
Russia; 6 Fundacion Galileo Galilei - INAF - Telescopio Nazionale Galileo, 38700 Brena Baja, Santa Cruz de Tenerife,
Spain; 7 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany; 8INAF - Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, 35122, Padova, Italy
E-mail contact: manuele.gangi at inaf.it
Disk winds play a fundamental role in the evolution of protoplanetary systems. The complex structure and dynamics
can be investigated through the emission of atomic and molecular lines detected in high-resolution optical/IR spectraof young stellar objects. Despite their great importance, however, studies connecting the atomic and molecular components are lacking so far.
In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we aim to characterize the atomic and molecular winds in a sample of classical T Tauri stars (CTTs) of the Taurus-Auriga region,
focusing on a statistical analysis of the kinematic properties of the [OI] 630 nm and H2 2.12 µm lines and their mutual
relationship.
We analyzed the flux calibrated [OI] 630 nm and H2 2.12 µm lines in a sample of 36 CTTs observed at the Telescopio
Nazionale Galileo with the HARPS-N spectrograph (resolving power of R = 115000) and with the GIANO spectrograph (R = 50000). We decomposed the line profiles into different kinematic Gaussian components and focused on
the most frequently detected component, the narrow low-velocity (vp < 20 km s−1 ) component (NLVC).
We found that the H2 line is detected in 17 sources (∼ 50% detection rate), and [OI] is detected in all sources but
one. The NLV components of the H2 and [OI] emission are kinematically linked, with a strong correlation between thepeak velocities and the full widths at half maximum of the two lines. Assuming that the line width is dominated by
Keplerian broadening, we found that the [OI] NVLC originates from a disk region between 0.05 and 20 au and that of
H2 in a region from 2 and 20 au. We also found that H2 is never detected in sources where [OI] originates in regions
below 1 au, as well as in sources of early (∼ F-G) spectral type with a luminosity > 1 L⊙ . Moreover, in seven sources,
both H2 and [OI] have clear blueshifted peaks and prominent [OI] high-velocity components. These components havealso been detected in sources with no relevant centroid shift. Finally, we did not find any clear correlation between vp
of the H2 and [OI] NVLC and the outer disk inclination. This result is in line with previous studies.
Our results suggest that molecular and neutral atomic emission in disk winds originate from regions that might overlap, and that the survival of molecular winds in disks strongly depends on the gas exposure to the radiation from thecentral star. The presence of jets does not necessarily affect the kinematics of the low-velocity winds. Our results
demonstrate the potential of wide-band high-resolution spectroscopy in linking tracers of different manifestations of
the same phenomenon.
Accepted by A&A
https://arxiv.org/pdf/2008.01977

17. The µ Tau Association: A 60 Myr-Old Coeval Group at 150 pc from the Sun
Jonathan Gagné1,2 , Trevor J. David3,4 , Eric E. Mamajek4,5 , Andrew W. Mann6 , Jacqueline K. Faherty7
and Antoine Bédard8
Planétarium Rio Tinto Alcan, Espace pour la Vie, 4801 av. Pierre-de Coubertin, Montréal, Québec, Canada; 2Institute for Research on Exoplanets, Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville,
Montréal, QC H3C 3J7, Canada; 3 Center for Computational Astrophysics, Flatiron Institute, New York, NY 10010,
USA; 4 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109,
USA; 5 Department of Physics & Astronomy, University of Rochester, Rochester, NY 14627, USA; 6 Department of
Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255, USA; 7 Departmentof Astrophysics, American Museum of Natural History, Central Park West at 79th St., New York, NY 10024, USA; 8
Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7, Canada
1E-mail contact: gagne at astro.umontreal.ca
We present an analysis of the newly identified µ Tau Association (MUTA) of young stars at ∼150 pc from the Sunthat is part of the large Cas-Tau structure, coeval and co-moving with the α Persei cluster. We identify more than
500 candidate members using Gaia DR2 data and the BANYAN Σ tool (Gagné et al. 2018) and we determine an age
26

of 62±7 Myr for its population based on an empirical comparison of its color-magnitude diagram sequence with thoseof other nearby young associations. The MUTA is related to the Theia 160 group of Kounkel & Covey (2019) andcorresponds to the e Tau group of Liu et al. (2020). As part of this analysis, we introduce an iterative method basedon spectral templates to perform an accurate correction of interstellar extinction of Gaia DR2 photometry, needed
because of its wide photometric bandpasses. We show that the members of the MUTA display an expected increased
rate of stellar activity and faster rotation rates compared with older stars, and that literature measurements of thelithium equivalent width of nine G0 to K3-type members are consistent with our age determination. We show that thepresent-day mass function of the MUTA is consistent with other known nearby young associations. We identify WD
0340+103 as a hot, massive white dwarf remnant of a B2 member that left its planetary nebula phase only 270,000
years ago, posing an independent age constraint of 60+8
−6 Myr for the MUTA.
Accepted by ApJ
http://arxiv.org/pdf/2008.06139

18. A measure of the size of the magnetospheric accretion region in TW Hydrae
R. Garcia Lopez1,2,3 , A. Natta1 , A. Caratti o Garatti1,2,3 , T. Ray1 , R. Fedriani4 , M. Koutoulaki5 etal.6,7Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, D02 XF86 Dublin, Ireland; 2 Max Planck Institute for
Astronomy, Königstuhl 17, Heidelberg, Germany, D-69117; 3 University College Dublin, School of Physics, Belfield,
Dublin 4, Ireland; 4 Department of Space, Earth & Environment, Chalmers University of Technology, SE-412 93
Gothenburg, Sweden; 5 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748, Garching, Germany; 6
Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 7 Universidade do Porto - Faculdade de Engenharia,
Rua Dr. Roberto Frias, 4200-465 Porto, Portugal

1

E-mail contact: rebeca.garcialopez at ucd.ie
Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through thedisk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate
the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometricstudies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comesfrom a region a few milliarcseconds across, usually located within the dust sublimation radius. The origin of thehydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass
Herbig AeBe stars, the fact that Brγ emission is spatially resolved rules out the possibility that most of the emission
comes from the magnetosphere because the weak magnetic fields (some tenths of a gauss) detected in these sources
result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make themeasier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along withthe presence of winds make the interpretation of the observations challenging. Here we report optical long-baseline
interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that thenear-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within thecontinuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as
big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting
onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance(more than one astronomical unit).
Accepted by Nature, Volume 584, Issue 7822, p.547-550
https://www.nature.com/articles/s41586-020-2613-1

Quantitative inference of the H2 column densities from 3 mm molecular emission: A

19. case study towards Orion B

Pierre Gratier1 , Jérôme Pety2,3 , Emeric Bron4 , Antoine Roueff5 , Jan H. Orkisz6 et al.
Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, Allee Geoffroy Saint-Hilaire,33615 Pessac,
France; 2 IRAM, 300 rue de la Piscine, 38406 Saint Martin d’Hères, France; 3 LERMA, Observatoire de Paris,
PSL Research University, CNRS, Sorbonne Universités, 75014 Paris, France; 4 LERMA, Observatoire de Paris, PSL
1

27

Research University, CNRS, Sorbonne Universités, 92190 Meudon, France; 5 Aix Marseille Univ, CNRS, Centrale
Marseille, Institut Fresnel, Marseille, France; 6 Chalmers University of Technology, Department of Space, Earth andEnvironment, 412 93 Gothenburg, Sweden
E-mail contact: pierre.gratier at u-bordeaux.fr
Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of molecular gas
currently rely either on dust emission observation in the far-IR or on star counting. (Sub-)millimeter observationsof numerous trace molecules are effective from ground based telescopes, but the relationships between the emissionof one molecular line and the H2 column density (NH2 ) is non-linear and sensitive to excitation conditions, opticaldepths, abundance variations due to the underlying physico-chemistry. We aim to use multi-molecule line emission toinfer NH2 from radio observations. We propose a data-driven approach to determine NH2 from radio molecular line
observations. We use supervised machine learning methods (Random Forests) on wide-field hyperspectral IRAM-30m
observations of the Orion B molecular cloud to train a predictor of NH2 , using a limited set of molecular lines as input,
and the Herschel-based dust-derived NH2 as ground truth output. For conditions similar to the Orion B molecular
cloud, we obtain predictions of NH2 within a typical factor of 1.2 from the Herschel-based estimates. An analysis of thecontributions of the different lines to the predictions show that the most important lines are 13 CO(1–0), 12 CO(1–0),
C18 O(1–0), and HCO+ (1–0). A detailed analysis distinguishing between diffuse, translucent, filamentary, and dense
core conditions show that the importance of these four lines depends on the regime, and that it is recommended to
add the N2 H+ (1–0) and CH3 OH(20 –10 ) lines for the prediction of NH2 in dense core conditions. This article opens apromising avenue to directly infer important physical parameters from the molecular line emission in the millimeterdomain. The next step will be to try to infer several parameters simultaneously (e.g., NH2 and far-UV illumination
field) to further test the method.
Accepted by A&A
http://arxiv.org/pdf/2008.13417

20. The GRAVITY young stellar object survey III. The dusty disk of RY Lup
GRAVITY Collaboration: Y.-I. Bouarour1,2,3 , K. Perraut1 , F. Ménard1 , W. Brandner5 et al.
Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 2 Dublin Institute for Advanced Studies, 31
Fitzwilliam Place, D02 XF86 Dublin, Ireland; 3 School of Physics, University College Dublin, Belfield, Dublin 4,
Ireland; 4 I. Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, 50937, Köln, Germany; 5 Max Planck
Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
1E-mail contact: youcef.bouarour at ucdconnect.ie
We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8mtelescopes. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the Spectral
Energy Distribution and match the interferometric observations. To match the SED , our model requires a stellar
luminosity of 2.5 L⊙ , higher than any previously determined values. Such a high value is needed to accommodate thecircumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using
an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29
R⊙ . These revised fundamental parameters, when combined with the mass estimates available , lead to an age of
0.5–2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our
disk model nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones.
We derive an inner rim location at 0.12 au from the central star. This model corresponds to an inclination of the innerdisk of 50◦ , which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70◦in NIR) and ALMA(67◦ ±5◦ ) images, but consistent with the inclination determination from the ALMA CO spectra(55◦ ±5◦ ). Increasing the inclination of the inner disk to 70◦ leads to a higher line-of-sight extinction and therefore
requires a higher stellar luminosity of 4.65 L⊙ to match the observed flux levels. This luminosity would translate toa stellar radius of 3.13 R⊙ , leading to an age of 2–3 Ma, and a stellar mass of about 2 M⊙ , in disagreement withthe observed dynamical mass estimate of 1.3–1.5 M⊙ . Critically, this high-inclination inner disk model also fails to
reproduce the visibilities observed with GRAVITY.
Accepted by A&A
http://arxiv.org/pdf/2008.08527
28

21.

The Gaia-ESO Survey: Calibrating the lithium-age relation with open clusters andassociations. I. Cluster age range and initial membership selections.
M.L. Gutiérrez Albarrán1 , D. Montes1 , M. Gómez Garrido1,2 , H.M. Tabernero1,3 , J.I. Gónzalez Hernández4,5 ,E. Marfil1 , A. Frasca6 , A. C. Lanzafame7,6 , A. Klutsch8,6 , E. Franciosini9 , S. Randich9 , R. Smiljanic10 ,A. J. Korn11 , G. Gilmore12 , E.J. Alfaro23 , M. Baratella24 , A. Bayo20,21 , T. Bensby13 , R. Bonito14 , G.
Carraro15 , E. Delgado Mena3 , S. Feltzing13 , A. Gonneau12 , U. Heiter11 , A. Hourihane12 , F. Jiménez
Esteban16 , P. Jofre22 , T. Masseron4 , L. Monaco17 , L. Morbidelli9, L. Prisinzano14 , V. Roccatagliata18 ,S. Sousa3 , M. Van der Swaelmen9 , C.C. Worley12 and S. Zaggia19
Departamento de Física de la Tierra y Astrofísica and IPARCOS-UCM (Instituto de Física de Partículas y delCosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, E-28040, Madrid, Spain;2
Observatorio Astronómico Nacional (OAN-IGN), Apdo 112, 28803 Alcalá de Henares, Madrid, Spain; 3 Institutode Astrofísica e Ciências do Espaçø, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal;
4
Instituto de Astrofísica de Canarias (IAC), E-38205 La Laguna, Tenerife, Spain; 5 Universidad de la Laguna,Dept. Astrofísica, E-38206 La Laguna, Tenerife, Spain; 6 INAF - Osservatorio Astrofisico di Catania, via S. Sofia,
78, 95123 Catania, Italy; 7 Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S.
Sofia 78, I-95123 Catania, Italy; 8 Institut für Astronomie und Astrophysik, Eberhard Karls Universität, Sand 1,
D-72076 Tübingen, Germany; 9 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy; 10
Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716, Warsaw, Poland; 11
Observational Astrophysics, Division of Astronomy and Space Physics, Department of Physics and Astronomy, Uppsala
University, Box 516, SE-751 20 Uppsala, Sweden; 12 Institute of Astronomy, University of Cambridge, Madingley Road,
Cambridge CB3 0HA, United Kingdom; 13 Lund Observatory, Department of Astronomy and Theoretical Physics,
Box 43, SE-221 00 Lund, Sweden; 14 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134
Palermo, Italy; 15 Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell’Osservatorio 3, 35122
Padova, Italy; 16 Spanish Virtual Observatory, Centro de Astrobiología (INTA-CSIC), P.O. Box 78, 28691 Villanueva
de la Canada, Madrid, Spain; 17 Departamento de Ciencias Físicas, Universidad Andrés Bello, Fernández Concha
700, Las Condes, Santiago, Chile; 18 Dipartimento di Fisica “E. Fermi", Università di Pisa, Largo Bruno Pontecorvo
3, 56127 Pisa, Italy; 19 INAF - Padova Observatory, Vicolo dell’Osservatorio 5, 35122 Padova, Italy; 20 Instituto deFísica y Astronomía, Universidad de Valparaíso, Chile; 21 Núcleo Milenio Formación Planetaria - NPF, Universidad de
Valparaíso; 22 Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales (UDP), Santiago
de Chile; 23 Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, Granada 18008, Spain; 24
Dipartimento di Fisica e Astronomia Galileo Galilei, Vicolo Osservatorio 3, I-35122, Padova, Italy

1E-mail contact: mlgutierrez at ucm.es
Previous studies of open clusters have shown that lithium depletion is not only strongly age dependent but also shows
a complex pattern with other parameters that is not yet understood. For pre- and main-sequence late-type stars,
these parameters include metallicity, mixing mechanisms, convection structure, rotation, and magnetic activity. We
perform a thorough membership analysis for a large number of stars observed within the Gaia-ESO survey (GES) in
the field of 20 open clusters, ranging in age from young clusters and associations, to intermediate-age and old open
clusters. Based on the parameters derived from the GES spectroscopic observations, we obtained lists of candidate
members for each of the clusters in the sample by deriving RV distributions and studying the position of the kinematic
selections in the EW(Li) versus Teff plane to obtain lithium members. We used gravity indicators to discard fieldcontaminants and studied [Fe/H] metallicity to further confirm the membership of the candidates. We also made useof studies using recent data from the Gaia DR1 and DR2 releases to assess our member selections. We identified likely
member candidates for the sample of 20 clusters observed in GES (iDR4) with UVES and GIRAFFE, and conducted acomparative study that allowed us to characterize the properties of these members, as well as identify field contaminantstars, both lithium-rich giants and non-giant outliers. This work is the first step towards the calibration of the lithiumage relation and its dependence on other GES parameters. During this project we aim to use this relation to infer theages of GES field stars, and identify their potential membership to young associations and stellar kinematic groups ofdifferent ages.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2009.00610

2922. Emission-Line Datacubes of the HH 32 Stellar Jet
Patrick Hartigan1 , Lynne Hillenbrand2 , Matuesz Matuszewski3 , Arlindo Chan Borges2 , James D. Neill3,
D. Christopher Martin3 , Patrick Morrissey3 and Anna M. Moore4
Physics and Astronomy Dept., Rice University, 6100 S. Main, Houston, TX 77005-1892; 2 Department of Astronomy,
MC 249-17, California Institute of Technology, Pasadena, California 91125; 3 Cahill Center for Astrophysics, California
Institute of Technology, 1216 East California Boulevard, Pasadena, California 91125; 4 Research School of Astronomy
and Astrophysics, Australian National University, Canberra, ACT 2611, Australia

1E-mail contact: hartigan at sparky.rice.edu
We analyze datacubes of over 60 emission lines in the HH 32 stellar jet acquired with the Keck Cosmic Web Imager(KCWI). The data cover the less-explored blue portion of the spectrum between 3586Å and 6351Å, and have both
high spectral (R ∼ 10000) and spatial (<∼ 1") resolution. The study includes all three major ionization states ofoxygen, three Balmer lines, multiple lines of Fe II and Fe III, as well as the first datacubes ever acquired for important
unblended diagnostic lines such as He II λ4686, Ca I λ3933, and Mg I] λ4571. The data cubes generally sort according
to excitation, and have a relatively continuous progression from the highest-excitation ions (He II, O III) through theintermediate-excitation ions (O I and H I) to the lowest-excitation ions (Ca II and Mg I). Merging the KCWI cubeswith HST images leads to several new insights about the flow, including evidence for bow shocks, partial bow shocks,
spur shocks, Mach disks, jet deflection shocks, a wiggling jet, and potential shock precursors. The most surprising
result is that one of the velocity components of Fe II in the Mach disk suddenly increases in flux relative to other lines
by a factor of two, implying that the Mach disk vaporizes dust in the jet. Hence, jets must accelerate or entrain dust
to speeds of over 300 km/s without destroying the grains.
Accepted by Astronomical Journal
https://arxiv.org/pdf/2008.03466

A JWST Preview: Adaptive-Optics Images of H2, Br-gamma, and K-continuum in

23. Carina’s Western Wall

Patrick Hartigan1 , Turlough Downes2 and Andrea Isella1
1

Rice University; 2 Dublin City University

E-mail contact: hartigan at sparky.rice.edu
We present the first wide-field near-infrared adaptive optics images of Carina’s Western Wall (G287.38-0.62), one of thebrightest and most well-defined irradiated interfaces known in a region of massive star formation. The new narrowband
H2 2.12µm, Br-γ and K-continuum images from Gemini South trace the photoevaporative flow from the cloud andidentify locations where UV-radiation from the surrounding massive stars excites molecular hydrogen to fluoresce.
With a field of view of ∼ 1.5’ × 2.9’ and spatial resolution between 60 − 110 mas, the new images show a spectacularlevel of detail over a large area, and presage what JWST should achieve. The Wall is convex in shape, with a large
triangular-shaped extension near its apex. The interface near the apex consists of 3 − 4 regularly-spaced ridges withprojected spacings of ∼ 2000 AU, suggestive of a large-scale dynamically-important magnetic field. The northern edgeof the Wall breaks into several swept-back fragments of width ∼ 1800 AU that resemble Kelvin-Helmholtz instabilities,
and the southern part of the Wall also shows complex morphologies including a sinusoidal-like variation with a halfwavelength of 2500 AU. Though the dissociation front must increase the density along the surface of the Wall, it does
not resolve into pillars that point back to the ionization sources, as could occur if the front triggered new stars toform. We discovered a new H2 jet with no clear driving source, MHO 1630, in the northern portion of the Wall, visible
as a series of bow shocks arrayed in a line.
Accepted by ApJ Letters
http://arxiv.org/pdf/2008.01364

24.

Searching for wide-orbit gravitational instability protoplanets with ALMA in the dust
continuum
J. Humphries1 , C. Hall1,2,3 , T.J. Haworth4 & S. Nayakshin1
1

Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK; 2 Department of Physics
30

and Astronomy, The University of Georgia, Athens, GA 30602, USA; 3 Center for Simulational Physics, The Universityof Georgia, Athens, GA 30602, USA; 4 Astronomy Unit, School of Physics and Astronomy, Queen Mary University of
London, London E1 4NS, UK
E-mail contact: cassandra.hall at uga.edu
Searches for young gas giant planets at wide separations have so far focused on techniques appropriate for compact(Jupiter sized) planets. Here we point out that protoplanets born through Gravitational Instability (GI) may remain in
an initial pre-collapse phase for as long as the first 105 –107 years after formation. These objects are hundreds of times
larger than Jupiter and their atmospheres are too cold (T ∼ tens of K) to emit in the NIR or Hα via accretion shocks.
However, it is possible that their dust emission can be detected with ALMA, even around Class I and II protoplanetary
discs. In this paper we produce synthetic observations of these protoplanets. We find that making a detection in adisc at 140 parsecs would require a few hundred minutes of ALMA band 6 observation time. Protoplanets with masses
of 3–5 MJ have the highest chance of being detected; less massive objects require unreasonably long observation times(1000 minutes) while more massive ones collapse into giant planets before 105 years. We propose that high resolution
surveys of young (105 –106 years), massive and face on discs offer the best chance for observing protoplanets. Such a
detection would help to place constraints on the protoplanet mass spectrum, explain the turnover in the occurrence
frequency of gas giants with system metallicity and constrain the prevalence of GI as a planet formation mechanism.
Consistent lack of detection would be evidence against GI as a common planet formation mechanism.
Accepted by MNRAS
http://arxiv.org/pdf/2008.04014

25.

Observing protoplanetary discs with the Square Kilometre Array – I. Characterisingpebble substructure caused by forming planets
John D. Ilee1 , Cassandra Hall2,3,4 , Catherine Walsh1 , Izaskun Jimenez-Serra5 , Christophe Pinte6,7 ,Jason Terry3,4 , Tyler L. Bourke8 and Melvin Hoare1
School of Physics and Astronomy, University of Leeds; 2 Department of Physics and Astronomy, University ofLeicester; 3 Department of Physics and Astronomy, The University of Georgia; 4 Center for Simulational Physics, The
University of Georgia; 5 Departamento de Astrofisica, Centro de Astrobiologia CSIC-INTA; 6 School of Physics andAstronomy, Monash University; 7 Univ. Grenoble Alpes, CNRS; 8 SKA Organisation, Jodrell Bank
1

E-mail contact: j.d.ilee at leeds.ac.uk
High angular resolution observations of discs at mm wavelengths (on scales of a few au) are now commonplace,but there is a current lack of a comparable angular resolution for observations at cm wavelengths. This presents asignificant barrier to improving our understanding of planet formation, in particular how dust grains grow from mm
to cm sizes. In this paper, we examine the ability of the Square Kilometre Array (SKA) to observe dust substructure
in a young, planet-forming disc at cm wavelengths. We use dusty hydrodynamics and continuum radiative transfer
to predict the distribution and emission of 1 cm dust grains (or pebbles) within the disc, and simulate continuum
observations with the current SKA1-MID design baseline at frequencies of 12.5 GHz (Band 5b, 2.4 cm) on 5-10 au
scales. The SKA will provide high-fidelity observations of the cm dust emission substructure in discs for integration
times totalling 100’s of hours. Radial structure can be obtained at a sufficient resolution and S/N from shorter (10’s ofhours) integration times by azimuthal averaging in the image plane. By modelling the intensity distribution directlyin the visibility plane, it is possible to recover a similar level of (axisymmetric) structural detail from observations
with integration times 1-2 orders of magnitude lower than required for high-fidelity imaging. Our results demonstratethat SKA1-MID will provide crucial constraints on the distribution and morphology of the raw material for building
planets, the pebbles in protoplanetary discs.
Accepted by MNRAS
https://arxiv.org/pdf/2009.00562

Revisiting the Magnetic Field of the L183 Starless Core
26.

Janik Karoly1,2 , Archana Soam2 , B-G Andersson2 , Simon Coudé2 , Pierre Bastien3 et al.
Dept of Physics, Santa Clara University, Santa Clara, 500 El Camino Real, Santa Clara, CA, USA; 2 SOFIA Science
Center, Universities Space Research Association, NASA Ames Research Center, M.S. N232-12, Moffett Field, CA
1

31

94035, USA; 3 Institut de Recherche sur les Exoplanètes (iREx) & Centre de Recherche en Astrophysique du Québec(CRAQ), Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville, Montréal, Canada
E-mail contact: jkaroly at alumni.scu.edu
We present observations of linear polarization from dust thermal emission at 850 µm towards the starless cloud L183.
These data were obtained at the James Clerk Maxwell Telescope (JCMT) using the Submillimetre Common-User
Bolometer Array 2 (SCUBA-2) camera in conjunction with its polarimeter POL-2. Polarized dust emission traces theplane-of-sky magnetic field structure in the cloud, thus allowing us to investigate the role of magnetic fields in theformation and evolution of its starless core. To interpret these measurements, we first calculate the dust temperatureand column density in L183 by fitting the spectral energy distribution obtained by combining data from the JCMTand the Herschel space observatory. We used the Davis-Chandrasekhar-Fermi technique to measure the magnetic fieldstrength in five sub-regions of the cloud, and we find values ranging from ∼120±18 µG to ∼270±64 µG in agreementwith previous studies. Combined with an average hydrogen column density (NH2 ) of ∼1.5×1022 cm−2 in the cloud,
we also find that all five sub-regions are magnetically subcritical. These results indicate that the magnetic field in
L183 is sufficiently strong to oppose the gravitational collapse of the cloud.
Accepted by ApJ
http://arxiv.org/pdf/2008.02841

27.

First L band detection of hot exozodiacal dust with VLTI/MATISSE
Florian Kirchschlager1 , Steve Ertel2,3 , Sebastian Wolf4 , Alexis Matter5 and Alexander V. Krivov6
Dept of Physics and Astronomy, University College London, Gower Street, WC1E 6BT London, UK; 2 Large
Binocular Telescope Observatory, 933 North Cherry Avenue, Tucson, AZ 85721, USA; 3 Steward Observatory, Deptof Astronomy, University of Arizona, 993 N. Cherry Ave, Tucson, AZ, 85721, USA; 4 Institute of Theoretical Physics
and Astrophysics, Kiel University, Leibnizstraße 15, 24118, Kiel, Germany; 5 Laboratoire Lagrange, Université Côted’Azur, Observatoire de la Côte d’Azur, CNRS, 06304 Nice Cedex 4, France; 6 Astrophysical Institute and University
Observatory, Friedrich Schiller University Jena, Schillergäßchen 2-3, 07745 Jena, Germany
1E-mail contact: f.kirchschlager at ucl.ac.uk
For the first time we observed the emission of hot exozodiacal dust in L band. We used the new instrument MATISSE
at the Very Large Telescope Interferometer to detect the hot dust around κ Tuc with a significance of 3σ to 6σ atwavelengths between 3.37 and 3.85 µm and a dust-to-star flux ratio of 5 to 7 %. We modelled the spectral energy
distribution based on the new L band data alone and in combination with H band data published previously. In allcases we find 0.58 µm grains of amorphous carbon to fit the κ Tuc observations the best, however, also nanometreor micrometre grains and other carbons or silicates reproduce the observations well. Since the H band data revealed
a temporal variability, while our L band data were taken at a different epoch, we combine them in different ways.
Depending on the approach, the best fits are obtained for a narrow dust ring at a stellar distance in the 0.1 to 0.29 au
range and thus with a temperature between 940 and 1430 K. Within the 1σ uncertainty dust location and temperatureare confined to 0.032 − 1.18 au and 600 − 2000 K.
Accepted by MNRAS Letters
https://arxiv.org/pdf/2009.02334

Interferometric study on the temporal variability of the brightness distributions of

28. protoplanetary disks

J. Kobus1 , S. Wolf1 , T. Ratzka2,3 and R. Brunngräber1
Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstraße 15, 24118 Kiel, Germany; 2Institute for Physics/IGAM, NAWI Graz, University of Graz, Universitätsplatz 5/II, 8010 Graz, Austria; 3 Planetarium
im Museum am Schölerberg, Klaus-Strick-Weg 10, 49082 Osnabrück, Germany
1E-mail contact: jkobus at astrophysik.uni-kiel.deContext. Optical and infrared spatially unresolved multi-epoch observations have revealed the variability of pre-main
sequence stars and/or their environment. Moreover, structures in orbital motion around the central star, resulting fromplanet-disk interaction, are predicted to cause temporal variations in the brightness distributions of protoplanetary32

disks. Through repeated observations of pre-main sequence stars with the Very Large Telescope Interferometer (VLTI)
over nearly two decades, the ESO Archive has become a treasure chest containing unprecedented high-resolution multiepoch near- and mid-infrared observations of the potential planet-forming regions in protoplanetary disks.
Aims. We aim to investigate whether the existing multi-epoch observations provide evidence for the variability of thebrightness distributions of the innermost few astronomical units of protoplanetary disks and to quantify any variations
detected.
Methods. We present different approaches to search for evidence of temporal variations based on multi-epoch observations obtained with the VLTI instruments PIONIER, AMBER, and MIDI for 68 pre-main sequence stars.
Results. For nine objects in our sample, multi-epoch data obtained using equal baselines are available that allow us todirectly detect variations in the visibilities due to temporally variable brightness distributions. Significant variationsof the near-infrared visibilities obtained in different epochs with PIONIER and/or AMBER for HD 50138, DX Cha,
HD 142527, V856 Sco, HD 163296, and R CrA were found. HD 37806, TW Hya, and CPD-36 6759 show no significant
variations. By estimating the impact of a small variation of the baseline on the measured squared visibilities, we areable to compare the data of another 12 pre-main sequence stars. Thereby, we find evidence for temporal variationsof the brightness distribution of one additional object, AK Sco. Besides the two binaries DX Cha and AK Sco, HD
50138 and V856 Sco also show signs of variability caused by variations of asymmetric structures in the brightness
distribution.
Accepted by A&A
https://arxiv.org/pdf/2008.08374

A triple-star system with a misaligned and warped circumstellar disk shaped by disk
29. tearing
Stefan Kraus1 , Alexander Kreplin1 , Alison K. Young1,2 , Matthew R. Bate1 , John D. Monnier3 , Tim J.
Harries1 , Henning Avenhaus4 , Jacques Kluska1,5 , Anna S. E. Laws1 , Evan A. Rich3 , Matthew Willson1,6,
Alicia N. Aarnio7 , Fred C. Adams3 , Sean M. Andrews8 , Narsireddy Anugu1,3,9 , Jaehan Bae3,10 , Theo ten
Brummelaar11 , Nuria Calvet3 , Michel Curé12 , Claire L. Davies1 , Jacob Ennis3 , Catherine Espaillat13 ,Tyler Gardner3 , Lee Hartmann3 , Sasha Hinkley1 , Aaron Labdon1 , Cyprien Lanthermann5 , JeanBaptiste LeBouquin3,14 , Gail H. Schaefer11 , Benjamin R. Setterholm3 , David Wilner7 and Zhaohuan
Zhu15
School of Physics and Astronomy, University of Exeter, Exeter EX4 4QL,UK; 2 School of Physics and Astronomy,
University of Leicester, Leicester LE17 RH, UK; 3 Dept of Astronomy, University of Michigan, Ann Arbor, MI 48109,
USA; 4 no academic affiliation; 5 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium; 6
Dept of Physics and Astronomy, Georgia State University, Atlanta, GA 30302,USA; 7 Dept of Physics and Astronomy,
University of North Carolina Greensboro, Greensboro, NC 27402, USA; 8 CfA, Harvard and Smithsonian, Cambridge,
MA 02138, USA; 9 Steward Observatory, University of Arizona, Tucson, AZ 85721, USA; 10 Carnegie Institution for
Science, Washington, DC 20015, USA; 11 Center for High Angular Resolution Astronomy Array of Georgia State
University, Mount Wilson, CA 91023, USA; 12 Instituto de Fisica y Astronomia, Universidad de Valparaiso, 12 Casilla
5030, Valparaiso, Chile; 13 Dept of Astronomy, Boston University, Boston, MA 02215, USA; 14 Université Grenoble
Alpes, Institut de Planétologie et d’Astrophysique, 38000; 15 Dept of Physics and Astronomy, University of Nevada,
Las Vegas, NV 89154, USA
1E-mail contact: s.kraus at exeter.ac.uk
Young stars are surrounded by a circumstellar disk of gas and dust, within which planet formation can occur. Gravitational forces in multiple star systems can disrupt the disk. Theoretical models predict that if the disk is misalignedwith the orbital plane of the stars, the disk should warp and break into precessing rings, a phenomenon known asdisk tearing. We present observations of the triple-star system GW Orionis, finding evidence for disk tearing. Our
images show an eccentric ring that is misaligned with the orbital planes and the outer disk. The ring casts shadowson a strongly warped intermediate region of the disk. If planets can form within the warped disk, disk tearing could
provide a mechanism for forming wide-separation planets on oblique orbits.
Accepted by Science (369, 1233-1238)
https://arxiv.org/pdf/2004.01204, https://science.sciencemag.org/content/369/6508/1233

33

30. Physicochemical models: source-tailored or generic?
Beatrice M. Kulterer1 , Maria N. Drozdovskaya1 , Audrey Coutens2 , Sébastien Manigand3 and Gwendoline Stéphan4Center for Space and Habitability, University of Bern, 3012 Bern, Switzerland; 2 Laboratoire d’astrophysique de
Bordeaux, Univ. Bordeaux, CNRS, 33615 Pessac, France; 3 Center for Star and Planet Formation, Niels Bohr
Institute & Natural History Museum of Denmark, University of Copenhagen, 1350 Copenhagen K., Denmark; 4 Deptof Chemistry, University of Virginia, Charlottesville, VA 22904, USA
1E-mail contact: beatrice.kulterer at csh.unibe.ch
Physicochemical models can be powerful tools to trace the chemical evolution of a protostellar system and allow toconstrain its physical conditions at formation. The aim of this work is to assess whether source-tailored modelling isneeded to explain the observed molecular abundances around young, low-mass protostars or if, and to what extent,
generic models can improve our understanding of the chemistry in the earliest stages of star formation. The physicalconditions and the abundances of simple, most abundant molecules based on three models are compared. Afterestablishing the discrepancies between the calculated chemical output, the calculations are redone with the samechemical model for all three sets of physical input parameters. With the differences arising from the chemical models
eliminated, the output is compared based on the influence of the physical model. Results suggest that the impact of
the chemical model is small compared to the influence of the physical conditions, with considered timescales having
the most drastic effect. Source-tailored models may be simpler by design; however, likely do not sufficiently constrain
the physical and chemical parameters within the global picture of star-forming regions. Generic models with morecomprehensive physics may not provide the optimal match to observations of a particular protostellar system, butallow a source to be studied in perspective of other star-forming regions.
Accepted by MNRAS
https://arxiv.org/pdf/2008.04798

31.

SCExAO/CHARIS Near-IR Integral Field Spectroscopy of the HD 15115 Debris Disk
Kellen Lawson1 , Thayne Currie2,3,4 , John P. Wisniewski1, Motohide Tamura5,6,7 , Glenn Schneider8 etal.
Dept of Physics and Astronomy, Univ. of Oklahoma, Norman, OK; 2 Subaru Telescope, NAOJ, Hilo, HI 96720,
USA; 3 NASA-Ames Research Center, Moffett Field, CA, USA; 4 Eureka Scientific, Oakland, CA, USA; 5 Astrobiology
Center of NINS, Tokyo, Japan; 6 Dept of Astronomy, Graduate School of Science, Univ. of Tokyo, 113-0033, Japan;
7
NAOJ, Tokyo 181-8588, Japan; 8 Steward Obs., Univ. of Arizona, Tucson, AZ 85721, USA
1E-mail contact: kellenlawson at gmail.com
We present new, near-infrared (1.1–2.4 µm) high-contrast imaging of the debris disk around HD 15115 with the Subaru
Coronagraphic Extreme Adaptive Optics system (SCExAO) coupled with the Coronagraphic High Angular Resolution
Imaging Spectrograph (CHARIS). SCExAO/CHARIS resolves the disk down to ρ ∼ 0.′′ 2 (rproj ∼ 10 au), a factor of∼3–5 smaller than previous recent studies. We derive a disk position angle of PA ∼279.◦4–280.◦5 and an inclination ofi ∼ 85.◦ 3–86.◦ 2. While recent SPHERE/IRDIS imagery of the system could suggest a significantly misaligned two ringdisk geometry, CHARIS imagery does not reveal conclusive evidence for this hypothesis. Moreover, optimizing models
of both one and two ring geometries using differential evolution, we find that a single ring having a Hong-like scattering′′
phase function matches the data equally well within the CHARIS field of view (ρ <∼ 1 ). The disk’s asymmetry, wellevidenced at larger separations, is also recovered; the west side of the disk appears on average around 0.4 magnitudes
brighter across the CHARIS bandpass between 0.′′ 25 and 1′′ . Comparing STIS/50CCD optical photometry (2000–
10500 Å) with CHARIS NIR photometry, we find a red (STIS/50CCD–CHARIS broadband) color for both sides ofthe disk throughout the 0.′′ 4–1′′ region of overlap, in contrast to the blue color reported at similar wavelengths forregions exterior to ∼2′′ . Further, this color may suggest a smaller minimum grain size than previously estimated atlarger separations. Finally, we provide constraints on planetary companions, and discuss possible mechanisms for theobserved inner disk flux asymmetry and color.
Accepted by AJ
http://arxiv.org/pdf/2008.00309

34

32.

A 3 mm Chemical Exploration of Small Organics in Class I YSOs
Romane Le Gal1 , Karin I. Öberg1 , Jane Huang1 , Charles J. Law1 , François Ménard2 , Bertrand Lefloch2 ,Charlotte Vastel3 , Ana Lopez-Sepulcre2,4 , Cécile Favre2 , Eleonora Bianchi2 , Cecilia Ceccarelli2
Center for Astrophysics |Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA; 2 Université Grenoble
Alpes, CNRS, IPAG, F-38000 Grenoble, France; 3 IRAP, Université de Toulouse, CNRS, UPS, CNES, 31400 Toulouse,
France 4 IRAM, 300 rue de la piscine, F-38406 Saint-Martin d’Heres, France
1

E-mail contact: romane.le_gal at cfa.harvard.edu
There is mounting evidence that the composition and structure of planetary systems are intimately linked to theirbirth environments. During the past decade, several spectral surveys probed the chemistry of the earliest stages ofstar formation and of late planet-forming disks. However, very little is known about the chemistry of intermediate
protostellar stages, i.e., Class I Young Stellar Objects (YSOs), where planet formation may have already begun. We
present here the first results of a 3mm spectral survey performed with the IRAM-30m telescope to investigate thechemistry of a sample of seven Class I YSOs located in the Taurus star-forming region. These sources were selected
to embrace the wide diversity identified for low-mass protostellar envelope and disk systems. We present detections
and upper limits of thirteen small (Natoms ≤ 3) C, N, O, and S carriers - namely CO, HCO+ , HCN, HNC, CN, N2 H+ ,C2 H, CS, SO, HCS+ , C2 S, SO2 , OCS - and some of their D, 13 C, 15 N, 18 O, 17 O, and 34 S isotopologues. Together,
these species provide constraints on gas-phase C/N/O ratios, D- and 15 N-fractionation, source temperature and UV
exposure, as well as the overall S-chemistry. We find substantial evidence of chemical differentiation among our source
sample, some of which can be traced back to Class I physical parameters, such as the disk-to-envelope mass ratio(proxy for Class I evolutionary stage), the source luminosity, and the UV-field strength. Overall, these first results
allow us to start investigating the astrochemistry of Class I objects, however, interferometric observations are needed
to differentiate envelope versus disk chemistry.
Accepted by ApJ (898,131)
https://iopscience.iop.org/article/10.3847/1538-4357/ab9ebf/pdf

33.

Wind-MRI interactions in local models of protoplanetary discs: I. Ohmic resistivity
Philip K C. Leung1 , Gordon I. Ogilvie1
Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University ofCambridge, Wilberforce Road, Cambridge CB3 0WA
1E-mail contact: pkcl2 at cam.ac.uk
A magnetic disc wind is an important mechanism that may be responsible for driving accretion and structure formationin protoplanetary discs. Recent numerical simulations have shown that these winds can take either the traditional‘hourglass’ symmetry about the mid-plane, or a ‘slanted’ symmetry dominated by a mid-plane toroidal field of asingle sign. The formation of this slanted symmetry state has not previously been explained. We use radially local
1D vertical shearing box simulations to assess the importance of large-scale MRI channel modes in influencing theformation and morphologies of these wind solutions. We consider only Ohmic resistivity and explore the effect ofdifferent magnetisations, with the mid-plane β parameter ranging from 105 to 102 . We find that our magnetic winds
go through three stages of development: cyclic, transitive and steady, with the steady wind taking a slanted symmetry
profile similar to those observed in local and global simulations. We show that the cycles are driven by periodic
excitation of the n = 2 or 3 MRI channel mode coupled with advective eviction, and that the transition to the steadywind is caused by a much more slowly growing n = 1 mode altering the wind structure. Saturation is achieved
through a combination of advective damping from the strong wind, and suppression of the instability due to a strong
toroidal field. A higher disc magnetisation leads to a greater tendency towards, and more rapid settling into the slanted
symmetry steady wind, which may have important implications for mass and flux transport processes in protoplanetary
discs.
Accepted by MNRAS
http://arxiv.org/pdf/2008.00906

3534. Evidence for dense gas heated by the explosion in Orion KL
Dalei Li1,2 , Xindi Tang1,2 , Christian Henkel3,4,1 , Karl M. Menten3 , Friedrich Wyrowski3 , Yan Gong3 ,Gang Wu1,2 , Yuxin He1,2 , Jarken Esimbek1,2 and Jianjun Zhou1,2
Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 830011 Urumqi, PR China; 2 Key Laboratoryof Radio Astronomy, Chinese Academy of Sciences, 830011 Urumqi, PR China; 3 MPIfR, Auf dem Hügel 69, 53121
Bonn, Germany; 4 Astron. Dept, King Abdulaziz Univ., 21589 Jeddah, Saudi Arabia
1

E-mail contact: tangxindi at xao.ac.cn
We mapped the kinetic temperature structure of Orion KL in a ∼20′′ (∼8000 AU) sized region with para-H2 CS 707 −606 ,
726 −625 , and 725 −624 making use of ALMA Band 6 Science Verification data. The kinetic temperatures obtained witha resolution of 1 ′′. 65×1 ′′. 14 (∼550 AU) are deduced by modeling the measured averaged velocity-integrated intensity
ratios of para-H2 CS 726 −625 /707 −606 and 725 −624 /707 −606 with a RADEX non-LTE model. The kinetic temperaturesof the dense gas, derived from the para-H2 CS line ratios at a spatial density of 107 cm−3 , are high, ranging from 43 to>500 K with an unweighted average of ∼170 K. There is no evidence for internal sources playing an important role in
the heating of the various structures identified in previous work, namely the elongated ridge, the northwestern clump,and the eastern region of the compact ridge, while the high temperatures in the western region of the compact ridge
may be dominated by internal massive star formation. Significant gradients of kinetic temperature along molecularfilaments traced by H2 CS indicate that the dense gas is heated by the shocks induced by the enigmatic explosive
event, which occurred several hundred years ago greatly affecting the energetics of the Orion KL region. Thus, with
the notable exception of the western region of the compact ridge, the high temperatures of the dense gas in Orion KL
are probably caused by shocks from the explosive event, leading to a dominant component of externally heated densegas.
Accepted by ApJ
http://arxiv.org/pdf/2008.04564

35. The family of amide molecules toward NGC 6334I
Niels F.W. Ligterink1 , Samer J. El-Abd2,3 , Crystal L. Brogan3 , Todd R. Hunter3 et al.
Center for Space and Habitability, Univ. of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland; 2 Dept of Astronomy,
Univ. of Virginia, Charlottesville, VA 22904, USA; 3 NRAO, Charlottesville, VA 22903, USA
1E-mail contact: niels.ligterink at csh.unibe.ch
Amide molecules produced in space could play a key role in the formation of biomolecules on a young planetary object.
However, the formation and chemical network of amide molecules in space is not well understood. In this work, ALMA
observations are used to study a number of amide(-like) molecules toward the high-mass star-forming region NGC
6334I. The first detections of cyanamide (NH2 CN), acetamide (CH3 C(O)NH2 ) and N-methylformamide (CH3 NHCHO)
are presented for this source. These are combined with analyses of isocyanic acid (HNCO) and formamide (NH2 CHO)
and a tentative detection of urea (carbamide; NH2 C(O)NH2). Abundance correlations show that most amides arelikely formed in related reactions occurring in ices on interstellar dust grains in NGC 6334I. However, in an expanded
sample of sources, large abundance variations are seen for NH2 CN that seem to depend on the source type, whichsuggests that the physical conditions within the source heavily influence the production of this species. The richamide inventory of NGC 6334I strengthens the case that interstellar molecules can contribute to the emergence of
biomolecules on planets.
Accepted by ApJ
http://arxiv.org/pdf/2008.09157

36. Gas-grain model of carbon fractionation in dense molecular clouds
Jean-Christophe Loison1 , Valentine Wakelam2 , Pierre Gratier2 and Kevin M. Hickson1
1
2

Institut des Sciences Moléculaires (ISM), CNRS, Univ. Bordeaux, 351 cours de la Libération, 33400, Talence, France;
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, 33615 Pessac, France

E-mail contact: jean-christophe.loison at u-bordeaux.fr

36

Carbon containing molecules in cold molecular clouds show various levels of isotopic fractionation through multiple
observations. To understand such effects, we have developed a new gas-grain chemical model with updated 13 C
fractionation reactions (also including the corresponding reactions for 15 N, 18 O and 34 S). For chemical ages typicalof dense clouds, our nominal model leads to two 13 C reservoirs: CO and the species that derive from CO, mainly
s-CO and s-CH3 OH, as well as C3 in the gas phase. The nominal model leads to strong enrichment in C3 , c-C3 H2and C2 H in contradiction with observations. When C3 reacts with oxygen atoms the global agreement between thevarious observations and the simulations is rather good showing variable 13 C fractionation levels which are specificto each species. Alternatively, hydrogen atom reactions lead to notable relative 13 C fractionation effects for the two
non-equivalent isotopologues of C2 H, c-C3 H2 and C2 S. As there are several important fractionation reactions, somecarbon bearing species are enriched in 13 C, particularly CO, depleting atomic 13 C in the gas phase. This induces a 13 C
depletion in CH4 formed on grain surfaces, an effect that is not observed in the CH4 in the solar system, in particularon Titan. This seems to indicate a transformation of matter between the collapse of the molecular clouds, leading to
the formation of the protostellar disc, and the formation of the planets. Or it means that the atomic carbon sticking
to the grains reacts with the species already on the grains giving very little CH4 .
Accepted by MNRAS
http://arxiv.org/pdf/2008.13411

37.

Herbig-Haro flows around BBWo 192E (GM 1-23) nebula
T.Yu. Magakian1 , T.A. Movsessian1 , H.R. Andreasyan1 , J.Bally2 and A.S. Rastorguev3,4
Byurakan Observatory of the Nat.Acad.Sci. of Armenia, Byurakan, Aragatsotn prov., 0213, Armenia; 2 Departmentof Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO,USA; 3 Faculty of Physics, Lomonosov
Moscow State University, Leninskie Gory 1, bldg.2, Moscow, Russia; 4 Sternberg Astronomical Institute, Lomonosov
Moscow State University, Universitetskii prospect, 13, Moscow, Russia
1E-mail contact: tigmag at sci.am
We studied a small comet-shape reflection nebula, located in the dark cloud SL 4 in the Vela Molecular Ridge cloud C,
known as BBWo 192E (GM 1-23), and a young infrared cluster embedded into the nebula, for the evidences of recent
star formation. We obtained the images of BBWo 192E in Hα and [SII] lines and in SDSS i’ with Blanco telescopeat the Cerro Tololo Interamerican Observatory to discover new Herbig-Haro (HH) flows. 2MASS and WISE surveys
were used for the search of the additional member stars of the cluster. We also studied proper motions and parallaxesof the cluster members with the aid of GAIA DR2. Five new groups containing at least 9 HH objects tracing several
distinct outflows were revealed. A previously unreported reflection nebula and a number of probable outflow sourceswere found in the infrared range. The proper motions allowed selecting eight probable member stars in the visualrange. Their parallaxes correspond to a mean distance 800 ± 100 pc for this cluster. The bolometric luminosities ofthe brightest cluster members are 1010 L⊙ (IRAS 08513−4201, the strong source in the center of the cluster) and 2 to
6 L⊙ for the five other stars. The existence of the optical HH flows around the infrared cluster of YSOs suggests thatstar formation in this cloud is on-going around the more massive HAeBe star. By its morphology and other features
this star-forming region is similar to the zone of star formation near CPM 19.
Accepted by MNRAS
http://arxiv.org/pdf/2009.00642

38. Accretion discs with non-zero central torque
Chris Nixon1 and Jim Pringle1,2
1

School of Phrm P3(n)1.34903(d)-384.084(t)34518422strog eoys1iversity oter, Coacuboundary is zero, is represented by f → ∞. For f > 0 a torque is applied to the disc at the inner boundary, whichfeeds both angular momentum and energy into the disc. This can arise, for example, in the case of a circumbinary
disc where resonances transfer energy and angular momentum from the binary to the disc orbits, or where the discis around a rotating magnetic star which can allow the disc orbits to be accelerated outwards at the magnetosphericradius. We present steady-state solutions to the disc structure as a function of f , and for arbitrary kinematic viscosity
ν. For time-dependent discs, we solve the equations using a Green’s function approach for the specific case of ν ∝ R
and provide an example numerical solution to the equations for the case of ν ∝ R3/2 . We find that for values of f < 0.1
the disc solutions closely resemble “accretion” discs. For values of f > 10 the solutions initially resemble “decretion”
discs, but at sufficiently late times exhibit the properties of “accretion” discs. We discuss the application of this theory
to different astrophysical systems, and in particular the values of the f parameter that are expected in different cases.
Accepted by New Astronomy
https://arxiv.org/pdf/2008.07565

39. Solving grain size inconsistency between ALMA polarization and VLA continuum in

the Ophiuchus IRS 48 protoplanetary disk

Satoshi Ohashi1 , Akimasa Kataoka2 , Nienke Van der Marel3 , Charles L. H. Hull4,5 , William R. F.
Dent5 , Adriana Pohl6 , Paola Pinilla6 , Ewine F. van Dishoeck7 and Thomas Henning6
RIKEN Cluster for Pioneering Research, 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan; 2 National Astronomical
Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Department of Physics and Astronomy,
University of Victoria 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada; 4 National Astronomical Observatoryof Japan, NAOJ Chile, Alonso de Córdova 3788, Office 61B, 7630422, Vitacura, Santiago, Chile; 5 Joint ALMA
Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile; 6 Max Planck Institute for Astronomy, Königstuhl
17, 69117 Heidelberg, Germany; 7 Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The
Netherlands
1E-mail contact: satoshi.ohashi at riken.jp
The protoplanetary disk around Ophiuchus IRS 48 shows an azimuthally asymmetric dust distribution in (sub)millimeter observations, which is interpreted as a vortex, where millimeter/centimeter-sized particles are trappedat the location of the continuum peak. In this paper, we present 860 µm ALMA observations of polarized dust emission of this disk. The polarized emission was detected toward a part of the disk. The polarization vectors are parallelto the disk minor axis, and the polarization fraction was derived to be 1 − 2%. These characteristics are consistent
with models of self-scattering of submillimeter-wave emission, which indicate a maximum grain size of ∼ 100 µm.
However, this is inconsistent with the previous interpretation of millimeter/centimeter dust particles being trappedby a vortex. To explain both, ALMA polarization and previous ALMA and VLA observations, we suggest that thethermal emission at 860 µm wavelength is optically thick (τabs ∼ 7.3) at the dust trap with the maximum observablegrain size of ∼ 100 µm rather than an optically thin case with ∼ cm dust grains. We note that we cannot rule outthat larger dust grains are accumulated near the midplane if the 860 µm thermal emission is optically thick.
Accepted by ApJ
https://arxiv.org/pdf/2007.15014.pdf

40.

Modeling disk fragmentation and multiplicity in massive star formation
G. André Oliva1 and Rolf Kuiper1
Institute for Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, 72076, Tübingen,Germany

1E-mail contact: andree.oliva at uni-tuebingen.deContext: There is growing evidence that massive stars grow by disk accretion similar to their low-mass counterparts.
Early in evolution, these disks can achieve masses which are comparable to the current stellar mass, and hence, theforming disks are highly susceptible for gravitational fragmentation.
Aims: We investigate the formation and early evolution of an accretion disk around a forming massive protostar,
focussing on its fragmentation physics. For this, we follow the collapse of a molecular cloud of gas and dust, the38

formation of a massive protostar, the formation of its circumstellar disk, and the formation and evolution of the disk
fragments.
Methods: We use a grid-based self-gravity-radiation-hydrodynamics code including a sub-grid module for stellar evolution and dust evolution. On purpose, we do not use a sub-grid module for fragmentation such as sink particles toallow for all paths of fragment formation and destruction, but instead keeping the spatial grid resolution high enoughto properly resolve the physical length scales of the problem, namely the pressure scale height and Jeans length ofthe disk. Simulations are performed on a grid in spherical coordinates with a logarithmic spacing of the grid cells in
the radial direction and a cosine-distribution of the grid cells in the polar direction, focusing the spatial resolution on
the disk midplane. Because of that, roughly 25% of the total number of grid cells, corresponding to ∼ 26 million gridcells, are used to model the disk physics. They constitute the highest resolution simulations performed up to now on
disk fragmentation around a forming massive star with the physics considered here. For a better understanding of
the effects of spatial resolution and to compare our high-resolution results with previous lower resolution studies in
the literature, we perform the same simulation for five different resolutions, each of them with a factor of two lower
resolution than the predecessor run.
Results: The cloud collapses and a massive (proto)star is formed in its center, surrounded by a fragmenting Keplerianlike accretion disk with spiral arms. The fragments have masses of ∼ 1 M⊙ , and their continuous interactions withthe disk, spiral arms and other fragments results in eccentric orbits. Fragments form hydrostatic cores, surroundedby secondary disks with spiral arms that also produce new fragments. We identified several mechanisms of fragment
formation, interaction and destruction. Central temperatures of the fragments can reach the hydrogen dissociation
limit, form second Larson cores and evolve into companion stars. Based on this, we study the multiplicity predictedby the simulations and find ∼ 6 companions at different distances from the primary: from possible spectroscopic
multiples, to companions at distances between 1000 and 2000 au.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2008.13653

41.

Different Fates of Young Star Clusters After Gas Expulsion
Xiaoying Pang1,2 , Yuqian Li1 , Shih-Yun Tang3,4 , Mario Pasquato5,6 and M.B.N. Kouwenhoven1
Department of Physics, Xi’an Jiaotong-Liverpool University, 111 Renai Road, Dushu Lake Science and Education
Innovation District, Suzhou 215123, Jiangsu Province, P. R. China; 2 Shanghai Key Laboratory for Astrophysics,
Shanghai Normal University, 100 Guilin Road, Shanghai 200234, P. R. China; 3 Lowell Observatory, 1400 W. Mars Hill
Road, Flagstaff, AZ 86001, USA; 4 Department of Astronomy and Planetary Sciences, Northern Arizona University,
Flagstaff, AZ 86011, USA; 5 INAF-Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, 35122 Padova,
Italy; 6 INFN- Sezione di Padova, Via Marzolo 8, I35131 Padova, Italy

1E-mail contact: Xiaoying.Pang at xjtlu.edu.cn
We identify structures of the young star cluster NGC 2232 in the solar neighborhood (323.0 pc), and a newly discoveredstar cluster LP 2439 (289.1 pc). Member candidates are identified using the Gaia DR2 sky position, parallax andproper motion data, by an unsupervised machine learning method, StarGO. Member contamination from the Galactic
disk is further removed using the color magnitude diagram. The four identified groups (NGC 2232, LP 2439 and two
filamentary structures) of stars are coeval with an age of 25 Myr and were likely formed in the same giant molecular
cloud. We correct the distance asymmetry from the parallax error with a Bayesian method. The 3D morphology
shows the two spherical distributions of clusters NGC 2232 and LP 2439. Two filamentary structures are spatiallyand kinematically connected to NGC 2232. Both NGC 2232 and LP 2439 are expanding. The expansion is moresignificant in LP 2439, generating a loose spatial distribution with shallow volume number and mass density profiles.
The expansion is suggested to be mainly driven by gas expulsion. NGC 2232, with 73 percent of the cluster mass
bound, is currently experiencing a process of re-virialization, However, LP 2439, with 52 percent cluster mass being
unbound, may fully dissolve in the near future. The different survivability traces different dynamical states of NGC
2232 and LP 2439 prior to the onset of gas expulsion. NGC 2232 may have been substructured and subvirial, while
LP 2439 may either have been virial/supervirial, or it has experienced a much faster rate of gas removal.
Accepted by ApJL
http://arxiv.org/pdf/2008.02803

3942. Magnetic torques on T Tauri stars: accreting vs. non-accreting systems
G. Pantolmos1 , C. Zanni2 and J. Bouvier1
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 INAF - Osservatorio Astrofisico di Torino, Strada
Osservatorio 20, 10025 Pino Torinese, Italy
1E-mail contact: george.pantolmos at univ-grenoble-alpes.fr
Classical T Tauri stars (CTTs) magnetically interact with their surrounding disks, a process that is thought toregulate their rotational evolution. In this work, we compute torques acting onto the stellar surface of CTTs arisingfrom different accreting (accretion funnels) and ejecting (stellar winds and magnetospheric ejections) flow components.
Furthermore, we compare the magnetic braking due to stellar winds in two different systems: isolated and accretingstars. 2.5D magnetohydrodynamic, time-dependent, axisymmetric simulations are employed. For both systems thestellar wind is thermally driven. In the star-disk-interaction (SDI) simulations the accretion disk is Keplerian, viscous,and resistive. Two series of simulations are presented, one for each system. We find that in classical T Tauri systems thepresence of magnetospheric ejections confines the stellar-wind expansion, resulting in an hourglass-shaped geometry of
the outflow. In addition, the formation of the accretion columns modifies the amount of open magnetic flux exploitedby the stellar wind. These effects have a strong impact on the stellar wind properties and we show that the stellar-windbraking is more efficient in the star-disk-interacting systems than in the isolated ones. We also derive torque scalings,
over a wide range of magnetic field strengths, for each flow component in a SDI system that directly applies a torqueon the stellar surface. In all the performed SDI simulations the stellar wind extracts less than 2% of the mass accretion
rate and the disk is truncated up to 66% of the corotation radius. All the simulations show a net spin-up torque. In
order to achieve a stellar-spin equilibrium we need either more massive stellar winds or disks being truncated closer
to the corotation radius, which increases the torque efficiency by the magnetospheric ejections.
Accepted by A&A
http://arxiv.org/pdf/2009.00940

43.

Gas trapping of hot dust around main-sequence stars
Tim D. Pearce1 , Alexander V. Krivov1 and Mark Booth1
Astrophysikalisches Institut und Universitätssternwarte, Friedrich-Schiller-Universität Jena, Schillergäßchen 2-3, D07745 Jena, Germany

1E-mail contact: timothy.pearce at uni-jena.de
In 2006 Vega was discovered to display excess near-infrared emission. Surveys now detect this phenomenon for one fifthof main-sequence stars, across various spectral types and ages. The excesses are interpreted as populations of small,
hot dust grains very close to their stars, which must originate from comets or asteroids. However, the presence of suchgrains in copious amounts is mysterious, since they should rapidly sublimate or be blown out of the system. Here
we investigate a potential mechanism to generate excesses: dust migrating inwards under radiation forces sublimatesnear the star, releasing modest quantities of gas which then traps subsequent grains. This mechanism requires neither
specialised system architectures nor high dust supply rates, and could operate across diverse stellar types and ages.
The model naturally reproduces many features of inferred dust populations, in particular their location, preference forsmall grains, steep size distribution, and dust location scaling with stellar luminosity. For Sun-like stars the mechanism
can produce 2.2 µm excesses that are an order of magnitude larger than those at 8.5 µm, as required by observations.
However, for A-type stars the simulated near-infrared excesses were only twice those in the mid infrared; grains would
have to be 5 − 10 times smaller than those trapped in our model to be able to explain observed near-infrared excesses
around A stars. Further progress with any hot dust explanation for A stars requires a means for grains to become
very hot without either rapidly sublimating or being blown out of the system.
Accepted by MNRAS
https://arxiv.org/pdf/2008.07505.pdf

40

44.

Linking ice and gas in the Serpens low-mass star-forming region
G. Perotti1 , W. R. M. Rocha1 , J. K. Jørgensen1 , L.E. Kristensen1 , H. J. Fraser2 and K. M. Pontoppidan3
Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 5−7, 1350
Copenhagen K., Denmark; 2 School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7
6AA, United Kingdom; 3 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
1E-mail contact: giulia.perotti at nbi.ku.dk
The interaction between dust, ice, and gas during the formation of stars produces complex organic molecules. Whileobservations indicate that several species are formed on ice-covered dust grains and are released into the gas phase,the exact chemical interplay between solid and gas phases and their relative importance remain unclear. Our goal is to
study the interplay between dust, ice, and gas in regions of low-mass star formation through ice- and gas-mapping andby directly measuring gas-to-ice ratios. This provides constraints on the routes that lead to the chemical complexitythat is observed in solid and gas phases. We present observations of gas-phase methanol (CH3 OH) and carbon
monoxide (13 CO and C18 O) at 1.3 mm towards ten low-mass young protostars in the Serpens SVS 4 cluster from the
SubMillimeter Array (SMA) and the Atacama Pathfinder EXperiment (APEX) telescope. We used archival data fromthe Very Large Telescope (VLT) to derive abundances of ice H2 O, CO, and CH3 OH towards the same region. Finally,
we constructed gas-ice maps of SVS 4 and directly measured CO and CH3 OH gas-to-ice ratios. The SVS 4 cluster ischaracterised by a global temperature of 15 ± 5 K. At this temperature, the chemical behaviours of CH3 OH and CO
are anti-correlated: larger variations are observed for CH3 OH gas than for CH3 OH ice, whereas the opposite is seen
for CO. The gas-to-ice ratios (Ngas /Nice ) range from 1 − 6 for CO and 1.4 × 10−4 − 3.7 × 10−3 for CH3 OH. The CO
gas-maps trace an extended gaseous component that is not sensitive to the effect of freeze-out. Because of temperature
variations and dust heating around 20 K, the frozen CO is efficiently desorbed. The CH3 OH gas-maps, in contrast,
probe regions where methanol is predominantly formed and present in ices and is released into the gas phase throughnon-thermal desorption mechanisms. Combining gas- and ice-mapping techniques, we measure gas-to-ice ratios of
CO and CH3 OH in the SVS 4 cluster. The CH3 OH gas-to-ice ratio agrees with values that were previously reported
for embedded Class 0/I low-mass protostars. We find that there is no straightforward correlation between CO andCH3 OH gas with their ice counterparts in the cluster. This is likely related to the complex morphology of SVS 4: theClass 0 protostar SMM 4 and its envelope lie in the vicinity, and the outflow associated with SMM 4 intersects thecluster. This study serves as a pathfinder for future observations with ALMA and the James Webb Space Telescope(JWST) that will provide high-sensitivity gas-ice maps of molecules more complex than methanol. Such comparative
maps will be essential to constrain the chemical routes that regulate the chemical complexity in star-forming regions.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2008.02827

45. ALMA chemical survey of disk-outflow sources in Taurus (ALMA-DOT) II: Verticalstratification of CO, CS, CN, H2 CO, and CH3 OH in a Class I disk

L. Podio1 , A. Garufi1 , C. Codella1,2, D. Fedele1 , E. Bianchi2 , F. Bacciotti1 , C. Ceccarelli2 , C. Favre2 ,S. Mercimek1,4 , K. Rygl3 and L. Testi5,6,1
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy; 2 Univ. Grenoble Alpes, CNRS,
IPAG, 38000 Grenoble, France; 3 INAF - Istituto di Radioastronomia & Italian ALMA Regional Centre, via P. Gobetti
101, 40129 Bologna, Italy; 4 Università degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Via G. Sansone
1, 50019 Sesto Fiorentino, Italy; 5 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei
München, Germany; 6 Excellence Cluster Origins, Boltzmannstrasse 2, 85748 Garching bei München, Germany
1E-mail contact: lpodio at arcetri.astro.it
The chemical composition of planets is inherited from the one of protoplanetary disks at the time of their formation.
Increasing observational evidence suggests that planet formation occurs in less than 1−2 Myr. This motivates theneed for spatially resolved spectral observations of young Class I disks, as carried out by the ALMA-DOT campaign inTaurus. In the context of ALMA-DOT, we observe the edge-on disk around the Class I source IRAS 04302+2247 (thebutterfly star) in the 1.3 mm continuum and five molecular lines. We report the first tentative detection of methanol(CH3 OH) in a Class I disk and resolve for the first time the vertical structure of a disk with multiple molecular tracers.
The bulk of the emission in the CO 2 − 1, CS 5 − 4, and o-H2 CO 31,2 − 21,1 lines originates from the warm molecular

41

layer, with the line intensity peaking at increasing disk heights, z, for increasing radial distances, r. Molecular emission
is vertically stratified, with CO observed at larger disk heights (aperture z/r ∼ 0.41 − 0.45) compared to both CS
and H2 CO, which are nearly co-spatial (z/r ∼ 0.21 − 0.28). In the outer midplane, the line emission decreases due tomolecular freeze-out onto dust grains (freeze-out layer) by a factor of > 100 (CO) and 15 (CS). H2 CO decreases by afactor of only about 2, possibly due to H2 CO formation on icy grains, followed by non-thermal release into gas-phase.
The inferred [CH3 OH]/[H2 CO] abundance ratio is 0.5 − 0.6, which is 1 − 2 orders of magnitude lower than for Class 0
hot-corinos, a factor ∼ 2.5 lower than the only other value inferred for a protoplanetary disk (in TW Hya, 1.3 − 1.7),
and at the lower edge but still consistent with the values in comets. This may indicate that some chemical reprocessing
occurs in disks before the formation of planets and comets.
Accepted by Astronomy & Astrophysics Letters
https://arxiv.org/pdf/2008.12648

46.

Magnetospheric accretion in the intermediate-mass T Tauri star HQ Tau
K. Pouilly1 , J. Bouvier1 , E. Alecian1 , S. H. P. Alencar2 , A. -M. Cody3 , J. -F. Donati4 , K. Grankin5 , G.
A. J. Hussain6 , L. Rebull7 and C. P. Folsom4
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 2 Dept de Fisica - ICEx - UFMG, Av. Antonio
Carlos 6627, 30270-901 Belo Horizonte, MG, Brazil; 3 Bay Area Environmental Research Institute, 625 2nd St Ste.
209, Petaluma, CA 94952; 4 Univ. de Toulouse, CNRS, IRAP, 14 avenue Belin, 31400 Toulouse, France; 5 Crimean
Astrophysical Observatory, Nauchny, Crimea 298409; 6 ESO, Karl-Schwarzschild-Str. 2, 85748 Garching bei München,
Germany; 7 Infrared Science Archive, IPAC, California Institute of Technology, 1200 E. California Blvd, MS 100-22,
Pasadena, CA91125 USA
1E-mail contact: kim.pouilly at univ-grenoble-alpes.fr
Context: Classical T Tauri stars (cTTs) are pre-main sequence stars surrounded by an accretion disk. They host astrong magneticfield, and both magnetospheric accretion and ejection processes develop as the young magnetic starinteracts with its disk. Studyingthis interaction is a major goal toward understanding the properties of young stars
and their evolution.
Aims: The goal of this study is to investigate the accretion process in the young stellar system HQ Tau, an intermediatemass T Tauristar (1.9 M⊙ ).
Methods: The time variability of the system is investigated both photometrically, using Kepler-K2 and complementary
light curves,and from a high-resolution spectropolarimetric time series obtained with ESPaDOnS at CFHT.
Results: The quasi-sinusoidal Kepler-K2 light curve exhibits a period of 2.424 d, which we ascribe to the rotational
period of thestar. The radial velocity of the system shows the same periodicity, as expected from the modulation of
the photospheric line profilesby surface spots. A similar period is found in the red wing of several emission lines (e.g.,
HI, CaII, NaI), due to the appearance ofinverse P Cygni components, indicative of accretion funnel flows. Signaturesof outflows are also seen in the line profiles, some beingperiodic, others transient. The polarimetric analysis indicates acomplex, moderately strong magnetic field which is possibly sufficientto truncate the inner disk close to the corotation
radius,rcor ∼ 3.5 R⋆ . Additionally, we report HQ Tau to be a spectroscopic binarycandidate whose orbit remains to
be determined.
Conclusions: The results of this study expand upon those previously reported for low-mass T Tauri stars, as they
indicate that themagnetospheric accretion process may still operate in intermediate-mass pre-main sequence stars,
such as HQ Tau.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2008.12531.pdf

Interpreting high spatial resolution line observations of planet-forming disks with gaps
47. and rings - The case of HD 163296
Ch. Rab1,5 , I. Kamp1 , C. Dominik2 , C. Ginski2,3 , G. A. Muro-Arena2 , W.-F. Thi5 , L. B. F. M. Waters4,2
and P. Woitke6,7Kapteyn Astronomical Institute, Univ. of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands; 2
Anton Pannekoek Inst. for Astronomy, Univ. of Amsterdam, 1098 XH Amsterdam, The Netherlands; 3 Leiden
142Observatory, Leiden Univ., 2300 RA Leiden, The Netherlands; 4 SRON Netherlands Institute for Space Research,3584 CA Utrecht, The Netherlands; 5 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748
Garching, Germany; 6 SUPA, School of Physics & Astronomy, Univ. of St. Andrews, North Haugh, St. Andrews
KY16 9SS, UK; 7 Centre for Exoplanet Science, Univ. of St Andrews, North Haugh, St Andrews, KY169SS, UK
E-mail contact: rab at mpe.mpg.de
Spatially resolved continuum observations of planet-forming disks show prominent ring and gap structures in theirdust distribution. However, the picture from gas observations is much less clear and constraints on the radial gas
density structure (i.e. gas gaps) remain rare and uncertain. We want to investigate the importance of thermochemical processes for the interpretation of high-spatial-resolution gas observations of planet-forming disks and theirimpact on derived gas properties. We apply the radiation thermo-chemical disk code ProDiMo (PROtoplanetary DIsk
MOdel) to model self-consistently the dust and gas disk of HD 163296, using the DSHARP (Disk Substructure at
High Angular Resolution) gas and dust observations. With this model we investigate the impact of dust gaps and gas
gaps, considering chemistry and heating/cooling processes, on the observables and the derived gas properties. We finddistinct peaks in the radial line intensity profiles of the CO line data of HD 163296 at the location of the dust gaps.
Our model indicates that those peaks are not only a consequence of a gas temperature increase within the gaps but are
mainly caused by the absorption of line emission from the back side of the disk by the dust rings. For two of the threeprominent dust gaps in HD 163296, we find that thermo-chemical effects are negligible for deriving density gradients
via measurements of the rotation velocity. However, for the gap with the highest dust depletion, the temperature
gradient can be dominant and needs to be considered to derive accurate gas density profiles. Self-consistent gas anddust thermo-chemical modelling in combination with high-quality observations of multiple molecules are necessary toaccurately derive gas gap depths and shapes. This is crucial to determine the origin of gaps and rings in planet-forming
disks and to improve the mass estimates of forming planets if they are the cause of the gap.
Accepted by A&A
https://arxiv.org/pdf/2008.05941

48.

Illuminating a tadpole’s metamorphosis III: quantifying past and present environmental
impactMegan Reiter1 , Thomas J. Haworth2 , Andres E. Guzman3 , Pamela D. Klaassen1 , Anna F. McLeod4,5
and Guido Garay6
UK Astronomy Technology Centre, Blackford Hill, Edinburgh, EH9 3HJ, UK; 2 Astronomy Unit, School of Physics
and Astronomy, Queen Mary University of London, London E1 4NS, UK; 3 NAOJ, National Institutes of Natural
Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 4 Dept of Astronomy, Univ. of California, Berkeley, CA 94720,
USA; 5 Dept of Physics and Astronomy, Texas Tech University, Lubbock, TX 79409, USA; 6 Dept de Astronomia,
Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile

1

E-mail contact: megan.reiter at stfc.ac.uk
We combine MUSE and ALMA observations with theoretical models to evaluate how a tadpole-shaped globule locatedin the Carina Nebula has been influenced by its environment. This globule is now relatively small (radius ∼ 2500 au),hosts a protostellar jet+outflow (HH 900) and, with a blue-shifted velocity of ∼ 10 km s−1 , is travelling faster thanit should be if its kinematics were set by the turbulent velocity dispersion of the precursor cloud. Its outer layers are
currently still subject to heating, but comparing the internal and external pressures implies that the globule is in a
post-collapse phase. Intriguingly the outflow is bent, implying that the YSO responsible for launching it is comoving
with the globule, which requires that the star formed after the globule was up to speed since otherwise it would
have been left behind. We conclude that the most likely scenario is one in which the cloud was much larger before
being subject to radiatively-driven implosion, which accelerated the globule to the high observed speeds under thephotoevaporative rocket effect and triggered the formation of the star responsible for the outflow. The globule may
now be in a quasi-steady state following collapse. Finally, the HH 900 YSO is likely > 1 M⊙ and may be the only
star forming in the globule. It may be that this process of triggered star formation has prevented the globule fromfragmenting to form multiple stars (e.g., due to heating) and has produced a single higher mass star.
Accepted by MNRAS
https://arxiv.org/pdf/2007.10341

43

AB Aur, a Rosetta stone for studies of planet formation (I): chemical study of a planet-

49. forming disk

P. Riviére-Marichalar1 , A. Fuente1 , R. Le Gal2 , C. Baruteau3 , R. Neri4 et al.
Observatorio Astronómico Nacional (OAN,IGN), Calle Alfonso XII, 3. 28014 Madrid, Spain; 2 Center for Astrophysics, Harvard & Smithsonian, 60 Garden St, Cambridge, MA 02138, USA; 3 CNRS / Institut de Recherche en
Astrophysique et Planétologie, 14 avenue Edouard Belin, F-31400 Toulouse, France; 4 Institut de Radioastronomie
Millimétrique, 300 rue de la Piscine, F-38406 Saint-Martin d’Héres, France
1

E-mail contact: p.riviere at oan.es
AB Aur is a Herbig Ae star that hosts a prototypical transition disk. The disk shows a plethora of features connectedwith planet formation mechanisms. Understanding the physical and chemical characteristics of these features is crucial
to advancing our knowledge of planet formation. We aim to characterize the gaseous disk around the Herbig Ae star
AB Aur. A complete spectroscopic study was performed using NOEMA to determine the physical and chemical
conditions. We present new observations of the continuum and 12 CO, 13 CO, C18 O, H2 CO, and SO lines. We used theintegrated intensity maps and stacked spectra to derive estimates of the disk temperature. By combining our 13 CO
and C18 O observations, we computed the gas-to-dust ratio along the disk. We also derived column density maps forthe different species and used them to compute abundance maps. The results of our observations were compared with
Nautilus astrochemical models. We detected continuum emission in a ring that extends from 0.′′ 6 to 2.′′ 0, peaking at
0.′′ 97 and with a strong azimuthal asymmetry. The molecules observed show different spatial distributions, and thepeaks of the distributions are not correlated with the binding energy. Using H2 CO and SO lines, we derived a mean disk
temperature of 39 K. We derived a gas-to-dust ratio that ranges from 10 to 40. The comparison with Nautilus models
favors a disk with a low gas-to-dust ratio (40) and prominent sulfur depletion. From a very complete spectroscopic
study of the prototypical disk around AB Aur, we derived, for the first time, the gas temperature and the gas-to-dust
ratio along the disk, providing information that is essential to constraining hydrodynamical simulations.Moreover, we
explored the gas chemistry and, in particular, the sulfur depletion. The derived sulfur depletion is dependent on theassumed C/O ratio. Our data are better explained with C/O ∼ 0.7 and S/H = 8×10−8.
Accepted by A&A
http://arxiv.org/pdf/2008.00751

50. A dusty origin for the correlation between protoplanetary disc accretion rates and dust

massesAndrew D. Sellek1 , Richard A. Booth1 and Cathie J. Clarke1
1

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

E-mail contact: ads79 at cam.ac.uk
Recent observations have uncovered a correlation between the accretion rates (measured from the UV continuum
excess) of protoplanetary discs and their masses inferred from observations of the sub-mm continuum. While viscous
evolution models predict such a correlation, the predicted values are in tension with data obtained from the Lupus
and Upper Scorpius star forming regions; for example, they underpredict the scatter in accretion rates, particularly
in older regions. Here we argue that since the sub-mm observations trace the discs’ dust, by explicitly modelling thedust grain growth, evolution, and emission, we can better understand the correlation. We show that for turbulent
viscosities with α ≤ 10−3 , the depletion of dust from the disc due to radial drift means we can reproduce the rangeof masses and accretion rates seen in the Lupus and Upper Sco datasets. One consequence of this model is that theupper locus of accretion rates at a given dust mass does not evolve with the age of the region. Moreover, we findthat internal photoevaporation is necessary to produce the lowest accretion rates observed. In order to replicate thecorrect dust masses at the time of disc dispersal, we favour relatively low photoevaporation rates ≤ 10−9 M⊙ yr−1 formost sources but cannot discriminate between EUV or X-ray driven winds. A limited number of sources, particularly
in Lupus, are shown to have higher masses than predicted by our models which may be evidence for variations in theproperties of the dust or dust trapping induced in substructures.
Accepted by MNRAS
https://arxiv.org/pdf/2008.07530

44

Reading between the lines:
51. Disk emission, wind, and accretion during the ZCMa NW outburst
A. Sicilia-Aguilar1 , J. Bouvier2 , C. Dougados2 , K. Grankin3 and J.-F. Donati4
SUPA, School of Science and Engineering, University of Dundee, Nethergate, Dundee DD1 4HN, UK; 2 Université
Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France; 3 Crimean Astrophysical Observatory, 298409 Nauchny,
Crimea; 4 IRAP Observatoire Midi-Pyrénées, 14 Avenue E Belin, 31400 Toulouse, France

152.

matrix method in combination with tools from circular statistics, we find that the majority of the filamentary structuresin the HI emission are aligned with the Galactic plane. Part of this trend can be assigned to long filamentary structuresthat are coherent across several velocity channels. However, we also find ranges of Galactic longitude and radial velocity
where the HI filamentary structures are preferentially oriented perpendicular to the Galactic plane. These are located(i) around the tangent point of the Scutum spiral arm, l ≈ 28◦ and vLSR ≈ 100 km/s, (ii) toward l ≈ 45◦ andvLSR ≈ 50 km/s, (iii) around the Riegel-Crutcher cloud, and (iv) toward the terminal velocities. Comparison withnumerical simulations indicates that the prevalence of horizontal filamentary structures is most likely the result of
the large-scale dynamics and that vertical structures identified in (i) and (ii) may arise from the combined effect ofsupernova (SN) feedback and strong magnetic fields. The vertical filamentary structures in (iv) can be related to thepresence of clouds from extra-planar HI gas falling back into the Galactic plane after being expelled by SNe. Our
results indicate that a systematic characterization of the emission morphology toward the Galactic plane provides an
unexplored link between the observations and the dynamical behaviour of the interstellar medium, from the effect oflarge-scale Galactic dynamics to the Galactic fountains driven by SNe.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2007.07285

Low Level Carbon Monoxide Line Polarization in two Protoplanetary Disks: HD 142527

53. and IM Lup

Ian W. Stephens1 , Manuel Fernández-López2 , Zhi-Yun Li3 , Leslie W. Looney4 and Richard Teague1
Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA; 2 Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET; CICPBA), C.C. No. 5, 1894, Villa Elisa, Buenos Aires,
Argentina; 3 Astronomy Department, University of Virginia, Charlottesville, VA 22904, USA; 4 Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA
1E-mail contact: ian.stephens at cfa.harvard.edu
Magnetic fields are expected to play an important role in accretion processes for circumstellar disks. Measuring
the magnetic field morphology is difficult, especially since polarimetric (sub)millimeter continuum observations may
not trace fields in most disks. The Goldreich-Kylafis (GK) effect suggests that line polarization is perpendicular orparallel to the magnetic field direction. We attempt to observe CO(2–1), 13 CO(2–1), and C18 O(2–1) line polarization
toward HD 142527 and IM Lup, which are large, bright protoplanetary disks. We use spatial averaging and spectral
integration to search for signals in both disks, and detect a potential CO(2–1) Stokes Q signal toward both disks.
The total CO(2–1) polarization fractions are 1.57±0.18% and 1.01±0.10% for HD 142527 and IM Lup, respectively.
Our Monte Carlo simulations indicate that these signals are marginal. We also stack Stokes parameters based on the
Keplerian rotation, but no signal was found. Across the disk traced by dust of HD 142527, the 3σ upper limits for
Pfrac at 0.′′ 5 (∼80 au) resolution are typically less than 3% for CO(2–1) and 13 CO(2–1) and 4% for C18 O(2–1). For
IM Lup, the 3σ upper limits for these three lines are typically less than 3%, 4%, and 12%, respectively. Upper limits
based on our stacking technique are up to a factor of ∼10 lower, though stacking areas can potentially average out
small-scale polarization structure. We also compare our continuum polarization at 1.3 mm to observations at 870µm from previous studies. The polarization in the northern dust trap of HD 142527 shows a significant change inmorphology and an increase in Pfrac as compared to 870 µm. For IM Lup, the 1.3 mm polarization may be moreazimuthal and has a higher Pfrac than at 870 µm.
Accepted by ApJ
http://arxiv.org/pdf/2008.04952

54. Atomic and molecular gas properties during cloud formation
J. Syed1 , Y. Wang1 , H. Beuther1 , J. D. Soler1 , M. R. Rugel2 , J. Ott3 , A. Brunthaler2 , J. Kerp4 , M.
Heyer5 , R. S. Klessen6,7, Th. Henning1 , S. C. O. Glover6 , P. F. Goldsmith8, H. Linz1 , J. S. Urquhart9 ,S. E. Ragan10 , K. G. Johnston11 and F. Bigiel4
1
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany; 3 National Radio Astronomy Observatory, PO Box O,
1003 Lopezville Road, Socorro, NM 87801, USA; 4 Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121

46Bonn, Germany; 5 Department of Astronomy, University of Massachusetts, Amherst, MA01003, USA; 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 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena,
CA 91109, USA; 9 Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK;
10
School of Physics and Astronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff CF24 3AA, UK; 11
School of Physics and Astronomy, E.C. Stoner Building, The University of Leeds, Leeds LS2 9JT, UK
E-mail contact: syed at mpia.de
Molecular clouds, which harbor the birthplaces of stars, form out of the atomic phase of the interstellar medium(ISM). To understand this transition process, it is crucial to investigate the spatial and kinematic relationships between
atomic and molecular gas. We aim to characterize the atomic and molecular phases of the ISM and set their physicalproperties into the context of cloud formation processes. We studied the cold neutral medium (CNM) by means of
HI self-absorption (HISA) toward the giant molecular filament GMF20.0-17.9 (distance=3.5 kpc, length ∼170 pc) andcompared our results with molecular gas traced by 13 CO emission. We fitted baselines of HISA features to HI emission
spectra using first and second order polynomial functions. The CNM identified by this method spatially correlateswith the morphology of the molecular gas toward the western region. However, no spatial correlation between HISA
and 13 CO is evident toward the eastern part of the filament. The distribution of HISA peak velocities and line widths
agrees well with 13 CO within the whole filament. The column densities of the CNM probed by HISA are on theorder of 1020 cm−2 while those of molecular hydrogen traced by 13 CO are an order of magnitude higher. The column
density probability density functions (N-PDFs) of HISA (CNM) and HI emission (tracing both the CNM and thewarm neutral medium, WNM) have a log-normal shape for all parts of the filament, indicative of turbulent motions
as the main driver for these structures. The H2 N-PDFs show a broad log-normal distribution with a power-law tailsuggesting the onset of gravitational contraction. The saturation of HI column density is observed at ∼25 M⊙ pc−2 .
We conjecture that different evolutionary stages are evident within the filament. In the eastern region, we witness theonset of molecular cloud formation out of the atomic gas reservoir while the western part is more evolved, as it reveals
pronounced H2 column density peaks and signs of active star formation.
Accepted by A&A
http://arxiv.org/pdf/2008.13502

55. Salt, Hot Water, and Silicon Compounds Tracing Massive Twin DisksKei E. I. Tanaka1,2 , Yichen Zhang3 , Tomoya Hirota1,4 , Nami Sakai3 , Kazuhito Motogi5, Kengo Tomida6 ,Jonathan C. Tan7,8 , Viviana Rosero9 , Aya E. Higuchi1 , Satoshi Ohashi3 , Mengyao Liu8 and Koichiro
Sugiyama10,1
National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 2 Department of Earth and Space
Science, Osaka University, Toyonaka, Osaka 560-0043, Japan; 3 Star and Planet Formation Laboratory, RIKEN Cluster
for Pioneering Research, Wako, Saitama 351-0198, Japan; 4 Department of Astronomical Sciences, SOKENDAI (The
Graduate University for Advanced Studies), Mitaka, Tokyo 181-8588, Japan; 5 Graduate School of Sciences andTechnology for Innovation, Yamaguchi University, Yamaguchi 753-8512, Japan; 6 Astronomical Institute, Tohoku
University, Sendai 980-8578, Japan; 7 Department of Space, Earth & Environment, Chalmers University of Technology,
SE-412 96 Gothenburg, Sweden; 8 Department of Astronomy, University of Virginia, Charlottesville, VA 229044325, USA; 9 National Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801, USA; 10 National
Astronomical Research Institute of Thailand, 260 Moo 4, T. Donkaew, A. Maerim, Chiang Mai 50180, Thailand
1

E-mail contact: kei.tanaka at nao.ac.jp
We report results of 0.05′′ -resolution observations toward the O-type proto-binary system IRAS 16547–4247 with
the Atacama Large Millimeter/submillimeter Array (ALMA). We present dynamical and chemical structures of thecircumbinary disk, circumstellar disks, outflows and jets, illustrated by multi-wavelength continuum and various
molecular lines. In particular, we detect sodium chloride, silicon compounds, and vibrationally-excited water lines asprobes of the individual protostellar disks at a scale of 100 au. These are complementary to typical hot-core molecules
tracing the circumbinary structures on a 1000-au scale. The H2 O line tracing inner-disks has an upper-state energyof Eu /k > 3000 K, indicating a high temperature of the disks. On the other hand, despite the detected transitionsof NaCl, SiO, and SiS not necessarily having high upper-state energies, they are enhanced only in the vicinity of the47

protostars. We interpret that these molecules are the products of dust destruction, which only happens in the inner
disks. This is the second detection of alkali metal halide in protostellar systems after the case of the disk of Orion Source
I, and also one of few massive protostellar disks associated with high-energy transition water and silicon compounds.
These new results suggest these “hot-disk" lines may be common in innermost disks around massive protostars, andhave great potential for future research of massive star formation. We also tentatively find that the twin disks arecounter-rotating, which might give a hint of the origin of the massive proto-binary system IRAS 16547–4247.
Accepted by ApJ Letters
https://arxiv.org/pdf/2007.02962.pdf

Secular Gravitational Instability of Drifting Dust in Protoplanetary Disks: Formation

56. of Dusty Rings without Significant Gas Substructures

Ryosuke T. Tominaga1 , Sanemichi Z. Takahashi2 and Shu-ichiro Inutsuka1
Department of Physics, Nagoya University, Nagoya, Aichi 464-8692, Japan; 2 National Astronomical Observatory ofJapan, Osawa, Mitaka, Tokyo 181-8588, Japan1

E-mail contact: tominaga.ryosuke at a.mbox.nagoya-u.ac.jp
Secular gravitational instability (GI) is one of the promising mechanisms for creating annular substructures andplanetesimals in protoplanetary disks. We perform numerical simulations of the secular GI in a radially extended disk
with inward drifting dust grains. The results show that, even in the presence of the dust diffusion, the dust rings form
via the secular GI while the dust grains are moving inward, and the dust surface density increases by a factor of ten.
Once the secular GI develops into a nonlinear regime, the total mass of the resultant rings can be a significant fractionof the dust disk mass. In this way, a large amount of drifting dust grains can be collected in the dusty rings andstored for planetesimal formation. In contrast to the emergence of remarkable dust substructures, the secular GI does
not create significant gas substructures. This result indicates that observations of a gas density profile near the disk
midplane enable us to distinguish the mechanisms for creating the annular substructures in the observed disks. The
resultant rings start decaying once they enter the inner region stable to the secular GI. Since the ring-gap contrast
smoothly decreases, it seems possible that the rings are observed even in the stable region. We also discuss the likely
outcome of the non-linear growth and indicate the possibility that a significantly developed region of the secular GI
may appear as a gap-like substructure in dust continuum emission since dust growth into larger solid bodies andplanetesimal formation reduce the total emissivity.
Accepted by ApJ
http://arxiv.org/pdf/2008.02564

57.

Temperature structures of embedded disks: young disks in Taurus are warm
Merel L.R. van ’t Hoff1,2 , Daniel Harsono3 , John J. Tobin4 , Arthur D. Bosman1,2 , Ewine F. van
Dishoeck1,5 , Jes K. Jørgensen6 , Anna Miotello7, Nadia M. Murillo1,8 and Catherine Walsh9
Leiden Observatory, Leiden University, P.O. box 9513, 2300 RA Leiden, The Netherlands; 2 Department of Astronomy, University of Michigan, 1085 S University Ave, Ann Arbor, MI 48109, USA; 3 Institute of Astronomy andAstrophysics, Academia Sinica, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, R. O. C.; 4 National Radio
Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903, USA; 5 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei München, Germany; 6 Niels Bohr Institute, Universityof Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K., Denmark; 7 European Southern Observatory, KarlSchwarzschild-Str. 2, D-85748 Garching bei München, Germany; 8 The Institute of Physical and Chemical Research(RIKEN), 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan; 9 School of Physics and Astronomy, University of Leeds,
Leeds LS2 9JT, UK
1E-mail contact: mervth at umich.edu
The chemical composition of gas and ice in disks around young stars set the bulk composition of planets. In contrast
to protoplanetary disks (Class II), young disks that are still embedded in their natal envelope (Class 0 and I) are
predicted to be too warm for CO to freeze out, as has been confirmed observationally for L1527 IRS. To establish
whether young disks are generally warmer than their more evolved counterparts, we observed five young (Class 0/I48

and Class I) disks in Taurus with the Atacama Large Millimeter/submillimeter Array (ALMA), targeting C17 O 2 − 1,
H2 CO 31,2 − 21,1 , HDO 31,2 − 22,1 and CH3 OH 5K − 4K transitions at 0.48′′ × 0.31′′ resolution. The different freeze-out
temperatures of these species allow us to derive a global temperature structure. C17 O and H2 CO are detected in all
disks, with no signs of CO freeze-out in the inner ∼100 au, and a CO abundance close to ∼10−4 . H2 CO emission
originates in the surface layers of the two edge-on disks, as witnessed by the especially beautiful V-shaped emission
pattern in IRAS 04302+2247. HDO and CH3 OH are not detected, with column density upper limits more than 100
times lower than for hot cores. Young disks are thus found to be warmer than more evolved protoplanetary disks
around solar analogues, with no CO freeze-out (or only in the outermost part of >∼100 au disks) or CO processing.
However, they are not as warm as hot cores or disks around outbursting sources, and therefore do not have a large
gas-phase reservoir of complex molecules.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/2008.08106.pdf

Observations of edge-on protoplanetary disks with ALMA. I. Results from continuum

58. data

M. Villenave1,2 , F. Ménard1 , W. R. F. Dent3 , G. Duchêne4,1 , K. R. Stapelfeldt5 , M. Benisty6,1 , Y.
Boehlerur ru1.34781(s)-3.9251.589n

are consistent with a small millimeter dust scale height, of a few au (measured at r=100 au). This is in contrast withthe more classical value of hg ∼10 au derived from scattered light images and from gas line measurements. These
results confirm, by direct observations, that large (millimeter) grains are subject to significant vertical settling in
protoplanetary disks.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2008.06518.pdf

59.

The effect of luminosity outbursts on the protoplanetary disk dynamics
Eduard Vorobyov1,2 , Vardan Elbakyan2 , Michihiro Takami3 and Hauyu Baobab Liu3
Department of Astrophysics, University of Vienna, Vienna, Austria; 2 Research Institute of Physics, Southern
Federal University, Rostov-on-Don, 344090 Russia; 3 Institute of Astronomy and Astrophysics, Academia Sinica, 11F
of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan, R.O.C.

1

E-mail contact: eduard.vorobiev at univie.ac.at
Response of a protoplanetary disk to luminosity bursts of various duration is studied with the purpose to determine
the effect of the bursts on the strength and sustainability of gravitational instability in the disk. A special emphasis
is paid to the spatial distribution of gas and grown dust (from 1 mm to a few cm) during and after the burst.
Numerical hydrodynamics simulations using the FEOSAD code were employed to study the dynamics of gas and dustin the thin-disk limit. Dust-to-gas friction including back reaction and dust growth were also considered. Burstsof various duration (from 100 to 500 yr) were initiated in accordance with a thermally ignited magnetorotational
instability. Luminosity curves for constant- and declining-magnitude bursts were adopted to represent two typicallimiting cases for FU-Orionis-type eruptions.
The short-term effect of the burst is to reduce the strength of gravitational instability by heating and expanding the
disk. The longest bursts with duration comparable to the revolution period of the spiral can completely dissolve theoriginal two-armed spiral pattern in the gas disk by the end of the burst, while the shortest bursts only weaken the
spiral pattern. The reaction of grown dust to the burst is somewhat different. The spiral-like initial distribution withdeep cavities in the inter-armed regions transforms into a ring-like distribution with deep gaps. This transformation ismost expressed for the longest-duration bursts. The long-term effect of the burst depends on the initial disk conditions
at the onset of the burst. In some cases, vigorous disk fragmentation sets in several thousand years after the burst,
which was absent in the model without the burst. Several clumps with masses in the giant-planet mass range form in
the outer disk regions. After the disk fragmentation phase, the spatial distribution of grown dust is characterized bymultiple sharp rings located from tens to hundreds of astronomical units. The arrangement and sharpness of the rings
depends on the strength of dust turbulent diffusion. The wide-orbit rings are likely formed as the result of dust-richclump dispersal in the preceding gravitationally unstable phase.
Luminosity bursts similar in magnitude to FU-Orionis-type eruptions can have a profound effect on the dynamics ofgas and dust in protoplanetary disks if the burst duration is comparable to or longer than the dynamical timescales.
In this context, the spatial morphology of the gas-dust disk of V883 Ori, a FUor-like object that is thought to bein the outburst phase for more than a century with the unknown onset date, may be used as test case for the burst
models considered here. A potential relation of the obtained ring structures to a variety of gaps and rings observed in
T Tauri disks remains to be established.
Accepted by Astronomy & Astrophysics
http://arxiv.org/pdf/2009.01888

60. High-resolution survey for planetary companions to young stars in the Taurus Molecular

Cloud

A.L. Wallace1 , J. Kammerer1,2 , M.J. Ireland1 , C. Federrath1 , A.L. Kraus3 et al.
Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia; 2European Southern Observatory, Karl-Schwarzschild-Str 2, 85748, Garching, Germany; 3 Department of Astronomy,
University of Texas, Austin, TX 78712, United States of America
1E-mail contact: alexander.wallace at anu.edu.au
50Direct imaging in the infrared at the diffraction limit of large telescopes is a unique probe of the properties of youngplanetary systems. We survey 55 single class I and class II stars in Taurus in the L′ filter using natural and laser guidestar adaptive optics and the near-infrared camera (NIRC2) of the Keck II telescope, in order to search for planetary
mass companions. We use both reference star differential imaging and kernel phase techniques, achieving typical 5σ
contrasts of ∼6 magnitudes at separations of 0.′′ 2 and ∼8 magnitudes beyond 0.′′ 5. Although we do not detect any new
faint companions, we constrain the frequency of wide separation massive planets, such as HR 8799 analogues. We findthat, assuming hot-start models and a planet distribution with power-law mass and semi-major axis indices of −0.5
and −1, respectively, less than 20% of our target stars host planets with masses >2 MJ at separations >10 AU.
Accepted by MNRAS
http://arxiv.org/pdf/2008.06065

Abstracts of recently accepted major reviews

Magnetohydrodynamics of protoplanetary discs
Geoffroy R.J. Lesur1
1

Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France

E-mail contact: geoffroy.lesur at univ-grenoble-alpes.fr
Protoplanetary discs are made of gas and dust orbiting a young star. They are also the birth place of planetarysystems, which motivates a large amount of observational and theoretical research.
In these lecture notes, I present a review of the magnetic mechanisms applied to the outer regions R > 1 AU of thesediscs, which are the planet-formation regions. In contrast to usual astrophysical plasmas, the gas in these regions is
noticeably cold (T < 300 K) and dense, which implies a very low ionisation fraction close to the disc midplane. In
these notes, I deliberately ignore the innermost R 0.1 AU region which is influenced by the star-disk interaction andvarious radiative effects.
I start by presenting a short overview of the observational evidence for the dynamics of these objects. I then introduce
the methods and approximations used to model these plasmas, including non-ideal MHD, and the uncertainties associated with this approach. In this framework, I explain how the global dynamics of these discs is modelled, and I present
a stability analysis of this plasma in the local approximation, introducing the non-ideal magneto-rotational instability.
Following this mostly analytical part, I discuss numerical models which have been used to describe the saturation
mechanisms of this instability, and the formation of large-scale structures by various saturation mechanisms. Finally,
I show that local numerical models are insufficient since magnetised winds are also emitted from the surface of theseobjects. After a short introduction on winds physics, I present global models of protoplanetary discs, including botha large-scale wind and the non-ideal dynamics of the disc.
Accepted by the lecture notes series of the Journal of Plasma Physics
http://arxiv.org/pdf/2007.15967
51

Dissertation Abstracts

A closer look at protoplanetary discs: the inner few au probed with
spectroscopy and optical interferometry
Maria Kalliopi Koutoulaki

Thesis work conducted at: Dublin Institute for Advanced Studies & University College Dublin, Ireland
Address as of 1 October 2020: European Southern Observatory, 85748 Garching bei München, Germany
Electronic mail: maria.koutoulaki@eso.org
Ph.D dissertation directed by: Dr. Rebeca Garcia-Lopez, Prof. Antonella Natta, Dr. Deirdre Coffey and Prof. Tom
Ray
Ph.D degree awarded: June 2020
A first step towards understanding planetary formation is the characterisation of the structure and evolution of
protoplanetary discs. Although the large scale disc is understood in some detail, much less is known about the inner 5
au in which the main physical processes take place: accretion, ejection, and planetary formation. Even in the nearest
sites of star formation, this region cannot be spatially resolved by stand-alone telescopes; only in recent years have
optical and infrared interferometers been able to achieve this, and only in the case of the brightest sources.
Hydrogen recombination lines are present in the spectra of young stars. In particular, the Brackett-γ line is thebrightest line in the K-band. HD 50138 is a target that exhibits bright Brackett-γ and faint high-n Pfund (from leveln=24 to n=19) emission. Our results show that the circumstellar environment of the target is complex and shows
asymmetries in both the Brackett-γ and the continuum emitting regions. The Brackett-γ is more compact than thecontinuum emitting region and originates from a wind with a wide opening angle.
The origin of the Brackett-γ line is still controversial, and it has been found to be associated with both accretion andejection processes. Thus, more tracers are needed to better constrain the inner gaseous disc properties. Molecules arealso present in this part of the disc. In particular, the CO overtone emission at 2.3 mµ is a good tracer of the inner discproperties. This emission is not common and in the case of T Tauri stars it has been observed in only three sources.
RW Aur A is a CTTS that exhibits irregular dimming events. It shows CO overtone emission in both the bright anddim states. Modelling this emission with an LTE CO ring in Keplerian rotation, we find that the CO conditions do notchange during the dimming events. Moreover, no significant accretion variation is detected between the two states,
leading to the conclusion that the dimmings are caused by occulting material very close to the star (within 1 au).
The CO ro-vibrational emission at 2.3 mµ observed with the second generation interferometer VLTI/GRAVITY opens
a new window on constraining the physical properties of the inner gaseous disc, by spatially resolving the CO emission.
51 Oph is a target which shows bright CO overtone emission.
By modelling the CO emission, the CO is found to emitt very close to the star from a warm and dense gas.
This is the first observational evidence of the physical properties so close to the star (∼0.1 au) where there is no dust.
This is consistent with previous LTE models of the physical conditions in the dust-free disc.
52

The Dynamics of Star Cluster Formation
Juan Pablo Farias

Chalmers University of Technology, Department of Space, Earth and Environment, SE-412 96, Gothenburg, Sweden
Electronic mail: juanfariaso at gmail.com
Ph.D dissertation directed by: Prof. Dr. Jonathan C. Tan
Ph.D degree awarded: August 2020

How do star clusters form? We care, since these are the birth sites of most stars, perhaps including our own Sun.
There are a great variety of different theoretical models of cluster formation and our main goal in this thesis is to
examine the implications of these for the dynamical evolution of a cluster’s stellar population, including the ejectedstars. In contrast to the majority of previous cluster formation studie pusng ieswith the strctre
inematic
and-2476..8(s)-3.13672(t)3.35237(a)-6.01368(r)-355.295(f)4.3711(o)-6.01368(r)thenatalionsressre-trncate
ts gloalars.

From parsec to au scales: zooming-in on the formation of high-mass
young stellar objects
Rubén Fedriani

Thesis work conducted at: Dublin Institute for Advanced Studies and University College Dublin, Ireland
Current address: Chalmers University of Technology, Gothenburg, Sweden
Electronic mail: ruben.fedriani@chalmers.se
Ph.D dissertation directed by: Alessio Caratti o Garatti, Deirdre Coffey, and Tom Ray
Ph.D degree awarded: June 2020
In this thesis, I investigate the formation of high-mass young stellar objects (HMYSOs) and the properties of their
protostellar jets.
My first science chapter is a study of the kinematic and dynamic properties of the 20 M⊙ HMYSO IRAS 13481-6124(Fedriani et al. 2018). I measured mass-loss and momentum rates on the order of 10−4 M⊙ yr−1 and 10−2 M⊙ yr−1 km s−1 ,respectively. I used HI emission lines to perform spectro-astrometry to probe the massive protostellar jet at au-scales
and connect it with the parsec-scale jet.
In the second science chapter, I study the unique case of G35.2-0.74N, a 10 M⊙ HMYSO Fedriani et al. 2019. I observe, spatially coincident atomic near-infrared (NIR) and ionised radio jet emission. For the first time, the ionisation
fraction from a jet driven by a massive protostar has been measured. The value obtained (∼ 10%) is similar to thatfound in jets driven by low-mass protostars. This suggests a common launching mechanism, i. e., the jet is launchedmagneto-centrifugally. It was possible to measure mass-loss and momentum rates on the order of 10−5 M⊙ yr−1 and10−2 M⊙ yr−1 km s−1 , respectively, without relying on assumptions on the ionisation fraction. This study also confirmsthat the ionisation mechanism is related to shocks instead of UV radiation from the central source. The new method
used in this paper, which combines NIR and radio measurements, opens up a new way to measure ionisation fractionof jets for both the low- and high-mass regime.
Lastly, the jet and the accretion disc of the driving source of the Herbig-Haro object 135/136, IRAS 11101-5829, wasinvestigated in the third science chapter (Fedriani et al. 2020). I found disc emission, for the first time, in this object
revealed by the NIR CO overtone bandhead emission at 2.29 − 2.5 µm. By using our own developed LTE model, I
infer that the emission is consistent with a relatively warm (T ∼ 3000 K) and dense (NCO ∼ 1022 cm−2 ) disc. Notably,
the model also suggests a geometry different from that inferred in the jet, retrieved from both spectral emission lines
and imaging. This implies that the disc emission is reflected off the outflow cavity walls. This approach has been used
for the first time in this thesis and indicates that to obtain the correct geometry of the system, one needs both highspectral and spatial resolution to avoid retrieving possible erroneous results.
The results presented in this thesis show further observational evidence that the formation of high-mass protostars
and their jets are a scaled-up version of their low-mass counterparts and that their properties scale with mass. In lightof these results, we are then one step closer to confirm that star formation proceeds in a similar fashion independentlyof mass.
54

Searching for gas in debris disks
Daniela Iglesias

Instituto de Fisica y Astronomia, Facultad de Ciencias, Universidad de Valparaiso, Valparaiso, Chile
Electronic mail: dpiglesi at uc.cl
Ph.D dissertation directed by: Amelia Bayo – Ph.D degree awarded: April 2020
A debris disk is commonly described as a second generation circumstellar disk composed of dust grains, planetesimals
and possibly already formed giant planets. It was long thought that debris disks were systems fully depleted of gas,
but in the last few years the presence of gas has been detected in a increasing number of them. The nature ofthis gas is still under debate; it may be residual gas (leftover from earlier stages of the disk) or second generationgas (generated by the sublimation of exocomets or collisions of icy bodies), however, both possibilities would havegreat implications in the process of planet formation and evolution. An efficient way to search for this gas in debris
disks is monitoring gas tracers using multi-epoch high-resolution UV-optical spectroscopy. A detection of gas in theline of sight of the star shows up as a very narrow absorption feature superposed to the photospheric absorptionof lines such as Ca ii or Na i, which are very sensitive gas tracers. This Thesis is devoted to the search for gas via
high-resolution spectroscopy in a sample of 301 debris disks with the purpose of estimating the frequency of gas indebris disks. We collected high-resolution UV-optical spectroscopic data from our own observations and the ESO
archive for 273 objects, completing 91% of our sample. We analysed the multi-epoch spectra of each object searchingfor variable and stable non-photospheric absorption features of circumstellar origin. Firstly, we performed a detailed
analysis of a sub-sample of 27 objects having multiple stable absorption features with the aim of determining whether
their features were of circumstellar or interstellar origin. In this group we found two objects; c Aql and HR 4796,
with variable absorption features attributable to the presence of star-grazing exocomets, and one object; HD 110058
with a stable circumstellar gas absorption. We concluded from these preliminary results that the presence of gas indebris disks might be a common phenomenon. Secondly, we studied the presence of unusually large non-photosphericabsorption features found in several ionized lines of the object HD 37306, that lasted for several days. After analysing
different possibilities we concluded that the most likely explanation might be an exocometary break-up releasing a
stream of gas that remained in orbit for at least a week around the star. Then, we analyzed the variability found in
the Ca ii K lines of 97 objects with the purpose of distinguishing variable absorption features most likely produced
by exocometary activity from variability of a different nature, like stellar pulsations, spots or radial velocity shifts,
for instance. We found five candidates with variability consistent with exocometary activity: c Aql, 49 Cet, gam Tri,HR 4796 and HD 37306, two of them with no previous reports of exocomets besides this work. Finally, we studied
a sub-sample of 107 objects presenting stable non-photospheric features in their Ca ii K lines within our updated
database of observations in addition to those in our first sub-sample of analysis. Similarly, the absorption features
observed in these objects were analysed in order to determine whether they were of circumstellar or interstellar origin.
We confirmed an interstellar origin for the features in 104 of these objects, one of them, 49 Cet having a blendedfeature of combined circumstellar and interstellar origin. In addition, we found three candidates with features of yet
inconclusive origin that might be circumstellar but need further study to confirm it. Putting together our results,
we found six debris disks with presence of circumstellar gas, five of them presenting variable absorption features
attributable to exocometary activity and one of them with a stable circumstellar gas component. Considering that
our sample is unbiased with respect to inclination, that the gas is more likely to be detected when the disk is observed
close to edge-on, more easily detected in the spectra of early-type stars, the many detection challenges related to thesporadical nature of exocometary transits, and the interlopers of gas detection, then the evidence of circumstellar gas
is significant. Taking into account the currently increasing number of detections, this imply the possibility that mostdebris disks may harbor some gas, challenging the current paradigm of debris disks.
55

New Jobs

KIAA-SHAO Joint Postdocs in Star Formation
The Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University and the Shanghai Astronomical
Observatory (SHAO), Chinese Academy of Sciences invite applications for 1-2 postdocs, as part of a new Joint Centerof Astrophysics that establishes close links between KIAA and SHAO.
The postdocs will work in projects on star formation using ALMA, JVLA, SMA, FAST and other telescopes, led by
Dr. Ke Wang (KIAA) and Dr. Tie Liu (SHAO). Independent research is also encouraged. The salary and researchbudget are competitive and commensurate with qualifications and experience. Generous research grants are available
from national and regional funding resources. The postdocs are strongly encouraged and fully supported to apply,and grant proposals written in English are acceptable. Our postdocs have been very successful in obtaining grants as
principle investigator: http://kiaa.pku.edu.cn/People/Postdoctoral_Research_Fellows.htm.
The postdocs will spend 1-2 years at SHAO and 1-2 years at KIAA in either order, with the second part pending
satisfactory performance. The postdoc positions are open to applicants of any nationality who will graduate prior totheir appointment, with a preference for those who received their PhD after January 2017, per requirement by the
China Postdoctoral Office.
KIAA is located on the historic grounds of Peking University in China, has English as the working language, andregularly sponsors thematic workshops and conferences to provide a platform for national and international scientificexchanges. Astronomy at PKU includes 25 faculty, 35 postdocs, 60 graduate students, 120 undergraduates, and many
visiting scholars.
SHAO is located in the downtown of Shanghai, one of the most international and developed cities of China. SHAO
provides a diverse setting and research facilities. In addition to the involvement of some domestic and international
projects such as SKA, EHT, LAMOST, CSST, FAST and HUBS, the institute also possesses its own facilities, suchas the 65-m radio telescope, and excellent computational facilities. Astronomy at SHAO includes 174 faculty, 17
postdocs, and 103 PhD students.
Start date: negotiable, as soon as possible
Application process: Applicants should send a single PDF file which includes (1) CV with list of publications, (2) 3page research statement, to the contacts. Applicants should also arrange three confidential letters of recommendation
to be sent to the same contacts.
Deadline: Applications will be evaluated until the positions are filled. However, applications received prior to October
15, 2020 will be given full consideration.
Related URLs:
PKU-SHAO Joint Research Center for Astrophysics: http://kavli.pku.edu.cn/pkushao/
KIAA: http://kiaa.pku.edu.cn/
SHAO: http://english.shao.cas.cn/
Application Deadline: Thursday, October 15, 2020
Inquiries To: Ke Wang; Tie Liu
Email: kwang.astro@pku.edu.cn; liutie@shao.ac.cn

56PhD Position in experimental astrochemistry and planetary science
Full-time, 4 years, 47 000 - 50 000 CHF per year (Brutto, as set by the SNSF).
Starting date: between November 1st, 2020 and April 1st, 2021
Under the supervision of Dr. Niels Ligterink, a PhD project is available on the investigation of molecules in ices thatare present in star-forming regions and on Solar System bodies. Using laboratory experiments that make use of Laser
Desorption Mass Spectrometry and cryogenic cooling techniques, these molecules are analysed and their chemical
reactions and physical processes are studied. The results of this work will provide insight into how molecules formin ice, evolve over time, and contribute to the chemical complexity seen in star-forming regions and on Solar Systembodies.
The main activities of the position are: laboratory work with advanced Laser Desorption Mass Spectrometry equipment, active participation in the scientific life of the Space Research and Planetary Sciences division, the Center forSpace and Habitability (CSH), and the Bern Astrochemistry Research (BEAR) group, teaching assistant assignments,
participation in national and international conferences, possibility to be involved in astrobiology projects, instrument
development for planetary science missions, and/or radio telescope observations (e.g., ALMA observations).
Skills of the candidate: The candidate must be in possession of a Master-level degree (or equivalent) in a relevant field(e.g., chemistry, physics, astronomy) by the starting date. Experience with laboratory experiments and techniques
relevant to this position (e.g., vacuum technology, laser systems, mass spectrometry, cryogenics) is preferred. The
candidate must be competent in spoken and written English.
How to apply: Applicants should send all application materials in English in one PDF file to niels.ligterink@csh.unibe.chby the deadline of November 1st, 2020. Note that applications are considered on a rolling basis meaning that theposition may be filled earlier. A complete application consists of: a cover letter (max. 1 page), curriculum vitae(CV), a personal statement detailing (but not limited to): past research experience and the skills obtained, reasonsfor pursuing a 4-year PhD research project, aspirations for the future (max. 2 pages in total), full list and transcripts(grades) of all university-level courses (Bachelor- and Master-level) and a translated version if not in English, German,
or Dutch (notarised translation is not needed), preferably two, but at least one reference letter.
University of Bern: The Space Research and Planetary Sciences division is involved in the experimental and theoreticalinvestigation of our Solar System and extra-solar planets. The division participates in NASA, ESA, and Roscosmos
spacecraft missions through the provision of instruments for both remote-sensing and in situ mass spectrometry.
Any question can be addressed to Dr. Niels Ligterink - niels.ligterink@csh.unibe.ch

57

Discs and planet formation - Ens de Lyon (postdoctoral position)
Applications are invited for one or several 2+1-year Postdoctoral Research Fellows to work with Dr. Guillaume Laibeon discs and planet formation (ERC-CoG project PODCAST) at the Ecole Normale Supérieure de Lyon (AstroENS
team, Centre de Recherche Astrophysique de Lyon).
The project includes any of the following aspects:- Formation and evolution of protostellar discs,- Dust dynamics and evolution inside the disc,- Numerical simulations of discs,- Theoretical aspects of planet formation.
The successful candidate should have a Ph.D. in Astrophysics, Physics or Applied mathematics in relation withhydrodynamics with experience computational or theoretical discs or star and planet formation.
By Nov, 15, enthusiastic candidates should send:i) a CV including a publication list,ii) a statement of research interests,iii) arrange for three letters of reference to be provided separately (to be sent to guillaume.laibe@ens-lyon.fr).
Later applications will be considered until the position has been filled.
Included Benefits: The initial monthly net salary is around 2000Euro and is commensurate with experience.
Included : National medical insurance, maternity/paternity leaves, family supplement for children, participation to
public transport fees, pension contributions. School is free in France for children above 3. The Université de Lyon
provides support for settling in Lyon and France.
Miscellaneous : Since 2016, the Ecole Normale Supérieure de Lyon appears in the world’s Top 5 small universities of
the Times Higher Education ranking. Lyon is a vibrant city with high quality of life.
The project is funded by the ERC-CoG project PODCAST (contract n?864965).
Application Deadline: Sunday, November 15, 2020
Selection Deadline: Tuesday, December 1, 2020
Attention To: Dr Guillaume Laibe
Phone: +33472728917
Email: guillaume.laibe@ens-lyon.fr

Short Announcements

Dear colleagues,
A new website for the UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director’s
Discretionary program is now live at https://ullyses.stsci.edu. In particular, the ULLYSES website contains
the program ID and scheduling information for targets already observed or in the long-range plan; currently thisincludes stars in the Large and Small Magellanic Clouds, and the Orion T Tauri stars scheduled to be observed in
November-December 2020 to coincide with TESS observations. The ULLYSES website will continue to be updatedwith additional program and scheduling information as it becomes available.
The ULLYSES implementation team at STScI
58

Meetings

Chemical processes in Solar-type star forming regions
13 - 17 September 2021 - Torino, Italy
https://sites.google.com/inaf.it/aco-conference
How the chemical complexity evolves during the process leading to the formation of a Sun and its planetary system?
Is the chemical richness of a Solar-like planetary system, at least partially, inherited from the earliest stages or is there
a complete chemical reset? A powerful way to answering these questions is by comparing the chemical content inyoung protostars and primitive bodies of the Solar System, using astrochemistry as a tool. Yet, to do so, we need to
fully understand the processes that govern the chemical evolution of a molecular cloud into a young planetary system.
The goal of the conference is to gather together the actors of this intrinsically interdisciplinary endeavor: astronomers,
chemists and modelers. The recent huge progresses in the three areas make the time ripe for these communities tojoin and ride this scientific wave.
The conference aims to review:• The new results from the powerful observing facilities, such as the IRAM-NOEMA, ALMA and VLA interferometers, and the chemical composition during the youngest phases of Solar-like planetary systems, from prestellar
cores to protoplanetary disks, with particular emphasis on the interstellar complex organic molecules;• The recent progresses due to the enhancement of high-performance computing facilities combined with efficientquantum chemistry algorithms, which allow for the in-silico simulation of many chemical processes occurring
both in gas-phase and at grain surfaces;• The latest laboratory experiments which have provided new insights on the possible processes occurring in theinterstellar conditions;• The new generation astrochemical models as well as the innovative tools to interpret the astronomical observations that have seen the light in the last few years;• The most recent results on the chemical composition of the small bodies of the Solar System.
This will naturally pave the way for discussing the future developments in front of us.
The meeting will consist of invited reviews, invited and contributed talks, and posters.
A limited amount of financial support will be dedicated to students and young researchers.

SOC: P. Ugliengo (Chair, Università di Torino, Italy), C. Codella (Co-chair, INAF - Osservatost8(t.7571(h)1.34903(e)-1.67559(h)1.f2

Summary of Upcoming Meetings

Check the websites of these meetings for the latest information on how they are affected by Covid-19
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
From Clouds to Planets II: The Astrochemical Link
28 September - 2 October 2020, Berlin, Germany
https://events.mpe.mpg.de/event/12/
Threats from the Surroundings – VIRTUAL MEETING
10 - 12 November 2020
http://www.eso.org/sci/meetings/2020/tfts2020.html
Five Years after HL Tau: A New Era in Planet Formation – VIRTUAL MEETING
7 - 11 December 2020
https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org
Gordon Conference on Origins of Solar Systems
19 - 25 June 2021, MA, USA
https://www.grc.org/origins-of-solar-systems-conference/2021
Cool Stars, Stellar Systems, and the Sun 21
5 - 9 July 2021, Toulouse, France
https://coolstars21.github.io/Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann
16 - 19 August 2021, Malahide, Ireland
https://www.dias.ie/cloudstodiscs/
Chemical Processes in Solar-type Star Forming Regions
13 - 17 September 2021, Torino, Italy
https://sites.google.com/inaf.it/aco-conference
Wheel of Star Formation: A conference dedicated to Prof. Jan Palouš
20 - 24 September 2020, Prague, Czech Republic
https://janfest2020.asu.cas.cz
The Physics of Star Formation: From Stellar Cores to Galactic Scales∼June - July 2022, Lyon, France
http:/staratlyon.univ-lyon1.fr/en

60

New Books

The Physics of the Interstellar Medium
A. C. Raga, J. Cantó, and A. Rodríguez-González

This book about the interstellar medium is based on the ISM course that the authors have taught at Universidad
Nacional Autónoma de México for over 25 years. All three authors are theoreticians, and the book is primarily dealing
with theoretical concepts. The subject of the ISM is enormous and so all books emphasize somewhat different subjects.
The present book broadly focuses on three areas: a) the ionized ISM and static models, b) dynamics of the ISM, andc) astrophysical jets. These are areas where the authors have made major contributions of their own. At the sametime, subjects such as magnetic fields, stellar winds, dust, and accretion disks are omitted. The book is directed tomaster’s and PhD students, or researchers interested in calculating dynamical models of the ISM. The authors havealso made the book freely available at the website listed below, instead of publishing another very expensive textbook.
This implies that changes and additions are easily made, and the authors welcome feedback for future editions.
The following lists the chapters of the book:
1. General comments
2. Observational characteristics of the ISM
3. Photoionized regions
4. The emitted spectrum
5. The equations of gasdynamics
6. Sound waves and linear stability analysis
7. Shock waves
8. 1D, stationary, radiative shocks
9. The hydrodynamic expansion of an HII region
10. Wind-driven HII regions
11. Supernova remnants
12. Gravitational collapse
6113. Astrophysical and laboratory jets
14. Hypersonic, variable velocity jets
15. The centre of mass equation of motion
16. The uniformly accelerating jet in a homogeneous environment
17. Time-dependent ejection direction
18. Steady jet in a sidewind
19. Bullets
The book can be downloaded from this URL:
https://bigbang.nucleares.unam.mx/astroplasmas/index.php/the-physics-of-the-interstellar-medium-bookStudies in Star Formation - 77 Perspectives
Edited by Bo Reipurth

Since 2012, the Star Formation Newsletter has brought interviews with scientists working in the field of star andplanet formation, molecular clouds, and the early solar system. While the interviews have remained accessible on theNewsletter webpage, they have not been easy to find. I have therefore decided to compile all the 77 interviews done
so far into a single compendium, which will be expanded once a year with new interviews. The compilation can be
downloaded from this link:
http://www.ifa.hawaii.edu/SP2/77interviews.pdf
Each interview provides a glimpse into the scientific lives of researchers who have made important contributions to
our field. But taken together, the 77 interviews also provide an overview of the past 40-50 years of tremendous
development in our understanding of star and planet formation. As such, it may be helpful for new generations ofastronomers in understanding how different topics have come to their present state. The compendium could also serve
as supplementary material for courses on star formation.
The current 2020 version is 199 pages.
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Passings

Martin Cohen 1950-2020
Martin Cohen, a native of Manchester, England and pioneer in infrared astronomy and studies of pre-Main Sequencestars, passed away on March 7, 2020, of a rare form of Alzheimer’s disease.
He was born in 1950. His interest in astronomy was kindled in Manchester Grammar School and strengthened inhigh school, both institutions having small telescopes that Martin was allowed to use and restore to working order.
This early interest led him to a personal quest for ever bigger and sophisticated telescopes in pursuit of his career inastronomy. That journey was described in detail in his book ’In Quest of Telescopes’ published in 1979 and continued
to the present day as he made use of the Kuiper Airborne Observatory, the Hubble and Spitzer Space Telescopes.
Martin was a summer student at the Royal Greenwich Observatory in 1968 and earned his undergraduate degree inmathematics from the University of Cambridge in 1969. He became interested in the new field of infrared astronomy
and was one of three British students sent to the University of Minnesota to pursue their graduate studies. He helped
build the 60-inch metal mirror infrared telescope at Mt. Lemmon and received his PhD in 1975 observing the spectralenergy distributions of pre-Main Sequence stars. The study of young stars fascinated him for most of his life and led
to the publication of another book in 1988, ’In Darkness Born-The Story of Star Formation’. It was a subject he loved
to talk about and was the focus of many of his lectures popularizing astronomy.
After his graduate degree he embarked upon a long time association with the University of California at Berkeley andNASA Ames. I was fortunate to work with him for several years, using the Wampler Scanner at Lick Observatory
combined with his infrared observations to undertake a massive study of the properties of ∼500 pre-Main Sequencestars resulting in the HR diagrams for the Taurus-Auriga complex, Orion, NGC 2264, NGC 7000/IC 5070, and the
Rho Ophiuchi association. His dedication to hard work and his enthusiasm for research were inspiring. We would
observe all night and he would search for additional objects on the Palomar sky survey prints during the day. He wasindefatigable as his collaborators will attest to.
Martin continued his infrared observations which extended to ever longer wavelengths as the instrumentation improved.
Many papers were published dealing with T Tauri stars, Herbig Haro objects, bipolar nebulae, bipolar flows, jets,carbon stars, planetary nebulae, Wolf Rayet stars, cometary nebulae and other objects of interest that were detectedby AFCRL rocket infrared observations and later IRAS observations. His infrared work on T Tauri stars detected ice
around HL Tauri and eventually led to the conclusion that about one third of T Tauri stars had circumstellar dust
disks. His prolific research laid the groundwork for our understanding of the nature of very young stars and their early
evolution. In later years he devoted his energies to the problem of absolute calibration at infrared wavelengths, andpublished a series of highly cited papers on the subject.
Len Kuhi63