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
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in
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Department of Physics
andWalnut
Astronomy, St.,
Universityof Leicester,
LE1 CO,
7RH, 80302, USA
1050
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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
includemagnetic
fieldsprovideMarco
Padovani,
Daniele
Galli
V.
Ivlev
Casellibecomeunstableduringtheearly stages [3] with Jupiterhaving scatteringAT561
Typesetusing
LX
twocolumn
style
inAASTeX61
E
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
hosts aJapan;&80 M
3anddiﬀusivity.
obtainedcurrent
orbitaleccentricity.
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magnetic
Theitsartificiallyhighanduncontrolled)
ScuolaNormaleSuperiore,
PiazzadeiWR62-2,
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7,(numerical
56126
Pisa,
Italy
okoda@taurus.phys.s.u-tokyo.ac.jp
star,
which
appears
to violate
the existenceof the mmaxof–Meclthese
relationevents
since theA2 TRANSITIONALDISKAROUNDAN
INTERMEDIATEMASSSTARfrom
IN theTHE
SPARSEPOPULATION OF THE ORION
1⋆
2forme-mail:andrea.ferrara@sns.it
mass
of
the
star
is
almosttwo
times
higherthan
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expectedrelation.
Bymagnetic
diﬀusivity
leads
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Research,
Wako,
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is3 RIKEN
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directN-bodycalculations
with
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CL041
OB1
ASSOCIATION
1 Department
ing region.
We
argue
furtherthatinrealitythedynamics
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
2
after
the
dispersaloftheprotosolar
nebula(t0 )5BG,[7,8].
Here
weshowinsteadthat– Tsukuba,
Prandtlnumber turbulencemay
lead
to localof inmagnetic
energyAstrophysics
Group,forKeele
Keele,
Staﬀordshire
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Tomonaga
Centerthe University,
History
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Facultyof
PureandAppliedSciences,
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inducedstellarcollisions
a ST5
binary-richstardisclusterthat initiallyfollows
the mmaxof
sipationthroughreconnection,
meaningthat Eightthe regionsof molecular
cloudsTsukuba,
Ibaraki
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M
relation.
out
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form
aearlystar more
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80 M
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ABSTRACT
planetary
migration
startedshortly
after
t
.
Such
migration
inferred0stellarcollisions.
Thissuggests
thatNatural
theCL041 clustermay
becomewhich5 Centre
are forming
stars
might
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essentiallyfreeof magnetic
fields.
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theVVVfor StarandPlanetFormation,
Niels
Bohr
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1 multiple
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A LICE
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ARINA
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URIA
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ATHERINEE
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Thesurvival
presenceofVoldgade
small
ofon
atomichydrogen,detectedasthe
absorption
dips Jupiterin the 21 cm
line
spectrum,a well-known
anoutlieroftherelation
becauseofitsearly-dynamical
evolution,even [9].
ifis theclusterfromtheof amounts
thePatroclus-Menoetius
binaryTrojanThe
Copenhagen,Østermagnetic
5-7,
DK-1350,
Copenhagen
K,
Denmarksimulations
thatignorefieldsthescalesonwhichproperties7
5
5
8
dark clouds.
Thefollowed
abundancehydrogeninthemoredensestregions
cloudscanhostbe only
theofrelation
atatomsbirth.measured
We
find
that
than
half, ofofLmolecularourclustersa AND PAOLA D’A LESSIO2
BRICEÑO,CONNORROBINSON,D
ANIELF
ELDMAN
UISmodelV
ILLARREAL,
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LeidenObservatory,
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PO
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The
Max-Plankof stellar
masses,and planet-forming
discs
are
explainedby thestellar
dissociationdue
to productcosmicrays.
as itsmost
massivemember
within thefirstNetherlands
5 Myr ofcluster
evolution.Institut fürbinaryformedat multiplicities
t !of tH0merger[10,11]
withinamassiveplanetesimal
disk
once
located
ABSTRACT(MPE),
Giessenbachstr.1,
85748,
Garching,
Germany
Aims.
to assessthe roleof Galactic
cosmicthe magnetic
formationofatomichydrogen,
by–M
using
recent developmentsin themined,Extrsterrestrische
mayWe
be want
closerto Physik
realitythan
thosewhichrays
includefields,
but
Thus,
the
existence
ofinstars
more
massive
than
the
mmax
in some young
ecl relation
characterisation
the low-energy
spectraofiscosmic
raysofdue
andadvancesin the modellingof
theirthepropagation
molecular
clouds.
The
Friends
Friends
algorithm
identifies
groupsof inobjectswithsimilarspatial andclusters
expected
to dynamical
processes
despitethe disk,validityof thegreatermmax–M[12,13].
The
longerthebinarystayedintheecl
canbeyondonly
do soNeptune
in anof unrealistic
parameter
regime.
Methods. We model the attenuation
ofkinematicthe interstellar
cosmicrays
entering
a recently
cloud
andpopulations
computethe indissociation
ratetoof molecular
relation.
We briefly
discuss
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binaryour model.
properties,
and
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quantify the distribuhydrogendue
to collisions
withprotons
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asinwell
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1 University
Keywords:
accretion,accretion
discs,
dynamo,magnetic
fields,thelikelihoodthatcollisions
would
strip
its
components
one
another.
The(Received;
Revised;Accepted5,
2018)
of Leeds,Schoolof cosmic-ray
Physics
andAstronomy,
LS29JT,
Leeds,
UK.
tions
of
gas
and
stars
young
star-forming
regions.
We
apply
the
Friends
of Friends
Key words: methods: numerical – stars: kinematics and dynamics – stars: massive
available observations.
maxular 1the high value of the magnetic Prandtl number, and thelow value of

43

44
45

Richard J. Parker † and Nicholas J. Wrightmagnetohydrodynamics(MHD), planetsand satellites:
formation,stars:of the dynamical evolution of subvirial (collapsing)algorithm
to N-bodysimulations2

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

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”2

13(b) History of the Universe, Faculty of Pure and Applied Sciences, University of Tsukuba,
2
Tomonaga
Centerforthe
RIKEN Cluster for 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, Copenhagen K, Denmark
Tsukuba, Ibaraki 305-8571, Japan
6
Leiden5 Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands Max-Plank Institut für
Centre for Physik
Star and
PlanetFormation, Niels
Bohr
InstituteGermany
and Natural History of Denmark, University ofExtrsterrestrische(MPE),
Giessenbachstr.1,
85748,
Garching,
4(Jy/Beam)・(km/s)(a)1

Copenhagen, Øster Voldgade 5-7, DK-1350, Copenhagen K, Denmark
6
Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands Max-Plank Institut für
(Received;
Accepted September
5, 2018)
Extrsterrestrische Physik(MPE),Revised;
Giessenbachstr.1,
85748, Garching,
Germany
CCH( =3-2, =7/2-5/2, =4-3 and 3-2)
P.A. 220°

color: 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)

01.75ｓSubmitted to(Received; Revised; Accepted September 5, 2018)

Contour: Continuum

ABSTRACT
Submitted to

We have observed the CCH (N = 3−2, J = 7/2−5/2, F = 4−3 and 3−2) and SO (67 −56 ) emission′′

ABSTRACT

at a 0. 2 angular resolution toward the low-mass Class 0 protostellar source IRAS 15398−3359 withCCH
= 3−2, J = 7/2−5/2,
F =the4−3
and 3−2)(67 −56 ) emission
ALMA.We
Thehave
CCHobserved
emission the
tracesthe(Ninfalling-rotatingenvelope near
protostar
withand
theSO
outflow
a 0.′′ 2 angularresolution
toward the low-mass
0 protostellar
IRAS has
15398−3359
withcavityatextended
along thenortheast-southwest
axis. On Class
the otherhand, the source
SO emissionacompact
distribution
aroundthe protostar.
The
CCH emission is envelope
relativelynear
weaktheat thecontinuum
ALMA.
The CCHemissiontraces theinfalling-rotating
protostarwith the outflow

17

(a)

5

Jy/beam

VLSR [km/s]

6

0.04

0.02
0.00

4

[ ⦿]

(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)

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

1,2 ?
1,3
Seungkyung
Oh
and
Pavel
Kroupa1 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 of
Mathematics
Physics,University
AstronomicalInstitute,Charles
University
in Prague,
V Holešovičkách
2, CZ-180 00 Praha 8, Czech Republic
2 Department
Physics andand
Astronomy,of Sheffield,
Hicks
Building,
Hounsfield
Road, Sheffield
S3 7RH, UK:1809.04596v1 [astro-ph.GA] 12 Sep 2018

3 Faculty of Mathematics and Physics, Astronomical Institute, Charles University in Prague, V Holešovičkách 2, CZ-180 00 Praha 8, Czech Republic

Accepted Received
Accepted Received

ABSTRACTABSTRACT

Very young star clusters in the Milky Way exhibit a well-defined relation between
Verymaximum
young starstellar
clustersin theMilkyWayexhibitwell-defined
between
their
mass,
mmax
, and
their
massainstars, Meclrelation. A recent
study showstheirmaximumstellarmass, mmax , and theirin VVVstars, M
study
shows
ecl . A recent
that
the youngintermediate-massstar masscluster
CL041
possiblyhosts
a &80 M
that
theWR62-2,
young intermediate-masscluster
CL041
possibly
hosts relation
a &80 Msince thestar,which appears tostar
violatetheVVV
existenceof themmax –Mecl
star,
WR62-2,
appears
violatethehigher
existenceof the–Mecl relation
since
the
mass
of thewhichstar isalmosttotwo
times
than
thatmmax
expectedfrom therelation.
By
mass of the star is almost two times higher than that expected from the relation. By
performing direct N-body calculations with the same mass as the cluster VVV CL041
performing direct N-body calculations with the same mass as the cluster VVV CL041(⇡3000 M ), we study whether such a very massive star can be formed via dynamically(⇡3000 M ), we study whether such a very massive star can be formed via dynamicallyinducedstellarcollisions
a binary-richstar clusterthat initiallytheinducedstellarcollisions
in a inbinary-richstar clusterthat initiallyfollowsfollows
the mmax– mmax –Eightof clusters
100 clusters
star more
massivethan
M throughecl relation.
MeclMrelation.
Eightout outof 100form forma staramore
massivethan 80
M 80
throughmultiplestellarcollisions.
suggests
thatVVV
the VVV
maybecomehave become
multiplestellarcollisions.
ThisThissuggeststhat theCL041CL041
clustercluster
may haveoutlierof therelation
becauseits early-dynamical
evolution,
if the clusteran anoutlierof therelation
becauseof itsofearly-dynamical
evolution,even ifeventhe cluster
followed
relationat birth.
We thatfind morethat morethanofhalf
our model
followed
the therelationat birth.
We findthan half
our ofmodel
clustersclusters
host a host amergerproduct
asmostits most
massivemember
withinthe5firstof cluster
evolution.
mergerproduct
as itsmassivemember
withinthe first
Myr 5ofMyrcluster
evolution.
Thus,
existenceof stars
massivemmax
some youngThus,thetheexistenceof stars
moremoremassivethan thanthe mtherelationin someinyoung
ecl relation
max –Mecl –M
clusters
is expected
to dynamical
processes
despitethe validity
theclusters
is expected
due dueto dynamical
processes
despitethe validityof the ofmmax–Mmeclmax –Mecl
relation.
briefly
discuss
evolutionof binarypopulations
our model.
relation.
We We
briefly
discuss
evolutionof binarypopulations
in ourinmodel.
Key
words:
methods:
numerical– stars:
kinematics
and dynamics– stars:– massive
Keywords:
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:
general1 1 INTRODUCTIONINTRODUCTION

the same methods and telescopes. Especially noteworthy is
the Stephens et al. (2017) study that targeted seven MYSOs
Very young (.4 Myr) star clusters in the Milky way show
Very young (.4 Myr) star clusters in the Milky way show in the LMC which were thought to be, based on Spitzer oba well defined relation between the mass of the most masa well defined relation between the mass of the most mas- servations, single stars formed in isolation. Stephens et al.
sive star in the cluster, mmax , and the cluster mass in stars,
sive
star
in
the
cluster,mmax , and the cluster mass in stars, found, with their HST data, very compact massive clusters
Mecl (Fig. 1). That is, the maximum stellar mass in a veryat the positions of these seven stars, with all seven being

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

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 theof theirpropagationin molecular
clouds.can be only
characteristic of dark clouds. The abundance of hydrogen atoms measured
in modellingthe densest
regionsof molecular
clouds
Methods. We model the attenuation of the interstellar cosmic rays entering a cloud and compute the dissociation rate of molecularexplained by the
dissociation of H2 due
to cosmic rays.
hydrogen due to collisions
with cosmic-ray protons and electrons as well as fast hydrogen atoms. We compare our results with theAims. We wantavailable
to assessthe role of Galactic cosmic rays in the formation of atomic hydrogen, by using recent developments in theobservations.
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
These secondary
particles constitutethe only sourceof atomic
at column
densities
above ⇠ 10cm
. We also findthatofthe
Methods. We model
the attenuationof the 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.
secondary electrons produced in primary ionisation collisions.
spectrum of low-energy
protons
neededto explain
most of the
21 can explain
Conclusions.
Our findingsthe
show
thatsourcea carefulofdescriptionof molecularby cosmic
rays
These secondary
particles constituteonly
atomic hydrogenat hydrogencolumn dissociation
densities above⇠ 10
cm 2 . We thealsoabunfind that theof atomichydrogenin darkclouds.
An accuratecharacterisation
this process atandhighionisation
densities is rates
crucialvaries
for understanding
dissociation ratedance
decreaseswithcolumndensity,while
the ratio
between theofdissociation
between about 0.6
the chemical evolution of star-forming regions.
and 0.7. From comparison
with observations we conclude that a relatively flat spectrum of interstellar cosmic-ray protons, as the one
Keywords.
ISM:
cosmic rays
– ISM:
atomic processes
molecular
suggested by the
mostrecentVoyager
1 data,canclouds
only–provide
a lower–boundforprocesses
the observed atomic hydrogen fraction. An enhanced
spectrum of low-energy protons is needed to explain most of the observations.
Conclusions. Our findings show that a careful description of molecular hydrogen dissociation by cosmic rays can explain the abun1. Introduction
protonfluxesare not for
ableunderstanding
to explain
dance of atomic
hydrogen in dark clouds. An accurate characterisationtheofmeasured
this process
at andhighelectron
densities
is crucial
the values of the CR ionisation rate estimated in di↵use clouds
the chemical
evolutionofstar-forming
regions.
The formation of molecular hydrogen occurs on dust grains in

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

1 [astro-ph.GA] 11 Sep 2018e-mail: andrea.ferrara@sns.it(e.g. Indriolo et al. 2015; Phan et al. 2018). In our previous work
molecular
clouds throughthe reactionhydrogen(e.g. Padovani
et al. 2009; Padovani & Galli 2013; Padovani et al.
Key words.
ISM: cosmic
rays – ISM:
clouds between– atomictwo
processes– molecular
processes
atoms. Being an exothermic process, H2 is then released into the 2013; Ivlev et al. 2015; Padovani et al. 2018) we postulated thegas phase. Depending on position in the cloud (or the amount of presence of a low-energy component in the IS CR proton spec-

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

1⋆

† 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

2

2

1 Department of Physics and Astronomy, The University of Sheﬃeld, Hicks Building, Hounsfield Road, Sheﬃeld, S3 7RH, UK
2 Astrophysics Group, Keele University, Keele, Staﬀordshire ST5 5BG, UK

ABSTRACTThe Friends of Friends algorithm identifies groups of objects with similar spatial andkinematic properties, and has recently been used extensively to quantify the distribuABSTRACT
tions
of gas and stars in young star-forming regions. We apply the Friends of Friends
The Friendsof Friends
algorithm
identifies evolutiongroups ofofobjects
withsimilar spatial andalgorithm
to N-bodysimulationsof the dynamical
subvirial(collapsing)has recently
beenWeused
to quantify
andkinematic
supervirialproperties,(expanding)and
star-forming
regions.
findextensively
that the algorithm
picksthe distribugas andstars instar-forming
apply
the Friends
out tionsa wideofrangeof groups(1 young– 25) forstatistically regions.
identical We
initialconditions,and of Friends
cannotdistinguishbetween simulations
subvirial and of
supervirial
regions inthat we obtain
similar(collapsing)algorithm
to N-bodythe dynamical
evolutionof subvirial
mode
andsupervirial
median values
for the numberof groups it
identifies.
findthatno correlation
and(expanding)star-forming
regions.
WeWefindthe algorithm picks
betweennumberof ofgroupsidentified
initiallyand either theidentical
initial orinitial
subsequentout athewide
rangegroups
(1 – 25)for statisticallyconditions, andspatialand distinguishkinematic tracersof theregions’ andevolution,such asregions
the amountof spatial
cannotbetweensubvirial
supervirial
in that
we obtain similar
substructure, dynamical mass segregation, or velocity dispersion. We therefore urge
mode and median values for the number of groups it identifies. We find no correlation
caution in using the Friends of Friends algorithm to quantify the initial conditions of
the number of groups identified initially and either the initial or subsequent
starbetween
formation.

spatial and kinematic tracers of the regions’ evolution, such as the amount of spatial
Keywords: stars:dynamical
formation –masskinematics
and dynamics– opendispersion.
clusters andWe
associsubstructure,
segregation,or velocity
therefore urge
ations: 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, and
The majority of stars form in regions where the methe implications for planet formation and stability (e.g.
dian stellar density exceeds the density in the Galactic
Scally & Clarke 2001; Adams et al. 2004; Parker & Quanz
field by several orders of magnitude (e.g. Lada & Lada
2012; Vincke et al. 2015; Portegies Zwart 2016; Cai et al.
2003;
Bressert et al. 2010). These young stars often fol1 INTRODUCTION
form
evolveis crucial
in order2017) astures
well astheir andcollective
evolutionin the context
of to underlow a hierarchical or substructured spatial distribution
standastrophysicalthe typical processes
environment
whereet moststars form, andGalaxy-scale(e.g. Kereš
al. 2009).
(Cartwright& Whitworth
Gutermuthal. 2009;
The majorityof stars 2004;
form inregions etwhere
the meA thesignificant
amount forof eﬀort
been invested
implications
planethasformationand instability (e.g.
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
Jaehnig
et
al.
2015)
and
also
displaycorrelated
velocifield by several orders of magnitude (e.g. Lada & Ladaforming regions (Larson 1995;
2012; Vincke et al. 2015; Portegies Zwart 2016; Cai et al.

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-