Star Formation Newsletter#332 33-40
Yusuke Aso (KASI)CO Depletion in Protoplanetary Disks: A Uniﬁed Picture Combining PhysicalSequestration and Chemical Processing
Sebastiaan Krijt1,5,7
1, Arthur D. Bosman2, Ke Zhang2,5 , Kamber R. Schwarz3,6
Edwin A. Bergin2, Fred J. Ciesla4,7, and

Department of Astronomy/Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; skrijt@email.arizona.edu
2
The Astrophysical899:134 (16pp),
2020 August
University of Michigan, Department of Astronomy,
1085 S.Journal,
University,
Ann Arbor,
MI2048109, USA
3
Lunar and Planetary Laboratory, University of Arizona,
1629 E. University
Boulevard,
85721, USA
how appropriate
ISM-level valuesfor ζCR Tucson,
are insideAZ
proto4
Department of the Geophysical Sciences, The Universityof Chicago,5734et S.
planetarydisks (Cleevesal. Ellis2015).Avenue, Chicago, IL 60637, USA
Received 2020 June 6; revised 2020 July 15;Alternatively,
accepted 2020
published
2020sequestration
August 24
othersJuly
have17;
consideredphysicalKrijt et al.

Ø 最近の観測からCOは1-3 Myrで10-100倍消失。惑星組成にも影響。
Ø 化学反応、z+r⽅向の輸送、宇宙線によるイオン化を調べる。
of CO in the cold (120 K) outer disk midplane, often requiring
vertical transport with either grain growth (e.g., Kama et al.

Abstract
2016; Krijt et al. 2018), or a vertically varying diffusion

coefﬁcient (Xu et al. 2017). A natural byproduct of models thatl Journal, 899:134(16pp), 2020
August20 COM
Krijt et al.
Ø 円盤モデル：r=0.1, toT1au=135
K,dustg/d=100,
a=0.1µm。
c=80 au,
disk/M*(relative
The gas-phaseabundancehydrogen)
protoplanetary
disks
by up
relyinon
coagulation and transport
isdecreases
that in theabsenceof to two orders of−4chemicalprocessing,the inward radialof icy pebblesand
will photodissociation.
magnitude from its
interstellar
medium valueof ∼10, evenafter
accounting
fordriftfreeze-outØ
化学：CO
iceからCH
OH,
表⾯でCO
+
OH
à
CO
,
ガスCO
+
He+
à
increasethegas-phase CO abundanceinterior
to CH
the CO32
4
es on which the chemical reactions
takehaveplace
is that while 2.
We
approximate
dust-to-pebble
conversion
Previous studies
shown
local
chemicalprocessingof COsequestration
on solids as
snowline,
in some the
cases
by
anand
ordertheof magnitude(Piso
et al.of CO icetimescale-4の乱流で拡散係数D
2015;
Stammler
et
al.
2017;
Krijt
et
al.
2018).
Ø
温度でガス相へ。初期雪線は34au,
23K。α=10=αc
H。
the midplane
processes
appears capable of consistently
gs reaching thesmic-ray ionization rate,in which
we cansetbothtocontribute, neither of theseRecently,
Zhang et al. (2019) inferred radially resolved CO
observed depletion factors on the relevant timescaleof proﬁles
1–3 Myr.
In thisof nearby
study,disks
modelthese processes
depletion
for a handful
Tau,
we
1 (DM
1 for our standard model. The⎛⎞
surfacemmのペブルへ（adensities
TW
Hya, HD 163296,
and IM on
Lup),carbon
concludingthat whiletheØ τdàpでダストから1=10）。
simultaneouslybyincluding a compact 1chemical
network(centeredandoxygen)to 2D(r +andz)temperature structure used throughout this study (seeFigure1. Gas densityS
a1 ⎜ ared ⎟similar to thoseradial variations in the CO abundance
Section 2.1). Dashed lines indicate z H  {1, 2, 3, 4}.

2
U

,
of the outerthe(r>20 au) disk regions that
includeturbulent
pebbleformation, and pebble (1)dl
100 gsimulations
cm , justifying
d in do notpredicted
by Krijt
et al.p(2018),diffusion,
the observed
depletion factors⎜⎟
Ø exceed
ペブルが動いてCOを放出。ペブル上化学反応なし。
8 ⎝foundSofg intime
can be signiﬁcantly
higher than
thoseis a complex
functionand location. Focusing on
dynamics. In general, we ﬁnd that the CO/H2 abundance
Table 1⎠the simulations,nt ζCR (Umebayashi&
Nakano1981;
Padovanisuggesting that both ongoing chemical processing and dust
Properties of Molecular Species that Are Followed
衝突破壊なし。3
CO in the Myrまで。
warm molecular layer, we ﬁnd that only themostcomplete
model
(with
chemistryandpebbleevolution
evolution and transport play a role in setting the CO
Molecule
E /K
do not include X-rays as aincluded)
source canof ionization,
For HD163296,
only caseof
in whichthe region
reach depletion factors consistent with abundance.
observations.
In the theabsencepressuretraps, highly
efﬁcient Initial Abundance
1.2×10
5770
HO
interiortothemidplaneCOsnowline
couldberesolved,Ωevidencethelocal
frequency,
and aCO1ofaCOconstant.
planetesimalor high cosmic-raywith
ionization
rates,
this Keplerianmodel also predicts
a resurgencevapor
1.0×10855
of which could potentiallyspeedformation,
up CO
for an increased CO abundance in the inner regions
CO (C/O) and
1.0×102990
interior to the CO ice-line. We show the impact of physicalandlaterchemicalprocesses
the elemental
was found, andconﬁrmed using
additionalon
observations
Ø Warm(-molecular
CH OH
1.0×104930
very low-mass
disks
0.003M
etof
al. CO
2020a).
:) layerは化学だ(C/H)
ratios (in(Schwarz
the gas and ice phases),the(Zhanguseform,
as a disk
mass tracer,and, composition
ﬁnally,Whendiscuss
pebblesthey
inheritthe iceof the1.0×10
1200
CH connect our
While theoretical studies have started to combine physical
けではXCO変化なし。
predicted pebble ice compositions tosmall
those ofgrains
pristineandplanetesimals
as
found
in
the
Cold
Classical
KuiperBelt
andchemicalevolution(Boothetal.
2017;
Bosmanetal.
present in that particular grid cell.
Theenergies
local
Note. Desorption
taken from Bosman et al. (2018b). Initial2018a; Booth & Ilee 2019), most of these works focused on thedebrisdisks.
abundances in molecules per H.
Ø 拡散を⼊れると上層à⾚道⾯
effectofinwardradialtransportonmolecular
abundancesinabundance ofsmall
grainsistheirloweredaccordingly, and thethe disk
midplane,thus limiting
models to(75);
1D without
Uniﬁed Astronomy Thesaurus concepts: Protoplanetarydisks(1300);
Astrochemistry
Circumstellar
matterAt t=0, we assume that all grains are 0.1 N m in size andthe warm molecularlayer (WML).
àCH3OHでX(241);
effect of thediscussing
decreasing
small-dust-to-gas
ratio
isincludedin
COが数倍減少。
Computational methods (1965)arepresent
everywhere in the disk at a dust-to-gas mass ratio of
We set out to study how processes associated with the(S S )  10 . For this setup, x225 M of dust (excluding
stages of planet/planetesimal formation (i.e., the2.3. Freeze-out
and Desorption
the chemicalearliest
network.
Ø 化学反応＋雪線以内へ落下でよ
全部⼊りモデルices) is located beyond r=20 au at the beginning of theformation of pebbles, their accumulation in the midplane, andsimulations.
theirsubsequent
inwardmigration)interactwithongoing
Vertical settling,radialdrift,
andgas-phaseturbulent
transport are
COが100倍減少。
網はアイス
nergies for うやくX
the ﬁve major
species are listed inchemical processingof CO (througheither as
CO abundances
as low
10−6 orhave been reported (Bergingrain-surface reactions).
Our mainto (2018).
explore whether We include theincluded following
et goalal.
100倍2.2. Chemistry
et al.Krijt
2013;
Favre
et isal.
2013; McClure et al. 2016). Recently,
alance between freeze-out
and desorption
these processes, acting together, can explain the extreme CO
The carbon-monoxide(CO) onmolecule has played an
Our focusparticles
is of
on understanding
Zhangas specieset(2020b),by contrastingobservations
multiple ﬁve major carbon- anddepletion
factors,
wellal.
as theirradialvariations,that havesublimationofvolatile
presentonpebble-size
importantrole statein our forunderstanding
disks.
oxygen-carrying molecules: H O, CO, CO , CH , and CH OH.
ns is assumed to reachsteadyall ﬁve of protoplanetary
been reported in the literature (e.g., Zhang et al. 2019, 2020b),
class
0/Ilinkand
class
II disks,regions
found that withCO
factorsof because together, they
Thesedepletion
speciesbeen chosenestablishinga direct
betweenconstraints
if andtransitions
when
they
move
to observationaldisk
a havehigherBeing abundant, volatile, and having rotational
The Astrophysical Journal, 899:134 (16pp), 2020 August 20

The Astrophysical Journal, 899:134 (16pp), 2020 August 20

Krijt et al.

bind

−4

2

−4
−5

2

−6

3

−9

4

Figure 7. Total(Figures 4 and 5
are currently loc
interior to r=2
initial solid cont

d

g

2



2

2

4

Figure 5. Snapshots of the most complete model presented here, which includes chemical reactions, dust coagulation, and material transport (FULL, see Section 3.4
Figure 6. Radial proﬁles of the gas-phase CO abundance for the models
and Table 2).

transported in
has ceased alin Kama etaccreting ont
typical T Tau
the inner disk
in planetesim
We note tmassive (seesimilarly in lo
3 depend on diratio (for pebvertical mixinCO Depletion in Protoplanetary Disks: A Uniﬁed Picture Combining PhysicalSequestration and Chemical Processing
1,5,7

Sebastiaan Krijt
1, Arthur D. Bosman

22,5, Ke Zhang, Kamber R. Schwarz
Edwin A. Bergin2

3,6

4,7

, Fred J. Ciesla

, and

の続き

Department of Astronomy/Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA; skrijt@email.arizona.edu
Krijt et al.
Krijt et al.
University of Michigan, Department of Astronomy, 1085 S. University,
Ann Journal,
Arbor,
MI
48109,USA
The Astrophysical899:134(16pp),
2020 August 20
3
Lunar and-16
Planetary Laboratory, University of Arizona, 1629 E. University Boulevard, Tucson, AZ 85721, USA
4
Department of the Geophysical Sciences, The University of Chicago, 5734 S. Ellis Avenue, Chicago, IL 60637, USA
Received 2020 June 6; revised 2020 July 15; accepted 2020 July 17; published 2020 August 24

The Astrophysical Journal, 899:134 (16pp), 2020 August 20 The Astrophysical Journal, 899:134
2 (16pp), 2020 August 20ß ζ=10 だと外でCO2になって雪線以内も減る。

Krijt et al.

Abstract

The gas-phase CO abundance (relative to hydrogen) in protoplanetary disks decreases by up to two orders ofmagnitude from its interstellar medium value of ∼10−4, even after accounting for freeze-out and photodissociation.
Previous studies have shown that while local chemical processing of CO and the sequestration of CO ice on solids
à ドリフトをin the midplane
can both contribute, neither of these processes appears capable of consistently reaching theobserved depletion
factors on the relevant timescale of 1–3 Myr. In this study, we model these processes
1％にしても雪
simultaneously by including a compact chemical network (centered on carbon and oxygen) to 2D (r + z)
線以内で減る。
simulations of
the outer (r>20 au) disk regions that include turbulent diffusion, pebble formation, and pebble
dynamics. In general, we ﬁnd that the CO/H2 abundance is a complex function of time and location. Focusing on
CO in the warm molecular layer, we ﬁnd that only the most complete model (with chemistry and pebble evolution
included) can reach depletion factors consistent with observations. In the absence of pressure traps, highly efﬁcientØ ドリフトが弱い（DR99）ならM
dustがOK。
planetesimal formation, or high cosmic-ray ionization rates, this model
also predicts a resurgence of ratioCO
vapor(C/O) >1 as the more oxygen-rich products (e.g., H O,
being slightly lower than in the DIFF model, but still
signiﬁcantly∼3–10.
freeze out. Thison
effectthe
is similar
to the oneCO ) readilyinterior
thedepletion
COproﬁles
ice-line.
We
show
the
of physicalprocesses
elemental(C/O)
and on theがOK。
TheCOAstrophysical(16pp),
2020rates
August20
Krijt et al. and chemicalØdescribed
Figure 8. Impact on radial
depletion proﬁlesJournal,
for varying899:134
cosmic-ray
ionizationζto(left)pebbledrift
efﬁciencies
Theseionization
modelsarerates
discussed
inimpact
Figure8. Impact
on radial
CO andfor varying(right).
cosmic-ray
ζ (left)and pebble drift efﬁciencies (right). These models are discussedinζが⼩さい（CR16）ならM
Designed to be focusedCO
processing of CO, the reducedin Schwarz et al. (2019, Section 4.3.3), who reported
Section 4.
Section 4.
chemical
network
we have used here does not consider further
_10
(C/O)
as
high
as
in
the
midplaneatr=12auafter(C/H) ratios (in the gas and ice phases), discuss the use of CO as a 6disk
masstracer,and,ﬁnally,connect
ourprocessing of CH and the formation of other, generally less
Myr , when virtually all CO had been processed.
Øfoundの進化の議論はg/d,の進化を除
volatile, hydrocarbons. As such,X
theCO
abundanceof CH at theIn特にM
our simulations,the diskmagnitudeofClassicalthe increase in (C/O)
predicted pebble ice compositions to those of pristine planetesimals as
inof theCold
KuiperBelt andend of our calculations, and the increase of (C/O) associatedandtheextenttheregion
where
it
is
seen
dependontheshown in Figure 8. The left panel shows warm CO interiordiskmassescomparingstar-forming
regions
different
shown toin Figure8. Theleft bypanel
shows warm
CO interior
to of disk
masses by comparing star-forming regions of different
with its appearance, should be treated as an upper limit.
transport processes that are included. In the static CHEM model
disks.
have to bewhile
carefulCO/H
the midplane CO snowline, while the panel on theright
く必要あり。
ages have to be careful when using CO/H or dust-to-gas
thedebris
midplane ages
CO snowline,
thewhenpanelusing
on theright or dust-to-gas(left panels of Figure 10), only a relatively small region shows
Figure 9. Evolution of the (mass-weighted) CO/H2 in the gas inside the midplane CO snowline (left) and in the WML outside the CO midplane snowline (right),
compared to the total mass of solids (dust + pebbles) present exterior to r=20 au (both panels). Background colors represent factors of 3q reductions in the COabundance (blue) or solids-to-gas ratio (red).
gas

2

2

CR

CR

gas

8

4

4

gas

gas

2

2

conversion
factors
thatin are
in Intime,
if a factors that are constant in time, especially if(C/O)
illustrates the warm molecular layer in the outer disk.illustrates
In both the warm
conversion
a gas>1 because a signiﬁcant fraction of the initial CO ismolecularlayer
the constantouter disk.
bothespeciallysigniﬁcantaxis
fractionof the disk
locatedthe CO fraction of the disk mass is located beyond the CO
panels, the horizontal axis represents the total (i.e.,
dustthe horizontal
still present after 3 Myr (see Figure 2).
panels,represents
the mass
total is(i.e.,
dustbeyondsigniﬁcant
For the DIFF model, the combination of more efﬁcient CO
snowline.
+pebble) solid-to-gas mass ratio integrated over the entire
disk. solid-to-gas
snowline.
+pebble)mass ratio integrated over the entire disk.
removal combined with the upward transport of CH4 formed
The background colors represent factors of 3q reductions
theTheinbackgroundcolors represent factors of 3q reductions in thecloser to the midplane results in a large portion of the WML
CO abundance (blue) or solids-to-gas ratio (red).
CO abundance (blue)
orElemental
solids-to-gas
ratioand(red).
4.4.
RatiosHydrocarbon Production 4.4. Elemental Ratios and Hydrocarbon Production having (C/O)gas∼10–30. There is a small region in the upper
The trajectories depicted in Figure 9 illustrate that
Thethetrajectories depicted in Figure 9 illustrate that the
inner part of the disk that has (C/O)gas<1, due to sublimation
processes
described
described
in Section
Thekeyprocesses described described in Section 3 will alter key
accuracy of using either CO emission (while assumingaccuracy
an ISM- of usingTheof CO2 that formed at lower temperatures and was subseeither
CO emission(whileassuming
an ISM-3 will alterelemental
ratiosindifferent
ways.
Recognizingthattheeffectelemental ratios in different ways. Recognizing that the effectquently transported there.
like abundance) or dust emission (while assuming an ISM-like
like abundance) or dust emission (while assuming an ISM-like−6ofradial
drift
on
gas
and
solid
elemental
abundances
inthe
The FULL model also results in carbon-rich gas in the WML,of radial drift on gas and solid elemental abundances in the
dust-to-gas ratio) as a total disk mass tracer depends sensitively
dust-to-gas ratio) as a total disk mass tracer depends sensitively
buttheincreaseisnotasextremeasforthe DIFF model
midplanehas
beendiscussedindetailbymultipleauthors(e.g.,
midplane has been discussed in detail by multiple authors (e.g.,on the details of the ongoing chemical and dust evolution.
on theFor
details of
the ongoingchemicaldust&evolution.
For Estrada
without pebble formation and evolution. There are two reasons
Cuzzi& Zahnle
2004; andCieslaCuzzi 2006;
et al.
Cuzzi&
Zahnle2004;
Ciesla
&
Cuzzi
2006;
Estradaetal.
example, in the FULL-DR90 and FULL-DR99 models,theexample, in the
FULL-DR90
FULL-DR99
models,for this. First, in the inner disk, the enhancement in CO vapor
2016;Öberg & andBergin2016; Boothet al.the2017; Booth
2016; &
Öberg & Bergin 2016; Booth et al. 2017; Boothinterior& to the CO snowline (see Section 3.4) dominates all
reduced drift efﬁciency means that the the solid mass
hardly drift efﬁciency means that the the solid mass hardly
reducedIlee 2019), we focus here primarily on the warm molecularIlee2019),
we
focus
here
primarily
on
the
warm
molecular
other effects, forcing (C/O)gas≈1. Thus, if radial drift ischanges, while the warmin the outermass-weighted
disk drops bya factor whilechanges,
the
warm
CO
in
the
outer
disk
drops
by
a
factorFigure CO
12. Normalizedcompositionsof pebbles
locatedbetween
r
=
42
and
47
au
as
a
function
of
time
for
the
FULL-CR18,
FULL,
and
FULL-CR16
layer.
layer.
taking place, we would not expect to see the extremely high
_10 2 over the modeledin 2thisover the modeled 3 Myr. In disks evolving in thismodels. 3 Myr. In disks evolving_10(C/O) ratios in the inner disk midplane gas as found byfashion, the dust mass would be a more reliable gas
mass the dust mass would be a more reliable gas mass
fashion,

4.4.2. Total Volatile C/H and C/O

In models
without dust coagulation and pebble dynamics,
Uniﬁed Astronomy Thesaurus concepts: Protoplanetary disks (1300); Astrochemistry (75); Circumstellar
matterthe total volatile (i.e., gas + ice) C/O ratio does not changewith time, since there is either no transport between(241); Computational methods (1965)
neighboring cells (for the static CHEM model) or because the

The carbon-monoxide (CO) molecule has played an
important role in our understanding of protoplanetary disks.
Being abundant, volatile, and having rotational transitions

Ø Cold Classical Kuiper Beltの半径~45 au。
Ø abundances
CO richasiceの彗星の起源は雪線の外だけでCO
low as 10 have been reported (Bergin
et al. 2013;
Favre et al. 2013; McClure et al. 2016). Recently,
なく、化学反応が進む前でも可能。

dynamics of gas-phase species and small ice-carrying grains are
essentially identical (for the DIFF calculation). For thesemodels, the initial concentrations described in Table 1 result in(C O)gas ice x 0.5 and (C H)gas ice x 104 everywhere in
the disk.
When dust evolution is included, however, the dynamics ofcarbon and oxygen can differ depending on how they arepartitioned between gas and ice, leading to spatial and temporalvariations in the total elemental ratios (e.g., Öberg &Bergin 2016; Booth & Ilee 2019). Figure 11 shows the total12
volatile C/H and C/O ratios for the FULL-CR18, FULL, andFULL-CR16 models (described earlier in Section 4.1).

Zhang et al. (2020b), by contrasting observations of multiple
class 0/I and class II disks, found that CO depletion factors ofUnifying low- and high-mass star formation throughdensity-amplified hubs of filaments

M. S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters, high mass stars and hubs

The highest mass stars (>100M ) form only in hubs
M. S. N. Kumar1 , P. Palmeirim1 , D. Arzoumanian1 , and S. I. Inutsuka2

Instituto de Astrofı́sica e Ciências do Espao, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
Ø ⼤質量星はGMCの中⼼。⼩質量星形成は⼤質量形成に⽌められる前。Salpeter
IMF。105 yrで100 M⨀。
Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japane-mail: nanda@astro.up.pt
Ø これらを統⼀的に理解するためにHub-filament
systemを観測する。
Received April 23, 2020; accepted July 31, 2020
Ø Herschel Infrared Galactic
plane survey 250 µmでフィラメント、160, 250, 350, 500 µmで柱密度と温度。
ABSTRACT
M. S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters, high mØ robustなクランプを抽出。DisPerSEでフィラメントのスケルトン。8µmでフィラメント以外を除去。
1008.00295v2 [astro-ph.GA] 20 Aug 20202
Fig. 5. Computing the column density profile for HFSs: The column density map of each target is masked by the skeleton (left panel)and then averaged for all target hubs (middle panel) and non-hubs (right panel). The radial profile shown in Fig. 11 is computed
using these average images for di↵erent evolutionary groups. The example shown here is for the group of proto-stellar hubs andnon-hubs, and the units of the colour bar are cm 2 .
M. S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters, high mass stars and hubs

Fig. 5. Computing the column density profile for HFSs: The column density map of each target is masked by the skeleton (left panel)and then averaged for all target hubs (middle panel) and non-hubs (right panel). The radial profile shown in Fig. 11 is computed
using these average images for di↵erent evolutionary groups. The example shown here is for the group of proto-stellar hubs andnon-hubs, and the units of the colour bar are cm 2 .

M. S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters,Context. Star formation takes place in giant molecular clouds, resulting in mass-segregated young stellar clusters composed of Sun-detected skeletons are therefor
like stars, brown dwarfs, and massive O-type(50-100M ) stars.
ground variations in each targ
Aims. We aim to identify candidate hub-filament systems (HFSs) in the Milky Way and examine their role in the formation of theare located in the midst of gianhighest mass stars and star clusters.
where the estimated backgrou
M. S.10
N. 5Kumar,
P. Palmeirim,
D. Arzoumanian,and S. I. Inutsuka:Youngclusters,
highdetectedmass stars andMethods. The Herschel survey HiGAL has catalogued aboutclumps.
Of these,approximately
35000
targetsareat hubs
thedensity of the cloud or nebulos
00
3 level in a minimum of four bands. Using the DisPerSE algorithm we detect filamentary skeletons
10 ⇥ 10
cut-outs
of canthebe roughly comscenario ison
represented
by fourstages thattence level is set to pick up sk
SPIRE 250µm images (1800 beam width) of the targets. Any filament with a total length of at least
5500evolutionary(3 ⇥ 1800 )snapshots
and at ofleast
1800 in molecularpared withstar formation
column density fluctuations.
StagesII, III,filaments.
and IV respectively
represent low-massinside the clump was considered to form a junction at the clump. A hub is defined as a junction clouds.
of threeor I,more
Column
The DisPerSE algorithm istarformationinfilaments
withouthubs,
pre-stellar
HFSs
surFig. 6. Histograms (normalised by maximum y-value) of dis-density
Fig. 8. Histogram(normalisedby maximumof filament
maps weremaskedby they-value)
filament
skeletons and averaged for HFS and non-HFS samplesrounded
to computeradialby youngthe
clustersof profile
low-massalongstars, HFSs with highimage of each target using thetances of all clumps compared with those of HFSs, demonstrat- masses in HFS and non-HFS samples, showing the e↵ect of masfilaments
themass protostars surrounded by young cluster of low-mass stars,
ing that HFSs are uniformly distributed over the range coveredthe
sive
ininto
HFSs.
Theclumps.
lines represent
the mean Fig. 11. Circularly averaged radial column density profiles cenis accomplished by running t
Fig.
9.filaments
Mass–length
relationofverticalthe filaments
around clumps.
by all clumps.
values. Approximately 3700 (11%) are candidate
and anda full-blown
HII region
embedded clusters such as thetred HFSs,
on the studied
clumps.about
The column
densityis plotted
as aResults.
of which
2150(60%)
are pre-stellar
1400 (40%)
arewithproto-stellar.
gorithm. In the next step, DisP
function of pixel (each pixel is an azimuthal average) distanceOrion
Nebular
Cluster(ONC).
4
The filaments constituting the HFSs have a meanofThe⇠10-20pc,display
a massof ⇠5⇥10line masses (M/L) of ⇠2⇥103
fromlength
the centre.
error bars
the standard
deviation M , andtraced by the arcs above the giv
Low- to intermediate-mass star formation alone cantakeFig. 6. Histograms (normalised by maximum y-value) of dis- Fig. 8. 1Histogram (normalised by maximum
4 y-value) of filament
500 on the azimuthal average at each pixel. Saturated proto-stellar
3. Example of an HFS candidate: skeletons passing the HFS criteria (left panel) and al
measurement
towithdistinguish
those
The
pc is inno
. All
clumpsL>10
Le↵ects.
andL>10
in thehubswhereasof HFSs.
The stars formFig.
placelocatedin individual
filaments,
high-mass
prefpanel)are overlaid on a 250µm image.
tances of all clumps compared with those of HFSs, demonstrat-M there
massesHFS
andnon-HFS
samples,
showing
thee↵ectof18.2
mas-L at distances within 2kpc and 5kpc respectively areare assembled into individual
clumps are plotted separately because the fluxes are modelledbeam
resolution
of
the
250µm
imagescorresponds
totheproerentially inIn the following,
we elaborate on this scenario
ing that HFSs are uniformly distributed over the range coveredcolumn
sive filaments
in HFSs.
The
verticallines
representmeandensities
ofand
hubs
are
found
to3kpcbetheenhanceda factor
approximately
two (pre-stellar sources)
uphubs.
to aboutten (proto-stellar
and byrecoveredfrom ofGaussianfitting.
jectedscalesof
0.26pc0.7pc
atdistances
of
and
8kpc,
critical
angle
betwd
nationfilaments inby
everyasource(see in Fig.
11. The standard
by all clumps.
values.
using the simplest case of two filaments coming together
at shows
a dense networks of finedsources).
respectively. The filament widths are clearly unresolved in theFig. 13).
as the corresponding erro
this
angle
at
55
,
similarto pjunctionandthus
formingahub.
A catalogue was assembled listing the indicative properties puted for pre-stellar and
HFS sample; indeed
HFS detected filaments
are either highConclusions.
Allthehigh-massstars preferentiallyform in the density-enhanced hubs of HFSs. This amplification can drive the obof the filaments and the associatedclump properties.
TheArzoumanian+20
total HFS and non-HFS groupline-mass filaments or elongated clouds, and are not comparable00 4.2. Density enhancement and massive star formation in
tection(e.g.
filament
lengths
wereseparated
into
lengthinsideandoutsidethere
no measuremente↵ects.
The 18.2
hubs
servedlongitudinal
flows
along
filaments
providingfurther mass accretion. Radiation pressure and feedback can escape into thetotheisfilaments
describedto
bydistinguishstudiesof thosenearbystar forming
rethe clump. An indicative columntagged
density of theby
respectiveparts
a numberthat is ba
5.1. Stage I: Initial conditions
beam inresolution
ofbeltthe (Arzoumanian
250µm imagesetcorresponds
toFig.
the7,proof the skeleton was computed by reading out the values of each 4. Results
gions
the Gould
al. 2019).a In
we Circularly
averagedunified
radial profilesof columnfor
densityoninter-filamentary
voids.
We
propose‘filaments
to clusters’
paradigm
starcentred
formation,with the following salient features:
jectedscalesof
0.26pcand
0.7pc
atdistances
of
3kpc
and
8kpc,
skeleton pixel from the Hi-GAL column
density maps.
Also,skeleton
thedetected:thepickedplot the normalised histogram of filament lengths; this is taken thelocated in hubs and non-hubs are shown in Fig. 11.
total column
Flow-driven
either (b)due theto intra-molecularcloudve- density within a circle of radius equal to the source In searching the 34,575
respectively.
Thewidthsareclearly
unresolved
inthatthe(a)as
low-intermediate-mass
stars
form
slowly(106 yr)clumps
in thefilaments and massive stars form quickly(105 yr)filaments,
in the hub,initiallengthoutpc)filament
instead of
total filament
lengthtoensureFWHM was computed. For eachassigned
target, the mode fromthevaluecol- scribed
f il (inabove,
we found
the
1,
and
so
HFS sample;
indeed the HFS detected filaments are either high- These profiles are also separated for pre-stellar and proto-stellar
locity dispersions (⇠1 km s 1 ) or externally driven by expanding
umn density maps of 10 ⇥10 (similar to the 250µm maps) was sources, all of which are
the fractionof the isfilament
within of
the target
clump
FWHM is ex- objects. Targets
saturated
are all proto-stellar
butmassfunctionsum
stars
continuously
in thewith
HFS
withpixels
all massive
stars formedin thehub,
line-massfilaments
orthe
elongatedclouds,and arenot comparable createdas a background value that was
subtracted fromof
the column
shells(⇠10km (c)s 1 ) feedback
join to form dissipationa hub. Observations of usedcollid⇠10.7% of the Hi-GAL
indicator
theprominenceocluded from consideration. We note that, ‘individual filaments’Fig.they
are
shown
separately
todistinguishmodelled
fluxesusing
A sample of the HFS junction of filamentary s
12. All massiveandstarsexplain
form in hubs:with a lumito mass
the filaments
described by studiesnaturallyof nearby star
formingre- properties,
andin
segregation
due
to
HFS
the All(d)sourcesagespreads
withinandtheformation
ing boundfilamentsclusters
in the Mon
OB1star-forming
region showdensities
a pairread out for each skeletonthepixel.
the following
figures refersarise
to the constituent filamentsof non5Gaussian
the rest.
Movingalong
the filaments
tocatalogue is shown in Table 1 andis
full list is made available bycatedrunningon a single filame
accomplishedth
L 10fitting
L in fromthe inner
Milky
Way andlocatedat a distancegions in the Gould belt (Arzoumanian et al. 2019). In Fig. 7, wenosityoffilaments
approaching
each
other
with
relative
velocities
ofvia CDS and Vizier platforms.
Fig. 2. Hub-filament systems selection criteria
are called non-hubs in thclumps. OB
Figureassociations.
7 shows that the hub systems are dominated the clump centre, the column densities of the clumps representof hub
isolatedplot the normalised histogram of filament lengths; this is takenof <5
kpc are found to be HFSs. All hubs are marked by green 2-4 km s 1 (Montillaud et al. 2019). A variety of external trigThe filament mass was computed
using thetwo
measuredcolumn is
above
steps
a fitsfile10380
wiclumps,of whichby longeroutfilaments (mean length ⇠18 pc) compared to the non- ing hubs display enhancements
compared to those locatedFig. 7. Histogram (normalised by maximum y-value) of filament Fig.
density NH and using the formula M= NH ⇥ area
ment skeletons and 15755
10. Histograms(normalised
byfilament
maximumy-value)of filaas length(in pc) insteadof totallengthto ensurethatcircles. Clumps (with L 105 L when
)
that
are
not
found
to
be
hubs
f
il
gerssystems
can also drive such motions, of which stellar wind⇥ µbubhubwords.
clump (meanlength ⇠8 pc)medium
average. Figure
8 displays
the in –non-hub
systems; i.e.
clumps locatedon individual
filaments.
⇥ m where µ is the mean
molecularpersistence
weight per H
certainlevel,of theselatter tagge
10380 nolengths for HFS and non-HFS samples, showing that HFSs areKey
interstellar–
starformationembeddedclusters–
massivestars
hub-filament
00
ment
line
mass.
the fraction of the filament within the target clump FWHM is ex-(blue triangles) are located farther than 5 kpc because the 18

ハブの例。

ハブの定義。
0Ø ハブフィラメントはどこにでもあって、線密度は同じだが⻑くて重い。

Ø エディントン限界以上は全て
ハブ（not-hubsは>5 kpc）。
à ハブで⼤質量星形成。
Not all star formation results in dense clusters with OB stars,

H2

out
2
H

0

FIL

H2

out
2

Fil

2

taken
as 2.33 and mH is the atomic weight of hydrogen. The clump that is actually loc
normalised histogram of filament masses, where one can see the The ratio of the peak column density at the centre of the clump
bles and HII region shells are observationally prominent(see
composed of longer filaments.
filament length is multiplied by one pixel width (600 ) to obtain the There are also 4736 clum
cluded frome↵ect
consideration.
We note that,‘individual
filaments’
resolution
ofand
the non-hub
data is insufficient
to resolve
struc- Myers 2009, for a discussion); but late phases of supernova
immediateof longer filaments
influencing
the mass.
Thebeambetweenthe hub
systems is taken
as the theseenhanceremarea. Additionally, we also provide overlays of HFS skeletons aments (0 skeletons) andFil4
in the following figures refers to the constituent filaments of non-tures.
0The
yellowlineisat1.9
L =for10pre-stellar
L indicatesthe 2.1
Eddington
ratio nants
ment
factorwhich
clumps,for protothethe
250µm
images for visualisation of the candidate systems Using the evolutionary s
250µm
image
⇥100 cut-outs)
variesshould
between
10ontoand⇠18000,are (10also important.
Such filaments
be similar
hub clumps. Figure 7 shows that the hub systems are dominatedat which
as shown in Fig. 3a.
3.2. Selecting thelogue,
hub-filame
we find that 156
radiationpressures
becomeroughly filaments in Taurus (Palmeirim et al. 2013) and are often
stellar sources,
andand⇠10gravitationalin saturated sources.
It should
be noted
ferwithastandard
deviation
of
⇠800,
all
in
units
of
MJy/Sr.
This
bylongerfilaments(mean
length⇠18
pc)
comparedtothenonthe 3704 HFSs are respe
7
Fig. 7. Histogram (normalised by maximum y-value) of filamentthat mostnearbyof intense
starthisformation,
producingequal;
at <2
kpc, regions
all objects
above
luminosity
are thehubs, tile (Hacar et al. 2018), with ongoing low-mass star formation. 19
and proto-stellar in natur
2
hub
clump
(mean
length⇠8pc)
average.
Figure8displaysthe5
Column density
systems
lengths for HFS and non-HFS samples, showing that HFSs are mean mass of the HFS filaments (1.4 ⇥10 M ) is higher thandemonstrating
high-luminosity
arestars
all saturated
in one or
morecorresponds
to column
density variations between3.3.9⇥10
cmprofile of hub-filament
one or more ofof
the Hersc
The working
definitiona fithatsources,massivepreferentiallyform
in bands.
hubs.
This is23because
large populations of young low-mass stars
have
normalised
histogramof filamentmasses,where
one canthe
4composed of longer filaments.
The distribution of hub and non-hub systems on a luminosthatof the non-hub
clumps(⇠6.3⇥10
M ).
However,thisseemay
The DisPerSE output skeletons were used as a mask on the cor- they are among the most2
and
1.5⇥10cmonthe
cut-outs.
These
numbers
demonstrate
immediatee↵ectof
longerfilaments
influencing
the
mass.
The
been
found
aroundhigh-mass
protostars(Kumar
et
al.
2006)
and
aspect
ratio
of
at
least
three,
L
responding
columndensitymap
cut-outsofeachtarget,allowing
Inspection
of
the
skel
not be significant given the broad distribution of the masses. For ity vs. distance plot is shown in Fig. 12. Saturated sources areto measure it along the filaments and clumps located on the the filamentary structurearound cases
HFSs (Dewangan
et al.image
2017; Bauget al. 2018).
the cut-out
is filled
mostlyusfilaments.
by theemistwo in somea given sensitivity of the Hi-GAL maps, one of the most pro- plotted separately and are all proto-stellar in nature. The that
(Arzoumaniane
The resultis shown inous
the left exercises
panel of Fig. 5. These
cold dense filaments suc

1. Introduction

and not all clusters remain bound following gas dispersal (Lada& Lada 2003; Portegies Zwart et al. 2010; Krumholz et al.

Unifying low- and high-mass star formation throughdensity-amplified hubs of filamentsの続き

The highest mass stars (>100M ) form only in hubs
M. S. N. Kumar1 , P. Palmeirim1 , D. Arzoumanian1 , and S. I. Inutsuka2
M. S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters, high mass stars and hubs

Ø 中⼼で⼤質量。
Ø ⼩質量はハブ形成前から。
Received April 23, 2020; accepted July 31, 2020
Ø 全部合わせるとSalpeter IMF。
ABSTRACTØ フィラメントごとの形成時期が年齢の幅に。
Context. Star formation takes place in giant molecular clouds, resulting in mass-segregated young stellar clusters composed of SunØ 個々のフィラメントが肥えていないとハブ
like stars, brown dwarfs, and massive O-type(50-100M ) stars.
Aims. We aim to identify candidate hub-filament systems (HFSs) in the Milky Way and examine their role in the formation of the
でOB associationに。
highest mass stars and star clusters.
1008.00295v2 [astro-ph.GA] 20 Aug 2020

2

Instituto de Astrofı́sica e Ciências do Espao, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japane-mail: nanda@astro.up.pt

Methods. The Herschel survey HiGAL has catalogued about 105 clumps. Of these, approximately 35000 targets are detected at the

NGC2264 Stage III

S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters, high mass stars and hubs0
3 level in a minimum of four bands. Using theM.DisPerSE
algorithm we detect filamentary skeletons on 10 ⇥ 100 cut-outs of the00
in swirlingspiraltargets.
arm patterns
as evidenced
in the with
MonR2are-total length of at least 5500 (3 ⇥ 1800 ) and at least 1800
SPIRE 250µm images (18 beam width)of theAnyfilamentgion (Treviño-Morales et al. 2019). Examples of very high mass
inside the clump was considered to form
junction
atregionsthe clump.
A W43,
hubandis sodefined
as a junction of three or more filaments. Column
HFSsa arestar forming
such as W51,
on.
Recently,
there was anandinterestingclaim offor
a top-heavy
CMF non-HFS samples to compute the radial profile along
density maps were masked by the filamentskeletons
averaged
HFS andin W43 (Motte et al. 2018b), where the region traced may represent the main hub of that target. Other observations of HFSs
the filaments into the clumps.
with ALMA (Henshaw et al. 2017) indicate that hubs can form
Results. Approximately 3700 (11%) are
candidateof which
about 2150
a spectrumof low-HFSs,
and high-mass
objects. However,from our(60%) are pre-stellar and 1400 (40%) are proto-stellar.
arguments
for Stagelength
III and IV,ofsuch⇠10-20
a spectrumpc,
of objects
may of ⇠5⇥104 M , and line masses (M/L) of ⇠2⇥103
The filaments constituting the HFSs havea meana masssimply represent
the seeds that can grow further by mass accre5
M pc 1 . All clumps with L>104 L andtion
L>10
L
at
distances
within2kpc
andthrough longitudinal flows. The result will be an association5kpc respectively are located in the hubs of HFSs. The
of OB stars, especially when the lower mass stars grow to becolumn densities of hubs are found to beenhancedby a factor of approximately two (pre-stellar sources) up to about ten (proto-stellar
come intermediate-mass stars.
Age spreads in bound clusters: When a hub is composed ofsources).
a large network of filaments, the individual filaments may beConclusions. All high-mass stars preferentiallyformof fertilein thedensity-enhanced
drawn from a sample
filamentsthat represent a wide hubs of HFSs. This amplification can drive the obrange ofevolutionary timescales
star formation
histories.Radiation pressure and feedback can escape into theserved longitudinal flows along filaments
providingfurtherandmass
accretion.
Based on an estimate of core life times that reside within filainter-filamentary voids. We propose a ‘filaments
clusters’ments, André et toal. (2014)
suggestunified
a minimumparadigmof 106 yr as thefor star formation, with the following salient features:
lifetime of filaments.
absence of massive star formation,(a) low-intermediate-mass stars form slowly(106 yr) In
inthethefilaments and massive stars form quickly (105 yr) in the hub, (b) the initialwhich will clear o↵ the molecular gas in about ⇠3-5 Myr, molecular cloud lifetimes
can bein
as long
10 Myrwith
or moreall(Inutsuka
mass function is the sum of stars continuously
createdtheasHFS
massive stars formed in the hub, (c) feedback dissipation
et al. 2015), during which time filament formation and destrucand mass segregation arise naturally duetoHFS
properties,
andexplainthe
spreads within bound clusters and the formation
tion may happen. Lada et al. (2010) suggest that, at least in(d)the ageFig. 15. NGC2264 as an example of StageIII: This is a HFS
star forming regions such as Ophiuchus, Pipe, Taurus, Perseus, spanning ⇠10pc, where IRS 1 (above cone nebula) and IRS 2
of isolated OB associations.
and Lupus, the star formation timescale is ⇠2Myr and has not

W40 Stage IV

M. S. N. Kumar, P. Palmeirim, D. Arzoumanian, and S. I. Inutsuka: Young clusters, high mass stars and hubs

それぞれの重⼼２つ。

フィードバックは抜ける。

輻射バブル

年齢が違うOB

バブルでピラーFig. 17. W40 in the Aquila Rift as an example of StageIV: The formation of the W40 cluster in a hub has blown out the bipolar
HII region (seen in blue-green; see Mallick et al. 2013, for details). The e↵ects of radiation from OB stars ‘burning out’ the hubcomposing filaments can be seen as pillars. The ionising gas shock front sweeping up some filaments as it moves past it can also
be seen. The colour composite uses Herschel SPIRE 500µm image (tracing the filaments) as red, PACS 70µm as green, and Spitzer
MIPS 24µm as blue.

1. Introduction
重い重⼼が先にOB形成。

cause the ‘two nodes of activity with an evolutionary skewness’ within hubs is very frequently observed for which we
do not have an explanation. These nodes are well represented
by the BN/KL and Trapezium pair in Orion, and the IRS1
and IRS2 pair in NGC2264 described in the previous section.
Such pairs are good representations of the GHC scenario.
The CB model predicts that the density of the hub remains
roughly constant over many free-fall times, and any acceleration of star formation is the result of an increasing mass andnot density. This is in contradiction to the result shown in
Fig. 11, where the density increases in the hub from the prestellar to proto-stellar stages. The HFS scenario is primarily
based on the density amplification of hubs and therefore differs from CB in that respect.
– According to GHC, all massive clumps lead to massive starformation, whereas in the HFS paradigm, only those massive clumps that form junctions of large networks of filaments are conducive to the formation of massive stars. In
the HFS, density amplification (with its associated mass increase) is responsible for massive star formation and not the

sheer mass of the clump. Instead, we predict that the mass ofthe most massive star
the netP formedlinewill bef il correlatedMwith
linework factor fnet = nf il=1 N M
f il ⇥ Mline where N f il representØ ハブは円盤より低密度なので磁場で安定化。
⼩質量星に分裂せずトーラス状に。

(centre of spokes cluster) represent the two eyes of the hub
led to modification of the total mass of the high-extinction mate- shown by the green ellipse.
Key words. interstellar medium – star rialformation– embedded– massivestars hub-filament systems
within the clouds.
This implies thatclusters
low-mass-starformation
can take place inside dense fertile filaments without destroying
them. Therefore, if star formation began in the individual filaments at di↵erent times before joining to form the hub, it can sometimes better explained when viewed in, the HFS paradigm.
result in age spreads of a few million years for low-mass stars. We caution that the arguments made below do not necessarily
Once the hub forms, it can accrete several smaller infertile fila- reflect the interpretations of the original literature.
ments. The overall age spread of stars in a cluster can therefore
result from the oldest fertile filament to the last star forming core
6.1. NGC2264: Stage III
in the hub. An interesting alternative explanation for age spreads
can be found in Kroupa et al. (2018).
Located in the constellation of Monoceros, the star S Mon
OB associations: The star formation scenario in HFSs can also輻射でピラー

Not all star formation results in dense clusters with OB stars,
and not all clusters remain bound following gas dispersal (Lada& Lada 2003; Portegies Zwart et al. 2010; Krumholz et al.
16

f il
the number of filaments with a certain line mass Mline. On
the contrary, GHC suggests a correlation between the most
massive star and the clump mass which Vázquez-Semadeni
et al. (2019) claim to be represented by the known correlation of the most massive star with the cluster mass where it
resides.
– Longitudinal flows within filaments are representations ofglobal infall in GHC moving towards a massive clump where
high-mass stars form. In the CB model, they serve the purpose of mass transport which is similar to HFS. VázquezSemadeni et al. (2019) use the analogy of rivers from high altitudes to lakes to describe longitudinal flow. On the contrary,
we have used the analogy of an electric current driven by apotential di↵erence. In the HFS, longitudinal flows are bestviewed as the current in a parallel electric circuit, where thecurrents in individual circuit paths add up at the source whichis represented by the hub. According to HFS, detectable lon-

Downloaded from https://academic.oup.com/mnras/article/496/3/2821/5854212 by KASI user on 18 September 2020

Table 2. Correlations between parameters.

Downloaded from https://academic.oup.com/mnras/article/496/3/2821/5854212 by KASI user on 18 September 2020

Tie Liu ,1,2,3‹ Neal J. Evans,2,4 Kee-Tae Kim ,2,5 Paul F. Goldsmith,6
Sheng-Yuan Liu,7 Qizhou Zhang,8 Ken’ichi Tatematsu ,9 Ke Wang,10 Mika Juvela,11Leonardo Bronfman,12 Maria. R. Cunningham,13 Guido Garay,12 Tomoya Hirota ,912Jeong-Eun Lee,14 Sung-Ju Kang,2 Di Li ,15,16,17 Pak-Shing
Li,18 Diego
Mardones,
Ø ⾚外SFRと、ガスの総量ではなく、⾼密度ガスの量に相関
à
dense
gas
star
formation
law。
19
20
21
22
Sheng-Li
Qin,
Isabelle
Ristorcelli,Anandmayee
Tej,
L.
ViktorToth,Ø HCN, HCO+ J=1-0が使われるが低密度でも厚くなる
à 同位体で確認したい。
Jing-Wen Wu,15 Yue-Fang Wu,23 Hee-weon Yi,14 Hyeong-Sik Yun,14 Hong-Li Liu ,24
1
1,26
Ø ALMA large, ATOMSのACA（銀河⾯クランプ>0.2pc）、13"-60",
km/s,
50-90 mJy/beam。
Ya-Ping Peng,25 Juan Li ,1,26 Shang Huo Li,
Chang Won Lee,2,5dv=0.2-0.4
Zhi-Qiang Shen,
Tapas Baug,10 Jun-Zhi Wang,1,26 Yong Zhang,27 Namitha Issac,21 Feng-Yao Zhu,1
Qiu-Yi Luo,1 Xun-Chuan Liu,23 Feng-Wei Xu,23 Yu Wang,23 Chao Zhang,192828 15T. Liu et al.
Ø free-freeを避けるためReff, MclumpはZhiyuan Ren15 and Chao Zhang

単⼀鏡（0.87, 1.2 mm）。

implies that HCO+ abundance is sensitive to the ionization degreeof molecular gas. In more far-UV irradiated environments, HCO+
Relationabr
is more easily recombined with free electrons, leading to a decrease+
with increasing
its abundance.
Increasing
HCN-to-HCO
Figurefor
identified
in 3 mmcontinuumratios
emission.
(a) peak flux density; (b) total flux density; (c) aspect
Mclump– Lbol 2. Histograms
1.12(0.06) of parameters1.12(0.21)
0.83the compactinobjects
Accepted 2020 May 25. Received 2020 May 19; in original
2020
April
27
infrared luminosity have been found in LIRGs (Papadopoulos
Mvirratios;–form
Lbol (d)1.04(0.11)
2.12(0.31)
0.68
effective radii. The red solid lines are median values.
2007). In the Galaxy, more evolved H II regions also show higher
Mvir – Mclump
0.83(0.08)
1.14(0.22)
0.73
HCN-to-HCO+ ratios than infrared dark clouds (Nguyen-Luong
L!HCN – Lbol
0.99(0.08)
3.68(0.11)
0.73
!
LHCO
0.94(0.07) will3.91(0.09)
0.73 in forthcoming
et al. 2020).
However,in our data, we do not see any trend of HCN+ – Lbol
continuum
objectsbediscussed
papers.
The!
1.03(0.08)
4.37(0.07)
0.76
to-HCO+ ratios against the Lbol spanning 4 orders of magnitude.
13 CN – Lbol
A B S T R A CLH!T3-mm
continuum
emissioncanhaveasignificant
contribution
from
LH13 CO+ – Lbol
1.00(0.08)
4.59(0.05)
0.74This may imply that the majority of HCN and HCO+ J = 1 − 0 line
We report studiesof theemission,
relationships
betweenour
theability
total bolometricluminosity
LTIRfrom) andfree–freecompromising
toemission
determine
massesbol or
withinthe ‘ATOMS’(Lclumpscomes
regions that are
13 the toliterature
13 local+strongradiation
field.
This scenario
needs
dust continuum
We use instead
CN, H
CO+FUV, HCN,
andHCO
the molecularfrom
line theluminosities
of J =emission.
1 − 0 transitions
ofnotHexposed
to be tested from detailed analysis of the spatial distributions of
),
mass
(M
),
etc.
of
the
clumps(seevalues
for
the
size
(R
eff
clump‘ATOMS’
with data obtained from ACA observationsin thesurveyof 146insideactiveGalactic
molecularline emission
the clumps,
whichstarwill be presented
TableThe
A6).correlations
These are taken
fromL single-dishatline0.87
mm"
inmapsforthcoming
works
using the high resolution(∼2
arcsec) ALMA
andmolecular
luminosities
Loftheforming
regions.
betweenbol
Figure 1. Integrated intensity maps of four molecular lines are shown as colour-scale images for three example sources.
I13111–6228,
and2018) or 1.2 mm
12-m(Faúndez
array data of(see Liu et al. 2020, for(Urquhart,KönigI17136–3617,& Giannetti
ettheal.‘ATOMS’ surveymoltransitions
all appear
to from
be approximately
linear. Lineexample).
emission of isotopologues shows as
I19095+0930 are shown in upper, middle, and lower panels, respectively. The 3 mm continuum is shownfour
in contours.
The2004),
contourlevels are
per cent to+minimizing
the30contamination
by free–freeTheemission.
) and log( HHCO
densityfor"log( HCN
13 CO+ ) are also
90 per cent in steps of 20 per cent of peak values. The peak values of 3 mm continuum emission for I13111–6228,
I17136–3617,
and"mol
I19095+0930
are their
0.088,main line emission.
CN different–Lrelationsas
Thedistributions
log(L
for
large scatters
inIn
Lbol
bol /Lmol )H13
forcompact
objects
Fig.
3,
wecomparethe
distributionsofR
eff quite similar to each other but with large scatter (σ ∼0.6) in the"
1.814, and 0.307 Jy beam−1 , respectively.
ratiosdo scatter
not change
molecular line
tracersinhave
distributions.
The
Lbol
data-to-L
(see
Fig.
12).
The largemeans thatwith
the optical depths
identified
3 mmsimilar
continuum
emission andmolecularlineemission.
molofThethe mainlines show line
significant
variations among
)
and
clump
masses(M).
molecular
luminosity
ratiossources. The
galactocentric
distances
(R
The
data
are
plottedwithaGaussiankerneldensityestimate
using
GC
clump
√
non-parametric tests in Table 3 confirm that their distributions
3 mm continuum emission, H13 CN, H13 CO+ , HCN, and HCO+
+ function
13identified
13
and Reff is defined as
Reff = ab.theForobjectsin
PYTHON 13
package
SEABORN.+1 -to-H
The‘kdeplot’, compact
H13 CN-to-H
COin+ ,theHCN-to-H
CN, areand
HCO
CO+the) distributions
all appear(HCN-to-HCO
nearlythe same
after shiftingby their mean
13++
line emission, respectively.
13that HCN J = 1 − 0 and HCO+ J = 1 − 0
and HCO
J
=
1
−
0
line
emission,wealso
H CO J = 1 − 0constantvalues,indicatingCN,
medianradii
forcompact
objectsin3
mm
continuum,Hagainst Lbol , dust temperature (Td ), Mclump , and RGC . Our studies suggest that both thehave similar opacity in sources of the ‘ATOMS’ sample. The
As shown in Fig. 1 for I13111–6228, we identified multiple+
and velocity
dispersion
derived the source-averaged velocity(Vlsr+) HCN,
CO
andlinetracers
emissionaremay0.18,
0.25, 130.28,
H13
13main lines andisotopologue
linesHCO
are goodof thetotal
massesof ratiodense
GalacticCNand gas
HCO+in-to-H
CO+ ratio are ∼5.0
mean
HCN-to-H
compact objects in 3 mm continuum in 27 targets. Some targeted(σ ) from their corresponding Moment
1andMoment2maps.
All0.33, and 0.34 pc, respectively. Compact objects in
3∼5.4,
mm respectively.
continuumAssuming an isotopic 12 C/13 C ratio of 55 at
andThearelarge
opticalin depths
main lines do not affect the interpretation ofsources also contain multiple objects in molecular line emission asof these parametersmolecular
for compactclumps.
objects
thatidentified
3 mm Rof
median galactocentricof 5.8 kpc
et al. 2005),
of compact
objects distanceFigure
emission
have statisticallysmaller
3. (Milam
Distributionof Reff for compact objects identified in 3 mm
eff than that the13+ slopes13+ formation relations. We find that the mean
the
in
star
star formation
efficiency(SFE)
the representative
optical depths
inferred fromthese ofmean ratios areshown in Fig. 1 for I17136–3617. We identified multiple objects, and HCN
are summerizedincontinuum, H CO , H CN, HCO
continuum
emissionand molecular line emission, which are plotted usingforcompact
objects
identifiedinmolecularlineemission.
R
eff
+
13
13
+
J
=
1
−
0,
respectively.
∼12
and
∼11
for
HCN
J
=
1
−
0
and
HCO
in 30, 32, 35, and 27 sources from H CN, H CO , HCN,
13 theGalactic‘ATOMS’is reasonably
consistent with othermeasures
Table A1 , Table A2,massive
Table A3,
Table
A4clumps
andin
Table
A5 ,andrespectively.
theandfunctionin theCN
H13 CO+survey
line emission
arealso
identified
Hinderived fromthe PYTHON package SEABORN. The numbers in theThus,the statisticallycolumn densities of HCN
HCO+‘kdeplot’+
integrated
intensity
maps,
respectively.
However, theandandHCO+examining
Figure6.
Thedense
correlation
between
LTIR ,thoseand
L!HCNusing. ratio,
The datavery
for compact
m observations
effective
radii of whole
clumpsin single
dish,S
aspectFig. 2 presents histogramsof parameters
(S
upper
right
are mean, median, and standard deviation values.
of the SFE
for
gas,
even
different
tracersorvery
different
peak
total
main
lines
with
optically
thin
assumption
couldbox
be underestimatedline
smallerthancompact
objects
identified
in
HCN
and
HCO
objects in this study are shown as the green filled circles. The data points
mparison of systemic
velocities
in ACA
single-disha factor of ∼10 for such high optical depths.
majority(∼80 percent)observationsof sources andcontain
only a single compact
sourcesin emission.
3clumps
mm (thecontinuum
emission.
The
and Reff ) for compact
spatialscales.
Interestingly,
there
seems
bereda trendbybetween
Reff andfor
Galactic
blue
filled circles) andexternalgalaxiesto(the+ (the black crosses) and HCO+ (the blue crosses) line emission
However, there
is no trend between−1
object in 3 mm continuum emission and in molecular line emission
with molecular
the idea line
thatluminosity
lines with higher effective excitation density trace

Affiliations are listed at the end of the paper

コントア: 3 mm

2825

Ø HCO+は単⼀鏡と同じものを⾒ていて、H13CO+は⼩さい。
H13CO+
HCO+
Downloaded

median values for S

今回（SFEが⾼い、束縛）
単⼀鏡Gal, ex-gal

andScircles)are
0.12 Jyobservations
beam wereand0.20byJy,
filledin single-dishcompiled
Jiménez-Donaire

Downloaded from https://academic.oup.com/mnras/article/496/3/2821

ATOMS II

Ø ⾼密度トレーサーほど⼩さい。

Downloaded from https://academic.oup.com/mnras/article/496/3/2821/5854212 by KASI user on 18 September 2020

ATOMS: ALMA three-millimeter observations of massive star-forming
regions – II. Compact objects in ACA observations and star formation
scaling relations

ATOMS: ALMA three-millimeter observations of massive star-forming 2832 T. Liu et al.
Table 4. Statistics of the log of star formation efficiency.
regions – II. Compact objects in ACA observations and star formation
SFR/M (HCO )SFR/M
scaling relations
NumberMeanMedianStd
MeanMedianの続き+

vir

1,2,3‹

2,4

2,5

119
75
75
44

6

Tie Liu ,Neal J. Evans, Kee-Tae Kim , Paul F. Goldsmith,
10 II
ATOMS
2829 11
Sheng-Yuan Liu,7 Qizhou Zhang,8 Ken’ichi Tatematsu ,9 Ke Wang,
Mika Juvela,
Leonardo Bronfman,12 Maria. R. Cunningham,13 Guido Garay,12 Tomoya Hirota ,9Jeong-Eun Lee,14 Sung-Ju Kang,2 Di Li ,15,16,17 Pak-Shing Li,18 Diego Mardones,12
Sheng-Li Qin,19 Isabelle Ristorcelli,20 Anandmayee Tej,21 L. Viktor Toth ,22
Jing-Wen Wu,15 Yue-Fang Wu,23 Hee-weon Yi,14 Hyeong-Sik Yun,14 Hong-Li Liu ,24
Ya-Ping Peng,25 Juan Li ,1,26 Shang Huo Li,1 Chang Won Lee,2,5 Zhi-Qiang Shen,1,26
Tapas Baug,10 Jun-Zhi Wang,1,26 Yong Zhang,27 Namitha Issac,21 Feng-Yao Zhu,1
Qiu-Yi Luo,1 Xun-Chuan Liu,23 Feng-Wei Xu,23 Yu Wang,23 Chao Zhang,1915
Zhiyuan Ren152832
and Chao
Zhang
T. Liu et
al.

−2.38
−2.09
−2.09
−2.89

−2.33
−2.11
−2.11
−2.79

0.63
0.50
0.50
0.50

a Selection criteria explained in the text.

Mean

SFR/Mclump
Median

−2.33
−2.13
−2.13
−2.66

−2.29
−2.10
−2.10
−2.69

SFR/Mvir (H13 CO+ )MeanMedian
Std

Std

0.43
0.36
0.36
0.32

−1.62
−1.35
−1.35
−2.08

13

13

All
SFR > 5
SFR > 5, r > 0.2
SFR < 5, r > 0.2

bol

TIR

+

+

"
mol

0.63
0.50
0.50
0.50

−2.33
−2.13
−2.13
−2.66

−2.29
−2.10
−2.10
−2.69

are five outliers with highest dust temperature in the sample.
galactocentric distances (RGC ) and clump masses (Mclump ). The molecular line luminosity ratios

Ø L , L からSFRを求めてMで割る à SFE。
data.
main lines and isotopologue lines are good tracers of the total masses of dense gas in Galactic(6) If we use extragalactic calibrations to convert L to a SFR
Ø SFEに傾向はないが、暗い（軽い）ものはSFRが⼩さい。
andcompare it to masses of clumps from single-dish observations
molecular
clumps.
The
large
opticaldepths
of
main
lines
do
not
affecttheinterpretationofTable 3. Asymptotic significances (P-value) in non-parametric
et al. 2004). We also use, secondly, the virial masses derived from or to virial masses from HCO , we can estimate a dense gas SFE.
the slopes in star formation
relations.
mean star formation efficiency (SFE)Whileof this procedure is not fully justified for the scales we are13
12 that the 13
Ø tests.
SFEの値は近傍の雲や遠⽅銀河と同じ。
CO+We(Mfindboth HCO+ and H
vir and Mvir in Table A6).
Kolmogorov–Sminova
!

"

0.43
0.36
0.36
0.32

Figur
with bfrom tnearbysame aVutisacircle(heptacontaiChenfor inn
represfrom C

Figure 8. Lbol -to-L!mol ratios (panels a–d) and line luminosity ratios (panels(HCN-to-HCOe–h) as a function
bolometric
Lbol
+
13
+
13. The solid line+is the 13, H13ofCN-to-H
COluminosity, HCN-to-H
CN, and HCO -to-H mean
CO+ )value.
all appear
molecular line luminosity ratios against Td , Mclump , and RGC in our
The dashedbol
lines showat the upper
right
cornerineachpanel.
TIRstandard deviation. The name of the ratio is labelled constantagainst Lbol , dust temperature (Td ), Mclump , and RGC . Our studies suggest that both theDistributions
"
!

Std

Tdが⾼い５個ほぼ星。

"
Figure 13. SFR/Mclump is plotted versus Mclump . The red points represent
bol mol
the sources with SFR < 5 M" Myr−1 , while the black points represent the"molecular line tracers have similar distributions. The Lbol -to-Lmol ratios do not change withsources with SFR ≥ 5 M" Myr−1 . The points inside the green-dashed ellipse
bol

"
mol

0.55
0.46
0.46
0.35

Downloaded from https://academic.oup.com/mnras/article

bol

−1.66
−1.39
−1.39
−2.13

Selectiona

Downloaded from https://academic.oup.com/mnra

119
75
75
44

SFR/Mvir (HCO+ )MeanMedianStd

Downloaded from https://academic.oup.com/mnras/article/496/3/2821/5854212 by KASI user on 18 September 2020

Number

−2.33
−2.11
−2.11
−2.79

a Selection criteria explained in the text.

Affiliations are listed at the end ofTable
the 4.
paper
Statistics of the log of star formation efficiency.

Ø Lbol/Lmolが４つの分⼦で似ている
Accepted 2020 May 25. Received 2020 May 19; in original form 2020 April 27
à dg-sf lawは光学的厚さの影響を受けない。
ABSTRACTØ HCN/H13CNとHCO+/H13CO+が似ている
à τが同じ（~12, 11）。
We report studies of the relationships between the total bolometric luminosity (L or L ) andthe molecular line luminosities of J = 1 − 0 transitions of H CN, H CO , HCN, and HCO
Ø Lbolに対する増加は進化（ß Tdに対しても増加）。
with data obtained from ACA observations in the ‘ATOMS’ survey of 146 active Galactic starØ FUVを反映するHCN/HCO+はATOMSサンプルでは
forming regions. The correlations between L and molecular line luminosities L of thefour transitions all appear to be approximately linear. Line emission of isotopologues shows as
銀河中⼼からの距離（環境）には依らない。
large scatters in L –L relations as their main line emission. The log(L /L ) for different

−2.38
−2.09
−2.09
−2.89

clump

bol

+

studying, we find that the logarithmic mean SFE is reasonably
massive Galactic clumps in the ‘ATOMS’ survey is reasonably consistent with other measures
We compare our results for
SFETheto
those
ofor examining
Vutisalchavakul
consistent with other measures of SFE for dense gas, even thoselogarithmic
mean SFE(SFR/Mdense ) is plotted
Mdenseof the SFE for dense gas, even those usingFigure
very14.different
tracers
veryversus
differentwithbothshowingthestandard
deviation
in
the
log.
The
black
diamondis very different tracers or examining very different spatial
et al. (2016) first. They determined the SFR from the mid-infrared using
spatial scales.
from this work, and the magenta diamond is from the EMPIRE studyscales.
of

Techn
projecScien
dation
Scien
suppo
114A
data:
of ES
(Japa
and K
of Ch
AUI/N

c ESO 2020&

Astrophysics
Rajika L. Kuruwita1 , Christoph Federrath2 , and Troels Haugbølle1

1

Niels Bohr Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark
e-mail:The
rajika.kuruwita@nbi.ku.dk
dependence of episodic accretion on eccentricity during the2
Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia

formation of binary stars

Received 16 April 2020 / Accepted 21 June 2020
Rajika L. Kuruwita1 , Christoph Federrath2 , and Troels Haugbølle1
1

ABSTRACT

Niels Bohr Institute, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen K, Denmark
e-mail: rajika.kuruwita@nbi.ku.dk
2
Context. Episodic
accretion
been observedin short-period
where burstsof accretionoccur at periastron. The binary
Research
School ofhas
Astronomy
and Astrophysics,
Australian binaries,
National University,
Canberra,
ACT 2611, Australia

trigger hypothesis has also been suggested as a driver for accretion during protostellar stages.
Received
April 2020 how/ Accepted
21 June 2020
Aims. Our goal
is to 16
investigate
the strengthof episodic accretion bursts depends on eccentricity.
Methods. We investigate the binary trigger hypothesis in longer-period (>20 yr) binaries by carrying out three-dimensional magnetoABSTRACT
hydrodynamical simulations of the formation of low-mass binarystars down to final separations of ⇠10 AU, including the e↵ects ofgas turbulence
and magnetic fields. We ran two simulations with an initial turbulent gas core of one solar mass each and two di↵erent
Context. Episodic accretion has been observed in short-period binaries, where bursts of accretion occur at periastron. The binary
initial turbulent
Machnumbers,Mbeen= suggested
Mfor= accretion
0.2, for during
6500 yrafter protostar
v /c s = 0.1
triggerhypothesis
has also
as aanddriverprotostellar
stages. formation.
Results. WeAims.
observeburstsaccretionat theperiastronearly stages
when ontheeccentricity.
eccentricity of the binary system is still high.
Our goal
is toofinvestigate
howstrength ofduring
episodicthe
accretion
bursts depends
We investigate
the binary
triggerhypothesis inand
longer-period(>20 yr) binaries
by carrying
outlaterthree-dimensional
magnetoWe find thatMethods.
this correlation
betweenburstsof accretionpassing periastronbreaksdown atstages becauseof the gradualhydrodynamical
simulationsoftheformationof
low-massbinary
stars
down
to
final
separations
of
⇠10
AU,
includingthee↵ectsof However,circularisation of the orbits. For eccentricities greater than e = 0.2, we observe episodic accretion triggered near periastron.
gas turbulence and magnetic fields. We ran two simulations with an initial turbulent gas core of one solar mass each and two di↵erent
we do not findany strong correlation between the strength of episodic accretion and eccentricity. The strength of accretion is defined
initial turbulent Mach numbers, M = v /c s = 0.1 and M = 0.2, for 6500 yr after protostar formation.
as the ratio ofResults.
the burst
rateoftoaccretion
the quiescentaccretionrate.
Westages
determinethataccretionofevents
aresystem
likelyistriggered
We accretion
observe bursts
at periastron
during theearlywhen theeccentricity
the binary
still high. by torques
between theWerotation
thecorrelation
circumstellar
discandoftheapproaching
binarystars.breaks
We compare
ourstages
results
withofobservational
data offind thatofthis
betweenburstsaccretionand passing
periastron
down at laterbecausethe gradualcircularisationof the orbits.binaries
For eccentricities
e = 0.2, weobserve our
episodicaccretion triggered
periastron. However,
episodic accretionin short-period
and findgreater
goodthanagreement
betweensimulations
and the nearobservations.
we
do
not
find
any
strongcorrelation
betweenthestrengthof
episodicaccretionandeccentricity.
The
strengthofis definedConclusions. We conclude that episodic accretion is a universal mechanism operating in eccentric youngaccretion
binary-starsystems, indeas the ratio of the burst accretion rate to the quiescent accretion rate. We determine that accretion events are likely triggered by torques
pendent of separation,and it should be observable in long-period binaries as well as in short-period binaries. Nevertheless, the strength
between the rotation of the circumstellar disc and the approaching binary stars. We compare our results with observational data of
depends on thetorquesand inhence
the separation
at find
periastron.
episodicaccretionshort-periodbinaries andgood agreement between our simulations and the observations.
Conclusions. We conclude that episodic accretion is a universal mechanism operating in eccentric young binary-star systems, inde-Keywords.pendent
magnetohydrodynamics(MHD)– binaries:
general binaries– stars:asformation– stars: kinematics
and dynamics連星で起きるaccretionof separation, andburstの強さは離⼼率とは関係なく、近星点の距離で決まる。
it should
be observablein long-period
well as in short-periodbinaries. Nevertheless,the strength
depends on the torques and hence the separation at periastron.

Key words. magnetohydrodynamics (MHD) – binaries: general – stars: formation – stars: kinematics and dynamics
1. Introduction
During this dynamical evolution, accretion events may becollaboration
MNRAS 497, 632–642 (2020)

1 Department
Advance
Accessandpublication
2020
July 9 University, Box 516, SE-751 20 Uppsala, Swedenof Physics
Astronomy,
Uppsaladoi:10.1093/mnras/staa1993

2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany

3 Department of Physics and Chemistry, University of Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy
5 Université Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France

A. Lavail ,1‹ O. Kochukhov,1 G. A. J. Hussain,2 C. Argiroffi,3,4 E. Alecian,5 J. Morin6 and the BinaMIcS
Accepted 2020 July 2. Received 2020 June 30; in original form 2020 April 17
collaboration
1 Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden
2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching, Germany
3

Department
A B S T4R
A C T of Physics and Chemistry, University of Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy

Downloaded from https://academic.oup.com/mnras/article/497/1/632/58

INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy

We report
time-resolved,
high-resolution
opticalspectropolarimetricobservations of the young double-lined spectroscopic binary
5 UniversitéGrenoble Alpes,
CNRS, IPAG, F-38000
Grenoble,
France6
V1878 LUPM,
Ori. Ourobservations
werecollected
with
the ESPaDOnS
spectropolarimeterat the Canada–France–Hawaii Telescope
Universitéde Montpellier,
CNRS,
Place Eugène
Bataillon,
F-34095 Montpellier,Francethrough the BinaMIcS large programme. V1878 Ori A and B are partially convective intermediate mass weak-line T Tauri stars
on an Accepted
eccentric
and asynchronous orbit. We also acquired X-ray observations at periastron and outside periastron. Using the2020 July 2. Received 2020 June 30; in original form 2020 April 17
least-squares deconvolution technique (LSD) to combine information from many spectral lines, we clearly detected circularpolarization signals in both components throughout the orbit. We refined the orbital solution for the system and obtained
A B S T Rspectra
A C T for the primary and secondary components. The disentangled spectra were then employed to determine
disentangled
We report
time-resolved,
high-resolution
optical spectropolarimetricobservationsof the youngspectroscopic
binaryatmosphericparametersof thetwo components
using spectrum synthesis.
Applying
our double-lined
Zeeman Doppler
imagingcode to
V1878
Ori.
Our
observations
werecollected
with
the
ESPaDOnS
spectropolarimeterattheCanada–France–Hawaii
Telescopecomposite Stokes IV LSD profiles, we reconstructed brightness maps and the global magnetic field topologies of the two
throughWe
the find
BinaMIcS
large programme.
A and Bdifferent
are partiallyconvective
intermediate
mass weak-line
T Tauristars
components.
that V1878
Ori A and BV1878
have Ori
strikingly
globalmagnetic
field topologies
and meanfield strengths.
on an eccentric and asynchronous orbit. We also acquired X-ray observations at periastron and outside periastron. Using the
The global magnetic field of the primary is predominantly poloidal and non-axisymmetric (with a mean field strength of 180 G).
least-squares deconvolution technique (LSD) to combine information from many spectral lines, we clearly detected circular
While the secondary has a mostly toroidal and axisymmetric global field (mean strength of 310 G). These findings confirm thatpolarization signals in both components throughout the orbit. We refined the orbital solution for the system and obtainedstars withvery similarparameters
can exhibit
radicallycomponents.
different global
magnetic fieldcharacteristics.
The analysisof the X-ray
disentangled
spectrafor the primaryand secondary
The disentangled
spectrawere then employed
to determine
data showsno signparametersof enhanced
activityat periastron,suggestinglack of Applying
strong magnetosphericinteraction
at thisepoch.
atmosphericof thetwo components
using
spectrumthe
synthesis.
our Zeeman Doppler
imagingcode
tocomposite Stokes IV LSD profiles, we reconstructed brightness maps and the global magnetic field topologies of the twoKeywords:
techniques: polarimetric – techniques: spectroscopic – binaries: spectroscopic – stars: individual: V1878 Ori – stars:
離⼼率の⾼いWTTSの連星の円偏光。主星はポロイダル。伴星はトロイダル。相互作⽤なし。
components. We find that V1878 Ori A and B have strikingly different global magnetic field topologies and mean field strengths.
magnetic field.
The global magnetic field of the primary is predominantly poloidal and non-axisymmetric (with a mean field strength of 180 G).
While the secondary has a mostly toroidal and axisymmetric global field (mean strength of 310 G). These findings confirm that

Downloaded from https://academic.oup.com/mnras/article/497/1/632/5869265 by KASI user

The large-scale magnetic field of the eccentric pre-main-sequence binary
6 LUPM,system
Université deV1878
Montpellier, Ori
CNRS, Place Eugène Bataillon, F-34095 Montpellier, France
4 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy

protoplanetary disks.
U. Lebreuilly1 , B. Commerçon1 , and G. Laibe1

Protostellar collapse: the conditions to form dust richÉcole normale supérieure de Lyon, CRAL,protoplanetary
UMR CNRS 5574, Universitédisks.
de Lyon , 46 Allée d Italie, 69364 Lyon Cedex 07, France
e-mail: ugo.lebreuilly@ens-lyon.fr
ABSTRACT
École normale supérieure de Lyon, CRAL, UMR CNRS 5574, Université de Lyon , 46 Allée d Italie, 69364 Lyon Cedex 07, France
Context.
plays a key role during star, disk and planet formation. Yet, its dynamics during the protostellar collapse remains ae-mail:Dust
ugo.lebreuilly@ens-lyon.fr

tro-ph.SR] 12 Jul 2020

[astro-ph.SR] 12 Jul 2020

U. Lebreuilly1 , B. Commerçon1 , and G. Laibe1

poorly investigated field. Recent studies seem to indicate that dust may decouple efficiently from the gas during these early stages.
Aims. We aim to understand how much and in which regions dust grains concentrate during the early phases of the protostellar
ABSTRACT
collapse, and see how it depends on the properties of the initialcloud and of the solid particles.
Methods. We use the multiple species dust dynamics solver multigrain of the grid-based code RAMSES to perform various simulations
Context. Dust plays a key role during star, disk and planet formation. Yet, its dynamics during the protostellar collapse remains aof dustyWe
perform
and magnetohydrodynamical
simulations
vary
theearly
maximum
poorlycollapses.
investigatedfield.
Recenthydrodynamical
studies seem to indicatethat dust may decouple efficiently
from where
the gas weduringthesestages. size of the
dustAims.
distribution,
theunderstandthermal-to-gravitationalenergyanddustthe grains
magnetic
propertiesof thecloud.phases
We simulate
the simultaneous
We aim tohow much and inwhichratio
regions
concentrateduringthe earlyof the protostellar
evolution
ofand
ten seeneutralgrainsonspecies
with grain
from
a few
nanometerscollapse,
how itdust
depends
the propertiesof thesizes
initialvarying
cloud andof thesolid
particles. to a few hundredth of microns.
Results.
We We
obtaina significant
decoupling
betweensolver
the gasand theofdust
for grains codeof typicalsizes
a few ⇠various
10 µm.
This decoupling
Methods.
use themultiple species
dust dynamics
multigrain
the grid-based
RAMSES
to perform
simulations
strongly
depends
on theenergyratio, the grain sizessimulationsor the inclusion
magnetic
field. Withsemi-analyticof dusty
collapses.
Wethermal-to-gravitational
perform hydrodynamical andmagnetohydrodynamical
whereofwea vary
the maximum
sizea ofthedustcalibrated
distribution,
ratio
andmostly
the magneticof thewith
cloud.
simulate
the number
simultaneous
model
onthe
ourthermal-to-gravitational
results, we show thatenergy
the dust
ratio
varies properties
exponentiallytheWeinitial
Stokesat a rate thatevolutionoftenneutraldust
grainsspecies
with
grain
sizes
varyingfromafew
nanometerstoafew
hundredthofmicrons.
depends on the local cloud properties.
Results. WeWe
obtainbetweenthe andgas anddust for grainsof first-core
typical sizes
a few⇠ 10newlyµm. Thisdecoupling
Conclusions.
finda significant
that largerdecouplinggrains tend
to settle
drifttheefficiently
in theandin theformeddisk. This canstrongly
dependsonthethermal-to-gravitationalenergyratio,
the
grain
sizes
or
the
inclusionofamagnetic
field.
Withasemi-analytic
produce dust-to-gas ratios of several times the initial value. Dust concentrates in high density regions (cores, disk and pseudo-disk)
calibrated
on ourresults,
we showthat theanddustoutflows).
ratio mostly
varieswithdecouple
the initial from
Stokesthenumberat a rateon
thatthe initial
andmodelis depleted
in lowdensityregions(envelopeThesizeexponentiallyat which grains
gas depends
depends on the local cloud properties.
propertiesof the clouds. Since dust can not necessarily be used as a proxy for gas during the collapse, we emphasize on the necessity
Conclusions. We find that larger grains tend to settle and drift efficiently in the first-core and in the newly formed disk. This canof including
the treatment
dynamics
simulations.
produce dust-to-gas
ratiosofofits
severaltimesin
theprotostellar
initial value.collapse
Dust concentrates
in high density regions (cores, disk and pseudo-disk)

is depleted
low densityand
regions(envelopeand outflows). The
sizeformation
at which grainsdecouple fromthe methods:
gas depends
on the initial
Keyandwords.
ISM:inkinematics
dynamics
hydrodynamics
stars:
protoplanetarydisks
numerical
properties of the clouds.
Since dust can not necessarily be used as a proxy for gas during the collapse, we emphasize on the necessity
ダストサイズ、圧⼒β、磁場などを変えてダストとガスの乖離度合いを調べた。
of including the treatment of its dynamics in protostellar collapse simulations.

エンベロープ、分⼦流よりコア、円盤に集中。つまりガス分布と違う。

Key words. ISM: kinematics and dynamics hydrodynamics stars: formation protoplanetary disks methods: numerical

1. Introduction

Galametz et al. (2019) has also shown that the low values of the1 Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing

210023, China
2 University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, China

THE MOLECULAR CLOUDS ASSOCIATED WITH THE H II REGIONS/CANDIDATES BETWEEN L = 207.7

3 School of Astronomy and Space Science, University of Scienceof China, 96 Jinzhai Road, Hefei 230026, China
AND and
L =Technology
211.7

1
Submitted
to ApJS
Chong Li,1, 2 Hongchi Wang,1, 3 Miaomiao
Zhang,
Yuehui Ma,1, 2 and Lianghao Lin1, 3

ABSTRACT

53v1 [astro-ph.GA] 4 Aug 2020

v:2008.01453v1 [astro-ph.GA] 4 Aug 2020

Typeset using LATEX default style in AASTeX61

1 Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing
Using
the PMO-13.7 m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous
13
China
survey2 210023,
of 12 CO,CO, and C18 O J = 1 0 emission toward the sky region centered at l=209.7 , b= 2.25 with a
University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, China
coverageof 4.0 ⇥ 4.5 . The majority of the emission in the region comes from the clouds with velocities lying in the
3 School of Astronomy and Space Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei 230026, China
range from 3 km s 1 to 55 km s 1 , at kinematic distances from 0.5 kpc to 7.0 kpc. The molecular clouds in the region
are concentrated into three velocity ranges. The molecular clouds associated with the ten H II regions/candidates are
Submitted
to ApJS
identified and their physical properties are presented.
Massivestars are found within Sh2-280, Sh2-282, Sh2-283, and
BFS54, and we suggest them to be the candidate excitation sources of the H II regions. The distributions of excitation
ABSTRACTtemperature and line width with the projected distance from the center of H II region/candidate suggest that theUsing the PMO-13.7 m millimeter telescope at Delingha in China, we have conducted a large-scale simultaneous
majorityof the ten H II regions/candidates and their associated molecular gas are three-dimensional structures, rather
survey of 12 CO, 13 CO, and C18 O J = 1 0 emission toward the sky region centered at l=209.7 , b= 2.25 with athan two-dimensional structures.

coverage of 4.0 ⇥ 4.5 . The majority of the emission in the region comes from the clouds with velocities lying in therange from 3 km s 1 to 55 km s 1 , at kinematic distances from 0.5 kpc to 7.0 kpc. The molecular clouds in the region
COサーベイ。分⼦雲は３個の速度に集中。HII領域に付随する分⼦雲と⼤質量星。
Keywords: H II region—ISM: clouds—ISM: Sh2-280—stars: formation—surveys
are concentrated into three velocity ranges. The molecular clouds associated with the ten H II regions/candidates are
励起温度、線幅はHII領域と分⼦雲の３次元構造を⽰唆。
identified and their physical properties are presented. Massive stars are found within Sh2-280, Sh2-282, Sh2-283, and
BFS54, and we suggest them to be the candidate excitation sources of the H II regions. The distributions of excitation
temperature and line width with the projected distance from the center of H II region/candidate suggest that the
majority of the ten H II regions/candidates and their associated molecular gas are three-dimensional structures, rather
than two-dimensional structures.
Keywords: H II region—ISM: clouds—ISM: Sh2-280—stars: formation—surveys

The Astrophysical Journal, 900:15 (24pp), 2020 September 1© 2020. The Author(s). Published by the American Astronomical
Society.
1

Lichen Liang
1, Doug Johnstone2,3

https://doi.org/10.3847/1538-4357/aba830, Sylvie Cabrit4, and Lars E. Kristensen5

Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland
National Research Council Canada, Herzberg Astronomy & Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
doug.johnstone@nrc-cnrc.gc.ca
3
Department of Physics & Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada
4
Observatoire de Paris, PSL University, Sorbonne Université, CNRS, LERMA, 61 Av. de l’Observatoire, F-75014, Paris, France
5
Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K, Denmark
1 June 4; revised 2020 July
4 20; published 2020 August 27 5
Received
2020
2020 July
LichenLiang, Doug Johnstone2,3 18;, accepted
Sylvie Cabrit, and Lars E. Kristensen
1
Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, Zurich, Switzerland
2
National Research Council Canada, Herzberg Astronomy &Abstract
Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
doug.johnstone@nrc-cnrc.gc.ca
3Wind-driven outﬂows
are observed
arounda broad rangeof accreting
theCanada
universe, ranging from
Departmentof Physics& Astronomy,
Universityof Victoria,objects
Victoria,throughout
BC, V8P 5C2,
4
Observatoire
Paris,toPSL
University, Sorbonne
Université,
CNRS,theLERMA,
61 Av.between
de l’Observatoire,
Paris,
Franceforming
low-massdestars
supermassive
black holes.
We study
interaction
a centralF-75014,
isotropicwind
and an5
Niels
Bohr
Institute&
CentreforStar
andPlanetFormation,
UniversityofCopenhagen,ØsterVoldgade
5–7,
DK-1350
Copenhagen
K, Denmark
infalling, rotating envelope, which determines the steady-state cavity shape formed at their interface underthe
Received 2020 June 4; revised 2020 July 18; accepted 2020 July 20; published 2020 August 27
2

Steady Wind-blown Cavities within Infalling Rotating Envelopes: Application to the
Broad Velocity Component in Young Protostars

assumption of weak mixing. The shape of the resulting wind-blown cavity is elongated and self-similar, with aphysical size determined by the ratio between wind ram pressure and envelope thermal pressure. We compute thegrowth of a warm turbulent mixing layer between theAbstract
shocked wind and the deﬂected envelope, and calculate theresultantbroad-line
proﬁle,under thearoundassumptionof arange
linearof(Couette-type)velocity
proﬁletheacrossthe layer.
We then
Wind-driven
outﬂows
are observeda broadaccreting objects
throughout
universe,
ranging
from
test
our
model
against
the
warm
broad
velocity
component
observedinCOJ=16–15
byHerschel/HIFI
informing low-mass stars to supermassive black holes. We study the interaction between a central isotropic wind andtheanprotostar
Serpens-Main
SMM1.
Given
independent
observational
constraints
onthetemperatureanddensityoftheinfalling, rotating envelope, which determines the steady-state cavity shape formed at their interface under thedust
envelopeofaround
SMM1, The
we ﬁndmatchwind-blown
to all its observed
momentum,
assumption
weak mixing.
shapeanofexcellent
the resulting
cavity isproperties
elongated(lineandproﬁle,self-similar,
with atemperature)to the SMM1
cavity width
reasonableof parameters:
ratiocomputeof wind thetophysical sizeand
determinedby theoutﬂow
ratio between
windforrama physicallypressure andenvelopesetthermalpressure.aWe−1, an interstellarof COand H2and, andcalculate
a turbulent
infallmassof;4%,
a windspeed
of vbetween
growthof aﬂux
warm
turbulent
mixinglayer
thesshocked
wind andabundance
the deﬂectedenvelope,thew ; 30 km
entrainment
efﬁciency
consistentlaboratory ofexperiments.
The inferredvelocity
ratio ofproﬁleejection
to disk
resultant broad-line
proﬁle,under withthe assumption
a linear (Couette-type)acrossthe accretion
layer. Werate,then;6%–20%,is inagainst
agreement
windcomponent
theories. Thus,
the model
providesa newbyframework
to reconcile
test our model
the withwarmcurrent
broad disk
velocity
observed
in COJ=16–15
Herschel/HIFIin thethemodestSerpens-Main
outﬂow cavitySMM1.
widths Givenin protostars
with large
observed ﬂow
velocities.
Being
self-similar,
is applicable
protostar
independent
observational
constraints
on thetemperature
anditdensityof theoverbroader range
astrophysicalcontexts
as well.
dust aenvelope
aroundofSMM1,
we ﬁndan excellent
match to all its observed properties (line proﬁle, momentum,
temperature)and toThesaurus
the SMM1concepts:
outﬂow cavity
for a physicallyreasonableof parameters:
ratio of windto
UniﬁedAstronomy
Stellarwidth
jets (1607);
Stellar winds(1636);set
Protostars(1302);a Accretion(14);−1
infall mass ﬂux of;4%,a windspeed Astrochemistryof vw ; 30 km s(75), an interstellar abundance of CO and H2, and a turbulent
Stellar-interstellarinteractions(1576);
等⽅⾵と回転落下エンベロープの相互作⽤から⾃⼰相似なキャビティを導出。
entrainment
efﬁciency consistent with laboratory experiments. The inferred ratio of ejection to disk accretion rate,;6%–20%, is in agreement with current disk wind theories. Thus, the model provides a new framework to reconcile
the modest outﬂow
cavity widths in protostars with large observed
velocities.
Being
self-similar,
it is applicable
outﬂowﬂow
componentfromthe low-J
CO transitions
observed from
1. Introduction
over a broader range of astrophysical contexts as well.
the ground, such as J=2–1 and 3–2 (e.g., Yildiz et al. 2013).
Massive outﬂows are observed everywhere in the universe,
This Herschel-brightcomponent
has both a(14);signiﬁcantly
Uniﬁed Astronomy Thesaurus concepts: Stellar jets (1607); Stellar
winds (1636); outﬂow
Protostars(1302); Accretion

E

State University of New York Fredonia, Fredonia, New York 14063, USAnomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile
Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
ALMA observations of envelopes around first hydrostatic
rell Bank, Lower Withington, Macclesfield SK11 9FT, UK

core candidates

Marı́a José Maureira,1,2? Héctor G. Arce,1 Michael M. Dunham,3,4 Diego Mardones,5,2AndrésE. Guzmán,6 , Jaime E. Pineda,2 and Tyler L. Bourke, 7,3
1

YYY; in original form ZZZAstronomy Department, Yale University, New Haven, CT 06511, USA

ABSTRACT

Xiv:2009.08740v1 [astro-ph.SR] 18 Sep 2020

2 Max-Planck-Institut fÃijr extraterrestrische Physik (MPE), GieÃ§enbachstr. 1, D-85741 Garching, Germany
3 Center for Astrophysics | Harvard & Smithsonian, Cambridge, MA 02138, USA

4 Department of Physics, State University of New York Fredonia, Fredonia, New York 14063, USA
5

Departamento de Astronomı́a, Universidad de Chile, Casilla 36-D, Santiago, Chile
We present ALMA 3 mm
molecularline and continuum observations with a resolution
6 National
Astronomical Observatory of Japan, National Institutes of Natural Sciences, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
7 SKA Organization, Jodrell Bank, Lower Withington, Macclesfield SK11 9FT, UKof ⇠3.5” towards five first hydrostatic core (FHSC) candidates (L1451-mm, Per-bolo
58, Per-bolo 45, L1448-IRS2E and Cha-MMS1). Our goal is to characterize their en５個のファーストコア候補のvelopes and identify the most promising sources that could be bona fide FHSCs. We
ALMA 3 mm。
XXX. Received YYY; in original form ZZZ
identify two candidatesAcceptedwhich
are consistent with an extremely young evolutionary
エンベロープからL1451-mmが最state (L1451-mm and Cha-MMS1), with L1451-mm being the most promising FHSC
ABSTRACT
candidate. Although our envelope observations
cannot rule out Cha-MMS1 as a FHSC
有⼒。Cha-MMS1とPer-bolo 58
We present ALMA 3 mm molecular line and continuum observations with a resolution
yet, the properties of its CO outflow and SED
publishedstudiesare inbet- (L1451-mm,
of ⇠3.5”
towards fivein
firstrecent
hydrostatic
core (FHSC)
candidates
Per-boloは原始星。Per-bolo
45とL1448
58,
Per-bolo45,
L1448-IRS2E
andCha-MMS1).
Our
goal
is
to
characterize
theirenter agreement with the predictions for a young
protostar.
Fortheremaining
threevelopes and identify the most promising sources that could be bona fide FHSCs. We
IRS2Eはprestellar。
sources, our observations favor a prestellaridentify
naturePer-bolo
45consistentand rule
the youngtwo forcandidates
which arewithout
an extremely
evolutionary
state(L1451-mm
and
Cha-MMS1),
with
L1451-mm
being
the
most
promising
FHSC
rest as FHSC candidates. Per-bolo 58 is fully
consistent with being a Class0, while
candidate. Although our envelope observations
cannot rule out Cha-MMS1 as a FHSC+
L1448 IRS2E shows no emission of high-density
tracers
(NH
N2and
H SED
) atpublishedthe locayet, thepropertiesof its2 D
COandoutflow
in recent studies are in better
agreementwiththepredictions
for
a
young
protostar.
tion of the previously identified compact continuum source, which is also undetectedFor the remaining threesources, our observations favor a prestellar nature for Per-bolo 45 and rule out thein our observations. Thus we argue that there
no embedded
source58attheconsistentpresumprest is
as FHSC
candidates. Per-bolo
is fully
with being a Class 0, while
+
L1448
IRS2E
shows
no
emissionofhigh-density
tracers(NH
2 D and N2 H ) at the locative location of the FHSC candidate L1448 IRS2E. We propose instead, that whattion of the previously identified compact continuum source, which is also undetected
was thought to be emission from the presumed
L1448 IRS2E
to source at the presumpin our observations.
Thus weoutflow
argue that corresponds
there is no embedded
tive
location
of
the
FHSC
candidate
L1448
IRS2E.
We
proposeoutflow emission from a nearby Class 0 system, deflected by the dense ambient mate- instead, that what
was thought to be emission from the presumed L1448 IRS2E outflow corresponds torial. We compare the properties of the FHSC
candidates
studiedthisworkdeflected
and theoutflow
emission froma nearby inClass
0 system,by the dense ambient material. Weas
comparethe propertiesof the FHSCsource
candidates
studied in this work and theliterature, which shows that L1451-mm appears
possibly
the youngest
withliterature, which shows that L1451-mm appears as possibly the youngest source witha confirmed outflow.
a confirmed outflow.

Key words: andstars:dynamics
protostars – stars:
kinematics
and dynamics – ISM: individual
Key words: stars: protostars – stars: kinematics– ISM:
individual
objects
objects