THESTAR

FORMATION

NEWSLETTER

An electronic publication dedicated to early stellar/planetary evolution and molecular clouds
No. 329 — 13 May 2020

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

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

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Abstracts of Newly Accepted Papers . . . . . . . . . . 10

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

Abstracts of Newly Accepted Major Reviews . . 43

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

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Summary of Upcoming Meetings . . . . . . . . . . . . . . 48

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

Newsletter Archive

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

Cover Picture
HBC 672 is a young low-mass star in the Serpens
star forming region, seen here in a WFC3/IR image
about 2 arcmin across. Filters are F125W (cyan)
and F164N (orange).
Image credit: STScI/M. Mutchler

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

can be performed on the same CAI. The concentration
for such large CAIs is probably one large CAI per kg.
Thus, Allende can offer around 2,000 large CAIs, while atypical carbonaceous meteorite will bring barely one large
CAI. The large size of the sample enabled us to study rarecomponents with unusual properties, such as the discovery that Al-26 had been present in large CAIs during theirformation.

Typhoon Lee
in conversation with Bo Reipurth

In my thesis research I also found Mg as well as Ca isotopic variations in different samples relative to the solar
system normal. Before that time, only oxygen and neon
were known to be isotopically heterogeneous. One of oursamples showed isotopic anomalies in EVERY element,
measured until then, from Mg to Sm. Moreover, this sample only deviates from the normal by a few per mil suggesting that it came from the late stage of the mixing ofinterstellar material. It would be really exciting to learn
more, but unfortunately such interesting samples are exceedingly rare, existing at very low levels of 1/100 relative
to the number of large CAIs. Therefore, we may neverlearn what other secrets they could bring us.

Q: You won the Trumpler Award for your 1977 PhD thesis. What was the subject and who was your adviser?
A: My thesis was supervised by Prof. Gerald J. Wasserburg of Caltech, although my degree came from Universityof Texas at Austin where I studied nuclear astrophysics under Dave Arnett and Dave Schramm. The title of my thesis was “Isotopic Studies of the Allende Meteorite”, which
resulted in the discovery of the extinct radio-nuclide Al-26.

Q: The key result, namely the discovery of the presence of26
Al in the early solar system, was published by you andyour collaborators in a paper in 1977. What has happenedin this field in the past 40 years?
A: It has been found that the aluminum in most CAI
contained 50 ppm Al-26 when they cooled through theircondensation temperature of about 1500C. If we identify
this cooling event with the absolute age derived from UPb decay, we find that the solar system formed 4.567 ±
0.0005 billion years ago. This is the best (1 per mil error)
determination of the age of our solar system. A relative
chronology can be built up using the amount of Al-26 in
the CAIs with an uncertainty of 0.1 million years.

Specifically I studied Calcium Aluminum rich Inclusions(CAIs) in the Allende meteorite. Although CAIs only constitute a small fraction of the mass of chondrites they arevery important, because they preserve information about
the physical environment and the processes occurring in
the circumsolar disk prior to the formation of the planets. They were the first solid material that formed in thecooling solar nebula.

It is interesting to note that Wasserburg’s thesis advisor,
Nobel Prize winner Harold Urey, already in the 1950’s proposed the importance of Al-26 when it was first producedin the lab. He realized that most meteorites have beenheated, some to the point of melting, but that they do
not contain enough long lived radioactive nuclei such as
U and Th today for these to have been the heat source.
Therefore there must have been a transient source of heatsuch as the short lived isotopes Al-26 or Fe-60 to heat theparent bodies of meteorites in the early solar system. So,
this problem has been around for about seven decades.

The unstable short-lived isotope Al-26 decays to Mg-26
thus creating excesses in measured Mg-26/Mg-24 ratios.
Large excess Mg-26/Mg-24 up to 10% were found in coexisting phases in CAIs. They correlate linearly with Al27/Mg-24, indicating that these excess Mg atoms behavedchemically like Al, not Mg, at that time. The evidence for
Al-26 in Allende thus implies that this now extinct nuclide
was present in the early solar system. We interpreted thisresult to mean that either a supernova injected material
into the solar nebula within the first few million years,
or there was an epoch of intense irradiation of the solar
nebula by energetic protons from the primeval sun.

The origin of Al-26 is still uncertain and its source is best
discussed in the frame work of origin of all extinct nuclides.
In the early solar system, there have most likely been five
radio-nuclides with half lives between 0.1 to 10 Mega-year,
they are Be-10, Ca-41, Al-26, Mn-53, and Fe-60. Evidence
for Ca-41 has been put into doubt recently. Among theremaining four nuclides, Mn-53 and Al-26 can be produced

Allende was ideal for this study because of its total mass,
which is at least 2000kg, while a typical carbonaceous meteorite weighs <1 kg. The decay-product Mg-26 of Al26 was found in minerals of CAIs, especially those thatare coarse grained (>0.1mm) and have a large size (>1g).
This allows to maximize the number of experiments that3

by either a supernova or an active early sun. The Fe-60
can be made only in the center of supernovae where hightemperature and density fuse all nuclides towards the ironpeak. On the other hand, Be-10 can be made in the earlysolar environment by spallation reactions with O-16 andenergetic particles from magnetic field reconnection. Notethat Be-10 is destroyed in a young star and CANNOT be
made anywhere inside the star.
Since Fe-60 seems to be present in the early solar systemand Fe-60 can only be made in the core of a supernova,
we must conclude that there was at least one nearby supernova explosion when the sun formed.
Q: You have worked with Frank Shu and Hsien Shang on
an astrophysical theory of chondrite formation. What was
the basic idea?
A: At that time, Frank Shu had already suggested thatbipolar outflows are driven by high angular momentum gas
ejected from an accretion disc, allowing the formation of ayoung star by the accretion of low angular momentum material. Our paper extends the idea to explore whether thesame model can explain the formation of chondrites (thegeometric arrangement is shown graphically in our paperin Science in 1996). In this X-wind model, the CAIs arethought initially to be pre-solar dust grains in the molecular cloud. When the cloud accreted towards the inner edgeof the disc, the dust was suddenly exposed to the young
sun and melted instantly. Thus the fine dust turned to liquid droplets and homogenized internally. These droplets(chondrules and CAIs) also reacted with solar energetic
particles to form radio-nuclides such as Al-26 and Be-10.
The majority (about 2/3) of this material would fall into
the forming sun. The remaining about 1/3 was ejectedwith the X-wind. Most chondrules then fell back to thedisc and accreted toward the central star again. Thismodel implies that most dust in the comet-forming region
has been recycled through the central region. Our modelis the only one so far that explains the data from NASA’s’Stardust’ sample return mission to comet 81P/Wild-2.
When examined in the lab, the Stardust data show thatinstead of being an assemblage of pre-solar grains withlarge isotopic variation, the vast majority consist of material with normal solar abundances. The best explanation,
we believe, is that this material was transferred in the discto the surface of the sun, melted and homogenized near thesun, recycled to the comet forming region and then rejoining the accretion. Another likely sample of cometary dust
are the IDPs - Interplanetary Dust Particles - which are
dust collected by highflying airplanes after meteor showers. They show essentially the same results as the dust
from 81P/Wild-2, thus also supporting our model.

4

we also concluded that the accumulated evidence for disks
in young OB-type stars did not extend to stars beyonda mass limit of ∼30 M⊙, that is, to early O-type stars.
Instead, what had been observed towards these sourceswere more massive (> 100 M⊙) and larger (> 103 au) rotating structures called toroids. When we published thestudy, the ALMA era had just started, and up to then,no high-angular resolution ALMA observations of O-type
disk candidates had been yet reported (note that the work
by Johnston et al. 2015 appeared when our review was
already in press). More than five years later, ALMA
has reached an almost complete configuration and longbaseline observations have become available, so, it is time
to reformulate our original question and this time confirm
or discard the existence of true accretion disks around Otype young stars„ in particular around early O-type stars.
If confirmed, this would mean that accretion disks are essential for the formation of stars of all luminosities.

Perspective
Disks Around O-type Young
Stellar Objects
Maite Beltrán

ALMA observations of O-type YSOs
O-type YSOs with Lbol > 105 L⊙
Accretion disks are one of the key ingredients of the starformation process. They redistribute angular momentum
and, in the case of high-mass stars (M > 8 M⊙ ), disks
would relieve the radiation pressure on the accreting material, in particular in the equatorial direction, by beaming the radiation through the poles of the system and thiswould allow the accretion to proceed onto the central protostar (e.g., Tan et al. 2014 for a review on massive starformation). In fact, in recent years, all high-mass starforming theories appear to converge to a disk-mediatedaccretion scenario (e.g., Krumholz et al. 2007; Kuiper et
al. 2011; Bonnell & Bate 2006; Keto 2007). But do theobservations of high-mass young stellar objects (YSOs)
confirm the theory predictions? Or in other words, dotrue accretion disks around massive stars really exist?

Johnston et al. (2015) reported the first candidate disk
around an O-type (proto)star of ∼ 2×105 L⊙ , AFGL 4176,
observed with ALMA. For this source, the emission of
CH3 CN, a typical high-density tracer, shows a velocity
gradient along the major axis of the source that was consistent with Keplerian-like rotation. The position-velocity(PV) plots show a clear “butterfly" pattern with low-velocity“spurs” and high-velocity spikes close to the position of theembedded protostar, that is consistent with the pattern
expected for an edge-on Keplerian disk rotating about a
25 M⊙ O7 star.
Cesaroni et al. (2017) carried out ALMA observations
with an angular resolution of ∼ 0.2′′ of a small sampleof six star-forming regions containing the most luminous(Lbol > 105 L⊙ ) O-type sources. The observations spatially resolved the CH3 CN emission in seven cores andfound evidence of rotation for six of them (G24.78+0.08
A1, G29.96−0.02 HMC, G345.49+1.47 M, G345.50+0.35
M and G345.50+0.35 S). However, only three of them(G29.96−0.02 HMC, G345.50+0.35 M and G345.50+0.35
S) show evidence of Keplerian-like rotation. For one source,
G17.64+0.16, these observations did not find any evidenceof rotation. Cesaroni et al. (2017) plotted the luminosityto-mass ratio (Lbol /Mgas ), which is an evolutionary stage
indicator, versus the distance to the source, including theO-type star AFGL4176, and concluded that the true accretion disk detection rate could be sensitive to the evolutionary stage of the young stellar object. For the youngest
sources, the non-detection of Keplerian disks could be dueto the fact that the emission of disks is difficult to disentangle from that of the envelopes. Alternatively, disks mightstart small and grow up with time. On the other hand,for the most evolved source in the sample (G17.64+0.16),

In 2016, Willem-Jan de Wit and myself wrote a review on
accretion disks in luminous YSOs to try to answer suchquestions (Beltrán & de Wit 2016). We concluded thatthe clear signatures of rotating and/or accretion disks reported in the literature confirmed the existence of circumstellar disks around stars with masses up to 20–30 M⊙ or∼ 105 L⊙ , which would correspond to early B-type or lateO-type stars (see Fig. 1). The disks of these sources havebeen spatially resolved using line and continuum tracers
from infrared to centimeter wavelengths, and maser emission (e.g., IRAS 20126+4104: Cesaroni et al., 2005, 2014;
Cepheus A HW2: Patel et al., 2005; IRAS 13481−6214:
Kraus et al., 2010; CRL 2136: de Wit et al., 2011), andtheir kinematics appear to be consistent, for most cases,
with Keplerian rotation (e.g., Bik & Thi, 2004; Blum etal. 2004: Cesaroni et al. 2005, 2014; Wheelwright et al.
2010; Wang et al. 2012; Ilee et al. 2013; Sánchez-Mongeet al. 2013; Beltrán et al. 2014). As a result of our study,5∼20 M⊙. In the first case, Sanna et al. (2019) have reported sub-Keplerian velocities, while in the latter casethe spatially resolved asymmetric disk observed by Zapata et al. (2019) would be Keplerian.

NGC 7538IRS1, the observations have resolved the line
emission in more than one rotating structure. Therefore,
the number of rotating disk-like structures is seven for
Lbol > 105 L⊙ and eight for Lbol < 105 L⊙ . Finally, five
Keplerian rotation signatures
On the other hand, several authors have also reported the out of seven structures show5forsources
with
L
>
10
L
bol
⊙ , and three out of eight forexistence of rotating disk-like structures with velocity gra5
sources
with
L
<
10
L
.
bol
⊙
dients that are not (fully) consistent with Keplerian rotation. In particular, Beuther et al. (2017a) observed in Disk kinematics
CH3 CN the 1.7 × 104 L⊙ O-type YSO G351.77−0.54 with Following Cesaroni et al. (2017), with this new statistics
ALMA at an angular resolution of only 60 mas (∼ 130 au) on disk-like structures around O-type YSOs, it is posand concluded that although the line emission shows hints sible to investigate whether the presence of true accreof Keplerian rotation, to properly model the velocity field tion disks around these massive stars is associated within this region one should take into account also the con- their evolutionary stage. To do this, we estimated thetribution of infalling and outflowing material. In a simi- L /Mbolgas ratio for each of the thirteen, where the masslar way, Maud et al. (2017) observed, also in CH3 CN, the of the molecular clump, M was computed from the ATgas
W33A MM1-Main O-type YSO with a spatial resolution of LASGAL 870 µm flux density (Schuller et al. 2009) cata∼ 500 au, and found that the emission showed a very com- logued by Contreras et al. (2013), assuming, like Cesaroni
plex morphology with a filamentary and spiraling struc- et al. (2017), a dust temperature T
dust of 50 K, a dust
ture that could feed an embedded and not resolved circum- absorption coefficient κ
2 −1
at 870 µm (Osdust of 2 cm gstellar disk. After analyzing the velocity field, these au- senkopf & Henning 1994), and a gas-to-dust mass ratio ofthors concluded that Keplerian rotation alone cannot sat- 100. Note that in our case, the masses have been estimatedisfactorily reproduce the kinematic signatures, although from the flux density obtained from the ATLASGAL catathe possibility of the existence of a small (<500 au) Ke- logue (Contreras et al. 2013), while Cesaroni et al. (2017)
plerian disk embedded in the core cannot be discarded. estimated the flux density of the sources from the ATFinally, although the observations were not carried out LASGAL maps. Therefore, the L /Mbolgas values in bothwith ALMA but with the VLA, it is worth to mention cases are slightly different. For NGC 7538IRS1 for which
the case of the 8 × 104 L⊙ O-type YSO NGC 7538IRS1 no ATLASGAL data are available, we have used the fluxes(Beuther et al. 2017b). VLA CH3 OH observations at of BOLOCAM at 1.1 mm (Ginsburg et al. 2013), using the∼150 au spatial resolution revealed two disk-like structures same T
dust of 50 K and a dust absorption coefficient κdustwith velocity gradients consistent with rotation but with of 1.24 cm2 g−1 . Figure 2 is an update of Fig. 29 of Cesano Keplerian signatures. Beuther et al. (2017b) concluded roni et al. (2017), where we plot the L /Mbolgas ratio as athat taking into account the early evolutionary stage of function of distance for sources with L
5bol > 10 L⊙ . We
NGC 7538IRS1, which is still undergoing a major accre- have removed G31.41+0.31 from the plot because, withtion phase as indicated by redshifted absorption, the Ke- the new distance estimate, its luminosity is of 5.7×104 L⊙
plerian disks could still be too small (< 190 au) to be de- and have changed the "status" to G17.64+0.16, after thetected and this would be in line with the simulations of discovery of a disk with Keplerian rotation signatures byKuiper et al. (2011). In addition, this material should Maud et al. (2018). Unfortunately, no new disk candidates
be ionized, as indicated by the presence of hyper-compact with luminosities > 105 L have been discovered since the⊙
HII regions and therefore, the thermal emission of CH3 OH study of Cesaroni et al. (2017). As seen in Fig. 2, thecould not be the best tracer of the accreting and rotating evolutionary trend observed by Cesaroni et al. still holds;
putative Keplerian disk.
that is, O-type stars can be surrounded by true accretion
It is worth to mention here that, as recently demonstrated
by Ahmadi et al. (2019), one has to be cautious whenruling out the existence of true accretion disks based on
the appearance of the PV plots because Keplerian disks
can mimic solid-body rotation when observed with poor
angular resolution.

disks, and the fact that such disks are not detected forall of them is because the youngest sources are too deeply
embedded to properly disentangle the velocity field of thedisk from that of the surrounding envelope or toroid.
To check whether this trend is still valid if one takes into
account all O-type sources for which velocity gradientssuggestive of rotation have been observed, in Fig. 3 wehave plotted the Lbol /Mgas ratio as a function of distance but this time for sources with Lbol > 104 L⊙ . As
seen in Fig. 3, when taking into account all the O-typesources (early and late) the evolutionary trend disappears
and there is no more a correlation between the youth

In summary, in recent years very high-angular resolution
ALMA (and VLA) observations have revealed velocity gradients consistent with rotation at disk scales in thirteen
star-forming regions associated with O-type YSOs, withsix of them with luminosity > 105 L⊙ , and seven with< 105 L⊙ . In a couple of regions, G345.50+0.35 and7Figure 2: Luminosity-to-mass ratio versus source distancefor high-mass star-forming regions with Lbol > 105 L⊙ .
Red and blue points indicate sources with disk candidates(Keplerian rotation) and with questionable disk candidates (no Keplerian rotation evidence), respectively.

Figure 3: Same as Fig. 2 for high-mass star-forming regions with Lbol > 105 L⊙ (dots) and Lbol < 105 L⊙ (stars).
Red and blue symbols indicate sources with disk candidates (Keplerian rotation) and with questionable disk candidates (no Keplerian rotation evidence), respectively.

of the YSOs and their lack of accretion disks. In fact,
the youngest YSOs, with Lbol /Mgas ∼ 15, have Keplerian disks around them. However, while for early O-type
YSOs, the Lbol /Mgas ratio spans more than one order ofmagnitude, for late O-type sources the range of this ratio
is very limited and only ranges from ∼ 15 to 80. Therefore, it is more difficult to clearly establish a differencein the evolutionary stage of the sources. In any case, apossible explanation of the fact that Keplerian disks weredetected around the younger sources for late O-type YSOs
but were not detected for early O-type ones could be due tothe fact that the former objects have less material aroundthem and therefore, it is possible to disentangle the surrounding envelope from the disk.

Disk substructure and stability
Interestingly, very high angular resolution observations ofsome Keplerian disk candidates have revealed the existence of substructure in the disk, in the form of spirals(G23.01−0.41: Sanna et al. 2019; AFGL 4176: Johnston
et al. 2020) and rings (G17.64+0.16: Maud et al. 2019).
ALMA observations at a spatial resolution of ∼ 500 au
have also revealed a spiral arm in W33A, for which no
Keplerian rotation signature has been found (Maud et al.
2017). Spiral arms feeding the central star could develop
by the growth of eccentric gravitational instabilities in thestar/disk system (the SLING mechanism of Adams et al.
1989) and have been predicted by numerical simulationsof disk formation around high-mass YSOs (e.g., Krumholz
et al. 2007; Kuiper et al. 2011; Ahmadi et al. 2019). The
same simulations show that, at larger scales, spiral structures channel material from the surrounding large-scale
infalling envelope onto the embedded circumstellar disk.
The latter would be the case of W33A, where the spiralarm observed has been interpreted as an accreting filamentthat would feed a likely embedded disk with material fromthe large-scale infalling envelope (Maud et al. 2017).

That no Keplerian disks have been found for some lateO-type YSOs does not mean that true accretion disks do
not exist in these sources. In fact, recent observations
suggest that Keplerian accretion disks may be small andhidden on scales < 500 au (e.g., W33A: Maud et al. 2017;
NGC 7538IRS1: Beuther et al. 2017b). This would be supported by models and simulations that predict that Keplerian disks, constantly replenished by infalling and rotating
material from large-scale non-Keplerian structures, would The stability of the disks against gravitational instabiligrow with time, from the inside outward, from ∼ 10 au up ties can be estimated by means of the Toomre Q parameterto >1000 au (Kuiper et al. 2011).
(Toomre 1964). According to this stability criterion, a thindisk becomes unstable against axisymmetric gravitational8

instabilities and prone to fragmentation if Q < 1, while
non-axisymmetric instabilities, which grow as multi-armed
spirals, become unstable for values of Q slightly higher, between 1 and 2 (e.g., Papaloizou & Savonije 1991; Durisen
et al. 2007). For AFGL 4176, Johnston et al. (2020) haveestimated Q across the disk and have found that the spiral arms are Toomre unstable, with Q < 2, and therefore,
they could undergo fragmentation. For the other source
exhibiting spiral arms, G23.01−0.41, no study of the stability of the disk has been carried out. For the other Keplerian disk candidate showing structure, G17.64+0.16,
Maud et al. (2019) conducted a Toomre Q stability analysis, and found the disk, and in particular the rings, tobe stable against fragmentation (Q > 2). These authors
propose that the substructures observed in the disk (therings) might have formed from fragmentation in an earlier
unstable phase. Regarding the other O-type YSOs withrotating structures, a Toomre Q parameter stability study
has only been performed for G351.77−0.54 by Beuther etal. (2017a), who, having found Q > 1.5, have concluded
that the rotating structure should be stable against axisymmetric gravitational fragmentation.

also deserves special mention because despite having a luminosity of only 104 L⊙ , this source could be hosting a
Keplerian disk rotating about a 34–38 M⊙ YSO. The factthat the luminosity of this object is so low is because
G11.92−0.61 MM1 is a proto-O star and is still deeply
embedded in the parental cloud. These cases are encouraging, but the numbers are still too small to establish, on
statistical grounds, that stars of all luminosities are formed
via disk-mediated accretion. However, since the Kepleriandisk detections around early O-type stars are very recent,the situation is bound to change, and we expect more confirmed cases in the coming years. In particular, when the
future baseline expansion of ALMA (aiming at an angularresolution of 0.001′′ –0.003′′) becomes a reality.
References:
Adams, F. C., Ruden, S. P., & Shu, F. H. 1989, ApJ, 347, 959
Ahmadi, A., Kuiper, R., Beuther, H. 2019, A&A, 632, A50
Beltrán, M. T., & de Wit 2016, A&ARv, 24, 6
Beltrán, M. T., et al. 2014, A&A, 571, A52
Beuther, H., et al. 2017a, A&A, 603, A10
Beuther, H., et al. 2017b, A&A, 605, A61
Bik, A., & Thi, W. 2004, A&A, 427, L13
Blum, R., et al. 2004, ApJ, 617, 1167
Bonnell, I., & Bate, M. 2006, MNRAS, 370, 488
Cesaroni, R., et al. 2005, A&A, 434, 1039
Cesaroni, R., et al. 2014, A&A, 566, A73
Cesaroni, R., et al. 2017, A&A, 609, A59
Chabrier, G. 2005, in Initial Mass Function 50 Years Later, vol. 327
of Astrophysics and Space Science Library, 41
Contreras, Y., et al. 2013, A&A 549, A45
Durisen, R. H., et al. 2007, in Protostars & Planets V, 607
Hosokawa, T., & Omukai, K. 2009, ApJ, 691, 823
Ilee, J. D., et al. 2013, MNRAS, 429, 2960
Ilee, J. D., et al. 2016, MNRAS, 462, 4386
Ilee, J. D., et al. 2018, ApJ, 869, L24
Johnston, K. G., et al. 2015, ApJL, 813, L19
Johnston, K. G., et al. 2020, A&A, 634, L11
Keto, E. 2007, ApJ, 666, 976
Krumholz, M. R., Klein, R. I., & McKee, C. F. 2007, ApJ, 665, 478
Kuiper, R., et al. 2011, ApJ, 732, 20
Laughlin, G., & Bodenheimer, P. 1994, ApJ, 436, 335
Maud, L. T., et al. 2017, MNRAS, 467, L120
Maud, L. T., et al. 2018, A&A, 620, A31
Maud, L. T., et al. 2019, A&A, 627, L6
Papaloizou, J. C., & Savonije, G. J. 1991, MNRAS, 248, 353
Patel, N., et al. 2005, Nature, 437, 109
Reid, M., et al. 2019, ApJ, 885, 131
Sánchez-Monge, Á., et al. 2013, A&A, 552, L10
Sanna, A., et al. 2019, A&A, 623, A77
Schuller, F., et al. 2009, A&A, 504, 415
Tan, J. C., et al. 2014, in Protostars and Planets, VI, 149
Toomre, A. 1964, ApJ, 139, 1217
Wang, K.-S., van der Tak, F. F. S., & Hogerheijde, M. R. 2012,
A&A, 543, A22
Wheelwright, H., et al. 2010, MNRAS, 408, 1840
Yorke, H. 1995, RevMexAA, Conference Series 1, 35
Zapata, L. A., et al. 2019, ApJ, 872, 176

The stability of the rotating structures can also be investigated via the ratio of the mass of the rotating structure and the mass of the central star, Mrot /M⋆ . According to theory, for Mrot /M⋆ > 3, gravitational instabilities
that induce spiral density waves appear, leading to a rapid
fragmentation of the disk (Laughlin & Bodenheimer 1994;
Yorke 1995). We have compiled the Mrot /M⋆ for thoseobjects for which it has been possible to find an estimateof the mass of the rotating structure, nine out of fifteen.
For all but one case (G31.41+0.31), we have found that
Mrot /M⋆ <∼ 3, which would suggest that almost all the rotating structures should be stable. However, because all
the observations have been carried out with interferometers at very high-angular resolution, the possibility cannot
be discarded that some emission of the rotating structure
has been filtered out and, therefore, Mrot should be taken
as a lower limit.
Conclusions
Accretion disks around high-mass YSOs are fundamental
to understand how such stars form. The existence of true
accretion disks has been been well established for stars
with masses up to ∼ 20 M⊙, which correspond to earlyB-type or late O-type stars, thanks to the unprecedented
angular resolution and sensitivity provided by ALMA in
recent years. However, despite the progress made in thisfield, the number of early O-type (proto)stars (L > 105 L⊙ )with Keplerian rotation signatures is still very limited. Up
to now, the best true disk candidates are AFLG 4176 andG17.64+0.16 that host a Keplerian disk rotating about
a 25 M⊙ and a 45 M⊙ star, respectively (Johnston et al.
2015, 2020; Maud et al. 2018, 2019). G11.92−0.61 MM1

9Abstracts of recently accepted papers

1. Dust clearing by radial drift in evolving protoplanetary disks
Johan Appelgren1 , Michiel Lambrechts1 , and Anders Johansen1
1Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden

E-mail contact: johan at astro.lu.se
Recent surveys have revealed that protoplanetary disks typically have dust masses that appear to be insufficient toaccount for the high occurrence rate of exoplanet systems. We demonstrate that this observed dust depletion isconsistent with the radial drift of pebbles. Using a Monte Carlo method we simulate the evolution of a cluster ofprotoplanetary disks, using a 1D numerical method to viscously evolve each gas disk together with the radial drift ofdust particles that have grown to 100 µm in size. For a 2 Myr old cluster of stars, we find a slightly sub-linear scaling
between the gas disk mass and the gas accretion rate (Mg ∝ Ṁ 0.9 ). However, for the dust mass we find that evolved
dust disks have a much weaker scaling with the gas accretion rate, with the precise scaling depending on the age at
which the cluster is sampled and the intrinsic age spread of the disks in the cluster. Ultimately, we find that the dust
mass present in protoplanetary disk is on the order of 10–100 Earth masses in 1–3 Myr old star-forming regions, afactor of 10 to 100 depleted from the original dust budget. As the dust drains from the outer disk, pebbles pile up in
the inner disk and locally increase the dust-to-gas ratio by a factor of up to 4 above the initial value. In these highdust-to-gas ratio regions we find conditions that are favourable for planetesimal formation via the streaming instability
and subsequent growth by pebble accretion. We also find the following scaling relations with stellar mass within a
1–2 Myr old cluster: a slightly super-linear scaling between the gas accretion rate and stellar mass (Ṁ ∝ M⋆ 1.4 ), aslightly super-linear scaling between the gas disk mass and the stellar mass (Mg ∝ M⋆ 1.4 ) and a super-linear relation
between the dust disk mass and stellar mass (Md ∝ M⋆ 1.4–4.1 ).
Accepted by A&A
http://arxiv.org/pdf/2004.02918

2. Radiative Transfer modeling of EC 53: An Episodically Accreting Class I Young Stellar

ObjectGiseon Baek1 , Benjamin A. MacFarlane2 , Jeong-Eun Lee1 , Dimitris Stamatellos2 , Gregory Herczeg3 ,Doug Johnstone4,5 , Carlos Contreras Pena6 , Watson Varricatt7 , Klaus W. Hodapp7 , Huei-Ru Vivien
Chen8 and Sung-Ju Kang9
School of Space Research and Institute of Natural Sciences, Kyung Hee University, 1732 Deogyeong-daero, Giheunggu, Yongin-si, Gyeonggi-do 446-701, Korea; 2 Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy,
University of Central Lancashire, Preston, PR1 2HE, UK; 3 Kavli Institute for Astronomy and Astrophysics, Peking
University, Yiheyuan 5, Haidian Qu, 100871 Beijing, China; 4 NRC Herzberg Astronomy and Astrophysics, 5071 West
Saanich Rd, Victoria, BC, V9E 2E7, Canada; 5 Department of Physics and Astronomy, University of Victoria, Victoria,
BC, V8P 1A1, Canada; 6 School of Physics, Astrophysics Group, University of Exeter, Stocker Road, Exeter EX4
4QL, UK; 7 Institute for Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720, USA; 8 Departmentof Physics and Institute of Astronomy, National Tsing Hua University, Taiwan; 9 Korea Astronomy and Space Science
Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
1E-mail contact: giseon at khu.ac.kr
In the episodic accretion scenario, a large fraction of the protostellar mass accretes during repeated and large burstsof accretion. Since outbursts on protostars are typically identified at specific wavelengths, interpreting these outbursts
requires converting this change in flux to a change in total luminosity. The Class I young stellar object EC 53 in
the Serpens Main cloud has undergone repeated increases in brightness at 850 µm that are likely caused by bursts ofaccretion. In this study, we perform two- and three-dimensional continuum radiative transfer modeling to quantify
10the internal luminosity rise in EC 53 that corresponds to the factor of ∼1.5 enhancement in flux at 850 µm. We model
the spectral energy distribution and radial intensity profile in both the quiescent and outburst phases. The internal
luminosity in the outburst phase is ∼3.3 times brighter than the luminosity in the quiescent phase. The radial intensity
profile analysis demonstrates that the detected sub-mm flux variation of EC 53 comes from the heated envelope by
the accretion burst. We also find that the role of external heating of the EC 53 envelope by the interstellar radiation
field is insignificant.
Accepted by ApJ
https://arxiv.org/pdf/2004.05600.pdf

3. The nature of the methanol maser ring G23.657−00.127. II. Expansion of the maser

structure
Anna Bartkiewicz1 , Alberto Sanna2,3 , Marian Szymczak1 , Luca Moscadelli4, Huib Jan van Langevelde5,6
and Pawel Wolak1
Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka
5, 87-100 Torun, Poland; 2 INAF, Istituto di Radioastronomia & Italian ALMA Regional Centre, Via P. Gobetti 101,
40129, Bologna, Italy; 3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121, Bonn, Germany; 4 INAF,
Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy; 5 Joint Institute for VLBI ERIC (JIVE),
Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands; 6 Sterrewacht Leiden, Leiden University, Postbus
9513, 2300 RA Leiden, The Netherlands
1E-mail contact: annan at astro.umk.pl
Ring-like distributions of the 6.7 GHz methanol maser spots at milliarcsecond scales represent a family of molecular structures of unknown origin associated with high-mass young stellar objects (HMYSOs). We aim to study
G23.657−00.127, which has a nearly circular ring of the 6.7 GHz methanol masers, and is the most suitable target totest hypotheses on the origin of the maser rings. The European Very Long Baseline Interferometry Network (EVN)
was used at three epochs spanning 10.3 yr to derive the spatio-kinematical structure of the 6.7 GHz methanol maser
emission in the target. The maser cloudlets, lying in a nearly symmetric ring, expand mainly in the radial direction
with a mean velocity of 3.2 km s−1 . There is an indication that the radial component of the velocity increases withcloudlet’s distance from the ring centre. The tangential component does not show any clear evidence for rotation of thecloudlets or any relationship with distance from the ring centre. The blue-shifted masers may hint at an anticlockwise
rotation of cloudlets in the southern part of the ring. The nearly circular structure of the ring clearly persisted formore than 10 yr. Interferometric data demonstrated that about one quarter of cloudlets show significant variability
in their brightness, although the overall spectrum was non-variable in single-dish studies. Taking into account thethree-dimensional motion of the maser cloudlets and their spatial distribution along a small ring, we speculate about
two possible scenarios where the methanol masers trace either a spherical outflow arising from an (almost) edge-on
disc, or a wide angle wind at the base of a protostellar jet. The latter is associated with near- and mid-infraredemission detected towards the ring. High angular resolution images of complementary (thermal) tracers are needed tointerpret the environment of methanol masers.
Accepted by Astronomy and Astrophysics
http://arxiv.org/pdf/2004.00916

4. Dynamical cloud formation traced by atomic and molecular gas
H. Beuther1 , Y. Wang1 , J. Soler1 , H. Linz1 , J. Henshaw1 , E. Vazquez-Semadeni2 , G. Gomez2 , S. Ragan3 ,Th. Henning1 , S.C.O. Glover4 , M.-Y. Lee5 and R. Guesten6
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 2 Instituto de Radioastronomia y
Astrofisica, Universidad Nacional Autonoma de Mexico, Morelia, Michoacan 58089, Mexico; 3 School of Physics andAstronomy, Cardiff University, Queen’s Buildings, The Parade, Cardiff CF24 3AA, UK; 4 University of Heidelberg,
Institute for Theoretical Astrophysics, Albert-Ueberle-Str. 2, 69120 Heidelberg; 5 Korea Astronomy and Space Science
Institute, 776 Daedeok-daero, 34055 Daejeon, Republic of Korea; 6 Max-Planck-Institut für Radioastronomie, Auf
dem Hügel 69, 53121 Bonn1

11

E-mail contact: beuther at mpia.de
Context: Atomic and molecular cloud formation is a dynamical process. However, kinematic signatures of theseprocesses are still observationally poorly constrained.
Aims: Identify and characterize the cloud formation signatures in atomic and molecular gas.
Methods: Targeting the cloud-scale environment of the prototypical infrared dark cloud G28.3, we employ spectralline imaging observations of the two atomic lines HI and [CI] as well as molecular lines observations in 13CO in the
1–0 and 3–2 transitions. The analysis comprises investigations of the kinematic properties of the different tracers,
estimates of the mass flow rates, velocity structure functions, a Histogram of Oriented Gradients (HOG) study as wellas comparisons to simulations.
Results: The central IRDC is embedded in a more diffuse envelope of cold neutral medium (CNM) traced by HI
self-absorption (HISA) and molecular gas. The spectral line data as well as the HOG and structure function analysis
indicate a possible kinematic decoupling of the HI from the other gas compounds. Spectral analysis and positionvelocity diagrams reveal two velocity components that converge at the position of the IRDC. Estimated mass flow rates
appear rather constant from the cloud edge toward the center. The velocity structure function analysis is consistent
with gas flows being dominated by the formation of hierarchical structures.
Conclusions: The observations and analysis are consistent with a picture where the IRDC G28 is formed at the centerof two converging gas flows. While the approximately constant mass flow rates are consistent with a self-similar,
gravitationally driven collapse of the cloud, external compression by, e.g., spiral arm shocks or supernovae explosions
cannot be excluded yet. Future investigations should aim at differentiating the origin of such converging gas flows.
Accepted by Astronomy & Astrophysics
http://www.mpia.de/homes/beuther/papers.html

5. Birth of convective low-mass to high-mass second Larson cores
Asmita Bhandare1 , Rolf Kuiper2,1 , Thomas Henning1 , Christian Fendt1 , Mario Flock1 , and GabrielDominique Marleau2,3,1
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 2 Institut für Astronomie undAstrophysik, Universität Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen, Germany; 3 Physikalisches Institut,
Universität Bern, Gesellschaftsstr. 6, CH-3012 Bern, Switzerland

1

E-mail contact: bhandare at mpia.de
Stars form as an end product of the gravitational collapse of cold, dense gas in magnetized molecular clouds. This
multi-scale scenario occurs via the formation of two quasi-hydrostatic cores and involves complex physical processes,
which require a robust, self-consistent numerical treatment. The aim of this study is to understand the formationand evolution of the second Larson core and the dependence of its properties on the initial cloud core mass. We
used the PLUTO code to perform high resolution, 1D and 2D RHD collapse simulations. We include self-gravity
and use a grey FLD approximation for the radiative transfer. Additionally, we use for the gas EOS density- andtemperature-dependent thermodynamic quantities to account for the effects such as dissociation, ionisation, andmolecular vibrations and rotations. Properties of the second core are investigated using 1D studies spanning a wide
range of initial cloud core masses from 0.5 to 100 M⊙ . Furthermore, we expand to 2D collapse simulations for a few
cases of 1, 5, 10, and 20 M⊙ . We follow the evolution of the second core for ≥ 100 years after its formation, for eachof these non-rotating cases. Our results indicate a dependence of several second core properties on the initial cloudcore mass. For the first time, due to an unprecedented resolution, our 2D non-rotating collapse studies indicate thatconvection is generated in the outer layers of the second core, which is formed due to the gravitational collapse of a
1 M⊙ cloud core. Additionally, we find large-scale oscillations of the second accretion shock front triggered by thestanding accretion shock instability, which has not been seen before in early evolutionary stages of stars. We predictthat the physics within the second core would not be significantly influenced by the effects of magnetic fields or an
initial cloud rotation.
Accepted by A&A
http://arxiv.org/pdf/2004.12419

12

6. GW Ori: Interactions Between a Triple-star System and its Circumtriple Disk in Action
Jiaqing Bi1 , Nienke van der Marel1,2 , Ruobing Dong1 , Takayuki Muto3 , Rebecca G. Martin4 , Jeremy
L. Smallwood4, Jun Hashimoto5 , Hauyu Baobab Liu6 , Hideko Nomura7,8 , Yasuhiro Hasegawa9 , Michihiro Takami6 , Mihoko Konishi10 , Munetake Momose11, Kazuhiro D. Kanagawa12 , Akimasa Kataoka7 ,Tomohiro Ono13,14 , Michael L. Sitko15,16 , Sanemichi Z. Takahashi7,17 , Kengo Tomida14,18 and Takashi
Tsukagoshi7
Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2, Canada; 2 Herzberg Astronomy
and Astrophysics Programs, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E
2E7,Canada; 3 Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677,
Japan; 4 Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las
Vegas, NV 89154, USA; 5 Astrobiology Center, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo
181-8588, Japan; 6 Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Sec. 4, Roosevelt Rd, Taipei
10617, Taiwan; 7 Division of Science, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 1818588, Japan; 8 Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro,
Tokyo 152-8551, Japan; 9 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA;
10
Faculty of Science and Technology, Oita University, 700 Dannoharu, Oita 870-1192, Japan; 11 College of Science,
Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512, Japan; 12 Research Center for the Early Universe, Graduate
School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan; 13 Department of Astrophysical Sciences,
Princeton University, Princeton, NJ 08544, USA; 14 Department of Earth and Space Science, Osaka University,
Toyonaka, Osaka 560-0043, Japan; 15 Department of Physics, University of Cincinnati, Cincinnati, OH 45221, USA;
16
Space Science Institute, 475 Walnut Street, Suite 205, Boulder, CO 80301, USA; 17 Department of Applied Physics,
Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677, Japan; 18 Astronomical Institute, Tohoku
University, Sendai, Miyagi 980-8578, Japan1

E-mail contact: jiaqing.bi at gmail.com
GW Ori is a hierarchical triple system with a rare circumtriple disk. We present Atacama Large Millimeter/submillimeter
Array (ALMA) observations of 1.3 mm dust continuum and 12 CO J = 2 − 1 molecular gas emission of the disk. For
the first time, we identify three dust rings in the GW Ori disk at ∼ 46, 188, and 338 AU, with estimated dust mass of
74, 168, and 245 Earth masses, respectively. To our knowledge, its outermost ring is the largest dust ring ever foundin protoplanetary disks. We use visibility modelling of dust continuum to show that the disk has misaligned parts,and the innermost dust ring is eccentric. The disk misalignment is also suggested by the CO kinematics. We interpretthese substructures as evidence of ongoing dynamical interactions between the triple stars and the circumtriple disk.
Accepted by ApJL
https://arxiv.org/pdf/2004.03135

7. Kinematics of T Tauri Stars Close to the Sun from the Gaia DR2 Catalogue
V.V. Bobylev1
1

Pulkovo Astronomical Observatory, Russian Academy of Sciences, Pulkovskoe sh. 65, St. Petersburg, 196140 Russia

E-mail contact: vbobylev at gaoran.ru
The spatial and kinematic properties of a large sample of young T Tauri stars from the solar neighborhood 500 pc
in radius have been studied. The following parameters of the position ellipsoid have been determined from the mostprobable members of the Gould Belt: its sizes are 350 × 270 × 87 pc and it is oriented at an angle of 14◦ ±1◦ to the
Galactic plane with a longitude of the ascending node of 297◦±1◦ . An analysis of the motions of stars from this sample
has shown that the residual velocity ellipsoid with principal semiaxes σ1,2,3 = (8.87, 5.58, 3.03)±(0.10, 0.20, 0.04) km s−1
is oriented at an angle of 22◦ ±1◦ to the Galactic plane with a longitude of the ascending node of 298◦±2◦ . It has been
established that much of the expansion effect (kinematic K effect) typical for Gould Belt stars, 5–6 km s−1 kpc−1 , canbe explained by the influence of a Galactic spiral density wave with a radial perturbation amplitude fR ∼ 5 km s−1 .
Accepted by Astronomy Letters
http://arxiv.org/pdf/2004.07291

13

8. Self-gravitating Filament Formation from Shocked Flows: Velocity Gradients acrossFilaments
Che-Yu Chen1 , Lee G. Mundy2 , Eve C. Ostriker3 , Shaye Storm4 and Arnab Dhabal2
Department of Astronomy, University of Virginia, Charlottesville 22904, VA, USA; 2 Department of Astronomy,
University of Maryland, College Park 20742, MD, USA; 3 Department of Astrophysical Sciences, Princeton University,
Princeton 08544, NJ, USA; 4 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

1E-mail contact: cc6pg at virginia.edu
In typical environments of star-forming clouds, converging supersonic turbulence generates shock-compressed regions,and can create strongly-magnetized sheet-like layers. Numerical MHD simulations show that within these post-shock
layers, dense filaments and embedded self-gravitating cores form via gathering material along the magnetic field lines.
As a result of the preferred-direction mass collection, a velocity gradient perpendicular to the filament major axis is
a common feature seen in simulations. We show that this prediction is in good agreement with recent observations
from the CARMA Large Area Star Formation Survey (CLASSy), from which we identified several filaments withprominent velocity gradients perpendicular to their major axes. Highlighting a filament from the northwest part ofSerpens South, we provide both qualitative and quantitative comparisons between simulation results and observational
data. In particular, we show that the dimensionless ratio Cv ≡ ∆vh 2 /(GM/L), where ∆vh is half of the observed
perpendicular velocity difference across a filament, and M/L is the filament’s mass per unit length, can distinguishbetween filaments formed purely due to turbulent compression and those formed due to gravity-induced accretion. We
conclude that the perpendicular velocity gradient observed in the Serpens South northwest filament can be caused bygravity-induced anisotropic accretion of material from a flattened layer. Using synthetic observations of our simulated
filaments, we also propose that a density-selection effect may explain observed subfilaments (one filament breaking
into two components in velocity space) as reported in Dhabal et al. (2018).
Accepted by MNRAS
http://arxiv.org/pdf/2004.02898

9. The formation of young massive clusters by colliding flows
C. L. Dobbs1 , K. Y. Liow1 and S. Rieder1
1

Department of Physics & Astronomy, University of Exeter, Exeter, UK

E-mail contact: C.L.Dobbs at exeter.ac.uk
Young massive clusters (YMCs) are the most intense regions of star formation in galaxies. Formulating a model for
YMC formation whilst at the same time meeting the constraints from observations is highly challenging however. We−3−1
show that forming YMCs requires clouds with densities >∼ 100 cm to collide with high velocities (>∼ 20 km s ).
−3
We present the first simulations which, starting from moderate cloud densities of ∼ 100 cm , are able to convert alarge amount of mass into stars over a time period of around 1 Myr, to produce dense massive clusters similar to thoseobserved. Such conditions are commonplace in more extreme environments, where YMCs are common, but atypicalfor our Galaxy, where YMCs are rare.
Accepted by MNRAS Letters
https://arxiv.org/pdf/2004.09438

10. The Gemini Planet Imager view of the HD 32297 debris disk
Gaspard Duchêne1,2 , Malena Rice3 , Justin Hom4 , Joseph Zalesky4 , Thomas M. Esposito1, Maxwell
A. Millar-Blanchaer5 , Bin Ren6,7,8 , Paul Kalas1,9,10 , Michael Fitzgerald11 , Pauline Arriaga11 , SebastianBruzzone12 , Joanna Bulger13 , Christine H. Chen7 , Eugene Chiang1,14 , Tara Cotten15 , Ian Czekala1 ,Robert J. De Rosa16 , Ruobin Dong17 , Zachary H. Draper17,18 , Katherine B. Follette19 , James R.
Graham1 , Li-Wie Hung11 , Ronald Lopez11 , Bruce Macintosh16 , Brenda C. Matthews18,17 , Johan Mazoyer20 ,Stan Metchev12,21 , Jennifer Patience4 , Marshall D. Perrin7 , Julien Rameau22 , Inseok Song15 , Kevin
Stahl11 , Jason Wang8,1 , Schuyler Wolff23 , Ben Zuckerman11 , S. Mark Ammons24 , Vanessa P. Bailey5 ,Travis Barman25 , Jeffrey Chilcotte16,26 , Rene Doyon22 , Benjamin L. Gerard17,18 , Stephen J. Goodsell27,

14

Alexandra Z. Greenbaum28 , Pascale Hibon29 , Patrick Ingraham30 , Quinn Konopacky31 , Jérôme Maire31 ,Franck Marchis9 , Mark S. Marley32 , Christian Marois18,17 , Eric L. Nielsen9,16, Rebecca Oppenheimer33,
David Palmer24 , Lisa Poyneer24 , Abhijith Rajan7 , Fredrik T. Rantakyro31 , Jean-Baptiste Ruffio16 ,Dmitry Savransky34 , Adam C. Schneider4 , Anand Sivaramakrishnan7 , Rémi Soummer7 and Sandrine
Thomas30
Astronomy Department, University of California, Berkeley, CA 94720, USA; 2 Université Grenoble Alpes / CNRS,
Institut de Planétologie et d’Astrophysique de Grenoble, 38000 Grenoble, France; 3 Department of Astronomy, Yale
University, New Haven, CT 06511, USA; 4 School of Earth and Space Exploration, Arizona State University, PO Box
871404, Tempe, AZ 85287, USA; 5 NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena,
CA 91109, USA; 6 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA;
7
Space Telescope Science Institute, Baltimore, MD 21218, USA; 8 Department of Astronomy, California Instituteof Technology, 1216 East California Blvd, Pasadena, CA 91125, USA; 9 SETI Institute, Carl Sagan Center, 189
Bernardo Ave., Mountain View CA 94043, USA; 10 Institute of Astrophysics, FORTH, GR-71110 Heraklion, Greece;
11
Department of Physics & Astronomy, 430 Portola Plaza, University of California, Los Angeles, CA 90095, USA;12
Department of Physics and Astronomy, Centre for Planetary Science and Exploration, The University of Western
Ontario, London, ON N6A 3K7, Canada; 13 Pan-STARRS Observatory, Institute for Astronomy, University of Hawaii,
2680 Woodlawn Dr, Honolulu, HI 96822, USA; 14 Earth and Planetary Science Department, University of California,
Berkeley, CA 94720, USA; 15 Physics and Astronomy, University of Georgia, 240 Physics, Athens, GA 30602, USA; 16
Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305, USA; 17 Universityof Victoria, 3800 Finnerty Rd, Victoria, BC, V8P5C2, Canada; 18 National Research Council of Canada Herzberg,
5071 West Saanich Road, Victoria, BC V9E 2E7, Canada; 19 Physics and Astronomy Department, Amherst College, 21
Merrill Science Drive, Amherst, MA 01002, USA; 20 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne
Université, Université Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France; 21 Departmentof Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA; 22 Institut de Recherche surles Exoplanètes, Département de Physique, Université de Montréal, Montréal, QC, H3C 3J7, Canada; 23 Leiden
Observatory, Leiden University, P.O. Box 9513, 2300RA Leiden, The Netherlands; 24 Lawrence Livermore National
Laboratory, 7000 East Ave, Livermore, CA 94550, USA; 25 Lunar and Planetary Laboratory, University of Arizona,
Tucson AZ 85721, USA; 26 Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre
Dame, IN, 46556, USA; 27 Gemini Observatory, 670 N. A’ohoku Place, Hilo, HI 96720, USA; 28 Department of
Astronomy, University of Michigan, Ann Arbor, MI 48109, USA; 29 Gemini Observatory, Casilla 603, La Serena,
Chile; 30 Large Synoptic Survey Telescope, 950N Cherry Ave., Tucson, AZ 85719, USA; 31 Center for Astrophysics
and Space Science, University of California San Diego, La Jolla, CA 92093, USA; 32 Space Science Division, NASA
Ames Research Center, Mail Stop 245-3, Moffett Field CA 94035, USA; 33 Department of Astrophysics, American
Museum of Natural History, New York, NY 10024, USA; 34 Sibley School of Mechanical and Aerospace Engineering,
Cornell University, Ithaca, NY 14853, USA
1E-mail contact: gduchene at berkeley.edu
We present new H-band scattered light images of the HD 32297 edge-on debris disk obtained with the Gemini Planet
Imager (GPI). The disk is detected in total and polarized intensity down to a projected angular separation of 0.15 arcsec, or 20au. On the other hand, the large scale swept-back halo remains undetected, likely a consequence of its
markedly blue color relative to the parent body belt. We analyze the curvature of the disk spine and estimate a radiusof ≈100au for the parent body belt, smaller than past scattered light studies but consistent with thermal emission mapsof the system. We employ three different flux-preserving post-processing methods to suppress the residual starlightand evaluate the surface brightness and polarization profile along the disk spine. Unlike past studies of the system,
our high fidelity images reveal the disk to be highly symmetric and devoid of morphological and surface brightness
perturbations. We find the dust scattering properties of the system to be consistent with those observed in otherdebris disks, with the exception of HR 4796. Finally, we find no direct evidence for the presence of a planetary-mass
object in the system.
Accepted by the Astronomical Journal
https://arxiv.org/pdf/2004.06027

15

11. Gravitoviscous protoplanetary disks with a dust component. III. Evolution of gas, dust,

and pebbles

Vardan G. Elbakyan1,2 , Anders Johansen1 , Michiel Lambrechts1 , Vitaly Akimkin3 , and Eduard I.
Vorobyov2,4,5
Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden;
Research Institute of Physics, Southern Federal University, Rostov-on-Don, 344090 Russia; 3 Institute of Astronomy,
Russian Academy of Sciences, Pyatnitskaya str 48, Moscow 119017, Russia; 4 University of Vienna, Department of
Astrophysics, Vienna, 1180, Austria; 5 Ural Federal University, 51 Lenin Str., 620051 Ekaterinburg, Russia

1
2

E-mail contact: vgelbakyan at sfedu.ru
We study the dynamics and growth of dust particles in circumstellar disks of different masses that are prone togravitational instability during the critical first Myr of their evolution. The dust component is made up of two
different components: micron-sized dust and grown dust of evolving size. For the dust component, we considered
the dust coagulation, fragmentation, momentum exchange with the gas, and dust self-gravity. We found that the
micron-sized dust particles grow rapidly in the circumstellar disk, reaching a few cm in size in the inner 100 au ofthe disk during less than 100 kyr after the disk formation, provided that fragmentation velocity is 30 m s−1 . Due tothe accretion of micron dust particles from the surrounding envelope, which serves as a micron dust reservoir, theapproximately cm-sized dust particles continue to be present in the disk for more than 900 kyr after the disk formationand maintain a dust-to-gas ratio close to 0.01. We show that a strong correlation exists between the gas and pebble
fluxes in the disk. We find that radial surface density distribution of pebbles in the disk shows power-law distribution
with an index similar to that of the Minimum-mass solar nebula (MMSN) regardless the disk mass. We also showthat the gas surface density in our models agrees well with measurements of dust in protoplanetary disks of AS 209,
HD 163296, and DoAr 25 systems. Pebbles are formed during the very early stages of protoplanetary disk evolution.
They play a crucial role in the planet formation process. Our disc simulations reveal the early onset (<105 yr) of an
inwards-drifting flux of pebble-sized particles that makes up approximately between one hundredth and one tenth of
the gas mass flux, which appears consistent with mm-observations of discs.
Accepted by A&A
http://arxiv.org/pdf/2004.00126

12. Star Formation Occurs in Dense Gas, but What Does “Dense" Mean?
Neal J. Evans II1,2,3 , Kee-Tae Kim2,4 , Jingwen Wu5 , Zhang Chao5 , Mark Heyer5 , Tie Liu7,2 , Quang
Nguyen-Lu’o’ng8,9,10, and Jens Kauffmann11
Department of Astronomy The University of Texas at Austin 2515 Speedway, Stop C1400 Austin, Texas 787121205, USA; 2 Korea Astronomy and Space Science Institute 776 Daedeokdae-ro, Yuseong-gu Daejeon, 34055, Korea;
3
Humanitas College, Global Campus, Kyung Hee University, Yongin-shi 17104, Korea 4 University of Science andTechnology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea 5 National Astronomical
Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100012, China 6 Department of Astronomy University of Massachusetts Amherst, Massachusetts 01003, USA 7 Shanghai Astronomical
Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, PR China 8 McMaster University,
1 James St N, Hamilton, ON, L8P 1A2, Canada 9 Graduate School of Natural Sciences, Nagoya City University,
Mizuho-ku, Nagoya, Aichi 467-8601, Japan 10 IBM Canada, 120 Bloor Street East, Toronto, ON, M4Y 1B7, Canada
11
Haystack Observatory MIT 99 Milstone Rd. Westford, MA 01886 USA
1E-mail contact: nje at astro.as.utexas.edu
We report results of a project to map HCN and HCO+ J = 1-0 emission toward a sample of molecular clouds inthe inner Galaxy, all containing dense clumps that are actively engaged in star formation. We compare these twomolecular line tracers with millimeter continuum emission and extinction, as inferred from 13 CO, as tracers of dense
gas in molecular clouds. The fraction of the line luminosity from each tracer that comes from the dense gas, asmeasured by AV > 8 mag, varies substantially from cloud to cloud. In all cases, a substantial fraction (in most cases,
the majority) of the total luminosity arises in gas below the AV > 8 mag threshold and outside the region of strong
mm continuum emission. Measurements of the luminosity of HCN toward other galaxies will likely be dominated bysuch gas at lower surface density. Substantial, even dominant, contributions to the total line luminosity can arise in16

gas with densities typical of the cloud as a whole (densities about 100 cm−3 ). Defining the dense clump from the HCNor HCO+ emission itself, similarly to previous studies, leads to a wide range of clump properties, with some being
considerably larger and less dense than in previous studies. HCN and HCO+ have similar ability to trace dense gas
for the clouds in this sample. For the two clouds with low virial parameters, the 13 CO is definitely a worse tracer ofthe dense gas, but for the other four, it is equally good (or bad) at tracing dense gas.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2004.06631

13. The CARMA-NRO Orion Survey: Protostellar Outflows, Energetics, and Filamentary

Alignment

Jesse R. Feddersen1 , Héctor G. Arce1 , Shuo Kong1 , Sümeyye Suri2 , Álvaro Sánchez-Monge2 et al.
Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101, USA; 2 I. Physikalisches
Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany

1E-mail contact: jesse.feddersen at yale.edu
We identify 45 protostellar outflows in CO maps of the Orion A giant molecular cloud from the CARMA-NRO Orionsurvey. Our sample includes 11 newly detected outflows. We measure the mass and energetics of the outflows, including
material at low-velocities by correcting for cloud contributions. The total momentum and kinetic energy injection ratesof outflows is comparable to the turbulent dissipation rate of the cloud. We also compare the outflow position angles tothe orientation of C18 O filaments. We find that the full sample of outflows is consistent with being randomly oriented
with respect to the filaments. A subsample of the most reliable measurements shows a moderately perpendicular
outflow-filament alignment which may reflect accretion of mass across filaments and onto the protostellar cores.
Accepted by ApJ
http://arxiv.org/pdf/2004.03504

14. Measuring turbulent motion in planet-forming disks with ALMA: A detection around

DM Tau and non-detections around MWC 480 and V4046 SgrKevin Flaherty1 , A. Meredith Hughes2 , Jacob B. Simon3,4,5 , Chunhua Qi6 , Xue-Ning Bai7,8 et al.
1
Department of Astronomy and Department of Physics Williams College, Williamstown, MA 01267 USA; 2 Van
Vleck Observatory, Astronomy Department, Wesleyan University 96 Foss Hill Drive Middletown, CT 06459, USA; 3
Department of Physics and Astronomy, Iowa State University, Ames, IA, 50010, USA; 4 Department of Space Studies,Southwest Research Institute Boulder, CO 80302; 5 JILA, University of Colorado and NIST 440 UCB, Boulder, CO
80309; 6 Harvard-Smithsonian Center for Astrophysics 60 Garden St Cambridge, MA 02138; 7 Institute for Advanced
Study Tsinghua University Beijing 100084, China; 8 Tsinghua Center for Astrophysics Tsinghua University Beijing
100084, China

E-mail contact: kmf4 at williams.edu
Turbulence is a crucial factor in many models of planet formation, but it has only been directly constrained among asmall number of planet forming disks. Building on the upper limits on turbulence placed in disks around HD 163296
and TW Hya, we present ALMA CO J=2–1 line observations at ∼0.′′ 3 (20–50 au) resolution and 80 m s−1 channel
spacing of the disks around DM Tau, MWC 480, and V4046 Sgr. Using parametric models of disk structure, werobustly detect non-thermal gas motions around DM Tau of between 0.25 cs and 0.33 cs , with the range dominatedby systematic effects, making this one of the only systems with directly measured non-zero turbulence. Using thesame methodology, we place stringent upper limits on the non-thermal gas motion around MWC 480 (<0.08 cs ) and
V4046 Sgr (<0.12 cs ). The preponderance of upper limits in this small sample, and the modest turbulence levels−3
consistent with dust studies, suggest that weak turbulence (α <∼ 10 ) may be a common, albeit not universal, featureof planet-forming disks. We explore the particular physical conditions around DM Tau that could lead this system to
be more turbulent than the others.
Accepted by ApJ
http://arxiv.org/pdf/2004.12176
1715. New HST data and modeling reveal a massive planetesimal collision around Fomalhaut
András Gáspár1 and George H. Rieke1
1

Steward Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ, 85719

E-mail contact: agaspar at arizona.edu
The apparent detection of an exoplanet orbiting Fomalhaut was announced in 2008. However, subsequent observationsof Fomalhaut b raised questions about its status: Unlike other exoplanets, it is bright in the optical and nondetectedin the infrared, and its orbit appears to cross the debris ring around the star without the expected gravitational
perturbations. We revisit previously published data and analyze additional Hubble Space Telescope (HST) data,
finding that the source is likely on a radial trajectory and has faded and become extended. Dynamical and collisionalmodeling of a recently produced dust cloud yields results consistent with the observations. Fomalhaut b appears to
be a directly imaged catastrophic collision between two large planetesimals in an extrasolar planetary system. Similar
events should be very rare in quiescent planetary systems of the age of Fomalhaut, suggesting that we are possibly
witnessing the effects of gravitational stirring due to the orbital evolution of hypothetical planet(s) around the star.
Accepted by PNAS
http://arxiv.org/pdf/2004.08736

16. HST survey of the Orion Nebula Cluster in the H2 O 1.4 µm absorption band: II. The

substellar IMF down to planetary masses
Mario Gennaro1 and Massimo Robberto1,2

Space Telescope Science Institute, 3700 San Martin Drive Baltimore, 21218, USA; 2 Department of Physics andAstronomy, The Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA

1E-mail contact: gennaro at stsci.edu
We exploit the ability of the Hubble Space Telescope to probe near infrared water absorption present in the atmosphereof low-mass stars, brown dwarfs and planetary mass objects to create a very pure sample of Orion Nebula Cluster(ONC) members, not affected by contamination from background stars and galaxies which lack water absorption.
Thanks to these data we infer the Initial Mass Function (IMF) of the ONC in the 0.005–1.4 M⊙ regime, i.e. down
to few Jupiter masses. The young age of the ONC, ∼1 Myr, provides a snapshot of the outcome of star formation
for the present-day conditions (metallicity, temperature, pressure) of typical Milky Way disk molecular clouds. We
demonstrate that the IMF of the ONC is well described by either a log-normal function or a broken power-law, withparameter values qualitatively in agreement with the canonical Chabrier or Kroupa forms for the Milky Way disk IMF.
This continuity in the mass distribution provides clues to the fact that the same physical processes may be regulating
formation of stars, brown dwarfs, and planetary mass objects. Both the canonical IMF forms under-predict theobserved number of very low mass members (below 0.1 M⊙ ), a regime where our data allows more precise constraints.
Nevertheless, we do not observe a rise or secondary peak in the brown dwarfs or planetary mass regimes. Our study
thus contradicts findings based on broad-band near infrared ground-based photometry, which predict an extremely
high number of free-floating planets, but likely suffer from unaccounted background contamination.
Accepted by ApJ
http://arxiv.org/pdf/2004.13920

17. Mon-735: A new low-mass pre-main sequence eclipsing binary in NGC 2264
Edward Gillen1 , Lynne A. Hillenbrand2 , John Stauffer3 , Suzanne Aigrain4 , Luisa Rebull5 and Ann
Marie Cody6
Astrophysics Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK; 2 Department of
Astronomy, California Institute of Technology, Pasadena, CA 91125, USA; 3 Spitzer Science Center, California Instituteof Technology, 1200 E California Blvd., Pasadena, CA 91125, USA; 4 Sub-department of Astrophysics, Department of
Physics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK; 5 Infrared Science Archive (IRSA), IPAC, 1200
E. California Blvd., California Institute of Technology, Pasadena, CA 91125, USA; 6 NASA Ames Research Center,
Moffet Field, CA 94035, USA118

E-mail contact: ecg41 at cam.ac.uk
We present Mon-735, a detached double-lined eclipsing binary (EB) member of the ∼3 Myr old NGC 2264 star forming region, detected by Spitzer. We simultaneously model the Spitzer light curves, follow-up Keck/HIRES radial
velocities, and the system’s spectral energy distribution to determine self-consistent masses, radii and effective temperatures for both stars. We find that Mon-735 comprises two pre-main sequence M dwarfs with component massesof M = 0.2918 ± 0.0099 and 0.2661 ± 0.0095 M⊙ , radii of R = 0.762 ± 0.022 and 0.748 ± 0.023 R⊙ , and effective
temperatures of Teff = 3260 ± 73 and 3213 ± 73 K. The two stars travel on circular orbits around their common centre of mass in P = 1.9751388 ± 0.0000050 days. We compare our results for Mon-735, along with another EB in
NGC 2264 (CoRoT 223992193), to the predictions of five stellar evolution models. These suggest that the lower mass
EB system Mon-735 is older than CoRoT 223992193 in the mass–radius diagram (MRD) and, to a lesser extent, inthe Hertzsprung–Russell diagram (HRD). The MRD ages of Mon-735 and CoRoT 223992193 are ∼7–9 and 4–6 Myr,
respectively, with the two components in each EB system possessing consistent ages.
Accepted by MNRAS
http://arxiv.org/pdf/2004.04753

18. Molecular globules in the Veil bubble of Orion. IRAM 30m

expanded maps of Orion A

12

CO, 13 CO, and C18 O 2–1

J.R. Goicoechea1 , C.H.M. Pabst2 , S. Kabanovic3 , M.G. Santa-Maria1 , N. Marcelino1 et al.
Instituto de Física Fundamental (CSIC). Calle Serrano 121-123, 28006, Madrid, Spain; 2 Leiden Observatory, Leiden
University, Leiden, The Netherlands; 3 I. Physikalisches Institut der Universität zu Köln, Cologne, Germany
1E-mail contact: javier.r.goicoechea at csic.es
Strong winds and ultraviolet (UV) radiation from O-type stars disrupt and ionize their molecular core birthplaces,
sweeping up material into parsec-size shells. Owing to dissociation by starlight, the thinnest shells are expected to host
low molecular abundances and therefore little star formation. Here, we expand previous maps taken with the IRAM
30m telescope and present square-degree 12 CO and 13 CO (J=2–1) maps of the wind-driven “Veil bubble” that surrounds
the Trapezium cluster and its natal Orion molecular core (OMC). Although widespread and extended CO emissionis largely absent from the Veil, we show that several CO “globules” exist and are embedded in the [CII]158µm-brightshell that confines the bubble. This includes the first detection of quiescent CO at negative LSR velocities in Orion.
Given the harsh UV irradiation conditions in this translucent material, the detection of CO globules is surprising.
These globules are small (R = 7, 100 AU), not massive (M = 0.3 M⊙ ), and are moderately dense: nH = 4 × 104 cm−3
(median values). They are confined by the external pressure of the shell, Pext /k ∼ 107 cm−3 K, and are likely
magnetically supported. They are either transient objects formed by instabilities or have detached from pre-existing
molecular structures, sculpted by the passing shock associated with the expanding shell and by UV radiation fromthe Trapezium. Some represent the first stages in the formation of small pillars, others of isolated small globules.
Although their masses do not suggest they will form stars, one globule matches the position of a known YSO. The
lack of extended CO in the “Veil shell” demonstrates that feedback from massive stars expels, agitates, and reprocesses
most of the disrupted molecular cloud gas, thereby limiting the star-formation rate in the region. The presence ofglobules is a result of this feedback.
Accepted by A&A
http://arxiv.org/pdf/2004.12938

19. Accretion driven turbulence in filaments II: Effects of self-gravity
Stefan Heigl1,2, Matthias Gritschneder1 and Andreas Burkert1,2
Universitaets-Sternwarte, Ludwig-Maximilians-Universitaet Muenchen, Scheinerstr. 1, 81679 Munich, Germany; 2
Max-Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany

1E-mail contact: heigl at usm.lmu.deWe extend our previous work on simulations with the code RAMSES on accretion driven turbulence by including
self-gravity and study the effects of core formation and collapse. We show that radial accretion onto filaments drives

19

turbulent motions which are not isotropic but radially dominated. In contrast to filaments without gravity, the velocity
dispersion of self-gravitating filaments does not settle in an equilibrium. Despite showing similar amounts of driven
turbulence, they continually dissipate their velocity dispersion until the onset of core formation. This difference isconnected to the evolution of the radius as it determines the dissipation rate. In the non-gravitational case filament
growth is not limited and its radius grows linearly with time. In contrast, there is a maximum extent in the selfgravitational case resulting in an increased dissipation rate. Furthermore, accretion driven turbulence shows a radial
profile which is anti-correlated with density. This leads to a constant turbulent pressure throughout the filament. As
the additional turbulent pressure does not have a radial gradient it does not contribute to the stability of filaments anddoes not increase the critical line-mass. However, this radial turbulence does affect the radius of a filament, adding to
the extent and setting its maximum value. Moreover, the radius evolution also affects the growth timescale of cores
which compared to the timescale of collapse of an accreting filament limits core formation to high line-masses.
Accepted by MNRAS
https://arxiv.org/pdf/2004.13736

20. The H2 O Spectrum of the Massive Protostar AFGL 2136 IRS 1 from 2 to 13 µm at

High Resolution: Probing the Circumstellar Disk

Nick Indriolo1 , D.A. Neufeld2 , A.G. Barr3 , A.C.A. Boogert4 , C.N. DeWitt5 et al.
ALMA Project, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa,
Mitaka, Tokyo 181-8588, Japan; 2 Department of Physics & Astronomy, Johns Hopkins University, Baltimore, MD
21218, USA; 3 Leiden Observatory, Leiden University, Leiden, The Netherlands; 4 Institute for Astronomy, Universityof Hawaii at Manoa, Honolulu, HI, 96822, USA; 5 USRA, SOFIA, NASA Ames Research Center MS 232-11, Moffett
Field, CA 94035, USA
1E-mail contact: nick.indriolo at nao.ac.jp
We have observed the massive protostar AFGL 2136 IRS 1 in multiple wavelength windows in the near-to-mid-infrared
at high (∼3 km s−1 ) spectral resolution using VLT+CRIRES, SOFIA+EXES, and Gemini North+TEXES. There isan abundance of H2 O absorption lines from the ν1 and ν3 vibrational bands at 2.7 µm, from the ν2 vibrational band at
6.1 µm, and from pure rotational transitions near 10–13 µm. Analysis of state-specific column densities derived fromthe resolved absorption features reveals that an isothermal absorbing slab model is incapable of explaining the relative
depths of different absorption features. In particular, the strongest absorption features are much weaker than expected,
indicating optical depth effects resulting from the absorbing gas being well-mixed with the warm dust that serves as
the “background” continuum source at all observed wavelengths. The velocity at which the strongest H2 O absorption
occurs coincides with the velocity centroid along the minor axis of the compact disk in Keplerian rotation recently
observed in H2 O emission with ALMA. We postulate that the warm regions of this dust disk dominate the continuum
emission at near-to-mid infrared wavelengths, and that H2 O and several other molecules observed in absorption areprobing this disk. Absorption line profiles are not symmetric, possibly indicating that the warm dust in the diskthat produces the infrared continuum has a non-uniform distribution similar to the substructure observed in 1.3 mm
continuum emission.
Accepted by A&A
http://arxiv.org/pdf/2004.05818

21. CAB: Towards the RNA-world in the interstellar medium – detection of urea, and searchof 2-amino-oxazole and simple sugars

Izaskun Jimenez-Serra1 , Jesus Martin-Pintado1 , Victor M. Rivilla2 , Lucas F. Rodriguez Almeida1 ,Elena R. Alonso Alonso3,4, Shaoshan Zeng5 , Emilio J. Cocinero3,4 , Sergio Martin6,7 , Miguel RequenaTorres8 , Rafael Martin-Domenech9 and Leonardo Testi10,2Centro de Astrobiologia (CSIC/INTA), Spain; 2 INAF-Osservatorio Astrofisico di Arcetri, Italy; 3 Universidad delPais Vasco (UPV-EHU), Spain; 4 Biofisika Institute (CSIC, UPV/EHU), Spain; 5 Queen Mary University of London,
UK; 6 European Southern Observatory, Chile; 7 Joint ALMA Observatory, Chile; 8 University of Maryland, USA; 9Harvard-Smithsonian Center for Astrophysics, USA; 10 European Southern Observatory, Germany
1E-mail contact: ijimenez at cab.inta-csic.es
20

In the past decade, Astrochemistry has witnessed an impressive increase in the number of detections of complex
organic molecules. Some of these species are of prebiotic interest such as glycolaldehyde, the simplest sugar, or amino
acetonitrile, a possible precursor of glycine. Recently, we have reported the detection of two new nitrogen-bearing
complex organics, glycolonitrile and Z-cyanomethanimine, known to be intermediate species in the formation processof ribonucleotides within theories of a primordial ribonucleic acid (RNA)-world for the origin of life. In this paper,
we present deep and high-sensitivity observations toward two of the most chemically rich sources in the Galaxy: aGiant Molecular Cloud in the center of the Milky Way (G+0.693-0.027) and a proto-Sun (IRAS16293-2422 B). Our
aim is to explore whether the key precursors considered to drive the primordial RNA-world chemistry, are also foundin space. Our high-sensitivity observations reveal that urea is present in G+0.693-0.027 with an abundance of about
5x10-11. This is the first detection of this prebiotic species outside a star-forming region. Urea remains undetected
toward the proto-Sun IRAS16293-2422 B (upper limit to its abundance of less than 2x10-11). Other precursors of the
RNA-world chemical scheme such as glycolaldehyde or cyanamide are abundant in space, but key prebiotic species
such as 2- amino-oxazole, glyceraldehyde or dihydroxyacetone are not detected in either source. Future more sensitive
observations targeting the brightest transitions of these species will be needed to disentangle whether these large
prebiotic organics are certainly present in space.
Accepted by Astrobiology
https://arxiv.org/pdf/2004.07834

22. A Detailed View of the Circumstellar Environment and Disk of the Forming O-star

AFGL 4176

K. G. Johnston1 , M. G. Hoare1 , H. Beuther2 , H. Linz2 , P. Boley3,4 , R. Kuiper5 , N. D. Kee6 and T. P.
Robitaille7
School of Physics & Astronomy, E.C. Stoner Building, The University of Leeds, Leeds, LS2 9JT, UK; 2 Max Planck
Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg, Germany; 3 Moscow Institute of Physics and Technology,
9 Institutskiy per., Dolgoprudny 141701, Russia; 4 Ural Federal University, 19 Mira St., Ekaterinburg 620075, Russia;
5
Institute of Astronomy and Astrophysics, Eberhard Karls University Teubingen, Auf der Morgenstelle 10, D-72076
Teubingen, Germany; 6 Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium; 7 Aperio
Software, Headingley Enterprise and Arts Centre, Bennett Road, Headingley, Leeds, LS6 3HN, UK

1E-mail contact: k.g.johnston at leeds.ac.uk
We present a detailed analysis of the disk and circumstellar environment of the forming O-type star AFGL 4176 mm1,
placing results from the Atacama Large Millimeter/submillimeter Array (ALMA) into context with multi-wavelength
data. With ALMA, we detect seventeen 1.2 mm continuum sources within 5′′ (21,000 au) of AFGL 4176 mm1. We
find that mm1 has a spectral index of 3.4±0.2 across the ALMA band, with >87 percent of its 1.2 mm continuum
emission from dust. The source mm2, projected 4200 au from mm1, may be a companion or a blueshifted knot in ajet. We also explore the morphological differences between the molecular lines with ALMA, detecting 203 lines from
25 molecules, which we categorize into several morphological types. Our results show that AFGL 4176 mm1 provides
an example of a forming O-star with a large and chemically complex disk, which is mainly traced by nitrogen-bearing
molecules. Lines that show strong emission on the blueshifted side of the disk are predominantly oxygen-bearing,which we suggest are tracing a disk accretion shock. The molecules C34 S, H2 CS and CH3 CCN trace a slow wide-angle
wind or dense structures in the outflow cavity walls. With the Australia Telescope Compact Array (ATCA), we detect
a compact continuum source (<2000 × 760 au) at 1.2 cm, associated with mm1, of which >96 percent is from ionizedgas. The ATCA NH3 (1,1) and (2,2) emission traces a large-scale (r∼0.5 pc) rotating toroid with the disk source mm1
in the blueshifted part of this structure offset to the NW.
Accepted by The Astrophysical Journal
http://arxiv.org/pdf/2004.13739

23. Unveiling the physical conditions in NGC 6910
Harmeen Kaur1 , Saurabh Sharma2 , Lokesh K. Dewangan3 , Devendra K. Ojha4 , Alok Durgapal1 andNeelam Panwar2
1

Center of Advanced Study, Department of Physics DSB Campus, Kumaun University Nainital, 263002, India; 221

Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263 002, India; 3 PhysicalResearch Laboratory, Navrangpura, Ahmedabad - 380 009, India; 4 Tata Institute of Fundamental Research (TIFR),
Homi Bhabha Road, Colaba, Mumbai - 400 005, India
E-mail contact: harmeenkaur.kaur229 at gmail.com
Deep and wide-field optical photometric observations along with multiwavelength archival datasets have been employed
to study the physical properties of the cluster NGC 6910. The study also examines the impact of massive stars totheir environment. The age, distance and reddening of the cluster are estimated to be ∼4.5 Myr, 1.72±0.08 kpc, andE(B − V )min = 0.95 mag, respectively. The mass function slope (Γ = −0.74 ± 0.15 in the cluster region is found to
be flatter than the Salpeter value (−1.35), indicating the presence of excess number of massive stars. The cluster also
shows mass segregation towards the central region due to their formation processes. The distribution of warm dust
emission is investigated towards the central region of the cluster, showing the signature of the impact of massive stars
within the cluster region. Radio continuum clumps powered by massive B-type stars (age range ∼ 0.07–0.12 Myr) aretraced, which are located away from the center of the stellar cluster NGC 6910 (age ∼ 4.5 Myr). Based on the valuesof different pressure components exerted by massive stars, the photoionized gas associated with the cluster is foundto be the dominant feedback mechanism in the cluster. Overall, the massive stars in the cluster might have triggered
the birth of young massive B-type stars in the cluster. This argument is supported with evidence of the observed age
gradient between the cluster and the powering sources of the radio clumps.
Accepted by ApJ
http://arxiv.org/pdf/2004.10500

24. Self-scattering of non-spherical dust grains
Florian Kirchschlager1 and Gesa H.-M. Bertrang2
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United
Kingdom; 2 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
1E-mail contact: f.kirchschlager at ucl.ac.uk
The understanding of (sub-)millimetre polarisation has made a leap forward since high-resolution imaging with the
Atacama Large (sub-)Mm Array (ALMA) came available. Amongst other effects, self-scattering (i.e., scattering ofthermal dust emission on other grains) is thought to be the origin of millimetre polarisation. This opens the firstwindow to a direct measurement of dust grain sizes in regions of optically thick continuum emission as it can be foundin protoplanetary disks and star-forming regions. However, the newly derived values of grain sizes are usually around∼100 µm and thus one order of magnitude smaller than those obtained from more indirect measurements as well as
those expected from theory (∼1 mm).
We see the origin of this contradiction in the applied dust model of today’s self-scattering simulations: a perfectcompact sphere. The aim of this study is to test our hypothesis by investigating the impact of non-spherical grain
shapes on the self-scattering signal.
We apply discrete dipole approximation simulations to investigate the influence of the grain shape on self-scatteringpolarisation in three scenarios: an unpolarised and polarised incoming wave under a fixed as well as a varying incident
polarisation angle.
We find significant deviations of the resulting self-scattering polarisation when comparing non-spherical to sphericalgrains. In particular, tremendous deviations are found for the polarisation signal of grains when observed outside
the Rayleigh regime, i.e. for >100 µm size grains observed at 870 µm wavelength. Self-scattering by oblate grains
produces higher polarisation degrees compared to spheres which challenges the interpretation of the origin of observed
millimetre polarisation. A (nearly) perfect alignment of the non-spherical grains is required to account for the observed
millimetre polarisation in protoplanetary disks. Furthermore, we find conditions under which the emerging scatteringpolarisation of non-spherical grains is flipped in orientation by 90◦ .
These results show clearly that the perfect compact sphere is an oversimplified model which reached its limit. Ourfindings point towards a necessary re-evaluation of the dust grain sizes derived from (sub-)mm polarisation.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2004.13742

2225. A family portrait of disk inner rims around Herbig Ae/Be stars: Hunting for warps,

rings, self shadowing, and misalignments in the inner astronomical units
J. Kluska1,2 , J.-P. Berger3 , F. Malbet3 , B. Lazareff3 , M. Benisty4,3 et al.

Instituut voor Sterrenkunde, 3001 Leuven, Belgium; 2 Univ. of Exeter, School of Physics and Astronomy, Exeter,EX4 4QL, UK; 3 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 4 Unidad Mixta Internacional
Franco-Chilena de Astronomía, CNRS/INSU UMI 3386 and Dept. de Astronomía, Univ. de Chile, Casilla 36-D
1

E-mail contact: jacques.kluska at kuleuven.be

The innermost astronomical unit in protoplanetary disks is a key region for stellar and planet formation, as exoplanet
searches have shown a large occurrence of close-in planets that are located within the first au around their hoststar. We aim to reveal the morphology of the disk inner rim using near-infrared interferometric observations withmilli-arcsecond resolution provided by infrared interferometry. We provide reconstructed images of 15 objects selectedfrom the Herbig AeBe survey carried out with PIONIER at the VLTI, using SPARCO. We find that 40% of thesystems are centrosymmetric at the angular resolution of the observations. For the rest of the objects, we findevidence for asymmetric emission due to moderate-to-strong inclination of a disk-like structure for 30% of the objects
and noncentrosymmetric morphology due to a nonaxisymmetric and possibly variable environment (30%). Amongthe systems with a disk-like structure, 20% show a resolved dust-free cavity. The image reconstruction process isa powerful tool to reveal complex disk inner rim morphologies. At the angular resolution reached by near-infraredinterferometric observations, most of the images are compatible with a centrally peaked emission (no cavity). For themost resolved targets, image reconstruction reveals morphologies that cannot be reproduced by generic parametricmodels. Moreover, the nonaxisymmetric disks show that the spatial resolution probed by optical interferometers makes
the observations of the near-infrared emission sensitive tore6(e)-1.33311(.13372679244.037(m)2.02416(a)-6.0185(d)1.34903(u26.

27. The dependence of episodic accretion on eccentricity during the formation of binarystars
Rajika L. Kuruwita1 , Christoph Federrath2 , and Troels Haugbølle1
Niels Bohr Institute, University of Copenhagen, Øster Voldgade 5-7, DK-1350, Copenhagen K, Denmark; 2 Research
School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
1E-mail contact: rajika.kuruwita at nbi.ku.dk
Aims. Investigate how the strength of episodic accretion bursts depends on eccentricity.
Methods. We investigate the binary trigger hypothesis in longer-period (>20yr) binaries by carrying out threedimensional magnetohydrodynamical (MHD) simulations of the formation of low-mass binary stars down to final
separations of ∼10AU, including the effects of gas turbulence and magnetic fields. We run two simulations with an
initial turbulent gas core of one solar mass each and two different initial turbulent Mach numbers, M = 0.1 and 0.2,
for 6500yr after protostar formation.
Results. We observe bursts of accretion at periastron during the early stages when the eccentricity of the binary systemis still high. We find that this correlation between bursts of accretion and passing periastron breaks down at laterstages, because of the gradual circularisation of the orbits. For eccentricities greater than e = 0.2, we observe episodic
accretion triggered near periastron. However, we do not find any strong correlation between the strength (the ratioof the burst accretion ratio to the quiescent accretion rate) of episodic accretion and eccentricity. We determine that
accretion events are likely triggered by torques between the rotation of the circumstellar disc and the approaching
binary stars. We compare our results with observational data of episodic accretion in short-period binaries and findgood agreement between our simulations and the observations.
Conclusions. We conclude that episodic accretion is a universal mechanism operating in eccentric young binary-starsystems, independent of separation, and should be observable in long-period binaries as well as in short-period binaries,
but that the strength will depend on the torques, and hence the separation at periastron.
Accepted by A&A
http://arxiv.org/pdf/2004.07523

28. Angular Momenta, Magnetization, and Accretion of Protostellar Cores
Aleksandra Kuznetsova1 , Lee Hartmann1 and Fabian Heitsch2
1

University of Michigan; 2 University of North Carolina - Chapel Hill

E-mail contact: kuza at umich.edu
Building on our previous hydrodynamic study of the angular momenta of cloud cores formed during gravitational
collapse of star-forming molecular gas in our previous work, we now examine core properties assuming ideal magnetohydrodynamics (MHD). Using the same sink-patch implementation for the Athena MHD code, we characterize thestatistical properties of cores, including the mass accretion rates, specific angular momenta, and alignments between
the magnetic field and the spin axis of the core on the 0.1 pc scale. Our simulations, which reproduce the observed
relation between magnetic field strength and gas density, show that magnetic fields can help collimate low density flows
and help seed the locations of filamentary structures. Consistent with our previous purely hydrodynamic simulations,stars (sinks) form within the heterogeneous environments of filaments, such that accretion onto cores is highly episodic
leading to short-term variability but no long-term monotonic growth of the specific angular momenta. With statistical characterization of protostellar cores properties and behaviors, we aim to provide a starting point for building
more realistic and self-consistent disk formation models, helping to address whether magnetic fields can prevent thedevelopment of (large) circumstellar disks in the ideal MHD limit.
Accepted by ApJ
https://arxiv.org/pdf/2003.13697

29. On the settling of small grains in dusty discs: analysis and formulas
Guillaume Laibe1 ,Charles-Edouard Bréhier2 and Maxime Lombart1
1

École normale supérieure de Lyon, CRAL, UMR CNRS 5574, Université de Lyon , 46 Allée d’Italie, 69364 Lyon
24

Cedex 07, France; 2 Univ Lyon, CNRS, Université Claude Bernard Lyon 1, UMR5208, Institut Camille Jordan, F-69622
Villeurbanne, France
E-mail contact: guillaume.laibe at ens-lyon.fr
Instruments achieve sharper and finer observations of micron-in-size dust grains in the top layers of young stellar
discs. To provide accurate models, we revisit the theory of dust settling for small grains, when gas stratification, dust
inertia and finite correlation times for the turbulence should be handled simultaneously. We start from a balance offorces and derive distributions at steady-state. Asymptotic expansions require caution since limits do not commute.
In particular, non-physical bumpy distributions appear when turbulence is purely diffusive. This excludes very shortcorrelation times for real discs, as predicted by numerical simulations.
Accepted by MNRAS
http://arxiv.org/pdf/2004.03689

30. Star Cluster Formation in Orion A
Wanggi Lim1 , Fumitaka Nakamura2 , Benjamin Wu2 , Thomas G. Bisbas3,4,5 , Jonathan C. Tan6,7 , Edward
Chambers1 , John Bally8 , Shuo Kong9 , Peregrine McGehee10 , Dariusz C. Lis11 , Volker Ossenkopf-Okada4
and Álvaro Sánchez-Monge4
SOFIA-USRA, NASA Ames Research Center, MS 232-12, Moffett Field, CA 94035, USA; 2 National Astronomical
Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; 3 National Observatory of Athens, Institute for Astronomy,
Astrophysics, Space Applications and Remote Sensing, Penteli, 15236, Athens, Greece; 4 I. Physikalisches Institut,
Universität zu Köln, Zülpicher Straße 77, Germany; 5 Department of Physics, Aristotle University of Thessaloniki,
GR-54124 Thessaloniki, Greece; 6 Department of Space, Earth & Environment, Chalmers University of Technology,
Gothenburg, Sweden; 7 Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA; 8 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO, USA; 9 Steward Observatory,
University of Arizona, AZ 85719; 10 Department of Earth and Space Sciences, College of the Canyons, Santa Clarita,
CA 91355, USA; 11 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena,
CA 91109, USA
1E-mail contact: wanggi.lim.astro at gmail.com
We introduce new analysis methods for studying the star cluster formation processes in Orion A, especially examining
the scenario of a cloud-cloud collision. We utilize the CARMA-NRO Orion survey 13 CO (1-0) data to compare
molecular gas to the properties of YSOs from the SDSS III IN-SYNC survey. We show that the increase of v13CO −vYSO
and Σ scatter of older YSOs can be signals of cloud-cloud collision. SOFIA-upGREAT 158µm [Cii] archival data
toward the northern part of Orion A are also compared to the 13 CO data to test whether the position and velocity
offsets between the emission from these two transitions resemble those predicted by a cloud-cloud collision model.
We find that the northern part of Orion A, including regions ONC-OMC-1, OMC-2, OMC-3 and OMC-4, shows
qualitative agreements with the cloud-cloud collision scenario, while in one of the southern regions, NGC1999, there
is no indication of such a process in causing the birth of new stars. On the other hand, another southern cluster,L1641N, shows slight tendencies of cloud-cloud collision. Overall, our results support the cloud-cloud collision process
as being an important mechanism for star cluster formation in Orion A.
Accepted by PASJ
http://arxiv.org/pdf/2004.03668

31. A Cold and Diffuse Giant Molecular Filament in the Region of l = 41◦ , b = −1◦
Liang-Hao Lin1,2 , Hong-Chi Wang1,2 , Yang Su1 , Chong Li1,3 and Ji Yang1,2
1
Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua
Road, Qixia District, Nanjing 210033, P.R. China; 2 School of Astronomy and Space Science, University of Scienceand Technology of China, 96 Jinzhai Road, Hefei 230026, P.R. China; 3 University of Chinese Academy of Sciences,
19A Yuquan Road, Shijingshan District, Beijing 100049, P.R. China

E-mail contact: lhlin at pmo.ac.cn

25Data of 12 CO/13 CO/C18 O J = 1 → 0 emission toward the Galactic plane region of l = 35◦ to 45◦ and b = −5◦ to+5◦ are available with the Milky Way Imaging Scroll Painting (MWISP) project. Using the data, we found a giant
molecular filament (GMF) around l ≈ 38 ∼ 42◦ , b ≈ −3.5 ∼ 0◦ , VLSR ≈ 27 ∼ 40 km s−1 , named the GMF MWISP
G041-01. At a distance of 1.7 kpc, the GMF is about 160 pc long. With a median excitation temperature about
7.5 K and a median column density about 1021 cm−2 , this GMF is very cold and very diffuse compared to known
GMFs. Using the morphology in the data cube, the GMF is divided into four components among which three show
filamentary structure. Masses of the components are 103 ∼ 104 M⊙ , with a total mass for the whole filament being
about 7 × 104M⊙ from the LTE method. 13 CO cores inside each component are searched. Virial parameters are about
2.5 for these cores and have a power-law index of -0.34 against the mass. The mass fraction of dense cores traced
by 13 CO to the diffuse clouds traced by 12 CO are about 7% for all components of the GMF. We found signatures ofpossible large scale filament-filament collision in the GMF.
Accepted by Research in Astronomy and Astrophysics
http://arxiv.org/pdf/2004.06926

32. Pebble-driven Planet Formation around Very Low-mass Stars and Brown Dwarfs
Beibei Liu1 , Michiel Lambrechts1 , Anders Johansen1 , Ilaria Pascucci2 and Thomas Henning3
Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund,
Sweden; 2
1

33.

E-mail contact: xinglv.nju at gmail.com
We report ALMA Band 6 continuum observations of 2000 AU resolution toward four massive molecular clouds in theCentral Molecular Zone of the Galaxy. To study gas fragmentation, we use the dendrogram method to identify cores
as traced by the dust continuum emission. The four clouds exhibit different fragmentation states at the observed
resolution despite having similar masses at the cloud scale (∼1–5 pc). Assuming a constant dust temperature of
20 K, we construct core mass functions of the clouds and find a slightly top-heavy shape as compared to the canonicalinitial mass function, but we note several significant uncertainties that may affect this result. The characteristic spatial
separation between the cores as identified by the minimum spanning tree method, ∼104 AU, and the characteristic coremass, 1–7 M⊙ , are consistent with predictions of thermal Jeans fragmentation. The three clouds showing fragmentation
may be forming OB associations (stellar mass ∼103 M⊙ ). None of the four clouds under investigation seem to be
4
currently able to form massive star clusters like the Arches and the Quintuplet (>∼10 M⊙ ), but they may form suchclusters by further gas accretion onto the cores.
Accepted by ApJ Letters
http://arxiv.org/pdf/2004.09532

34. Using the Modified Lognormal Power Law Distribution to Model the Mass Function of

NGC 1711

Deepakshi Madaan1 , Sophia Lianou2,1 and Shantanu Basu1
1

University of Western Ontario, London, Canada.; 2 National Observatory of Athens, Penteli, Greece.

E-mail contact: basu at uwo.ca
A determination of the mass function (MF) of stellar clusters can be quite dependent on the range of measured masses,
the fitting technique, and the analytic function that is being fit to the data. Here, we use HST/WFPC2 data of NGC
1711, a stellar cluster in the Large Magellanic Cloud, as a test case to explore a range of possible determinations of
the MF from a single dataset. We employ the analytic modified lognormal power-law (MLP) distribution, a hybrid
function that has a peaked lognormal-like body and a power-law tail at intermediate and high masses. A fit with
the MLP has the advantage that the resulting best-fit function can be either a hybrid function, a pure lognormal,
or a pure power law, in different limits of the function. The completeness limit for the observations means thatthe data contains masses above ∼ 0.90 M⊙. In this case, the MLP fits yield essentially a pure power-law MF. We
demonstrate that the nonlinear regression/least-squares approach is not justified since the underlying assumptions are
not satisfied. By using maximum likelihood estimation, which is independent of binning, we find a best-fit functional
form dN/d ln m ∝ m−α , where α = 1.72±0.05 or 1.75±0.05 for two different theoretical isochrone models, respectively.
Furthermore, we explore the possibility of systematic errors in the determination of the power-law index due to thedepth of the observations. When we combine the observational data with artificially generated data from the lognormal
Chabrier IMF for masses below 0.90 M⊙, the best fit MLP is a hybrid function but with a steeper asymptotic slopei.e., α = 2.04 ± 0.07. This illustrates the systematic uncertainties in commonly used MF parameters that can dependon the range of data that is fitted.
Accepted by ApJ
https://arxiv.org/pdf/2004.05701

35. The Evolution Of The Inner Regions Of Protoplanetary Disks
Ezequiel Manzo-Martínez1 , Nuria Calvet2 , Jesús Hernández3 , Susana Lizano1 , Ramiro Franco Hernández4 ,Christopher J. Miller2, Karina Maucó5,6 , César Briceño7 and Paola D’Alessio1
Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apartado Postal 3-72,
C.P. 58089 Morelia, Michoacán, México; 2 Department of Astronomy, University of Michigan, 323 West Hall, 1085
South University Avenue, Ann Arbor, MI 48109, USA; 3 Instituto de Astronomía, Universidad Nacional Autónoma
de México, Ensenada, México; 4 Instituto de Astronomía y Meteorología, Universidad de Guadalajara, México; 5
Núcleo Milenio Formación Planetaria - NPF, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile;
6
Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, 5030
Casilla, Valparaíso, Chile; 7 Cerro Tololo Inter-American Observatory, Casilla 603, La Serena 1700000, Chile
127

E-mail contact: Ezequiel Manzo-Martínez at e.manzo@irya.unam.mx
We present a study of the evolution of the inner few astronomical units of protoplanetary disks around low-mass stars.
We consider nearby stellar groups with ages spanning from 1 to 11 Myr, distributed into four age bins. Combining
PANSTARSS photometry with spectral types we derive the reddening consistently for each star, which we use (1) tomeasure the excess emission above the photosphere with a new indicator of IR excess and (2) to estimate the massaccretion rate (Ṁ ) from the equivalent width of the Hα line. Using the observed decay of Ṁ as a constrain to fix theinitial conditions and the viscosity parameter of viscous evolutionary models, we use approximate Bayesian modelingto infer the dust properties that produce the observed decrease of the IR excess with age, in the range between 4.5 and24 µm. We calculate an extensive grid of irradiated disk models with a two-layered wall to emulate a curved dust inneredge and obtain the vertical structure consistent with the surface density predicted by viscous evolution. We find thatthe median dust depletion in the disk upper layers is ǫ ∼ 3 × 10−3 at 1.5 Myr, consistent with previous studies, and it
decreases to ǫ ∼ 3 × 10−4 by 7.5 Myr. We include photoevaporation in a simple model of the disk evolution and findthat a photoevaporative wind mass-loss rate of ∼ 1 − 3 × 10−9 M⊙ yr−1 agrees with the decrease of the disk fraction
with age reasonably well. The models show the inward evolution of the H2 O and CO snowlines.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2004.02916

36. Planet formation by pebble accretion in ringed disks
A. Morbidelli1
1

Département Lagrange, University of Nice – Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France

E-mail contact: alessandro.morbidelli at obs-nice.fr
Context. Pebble accretion is expected to be the dominant process for the formation of massive solid planets, suchas the cores of giant planets and super-Earths. So, far, this process has been studied under the assumption that
dust coagulates and drifts throughout the full protoplanetary disk. However, observations show that many disks are
structured in rings that may be due to pressure maxima, preventing the global radial drift of the dust.
Aims. We study how the pebble-accretion paradigm changes if the dust is confined in a ring.
Results. Planet Type-I migration is stopped in a ring, but not necessarily at its center. If the entropy-driven corotation
torque is desaturated, the planet is located in a region with a low density of dust, which severely limits its accretion
rate. If instead the planet is near the ring’s center, its accretion rate can be similar to the one it would have in aclassic (ring-less) disk of equivalent dust density. However, the growth rate of the planet is limited by the diffusion ofdust in the ring and the final planet’s mass is bounded by the total ring’s mass. The DSHARP rings are too far fromthe star to allow the formation of massive planets within the disk’s lifetime. However, a similar ring rescaled to 5 AU
could lead to the formation of a planet incorporating the full ring’s mass in less than 1/2 My.
Conclusions. The existence of rings may not be an obstacle to planet formation by pebble-accretion. However, foraccretion to be effective the resting position of the planet has to be relatively near the ring’s center and the ring needs
to be not too far from the central star. The formation of planets in rings can explain the existence of giant planetswith core masses smaller than the so-called pebble isolation mass.
Accepted by A&A
http://arxiv.org/pdf/2004.04942

37. FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope(FUGIN). VII. molecular fraction of HI clouds

Hiroyuki Nakanishi1 , Shinji Fujita2 , Kengo Tachihara2 , Natsuko Izumi3 , Mitsuhiro Matsuo4 et al.
Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto Kagoshima; 2 Department of
Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; 3 College of Science, Ibaraki
University, Bunkyo 2-1-1, Mito, Ibaraki, 310-8512, Japan1

E-mail contact: hnakanis at sci.kagoshima-u.ac.jp
In this study, we analyze molecular gas formation in neutral atomic hydrogen (HI) clouds using the latest CO data

28

obtained from the four-beam receiver system on a 45-m telescope (FOREST) unbiased Galactic plane imaging survey
with the Nobeyama 45-m telescope (FUGIN) and HI data taken from the Very Large Array (VLA) Galactic plane
survey (VGPS). We applied a dendrogram algorithm to the HI data cube to identify HI clouds, and we calculated the
HI mass and molecular gas mass by summing the CO line intensity within each HI cloud. On the basis of the results,
we created a catalog of 5,737 identified HI clouds with local standard of rest (LSR) velocity of VLSR ≤ −20 km s−1 in
Galactic longitude and latitude ranges of 20◦ ≤ l ≤ 50◦ and −1◦ ≤ b ≤ 1◦ , respectively. We found that most of the
HI clouds are distributed within a Galactocentric distance of 16 kpc, most of which are in the Cold Neutral Medium(CNM) phase. In addition, we determined that the high-mass end of the mass HI function is well fitted with thepower-law function with an index of 2.3. Although two sequences of self-gravitating and diffuse clouds are expected toappear in the Mtot -MH2 diagram according to previous works based on a plane-parallel model, the observational data
show only a single sequence with large scattering within these two sequences. This implies that most of the clouds
are mixtures of these two 1(l)0.671454()-287.75(t)27.4438(w)av-3.1391.334386.757(t)27.4468(n)10160.035
types of clouds.iagre144 6.33311(q)-2ho

38.

39.

We present a detailed characterization of 2MASS J04435750+3723031, a low-mass companion orbiting the young M2star, 2MASS J04435686+3723033, at 7.′′ 6 (550 AU) with potential membership in the 23 Myr β Pictoris moving group(βPMG). Using near-infrared spectroscopy of the companion from IRTF/SpeX we have found a spectral type of M6±1
and indications of youth through age-sensitive absorption lines and a low surface gravity index (VL-G). A young age is
supported by Hα emission and lithium absorption in the host. We re-evaluate the membership of this system and findthat it is a marginally consistent kinematic match to the βPMG using Gaia parallaxes and new radial velocities forthe host and companion. If this system does belong to the βPMG, it would be a kinematic outlier and the companion
would be over-luminous compared to other similar ultracool objects like PZ Tel B; this would suggest 2M0443+3723
B could be a close brown dwarf binary (≈52+52 MJup if equal-flux, compared with 99±5 MJup if single), and would
make it the sixth substellar companion in this group. To test this hypothesis, we acquired NIR AO images withKeck II/NIRC2, but they do not resolve the companion to be a binary down to the diffraction limit of ∼3 AU. If
2M0443+3723 AB does not belong to any moving group then its age is more uncertain. In this case it is still young(<∼30 Myr), and the implied mass of the companion would be between ∼30–110 MJup .
Accepted by ApJ
http://arxiv.org/pdf/2004.07250

40. HST astrometry in the Orion Nebula Cluster: census of low-mass runaways
Imants Platais1 , Massimo Robberto2 , Andrea Bellini2, Vera Kozhurina-Platais2 , Mario Gennaro2 et al.
Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218,
USA; 2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
1E-mail contact: imants at jhu.edu
We present a catalog of high-precision proper motions in the Orion Nebula Cluster (ONC), based on Treasury Program
observations with the Hubble Space Telescope’s (HST) ACS/WFC camera. Our catalog contains 2,454 objects in themagnitude range of 14.2 < mF775W < 24.7, thus probing the stellar masses of the ONC from ∼0.4 M⊙ down to∼0.02 M⊙ over an area of ∼550 arcmin2 . We provide a number of internal velocity dispersion estimates for the ONC
that indicate a weak dependence on the stellar location and mass. There is good agreement with the published velocity
dispersion estimates, although nearly all of them (including ours at σv,x = 0.94 and σv,y = 1.25 mas yr−1 ) might bebiased by the overlapping young stellar populations of Orion A. We identified 4 new ONC candidate runaways basedon HST and the Gaia DR2 data, all with masses less than ∼1 M⊙ . The total census of known candidate runaway
sources is 10 — one of the largest samples ever found in any Milky Way open star cluster. Surprisingly, none ofthem has the tangential velocity exceeding 20 km s−1 . If most of them indeed originated in the ONC, it may compel
re-examination of dynamical processes in very young star clusters. It appears that the mass function of the ONC is
not significantly affected by the lost runaways.
Accepted by AJ
http://arxiv.org/pdf/2004.14472

41. Exocomets: A spectroscopic survey
I. Rebollido1, C. Eiroa1,2 , B. Montesinos3 , J. Maldonado4 , E. Villaver1 , O. Absil5 , A. Bayo6,7 , H.
Cánovas8 , A. Carmona9 , Ch. Chen10 , S. Ertel11 , Th. Henning12 , D.P. Iglesias6,7, R. Launhardt12 , R.
Liseau13 , G. Meeus1 , A. Moór14,15 , A. Mora16 , J. Olofsson6,7, G. Rauw5 and P. Riviere-Marichalar17
Dpto. Física Teórica, Universidad Autónoma de Madrid, Cantoblanco,28049 Madrid, Spain; 2 Observatorio Astrónomico de Calar Alto, CAHA, 04550 Gérgal, Almería, Spain; 3 Centro de Astrobiología (CAB, CSIC-INTA),ESAC Campus Camino Bajo del Castillo, s/n, Villanueva de la Cañada, 28692, Madrid, Spain; 4 INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy; 5 STAR Institute, Université de Liège,
F.R.S.-FNRS, 19c Allée du Six Août, B-4000 Liège, Belgium; 6 Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, 5030 Casilla, Valparaíso, Chile; 7 Núcleo Milenio de Formación Planetaria - NPF,
Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile; 8 European Space Astronomy Centre (ESA),PO Box, 78, 28691 Villanueva de la Cañada, Madrid, Spain; 9 Université de Toulouse, UPS-OMP, IRAP, Toulouse
F-31400, France; 10 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21212, USA; 11 Steward
130

Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA; 12 Max-Planck-Institut für
Astronomie (MPIA), Königstuhl 17, D-69117 Heidelberg, Germany; 13 Department of Space, Earth and Environment,
Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden; 14 Konkoly Observatory,
Research Centre for Astronomy and Earth Sciences, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary; 15
ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary; 16 Aurora
Technology B.V. for ESA, ESA-ESAC, Villanueva de la Cañada, 28691, Madrid, Spain; 17 Observatorio Astronómico
Nacional (OAN-IGN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain
E-mail contact: isabel.rebollido at uam.es
While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging.
Since the discovery of sporadic events interpreted as exocomets (Falling Evaporating Bodies) around β Pic in theearly 80s, only ∼ 20 stars have been reported to host exocomet-like events. We aim to expand the sample of known
exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometaryactivity. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the
spectral type range from B8 to G8. The data have been collected in 14 observing campaigns expanding over 2 years
from both hemispheres. We have analysed the Ca ii K & H and Na i D lines in order to search for non-photosphericabsorptions originated in the circumstellar environment, and for variable events that could be caused by outgassingof exocomet-like bodies. We have detected non-photospheric absorptions towards 50% of the sample, attributing acircumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas is detected in the metallic
lines inspected via narrow stable absorptions, and/or variable blue-/red-shifted absorption events. Such variable eventswere found in 18 stars in the Ca ii and/or Na i lines; 6 of them are reported in the context of this work for the firsttime. In some cases the variations we report in the Ca ii K line are similar to those observed in β Pic. While we do
not find a significant trend with the age or location of the stars, we do find that the probability of finding CS gas
in stars with larger vsin i is higher. We also find a weak trend with the presence of near-infrared excess, and withanomalous (λ Boo-like) abundances, but this would require confirmation by expanding the sample.
Accepted by Astronomy & Astrophysics
https://arxiv.org/pdf/2003.11084

42. Rotation of Low-Mass Stars in Taurus with K2
L. M. Rebull1 , J. R. Stauffer2 , A. M. Cody3 , L. A. Hillenbrand4 , J. Bouvier5 , N. Rogerro5 and T. J.
David6Caltech-IPAC/IRSA, Pasadena, CA; 2 Caltech-IPAC/SSC, Pasadena, CA; 3 Bay Area Environmental ResearchInstitute, Petaluma, CA; 4 Astronomy Department, Caltech, Pasadena, CA; 5 Université de Grenoble, IPAG, Grenoble,
France; 6 Center for Computational Astrophysics, Flatiron Institute, New York, NY
1

E-mail contact: rebull at ipac.caltech.edu
We present an analysis of K2 light curves (LCs) from Campaigns 4 and 13 for members of the young (∼3 Myr) Taurus
association, in addition to an older (∼30 Myr) population of stars that is largely in the foreground of the Taurus
molecular clouds. Out of 156 of the highest-confidence Taurus members, we find that 81% are periodic. Our sampleof young foreground stars is biased and incomplete, but nearly all (37/38) are periodic. The overall distribution ofrotation rates as a function of color (a proxy for mass) is similar to that found in other clusters: the slowest rotators areamong the early M spectral types, with faster rotation towards both earlier FGK and later M types. The relationshipbetween period and color/mass exhibited by older clusters such as the Pleiades is already in place by Taurus age.
The foreground population has very few stars, but is consistent with the USco and Pleiades period distributions. As
found in other young clusters, stars with disks rotate on average slower, and few with disks are found rotating fasterthan ∼2 d. The overall amplitude of the light curves decreases with age and higher mass stars have generally lower
amplitudes than lower mass stars. Stars with disks have on average larger amplitudes than stars without disks, though
the physical mechanisms driving the variability and the resulting light curve morphologies are also different between
these two classes.
Accepted by AJ
http://arxiv.org/pdf/2004.04236

3143. HST survey of the Orion Nebula Cluster in the H2 O 1.4 µm absorption band: I. A

census of substellar and planetary mass objects

Massimo Robberto1,2 , Mario Gennaro1 , Maria Giulia Ubeira Gabellini3,4, Lynne A. Hillenbrand5 ,Camilla Pacifici1 , Leonardo Ubeda1 , Morten Andersen6 , Travis Barman7 , Andrea Bellini1, Nicola Da
Rio8 , Selma E. de Mink9,10 , Giuseppe Lodato3 , Carlo Felice Manara4 , Imants Platais2 , Laurent Pueyo1 ,David R. Soderblom1 , Giovanni M. Strampelli2,1,11, Jonathan C. Tan12 and Leonardo Testi4
Space Telescope Science Institute, 3700 San Martin Dr, Baltimore, MD 21218, USA; 2 Johns Hopkins University,
3400 N. Charles Street, Baltimore, MD 21218, USA; 3 Dipartimento di Fisica, Università Degli Studi di Milano,
Via Giovanni Celoria, 16, 20133 Milano, MI, Italy; 4 European Southern Observatory, Karl-Schwarzschild-Str. 2,
85784 Garching, Germany; 5 California Institute of Technology, MC 249-17, 1200 East California Blvd, Pasadena
CA 91125, USA; 6 Gemini Observatory, NSF’s National Optical-Infrared Astronomy Research Laboratory, Casilla603, La Serena, Chile; 7 Lunar and Planetary Laboratory, 1629 E University Blvd, Tucson AZ 85721-0092, USA;
8
University of Virginia, Department of Astronomy, P.O. Box 400325, 530 McCormick Road, Charlottesville, VA
22904-4325, USA; 9 Center for Astrophysics, Harvard-Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA;
10
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098XH Amsterdam, The
Netherlands; 11 Department of Astrophysics, University of La Laguna, Av. Astrofsico Francisco Snchez, 38200 San
Cristbal de La Laguna, Tenerife, Canary Islands, Spain; 12 Dept. of Astronomy, University of Virginia, Charlottesville,
Virginia, USA
1E-mail contact:
In order to obtain a complete census of the stellar and sub-stellar population, down to a few MJup in the ∼ 1 Myr old
Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with
the F139M and F130N filters. These bandpasses correspond to the 1.4 µm H2 O absorption feature and an adjacentline-free continuum region. Out of 4,504 detected sources, 3,352 (about 75%) appear fainter than m130 = 14 (Vegamag) in the F130N filter, a brightness corresponding to the hydrogen-burning limit mass (M ≃ 0.072 M⊙ ) at ∼ 1 Myr.
Of these, however, only 742 sources have a negative F130M-139N color index, indicative of the presence of H2 O vapor
in absorption, and can therefore be classified as bona-fide M and L dwarfs, with effective temperatures T <∼ 2850 K
at an assumed 1 Myr cluster age. On our color-magnitude diagram, this population of sources with H2 O absorption
appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive
F130M-F139N color index, and can be traced down to the sensitivity limit of our survey, m130 ≃ 21.5, corresponding
to a 1 Myr old ≃ 3 MJup planetary mass object under about 2 magnitudes of visual extinction. Theoretical modelsof the BT-Settl family predicting substellar isochrones of 1, 2 and 3 Myr (down to ∼ 1 MJup ) fail to reproduce theobserved H2 O color index at M <∼ 20 MJup . We perform a Bayesian analysis to determine extinction, mass andeffective temperature of each sub-stellar member of our sample, together with its membership probability.
Accepted by The Astrophysical Journl
http://arxiv.org/pdf/2004.13915

44. The efficiency of dust trapping in ringed proto-planetary discs
Giovanni P. Rosotti1 , Richard Teague2,3 , Cornelis Dullemond4 , Richard A. Booth5 and Cathie Clarke5
Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, the Netherlands; 2 Department of
Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA; 3 Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138 USA; 4 Zentrum für Astronomie, Institut
für Theoretische Astrophysik, Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany; 5 Instituteof Astronomy, Madingley Road, Cambridge, CB3 0HA, UK
1E-mail contact: rosotti at strw.leidenuniv.nl
When imaged at high-resolution, many proto-planetary discs show gaps and rings in their dust sub-mm continuum
emission profile. These structures are widely considered to originate from local maxima in the gas pressure profile.
The properties of the underlying gas structures are however unknown. In this paper we present a method to measure
the dust-gas coupling α/St and the width of the gas pressure bumps affecting the dust distribution, applying highprecision techniques to extract the gas rotation curve from emission lines data-cubes. As a proof-of-concept, we thenapply the method to two discs with prominent sub-structure, HD163296 and AS 209. We find that in all cases the gas
32structures are larger than in the dust, confirming that the rings are pressure traps. Although the grains are sufficiently
decoupled from the gas to be radially concentrated, we find that the degree of coupling of the dust is relatively good
(α/St ∼ 0.1). We can therefore reject scenarios in which the disc turbulence is very low and the dust has grownsignificantly. If we further assume that the dust grain sizes are set by turbulent fragmentation, we find high valuesof the α turbulent parameter (α ∼ 10−2 ). Alternatively, solutions with smaller turbulence are still compatible with
our analysis if another process is limiting grain growth. For HD163296, recent measurements of the disc mass suggestthat this is the case if the grain size is 1mm. Future constraints on the dust spectral indices will help to discriminate
between the two alternatives.
Accepted by MNRAS
http://arxiv.org/pdf/2004.11394

45. Distance, magnetic field and kinematics of the filamentary cloud LDN 1157
Ekta Sharma1,2 , G. Maheswar1 , A. Soam3 , Chang Won Lee4,5 , Kim, Shinyoung4 , Tuhin Ghosh6 , Tej,
A7 , Kim, G9 , Neha S.8 and Piyali Saha1
Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India; 2 Department of Physics and Astrophysics,
University of Delhi, Delhi 110007, India; 3 SOFIA Science Centre, USRA, NASA Ames Research Centre, MS-12,
N232, Moffett Field, CA 94035, USA; 4 Korea Astronomy & Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu,
Daejeon, Republic of Korea; 5 University of Science and Technology, Korea, 217 Gajeong-ro, Yuseong-gu, Daejeon
34113, Republic of Korea; 6 School of Physical Sciences, National Institute of Science Education and Research, HBNI,
Jatni 752050, Odisha, India; 7 Indian Institute of Space Science and Technology, Valiamala P.O., Thiruvananthapuram- 695547 Kerala, India; 8 School of Space Research, Kyung-Hee University, 1732, Deogyeong-daero, Giheung-gu,
Yongin-si, Gyeonggi-do 17104, Korea; 9 Nobeyama Radio Observatory, National Astronomical Observatory of Japan,
National Institutes of Natural Sciences, Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan1

E-mail contact: ektasharma.astro at gmail.com
LDN 1157 is one of the several clouds situated in the cloud complex, LDN 1147/1158. The cloud presents a comashaped morphology with a well-collimated bipolar outflow emanating from a Class 0 protostar, LDN 1157-mm, residing
deep inside the cloud. The main goals of this work are (a) to map the inter-cloud magnetic field (ICMF) geometry of
the region surrounding LDN1157 to investigate its relationship with the cloud morphology, with the outflow direction
and with the core magnetic field (CMF) geometry inferred from the mm- and sub-mm polarization results from theliterature, and (b) to investigate the kinematic structure of the cloud. We carried out optical (R-band) polarization
observations of the stars projected on the cloud to map the parsec-scale magnetic field geometry and made spectroscopic
observations of the entire cloud in 12 CO, C18 O and N2 H+ (J=1-0) lines to investigate its kinematic structure. We
obtained a distance of 340±3 pc to the LDN 1147/1158, complex based on the Gaia DR2 parallaxes and proper motion
values of the three young stellar objects (YSOs) associated with the complex. A single filament of ∼1.2 pc in length(traced by the Filfinder algorithm) and ∼0.09 pc in width (estimated using the Radfil algorithm) is found to run allalong the coma-shaped cloud. Based on the relationships between the ICMF, CMF, filament orientations, outflow
direction, and the presence of an hour-glass morphology of the magnetic field, it is likely that the magnetic field had
played an important role in the star formation process in LDN 1157. LDN 1157-mm is embedded in one of the twohigh density peaks detected using the Clumpfind algorithm. Both the detected clumps are lying on the filament andshow a blue-red asymmetry in the 12 CO line. The C18 O emission is well correlated with the filament and presents
a coherent structure in velocity space. Combining the proper motions of the YSOs and the radial velocity of LDN
1147/1158 and an another complex LDN 1172/1174 which is situated ∼2◦ east of it, we found that both the complexes
are moving collectively toward the Galactic plane. The filamentary morphology of the east-west segment of LDN 1157
may have formed as a result of mass lost by ablation due to the interaction of the moving cloud with the ambientinterstellar medium.
Accepted by Astronomy & Astrophysics

46. A detailed analysis on the cloud structure and dynamics in Aquila Rift
Tomomi Shimoikura1 , Kazuhito Dobashi2 , Yoshiko Hatano2 and Fumitaka Nakamura3
1

Otsuma Women’s University; 2 Tokyo Gakugei University; 3 National Astronomical Observatory of Japan33

E-mail contact: ikura at otsuma.ac.jp
We present maps in several molecular emission lines of a 1 square-degree region covering the W40 and Serpens
South molecular clouds belonging to the Aquila Rift complex. The observations were made with the 45 m telescopeat the Nobeyama Radio Observatory. We found that the 12 CO and 13 CO emission lines consist of several velocity
components with different spatial distributions. The component that forms the main cloud of W40 and Serpens South,
which we call the “main component", has a velocity of VLSR ≃ 7 km s−1 . There is another significant component at
VLSR ≃ 40 km s−1 , which we call the “40 km s−1 component". The latter component is mainly distributed around two
young clusters: W40 and Serpens South. Moreover, the two components look spatially anti-correlated. Such spatial

47.

48.

the mass function of the binaries, finding differences between the mass distribution of binaries and single stars andbetween primary and companion mass distributions. The mass ratio shows a bottom-heavy distribution with medianvalue of Mc /Mp ∼ 0.25. Overall our results suggest that ONC binaries may represent a template for the typical
population of field binaries, supporting the hypothesis that the ONC may be regarded as a most typical star forming
region in the Milky Way.
Accepted by Astrophysical Journal
https://arxiv.org/pdf/2004.13924

49. Constraining MHD disk winds with ALMA. Apparent rotation signatures and applica-tion to HH212

B. Tabone1,2 , S. Cabrit2,3 , G. Pineau des Forêts2,4 , J. Ferreira3 , A. Gusdorf5 , L. Podio6 , E. Bianchi3 ,E. Chapillon7,8 , C. Codella6,3 and F. Gueth7
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 PSL Research University,
Sorbonne Universités, Observatoire de Paris, LERMA, CNRS, Paris France; 3 Univ. Grenoble Alpes, CNRS, IPAG,
38000 Grenoble, France; 4 Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405, Orsay, France;
5
Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, PSL Research University, Sorbonne Universités,
CNRS, Paris, France; 6 INAF, Osservatorio Astrofisico di Arceti, Largo E. Fermi 5, 50125 Firenze, Italy; 7 Institut
de Radioastronomie Millimétrique, 38406 Saint-Martin-d’Hères, France; 8 OASU/LAB-UMR5804, CNRS, Université
Bordeaux, 33615 Pessac, France
1

E-mail contact: tabone at strw.leidenuniv.nl
Large millimeter interferometers are revealing a growing number of rotating outflows, which are suggested to trace
magneto-centrifugal disk winds (MHD DWs). However, their impact on disk accretion is not yet well quantified. Here
we identify systematic biases in retrieving the true launch zone, magnetic lever arm, and angular momentum flux of an
MHD DW from apparent rotation signatures. Synthetic position-velocity cuts are constructed from self-similar MHD
DWs over a broad range of parameters, and three different methods are applied for estimating the specific angularmomentum. We find that the launch radius inferred using the well-known relation from Anderson et al. (2006) canmarkedly differ from the true outermost launch radius rout of the DW. The "double-peak separation" and "flow width"
methods provide only a strict lower limit to rout. This bias is independent of angular resolution and can reach a factor
ten. In contrast, the "rotation curve" method gives a good estimate of rout when the flow is well resolved, and an
upper limit otherwise. The magnetic lever arm is always underestimated. Only comparison with synthetic predictions
can take into account properly all observational effects. As an application, we present a comparison with ALMA
observations of HH212 at resolutions from 250 au to 16 au, which represents the most stringent observational testof MHD DW to date. This comparison confirms our predicted biases for the double-peak separation method, andthe large rout ∼ 40 au and small magnetic lever arm first suggested by Tabone et al. (2017). We also derive thefirst accurate analytical expression for the fraction of disk angular momentum extracted by an MHD disk wind of
given radial extent, magnetic lever arm, and mass flux. Application to HH212 confirms that MHD DWs are serious
candidates for the steady angular momentum extraction process in young disks.
Accepted by A&A
http://arxiv.org/pdf/2004.08804

50. ALMA ACA and Nobeyama observations of two Orion cores in deuterated molecularlines
Ken’ichi Tatematsu1,2 , Tie Liu3,4,5 , Gwanjeong Kim1 , Hee-Weon Yi6 , Jeong-Eun Lee6 , Naomi Hirano7 ,Sheng-Yuan Liu7 , Satoshi Ohashi8 , Patricio Sanhueza9,2 , James Di Francesco10,11 , Neal J. Evans II12 ,Gary A. Fuller13 , Ryo Kandori9 , Minho Choi4 , Miju Kang4 , Siyi Feng14,9 , Tomoya Hirota9,2 , Takeshi
Sakai15 , Xing Lu9 , Quang Nguyen Lu’o’ng16,4,9,17 , Mark A. Thompson18 , Yuefang Wu19 , Di Li20 , Kee-Tae
Kim4 , Ke Wang14,21 , Isabelle Ristorcelli22, Mika Juvela23 and L. Viktor Tóth24
Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes of Natural Sciences,462-2 Nobeyama, Minamimaki, Minamisaku, Nagano 384-1305, Japan; 2 Department of Astronomical Science, SOK-

1

35

ENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 Shanghai
Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, P. R. China; 4 Korea
Astronomy and Space Science Institute, Daedeokdaero 776, Yuseong, Daejeon 305-348, South Korea; 5 East Asian
Observatory, 660 N. A’ohoku Place, Hilo, HI 96720, USA; 6 School of Space Research, Kyung Hee University, SeocheonDong, Giheung-Gu, Yongin-Si, Gyeonggi-Do, 446-701, South Korea; 7 School of Space Research, Kyung Hee University,
Seocheon-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-Do, 446-701, South Korea; 8 The Institute of Physical and Chemical Research (RIKEN), 2-1, Hirosawa, Wako-shi, Saitama 351-0198, Japan; 9 National Astronomical Observatory ofJapan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 10 Herzberg Astronomy& Astrophysics, National Research Council of Canada, 5071 West Saanich Rd, Victoria, BC V9E 2E7, Canada; 11
Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 2Y2, Canada; 12 Department of
Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712−1205, USA; 13 JodrellBank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester,M13 9PL, UK; 14 The Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian
District, Beijing 100871, P. R. China; 15 Graduate School of Informatics and Engineering, The University of ElectroCommunications, Chofu, Tokyo 182-8585, Japan; 16 McMaster University, 1 James St N, Hamilton, ON, L8P 1A2,
Canada; 17 IBM, Canada; 18 Centre for Astrophysics Research, Science & Technology Research Institute, University
of Hertfordshire, Hatfield, AL10 9AB, UK; 19 Department of Astronomy, Peking University, 100871, Beijing, China;
20
National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China; 21 European Southern
Observatory, Karl-Schwarzschild-Str. 2 85748 Garching bei Mü; 22 RAP, CNRS (UMR5277), Université Paul Sabatier,
9 avenue du Colonel Roche, BP 44346, 31028, Toulouse Cedex 4, France; 23 Department of Physics, P.O. Box 64,
FI-00014, University of Helsinki, Finland; 24 Department of Astronomy, Eötvös Loránd Unviersity, Pázmány Péter
sétány 1/A, H-1117 Budapest, Hungary
E-mail contact: k.tatematsu at nao.ac.jp
We mapped two molecular cloud cores in the Orion A cloud with the ALMA ACA 7-m Array and with the Nobeyama
45-m radio telescope. These cores have bright N2 D+ emission in single-pointing observations with the Nobeyama 45-m
radio telescope, have relatively high deuterium fraction, and are thought to be close to the onset of star formation.
One is a star-forming core, and the other is starless. These cores are located along filaments observed in N2 H+ , andshow narrow linewidths of 0.41 km s−1 and 0.45 km s−1 in N2 D+ , respectively, with the Nobeyama 45-m telescope.
Both cores were detected with the ALMA ACA 7m Array in the continuum and molecular lines at Band 6. The
starless core G211 shows clumpy structure with several sub-cores, which in turn show chemical differences. Also, thesub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular,
shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting
spatial feature of two N2 D+ peaks of similar intensity and radial velocity located symmetrically with respect to thesingle dust continuum peak. One interpretation is that the two N2 D+ peaks represent an edge-on pseudo-disk. The
CO outflow lobes, however, are not directed perpendicular to the line connecting both N2 D+ peaks.
Accepted by ApJ
http://arxiv.org/pdf/2004.12548

51. Protostellar accretion in low mass metal poor stars and the cosmological lithium problem
Emanuele Tognelli1, Pier Giorgio Prada Moroni1,2 , Scilla Degl’Innocenti1,2 , Maurizio Salaris3 , and Santi
Cassisi2,4
Dipartimento di Fisica, Università di Pisa, Largo Bruno Pontecorvo 3, I-56127, Pisa, Italy; 2 INFN - Sezione di Pisa,
Largo Bruno Pontecorvo 3, I-56127, Pisa, Italy; 3 Astrophysics Research Institute, Liverpool John Moores University,
146 Brownlow Hill, Liverpool L3 5RF, UK; 4 INAF - Osservatorio Astronomico d’Abruzzo, Via M. Maggini, I-64100,
Teramo, Italy
1E-mail contact: ema.tog at gmail.com
The cosmological lithium problem, that is, the discrepancy between the lithium abundance predicted by the Big Bang
nucleosynthesis and the one observed for the stars of the ‘Spite plateau’, is one of the long standing problems of modern
astrophysics. Recent hints for a possible solution involve lithium burning induced by protostellar mass accretion on
Spite plateau stars.
The purpose of this paper is to analyze the effect of protostellar accretion on low metallicity low-mass stars with a focus
36

on PMS lithium evolution. We computed the evolution from the protostar to the MS phase of accreting models withfinal masses of 0.7 and 0.8 M⊙ , and three metallicities Z=0.0001, Z=0.0010, and Z=0.0050. The effects of changing
the main parameters affecting accreting models, that is the accretion energy (cold versus hot accretion), the initial
seed mass Mseed and radius Rseed , and the mass accretion rate ṁ, have been investigated in detail.
As for the main stellar properties and the surface 7 Li abundance, hot accretion models converge to standard nonaccreting ones within 1 Myr, regardless of the actual value of Mseed, Rseed , and ṁ. Also, cold accretion models with<a relatively large Mseed (<∼10 Mjup) or Rseed (∼1 R⊙ ) converge to standard non-accreting ones in less than about
10–20 Myr. A drastically different evolution occurs whenever a cold protostellar accretion process starts from smallvalues of Mseed and Rseed (Mseed ∼ 1 Mjup, Rseed <∼ 1 R⊙ ). These models almost entirely skip the standard Hayashi
track evolution and deplete Li before the end of the accretion phase. The exact amount of depletion depends on theactual combination of the accretion parameters (ṁ, Mseed, and Rseed ), achieving in some cases the complete exhaustionof Li in the whole star.
Accepted by A&A
http://arxiv.org/pdf/2004.14857

52. ALMA Observations of Giant Molecular Clouds in M33 I: Resolving Star Formation

Activities in the Giant Molecular Filaments Possibly Formed by a Spiral Shock

Kazuki Tokuda1,2 , Kazuyuki Muraoka1 , Hiroshi Kondo1 , Atsushi Nishimura1 , Tomoka Tosaki3 , Sarolta
Zahorecz1,2 , Sachiko Onodera4 , Rie E. Miura2 , Kazufumi Torii5 , Nario Kuno6,7 , Shinji Fujita1 , Hidetoshi
Sano8,9 , Toshikazu Onishi1 , Kazuya Saigo2 , Yasuo Fukui8,9 , Akiko Kawamura2 and Kengo Tachihara8
Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan; 2 National Astronomical Observatory of Japan, National Institutes of Natural
Science, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan; 3 oetsu University of Education, Yamayashiki-machi, Joetsu,
Niigata 943-8512, Japan; 4 Meisei University, 2-1-1 Hodokubo, Hino, Tokyo 191-0042, Japan; 5 Nobeyama Radio
Observatory, National Astronomical Observatory of Japan (NAOJ), National Institutes of Natural Sciences (NINS),462-2 Nobeyama, Minamimaki, Minamisaku-gun, Nagano 384-1305, Japan; 6 Department of Physics, Graduate Schoolof Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan; 7 Tomonaga
Center for the History of the Universe, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan; 8 Departmentof Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan; 9 Institute for Advanced Research, Nagoya
University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan1

E-mail contact: tokuda at p.s.osakafu-u.ac.jp
We report molecular line and continuum observations toward one of the most massive giant molecular clouds (GMCs),
GMC-16, in M33 using ALMA with an angular resolution of 0′′ 44 × 0′′ 27 (∼2 pc × 1 pc). We have found that the
GMC is composed of several filamentary structures in 12 CO and 13 CO (J = 2-1). The typical length, width, and total
mass are ∼50-70 pc, ∼5–6 pc, and ∼105 M⊙ , respectively, which are consistent with those of giant molecular filaments(GMFs) as seen in the Galactic GMCs. The elongations of the GMFs are roughly perpendicular to the direction of thegalaxy’s rotation, and several H ii regions are located at the downstream side relative to the filaments with an offset
of ∼10–20 pc. These observational results indicate that the GMFs are considered to be produced by a galactic spiralshock. The 1.3 mm continuum and C18 O (J = 2-1) observations detected a dense clump with the size of ∼2 pc at
the intersection of several filamentary clouds, which is referred to as “hub filament,” possibly formed by a cloud-cloud
collision. A strong candidate for protostellar outflow in M33 also has been identified at the center of the clump. We
have successfully resolved the pc-scale local star formation activity in which the galactic scale kinematics may induce
the formation of the parental filamentary clouds.
Accepted by ApJ
https://arxiv.org/pdf/1909.04262

53. Protoplanetary disk masses in NGC 2024: Evidence for two populations
S.E. van Terwisga1,2 , E.F. van Dishoeck1,3 , R.K. Mann4 , J. Di Francesco4 , N. van der Marel4 et al.
1

Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands; 2 Max-Planck-Institut

37

für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany; 3 Max-Planck-Institut für Extraterrestrische Physik,
Gießenbachstraße, D-85741 Garching bei München, Germany; 4 NRC Herzberg Astronomy & Astrophysics, 5071 W
Saanich Rd, Victoria BC V9E 2E7, Canada
E-mail contact: terwisga at mpia.de
Protoplanetary disks in dense, massive star-forming regions are strongly affected by their environment. How thisenvironmental impact changes over time is an important constraint on disk evolution and external photoevaporation
models. We characterize the dust emission from 179 disks in the core of the young (0.5 Myr) NGC 2024 cluster.
By studying how the disk mass varies within the cluster, and comparing these disks to those in other regions, we
aim to determine how external photoevaporation influences disk properties over time. Using the Atacama Large
Millimeter/submillimeter Array, a 2.′ 9 × 2.′ 9 mosaic centered on NGC 2024 FIR 3 was observed at 225 GHz with aresolution of 0.′′ 25, or ∼100 AU. The imaged region contains 179 disks identified at IR wavelengths, seven new disk
candidates, and several protostars. The overall detection rate of disks is 32±4%. Few of the disks are resolved, withthe exception of a giant (R = 300 AU) transition disk. Serendipitously, we observe a millimeter flare from an X-ray
bright young stellar object (YSO), and resolve continuum emission from a Class 0 YSO in the FIR 3 core. Two distinct
disk populations are present: a more massive one in the east, along the dense molecular ridge hosting the FIR 1–5
YSOs, with a detection rate of 45±7%. In the western population, towards IRS 1, only 15±4% of disks are detected.
NGC 2024 hosts two distinct disk populations. Disks along the dense molecular ridge are young (0.2–0.5 Myr) andpartly shielded from the far ultraviolet radiation of IRS 2b; their masses are similar to isolated 1–3 Myr old SFRs.
The western population is older and at lower extinctions, and may be affected by external photoevaporation from both
IRS 1 and IRS 2b. However, it is possible these disks had lower masses to begin with.
Accepted by A&A
http://arxiv.org/pdf/2004.13551

54. Thermal evolution of protoplanetary disks: from β-cooling to decoupled gas and dust

temperatures
Eduard I. Vorobyov1,2 , Ryoki Matsukoba3 , Kazuyuki Omukai3 , and Manuel Guedel1
University of Vienna, Department of Astrophysics, Vienna, 1180, Austria; 2 Ural Federal University, 51 Lenin Str.,
620051 Ekaterinburg, Russia; 3 Astronomical Institute, Graduate School of Sciences, Tohoku University, Aoba, Sendai,
Miyagi 980-8578, Japan1

E-mail contact: eduard.vorobiev at univie.ac.at
Aims. We explore the long-term evolution of young protoplanetary disks with different approaches to computing thethermal structure determined by various cooling and heating processes in the disk and its surroundings.
Methods. Numerical hydrodynamics simulations in the thin-disk limit were complemented with three thermal evolution
schemes: a simplified β-cooling approach with and without irradiation, in which the rate of disk cooling is proportional
to the local dynamical time, a fiducial model with equal dust and gas temperatures calculated taking viscous heating,irradiation, and radiative cooling into account, and also a more sophisticated approach allowing decoupled dust andgas temperatures.
Results. We found that the gas temperature may significantly exceed that of dust in the outer regions of young disks
thanks to additional compressional heating caused by the infalling envelope material in the early stages of disk evolution
and slow collisional exchange of energy between gas and dust in low-density disk regions. The outer envelope howevershows an inverse trend with the gas temperatures dropping below that of dust. The global disk evolution is only
weakly sensitive to temperature decoupling. Nevertheless, separate dust and gas temperatures may affect the chemicalcomposition, dust evolution, and disk mass estimates. Constant-β models without stellar and background irradiation
fail to reproduce the disk evolution with more sophisticated thermal schemes because of intrinsically variable natureof the β-parameter. Constant-β models with irradiation can better match the dynamical and thermal evolution, but
the agreement is still incomplete.
Conclusions. Models allowing separate dust and gas temperatures are needed when emphasis is placed on the chemicalor dust evolution in protoplanetary disks, particularly in sub-solar metallicity environments.
Accepted by A&A
http://arxiv.org/pdf/2004.13561
38

55. A new look at Sco OB1 association with Gaia DR2
L. Yalyalieva1,2,3 , G. Carraro3 , R. Vazquez4 , L. Rizzo4 , E. Glushkova1,2 , and E. Costa5
Physics Department, Lomonosov Moscow State University, Leninskie Gory, Moscow, 119991, Russian Federation; 2
Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetsky pr.13, Moscow, 119234, RussianFederation; 3 Department of Physics and Astronomy, Padova University, Vicolo Osservatorio 3, I-35122, Padova, Italy;
4
Instituto de Astrofísica de La Plata (CONICET, UNLP), Paseo del Bosque s/n, La Plata, Argentina; 5 Departamentode Astronomia, Universidad de Chile, Casilla 36-D, Santiago, Chile
1

E-mail contact: yalyalieva at yandex.ru
We present and discuss photometric optical data in the area of the OB association Sco OB1 covering about 1 squared
degree. UBVI photometry is employed in tandem with Gaia DR2 data to investigate the 3 dimensional structure
and the star formation history of the region. By combining parallaxes and proper motions we identify 7 physicalgroups located between the young open cluster NGC 6231 and the bright nebula IC4628. The most prominent groupcoincides with the sparse open cluster Trumpler 24. We confirm the presence of the intermediate age star cluster
VdB-Hagen 202, which is unexpected in this environment, and provide for the first time estimates of its fundamental
parameters. After assessing individual groups membership, we derive mean proper motion components, distances, andages. The seven groups belong to two different families. To the younger family (family I) belong several pre-Main
Sequence stars as well. These are evenly spread across the field, and also in front of VdB-Hagen 202. VdB-Hagen 202
and two smaller, slightly detached, groups of similar properties form family II, which do not belong to the association,
but are caught in the act of passing through it. As for the younger population, this forms an arc-like structure fromthe bright nebula IC 4628 down to NGC 6231, as previously found. Moreover, the pre-Main Sequence stars density
seems to increase from NGC 6231 northward to Trumpler 24.
Accepted by MNRAS
http://arxiv.org/pdf/2004.13418

56. Edge collapse and subsequent longitudinal accretion in Filament S242
Lixia Yuan1,2,3 , Guang-Xing Li4 , Ming Zhu1,2,3 , Tie Liu5 , Ke Wang6 et al.
National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing
100012, China; 2 University of Chinese Academy of Sciences, 100049, Beijing, PR China; 3 Key Laboratory of FAST,
NAOC, Chinese Academy of Sciences, Beijing 100012, PR China; 4 South-Western Institute for Astronomy Research,
Yunnan University, Kunming, 650500 Yunnan, PR China; 5 Key Laboratory for Research in Galaxies and Cosmology,
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, China; 6 Kavli
Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Road, Haidian District, Beijing 100871, PR
China

1

E-mail contact: lxyuan at nao.cas.cn
Filament S242 is 25 pc long with massive clumps and YSO clusters concentrated in its end regions; it is considered
a good example of edge collapse. We mapped this filament in the 12 CO (1–0) and 13 CO (1–0) lines. A large-scale
velocity gradient along filament S242 has been detected; the relative velocity between the two end-clumps is ∼3 km s−1 ,indicating an approaching motion between them. These signatures are consistent with the filament S242 being formed
through the collapse of a single elongated entity, where an effect known as “gravitational focusing” drives the ends ofthe filament to collapse (edge collapse). Based on this picture, we estimate a collapse timescale of ∼4.2 Myr, whichis the time needed for a finite and elongated entity evolving to the observed filament S242. For the whole filament,
we find that increases in surface densities lead to increases in velocity dispersion, which can be consistently explained
as the result of self-gravity. We also calculated the contribution of longitudinalic

57. Tidal Interaction between the UX Tauri Disk A/C System Revealed by ALMA
Luis A. Zapata1 , Luis F. Rodríguez1 , Manuel Fernández-López2 , Aina Palau1 , Robert Estalella3 , Mayra
Osorio4 , Guillem Anglada4 , and Nuria Huelamo5
Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090,
Morelia, Michoacán, México; 2 Instituto Argentino de Radioastronomía (CCT-La Plata, CONICET; CICPBA), C.C.
No. 5, 1894, Villa Elisa, Buenos Aires, Argentina; 3 Dep. de Física Quàntica i Astrofísica, Institut de Ciencies delCosmos, Universitat de Barcelona, IEEC-UB, Marti i Franques 1, 08028 Barcelona, Spain 4 Instituto de Astrofísica deAndalucía(CSIC), Glorieta de la Astronomía s/n E-18008 Granada, Spain 5 Centro de Astrobiología (CSIC-INTA),
Camino bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
1

E-mail contact: l.zapata at irya.unam.mx
We present sensitive and high angular resolution (∼0.2-0.3′′) (sub)millimeter (230 and 345 GHz) continuum andCO(2−1)/CO(3−2) line archive observations of the disk star system in UX Tauri carried out with ALMA (The
Atacama Large Millimeter/Submillimeter Array). These observations reveal the gas and dusty disk surrounding theyoung star UX Tauri A with a large signal-to-noise ratio (>400 in the continuum and >50 in the line), and for the firsttime is detected the molecular gas emission associated with the disk of UX Tauri C (with a size for the disk of <56au). No (sub)millimeter continuum emission is detected at 5σ-level (0.2 mJy at 0.85 mm) associated with UX Tauri
C. For the component UX Tauri C, we estimate a dust disk mass of ≤ 0.05 M⊕ . Additionally, we report a strong tidal
disk interaction between both disks UX Tauri A/C, separated 360 au in projected distance. The CO line observations
reveal marked spiral arms in the disk of UX Tauri A and an extended redshifted stream of gas associated with the
UX Tauri C disk. No spiral arms are observed in the dust continuum emission of UX Tauri A. Assuming a Keplerianrotation we estimate the enclosed masses (disk+star) from their radial velocities in 1.4 ± 0.6 M⊙ for UX Tauri A,
and 70 ± 30 / sin i Jupiter masses for UX Tauri C (the latter coincides with the mass upper limit value for a browndwarf). The observational evidence presented here lead us to propose that UX Tauri C is having a close approach ofa possible wide, evolving and eccentric orbit around the disk of UX Tauri A causing the formation of spiral arms andthe stream of molecular gas falling towards UX Tauri C.
Accepted by The Astrophysical Journal
https://arxiv.org/pdf/2005.01652.pdf

58. The role of Galactic HII regions in the formation of filaments. High-resolution sub-milimeter imaging of RCW 120 with ArTéMiS

A. Zavagno1,2 , Ph. André3 , F. Schuller3,4 , N. Peretto5 , Y. Shimajiri3,6 et al.
Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France; 2 Institut Universitaire de France; 3 Laboratoired’Astrophysique (AIM), CEA/DRF, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris-Cité,
91191 Gif-sur-Yvette, France; 4 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany; 5 School of Physics & Astronomy, Cardiff University, Cardiff CF24 3AA, UK; 6 Department of Physics
and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima,
Kagoshima 890-0065, Japan1

E-mail contact: annie.zavagno at lam.fr
Massive stars and their associated ionized (HII) regions could play a key role in the formation and evolution of filamentsthat host star formation. However, the properties of filaments that interact with H regions are still poorly known.
To investigate the impact of HII regions on the formation of filaments, we imaged the Galactic HII region RCW 120
and its surroundings where active star formation takes place and where the role of ionization feedback on the starformation process has already been studied. We used the ArTéMiS camera on the APEX telescope and combined the
ArTéMiS data at 350 and 450 microns with Herschel-SPIRE/HOBYS. We studied the dense gas distribution around
RCW 120 with a resolution of 8′′ (0.05 pc at a distance of 1.34 kpc). Our study allows us to trace the median radialintensity profile of the dense shell of RCW 120. This profile is asymmetric, indicating a clear compression from the
HII region on the inner part of the shell. The profile is observed to be similarly asymmetric on both lateral sides of theshell, indicating a homogeneous compression over the surface. On the contrary, the profile analysis of a radial filament
associated with the shell, but located outside of it, reveals a symmetric profile, suggesting that the compression fromthe ionized region is limited to the dense shell. The mean intensity profile of the internal part of the shell is well40

fitted by a Plummer like profile with a deconvolved Gaussian FWHM of 0.09 pc, as observed for filaments in low-massstar-forming regions. This study suggests that compression exerted by HII regions may play a key role in the formationof filaments and may further act on their hosted star formation. ArTéMiS data also suggest that RCW 120 might be
a 3D ring, rather than a spherical structure.
Accepted by A&A
http://arxiv.org/pdf/2004.05604

59. Probing the initial conditions of high-mass star formation — IV. Gas dynamics andNH2D chemistry in high-mass pre/protocluster clumps

Chuan-Peng Zhang1,2,3 , Guang-Xing Li4 , Thushara Pillai5 , Timea Csengeri6 , Friedrich Wyrowski6 , etal.
National Astronomical Observatories, Chinese Academy of Sciences, 100101 Beijing, P.R. China; 2 CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, 100101 Beijing, P.R. China; 3
Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany; 4 South-Western Institute for Astronomy Research, Yunnan University, Kunming, 650500 Yunnan, P.R. China; 5 Institute for Astrophysical Research,
725 Commonwealth Ave, Boston University Boston, MA 02215, USA; 6 Max-Planck-Institut für Radioastronomie, Auf
dem Hügel 69, D-53121 Bonn, Germany
1E-mail contact: cpzhang at nao.cas.cn
The initial stage of star formation is very difficult to study because of its high density and low temperature. Under
such conditions, many molecules become depleted from the gas phase by freezing out onto dust grains. However,the deuterated species could remain gaseous and are thus ideal tracers. We investigate the gas dynamics and NH2 D
chemistry in eight massive pre/protocluster clumps. We present NH2 D 111 –101 (at 85.926 GHz), NH3 (1, 1) and (2,2) observations in the eight clumps using the PdBI and the VLA, respectively. We find that the distribution between
deuterium fractionation and kinetic temperature shows a number density peak at around Tkin = 16.1 K, and theNH2 D cores are mainly located at a temperature range of 13.0 to 22.0 K. We detect seven extremely high deuterium<
fractionation of 1.0 <∼ Dfrac ∼ 1.41. We find that the NH2 D emission does not appear to coincide exactly with either dust
continuum or NH3 peak positions, but often surrounds the star-formation active regions. This suggests that the NH2 D
has been destroyed by the central young stellar object (YSO) due to its heating. The detected NH2 D lines are very
narrow with a median width of 0.98±0.02 km s−1 . The extracted NH2 D cores are gravitationally bound (αvir < 1),
are likely prestellar or starless, and can potentially form intermediate-mass or high-mass stars. Using NH3 (1, 1) as adynamical tracer, we find very complicated dynamical movement, which can be explained by a combined process with
outflow, rotation, convergent flow, collision, large velocity gradient, and rotating toroids. We find that high deuterium
fractionation strongly depends on the temperature condition, and NH2 D is a poor evolutionary indicator of high-massstar formation in evolved stages, but a useful tracer in the starless and prestellar cores.
Accepted by A&A
http://arxiv.org/pdf/2004.13946

60. Searching for Molecular Outflows with Support Vector Machines: Dark Cloud Complex

in Cygnus

Shaobo Zhang1 , Ji Yang1 , Ye Xu1 , Xuepeng Chen1 , Yang Su1 et al.
Purple Mountain Observatory, & Key Laboratory for Radio Astronomy, Chinese Academy of Sciences, Nanjing
210023, China
1E-mail contact: shbzhang at pmo.ac.cn
We present a survey of molecular outflows across the dark cloud complex in the Cygnus region, based on 46.75 deg2 fieldof CO isotopologues data from Milky Way Imaging Scroll Painting (MWISP) survey. A supervised machine learningalgorithm, Support Vector Machine (SVM), is introduced to accelerate our visual assessment of outflow features inthe data cube of 12 CO and 13 CO J = 1–0 emission. A total of 130 outflow candidates are identified, of which 77 show
bipolar structures and 118 are new detections. Spatially, these outflows are located inside dense molecular clouds andsome of them are found in clusters or in elongated linear structures tracing the underlying gas filament morphology.
41

Along the line of sight, 97, 31, and 2 candidates reside in the Local, Perseus, and Outer arm, respectively. Youngstellar objects as outflow drivers are found near most outflows, while 36 candidates show no associated source. The
clusters of outflows that we detect are inhomogeneous in their properties; nevertheless, we show that the outflows
cannot inject turbulent energy on cloud scales. Instead, at best, they are restricted to affecting the so called “clump”
and “core” scales, and this only on short (∼0.3 Myr) estimated timescales. Combined with outflow samples in theliterature, our work shows a tight outflow mass-size correlation.
Accepted by ApJS
http://arxiv.org/pdf/2004.04887

61. Solid accretion onto planetary cores in radiative disks
Apostolos Zormpas1 , Giovanni Picogna1 , Barbara Ercolano1,2 , and Wilhelm Kley3
Universitäts-Sternwarte, Ludwig-Maximilians-Universität München, Scheinerstr. 1, 81679 München, Germany; 2Excellence Cluster Origin and Structure of the Universe, Boltzmannstr. 2, 85748 Garching bei München, Germany; 3Institut für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
1E-mail contact: zormpas at usm.lmu.de
The solid accretion rate, necessary to grow gas giant planetary cores within the disk lifetime, has been a major
constraint for theories of planet formation. We tested the solid accretion rate efficiency on planetary cores of different
masses embedded in their birth disk, by means of 3D radiation-hydrodynamics, where we followed the evolution of aswarm of embedded solids of different sizes. We found that using a realistic equation of state and radiative cooling,
the disk at 5 au is able to cool efficiently and reduce its aspect ratio. As a result, the pebble isolation mass is reached
before the core grows to 10 Earth masses, stopping efficiently the pebble flux and creating a transition disk. Moreover,
the reduced isolation mass halts the solid accretion before the core reaches the critical mass, leading to a barrier togiant planet formation, and it explains the large abundance of super-Earth planets in the observed population.
Accepted by A&A
http://arxiv.org/pdf/2004.01745

42

Abstracts of recently accepted major reviews

The molecular cloud lifecycle
Mélanie Chevance1 , J.M. Diederik Kruijssen1 , Enrique Vazquez-Semadeni2 , Fumitaka Nakamura3,4,5 ,Ralf Klessen6 et al.
1
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12- 14, 69120
Heidelberg, Germany; 2 Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de Méxíco,
Campus Morelia, Apdo. Postal 3-72, Morelia 58089, México; 3 National Astronomical Observatory of Japan, 2-21-1
Osawa, Mitaka, Tokyo 181-8588, Japan; 4 Department of Astronomy, The University of Tokyo, Hongo, Tokyo 1130033, Japan; 5 The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-0015,
Japan; 6 Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle- Str.
2, 69120 Heidelberg, Germany;

E-mail contact: chevance at uni-heidelberg.de
Giant molecular clouds (GMCs) and their stellar offspring are the building blocks of galaxies. The physical characteristics of GMCs and their evolution are tightly connected to galaxy evolution. The macroscopic properties of theinterstellar medium propagate into the properties of GMCs condensing out of it, with correlations between e.g. thegalactic and GMC scale gas pressures, surface densities and volume densities. That way, the galactic environment sets
the initial conditions for star formation within GMCs. After the onset of massive star formation, stellar feedback frome.g. photoionisation, stellar winds, and supernovae eventually contributes to dispersing the parent cloud, depositingenergy, momentum and metals into the surrounding medium, thereby changing the properties of galaxies. This cycling of matter between gas and stars, governed by star formation and feedback, is therefore a major driver of galaxy
evolution. Much of the recent debate has focused on the durations of the various evolutionary phases that constitutethis cycle in galaxies, and what these can teach us about the physical mechanisms driving the cycle. We review resultsfrom observational, theoretical, and numerical work to build a dynamical picture of the evolutionary lifecycle of GMC
evolution, star formation, and feedback in galaxies.
Accepted by Space Science Reviews
http://arxiv.org/pdf/2004.06113

The Leiden Atomic and Molecular Database (LAMDA): Current status, recent updates,
and future plans
Floris van der Tak1,2 , François Lique3 , Alex Faure4 , John H. Black5 , and Ewine F. van Dishoeck6
SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands; 2 Kapteyn
Astronomical Institute, University of Groningen, The Netherlands; 3 Normandie Université, Université du Havre &CNRS, LOMC, F-76063 Le Havre, France; 4 Univ. Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France; 5
Department of Space, Earth, and Environment, Chalmers University of Technology, Sweden; 6 Leiden Observatory,
Leiden University, The Netherlands
1E-mail contact: f.f.s.van.der.tak at sron.nl
The Leiden Atomic and Molecular Database (LAMDA) collects spectroscopic information and collisional rate coefficients for molecules, atoms, and ions of astrophysical and astrochemical interest. We describe the developments of thedatabase since its inception in 2005, and outline our plans for the near future. Such a database is constrained both by
the nature of its uses and by the availability of accurate data: we suggest ways to improve the synergies among users
and suppliers of data. We summarize some recent developments in computation of collisional cross sections and rate
coefficients. We consider atomic and molecular data that are needed to support astrophysics and astrochemistry withupcoming instruments that operate in the mid- and far-infrared parts of the spectrum.
Accepted by Atoms (special issue about Atomic and Molecular Databases)
43

Preprint at https://arxiv.org/pdf/2004.11230
Link to LAMDA database https://home.strw.leidenuniv.nl/$\sim$moldata/

Formation and Evolution of Disks around Young Stellar Objects
Bo Zhao1 , Kengo Tomida2 , Patrick Hennebell3, John J. Tobin4 , Anaëlle Maury3 , Tomoya Hirota5 ,Álvaro Sánchez-Monge6 , Rolf Kuiper7 , Anna Rosen8 , Asmita Bhandare9 , Marco Padovani10 , andYueh-Ning Lee11
Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching, Germany; 2 AstronomicalInstitute, Tohoku University, 6-3, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan; 3 AIM/CEA/CNRS, Université
Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif sur Yvette, France; 4 National Radio Astronomy
Observatory 520 Edgemont Road, Charlottesville, VA 22901, USA; 5 National Astronomical Observatory of Japan,
Osawa, Mitaka, Tokyo 181-8588, Japan; 6 I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937
Köln, Germany; 7 Institute of Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, 72076,
Tübingen, Germany; 8 Center for Astrophysics, Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA;
9
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany; 10 INAF-Osservatorio Astrofisico
di Arcetri, Largo E. Fermi, 5 - 50125 Firenze, Italy; 11 Department of Earth Sciences, National Taiwan Normal
University, 88, Sec. 4, Ting-Chou Road, Taipei 11677, Taiwan
1E-mail contact: bo.zhao@mpe.mpg.de
Recent observations have suggested that circumstellar disks may commonly form around young stellar objects. Although the formation of circumstellar disks can be a natural result of the conservation of angular momentum in theparent cloud, theoretical studies instead show disk formation to be difficult from dense molecular cores magnetized toa realistic level, owing to efficient magnetic braking that transports a large fraction of the angular momentum awayfrom the circumstellar region. We review recent progress in the formation and early evolution of disks around youngstellar objects of both low-mass and high-mass, with an emphasis on mechanisms that may bridge the gap between
observation and theory, including non-ideal MHD effects and asymmetric perturbations in the collapsing core (e.g.,magnetic field misalignment and turbulence). We also address the associated processes of outflow launching and theformation of multiple systems, and discuss possible implications in properties of protoplanetary disks.
Accepted by Space Science Reviews, topical collection Star Formation
https://arxiv.org/pdf/2004.01342.pdf

44New Jobs

PhD fellowship at IPAG (Grenoble, FR) and MPE (Garching, GE)
We are pleased to announce the availability of one Early Stage Researchers (ESRs) position.
Thesis title:
A new model of the Proto Solar Nebula: organic and molecular fractionation chemistry.
Supervisor:
Prof. C. Ceccarelli (University Grenoble Alpes - IPAG)
Co-Supervisors:
Prof. P. Caselli (Max Planck Institute for Extraterrestrial Studies) and Dr. P. Beck (University Grenoble Alpes IPAG)
Recruitment Institutions:the first 18 months at University Grenoble Alpes, Grenoble (France); the second 18 months at Max Planck institutefor Extraterrestrial Studies, Garching (Germany)
Doctoral School:
University Grenoble Alpes, Grenoble (France)
Mobility:
The ESR will spend the first 18 months at University Grenoble Alpes (Grenoble, France) and the second 18 months
at Max Planck institute for Extraterrestrial Studies (Garching, Germany).
Eligibility:
European and non-European students who have not resided or carried out their main activity (work, studies, ect.) in
France for more than 12 months in the 3 years immediately before the recruitment date.
Thesis description:
The formation of the Solar System has left traces in the chemical composition of early-accreted bodies. Particularlyrich in this information are the so-called small bodies: comets, asteroids, and their fragments that reach the Earth
as meteorites, Interplanetary Dust Particles (IDPs), Trans-Neptunians Objects (TNOs)... Specifically, their content
in complex organics as well as the so-called isotopic anomalies turns out to be an extremely useful testimony of what
happened to the Solar System at its birth. The goal of the thesis is to construct a model of the early phases of
the Proto Solar Nebula (PSN) based on the chemical link between the Solar System small bodies and the currently
forming Solar-like planetary systems. To this end, the thesis will develop a model coupling the dynamic evolution of
the first phases of the collapse with a dedicated astrochemical model to predict the evolution of organic matter andthe molecular fractionation during the earliest phases the Solar System, namely up to the hot corino and the onset of
disk phase. The student will include the new reactions studied by the ACO project and make use of the comparison
between the model predictions and the observations obtained by ACO members to constrain the model.
The thesis is part of the ACO network, whose ultimate goal is to reconstruct the early history of the Solar System bycomparing the chemical composition of presently forming Solar-like planetary systems with that of small bodies in our
Solar System. The comparison will be based on the most advanced astrochemical knowledge, which will be developedby the interdisciplinary ACO team.
Requested background:
The successful applicant must have a Master’s degree in Physics or Astrophysics or Computer Science or similar by
the time of enrollment and be highly motivated. Knowledge of relevant program languages and/or previous experiencein astrochemistry and modeling will be appreciated. Excellent Master’s degree grades are expected as well as a highlevel of written and spoken English. Team work ability is essential.
45

Salary:
The gross amount of the Research fellowship is paid as follows: - for the first 18 months: Euro 2708/month(living allowance) + Euro 430/month (mobility allowance) = Euro 3138 (monthly gross amount) plus possible
Family Allowance in addition to coverage of study and research relates expenses; - for the last 18 months: Euro
2599/month. Social security is fully covered. See details on the financial aspects of Marie Sklodowska-Curie-ITN
in the Guide for applicants Marie Sklodowska-Curie Actions Innovative Training Networks (ITN) 2018, published at
http://ec.europa.eu/research/participants/data/ref/h2020/other/guides_for_applicants/h2020-guide-appl-msca-it
How to apply:
Send the application in pdf format to the address aco-esr17@univ-grenoble-alpes.fr. The application should include a
letter of interest, a CV with the marks of the Master year, and at least one recommendation letter, which could also
be sent separately to the same e-mail address.
Closing date for application: 2 June 2020 Selection announcement: by 15th June 2020 Expected date of recruitment:
between 1 October and 1 December 2020.
Selection procedure:
A short list of candidates will be selected by the 4th June. The short listed candidates will be interviewed the following
week and the final selection will be announced by the 15th June.
For more information please look at the website of the project ACO:
https://aco-itn.oapd.inaf.it/job-opportunities

46

Meetings

Astrochemical Frontiers – Quarantine Edition
Sponsored by IAU Commission H2 Steering Committee:
E. Bergin (President), P. Caselli (Vice-President), J. Jørgensen (Secretary),
Y. Aikawa, M. Cunningham, W. Geppert, K. Öberg, T. Millar (Ex-officio)
Dear Fellow Astrochemists and others interested in the field.
This has been a trying time for all of us throughout the world. There are so many layers to the situation we findourselves in that the lack of scientific sharing in conferences seems trite. Despite this, we know that there is somewonderful work by numerous scientists that would traditionally be highlighted in an international forum during thesummer. Further, there are so many early-career scholars who deserve the opportunity to showcase their work. IAU
Commission H2 “Astrochemistry” offers this opportunity via a remote conference (general details on the website below)
to give a remote talk, participate in remote questions and answers - and continue to share the science that unites us
all.
The meeting will be held on June 15th–19th from 08:00-11:30am EDT (12:00-15:30 GMT) using Zoom. There will be
no registration fee, but attendance at the conference will be for admitted registrants only. Talks will be 15 minutes(10 min talk/5 for questions). We will manage the schedule such that talks from Asia will be placed in early slots andUS west coast late slots. All talks will be recorded and placed on the conference web site. For those watching therecordings, we will enable Q&A with the speakers during the week of the meeting.
To register and submit an abstract, if desired, fill out the form at the following website:
https://sites.google.com/cfa.harvard.edu/astrochemicalfrontiers• Abstract submission/Registration is due May 18.
• Talks will be announced on May 29.
• Registration will close on June 1.
For questions, you are welcome to contact Ted Bergin (ebergin@umich.edu) or other members of the SOC.

The Physics of Star Formation: from Stellar Cores to Galactic Scales
Dear participants,
We deeply regret to inform you that we have decided to postpone the conference ’The Physics of Star Formation:from Stellar Cores to Galactic Scales’ given the continuously evolving situation with Covid19 and the impact it has
and will keep having on travels in the near future.
We have been closely monitoring the situation in France and around the world over the last weeks. The situation is
evolving at different paces in different countries, making travels and large meetings impossible for the next couple ofmonths. We hope that the epidemic will decline by June, but the safety and health of all participants is our priority.
Also, we believe that the situation is not in favour of a postponement until next fall. We thus have decided to postpone
the conference to 2022, around the same period (end of June - early July). 2021 is also the year of Protostars andPlanets VII where we hope to meet all of you. So please tick already your 2022 agenda at these dates. Meanwhile, wewish the very best to our Japanese colleagues for the PPVII conference !
We deeply thank the SOC, the invited speakers, and all the participants who applied for a contributed slot (180 intotal !). All of you participated in developing a promising and high-level program, and we hope to see all of you in
Lyon in 2022. The good part of all this involvement is that it should significantly facilitate the organisation of the
Star@Lyon 2022.
Benoît Commerçon and Gilles Chabrier47

Summary of Upcoming Meetings

Check the websites of these meetings for the latest information on how they are affected by Covid-19
Astrochemical Frontiers – Quarantine Edition
15 - 19 June 2020 via Zoom
https://sites.google.com/cfa.harvard.edu/astrochemicalfrontiers
Planet Formation: From Dust Coagulation to Final Orbital Assembly
1 - 26 June 2020, Munich, Germany
http://www.munich-iapp.de/planetformation
Illuminating the Dusty Universe: A Tribute to the Work of Bruce Draine
6 - 10 July 2020, Florence, Italy
https://web.astro.princeton.edu/IlluminatingTheDusty Universe
The Early Phase of Star Formation
12 - 17 July 2020, Ringberg, Germany
http://www.mpia.de/homes/stein/EPoS/2020/2020.php
Star Formation: From Clouds to Discs - A Tribute to the Career of Lee Hartmann
17 - 20 August 2020, Malahide, Ireland
https://www.dias.ie/cloudstodiscs/
Star Formation in Different Environments 202024 - 28 August 2020, Quy Nhon, Vietnam
http://icisequynhon.com/conferences/sfde/
Planetary Science: The Young Solar System
6 - 12 September 2020, Quy Nhon, Vietnam
http://www.icisequynhon.com/conferences/planetary_science/
Wheel of Star Formation: A conference dedicated to Prof. Jan Palouš
14 - 18 September 2020, Prague, Czech Republic
https://janfest2020.asu.cas.cz
Conditions and Impact of Star Formation - Across Times and Scales
28 September - 2 October 2020, Chile
https://astro.uni-koeln.de/symposium-star-formation-2020.html
From Clouds to Planets II: The Astrochemical Link
28 September - 2 October 2020, Berlin, Germany
https://events.mpe.mpg.de/event/12/
The Aftermath of a Revolution: Planet Formation Five Years after HL Tau
7 - 11 December 2020, Chile
https://www.eso.org/sci/meetings/2020/hltau2020.html
Protostars & Planets VII
1 - 7 April 2021, Kyoto, Japan
http://www.ppvii.org
Cool Stars, Stellar Systems, and the Sun 21
postponed to summer 2021, Toulouse, France
https://coolstars21.github.io/
Chemical Processes in Solar-type Star Forming Regions
13 - 17 September 2021, Torino, Italy
https://sites.google.com/inaf.it/aco-conference48The Physics of Star Formation: From Stellar Cores to Galactic Scales∼June - July 2022, Lyon, France
http:/staratlyon.univ-lyon1.fr/en

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

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

49