Star Formation NewsletterNo. 302 14-21
高橋実道（工学院大学）

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15
16
17
18
19
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21

from
the
via theenergyflux.to perform an MK spectral classification13and to determine(SB2),
andStefan-Boltzmann
multiplesystems. law
Weyusedthefullcode
ROTFIT
12
InstitutodeRadioastronomı́aAstrofı́sica,
UNAM,
A.P. 3-72, Xangari, Morelia, 58089, Mexico; 2 Departamento
1
Carnegie
Institutionof Washington
DTM,
5241 Broad
NW,
DCsystems.
20015, USA;NASA
theatmosphericparameters(T, logg,Casilla[Fe/H])
andSantiago,
vBranchsin i of Road
the single
stars and SB1
For these
objects,
we
14 Washington,eﬀ
AcceptedbyMNRAS
de Astronomı́a,
Universidad
deChile,
36-D,
Chile;
Astronomisches
Rechen-Institut,
Zentrum
für
3
Sagan
Fellow;
Jet
Propulsion
Laboratory,
California
Instituteof Technology,
4800
Oak
Grove15Drive,
Pasadena,
The
structureandspectrumoftheaccretion
shock
in
the
atmospheres
of
young
stars
used
the
spectralsubtractionofslowlyrotating
templatestomeasuretheequivalent
widths
of
the
Hα
and
Lii
6708
Å
Astronomie
der Universität
Heidelberg,Mönchhofstrasse
12-14,
69120
Heidelberg,
Germany; NYNational
Astronomical
4
5CA
91109,
USA;
DepartmentofPhysics
andAstronomy,
UniversityofRochester,Rochester,
14627,
USA;
https://arxiv.org/pdf/1801.02404
1 us to derive their chromospheric activity level 16lines,
whichenabledandlithiumabundance.
We
made
use
of
Gaia
Alexandr
Dodin
ObservatoryofJapan,
2-21-1
Osawa,
Mitaka,Tokyo,
181-8588,
Japan;
I.
Physikalisches
Institut,
UniversiätzuKöln,
Institutefor Research
on Exoplanets,
Université
detheMontréal,Département
de Physique, C.P. (HR)6128 Succ.
Centre-ville,
17
DR1
parallaxes
andpropermotionstolocatetargets
intheHertzsprung-Russell
diagramtocomputeVLA
J043001.15+351724.6,
wasdetectedatfourepochsasasingleradiosource.
The
best
fit andto itsdisplacement
on
Str.H3C
77,3J7,50937
Köln,6 Space
Germany;San
JoseInstitute,
State University,
One Washington
Square,
San
Jose,
CA
1Zülpicher
Montréal,
QC
Canada;Telescope
Science
3700
San
MartinDrive,
Baltimore,MD
21218,
Sternberg
AstronomicalInstitute,
Moscow
M.V.
Lomonosov
University,
Universitetskij
pr.,13,
119992,18 skythespacevelocity
componentsof theyoungest
objects.
We 725
findStatea thatremarkable
percentage
(atto
least
35
%) Moscow,of101
binaries
the
plane
of
the
yieldsadistanceof
535±29
pc.
We
argue
this
is
the
distancethe
LkHα
cluster.
7 USA;
95192,
BostonUniversity
Astronomy
Department,
CommonwealthAvenue,Boston,MA
02215,
USA;
USA; Departmentof Astrophysics,
AmericanMuseum ofto
NaturalHistory,Star-forming
Central Park West Regions.
at 79th St., New
York, The LkHα
VLBA
DeterminationoftheDistance
NearbyVIII.
Russia19
20
andmultiplesystems.
On UTINAM,
the basisof theTHETA,
lithiumabundance,
theSocorro,sample ofsingle
stars
and
SB1
systems appears to
8
National
Radio
Astronomy
Observatory,
1003
Lopezville
Rd,
NM
87801
USA;
Max-Planck-Institut
NY10024,
USA;
Institut
OSU
Univ.
Bourgogne
Franche-Comté,Besançon,
France101
cluster
Accepted
by 60
ApJ
21
be
mostly(∼%)
composed
of at
stars
youngerthanthe membersof ALMA
the UMa
cluster. The
remainingsources3107,
are inE-mailcontact:samsebedodin
gmail.com
fürextraterrestrische
Physik,D-85748
Garching,
Germany;
Joint
Observatory,
AlonsodeCórdova
E-mail Dzib
contact:
1 jgagne at carnegiescience.edu
1,2
3,4
5
3
22
S.A.
,
G.N.
Ortiz-León,
Laurent
Loinard,A.J.
Mioduszewski,
L.F.
Rodrı́guez, S.-N.X.
the
age
range
betweenthe
UMa
andHyadesclusters
(∼
20
%)
or
older
(∼
20
%).
In
total,
we
identify
42
very
young
http://arxiv.org/pdf/1801.05231
Vitacura, Santiago, Chile;
National Astronomical Observatory of Japan, Alonso de Córdova 3788, 61B Vitacura,The
structure
spectrumof theaccretionshock
haveofbeen
self-consistently
simulated
forpca widerange
of parameters1Σ is aand6 algorithm
BANYAN
new
Bayesiantoidentify
members
young
stellarassociations
within
150
of
the
Sun.
Medina,R.M.
Torres(PMS-like)stars,
which
lie
above
or
very
close
to
the
Pleiadesupper
envelopeofthelithiumabundance.
Asignificant
Santiago, Chile
typicalfor(∼Classical
Tevolved
Tauri stars
Stars(CTTS).
cooling
ofmodelled
the shockedgas wascalculated,takingaccount
It includes
27
young
associations
with(giants
ages in andtheRadiative
range ∼1–800
Myr,present
withsample.
multivariate
Gaussians
in 6- (∼into
percentage
12%)ofsubgiants)
is
also
in
our
Some
of
these
stars
36
%)
1
2
3
Max-Planck-InstitutfürRadioastronomie,
Aufdem
Hügel69,
D-53121
Bonn,
Germany;
Humboldt
Fellow;
E-mailcontact:
aginsburatnrao.edu
dimensional
XYZUVW
space.
It1.4).
is theof
firstsuchmulti-association
classification
tool
toincludethe nearest
sub-groups
theself-absorption
andnon-equilibrium(time-dependent)
eﬀectsin thepopulations.
These
eﬀects modify
theA
spectroscopic
surveytheyoungest
field
stars
in levelthesolarneighborhood.
II. Thearealsolithiumrich (A(Li)>4
InstitutodeRadioastronomı́ayAstrofı́sica,
Universidad
Nacional
AutónomadeMéxico,Morelia
58089,
Mexico;′′protostars
on
the
CO
to
H
conversion
factor,X,
asafunctionofcluster
size,
gas
mass
and
star
formationeﬃciency.
ofthe
Sco-CenOB
star-forming
region,
the
IC
2602,
IC
2391,
PleiadesandPlatais8
clusters,
andtheρOphiuchi,
2 anwith
CO5 at 3 instandard
curvefor
opticallythin∼0.
plasmacoronalequilibrium,
howeverthetheshapeof high-temperature
We reportcoolingALMA
observations
resolution
mmof the extended
Sgr B2cloud inCentral
Molecular
optically
faintsampleAcceptedbyAX&
AhasTaurus
InstitutodeAstronomı́a,
Universidad
Nacional
de México,
Apartado
Postal70-264,
CdMx
C.P.
04510,
Coronaandstar-formation
regions.
AAutnomamodel
of fieldstars
is built
fromaAU.
mixtureof multivariate
5We
We
find
that
a of
weak
dependence
on theFUV
radiationfromembeddedsourcesforus
large
clustersdue
to highCO
Zone(CMZ).
detect271
compact
sources,
most
of
which
are
smaller
than
5000
By
rulingout
alternative(T>
3Australis,
×
10
K)
part
the
curve
remains
unchanged.
Theappliedmethodsallow
tosmoothlydescribe
the
1
2
1
2
1
16
3
5
A.
Frasca,weP.on
Guillout, A.
Klutsch, R.TheFreireFerrero,Socorro,
E.membership
Marilli,87801,
K. Biazzo, D.
Gandolfi
and D.
Gaussians
basedtheRadio
Galactic
model.
algorithm
canprobabilities
objects
Mexico;National
Astronomy
Observatory,P.O.
Box0,derive
NM
USA;
CentroUniversitario
cloud
opticaldepths.
InBesançonsmallerandmore
eﬃcient
clusters
theembedded
FUV
increasesX
to forlevelsconsistent
withCO
https://arxiv.org/pdf/1801.00671
possibilities,
concludethatthesesourcesconsistofamixofhypercompact
HII
regionsandyoungstellarobjectstransition
fromthecoolingflow
tothehydrostatic
stellaratmosphere.
Thankstothisapproach,
it
has
been
found
4
withTonalá,
only skyUniversidad
coordinatesandpropermotion,but
can also
includeparallax
andradialvelocity
measurements,
as wellaltered,
Montesdede
Guadalajara,
Avenida
Nuevo
Periférico
No.
555,
Ejido
Dan
José
Tatepozco,
C.P.
48525,
theaverageMilkyWayvalues.
The
internal
physicalandchemicalstructure
of
the
cloud
are
significantly
and(YSOs).
Mostof
the
newly-detectedsources
are
YSOs
with
gas
envelopes
which,
based
on
their
luminosities,
must
that
the
narrow
component
of
He
II
lines
is
formedpredominantly
intheirradiatedstationary
atmosphere(hotspot),as spectrophotometricdistance
constraints
fromsequencesinfor
color-magnitude
or clouds.
spectral type-magnitude diagrams.
>X
depends
strongly
ontheprotostellar
clustermasssmall
eﬃcient
Jalisco,México1Tonalá,−1COcontainobjectswithstellarmasses
M
8
M
.
Their
spatialdistribution
spreadoverregion
aItaly∼ 12×3
pc region demonstrates
∗<
⊙s
INAF
Osservatorio
AstrofisicodiCatania,
via
S.
Sofia,
78,
95123
Catania,∼i.e.
atvelocitiesofthesettling
gas
2
km
.
The
structureofthepre-shockis
calculated
simultaneously withBANYANΣ forbenefitsfrom an analyticalsolutionLuminosities
to the Bayesian marginalization
integrals thatmakes
it more accurateA
Model
Protostellar
ClusterandtheImpactonthe
CO-H
Conversion
2 protocluster
2E-mail
that
Sgr
B2
is
experiencing
anextendedstarformation
event,
notjustanisolated‘starburst’
withinthe
Acceptedby
ApJ
contact:
sdzibthanat mpifr-bonn.mpg.de
Universitéde Strasbourg,
Observatoire
astronomiquede Strasbourg,
7550,
F-67000
Strasbourg,
Francetheheatedatmosphere.
Thesimulationshows thatpre-shockgas produces
a noticeable
emissioncomponentinandsignificantly
faster
itsCNRS,predecessor
BANYANII.
A thecontamination
versushit rateUMR
analysis
is presented
andFactor
Using
this
new
sample,weexaminestaritself
formation
thresholds
andsurfacedensityrelationsin Sgr B2.
While
3regions.
demonstrates
that
BANYANΣachievesabetterclassification
performance
than
other
movinggroupclassification
He
II
lines
and
practicallydoesnotmanifest
in
He
I
lines
(λλ
5876,
10830
Å).
The
UV
spectrumofthehotspotis
Dipartimento
diFisica,UniversitàdiTorino,via
P.
Giuria,1,
10125
Torino,Italy
http://arxiv.org/pdf/1801.08555
23
−2
The
LkHα
101
cluster
takes
its
name
from
its
more
massivemember,the
LkHα
101star,
which
is
an
∼15
M
star
1
1,2
>
⊙
cm ), list
notofallregionsof high column
allof especiallytheA.L.
YSOs
resideinregionsof highcolumndensity(Nassociations.
(H2 ) ∼ 2 × 10
BrandtGachesandStellaS.R.
Oﬀner
4distorted
tools,
interms
ofcross-contamination
betweenyoung
An
updatedbona
fidemembers
bynature
the pre-shockgas, ynamely
numerous
red-shifted
emissionandabsorption
lines
overlap28040
each
other
forming
Departamento
de isAstrofı́sica
Cienciasdela Atmósfera,
Universidad
ComplutensedeMadrid,Madrid,
Spain
whose
true
still
unknown.
The
distance
to
the
LkHα
101
clusterhas
beencontroversial
for
the
last
few
densitycontain
YSOs.
The
observedcolumndensity
thresholdforstarformationissubstantiallyhigherthan
that
1in the 27 young associations, augmented by the Gaia-DR1 release, are presented. 2This new tool will make it14possible−3
DepartmentofAstronomy,
UniversityofMassachusetts
Amherst,USA;
DepartmentofAstronomy,
University
offormedapseudo-continuum.
The
spectrumoftheaccretion
regionathighpre-shockdensities∼
10cm
is members
fullyadecades,median
FWHM
of
0.035
pc
systematicallynarrowerthanthepreviously
proposed
universal
0.1
pc
filament
width.
withestimatedvaluesranging
from
160
to
800
pc.
We
have
observedmembers
andcandidateofE-mailcontact:
antonio.frasca
atoact.inaf.it
insolar
vicinity
clouds,
implying
eitherthat
high-mass
star
formationrequiresahighercolumndensity
or
that
any
to
analyze
large
data
sets
such
as
the
upcoming
Gaia-DR2
toidentify
newyoungstars.
IDL
andPythonversionsof
BANYAN.
XI.
The
BANYANΣ
multivariate
Bayesianalgorithm
toidentify
members
Texas
at
Austin,USAinthein-falling
gas
and
can
be
qualitatively
describedasaspectrum
of
a
star
with
an
eﬀectivetemperature
derivedOur
ALMA
observations
revealcomplexbundlesoffibersintheISF,
suggestingstrongsimilarities
betweenthe internaltheLkHαcluster
with
signs
of
magnetic
activity,
the VeryArray, into density
measuretheirstarformationin theCMZ
mustbe higher
than using
in nearby
clouds.Long
The Baseline
relation between
theordersurface
BANYANΣ101
arethreshold
made available
with
this
publication.
Starformation
in
the
solar
neighborhood
ismainlytraced
by
young
stars
in
open
clusters,
associations,andin theofyoung
associations
within
150
pc
from
the
Stefan-Boltzmann
law
via
the
full
energyflux.
E-mailcontact:
neil.vaytet
atnbi.ku.dk
substructureofthismassivefilament
andpreviously
studiedlower-mass
objects.
The
fibersshow
identical
dynamic
ofgas andbystars
is incompatible
withobtain
extrapolations
from local clouds,
and instead
stellarin Sgr
B2 follow
trigonometricparallaxand, thus,
a direct measurementof theirdistances.
A densities
young starmember,LkHα 101
Accepted
ApJS
1,2 identified, for example,
3,4
5
6 The determination 6of stellar parameters
5 forfield,
which
can
be
byand
their
X-ray
emission.
JonathanGagné,Eric
E.
Mamajek
,
Lison
Malo
,
Adric
Riedel,David
Rodriguez,David
Lafrenière,propertiesinbothlowandhigh-mass
regions,
theirwidespreaddetectionsuggestsapreferredorganizationalalinearΣ–Σ
relation,shallower
thanthat
observed
inlocal
clouds.
Together,these
pointssuggestthatahigher∗by MNRAS
gas
AcceptedWe
constructasemi-analytic
model
to
study
the
eﬀect
of
far-ultraviolet(FUV)
radiationongaschemistryfrom
http://arxiv.org/pdf/1801.09051
7of X-ray sources is crucial
5
6
5
the
opticalcounterpartsfor a(width
fullCMZ
characterizationofself-regulated
these 8stars.
This work
extendstheJacquelineK.
Faherty,
Olivier
Roy-Loubier,
Laurent
Pueyo
,
Annie
C.
Robin
,
and
René
Doyon
volumedensity
thresholdisrequiredtoexplainstar
formationinclouds.
mechanism
of
gas
in
which
the
physicalfiber
dimensions
andlength)aredependingon
theirembedded
protostars. We use the Protostellar Luminosity Function (PLF) formalism of Oﬀner & McKee (2011) tohttps://arxiv.org/pdf/1801.02404
11the cross-correlation
spectroscopic
study ofthe RasTyc
sample, works,
obtainedbyof the
TYCHO
and
ROSAT
All-Sky1
2 of fibers
intrinsic
gas
density.
Combinedwithprevious
weidentifyasystematicincreaseofthesurfacedensity
Carnegie
Washington
DTM, luminosity
5241 BroadforBranch
NW, Washington,
DC 20015,
USA; sizes.
NASA
calculatethetotal,
ionizing cluster
variousRoad
protostellar
accretion histories
and cluster
AcceptedbyInstitution
ApJ FUV,ofand
Surveycatalogs,
to totalstars
fainterthan V = 9.5inmag
and aimsclouds.
toidentify
sparsepopulationsof young stars
in the solar
3 theDistributed
formation
throughout
theGalactic
Centercloud
Sgr
B2findasacomparefunction
ofstarmass
per-unit-lengthfilamentary
Basedon thisempirical
correlation,
we
propose
We
the
model
predictions
withsurveys
of
Gould
Belt
star-forming
regionsandtheTaperedTurbulent
Sagan
Fellow;
Jet
Propulsion
Laboratory,
California
InstituteofTechnology,
4800
Oak
Grove
Drive,
Pasadena,
http://arxiv.org/pdf/1801.04941
neighborhood.
We6253 ,ofhigh-resolution
for University
443
young
four
diﬀerent
instruments
1,2
4spectra4presumably
5,6stars with
7 etnaturally
4,acquired
5aunifiedstar-formation
scenario
wheretheobserved
diﬀerences
betweenlowandhigh-masscloudsemergeal.
Adam
GinsburgJohn
Bally
AshleyBarnes,Nate
Bastian,
Cara
Battersby,
HenrikBeuther
,
Core
model
matches
best
the
mean
luminosities
andthespread
in
the
data.
We
combinethecluster
model
with
the
CA
91109,
USA;
Department
Physics
andAstronomy,ofRochester,Rochester,NY
14627,USA;
VLBA DeterminationoftheDistance
to
NearbyStar-forming
Regions.
VIII.
The
LkHα
8
9
8,10 velocity (v sin i) of
3 our targets were
11 measured by means of theinthethenorthernhemisphere.
Theradialand3d-pdr,
rotational
frominitialconcentrationoffibers.
CrystalBrogan,YanettContreras,
JoannaCorby,
JeremyDarling
,
Chris
De
Pree
, Roberto
photo-dissociation
regionastrochemistrycode,
tocomputetheimpactoftheFUV
luminosity
from embedded
InstituteforResearchon
Exoplanets,
UniversitédeMontréal,DépartementdePhysique,
C.P.
6128
Succ.
Centre-ville,
101 cluster 12
13
7
8
14
cross-correlation
technique,
which
also
helpfultodiscoversingle-lined(SB1),
double-lined
spectroscopic
binaries
6 , isGalván-Madrid
,
Guido
Garay
JonathanHenshaw,
Todd
Hunter,J.M.
Diederik
Kruijssen
, MD
An
ALMA
study
of
the
Orion
IntegralFilament:
I.
Evidencefor
narrow
fibersinaMontréal,
QC
H3C
3J7,
Canada;Space
Telescope
Science
Institute,
3700
San
MartinDrive,
Baltimore,
21218,
Accepted
by1 ,A&A
1,2
5
3
4
15
16 Loinard3,4 , A.J. Mioduszewski
17,18
19
S.A.
Dzib
G.N.
Ortiz-León,
Laurent,
L.F.
Rodrı́guez, S.-N.X.
StevenLongmore
,
Xing
Lu
,
Fanyi
Meng
,
Elisabeth
A.C.
Mills
,
Juergen
Ott
,
Jaime
E.
(SB2),
multipleofsystems.
We usedthe code
ROTFIT
to perform
anCentral
MK spectralclassification
andtodetermine
massive
cloud
USA; 7 andDepartment
Astrophysics,
AmericanMuseumof
NaturalHistory,
Park
West
at
79th
St.,
New
York,
201
16
16
16,20
4,21,22612
http://arxiv.org/pdf/1801.01500
Pineda,ÁlvaroSánchez-Monge,
Peter
Schilke,
Anika
Schmiedeke,
DanielWalker, For
andtheseMedina,R.M.
Torres8
theatmospheric
(T
,
log
g,
[Fe/H])
and
v
sin
i
of
the
stars
and
systems.
1 USA; parameters
2
3,4
5 Univ.
5 single
5SB1
5,6 objects, weeﬀ
NY
10024,
Institut
UTINAM,
OSU
THETA,
Bourgogne
Franche-Comté,Besançon,
France
A.
Hacar
,
M.
,
J.
Alves
,
S.
Meingast,
J.
Grossschedl
,
and
P.S.
Teixeira
5 Tafalla , J. ForbrichWilner1Davidused
thespectral subtractionof slowly rotating
templates
to measure
the equivalent
widthsof2 theHα andFellow;
Lii 67083 Å
Max-Planck-InstitutfürRadioastronomie,
Aufdem
Hügel69,
D-53121
Bonn,
Germany;
Humboldt
12E-mailcontact:
jgagneat carnegiescience.edu
1 Leiden
2 AstroObservatory,
LeidenUniversity,
P.O. Box
9513, 2300-RA
Leiden, The
Netherlands;
Observatorio
Janskyfellowofthe
National
Radio
Astronomy
Observatory,
1003
Lopezville
Rd,
Socorro,
NM
87801
USA;
4
lines,
whichenabledustoderivetheirchromosphericactivitylevel
andlithiumabundance.
We
made
use
of
Gaia
InstitutodeRadioastronomı́ayAstrofı́sica,
Universidad
Nacional
AutónomadeMéxico,Morelia
58089,
Mexico;3Onthe
RotationofStarsMadrid,3
nomicoNacional(IGN),
C/Supermassive
Alfonso
XII, 3,toE-28014,
Spain;
CentreAstrophysics
Research,
University
EuropeanSouthern
Observatory,Karl-Schwarzschild-Straße
2, D-85748
Garching
beiforMünchen,
Germany;CASA,
BANYANΣisanew
Bayesianalgorithm
identify
membersofyoungstellarassociations
within
150
pc of
the
Sun.
DR1
parallaxes
andpropermotionstolocatethetargets
intheHertzsprung-Russell(HR)diagramandtocomputeInstitutodeAstronomı́a,
Universidad
Nacional
AutnomadeMéxico,Apartado
Postal70-264,
CdMx
C.P.
04510,
4
4
1
2
3,4
2
5
of
Hertfordshire,College
Lane,
Hatfield,
AL10
9AB,
UK;
Harvard-Smithsonian
Centerfor
Astrophysics,
60
GardenUniversityofColorado,
389-UCB,
Boulder,CO
80309,USA;
Astrophysics
Research
Institute,
LiverpoolJohn
MooresLionelHaemmerlé,Tyrone
E.
Woods
,
Ralf
S.
Klessen,Alexander
Heger
andDanielJ.
Whalen
It includes
27 young
associations
with ages
in therange∼1–800Myr,modelled
withmultivariate
Gaussiansin binaries
65 velocity
6 leastthe
space
components
objects.
Wefindaremarkable
percentage
(at
%)
of
5of the youngest
6 35 Universitario
5
Mexico;National
Radio
Astronomy
Observatory,
P.O.
Box
0,
Socorro,NM
87801,
USA;
CentroUniversity,
146
Brownlow
Hill,
Liverpool
L3
5RF,
Harvard-Smithsonian
Centerfor Astrophysics,
60 nearest
GardenScottish
Cambridge,
MA 02138,
USA;
Universityof UK;
Vienna,Türkenschanzstrasse
17, A-1180
Vienna,Austria;
1St,
2dimensional
XYZUVW
space.
It
is
the
first
such
multi-association
classification
tool
toincludethesub-groups
ObservatoiredeGenève,
UniversitédeGenève,chemindesMaillettes
51,
CH-1290
Sauverny,
Switzerland;
Monashandmultiplesystems.
On
the
basis
of
the
lithiumabundance,thesampleofsingle
stars
and
SB1
systems
appearsdeTonalá, Universidadde (SUPA),
Guadalajara,
Avenida
Nuevo
Periférico University
No. 555, Ejido
Dan JoséNorth
Tatepozco,
C.P.
48525,toUniversities
Physics
Alliance
SchoolofPhysics
andAstronomy,ofSt.
Andrews,
Haugh,
St.
of the Sco-Cen
OB star-forming
region,the and
IC 2602,
IC 2391,
Pleiadesand Platais
clusters,
and the 3ρ Universität
Ophiuchi,Centrefor Astrophysics,
School of
Physics
Astronomy,
MonashUniversity,
VIC8 3800,
Australia;

mass
must
be
determinedindirectlybyassumingafixed
During star formation, knowdust-to-gas
ratio
or
some
simplerelationshipbetweenssitated A
byModelunderstanding
thefor Protostellar Cluster Luminosities and the Impact on the CO-H2 Conversion
17
H
andanothermolecular
species.
The
mostcommon2
Factorconversion
is
X
,
which
is
definedasCO
1
1,2
mposed primarily of molecular
Brandt A.L. Gaches and Stella S.R. Oﬀner

1no permanent dipole,2
H2 hasCluster
DepartmentofAstronomy,
UniversityofMassachusetts
Amherst,USA;
NH2 Department of Astronomy, University ofの光度のモデル構築、
XCO =
,
(1)
Texas at Austin, USA
WCO
XCOのcluster のパラメータに対する依存性を調べた

E-mail contact: neil.vaytet at nbi.ku.dk

モデル：星への降着で3種類

We construct a semi-analytic model
to studyof far-ultraviolet
radiationhydrogenon gas chemistry fromwhere
NH2theis eﬀect
the column
density (FUV)of molecular
Inside out(Shu 1977)
embedded
protostars.
We use the Protostellar
Functionformalismof Oﬀner& McKee (2011) to
降着率は温度のみに依存
in units ofLuminosity
cm 2 and
WCO(PLF)
is theintegrated
intensity
calculate
the Core
total, FUV,and &ionizing
cluster luminosityfor various protostellar accretion histories and cluster sizes.
Turbulent(McKee
Tan
2003)
1
Mstar
大ほど降着率大
in
K
km
s
.
The
typical
Milky
Way
value
is
X
=
CO
We compare the model predictions with surveys of Gould Belt star-forming regions and find the Tapered Turbulent
Tapered TC (Oﬀner & McKee 2011) 星形成が終了に近づくと降着率低下
9Core model matches best the mean luminosities and the spread in the data. We combine the cluster model with thephoto-dissociation region astrochemistry code, 3d-pdr, to compute the impact of the FUV luminosity from embedded
12

観測とモデルを比較
TTCが観測をもっとも良く再現TCだとN~10-100で過大評価

COlower dust extinction within the cloud. These clouds
have significantly less CO emission compared to their H2column density, i.e., they have a larger fraction of “CO星質量、星形成効率に対するXcoの依存性
dark” gas (i.e. Wolfire et al. 2010). Typically, CO-darkclouds are assumed to have faint CO emission due to
白線：典型的なXco,
点線が30%error
their
low densities, but the gas here
is CO deficient due
to dissociation caused by the embedded sources. Conse白帯が典型的な星形成効率
quently,
the MW average values occupy only a narrow
band across the parameter space. Within the range oftypical star formation efficiencies, XCO is only consistentfor clusters with masses between 103 - 104 M .
XCO：大きなClusterではMstar大で微減
Prior work has also found that XCO is sensitive tothe gas density (Bell et al. 2006; Shetty et al. 2011).
Mstar大でFUV大Densities
higher than 103 cm 3 make dust extinction
more efficient, while lower densities enhance the e↵ect
COのdissociation と温度の上昇がcancel してXcoの変化は小さい
embedded clusters since more of the cloud is influ14
Gaches & ofOffner
enced by photochemistry. Our models predict XCO is
一定、Mstar大ならビリアル速度大mosteﬃciency
sensitive to density
for clouds forming small clusFigure 10.
Contour plot of XCO as a function of the fiters with high star formation efficiencies. However, thisnal star cluster mass, M⇤ , and the efficiency, "g , for model→線幅が広がりCOの積分強度が増加、Xcoが減少
trend may not be evident in observations since di↵use
CE 1000D V 1⇠. The color scale indicates the logarithm of
XCO normalized by 1020 . The white solid contour is the typclouds are less likely to form stars with high efficiencies.
ical Milky Way XCO and the white dotted contours are the
30% error bars (Bolatto et al. 2013). The horizontal whiteband marks the star formation efficiency estimated for local
Gould Belt clouds (Dunham et al. 2013).

vey of Gould Belt clouds. Within the band, a significant
amount of the parameter space is consistent with thelocal Milky Way average XCO (in white contours). Furthermore, XCO is nearly constant for moderate cluster
sizes, so our model predicts the Milky Way average isrepresentative of local molecular clouds. The model also
predicts XCO decreases by a factor of 5-10 in the largest
clusters due to the increase in turbulent linewidth.
3.3.4. Mean Gas Density

3.3.5. Turbulent Velocity Dispersion
The turbulent内からのFUVを考慮、下では無視
velocity dispersion is an important fac上がCluster

tor in the calculated CO emission due to its influenceon the line width and, hence, the optical depth. The
典型的な値までXcoを上げるには中からのFUVの寄与が必要
line opticaldepth for a given line of sight is inversely
proportional to the velocity dispersion. There is ample evidence
that higher mass clouds have greater ve星からの寄与が最大で10倍程度Xcoを増加させる
locity dispersions and that many clouds are close tovirial equilibrium (Heyer & Dame 2015). Although aconstant linewidth model is unphysical, it is useful to
examine the importance of velocity information. In thissection, we study the e↵ects of the turbulent velocity dis-

20

An ALMA study of the Orion Integral Filament: I. Evidence for narrow fibers in a
massive cloud
A. Hacar1 , M. Tafalla2 , J. Forbrich3,4 , J. Alves5 , S. Meingast5 , J. Grossschedl5 , and P.S. Teixeira5,6
1

Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands; 2 Observatorio Astro重い Filament (Integral Shape Filament (ISF), M̲line~500Msun/pc)のnomico Nacional (IGN), C/ Alfonso XII, 3, E-28014, Madrid, Spain; 3 Centre for Astrophysics Research, University
4
substructure
A&A proofs: manuscript no
A&A proofs:9AB,
manuscriptUK;
no. Hacar_ISF_ALMAof Hertfordshire,(ﬁber)の観測→55本同定
College Lane, Hatfield, AL10
Harvard-Smithsonian Center for Astrophysics, 60 Garden
St, Cambridge, MA 02138, USA; 5 University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria; 6 Scottishw+
Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North Haugh, St.
tofi
H
Andrews, Fife KY16 9SS, UK

A. Hacar et al.: An ALMA study of the Orion Integral Filament: I. Evidence for narrow fibers in a massive cloudE-mail contact: hacar at strw.leidenuniv.nl
Are all filaments bundles of fibers? To address this question, we have investigated the gas organization within theparadigmatic Integral Shape Filament (ISF). We combined two new ALMA Cycle 3 mosaics with previous IRAM 30m
observations to produce a high-dynamic range N2 H+ (1–0) emission map of the ISF tracing its high-density material
and velocity structure down to scales of 0.009 pc. From the analysis of the gas kinematics, we identify a total of 55
dense fibers in the central region of the ISF. Independently of their location, these fibers are characterized by transonicinternal motions, Fig.
lengthsof ∼0.15 pc, and masses per-unit-length close to those expected in hydrostatic equilibrium.
5. Statistical properties of the ISF fibers (orange shaded area): (Left) Total fiber length; (Centre) average line-of-sight, non-thermal velocity
as a function of the local sound-speedc (T ); and (Right) total mass-per-unit length. The individual fiber propertiesmass
in OMC-1
左：乱流の速度分散/音速，右line
The ISF fibers aredispersion
spatiallyorganized
formingadensebundlewithmultiple
hub-like
associations likely shaped by the
and OMC-2 are highlighted by blue and red dashed lines, respectively.
local gravitational potential. Within this complex network, the ISF fibers show a compact radial emission profile with
NT

s

K

Table 1. Dense gas properties

ISF
OMC-1
N2 H+ fits (S/N 3)
25078
13305
TK (K)(a)24.8±10.3 29.0±12.5
0.294
0.318
hc s (TK )i (km s 1 )V (km s 1 )
0.607
0.722
0.240
0.288
h NT i (km s 1 )
0.81
0.91
h NT /c s (T K )i
76.4%
68.4%
NT /c s (T K )  1
1 < NT /c s (T K )  2
20.0%
25.7%
/c s (T(Left)
2K ) >SCUBA-850
Fig. 4. Main axis of the 55 fibers identified by our HiFIVE analysis along the ISF (red NT
segments).
µm3.6%
continuum emission 5.9%

OMC-2
11773
20.1±2.2
0.267
0.477
0.185
0.69
85.5%
13.6%
0.9%

ple gas components and local velocity gradients typically unresolved within a single-dish beam. We illustrate this e↵ect in
Fig. 6 by comparing the emission in a single position recovered
using di↵erent e↵ective beam sizes. At the native ALMA resolution (red spectrum; upper panel), the observed N2 H+ emission
shows three independent narrow lines, clearly separated in thehyperfine isolated component (grey dashed segments). Due tothe complex gas kinematics within this region, the above line
substructure is progressively smeared out when convolved withneighbouring positions to the resolution of previous single-dishstudies (e.g., blue spectrum; central panel). Dilution and blending e↵ects give the appearance of a single broad component at

14・亜音速乱流が効いている。
・約半分が重力で束縛されている。

+

Fig. 8. (Upper) Mass-per-unit-length (Mlin ) of the OMC-1 (blue dots)
and OMC-2 (red dots) fibers as function of their internal non-thermalvelocity dispersion normalized by the local sound speed ( NT /c s (T K )).
This plot includes the expected critical masses (mcrit ) for an infinite filament in hydrostatic equilibrium at temperatures of 10 K (thick dashedline), 20 K (dashed-dotted line), and 30 K (thick dotted line), respectively (see Eq. 3). (Lower) Individual critical mass ratio (Mlin /mcrit ) for
all the fibers in OMC-1 (blue) and OMC-2 (red). For every single fiber
the critical mass ratio is calculated relative to its local mcrit (T K , NT ).
The error bars indicate the factor of two uncertainties associated to our
Mlin estimates.

Critical line massとの比較

p
te
p
p
a
a
ti
IS
sh
th

d
to
E
e
IS
0
g
o
ti
ra
d
&
a
a
W
ti
u
g
In
a
o

3

A&A proofs: manuscript no. Hacar_ISF_ALMAﬁber の幅〜0.035pc<0.1pc

Fig. 10. Observed fiberA.FWHM
theAn
ISF.ALMA(Left) Median(redline)Integral
and minimum-maximum(red shadedarea) FWHM
obtained cloud
Hacaralong
et al.:
study ofthesolid
Orion
Filament: I. Evidence
for narrowfibersvalues
in a massivein each fiber. (Right) Total FWHM values (576 data points; red histogram) measured along the ISF fibers. The total median value of 0.035 pc(blue dashed line) in comparison with the ALMA 0.009 pc beamsize (grey dotted line) are indicated in both panels.

continuity between the di↵erent star-formation scenarios classically distinguished in the literature (see arrows in this figure).
highly idealized, it is instructive to compare the expected varia- unit-lengths (right)
both aOMC-1
and OMC-2Ratherinthan
distinct(blue)
physicalprocessregions(i.e., qualitative change),tions of the scale height of a filament in hydrostatic equilibrium (red). We also list the mean and 1- dispersion values in Table 2
in cloudsdi↵erences
like Orion(H0 ) as function of the gas temperature (TK ), non-thermal mo- (see col. 2 andthe
3). origin
Overall,ofweclusters
find no systematic
be- would be then explained asa scaled-up
version(i.e.,
quantitativechange) of those
tions ( NT ), and density (n(H2 )) (Ostriker 1964):
tween these properties
along
the ISF. On
average,both
OMC-1
low-mass,regions formingstars in isolation. Moressand OMC-2 regions
have Taurus-likefibers with statisticallysimilar length,
2 2e f fover, theof the above
networks introduces anvelocity dispersion,and detection
mass per-unit-length.
Minorfiber
variations
c s (T K )2 + 2NT
H0 (T K , n(H2 )) =/.
(4) are, however,observational
apparent in Figures
5 (left) and5 (centre).
Thelink between
lowand high-massstar-formation⇡ G n(H2 )n(H2 )
OMC-1 fibersmechanisms.
appear to show
larger velocity
dispersions andand forming low-mass
Individually
fragmenting
Following this equilibrium solution, denser filaments are thus gradients than those in OMC-2 (see additional parameters in Tathese fibers would likely collide and merge in compact
expected to show narrower radial configurations. For the ISF ble 2). Whilecores,
appealing, these di↵erences are found within the
networks
thebe
formationof as
localized
fibers, and consistent with our line opacity measurements (see 1- dispersion
estimatespromoting
and can only
considered
tenta- high-mass, superoverdensities
also Hacar
et al.are2017b). Interestingly,
Appendix B.3), we find typical gas densities of n(H2 ) ⇠ 107
tive. Despite Jeansthese local
variations, (seethe observed
ISF fibers
108 cm 3 assuming a cylindrical symmetry and the previously found to present
thisroughly
emergent
behaviourwould
be naturally
uniform
properties
regardlessof theirfavoured by the muderived Mlin and FWHM values (see Table 2). These estimates local environment.
tual gravitational attraction between fibers in densely populatedare (at least) 2 orders of magnitude higher than the densities meaenvironments explaining the formation of massive objects at theMorphologically speaking, the ISF fibers are distributed insured for typical low-mass filaments in clouds like IC5146, Pocentre of hub-like associations (Sect. 3.5).
laris, or Taurus. According to Eq. 4, the observed radii in both the multiple hub-like associations (Myers 2009) in both OMC-1 andTheseenabove
unifiedfiber
scenarioin Fig.
4, mostOMC-1
fibersprovides
are ori- a direct prediction
ISF fibers (TK ⇠ 25 K; NT = c s (25K); n(H2 ) = 108 cm 3 ) and OMC-2 regions. As
future observations.
According
to Fig.
converging
towards the OMC-1
South region(see 12, high-mass starHerschel filaments (e.g., Herschel: TK =10 K; NT = c s (10K); ented radiallyfor
formingwith M(total)500 M pc 1 are expected
et al.filaments
1992; Wiseman& lin
Ho1998). Althoughn(H2 ) = 5 ⇥ 105 cm 3 ) are expected to show a size dependency Rodriguez-Franco
Fig. 12. Empirical⇠correlation
betweenthe from
total filament
mass-per-unitpartially recovered
our fiber into
analysis,similarfan-like
to beinresolved
dense
bundlesof arrangefibers in which ⌃(fertile) &such that H0H(Herschel)
9.
Althoughdeviatingthesesim(ISF)0length (Mlin (total)) and the obtained surface
density of fertile
fibers2 be recognized at smaller scales towards
ments
of fibers
FWHM(Herschel)
50canpcalso. Following our results in Orion (see 3.4), these compact

ﬁber の密度とtotal massが2桁の範囲で比例？
ﬁber の密度が星・コアの面密度と正の相関 (Hacar+2017)

Low-mass とHigh-massの星形成メカニズムについての
uniﬁed theory がありそう

21 On the Rotation of Supermassive Stars
Lionel Haemmerlé1, Tyrone E. Woods2 , Ralf S. Klessen3,4 , Alexander Heger2 and Daniel J. Whalen5
1

42
ObservatoiredeGenève,
UniversitédeGenève,chemindesMaillettes
51,
CH-1290
Sauverny,
Switzerland;
Monash大質量初代星形成での自転の進化を調べたCentre for Astrophysics, School of Physics and Astronomy, Monash University, VIC 3800, Australia; 3 Universität輻射＋遠心力＜重力が必要(ΩΓ-limit)、大質量星は輻射力大→回転が小さい必要がある。
Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidel4
berg,
Germany;
Universität Heidelberg, Interdisziplinäres Zentrum für Wissenschaftliches Rechnen, Im Neuenheimer
回転を考慮した星の進化計算
Feld 205, D-69120 Heidelberg, Germany; 5 Institute of Cosmology and Gravitation, University of Portsmouth, Dennis
convective
regionでは剛体回転、radiative
regionではシアと子午面環流による角運動量輸送を考慮
Sciama Building, Portsmouth
PO1 é3FX,
L. Haemmerlé et al.
L. Haemmerl
et al.4UK

E-mail contact: lionel.haemmerle at unige.ch
Supermassive stars born from pristine gas in atomically-cooled haloes are thought to be the progenitors of supermassive
black holes at high redshifts. However,
the way they
accrete theirmass is still an unsolved problem. In particular,
M<500Msun
dJ/dM~1%of Kepler
for accretion to proceed, a large amount of angular momentum has to be extracted from the collapsing gas. Here,
M>500Msun
dJ/dM~0.3%
of Kepler
we investigate the constraints stellar
evolution imposeson this angularmomentum problem. We present an evolution
5Msun まで進化可能
model of a supermassive Population
III star including
simultaneously accretion and rotation. We find that, for
であれば>10supermassive stars to form by accretion, the accreted angular momentum has to be about 1% of the Keplerian angularmomentum. This tight constraint comes from the ΩΓ-limit, at which the combination of radiation pressure andcentrifugal force cancels gravity. It implies that supermassive stars are slow rotators, with a surface velocity less than収縮とともに中心の回転速度増加
10 – 20% of their first critical velocity,at which the centrifugal
force
alone
cancels
gravity.
At
such
low
velocities,
thecritical limit
deformation of the star due to rotationis negligible.
表面より4桁以上速い回転速度
critical limit
Accepted by ApJL

剛体回転を仮定するよりも
https://arxiv.org/pdf/1711.09916.pdf
ΩΓ-limitの条件が緩和される

The stellar IMF from Isothermal
MHD
Turbulence
Figure 2. Di↵erential
rotationin the star, for the samemodel as Fig. 1. The upper panel shows again the stellar

1Sternberg Astronomical Institute, Moscow M.V. Lomonosov State University, Universitetskij pr., 13, Moscow, 119992,
The structure and spectrum of the accretion shock in the atmospheres of young stars
14 Russia
Alexandr Dodin1
E-mail contact: samsebedodin at gmail.com
1
Sternberg Astronomical Institute, Moscow M.V. Lomonosov State University, Universitetskij pr., 13, Moscow, 119992,
The structure and spectrum of the accretion shock have been self-consistently simulated for a wide range of parameters
Russiatypical for Classical T Tauri Stars (CTTS). Radiative cooling of the shocked gas was calculated, taking into accountE-mailcontact: samsebedodin
at gmail.com
theself-absorption
and non-equilibrium(time-dependent) eﬀects in the level populations. These eﬀects modify thestandard
cooling
for anthinshockplasmain beencoronalequilibrium, simulated
however theof high-temperature
The structure
andcurve
spectrumof opticallythe accretionhave
self-consistently
for ashapewide rangeof parameters
5
(T
>
3
×
10
K) partof theStars
curve(CTTS).
remainsRadiative
unchanged.
Theofapplied
methods
allow
us to smoothly
describethetypical for ClassicalT Tauri
cooling
the shockedgas wascalculated,taking into
accounttransition
from the andcooling
flow to the hydrostatic
stellar eﬀects
atmosphere.
to this approach,it has modify
been foundthe self-absorption
non-equilibrium(time-dependent)
in the Thanks
level populations.
These eﬀects
thethat
the narrowof He
II linesthin
is formed
in the irradiated(hotspot),
standard
coolingcomponent
curve for an
optically
plasmapredominantly
in coronal equilibrium,
howeverstationary
the shapeatmosphereof high-temperaturei.e.
of the< 2remains
km s−1 . unchanged.
The structureof thepre-shockregionis calculated
simultaneously(T at> velocities
3 × 105 K)
partsettlingof the gas
curve
The
appliedmethods
allow
us to smoothly
describe withthetheheated fromatmosphere.
Theflowsimulationshows that stellar
the pre-shockgas produces
a noticeable
emissiontransition
the coolingto the hydrostatic
atmosphere.
Thanks tothis approach,it hascomponent
been foundinthat
the narrowcomponentof He
lines is formedin the10830
irradiatedstationary
atmosphereHe
II lines
and practically
does
notIImanifest
itself inpredominantly
He I lines (λλ 5876,
Å). TheUV spectrumof the(hotspot),
hotspot is
i.e. at velocitiesof the settling< 2 kms−1 . The
structure emissionof the pre-shock
region is lines
calculated
simultaneously
withdistortedby the pre-shockgas, gas
namelynumerous
red-shifted
and absorption
overlap
each other forming
14
heated atmosphere.
simulation
showsthat thepre-shockgas
producesdensities
a noticeable
componentinathe
pseudo-continuum.
TheThespectrumof theaccretion
regionat highpre-shock∼ 10emission
cm−3 isfully formed
II lines
and practicallydoesmanifest itself
in He Iaslines(λλ 5876,of10830
TheanUV
spectrumof the hotspot
isinHethein-falling
gas and canbe notqualitatively
described
a spectrum
a starÅ).
with
eﬀectivetemperature
deriveddistortedby the pre-shock gas,emission and absorption lines overlap each other forming
fromthe Stefan-Boltzmann
law namely
via the numerous
full energyred-shifted
flux.
a pseudo-continuum. The spectrum of the accretion region at high pre-shock densities ∼ 1014 cm−3 is fully formed
Accepted by MNRAS
in the in-falling gas and can be qualitatively described as a spectrum of a star with an eﬀective temperature derived
https://arxiv.org/pdf/1801.02404
from the Stefan-Boltzmann law via the full energy flux.
Accepted by MNRAS

VLBA
Determination of the Distance to Nearby Star-forming Regions. VIII. The LkHα
https://arxiv.org/pdf/1801.02404
101 cluster
S.A. Dzib1 , G.N. Ortiz-León1,2 , Laurent Loinard3,4 , A.J. Mioduszewski5 , L.F. Rodrı́guez3 , S.-N.X.

15 VLBA Determination of the Distance to Nearby Star-forming Regions. VIII. The LkHα
101 cluster

S.A. Dzib1 , G.N. Ortiz-León1,2 , Laurent Loinard3,4 , A.J. Mioduszewski5 , L.F. Rodrı́guez3 , S.-N.X.
Medina1 , R.M. Torres6
1

Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany; 2 Humboldt Fellow; 3
Instituto de Radioastronomı́a y Astrofı́sica, Universidad Nacional Autónoma de México, Morelia 58089, Mexico; 4
Instituto de Astronomı́a, Universidad Nacional Autnoma de México, Apartado Postal 70-264, CdMx C.P. 04510,
Mexico; 5 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801, USA; 6 Centro Universitariode Tonalá, Universidad de Guadalajara, Avenida Nuevo Periférico No. 555, Ejido Dan José Tatepozco, C.P. 48525,
Tonalá, Jalisco, México
E-mail contact: sdzib at mpifr-bonn.mpg.de
The LkHα 101 cluster takes its name from its more massive member, the LkHα 101star, which is an ∼15 M⊙ star
whose true nature is still unknown. The distance to the LkHα 101 cluster has been controversial for the last few
decades, with estimated values ranging from 160 to 800 pc. We have observed members and candidate members of
the LkHα 101 cluster with signs of magnetic activity, using the Very Long Baseline Array, in order to measure their
trigonometric parallax and, thus, obtain a direct measurement of their distances. A young star member, LkHα 101
VLA J043001.15+351724.6, was detected at four epochs as a single radio source. The best fit to its displacement on
the plane of the sky yields a distance of 535±29 pc. We argue that this is the distance to the LkHα 101 cluster.
11
Accepted by ApJ
http://arxiv.org/pdf/1801.05231

A spectroscopic survey of the youngest field stars in the solar neighborhood. II. The

16

1

INAF - Osservatorio Astrofisico di Catania, via S. Sofia, 78, 95123 Catania, Italy
2A spectroscopic survey of the youngest field stars in the solar neighborhood. II. The
Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, F-67000 Strasbourg, France
3optically faint sample
Dipartimento di Fisica, Università di Torino, via P. Giuria, 1, 10125 Torino, Italy
4
Departamento
Astrofı́sica
Ciencias 1dela Atmósfera,
Universidad
Complutensede Madrid,
Madrid,
Spain
2
2
1
1
3
A.
Frasca1 , P. de
Guillout, A.y Klutsch, R.
Freire Ferrero, E. Marilli, K. Biazzo, D.28040
Gandolfi
andD.
4MontesE-mailcontact:
antonio.frasca at oact.inaf.it
1
INAF- Osservatorio
Astrofisico
di Catania,
via S. Sofia,
Star
formationin the solar
neighborhood
is mainly
traced78,
by 95123
youngCatania,
stars in Italy
open clusters, associations, and in the2
UniversitéCNRS,
de Strasbourg,
UMR 7550, F-67000
Strasbourg,
Francefield,
which decanStrasbourg,
be identified,for Observatoire
example, by astronomiquetheir X-ray emission.
The determinationof stellar
parametersfor
3
Dipartimento
di Fisica,ofUniversità
di Torino,
via P.forGiuria,
10125 Torino, Italytheoptical counterparts
X-ray sources
is crucial
a full 1,
characterizationof these stars. This work extends the4
Departamentode Astrofı́sicay Cienciasde laAtmósfera,
Universidad
Complutense
Madrid, and28040
Madrid,All-Sky
Spain
spectroscopic
studyof the RasTyc
sample,obtainedby thecross-correlationof thedeTYCHO
ROSATSurveyto stars fainteratthan
V = 9.5 mag and aims to identify sparse populations of young stars in the solar
E-mail catalogs,
contact: antonio.frasca
oact.inaf.it
neighborhood. We acquired 625 high-resolution spectra for 443 presumably young stars with four diﬀerent instrumentsStar
the solar neighborhood
mainly tracedby young
in targets
open clusters,
associations,and inintheformation
northern inhemisphere.
The radial andis rotational
velocity(v sin i)starsof ourwere measured
by meansof thethefield,
whichcanbeidentified,forexample,
by
their
X-ray
emission.
The
determinationofstellarparametersforcross-correlation technique, which is also helpful to discover single-lined (SB1), double-lined spectroscopic binaries
the opticalcounterpartsof X-raysources
crucialfor a fullcharacterizationof theseclassificationstars. This work
extends
the(SB2),and multiple
systems.
We usedtheiscode
ROTFIT
to performan MK spectral
and todetermine
spectroscopic
study
of
the
RasTycsample,obtainedbythecross-correlation
of
the
TYCHO
and
ROSAT
All-Sky
the atmospheric parameters (Teﬀ , log g, [Fe/H]) and v sin i of the single stars and SB1 systems. For these objects, weSurveycatalogs,
tostars
fainter
than
V
=
9.5
mag
and
aims
to
identify
sparsepopulations
of
young
stars
in
the
solar
used the spectral subtraction of slowly rotating templates to measure the equivalent widths of the Hα and Lii 6708 Å
neighborhood.
Weacquired625
high-resolution
spectrafor443
presumably
young
stars
with
four
diﬀerent
instruments
lines, which enabled us to derive their chromospheric activity level and lithium abundance. We made use of Gaiainthenorthernhemisphere.
Theradialandrotational
velocity
(v
sin
i)
of
our
targetsweremeasured
by
means
of
the
DR1 parallaxes and proper motions to locate the targets in the Hertzsprung-Russell (HR) diagram and to computecross-correlation
technique,
which
is
also
helpfultodiscoversingle-lined(SB1),
double-lined
spectroscopic
binaries
the space velocity components of the youngest objects. We find a remarkable percentage (at least 35 %) of binaries(SB2), and multiple systems. We used the code ROTFIT to perform an MK spectral classification and to determine
and multiple systems. On the basis of the lithium abundance, the sample of single stars and SB1 systems appears to
the atmospheric parameters (Teﬀ , log g, [Fe/H]) and v sin i of the single stars and SB1 systems. For these objects, we
be mostly (∼ 60 %) composed of stars younger than the members of the UMa cluster. The remaining sources are in
used the spectral subtraction of slowly rotating templates to measure the equivalent widths of the Hα and Lii 6708 Å
the age range between the UMa and Hyades clusters (∼ 20 %) or older (∼ 20 %). In total, we identify 42 very younglines, which enabled us to derive their chromospheric activity level and lithium abundance. We made use of Gaia
(PMS-like) stars, which lie above or very close to the Pleiades upper envelope of the lithium abundance. A significant
DR1 parallaxes and proper motions to locate the targets in the Hertzsprung-Russell (HR) diagram and to computepercentage (∼ 12 %) of evolved stars (giants and subgiants) is also present in our sample. Some of these stars (∼ 36 %)the space velocity components of the youngest objects. We find a remarkable percentage (at least 35 %) of binaries
are also lithium rich (A(Li)> 1.4).
and multiple systems. On the basis of the lithium abundance, the sample of single stars and SB1 systems appears to
Accepted
A composed of stars younger than the members of the UMa cluster. The remaining sources are in
be mostlyby(∼A60&%)

CA 91109, USA; Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA;
Institute for Research on Exoplanets, Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville,
6
BANYAN.
XI.3J7,The
BANYANΣ multivariate
Bayesianalgorithm
to identify
18 Montréal,
QC H3C
Canada;Space Telescope
Science Institute,
3700 San
Martin Drive,
Baltimore, members
MD 21218,
7of young
associations
within150 pcMuseum of Natural History, Central Park West at 79th St., New York,USA;
Departmentof Astrophysics,
American8 1,2
3,4THETA, Univ.5 Bourgogne Franche-Comté,NY10024,USA;
OSU
Besançon,6 ,France
Jonathan Gagné Institut, Eric UTINAM,
E. Mamajek, Lison Malo , Adric Riedel6 , David Rodriguez
David Lafrenière5 ,
7
5
6
8
5
JacquelineK.
Faherty,
Olivier
Roy-Loubier,
Laurent
Pueyo
,
Annie
C.
Robin
,
and
René
Doyon
E-mail contact: jgagne at carnegiescience.edu
12Carnegie
Institutionof
Washington
DTM,
5241
Broad
BranchRoad
NW,
Washington,DC
20015,USA;
BANYAN Σ is a new Bayesian algorithm to identify members of young stellar associations within 150 pc of theNASA
Sun.
3
Sagan
Fellow;
Jet Propulsionof Technology,
4800 multivariate
Oak Grove Drive,
Pasadena,
It includes 27 young
associationsLaboratory,
with ages inCalifornia
the rangeInstitute∼1–800 Myr,modelled with
Gaussians
in 64
5
CA
91109,
USA;
DepartmentofPhysics
andAstronomy,
UniversityofRochester,Rochester,NY
14627,
USA;
dimensional XYZUVW space. It is the first such multi-association classification tool to include the nearest sub-groups
Institutefor Research
on Exoplanets,
Universitéde Montréal,
Physique,
C.P. 6128
ofthe Sco-Cen
OB star-forming
region,the IC 2602,
IC 2391,Département
Pleiades anddePlatais
8 clusters,
andSucc.
the ρCentre-ville,
Ophiuchi,6Montréal,
QC
H3C
3J7,
Canada;Space Telescope
Institute,
MartinDrive,
Baltimore,
MD 21218,
Corona Australis, and Taurus star-formation
regions.Science
A modelof field3700
starsSanis built
froma mixtureof multivariate
7
USA;
Department
AmericanMuseumNatural History,
CentralPark West
at 79th St.,for
New
York,
Gaussians
based on oftheAstrophysics,
Besançon Galactic
model.
Theofalgorithm
can derive
membershipprobabilities
objects
8
NY10024,
USA;
Institutand
UTINAM,OSU THETA,
Bourgogne
Franche-Comté,Besançon,
Francewith only sky coordinates
proper motion,
but can Univ.
also include
parallax
and radial velocity
measurements,
as wellas
spectrophotometricconstraints from sequences in color-magnitude or spectral type-magnitude diagrams.
E-mailcontact: jgagnedistanceat carnegiescience.edu
BANYAN Σ benefits from an analytical solution to the Bayesian marginalization integrals that makes it more accurate
BANYANΣisanew
Bayesianalgorithm
toidentify
membersofyoungstellarassociations
within
150
pc
of
the
Sun.
and significantly faster than its predecessor BANYAN II. A contamination versus hit rate analysis is presented andIt
includes27
young
associations
with
ages
in
the
range
∼1–800Myr,modelled
withmultivariate
Gaussiansin6demonstrates that BANYAN Σ achieves a better classification performance than other moving group classification
dimensional
XYZUVW
space.
It
is
the
first
such
multi-association
classification
tool
toincludethenearestsub-groups
tools, especially in terms of cross-contamination between young associations. An updated list of bona fide membersof thethe 27
Sco-Censtar-forming
region, bythetheIC Gaia-DR1
2602, IC 2391,
Pleiadesand Platais
clusters,
andmakethe ρit Ophiuchi,
inyoung OB
associations,
augmented
release,are presented.
This8newtool will
possibleCoronaAustralis,
andsets
Taurusregions.
A modelof fieldstars
is built
mixtureof multivariate
toanalyzelarge datasuch star-formation
as the upcoming
Gaia-DR2
to identify
new
young
stars.from
IDLa andPythonversions ofGaussians Σ
basedon theBesançonmodel. The algorithm can derive membership probabilities for objects
BANYANare madeavailable
withGalactic
this publication.
with only sky coordinates and proper motion, but can also include parallax and radial velocity measurements, as well
Acceptedby ApJSas spectrophotometricdistance constraints from sequences in color-magnitude or spectral type-magnitude diagrams.
BANYAN Σ benefits from an analytical solution to the Bayesian marginalization integrals that makes it more accurate
http://arxiv.org/pdf/1801.09051
and significantly faster than its predecessor BANYAN II. A contamination versus hit rate analysis is presented anddemonstrates that BANYAN Σ achieves a better classification performance than other moving group classification
Distributed
starformation
throughout
theGalactic
Centercloud
SgrB2
tools, especially in terms of cross-contamination between young associations. An updated list of bona fide members

19

Astronomie der Universität Heidelberg, Mönchhofstrasse 12-14, 69120 Heidelberg, Germany; 15 National Astronomical
Observatory of Japan, 2-21-1 Osawa, Mitaka,Tokyo, 181-8588, Japan; 16 I. Physikalisches Institut, Universiät zu Köln,Distributed
starformation
throughout
theGalactic
Center
cloud
Sgr
B2
17
Zülpicher Str. 77, 50937 Köln, Germany;
San Jose State University, One Washington Square, San Jose, CA
1,2
3
4
4
5,6
7
18
Adam
Ginsburg
,
John
Bally
,
AshleyBarnes,Nate
Bastian,
Cara
Battersby,
HenrikBeuther
95192, USA;
Boston University Astronomy Department, 725 Commonwealth Avenue, Boston, MA 02215, USA; ,
8
9
8,10
3
19
20De Pree11 , Roberto
CrystalBrogan,YanettContreras,
JoannaCorby,
JeremyDarling,
Chris
National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA;
Max-Planck-Institut
12
13
21 7 , Todd Hunter8 , J.M. Diederik Kruijssen14 ,Galván-Madrid
,
Guido
Garay
,
JonathanHenshawfür extraterrestrische Physik, D-85748 Garching, Germany;
Joint ALMA Observatory, Alonso de Córdova 3107,
4
22 Lu15 , Fanyi Meng16 , Elisabeth A.C. Mills17,18 , Juergen Ott19 , Jaime E.
StevenLongmore,
Xing
Vitacura, Santiago, Chile;
National Astronomical Observatory of Japan, Alonso de Córdova 3788, 61B Vitacura,
20
16
16
16,20
4,21,22
Pineda,ÁlvaroSánchez-Monge,
Peter
Schilke,
Anika
Schmiedeke,
DanielWalker, andSantiago, Chile
5
David
WilnerE-mail contact: aginsbur at nrao.edu
1

2
Janskyfellowofthe
National
Radio
Astronomy
Observatory,
1003
Lopezville
Rd,
Socorro,
NM
87801
USA;
We report ALMA observations with resolution ∼0.′′ 5 at 3 mm of the extended Sgr B2 cloud in the Central Molecular3
EuropeanSouthern
Observatory,Karl-Schwarzschild-Straße
2,D-85748
Garchingbei
München,Germany;
CASA,
Zone (CMZ). We detect 271 compact sources, most of which
are smaller than 5000 AU. By ruling out alternative
4
UniversityofColorado,
389-UCB,
Boulder,CO
80309,USA;
Astrophysics
Research
Institute,
LiverpoolJohn
Moorespossibilities, we conclude that these sources consist of a mixof hypercompact HII regions and young stellar objects
5
University,146ofBrownlow
Hill, Liverpool
L3 are5RF,UK;withHarvard-Smithsonian
Astrophysics,
60 Garden(YSOs).
Most
the newly-detectedsources
YSOs
gas envelopes which,Center
based foron theirluminosities,
must
contain objects with stellar masses M∗ >∼ 8 M⊙ . Their spatial distribution spread over a ∼ 12×3 pc region demonstrates
that Sgr B2 is experiencing an extended star formation event, not just an isolated ‘starburst’ within the protocluster
regions. Using this new sample, we examine star formation13thresholds and surface density relations in Sgr B2. While
23
−2
2
×
10
cm
), not all regions of high column
all of the YSOs reside in regions of high column density (N (H2 ) >∼density contain YSOs. The observed column density threshold for star formation is substantially higher than thatin solar vicinity clouds, implying either that high-mass star formation requires a higher column density or that any
star formation threshold in the CMZ must be higher than in nearby clouds. The relation between the surface densityof gas and stars is incompatible with extrapolations from local clouds, and instead stellar densities in Sgr B2 follow
a linear Σ∗ –Σgas relation, shallower than that observed in local clouds. Together, these points suggest that a higher
volume density threshold is required to explain star formation in CMZ clouds.

Accepted by ApJ
http://arxiv.org/pdf/1801.04941