Star Formation Newsletter#361 1-15
Yusuke Aso (KASI)

Time-dependent Monte Carlo continuum radiative transfer
A. Bensberg and S. Wolf
Institut für Theoretische Physik und Astrophysik, Christian-Albrechts-Universität zu Kiel, Leibnizstr. 15, 24118 Kiel, Germany
e-mail: abensberg@astrophysik.uni-kiel.deReceived 21 December 2021 / Accepted 21 October 2022

c/Δt

ABSTRACTare briefly described in Sects. 2.3 and 2.4. An overview of different tests of the implemented routines is given in Sect. 3. The
impactof theby
temporalwidth andthe numberof photon
Context. Variability is a characteristic feature of young stellar objects thatis causedvariousstep
underlying
physicalprocesses.
Multipackages
per time step
discussed
Sects.
3.1 and 3.2.
The
epoch observations in the optical and infrared combined with radiative transfer
simulations
are iskey
to studyintheseprocesses
in detail.
cinfluenceof theopticaldepthtransfer.
on the temperature
distribution
Aims. We present an implementation of an algorithm for 3D time-dependent
Monte
Carlo
radiative
It allows one
to simulate
simulationsfor 1D and
2Dandmodelsare examinedin radiation
Sects. 3.3fortemperature distributions as well as images and spectral energy distributionsof the scatteredlight
thermalreemission
and 4.1, respectively. In Sect. 4.2, we discuss the impact of avariable illuminating and heating sources embedded in dust distributions,luminosity
such as circumstellar
disks and dust shells on time scales up
outburst of a central star embedded in a circumstellar
to weeks.
dust disk on the resulting dust temperature distribution, as well as
Methods. We extended the publicly available 3D Monte Carlo radiative ontransfercode POLARIS
efficientmethods
for theFinally,
simulathe scattered
light and withthermalreemission
radiation.
tion of temperature distributions, scattering, and thermal reemission of dust
distributions
by temporally
variable radiation
a summaryas wellilluminatedas an outlook
on further applications
andsources. The influence of the chosen temporal step width and the numberof photon
packagesofper
step
key parameters
potential
improvements
the time
methodareasprovided
in Sect. 5.for a

T

Runge-Kutta-Fehlberg

104
103
102
101
100
10 1

given configuration is shown by simulating the temperature distribution in a spherical envelope around an embedded central star. The
10 2
effect of the optical depth on the temperature simulation is discussed for the
spherical envelope as well as for a model of a circumstellar
2. Computational method
disk with an embedded star. Finally, we present simulations of an outburst of a star surrounded by a circumstellar disk.
10 3
In thefollowing,
we outlineof time103
101
102
Results. The presented algorithm for time-dependent 3D continuum MonteCarloradiative
transfertheis theoreticala valuablebackgroundbasis for preparatory
T [K]dependent continuum
radiativesources,
transfer.such
After
the
studies as well as for the analysis of continuum observations of the dusty environment
around variable
as discussing
accreting young
A. Bensberg and S. Wolf: Time-dependent
thermalprocesses andwavelength
properties ofrange
the dust
in Sect.
2.1, westellar objects. In particular, the combined study of light echos in the opticaland near-infrared
and thecorresponding
Fig. 1. Cooling time described in Eq. (8) for different temperatures ofdescribe
theimplementationofatime-dependent
methodoftime-dependent thermal reemission observables of variable, for example outbursting sources, becomes possible on all involved spatial grains with different radii consisting of astronomical silicate.
radiative transfer simulations for temperature, dust reemission
scales.

τΔttstationary POLARIS

15nm
150nm
1.5 m
15 m
150 m

105

Cc [s]<<tc

A&A 668, A120 (2022)àPOLARIS

and scattering in Sect. 2.2. For this, we extend the publicly available–3DMonte Carlo disks
radiative
transfercode– POLARIS (Reissl
Key words. radiative transfer – methods: numerical – circumstellar matter
protoplanetary– ISM:
cloudset al. 2016).
phstars: variables: generalN

1. Introduction
Variability is known as a characteristic feature of young stellar objects (YSOs) since
3 their first
5 observations (Joy 1945). The
ph time-dependent phenomena can reveal different
study of theseunderlying physical mechanisms such as spots on the stellar surface caused by magnetic fields, variable mass accretion onto thestar, and obscuration by circumstellar material along the lineof sight to the observer (Herbst et al. 1994). Since all of thesemechanisms have an impact on the measured flux of the YSO,
observed light curves of variable YSOs show different shapes
ranging from periodical to linear or curved (Park et al. 2021). The
time scales of the underlying event can be on the order of hours
to years (e.g., Grankin et al. 2007; Cody & Hillenbrand 2014;
Günther et al. 2014). In the case of the extreme accretion events
that can be found in FUor and EXor objects, the outburst can

N =10 , 10 s
tc

2.1. Description of heating and cooling

We first focus on the thermal processes and corresponding properties of the dust. The ith photon package with wavelength
emitted by a radiation source with luminosity L that is emitting
Nph photon packages in the time-interval t carries the energy
L t
ei, =
.
Nph

(1)

Along its path through the model space, the dust absorbs energyof the photon package in relation to the wavelength-dependent
mass absorption coefficient  . The total absorption rate Ȧ in aregion with mean radiation intensity J is then given by:
Z 1
Ȧ = 4⇡
 J d .
(2)0

Following Lucy (1999), the mean intensity J of a discrete
number of photon packages with energy ei, within a wavelength range d traveling a path length li in a volume V in the

Under the assumption of local thermodynamic equilibrium(LTE), the dust will emit radiation with an emission rate Ė corresponding to its emission spectrum B at temperature T scaledwith the absorption coefficient  :Z 1
Ė(T ) = 4⇡
 B (T )d .
(6)0Considering the difference between absorption and emission rate
within one time step, that is combining Eqs. (4) and (6), we now
can estimate the enthalpy un+1 of the dust after n + 1 time steps
with step width t:
un+1 = un + (ȦĖ) t.

(7)

However, this holds only true if we assume the absorption andemission rate is constant over the step width t. We can constrain
the temporal step width by considering the time it takes to emit
the total enthalpy of a dust grain at temperature T , that is thecooling time tc (T ). For the case of emission without absorption,
we findtc (T ) =

u(T )
(8)
Ė(T ) Fig. 3. Sketch of the time-dependent ray tracing procedure for two dif-

0.04
60

τ=10

Δt=8s, Nph=105

65000s60

85000s105000s
180

40

160
140

T [K]

I [AU]

20
0

120
20
100
40
80
60

0

20

40

60

80

100

20

40

A [AU]

60

80

100

20

40

60

80

100

Fig. 11. Vertical cut through the temperature distribution of the outburst disk model after 65 000, 85 000 and 105 000 s described in Sect. 4.2. The
temporal step width of the simulation is set to 4 s; 105 photon package are emitted per time step.

1.0
0.9
0.8

550nm - face-on
550nm - 25

the afterglow in the thermal reemission case is small comparedto the one seen in the light curves of the scattered light. The reason for this is that the relative cold outer parts of the disk are notsignificantly contributing to the measured reemission radiation
flux before or during the outburst. This also causes the emission
peaks of the inclined and face-on disk to be closer together thanRelative Diﬀerence

A&A 668, A120 (2022)

dT/T

_

4

100

0

Relative Diﬀerence

I [AU]

10000s80

10 1 we performed simulations of a model for an outburst of
Lastly,40
star with a circumstellar disk. For this, we used the disk mode
10 2
described
in Sect. 4.1 (see also Table 2). For the sake of sim
0.02
plicityand to save computational time, we chose a low optica
20
10 3
depth of ⌧V = 0.01. In this case the dust temperature of the cellA&A 668, A120 (2022)
areafter about 50 000 s, that is roughly the time ligh4
10 converged[m] space. The luminosity o00.00
needs to travel once through the_ model
0.15
the central star was then increased by a factor of 4 for a duration of 10 000 s. The total simulation time was set to 120 000
20
0.02
to0.10make sure, that all grid cells return to their previous dus
temperature after the outburst.
40
The temperature simulation was performed using a tempora
0.05
0.04
step width of 4 s and 105 photon packages per time step. Th
temporalstep width was chosen such that the cooling time of th
0.00
60
3
0
20
40
60
80
100
10 7highest dust
10 6temperature
10 5 is not reached
10 4 within10one
expectedstep
A [AU][m]Three vertical cuts through the_ temperature
distribution of th
disk
model
for
different
time
steps
duringtheoutburst
areshow
Fig. 9. Difference plot of a vertical cut through the dust tempera- Fig. 10. Normalized SED (top) and relative difference (bottom) of thein Fig. 11. It caneasily bedistribution
seen that aofheat
wavemodel
corresponding
ture distribution of the disk model with ⌧ = 10 described in Sect. 4.1. time-dependent
temperature
the diskwith ⌧ = 10t
the outburst
in theis travelingthrough
the gri
The reference temperature distribution is calculated with the stationary discussed
in Sect.
4.1 source(dotted).luminosity
The reference
SED (solid)
is calculated
in radial
direction.distribution
Furthermore,thethermalmethod.
response times omethod using 108 photon packages.
using
the temperatureof thestationary
the dust are comparably small, that is the dust of a cell is heatin
or While
coolingtheto overall
the equilibrium
withinone time step
shape of temperature
the SED is well
reproduced,
the100
leading toplot
a discreteof difference
the heat wave.
difference
revealsforma peakof about 15% for waveFurthermore,investigatedthetoscatteredstellarlight anlengthsof around 20weµm.
This is close
the shortest
wavelength
10 1
reemissionof thedust asofobservables
thiatthermal
which thethermalradiation
reemission
radiation
the dust forof thesystem.
In
particular,
wesimulatedthethermalreemission
radigiven temperature distribution becomes significant. The differ10 2
ationplotsof theN band(10 µm)andthatthe thescatteredstellar lightofo
encein Figs.
8 and
9 show
dust temperaturethecells
V band
(550
nm)
using
respective
time-dependent
algo
10 3
the
in theinnerfew
AU theof themidplaneis underestimated.
rithmsforcorrespondray tracing toandSect.
2.3 anThese
cells
thescattering
cells with described
the highestindust
tempera4
Sect.
2.4. In thewith
casethethat
the observed
diskTheis inclined,is thenec
10
ture
determinedstationary
method.
spectrumit of_ [m]essary reemission
to take the radiationdifferent oflight
to the observe
thermalthetraveling
dust withtimes
the time-dependent
0.15
into account.
To illustrate
this effect,
intensity
maps wer
temperature
distribution
is thus
shifted theto longer
wavelengths
derived for
an inclinationof 25 aswith
welltheas forthe face-on
cascomparedto thespectrum calculated
stationary
method.
0.10
(0
).
Since
the
scatteringandreemission
simulationsaresen
However, this only affects the radiation of wavelengths notcorresitive to thetemporal
stepreemission
width, the ofstepthewidth
to 1000
sponding
to thethermalfew wascellssetwith
the
8
0.05
and a totalof photon
packagesthe
perflux
timeofstepof 10
highestdustnumber
temperature.
Therefore,
mostof wertheused for scatteringand reemission,respectively.
In orderavoi
wavelengths
larger than
10 µm is showing
not morethanto 10%
0.00
an impactto of
initial SED.
heating process, all simulations wer
difference
thethereference
10 7
10 6
10 5
10 4
10 3
started once a steady state was reached. To rule out an offset o_ [m]the light curves of the scattered and reemitted radiation cause
Fig. 10. Normalized SED (top) and relative difference (bottom) of the by additional light travel times due to different positioning of thtime-dependent temperature distribution of the disk model with ⌧ = 10 detector in the scattering and ray tracing treatments, the start odiscussed in Sect. 4.1 (dotted). The reference SED (solid) is calculated the outburst was set to 60 000 s in both cases.
using the temperature distribution of the stationary method.
The resulting light curve for the scattered light is shown iFig. 12. A sample of the corresponding scattering images for th
While the overall shape of the SED is well reproduced, the inclined disk can be found in Fig. 13. There are three effectdifference plot reveals a peak difference of about 15% for wave- that can be seen in the light curves: First, the overall flux ilengths of around 20 µm. This is close to the shortest wavelength higher in the case of the inclined disk. This is caused by that which the thermal reemission radiation of the dust for the different probabilities of the scattering direction. The scatter
given temperature distribution becomes significant. The differ- ing of the stellar light towards the observer is more probabl
ence plots in Figs. 8 and 9 show that the dust temperature of for the inclined than for the face-on disk. Secondly, the scat
the cells in the inner few AU of the midplane is underestimated. tered light of the outburst is first visible in the light curve oThese cells correspond to the cells with the highest dust tempera- the inclined disk. This shows the importance of the light travel
ture determined with the stationary method. The spectrum of the ing time toward the observer. Since the lower part of the disk ithermal reemission radiation of the dust with the time-dependent the images is closer to the observer, the outburst will be seetemperature distribution is thus shifted to longer wavelengths there first. This is also visible in the first image of Fig. 13
compared to the spectrum calculated with the stationary method. Furthermore, the outburst is stretched out compared to the face
However, this only affects the radiation of wavelengths corre- on case, because parts of the disk with the same radial distance t
sponding to the thermal reemission of the few cells with the the source will have different distances to the observer. This ca
highest dust temperature. Therefore, the flux of most of the be seen in the second of the scattering images. The third effect i_ [norm.]

50000sA [AU]

60

10
4.2.
2D disk outburst
0.04_

τ=0.01

40

SED

60

中心星光度が外へ伝わる20

Fig. 9. Difference plot of a vertical cut through the dust temperature distribution of the disk model with ⌧ = 10 described in Sect. 4.1.
The reference temperature distribution is calculated with the stationary
method using 108 photon packages.
A. Bensberg and S. Wolf: Time-dependent Monte Carlo continuum radiative transfer_ [norm.]

stationary0Articlehttps://doi.org/10.1038/s41550-022-01831-8

UV-driven chemistry as a signpost oflate-stage planet formation

Jenny K. Calahan 1 , Edwin A. Bergin 1, Arthur D. Bosman1, Evan A. Rich1,
Sean M. Andrews2, Jennifer B. Bergner 3, L. Ilsedore Cleeves4,
Viviana V. Guzmán5,6, Jane Huang1, John D. Ilee 7, Charles J. Law2,
Romane Le Gal8,9,10, Karin I. Öberg 2, Richard Teague11, Catherine Walsh 7,
David J. Wilner 2 & Ke Zhang12

Received: 19 July 2022

Accepted: 14 October 2022

Published online: 8 December 2022
Check for updates

Received: 19 July 2022

>1 mm

Accepted: 14 October 2022

Published online: 8 December 2022

CH CN, HC3N

Check for3 updates

Jenny K. Calahan 1 , Edwin A. Bergin 1, Arthur D. Bosman1,The
Evanchemical
A. Rich1, reservoir within protoplanetary disks has a direct impact on2
3
4
Sean M. Andrews , Jennifer B. Bergner , L. Ilsedore Cleeves planetary,compositions and the potential for life. A long-lived carbon- and2
Viviana V. Guzmán5,6, Jane Huang1, John D. Ilee 7, Charles J. Law,
nitrogen-rich chemistry at cold temperatures (≤ 50 K) is observed within
7
Romane Le Gal8,9,10, Karin I. Öberg 2, Richard Teague11, Catherine,
coldWalshand evolved
planet-forming disks. This is evidenced by bright emission
2
12David J. Wilner& Ke Zhang<10 µm

誘

CH3CN

J

1–10 MyrK
aged systems that would otherwise
K laddar from small organic radicals in25-50

have frozen out onto grains within 1 Myr. We explain how the chemistry ofa planet-forming
The chemical reservoir within protoplanetary disks has a direct
impact on disk evolves from a cosmic-ray/X-ray-dominated regime
toaultraviolet-dominatedchemical equilibrium. This, in turn, will bringplanetary compositions and the potential for life. A long-lived carbon- andabout awithin
temporal transition in the chemical reservoir from which planets will
nitrogen-rich chemistry at cold temperatures (≤ 50 K) is observed
accrete.
This photochemical dominated gas phase chemistry develops as
cold and evolved planet-forming disks. This is evidenced by bright emission
dust evolves
via growth, settling and drift, and the small grain population isfrom smallotherwise
3 organic radicals in 1–10 Myr aged systems that would
depletedfromhave frozen out onto grains
within 1 Myr. We explain how the chemistry of the disk atmosphere. A higher gas-to-dust mass ratio allows
https://doi.org/10.1038/s41550-022-01831-8
for deeper
penetration of ultraviolet photons is coupled with a carbon-richa planet-forming disk evolves from a cosmic-ray/X-ray-dominatedregime
gas
(C/O
>
1)
to a ultraviolet-dominated chemical equilibrium. This, in turn, will bring to form carbon-bearing radicals and ions. This further results ingas phaseformationof organic molecules, which then would be accreted by
ISM
about a temporal transition in Approximatethechemicalreservoir from whichplanets
will
number density
any
actively
formingplanets present in the evolved disk.
accrete. This photochemical dominated gas phase chemistry develops as

UV

àC/O

C2H, CH CN

ArticleEarly-stage planet formation <~1 Myr

Molecules with ALMA at Planet-forming Scales(MAPS) structures that are thought to be indicative of planet formation . The
compositions
their icy
mantles
1-2 Myr IM
Lup of pebbles
CH3andCN,
HC
3Ndirectly influence thefinal composition of a solid planetary core . After a core becomes
sufficiently
planetsCN,
the gaseous
1-2 Myr AS
209massive,CHHC3material
N fromz/r>0.1
3 start to accrete
reservoir surrounding the pebble-rich midplane of a protoplanetary
disk to form CH
their atmospheres
directlyprobe the>6 Myrladder3CN . It remains difficult toK
chemistry of actively forming planets. The solid cores of giant plan- gas within the planet-forming midplane owing to the high dust densi<10–3 cm–3

UV
Late-stage planet formation >~1 Myr

dust evolves via growth, settling and drift, and the small grain population isoutdepleted fromFreeze
the disk
atmosphere.
A arehighergas-to-dust
massforratio
allowsProtoplanetarydisks
the natal
environments
planets.
Disks
10–1 –10–3 cm–3
Numberfor deeper penetration
ultraviolet
photons
is coupledwitha carbon-richhaveofthreemain components:
a pebble-rich
dusty
midplane(dust grain
density of1> ~1 mm), a gaseousatmosphere
extendingwell above
and radismall
grainsgas (C/O > 1) to formradiuscarbon-bearing
radicalsandions.
This further
resultsin2
ally beyond 10(by–1 a factor–3 of ~2; ref. ) the pebble-rich midplane and a–10cm
gas phase formationsmallof organic
molecules, which then would be accreted by
dust population (radius < 10 µm) that is coupled to the gas. Eachany actively formingcomponent
planets present
in the evolvedof the protoplanetary
diskdisk.
has an impact on shaping the

à

4

5,6

7

–3

>10 cmets must form over a short timescale (~1 Myr) for the eventual planet
4 in atoobtain its
fullaremass
over thecourseof a typicallifetimeof gas. The
structuresthatthought
to beindicativeof planet
formation
3
disk
(3–10
Myr;
ref.
)
and
to
explainthewidelyobservedgap
andcompositions of pebbles and their icy mantles directly influenceringtheties leading to elevated dust optical depths that mask line emission, as
well as cold temperatures that lead to the freezing out of common gas
Protoplanetary disks are the natal environments for planets. Disks
tracers such as CO onto dust grains. However, constraining the chemical
have three main components: a pebble-rich dusty midplane (dust grain
UV flux
1
5,6
radius > ~1 mm), a gaseous atmosphere extending well above and radi- final composition of a solid planetary core . After a core becomes
Planet coreally beyond (by a factor of ~2; ref. 2) the pebble-rich midplane and a sufficiently massive,planets start to accrete material from the gaseous
Freeze out andsmall dust population (radius < 10 µm) that is coupled to the gas.
Eachreservoir
surrounding
the pebble-rich midplane of a protoplanetary
photodesorption
1
3
Dust grainAnn Arbor,
University
oftheir
Michigan,USA. 2Centerfor∣ Harvard
component of the protoplanetary disk has an impact on shaping the disk
to form
atmospheres7. ItMI,
remains
difficult
toAstrophysics
directly probe
the & Smithsonian, Cambridge, MA, USA. University of Chicago Department
4
5
of
the
GeophysicalSciences,
Chicago,USA.
Departmentof dustAstronomy,ig. 1 | A schematic chemistry
highlightingof
thephysicalevolutionof a diskTheand how
small
dustplansettles, UV
photons
make
their
way deeper
into
the IL,
disk,
allowing
actively
formingplanets.
solid cores of
giant
gas
withinthe planet-forming
midplane
owing
tofor
the high
densi- University of Virginia, Charlottesville, VA, USA. Instituto de Astrofísica,
6
7
Ponticia
Universidad
CatólicadeChile,
Macul,
Santiago,
Chile.
NúcleoMileniodeFormación
Planetaria(NPF),
Santiago,
Chile.
School of Physics
hat physical environment
canaffecttheachemistry.
At the top,
showfora the eventual
photodesorption
complex
species
off grains.dust
Now,optical
there is depths
a cycle ofthat
carbonets must
form
over
short timescale(~1weMyr)planet ofties
leading
to elevatedmask line emission, as
8

9

C

CH3CN

I (mJy beam–1 km s–1)

15

g/d

exp tailµm
1 mm
HD163296
Hya CH3CN, HCN, HC3NC
10
C/O=1-2
1 Myr
UV

1
TW

15

CH3CN J=

120–110
121–111
122–112
123–11310300

CH3CN J=

60–50
61–51

10

HC3N 29–28

20

HC3N 11–10

15

200

10

5

5

HCN 3–2
HCN 1–0

100
5

0

0
0

100

Radius (au)

200

0

0
0

100

200

Radius (au)

0

100

200

Radius (au)

300

0

100

200

Radius (au)Fig. 2 | Radial intensity profiles of the observed complex organic moleculesand HCN towards the disk around HD 163296. The molecules shown are CH3CN,
HCN and HC3N (left to right with two J transitions of CH3CN shown in the firsttwo panels). Solid thick lines in the background correspond to the observations
derived from Ilee et al.12 and Guzmán et al.79 (utilizing the results of Law et al.53),

while dashed lines correspond to modelled radial profiles. Our fina
includes an increase in C/O ratio beyond 20 au and a depletion of sm
represents 1 Myr of chemistry. This model can simultaneously fit th
ratios and general morphology of the observed radial profiles of thorganic molecules.

higher dust opacity than modelled. A comparison model without adepletion in small dust mass is shown in Supplementary Fig. 5.

of planet formation and its direct impact on the chemis
ing planet atmospheres. Within the early stages of plane
pebble growth and accretion into solid planet cores has
chemistry onto these cores are influenced primarily by t
make-up of large pebbles and their icy mantles. The chemin the midplane during this stage of formation is dominatand cosmic rays49. After timescales of order 1 Myr, at thepebble formation, small grains have grown and settled
midplane, allowing for UV photons to penetrate deeper inpreviously assumed. This excess UV flux in concert with an
C/O ratio produces a carbon-rich gas phase cycle of pro

UMIST, Rate12

Discussion

HC3N and CH3CN are built up in the gas from simple carbon andnitrogen-based volatiles (see Methods section ‘Chemical reactions’for details). A reservoir of these more simple molecules is maintainedin the gas phase because of photodesorption from dust grain surfacesby an enhanced UV field. The main destruction products from CH3CN
and HC3N are simple volatiles that can cycle back to create larger nitrile
molecules including their original parent molecule. Although there are© 2022. The Author(s). Published by the American Astronomical Society.

The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament

3,4
Tao-Chung Ching1,2,93, Di Li2,5,62,5,6, Zhiyuan Ren2 2, Shih-Ping Lai7,8 7,8, David Berry9 9, Kate Pattle10 10,
1,2,93, Keping Qiu
Tao-Chung Ching, Keping Qiu3,4 , Di
, Zhiyuan Ren, Kate,11,12
14,15 , Shih-Ping Lai
8 , David Berry
16,17 Pattle
Ray Furuya 11,12, Derek Ward-Thompson13 Li, Chang Won Lee
13, Doug Johnstone
14,15, Patrick M. Koch
16,17,Ray Furuya, Derek Ward-Thompson, Doug,21Patrick M. Koch8 , Chang
16,17
18
19,20 Johnstone
2,22 Won Lee
8,
Thiem Hoang 16,17, Tetsuo Hasegawa 18, Woojin Kwon 19,20, Pierre Bastien 21, Chakali Eswaraiah 2,22, Jia-Wei Wang 8,
Thiem Hoang, Tetsuo Hasegawa, Woojin16,17
Kwon, Pierre Bastien, Chakali Eswaraiah, Jia-Wei Wang ,Kyoung Hee Kim16,23, Archana Soam24 24, A-Ran Lyo16 16, Junhao Liu9 9,
16,23, Jihye Hwang
Kyoung Hee Kim25,26, Jihye Hwang16,17 18, Archana Soam
, A-Ran, Junhao Liu 14,15,
27 LyoValentin J. M. Le Gouellec 25,26, Doris Arzoumanian 18, Anthony Whitworth 27, James Di Francesco 14,15,
Valentin28,29
J. M. Le Gouellec, Doris Arzoumanian, Anthony 33,94
Whitworth, James,
30
31,32
34 Di Francesco
Frédérick Poidevin 28,29, Tie Liu 30, Simon Coudé 31,32, Mehrnoosh Tahani 33,94, Hong-Li Liu 34, Takashi Onaka35,36
35,36,
Frédérick, Tie
Liu, Simon Coudé, MehrnooshTahani, Hong-Li40Liu, Takashi Onaka,
37 Poidevin
18,36,38
39
37
41,42
Dalei Li , 37
Motohide Tamura 18,36,38, Zhiwei Chen 39, Xindi Tang 37, Florian Kirchschlager 40, Tyler L. Bourke 41,42,
Dalei Li , Motohide
Tamura,Zhiwei
Chen
,
Xindi
Tang
,
FlorianKirchschlager
,
Tyler
L.
Bourke,15
Do-Young Byun16,17
Huei-Ru Vivien Chen7,8 7,8, Wen Ping Chen43 43, Jungyeon Cho44 44, Yunhee Choi16,16
16,17, Mike Chen , 15
Do-Young Byun
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1 1

DR21,
4 pc,
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σ~3 mJy/beam, Ι/δI>3, p/δp>3, δp<4%, θ=14",

2

à

,
90°

,

ResearchCenterfor forIntelligent
ComputingPlatforms,
Zhejiang
Lab,Lab,Hangzhou311100,Peopleʼs
Republicof China;
chingtaochung@gmail.com
ResearchCenterIntelligent
ComputingPlatforms,
ZhejiangHangzhou311100,Peopleʼs
Republicof China;
chingtaochung@gmail.com
2
National
Astronomical
Observatories,
ChineseAcademyof Sciences,
Datun
Road,
Chaoyang
District,
Beijing
100012,Peopleʼs
Republicof China
National
Astronomical
Observatories,
ChineseAcademyof Sciences,
A20A20
Datun
Road,
Chaoyang
District,
Beijing
100012,Peopleʼs
Republicof China
3 3Schoolof Astronomy
Space
Science,Nanjing
University,
Xianlin
Avenue,Nanjing
210023,Peopleʼs
Republicof China
Schoolof Astronomy
andandSpace
Science,Nanjing
University,
163163
Xianlin
Avenue,Nanjing
210023,Peopleʼs
Republicof China
4
4
Laboratoryof Modern
Astronomy
Astrophysics(Nanjing
University),
Ministryof Education,
Nanjing
210023,Peopleʼs
Republicof China
KeyKeyLaboratoryof Modern
Astronomy
andandAstrophysics(Nanjing
University),
Ministryof Education,
Nanjing
210023,Peopleʼs
Republicof China
5 5
Departmentof Astronomy,
Universityof Chinese
Academyof Sciences,
Beijing
100049,Peopleʼs
Republicof China
Departmentof Astronomy,
Universityof Chinese
Academyof Sciences,
Beijing
100049,Peopleʼs
Republicof China
6 6
NAOC-UKZN
Computational
Astrophysics
Centre,Universityof KwaZulu-Natal,
Durban4000,
South
AfricaNAOC-UKZN
Computational
Astrophysics
Centre,Universityof KwaZulu-Natal,
Durban4000,
South
Africa7 7 Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
88Academia
SinicaInstituteof Astronomy
Astrophysics,
No.1,
Sec.3.,
Roosevelt
Road,
Taipei
10617,
TaiwanAcademia
SinicaInstituteof Astronomy
andandAstrophysics,
No.1,
Sec.3.,
Roosevelt
Road,
Taipei
10617,
Taiwan9 9 East Asian Observatory, 660 N. A’ohōkū Place, University Park, Hilo, HI 96720, USA
East
Asian
Observatory,
660
N.
A’ohōkūPlace,
University
Park,
Hilo,
HI
96720,
USA
10 10 Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
Department of
Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
11 11 Tokushima University, Minami Jousanajima-machi 1-1, Tokushima 770-8502, Japan
Tokushima University, Minami Jousanajima-machi 1-1, Tokushima 770-8502, Japan
12
12
Instituteof Liberal
Sciences
Tokushima
University,
Minami
Jousanajima-machi
Tokushima
770-8502,
Japan
Instituteof Liberal
ArtsArts
andandSciences
Tokushima
University,
Minami
Jousanajima-machi
1-1,1-1,
Tokushima
770-8502,Japan
13 13 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
Jeremiah
Horrocks
Institute,
UniversityofCentralLancashire,
Preston
PR1
2HE,
UK
14 14 NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
NRC15Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
15
Departmentof Physics
Astronomy,
Universityof Victoria,
Victoria,
V8W
2Y2,
CanadaDepartmentof Physics
andandAstronomy,
Universityof Victoria,
Victoria,
BCBC
V8W
2Y2,
Canada16
16
Korea
Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
Korea
17 Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 34055, Republic of Korea
17
Universityof Science
Technology,
Korea,
Gajeong-ro,
Yuseong-gu,
Daejeon34113,
Republicof Korea
Universityof Science
andandTechnology,
Korea,
217217
Gajeong-ro,
Yuseong-gu,
Daejeon34113,
Republicof Korea18
18
National
Astronomical
Observatoryof Japan,National
Institutesof Natural
Sciences,
Osawa,
Mitaka,Tokyo
181-8588,Japan
National
Astronomical
ObservatoryofJapan,
National
InstitutesofNaturalSciences,
Osawa,
Mitaka,Tokyo
181-8588,
Japan
19
19
Department of Earth Science Education, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea

dhandrasekhar &a 2aj l 2j , and numerical simulations(4 )Guerraetal.
2021)(Liu et al. 2021).

sed method. The j1lence to Houde
magneticet al. (2009) suggest that, if the correlation length δmuch smaller
the thickness
polarization
anglethandifference
between of the cloud %a, the(lfor) isBthef%'variation
tinistheation ratio
segments
separatedl, W is the
beam
δB/B
cana distancebe evaluatedfrom
thevsangular dispersion
of B
ΔΦ
𝑙
t to B0 by(i.e., function
the FWHM
beam
in theformdivided by 8 ln 2 ), thetion is a Taylor expansion representing the structure in2
1 isBthe
does not involve turbulence, and Ncellt § number of l 2 2(E 2 2W 2 )1   cos [%' (l )]§ 
q [1  e]nt cells along the line of sight obtained
Ncell byB 2§

Ncell (E 2

2W 2) %a2Q E 3.

0d

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(4 )
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, " ~
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Ncell B02§
width (i.e., the FWHM beam divided by 8 ln 2 ), the22e Bt isthe source ofin B0, the Brepresentingt § B0 §summationis perturbationa Taylor expansion
the structure ind from Equation (4) provides a good approximation of
B that does not involve turbulence, and N is the number of/Bpos in0 the DCF equation for evaluating the magnetic cell
cells
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rengthturbulent
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Bpos 

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Angular Dispersion Function of the JCMT and Planck Data
2

1 Bt §of the2 (l )  functionsl 2 JCMT
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re 7 shows the angularbdispersion(6 )e
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ably different
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Because
Btthoseis thesourceperturbation
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separately
forfromEquation(4) provides
a goodapproximation of#

LETTER TO THE EDITOR

Discovery of interstellar NC4 NH+ : Dicyanopolyynes are indeed
abundant in space?
M. Agúndez1 , C. Cabezas1 , N. Marcelino2,3 , R. Fuentetaja1 , B. Tercero2,3 ,P. de Vicente3 , and J. Cernicharo1
1

Instituto de Física Fundamental, CSIC, Calle Serrano 123, 28006 Madrid, Spaine-mail: marcelino.agundez@csic.es; jose.cernicharo@csic.es
2
Observatorio Astronómico Nacional, IGN, Calle Alfonso XII 3, 28014 Madrid, Spain
3
Observatorio de Yebes, IGN, Cerro de la Palera s/n, 19141 Yebes, Guadalajara, Spain
Received 17 November 2022 / Accepted 13 December 2022
ABSTRACTThe previous detection of two species related to the nonpolar molecule cyanogen (NCCN), its protonated form (NCCNH+ ) and one
metastable isomer (CNCN), in cold dense clouds supported the hypothesis that dicyanopolyynes are abundant in space. Here we
report the first identification in space of NC4 NH+ . This cation is the protonated form of NC4 N, which is the second member ofthe series of dicyanopolyynes after NCCN. The detection was based on the observation of six harmonically related lines within theYebes 40m line survey of TMC-1 QUIJOTE. The six lines can be fitted to a rotational constant B = 1293.90840 ± 0.00060 MHz anda centrifugal distortion constant D = 28.59 ± 1.21 Hz. We confidently assign this series of lines to NC4 NH+ based on high-level ab
initio calculations, which supports the previous identification of HC5 NH+ from the observation of a series of lines with a rotational
10
2
constant 2 MHz lower than that derived here. The column density of NC4 NH+ in TMC-1 is (1.1 +1.4
0.6 ) ⇥ 10 cm , which implies that
NC4 NH+ is eight times less abundant than NCCNH+ . The species CNCN, previously reported toward L483 and tentatively in TMC-1,
is confirmed in this latter source. We estimate that NCCN and NC4 N are present in TMC-1 with abundances a few times to one orderof magnitude lower than HC3 N and HC5 N, respectively. This means that dicyanopolyynes NC (CC)n CN are present at a lower level
than the corresponding monocyanopolyynes HCC (CC)n CN. The reactions of the radicals CN and C3 N with HNC arise as the most
likely formation pathways to NCCN and NC4 N in cold dense clouds.
Key words. astrochemistry – line: identification – molecular processes – ISM: molecules – radio lines: ISM

1. Introduction
Dicyanopolyynes are molecules with a linear unsaturated skeleton of carbon atoms that terminates at each edge by acyano group, that is to say N⌘C (C⌘C)n C⌘N. The simplest member of this family, cyanogen (NCCN), has been longknown to be present in the atmosphere of Titan (Kunde et al.
1981; Coustenis et al. 1991; Sylvestre et al. 2020) and has been
recently identified in the coma of comet 67P/ChuryumovGerasimenko (Hänni et al. 2021). The second member of theseries, dicyanoacetylene (NC4 N), has been observed in solidstate, although not in the gas phase, in the atmosphere of Titan(Samuelson et al. 1997; Jolly et al. 2015). It is also interesting to note that NCCP, a species chemically related to NCCN
that results from the substitution of one N atom by one P

well known that monocyanopolyynes H C⌘C (C⌘C)n C⌘N,
more commonly known as cyanopolyynes, are abundant in colddense clouds and circumstellar envelopes around evolved stars,
and thus it is conceivable that dicyanopolyynes are abundantReceived 12 August 2022 / Accepted 28 December 2022
Number of stars in the Sun’s birth cluster revisited
1,2 and Eiichiro Kokubo2
Sota Arakawa
ABSTRACT
1

Japan Agency for Marine-Earth Science and Technology, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 236-0001,

26
The Sun is thought to have been
Al-rich and 26 Al-poor calcium–aluminum-rich
Japan formed within a star cluster. The coexistence ofe-mail: arakawas@jamstec.go.jp
26
inclusions indicates that a direct
injectionofObservatory
Al-richmaterials
a nearby
supernova would be expected to occur
National
Astoronomicalof Japan,
2-21-1 Osawa, from
Mitaka, Tokyo
181-8588, core-collapseJapan5in the first 10 years of the existenceof 2022the / Solar
System.
Therefore, at least one core-collapse supernova ought to occur within the
Received 12 August
Accepted 28
December 2022
duration of star formation in the Sun’s birth cluster. Here, we revisit the number of stars in the Sun’s birth cluster from the point of
ABSTRACT
view of the probability of experiencing at least one core-collapse
supernova within the finite duration of star formation within the birth
The Sunof
is thought
havethebeen birth
formed withina star cluster.
of Al-rich andAl-poorthan
calcium–aluminum-richcluster. We find that the number
starstoincluster
mayThebecoexistence
significantly
greaterthat previously considered, depending
inclusions indicates that a direct injection of Al-rich materials from a nearby core-collapse supernova would be expected to occur
in the first 10 years of the existence of the Solar System. Therefore, at least one core-collapse supernova ought to occur within theon the duration of star formation.
2

26

26

26

5

duration of star formation in the Sun’s birth cluster. Here, we revisit the number of stars in the Sun’s birth cluster from the point ofview of the probability of experiencing at least one core-collapse supernova within the finite duration of star formation within the birthcluster. We find that the number of stars in the birth cluster may be significantly greater than that previously considered, dependingon the duration of star formation.

Key words. meteorites, meteors, meteoroids – supernovae: general – stars: Wolf-Rayet – open clusters and associations: general

26Al
1. Introduction

Key words. meteorites, meteors, meteoroids – supernovae: general – stars: Wolf-Rayet – open clusters and associations: general

10^5

1. Introduction
The majority of stars form within star clusters (e.g.,
Lada & Lada 2003) and our Solar System is also thought tohave been formed within a cluster, based on a number of indications (e.g., Adams 2010). For example, some of trans-Neptunian
objects, including (90 377) Sedna, exhibit a substantial heliocentric eccentricity and perihelion distance (e.g., Brown et al.
2004) and the most plausible scenario for their formation isa close encounter with a passing star in the Sun’s birth cluster (e.g., Morbidelli & Levison 2004; Brasser et al. 2006). Parts
of presolar grains, whose isotopic compositions are significantly anomalous by comparison with the average solar composition, originate from core-collapse supernovae (CCSNe; e.g.,
Nittler & Ciesla 2016), and the chromium isotopic heterogeneity found in various chondritic meteorites might be evidence of
the injection of dust grains from a CCSN (e.g., Sugiura & Fujiya
2014; Fukai & Arakawa 2021).
An injection of dust grains into the Solar System froma nearby CCSN is also a classical scenario for the originof short-lived radionuclides (SLRs) found in meteorites (e.g.,
Takigawa et al. 2008; Ouellette et al. 2010). Such SLRs areradioactive nuclides that were present in the early Solar Sys-

The majority of stars form within star clusters (e.g.,
Lada & Lada 2003) and our Solar System is also thought tohave been formed within a cluster, based on a number of indications (e.g., Adams 2010). For example, some of trans-Neptunian
objects, including (90 377) Sedna, exhibit a substantial heliocentric eccentricity and perihelion distance (e.g., Brown et al.
2004) and the most plausible scenario for their formation isa close encounter with a passing star in the Sun’s birth cluster (e.g., Morbidelli & Levison 2004; Brasser et al. 2006). Parts
of presolar grains, whose isotopic compositions are significantly anomalous by comparison with the average solar com-

2002). Although the majority of primitive (i.e., unmelted) CAIs
are uniformly enriched in Al (e.g., MacPherson et al. 2012),
some unusual CAIs show the order-of-magnitude lower initialabundance of Al. Platy hibonite crystals (PLACs) are classified into those unusual CAIs and they are regarded as theoldest CAIs based on their high condensation temperature andlarge nucleosynthetic anomalies (e.g., Sahijpal & Goswami 1998;
Kööp et al. 2016), although their origins are still under debate(e.g., Larsen et al. 2020; Desch et al. 2022). In addition, CAIs
with fractionation and unidentified nuclear e↵ects (FUN CAIs)
also have low and varied initial abundances of 26 Al, and they arethought to have been formed prior to normal CAIs (e.g., Park et al.
2017). The coexistence of Al-rich and 26 Al-poor CAIs would

2002). Although the majority of primitive (i.e., unmelted) CAIs
are uniformly enriched in 26 Al (e.g., MacPherson26
et al. 2012),
some unusual CAIs show the order-of-magnitude lower initialabundance of 26 Al. Platy hibonite crystals (PLACs) are classified into those unusual CAIs and they are regarded as theoldest CAIs based on their 26
high condensation temperature andlarge nucleosynthetic anomalies (e.g., Sahijpal & Goswami 1998;
Kööp et al. 2016), although their origins are still under debate(e.g., Larsen et al. 2020; Desch et al. 2022). In addition, CAIs
with fractionation and unidentified nuclear e↵ects (FUN CAIs)
also have low and varied initial abundances of 26 Al, and they arethought to have been formed prior to normal CAIs (e.g., Park et al.
2017). The coexistence of 26 Al-rich and 26 Al-poor CAIs would
serve as evidence of a direct injection of 26 Al-enriched dust
grains into the solar nebula (or the solar molecular cloud core)in the epoch of CAI formation (e.g., Sahijpal & Goswami 1998;
Holst et al. 2013). As the duration of CAI formation (i.e., theformation age spread of CAIs) is a few 105 years or less (e.g.,Thrane et al. 2006; Connelly et al. 2012; Kawasaki et al. 2020),
the direct injection event would have occurred in the first 105 yearsof Solar System formation. We note that the initial abundanceof 26 Al recorded in CAIs would not be altered26
even if additional injection of 26 Al-enriched materials into the solar nebula

ABSTRACT

Ryan D. Boyden1 and Josh Eisner1
Steward
University
Arizona,
N. Cherry Ave,
AZ, 85719,
USA
The stellar cluster environmentisObservatory,
expected
to ofplay
a933
centralroleTucson,in theevolutionof circumstellar disks. We
August 23, 2022;
2, 2022;
Accepted December
21, 2022)UV and X-ray radiation fields,
use thermochemical modeling (Received
to constrain
the Revised
dustDecember
and gasmasses,disk sizes,
viewing geometries, and central stellar masses of 20ABSTRACTClass II disks in the Orion Nebula Cluster (ONC). We fit+ disks. We
stellar cluster
environment
expected to play aCO
centralcircumstellara large grid of disk The
modelsto 350GHz iscontinuum,
J role= in3the evolution
2, andof HCO
J = 4 3 ALMA observations
use thermochemical modeling to constrain the dust and gas masses, disk sizes, UV and X-ray radiation fields,of each target, andviewing
we introduce
procedure
forofmodelinginterferometricobservations
geometries, andacentral
stellar masses
20 Class II disks
in the Orion Nebula Cluster(ONC). We fit of gas disks detected in+grid of molecular
disk models to 350
GHz continuum,
CO J = 3We2, andHCO
J =the4 3ONCALMA observations
absorption againstaalargebrightcloud
background.
find
that
disks are massive and compact,of each target, and we introduce a procedure for modeling interferometric observations of gas disks detected in3with typical radii <100 AU,masses10background.
M ,Weandgas-to-dust
100.
The ISM-like gas-to-dust
absorption
againstgas
a bright
molecular cloud
find that
the ONC disks ratios
are massive andcompact,with typical radii < 100 AU, gas masses 10 3 M , and gas-to-dust ratios 100. The ISM-like gas-to-dust
ratios derived fromratios
ourderived
modelingsuggest that compact, externally-irradiated disks in the ONC are less prone
from our modeling suggest that compact, externally-irradiated disks in the ONC are less prone
to gas-phase CO
depletion
the massive
and extended
gas disks
thatdisksare commonly
nearby lowto gas-phase CO depletion
thanthethanmassiveandextendedgasthat foundare incommonly
found in nearby lowmass star-forming regions. The presence of massive gas disks indicates that external photoevaporation may
mass star-forming haveregions.
The
presence
disksunclear
indicatesthatcluster
external
only recently
begun
operating inof
themassive
ONC, thoughgas
it remains
whether othermembers photoevaporation may
older andoperating
more evaporated
ones in our
sample. Finally,
we compare
our dynamically-derived
have only recentlyare
begun
inthanthetheONC,
thoughit remains
unclearwhether other cluster members
stellar masses with the stellar masses predicted from evolutionary models and find excellent agreement. Our
are older and more
evaporated
ones ofindynamical
our sample.
Finally,
we rangecomparedynamically-derived
study
has significantly thanincreasedthe
the number
mass measurementsin the mass
 0.5 M our,demonstrating that the ONC is an ideal region for obtaining large samples of dynamical mass measurements
stellar masses withtowards
the low-massstellarM-dwarfs.
masses predicted from evolutionary models and find excellent agreement. Our
study has significantly increased the number of dynamical mass measurements in the mass range  0.5 M ,Keywords: open clusters and associations: individual (Orion) — planetary systems — protoplanetarydemonstrating that the ONC disks
is anidealpre-main
regionfor obtaining large samples of dynamical mass measurements— stars:
sequence
towards low-mass M-dwarfs.1. INTRODUCTION
A key property of young stellar clusters is the presence1

arXiv:2212.12325v1 [astro-ph.EP] 22 Dec 2022

12.12325v1 [astro-ph.EP] 22 Dec 2022

(Received August 23, 2022; Revised December 2, 2022; Accepted December 21, 2022)

Chemical modeling of Orion Nebula Cluster disks: evidence for massive, compact gas
disks with ISM-like gas-to-dust ratios

Protoplanetary disks form in a variety of environments, and the natal environment has the potential toshape the evolution of disks and planetary systems (fora recent review, see Parker 2020). The most common
environments of star formation are young stellar clusters(e.g., Lada et al. 1993; Lada & Lada 2003; Krumholz
et al. 2019). Understanding how disks evolve in clustered star-formation environments is therefore essential
for interpreting the demographics of disks and exoplanets (e.g., Ndugu et al. 2018; Winter et al. 2020b),
and examining how our own solar system fits into theof massive O- and B-type stars. Strong UV fields frommassive stars launch photoevaporative winds from thesurfaces of disks surrounding lower-mass cluster members through a process known as external photevaporation (e.g., Johnstone et al.
1998; Störzer & Hollenbach 1999). In regions of high stellar density andradiation field strength, external photoevaporation acts
as the dominant mechanism of disk dispersal (Scally &Clarke 2001; Winter et al. 2018; Concha-Ramírez etal. 2019), and can eﬀectively deplete the disk of planetforming material within < 1 Myr of cluster evolution

ClassandII associations: individual (Orion)
ALMA,
CO 3-2, systems
HCO+ 4-3
Keywords: open clusters— planetary— protoplanetary— stars:
pre-main sequencer<100 au, Mgas>10^disks
3 Msun,g/d>100
CO deplete
1. INTRODUCTION

Protoplanetary disks form in a variety of environments, and the natal environment has the potential to

A key property of young stellar clusters is the presenceof massive O- and B-type stars. Strong UV fields frommassive stars launch photoevaporative winds from the3

Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
Received 2022 Julyrevised2022 November
accepted
November
29;Starpublished
2023 February 14
The 14;Star
Formation
History 29;of theMilky2022
Way’s
Nuclear
Cluster
Zhuo Chen1 , Tuan Do1 , Andrea M. Ghez1 , Matthew W. Hosek, Jr.1,4 , Anja Feldmeier-Krause2 , Devin S. Chu1 ,Abstract
Rory O. Bentley1 , Jessica
R. Lu3 , and Mark R. Morris1
1

Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547, USA; zhuochen@astro.ucla.edu

Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
We report the ﬁrst star formation history
study of the Milky Ways nuclear star cluster (NSC), which includes
Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
2022 Julysample
14; revised 2022
accepted 2022 November
29; published 2023 February
14
observational constraints fromReceived
a largeofNovember
stellar29; metallicity
measurements.
These
metallicity measurements
were obtained from recent surveys from Gemini and Abstract
the Very Large Telescope of 770 late-type stars within the
We report the ﬁrst
star formation historyalong
study ofwith
the Milky
Ways nuclear star(NSC), which includes derived temperatures,
central 1.5 pc. These metallicity
measurements,
photometry
andcluster
spectroscopicallyobservational constraints from a large sample of stellar metallicity measurements. These metallicity measurements
are forward modeled witha Bayesian
metallicity
measurements
were obtained
from recentinference
surveys from approach.
Gemini and the Including
Very Large Telescopeof 770 late-typestars within the improves the overall
central 1.5 pc. Thesered
metallicity
measurements,
along previouslywith photometry andspectroscopicallyderived temperatures,ﬁt quality, as the low-temperature
giantsthat were
difﬁcult
to constrain
are now accounted for, andare forward modeled with a Bayesian inference approach. Including metallicity measurements improves the overall
the best ﬁt favors a two-component
model. The
dominant
component± 3%for,ofandthe mass, is metal-rich
ﬁt quality, as the low-temperature
red giants
that were previously
difﬁcult tocontains
constrain are 93%
now accounted
3 model. The dominant component contains 93% ± 3% of the mass, is metal-richthe best ﬁt favors a two-component
hasH] anage of 52ageGyr,which is ∼3 Gyr younger than earlier studies with ﬁxed (solar)([M H] _ 0.45), and ([M_ 0.45), and has anof 523 Gyr, which is ∼3 Gyr younger than earlier studies with ﬁxed (solar)
metallicity;
younger age challenges
coevolutionary models
models in which
the NSC andblacksupermassive
holes
metallicity; this younger
age thischallenges
coevolutionary
in whichthesupermassive
NSC andblack holes
formed simultaneously at early times. The minor population component has low metallicity ([M H] _ 1.1) andformed simultaneouslycontains
at early
times.
The
minor
componenthas(0.1–5
lowGyrmetallicity∼7% ofthe stellar
mass.
The agepopulationof the minor component
is uncertainold). Using the ([M H] _  1.1) andestimatedparameters,
infer thefollowing
NSC stellar
remnant
population (withis∼18%
uncertainty): (0.1–5
1.5 × 105 Gyr old). Using thecontains ∼7% of theneutron
stellarmass.weTheageof theminor
component
uncertainstars, 2.5 × 105 stellar-mass black holes (BHs), and 2.2 × 104 BH–BH binaries. These predictions result in
estimated parameters, 2–4
wetimesinferfollowing
NSC
stellarremnant
population∼18%
uncertainty): 1.5 × 105
fewertheneutronstars comparedto earlier
predictions
that assume
solar metallicity,(withintroducing
a possible
5 path to understand the so-called “missing-pulsar problem”. Finally, we
present updated predictions for theneutron stars, 2.5 × 10new
stellar-mass black holes (BHs), and 2.2 × 104 BH–BH
binaries. These predictions result in
BH–BH merger rates (0.01–3 Gpc−3yr−1).
2–4 times fewer neutronstars
comparedearlier
predictions
thatassumesolar
UniﬁedAstronomy
Thesaurus toconcepts:
Galactic
center (565); Star
formation(1569);
Galaxymetallicity,formation (595); introducing a possible
Milky
Way
formation(1053);
Infrared
spectroscopy(2285);
Adaptive
optics(2281);
Adaptiveinterferometry(19)
new path to understand the so-called “missing-pulsar problem”. Finally, we present updated
predictions for the−1
Supporting material: −3
machine-readable
tables
BH–BH merger rates (0.01–3 Gpc yr ).
Uniﬁed Astronomy Thesaurus 1.concepts:
StarPrevious
formation(1569);
Galaxy(595);
Introduction Galactic center (565);
understood.
studies havesuggestedthat the formation
star
formation
history
of
the
NSC
is
complex.
The
stellarMilky Way formation(1053);
Infrared
spectroscopy(2285);
Adaptive optics (2281); Adaptive interferometry (19)The innermost
regionof most galaxies
is occupied byapopulation of the NSC is composed of cool, evolved giants;
spectacularly
dense
and
massiveassemblyofstars,
which
Gemini,Supporting
VLT, 770material:,machine-readable
1.5tablespc,
and hot, young main-sequence/post-main-sequence stars.
forms a nuclear
star cluster (NSC). The
star formation in thisBlum et al. (2003) combined spectroscopic and photometric23

region is believed to be affected by the central supermassive
black hole (SMBH), but the physical mechanisms behind it are
not entirely known. The center of the Milky Way galaxy is hostthe closest example of a SMBH (4.2 × 106Me; e.g., Ghez
1.ettoIntroduction
al. 2008; Gillessen et al. 2009; Do et al. 2019), embedded in
an NSC (∼2.5 × 107Me; e.g., Launhardt et al. 2002; Schödel
The innermost regionet ofmostgalaxiesaal. 2014).
Given
its proximity,isthe occupied
Milky Way NSCby
providesuniqueopportunity
to resolve thepopulationand tospectacularly dense andastudy
massiveassembly
ofstellarstars,
which
phenomena and physical processes that may beforms a nuclear star cluster(NSC).
formation in thishappeningin otherThegalacticstar
nuclei.

93%
5 asymptotic
Gyr giant branchobservations of the 79 most luminous(AGB) and supergiant stars in the central 5 pc. They
missing-pulsar
constructed
the Hertzsprung–Russell (H-R) diagram from COfeaturesin H- andhave
K-band suggested that the starandH2O molecular absorption
understood.
Previous
studies
spectra, and claimed that ∼75% of stars formed more thanhistoryof theis complex. The stellar
5 formation
Gyr ago. Maness etal. (2007) reported
the ﬁrstNSC
study using
adaptive
optics(AO)
observationsof329
giantsinthecentralpopulation of the NSC is composed1 of cool, evolved giants;
pc, including helium-burning red clump stars, red giants, and
AGB
These stars
with longer-lived
evolutionary phases
andstars.hot,
youngmain-sequence/post-main-sequencestars.
are better understood by theoretical evolutionary models. They

Received 2022 September 22; revised 2022 November 30; accepted 2022 December 5; published 2023 February 16
Making the Solar System

Abstract
We model the early stages of planet formation in the solar system, including continual planetesimal formation, andAbstract
planetesimal and pebble accretion onto planetary embryosin an evolving disk driven by a disk wind. The aim is to
We model the early stages of planet formation in the solar system, including continual planetesimal formation, andconstrain aspects of planet
formation
large
uncertainties
key
characteristicsof the solar
planetesimaland pebble that
accretionhave
onto planetary
embryosin an evolving diskby
drivenmatchingby a disk wind. The
aim istoconstrainaaspectsof planet
formationthat characteristics
have large uncertainties by
key characteristics
the solarsystem. The model produces
good
ﬁt to
these
formatchinga narrow
rangeof ofparameter space. Planetarysystem. The model produces a good ﬁt to these characteristics for a narrow range of parameter space. Planetary
growththe ice line isby
dominatedby pebble
accretion. Planetesimalaccretion is more
important inside
growth beyond the ice line
is beyonddominatedpebbleaccretion.
Planetesimalaccretionis themore important inside theice line. Pebble accretion inside the ice line is slowed by higher temperatures, partial removal of inﬂowing pebbles
ice line. Pebble accretion byinsidetheformation
ice lineis slowed
by highertemperatures,
partialdueremovalof inﬂowing pebbles
planetesimaland pebble
accretion further
out in the disk,
and increased radial velocities
to gasadvection. The terrestrial planets are prevented from accreting much water ice because embryos beyond the ice line
by planetesimal formationreachandpebble accretionoutin the disk,
andradial velocities due to gas
the pebble-isolation
mass before thefurther
ice line enters
the terrestrial-planet
region.
Whenincreased
only pebble accretionis considered, embryos typically remain near their initial mass or grow to the pebble-isolation mass. Adding
advection. The terrestrial planetesimalplanets accretionare prevented
from accreting much water ice because embryos beyond the ice line
allows Mars-sized objects to form inside the ice line, and allows giant-planet cores to forma widerbefore
region beyond
ice line.
In theentersregion occupied
Mercury, pebble Stokes numbers
are small.
This
reach the pebble-isolationover
mass
thethe iceline
the byterrestrial-planet
region.
When
only pebble accretion
delays the formation of embryos and stunts their growth, so that only low-mass planets can form here.
is considered, embryos typicallyremaininitial(1241);
mass
grow
to system
the pebble-isolation
mass. Adding
Uniﬁed Astronomy
Thesaurus nearconcepts:their
Planet formation
Solar orsystem(1528); Solargas giantplanets (1191); Solar system terrestrial planets (797); Solar nebulae (1508); Mercury (planet) (1024);
planetesimal accretion allows
Mars-sized objects to form inside the ice line, and allows giant-planet cores to form
Planetesimals (1259)
over a wider region beyond the ice line. In the region occupied by Mercury, pebble Stokes numbers are small. This
Introduction
causesa collapse
form asteroid-sized
bodiescancalledform here.
delays the formation of embryos 1.andstunts their growth, sothat
only tolow-massplanets
planetesimals (Johansen et al. 2007, 2012).
The recent discovery of several thousand extrasolar
Further growth can take place in two ways. The largest
planetary systems concepts:
has spurred greatPlanet
interest information
how these
Uniﬁed Astronomy Thesaurus(1241);
Solar system (1528); Solar system gas giant
planetesimals, also known as planetary embryos, can grow bysystems formed. While this emphasis on exoplanets is undersweeping
up planetesimals
or pebbles.
The accretionof pebbles (1024);
planets (1191); Solarstandable,
systemterrestrial
nebulae(1508);
Mercury(planet)it is worth
bearing in planets
mind that we(797);
still lack Solarais made more effective by drag with the disk gas, so thatmodel for how our own planetary system formed. This
pebbles lose energy during an encounter with an embryo
Planetesimals (1259)detailed
unresolved problem is made more compelling by the fact thatJohn Chambers

Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington, DC 20005, USA; jchambers@carnegiescience.edu
Received 2022 September 22; revised 2022 November 30; accepted 2022 December 5; published 2023 February 16

the solar system differs from most known exoplanet systems.
The absence of super-Earth-mass planets on short-period orbits
in the solar system is particularly noteworthy given that suchplanets are common elsewhere.
There are good reasons to focus on the origin of ourplanetary system. For example, it is the only system known tohost a habitable planet. We also know much more about thesolar system than other systems. We have a complete census ofplanetary-mass bodies out to at least 50 au, as well as much
more detailed information about the orbits of minor planet
populations in our system than elsewhere. In addition, the solar
system is the only system for which we have samples that canbe attributed to particular source objects. All this information
provides a strong test for planet formation theories.

1. Introduction

The recent discovery of several thousand extrasolar
planetary systems has spurred great interest in how thesesystems formed. While this emphasis on exoplanets is understandable, it is worth bearing in mind that we still lack a(Ormel & Klahr 2010). Planetesimal accretion is typicallyslower, especially far from the star (Morbidelli et al. 2015). For
this reason, pebble accretion is thought to be the main driver ofgrowth in the outer parts of disks (Lambrechts & Johansen2012), while both mechanisms may be important in the
inner disk.
Pebbles are expected to drift radially inwards over time due
to gas drag (Weidenschilling 1977). This drift provides acontinuous supply of material for embryos to grow by pebble
accretion, but it also removes pebbles that are not accreted
quickly enough. Thus, pebble accretion can form massive
planets by accessing material from a large fraction of the disk,
but the process is relatively inefﬁcient so a massive disk isrequired. When an embryo grows to a certain mass, it will
perturb the local gas pressure proﬁle sufﬁciently to halt thecauses a collapse to form asteroid-sized bodies called
planetesimals (Johansen et al. 2007, 2012).
Further growth can take place in two ways. The largest
planetesimals, also known as planetary embryos, can grow bysweeping up planetesimals or pebbles. The accretion of pebbles
is made more effective by drag with the disk gas, so that

Discovery of a New Molecular Bubble–Outﬂow Structure in the Taurus B18 Cloud
Yan Duan1,2 , Di Li1,3,4 , Paul F. Goldsmith5 , Laurent Pagani6 , Tao-Chung Ching1,7 , Shu Liu1 , Jinjin Xie8 , andChen Wang1
1

National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, Peopleʼs Republic of China; dili@nao.cas.cn
2
University of Chinese Academy of Sciences, Beijing 100049, Peopleʼs Republic of China
3
Research Center for Intelligent Computing Platforms, Zhejiang Laboratory, Hangzhou 311100, Peopleʼs Republic of China
4
NAOC–UKZN Computational Astrophysics Centre, University of KwaZulu-Natal, Durban 4000, South Africa
5
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
6
LERMA & UMR 8112 du CNRS, Observatoire de Paris, PSL University, Sorbonne Universités, CNRS, F-75014 Paris, France
7
Zhejiang Lab, Hangzhou, Zhejiang 311121, Peopleʼs Republic of China
8
Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, Peopleʼs Republic of China
Received 2022 June 28; revised 2022 November 30; accepted 2022 November 30; published 2023 February 7

Abstract
Star formation can produce bubbles and outﬂows, as a result of stellar feedback. Outﬂows and bubbles inject
momentum and energy into the surrounding interstellar medium, and so are related to the overall energy balance ofthe molecular cloud. Molecular bubbles can be resolved by higher-resolution radio telescopes to quantify the effectof star formation on molecular clouds. We report here the identiﬁcation of a new molecular bubble with an outﬂow,
and a Herbig–Haro object, HH 319, located at the bubble center. Multiwavelength data have been utilized to study
its spatial structure, energy injection, and dynamical timescale. This bubble has a kinetic energy of 5.8 × 1043 erg
within the smallest radius of a bubble in Taurus, 0.077 pc. The bubble formed ∼70,000 yr ago. According to theproper-motion velocities of protostars from Gaia EDR3, the T Tauri binary stars (FY Tau and FZ Tau) at thesouthwest edge of the bubble may have produced the outﬂow–bubble structure. This is an unusual new structure
found in low- and intermediate-mass star formation regions. Only a bubble in Orion A, driven by V380 Ori, has asimilar structure. The bubble–outﬂow structure provides additional observational evidence for the theory of stellar
wind from T Tauri stars. It enhances our understanding of how stellar feedback acts on molecular clouds.
Uniﬁed Astronomy Thesaurus concepts: Stellar wind bubbles (1635); Stellar winds (1636); Molecular clouds(1072); T Tauri stars (1681); Stellar feedback (1602)
1. Introduction
Star formation is related to the structure and evolution ofgalaxies and giant molecular clouds, the synthesis of chemicalelements, and the star formation rate and is intimately
connected with a critical astrophysical parameter, the initial
mass function (McKee & Ostriker 2007). Almost all youngstellar objects (YSOs) have undergone periods of substantial
mass loss. YSOs’ fast and collimated stellar wind sweeps
through the surrounding molecular gas. The molecular gas isexpelled from the cavities and expands as irregular lobes andincomplete shells (Bachiller 1996). These become visible asmolecular bubbles and molecular outﬂows. Herbig–Haro (HH)
objects, consisting of knots of ionized gas, are the opticalmanifestations of this mass-loss process (Reipurth &Bally 2001; McKee & Ostriker 2007).

bubbles have a greater impact on molecular clouds thanoutﬂows. The dynamical timescales of bubbles are longer thanthose of outﬂows in Taurus (Li et al. 2015). Thus, the energy
injection from bubbles into the molecular clouds could last
longer. The ensemble of bubbles in Taurus have about 110 times
greater mass and 24 times higher energy than the total of theoutﬂows (Li et al. 2015). Compared to supernova remnants,
molecular bubbles could exist for a longer period of time (Arceet al. 2011). Due to their complex morphologies, bubbles are
more difﬁcult to identify than relatively clear outﬂow features(Arce et al. 2011). Therefore, the study of molecular bubbles isboth important and challenging.
Bubbles arise from a largely spherical stellar wind.
Observationally, bubbles are similar to complete or partial
rings. Arce et al.

3Exzellenzcluster ORIGINS, Boltzmannstr. 2, D-85748 Garching, Germany e-mail: franceschi@mpia.de

Constraining the turbulence and the dust disk in IM Lup: onset ofplanetesimal formation
2, 3 , Thomas Henning1 , Anirudh Sharma2
Riccardo Franceschi1 , Tilman Birnstiel
ABSTRACT1

Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany

Context. Observations of 2protoplanetary
information
on planet
formationthereasons for the diversity of planetary
University Observatory,disks
Faculty provideof Physics, Ludwig
Maximilians University,
Scheinerstr.
1, 81679 andMunich,Germany

3
Exzellenzclusterplanet
ORIGINS,formation
Boltzmannstr. 2, isD-85748
e-mail:franceschi@mpia.de
systems. The key to understanding
the Garching,study Germanyof dustevolutionfrom small grains to pebbles. Smaller grains
December
5, 2022(⇠ 1 µm) are well-coupled
to thegas dynamics, and their distribution is significantly extended above the disk midplane. Larger
grains settle much faster and are efficiently formed only in the midplane. By combining near-infrared polarized light and millimeter
ABSTRACT
observations, it is possible to constrain the spatial distribution of both the small and large grains.
Context. Observations of protoplanetary disks provide information on planet formation and the reasons for the diversity of planetary
Aims. We aim to constructdetailed models of the size distribution and vertical/radial structure of the dust particles in protoplanetarysystems. The key to understanding planet formation is the study of dust evolution from small grains to pebbles. Smaller grains(⇠ 1 µm)
are well-coupled
to the gaswe
dynamics,
and their distribution
is significantly extended
abovedistribution
the disk midplane.in
Largerdisks based on observationaldata.
In particular,
are interested
in recovering
the dust
the IM Lup protoplanetary
grains settle much faster and are efficiently formed only in the midplane. By combining near-infrared polarized light and millimeter
disk.
observations, it is possible to constrain the spatial distribution of both the small and large grains.
Aims. We aim
to constructmodelsof the size distribution
and vertical/radial structureof theWedust particles
in protoplanetary
Methods. We create a physicalmodel
for detailed
the dust
distributionof protoplanetarydisks.
then simulate
the radiative transfer of thedisks based on observational data. In particular, we are interested in recovering the dust distribution in the IM Lup protoplanetary
millimeter continuum anddisk.
the near-infrared polarized radiation. Using a Markov chain Monte Carlo method, we compare the derived
Methods. We create a physical model for the dust distribution of protoplanetary disks. We then simulate the radiative transfer of theimages to the observations
available
forandthe
IM Lup polarized
disk toradiation.
constrain
best
modelwefor
IMtheLup
and to recover the verticalmillimeter
continuum
the near-infrared
Using a theMarkovchainphysicalMonte Carlo method,comparederivedto the observations available for the IM Lup disk to constrain the best physical model for IM Lup and to recover the verticalgrain size distribution. images
grain size distribution.
Results. The millimeter andnear-infrared
tightlytightly
constrainthemass
anddistribution
grain size
distributionof our model. We findResults.
The millimeter andemission
near-infrared emission
constrain the
dustdust
mass andgrain sizeof our model.
We findsize segregation in the dust distribution, with millimeter-sized grains in the disk midplane. These grains are efficiently formed insize segregation in the dust
distribution, with millimeter-sized grains in the disk midplane. These grains are efficiently formed in
the disk, possibly by sedimentation-driven coagulation, in accord with the short settling timescales predicted by our model. This alsosuggests a high dust-to-gas ratio
at smaller radii inin
the accord
midplane, possibly
streaming
instabilities
and planetesimalformation by our model. This also
the disk, possibly by sedimentation-driven
coagulation,with triggering
the shortsettling
timescales
predicted
in the inner disk. We obtain a turbulent ↵ parameter of 3 ⇥ 10 3 .
suggests a high dust-to-gas ratio at smaller radii in the midplane, possibly triggering streaming instabilities and planetesimal formation
Key words. protoplanetary disks – accretion disks – planetsand satellites: formation – circumstellar matter – stars: pre-mainin the inner disk. We obtaina turbulent↵ parameterof 3 ⇥ 10 3 .
sequence— radio continuum:
planetary systems

rXiv:2212.01291v1 [astro-ph.EP] 2 Dec 2022

01291v1 [astro-ph.EP] 2 Dec 2022

December 5, 2022

Key words. protoplanetary disks – accretion disks – planets and satellites: formation – circumstellar matter – stars: pre-main
1. Introduction
sequence — radio continuum:
planetary systems

1. Introduction

IM LupProtoplanetary disks around young stars are the nursery of planetary systems. These disks are almost entirely composed of gas
and a small mass fraction of dust. Small dust grains (⇠ 1 µm) are
well-coupled to the gas structure, and therefore extend verticallyover several scale heights, following the gas distribution. Dust
settling in turbulent disks was extensively studied (e.g. Dubrulle
et al. 1995; Schräpler & Henning 2004; Fromang & Nelson
2009; Zsom et al. 2011; Woitke et al. 2016). On the contrary,large millimeter grains settle much faster towards the disk midplane, where the growth process is particularly efficient becauseof the high densities. By constraining the distribution of both

MCMC

g/d

Protoplanetary disks around young stars are the nursery of planetary systems. These disks are almost entirely composed of gas
and a small mass fraction of dust. Small dust grains (⇠ 1 µm) arecently observed a correlation between the CO emitting height
and the disk size in a sample of disks observed with the Atacama Large Millimeter/submillimeter Array (ALMA). Using
the dust emission, Avenhaus et al. (2018) measured the flaring of V4046 Sgr, RXJ 1615, and IM Lup with the Very Large
Telescope (VLT) Spectro-Polarimetric High-contrast Exoplanet
REsearch (SPHERE) instrument. These near-infrared polarized
light images show unprecedented details of the disk’s surface
layer by tracing the scattering of small, micron-sized dust grains.
At these wavelengths, the disk is expected to be optically thickand the observed light is dominated by light scattered by the dust
grains on the disk surface. Among these disks, IM Lup observations are arguably among the most impressive images of a proto-

sedimentation-driven

cently observed a correlation between the CO emitting height
and the disk size in a sample of disks observed with the Atacama Large Millimeter/submillimeter Array (ALMA). Using
the dust emission, Avenhaus et al. (2018) measured the flaring of V4046 Sgr, RXJ 1615, and IM Lup with the Very Large

A 3D View of Orion: I. Barnard’s Loop
Michael M. Foley ,1, ⇤ Alyssa Goodman ,1 Catherine Zucker ,2, † John C. Forbes ,3 Ralf Konietzka
Cameren Swiggum ,5 João Alves ,5 John Bally ,6 Juan D. Soler ,7 Josefa E. Großschedl ,5Shmuel Bialy ,8 Michael Y. Grudić ,9, † Reimar Leike ,10, 4 and Torsten Enßlin 10, 4
1 Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA, USA 02138
2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

3 Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY, 10010, USA
4 Ludwig-Maximilians-Universität, Geschwister-Scholl Platz 1, 80539 Munich, Germany
5 Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, 1180 Wien, Austria
6 Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, Colorado 80389, USA
7 Instituto di Astrofisica e Planetologia Spaziali (IAPS). INAF. Via Fosso del Cavaliere 100, 00133 Roma, Italy
8 Department of Astronomy, University of Maryland, College Park, MD 20742, USA
9 Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101, USA
10 Max Planck Institute for Astrophysics, Karl-Schwarzschildstraße 1,85748 Garching, Germany

ABSTRACT
Barnard’s Loop is a famous arc of H↵ emission located in the Orion star-forming region. Here,
we provide evidence of a possible formation mechanism for Barnard’s Loop and compare our resultswith recent work suggesting a major feedback event occurred in the region around 6 Myr ago. We
present a 3D model of the large-scale Orion region, indicating coherent, radial, 3D expansion of the
OBP-Near/Briceño-1 (OBP-B1) cluster in the middle of a large dust cavity. The large-scale gas in theregion also appears to be expanding from a central point, originally proposed to be Orion X. OBP-B1
appears to serve as another possible center, and we evaluate whether Orion X or OBP-B1 is more

,1, 4

∗

E-mail: fujita@p.s.osakafu-u.ac.jp

Received 2022 March 8; Accepted 2022 December 1

Abstract

Shinji FUJITA ,1,2,∗ Atsushi M. ITO,3 Yusuke MIYAMOTO ,4,5
Yasutomo KAWANISHI ,6 Kazufumi TORII,5 Yoshito SHIMAJIRI ,7
Atsushi NISHIMURA ,8 Kazuki TOKUDA ,9 Toshikazu OHNISHI ,2
Hiroyuki KANEKO ,5,10 Tsuyoshi INOUE,11 Shunya TAKEKAWA ,12
Mikito KOHNO ,13,14 Shota UEDA,2 Shimpei NISHIMOTO,2 Ryuki YONEDA,2
Kaoru NISHIKAWA,14 and Daisuke YOSHIDA14
Publications of the Astronomical Society of Japan (2023), Vol. 75, No. 1
1
Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka,∗E-mail: fujita@p.s.osakafu-u.ac.jp

m, CO 2-1
CLUMPFIND

Downloaded from htt

280
Machinelearning has been successfully applied in various field but whether it is a viable
Tokyo 181-0015, Japan
tool for determining the distance to molecular
clouds in the Galaxy is an open question.
2
Department of Physical Science, Graduate School of Science, Osaka Prefecture University, 1-1
In
the Galaxy, the kinematic distance is Gakuen-cho,commonly
employed
to represent
the distance toNaka-ku,
Sakai,
Osaka
599-8531,
Japan"
C The Author(s) 2023. Published by Oxford University Press on behalfof the Astronomical
Societyof Japan.
3
National
Institute twofor Fusion
Science (NIFS),
National Institutesof Natural
Sciences (NINS), 322-6
a molecular
cloud.
However,forthe inner
Galaxy,different
solutions,
i.e., the“Near”
All
rights reserved. For
permissions,please e-mail:journals.permissions@oup.com
Oroshi-cho, Toki, Gifu 509-5292, Japansolution and the “Far” solution, can be4 Department
derivedof simultaneously.
We attemptElectrical and Electronic Engineering,
Facultytoof construct
Engineering, Fukui University of
PPV
Technology,
3-6-1
Gakuen,Fukui,
Fukui
910-8505,Japana two-class (“Near” or “Far”) inference
model using a convolutional neural network
5
National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa,(CNN), which is a form of deep learningMitaka,
thatTokyo
can181-8588,
captureJapanspatial features generally. In this6
RIKEN
Informationof
R&D
and Galactic
Strategy Headquarters,
2-2-2 Hikaridai, with
Seika-cho,study, we use the CO dataset in the first
quadranttheplane obtained
theSoraku-gun, Kyoto
619-0288,◦◦ Japan◦Nobeyama 45 m radio telescope (l = 62
–10Kyoritsu, |b| <
1 ). Inmodel,
we apply
the Fukuoka,
three-Fukuoka 807-8585,
7
KyushuUniversity,
1-8theJiyugaoka,
Yahatanishi-ku,
Kitakyushu,Japan
dimensional distribution (position–position–velocity)of the 12 CO (J = 1–0) emissions as
8Nobeyama Radio Observatory, National Astronomical Observatory of Japan, National Institutes ofthe main input. To train the model, a datasetwith “Near”
or “Far”
annotation
was384-1305,
createdNatural Sciences,462-2 Nobeyama,
Minamimaki,
Minamisaku, NaganoJapan
9
Department
of
Earth
and
Planetary
Sciences,
Facultyof
Science,
KyushuUniversity,from the H II region catalog of the infrared astronomy satellite WISE. Consequently, weNishi-ku, Fukuoka,
Fukuoka 819-0395, Japan
construct a CNN model with a 76% accuracy
rateon thetraining
Using the Joetsu, Niigata
10Graduate Schoolof Education,
JoetsuUniversity ofdataset.
Education, 1 Yamayashiki-machi,
943-8512, Japanproposed model, we determine the distanceto the molecular clouds identified by the11
Department of Physics, Konan University, 8-9-1 Okamoto, Higashinada-ku, Kobe, Hyogo 658-8501, Japan
CLUMPFIND algorithm. We found that12 Faculty
the massof molecular
clouds3-27-1
witha distanceofof Engineering,
Kanagawa University,
Rokkakubashi,
Kanagawa-ku,
Yokohama,
12
Kanagawa
221-8686,
Japan
a power-law distribution with an index of<8.15 kpc identified in the CO data follows
13
Astronomy Section,
Nagoya City Science Museum, 2-17-1 Sakae, Naka-ku, Nagoya, Aichi 460-0008,
approximately −2.3 in the mass range Japan
M > 103 M# . In addition, the detailed molecular
Departmentof Astrophysics,
University,
Chikusa-ku, Nagoya, Aichi 464-8602, Japangas distribution of the Galaxy, as seen14fromthe
GalacticNagoyaNorth
pole,Furo-cho,
was determined.

Downloaded from https://academic.oup.com/pasj/article/75/1/279/6988000 by KASI user on 23 February 2023

Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama,
Distance determination of molecular clouds in
Kanagawa 221-8686, Japan
13
Astronomy Section, Nagoya City Science Museum,
2-17-1
Sakae, Naka-ku,
Aichiplane
460-0008,
the first
quadrantof theNagoya,
Galactic
using
Japan
deep learning: I. Method and results
14
Department of Astrophysics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan

2023

12

WISE

HII

East Asian Observatory (EAO), 660 N. Aohoku Place, University Park, Hilo, HI 96720, USA
Department of Astronomy, University of Florida, P.O. Box 112055, Gainesville, FL 32611-2055, USA
Received 2022 November
11; Formation
revised 2022ofDecember
accepted2022
7; published2022 December 28
Clustered
Massive7;Stars
withinanDecember
Ionized Rotating
Disk
9

Roberto Galván-Madrid1 , Qizhou Zhang2 , Andrés Izquierdo3,4 , Charles J. Law2 , Thomas Peters5, Eric Keto2,
Hauyu Baobab Liu6,7 , Paul T. P. Ho7,8 , Adam Ginsburg9 , and Carlos Carrasco-González1

Abstract
We present Atacama Large Millimeter/submillimeter Array observations with a 800 au resolution and radiativetransfer modeling of the inner part (r ≈ 6000 au) of the ionized accretion ﬂow around a compact star cluster information at the center of the luminous ultracompact H II region G10.6-0.4. We modeled the ﬂow with an
ionized Keplerian disk with and without radial motions in its outer part, or with an external Ulrich envelope. The
Markov Chain Monte Carlo ﬁts to the data give total stellar masses M from 120 to 200 M , with much smaller
ionized-gas masses Mion-gas = 0.2–0.25 Me. The stellar mass is distributed within the gravitational radius
Abstract
wheretheionizedgas
isbound.
The viewing inclination angle from the face-on
Rg ≈ 1000 to 1500 au,
We present Atacama Large Millimeter/submillimeter Array observations with a 800 au resolution and radiative−1transfer modelingthe inner part at(r ≈radii
6000 au)r ofaccretion ﬂow
a compact
star scluster
to around
vr,0 ≈
8.7 km, inor about the speed oforientation is i = 49°–56°.
Radialof motions>theRionizedg converge
formation at the center of the luminous ultracompact H II region G10.6-0.4. We modeled the ﬂow with ansound of ionized gas, ionizedindicating
thisisradial
marginallyat anmost.
additional
constraints on the
Keplerian thatdisk withand gaswithout
motions in its unboundouter part, or withexternalFrom
Ulrich envelope.
The
to 200 theMe, withmuch smaller
Markov
Chain Monte
Carlo ﬁts to thetotal stellarwe
massesMå from 120 thationizing-photon rate andfar-IR
luminosity
ofdatathegiveregion,
concludestellarcluster consists of a few
ionized-gas masses Mion-gas = 0.2–0.25 Me. The stellar mass is distributed within the gravitational radius
32–60
or onestar inrange
massesaccompanied
a population of lowermassive stars with Mstar
1000
to 1500Mau,
the ionizedgasthisis bound.
The ofviewing
inclination
angle from the by
face-onRg ≈=e,whereorientation is i = 49°–56°. Radial motions at radii r > Rg converge to vr,0 ≈ 8.7 km s−1, or about the speed ofmass stars. Any active
accretion of ionized gas onto the massive (proto)stars is residual. The inferred clustersound of ionized gas, indicating that this gas is marginally unbound at most. From additional constraints on theionizing-photon rateto
andthatfar-IRreported
luminosity ofat
thesimilar
region, we scales
conclude thatcluster consistsof a few
density is very large, comparable
in thethestellar
Galactic
center.
Stellar interactions are
massive stars with Mstar = 32–60 Me, or one star in this range of masses accompanied by a population of lowerlikely to occur withinmass
thestars.
next
years.
Anymillion
active accretionof ionized gas onto the massive (proto)stars is residual. The inferred cluster
1

Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia, Michoacán 58089, México
2
Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
3
European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany
4
Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands
5
Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany
6
Physics Department, National Sun Yat-Sen University, No. 70, Lien-Hai Road, Kaosiung City 80424, Taiwan, R.O.C.
7
Institute of Astronomy and Astrophysics, Academia Sinica, 11F of Astronomy-Mathematics Building, AS/NTU No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan,
R.O.C.
8
East Asian Observatory (EAO), 660 N. Aohoku Place, University Park, Hilo, HI 96720, USA
9
Department of Astronomy, University of Florida, P.O. Box 112055, Gainesville, FL 32611-2055, USAe
Received 2022 November 11; revised 2022 December 7; accepted 2022 December 7;åpublished 2022 December 28

density is very large, comparable to that reported at similar scales in the Galactic center. Stellar interactions are

Uniﬁed Astronomy Thesaurus
II regions(694)
likely to occurconcepts:
within the nextH
millionyears.

UCHII G10.6-0.4

Uniﬁed Astronomy Thesaurus concepts: H II regions (694)

1. Introduction

1. Introduction

Stars with masses greater than 30 Me are rare among thestellar population
galaxies,
they playa main therole inamong
Stars with
massesgreaterthan 30in49-56
M
e arebutrare
0.2-0.25
Msun
shaping the dynamical evolution of the interstellar medium
stellar population in galaxies,
but theyplay
a mainrole
inthrough feedback
from theirradiation,
ionization,and supernovae (for a review
feedback
effects in starmedium
formation, seeshaping the dynamical evolutionof oftheinterstellar
Krumholz et al. 2014). Since these very massive stars arethrough feedback from theirradiation,
ionization,andsupermostly formed
in dense stellar
clusters, their
violent
death maylead to the formation of black holes or neutron-star binary
novae (for a review of feedback
effects in star formation, seesystems that give rise to gravitational-wave events (e.g.,
Mapelli very2018). Massive
protostars
must areaccreteKrumholz et al. 2014). Giacobbo
Since &these
massivestars
more than 30 Me to become early O-type stars, but they begin
mostly formed in dense stellar
clusters,
violent
maycore hydrogenburningtheirwell before
reachingdeath
their ﬁnal
massesr<6000 au
clustered environments
120-200(Goddi
Msun et al. 2020). In a clusteredscenario, and after the protostars have reached several tens of
Vr of extreme-UV
8.7 km/s
solar masses, the amountphotons is large

clustered environments (Goddi et al. 2020). In a clusteredscenario, and after the protostars have reached several tens ofsolar masses, the amount of extreme-UV photons is large
enough to ionize the otherwise molecular accretion ﬂow(s) andthe clump in which they reside (Keto 2003, 2007; Peters et al.
2010a, 2010b; Klaassen et al. 2018). This raises several
outstanding questions: How does star formation proceed insuch an environment? Is it through an ionized accretion disk?
Does this disk surround a single or a multiple stellar system?
When does active (proto)stellar accretion stop due to theincreasing photoionizing feedback?
We present the ﬁrst spatially resolved observations of an
accretion ﬂow in ionized gas around a dense star cluster inenough to ionize the otherwise molecular accretion ﬂow(s) and
100 in which they reside (Keto 2003, 2007; Peters et al.
the clump
2010a, 2010b; Klaassen et al. 2018). This raises several
outstanding questions: How does star formation proceed insuch an environment? Is it through an ionized accretion disk?