Transverse velocity shifts in protostellar jets: rotation or velo
Fabio De Colle1 , Adriano H. Cerqueira2 and Angels Riera3
1
2
3

Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México
LATO-DCET-UESC, Ilhéus, Brazil
Departament de Fı́sica, Universitat Politécnica de Catalunya, Barcelona, Spain

E-mail contact: fabio at nucleares.unam.mx

Observations of several protostellar jets show systematic differences in radial velocit
direction, which have been interpreted as evidence of rotation in the jets. In this pvelocity shifts, and show that they could be originated by rotation in the flow, orshock velocity, which could be due to asymmetries in the jet ejection velocity/dens> 10% can pro
typical poloidal jet velocities (∼ 100 − 200 km s−1 ), an asymmetry ∼those observed. We also present three dimensional numerical simulations of rotatin
and show that, even though for a given jet there is a clear degeneracy between thesewith different inclination angles can help to distinguish between the alternative or
Our analysis indicate that side to side velocities asymmetries could represent an imvelocity shifts, being the most important contributor for large jet inclination anglessky), and can not be neglected when interpreting the observations.

!
2016/12/2!
SFN!#286!11,15

Accepted by ApJ
http://arxiv.org/pdf/1609.04858

Ver.!2!


Massive stars reveal variations of the stellar initial mass fun
stellar clusters
1,2
Transverse velocity shifts in protostellar jets: rotation or velocity
asymmetries?
Sami Dib, Stefan Schmeja3,4 and Sacha Hony5
Fabio De Colle1 , Adriano H. Cerqueira2 and Angels Riera31

Niels Bohr Institute & Centre for Star and Planet Formation, University of Cope

Copenhagen, Denmark.
Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México 1350,
2
Unidad de Astronomı́a, Departamento de Fisica, Universidad de Atacama, Copay
2
LATO-DCET-UESC, Ilhéus, Brazil
3
3
Departament de Fı́sica, Universitat Politécnica de Catalunya, Barcelona, Spain Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelb
Heidelberg, Germany
4E-mail contact: fabio at nucleares.unam.mx
Technische Informationsbibliothek, Welfengarten 1b, 30167 Hannover, Germany
5
Institutfür Theoretische
Astrophysik,
Zentrum
Observations of several protostellar jets show systematic differences in radial velocity
transversetopropagation
Variationsof thethejetIMF
in the MilkyWay für3Astronomie der Universität H
Germany.
direction, which have been interpreted as evidence of rotation in the jets. In this 69120
paper Heidelberg,
we discuss theorigin of thesevelocity shifts, and showthat they
could
be originatedrotationin theby sideto side sami.dib
asymmetries
in theτE-maildurationof the Hydrogenand Helium burning
in a cluster
is called”single”
if it is the by
only
living star,or aflow, or
contact:
at gmail.com
15 is theshock velocity, whichbinary
couldsystembe duewith
to asymmetries
in the jetthat
ejectionambient
ForM! (Ekström et al.
phasesorforin athestarwith a medium.
mass of 15
any of its components,
has avelocity/density
massWe
investigate
whetherthestellarinitial mass function (IMF) is universal, or wh> 310%
typical poloidal jet velocities
(∼the
100
− 200Thekm fractions−1 ), anofasymmetrycanproducevelocity
shiftscomparableto2012).
This
bringsdown
thenumberofclusters useful forina! 15 M! incluster.
single O stars∼
young stellarinclusters
in theMilky Way.
We propose a method to uncover the ran
our purposes
to NMWSC,cl= 341. The inof threeclusters
is thus givenby:those observed. We population
also present
dimensional
numerical
simulations of rotating,precessing theandMWSCasymmetric
jets,
that
describe
the
shape
of
the
IMF
for
therelation
population
dividualstellarmasses are
estimatedfrom thebe- of young Galactic clusters.
and show that, even though for a given jet there is a clear degeneracy between theseeffects,a statisticalanalysisof jetsin thelogM
low andhighabsolute
stellar mass magnitude
regimes, γMandΓ, respectively, and the characand theV givenNO,single
with different inclination angles
can help to distinguish between the alternativetween
origins of ∗transverse
velocityvisual
shifts.
fO,single =,(1)
reliesexclusively
on the The
highabsolute
mass content
of thebut is able to yield in
Schilbachet al. (2006).
magnitude
MV clusters,is
Our analysis indicate that side to Nside
velocities asymmetries could represent an byimportantcontribution
to transverseOparametersthat
describe
theIMF overthe entire stellar mass range. This is achie
computedfromthetheapparent
magnitude
velocity shifts, beingwhere
the most
importantcontributor
largeOjet
inclination(with respect
the planeof the mV , the distance,NO,single
is the total
number offor
singlestars
and NO angles
singlelonelyEmassive
O starsa recent
andthe andextinction
are allin
listedin thecatalog
MWSC of the Milky Way clusters w
B−V whichsky), and can not beisneglected
when interpretingtheobservations.
the total numberof O stars in all
clusters.
We also measure(Kharchenko
et al 2013).
Out of thefunctions
total 341 clusters,
175 parameters.
ofbuilt with various
distributionof the IMF
The synthetic clus
thefractionof”lonely”
O
stars
in
the
clusters.
A
lonelyAccepted by ApJ
them
containpopulation,
at least one stellar
O star evolution,(M∗ ! 15 Msample
num! ). Theincompleteness,the binaryand ejected O stars
O star in a cluster is a single O star with the additionalberof single andoflonely
O stars
in the observational
sampledistributions
the IMFparameters
are requiredin order to reproduce the fractio
http://arxiv.org/pdf/1609.04858
constraint that the next massive system in the cluster is less
Variations
theIMF
in theMilky
Way
3the existence of a cluster ma
isGalactic
NO,singleclusters.
= 89ofandNO,lonely
respectively,
and totheTheyalso =do29,
notlend support
Variations of the I
massive than 10 M! (i.e., absence of high mass B stars with
total
number
of
O
stars
is
N
O = 688. Thus, the fractions
We propose a probabilistic formulation of the IMF whereby the parameters of thmassesbetween10and15M! ). The fraction of lonely Oτ15single
is theanddurationof starthe inHydrogenandcatalog
Heliummeasured
burningin a cluster is called ”single” if it is the only living star, or aoflonelyO
the
MWSC
Massive stars reveal
variationsof the stellar initial mass functionthe”single”
Milky
Way
distributionfunctionscenteredaround= 0.91,0.41 Mof" ,thathedurationina cluster isincalledif it isthe only γliving
star,Γor=a 1.37, τandstars is system
given
by:
ch =
15 isM
phasesEq.
for 1aandstarEq.
witha massof 15
M! (Ekströmal.
with any of its components, that has a mass
using
2 are
fO,single(MWSC)= 12.9%etandstellar clusters binary
phases for a star with abinarysystemwithany
its components,thathasvalues.
a massσΓ = 0.60,
andσM=ofthe0.27
M" aroundthesech2012).
This brings
down
numberof clusters
useful for! 15 M in the cluster. The fraction of single O stars3 in a1

1/2

fO,lonely (MWSC) = 4.2%.
2012). This brings down
! 15 M! in the cluster. The fraction of single O stars3 in aourpurposes
the MWSC to NMWSC,cl = 341. The inAccepted
byinMNRAS
our purposes in the MW
population of clusters is thus given by:dividual stellar masses are estimated from the relation beNiels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen,ØsterVoldgade
5-7,
DKdividual
stellar masses ar
http://arxiv.org/pdf/1605.08438
tween
logM∗ and the absolute visual magnitude MV given
N
4
MODELSO,single
where
N
is
the
total
numberoflonelystars
inthetween logM∗ and the abs
1350, Copenhagen, Denmark.
fO,single O,lonely=,(1)NO,single
bySchilbachThe absolute magnitude MV (1)is
NO idea of the method relies on the compari- “single”!–!if!the!O!star!(or!binary)!is!the!only!living!star!
Parameters!that!describe!the!shape!of!the!IMF!for!the!
fO,single= et al. (2006).
,
clusters. The basic
2
by Schilbach et al. (2006
Unidad de Astronomı́a, Departamento de Fisica, Universidad de Atacama, Copayapu
485,
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Nthe
O populations
computed
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wheretotalfürnumberof single
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derUniversität
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andtheNextinction
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areall listedOinstars
the MWSC
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Thepossibility
detectingmassiveofOsingle
stars in the andGalaxyis thetotalclusters
numberinofthe
O stars
in allclusters.
We alsomeasureandthe extinction EB−V
(Kharchenko
et al 2013).
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total 341We
clusters,
175 ofHeidelberg, Germany
is
the
total
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of
O
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also
measure12• Slopes!in!the!low!and!high!stellar!mass!regimes,!γ!and!Γ,!
populations
clusters
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anda
the fraction ofofstellar”lonely”
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et al 2013).
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15 is the duration4
themcontainatleast”single”
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star
(M
15
M
! ). The
Technische Informationsbibliothek,Welfengarten
1b, 30167
Germany
massive!system!<10!Msun
thethefractionof”lonely”
in ∗theclusters.
A lonelyous
priorinfunctions
distributionsof theHannover,
IMF
parameby
value
of
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The
O stara clusterfor
is thea single
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its
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berof single
lonelyintheobservational
OHeidelberg,
star
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O comparedstar2,
with totheadditional
Institut für Theoretische
Astrophysik,
ZentrumfürAstronomie
derapplied
UniversitätAlbert3ters.
A numberof important
corrections
havebemodelsofclusters
theobservaconstraintthat thenext
massivesysteminthe tocluster
is lessberof
singleandlonely2012). This brings downOina!N
15O,single
M! in =
the cluster.
The fraction
single O stars
isNO,lonely=
29,ofrespectively,
andtheconstraint
that89theandnext
massivesysteminassuming
the cluster
is less
FracCon!of!“single”!or!“lonely”!O!stars!among!O!stars!in!
69120 Heidelberg, Germany.
tothezero-age
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to
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stellarcon• CharacterisCc!mass,!M
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that
all
massivethan
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B
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with
is
N
=
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and
N
!
our
purposesintheMW
populationofclusters
is
thus
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by:
O,singleOchtotal
numberof M
O!stars
isabsence
NO = of688.
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fractionsmassivethan
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highmassthe
B the
stars
with
tent
beforethey canbe comparedto theobservations.
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stars
form
in clusters,
the total
mass containedinyoungmasses10 and15 M! ). The
fractionof lonely
Oa!populaCon!of!clusters
total number
O starsar
dividualstellarofmasses
E-mail contact: sami.dib
atbetween
gmail.com
ofsinglebetween
and lonelyO
star
inMthe
MWSC
catalogmeasured
The!method!!
masses
10
and
15
).
The
fractionoflonelyO!
descriptionof by:
the observational sample of clusters is given
population
Galacticclusters
that are=likely,
stars is givenof single
and∗ lonely
O abs
sta
tween
logM
and the
Nand
using
1of
Eq.
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are fO,single(MWSC)
12.9%based
andO,single
isEq.
given
by:contain
We investigate whether
stellarmass
function(IMF)areis described
universal, or whetheritsignificantly
amongfstars= varies, O stars (M(1)
in §. the3, while
theinitialsyntheticmodelsof clusters• relies!exclusively!on!the!high!mass!content!of!the!clusters,!
on
their
age,
to
O,singleusing
Eq. 1 andEq.(2006
2 ar∗ ! 15 M! ) is given by:
by
Schilbachet al.
fO,lonely(MWSC)NO = 4.2%.
young stellar clusters
the MilkyWay.
We
proposeamethodtouncover
the
range
of
variationoftheparameters
in in
§. 4.
f
(MWSC)=
4.2%
O,lonely
NO,lonely
computedfrom the appar
but!is!able!to!yield!informaCon!on!the!distribuCons!of!
!NO,single
fO,lonely= IMF for, the population of young Galactic(2)clusters.
whereis the total number of single O stars and NO
NO,lonelyτ15 parametersthat describe the shapeof theand the extinction EB−VNO
f =These= SFR(t) × ,dt, are the slopes
(2)
Σ
(3)
isO,lonely
the total numberof O .stars
in allclusters. We also measureclNO M
parameters!that!describe!the!IMF!over!the!enCre!stellar!
in the low and highwhere
stellarmass
regimes,γ
andΓ,
respectively,
andthecharacteristic
mass,
The
method(Kharchenko
et al 2013). Och0
4 MODELS
NO,lonely is the total number of lonely stars in thefraction
ofon”lonely”
O stars
in theclusters.
A inlonely4 MODELS
where
NO,lonelyisthe
the distributions
total
numberstars
therelies exclusively on3clusters.
theOBSERVATIONAL
high
mass
of
the
clusters,
buttheiscompariable to yieldthe
informationof lonely
CATALOGOFon
themcontain at least one
Thebasiccontent
idea of themethodreliesmass!range.!!
where
SFR(t)
isthetimedependent
star
formation
rate
over
O
star
in
a
clusterisasingle
O
star
with
the
additional
ObservaConal!data:!~3200!clusters,!age!1!Myr!!–!7!Gyr!
4.1
Generating
populationsof zero-age
clusters
clusters.
The
basic ideaof themethodrelies on thecompariber of single and lonely O
parameters that describe
IMFandover
the entire
stellarrange.
This is achievedbycomparingthefractionsofson CLUSTERSof thefO,single
fO,lonelymeasured
formassa recent
catalogue
4.1 Generating popu
thelast τ15thattimescaleofmassivethe lifetime
ofin theGalaxy.isTheconstraint
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systemfor
clusterlessson
ofpossibility
faO,single
andfsimulated
athe
recentcatalogue• Compare!the!fracCons!of!single!and!lonely!massive!O!stars!
is NO,single = 89 and NO• !341!clusters!with!age!<!t!(12.3!Myr)!
O,lonely
single and lonely massive
O stars
in useda recent
catalogofthethoseMilkyclusters
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ofdetecting
clustersof stellar
clusters
intheinMilky
Way withderivedfor
15measuredTheofM
massiveO stars
inBtheGalaxyGalactic
SFR
over
such
a relatively
periodofstars
time
can
The
observations
this
paper
come
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theWayMilkymassivethan
10(i.e.,
absenceofshort
high
mass
with
!
of
stellarclusters
in
the
Milky
Way
with
those
derivedfor
The possibility
total
number ofofOdetectistars
5
populationsofstellar clusters
that parameters.
are generated
withsynthetic
with various distribution
ofthe IMF
The
clusters
arecorrected
fortheeffects
of
is
bound
by
the
relatively
short
lifetime
of
these
stars
and
!=!89,!N!=!29,!N!=!688!
• built
a!recent!catalog!of!the!Milky!Way!clusters!
beassumedtobeconstant
and
Σ
can
be
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Stellarfunctions
Clusters
survey(MWSC)(Kharchenko
etvarial.• NO,!single
O,!lonely
O). Theclmassesbetween
10 and15 M!
ofwithlonelyO
populationsofstellarclusters
thatare fraction
generated(SFR).
variis boundby therelativelyofsingle andlonelyO staousstellar
prior
functionsforal.
thedistributionsof al.
the2014)
IMF
by
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value
ofby:
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Galactic
starformationThethe binary population,
evolution,
sampleincompleteness,
and4parameejected
Of stars.
Ourfindings
that
broad
by
Σ
≈
SFR×τ
We consider
threevaluesrateof the Galactic
2012;
Kharchenkoet2013;
Schmejaet,which
15 .indicate
cl
stars
is
given
•
!=!12.9%,!f!=!4.2%!
ous
priorfunctionsforthedistributions
of
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a!library!of!simulated!clusters!built!with!various!
by
the
value
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using
Eq.
1
and
Eq.
2 ar
−1
ters.
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have
to
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are comparedtotheobservaof the lists
IMF∼parameters
arewithrequiredin order∼to1 reproduceofsingleandlonely
in
SFR
of
0.68,
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and
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M
that
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ages between
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ters. Aof important
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fmodels(MWSC)= 4.2%
O,lonelyof
to thezero-ageclusters
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arenumbergeneratedin thefollowing
way:theassuming
all
tral,
and
upper
estimates
obtainedfromcountof young
distribuCon!funcCons!of!the!IMF!parameters.!!
Galacticclusters. They
also
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lend
supportthetoexistenceof aconcluster mass-maximum
stellarmass
relation.
Gyr.
Theclusters
are detectedastoanddensityand velocity
enN
to
the
zero-age
syntheticclusters
and
to
their
stellarcontions are generated in thO,lonely the total mass contained in the young
tent before theycanTwobe compared
to Skythe observations.
TheTotal!mass!contained!in!the!young!populaCon!of!
stars
form
clusters,
fthe
=in
,
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indescribed
the GLIMPSE
surveyof the Galactic planehancementsin theSurvey(2MASS)
We propose a probabilistic
formulationof Micronthe IMFAllwhereby
the parametersof stellar
IMF
areby Gaussian
tent
beforethey
comparedto theThe
stars form in clusters, theNOcan bestellar• The!syntheCc!clusters!are!corrected!for!the!eﬀects!of!the!
description of the observational sample of clusters is given
populationof
Galacticclusters
thatobservations.
arelikely,masses
based(Robitaille&
Whitney
2010).
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individual
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etaroundal. 2006)γ andthe propermotions
PPMXL
surGalacCc!stellar!clusters!that!are!likely,!based!on!their!
distribution functions
centered
=
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=
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M
=
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M
,
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dispersions
of
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=
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descriptionoftheobservational
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is
given
ch
"
γ
populationof Galactic stin §. 3, while the synthetic models of clusters are describedon
their
to containO stars(M!of15lonelyM
is given
by:
4
MODELS
where
Nage,
issampled
the total
numberinthe∗ mass! ) stars
O,lonelyarestochasticallyfromthereservoir
Σusvey(Röseretal.
2010).
The
surveyincludesclustersuptoclbinary!populaCon,!stellar!evoluCon,!sample!
σΓ = 0.60, and σMchin=§.0.27
in §. 3, while the synthetic
models ofclusters are described
age,!to!contain!O!stars!(M>=!15!M
on their age, to contain O
4. M" around these values.
)!!
clusters.
The cluster
basic ideaof!function
the method
relieson thecompariing
aninitialmass(i.e.,
themassfunctionofa distance of ∼ 10 kpc from the position of the Sun with!
4.1
Generatingpopu
in §. 4. τ15
incompleteness,!and!ejected!O!stars.!!
son of fO,single
andfO,lonelymeasured
for a recent
catalogue
Accepted by MNRAS! τ15
clusters
birth,ICLMF).
The ICLMF
is taken
to (3)
bea substantial fraction of the clusters being located within aΣcl = at their
SFR(t)
× dt,
ofstellarclusters
in
the
Milky
Way
with
those
derivedforThe
possibilityofdetectia power-law,
between the minimum and maximum cluster
Σcl =SFR(t) × dt,
0
distance " 1.8 kpc (see Figure 1 in Schmeja et al. 2014). The
Our!ﬁndings:!!
http://arxiv.org/pdf/1605.08438
populationsof stellar
clusters
that aregenerated
vari3 OBSERVATIONAL
CATALOG
is bound0 by the relatively
massesof Mcl,min
Mdependentis given
by: with
files
in the catalog list the B,
V, and J, H,OFK magnitudes ofcl,max , andstar
where
SFR(t)
is theandtime
formation
rate over3 priorOBSERVATIONAL
CATALOGofOF• Broad!distribuCons!of!the!IMF!parameters!are!required!!
ous
functions for the distributions
the IMF parameby
the
value
ofisthe
where
SFR(t)
theGalact
time
eachCLUSTERS
star in each cluster present in the catalog, along with ICLMF:!Distriburion!of!cluster!masses!at!their!birth!
the CLUSTERS
last τ15 timescale of the lifetime of the Galaxy. The
ters.
of important corrections have to be applied
modelsstellarclustersof
the lastofτ15
timescaleotherproperties suchage,come
clustermembership
dNcl A number• No!support!for!the!existence!of!a!cluster!mass,maximum!
Galactic
SFR overThe observations
usedasinposition,
this paper
fromthe Milky−βsuch a relatively short period of time can
=
A
×
M
,
(4)
cl
to
the
zero-age
syntheticclusters
and
to
their
stellarcon5
tions
are SFR
generatedin thecl usedGalactic
over suchaThe
observationsin thispaper
the Milky
probability,
motions,
when available,
the etspecbeto beconstantandΣcl come
can befrom
approximateddMassumed
Way Stellarproper
Clusters
surveyand,(MWSC)(Kharchenkoal.
clstellar!mass!relaCon.!!
tent
beforethey
can be consider
comparedto theobservations.
stars
form in toclusters,
the4
be assumed
be consta
12al.
Way
Stellar
Clusters(MWSC)(Kharchenko
etThe
al.
tral
The resolved
content etofeach
clusterarebyΣcl≈ SFR×τ
threevaluesofby:
the Galactic
2012;type.
Kharchenko
et al. stellar
2013; Schmeja
2014), which15 . Wesurvey
where
A
the
normalization
constant
given
cl isof4is given
description
theobservational
sampleofclusters−1
populationof
Galactic
ste
by
Σ
≈
SFR×τ
.
We
co
2012;
Kharchenko
et
al.
2013;
Schmeja
et
al.
2014)
,
which
15
cl
however
not corrected
for theof thepopulaSFR of 0.68, 1, and 1.45 M! yr
that are the lower, cenProposal:!a!probabilisCc!formulaCon!of!the!IMF!
lists ∼ 3200
clusters withageseffects
between∼ 1binary
Myr and∼ 7in§. and3, 3200
while
theestimates
syntheticmodelsof clusters
are describedon
theirage, toSFR
of 0.68,
1, containand 1.45O
lists∼
clusters
withobtained
ages
between∼ 1count
Myr
and
∼ 7
tion.
this
work, are
we areinterested
in clusters
that could,
tral,
upper
from
the
of
young
Gyr. In
The
clusters
detectedas densityand velocity
en!
Mcl,max•
parameters!with!Gaussian!distribuCon!funcCons!!
in§. 4.
tral, and upper estimates
−β+1
Gyr.
The
clusters
aredetectedasdensityandvelocityenbasedon theirhigh-mass
starsSurvey(M∗ !(2MASS)
15 M! ),
stellarobjects
inthe
GLIMPSEsurveyof theGalacticplane
hancements
in age,the harbor
Two Micron
All SkyAcl × Mcl
dMcl = Σcl .
(5)
! τ15
stellar objects in the GLIM
hancements
the Two
MicronSky Survey(2MASS)(Robitaille&inWhitney
2010).
TheAllindividual
clustermasseswhich
impliesclusters
than τ15motions≈ 12.3 PPMXL
Myrs, whereMcl,min(Skrutskie
et al.
2006) younger
and the !=!0.41!M
propersur•Center:!!γ!=!0.91,!Γ!=!1.37,!and!MΣ
SFR(t)
× dt,20ch!
cl =(Robitaille&
Whitney(Skrutskie
et al. 2006)
and themotions
PPMXL
arestochasticallysampledfromproper
the mass
reservoir
Σcl surusvey (Röser et al. 2010). The survey includes clusters up to0•
Dispersions:!σ!=!0.25,!σ!=!0.60,!and!σ!=!0.27!M!
are stochastically sample
vey(Röseretal.
2010).
The
surveyincludesclusters
up
to
4
ing
an
initialclustermassfunction(i.e.,
themassfunctionof
3 OBSERVATIONAL
CATALOG OFa γdistance of ∼ Γ10 kpc from the position
Mch of the Sun with!M,!M!=!50,!20,!10!M,!beta!=!2,!2.2,!1.8!
5 !=!5x10
3 For simplicity, we will use the term ”star” to define both indi-Mcl,max

cl,min
where
SFR(t)
istheinstantaneous
SFR
cannotbe in ofrealityaSun
constant
ing an initial cluster time
massd
a The
distanceof ∼ birth,
10Galactic
kpcICLMF).
fromthepositionwithclusters
at their
The
ICLMF
isthe
taken
to
be
CLUSTERSa substantial fraction of the clusters being located within athelast atτ15theirtimescaleof(i.e.,
the birth of
single massive
star in the
Galaxywill boost
thevidual stars or binary systems
clusters
birth, IC
fractionofclusters
being
locatedwithina substantial
power-law, between
thetheminimum
and maximum
clustera" 1.8 kpc (see Figure 1 in Schmeja et al. 2014). The
4distance
The
full
list
of
clusterparametersisavailSFR),
but the assumption
madepaper
here thatthefromtime thedependent
Galactic
SFR between
over suchtheaTheobservations
inis thisMilky
a power-law,
distance
1.8
kpcused(see M
FigureSchmejaal. 2014).
The
massesof"Mandand
iscomegivenet
by:
files
in
the
catalog
list
the
B,
V,
and
J,
H,
K
magnitudes
ofcl,mincl,max1, in
ableat
http://vizier.cfa.harvard.edu/viz-bin/VizieR?Galactic
SFR will
fluctuate
aroundthe values
chosen in thiset
work
beassumedto be and
constaWay
Clusters(MWSC)(Kharchenko
massesof Mcl,minMfiles inStellar
the catalog
list survey
the B, V,
and J, H,
K magnitudes al.
ofeach star in each cluster present in the catalog, along with
4 issue).
source=J/A+A/558/A53
(see
also
da
Silva
et
al.
2012
for
further
discussionon
thisby Σcl ≈ SFR×τ15 . We co
2012;
Kharchenkocluster
et al. 2013;
Schmejaal. 2014), whicheach
present
in the etcatalog,along
withother properties such as position, age, cluster membership
dNcl star in each−β
SFR
1.45
Acl ×clusters
M , with ages between ∼ 1 Myr and ∼(4)7
lists∼=3200other
dNcl of 0.68, 1, andprobability,
motions, and, when available, the spec−βdMcl properties clsuch as position, age, cluster membership
1–17 (2016)
MNRAS
000,proper= Auppercl × M
tral,andestimates
Gyr.
The
clusters
aredetectedasdensityandvelocity
encl ,
probability, proper motions, and, when available, the specdMcl
tral type. The resolved stellar content of each cluster are
where
Acl is in
the normalization
given
by: (2MASS)
stellar objects in the GLIM
hancements
Two stellar
Micronconstant
All Skyof
Surveytral type.
The theresolved
content
each clusterarehowever not corrected for the effects of the binary populawhere Acl is&the
normaliz(Robitaille
Whitney20(Skrutskie
et corrected
al. 2006) andmotions
PPMXL
surhowever not
for the proper
effects ofthe binary
population. In this work, we are interested in clusters that could,
!
!

5
N3,4
population ofclusters
thus given
by:O,lonelySami Dib1,2 , Stefan
and, isSacha
Honyf Schmeja=
O,lonely

1

1.

2.

3.

4.

NO

(2)

relies exclusively on the high mass content of the clusters, but is able to yield in
most massive clusters
in the MilkyWaythat(e.g.,sideFiger
et al.velocities asymmetries could represent an important
Our analysis
indicate
to sidecontribution to transverse
parameters that describe the IMF over the entire stellar mass range. This is achie
1999; Dib et al. 2007; Ascenco et al. 2007; Harayama et al.
velocity shifts, being the most important contributor for large jet inclination angles (with respect the the plane of the2008; Clark et al. 2009) and explore values of Mcl,min = 50
single and lonely massive O stars in a recent catalog of the Milky Way clusters wsky), and can not be neglected when interpreting the observations.
(fiducial), 20, and 10 M! . Our fiducial value of β is 2 as thisbuilt with various distribution functions of the IMF parameters. The synthetic clus
is in agreement withthe slopethe cluster mass function at
Accepted
byofApJ
the binary population, stellar evolution, sample incompleteness, and ejected O stars
intermediate- to high cluster masses in nearby galaxies (e.g.,
distributions of the IMF parameters are required in order to reproduce the fractio
http://arxiv.org/pdf/1609.04858
Elmegreen & Efremov 1997; Zhang & Fall 1999; Hunter et
Galactic clusters. They also do not lend support to the existence of a cluster ma
al. 2005; de Grijs & Anders 2006; Selman & Melnick 2008;
We propose a probabilistic formulation of the IMF whereby the parameters of thLarsen 2009; Chandar et al. 2010; Fall & Chandar 2012) and
Massive stars reveal variations of the stellar initial mass function
the Milky
distributioninfunctions
centeredWayaround γ = 0.91, Γ = 1.37, and Mch = 0.41 M" , awith theoretical expectations (Elmegreen 2006; Dib et al.
stellar clustersσΓ = 0.60, and σMch = 0.27 M" around these values.
2011; Dib 2011a,b; Dib et al. 2013). We also consider cases
3,4with β = 2.2 and Sami
β = 1.8.
For1,2eachclusterSchmejawith an assigned
Dib, Stefanand Sacha Hony5
Accepted by MNRAS
Variations of the IMF in the Milky Way 7
mass Mcl , the massesof star-systems (i.e., individual stars
1
Niels
Bohr
Institute&
CentreforStar and Planet Formation, University of Copenhagen,Øster Voldgade 5-7, DKhttp://arxiv.org/pdf/1605.08438
or binary systems) in the clusters are randomly sampled
1350, law
Copenhagen,Denmark.
using a tapered power(TPL) distributionfunction (de2For!each!cluster!with!an!assigned!mass!M,!the!masses!
de Astronomı́a,
Marchi et al. 2010;Unidad
Parravanoet al. 2011). Departamento
Without
any de Fisica, Universidad de Atacama, Copayapu 485, Copiapo, Chile.
cl3
Astronomisches
Rechen-Institut,für Astronomie der Universität Heidelberg, Mönchhofstraße
12-14, 69120
assigned binary fraction,a stellar ”system”
of mass M∗Zentrum
canof!star,systems!(i.e.,!individual!stars!or!binary!systems)!
10 Dib et al.
Germany
correspond to an Heidelberg,
individual staror to a binary system. The
12
in!the!clusters!are!randomly!sampled!using!a!tapered!
4
TPL function is givenbyTechnische
Informationsbibliothek, Welfengarten 1b, 30167 Hannover, Germany
to be negligible fo

2/2

power!law!(TPL)!distribuCon!funcCon!
5
Institut für Theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Albert-Überle-Straße 2,

M" . It increases u
M" and declines
et al. 2015). Noteclusters that obey
sess the same undKroupa IMF). As
actly the expectedof our synthetic cl
namical ejection o≈ 400 − 500 M" isdetails. Since mostmodels have mass
sive stars from th
affect the value o•of ejected O stars
imatedby ≈ NO,•
where NO,non−sin
M∗ ! 15 M! (CLMF-O), peaks at a few tens of stellar masses and most of the clusters in the CLMF-O have masses " 400 M! .
acteristic mass (MThe minimum
stellar mass,
M∗,min , 10
from!(Mcl!–!M*,max)!relaCon!
ch ).proposeWea probabilistic
formulationof theDib
IMF
whereby the parameters of the IMF are described by Gaussian
et al.
single, and fO,ejec
is always taken todistribution
be 0.02 M! .functions
The maximum
stellarmass, γ = 0.91, Γ = 1.37, and Mch = 0.41 M" , and with dispersions of σγ = 0.25,
centeredaroundtion of the cluster
either located at the values of the parameters derived by
5 × 104 M! which is the mass of the M∗,max , is either given by min[Mcl , 150 M! ] (correspondat forlargerdistances
fromthe Sun.
The completeness correction is calculated for each re- to be average,
negligible
clusters
whosemassesare "The
400normalized
− 500
σ
=
0.60,
and
σ
=
0.27
M
aroundthesevalues.
NO,non−single and
Γ
M
"
ch
Dib
(2014a),orthe
Galactic
fieldvalues
that
are
given
by
in the Milky Way (e.g., Figer et al.
function
fcomp= R
constitutes
alization of the cluster mass function with respect to the M" . It
2−10 )masses
increases
up to
≈2−10
25%/max(Rfor clusterof ≈ the3000coming to the case of stochastic sampling) or is dictated by acluster mass for th
Ascenco et al. 2007; Harayama et al.
Γfsample
0.57,
and Msurvey.
MM!" (Parpleteness
function.
clusteris admitted
for masses
the comparison
youngγclusters
the MWSC
In =this0.42
work,
ield =of1.35,
f ield =in
ch,f ield
anddeclines
to 5 − A10%
for higher
cluster(Oh
Accepted by MNRAS) and explore values of Mcl,min = 50 cluster mass-maximum stellar mass relation (Mcl − M∗,max )increases in fO,sin
theNoteobservationaldata
if its completenessprobability
the approach
we use Thesein orderfamilies
to accountfor the effectof et al. withravanoet al. 2011).
of models
are labeledδF2015).
that thesefractionswere evaluatedforby Vanbeveren (1982) and later by WeiM! . Our fiducial value of β is 2 as this relation proposedhttp://arxiv.org/pdf/1605.08438
els and ≈ 18 − 22
fcomp
largeranthanclusteris basedon thepopulations ofandlow clusters
thatis obey
Mcla −uniform
M∗,maxrandom
relationnumber
and alldrawn
pos- beOBS
andincompletenessδF-GF (Delta
Function
Observations
Galactice slope of the cluster mass function at dner & Kroupa (2004). We test models in which the distween
0 and
1. For theGalactic
families of
ICLMFsIMF
generatedin thismass B stars in the clusters (i.e., stars with masses between
correction to accou+ sess thesameunderlying
field-like(i.e.,
theField,
respectively). We also test flat probability
HCO distribuDetection
ofonlyDust-DepletedGas
in the Inner
Hole of thluster masses in nearby galaxies (e.g., tributions of the parameters (Γ, M , γ) are either given
work,
typically
aboutestimateshalf of themay
clustersin the ICLMF
2M!12.9+,1.4%
# M∗ # 10M! ) whose total number in a cluster is KroupachO stars increases t
IMF).
As such,these
not reflect
ex1997; Zhang & Fall 1999; Hunter ettions(FPD).
These
are describedby boxcar
beDiskpass
the filterfractionsof the completeness
functionandareused inN∗,2−10. For eachrealizationof the ICLMF,
after
thefunctions
cor- actly thebydeltafunction(allclusters
have
the
same
value
of
the
expectedofejected
O
stars
for
each
familymodelsand the obnders 2006; Selman & Melnick 2008;
tween
(0.4,
1.5)
for
γ,
(0.7,
2.4)
for
Γ,
and
(0.05,
1)M
forthe
comparison
withtheobservational
data.
Additional
exrectionsfortheeffectsofthebinarypopulation
andstellar!
1
2
3 substantially aof our synthetic clusters.
the1basic
result,that dyE. Drabek-Maunder,completenessS. However,
Mohanty, J.
Greaves, ofI.β Kampnot, R. Meijerin
et al. 2010; Fall & Chandar 2012) and parameters), Gaussian functions, or boxcar functions. A reamplesof thefunctionforvariousvaluesevolution
been takenfunctions
into account,we computethe namicalM
distributionoftheparametersofthech . The haveejection
of
O
stars
from
clusters
lessmassivethan
6tations (Elmegreen 2006; Dib et al. cent study found that the mean values of the parameters
the GPD-σobs moWoitkeits M
effecton the derived values of fO,single and fO,lonely
distributionof 12
low mass
B stars
6 (top∗,2−10 ). Fig.
IMF
for all ofthesemodelsareφ(N
displayedin Fig.
1.≈ 400and− 500" is insignificant, should not depend on theseb et al. 2013). We also consider cases among a relatively small sample of young Galactic stellar
areSince
discussed
App. B.
panel, left) displays an example of the distributionof φ details.
1most inclusters
that harbor
singleO starsConsort
in ourdisplays
arealizations
few examples
ofthegenerated
ICLMFsFig.of2theImperial
CollegeLondon,Blackett
Lab.,
PrinceRd, London SW7 2AZ,
1.8. For each cluster with an assigned clusters are Γ
for
one
ICLMF
from
the
GPD-σ
fam=
1.37,
γ
=
0.91
and
M
=
0.41
obs
obs
obs
ch,obsmodelshave masses " 400 − 500 M" , the ejection of mas2 SFR, theof star-systems (i.e., individual stars
5.2 3AA
Models wi
with
expoand Astronomy, Cardiff University, Cardiff CF24
ily ofvarious
models permutations(full black line) of
andthefor Galactic
the youngSchool
clusters of Physics
M! with standard deviations of σΓobs = 0.60, σγobs =sive stars from the clusters is not expected to significantly
the clusters are randomly sampled
3 cutoff
nent
of MWSCthe ICLMF
anddashed
the lower
in thecatalog(β),(purpleline) massplottedversusin cluster
Kapteyn
Institute,PO
Box 800, 9700 AV Groningen, The Netherlands
affect
the
value
of
f
Our
modeling
allO,single . If we account for the fraction
law (TPL) distribution function (de 0.25, and σMch,obs = 0.27 M! , respectively (Dib 2014a).
5 aCOMPARISON OF MODELS TO
log(N∗,2−10+ 1). ),
The
unnormalized
ratio ofthethese
two dis4system
masses(Mcl,minandFig. 3 displays
IMFs
for
LeidenObservatory,
LeidenUniversity,PO
2300 RA Leiden,
The NetherlaofejectedO stars,
The quantity
fO,single
canBox,be approxarravano et al. 2011). Without any When drawing the parameters from Gaussian distributions,4.2+,0.8%
strainingthe max
OBSERVATIONS
tributions(R2−10= φobs/φmodelfrom) is plottedFig.
6 (middle
5 realization
few
selectedclusters
drawn
one ofin theof theimatedby ≈ NO,single/(NO,single + fO,ejec NPhysisk,),n, a stellar ”system” of mass M∗ can the distributions are always centered on these observedO,non−single
Max-Planck-Institutfürextraterrestrische
Giessenbachstrasse
1,
85748(1982) and Weidn
panel, left). A similar example is shown in the right panel
5.1
Models based
stochastic
starthatformation
ICLMF
in the GPD-σ ICLMF
familyof models6(i.e.,
withvarying
idual star or to a binary system. The
where
NUniversity,
isSchool
the onnumberof O star
are notO,non−single
ministic relation
St.
Andrewsof Physics
andAstronomy,
St. Andrews
KY16 e9for one realization of theobs
from the δf-GF
familyofmean values. We test dispersions of the Gaussian distriby
single,and fO,ejec is the fraction of ejected O stars as a funcIMFs).
technical
details
onhavethecomputed
samplingof In
themodels.Additional
All completeness
functionsthat wethis family of models, stellar masses in eachsive star in a clus
butions of (σΓobs , σγobs , σMch ), (σΓobs , σγobs , σMch ) /2, andtion ofcluster
theclustermass.
Usingsampled
thevaluesinof theNO,single
andE-mailcontact:e.drabekmaunderatimperial.ac.uk
ICLMF
and
of
the
IMF
are
presented
in
App.
§.
A.
for
the
different
syntheticclustermassfunctionsdisplayaarerandomly
mass
range
!
" #
tence of a cluster(σΓobs, σγobs, σMfigure
and apply lower and upper cutoffs$γ+Γ %&
and adapted
values of fO,ejec as a function ofch ) /4,
Figure1. Thedisplays the probability distribution funcsimilar behavior, namely a peak at LogN∗,2−10 ≈ 1.8 − 2, NO,non−singlemin(MM∗cl , 150)]M! for the set of parameters (Γ, Mch ,an
LkCa 15Figure
is an[0.02,
extensively
studiedstar
the Taurus
regionknown highly
for itsdebated
pre-trans
1 − exp −,(6) of (0.4,(0.70, 2.4)
for Γ, the
and
The
top
panel
(A)
in
thein
comparesthe thefraccluster
mass
for
the
different
offiguremodelsyieldssmall
tions 1.5)of the forthreeγ,parametersthat describe
IMF(0.05,
used in1)thisM! forwith a decrease for both increasing and decreasing values
γ)8.
that
are
assigned
to families
thecluster.
When
comparingMchand hypothesis
galaxy propet
The acronym
δF-GFtorefersdelta functionsof the limits
pationsofsingleandlonelyO-starsystems(definedasM!
15
increases
in
f
of
≈
10
−
12%
for
GPD-σ
type
modin
dust
continuum
andnormalgas
accretion
rate.
The
most
popular∗
Mchwork.
, whichcorrespond
thetolower
and upper
deO,single
obsof N∗,2−10
around thepeak.
Weassume a completenessoffractions of single and lonely O stars (fO,single and fO,lonely )4.2
Assigningages
tosimulatedclusters
rameters at the positions of the Galactic field values, whereas
lationtoresults
in a
Mels
calculated
fromtheδF-GF
samplesofclusters
fromthethis
MWSC≈ 18 −the
22%
for
type
models.
Applying
ber of stellar systems with the loga- rived" ) andunity at the position of the peak by normalizing
theor
comby Dib (2014a). These models are labeled GPD-σ/ibetweenobservations
andthemodelsofsyntheticclusonemore
planets
to
carve
out
the
inner
cavity,while
gas continues
flow acroδF-OBS refers to delta functions located at the mean values ofcorrectiontoaccount
formainthefractionofdynamicallyejected modsurvey(dashedlines)two
with
those
measuredfor1)thebetween logM∗ and logM∗ + dlogM∗ ,at a fixed+pletenessfunctionby its value
peak, andfit central
linearters,
we
options:
optionwe different
comparetheJ=4–3 galaxies(for theGaussian
Probability
Distributions,where
2, or 4).
The
syntheticclusters
that atarethegeneratedfor
each
realizathe
star.
Wehavepresent
spatially
unresolved
HCO
observationsofparameters
derived by Dib(2014a) for a sample
of 8i=1,
young
ation coefficient which is given by:increasesthedisagreement
betweenthe δF-GF
typesame
elsOofstars
syntheticclusters(purplecircles
andfO,lonely
orangetriangles).
The
relationsforbothcomponentsofthecompleteness
function
observational
values
of
f
and
with
the
the
Hα
emissionO,single+
Galactic
stellar clusters.
The othercases GPD-σ
and distriobs , GPD-σ
obs /2, theThey
are contrasted
withmodelsin whichtion of the ICLMF are initially zero-age clusters.
Beforetheand6, model
the
data
the
ProDiMocode.
Wefiducial
find
that:
line-wingst
modelsandthewithobservations
atsample
the
same
time,
itindoesotherparametersof themodels
are
set
at
their
values (1) HCO
on each side of the peak. (triple dot-dash line, Fig.
lower
quantities
derivedforthewhile
entireofclusters
a given
GPD-σobs /4 correspond to cases with a Gaussian probability dislow
galactic
FUV
butionsof the IMF parameters are delta functions that are
stellarclusters
be corrected
for
bi" #
not
substantiallyaffectrelativethat
good
agreement
betweenpresenceofMthegas
in=thewithin<50
AUoffilterthe(2)
the obsof
50 cavity
Mmass
MfunctionM, theM∗,max=star.
150comM$γ+Γ %&
panel, populations
left and right).ofAsthestatedabove,canwe interpretthe deinitialclusterpassof
the" , the"" , Reproducing∗,min=0.02
tribution of the IMF parameters whose half-width is related tocl,minstudies found thaM∗
4 andthesuppression
andobservations.
crease in completeness at low values of N∗2−10 by
the non1, 0.5, and 0.25 the values of the dispersion of each parameter inand
βGPD-σ=2. Theorangepoints
and
error
are
the>10mean
obs models
pletenessfunction(ortheto dustanaveragevalueof thesequantidM∗ = Mcl .
− exp −
significant
of cavity(by barsa factorcomparedthe
toIMF
the leads
ISM) toaMchthe sample of Dib (2014a). FDP-σobs corresponds to a case wheredetection of faint clusters, whereas the non-detectionof sometiesdeviation
for a numberof realizationsof the ICLMF;
i.e., the”allall
MNRAS
000,
1–17
(2016)
standardoffandfcalculated
using
O,singleO,lonelyscale-height within the cavity (H0 /R0 ∼ 0.6). An ISM dust-to-gasluminosities
ratio (d : atg=low
the probability distribution function of each parameter is givenof the most massive clusters is most likely due to their relUnder
this approach,the assumption(7)
clustersclusters”
that passapproach).
the filter ofthe completeness
functionin 27 real5.2of is
Modelswithanofimposed
M=cl341− Myoung
relationby a boxcar function whose width is given by 2 × σobs . The lower∗,max
regardlessthescale-heightorcavitygas
geometry,
while
Weisz scale-heigh
et al. 2012
ative scarcity in the Galaxy and the fact that theylie, onthesampleNclusters
inthe
MWSC,clizations
ofthattheinitialclustermassfunction(ICLMF).
The 27real- a smaller+ of the parameters correspond toand upper truncations
for eachn describes the IMF with only three
HCO
DetectionofDust-Depleted
Gas
in
the
Inner
Hole
of
the
LkCa
15
Pre-Transitionalstarformingdensit
regiowith a reduced
d:g. variations(3)
The
cavitygasconsequencesmass
is consistent
with thesurfaceizations
includeGalactic
star formation
rates, theOur modelingallows
us of
tothe
test
the
of conthe lower and upper limits of these parameters derived by Dib
n the low mass regime (γ), the slope
MNRAS 000, 1–17 (2016)
relationH
Diskstrainingthe maximum
stellarmass
inandclusters.
Vanbeveren
drawn
ages of radius
the clusters,
seed numbers
used Mto d ∼ 0.03
inwardsrandomly
tothe sublimation(corresponding
to massM"between), and m(2014a).
high mass regime (Γ), and the char(1982)
andWeidner&
Kroupa(2004)
arguedthatadetersults
that
do
not
randomly
sample
the
ICLMF
and
the
stellarmasseswithin
each
1
1
2
3
4
3
5
to ,beruledout. , W.-F. Thi , P.
The minimum stellar mass, M∗,min ,E. Drabek-Maunder , S. Mohanty , J. Greaves , I. Kamp , R. Meijerink
M.
Spaansministic
relation
betweenthebars
massareof thethe grandmost mascluster.
The
purpleexists
pointsand error
mean andan Mcl − M∗,max.02 M! . The maximum stellar mass,either located atWoitke
the values6 of the parameters derived by
Acceptedby star
ApJin absolute
sive
a cluster deviationand the mass
the 27cluster.
Therealizations
exisgrand
mean
fromofthe
ICLMF
n by min[Mcl , 150 M! ] (correspondFollowing the
Dib (2014a), or the Galactic field values that are given by
tence
of athecluster-mass-dependent
truncationof the
IMF realizais
and
where
mean and mean absolutedeviationfor eachhastic sampling) or is dictated by a1erate additional mLab., Prince Consort Rd, London SW7 2AZ, http://arxiv.org/pdf/1609.05894
UKΓf ield = 1.35, γf ieldImperial= 0.57, andCollege
Mch,f ield London,= 0.42 M! Blackett(Parhighly
debated andhas10000
importantconsequences
for clustertion
are calculated
fromdrawings
of subsamples
of clusters
stellar mass relation (Mcl − M∗,max )Figure 8. The top panel (A) in the figure compares the fracstar-systems)
in t
2 These families of models are labeled δFravanoetal.
2011).
School of Physics and Astronomy, Cardiff
Cardiff
and ofgalaxyproperties
evolution.
Mcl − M∗,max
tions ofUniversity,
single and lonely
O-starCF24
systems3AA(defined as M∗ ! 15
Vanbeveren (1982) and later by Weieach
size N= 341.
Each Asubsampleof NMreM W SC,cl and
W SC,clrange M∗,min = 0
OBS and δF-GF (Delta
Function Observations and- Galactic
3
lation results
in a steeper
wideensemble
IMF for lower
mass thatfrom theof clusters from the MWSC). We test models in which the dis" ) calculated
clusters
is randomly
drawngalaxy
from theof clusters
Kapteyn
Institute,
PO Box800, 9700MAV
Groningen,
Thesamples
Netherlands
Field,
respectively).
We
also
test
flat
probability
distribuby
thelatestvers
survey (dashed lines) with those measured for the different Proper
modgalaxies
at a offixed
andandto a function
downturn
the realization
ratio
ofmotionsurveykinematic
analysismeters (Γ, Mch , γ) are either given4
pass
the filter
the SFR
completenessinineachof of the Rho Op
Observatory,
Leiden beUniversity,
PO Box, 2300 RA Leiden, The Netherlands
tions (FPD). TheseLeiden
are describedby boxcar functions
els of synthetic clusters (purple circles and orange triangles). The
dner et al. 2013).
theICLMF.
Hα emission
to theleft
Farpanel
Ultraviolet
emission(FUV)
at (C)
clusters have the same value of thethelower right
1,2 The lower
2,1 (B) and1 panel15 γ, (0.7, 2.4) for Γ, and (0.05, 1) M! for
tween
(0.4,
1.5)
for
C.
Ducourant,R.
Teixeira,
S.
Bontemps,
D.
Despois
,
P.
A.
B.
Gall
Max-Planck-Institutfürextraterrestrische
Physisk,
Giessenbachstrasse
1,85748
Garching,
Germanyotherparametersofthemodels
are
set
at
their
fiducial
valuesfunctions, or boxcar functions. A relow galactic
FUV luminosities. A numberofoftheobservational
log10 (M∗,max /M"
displaythe
ICLMF (β) andMch . The distributionof the parameters of the
1 effect of changing the exponent
5
6of Mcl,min
50 M" , M∗,min=0.02
M" , M∗,max= 150
M" ,UK
M.
Rapaport
andJ.C.
Cuillandre
the mean values of the parameters
St. functions
Andrews
University, School of Physics
and=Astronomy,
St. Andrews
KY16
9SS,
studies
found
that
amass
cluster-mass-dependent
truncationof the0.15 × [log10 (Mcl /theminimumcluster(Mcl,min ), respectively.
For clarity,
IMF for all of these models are displayed in Fig. 1.
and β = 2. The orange points and error bars are the mean andall sample of young Galactic stellar
the IMF
leads andto anpurple
under-predictionoftheshifted
observedHαorangetriangles
circleshave
beenhorizontally1
isto beG
standard deviation of fO,single and fO,lonely calculated usingLaboratoire
alla few examplesof thegenerated ICLMFs at imperial.ac.uk
Fig. 2 displaysd’astrophysiquede Bordeaux,Univ.
Bordeaux,
CNRS,assumed
B18N, alléeE-mailcontact:e.drabekmaunder37, γobs = 0.91 and Mch,obs = 0.41
lowbyFUV
luminosity
et al.respectively.
2011;
byluminosities[0.2, −0.2], at
and[1, −1]in panels(Fumagalli(B) and (C),clusters that pass the filter of the completeness function in 27 realM" which is the cwith various permutations of the Galactic SFR, the expoeviations of σ
= 0.60, σ=!
"$γ+Γ %&
69120 Heidelberg,# Germany.
M∗
dN∗= A∗ × M∗−Γ 1 − exp −,(6)
dlogM∗
Mch at gmail.com
E-mail contact: sami.dib

Figure 1. The figure displays the probability distribution functions of the three parameters that describe the IMF used in thiswork. The acronym δF-GF refers to delta functions of the parametersat thepositionsof the Galactic
field values,
whereasWe
investigate
whetherthestellarinitialmassfunction(IMF)
is universal,
or whether
it varies
significantly among
where dN∗ is the number of stellar systems with the logarefers to delta functions located at the mean values ofrithm of their masses
betweenlogM+ dlogM
young
stellarlogM
clustersthe∗ MilkyWay.
WeδF-OBS
proposea method to uncover the range of variation of the parameters∗ andin∗,the parameters derived by Dib (2014a) for a sample of 8 youngand A∗ is the normalization
coefficient
which
given
by:for the population of young Galactic clusters. These parameters are the slopesthat describe
the shapeof istheIMF
Galactic stellar clusters. The cases GPD-σobs , GPD-σobs /2, andin the low and high stellar mass regimes, γGPD-σand obs
Γ,/4respectively,
and withthe characteristic
mass,disMch . The method
correspond to cases
a Gaussian probability%& mass content tribution! exclusively" # on $the high' M∗,maxof the IMF
whose
is related
to distributions ofreliesof the clusters,
butparameters
is able toyieldhalf-width
informationon theγ+ΓM∗−Γ1, 0.5, and
0.25massthe valuesof thedispersionof eachbyparameterin the fractions of
Mcl . the entire
A∗ ×M∗parameters
1 − exp that− describe thedM∗ =over
IMF
stellarrange.
Thisis achieved
comparingMchM∗,minsampleof Dib(2014a).
FDP-σcorresponds
a casewhere in two realizations of the ICLMF. The left panel displays a
Figure5. Theinitial,present-day,singleO-star clustermassfunctionsobs
single and lonely massive O stars in a recentthe
catalogof theMilkyWayandclusters
withtheto
a IMF
library
ofcluster
simulatedclusters
caseprobability
in which thedistribution
set of three parametersthat
describe
ofiseachare each randomly drawn from a GPD-σobs probability
thefunctionofeachparametergiven(7) of thedistribution
built with various distribution functions
parameters.
The
syntheticclusters
corrected
theeffectsthatof describe the IMF is similar to thefunctionwhereastheright panel
displaysin whichthe set offor
threeparameters
by IMFa boxcarfunction
whose
width
is given
by 2a×case
σareobs . The lower
valuesof the parameters for theejected
Galactic fieldstars.
mass function.
All other parameters
set toMcl,min = 50 M! , M∗,min = 0.02 M! ,the binary
population,
evolution,
incompleteness,
Ourcorrespondfindings
indicateare
that
broad
and
upper truncations andfor each of theOparameters
to
The TPL function
describes
the IMFstellar
with only
three sampleM∗,max = 150 M! , and β = 2. The figure displays the initial cluster mass function (ICLMF) and the present-day cluster mass function
M*,min!=!0.02!Msun!
the
lower
andCLMF
upper
limitsof these
derivedby andDib lonely
distributions
the regime
IMF parameters
are requiredin Theorder
to isreproduce
thefractionsofsingleObeen
stars
in an age, and has been correctedparameters, the slope
in the lowofmass(γ), the slope(CLMF).
the conversionof parameters
the
ICLMF after
each
individual
cluster has
assigned
M*,max!=!min[Mcl,!150!Msun]!or!values!expected!
(2014a).
for theto
effects
the stellar binary
and mass-maximum
stellar evolution. The numberof clusters that contain single O stars (within the intermediate-to-highmass regime(Γ),also
anddo
thenotcharGalactic clusters.
Theylend support
theof existenceof afraction
clusterstellardistribution
mass relation.

LkCa!15!–!pre,transiConal!disk!with!a!large!inner!cavity!
in!dust!conCnuum!+!normal!gas!accreCon!rate.!!
• The!most!popular!hypothesis!–!one!or!more!
planets!to!carve!out!the!inner!cavity,!while!gas!
conCnues!to!ﬂow!across!the!gap!!
France Weisz et al. 2012). Other studies on the scale of resolvedof the initialclusterknown
mass function(ICLMF).
The 27 real- disk
nent of the ICLMF(β), andlower
mass cutoff incluster star inizations
LkCa
15 theis anextensively
studiedthe Taurus
regionfor its
pre-transitionalwith a large inner cavity
20.27 M , respectively (Dib 2014a).2.
star
regions using
the Hα/FUV
ratios Atmosféricas,
or the corSpaCally!unresolved!HCO+!J=4–3!observaCons!at!JCMT!
deforming
Astronomia,
Geofı́sicae Ciências
Universidade de Sãoizations include variations of the Galactic star formation rates, Instituto
themasses(M),inandFig. 3continuum
displays the system
IMFs for gasadust
and normal
accretion
rate.
The
most
popularhypothesis
toexplainthe LkCa
15 datainvokesameters from Gaussian distributions,relation
between
HαSãoandbolometricluminosities
randomly
drawn
ages
of
the
clusters,
andseednumbers
usedto
few selected clusters drawn from one of the realization of the
Universitária,
05508-900
Paulo
- SP,
Brazil found realways centered on these observed+!Model!with!the!ProDiMo!code!
one orfamily
moreofplanets
to withcarve
out the innercavity,while
gas continues
to masses
flow acrossthe gapsults
from
disk
ontosupport to the existence ofthatthedo outernot seemto lendrandomly
samplethe ICLMF
and the stellar
within3 each
ICLMF
in
the
GPD-σ
models(i.e.,
varying
CENTRA/SIM,
FaculdadedeCiências,etUniversidade
de Lisboa, Ed. C8, Lab.
dispersions of the Gaussian distri+ and error bars are the grand mean and
The purple
pointsM disk− M from
relation(Hermanowicz
al. 2013).
thecentralstar.
Wesamplingpresent
spatially cluster.
unresolved
HCO
J=4–3 observations of the LkCaan15
the JCMT
Additional
technical
details
on theof the3. IMFs).
We!ﬁnd!that:!!
,σ
), (σ
,σ
,σ
) /2, and
grand mean absolute deviation from the 27 ICLMF realizations
Portugal
Following the same procedure described above, we genICLMF and of the
IMFmodelare presented
in App.
§. A.the ProDiMo code. We find that: (1) HCO+ line-wings Lisboa,
andthe data
withdetected,
certifying
the the masses of stars (i.e.,
and apply lower and upper cutoffs
4are clearly
and where the mean and mean absolute deviation for each realiza+
erate
additionalmodelsinwhichCentrodeAstrobiologı́a,
Dptode
Astrofı́sica,
INTA-CSIC,
PO BOX 78, E-2869•(1)!HCO70, 2.4) for Γ, and (0.05, 1) M forare ofcalculated
from 10000
drawings of subsamples
of clusters line-wing flux requires both apresence!line,wings!are!clearly!detected!–!gas!in!
of gas in the cavity within <50tion
AUthe star.
(2) Reproducing
the observedin the clusters are randomly sampled in theCañada, star-systems)
Madrid, Spaind to the lower and upper limits deeach of size N
4 = 341. Each subsample of N
4.2 Assigningages
tosimulatedclusters
range
M
=
0.02
M
and
an
M
that
is
imposedsignificant
suppressionofcavitydust(byafactor>10
compared
to
the
ISM)
and
a
substantial
increaseinthegas
the!cavity!within!<50!AU!of!the!star.!!
clusters is randomly drawn from the ensemble of clusters5 that
These models are labeled GPD-σ/i
CEA/IRFU/SAp,
Laboratoire
AIM Paris-Saclay,
CNRS/INSU, Université Parisby theof theflux
M −M
relation (Weiscale-height
within thecavity(H0 /R0 ∼pass
0.6).
An ofISM
dust-to-gas
ratioin (dg = 10−2of) yields
toolatest
littleversion
line-wing
the filter
the completeness
function
each: realization
ity Distributions, where i=1, 2, or 4).
The synthetic clusters
that are generated
for eachrealizaResearch
University,
F-91191
Cedex,
dner
et al. 2013).
The M Gif-sur-Yvette−M
relationis givenFranceby(2)!Reproducing!the!observed!line,wing!ﬂux!
The lower
left panel(B) and lower
right panel also(C) under
ith other models in which the distrition•of the ICLMF
are initially ofzero-ageclusters. Before theregardlessthe scale-heightor cavity thegasICLMF.
geometry,while
a smallerscale-height
predicts
the
flux
even
log (M/M ) = −0.66 + 1.08 × [log (M /M )] −display the effect of changing the exponent of the ICLMF (β)
andrameters are delta functions that are
stellar populationsof the clusters can be corrected for the biE-mailcontact:
christine.ducourantatu-bordeaux.fr
requires;!!
witha reduced d:g. (3) The cavity gas themassisconsistentwiththesurfacedensity
profile
of
the
outer
disk
extended
0.15
×
[log
(M
/M
)]
+
0.0084
×
[log
(M
/M
)]
and
minimum cluster mass (M), respectively. For clarity, the29–to be validorange trianglestoand
purpleMcircleshorizontallyis assumedforclusterandmasses
M # 2.5 ×the
10 Lynds L1688 dark cloud ito theMNRAS
sublimation(correspondingmass
0.03beenM"shifted), andmassesby a– molecularfactor>10complex
appearThe ρlower
Ophiuchiin particulard ∼ have000, 1–17 radius(2016)• inwards
a!signiﬁcant!suppression!of!cavity!dust!(by!
by [0.2, −0.2], and by [1, −1] in panels (B) and (C), respectively.
M which is the case of the clusters considered in this work.
to be ruled out.
in its richness
in young stars and protostars, and in its youth (0.5 Myr). It is certai
4
a!factor!>10 !compared!to!the!ISM)!!
accessible from the ground to study theearly000,phasesof star-formation. Proper moti
MNRAS
1–17 (2016)
Accepted by ApJ
separating members of clusters from field stars, but very few proper motions are ava• http://arxiv.org/pdf/1609.05894
a!substanCal!increase!in!the!gas!scale,most of the young sources are deeply embedded in dust and gas. We aim at perfo
height!within!the!cavity!(H0/R0!!0.6).!An!
stellar objects (YSOs) in the ρ Ophiuchi F core and partially in the E core of the−2
motion program at the ESO New Technology Telescope (NTT) with the Son of I
ISM!dust,to,gas!raCo!(d:g!=!10)!yields!too!
Propermotion survey and kinematic
analysis of the Rho Ophiuchi
embedded cluster
years in the near-infrared. We complemented these observations with various pu
lisle!line,wing!ﬂux!regardless!of!the!scale,
1,2
2
4
1
C. Ducourant, R. Teixeira2,1 , S. Bontemps1 , D. Despois1 , P. A. B. Gallitime, H.base
Bouy, J.F. Le Campion, of investigation to 0.5◦ ×0.5◦ . We derived poof observations
and the field
1
M. Rapaport
and J.C. Cuillandre5
height!or!cavity!gas!geometry,!while!a!
objects. From these, 607 proper motions were derived from SOFI observations wit
1
Laboratoired’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac,
smaller!scale,height!also!under,predicts!
Francethe!ﬂux!even!with!a!reduced!d:g.!!
2
13Instituto de Astronomia, Geofı́sica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226 - Cidade•(3)!The!cavity!gas!mass!is!consistent!with!the!
Universitária, 05508-900 São Paulo - SP, Brazil
3
CENTRA/SIM, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Lab. 8.5.02, Campo Grande, 1749-016,
surface!density!proﬁle!of!the!outer!disk!extended!
Lisboa, Portugal
4inwards!to!the!sublimaCon!radius!(corresponding!
Centro de Astrobiologı́a, Dpto de Astrofı́sica, INTA-CSIC, PO BOX 78, E-28691, ESAC Campus, Villanueva de laCañada, Madrid,
Spain
Fig. 6.— Surface density profile of the gas (red) and dust (blue) of the final disk models.
to!mass!Mgas!!0.03!M),!and!masses!lower!by!a!
5
R Parisdenotes the
sublimation radius(the inner radiusde
for thedust cavity
at 0.1 AU), R
CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université
Diderot,
Observatoire
Paris,
PSL
denote the extent of the cavity (50 AU) and R denotes the characteristic tapering andfactor!>10!appear!to!be!ruled!out.
Research University, F-91191 Gif-sur-Yvette Cedex, France
scaling radius (300 AU).

s

1.

Γobs

γobs

!

cl,min

obs

cl

Mch

Γobs

γobs

∗,max

Mch

!

M W SC,cl

M W SC,cl

∗,min

"

∗,max

cl

cl

10

cl,min

∗,max

"

10

cl

∗,max

∗,max

cl

10

2

"

10

cl

cl

"

Rsub

Rcav

Rc

Outer Disk

Dust Cavity

Gas

d:g=10-2

d:g=10-6

Dust

sub

cav

c

E-mail contact: christine.ducourant at u-bordeaux.fr
The ρ Ophiuchi molecular complex and in particular the Lynds L1688 dark cloud is unique in its proximity (∼130 pc),
in its richness in young stars and protostars, and in its youth (0.5 Myr). It is certainly one of the best targets currently
accessible from the ground to study the early phases of star-formation. Proper motion analysis is a very efficient tool for
separating members of clusters from field stars, but very few proper motions are available in the ρ Ophiuchi region since

"
3

"

5

in dust continuum and normal gas accretion rate. The most popular hypothesis t
one or more planets to carve out the inner cavity, while gas continues to flow acro
the central star. We present spatially unresolved HCO+ J=4–3 observations ofand model the data with the ProDiMo code. We find that: (1) HCO+ line-wings
presence of gas in the cavity within <50 AU of the star. (2) Reproducing the obs
significant suppression of cavity dust (by a factor >104 compared to the ISM) a
scale-height within the cavity (H0 /R0 ∼ 0.6). An ISM dust-to-gas ratio (d : g =regardless of the scale-height or cavity gas geometry, while a smaller scale-heigh
HCO+ Detection of Dust-Depleted Gas in the Inner Hole of thewith
LkCa
15 Pre-Transitionala reduced
d:g. (3) The cavity gas mass is consistent with the surface densit
Disk
inwards to the sublimation radius (corresponding to mass Md ∼ 0.03 M" ), and m
to4 ,beruledout. 3 , W.-F. Thi5 , P.
E. Drabek-Maunder1 , S. Mohanty1 , J. Greaves2 , I. Kamp3 , R. Meijerink
M.
SpaansWoitke6

Accepted by ApJ

1Imperial College London, Blackett Lab., Prince Consort Rd, London SW7 2AZ, http://arxiv.org/pdf/1609.05894
UK
2
School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA
3
Institute, PO Box 800, 9700 AV Groningen, The Netherlands
Cavity!gasOuter!disk4 Kapteyn
Best,ﬁt!model
Proper motion survey and kinematic analysis of the Rho Op
Leiden Observatory, Leiden University, PO Box, 2300 RA Leiden, The Netherlands
1,2
5
Ducourant, R. Teixeira2,1 , S. Bontemps1 , D. Despois1 , P. A. B. Gall
Max-Planck-Institut für extraterrestrische Physisk, Giessenbachstrasse 1, 85748 C.
Garching,
Germany
6
M. UK
Rapaport1 and J.C. Cuillandre5
St. Andrews University, School of Physics and Astronomy, St. Andrews KY16 9SS,

1
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée G
E-mail contact: e.drabekmaunder at imperial.ac.uk
France
LkCa 15 is an extensively studied star in the Taurus region known for its pre-transitional
disk with a large inner cavity
2Instituto de Astronomia, Geofı́sica e Ciências Atmosféricas, Universidade de Sãoin dust continuum and normal gas accretion rate. The most popular hypothesis to explain the LkCa 15 data invokes
Universitária, 05508-900 São Paulo - SP, Brazil
one or more planets to carve out the inner cavity, while gas continues to flow across
3 the gap from the outer disk onto
CENTRA/SIM, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Lab.
the central star. We present spatially unresolved HCO+ J=4–3 observations of the LkCa 15 disk from the JCMT
Lisboa, Portugal+
and model the data with the ProDiMo code. We find that: (1) HCO line-wings 4are clearly detected, certifying theCentro de Astrobiologı́a, Dpto de Astrofı́sica, INTA-CSIC, PO BOX 78, E-2869
presence of gas in the cavity within <50 AU of the star. (2) Reproducing the observed line-wing flux requires both aCañada, Madrid, Spainsignificant suppression of cavity dust (by a factor >104 compared to the ISM) and5 a substantial increase in the gas
CEA/IRFU/SAp,
Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris
scale-height within the cavity (H0 /R0 ∼ 0.6). An ISM dust-to-gas ratio (d : g = 10−2 ) yields too little line-wing flux
Research University, F-91191 Gif-sur-Yvette Cedex, France
regardless of the scale-height or cavity gas geometry, while a smaller scale-height also under predicts the flux evenchristine.ducourantwith a reduced d:g. (3) The cavity gas mass is consistent with the surface densityE-mailprofilecontact:of the outerdisk extended at u-bordeaux.fr
inwards
the sublimation
radius (corresponding
to mass
MdInner∼ 0.03HoleM" ), andmassesa molecularfactor >10complex
appear and in particular the Lynds L1688 dark cloud iTheρlower
OphiuchiHCO+toDetectionof Dust-DepletedGas
in theof the
LkCa
15byPre-Transitionaltobe ruled out.
in its richness in young stars and protostars, and in its youth (0.5 Myr). It is certai
Disk
accessible from the ground to study the early phases of star-formation. Proper moti
1
Acceptedby ApJ
E. Drabek-Maunder, S. Mohanty1 , J. Greaves2 , I. Kamp3 , R. Meijerink4 , M. Spaans3 , W.-F. Thi5 , P.
separating members of clusters from field stars, but very few proper motions are ava
6
Woitkehttp://arxiv.org/pdf/1609.05894
most of the young sources are deeply embedded in dust and gas. We aim at perfo
1Imperial College London, Blackett Lab., Prince Consort Rd, London SW7 2AZ,stellar
UK objects (YSOs) in the ρ Ophiuchi F core and partially in the E core of the2
School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA
motion program at the ESO New Technology Telescope (NTT) with the Son of I
Propermotionsurveyandkinematic
analysisoftheRhoOphiuchiembedded cluster
3
Kapteyn Institute, PO Box 800, 9700 AV Groningen, The Netherlands
years in the near-infrared. We complemented these observations with various pu
4 Ducourant1,2 , R. Teixeira2,1 , S. Bontemps1 , D. Despois1 , P. A. B. Galli2 , H. Bouy4 , J.F. Le Campion1 ,C.
Leiden Observatory, Leiden University, PO Box, 2300 RA Leiden, The Netherlands
time base of observations and the field of investigation to 0.5◦ ×0.5◦ . We derived po
5M.
Rapaport1 and J.C.
Cuillandre5
Max-Planck-Institutfür extraterrestrische
Physisk, Giessenbachstrasse 1, 85748 objects.
Garching,
GermanyFromthese, 607 proper motions were derived from SOFI observations wit
16 St. Andrews University, School of Physics and Astronomy, St. Andrews KY16 9SS, UK
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac,
FranceE-mail contact: e.drabekmaunder at imperial.ac.uk
213Instituto de Astronomia,
Geofı́sica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226 - Cidade−γLkCa) 15 is an2−extensivelyγ,
studied star in the Taurus region known for its pre-transitional disk with a large inner cavity" R % Universitária," R % 05508-900
São Paulo - SP, Brazil
dust
andnormal gas accretion rate. The most popular hypothesis to explain the LkCa 15 data invokes+− $continuum
Σg = Σc $ ' 3inexp' . Faculdade!Eq.!(1)!of!Andrews+!2011
CENTRA/SIM,de Ciências, Universidade de Lisboa, Ed. C8, Lab. 8.5.02, Campo Grande, 1749-016,
one or+* more.- to carve out the inner cavity, while gas continues to flow across the gap from the outer disk onto
# Rc & Lisboa,# Rc &planets
Portugal+
J=4–3 observations of the LkCa 15 disk from the JCMT
4the central star. We present spatially unresolved HCO
Centro de Astrobiologı́a, Dpto de Astrofı́sica, INTA-CSIC, PO BOX 78, E-28691, ESAC Campus, Villanueva de la
and model the data with the ProDiMo code. We find that: (1) HCO+ line-wings are clearly detected, certifying theCañada, Madrid, Spain
5presence of gas in the cavity within <50 AU of the star. (2) Reproducing the observed line-wing flux requires both a
CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, Observatoire de Paris, PSL
significant suppression of cavity dust (by a factor >104 compared to the ISM) and a substantial increase in the gas
Research University, F-91191 Gif-sur-Yvette Cedex, France
scale-height within the cavity (H0 /R0 ∼ 0.6). An ISM dust-to-gas ratio (d : g = 10−2 ) yields too little line-wing flux
remainingobjects
werethemeasured
only from auxiliary data with a mean precision oE-mailcontact:
at u-bordeaux.fr
regardlessof thechristine.ducourant
scale-height or cavity
gas geometry, while a smaller scale-heightalso under
predicts
flux evena kinematic
analysisthe extended
most accurate proper motions derived in this work, w
withρ aOphiuchi
reduced moleculard:g. (3) The
cavityandgasinmass
is consistent
withL1688
the surface
density
profile in
ofits
the
outerofdisk
Thecomplexparticular
the Lynds
dark cloudis uniqueproximity(∼130 pc),
members
from fieldstars>10
and appear
to derive the mean properties of the cluster. From t
inwards
to theinsublimation(corresponding
0.03 MIt"is), certainly
and massesa factorin
its richness
young stars radiusand protostars,
and in toitsmass
youthM(0.5onelowerof thebybest
targets
currentlyd ∼ Myr).
list of 68 members and 14 candidate members, comprising 26 new objects with a h
to be ruled
out.the ground to study the early phases of star-formation. Proper motionaccessible
fromanalysis is a very efficient tool for
new members are generally fainter than the known ones. We measured a mean pro
separating
members
in the ρ Ophiuchi region since
Accepted by
ApJ of clusters from field stars, but very few proper motions are available-24.3)±0.8 mas/yr for the L1688 dark cloud. A supervised classification was applie
most of the young sources are deeply embedded in dust and gas. We aim at performing a kinematic census of young
to allocate a spectral energy distribution (SED) classification to the unclassified me
http://arxiv.org/pdf/1609.05894
stellar objects (YSOs) in the ρ Ophiuchi F core and partially in the E core of the L1688 dark cloud. We run a properthat the 56 members that were known from previous studies of the ρ Ophiuchi F
motion program at the ESO New Technology Telescope (NTT) with the Son of ISAAC (SOFI) instrument over nine
our survey are members of the cluster, and we added 26 new members. We defi
years
in themotion
near-infrared.
We andcomplemented
theseanalysis
observations
withvariouspublic imageembedded
databases to enlarge thePropersurveykinematic
of
the
Rho
Ophiuchiunclassified members of cluster
the cluster. We showed that a large part (23) of thesetime base of observations
and the2,1
field of investigation
to 0.5◦ ×0.51◦ . We derived positions
and propermotions for 2213
1,21
2
1 of known substellar objects in the cluster by
dwarfs,which4 ,multiplies
the number
C. Ducourant, R.
Teixeira, S. Bontemps, D.
Despois, P. A. B. Galli
, H.
Bouy
J.F.
Le Campion
objects.
From these,607
propermotionswerederived
from
SOFI
observations
with
a
∼1.8
mas/yraccuracy
while the,1
5
A&A proofs: manuscript no. Ducourantv2
M. Rapaport and J.C. Cuillandre
Accepted by A&A main
1
Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy
Saint-Hilaire, 33615 Pessac,
http://arxiv.org/pdf/1609.04963
13
Francepositions. These de2
Instituto de Astronomia, Geofı́sica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226 - Cidade
1. YSOs!in!the!ρ!Oph!F!and!parCally!E!
thesecatalogues.
A photo-evaporative gap in the closest planet
formingdisc W
Universitária, 05508-900 São Paulo - SP, Brazil• Near!IR!proper!moCon!program!at!the!ESO!New!
to these 1data, whic
3
1,2
3
CENTRA/SIM, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Lab.Barbara
8.5.02, CampoGrande,1749-016,
Ercolano , Giovanni P. Rosotti , Giovanni Picogna , Leonardo( ↵, )= (-182,+8
Technology!Telescope!(NTT)!with!the!Son!of!
Lisboa, Portugal
1
Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München,
Germany4217) masfor Spitz
CentrodeAstrobiologı́a,
Dptode
Astrofı́sica,
INTA-CSIC,
PO
BOX
78,
E-28691,
ESAC
Campus, Villanueva de la
2
ISAAC!(SOFI)!instrument!over!9!years.!
Excellence Cluster Origin and Structure of the Universe, Boltzmannstr.2, 85748
positions.
After appU
Cañada, Madrid, Spain
3
InstituteofAstronomy,
UniversityofCambridge,
MadingleyRoad,
Cambridge,
5• Public!image!databases!to!enlarge!the!Cme!
CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris4Diderot, Observatoire de Paris, PSL
catalogue that conta
European Southern Observatory, Garching bei München, Germany
Research University, F-91191 Gif-sur-Yvette Cedex, France
base!and!the!ﬁeld!of!invesCgaCon!to!0.5◦!×0.5◦!
5w
INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi 2MASS
5, I-50125positions
Firenze, Ita
E-mail contact: christine.ducourant at u-bordeaux.fr
2. PosiCons!and!proper!moCons!for!2213!objects.!!
and the whole data
E-mail contact: ercolano at usm.lmu.deThe ρ Ophiuchi molecular complex and in particular the Lynds L1688 dark cloud is unique in its proximity (∼130 pc),
An young
a posterior• 607!from!SOFI!(1.8!mas/yr!accuracy)!+!13!from!
The dispersal of the circumstellar discs of dust and gas surrounding
low- main its richness in young stars and protostars, and in its youth (0.5 Myr). It is certainly
oneformationof the best
currently
showedevidencethfor theof targets
planetarysystems. Photo- evaporation fromenergetic
radiation
auxiliary!data!(mean!precision!3!mas/yr).!!
accessible from the ground to study the early phases of star-formation. Proper motion
analysisisavery
efficienttool
for
to drive the dispersal in the majority of discs, by creating amations
gap whichdisconnec
wasdegra
separating members of clusters from field stars, but very few proper motions are available
intheρ
Ophiuchiregionsince
3. From!the!kinemaCc!analysis!we!derived;!!
of the disc and then disperses the outer disc from the inside-out,while
the inner
were toonumerous
most of the young sources are deeply embedded in dust and gas. We aim at performing
kinematic
censusof young
the star.a In
this Letterwe showthat the disc around TW Hya,
thetoclosest
protop• 68!members!and!14!candidate!members,!
cided
excludeobstellar objects (YSOs) in the ρ Ophiuchi F core and partially in the E core of thefirst
L1688
dark
cloud.
Werunaproperobject where a photoevaporative gap has been imaged around the time at whcomprising!26!new!objects!with!a!high!
meanvelocityof fimotion program at the ESO New Technology Telescope (NTT) with the Son of ISAAC(SOFI)
instrument
over
nine
detected gap in the ALMA images is consistent with the expectations of X-ray p
years in the near-infrared. We complemented these observations with various public
imagethedatabases
theThe photoevaporation model
plate-to-platetransfmembership!probability.!!
requiringpresencetoofenlarge
a planet.
is also consisten
time base of observations and the field of investigation to 0.5◦ ×0.5◦ . We derived positions
andHyapropermotions2213 rate and the locationblyof the TW
system,e.g.foraccretionof cluster
the gap member
at the on• mean!proper!moCon!!(μ!cosδ,!μ)=(,8.2,!
αδ were derived from SOFI observations with a ∼1.8 mas/yr accuracy while theobjects. From these, 607 propermotions
central, unresolved 870 µm continuum source might be produced by free free emi

1/2

•

,24.3)±0.8!mas/yr!for!the!L1688!dark!cloud.!!
ρ!Oph!F!cluster!
13• 56!previously!known!members!in!our!survey!
area!–!kinemaCcally!conﬁrmed!
• 26!new!members!added!with!evoluConary!
status!!
• a!large!part!(23)!of!them!are!probably!
brown!dwarfs!=>!mulCplies!the!number!
of!known!substellar!objects!in!the!cluster!
by!a!factor!of!3.3.

We finally obta
objects spread overAccepted by MNRAS Lettersarated into two gro
http://arxiv.org/pdf/1609.03903
13.80 x 10.80 and b
remaining objects hiliarydata. Weandpress
The link between turbulence, magnetic fields,
filaments,
Fig. 1: Areas coveredby the present
catalogue of our proper motio
tral MolecularZone proper
cloud motion
G0.253+0.016
overlaid on the C.
mapof the 1L1688
cloud 2from
Bontempsof thFederrath, J. M.dark
Rathborne, S. N.
Longmore3 , J. The
M. spread
D. Kruijsse
18
9
10,11,12
et al. (2001). Red
lines
delimitate
the NTT-SOFI
observations
R. M.
Crocker, G. Garay, J. M. Jackson, L. TestimaterialandA. J.toWa
propere
and blue lines givethe total
extensionof the andcatalogue
including1
fromthis figuretha
Research
Schoolof Astronomy
Astrophysics,
Australian
National
University
auxiliary data. 2 CSIRO Astronomy and Space Science, P.O. Box 76, Epping
NSW, 1710,
Austraotributionof SOFI
3
Astrophysics Research Institute, Liverpool John Moores University,
IC2, Liverpoo
precise thanthe oneLiverpool L3 5RF, United Kingdom
ple benefiting of th4
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelbe
catalogue that we w
delberg,dueGermany
where the absorption
to
dust
is
much
lower
and
objectsare5
Max-Planck Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
detectable in the6 visible wavelengths. For the vast majority of obCASA, University of Colorado, 389-UCB, Boulder, CO 80309, USA
jects, which are7only
detectablein theinfraredor NIR,
we 9513,
com-NL-2300 RA Leiden, the N
LeidenObservatory,
LeidenUniversity,
PO Boxbined the positions from 2MASS with those from the AllWISE
data release (Cutri et al. 2013) (central epoch⇠2010), matched in
a 300 search radius to estimate the proper motions. We excluded 14
dust inside the gap.

a kinematic
analysisthe extended
most accurate proper motions derived in this work, w
with a reduced d:g. (3) The cavity gas mass is consistent with the surface density
profile of theouterofdisk
members
fromstars>10
and appear
to derive the mean properties of the cluster. From t
inwards to the sublimation radius (corresponding to mass Md ∼ 0.03 M" ), and masses
lower
byfielda factorlist of 68 members and 14 candidate members, comprising 26 new objects with a h
to be ruled out.
new members are generally fainter than the known ones. We measured a mean pro
Accepted by ApJ-24.3)±0.8 mas/yr for the L1688 dark cloud. A supervised classification was applie
A&A proofs: manuscript no. Ducourantv2
to allocate a spectral energy distribution(SED) classification to the unclassified me
http://arxiv.org/pdf/1609.05894
thatthe 56members
thatthatwere
knownof theρ Ophiuchi
thekinematic
members.
We observe
they aremostly fromlocated previous
We presentstudies
the distributionof these
H absolute Fm
ourare membersof thecluster, andadded
26 new
We anddefin
inthe survey
region of highest
absorption where
star-formationis on- we
known
members(blackmembers.
dotted histogram)going.
We
also
note
that
class
I
objectsaregloballyaligned
on
a
(red)
in
Fig.
13
.
Proper motion survey and kinematic analysis of the Rho Ophiuchi
embeddedcluster
unclassified members of the cluster. We showed that a large part (23) of these
northwest-southeast axis, mostly located in the most embedded
As expected, most of the new members are2
4 multiplies
dwarfs,which
theof known with
substellar
objectsbyregion,which
was proposed
Motte
et al.number(1998)1toMH ranging
from 5 toin
12.theSincecluster
the transition
C. Ducourant1,2 , R. Teixeira2,1 , S. Bontemps1 , D. Despois1 , P. A. B. Galli
, H.
Bouy
, J.F.byLe
Campion, correspondtothe perpendicular to the direction of shock propagation by the and BDs occurs at MH ⇠5 mag, that is, M J ⇠6 m
1
5
M. Rapaport and J.C. Cuillandre
Accepted
by
A&A
main
Upper Scorpius OB association onto the core of the ⇢ Oph cloud clusters (e.g., Bara↵e et al. 2015), virtually all the

2/2Ducourant C. et al.: Kinematics in ⇢ Ophiuchi

A&A proofs: manuscript
no. Ducourantv2
complex.

fall in the substellar regime. The MH values of thLaboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy
Saint-Hilaire, 33615 Pessac,
http://arxiv.org/pdf/1609.04963
troscopically confirmed BDs in ⇢ Ophiuchi are als
FranceFig 13 together with their spectral type. Above MH
2find 23 new substellar members, which is 3.3 tim
Instituto de Astronomia, Geofı́sica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226 - Cidade
previously
known BDsformingin the surveyeddisc
area.
A
photo-evaporative
gap
in
the
closestplanetthe J, H, Ks bands (cenUniversitária, 05508-900 São Paulo - SP, Brazil
The weakest four new members (UGCS
3(0.290,0.297,0.275) µm)
1,23
1
BX162727602-24381862,
UGCS
CENTRA/SIM, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Lab.Barbara
8.5.02, CampoGrande,1749-016,P. Rosotti244059.1,
Ercolano,
Giovanni,
Giovanni
Picogna,
Leonardo
for fainter objects of the244339.5, and 2MASS-6X J16265864-2443281)
Ducourant
C. et al.: Kinematics in ⇢ Ophiuchi
Lisboa,Portugal1bution of the Ks magnimag
arepotentially
very
low
mass
BDs
that
reach
Universitäts-SternwarteMünchen,Scheinerstr.
1,
81679
München,Germany
4
Centrode Astrobiologı́a, Dpto de Astrofı́sica, INTA-CSIC, PO BOX 78, E-28691,
ESAC Campus, Villanueva de laphotometric data from Table 6. If there
are some contaminants
as cool as L0 (⇠2200K, see discussions in Tottl
2
ig. 3 and list in Table 6
Excellence Cluster Origin and Structure of the
Universe,
Boltzmannstr.2,
85748
in our kinematic members sample, then they will be incorrectly2015).
These
cool
young
BDs
are
expectedtobe vCañada,Madrid,Spainderived in this work for
attributed to one of the three YSO classes since we assume here
3
Institute of Astronomy, University of Cambridge,
Road, Cambridge,
Uof onlyMadingley
about 10 MJup (Chabrieret al. 2000).
that each of the 82 members and 5candidates are young stellar
hi core (see next section
A&A proofs: manuscript
no. Ducourantv2
CEA/IRFU/SAp, Laboratoire AIM Paris-Saclay,
CNRS/INSU,
Université Paris4Diderot, Observatoire de Paris, PSL
objects.
We summariseGermany
the evolutionary status of the 82
EuropeanSouthern
Observatory,
Garchingbei
München,Ducourant
C.
et
al.:
Kinematics
in⇢OphiuchiFor the classification we adopted a supervised learning
ether with the AllWISE
candidates
in
Table
4.
Seven
members
alreadykn
Research
University,
F-91191
Gif-sur-Yvette
Cedex,
France5method, whose principle is the following. The method considE. Fermi
5, I-50125
Firenze,ometry.
the field. On the one hand, it may also be interesting to test any
the classified
kinematic
members. We observe that they are mostly located We present the distribution of these INAF/Osservatorio
H absolute magnitudes forAstrofisico di Arcetri, Largo
are identified
BD (Alvesde Oliveira
et al. 2012)Itaaners the various magnitudes of each previously
memberobject of the catalogue for its membership to the F/E cores al(J,H,K s ,w1,w2,w3,w4) and all theirE-mailcolourin
combinations(J-H,ofJ- highest
are BD candidates (Alves de Oliveira et al. 2010).
christine.ducourant
u-bordeaux.fr
thecontact:regionabsorption where atstar-formationis on- known members (black dotted histogram) and new members
though its proper motion is not of high accuracy to have a census
K s , J-w1, etc.) and searches for regions in this magnitude-colour
E-mail contact: ercolano at usm.lmu.deof members as complete as possible. This is why we performed
going.
We
also
note
that
class
I
objectsaregloballyaligned
on
a
(red)
in
Fig.
13
.
hyperspace that are occupied by members of a same class (I, II
our analysis in two steps.
Table 4: Summary of evolutionary status of the
Thenorthwest-southeast
ρ theseOphiuchicomplexparticular
L1688mostdarkismembers
unique arein itsproximity(∼130 pc),
regions are molecular
We first selected the most reliable proper motions of and
our III). When the parameters characterisingaxis, mostly
located andin theinmostembedded the Lynds
As expected,
of cloudthe newTheweaksources
dispersalof thecircumstellar discs of dust members
and gas surrounding
young low- ma
SOFI catalogue to derive the kinematic properties of the clus“learned’, the algorithm considers the unclassified members andcandidates.
region,which
wasyoung
proposedby Motteal. (1998) to correspondwith MH(0.5ranging
fromIt5 to
Sinceremaining
the onetransition
betweenstars
objectsweremeasured
only from auxiliaryand
datawith a mean precision
inonits
richnessinstars
and etprotostars,
and in its youth
Myr).
is12.
certainlyof thebest
targets
currently
ter and of the field, using objects with at least a time baseattributesofa class to them depending
their
localisationin thisfor is,theMformationofplanetarysystems. Photo- evaporation from energetic radiation
observations of five years, with a number of observations greater
hyperspace.
totheperpendiculartothedirectionofshock
propagation
by
the
and
BDs
occurs
at
M
⇠5
mag,
that
⇠6
mag
for
young
H
J
than 20, and with 2mas/yr. From these, we excluded propera kinematic
analysisof the mostaccurate propermotions aderived
in thiswork,
w
accessible
fromthethe ground to study the early phases of star-formation. Proper motion
analysis
isdispersal
a very efficient
tool for
StatusMembers
Candidateadoptedmotions higher than 45 mas/yr, which correspond to foreground Of the various supervised methods available,todrivecreating
gap whichdisconnec
UpperweScorpius
OB association onto thecore of the ⇢ Oph cloud clusters (e.g., Bara↵e et al. 2015), virtuallyallthethe new
membersin the majority of discs, byand successful data classification non-parametric
w1 − w4 [mag]56 known
YSOs (CDS)
objects that do not belong to the ⇢ Ophiuchi complex. This well-known
leftmembers
from
field
stars
and toderivepropertiesof thewhilecluster.
From
separating
members of clusters fromfield stars, but veryfall
few
motions
areTheavailable
inoftheρsevenOphiuchiregionsince
in proper
the substellar
regime.
Mvaluesthe
spec2001; Breiman et al.
us with 342 objects with highly accurate proper motions. method called random forests (Breimancomplex.
H the
of
disc
and
then
disperses
theouter thediscmeanfrominside-out,
ClasstheI
4the inner
The membership analysis led to the following mean proper2003), complemented by a Monte most
Carlo trialof
to accountfor
er- Fig.sources
10: One of the arecolour deeply- colour diagramsfor kinematic memFig.
9:
K
distribution
of
known
young
stellarobjectsreferenced
list
of
68
members
and14
candidatemembers,
comprising26
newobjects
with
a
the
young
embedded
in
dust
and
gas.
We
aim
at
performingakinematic
censusofyoungtroscopically confirmed BDs in ⇢ Ophiuchis are also indicated inClass II TW Hya, the closest
34 protoph
motions and precisions for the cluster derived with 48 memrors in the observable quantities. We adopted the R language im- bers using 2MASS K s and WISE w1,w2, and w4 photometry.
the
star.
In thisLetter weshoworthat
the discaroundbers (µ , µ ) = (-7.4 -22.9) ±0.8 mas/yr (hereafter µ stands
the AboveCDS
andkinematic
members
candidatesof known
the Class III
Fig 13 together
their spectraltype.
MH new= 5aremag,
we runplementation of random forests bystellar
Liaw & Wiener(2002), and
13
Objects withknown in the literaturethat andwere partiallyobjects(YSOs)
inclasses
thepreviouslyρ Ophiuchi
F corein thewith
E coreof theatfirst
L1688
dark
cloud.
We
afainterpropernewmembers
generally
than
the
ones.
We
measureda meanprfor µ cos ) and for the field (µ , µ ) = (-3.5, -1.4) ± (0.4,0.3)
objectwhereaphotoevaporative
gap
has
been
imagedaround
the
time
at wh
to
take
all
the
errorsoftheavailablemeasurements
intoaccount,
used
for
the
trainingofthemethod(train)
are
shown
with
filledcluster.
mas/yr. The kinematic values derived for field stars agree reafind 23 new substellar members, which is 3.3 times more than
new YSOs
we followed a Monte Carlo approach,performing
30000 inde- at
motionprogramtheandESO
New
Technology(NTT)knownwith BDs
theof ISAAC(SOFI)
instrumentnine
symbols
the objects
we classified
are shown withTelescope
sonably well with predictions from the Besançon Galaxy model-24.3)±0.8
mas/yrforthe overL1688
dark
cloud. A26
supervisedclassificationof
was
applp
8: Distribution
onempty
the sky ofpreviously
kinematic
members,
candidate
Class
I
2
inSon
the surveyedarea.
detected
gap
in
the
ALMA
imagesisconsistentwiththeexpectations
X-raypendent classifications of the dataset. At each run the following symbols. Squares refer to Fig.
simulations in the direction of our field : (µ , µ )= (-2,-2) mas/yr.
class I, circles to class II, and trianFig. 12: Distribution on the sky of objects from our proper mowas performed: first the magnitudes
star atnear-infrared.
each gles to class III.
In a second step, we considered all the objects from process
ouryears ofineachthe
We members
complemented
observations
withfourpublicimage
databases
toof
themembers
ClassII(0.5<P<0.9)theseand field
starsThe
with weakest
indication
ofvarious
the new
local-members
to allocate
a J162746.78spectralenergydistribution(SED)
classification
to the
me
(UGCS
tions
catalogue(greydots) and of
theenlarge
kinematicandrequiringthepresence
a82 planet.
The photoevaporation
model
is unclassified
also114consisten
proper motion catalogue that were excluded from previous analfilter are sampled from Gaussian probability distribution func◦◦ Red circles corClass III studies of the ρ Ophiuchi
isationof ofthe investigation
B, C, E, and F coresof⇢ Ophiuchi.
ysis and selected those whose data were spread over five or more
244059.1,
UGCS
J162700.96tions with the mean equal to the measured
imputed,thetime (orbaseofseeobservations
and the
field
to
0.5
×0.5BX162727602-24381862,. We derived positions
motions
for
2213
that
the
56Hya
members
that
known
from
previousF
candidates
ofand
the
⇢proper
Ophiuchicluster(colouredsymbols)
derived1
Fig. 4:main-sequencestars(-6.3±0.3)km
swere(Prato2007;rate
Guentherobservational epochs with a time base of observations
longerDistribution on the sky of objects from our proper motion respond to the kinematic members (P>0.9) derived in this work,
of
the
TW
system,e.g.
accretionandthelocation
of
the
gap
at
the
on
Fig. 6:below)
Repartition
ofand
membershipprobabilitiesofthe936 ob- (orparagraph
value
the
sigma
equal
to
the
measured
244339.5, and 2MASS-6X J16265864-2443281)
withMHdesignate
11 class I, green circles class II
in
this
work.
Red
squaresthan six years and a precision better than 3.5 mas/yr. We thenjects.
The indication
filled blackcorresponds
tothenknown
objects.
From
these,
607
motionswerederived
from
SOFI
observations
with
∼1.8
mas/yraccuracytheetal.a 2007;
Kurosawa
2007;
James
etwhileal.
2006).
We summariseoursurveyaremembersofthecluster,
and weadded
26
new members.
Weemi
defi
computed
basedproperon the angulardistance
the positions
imputed)magnitude
errorhistogramat theof
relevant
all youngthe possicatalogue
withtheirfilter;
magnitude
range.
tested their membership to the two distributions
and retained
blue
circlesofbetween
tocandidatemembers(0.5<P<0.9).
Filledcircles
central,unresolved
870µm
continuum
sourcemight
beproduced
by
free
free
stellar combinations
objects (detectedbetween
by ISO (Bontemps
et al.
2001)
orw1,
Spitzermag
arepotentially
very
low
mass
BDs
that
reach
spectral
types
and
blue
triangles
class
III.
The
zones
with
few
grey
dots
correofeach
objectandthemedianpositionallmemberobjectsblecolourthefilters
J,
H,
K,
w2,
w3
those with a probability greater than 50%.
inunclassified
Table 3 the kinematic
propertiesof thecluster.
⇢ Ophiuchi (F core).
(Evans et al. 2003)) that are present in our catalogue. For visibildesignate
objects
belongingcatalogue
and triangles
membersofCrosses
theshowedthat a large part (23) of theseradii andthe absolute
median to theand w4then thea randomclassifierassigns a (Fig.11). The median projected
spond
the
mosttheobscureregions.
indicate theWeapproxWe thus end up with 82 objects with a membership probaas SOFI
cool asL0 (⇠2200K,
see discussions
in Tottle& gap.
Mohanty
ity arethe ycomputed;
axis is truncated;peak thatforests
corresponds
to a probadusttoinside
8. Conclusions
bility to the cluster higher than 50%. We present the repartitionshowsknown
that the di↵erent
class bility
to allofthe
objects
with unknownclasses. Finally, after all the deviation for each type of object⇠0.05
culminates
at 800 objects.
identify
youngclasses
stellar objects
detectedby ISOor Spitzer.
centresthe multiplies
E,F, and B cores;
dotted lineof
indicates2015).
These coolyoung
BDs are imative
expected
towhichbeofspatial
very
low
dwarfs,thethenumbersubstellar objects in the cluster byof membership probabilities for the 936 objects analysed hereindependentinruns, the frequency that each object was assigned to present di↵erent preferential projected radii and also di↵erent
Table
3:ofMeanandmass
kinematic
propertiesof (1998).
theknown⇢ Ophi-With
ourC. etastrometric
we have decorrespondFig.6. We observe in this figure two clear peaks that correspond
0 The black dots
0
0 to field objects (P<0.1).
thelineclumpsand
YSOs
identified
by
Motte
et
al.
Ducourantal.: Kinematics in observations⇢ Ophiuchi
Accepted
MNRAS
each class is computed and the class with the greatest frequency spread: RI = 5.6 ± 3.1 , RII = 8.8 ± 4.5 , RIII = 10.7 ± 5.3 .
of onlyal. 2000).
to field population (P<0.1) and cluster population (P>0.9) and13 about 10 MJup (Chabrier etuchi
F core asby
derivedfrom theLetters
68 kinematic members with theproper motionsof 2213 stellar and sub-stellar oThese results indicate that the youngest objects are more concenis adopted as the object class.
objects with intermediate probabilities. Sixty-eight
objectsComparison
have
Accepted
by
A&A
main
We summarise the evolutionaryhighest
status membershipof the 82
membersand (P>0.9).
4.1.
to PPMXL and 2MASS catalogues
probability
Breiman,L., Last,We
M., &performed
Rice, J. 2003, in StatisticalChaa probability P>0.9 and are considered as members, while14 ob- A special approach had to be adopted because some data trated in the central parts of the working zone (cores E and F),⇢ Ophiuchi cluster
region.
a kinem
http://arxiv.org/pdf/1609.03903(Springer
NewYork),
243–254
candidates in Table 4. Seven members already known as YSOs
jects have a membership probability 0.5<P<0.9 and are classipoints were missing in our dataset (e.g., many objects were ob- while more evolved objects are more spread towards the exterior.
150, 298
ship analysis andCabrera-Cano,derivedJ. a& Alfaro,
list E.ofJ. 1985,
82 A&A,
kinematic
fied as candidate members.
or detected only in some, but not all, of the 2MASS or
Cesarsky, C. J., Abergel, A., Agnese, P., et al. 1996, A&A
are identified BD (Alves de Oliveirahttp://arxiv.org/pdf/1609.04963
et al. 2012) and 6 new
YSOs
For theserved
opticalpart of our catalogue, the densest comparison catProperty
Value
1

●

Class

I − Train● II − Train

7.5

III − Train

K − w2 [mag]I − New●● II − New

III − New

5.0

●

●
●●
●
●●
● ● ●● ●● ●● ●●●● ●● ●●●●● ●●● ● ●●●
●●
● ●
●
●
● ●●
●
●
●
● ●
●
● ● ● ●●●● ●●●●●●●●● ●● ●●●● ●● ● ●●●●●● ●●●● ●● ●●
●●●●●
●●
●
●
● ●
● ●
● ●●
●
● ●●
●
●●● ●●● ●
●
●
●●
●
●●
●
●●
●
●●
● ●
●
●
●
●

●

2.5

●

0.0

µ

0.0

⇤
↵

↵

cl

⇤
↵

2.5

5.0

●

●

7.5

10.0

⇤
↵

f

⇤
↵

Membership analyses are very sensitive to outliers (e.g.,
WISE filters). The approach adopted was to perform data imforeground objects from the Galaxy with high proper motion)
putation and Monte Carlo sampling of error distributions. The
and need to be excluded to derive realistic solutions (see disfirst step is to perform data imputation, but to avoid mixing thecussion about the pruning of the data in Cabrera-Cano & Alfaro
well-known objects with the most uncertain objects, we split(1985)). We therefore excluded objects with µ⇤↵ or µ > 45 mas/yr
at step one and objects with proper motions beyond 2.5 of thethe missing data imputation into two phases: first, the data immean properties of the cluster and of field at the end of step two.
putation was performed using all the objects with previously
We present a list of objects in Table 5 that are considered as outknown classifications; then, the missing data imputation was perliers despite their high membership probability (P>0.9) because
formed considering all objects in our dataset. We adopted a nontheir proper motion di↵ers by more than 2.5 from that of theparametric missing data imputation method called missForest
cluster.
& Buehlmann 2012). This method is also based on
The resulting mean kinematic properties of the cluster (Stekhovenarea random forests algorithm to predict continuous missing vallisted in Table 3. We present the list of the members and candidate members with their astrometric solution and their memues from the observed values of all other objects in the dataset
bership probability in Table 7. Fig. 7 shows the vector plot anddi- from the relation of the object whose value is missing andagram of the cluster and indicates the membership probability,
all other objects considering the entire parameter space of theand Fig. 8 shows the distribution of field stars and of cluster
dataset.
members and candidate members across our field.
Figure 7 shows that the repartition of the kinematic members The results of the classification performed here are represented in one of the many possible colour-colour planes in Fig.
is globally circular, as expected. The dispersion of their proper
Fig. 7: Vector plot diagram. Red circles correspond to the kinemotions (< 5 mas/yr) is larger than expected from the astro10 whichthatmostderivedof theinobjects
lackingliteraturematicshows
members(P>0.9)this work,
blue circles
to can-clasphysical point of view (1-2 mas/yr) and reflects the difficulties
sification
assignedclassTheII black
status.
Ofcorrespondthe 53 unclassified
didatewere
members(0.5<Pa<0.9).
dots
to field↵of measuring proper motions in such obscured zones and themembers
re- objects
or(P<0.1).
candidates,
wereassigneda class
III status,
Filled 16
circlesdesignateobjects
belongingto the 32 a
ality of our accuracy. Twenty-six members are YSOs that have SOFI catalogue and triangles identify known young stellar obclass
II,
and
5
a
class
I.
been identified by ISO or Spitzer. Field stars and cluster mem- jects detected by ISO or Spitzer.
bers are separated in Fig.7 by a layer of objects with intermediate To analyse how probable it was to find a young stellar objectofclasses
I,
II,
or
III
at
a
given
distancefrom
thecentermembership probabilities (candidates).

cluster down to muchg catalogue and reaches

distribution on the sky ofhomogeneous, as shown
tially detected where thend coincide with the cluswhile the brighter objects
uster.

of our catalogue because
jects that are invisible atknowledge, no astrometexists in the NIR in thisSE catalogue (Cutri et al.
es in the NIR. Unfortuhelpful in a region suchstandard error on theseis µ ⇠300 mas/yr).

Densityf the proper motion cate whole catalogue while
SOFI catalogue.

candidate members,
26G., of
them
are
membe
Chabrier,
Bara↵e,I., Allard,F., &new
Hauschildt,
P. 2000,

5.2. New and known membershs
Cieza, L., Padgett, D. L., Stapelfeldt, K. R., et al. 2007, A
are BD candidates (Alves de Oliveiraet)al. 2010).
alogue is the PPMXL catalogue (Roeser et al. 2010). We notelished in a reliablemeankinematic
pro2( 16members
27m 22.51and, 24
41‘ 58.5” )7.(↵,
Natureof kinematic
candidates
Cutri,way
R. M. &the
IPAC/WISE
Science
Data Center Team.
members or candidate members derived in The
Abstracts, -24.3)±0.
Vol.
219, Ameris
turbulence,magnetic
fields,and
L1688 darkcloud tronomical(µfilaments,
cosSociety, µMeeting)=(-8.2,
that the present work included some PPMXL propermotions as Of the 82 kinematic(µ↵ coslink, µ ) between( -8.2, -24.3)±
0.8 mas/yr
Class
0.075
ciety↵Meeting Abstracts 219, 401.06
thephoto-evaporative
82 ofkinematic
members and candidate
members
in theclosest
Tableas4:
Summary
evolutionary
statusthe 82 kinematic
at CDS
young
stellar of
objects,
the OfA
Cutri, R. M.,
Skrutskie,F., vanS., etal. 2003
I
confirm thatthe velocityofthis M.
core
isDyk,
very
similagap
theplanetforming
disc(l,b)( 352.9816,16.5540) instarting point of the iterative reduction process but the final cata- this work, 56 are referenced
tral
Molecular
Zone
cloud
G0.253+0.016
Catalog,
2246,
0
we analysed, we proposed a classification for 53 ob- the Upper Scorpius
II
members
and candidates.
others are new members
or newcandidates.
Of the known ob- region
association.
Cutri,
R. M., Wright, E. L., Conrow, T., et al. 2013, Expla(µl cosb, µb ) (2MASS-6X( -23.8,-10.7)±
0.8 mas/yr
logue should be more or less independent of it. Another difficulty 26
1,2J16271965-2441487,
3
AllWISE Data Release1Products, Tech. rep.
Six objects
2 2MASSjects, 7 are brown IIIdwarfs (BDs) (Alves de Oliveira et al. 2012), jects.
0.050
assigned 3Dawson,
a,the
SED
class
toD.
the
53
unclassifi
Barbara, Giovanni
Rosotti,We
Giovanni
Picogna
LeonardT. ,P., etal. 2014,
MNRAS, 4
Position(X, Y,ErcolanoZ) 12MASS-15.6,+37.4) pc P.
C.
Federrath,( 126.9,
J. M.
Rathborne,2MASS
S. N. Longmore
J.P., Scholz,
M.A., Ray,
Kruijsse
results from the fact that the 239 objects common to our cata- 1 is a BD candidate (FHTWIR-Oph
J16272661-2440451,
de Zeeuw, P.usingT., Hoogerwerf,R., de Bruijne, J. H. J., Brown
StatusCandidates
80, Alves de Oliveira etMembers
al. J16272439-2441475,
members
or candidates
a non-parametricra1
8
9
10,11,12
Velocity
(U,
V,
W)
(
-5.9±0.1,-14.2±0.3,-8.1±0.4)
km/s
A.
1999,
AJ, 117, 354
1 M. Crocker
2MASS
J16274161-2446447,
and
2MASS
R.
, G.
Garay
, J. M.
Jackson,1,L.81679
Testi
and
A.
J.ApJ,
Wa
logue and PPMXL are mostly concentrated at the southern edge (2010)), and 26 were found by theDo,
T.,Martinez,
G. D.,
Yelda,
S.,
et al. 2013,
779, L
Universitäts-SternwarteMünchen,Scheinerstr.
München,Germanysupervised
methodforclassifying
objectsusingmajor spatial
NIR-surveys J16273272-2445004,
56 known
YSOs (CDS)
Dodson-Robinson, S. E. & Salyk, C. 2011, ApJ, 738, 131
0.025
J16273894-2440206)
have
been
listedbyAlves
deOliveiraetal.
of the field, which means that the cluster is almost completely ISO (Bontemps et al. 2001) or Spitzer
Ducourant,& Rapaport,
M. 1991,
A&A,2MASS
241, 303
tion ofthe (J, H, K,
w1,C.w2,
w3 andw4)
et al. 2003).
124Excellence
Notes.
The mean School
propermotionofthe core andgiven here
does
not accountClass(EvansI
0
Cluster
OriginStructureoftheUniverse,
Boltzmannstr.2,
85748
Researchof
Astronomy
andAstrophysics,
Australian
National
University
Ducourant,
C.,
Teixeira,R.,
Chauvin,
G.,
et
al.
2008,
A&A
as potential
brown dwarfs(BDs)
based on their position
remainingwere measured
onlyfrom auxiliarydatawith a mean precision(2010)
ofthe
about
∼32mas/yr.
We
performed
areC.,defined
class
as A&
c
excluded from this comparisonand onlyobjects
the brightest
objectsforprobable systematic
error (⇠ 2 mas/yr) of our proper motioncolours. Nine objects
Ducourant,
Teixeira, R., asHambly,N. C.,I,et 52
al. 2007,
The kinematic
members aremostlyClass IIlocated around the Oph in
3a colour-magnitude234
diagramamong
thecluster
faintest,
red
Eckart, A., Mužić,K., Yazici,Cambridge,
S., et al. 2013, A&A, 551, A
InstituteofAstronomy,
University
ofobjects.
Cambridge,
MadingleyRoad,
Astronomy
andSpace
Science,
P.O. Box76,
Epping
NSW,
1710,
Austraobjects
as
class
III.
catalogue.
a kinematic
analysismostaccurate
propermotions
derivedwork, Thatwhich
allowedseparate
F and
E cores, withseveralnew detections
to thisthese cores.
Erickson, K. L., Wilking, B. A., Meyer, M. R., Robinsonof our catalogue are concerned.
Nevertheless,we performed
0.000 of the theClass
III southin
13CSIRO
3 us toconfirm
we can kinematicallythat they are part of the clusL. N.new
2011, AJ,
142, 140
34 EuropeanWe
discovered
23
BDscandidates
as
part
0
5
10
15
20
Southern
Observatory,
Garchingbei
München,GermanySomepreviously
known
membersaround
Oph
B
core
are
also
Astrophysics
Research
Institute,
LiverpoolJohn
Moores
University,
IC2,
LiverpooEvans,II,
N.
J.,
Allen,
L.
E.,
Blake,
G.
A.,
et
al.
2003,
PAS
comparison of both sets of propermotions,
and
we
noted
a
sys26 new YSOs
members from field stars and toRadiusderivethekinematic
derived a
indicatesthat they analysis
are probablyweBDs.
[arcmin] the mean properties of the cluster. Fromter
Fritz, T., Gillessen,S., Trippe, S.,
2010, MNRAS,
the number
ofet al.
known
BDs40
52 We compared3these values with the kinematic characteristicspotentially multiplying
classified as kinematic members. The
highconcentration of kine- Liverpool
Fritz,5,T. K.,I-50125
Chatzopoulos, S., Gerhard,O., et al. 2016,It
Ap
Class
I new
tematic mean di↵erence (in list
the sense
thiswork minus
Using
the typical
IR excesses
in J, Kingdom
H, andK di
bands
for class Largo
INAF/Osservatorio
Astrofisico
Arcetri,Fermi
Firenze,
L3 5RF,
Unitedof 68
membersand14sky
candidatemembers,
comprisingobjects with a ofhighmembershipprobability.
These
cluster E.
by 3.3.
A few
themD.mightbeM.extremelyFig.
12:
Distribution
onPPMXL)
theof objects
fromour propermo- part
Furlan,ofE., Watson,
M., McClure,K., et al. 2009, Al
the Upper
(US)
since
⇢ Ophascluster
members
centralof26theFig. 11: Radial density plot.matic
The projected
densitiesinof theeach class
Gallagher, D. B., Irace, W. R., & Werner, M. W. 2003,
Class
II field covered by this II
5
andclass IIIScorpius
YSOs
andtheassociation
extinction law
inthe
near-IRin in the 10 M regime.
411
of ( µ cos( ), µ )=(-1,+6) mas/yr.
2
catalogueare
(grey
dots)
82
kinematic
membersandJup
Astronomisches
Rechen-Institut,
ZentrumfürAstronomie
derUniversität
Heidelbe
ofgenerally
YSOs
are andgivenofin thenumberofobjectspararcminandare
OpticalInstrumentation
Engineers(SPIE)
Conference
Fig.
13:
DistributionofabsoluteH
magnitudes
ofknown(blacknewtions
members
fainter
than
the
known
ones.
We
measuredameanpropermotion
of
(µ
cos
δ,
µ
)=(-8.2,
isE-mail
expected
toal.be(2001),
part ofercolano
theUpper theSco
association
Wilking
study
corresponds
to[oftheeachzone of deep
SOFI
observations.
α derivedatδ absolute
usm.lmu.de
Bontemps
etcontact:weJ(solidand(see
H members.
magClass
III
4
1
Space Telescopes and Instruments, ed. J. C. Mather, 17
displayed
versustheprojected
distancetothecenter
We
were
able
to
establishasecondaryastromedotted)
and
new
red)
Spectroscopicallyconof the class.
⇢di↵erence
Ophiuchi cluster
symbols)
To determine the origin of-24.3)±0.8
thecandidates
large systematic(es- (coloured
Girard, T. M., van Altena, W. F., Zacharias, N., et al. 20111 theetal. to(2008)).
We
observemembersthat theofandvelocity
heredefor
We present
in Fig.
9supervised
the repartitionclassificationin terms of K s magnitudes
delberg,
Germany
nitudesforphotometricthekinematic
candidates
members. et al. (2012)
mas/yrfor theL1688
dark
cloud.
Aderived
was applied
data
members
firmedbrownderived
dwarfs by
Alves
Oliveira
are indiN.,
Yano, T., where
Yamada, Y.,reference
et al. 2005, in sta
ESA
in theNIRGouda,
inVol.a576,
regionin this work.
squaresdesignate ofclass
circlesclass
sentially in declination), we considered
the Red2MASScatalogue
catedwetogether
with
their
type.
The Three-Dimensional
Universe
with mGaia
clustervery similar
thecircumstellar
one thatderiveforspectral
thedispersalof tothediscs
of sample
dustframeand17,
gas
surroundingyoung
low5The istheI,56green
known
and 26
newIImembers.
1 Max-Planck
Institutfür
Astronomie,Königstuhl
69117
Heidelberg,
GermanyO’Flaherty,& M. A. C.can
Perryman,77
existing
astrometriccatalogues
hardlybe foutoallocate
adensityspectralenergydistribution(SED)
to theunclassified
members.
We kinematicallyconfirmedOne
newmember(WISE
J162702.05-243938.6)
wasdetectedinthe ⇢ Ophiuchi
cluster F core,
weepochbuilt
andprobability
bluetriangles
classIII. The
zones withfew
grey
dotsclassification
correof117
members
of
Upper
Sco
OB2
group
with
Hipparcos
meawhich ofprovidespositionsforwitherrors⇠100
Guenther, E. W., Esposito, M., Mundt, R., et al. 2007, A&The
newmembersappearessentiallyfainter(downtoArticle number,⇠1999.3
page 7 of 16
6
for
the
formationofplanetarysystems.
Photoevaporation
fromR.USA
energetic
radiatio
estimations using kernel density estimators. The projected radii
This is also visible in Fig.12, which displays the distribution
catalogueCO
will undoubtedly
bea valuable
for
onlyCASA,
one near-IR
band therefore ofwe wereunable to derive
its absoluteBoulder,
Gutermuth,A.,
Megeath,S. T., Myers,
P.toolC., et al.
2009s
University
Colorado,
389-UCB,80309,
spond
to
the
most
obscureregions.
Crosses
indicatetheapproxthat
the56
members
that
were
known
from
previous
studiesoftheρOphiuchiF
cluster
and
that
were
also
part
of
surements
(de
Zeeuw
et
al.
1999)
(U,V,W)
=
(-5.0
,
-14.8
,
James,
D.
J.,
Melo,
C.,
Santos,N.
C.,&
Bouvier,J.
2006,
thancatalogue
the known
and were revealed by the magnitudes.
mas andcompared
its positions
USfor theobjects classified
as members of toeachthe
SEDPPMXL
class were andon thetoskyourof thecataobjects ofKs=18.1)
our proper motion
and of members
8. Conclusions
ciations
young Kurosawa,stars,
as2007,
Hipparcos
wasin its timview ofmajority
the star-formation ofprocesses
and toaccesstheof
youngestR.
in Multiplicity inStar Formation,
7to )drivethedispersal
inthediscs,
bycreating
a gap
which
disconnec
imativeoftheE, F, andcores;
thedottedobservations
lineweindicates
-6.5
± the
(0.1,Observatory,
0.4,
0.2)
km/s. Leiden
deep
Near-IR
performed
in thismembers.
work.
LeidenBox
9513,
RA
Leiden,the30Nclusters University,(< a few
astrometriccatalogues
willNL-2300
be Lada, C. J. & Lada,
E. A. 2003,
ARA&A, 41, 57
logue, each transported to theepochapplication
our2MASS
surveycentres
are bymembersof Bofthecluster,added
26 new
We defined
evolutionary
statusoftheMyr), infraredPO
Article andnumber, page
9 of16
the crucial tool, however. The future space infrared astrometric Lawrence, A., Warren, S. J., Almaini, O., et al. 2007, MNR
With ourastrometricobservations
wehavedetermined
the line
ofcomparisonsclumps and YSOs
identified by
et al.some(1998).
of
the
disc
and
the outer disc from the inside-out,
while
the
Articlenumber,page
10 ofthen
16 thedisperses
WeMottenote thatwell-attributed
membersof ⇢ Ophiuchi
Liaw, A. & Wiener, M.
2002, R News,2, 18 inne
its own proper motions. We unclassified
present
these
in Fig.
mission brown
Jasmine (Gouda et al. 2005) may in this respect be the Lindegren,
members of
the5.cluster.
We
showed
that
a
large
part
(23)
of
these
new
membersareprobably
L.
2010,
in
IAU
Symposium,Vol.
261, IAU S
proper motions
2213 stellar
sub-stellar objects in theto bring insight into embedded star-forming regions. The
are not included in our list of kinematic
membersofbecause
their and
Klioner, P. K.
Seidelmann,& M. H. So↵el,
296–305
star.
In 3.3.
thismemberLetter wefirstshow
that the disc around TW Hya,theclosestprotop
The resulting mean di↵erencesin position
the sense 2MASS
secondary reference frame established in this work is a first step Lodieu, N. 2013, MNRAS, 431, 3222
⇢ Ophiuchi
region.
We performeda kinematic
dwarfs,whichin multiplies
the number of known substellar
objectsin theclusterby6.theaClassification
factorofthem. cluster
Luhman, K. L. 2012, ARA&A, 50, 65
on this way.
minus catalogue are (+45,+41) mas for PPMXL (1321 objects) astrometry was too poor to analyse
firstobjectwhereaphotoevaporative
gap
has
been
imagedaround
the
time
at w
Luhman,K.
L.
&
Mamajek,
E.
E.
2012,
ApJ,
758,
ship analysis and derived a list ofOf82thekinematic
members
and or candidate
82 kinematic
members
29E. Morauxhaveand C. Alves de Oliveira14Luhman, K. L. & Rieke, G. H. 1999, ApJ, 525, 44031
Acknowledgements.members,
We are grateful toand (-11,+11) mas (504 objects)
for thisby
work.
Accepted
A&A mainproviding us with CFHT observational material. We acknowledge partial fi- Ma, C., Arias, E. F., Eubanks, T. M., et al. 1998, AJ, 116,
candidate members, 26 of them arenewmembers.
Wetheestabdetectedgap
in
imagesis organisationconsistent
with the expectations of X-ray
beenclassified
in termsof ALMA
their forspectralenergynancialsupport fromthe Frenchdistribution
COFECUB and the Brazilian or- Martin, E. L., Montmerle, T., Gregorio-Hetem, J., & Cas
5.3.
Spatialvelocities
lished in a reliable way the mean(SED)
kinematic
properties
ganisation FAPESP and CAPES. This research has made use of the SIMBADRAS, 300, 733
7. Natureof positions
kinematicwithout
members and candidates
When we assume that 2MASS
providesinto class
orof
IIIthe(Bontemps
etal. at(2001)
andphotoevaporation
Guterrequiring
theI, II,
presenceof database,a planet.
model
is alsooperated
CDS,TheStrasbourg,
France.
This publication makes use of Mignard,
F., Bailer-Jones,
C., Bastian,consisteU., et al. 2008, in I
http://arxiv.org/pdf/1609.04963
L1688 (Xdarkcloud the(µ↵ Galacticcos , µ )=(-8.2,
data products from the Wide-field Infrared Survey Explorer, which is a joint
248, IAU Symposium, ed. W. J. Jin, I. Platais, & M. A. C
bias, we can conclude that both Of
catalogues
su↵er from system- candidate
derived members
the Galactic
coordinates
towards
muth et-24.3)±0.8
al. (2009)),mas/yr
but 53andof themappear to be unclassified.
project of the University of California, Los Angeles, and the Jet Propulsion Lab- Monet, D. G. 1998, 30, 120.03
the 82 kinematic members andWein theofis theTWunclassifiedHya
accretionrateandthe location of the gap at the on
confirm
thatZthevelocityofthis corevery
similarto thesystem,
onemembersof e.g.
oratory/California
Institute of Technology,
fundedatby the National Aeronautics Motte, F., Andre, P., & Neri, R. 1998, A&A, 336, 150
atic e↵ects in their proper motions:⇠(+2.7,+2.5)
mas/yrforcentre,YindirectionofGalactic
rotation,
towards
the
North
Some
of
these
are
referenced
as
YSOsMužić,K.,
Scholz,A.,
Geers,
V.,
Jayawardhana,R., & Ta
andSpace
Administration.
Thispublication
makes
use
of
data
products
fromtheregion we analysed, we proposed a classification for 53 ob- the Upper Scorpius association.
744, 134
central,continuum
by free free em
Two Micron
All Sky Survey, whichsource
is a joint project mightof the Universitybeof Mas-produced
Galactic Pole) and 2MASS
heliocentric space velocity of the cluster the
CDS. unresolved 870 µm
PPMXL (mean epoch ⇠1982.6) andfor thisJ16271965-2441487,
jects.⇠(+1.3,-1.3)
Six objects mas/yr(2MASS-6X
sachusetts and the Infrared Processing and Analysis Center/California Institute Natta, A., Testi, L., Comerón, F., et al. 2002, A&A, 393, 5
We assigned
a SED classto the53 unclassified
kinematic
A thatphoto-evaporative
gap
in
the
closestplanetforming
discof Technology,
funded by theclassification
National Aeronautics and Space Administration Natta, A., Testi, L., & Randich, S. 2006, A&A, 452, 245
using
the
most
recentdistance
determination
d=133.3±3.6
pc
Accordingly,
wedecidedtoperformatentative
work (mean epoch ⇠2007) and
a
large
part
of
the
di↵erences
dust
insidethegap.
J16272439-2441475, 2MASS J16272661-2440451, 2MASS members or candidates using a non-parametric random forests
Ortiz-Leon, G. N. e. a. 2015, submitted to ApJ
and the National Science Foundation.
Ozawa, H., Grosso, N., & Montmerle, T. 2005, A&A, 429(Ortiz-Leon 2015) andmost significant YSO classes (I, II and III) using
1,2 PPMXL
3 the median radial velocity for
1 Oph pre- into the three
2,4,5
observed in the comparison Barbaraof ourproperErcolano
motions with
J16273272-2445004,
2MASS
J16274161-2446447,
and 2MASS
Parks, J. R., Plavchan, P., White, R. J., & Gee, A. H. 2014
, Giovanni
P. Rosotti, Giovanni
Picogna, Leonardo
Testi
supervised
method forclassifying objects
usingby
anyMNRAS
combina- Letters
Peña Ramírez, K., Béjar, V. J. S., & Zapatero Osorio, M
is due to PPMXL.
J16273894-2440206) have been listedby Alvesde page
Oliveira
et al. tion of the (J, H, K, w1, w2, w3 andAccepted
A157
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References
1
Peña Ramírez, K., Zapatero Osorio, M. R., & Béjar, V. J
Universitäts-SternwarteMünchen,Scheinerstr.
1,Rosotti,
81679
München,Germany(2010)as potential
brownincorpodwarfs(BDs)L4
basedon
their position
Ercolano,
Picogna,
Testi
A118
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catalogue
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colours. Nine objects are defined ashttp://arxiv.org/pdf/1609.03903
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85748 Garching bei München, Germany
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That
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part
of
the
clus3
Preibisch,T., Zeidler, P., Ratzka, T., Roccatagliata, V., &Weaccretion
discovered
23
newtheBDs
candidates
which diminishes the impact of
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the
TWofHyadisc – and/or
if the
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at
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of
de Oliveira, C., Moraux, E., Bouvier, J., et al. 2010, A&A, 515, A75
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ter indicates that they are probably BDs.
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Photo,!evaporaCon!of!the!circumstellar!
Robin, A. C., Reylé, C., Derrière, S., & Picaud, S. 2003, A
potentiallymultiplyingof known BDs in ⇢ Ophiuchi
4 section (PPMXL/this work, PPcomparisonsin thisgap opening isbei
high– againa probablescenariothe
innumber
TW HyaAndrews, S. M. & Williams, J. P. 2007, ApJ, 671, 1800
Robin, A.filaments,
C., Reylé, C., Derrière, S., & Picaud,
S. 2004, A
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V., et al. 2001, ApJ, 552, 380 fields,
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clusterby 3.3.
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them might
be extremely low mass BDs
MXL/2MASS,discs!of!dust!and!gas!surrounding!young!
this work/2MASS)
do not rely on the same set
given the strong X-ray flux
from
the A
centralwhich
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5Roeser, S., Demleitner, M., & Schilbach, E. 2010, AJ, 139
II and class III YSOs and the extinction
law in near-IR as in

INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi
5,MI-50125
Firenze, Italy
Boehle,cloudA., Ghez, A. M., Schödel,R., et al. 2016, ArXiv e-prints
tral Molecular Zone
G0.253+0.016
in the 10
Jup regime.
results in high photoevaporation rates. This lends credence

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Sanders, W. L. 1971, A&A, 14, 226
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T. 2014, Protostars and Planets VI, 219
Stekhoven, D. & Buehlmann, P. 2012, Bioinformatics, 28,

Bontemps et al. (2001), we derived the absolute J and H magWe wereable toto observe
establishthea secondary
astrometric reference
Article number,
page 5atof 16
1
1
the fact that
we might
indeedbe ablegap Federrath
low,!mass!stars!
E-mailcontact:
ercolanousm.lmu.de, J.
M. Rathborne2 , S. N. Longmore3 , J. M. D. Kruijss
nitudes
for the kinematic
members
andtocandidates
members.
the NIR in a region whereC.
reference stars in thelarge
opening phase in the TWframe
Hya indisc.
1
8
M.beCrocker
G. Garay, J. M. Jackson9 , L. Testi10,11,12 and A. J. W
astrometriccatalogues
canR.
hardlyfound.
The ,Gaia
One new member
J162702.05-243938.6)
detected
The dispersalof the(WISE
circumstellar
discs ofwas
dust
and ingas existingsurroundingyoung
low- massstars
has
important
implications• A!gap!disconnects!the!outer!from!
tool for studying assoonly one near-IR band therefore we were unable to derive its absolute catalogue will undoubtedly be a valuable
1 fromfor theformationofplanetarysystems.
Photoevaporationfromenergetic
radiation
thecentralobjectisthought
Research
Schoolof
Astronomy
and Astrophysics, Australian National Universit
magnitudes.
ciations of young stars, as Hipparcos was in its time. For a clear
the!inner!regions!of!the!disc!!
2 the outer from the inner regions
to drive the dispersal in the majorityof discs,
creating
a gap which
disconnects
CSIRO Astronomy and Space Science, P.O. Box 76, Epping NSW, 1710, Austra
4 GAS
ANDby
DUST
SURFACEDENSITY
Articlenumber,
page
10
of
16
• Outer!disc!–!disperses!from!the!
of the disc and then disperses the outerdisc from UNDER
the inside-out,
while theinner3 disckeeps draining
viscously
ontoLiverpool John Moores University, IC2, Liverpo
Astrophysics
Research
Institute,
EVOLUTIONVISCOSITYAND
the star. In this Letter we show that X-RAY
the discPHOTOEVAPORATION
around TW Hya, the closest protoplanetary
to Earth,may
be theLiverpooldisc
L3 5RF,
UnitedKingdom
inside,out!
4
first object where a photoevaporative
gap developed
has beenaimaged
aroundtime atmodel
which
it is being created.
Indeed theZentrum für Astronomie der Universität Heidelb
Astronomisches
Rechen-Institut,
We have
simple 1D
viscousthe
evolution• Inner!disc!–!keeps!draining!
detected gap in the ALMA images
is consistentwiththe expectations
photoevaporation
which
includes X-ray
photoevaporation
for a ofTWX-ray
Hya-likedelberg,
Germany models, thus not
5
system.
requiring the presence of a planet. The photoevaporation model is also consistent Max-Planckwith a broadInstitut
range ofviscously!onto!the!star!
fürproperties
Astronomie, Königstuhl 17, 69117 Heidelberg, German
1Dandgas surface
density ofevolutioncode,
Spock,
6is of dispersal. We show that theof the TW Hya system, e.g. accretionOur
rate
the location
the gap
at the
onset
CASA, University of Colorado, 389-UCB, Boulder, CO 80309, USA
The!disc!around!TW!Hya!may!be!the!ﬁrst!
described in detail in Ercolano & Rosotti (2015). At t =70
central, unresolved 870 µm continuum
source might be produced by free free emission fromthegasdriftand/orresidual
Figure1. Thetimescalesof the dust particles
of di↵erent
Observatory,
LeidenUniversity,
PO Box9513, NL-2300 RA Leiden, thethe disc has a mass of 0.15 M , a radius of 18 au and an Leiden
sizes are plotted at the location and at the time of gap opening.
object!where!a!photoevaporaCve!gap!
dust inside the gap.
accretion rate of 10
M /yr. We solve the viscous evoThe radial velocity of the gas is overplotted with a dashed line
lution equation, taking into account the photo-evaporative
has!been!imaged!around!the!Cme!at!
Accepted by MNRAS Lettersand its zero value is marked with a grey line.
mass-loss, on a grid of 2500 points uniformly spaced in R
14
which!it!is!being!created.!(i.e.,!no!planet!
http://arxiv.org/pdf/1609.03903
extending from 0.025 au to 2500 au.
In our model the gap opens between 1 and 2 au at
required)!!!
an age of 5.7 Myr. At this point the mass accretion rate
onto themagnetic
star is 3.6 ⇥ 10
M /yr.
3.5 ⇥ 10 years
The link between turbulence,
fields,filaments,
andlaterstar formation in the Cen• The!X,ray!photoevaporaCon!model!
of the global disc lifetime and 17% of the transition
tral Molecular Zone cloud(4.6%
G0.253+0.016
phase lifetime) the mass accretion rate has already dropped
is!consistent!with!a!broad!range!of!
2 ⇥ 103 gap outer radius is out to 4,5
to 8.6/yr and the
C. Federrath1 , J. M. Rathborne, S. N. M
Longmore, J. M. D. Kruijssen , J. Bally6 , Y. Contreras7 ,properCes!of!the!TW!Hya!system:!
10,11,12
13
implies9 that
expects
4.6%andof theA.
globalproR. M. Crocker1 , G. Garay8 , J.6 au.
M.ThisJackson, L. one
Testi
J. Walsh
toplanetary disc population and 17% of transition discs toe.g.,!!
1
Research School of Astronomy andAstrophysics,
Australian
University,
be observedin this earlyclearing National
phase . These
numbers Canberra, ACT 2611, Australia
show thata small,negligible
fractionof young
proAstronomy and Space Science,
P.O.
Boxbut76,notEpping
NSW,
1710,
Australia•2 CSIRO
accreCon!rate!
3
nearby star
forming regions
should be Science Park, 146 Brownlow Hill,
Astrophysics Research Institute, toplanetary
Liverpool disks
JohninMoores
University,
IC2, Liverpool•Liverpool
locaCon!of!the!gap!at!the!
in this evolutionary phase.
L3 5RF, United Kingdom
In order to verify the timescales for dispersal of dust
4
onset!of!dispersal.!!
Astronomisches
Rechen-Institut, particles
Zentrum
Astronomie
Universität
of fürvarioussizes from der
the innerdisc onceHeidelberg,
the gap is Mönchhofstraße 12-14, 69120 Heidelberg, Germany
opened, we have used the gas surface density distributions• The!central,!unresolved!870!μm!
5
obtainedwith Spock17,
as an
inputHeidelberg,
to the fargoGermanyhydro code
Max-Planck Institut für Astronomie,Königstuhl
69117
6
conCnuum!source!might!be!
(Masset 2000)
modified COby Picogna& USA
Kley (2015). We model
CASA, University of Colorado, 389-UCB,
Boulder,
80309,
the dust as individual particles, sampling the evolution of a
7
Leiden Observatory, Leiden University,
PO Box 9513, NL-2300 RA Leiden, the Netherlands
produced!by!free!free!emission!
larger ensemble of single dust particles and their interaction
with the surrounding environment.
from!the!gas!and/or!residual!dust!
In Figure 1 we show the drift timescales for particles ofsizes between 100 µm and 1 mm just after the opening of theinside!the!gap.
Figure 2. The 2D dust distribution for 870 µm size particles is
14

Article num

8

1/2

10

5

11

3

gap in the dust distribution (as it is shown in the 2D dust
distribution for 870 µm size particles in Figure 2), when thegas mass accretion rates is 3.7 ⇥ 10 10 M /yr. In the inner
regions (⇠ 0.5 au) particles of 870 µm have a drift timescaleof 2 ⇥ 106 yr.
The drift timescales have an abrupt change in their distribution inside 2.5 au because the strong gas radial velocity

shown at the time of gap opening.

(overplotted with a dashed line) is directed outwards anddrags with it the dust particles. Inside 1 au the gas radial
velocity is not strong enough and the bigger dust particles(870µm, 1 mm) are able to migrate inwards but with a long
drift time-scale.
It is thus likely that some of the 870 µm size particles

findonset
Wfil of≈ dispersal.
λsonic . A strong
velocity
is seen in the HNCO intensity-weighted
of the TW Hya system, e.g. accretion rate and the locationturbulence,of the gap andat theWe showthat gradienttheobtained
ALMA+Mopra.
Theis likely
caused by large-scale shearing of G0.253+0.016, pro
central, unresolved 870 µm continuum source might be produced
by withfree free
emission fromthegradientgas and/or
residual
double-peaked velocity PDF. After subtracting the gradient to isolate the turbulent motions, we find a ne
dust inside the gap.
velocity PDF typical for turbulence. We measure the total and turbulent velocity dispersion, 8.8 ± 0.2 km
Accepted by MNRAS Letters
0.1 km s−1 , respectively. Using magnetohydrodynamical turbulence simulations, we find that G0.253+0.0
magnetic field Bturb = 130 ± 50 µG is only <http://arxiv.org/pdf/1609.03903∼1/10 of the ordered field component. Combining these m
we reconstruct the dominant turbulence driving mode in G0.253+0.016 and find a driving parameter b
indicating solenoidal (divergence-free) driving. We compare this to spiral-arm clouds, which typically hav
The link between turbulence, magnetic fields,compressive
filaments,and starformation
Cen(curl-free)drivingcomponentin(b the> 0.4).
Motivated by previous reports of strong shearing m
tral Molecular Zone cloud G0.253+0.016
CMZ, we speculate that shear causes the solenoidal driving in G0.253+0.016 and show that this red
rate(SFR) by4,5a, factorof 6.9nearby clouds.
6 compared to typical
C. Federrath1 , J. M. Rathborne2 , S. N. Longmore3 ,formation
J. M. D.
Kruijssen
J. Bally, Y. Contreras7 ,1/4

R. M. Crocker1 , G. Garay8 , J. M. Jackson9 , L. Testi10,11,12
and
J. Walsh13
Accepted
byA.
ApJ
1

4

1.

http://adsabs.harvard.edu/pdf/2016arXiv160905911F
Research School of Astronomy and Astrophysics, Australian
National
Federrathet al.University, Canberra, ACT 2611, Australia

2
turbulence,!magneCc!ﬁeld!and!ﬁlamentary!structure!
CSIRO Astronomy and Space Science, P.O. Box 76, Epping NSW, 1710, Australia
3
Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill,
in!the!central!molecular!zone!(CMZ)!cloud!
Spitzer Observations of Long Term Infrared Variability Among Young Stella
Liverpool L3 5RF, United Kingdom
inUniversität
Chamaeleon
I Mönchhofstraße 12-14, 69120 Hei4
G0.253+0.016!
Astronomisches Rechen-Institut, Zentrum für Astronomie derHeidelberg,
Kevin M. Flaherty1 , Lindsay DeMarchi2,8 , James Muzerolle3 , Zoltan Balog4 , William
delberg, Germany
Dust,conCnuum!map!with!ALMA+Herschel:!ﬁlaments!
55Megeath, Elise Furlan6 , Robert Gutermuth7
Max-Planck Institut für Astronomie, Königstuhl 17, 69117Thomas
Heidelberg,
Germany
and!at!least!one!dense!core!along!them!
6remainingobjects were
measured 389-UCB,
only from Boulder,
auxiliary CO
data80309,
with
aUSA
mean
of about∼3 mas/yr.
WeWesleyan
performed
1
CASA, Universityof Colorado,
Van
Vleckprecision
Observatory,
Astronomy
Dept.,
University, 96 Foss Hill Drive, Middletown, CT
7 kinematic analysis of the most accurate proper motions derivedainofLeiden,
this
work,
which
allowed us
to separate
cluster2
Leiden Observatory,
Leiden University, PO Box 9513, NL-2300
RA
the
Netherlands• ﬁlament!width!W
Dept.
Physics
andAstronomy,
ColgateUniversity,
13 Oak Drive, Hamilton, NY 13346, USA
ﬁl!=!0.17!±!0.08!pc!
members from field stars and to derive the mean properties 3ofSpace
the cluster.
From
thekinematic
analysis
wederivedaTelescope Science Institute, 3700 San Martin Drive,
Baltimore, Maryland, 21218, USA• sonic!scale!of!turbulence!λsonic!=!0.15!±!0.11!pc!
list of 68 members and 14 candidate
members, comprising 264 newobjects
withahighmembershipprobability.
These
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany(the!transiCon!scale!from!supersonic!to!subsonic!
new members are generally fainter than the known ones. We5measuredamean
propermotion
of
(µ
cos
δ,
µ
)=(-8.2,αδ
14 Ritter Astrophysical Research Center, Dept. of Physics and Astronomy, University of Toledo, Toled-24.3)±0.8 mas/yr for the L1688 dark cloud. A supervised classification
was applied to photometric data of members
USAturbulence)!=>!!Wﬁl!≈!λsonic!!
to allocate a spectralenergydistribution (SED) classification 6toInfrared
the unclassified
members.
We kinematicallyconfirmed
Processing
and Analysis
Center, California
Institute of Technology, 770 S. Wilson Ave, Pasade
HNCO!intensity,weighted!velocity!maps!obtained!
that the 56 members that were known from previous studiesUSAof the ρ Ophiuchi F cluster and that were also part of7
our survey are members of the cluster, and we added 26 newmembers. We
defined theUniversity
evolutionary
status of the Amherst, MA 01003, USA
Departmentof Astronomy,of Massachusetts,
with!ALMA+Mopra!
8 part (23) of these new members are probably brown
unclassified members of the cluster. We showed that a large
Department of Physics, Syracuse University, Syracuse, NY, 13244, USA•
Velocity!gradient:!large,scale!shear!
dwarfs, which multiplies the number of known substellar objects in the cluster by a factor of 3.3.
E-mail contact: kflaherty at wesleyan.edu•
Turbulence:!nearly!Gaussian!velocity!PDF!
Accepted by A&A main
Infrared variability is common among young stellar objects, with surveys finding daily to weekly flu•
Velocity!dispersion:!8.8!±!0.2!km/s!(total),!!
http://arxiv.org/pdf/1609.04963
few tenths of a magnitude. Space-based observations can produce highly sampled infrared light curves,
limited to total baselines of about a month due to the orientation of the spacecraft. Here we presen
3.9!±!0.1!km/s!(turbulence)!
of the Chameleon I cluster whose low declination makes it observable by the Spitzer space telescope oComparison!with!MHD!turbulence!simulaCons!
A photo-evaporative gap in the closest planetperiod.
formingdisc
We observe 30 young stellar objects with a daily cadence to better sample variability on timesca
1,2
3
1
2,4,5
•
BturbBarbara!=!130!±!50!μG!is!only!<1/10!of!the!
Ercolano , Giovanni P. Rosotti , Giovanni We
Picogna, Leonardo
find suchvariabilityTesti
is common,
occurring in ∼80% of the detected cluster members. The change
color overGermany
200 days for many of the sources falls between that expected for extinction and fluctuations in
1
Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München,ordered!ﬁeld!component!!
8With
our high cadence
and long bei
baseline
we canderivedensity curves
2
Departamentode Astronomı́a,
Universidad
deChile, power
Casillaspectral
36-D, Santiago,
Chile covering two orders
Excellence Cluster Origin and Structure of the Universe, Boltzmannstr.2,
85748
GarchingMünchen,Germany•
Driving!parameter!b!=!0.22!±!0.12!indicates!
9 frequency and find significant power at low frequencies, up to the boundaries of our 200 day survin3
Institutefor AstrophysicalResearch, Boston University, Boston, MA 02215, USA
Institute of Astronomy, University of Cambridge, Madingley
Road, Cambridge,UK
104
European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei München, Germsolenoidal!(divergence,free)!driving!!
European Southern Observatory, Garching bei München, Germany
11
INAF-Arcetri,
Astrofisico di Arcetri, Largo E. Fermi 5, I-50125
Firenze,Largo
Italy E. Fermi 5, I-50125 Firenze, Italy15• 5 INAF/Osservatorio
cf.!b!>!0.4!in!spiral,arm!clouds:!signiﬁcant!
12
Excellence Cluster Universe, Boltzmannstraße 2, D-85748, Garching, Germany
E-mailcontact:
13 Federrath et al.
12 ercolano at usm.lmu.decompressive!(curl,free)!driving!
International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth WA 6
Thecomponent!
dispersal of the circumstellar discs of dust and gas surrounding
young lowmass stars has important
implications
E-mailchristoph.federrathat anu.edu.au
to universal(Arzoumanianal. 2011;
Benedettini
etenergetic
al.contact:
withfor the formationof planetarysystems. et
Photoevaporation
fromradiation from the central object is thought
2015;
Kainulainen
et
al.
2016;
Federrath2016).
Itiseven
is primarily
controlled
theinnerinterplay
between gravity, turbulence, and magnetic fields.
•
SpeculaCon:!!
: purely
driving
to drive themore
dispersal
in the majorityof discs,
creating widthaStar
gap formation
which disconnects
the
outer
frombysolenoidaltheregions1/3
remarkablethat we findhere bya filamentofturbulencemolecular
clouds near
0.4
: innaturalmixture= fields(8) Center may differ substantially frof the=>!solenoidal!driving!=>!SFR!
disc and
disperses
theforouterdisc frominside-out,
whileandthemagnetic
innerb disckeeps
draining
viscously
ontothe Galactic
Wfil then= 0.17± 0.08 pc
the CMZ
cloudtheG0.253+0.016,
shear
clouds. Here we determine the physical parameters of the central molecular zone (CMZ) cloud G0.2

2.

3.

4.

the star. Inconsistent
this Letterwith
we showthatdiscneighborhood.
around TW Hya,
the closest protoplanetary
disc tocompressive
Earth, maydriving.
be the1 : purely
Wfil inthethesolar
We canturbulence,magnetic
field itand
filamentary
structure.
Using column-density maps based on dust-contin
similar widths gapof thein bothenvi- the timefirst object explain
where a thephotoevaporative
hasfilaments
been imaged
aroundat whichis being
created.
Indeed theincludesthemagneticpressurecontribution
Equation(7)
Figure 1.
Hcolumndensitymapsof
G0.253+0.016
from
Herschel(Longmore
et
al.
2012)
(left-handpanel)
and
ALMA+Herschelobservations
with
ALMA+Herschel,we
identify
filamentsand show that at least one dense core is
2 gap
ronments
with thefollowing
theoreticalmodel.
detectedin the ALMA
imagesis consistentwiththe expectations of
X-ray
photoevaporation
models,thus
notthroughstructurethethermal-to-magnetic
pressure
plasma(Rathborne et al. 2014b)(right-hand
The
Herschel
map traces
theWelarge-scale
well,width
while thecombined
ALMA+Herschelthem.
measurethewithfilament
Wfil=
0.17 ±ratio,
0.08 pc
and the sonic scale λsonic = 0.15 ±In
ourmodel,
thepanel).
filament
width
is determinedby therequiringthepresenceofaplanet.
The
photoevaporation
model
is
also
consistent
a
broad
range
of
propertiesβ(Padoan&Nordlund2011;
Molinaetal.
2012).
map reveals the internalof G0.253+0.016.
Using the et
DisPerSE
we W
identify
11 filaments
invelocity
the ALMA+Herschelsonic structure
scale of the
turbulence (Arzoumanianal.
2011;algorithm
turbulence,andfind
λsonic. A strong
gradient
isNoteseenmap,
in the HNCO intensity-weighted
fil ≈ dispersal.
ofhighlighted
the TW Hya
system,e.g.
accretion
rate
and
the
location
of
the
gap
at
the
onset
We
show
that
the
that
in
the
absenceofmagnetic
fields,
where
β
→
∞,
the Thewhich areandlabelled
byartificially
increasing
thecolumndensitybyafactor
of
5
for
each
pixel
belongingtoafilament.
Federrath 2016). The sonic scale marks the22transition
obtained
ALMA+Mopra.
The
gradient
is likely
causedby large-scale
shearing of G0.253+0.016, pro−2 (lower
relation
simplifies
tothe
σρ/ρ
=and/orbM.
While
Equation(8)
central,unresolved
870 µmcontinuum
sourcemight
producedby withfreecolumn
freeemissionfromgas
residualgray contour
enclosesgassupersonicwitha column
density≥
5scales
× be
10 to
cm
densities
have
relatively
low
S/N).
The position
of
0
from
turbulence
on N
large
subsonic
double-peaked
PDF.
Aftercases
subtracting the gradienttoisolate the turbulent motions, we find a ne
23velocity−2threethespecialmixed,
compresdust insidethegap.
a water maser
is labelled
and isonlocated
1, where N ≥cm(blackcontours). (solenoidal,
Another two
over-dense
regions
turbulencesmall along
scalesfilament(Vázquez-Semadeni
et 2.5al. × 10lists
velocity
PDFsive),turbulence.
We measurethetotalofandvelocity dispersion, 8.8 ± 0.2 km
driving
parametercancontinuouslyinthe(‘dense-core candidates’)
above isthedefinedsame thresholdstand&out
alongfilaments
2typicalandthe
4.for
Red
lines
indicate
thevary
direction
theturbulent
large-scaleas (Federrath
Klessen2012;−1
by2003).
MNRASItLetters
0.1etkm, respectively.
magnetohydrodynamical
simulations, we find that G0.253+0.0
23
rangesee
1/3!Using
b et
! al.
1.
An increasingb valueturbulencecorrespondsal.s (2010);
Pillai(2015).
Both imagesarein equatorial
magneticAccepted
field frompolarization
measurements
obtained in Dotson
Federrath2016)<
magnetic field=
130 ± 50
µG
is of
only
of theorderedfield component. Combining these m
to Banincreasing
fractioncompressivemodes
in thecoordinates:the (0,0) offset position in right ascension
(RA)
(DEC)
is
17:46:09.59,−28:42:34.2
J2000.
turb
http://arxiv.org/pdf/1609.03903∼1/10!
" and declination
turbulent
drivingturbulencemechanism.
Themodespecialcase called and find a driving parameter b
we reconstruct
the dominant
driving
in G0.253+0.016
λsonic = LM−2 1 + β −1 ,(5)‘natural
mixture’
is
close
to
solenoidal
drivingandreferssolenoidal(divergence-free)driving.1 We
compare three
this to promispiral-arm clouds, which typically hav
that the most importantparameterin the DisPerSE
al- indicating
The
black
contours
In theFigurehighlight
to
the
where
turbulent
drivingmodesbyare
where
L, Mturbulence,= σv,3D /cs andβ are thecloud filaments,
scale
link
betweenmagnetic
fields,andsituation
star
formationin23−2 reports of strong shearing m(curl-free)drivingcomponent(b the> 0.4).
Motivatedprevious
gorithmTheis thepersistence
threshold,which
weMachhave
set compressive
nent randomly
over-dense
regionswith≥Cen2.5 (see× 10
distributedin allthreeNdimensions
Fig. 8cm
the
3D turbulent
sonic
number,andtral
Molecular
Zone
cloud
G0.253+0.016
CMZ,
we
speculate
that
shear
causesthesolenoidal
drivingin
G0.253+0.016
and show that this red
22 (diameter),−2
inFederrathetal.
2010).
here to 5×10 cmthe ratio, i.e.,of10thermal
σ of thesensitivity
threshold(one
potentially
activeregionofstarformationas
into magnetic pressure, plasma
β =(SFR)ourby4,5ameasurements
factorof 6.9typicalnearby1
2 2
3 formation rate Given
6 comparedof σContreras=to1.30.5,
M maser;=clouds.
C. Federrath, J./pSec.
M.
Rathborne
S.
, J. M.
D. Kruijssen,map
J. Bally, Y.
, waterρ/ρ0 bypthermal= order
2c2s /v,A
theLongmore
cloud.theInsertingof the observations(see2), intoofN.
find
only
dicatedin theandtraceda7 ±magnetic11±and
β 13= 0.34
± 0.35
in G0.253+0.016
theet al.
1711Jackson
L = 1dense
4.7± Garay
0.1
pc, 8M± 3,haveand9 , βexperi0.3410,11,12± 0.35R. M. Crocker, G.
, J.=M.
L.=TestiandA.
J.3al.
Walsh
Accepted
by
ApJ
see
Lis
et
1994;
Breen
& Ellingsen
2011;from
Mills
We
most significant
andfilaments.
previous
sections and summarized in Table 1, we can
The CMZ cloud G0.253+0.016
based5 on our measurements
and values taken from the8Federrath etRathborneal.
12015).
et al.
(2014b)a 2× higher
threshhttp://adsabs.harvard.edu/pdf/2016arXiv160905911F
Research
Schoolof lower
Astronomy
andAstrophysics,
Australian
National
University,
Canberra,ACT2611,used
Australia
mentedwithhigherandpersistence
thresholds
and
solve
Equation
(7)
for
the
turbulence
driving
parameter
literaturesummarized
in
Table
1,
we
find
a
sonic
scale
of
rmal distribution to a high column-density
2
CSIROfilaments
Astronomyandandsimilar
Space Science,
P.O.column
Box 76, denEpping NSW,
1710,
Australia
Rathborne et al. (2014b).
found
similarfilament
old
(N
>
and
find5 × 1023 cm−2 ) based on the fact that thee effective diameter of the water maser and3= 0.15 ± the
0.11
pcMoores University,(6)
Astrophysics
Research Institute,
Liverpool
Johnthreshold
IC2, Liverpool Science
Park, 146
Hill, a log-normal−1−1Brownlow
e-core candidates is 0.09 pc with a variasities andwidths. Decreasing
orλsonic
increasingcolumn-density
deviatefromb = σPDF(1 + βto)1/2 =Infrared
0.22± 0.12.Variability(9)ρ/ρ0 Ma factor of 2. The filling fraction of these
Spitzer
Observations
ofstartsLong
Term
Among Young Stella
Liverpool
L3for
5RF,
UnitedKingdom
res is only 0.0011 ± 0.0001 of the total areabyafactoroftwoneithersignificantly
affects
thenumberPDF
atthiscolumn-density
threshold.
Using N > 5 ×
G0.253+0.016.
This
is
in
excellentagreement
withinUniversität
Chamaeleon
I means
016, indicating inefficient dense-core and
4
18
23
−2
This
resultthat
turbulenceinG0.253+0.016
isAstronomisches
Rechen-Institut,
ZentrumfürAstronomiederHeidelberg,Mönchhofstraße
12-14,
69120
Hein (see also Kauffmann et al. 2013). The
the filament
widthaveragethat we measured
for G0.253+0.016
ofidentified
filamentsnor
theirproperties.
10
cm
only
selects
thewater-maser
location,
which
1
2,8
3
and the two dense-core candidates are locaused
by a solenoidal driving
mechanism.
Kevin
M. primarily
Flaherty, Lindsay, JamesMuzerolle, Zoltan Balog4 , William
delberg, Germanyin Figure 2. It supports the idea that the sonic scaleoffilaments 1, 2 and 4. Dense cores are ofRathborne
etal.
(2014b)DeMarchi
confirmed to
be a coherent
and
5
6
7
5
d with filaments and their intersections,magnetizedturbulence
givenKönigstuhl
by Equation
may
conThomas
Megeath, HereElise
Furlan, Robert
Gutermuth
Max-Planck
Institutfür
Astronomie,
17, (5)69117
Heidelberg,
Germany
6.1. Thedensitydispersion–Machnumber relation
seen in clouds in the spiral arms of the
bound
core.
we
reducethethresholdbyafactorSection7),
so
we
restrictourselvestotheanalysisoftheprojected
6trol the widthof interstellar
filaments,
not CO
only80309,
in nearbychneider et al. 2012; Polychroni et al. 2013;
Universityof Colorado,
389-UCB,
Boulder,USAfilaments. CASA,
Thus individual
filaments
in
the
map
may
con- 1 Van
Vleck
Observatory,
Astronomy
Dept.,
Wesleyan
University,
96 Foss. 2015). This suggests that filaments may
Figureyields
6 shows
a graphicalof the denof
2, which
another
tworepresentation
dense
structures
that
we Hill Drive, Middletown, CT
2016),
but also
inactuallythe
CMZ.
clouds (Federrath
7
tal building blocks of molecular clouds, ir2
Leidensub-filaments
Observatory,
LeidenUniversity,
PO
Box
9513,
NL-2300
RA
the
Netherlands
sist of multiple
along
the
LOS,
butthatsimulations
havesity dispersion–Machnumberby EquaDept.
ofLeiden,
Physics
andAstronomy,
ColgateUniversity,
13 OakDrive,
NY 13346, USA
whether the clouds are located along spiralcall‘dense-core
candidates’.
Werelation
cannotgiven
confirm
themHamilton,
as
We
have
to
add
the
caveatEquation(5)
isgenerthe Galactic Center.
shown that the average width of these projected filaments agrees 3 Space Telescope
tion
(7).
In
order
to
put
our
result
for
the
CMZ
cloud
Science
Institute,
3700
San
MartinDrive,
Baltimore,
Maryland, 21218, USAally only
applicableclouds wherefilaments
the magnetic
isred lines in the right-hand panel of Figstructuresinvelocity
space threeat thispoint (seewith the average widthof theintrinsicfor
3-dimensional
to 4 field coherent
the projected large-scale magnetic field diG0.253+0.016
incontext,
we
includespiral-arm
primarily
turbulent,
i.e.,
B
>
B
.
This
does
not
seem
Max-Planck-InstitutfürAstronomie,Königstuhl
17,
69117
Heidelberg,
Germanyturb
0nferred from polarization measurements bydiscussion
the6,correlationof density
dust andmolecular
within a factor of 2 (Sec. 7).
clouds aboutin Figurefor whichthedispersion–(2010) and further analysed in Pillai et al.
to be the case in G0.253+0.016 (see Section 3.3),
we AstrophysicalRitterResearchCenter,
Dept. of Physics
anduncertainAstronomy, University of Toledo, Toled
17 All other DisPerSE
14 5 soee that some filaments are mainly parallel
parameters were set to the recommended
line emission
in
Sec.
7).
However,theMach number
relationwasmeasuredgiven
in previous
works.
havefulltoperforma morecareful analysisof theorientation
laments 1 and 5), while others are primarUSA
standard
values.
The
DisPerSE
command
lines
used
were:
Measurements
in Taurus wereobtained in(seeBrunt(2010),
ular to B0 (e.g., filaments 2 and 4). We do
ties
in
the
column-density
calibration
Sec.
7), theofthefilaments
withrespecttothelarge-scaleordered6
the filaments have a preferred orientation
mse map.fits -noTags -upSkl -periodicity 0 -cut 4.75e22
Infrared Processing
and Analysis
California
Instituteof Technology,
770 S. Wilson Ave, Pasadewith corrections
the Mach
numberestimatein−2to Center,o the large-scale magnetic field. In the folmagneticmap.fits.up.NDskl
field component B0 . -noTags
In Figure-toFITS
2 we found thatN ≥ 2.5
× 1023 cm
thresholdusedherehereis stillconsis-robustness and skelconv
etermine the width of these filaments andUSA
Kainulainen&Tan(2013),
andcombinedwithanfilaments
parallel robustness
to B0 are somewhat
wider than
filaaments primarily parallel or perpendicular-breakdown-smooth6-trimBelow
4.75e22
7
tent
with
the
deviation
point
in
the
column-density
PDF
Alfvén
Mach numberof MA
1 estimated forthe gasMA 01003, USAr to test whether the width depends on the
Departmentof Astronomy,
Universityof >Massachusetts,
Amherst,perpendicular
B0 , however,this ofis 5merelyatation.
-assemble 70. Wements
further
enforced a tominimum
number8
insidethe cloud(Heyer& Brunt Syracuse,2012).24 NY,
The 13244,
Galac- USA
Departmentof Physics,
Syracuse
University,
3.1.1. Filament profiles
pixels per filament. trend that is not statistically significant given the uncerwidth tic
does
notSurvey
significantly
dependonthe choice of persistenceRingmolecular
cloud
GRSMC43.30-0.33
datatainties inthemeasuredfilament width.
So while
Equameasure the characteristic width of the
18 A systematic analysis
threshold,
while
the
averagecolumndensityofthefilamentsofvaryingthepersistence
thresholdisE-mailcontact:
kflaherty
atwesleyan.edu
G0.253+0.016, we construct radial profiles
are from Ginsburg et al. (2013) and the IC5146 data are detion (2016),(5) onlyshowing
takes thethat
turbulentmagneticpressure into
ach individual filament in Figure 1. The
creasesfrom
withPadoan
decreasing
threshold,as expected.
performed in Federrath
the averagefilamentetal.
(1997a).
For
GRSMC43.30-0.33
andsurveys finding daily to weekly flu
similar to that applied in previous studies
account and would thus theoretically only applyInfrared
to the variability is common among young stellar objects, withn et al. 2011; Federrath 2016). The radial
we hadSpace-based
to neglect themagnetic canfieldproduce(assumed
filaments perpendicular to B0 , it seems to providefew
a goodomputed by selecting all pixels belonging
tenths ofIC5146,
a magnitude.
observations
highly sampled infrared light curves,and then tracing the column density cells
MA → ∞), because there are no measurements of Bturb
match to the measured filament widths, irrespectiveof to total
cular distance r to the filament as in previlimited
baselinesof abouta monthdue toorientation
available
for these
clouds.
However,
we theemphasize
thatof the spacecraft. Here we presen.g., Federrath 2016, and references therein).
the filament orientation.
of the Chameleon
I clusterwhosemagnetic
low declination
makes itBobservableby the Spitzer space telescope overage column density and column density
includinga realistic
field strength
turb > 0
the radial distance r from each filament
period. We observe
30 young
stellarwitha daily
cadenceto better sample
will always
lead tohighervaluesof thedriving
parameThe
CMZ objects
cloudG0.253+0.016
13 variability on timesca
ment profile.
6. THE EFFECTIVE TURBULENT DRIVING
hows the filament profile of G0.253+0.016
Figure 2.
Top panel: Average radial profile of all the
Figure 4. Top panels: maps of the HNCO intensity-weighted
velocity
intheG0.253+0.016,
beforesubtracting
thelarge-scale
velocity
ter
b.
The
data
pointsfor
GRSMC43.30-0.33
andIC5146
We find such variability is common, occurring in ∼80% of the detected cluster members. The change
G0.253+0.016 filaments in Figure 1. Middle panel: same as top
e is the average profile and the shaded regradient (left-hand panel) and after subtracting it (right-hand panel). The middle panel shows the fitted gradient across G0.253+0.016,
panel, but only for the filaments that are primarily parallelTheoreticalto thee 1σ-dispersion). In order to determine theand numericalstudieshave motions,shownwhich is likely associatedwith systematic
such thatas large-scale
shear
or rotationofFigure
thecloud. Thissystematic
contribution
must
be lower that
shown
in
6
therefore
represent
limitsofb.
large-scale magnetic field (B ). Bottom panel: same as top panel,
color
over
200
days
for
many
of
the
sourcesfalls
betweenexpectedfor
extinction
and fluctuations in
h Wfil , we apply two fits, one with a Gaussubtracted in order to isolate the turbulent motions in the cloud. The coordinates and field of view of the maps are identical to Figure 1.
but only for the filaments that are primarily perpendicular to B .
density fluctuations(σρ/ρHNCO) invelocity
a turbulent
medium
We
see
that
all
three
available
spiral-arm
cloudshave density curves covering two orders
Bottom panels:
PDF before subtracting
the large-scale gradient(left-handpanel)
andafter subtracting
it (right-handhe other with a Plummer profile.
In all panels, the shaded region shows the 1σ-dispersionthe
about the
0
With
our
highGaussiancadenceandlongbaselinewecanderive power
spectralpanel). The velocity PDF after subtraction is consistentwiththe typical
distribution(dottedline)
of a turbulent
mediumwithaverage profile. Plummer fits with Equation (2) and a Gaussianan filament profile (shown as the dotted lineasignificant
compressive
drivingcomponent,
i.e.,
they
correlatewith the aMach
number(M) ofandthelines, refits with Equation (1) are shown as dashed and dotted
one-dimensional
velocity dispersion
σv,1D =
3.9 ± 0.1
km s−1 .
s defined asin drivfrequency
and find significant power at low frequencies, up to the boundaries of our 200 day surv
spectively. The beam size is shown as a ruler. Both Gaussian and"!
have b parameters exceeding the natural driving mixture,
Plummer fits yield consistent beam-corrected filamenting
widthsofof the turbulence, which is controlled by the turbur2
W = 0.17 ± 0.08 pc for all filaments, W = 0.19 ± 0.09 pc for the+ Σoffset ,(1)= Σ(0) exp − 2Here we use the HNCO line emission of G0.253+0.016
This
velocityby
gradient
likely associatedfilaments primarily parallel to B , and W = 0.13 ± 0.07
pc for the driving parameter b (Federrath et al. 2008b, 2010;b>large-scale
0.4,rotation
given
the isblue
dotted withline (Federrath et al.
lence
2σGaussbyRathborneetal.
(2015),
inorder
toobtainglobalsystematicor shearing of the cloud. By confilaments mainly perpendicular to B .
2010).
G0.253+0.016(shownas the red cirPrice et al. 2011; Konstandin
et al.velocity
2012;
Nolan
et al.
kinematics (large-scale
gradient
and dispersion)
trast,
stellarHowever,feedback or gravitational
infall would
proparametersΣ(0) and σGauss . The filament√
15 disperthat we will 2015),
then correlate with the global gas density
duce
ainshock,i.e.,6)a discontinuity,
but we see a rather
2 2 ln 2 σGauss ≈ 2.355 σGauss is definedwith the fit parameters Σ(0), p and Rflat , where
the lat- Federrath & Banerjee
cle
Fig.
has
a
significantly
lowerdensity2015;
dispersion obtained in the previous section. The final
smooth gradient, which is most likely associated with
M of the Gaussian. The constant column
terisrelatedtothefilament
width
W
≈
3
R
for
fil
flat
sion
σ
and
significantly
lower
b
than
any of theΣoffset = 1 × 1023 cm−2 was chosen to begoal is to determine the sonic scale and the turbulence
shear(Kruijssen
et al.,thus
in preparation).
Such large-scaleρ/ρp = 2 (Arzoumanian et al. 2011). Arzoumanian et al.
0"−1/2 or compressive). The! (solenoidal,th the average column density inside themodesystematic motions must be subtracted in order to iso(2011), Contreras et al. (2013), Federrath
Smith et al. (2014)
etand
al.
2
σρ/ρ0 driving= bM+ β −1 mixed,
contour of G0.253+0.016, providing highFederrath (2016) experimented with the power p and(2015)
HNCO
line 1
measurementsfrom ,Rathborne et al. (7)late24the turbulent motions on scales smaller or equal todensity values.
mer filament profile (shown as the dashed

2/4

0

0

fil

fil
fil

0

0

found that the best fits to the filament profiles were

provide the best available correlation with the ALMA

As a reasonable estimate of M

in Taurus, we adopt MA = 2

A2000;
the size of the cloud (e.g., Burkert & Bodenheimer

6 thehorizontal
andetplot
in Fig.
obtained with p ≈ 2. Here we find p = 2.1 ± 1.0 for
dust emission and also provide the best available spatialSur
al. 2010;
Federrathet al.
2011b). In error
order tobars
iso- from the lower limit
niversal
et al. 2011;
Benedettini
et al.
23 2.Note that the definition
2) is defined (Arzoumanianas
G0.253+0.016
from the Plummer
fit shown in with
Figure(Mthe1) to motions,
4 times(Mwithof theEq. (45)inA =A =cloud coverage,
so wesonicuse it scale
here to in
determine
the turbulate
turbulent
we thisfit thevalue
gradienta 4). Given the low
is similar#$(1−p)/2
Federrath2016).
(2016) provided
theoretical model
for p = (2013a)5;Σ(0)
Kainulainen
et +al.
2016; Federrath
It isa even
AlfvénMach
numbertheandperipheryof Taurus(MA ∼ 0.5; see
Hopkinsours
and yields
the same dependence
lent tovelocity
dispersionof G0.253+0.016(cf. Sec. 2.2).
plane,
shownin themiddle inpanel,
then subtractit2
1 + (r/Rflat )Σoffset , (2)2, which is given by the radial dependence of the den1/3:
purelysolenoidal
drivingfromthe&original
map
in the top
righton M, but it does not incorporate the magnetic pressure contriHeyer
Bruntvelocity2012),
it (shownis unlikely
that
MA could reach values
e remarkable that we find here a filament width of
hand
panel
of Figuregradient-subtracted
3.2.1. Velocityas
maps
0.4 : naturalb=(8)bution that
we include
here andmixture
first introduced
the ’magnetohigher
than
M 4).
= This4 inside
Taurus. Wevelocfurther include the uncer= 0.17 ± 0.08 pc for the CMZ cloud G0.253+0.016,
ity map depicts theAturbulent gas motions along the linesonic’ scale in Eq. (22) inThe
tainty of the sonic Mach number into the horizontal error bars.
Federrathtop
panels&ofKlessen
Figure4 (2012).
show maps of the HNCO
of sight (LOS), centered on v = 0.
1 : purelycompressive
driving.
istent with Wfil in the solar neighborhood. We canintensity-weighted velocity (centroid velocity). The lefthand panel shows a strong and prominent velocity graain the similar widths of the filaments in both envidientacrossthe long axisof G0.253+0.016,
which6. had
includesthemagneticpressurecontribution
Equation(7)
3.2.2.
Velocity
PDF (σρ/ρ ) and the combination of sonic Mach number (M) and plasma β.
FigureRelation
between the turbulent
densityfluctuations
ments with the following theoretical model.
been seen in earlier works (e.g., RathborneThis
et al.
2015).given by Equation (7), defines the turbulence driving parameter b (Federrath et al. 2008b, 2010). The three dotted lines
relationthrough the thermal-to-magnetic
pressure ratio, show
plasmaEq. (7) for three representative driving cases: purely solenoidal driving (b = 1/3, gold), naturally-mixed driving (b ∼ 0.4, blue),
our model, the filament width is determined by theand Note
purely compressive driving (b = 1, purple); see Eq. (8). Numerical simulations are shown as symbols (with the color indicating theβ(Padoan&Nordlund2011;
Molinaetal.
2012).
c scale of the turbulence (Arzoumanian et al. 2011;
applied driving mode: sol, mix or comp): from Federrath et al. (2008b, 2010) (diamonds), Price et al. (2011) (pentagon), Molina et al.
(squares), Konstandin et al. (2012) (stars), Nolan et al. (2015) (triangles), and Federrath & Banerjee (2015) (upside-down triangle).
that in the absence of magnetic fields, where β → (2012)∞, theerrath 2016). The sonic scale marks the transition
The black crosses are measurements in the Milky Way spiral-arm clouds Taurus (Brunt 2010), GRSMC43.30-0.33 (Ginsburg et al. 2013),
relation simplifies to σρ/ρ0 = bM. While Equation(8) (Padoan et al. 1997a). Our measurement for G0.253+0.016 is shown as the red circle with 1σ uncertainties drawn from theand IC5146
m supersonic turbulence on large scales to subsonic
PDFs in the top and right panels. This indicates solenoidal driving of the turbulence in G0.253+0.016, i.e., b < 0.4. By contrast, all three
spiral-arm clouds show a significant compressive driving component, b > 0.4.
lists the three special cases (solenoidal, mixed, compresulence on small scales (Vázquez-Semadeni et al.
sive),
thedriving
parametercanvarycontinuously
inthe3). It is defined as (Federrath & Klessen 2012;0

findonset
Wfil of≈ dispersal.
λsonic . A strong
velocity
is seen in the HNCO intensity-weighted
of the TW Hya system, e.g. accretion rate and the locationturbulence,of the gap andat theWe showthat gradienttheobtained
ALMA+Mopra.
Theis likely
caused by large-scale shearing of G0.253+0.016, pro
central, unresolved 870 µm continuum source might be produced
by withfree free
emission fromthegradientgas and/or
residual
double-peaked velocity PDF. After subtracting the gradient to isolate the turbulent motions, we find a ne
dust inside the gap.
velocity PDF typical for turbulence. We measure the total and turbulent velocity dispersion, 8.8 ± 0.2 km
Accepted by MNRAS Letters
0.1 km s−1 , respectively. Using magnetohydrodynamical turbulence simulations, we find that G0.253+0.0
magnetic field Bturb = 130 ± 50 µG is only <http://arxiv.org/pdf/1609.03903∼1/10 of the ordered field component. Combining these m
we reconstruct the dominant turbulence driving mode in G0.253+0.016 and find a driving parameter b
indicating solenoidal (divergence-free) driving. We compare this to spiral-arm clouds, which typically hav
The link between turbulence, magnetic fields,compressive
filaments,and starformation
Cen(curl-free)drivingcomponentin(b the> 0.4).
Motivated by previous reports of strong shearing m
tral Molecular Zone cloud G0.253+0.016
CMZ, we speculate that shear causes the solenoidal driving in G0.253+0.016 and show that this red
The
CMZ
cloud
G0.253+0.016
11rate(SFR) by4,5a, factorof 6.9nearby clouds.
6 compared to typical
C. Federrath1 , J. M. Rathborne2 , S. N. Longmore3 ,formation
J. M. D.
Kruijssen
J. Bally, Y. Contreras7 ,3/4

R. M. Crocker1 , G. Garay8 , J. M. Jackson9 , L. Testi10,11,12
and
J. Walsh13
Accepted
byA.
ApJ
1

Table 1
Physical parameters of G0.253+0.016 in the CMZ.

The CMZ cloud G0.253+0.016

3

Physical Parameter
Symbol/Definition
Mean (Standard Deviation)
Comment (Reference)
Measured physical parameters:
Area
A
17 (1) pc2
From Figs. 1, 4; (Refs. 1)
H2 column density
N0
1.9 (1.0) × 1023 cm−2
From Fig. 1; (Refs. 2)
Filament width
Wfil
0.17 (0.08) pc
From Figs. 1, 2
2D-to-3D density dispersion ratio
R1/2
0.28 (0.11)
From Fig. 1; Eq. (3); (Ref. 3)
1D turbulent+shear velocity dispersion
σv,tot,1D
8.8 (0.2) km s−1
From Fig. 4, with gradient
1D turbulent velocity dispersion
σv,1D
3.9 (0.1) km s−1
From Fig. 4, grad. subtracted
Derived from numerical simulations:Turbulent magnetic field
Bturb
130 (50) µG
From Fig. 5; Sec. 3.3
Taken from the literature:
Log. column density dispersionση
0.34 (0.02)
η = ln(N/N0 ); (Refs. 2)
Gas temperatureT
100 (50) K(Refs. 4)
Dust temperature
Tdust
20 (1) K(Refs. 2)
Total (ordered+turbulent) magnetic fieldBtot
2.2 (0.9) mG(Ref. 5)
Mean molecular weight per unit mHµmol
2.8mH : mass of an H atom (Ref. 6)
Derived physical parameters:
Effective diameter
L = 2 (A/π)1/2
4.7 (0.1) pc
Massa
M = N0 µmol mH A
7.2 (3.8) × 104 M"
H2 volume number densityb
n0 = N0 /L
1.3 (0.7) × 104 cm−3
Volume density
ρ0 = n0 µmol mH
6.2 (3.3) × 10−20 g cm−3
Column density dispersion
σN/N0 = [exp(ση2 ) − 1]1/2
0.35 (0.02)(Ref. 7)
1/2
Volume density dispersion
σρ/ρ0 = σN/N0 /R
1.3 (0.5)
Eq. (3); (Ref. 3)
Sound speed (isothermal)
cs = [kB T /(µp mH )]1/2
0.60 (0.15) km s−1µp = 2.33 (Ref. 6)
Turbulent Alfvén speedvA = Bturb /(4πρ0 )1/2
1.5 (0.7) km s−1
2
Turbulent plasma beta
β = 2 c2s /vA
0.34 (0.35)
1/2
3D turbulent+shear velocity dispersion
σv,tot,3D = 3 σv,tot,1D
15.2 (0.3) km s−1
3D turbulent velocity dispersion
σv,3D = 31/2 σv,1D
6.8 (0.2) km s−1
2
Virial parameter (turbulence+shear)
αvir,tot = 5σv,tot,3D/(πGL2 ρ0 )
4.3 (2.3)
2Virial parameter (turbulence only)
αvir = 5σv,3D/(πGL2 ρ0 )0.85 (0.45)
Freefall time
tff = [3π/(32Gρ0 )]1/2
0.27 (0.14) Myr
Turbulent crossing time
tturb = L/σv,3D0.67 (0.03) Myr
2
Turbulent energy dissipation rate
'turb = M σv,3D/(2tturb )1.5 (0.8) × 1036 erg s−1
3D turbulent sonic Mach number
M = σv,3D /cs
11 (3)
3D turbulent Alfvén Mach number
MA = σv,3D /vA
4.6 (2.1)
Sonic scale
λsonic = LM−2 (1 + β −1 )0.15 (0.11) pc
Eq. (5); (Refs. 8)
Turbulence driving parameterb = σρ/ρ0 M−1 (1 + β −1 )1/2
0.22 (0.12)
Eq. (7); (Refs. 9)
Derived star formation parameters:
2.3 (1.2)
Eq. (10); (Ref. 10)
Log-critical density
scrit = Eq. (10)Critical number density
ncrit = n0 exp(scrit )1.0 (1.4) × 105 cm−3
(Ref. 10)
Star formation rate per freefall time
'ff = Eq. (11)0.042 (0.030)
Eq. (11); (Ref. 10)
Star formation rate
SFR = 'ff M/tff
1.1 (0.8) × 10−2 M" yr−1
Eq. (13); (Ref. 10)
Notes. All physical parameters are derived for pixels that fall within the 5 × 1022 cm−2 (10 σ sensitivity) column density contour shown in
Figure 1 and where the HNCO intensity-weighted velocity has valid measurements (see Figure 4). This defines the fixed area A = 17 (1) pc2
within which we derive and report all physical parameters of G0.253+0.016. All uncertainties were propagated based on each independent
parameter. The standard deviation of each parameter is provided in brackets; we note that some of the parameters do not have Gaussian
probability distributions, e.g., β = 0.34(0.35), which must not be read as β having a finite probability to be negative (by definition it
must not), instead this is a consequence of the skewed distribution of β. Nevertheless, the standard deviation is always a useful measureof the uncertainty in each parameter (D’Agostini 2004). References: (1) assuming a distance of 8.3 (0.3) kpc (Malkin 2013; Zhu & Shen
2013; Reid et al. 2014), (2) Longmore et al. (2012), Rathborne et al. (2014b), (3) Brunt et al. (2010b), (4) Lis et al. (2001), Mills & Morris(2013), Ao et al. (2013), Bally et al. (2014), Ginsburg et al. (2016), (5) Pillai et al. (2015); note that the magnetic field measurement of
5.4 (0.5) mG in Pillai et al. (2015) was adjusted to reflect the correct volume density n0 = 1.3 (0.7) × 104 cm−3 of G0.253+0.016, because
the volume density reported in Longmore et al. (2012) is incorrect. We further propagated the uncertainty of n into the uncertaintyof Btot . (6) Kauffmann et al. (2008). (7) Price et al. (2011). (8) Federrath & Klessen (2012), Federrath (2016). (9) Federrath et al.
(2008b), Federrath et al. (2010), Padoan & Nordlund (2011), Molina et al. (2012), Federrath & Banerjee (2015), Nolan et al. (2015). (10)Federrath & Klessen (2012). a Note that the mass of 1.3 × 105 M" derived by Longmore et al. (2012) is a factor of 1.8 higher than ourestimate, because Longmore et al. (2012) computed the mass in an area of 1.3×105 M" /(1023 cm−2 µmol mH ) = 58 pc2 , which is significantly
larger than what we define here for the area of G0.253+0.016. Note that the effective radius of 2.8 pc reported in Longmore et al. (2012) also
corresponds to a significantly smaller area (25 pc2 ) compared to the area used for their mass estimate. Here we derive all physical quantities
consistently in a fixed area A = 17 (1) pc2 (see above). b The average volume density of 8 × 104 cm−3 reported in Longmore et al. (2012) isincorrect because of an error in the script from which that value was derived. The corrected value derived here is n0 = 1.3 (0.7) × 104 cm−3 .

11

http://adsabs.harvard.edu/pdf/2016arXiv160905911F
Research School of Astronomy andTable
Astrophysics,
Australian
National University, Canberra, ACT 2611, Australia
1parametersof G0.253+0.016
CMZ. NSW, 1710, Australia
CSIRO AstronomyPhysicaland Space
Science,
P.O. Box in
76,theEpping
Institute, Liverpool John
Liverpool
Science Park, 146 Brownlow Hill,
Physical Parameter Astrophysics Research Symbol/Definition
MeanMoores(StandardUniversity,
Deviation) IC2,Comment(Reference)
Spitzer Observationsof Long Term Infrared Variability Among Young Stella
Measured physical Liverpool
parameters: L3 5RF, United Kingdom
I
4
2in Chamaeleon
Area
A
17
(1)
pc
From
Figs.
1,
4;
1)
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, (Refs.
Mönchhofstraße
12-14, 69120 Hei2)
H2 column density delberg, Germany
N0
1.9 (1.0) × 1023Kevincm−2
From Fig. 1;1 ,(Refs.
M. Flaherty
Lindsay
DeMarchi2,8 , James Muzerolle3 , Zoltan Balog4 , William
Filament width
Wfil
0.17 (0.08) pc
From5Figs.
1, 2 Furlan6 , Robert Gutermuth7
5
ThomasMegeath,Elise
Max-Planck Institut für Astronomie,Königstuhl
17,
69117
Heidelberg,
Germany
2D-to-3D density dispersion
ratio
R1/2
(0.11)
From Fig. 1; Eq. (3); (Ref. 3)
6remainingobjects were
measured
only from Boulder,
auxiliary0.28
data
with
aUSA
mean
precisionof about∼3 mas/yr.
WeWesleyan
performed
1
CASA,dispersion
Universityof Colorado,
389-UCB,CO
80309,
VleckFrom
Observatory,
Astronomy
Dept.,
University, 96 Foss Hill Drive, Middletown, CT
1D turbulent+shear velocity
σv,tot,1D
8.8 (0.2)km
s−1VanFig. 4, with gradient7akinematic
analysis
of
the
most
accurate
propermotions
derived
in
this
work,
which
allowed us
to separate
cluster2−1
LeidenObservatory,
LeidenUniversity,
PO
Box
9513,
NL-2300
RA
Leiden,Netherlands
4,
grad.
subtracted
1D turbulent velocity dispersion
σv,1D
3.9 (0.1) km s Dept. ofFrom
Fig.thePhysics
andAstronomy,
ColgateUniversity,
13 Oak Drive, Hamilton, NY 13346, USA
members
from field stars and to derive the mean properties 3ofSpace
the cluster.
From
thekinematic
analysis
wederivedaDerived from numericalsimulations:
Telescope Science Institute, 3700 San Martin Drive,
Baltimore, Maryland, 21218, USAof 68 members and 14 candidate
members, comprising
with
a
high
membershipprobability.
These
5;
Sec.
3.3
Turbulent magneticlist
field
Bturb
130 (50)26µG
Fig.
4 new objects From
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
16
Federrathet al.
Taken from the literature:
new members are generally fainterthan the known ones. We5measuredamean
propermotion
of
(µ
cos
δ,
µ
)=(-8.2,αδResearch Center, Dept. of Physics and Astronomy, University of Toledo, Toled
14 Ritter AstrophysicalLog. column density
dispersion mas/yr for the L1688ση dark cloud. A supervised
0.34 (0.02)
η = ln(N/N(Refs.
2)0 ); to-24.3)±0.8
classification wasappliedphotometricdata of members
dominating
thecloud andgalaxy-center clouds
8. We measure the effective cloud diameter L =Gas temperatureT
100possibly(50) KUSA(Refs. 4)
6to the unclassified members. We kinematically confirmed
to allocate a spectral energy distribution(SED) classification
Infrared
Processing
andAnalysisCenter,California
Instituteitof withTechnology,
770numS. Wilson Ave, Pasade
Dust temperature
20 (1) K and results are summa(Refs. 2)
inTdustgeneral. Our measurements
4.7 ± 0.1
pc and combine
the Machthat the56 membersthat were
known
from
studiesof theimportantρ Ophiuchi
F clusterand that
wereplasma
also part
USA
Total (ordered+turbulent)magnetic
field
Btot
2.2list(0.9)the
mG
(Ref.
5)
rized
in Table
1. previous
Here wemostresults
ber and
β toofderive the sonic scale λsonic of7
our persurveyarecluster,
and we added 26
members.
We
the(Ref.
evolutionary
status inof G0.253+0.016.
the Amherst, MA
Mean molecular weight
unit mµmol
2.8 new
mH : massofdefined
an H atom
6)the turbulence
andconclusions:
We find
λsonic=H members of the
Departmentof Astronomy,
Universityof Massachusetts,
01003,
USA
8 part (23) of these new members
unclassified members of the cluster. We showed that a large
are−2probably
Derived physical parameters:(1 + Syracuse,
β −1brown) = 0.15
0.11 pc,
in agreement
Department of Physics, Syracuse LM
University,
NY,±13244,
USA
1/2
Effective diameter dwarfs, which multiplies the
L =number
2 (A/π)
4.7
(0.1)
pc
with
our
measurementofthefilament
width,
W=of known
substellar
objectsdetectionin the cluster
by a factor of 3.3.
fil
1. Using
the DisPerSE
filament
algorithm,
Massa
M = N0 µmol
mHfindA
7.2 (3.8)filaments
× 104E-mailM" in contact:
0.17 ± 0.08 pc. This supports the idea that thewe
11 high-S/N
the densekflaherty
gas of at wesleyan.edu
4 cm−3
by A&A main n0 = N0G0.253+0.016
H2 volume numberAccepted
densityb
/L
1.3
(0.7)
× 10
filament
width
is objects,
determined
bysurveys
the sonic
scale,
(see
Fig.
1).
Located
along
some
of
Infraredvariability
iscommonamong
youngstellarwithfindingdaily to weekly flu
Volume density
ρ0 = n0 µmol
mH filaments
6.2 (3.3)
10−20over-denseg cm−3Equation(5), bothcan
in theCMZhighly
and insampled
spiral-arm
these
are ×three
regionswith
http://arxiv.org/pdf/1609.04963
few tenths ofa magnitude.
Space-based
observations
produceinfrared light curves,
Column density dispersion
σN/N0 = [exp(σaη2 )column− 1]1/2 density exceeding
0.35 (0.02) 2.5 × 1023 cm−2(Ref.
7)
clouds (Federrath 2016). We caution that Equa.
As
to totalEq.
baselinesa monthdue toonly
the applies
orientationof filament
the spacecraft.
Volume density dispersion
σρ/ρ0 = σN/Nshown/R1/2 in previous studies,1.3 (0.5) limited(3);(Ref.of3) about tion(5) strictly
to thepopu- Here we presen0
one of these cores
has
Chameleon
I2.33
cluster
whose low
declination
makestoit theobservableby the Spitzer
Sound speed (isothermal)
cs = [kB T /(µpamH)]1/2 maser,0.60(0.15) may
kmof
s−1theµp =active(Ref. 6)
lations
perpendicularordered magnetic
field; space telescope o
water
which
indicate
local
A
photo-evaporative
gap
in
the
closestplanetforming
disc
1/2−1
Turbulent Alfvén speedvA = Bturb /(4πρ
1.5
(0.7)
km speriod.
observe
30 young stellarhowever,
objects witha daily
cadencesamplevariability on timesca
we findsimilarwidthstoforbetter
paralleland perstar0 ) formation.
We
findthat theWefilling
fraction
2 /v 2
1,2
3
1
2,4,5
Turbulent plasma beta
β
=
2
c
0.34
(0.35)
Barbara Ercolano , Giovanni
Rosotti
Giovanni
Picogna,totalLeonardo
pendicularFig.
2).
s ofP.
We
findvariability
is common,
occurringfilamentsin ∼80% (seeof thedetectedcluster members. The change
A thesecores, isonly 0.1%
ofthesucharea ofTesti
1/2 σ−1
3D turbulent+shear
velocity
dispersion
σ
=
3
15.2
(0.3)
km
s
v,tot,3Dv,tot,1D
color
overGermany
200 days formany of the sources falls between that expected for extinction and fluctuations in
G0.253+0.016,
inefficient
dense-coreand1−1München,Scheinerstr. indicating
1, 81679 München,
3D turbulent velocityUniversitäts-Sternwarte
dispersion
σv,3D= 31/2 σv,1D
9. Our results
imply powerthat spectral
the filamentinstar formation. 6.8 (0.2) km sWith
8
our high cadence
and long bei
baseline
we canderivedensitywidth
curvescovering two orders2
2
Departamentode Astronomı́a,
Universidad
deChile,
CasillaSantiago,
Chilein
Excellence Clusterαvir,tot
OriginandStructure2 of the Universe,
85748
GarchingMünchen,Germany
Virial parameter (turbulence+shear)= 5σ
4.3 (2.3)Boltzmannstr.2,
G0.253+0.016
is similar
to 36-D,the filament
widthv,tot,3D /(πGL ρ0 )9frequency
findUK
significant
power
atclouds,
lowUniversity,
frequencies,up
to MA
the boundaries
of our 200 day surv
322ρ )forandAstrophysicalResearch,
BostonBoston,02215, USAdifVirial parameter (turbulence
only)αvir =
5σv,3D/(πGL
0.85 (0.45)inInstitutenearbydespitetheorders-of-magnitude
Instituteof Astronomy,
UniversityofCambridge,
MadingleyRoad,
Cambridge,
02.
We
constructtheaverageradialprofileofthefila101/2
4EuropeanObservatory,ferenceKarl-Schwarzschild-Straße
2, D-85748 Garchingin some physical parametersof nearbybei München, Germ
Freefall time
tff = [3π/(32Gρ(0.14)filament
Myr
0 )]European Southern Observatory,
Garching
bei München,
Germanyments
and finda 0.27
typicalcolumnSouthern
density of
11compared
the CMZ. The reason behind
Turbulent crossing 5time
tturb = L/σ
0.67
MyrINAF-Arcetri,I-50125
Firenze, to
Italy
INAF/Osservatorio Astrofisicodi∼v,3D
Arcetri,
Largo
E. Fermi
5, I-50125
Firenze,Largo
Italy E. Fermi 5,clouds
1023 cm−2, whichis(0.03)an orderof magnitude
higher15is the sonic scale, Equa2
12 s−1
Turbulent energy dissipation rate
'turb = M σv,3D/(2tturb )1.5 (0.8) × 1036 erg
thesimilarity
inW
fil
Excellence
Universe, Boltzmannstraße 2, D-85748, Garching, Germany
than the average filament column
densityCluster
observed
contact: ercolano attion (5). Research,
It depends
only University,on L, M GPO= σv,3D
3D turbulent sonic E-mailMach number
Musm.lmu.de= σv,3D(3) 13 Internationalssin/cnearby
spiral-arm11
clouds.
We measure anaver-for Radio Astronomy
CentreCurtinBox/cU1987,
Perth WA 6
3D turbulent Alfvén Mach number
MA = σv,3D/vAwidth of W = 4.6(2.1)
and β = pimplications
thermal /pmagnetic. While the thermal and
age
0.17
±
0.08
pc
(see
Fig.
2).
The dispersal of the circumstellar
discs
of
dust
and
gas
surrounding
young
lowmassstars has importantfil
E-mail contact:Eq.
christoph.federrathat anu.edu.au
Sonic scale
λsonic = LM−2 (1 + β −1 )0.15 (0.11) pc(5); (Refs. 8)
magneticpressure are both an order of magnitude
fortheformationofplanetarysystems.
Photoevaporationfromenergetic
radiationfromthecentralobjectisthought−1−1
1/2
Turbulence driving parameterb = σρ/ρ0 M (1 + β )0.22 (0.12)
Eq. (7); (Refs. 9)higherin G0.253+0.016
compared
clouds in so3. We findthat by
thecreating
filament
width
doesdisconnects
notis signifiprimarily
bythe
the
interplay
betweengravity,toturbulence,and magnetic fields.
to drivethe dispersal in the majorityof discs,
aStar
gap formation
which
thecontrolled
outer frominner
regions
Derived star formation
parameters:
lar neighborhood,
the ratio (plasma β ∼ 0.3) iscantly depend on the orientationof thefilaments
andmagnetic
fieldsin draining
molecular
clouds near
the Galactic Center may differ substantially fr
outer
disc
from
the
while
the
inner
disc
keeps
viscously
onto
2.3inside-out,(1.2) turbulenceEq.
(10); (Ref.
10)
Log-critical densityof the disc and then disperses
scrit =theEq. (10)similarinbothenvironments.
The
same
applieswith respect to the orderedmagnetic
field
compo5−3clouds.
Here wedetermine
thediscphysicalofthe central molecular
Critical number density
ncritshow= n0 exp(s) disc around
1.0 (1.4)
× 10Hya,cm the closest(Ref. 10)
critforthe parameters
sonic
Mach
number—both
σv,3D and zone
cs are(CMZ) cloud G0.2
the star. In this Letter we
that
the
TW
protoplanetary
to Earth,may
be thenent
in
G0.253+0.016.
turbulence,magneticfield
andfilamentary
structure.
Usingcolumn-densityby
maps
based on dust-contin
Star formation ratefirst
per freefall'ff = Eq. (11) gap has been 0.042(0.030)Eq.at(11);(Ref.it10)
individuallyenhanced
in G0.253+0.016
factors
objecttime
where a photoevaporative
imagedaroundthe timewhich
is being
created.
Indeedthe−1(Ref. 10)
Star formation rate
SFR = 'ff M/tff
1.1 (0.8) × 10−2 M
Eq. (13);" yrobservations
with
ALMA+Herschel,we
identify
filaments
and
show
that
at
least
one dense core is
of
a
few,
but
their
ratio
(M
∼
10)
is
again
similardetected gap in the ALMA images
is consistent
with−2thedensity
expectations
X-ray photoevaporation
models, thus not
4. Basedon the 22column
PDF ofanalyzedinNotes. All physical parameters are derived for pixels that fall within the 5 × 10 cm(10 σ sensitivity)
column densitythe
contourshown into nearby(Schneider
al. 2013).
them.combinedWe
filament
width
Wfilclouds= 0.17± 0.08 pcetandthe sonic scale λsonic = 0.15 ±Rathborne
et al. (see(2014b)andwith
the Aetthe presence ofa planet.
The
photoevaporation
alsomeasureconsistent
a (1)
broad
16
FederrathFigure 1 and where requiring
the HNCO intensity-weighted
velocity
has validmeasurements
Figuremodel4). Thisisdefinesthefixed areawith= al.
17
pc2 range of properties
turbulence,andfindonset
W≈
λsonic . A strong
velocity
is seen in the HNCO intensity-weighted
fil ofcolumndensitypower
spectrum,
wegap
reconstructwithin which we deriveand TW
reportHya
all physicalparametersof G0.253+0.016.
Alltheuncertainties
were
propagated
onthe
each
independentof thesystem,e.g. accretionrate
andlocationof theatbasedthedispersal.
Wethe
show
that gradient
the volume
10. Usingreconstructed
density dispersion
parameter. The standard deviation of each parameter is provided
brackets;
wedispersion,note that someof0thenot have Gaussian
obtainedwith
ALMA+Mopra.
The
gradient
is likely
causedby large-scale
shearing of G0.253+0.016, pro
volumedensityσρ/ρ= parameters
1.3±
0.5, dousing
theincloud
andhavingpossiblygalaxy-center
clouds8.fromWe
measuretheeffective
cloud
central,870dominatingµm continuum
sourcebeproducedbyfreeemissionthegas
and/orresidualσρ/ρtogetherwith Mand diameterβ allows Lus =to deprobability distributions,e.g.,unresolved
β = 0.34(0.35),
whichmust not be readas βmighta finiteprobability
to befreenegative(by definition
it0
double-peaked
velocity
PDF.
After
subtracting
thegradienttoisolatethe turbulent
motions, we find a nethemethoddeveloped
in
Brunt
et
al.
(2010b).
ingeneral.
Ourmeasurements
andresultsaresumma4.7
±
0.1
pc
and
combineitwiththenum-turbumust not), instead thisa consequenceof the skewed distribution of β. Nevertheless, the standard deviation is always a useful measure
rive the driving mode parameterMachb of thedustis inside
the gap.
2004).
References:(1) assuming
a distanceof 8.3 (0.3)
kpc(Malkin for2013;
Zhu ber& Shenof the uncertainty in each parameter (D’Agostini
PDF
typicalturbulence.
We
measuretotaltheandsonic
turbulent
8.8 ± 0.2 km
rized
in Table
1. Herewe list the
mostvelocity
importantresultsandplasmaβ tothederiveλvelocityof dispersion,
sonicWelence,
following
Equations(7) scaleand (8).
find
2013; Reid et al. 2014),(2)
Longmoreetal.
(2012),
Rathborneetal.
(2014b),
(3)
Brunt
et
al.
(2010b),
(4)
Lis
et
al.
(2001),
Mills&
Morris−1
Accepted by MNRAS Letters
5. Analyzing the spatial distribution
ofrespectively.
the HNCO
and conclusions:turbulencein G0.253+0.016.
find λsonic =we find that G0.253+0.0
0.1 kmUsingthemagnetohydrodynamical−1 1/2 We simulations,(2013), Ao et al. (2013), Bally et al. (2014), Ginsburg et al. (2016), (5) Pillai et al. (2015); notethatsthe, magnetic
field measurement
of
b (1
=σ
M−1 (1 + βturbulence)= 0.22 ± 0.12,
indicat−2−1ρ/ρ0 ) = 0.15 ± 0.11 pc, in agreement
intensity-weighted
velocity,weseeastronglargeLM+β4−3<field B
= 130 ± because
50 µGing
is solenoidal
only ∼1/10of theinordered
field component. Combining these m
5.4 (0.5) mG in Pillai
et al. (2015) was adjusted to reflect the correct volume density n0 = 1.3magnetic(0.7) × 10 cm
of turb
G0.253+0.016,
http://arxiv.org/pdf/1609.03903
drivingG0.253+0.016.
scalevelocity
gradient
acrossthealgorithm,
wholewith ourmeasurementof thefilament
width,
Wfilfind= a driving parameter b
the volume density reported in Longmore et al. (2012)is incorrect.
We further
propagatedthereconstructuncertaintyofncloud,into the uncertainty
1. Using
the DisPerSE
filament
detection
wethedominant
turbulence
driving modein G0.253+0.016
and(2011).
(8) high-S/NFederrath&filaments
Klessen (2012),
Federrath(2016).
(9)et al.
of Btot . (6) Kauffmann et al. (2008). (7) Price et al.we
which
is likely associatedwithstrongshearing
mo-Federrath0.17± 0.08 pc. This supports the idea that the
find
11
in
the
dense
gas
of
Wedriving.
argue isWethat
the solenoidal
drivingin thiswhich typically hav
indicating
solenoidal(divergence-free)comparethistospiral-arm
clouds,(2008b), Federrath et al. (2010), Padoan & Nordlund (2011), tions
Molina(Kruijssen
et al. (2012),etFederrath&
Banerjee (2015),
Nolan
et al. (2015).11.
(10)
al.,
in
preparation).
We
subfilament
width
determined
by
the
sonic
scale,
G0.253+0.016(seebyFig.
1).
Locatedalong
ofof 1.8star
a Note that the mass of 1.3
Federrath & KlessenThe(2012).
× 105 M" derived
Longmore
et al.
(2012)
is asome
factorthan
ourGalactic-Centercloud
is causedbystrongshear,
link
between turbulence,magnetic
fields,filaments,
formation
inthecompressive(curl-free)drivingcomponent(bboth
> 0.4).
Motivatedby inprevious
reportsof strong shearing m
tract
the
large-scale
gradient
order
toand
obtainhigher
16
Federrathetal.
Equation(5),
inCentheCMZ
andspiral-arm
5 M /(1023 cm−2 µ in2
these
are three
over-dense
regionswithestimate, because Longmore
et al. (2012) computed
mass infilaments
anarea of 1.3×10
in agreementwith driving
thelarge-scale
velocity
mol mH ) = 58 pc , which is significantly
tral MolecularZonethecloudG0.253+0.016
23
−2
CMZ,
we
shear
causesthe solenoidal
in G0.253+0.016
and show that this red
theof"radius
turbulentFromtheclouds2016).
Westrong
cautionthat Equaet al.
(2012)
also (Federrathlarger than what we define here for the area of G0.253+0.016.
Note distribution
thatthe effectiveofreportedin .Longmore
a column
densityexceeding
2.52.8×pcvelocities.
10cmspeculate
As thatgradient(c.f.
Fig.
4)7 andwithfilamentdetailed
numerical
Gaussian
shapeof thevelocity
PDF
4),
we
rate
(SFR)
by4,5a,Lfactorof
6.9
comparedtotypicalclouds.popu1
3 effective
6strictly
tion
(5)
only
applies
to nearbythedominating
the cloudpossiblygalaxy-centerWemeasurethecloud
diameter=corresponds
to aandsignificantly
smallerarea(25 M.
pc2 )clouds
compared
to
the
area
used
for
their
mass
estimate.
Here
we(Fig.
deriveall physicalquantities
shown
in2 ,8.
previous
studies,
oneofJ.these
cores
has
C.
Federrath, J.
RathborneS.
N.
Longmore,formation
M.
D.
Kruijssen
J.
Bally
, Y.
Contreras
simulationsof CMZ , clouds. We speculate that
4 cm
−3 reportedof
findmaser,
avolumeturbulentdispersion= et 13in a fixed area A= 17(1) pc12 (seeabove).
averagedensityofand
8 × 10in σLongmoreal. (2012)is perpendicular to the ordered magnetic field;
lations
in general.consistently
Our measurements
andresultsaresumma4.7±which0.1
combine
it by
with
the
Mach
numv,1D
8 water
9 pcvelocity
10,11,12
ab Themay
indicate
local
activeR.
M.
Crocker
,
G.
Garay
,
J.
M.
Jackson
,
L.
Testi
and
A.
J.
Walsh
AcceptedApJ
thissolenoidal
modeofturbulence
driving4−3−1
incorrect
becausean errorthe scriptfrom which
that
value
derived.
corrected
derivedhere
is n0 =
1.3
(0.7)
× 10ofcm .
however,
we find similar widths for parallel and per-might
rized in Table
1. Hereweoflist
the inmost
importantresultsberβvaluetothe
derive
the
sonic
scale
λsonic
3.9was± 0.1
kmand
sThe,plasmawhichissignificantly
smallerthanstarformation.
We
find
that
filling
fractionbe thefilaments
typical driving
mode
1
pendicular(see Fig.
2). in the centers of galaxand conclusions:
thevelocity
λsonic =http://adsabs.harvard.edu/pdf/2016arXiv160905911F
Research School of Astronomy
andNational
University,
ACT
2611, Australia
the Astrophysics,
total
dispersion(8.8± 0.2area
kmWe
s−1). Canberra,of thesecores
isturbulence
only Australian
0.1%inofG0.253+0.016.
the
total
of findies,
becauseof the enhanced shear in such envi−2
−1
2
LM
(1 +
) = 0.15± 1710,0.11 pc,
G0.253+0.016,
indicating
dense-coreandin agreement
CSIRO Astronomy and Space
Science, P.O.
Box76,βinefficient
Epping
NSW,
Australiaronments.
Thesolenoidal(shearing)widthmode inof turOur results imply that the filament
with
our Moores
measurementof turbulence
theIC2,filament
width,Science
W9.
fil =
star
6. formation.
Using
magnetohydrodynamical
simula1. Using the DisPerSE3 filament
detection
algorithm,
Astrophysics
Research
Institute,
Liverpool
John
University,
LiverpoolPark,
146 Brownlow
Hill,
bulencemight
explainthe filament
low SFRs
observed
inG0.253+0.016
is similar
to thewidth
in
0.17 take± 0.08This
supports
thevelocity
idea that theSpitzer
Observations
of
Long
Term
Infrared
Variability
Among
Young Stella
tions thatthepc.measured
turbulent
we find 11 high-S/NLiverpool
filamentsL3
in 5RF,the dense
gasKingdom
of
the
CMZ
comparedtospiral-arm
clouds,where
Unitednearby clouds, despite the orders-of-magnitude dif- thefilament
widthis(ordered+turbulent)
determinedby filathe magsonicscale,
dispersion
and
the
total
G0.253+0.016 (see Fig.
1). Located along some
2. ofWe constructtheaverageradialprofileof thein
Chamaeleon
I Mönchhofstraße
4
drivingappearstohaveasignificantly
more
comAstronomisches Rechen-Institut, netic
ZentrumfürAstronomie
derUniversität
Heidelberg,
12-14,
69120
Heiference in some physical parameters of nearby
Equationthe(0.9)
CMZ
and
field
Bboth
2.2
mG
adaptedthese filaments are three over-dense regions withments and finda strength
typical(5),filament
columndensityofin spiral-arm
tot =in
1
2,8
3
component,b >Muzerolle
0.4 (seeFig.
6). Using
Kevin
M.
Flaherty
Lindsay
DeMarchiJames,behind
ZoltanBalog4 , William
cloudspressive
compared
to ,the
CMZ.
The
reasondelberg, Germany(FederrathWecautionthat
from
Pillaiet al.
(2015)
input,
wedeterminethe, Equaa column density exceeding
2.5 × 1023 cm−2 . As
∼ 1023cm−2,cloudswhich
is anorderasof2016).
magnitudehigherSFR
theoryturbulence,find that56
5
the similarity
inbasedWfil onis MHDthe 7sonicscale, we
EquaThomas
MegeathElise
Furlan, Robert
Gutermuthtion(5) strictly
only
applies tothepopuMax-Planckfür Astronomie,Königstuhl
17,field
69117
Heidelberg,
Germany
turbulentmagnetic
componentB=filament
130, ±
shown in previous studies,
one of Institut
these coreshasthan theaveragefilament
columndensityobserved
turb
b
=
0.22
yieldsafactor
of
6.9
lower
SFR
comparedtion (5). It depends only on L, M = σv,3D /cs
6lationstoUSA
theorderedmagnetic
field;
50 µGspiral-arm(Fig.
5).perpendicularGivendispersion
and Astronomy
a water maser, which
may University
indicate local
activeCASA,of Colorado,
389-UCB,
Boulder,
CO the80309,
in nearby
clouds.
We1velocity
measureanObservatory,
aver0.5,Wesleyanemphasizing
the role96ofFoss
the Hill
turbulence
Van
Vleck
University,
Drive, Middletown, CT
and βto=bDept.,p=
however,we ±findsimilarwidthsforand perthermal /pmagnetic. While the thermal andstrongof ordered
field
in0.08G0.253+0.016,
ourparallel
simulastar formation. We7 findthatthe filling Leiden
fractionage
width
WfilBox= 0.17pc
Fig.
2).
2 (seeLeidenObservatory,
University,
PO9513,
NL-2300
RA
the
Netherlands
driving
parameter.
Dept.
ofLeiden,
Physics
andAstronomy,
ColgateUniversity,
13an
Oak
Drive,
Hamilton, NY 13346, USA
magneticpressure
are bothorderof magnitude
pendicularfilaments
(see
Fig.
2).
tions showthat Bturb
can only
grow
to
!
B
/10.
of these cores is only 0.1% of the total area of
tot
3
Space
Telescope
Science
Institute,
3700
San
MartinDrive,
Baltimore,
Maryland,higher in G0.253+0.016 compared to clouds in so- 21218, USA
G0.253+0.016, indicating inefficient dense-core3.andWe find that the filament width
does not signifi4 that
9. BOur
results
imply
thefilaments
filamentT widthin
Max-Planck-Institutfür Astronomie,Königstuhl
69117
Heidelberg,
lar neighborhood,the17,ratio(plasmaβ ∼ Germany0.3) isstar formation.
7. Usingthegas
temperature=cantlydependon andthe adding
orientation
of
the
turb
5
G0.253+0.016
tothefilament
width
insimilarin both
The
same onapplies
RitterAstrophysicalResearchCenter,Dept.
of Physics
Astronomy,
University
14
We
thank
A. environments.
Ginsburg
foranddiscussions
the ther- of Toledo, Toled
100 ± 50
constrained
insimilartheliterature,
we derivewith respect
toKtheordered ismagnetic
field
componearby
clouds,despitethe orders-of-magnitudediffor thesonic Mach
number—bothand cs areUSA
mal
structure
and T.
Pillai and J.σv,3D
Kauffmannfor distheG0.253+0.016.
soundspeed,
the Alfvén
speed
and the ratio of
2. We construct the average radial profile of the filanent inferenceinsomephysicalparametersofnearbyindividuallyenhancedinG0.253+0.016
byfactors
6
cussions
on theordered Institutemagneticoffieldin G0.253+0.016.
1). Analysis
thermal to magnetic pressure,plasmaβ (Tab. andments and find a typical filament column density of
Infrared
Processing
Center,California
Technology,
770 S. Wilson Ave, Pasade
cloudscompared
to
the
CMZ.
The
reasonbehind
23
−2
of
a
few,
but
their
ratio
(M
∼
10)
is
again
similarWe further thank T. Csengeri, R. Klessen, V. Osthesemeasurements,
we derive
a 3Dinturbu∼ 10 cm , which is an order of magnitude higher
4. BasedUsingon thecolumndensity USA
PDF
analyzedsimilarity
in ofcombined
W
is 11
the
to nearbyandclouds2013).
fil =
senkopf
N. (Schneider
Schneider etforal.discussions
on noise,lent sonicnumber±3sonicandascale,tur- Equathan the average filament column density observed
7M
Rathborne
ettheal.Mach(2014b)
and
with
the
Department
Astronomy,
Universityof Massachusetts,
Amherst,MA 01003,
USA
tionpower(5).
It numberdepends
L,of±Msforegroundcorrections and uncertainties in columnbulent
AlfvénMachofonlyMA on= 4.6
2.1=forσv,3D /cin nearby spiral-arm clouds. We measure an avercolumn
densityspectrum,reconstructthe
8weDepartmentofPhysics,
Syracuse
University,
Syracuse,NY,
13244,
USA
10.
Using
the
reconstructedvolumedensitydispersion
16
Federrath
et
al.
and
β
=
p
/p
.
While
the
thermalandthermalmagnetic
density PDFs constructed from interferometric data.
G0.253+0.016.
age width of Wfil = 0.17 ± 0.08 pc (see Fig. 2). volume
density dispersion, σρ/ρ0 = 1.3 ± 0.5, usingσρ/ρ0 together with M and β allows us to demagnetic pressure arebothcontact:
an orderkflahertyof magnitude
at wesleyan.edu
the method developed
ineffective
Brunt E-mailetcloudal. (2010b).
rive the driving mode parameter b of the turbudominating
and thepossiblygalaxy-center
cloudstheG0.253+0.016
diameter
L = in sohigher incompared
to clouds
3. theWe cloudfind thatfilament
width does
not signifi- 8. We measure
Infraredvariability
iscommonyoung Equations
stellar objects,
with(8).
surveysdaily to weekly flu
lence,
following(7) andWe findingfindin general. Our
measurements
andresultsaresumma4.7
±
0.1
pc
and
combine
it
with
the
Mach
numlarneighborhood,
the
ratio
(plasmaβ∼
0.3)
is among
cantly depend on the orientation of the filaments
5.
Analyzingthespatialdistribution
of
the
HNCO
−1
1/2 produce highly sampled infrared light curves,
rized in Tablewith
1. Herewe tolistthetheorderedmost important
ber andsimilar
plasmainβ bothto derive
thetenths
sonic ofscale
λsonicenvironments.
Thesameofapplies
few
a magnitude.
Space-based
b = σρ/ρ0 Mobservations(1 + β −1 )can
= 0.22 ± 0.12, indicatrespectmagneticresults
field compointensity-weighted
velocity,weseeastronglargeand conclusions:the turbulencein G0.253+0.016.
Wetotalfindσbaselines
λ= cof
for the sonic
Mach limited
number—bothsonicand
v,3D
s are
to
about
a monthdriving
due to intheorientation of the spacecraft. Here we presen
ing solenoidal
G0.253+0.016.
nent in G0.253+0.016.
scale LMvelocity
gradient−2(1+
β −1 ) =across
0.15 of±the0.11
pc, incloud,agreement
individuallyenhancedinwholeG0.253+0.016
by factors
theChameleon
I clusterwhose low declination makes it observable by the Spitzer space telescope owhichwithis likely
associatedwithstrongshearingmoour
measurementofthefilament
width,
W
=
of
a
few,
but
their
ratio
(M
∼
10)
is
again
similar
fil
11.
We
argue
that
the
solenoidal
this variability on timesca
1. Using
the
DisPerSE
filament
detection
algorithm,
4. Based on the column density PDF analyzed inperiod. WeWeobserve
30 young stellar objects with a daily cadencedriving
to betterinsample
tions 0.17
(Kruijssen
etin preparation).
± to
0.08
pc.al.,This
supports
theetideathat thenearbyclouds(Schneider
al.sub2013).
Galactic-Centeris caused
strongcluster
shear,members. The change
we findRathborne
11 high-S/Nfilaments
the combined
dense gas withof
et al.
(2014b)inandthetract filament
the large-scale
gradientinto obtain
Weorderfindsuchvariability
is common,
occurring cloudin ∼80%of the bydetectedwidth
isdetermined
by
the
sonic
scale,
inagreementwiththestronglarge-scale
velocity
G0.253+0.016(see Fig.power1). Locatedalongsome ofcolumn density
spectrum,
we reconstruct
thethe distributionof theturbulentvelocities.
From
the fordispersion
color
200
days
many ofgradient
the sourcesthat expected
extinction and fluctuations in
10. UsingreconstructedvolumeEquation(5),
bothin theCMZoverandindensity
spiral-arm(c.f. falls
Fig.between
4) and withdetailed fornumerical
these filaments
are three
over-dense
regionswithvolume density
dispersion,σρ/ρ23= 1.3±
0.5, using
Gaussian
shapeof the velocity
PDF
(Fig.
weEqua0−2With
ourcadencebaseline wecanderivepower We
spectraldensitythat
curves covering two ordersσ(FederrathwithMcaution
andhighβ4),
allowsusand
to long
declouds2016).
Wethat
ρ/ρ0 together
simulationsof
CMZ
clouds.
speculatea column
densityexceeding
2.5
×
10
cm
.
As
turbulentvelocity
dispersionof filament
σv,1D
the method developed in Brunt et al. (2010b). find ation
thedriving
mode
b =of
the
turbu(5)rive
strictly
only applies
toparameterthepopuin frequency
andfindsignificant
at low
frequencies,
up to driving
the boundaries
this powersolenoidal
modeof turbulence
might of our 200 day surv
shown in previous studies, one of these cores has
−1
3.9
±
0.1
km
s
,
which
is
significantly
smallerthanfollowingto Equationsand (8).
We findlations lence,
perpendicular
the ordered(7)magnetic
field;
be the typical driving mode in the centers of galaxa watermaser, which
may indicate
localofactive−1
5. Analyzing
the spatial
distribution
the HNCO
the total
velocitykm). ±−1 (8.8−10.2
1/2
however,findsimilarparallelandper-indicaties, because of the enhanced shear in such envistar formation.
We find velocity,that the wefillingb =weσdispersion(1 widths+ β±)for=s0.220.12,
ρ/ρ0 M
intensity-weighted
see afraction
strong largependicularfilaments
(see
Fig.
2).
15
ronments. The solenoidal (shearing)mode of turof thesecores
is onlygradient
0.1% of acrossthe totalof cloud,ing solenoidal driving
in G0.253+0.016.
scalevelocity
the areawhole
6. Using magnetohydrodynamical
turbulencesimulabulence might explain the low SFRs observed in
G0.253+0.016,
indicating
inefficient
dense-core
andwhich is likely associated with strong shearing motions
that
take
the
measured
turbulentvelocity9.
Our
results
imply
that
the
filamentwidth
inthe CMZ compared to spiral-arm clouds, where thestar formation.
11. We argue that the solenoidal driving in thistions (Kruijssen et al., in preparation). We subdispersion
andthe total(ordered+turbulent)
G0.253+0.016
is similar
to thewidth
in shear,driving appears to have a significantly more comGalactic-Centercloud
is filamentcaused magby
strongtract the large-scale gradient in order to obtain
netic nearby
field strengthB
2.2orders-of-magnitude(0.9)strongmG adapted
clouds,despitethedif-velocity
tot =pressive component, b > 0.4 (see Fig. 6). Usinginagreementwiththelarge-scale
2. We constructtheaverageradialprofileofthefilathe distribution of turbulent velocities. From thefrom Pillai
etgradiental.
asinput,
wedetermine
ferencein (2015)
some(c.f.
physicalparameters
ofthenearby
SFR theory based on MHD turbulence, we find that
Fig.
4)
and
with
detailed
numerical
ments andfindatypicalfilament
columndensityofshape of the velocity PDF (Fig. 4), we
turbulentmagnetic
field
componentB=
130±
cloudscompared
to
the
CMZ.
The
reasonbehind23 Gaussian−2
turb
b = 0.22 yields a factor of 6.9 lower SFR compared
simulations of CMZ clouds. We speculate that∼ 10 find
cm a, which
is an orderof magnitude
turbulentvelocity
dispersionhigherof σv,1D 50= µGthe
(Fig.
5).
Given
and
similarity
in theWfilvelocity
is theofdispersion
sonic
scale,
Equa- mighttob = 0.5, emphasizing the role of the turbulencethissolenoidal
mode
turbulence
driving
than the average filamentcolumndensityobserved
strongtion
orderedin G0.253+0.016,
simula3.9 ±0.1 km s−1clouds.
, whichWe
is significantly(5).
It depends
only onL,ourMthe= centers
σv,3D /cofs galaxdriving parameter.
be fieldthetypicaldrivingmode
inin nearby
spiral-arm
measure an smaller
aver-−1 thantions show
that
B
can
only
grow
to
!
B
/10.
the
total
velocity
dispersion
(8.8
±
0.2
km
s
).
turb
tot
and
β
=
p
/p
.
While
the
thermalandies,thermal
becausemagneticof the enhanced shear in such enviage width of Wfil = 0.17 ± 0.08 pc (see Fig. 2).
magneticpressureTheare bothan orderof magnitude
ronments.
solenoidal(shearing)mode of tur7. Using higher
Bturb bulenceandaddingtheexplaingas
temperature
T = inUsing magnetohydrodynamical turbulence simulain G0.253+0.016
compared
to clouds
somight
the low
SFRs
observedin
3. We 6.
findthat the filament width does not signifi100 ±lar
50 K
constrainedintheliterature,
wederivetions that take the measured turbulent velocity
neighborhood,
the
ratio
(plasmaβ∼
0.3)
is Wethethank A. Ginsburg for discussions on the therthe CMZ compared to spiral-arm clouds, where
cantly depend on the orientation of the filaments
malcomstructure and T. Pillai and J. Kauffmann for disthe soundspeed,
theappears
Alfvénspeed
andaThetheratio
ofapplies
dispersion and the total (ordered+turbulent) magsimilarinbothenvironments.
samedrivingtohavesignificantly
morewith respect to the ordered magnetic field compo1).
thermalpressure,
plasmaβσ(Tab.
netic field strength Btot = 2.2 (0.9) mG adapted
for tothemagnetic
sonic Mach
number—bothcs 6).
arecussions
v,3D
pressive
component,b > 0.4(seeandFig.
Using on the ordered magnetic field in G0.253+0.016.
nent in G0.253+0.016.
We thatfurther thank T. Csengeri, R. Klessen, V. OsUsing individuallythese measurements,
wederive3D turbufrom Pillai et al. (2015) as input, we determine theenhanced
in on
G0.253+0.016
by factors
SFR theory
based
MHDa turbulence,
we findsenkopf and N. Schneider for discussions on noise,
numberofM= 11∼±
36.9
anda turturbulent magnetic field component Bturb = 130 lent
± sonic
of a Mach
few,
their
ratio
(M
isloweragainsimilarb =but0.22
yieldsa factorof10)
SFR
compared
4. Based on the column density PDF analyzed
in2

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