Star Formation NewsletterNo. 310 37-45
高橋実道（工学院大学）

Evidence for Very Early Migration of the Solar System Planetsfrom the Patroclus-Menoetius binary Jupiter Trojan

38

1
1,2
1
David
Nesvorný
,David
Vokrouhlický
,WilliamF.
BottkeMNRAS 000, 1–12 (0000)
Preprint 14 September 2018
Compiled using MNRAS LAT,EX style file v3.0
On the role of magnetic fields in star formation
1
Draft version September 5, 2018Harold F. Levison:1809.04007v1 [astro-ph.EP] 11 Sep 20182018
v1
3 Sep 2018
] 11[astro-ph.SR]
Sep 2018
Sep 2018 12 Sep 201813 [astro-ph.GA]

iv:1809.04921v1 [astro-ph.SR] 13 Sep 2018

37

39

40

Typeset using LATEX manuscript
style in AASTeX61
a,∗
a,b
C.
J.
Nixon
,
J.
E.
Pringle(1) Department of Space Studies, Southwest Research Institute,aVerymassive
stars
in
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so
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Department of Physics
andWalnut
Astronomy, St.,
Universityof Leicester,
LE1 CO,
7RH, 80302, USA
1050
Suite
300, Leicester,
Boulder,
Astronomy & Astrophysics manuscript no. dissociation_v8_acceptedUK
September13, 2018bc ESO 2018

Instituteof Astronomy,
Road,
Cambridge,
CB3 University,
0HA,
UK
(2)
InstituteofAstronomy,Charles
V Holešovičkách2,CASE OF THE
THE
CO-EVOLUTION
OF
DISK
AND
STAR
IN
EMBEDDED
STAGES: THE
1,2?Madingley
1,3
Seungkyung
Oh
and
Pavel
Kroupa1 Helmholtz-Institut für Strahlen- und Kernphysik (HISKP), University of Bonn, Nussallee 14-16, 53115 Bonn, Germany
CZ–18000 Prague 8, Czech Republic
2 Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK
VERY LOW-MASS PROTOSTAR IRAS 15398−3359
3
Faculty of Mathematics and Physics, Astronomical Institute, Charles University in Prague, V Holešovičkách 2, CZ-180 00 Praha 8, Czech Republic

MNRAS 000, 1–12 (2018)

Preprint 5 September 2018
Compiled using MNRAS L TEX style file v3.0
The
orbitaldistributionoftrans-Neptunian
objects
providesstrong evidence
Abstract
A

Productionofatomichydrogenbycosmicrays
indark
clouds
Accepted Received

41 Magnetic
for theradialmigration
offorming
Neptune[1,2].
The simulations
outer planets’
orbits are thought tofieldsareobserved
instar
regions.
Howeverof
YUKI OKODA, YOKO OYA, NAMI SAKAI, YOSHIMASA WATANABE,

1
1
2
3, 4
127,
1 , Alexei
2 , Paola
2 , Andrea Ferrara3
D RAFT
VERSIONS EPTEMBER
2018
thehavelatestagesofstarformation
that
do
not
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fieldsprovideMarco
Padovani,
Daniele
Galli
V.
Ivlev
Casellibecomeunstableduringtheearly stages [3] with Jupiterhaving scatteringAT561
Typesetusing
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inAASTeX61
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K.propertiesJØRGENSEN,
EWINE
F.
VAN
DISHOECK,andSATOSHIYAMAMOTO
a good fitJES
to theof young
stars
includingtheinitialmass
funcABSTRACT

Evolution of spatio-kinematic structures in star-forming
encountersa Neptune-classplanet[4].
As aItaly
consequence,
Jupiter jumped(IMF)
and thewith
multiplicity.
WeargueLargo
hereE.
thatsimulations
that
doINAF–Osservatorio
Astrofisico
di Arcetri,
Fermithe5, 50125
Firenze,
42 tione-mail: [padovani,galli]@arcetri.astro.it
Veryyoungthestarcorrectclustersin the Milky
Way exhibit knowing?
a well-defined relation between
regions:areFriends
ofFriends
worth
includemagnetic
fieldsareunabletocapturephysics,
inparticinward by a fraction of an au, as required from inner solar system constraints
1
2

Max-Planck-Institut für Extraterrestrische
Physik,stellar
Giessenbachstr.
Garching,
their maximum
mass, m 1, 85741, and theirmassGermany
in stars, Mecl . A recent study shows
Departmentof Physics, Thethat
University
Tokyo, 7-3-1, Hongo,
Bunkyo-ku,
Tokyo
113-0033,
e-mail: [ivlev,caselli]@mpe.mpg.dethe youngofintermediate-massstar cluster
VVV CL041
possibly
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3anddiﬀusivity.
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56126
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okoda@taurus.phys.s.u-tokyo.ac.jp
star,
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2 TRANSITIONAL
mass
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Research,
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ofhighmagnetic
DepartmentofPhysics,
The
UniversityofTsukuba,
Tsukuba,
Ibaraki
305-8577,
Japan
of Physics and Astronomy, The University of Sheﬃeld, Hicks Building, Hounsfield Road, Sheﬃeld, S3 7RH, UK
September 13, 2018(⇡3000 M ), we study whether such a very massive star can be formed via dynamically
4
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sipationthroughreconnection,
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ABSTRACT
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.
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ifis theclusterfromtheof amounts
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5
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dark clouds.
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ANIELF
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5 Myr ofcluster
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withinamassiveplanetesimal
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ABSTRACT(MPE),
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Garching,
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Aims.
to assessthe roleof Galactic
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by–M
using
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Thus,
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binaryour model.
properties,
and
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asin4,
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1 University
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32cosmic-ray
1Leeds,5, 6 another.
Keywords:
accretion
discs,
dynamo,magnetic
fields,thelikelihoodthatcollisions
would
strip
its
components
one
The(Received;
Revised;Accepted5,
2018)
of Leeds,School
Physics
andAstronomy,
LS29JT,
UK.
tions
of
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and
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young
star-forming
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David Quénard,
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1
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max
ular 1the high value of the magnetic Prandtl number, and thelow value of

43

Richard J. Parker † and Nicholas J. Wright

44

Constraining the nature of DG Tau A’s thermal andnon-thermal radio emission

45

S. J. D. Purser, R. E. Ainsworth,and A. M. M. Scaife

T. P. Ray, D. A. Green, A. M. Taylor

magnetohydrodynamics(MHD),
andsatellites:
formation,stars:ofPlace,
Dublinplanets
Institutefor Advanced
Studies,
31 Fitzwilliam
2, Irelandalgorithm
to N-bodysimulations
the Dublin
dynamical
evolution of subvirial (collapsing)2 School of Cosmic Physics,
Ken
Rice

37 Evidence for Very Early Migration of the Solar System Planets
arXiv:1809.04007v1 [astro-ph.EP] 11 Sep 2018from the Patroclus-Menoetius binary Jupiter Trojan
David Nesvorný1 , David Vokrouhlický1,2 , William F. Bottke1,
Harold F. Levison1(1) Department of Space Studies, Southwest Research Institute,1050 Walnut St., Suite 300, Boulder, CO, 80302, USA

トロヤ群に小惑星の連星が存在(Patroclus-Menoetius)(2) Institute of Astronomy, Charles University, V Holešovičkách 2,
ニースモデルでは、惑星移動時に20­30au
から落下したとされる
CZ–18000 Prague 8, Czech Republic
The orbital distribution of trans-Neptunian objects provides strong evidence連星の生存確率をN体計算で評価、モデルのパラメータを制限–9–

for the radial migration of Neptune [1,2]. The outer planets’ orbits are thought to（１）軌道移動時の生存率
初期のseparationが大きいほど解体されやすい
encounters with a Neptune-class planet [4]. As a consequence, Jupiter jumped
inward by a fraction of an au, as required from inner solar system constraints
P-Mの生存率~72%[5,6], and obtained its current orbital eccentricity. The timing of these events
is often linked to the lunar Late Heavy Bombardment that ended ∼700 Myr
12-15%は惑星に落下
have become unstable during the early stages [3] with Jupiter having scattering

after the dispersal of the protosolar nebula (t0 ) [7,8]. Here we show instead thatplanetary migration started shortly after t0 . Such early migration is inferredfrom the survival of the Patroclus-Menoetius binary Jupiter Trojan [9]. The
binary formed at t ! t0 [10,11] within a massive planetesimal disk once locatedbeyond Neptune [12,13]. The longer the binary stayed in the disk, the greater
the likelihood that collisions would strip its components from one another. The
simulations of its survival indicate that the disk had to have been dispersedby migrating planets within !100 Myr of t0 . This constraint implies that theplanetary migration is unrelated to the formation of the youngest lunar basins.

Fig. 1.— The dynamical survival of binaries before their implantation onto JT orbits. The（２）微惑星円盤(20-30au)中での衝突に対する生存率
・原始惑星系円盤の散逸(t0)から
惑星移動開始までの時間に強く依存・一般的な値(~700Myr 後期重爆撃期)だと小さすぎる
・<100Myr 程度が必要

The collisional survival of binaries in the outer planetesimal disk. The surviving
shown for the P-M mass binaries as a function of the initial separation and disk

Fig. 4.— The survival of binaries in the case when the planet migration was initiatedmmediately after t0 (i.e., tdisk = 0). The red line shows the collisional survival of P-M
mass binaries as a function of aB . The black line combines the collisional survival with the
dynamical survival from Figure 1. It expresses our expectation for the fraction of the P-M–
class binaries that should have survived to the present time (tdisk > 0 would imply lower
fractions; Figure 2). The grey area displays the conditions for which the P-M components
are in contact.

二つを合わせた最終的な生存割合（黒実線）
P-M binary の生存率62%
P-M binary はトロヤ群で唯一の連星（直径>100kmの小惑星は全25個）→separation <1000km の連星の形成率〜6.5％
太陽系外縁天体の30%はseparation >1000kmのwide binary→生存率が低いことと整合的

THE CO-EVOLUTION OF DISK AND STAR IN EMBEDDED STAGES: THE CASE OF THE
VERY LOW-MASS PROTOSTAR IRAS 15398−3359

VERY LOW-MASS PROTOSTAR IRAS 15398−3359

Xiv:1809.00500v1 [astro-ph.SR] 3 Sep 2018arXiv:1809.00500v1 [astro-ph.SR] 3 Sep 201840

THE CO-EVOLUTION OF DISK AND STAR IN EMBEDDED STAGES: THE CASE OF THE

YUKI OKODA,1 YOKO OYA,1 NAMI SAKAI,2 YOSHIMASA WATANABE,3, 4
5 EWINE
6 and SATOSHI
1
1 YOKO
1 NAMI SAKAI,
2 YOSHIMASA
3, 4
JES K. JØRGENSEN,
F. VANDISHOECK,YAMAMOTOYUKI OKODA,OYA,WATANABE,JES K. JØRGENSEN,5 EWINE F. VAN DISHOECK,6 and SATOSHI YAMAMOTO1

概要 Department of Physics, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;
okoda@taurus.phys.s.u-tokyo.ac.jp
15
RIKEN
Clusterfor
Pioneering
Research,
Wako,
Saitama
351-0198,
Japan Bunkyo-ku, Tokyo 113-0033, Japan; envelope (CCH)を観測
Department of Physics, The University of Tokyo, 7-3-1, Hongo,
非常に軽い原始星（~0.007Msun）の円盤(SO)とinfalling
Departmentof Physics, The University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan
okoda@taurus.phys.s.u-tokyo.ac.jp

Declination(J2000)

310 au-09ʼ05”-09ʼ10”1

3(b) History of the Universe, Faculty of Pure and Applied Sciences, University of Tsukuba,
2
Tomonaga
Centerforthe
RIKEN Cluster-34°for
09ʼ06” Pioneering Research, Wako, Saitama 351-0198, Japan
Tsukuba,
Ibaraki 305-8571,
JapanThe University of Tsukuba,
3
0.04
DepartmentofPhysics,
Tsukuba, Ibaraki 305-8577, Japan
155 au5
Centre4 for Star and Planet Formation, Niels Bohr Institute and Natural History of Denmark, University ofTomonaga Center for the History of the Universe, Faculty of Pure and Applied Sciences, University of Tsukuba,
Copenhagen, Øster Voldgade 5-7, DK-1350, Copenhagen0.02K, Denmark
Tsukuba, Ibaraki 305-8571, Japan
6-09ʼ07” University, PO Box 9513, 2300 RA, Leiden, The Netherlands Max-Plank Institut für
Leiden5 Observatory, Leiden
Centre for Physik
Star and
PlanetFormation, Niels
Bohr Institute and Natural History of Denmark, University ofExtrsterrestrische(MPE),
Giessenbachstr.1,
85748,
0.00 Garching, Germany
4

6

全体像
アウトフローがPA220
垂直方向に円盤
Copenhagen, Øster Voldgade 5-7, DK-1350, Copenhagen K, Denmark
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands Max-Plank Institut für
SOはダスト連続波の位置とほぼ一致：円盤(Received;
Accepted September
5, 2018)
Extrsterrestrische Physik(MPE),Revised;
Giessenbachstr.1,
85748,
Garching,
Germany
Submitted to CCHがinfalling envelope(Received; Revised; Accepted September 5, 2018)(Jy/Beam)・(km/s)-34°09ʼ00”

2

P.A. 130°-09ʼ08”15ʰ43m02.3s-0.02

02.25s02.2s

CCH( =3-2, =7/2-5/2, =4-3 and 3-2)

P.A. 220°

Contour: Continuum(c)-34°09ʼ06”
0.04
ABSTRACT
Submitted tocolor: CCH( =3-2, =7/2-5/2, =4-3 and 3-2)

15 h 43m 02.75ｓ

02.50ｓ 02.25ｓ 02.00ｓ
Right Ascension(J2000)

01.75ｓ0.02(Jy/Beam)・(km/s)(a)1

We have observed theCCH (N = 3−2, J = 7/2−5/2, F = 4−3 and 3−2) and SO (67 −56 ) emission-09ʼ07”0.00′′

ABSTRACT

at a 0. 2 angular resolution toward
the low-mass Class 0 protostellar source IRAS 15398−3359 with
P.A. 130°-0.02-09ʼ08”We
have
observed
theCCH(N 02.2= 3−2, J = 7/2−5/2,
F =the4−3
and 3−2)(67 −56 ) emission
ALMA. The CCH emission15ʰ43
tracesenvelope near
protostar
withand
theSO
outflow
02.3 the02.25 infalling-rotating
m

′′

s

s

s

CCH( =3-2, =7/2-5/2, =4-3 and 3-2)

a 0. 2 angularresolution
towardthelow-mass
Class
0
protostellar
sourceIRAS
15398−3359
withcavityatextended
along thenortheast-southwest
axis.
On
the
other
hand,
the
SO
emissionhasaContour: SO(6₇-5₆)(d)12
compact
distribution
aroundtheprotostar.
The
CCH emission is envelope
relativelynear
weaktheat thecontinuum
ALMA.
The
CCH
emissiontracestheinfalling-rotating
protostarwith the outflow
Continuum
Beamsize

0.06

17

P.A. 130°

P.A. 220°

0.01

6

0.00

4

-0.01

NW

2
8

62 au

Beam size

(c)

-0.02

SW

NE

SE

Beam size(d)Envelope direction

Envelope direction

P.A. 130°

P.A. 130°

0.010
0.004

Counter velocity
component

VLSR [km/s]

infall envelopeのモデルだとﬁtできない

極方向には0.02
目立った速度構造はなし

⦿

0.02
0.01
0.00

0.007

⦿

Counter velocity
component

4
NW

SE

-0.01

NW

SE
62 au

Beam size

Beam size-0.8”

中心星質量~0.007Msun

⦿

6

2

Jy/beam

VLSR [km/s]

コントアが
円盤モデル
〜40au

8

(b)

Envelope direction

0”0.8” -0.8”

0”

0.8”

-0.02

Jy/beam

SOのPV図(a)

Perpendicular to
the envelope direction

(a)P.A. 130°

0.04

VLSR [km/s]

Jy/beam

6

0.02

5

SE

NW
4

0.00

Beam size

円盤方向

(b)

0.02

Jy/beam

VLSR [km/s]

極方向
0.03

P.A. 220°

6

0.01

5

4

CCHのPV図白実線がinfalling envelope モデル
黒破線がケプラー円盤モデル

NE

0.00

SW

Beam size

-2”

-1”

0”
1”
Angular Oﬀset

2”

-0.01

ure 3. The PV diagram of the CCH (N = 3 − 2, J = 7/2 − 5/2, F = 4 − 3) emission along the envelope

ction (a), and along the line perpendicular to the envelope direction (b). The dashed lines show the

ズレはoutﬂow cavity 起源?

[ ⦿](a) 1.5

(3)

1

(12)

bol

log 10

(10)

(17)

0.5
(1)

(16)

(8)
(6)

(5)

(2)
(15)
(9)

0

星質量に対するLbol と円盤質量の分布(1)がこの天体
中心星質量は最も小さい
円盤質量は中心星質量と正の相関
Lbolは平均的な値→星質量の指標にならない

(11)

(14)

(4)

(7)

-0.5
(13)

-1
-2.5

-2.0

-1.5

-1.0

log 10

-0.5

[

star

⦿

0

]

(b) 0

]

(15)

⦿

(14)
(17)

-1

disk

[

ダスト連続はから円盤質量を見積もる
温度20-100Kで0.006-0.001Msun
円盤のQ~0.4-5 重力不安定の可能性

(4)

-0.5

(13)
(9)

(16)

-1.5

log 10

0.5

(12)

(3)

(5)

(11)

(10)
(6)

(7)

-2

(8)

(2)

(1)

-2.5
-3
-2.5

-2.0

-1.5

log 10

-1.0
star

[

-0.5
⦿

]

0

0.5

概要
非常に軽い原始星（~0.007Msun）の円盤(SO)とinfalling envelope (CCH)を観測

1

1

2, 3

David Quénard, John D. Ilee,

2, 3

4, 1

4, 1

Izaskun Jiménez-Serra, 8,Duncan
H. Forgan,
99
Ken 8,RiceKen Rice

5, 5,
66

7 7

Cassandra Hall, and1

School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK
1 School of Physics
and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, UK
2 School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK

2 School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, UK

生命の起源は？彗星由来？
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
Centro de Astrobiologı́a (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4, 28850, Torrejón de Ardoz, Spain
SUPA, School of Physics and Astronomy, University of St Andrews,
North Haugh, St Andrews KY16 9SS,
UK
ホルムアミド(NH2CHO)に着目
原始星のenvelope
で観測例ありSt Andrews Centre for Exoplanet Science, University of St Andrews, St Andrews KY16 9SS, UK
Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
円盤中で気相で観測されたのはCH3CNとCH3OHのみ、多くはダストに
SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
809.09900v1 [astro-ph.GA] 26 Sep 2018

9900v1 [astro-ph.GA] 26 Sep 201845 David Quénard, John D. Ilee, Izaskun Jiménez-Serra, Duncan H. Forgan, Cassandra Hall, and
THE FATETHE
OFFATEFORMAMIDE
IN A FRAGMENTING
PROTOPLANETARY
OF FORMAMIDE
IN A FRAGMENTING
PROTOPLANETARY DISC
DISC

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

3

4 Centro de Astrobiologı́a (CSIC/INTA), Ctra. de Torrejón a Ajalvir km 4, 28850, Torrejón de Ardoz, Spain

4

5 SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
6 St Andrews Centre for Exoplanet Science, University of St Andrews, St Andrews KY16 9SS, UK

5

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

6

7

8

8 SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
9 Centre for Exoplanet Science, University of Edinburgh, Edinburgh EH9 3HJ, UK

9 Centre for Exoplanet Science, University of Edinburgh, Edinburgh EH9 3HJ, UK(Received May 11, 2018; Revised September 12, 2018; Accepted September 25, 2018)

Submitted
to ApJ(Received May 11, 2018; Revised September
12, 2018;
Accepted September 25, 2018)

若い円盤、重力不安定な円盤に対する理論計算が少ない
ABSTRACT
Submitted
to ApJ
Recent high-sensitivity observations carried out with ALMA have revealed the presence of complex→SPHシミュレーション上で化学計算
organic molecules (COMs) such as methyl
cyanide (CH CN) and methanol (CH OH) in relatively
ABSTRACT
evolved protoplanetary discs. The behaviour and abundance of COMs in earlier phases of disc evolution
Recent high-sensitivity observations carried out with ALMA have revealed the presence of complex
remains unclear. Here we combine a smoothed
particle hydrodynamics simulation of a fragmenting,
ホルムアミドのgas/grain
比などを調べる
organic molecules (COMs) such as methyl cyanide (CH CN) and methanol (CH OH) in relatively
3

3

3 code. We use this to investigate
3
gravitationally unstable disc with a gas-grain chemical
the evolution
evolved protoplanetary
The behaviour
abundanceof COMs
phases thatof discevolutionof formamide discs.
(NH2 CHO),
a pre-bioticand
species,in both thedisc andininearlier
the fragments
form
withinremains unclear.
weshowcombinea smoothed
particlehydrodynamics
simulation
it. OurHere
results
that formamide
remainsfrozenonto grains in the
majority ofof athefragmenting,disc where
the temperatures
arewith<100aK,
with a predicted
solid-phaseabundance
matches thoseobserved
ingravitationallyunstable discgas-grainchemicalcode. Weuse thisthat
to investigate
theevolution
comets.
is present in
the gas-phasein threefragmentsa resultof the highof formamide(NH2Formamide
CHO), a pre-biotic
species,in boththe disc
and inasthe
fragments
thattemperatures
form within( 200 K), but remains in the solid-phase in one colder (150 K) fragment. The timescale over which
it. Our results
show that formamide remains frozen onto grains in the majority of the disc where
this occurs is comparable to the dust sedimentation timescales, suggesting that any rocky core which
the temperatures
are
<100
K,
with
a
predicted
solid-phaseabundance
thatmatchesthoseobserved
inis formed would inherit their formamide content directly from the protosolar nebula.

comets. Formamide is present in the gas-phase in three fragments as a result of the high temperatures( 200 K), but
remainsin the solid-phasein one colder(150andK) fragment.
The timescale
over which
Keywords:
astrochemistry— hydrodynamics— planets
satellites: formation— protoplanetary
this occurs is comparable
discs to the dust sedimentation timescales, suggesting that any rocky core which
is formed would inherit their formamide content directly from the protosolar nebula.

4Quénard et al.

初めは気相にいるホルムアミド~1000yr で r>15auではダストにfroze in
分裂片は4つうち3つでは温度が上がり気相に戻る
一つはダストに残る→tidal downsizing で岩石惑星ができると、
pre-biotic material が円盤由来となる可能性
Figure 2. Gas-phase abundance of formamide across the protoplanetary disc for four di↵erent snapshots covering 4100 yr ofdisc evolution. Formamide is kept on the grain surface in the majority of the disc but, with time, it goes back to the gas-phasein the central part of the disc and around some fragments.

6

Quénard et al.
that any photo-processing can be considered negligible.
For all phases, we assume an external radiation field of
G0 = 1 Habing and a standard cosmic ray ionisation rateof ⇣ = 1.3 ⇥ 10 17 s 1 .

3. RESULTS

3.1. Formamide (NH2 CHO) in the disc

CO, NH2CHO, H2Oの赤道面のスノーライン
NH2CHO, H2Oはほぼ同じ、COは遠い

Fig. 2 shows the abundance of formamide in four different time snapshots in the protoplanetary disc. The
We have benchmarked the chemical abundances obfirst snapshot at 204 yr shows the initial high gas-phasetained in our work with those calculated by Ilee et al.
abundance of formamide across the disc, inherited from(2017), who used a smaller chemical network (125the protostellar (hot corino) phase. Rapidly, around
species
89 in the gas, 36 on dust grains
and 1334
850 yr, all species are frozen-out onto dust grains bereactions; see their Section 2.2). We find a good agreecause of the cold temperatures of the disc (T .20 K)
ment between the two networks, especially for molecules
combined with high densities (n(H2 )&1010 cm 3 ).
which are key in the production of formamide (e.g. CO,
Later, formamide is released back into the gas-phase
CO2 , H2 CO, H2 O, NH2 and NH3 ), with abundances
via thermal desorption in regions where T &100 K. The
di↵ering by less than a dex. Such a result is reassurmagnitude of these e↵ects depends strongly on the poing given the large discrepancy in size between the twosition of the particle within the disc (e.g. whether they
Figure3. Evolution of the total column density of the disc (grey-scale) overlaid with the snow lines of CO (red), NH2 CHO
networks.
(green) and H2 O (blue). The snow lines quickly deviate from the expected concentric ring structure due to the dynamic evolutionof the disc.

nt).
Species
NH2 CHO
NH3
H2 CO
CO
CO2
CH4
CH3 OHHCN

8Model (%)
0.02
1.08
0.23
9.65
27.4
1.65
1.00
0.766

Observed1 (%)
0.01–0.021
0.61–0.7
0.7–1.1
4.0–23.0
6
0.6–0.67
1.6–2.6
0.14–0.25

シミュレーションで得られたダストの組成と彗星の組成の比較
誤差5倍以内で合う
Quénard et al.

Long-period comets: C/1995 O1 (Hale-Bopp), C/2012 F6
Lemmon) and C/2013 R1 (Lovejoy).
George Values taken from
Biver1et al. (2014), Bockelée-Morvan et al. (2000) andLe Roy et al. (2015) (and references therein).
0.9
0.8

Scaled abundance

ough0.7to further contract and heat up its surroundingsT 150 K), so that water and many other molecules
main0.6on icy grain surfaces. As proposed by Ilee et al.
017),0.5this e↵ect may have important consequences for
e formation of protoplanetary objects if the timescale
0.4
r dust settling within the fragments is small enough.
0.3Ilee et al. (2017) inferred that the timescale
2037 yrdeed,for3285 yryrntimetre-sized
silicate grains to settle to the3820
centreof
0.24100 yre fragment would be 1000 2000 yr, which is within the
0.1
2000 yr of existence of Paul. Such dust settling might0
en occurmore
quickly,eitherdue0.6to 0.7
icy grains
pos-1
0
0.1
0.2
0.3
0.4
0.5
0.8
0.9
Scaled distancessing a high sticking co-efficientthan bare grains (e.g.
hrenfreund et al. 2003; Wang et al. 2005), or via hydroFigure 5. Scaled water (full coloured lines) and formamide
ynamic instabilities within the fragments themselves(dashed coloured lines) abundances on the grain surface as a
NayakshinBothe↵ectsThe
would
allow
a higherfunction of2018).
the radiusof George.
scaleddistanceused foroportionsolidtomaterial
to sedimenttoward thecenGeorge isofequal
12 au. Eachcolour representsa di↵erent

分裂片周囲のダストの組成
tem (e.g. whether the planet is formed via core accretion or gravitational instability; Canup & Ward 2002;
Mosqueira & Estrada 2003), because the expected shape
実線：H2Oof the radial temperature profile around nascent protoplanets formed via either mechanism are the same (see
破線：NH2CHO
Cleeves et al. 2015; Szulágyi et al. 2017). As such,
water and formamide will always follow a similar radial behaviour as shown in Fig. 5. Thus, while sig黒線：木星のガリレオ衛星
nificant chemical processing can still occur in the later,
Class II stages of protoplanetary disc evolution, our re傾向は似ている（？スケールが全く違う）
sults demonstrate that such processing is not required
to match the radial abundance profiles of Solar System
シミュレーションは12au,
satellites, and similarities can be in placeat early times
for objects formed via gravitational fragmentation of thedisc.
Callistoの軌道は0.01au
5. SUMMARY

We have studied the formation and evolution of the
key prebiotic molecule formamide in the context of ayoung, massive circumstellar disc which gravitationallyfragments into bound protoplanets. We find that formamide is located in the gas-phase in the innermost

分裂で惑星ができた場合でも衛星にはNH2CHOが残る可能性

time. The black line show the water content inside the fourOn the role of magnetic fields in star formation

On
the
role
of
magnetic
fieldsinstarformation
38
a,∗
a,b
C.
J.
Nixon
,
J.
E.
PringleAbstract

arXiv:1809.04921v1 [astro-ph.SR] 13 Sep 2018a

C. J. Nixona,∗, J. E. Pringlea,bDepartment of Physics
and Astronomy,
Universityof Leicester,
Leicester,LE1regions.
7RH,
Magnetic
fieldsareobserved
instarforming
However simulations ofa
Department of Physics
UKand Astronomy, University of Leicester, Leicester, LE1 7RH,
late stagesof starthat0HA,
do UK
not include magnetic fields provideb
UK CB3
Institute ofthe
Astronomy,
Madingley
Road,formation
Cambridge,b

Astronomy,
Madingley
Road, Cambridge,
CB3 0HA, UK
a good Institute
fit to ofthe
propertiesof young
stars including
the initial mass function (IMF) and the multiplicity. We argue here that the simulations that doinclude magnetic fields are unable to capture the correct physics, in particAbstractular the high value of the magnetic Prandtl number, and the low value of
Abstract
Magnetic fields areobservedin starforming regions.
Howeversimulationsof simulations
themagnetic
diﬀusivity.
Theforming
artificiallyhigh(numericalandof uncontrolled)
Magnetic
fieldsareobservedin starregions.
Howeverthe late stages of thestarlate
formationnotincludefieldsmagnetic
providemagnetic
diﬀusivity
leads
toa magneticlarge
magnetic
flux pervading
stagesofthatstardoformationthatdo
not include
fields providethe star forma good fit to the aing
properties
young
starsfurther
includingthe ininitialmassthefuncgood
fit toofthe
propertiesof youngthat
stars
includinginitialmass funcregion.
We
argue
realitythedynamics
of high magnetic
tion (IMF) and themultiplicity.
We multiplicity.
argue here thatthe simulations
that
do
tion
(IMF)
and
the
We
argue
here
that
the
simulations
that do energy disPrandtl number turbulence may lead to local regions of magnetic
include magnetic include
fields areunablefields
to capture
the correct
physics,
in particmagnetic
are unable
to capture
the correct
physics, in particsipation
through Prandtl
reconnection,
meaning
thatvalue
the ofregions of molecular clouds
ular the high valueofthemagnetic
number,andthelowular the high value of the magnetic Prandtl number, and the low value of
which
are
stars
be essentially
freeandof magnetic
fields. Thus thethe magnetic diﬀusivity.
Theforming
artificiallyhigh(numericaland(numericaluncontrolled)themagnetic
diﬀusivity.
Themight
artificiallyhighuncontrolled)
simulations
that magnetic
ignorefieldsflux
on starthe formscalestheonstar
whichmagnetic diﬀusivity
leads toa largethemagnetic
diﬀusivity
leads
to magnetic
a fluxlargepervading
magnetic
pervadingform-the properties
ing
argue
furtherthatin realityofthe
dynamics
of high magnetic
ing region. We argue
furtherWethat
in reality
dynamics
highmagneticof region.
stellarmasses,stellarthe
multiplicities
andplanet-forming
discs are deterPrandtl
turbulence
lead tolocal
regionsof magnetic
energydisPrandtl number turbulence
maybe
lead
to localregionsofmagnetic
energydismined,number
mayclosertomay
reality
than
those
which
includemagnetic
fields, but
sipation throughreconnection,
meaning
thatthe regionscloudsof molecular clouds
sipation through reconnection,
meaningthattheregionsofmolecular
can only do so in an unrealistic parameter regime.
which are forming stars might be essentially free of magnetic fields. Thus thewhich are forming stars might be essentially free of magnetic fields. Thus thesimulations
thataccretion,
ignoremagnetic
fieldsthe scales
on whichthe properties
simulations that ignore
magnetic
fields onthescales
onon
which
the
properties
Keywords:
accretion
discs,
dynamo,magnetic
fields,stellarmultiplicities
masses, stellarand
multiplicities
and planet-forming
discs are deterof stellar masses,ofstellarplanet-forming
discs
are
determagnetohydrodynamics (MHD), planets and satellites: formation, stars:
mined,
may bethan
closerthose
to reality
thanthosemagnetic
which include
magnetic
fields, but
mined, may be closer
torealitywhich
includefields,but
formationcanonly do so in
an unrealistic
parameter regime.
can only do so in an unrealistic
parameter
regime.

Keywords: accretion, accretion discs, dynamo, magnetic fields,
Keywords: accretion, accretion discs, dynamo, magnetic fields,
magnetohydrodynamics (MHD), planets and satellites: formation, stars:∗
magnetohydrodynamics(MHD), planetsand satellites: formation, stars:
Corresponding
authorformationformation
Email address: cjn@leicester.ac.uk (C. J. Nixon)∗∗

Corresponding author
Corresponding author
Email address: cjn@leicester.ac.uk (C. J. Nixon)

1,2 ?
1,3
Seungkyung
Oh
and
Pavel
KroupaABSTRACT
1 Helmholtz-Institut für1,2?
1,3University of Bonn, Nussallee 14-16, 53115 Bonn, Germany
Strahlenund Kernphysik (HISKP),
Seungkyung
Oh
and
Pavel
Kroupa2 Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, UK
1 Helmholtz-Institut für Strahlen- und Kernphysik (HISKP), University of Bonn, Nussallee 14-16, 53115 Bonn, Germany

3 Faculty of Mathematics and Physics, Astronomical Institute, Charles University in Prague, V Holešovičkách 2, CZ-180 00 Praha 8, Czech Republic
2 Department
Veryyoungof starin theMilky
Way exhibit
a well-defined
betweenPhysicsclusters
and Astronomy,
Universityof Sheffield,
Hicks Building,Hounsfield Road, relation
Sheffield S3 7RH,
UK
3 Faculty of Mathematics and Physics, Astronomical Institute, Charles University in Prague, V Holešovičkách 2, CZ-180 00 Praha 8, Czech Republictheir maximum stellar mass, mmax , and their mass in stars, Mecl . A recent study showsthat theyoung
intermediate-mass star cluster VVV CL041 possibly hosts a &80 M
Accepted
Received
star, WR62-2,
which appears to violate the existence of the mmax –Mecl relation since theAccepted Received
mass of the star is almost two times higher than that expected from the relation. By
ABSTRACT
performing direct N-body calculations
ABSTRACT with the same mass as the cluster VVV CL041(⇡3000 M ), we study whether sucha verystar
canMilky
be formed
via adynamicallyVeryyoung massive
star clusters
in theWay exhibit
well-defined relation between
Verymaximum
young starclustersin theMilkyWayexhibitainwell-defined
betweentheirstellar
mass,
mmax
, and
their
mass
stars,theMeclrelation.mAmax
recentstudy shows
induced stellar collisions in theira binary-richstarclusterthat
initiallyfollows–
maximumstellarmass, mmax , and their
mass
in VVVstars, M
study
shows
ecl . A recent
that
the
young
intermediate-massstarcluster
CL041
possiblyhosts
a &80 M
Mecl relation. Eight out of 100
clusters
form
a
star
more
massivethan
80Mthroughthat
theWR62-2,
young intermediate-masscluster
CL041
possibly
hosts relation
a &80 Msince thestar,which appears tostar
violatetheVVV
existenceof themmax –Mecl
star,
WR62-2,
appears
totwo
violatethehigher
existenceofmay
the–Meclbecome
relationsincethemultiple stellar collisions. Thissuggests
that
the
VVV
CL041
clusterhave
massof thewhichstar isalmosttimes
thanthatmmax
expectedfrom therelation.
By
mass of of
the its
starearly-dynamical
is almost two times higher
than thateven
expected
fromcluster
the relation. Byan outlier of the relation because
evolution,iftheperforming
directN-body calculations
withthe same
mass
as thecluster VVV CL041
performing direct N-body calculations with the same mass as the cluster VVV CL041(⇡3000M that), we morestudy whether
such ofa verystar can be formed
followed the relation at birth.(⇡3000
We
find
than
ourmassivemodel
avia dynamicallyM ), westudy whether
suchhalfa very massive
star canclusters
be formedhost
via dynamicallyinducedstellarcollisions
a binary-richstar clusterthat initiallytheinducedstellarcollisions
in a inbinary-richstarclusterthat initiallyfollowsfollows
the mmax– mmax –merger product as its most massive
member
within
the
first
5
Myr
of
cluster
evolution.
Eightof clusters
100 clusters
star more
massivethan
M throughecl relation.
MeclMrelation.
Eightout outof 100form forma staramore
massivethan 80
M 80
throughThus, the existence of stars multiple
moremassive
thanThistheThismmax–M
relationin cluster
somecluster
young
eclthemultiplestellarcollisions.
suggeststhat
the VVV
maybecomehave become
stellarcollisions.
suggeststhat
VVV
CL041CL041
may haveoutlieroftherelation
becauseofearly-dynamical
itsvalidity
early-dynamical
if the cluster
clusters is expected due to dynamical
processes
despiteofevolution,
theevolution,
mmax
–M
ecl
an an
outlierof therelation
becauseof itstheeven
ifeventhe cluster
followed
atpopulations
birth.
We thatfind inthatourmorethanofhalf
our model
followed
the therelationat birth.
We find
more
than
half
our ofmodel
clustersclusters
host a host arelation. We briefly discuss evolutionof relation
binarymodel.

:1809.04596v1 [astro-ph.GA][astro-ph.GA] 12:1809.04596v1
12Sep
Sep2018
2018

CTION

Very massive stars in not so massive clusters
Verymassive
stars
in
not
so
massiveclusters
39

mergerproduct
asmostits most
massivemember
withinthe5firstof cluster
evolution.
mergerproduct
as itsmassivemember
withinthe first
Myr 5ofMyrcluster
evolution.
Thus,
the
existenceof stars
massivemstars:relationsome young
Thus,
the–
existenceofstars
moremoremassivethan thanthe mtherelationin someinyoungmax
ecl
max––Mecl –M
Key words: methods: numericalstars:
kinematics
anddynamics
massiveclusters
is expected
to dynamical
processes
despitethe validity
theclusters
is expected
due dueto dynamical
processes
despitethe validityof the ofmmax–Mmeclmax –Mecl– open clusters and associations:general– discussopen
clusters
individual:
relation.
briefly
discuss
evolutionof associations:binarypopulations
inour model.
relation.
We We
brieflyevolution
ofandbinarypopulations
in ourmodel.

VVV CL041 – galaxies: starKey
clusters:
generalwords: methods: numerical – stars: kinematics and dynamics – stars: massive

Key words: methods: numerical – stars: kinematics and dynamics – stars: massive– openclusters
andandassociations:general– openclusters
and associations:individual:– openclusters
associations:general– openclusters
and associations:individual:
VVV
CL041
– galaxies:
star starclusters:
generalVVV
CL041– galaxies:
clusters:
generalthe same methods and telescopes. Especially noteworthy is
1 1 INTRODUCTION
the samemethods
andtelescopes.
Especially
noteworthy
isthe Stephens et al. (2017)
study
that
targeted
seven
MYSOs
INTRODUCTIONthesamemethods
and telescopes.
Especially
noteworthyisMyr) star clusters in the Milky way show
the Stephens et al. (2017) study that targeted seven MYSOs
the Stephenset al.based(2017)on
study
that targeted
seven MYSOs
Very young (.4 Myr) star clusters inin theMilky
waywhichshow were thought
the
LMC
to
be,
Spitzer
obin
the
LMC
which
were
thought
to
be,
based
on
SpitzerobVeryyoung(.4 Myr)star clusters in the Milky way show
ation between the mass
of
the
most
masin
the
LMC
which
were
thought
to
be,
based
on
Spitzeroba well defined relation between the servations,mass of the mostmas- stars formed in isolation. Stephens et al.
singleservations,
singlestars
formedinisolation.
Stephensetal.
a well defined relation between the mass of the most massive star in
the cluster,
mmax , and the cluster mass in stars,
servations, single stars formed in isolation. Stephens et al.
luster, mmax , and the cluster
mass
incluster,stars,
found,
withtheircompact
HST data, massive
very compact
massive clusters
sive
star
in
the
m
,
and
the
clustermass
instars,
max
found,
with
their
HST
data,
very
clusters
Mecl (Fig. 1). That is, the maximum stellar mass in a very
found,
with of
their
HST
data,
very
compact
massiveat thepositions
these
seven
stars,
withall sevenbeingclusters
at is, the maximum stellar
mass in a very

e-mail: andrea.ferrara@sns.it

1 [astro-ph.GA] 11 Sep 2018
iv:1809.04168v1 [astro-ph.GA] 11 Sep 2018

Productionhydrogenbycosmicrays
indark
clouds
September13, 2018of atomic
Productionofatomichydrogenbycosmicrays
indark
clouds41
1

1 , Daniele
2 ,2 ,Paola
3
1 , Daniele 1Galli1 , Alexei V. Ivlev
2 , 2Andrea Ferrara3
Marco Padovani
Paola
Caselli
Marco Padovani
Galli , Alexei
V.
Ivlev
Caselli,AndreaFerrara
ABSTRACT

Context. 1The
presence of small
amountsof atomichydrogen,detected
as absorption
dips in the 21 cm line spectrum, is a well-known
INAF–Osservatorio
Astrofisico
di Arcetri,
Largo
E. Fermi 5,50125 Firenze,
Italy

9.04168v1 [astro-ph.GA] 11 Sep 2018

INAF–Osservatorio
Arcetri,
LargoofE.hydrogen
Fermi 5, atoms
50125 measured
Firenze, Italye-mail:[padovani,galli]@arcetri.astro.it
characteristicof Astrofisico
darkclouds.diTheabundancein the densest regions of molecular clouds can be only2e-mail:[padovani,galli]@arcetri.astro.it
Max-Planck-Institut
Physik,explainedby
the dissociationfür
ofExtraterrestrische
H2 due to cosmic
rays.Giessenbachstr. 1, 85741 Garching, Germany
2e-mail:tofür[ivlev,caselli]@mpe.mpg.de
Max-Planck-Institut
Extraterrestrische
Physik,Giessenbachstr.
1, 85741 ofGarching,
Germany by using recent developments in the
Aims. We3 wantassessthe role of Galactic
cosmicrays in the formation
atomic hydrogen,
Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italye-mail:[ivlev,caselli]@mpe.mpg.decharacterisationof the low-energy spectra of cosmic rays and advances in the modelling of their propagation in molecular clouds.
e-mail: andrea.ferrara@sns.it
3
ScuolaNormaledei Cavalieri
7, 56126cosmic
Pisa, Italy
Methods.
WeSuperiore,model thePiazza
attenuationof the interstellarrays entering a cloud and compute the dissociation rate of moleculare-mail:andrea.ferrara@sns.it
September13, 2018 with cosmic-ray protons and electrons as well as fast hydrogen atoms. We compare our results with thehydrogendue to collisions
available observations.
September13, 2018
Results.
The cosmic-ray dissociation rate is entirely determinedby secondary electrons produced in primary ionisation collisions.
ABSTRACT
These secondary particles constitute the only source of atomic hydrogen at column densities above ⇠ 1021 cm 2 . We also find that theContext.
presenceof smallamountsof atomichydrogen,as absorption
dips in the
cm line spectrum,is a well-known
dissociation
rate The
decreaseswithcolumndensity,while
the ratiodetected
betweenthe dissociation
and21ionisation
rates varies
between about 0.6
ABSTRACTcharacteristicof darkwith
clouds.
The abundancehydrogenatoms
measured flatin thedensest regionsof molecular
clouds canbe onlyas the one
and 0.7. Fromcomparison
observations
we ofconcludethata relatively
spectrumof interstellar
cosmic-ray
protons,by the dissociation of H2 due to cosmic rays.
suggestedexplainedby the mostrecent Voyager 1 data, can only provide a lower bound for the observed atomic hydrogen fraction. An enhanced
Aims. Weofwant
to assessthe role
ofatomic
Galactichydrogen,cosmic raysdetectedin the formationof atomicdips
hydrogen,
by21
using
recentdevelopments
in well-known
theContext. The presence
smallamountsofasabsorption
in
the
cm
line
spectrum,isaspectrumcharacterisationof low-energyofprotons
is needed
to explain
mostof theobservations.
thelow-energy
spectraofcosmicrays
andadvancesin themodellingof theirpropagationin molecular
clouds.can be only
characteristicofdark
clouds.
The
abundanceofhydrogenatoms
measuredinthedensestregionsofmolecular
cloudsConclusions.
OurWefindings
showthat a careful
descriptionof molecularhydrogendissociation
cosmic rays
explain the abunMethods.
model theattenuationof the interstellar
cosmicrays entering
a cloud andcompute thebydissociation
rate canof molecularexplained
by ofthedissociation
of H
due
to
cosmicdance
atomichydrogenin2 dark
clouds.
Anrays.
accuratecharacterisation
process at
highWedensities
crucialhydrogendue to collisions
withcosmic-ray
protons andelectrons as wellof
as thisfast hydrogenatoms.
compareisour
resultsfor
withunderstanding
theAims. Wewantavailable
to assessthe ofroleof Galacticregions.
cosmic rays in the formation of atomic hydrogen, by using recent developments in theobservations.
the chemical
evolution
star-forming
characterisationResults.
of the The
low-energyof cosmic
rays andadvancesthe modelling
their propagationin molecular
clouds.
cosmic-rayspectra
dissociation
rate is entirely
determinedby insecondaryelectrons of
producedin primary ionisation
collisions.
21
2
KeyWe
words.
cosmicraysconstitute– ISM:
cloudsatomicprocesses– molecular
processes
These ISM:
secondaryparticles
the only–sourceof atomic
at column
densities
above ⇠ 10cm
. We also findthatofthe
Methods.
model
the attenuationofthe interstellar
cosmicrayshydrogenenteringa cloudand compute
thedissociation
ratemolecular
dissociation
ratewithdecreases
with column
density,while
the ratio between
and ionisation
between
0.6 with thehydrogen due tocollisions
cosmic-ray
protons
andelectrons
as wellthe
asdissociation
fast hydrogenatoms. rates
We varies
compareourabout
results
and 0.7. From comparison with observations we conclude that a relatively flat spectrum of interstellar cosmic-ray protons, as the one
available observations.
suggested by the most recent Voyager 1 data, can only provide a lower bound for the observed atomic hydrogen fraction. An enhanced
Results.
The cosmic-ray
dissociation
rateis isentirely
determinedbyobservations.
secondaryelectrons
producedin primary
ionisation
collisions.
spectrum of low-energy
protons
neededto explain
most of the
1. Introduction
the measured
protonand electron
fluxesarenotable to explain
21
2Conclusions.
Our findingsthe
show
thatsourcea carefulofdescriptionof moleculardissociation
byionisation
cosmicrays rate
can explain
These secondary
particles constituteonly
atomic hydrogenat hydrogencolumndensities
above
⇠ 10
cm
. We thealsoabunfindthat theclouds
thevaluesoftheCR
estimatedindi↵useof atomichydrogenin darkclouds.
Ancharacterisation
this process atandhighionisation
densities is rates
crucialvaries
for understanding
The formationof molecularhydrogenoccurson accurate
dust
grainsin (e.g.
dissociation
ratedance
decreaseswithcolumndensity,while
the ratio
between
theofdissociation
betweenabout
0.6 work
Indriolo
et
al.
2015;
Phan
et
al.
2018).
In
ourprevious
the chemical evolution of star-forming regions.
and0.7. Fromcomparison
withwe conclude
a relatively
flatPadovani
spectrumetofal.interstellar
cosmic-ray
protons,
the one et al.
molecular
cloudsthroughtheobservations
reaction between
two thathydrogen(e.g.
2009; Padovani& Galli
2013;asPadovani
Keywords.
ISM:
cosmic rays
clouds–provide
atomicinto
processes
molecular
processes
suggestedby therecentVoyager
1 data,only
a lowerforthe observed
atomichydrogenfraction.
atoms. Being
anmostexothermic
process,
H–2ISM:
iscan
thenreleasedthe –bound2013; Ivlev
et al. 2015;
Padovani
et al.
2018)Anweenhanced
postulated thespectrumof Depending
low-energy protons
is needed
explainof the observations.
gas phase.
on positionin thetocloud(ormostthe amountof presence of a low-energy component in the IS CR proton specConclusions.
Our findings
showthat afrom
carefulof molecularhydrogen dissociation by cosmic rays can explain the abunvisual extinction
measuredinwardthedescription
cloud’s edge),
two trum,
with
which
itand
is electron
possible
toisrecoverthehighionisation rates
1.
Introduction
themeasured
protonfluxes
are
not
able
to
explaindanceofatomichydrogenindarkclouds.
An
accuratecharacterisationof
thisprocessathighdensities
crucialforunderstanding
processes determine the destruction of H2 and the restoration of observed in di↵use clouds.
the values of the CR ionisation rate estimated in di↵use clouds
thechemicalevolutionofstar-forming
regions.
the atomic
photodissociation
due to occurs
interstellar
Theform:
formationof molecular hydrogenon dust(hereaftergrains in(e.g. Indriolo
et al.
2015; Phanal. 2018). In ourprevious
We treata cloud
as aetsemi-infinite
slab.
Suchworka simplificamolecular
cloudsthroughtheduereaction
betweentwohydrogenIS) UV
photons
dissociation
to cosmic
rays(hereafter(e.g.
Padovani
et al. 2009;
Padovani& Galli
2013; Padovani
etal. following
Keywords.
ISM:andcosmicrays – ISM:
clouds– atomic
processes– molecular
processes
tioniscompletely
justifiedfor
ourpurposes,fortheBeing partan exothermic
process,
H2 is thenthe 2013; Ivlev et al. 2015; Padovani et al. 2018) we postulated theCRs). In atoms.
the di↵useof molecular
clouds,
UVreleased
photonsinto
regureasons. First, attenuation of IS UV photons occurs in a thingasphase.
Dependingonposition
in
the
cloud
(or
the
amountoflate the abundance of atomic hydrogen by dissociating H2 , while presence of a low-energy component in the IS CR proton spec-

gas layer near the cloud’s surface (with a visual extinction of

, Keele University, Keele, Staﬀordshire ST5 5BG, UK

Evolution of spatio-kinematic structures in star-forming
Evolutionofspatio-kinematic
structuresinstar-forming
42 regions:
are Friends of Friends worth knowing?

regions: are Friends of Friends worth knowing?

Richard J. Parker1⋆ † and Nicholas J. Wright2
1 Department of Physics and Astronomy, The University of Sheﬃeld, Hicks Building, Hounsfield Road, Sheﬃeld, S3 7RH, UK
ABSTRACT
1⋆
2
2

† and
RichardJ. Parker
Nicholas
WrightAstrophysics Group,
Keele University,
Keele, Staﬀordshire
ST5J.
5BG,
UK

9.00674v1[astro-ph.GA]
3 Sep
2018
iv:1809.00674v1[astro-ph.GA]
3 Sep
2018

The Friendsof Friends
algorithm identifies groups of objects with similar spatial and1 Departmentof Physics and Astronomy, The University of Sheﬃeld, Hicks Building, Hounsfield Road, Sheﬃeld, S3 7RH, UK
2 Astrophysics
kinematic
properties,
recentlyused ST5
extensively
to quantify the distribuGroup,and
Keelehas
University,
Keele,been
Staﬀordshire
5BG, UK
tions of gas and stars in young star-forming regions. We apply the Friends of Friends
algorithm to N-body simulationsof the dynamical evolution of subvirial (collapsing)
ABSTRACTand supervirial (expanding) The
star-forming
regions.
We
find groups
that ofthealgorithm
picks
Friends of Friends
algorithm
identifies
objects
with similar
spatial andkinematic
properties,
and has recently
been usedinitialextensively
to quantify the
distribuout a wide range of groups (1
–
25)
for
statistically
identical
conditions,andABSTRACT
tions
of gas and stars in young star-forming regions. We apply the Friends of Friends
cannot distinguish between subvirial
supervirial
regionsin that
we obtain
similar
The Friendsof Friends
algorithm
identifies
groupsofofobjects
withsimilar spatial andalgorithm
toand
N-bodysimulationsof the dynamical
evolutionsubvirial(collapsing)andrecently
been
used
to quantify
andkinematic
supervirial(expanding)star-forming
regions.
findextensively
thatcorrelation
the algorithm
picksthe distribumode and median values for thenumberproperties,of groups
ithas
identifies.
WeWe
find
no
gas andstars instar-forming
apply
the Friends
out tionsa wideofrangeof groups(1 young– 25) forstatistically regions.
identical We
initialconditions,and of Friends
between the number of groups
identified
initially
andeithertheinitialorsubsequentcannotdistinguishbetween simulations
subvirial and of
supervirial
regions inthat we obtain
similar(collapsing)algorithm
to N-bodythe dynamical
evolutionof subvirial
spatial and kinematic tracersmode
ofand
the
regions’
evolution,suchas theamountofandsupervirial
medianvaluesfor the numberof groups
itidentifies.
findspatial
no correlation(expanding)star-forming
regions.
WeWefindthat
the algorithm picks
betweennumberof ofgroupsidentified
initiallyandWe
eithertherefore
theidentical
initial orurge
subsequent
substructure, dynamical masssegregation,orvelocityout athewide
rangegroups(1dispersion.
– 25)
for statisticallyinitialconditions, andspatialand distinguishkinematic tracersof theregions’ andevolution,such asregions
the amountof spatial
cannotbetweensubvirial
supervirialinthat
we obtain similar
caution in using the Friends ofFriends
algorithm
toquantify
theinitialconditionsofsubstructure, dynamical mass segregation, or velocity dispersion. We therefore urgemode
andmedianvaluesforthe algorithm
number oftogroups
it theidentifies.
We find nocorrelation
caution
in
using
the
Friends
ofFriends
quantify
initialconditionsofstar formation.
between the number of groups identified initially and either the initial or subsequent
star formation.

spatialand kinematic
tracers of theregions’
evolution,and
suchassocias the amount of spatial
Key words: stars: formation–
kinematics
anddynamics–
openclusters
Keywords: stars:dynamical
formation –masskinematics
and dynamics– opendispersion.
clusters andWe
associsubstructure,
segregation,or velocity
therefore urge
ations: general – methods: numericalations: general – methods: numericalcaution in using the Friends of Friends algorithm to quantify the initial conditions ofstar formation.
1

INTRODUCTION

Key words: stars: formation – kinematics and dynamics – open clusters and associtures
form and evolve is crucial in order to underations: general – methods:
numerical

stand the typical environment where most stars form, andThe
majority
of
stars
form
in
regions
where
themeTIONtures form and evolveis crucial
in orderthe implications
for planet
formationtoandunderstability (e.g.
dian stellar density exceeds the density in the Galactic
Scally & Clarke 2001; Adams et al. 2004; Parker & Quanz
standtypicalfield by several orders of magnitude(e.g.theLada& Lada environment where most stars form, andtars form in regions
where
the
me2012; Vincke et al. 2015; Portegies Zwart 2016; Cai et al.
2003;
Bressert et al. 2010). Thesethe
young
stars often fol- for planet
implications
formationandstability(e.g.
1 INTRODUCTION
tures
form
and
evolveis crucial
in order
2017)
as
well
as
their
collective
evolution
inthecontext
of to undery exceeds the density
intheGalactic
low a hierarchical or substructured spatial distribution
standetthetypicalenvironment
wherestars form, andGalaxy-scaleastrophysicalprocesses(e.g.&
Kereš
et mostal. 2009).
Scally&Clarke
2001;
Adams
al.
2004;
ParkerQuanz(Cartwright& Whitworth
Gutermuthal. 2009;
The majority
stars 2004;
form inregions etwhere
the meders of magnitude (e.g.
Lada&ofLadaA Portegies
significant
amountof 2016;
eﬀort
been
investedtheimplicationsforplanethasCai
formationand instability (e.g.
2012;Vincke
et
al.
2015;
Zwart
et
al.
Gouliermis
et
al.
2014;
Kuhn
et
al.
2014;
Wrightetal.
2014;dian stellar density exceeds the density in the Galacticquantifying both the spatial distributions in young starScally & Clarke 2001; Adams et al. 2004; Parker & Quanz. 2010). These young
stars
often
folJaehnig
et
al.
2015)
and
also
displaycorrelated
velocifield by several orders of magnitude
Lada
Ladaforming2017) as(e.g.
well
as &theircollective
evolution
inthecontextWhitworthof 2016; Cai et al.
Cartwrightregions(Larson2012;
Vinckeet al.1995;
2015;
Portegies& Zwart

OB1 ASSOCIATION

6 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands

A TRANSITIONAL DISK AROUND AN INTERMEDIATE MASS STAR IN THE SPARSE POPULATION OF THE ORION
8 Postgrado de Física Fundamental, Universidad de Los Andes, Mérida, Venezuela
OB1 ASSOCIATION

43

7 Cerro Tololo Interamerican Observatory, Casilla 603, la Serena, Chile

2
3
4
5
6
A LICE P ÉREZ -B LANCO ,1 K(Received
ARINA M
AUCÓ
,
J
ESÚS
H
ERNÁNDEZ
,
N
URIA
C
ALVET
,
C
ATHERINEE
SPAILLAT,M
ELISSA
M
C
C
LURE,
2018; Revised 2018; Accepted)
C ESAR B RICEÑO ,7 C ONNOR ROBINSON ,5 DANIEL F ELDMAN ,5 L UIS V ILLARREAL ,8 AND PAOLA D’A LESSIO2

2
3
4
5
6
ABSTRACTA LICE P ÉREZ -B LANCO ,1 K ARINA M
AUCÓ , J ESÚS H ERNÁNDEZ , N URIA C ALVET , C ATHERINE E SPAILLAT , M ELISSA M C C LURE ,We present a detailed studyof thedisk aroundtheONNOR
intermediate
mass star ,5SOD411,
aimingto explain,5thespectralenergyC ESARB RICEÑO
,7 C
ROBINSONANIELF ELDMANL UIS
V ILLARREAL,8 AND PAOLA D’A LESSIO2.09746v1[astro-ph.SR]
25 Sep2018
46v1[astro-ph.SR]
25 Sep2018

arXiv:1809.09746v1 [astro-ph.SR] 25

5 Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215, USA

distribution of this star. We show that this is a transitional disk truncated at ∼11 au, with ∼0.03 lunar masses of optically thinof Leeds,Schoolof Physics
and since
Astronomy,
Leeds,
UK.accreting mass onto the star, at a rate ofdust inside1 University
the cavity. Gas
also flows throughthe cavity,
we findLS29JT,
that the disk
is still−1∼ 5 × 10−92M
now, SO 411 hasy beenthought(IRyA),
to belongto the ∼3 Myr
old σ Autónoma
Orionis cluster.
However,
we analyzed⊙ yr . Until
Instituto
de Radioastronomía
Astrofísica
Universidad
Nacionalde México,Morelia,
Mexicothe second31Gaia Data Release in combination with kinematic data previously reported, and found that SO 411 can be associatedInstitutode Astronomía,
Universidad
Nacional
Autónoma LS29JT,de México,
Ensenada,
Universityof Leeds,Schoolof Physics
and Astronomy,
Leeds,
UK. BC, Mexico
with an sparse stellar population located in front of the σ Orionis cluster. If this is the case, then SO 411 is older and even more
42Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109, USA
Instituto
de Radioastronomía
Astrofísica
(IRyA),
Nacional
Autónomade México,Morelia,
peculiar, sinceprimordial
disks in this stellarymass
range arescarce Universidad
for ages >5 Myr.
Analysisof the silicate
10µm featureof Mexico
53Department
SO 411 indicatesthat theobservedfeaturearisesUniversity,
at theNacionaledge 725
of theouter disk, deandMéxico,
displaysaBoston,very highratio of ∼0.5,
Astronomy,
BostonCommonwealthAvenue, Ensenada,
MAcrystallinity
02215,
USA
Instituto
deofAstronomía,
Universidad
AutónomaBC,
Mexico6 Antonwith forsterite
the Pannekoek
most abundantsilicate
crystal.
The high
forsterite
abundance points
to crystal
formationin non-equilibrium
Institutefor
Astronomy,
UniversityofAmsterdam,
Science
Park
904,
1098
XH
Amsterdam,
The Netherlands
4 DepartmentofAstronomy,
UniversityofMichigan,
500
ChurchStreet,Ann
Arbor,
MI
48109,
USA
conditions.7 The PAH spectrum of SO 411 is consistent with this intermediate state between the hot and luminous Herbig Ae andTololo Interamerican Observatory,
Casilla 603,Commonwealthla Serena, Chile Avenue, Boston, MA 02215, USA
5CerroDepartment
Boston ofUniversity,
the less massive
and coolerofTAstronomy,
Tauri stars. Analysis
the 7.7µm725
PAH feature indicates that
small PAHs still remain in the SO 411
8 Postgrado de Física Fundamental, Universidad de Los Andes, Mérida, Venezuela
6 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
disk.
7 Cerro Tololo Interamerican Observatory, Casilla 603, la Serena, Chile

Keywords: open clusters and associations: individual σ Orionis— stars:pre-main
sequence2018;— accretion
disks(Received
2018; Revised
Accepted)
8 Postgrado de Física Fundamental, Universidad de Los Andes, Mérida, Venezuela

ABSTRACT(Received 2018; Revised 2018; Accepted)
We present a detailed study of the disk around the intermediate mass star SO 411, aiming to explain the spectral energy
distribution of this star. We show that this is a transitional disk
truncated at ∼11 au, with ∼0.03 lunar masses of optically thin
ABSTRACT
dust inside the cavity. Gas also flows through the cavity, since we find that the disk is still accreting mass onto the star, at a rate ofpresent
study
thehasdisk
aroundthetointermediatestaroldSO
411, aiming
explain the
spectral energy
−9
∼ 5We
× 10
M⊙ yra−1detailed. Until now,
SOof411been
thoughtbelong to the mass
∼3 Myrσ Orionis
cluster.toHowever,
we analyzed
distributionof thisWe inshowthat this withis a transitional
disk
truncatedreported,
at ∼11 andau, withof optically thinthesecond Gaia
Datastar.
Releasecombination
kinematic datapreviously
found∼0.03
that SOlunar
411 masses
can be associateddust aninsidethestellar
cavity.
Gas also locatedflows throughcavity,since cluster.
we find Ifthat
is still
accreting
onto
star,
at a rate ofwithsparsepopulationin front theof theσ Orionis
thistheis disk
the case,then
SO 411 massis olderandthe
even
more
−9
−1
∼
5
×
10
M
yr
. Untildisks
now,inSO
hasmass
beenrange
thoughtbelongthe>5∼3Myr.
MyrAnalysis
old σ Orionis
However,
we ofanalyzed
peculiar, since⊙primordial
this411stellarare toscarcefor toagesof the cluster.
silicate 10µm
featurethe411secondGaia that
DatatheReleasein feature
combination
withreported,
and high
foundthat SO 411
canassociatedSO
indicates
observed
arises at
the kinematicedge of thedata
outerpreviously
disk, and displays
a verycrystallinity
ratio
of be
∼0.5,
withforsterite
an sparsethe
stellarlocatedcrystal.
in frontTheof highthe σforsterite
Orionis cluster.
If thisis thecase, thenSO 411is older and even morewith
mostpopulation
abundant silicate
abundance
pointsto crystal
formationin non-equilibrium
conditions.
The PAH
spectrumof SO
411 stellar
is consistentstate >5
betweenhot and ofluminous
HerbigAe andpeculiar, sinceprimordialdisks
in thismass withrangethisareintermediatescarce for ages
Myr.theAnalysisthe silicate
10µmfeature oftheandthatcoolerTauri stars.
Analysissmall aPAHs
in the SO
411of ∼0.5,
SOless411massive
indicates
the T
observedfeaturearisesofatthe
the7.7µm
edge PAHof thefeatureouter indicates
disk, andthat
displays
verystill
highremain
crystallinity
ratio

nallee 6, D-15738 Zeuthen, Germany

Constraining the nature of DG Tau A’s thermal andConstraining
thenature
of
DG
Tau
A’s
thermalandnon-thermalradio
emission44

non-thermal radio emission

eceived YYY; in original form ZZZ

S. J. D. Purser,1? R. E. Ainsworth,1,2 T. P. Ray,1 D. A. Green,3 A. M. Taylor1,4
2
and
A.
M.
M.
Scaife
1?
1,2
1
3
1

1,4
S.
J.
D.
Purser,R.
E.
Ainsworth,
T.
P.
Ray,
D.
A.
Green,A.
M.
Taylor
ABSTRACT
School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2, Ireland
Jodrell Bank Centre for Astrophysics, Alan
Turing Building, School of Physics and Astronomy, University of Manchester,
2
DG TauA,aclass-II
youngstellarobject (YSO) displays both thermal, and nonand
A.
M.
M.
ScaifeOxford Road,
Manchester,
M13
9PL, United Kingdom
1
20065v1 [astro-ph.GA]
26 Sep262018
arXiv:1809.10065v1[astro-ph.GA]
Sep 2018

3 Astrophysics Group, Cavendish Laboratory, 19 J. J. Thomson Avenue, Cambridge CB3 0HE
Schoolof Cosmic
Physics,
Dublin Institutefor Advanced
Studies,
31 To
Fitzwilliam
Place, Dublin
2, Ireland of thisthermal,radio
emissionassociatedwith
its bipolarjet.
investigate
the nature
42DESY, Platanenallee 6, D-15738 Zeuthen, Germany
Jodrell Bank Centre for Astrophysics, Alan Turing Building,1School of Physics and Astronomy, University of Manchester,
emission,
we present sensitive ( ⇠ 2 µJy beam ), Karl G. Jansky Very Large Array
Oxford Road, Manchester, M13 9PL, United Kingdom(VLA)3 Astrophysics
6 and 10 Group,
GHz Cavendish
observations.
Overyr, noAvenue,
propermotionobserved towards
Laboratory,
19 J.3.81
J. Thomson
Cambridge
CB3is0HE
Accepted
XXX. Received YYY; in original form ZZZ
4 DESY,
Platanenallee
D-15738
Germanythought to be a bowshock. Its quasi-static
the non-thermal
radio6, knot
C,Zeuthen,previously
nature, spatially-resolved variability and o↵set from the central jet axis supports a
ABSTRACT
scenario
whereby it is insteada A,stationary
shock
intodisplays
the surrounding
mediumDGinTaua formclass-II
youngstellardriven
object (YSO)
both thermal, andnonAccepted XXX. Received YYY;
original
ZZZ
radioworking
emission associatedwith knot
its bipolar
jet.weTo investigate
the natureof thisby the jet. Towards the thermal,internal
surface,A,
derive aninclination1
emission, we present sensitive ( 1 ⇠ 2 µJy beam ), Karl G. Jansky Very Large Arraycorrected, absolute velocityof6 258
23 observations.
km s . OverDG3.81
Tau
A’sreceding
counterjet(VLA)
and 10±GHz
yr, nopropermotion is observed
towardsdisABSTRACT
non-thermal
radio knot
C, previously
thought toa bowshock.
Its quasi-static
plays a spatially-resolved theincreasein flux
density,indicating
a bevariablemass
loss event,nature,DG
spatially-resolved
variability
and o↵setfromthe central
jet displays
axis supports
Tau A, a class-II
youngstellarobject(YSO)
botha thermal, and nonthe first time such an event
has
beenradioinassociatedthe counterjet.
For
thisejection,
scenario
whereby
itobserved
is insteada stationary
shockwithdriveninto
the surrounding
medium wethermal,emissionitsbipolarjet.
Toinvestigate
the nature of this8
11
theemission,
jet.
Towards
theinternal
workingknotA, wederiveaninclinationmeasure an ionised massbyloss
rate
of we
(3.7
± 1.0)⇥ 10 surface,yrduringthepresent
sensitive
( M
⇠
2
µJy
beam
),
Karl
G.event.
Jansky A
Very Large Array1
corrected, absolute velocity of 258 ± 23 km s . DG Tau A’s receding counterjet dis(VLA)
6 and 10 increase
GHzjetobservations.
Over
3.81a yr,nopropermotionis observed towards
contemporaneous ejectionplays
in atheapproaching
seen,
showing
it tobelossanasymspatially-resolved
in isn’t
flux density,
indicating
variablemass
event,
thenon-thermal
knotC, previously
thought
beejection,a extent
bowshock.
the first
timesuch an transfer
eventradio
has beenobservedin thecounterjet.
Forto
this
we of Its quasi-static
metric process. Finally, using
radiativemodelling,
we
find
that
the
8 M yr 1 during the event. A
measurean ionised
mass loss rate of (3.7
± 1.0) ⇥ 10
nature,spatially-resolved
variability
ando↵set from the central jet axis supports a
the radio emission can onlybeexplained
the presenceof shockshocks,therefore
contemporaneousejection with
initthejet isn’t seen,
showing
it andto beanasymscenario
wherebyis approaching
insteada stationary
driveninto
the surrounding medium
process.
Finally,using
radiative
transfermodelling,
we find thatofreionisation, in the flow. metric
Ourby
modellinghighlights
the needtosurface,considertherelativethe jet.
Towards
the internal
workingknottheA,extent
wederivean inclinationthe radio emission can only be explained with the presence of1 shocks, and therefore
corrected,
ofhighlights
258from± 23theakms toto. consider
DG
Tau
receding counterjet disangular size of optically thick,andin thin,emissionjet,thesynthesised
reionisation,
theabsolute
flow.radio
Our velocity
modelling
need
theA’srelativea opticallyspatially-resolved
increasein flux index.
density,indicatinga variable mass loss event,angularplays
size ofthick,fromand thin,emissionfrom a jet,to the synthesised
beam, when deriving its physicalconditions
itsradio
spectralbeam, thewhenfirst
deriving
physicalconditions
spectral index.
timeitssuch
an eventhas from
beenitsobservedin the counterjet. For this ejection, we

measure an ionised mass loss rate of (3.7 ± 1.0) ⇥ 10 8 M yr 1 during the event. A
Key words: â–Ăćstars:
stars: low-mass– stars: (DG
individual(DGA)
Tau–A)– stars:jets
jets – –stars:
Key words: âĂć stars: low-massindividualTaustars:
stars:
contemporaneousejectionintheapproaching
jet
isn’t
seen,
showing
it to be an asymformation – radio continuum: general – radiation mechanisms: non-thermal
formation – radio continuum:metric
general– radiation
mechanisms:
non-thermal
process.
Finally, using
radiative transfer
modelling, we find that the extent of
the radio emission can only be explained with the presence of shocks, and therefore
reionisation, in the flow. Our modelling highlights the need to consider the relative
1 INTRODUCTION
literature,
manyof thin,their physicalproperties are
relatively
angular size of opticallythick,
andradio emission
froma jet, to the synthesised
well
known.
Mass conditions
loss rates ( M€ jet), ionisation
fractionsindex.
( i)
beam,
when
deriving
its
physicalfrom
its spectral
At radio wavelengths, partially-ionised jets are almost ubiq-

and hydrogen total densities (nH ) have been widely deduced
uitously(Anglada
1995;
Furuya
et
al.
2003;
AMI
ConsorCTION
literature, manyfromof linetheirratios,physicalwith typical properties
values calculatedare
to be relatively
betweenKey
words:âĂć stars:
low-mass–stars:
individual(DG
TauA) – stars: jets – stars:
tium et al. 2011) observed towards class0, I andII proto9 M yr 1  M€ jet€  10 6 M yr 1 (dependent on evo10
well
known.
Mass
loss rates( Mjet),ionisation
fractionsnon-thermal( i)stars. Launched as by-products of accretion
processes,
theseformation–
radio
continuum:
general–radiationmechanisms:
lutionary class and YSO mass, Caratti o Garatti et al. 2012),
gths, partially-ionised jets are almost ubiq-