#41 Stellar energetic particle ionization in protoplanetary disks around
T Tauri stars
Ch. Rab,1 , M. Güdel1 , M. Padovani2 , I. Kamp3 , W.-F. Thi4 , P. Woitke5 , and G. Aresu61.07522v1 [astro-ph.SR] 24 Feb 2017

University of Vienna, Dept. of Astrophysics, Türkenschanzstr. 17, 1180 Wien, Austria
e-mail: christian.rab@univie.ac.at
Stellar energetic
particle(SP) がdisk
chemistryに与える影響を調べた
2
INAF-Ossevatorio
Astrofisico
di Arcetri, Largo
E. Fermi, 5 - 50125 Firenze, Italy
3
Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands
4+とNGiessenbachstrasse+
Max-Planck-Institut für extraterrestrische Physik,
1, 85748 Garching, Germany
ディスクの電離トレーサーであるHCO
2H に焦点5
SUPA, School of Physics & Astronomy, University7of St. Andrews, North-2Haugh,
St. Andrews KY16 9SS, UK※ 典型的なT
Tauri型星のSP
fp ~ via
10dellaphotons
cmSelargius,s-1 @1auを仮定
6
INAF, Osservatorio
Astronomicoﬂux
di Cagliari,
Scienza 5, 09047
Italy※ SP電離度はH柱密度と半径の関数として算出（粒子は半径方向のみに動くとする）
Received 14 December 2016 / Accepted 24 February 2017
※ その他の電離源（X線・宇宙線）の変化も考慮。

ABSTRACT

Context. Anomalies in the abundance measurements of short lived radionuclides in meteorites indicate that the protosolar nebulae=> 他の電離源との相互作用を調べ、SP電離のトレーサーを同定する
Ch. Rab et al.: Stellar energetic particle ionization.

was irradiated by a high amount of energetic particles (E & 10 MeV). The particle flux of the contemporary Sun cannot explain theseanomalies. However, similar to T Tauri stars the young Sun was more active and probably produced enough high energy particles to
explain those anomalies.
Aims. We want to study the interaction of stellar energetic particles with the gas component
CI of
XNthe
SP disk (i.e. ionization of molecular CL XH SP
hydrogen) and identify possible observational tracers of this interaction.
① SPsはディスクを突き抜けることができない
Methods. We use a 2D radiation thermo-chemical protoplanetary disk code to model a disk representative for T Tauri stars. We use aparticleenergydistribution derived from solar flare observations and an enhanced stellar particle flux proposed for T Tauri stars. For
25 cm
-2：
N<H> > 10
this particle spectrum we calculate the stellar particle ionization rate throughout the disk with an accurate particle transport model.
We study the impact of stellar particles for models with varying X-ray and cosmic-ray ionization rates.
たいていのエネルギー粒子は止まり、Results. We find that stellar particle ionization has a significant impact on the abundances of the common disk ionization tracers
HCO+ and N2 H+ , especially in models with low cosmic-ray ionization rates (e.g. 10 19 s 1 for molecular hydrogen). In contrast toSP電離度は急速に落ちる
cosmic rays and X-rays, stellar particles cannot reach the midplane of the disk. Therefore molecular ions residing in the disk surface
and dashed lines respectively). The
25 Fig. 6. Ionization rates ⇣ as a function of vertical column density N <H>,ver at25 radii2 of 1 and 100 au (solid
Tタウリ型星の半径方向柱密度はN>> 10than<H>ionization
layers are more a↵ected by stellar particle
molecular
theofcoldlayers/midplane
the
disk.
maximum
values forions
N<H>,vertracingat the midplanethe disk,
are N<H>,ver ⇡ 4 ⇥ 10 cmofand
N <H>,ver⇡ 2 ⇥ 1023 cm 2 at 1 au and 100 au, respectively.
Red lines are for X-rays, blue lines are for SPs and the black lines are for CRs. Left panel: model CI_XN_SP with ISM CRs and normal X-rays;
Conclusions. Spatially resolved -1
observations of molecularions tracing di↵erent vertical layers of the disk allow to disentangle theright panel: model CL_XH_SP with low CRs and high X-rays.
cm-2なので、ζ
<<
10-20
s
@1au
SP
contribution of stellar particle ionization from other competing ionization sources. Modeling such observations with a model like theone presented here allows to constrain the stellar particle flux in disks around T Tauri stars.
Key words. Stars: formation - Stars: circumstellar matter - Stars: activity - Radiative transfer - Astrochemistry - Methods: numerical② SPsはH2の主要な電離源となる＠CO ice line
上の暖かい分子層1. Introduction

Our Sun acts as a particle accelerator and produces energetic

assumptions T Tauri stars might show on average a continuous
proton flux of fp (Ep
10 MeV) ⇡ 107 protons cm 2 s 1 at a
distance of 1 au from the star.

#41の続き④ SP電離はTタウリ型星の出す値より１桁小さくなると重要ではなくなる
その場合、X線とCRによってH2は電離される=> そのようΞ返てH10”$The Dusty Silhouette Jet HH 1019 in the Carina Nebula
1?
2
2
3
Megan
Reiter,Megan
M.
Kiminki,Nathan
Smith
,
and
John
Bally
1
University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109, USA

2 Steward Observatory, 933 N. Cherry Ave., Tucson, AZ 85721, USA
3 Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309, USA2

Tr 14星団付近のHST画像から、新たなHH 1019を発見

Reiter et al.

HαAccepted 2017 February 10. Received 2017 February 10; in original form 2016 November 41702.03893v1 [astro-ph.SR] 13 Feb 2017$1019$

#42

Tr14%

Hα
[O$III]

dark dust pillarの先端からbipolar ﬂow
We report the discovery in Hubble Space Telescope (HST) images of the new
dark%pillar%
7つほどのknotsがシルエットとして見える
Herbig-Haro jet, HH 1019,
located near the Tr 14 cluster in the Carina Nebula. Like

[O$III][S$II]
dusty%knots% [S$II]
ABSTRACT
star%

(サイズ<
other HH jets in the region, this bipolar
collimated0.5ʼʼ)flow emerges from the head of adark dust pillar. However, HH 1019 is unique because – unlike all other HH jets known
to date – it is identified by a linear chain of dark, dusty knots that are seen primarily
unseen%in silhouetteagainst the background screen of the H ii region. Propermotions
confirm
4 Reiter
et al.
driving%
that
these dark condensations move along the jet axis at high speed. [S ii] emission
source%traces a highly collimated jet that is spatially coincident with these dust
A knots. The
high extinction in the body of the jet suggests that this outflow has lifted a large
HH$1019$amount of dust directly from the disk, although it is possible that it has entrained
dustemission%from%from its surrounding protostellar envelope before exiting the dust pillar.
If dustB
η%Car%
in HH
1019
originatesfromthecircumstellar
disk,
this
providesfurther
evidence
for aweakly%irradiated%10”$
jet launchedgas%in%the%jet?%from a range of radii in the disk, including those outside the dust sublimation
radius. HH 1019 may be the prototype for a new subclass of dusty HH objects
Figure 1. Left: HST /ACS H↵ image of HH 1019 that shows the chain of dusty knots that make up the jet seen in silhouette against theseen
primarily
intheextinction
bright background of the H ii region. Middle: [S ii] emission clearly traces a narrow,collimatedjet even thoughdetailed structure isagainst the background screen of a bright H ii region.
unresolved in the seeing-limited ground-based image. Right: Cartoon showing the structure of HH 1019. Dark, dusty knots (black) tracejets
may
beweaklycommon,difficult to observe because they require the special
out a collimated bipolar jet emerging from an opaque dust pillar. Faint H↵ and [SSuchii] emission(gray)
trace theirradiated gas but
inthe jet.
condition of a very bright background in order to be seen in silhouette.
C[S II]禁制線： dust knotsと一致

Key words: stars: formation — stars: pre-main-sequence — ISM: Herbig-Haro ob6天体で固有運動の測定（2005年と2015年のHα画像）:
jects — ISM: jets and outflows

cooling zones. However, few comparable examples of dust in
These sources are associated with CO outflows and young
driving sources, leading Chini et al. (2001) to suggest thatthe jet body exist.
Ddust is heated in the interaction between the jet and theIn this paper, we present the discovery of another memenvironment. Extended (sub)-mm continuum emission that
ber of this rarefied group of jets with direct evidence forEtraces the bipolar outflow lobes has been detected in thedust. Unlike other Herbig-Haro (HH) jets, HH 1019 in the
L 1157 molecular outflow (Shirley et al. 2000; Gueth et al.
Carina Nebula appears to be composed of a chain of dark,2003). Many molecular lines contribute to the flux observed
dusty knots seen in silhouette against the background screen
HH 1019
F
at 1.3 mm and 850 µm, however Gueth et al. (2003) concludeof the H ii region (see Figure 1). UV photons from nearby
200 km s-1
that line emission can only
for . 50% of the continTr14 and Tr16 illuminate the edges of dusty knots. This is sources, higher luminosities may evaporate grains near the
1 account
INTRODUCTION
5"
uum flux. In addition, the spectral index of the 1.3 mm anddistinct from the illumination of the body observed in most
850 µm emission is consistent with thermal dust emission.
of the other 40 HH jets discovered in the same H↵ imaging star so that material launched from the inner disk may be
Protostellar
jets
accompany
activedisk
accretion
onto
formHowever, these observations have an angular resolution ofsurvey of Carina (Smith et al. 2010a). The high mass-loss dust-free (e.g. Kama et al. 2009). Figure 3. H↵ image of HH 1019 with boxes marking the jet knots
00
used to measure proper motions. Vectors indicate the magnitude
several arcsec (in the caseof Lstars.
1157, 12Whilecorresponding
torate physics
inferred for thosejetslaunch
implies intermediate-massing
the detailedof jetand colli- driving
and direction
the motionof the5280 AU a distance of 440 pc, Gueth et al. 2003), making
sources, suggesting that the HH jets in Carina o↵er a uniqueDustinprotostellar
jets,
especially
inofthebodyofsilhouette
the knots.
mationremainuncertain,
accretionenergythein the forit unclear whether the dustin the outflow
is entrained
from
view
of the underlying
jets mustthat maypower
be common

ジェット軸に沿って高速移動（~50-100 km s-1）
molecular outﬂowよりも速い=> knotsはjetをトレース

wide-angle outﬂow

narrowband
is a forbidd
increased ab
associatedthe knots aview, we idof the pillar
jet. These t
H↵ image.
limb of the(features I[S ii] e
Figure 1). [Sseen in silh
the seeing-lof the seeinof the HST
extends at lseen in silho
from the pi
irradiated j
the [S ii] mH↵, both tr
and H↵ ma
Tr16, perhaWith tmeasure theknots clearlcontrast wi
and cannot
proper mot

HH 1019 D
HH 1019 E
HH 1019 F
HH 1019 G
HH 1019 H
HH 1019 I
HH 1019 J#42の続き-1 (3)-15 (3)-26 (3)
...
...
...
...

40 (3)
74 (3)
102 (3)
...
...
...
...

43 (3)
83 (3)
115 (3)
...
...
...
...

2912 (812)1842 (463)1841 (328)
...
...
...
...

0.1
0.1
0.1
0.1
0.05
0.1
0.1

-5.1
-4.6
-4.1
-4.8
-5.4
-4.6
-5.2

The Silhouette Jet HH
H_[O III]

1.0
0.9

J

1.1
1.0

normalized intensity

0.9

Table 1. HH 1019 knot proper motions

C

0.9

C

1.1

0.9

D

D
E

1.1
1.0

A

0.9

E

1.1

1.1

1.0
0.9

1.0

F
G

1.0

B

0.9

F

H

1.1

0.9

Knot
name

1.0

G
B

1.0

1.1
1.0

J
IA

I

1.1

0.9

H_
[O III]

1.1
1.0[O III]0.9

H-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
position [arcsec]

normalized intensity

1.1

HH 1019 A
HH 1019 B
HH 1019 C
HH 1019 D
HH 1019 E
HH 1019 F
HH 1019 G
HH 1019 H
HH 1019 I
HH 1019 J

x
mas

y
mas

38 (3)0 (3)3 (3)-1 (3)-15 (3)-26 (3)
...
...
...
...

-86 (3)-45 (3)90 (3)
40 (3)
74 (3)
102 (3)
...
...
...
...

age
[yr]

⌧

log(Mknot )M

103 (3)50 (3)
98 (4)
43 (3)
83 (3)
115 (3)
...
...
...
...

1754 (377)2030 (753)532 (423)
2912 (812)1842 (463)1841 (328)
...
...
...
...

0.2
0.03
0.2
0.1
0.1
0.1
0.1
0.05
0.1
0.1

-4.4
-6.4
-4.8
-5.1
-4.6
-4.1
-4.8
-5.4
-4.6
-5.2

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
position [arcsec]

Figure 4. An HST /ACS [O iii] image (center) shows dusty jets knots with lines and labels indicating the locationof theH_intensity
1.1
tracings plotted to the right and left. The H↵ intensity is plotted with a solid line while [O iii] is shown with a dashed line. Absorption[O III]
dips are deeper in [O iii] than H↵ due to emission from the ionization front seen at the edge of the jet (negative positions in the plots).
1.0[O III]禁制線の強度からdust質量を算出

Indirect evidence for dust in jets points to an origin in a
dusty disk wind. For example, Agra-Amboage et al. (2011)
infer the presence of dust in the DG Tau jet from Fe depletion. In this case, depletion is higher in the lower velocity
components that surround the fast spine of the jet (see also
Podio et al. 2011). For a disk wind, the outflow terminal
velocity is related to the Keplerian velocity at the launch
point in the disk, suggesting that slower jet material originates from larger radii. Disk rotation studies also place theorigin point of these slower, outer jet layers at larger disk
radii (see, e.g. Ferreira et al. 2006) that are more likely toreach outside the dust sublimation radius. Evidence for asimilar, onion-like velocity structure has been observed in a
few jets in Carina (Reiter et al. 2015b,a), as expected fora jet launched from a range of disk radii. However, unlike

vT
1]

[km s

DG Tau, HH 1019 emerges from a deeply embedded proto0.9
star. It is therefore possible that the jet entrained dust fromJ
the circumstellar envelope (see, e.g. Shadmehri & Downes
2008; O↵ner & Arce 2014).
1.1
Bright gas-phase [Fe ii], as seen in many of the jets
in Carina (Reiter et al. 2016), may indicate
little depletion
1.0
onto grains (e.g. Ellerbroek et al. 2014). However, HH 1019
provides evidence that dust survives in at least one jet in Carina. Multi-wavelength observations of0.9
other jets in Carina
I and ionizationsuggest the coexistence of multiple excitation
states, similar to the jets in Orion where
Smith et al. (2005b)
1.1
detect thermal dust emission. The physical conditions in thejet must allow dust in HH 1019 to survive processing throughshocks and external photoevaporation1.0
in the H ii region.
To estimate the dust mass of the silhouette knots, we

H_
[O II

J
IA

C

MNRAS 000, 1–?? (2016)

normalized intensity※前景放射の補正をしていないので下限値
・星周ディスクに対するOʼdell & Wen 94の手法でτを柱密度にG
・典型的なknot質量 ~10-5 Msun
B
0.9

C

D

D
E

A

E

1.1

HH 1019はHH天体の新しいサブクラスの典型になるかも
1.0
0.9

このようなjetは共通して起こるのかもしれないが、
G

1.1

非常に明るい背景が必要なのでシルエットで見るのは難しいだろう[O III]

F
H

F

1.0
0.9

B

H

-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6
position [arcsec]-0.6 -0.4 -0
po

#43

#43の続きResolving the centrifugal barrier in L1527(c) mid-planeに沿ったSOの位置速度図

白点線：IRE model
黒実線：Keplerian motion（0.18 Msun）の速度場

・100auの遠心力バリア付近に低速度成分が付随
この回転速度はIREモデルの回転速度よりも遅い
・高速度成分はKeplerian motionと一致し、
inner disc起源と思われる

CH (N = 4 − 3 J = 9/2 − 5/2 F = 5 − 4: upper panels; N = 4 − 3 J = 9/2 − 5/2 F = 4 − 3: lower panels)
ocity range described at bottom in the panel. (b) PV diagram of the CCH lines (colour) superposed to the IRE
e every 20 per cent of the peak intensity. (c) PV diagram of the SO line (JN = 87 − 76 : colour) superposed
he Keplerian model (black contours). Note that the small undulation of the lowest contour of the Keplerian
tefact due to a limited mesh size of the model. In addition to the componentFigure
associatedwithintensity
the centrifugal
2. (a) Integrated
maps of the CCH (N = 4 − 3 J = 9/2 − 5/2 F = 5 − 4: upper panels; N = 4 − 3 J = 9/2 − 5/2 F = 4 − 3: lower
line.
Each
map
is
obtained
integrating theof
velocity range described at bottom in the panel. (b) PV diagram of the CCH lines (colour) superposed toeen (pink dotted lines). Yellow dotted arrows indicate the voids of the emission. (d) Schematic by
illustration
model (dotted contours). The model contours are every 20 per cent of the peak intensity. (c) PV diagram of the SO line (JN = 87 − 76 : colour) sup
7 envelope/disc system.
to the IRE model (dotted white contours) and the Keplerian model (black contours). Note that the small undulation of the lowest contour of the K

IREが遠心力バリアの手前で停滞・弱い降着ショックを生じ、温度が上昇（~190 K）することでIREが膨張し、一部ガスは垂直方向へ流れだす

遠心力バリア付近のSOの速度がIREの回転速度より遅い（図c）=> 衝撃により回転エネルギー → 熱に変わるとともに、model within 0.2 arcsec from the centre is an artefact due to a limited mesh size of the model. In addition to the component associated with the cenbarrier, a faint high-velocity component can be seen (pink dotted lines). Yellow dotted arrows indicate the voids of the emission. (d) Schematic illustr
the physical and chemical structures of the L1527 envelope/disc system.

absent in the IRE exshown by the black contours in Fig. 2(c). Here, the outer radius
角運動量を垂直方向に放出している
ier. The SO emission isis arbitrarily set to be 160 au. Althoughestimated
It istheconfirmedthat the velocity
SO emissionisis absent in the IRE except
forthevicinityofthecentrifugal
barrier. The SO emission is
CCH emission. In orderstill higher than the observed one in some parts, the observed PVseen inside the broadened region of the CCH emission. In ordershown by the black contours in Fig. 2(c). Here, the outeris arbitrarily set to be 160 au. Although the estimated velo
still higher than the observed one in some parts, the observ

#44

A dearth of short-period massive binaries in the young massive
star forming region M17:
Evidence for a large orbital separation at birth?
H. Sana1 , M. Ramírez-Tannus2 , A. de Koter1, 2 , L. Kaper2 , F. Tramper3 , and A. Bik4
1e-mail: hugues.sana@kuleuven.be・大質量連星の誕生時の特性はよくわかっていない。
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
e-mail: m.c.ramireztannus@uva.nl=> 非常に若い大質量星形成領域M17に注目
European Space Astronomy Centre (ESAC), Camino bajo del Castillo, s/n Urbanizacion Villafranca del Castillo, Villanueva de laInstitute of astrophysics, KU Leuven, Celestijnlaan 200D, 3001 Leuven, Belgium

2.02153v1 [astro-ph.SR] 7 Feb 2017

2
3
4

Canada, E-28 692 Madrid, Spain
Department of Astronomy, Stockholm University, Oskar Klein Center, SE-106 91 Stockholm, Sweden

Received September 15, 1996; accepted March
16, 1997 Msun）の視線速度を調べた
・大質量前主系列星11天体（M~6-20&A proofs: manuscript no. m17_PaperII_v2

al. 2012; Kobulthus particularly
one of the largest
ere massive stars

roscopic binaries
1
rad < 20 km s ).
ies of small andce massive stars
013a; Kiminki &nstall et al. 2015;
d established thatof one month or
km s 1 ). Here wef the massive starat quantifying its

ndidate mYSOs1
which were conB stars observednce (B111, B164
253). The known
well as the CEN
ecause they wereTable 1. Sample stars and journal of the observations. Sources classified as PMS in Paper I appear in bold. Sp.Types are from Paper I.

ABSTRACT

σ1D = 5.6

0.2 km s-1

Aims. The formation of massive stars remains poorly understood and little is known about their birth multiplicity properties. Here,↓（若い星の集団でよく見られる）短周期連星がIdentifierwe aim
Sp.TypeMJD
vradd(3)the strikingly low radial-velocity dispersion measured for a sample of 11 massive pre- and nearto quantitatively
investigate
(2)
1
1
B92
CEN(OI)
000( (kms )(pc)
main-sequence2 450
stars
1D = 5.6 ± 0.2 km s ) in the very young massive star forming region M17, in order to obtain first constraints
B111
2 (337)
O4.5V 6490.116 3.4 ± 0.8 0.695
properties
B163. . on. the multiplicity
kA55455.982. . . of young
0.154 massive stellar objects.
compute thedispersion of synthetic populations of massive stars for various multiplicity properties and
B164
25Methods.
O6VWe 6490.123
1.8 radial-velocity± 2.3 0.372
B215. . we. compareO9-B1Vthe
6115.249
12.3 1D± 1.0
0.856
obtained
distributions
to the observed value. We specifically investigate two scenarios: a low binary fraction and
B243
51a dearthB8V
6114.188 19.5
± 1.8systems.
0.607
ofshort-periodbinary...
...
...
6490.140 20.2 ± 1.5 . . .
+0.16
Simulated
populations
B253
26Results.
B3-B5III
6490.197
9.5 ± 0.8 with
0.573low binary fractions ( fbin = 0.12 0.09 ) or with truncated period distributions (Pcuto↵ > 9 months)
to reproduce
observed within their 68%-confidence intervals. Furthermore, parent populations with fbin > 0.42
B268
49are able
B9-A0
6114.236 the1.4low± 1.0 1D0.686...
. . or
. Pcuto↵. .<. 476114.259± 1.1 at . the. . 5%-significance level. Both constraints are in stark contrast with the highd can be 17.1
rejected
1D binary fraction and
...
...
...
6490.169 4.3 ± 1.3...
plethoraofshort-period
systemsinfew
Myr-old,
well
characterized
OB-type
populations.
To
explainthedi↵erencein the context of
B275
24
B7III 5054.125 11.2 ± 1.4 0.698
scenario
would requireof the outcome of the massive star formation process. In the context of the second scenario,
B289
31the firstO9.7V
5456.024
2.0 ± 2.5a variation
1.390
...
. . compact.
. .binaries.
6114.290
2.3 ± 2.0
. . and the cut-o↵ period may be related to physical length-scales representative of the bloatedmust form
later .on,
B311
16 (258)
O8.5Vz 6490.097
4.2radii± 0.4 or1.601
pre-main-sequencestellarof their accretion disks.
B331
92
late-B 6115.276 13.9 ± 1.5 1.194
Conclusions.
Iftheobtained
constraints
for the M17’s massive-star population are representative of the multiplicity properties ofB337
93
late-B 6489.185 7.5 ± 0.6 1.171
massiveyoung
stellarobjects,
ourresults
may provide support to a massive star formation process in which binaries are initially
...
...
...
5.6 ± 0.2
...
1D
(1)

M17のmYSOsにもあるとすると、あり得ない数値
参考：他のOB型星の集団 σ

２つの可能性：~25 - 35 km s-1↓(i) 連星率が低い(ii) 短周期連星を持たない
Key words. binaries: spectroscopic — Stars: early-type— Stars: formation — open clusters and associations: individual: M17

formed at larger separations, then harden or migrate to produce the typical (untruncated) power-law period distribution observed in

Notes. (1) Bumgardner (1992). (2) Alternative IDs: CEN (Chini et al.
few Myr-old OB binaries.
1980) and OI (Ogura & Ishida 1976). (3) Projected distance of the stars
to the center of the cluster (↵ = 275.124574 , = 16.179031 ).

the candidate mYSOs or to the confirmed PMS stars in our sample (Table 1) yield similar values of 5.9±0.2 and 6.9±0.4 km s 1 ,#44の続き
・観測結果とMonte Carlo population synthesisから得られる結果の比較
Sana et al.: Binarity in M17初期星団の速度分散σcl = 2 km s-1
連星率fbin： 0.00から1.00まで0.01刻みで変化=>
Fig. 1. Simulated 1D distributions for di↵erent parent binary fractions.
The vertical dashed line indicates the observed 1D for our M17 sample stars. The median, 0.16 and 0.84 percentiles of the simulated distributions are indicated on the upper part of the graph. The distribution
corresponding to fbin = 0.03 is not shown for clarity; it is almost entirely dominated by the velocity dispersion of the cluster and thus peaks
strongly at 2 km s 1 (⇡ cl ).

the multiplicity properties derived by Sana et al. (2013a) for
Galactic young open clusters as the baseline in our population
synthesis. These include fbin = 0.7 and fPorb / (log10 Porb ) 0.5 ,with 0.15  log10 (Porb /day)  3.5 and a flat mass-ratio distribution. Adopting an Öpik law all the way down to orbital periodsof 1 day would not change our conclusions.
The cluster velocity dispersion ( cl ) is computed from thevirial theorem, assuming a total mass for the M17 cluster of
1.4 ⇥ 103 M (Stutzki & Guesten 1990) and a typical 1 pc cluster
radius. This yields cl = 2 km s 1 . Other published mass estimates range from a few times 103 to 6⇥104 M (Pérez-Beaupuits
et al. 2015; Povich et al. 2009), corresponding to cl = 1.4 to
5.2 km s 1 . Adopting the former value has no impact on our
results while picking the latter one would only strengthen ourconclusions because it leaves almost no room for binary contributions to the observed 1D value. In the following, we adopt
1
cl = 2 km s .
Each Monte Carlo run is formed by 105 realisations and uses
the sample size, number of epochs, time sampling and measurement accuracy of the observational sample. The density distributions of the simulated 1D for given parent multiplicity properties are then constructed and used for tests of hypotheses thatallow us to accept or reject the specific parent population at various significance levels.
3.2. A low binary fraction

We first investigate the possibility that the low RV dispersion observed in M17 results from a low binary fraction. In our MC experiment, we keep the distribution of the orbital properties fixed
and we vary the binary fraction from 0.00 to 1.00 in steps of
0.01. The obtained 1D distributions for representative values ofFig. 2. Same as Fig. 1 for di↵erent cuto↵ periods (Pcuto↵ ). The distribution corresponding to Pcuto↵ ⇡ 9 mo is intermediate between those of
Pcuto↵ ⇡ 8 yr and 1 month and is not shown for clarity.

rameter distributions, the observed velocity dispersion in M17 isbest reproduced by a low binary fraction fbin = 0.12+0.16
0.09 .
Similarly, no simulation with fbin
0.34 (resp. 0.42) canreproduce M17’s 1D within their 0.90 (resp. 0.95) percentiles
and the corresponding hypotheses can thus be rejected at the 10
and 5%-significance levels, respectively.
3.3. A truncated period distribution

We now assume that the binary fraction is consistent with constraints from OB stars in young open clusters, that is, fbin = 0.7
for Porb < 3500 d (Sana et al. 2012), but that the binary
population is composed of longer-period binaries, which typically results in a lower 1D (Gieles et al. 2010; Hénault-Brunet
et al. 2012). In practice, we adopt a truncated period distribution
where the orbital periods of all binaries with Porb < Pcuto↵ areiteratively re-drawn from the parent distribution until they are
equal to or larger than Pcuto↵ .
Resulting distributions for representative values of Pcuto↵ areshown in Fig. 2. Distributions with Pcuto↵ ⇡ 8 yr have a medianthat best matches the M17’s observed 1D while distributions
with Pcuto↵ & 283 d (⇡ 9 months) are all able to reproduce theobserved 1D within their 68% confidence range. Parent populations with Pcuto↵ < 131 d (resp. 47 d) can be rejected at the 10
and 5%-significance levels, respectively.

4. Discussion
4.1. A low binary fraction?

Under the assumption that the distribution of orbital parametersin M17 is not di↵erent from that of other well characterized OBstar populations, a low RV dispersion can only be explained by a
low binary fraction. This, however, would make M17 quite atypical. Populations of massive stars in clusters across the entire
mass range have all revealed a large binary fraction, from mod-

71v2 [astro-ph.GA] 22 Apr 2017#45

YOUNG STELLAR OBJECTS IN THE MASSIVE STAR-FORMING REGIONS W51 AND W43

G. S ARAL 1,2,3 , J. L. H ORA 2 , M. AUDARD 1 , X. P. KOENIG 4 , J. R. M ARTÍNEZ -G ALARZA 2 , F. M OTTE 5,6 , Q. N GUYEN -L UONG 7,8 A. T.
S AYGAC 9,10 , H. A. S MITH 2
20 April 2017; Published in ApJ

ABSTRACT
星形成過程の理解には、大質量星形成を理解する必要がある

We present the results of our investigation of the star-forming complexes W51 and W43, two of the brightest in
the2MASSとSpitzerのデータを使って、W51とW43でYSO候補天体を同定した
first Galactic quadrant. In order to determine the young stellar object (YSO) populations in W51 and W43=>
we used color-magnitude relations based on Spitzer mid-infrared and 2MASS/UKIDSS near-infrared data. We
identified 302 Class I YSOs and 1178 Class II/transition disk candidates in W51, and 917 Class I YSOs and5187 Class II/transition disk candidates in W43. We also identified tens of groups of YSOs in both regions
using the Minimal Spanning Tree (MST) method. We found similar cluster densities in both regions, eventhough Spitzer was not able to probe the densest part of W43. By using the Class II/I ratios, we traced therelative ages within the regions, and based on the morphology of the clusters, we argue that several sites ofstar formation are independent of one another in terms of their ages and physical conditions. We used spectralenergy distribution-fitting to identify the massive YSO (MYSO) candidates since they play a vital role in thestar formation process, and then examined them to see if they are related to any massive star formation tracers
such as UCH II regions, masers, or dense fragments. We identified 17 MYSO candidates in W51, and 14 in
W43, respectively, and found that groups of YSOs hosting MYSO candidates are positionally associated withH II regions in W51, though we do not see any MYSO candidates associated with previously identified massive
dense fragments in W43.
Keywords: infrared: stars — stars: early-type — stars: formation — stars: pre-main sequence
1. INTRODUCTION

Near-infrared and mid-infrared observations have revealed
a broad range of stellar densities of YSOs in star-forming regions (Bressert et al. 2010). While we have a detailed pictureof the formation of low-mass stars with advances in observational techniques and improved theoretical knowledge in thelast decade, our understanding of massive star formation isstill lagging. Massive stars form and evolve quickly and they
produce strong winds and outflows which heat, ionize, anddisrupt their natal molecular cloud, which makes the observa-

Galactic star-forming regions are the ideal places for this purpose, since they host many active sites of star formation indifferent environments at various stages of evolution.
We started a detailed study of a sample of mini-starburst
complexes (Motte et al. 2003) to better understand how massive stars form and affect their environments and the effects
that they have on the formation of lower-mass stars (Saral& Hora 2013). Precursor clouds of young massive clusters(YMC) (Bressert et al. 2012; Ginsburg et al. 2012; Walker et
al. 2016) are thought to be the potential descendant of mini-

#45の続き・Minimal Spanning Tree (MST) 法を使ってYSOの空間分布からクラスターを同定=> W51で９つ（YSOの60%）
W43で51つ（YSOの73%）

YOUNG S TELLAR O BJECTS IN W43 AND W51

11