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,
Copiapo,Chile.magnitude
4.1
Generatingof zero-age
clusters
Nthe
O populations
computed
fromapparent
mV , thedistance,
sonof fNO,single
andthefO,lonelymeasured
for a recent
catalogue
Variationsof the3
wheretotalfürnumberof single
O stars
and NO with!>=15!Msun!
computedfrom theappaIO,single ispopulaCon!of!young!GalacCc!clusters:!!
Astronomisches Rechen-Institut,
Zentrum
Astronomie
derUniversität
Heidelberg,Mönchhofstraße
12-14,
69120
andtheNextinction
EB−V
areall listedOinstars
the MWSC
where
is thetotalwhich
numberNOO,single ofofstellarMilkyWaywith thosederivedfor “lonely”!–!the!single!O!star!(or!binary)!with!the!next!
Thepossibility
detectingmassiveofOsingle
stars in the andGalaxyis thetotalclusters
numberinofthe
O stars
in allclusters.
We alsomeasureandthe extinction EB−V
(Kharchenko
et al 2013).
Out inof alltheclusters.
total 341We
clusters,
175 ofHeidelberg, Germany
is
the
total
number
of
O
stars
also
measure12• Slopes!in!the!low!and!high!stellar!mass!regimes,!γ!and!Γ,!
populations
clusters
thatinaregeneratedvariisbyistherelatively shortof thesestars
anda
the fraction ofofstellar”lonely”
O stars
theclusters.with
A lonely
et al 2013).
τ(Kharchenkoof thO
in bounda clustercalledif it lifetimeisthe!onlylivingstar,numor
15 is the duration4
themcontainatleast”single”
oneOO stars
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
the
Galactic
starformation
rate
The
O stara clusterfor
is thea single
O star withtheadditionalthem containat leastphasesfor a star
withoneabinarysystemwithany Oof stars
its
components,
that(SFR).
has sample
a mass5respecCvely!
berof single
lonelyintheobservational
OHeidelberg,
star
in stellar
a andclusterisÜberle-Straßea thatsingleare
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
syntheticclusters
and
to
their
stellarcon• CharacterisCc!mass,!M
.!!
tions
are
generatedinthefollowing
way:
that
all
massivethan
10M(i.e.,
absence
of
high
mass
B
stars
with
is
N
=
89
and
N
!
our
purposesintheMW
populationofclusters
is
thus
given
by:
O,singleOchtotal
numberof M
O!stars
isabsence
NO = of688.
Thus,
fractionsmassivethan
10(i.e.,
highmassthe
B the
stars
with
tent
beforethey canbe comparedto theobservations.
The
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.
2 stellar
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
the next
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
withlibrary
ofdetecting
clustersof stellar
clusters
intheinMilky
Way withderivedfor
15measuredTheofM
massiveO stars
inBtheGalaxyGalactic
SFR
over
such
a relatively
periodofstars
time
can
The
observations
this
paper
come
from
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
approximatedWay
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
the
value
ofby:
the
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
the
IMF
parameO,!single
O,!lonely• distributions
a!library!of!simulated!clusters!built!with!various!
by
the
value
of
the
Galact
using
Eq.
1
and
Eq.
2 ar
−1
ters.
A
numberofimportantcorrections
have
to
be
appliedmodelsofstellarclusters
that
are comparedtotheobservaof the lists
IMF∼parameters
arewithrequiredin order∼to1 reproduceofsingleandlonely
in
SFR
of
0.68,
1,
and
1.45
M
that
are
the
lower,
cen3200 clusters
ages between
Myr and ∼the7! fractions!Oyrstars
ters. Aof important
corrections
haveto be thatappliedstellar clusters
fmodels(MWSC)= 4.2%
O,lonelyof
to thezero-ageclusters
theirstellartions
arenumbergeneratedin thefollowing
way:theassuming
all
tral,
and
upper
estimates
obtainedfromcountof young
distribuCon!funcCons!of!the!IMF!parameters.!!
Galacticclusters. They
also
donotsynthetic
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
,
(2)
O,lonelyobjects
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).
The
individual
cluster(Skrutskie
etaroundal. 2006)γ andthe propermotions
PPMXL
surGalacCc!stellar!clusters!that!are!likely,!based!on!their!
distribution functions
centered
=
0.91,
Γ
=
1.37,
and
M
=
0.41
M
,
and
with
dispersions
of
σ
=
0.25,
descriptionoftheobservational
sampleofclusters
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
Our analysis indicate that side to side velocities asymmetries could represent an important contribution to transverse
parameters that describe the IMF over the entire stellar mass range. This is achie
velocity shifts, being the most important contributor for large jet inclination angles (with respect the the plane of thesingle and lonely massive O stars in a recent catalog of the Milky Way clusters wsky), and can not be neglected when interpreting the observations.
built with various distribution functions of the IMF parameters. The synthetic clus
Accepted by ApJ
the binary population, stellar evolution, sample incompleteness, and ejected O stars
distributions of the IMF parameters are required in order to reproduce the fractio
http://arxiv.org/pdf/1609.04858
Galactic clusters. They also do not lend support to the existence of a cluster ma
We propose a probabilistic formulation of the IMF whereby the parameters of th
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" , astellar clustersσΓ = 0.60, and σMch = 0.27 M" around these values.

2/2Sami Dib1,2 , Stefan Schmeja3,4 and Sacha Hony5

Accepted by MNRAS
Variations of the IMF in the Milky Way

71

Niels Bohr Institute & Centre for Star and Planet Formation, University of Copenhagen,Øster Voldgade 5-7, DKhttp://arxiv.org/pdf/1605.08438
1350, Copenhagen, Denmark.
2
Unidad de Astronomı́a, Departamento de Fisica, Universidad de Atacama, Copayapu 485, Copiapo, Chile.
3
Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120
Heidelberg, Germany
4
Technische Informationsbibliothek, Welfengarten 1b, 30167 Hannover, Germany
5
Institut für Theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Albert-Überle-Straße 2,69120 Heidelberg, Germany.
E-mail contact: sami.dib at gmail.com
We investigate whether the stellar initial mass function (IMF) is universal, or whether it varies significantly among
young stellar clusters in the Milky Way. We propose a method to uncover the range of variation of the parametersthat describe the shape of the IMF for the population of young Galactic clusters. These parameters are the slopesin the low and high stellar mass regimes, γ and Γ, respectively, and the characteristic mass, Mch . The method
relies exclusively on the high mass content of the clusters, but is able to yield information on the distributions ofparameters that describe the IMF over the entire stellar mass range. This is achieved by comparing the fractions of
single and lonely massive O stars in a recent catalog of the Milky Way clusters with a library of simulated clusters
built with various distribution functions of the IMF parameters. The synthetic clusters are corrected for the effects ofthe binary population, stellar evolution, sample incompleteness, and ejected O stars. Our findings indicate that broad
distributions of the IMF parameters are required in order to reproduce the fractions of single and lonely O stars in
Galactic clusters. They also do not lend support to the existence of a cluster mass-maximum stellar mass relation.
We propose a probabilistic formulation of the IMF whereby the parameters of the IMF are described by Gaussian
distribution functions centered around γ = 0.91, Γ = 1.37, and Mch = 0.41 M" , and with dispersions of σγ = 0.25,σΓ = 0.60, and σMch = 0.27 M" around these values.
Accepted by MNRAS
http://arxiv.org/pdf/1605.08438

12

12

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.

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

1.
2.

3.

4.

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!
6
1
CASA, University of Colorado, 389-UCB, Boulder, CO 80309,
USA
Van
Vleck Observatory, Astronomy Dept., Wesleyan University, 96 Foss Hill Drive, Middletown, CT
7
2
Leiden Observatory,
Leiden University, PO Box 9513, NL-2300
RAofLeiden,
Netherlands• ﬁlament!width!W
Dept.
PhysicstheandAstronomy, Colgate University, 13 Oak Drive, Hamilton, NY 13346, USA
ﬁl!=!0.17!±!0.08!pc!
3
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland, 21218, USA• sonic!scale!of!turbulence!λsonic!=!0.15!±!0.11!pc!
4
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany(the!transiCon!scale!from!supersonic!to!subsonic!14 5 Ritter Astrophysical Research Center, Dept. of Physics and Astronomy, University of Toledo, ToledUSA
turbulence)!=>!!Wﬁl!≈!λsonic!!
6
Infrared Processing and Analysis Center, California Institute of Technology, 770 S. Wilson Ave, Pasade
HNCO!intensity,weighted!velocity!maps!obtained!
USA
7
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
with!ALMA+Mopra!
8
Department of Physics, Syracuse University, Syracuse, NY, 13244, USA•
Velocity!gradient:!large,scale!shear!
E-mail contact: kflaherty at wesleyan.edu•
Turbulence:!nearly!Gaussian!velocity!PDF!
Infrared variability is common among young stellar objects, with surveys finding daily to weekly flu•
Velocity!dispersion:!8.8!±!0.2!km/s!(total),!!
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!
period. We observe 30 young stellar objects with a daily cadence to better sample variability on timesca•
Bturb!=!130!±!50!μG!is!only!<1/10!of!the!
We find such variability is common, occurring in ∼80% of the detected cluster members. The change
color over 200 days for many of the sources falls between that expected for extinction and fluctuations inordered!ﬁeld!component!!
With our high cadence and long baseline we can derive power spectral density curves covering two orders•
Driving!parameter!b!=!0.22!±!0.12!indicates!
in frequency and find significant power at low frequencies, up to the boundaries of our 200 day surv
solenoidal!(divergence,free)!driving!!
•
cf.!b!>!0.4!in!spiral,arm!clouds:!signiﬁcant!
15
compressive!(curl,free)!driving!
component!
•
SpeculaCon:!!
shear =>!solenoidal!driving!=>!SFR!

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
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 Institute of Technology, 770 S. Wilson Ave, Pasade
Dust temperature
20 (1) K and results are summa(Refs. 2)
inTdustgeneral. Our measurementsthat the56 membersthat were
known
from
studiesof theimportantρ Ophiuchi
F clusterand that were also part ofUSA
Total (ordered+turbulent)magnetic
field
Btot
2.2list(0.9)the
mG
(Ref.
5)
rized
in Table
1. previous
Here wemostresults7
our persurveyarecluster,
and we added 26
members.
We
the(Ref.
evolutionary
status of the Amherst, MA 01003, USA
Mean molecular weight
unit mµmol
2.8 new
mH : massofdefined
an H atom
6)
andconclusions:
H members of the
Departmentof Astronomy,
Universityof Massachusetts,
8
unclassified members of the cluster. We showed that a largeDepartment
part (23) ofofthese
newSyracuse
membersUniversity,
are probably
brown NY, 13244, USA
Derived physical parameters:
Physics,
Syracuse,
1/2
Effective diameter dwarfs, which multiplies the
L =number
2 (A/π)
4.7
(0.1)
pc
of known
substellar
objectsdetectionin the cluster
by a factor of 3.3.
1. Using
the DisPerSE
filament
algorithm,
kflaherty
at wesleyan.edu
Massa
M = N0 µmol
mHfindA
7.2 (3.8)filaments
× 104E-mailM" in contact:we
11high-S/N
the
dense
gas
of
4 cm−3
by A&A main n0 = N0G0.253+0.016
H2 volume numberAccepted
densityb
/L
1.3
(0.7)
× 10
(see
Fig.
1).Infrared
Locatedvariability
along someis ofcommon among young stellar objects, with surveys finding daily to weekly flu
Volume density
ρ0 = n0 µmol mH
6.2 (3.3) × 10−20 g cm−3
http://arxiv.org/pdf/1609.04963
few tenths of a magnitude.
Space-based observations can produce highly sampled infrared light curves,2
1/2
Column density dispersion
σN/N0 = [exp(ση ) − 1]
0.35 (0.02)(Ref. 7)baselines
Volume density dispersion
σρ/ρ0 = σN/N0 /R1/2
1.3 (0.5) limited to totalEq.
(3); (Ref.of
3) about a month due to the orientation of the spacecraft. Here we presencluster
whose low declination makes it observable by the Spitzer space telescope oSound speed (isothermal)
cs = [kB T /(µp mH )]1/2
0.60 (0.15) kmofs−1the Chameleonµp =I2.33(Ref. 6)
A photo-evaporative
gap in the closest
planet−1
forming
disc
Turbulent Alfvén speedvA = Bturb /(4πρ0 )1/2
1.5 (0.7) km speriod.
We observe 30 young stellar objects with a daily cadence to better sample variability on timesca
2 /v 2
1,2
3
1
2,4,5
Turbulent plasma beta
β
=
2
c
0.34
(0.35)
Barbara Ercolano , Giovanni
P.
Rosotti , Giovanni We
Picogna, Leonardosfind suchvariabilityTesti
is common,
occurring in ∼80% of the detected cluster members. The changeA
3D turbulent+shear
velocity dispersion
σv,tot,3D = 31/2 σv,tot,1D
15.2 (0.3) kmcolor
s−1 over 200 days for many of the sources falls between that expected for extinction and fluctuations in
1
1/2−1
Universitäts-SternwarteMünchen,Scheinerstr.
1,
81679
München,Germany
3D turbulent velocity dispersion
σv,3D = 3 σv,1D
6.8 (0.2) km s
8With
our high cadence
and long bei
baseline
we canderivedensity curves
2
2
Departamentode Astronomı́a,
Universidad
deChile, power
Casillaspectral
36-D, Santiago,
Chile covering two orders
Excellence Clusterαvir,tot
OriginandStructure2 of the Universe,
85748
GarchingMünchen,Germany
Virial parameter (turbulence+shear)= 5σ
4.3 (2.3)Boltzmannstr.2,
v,tot,3D /(πGL ρ0 )9 frequency and find significant power at low frequencies, up to the boundaries of our 200 day surv
3
2
for AstrophysicalResearch, Boston University, Boston, MA 02215, USA
Virial parameter (turbulence
only)αvir =
5σv,3D/(πGL
0.85 (0.45)inInstitute
Instituteof Astronomy,
Universityof2 ρCambridge,
Madingley
Road, Cambridge,
UK
0)
10
1/2
4
European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching bei München, Germ
Freefall time
tff = [3π/(32GρGarching
0.27 (0.14) Myr
0 )]European Southern Observatory,
bei München,
Germany
11
Turbulent crossing 5time
tturb = L/σ(0.03) Myr
INAF-Arcetri,
INAF/Osservatorio Astrofisico
div,3D
Arcetri, Largo 0.67
E. Fermi
5, I-50125
Firenze,Largo
Italy E. Fermi 5, I-50125 Firenze, Italy15
212 s−1
Turbulent energy dissipation rate
'turb = M σv,3D/(2tturb )1.5 (0.8) × 1036 erg
Excellence Cluster Universe, Boltzmannstraße 2, D-85748, Garching, Germany
contact: ercolano at
3D turbulent sonic E-mailMach number
Musm.lmu.de= σv,3D /cs
11 (3) 13 International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth WA 6
3D turbulent Alfvén Mach number
MA = σv,3D /vA(2.1)
The dispersal of the circumstellar
discs of dust and gas4.6surrounding
young lowmass stars has important
implications
E-mail contact:
christoph.federrathat anu.edu.au
Sonic scale
λsonic = LM−2 (1 + β −1 )0.15 (0.11) pc
Eq.
(5); (Refs. 8)
the formation of planetaryevaporationfrom energetic radiation
from9)the central object is thought−1 (1 + β −1PhotoTurbulence drivingfor
parameterb = σρ/ρ0 Msystems.
)1/2
0.22 (0.12)
Eq. (7); (Refs.
is primarily
theinnerinterplay
between gravity, turbulence, and magnetic fields.
to drivethe dispersal in the majority of discs, by creating aStar
gap formation
which disconnects
thecontrolled
outer frombythe
regions
Derived star formation
parameters:
magnetic
in draining
molecular
clouds nearouter disc from the2.3inside-out,
whileandtheinner
discfields
keeps
viscously
ontothe Galactic Center may differ substantially fr(1.2) turbulenceEq.
(10); (Ref.
10)
Log-critical densityof the disc and then disperses
scrit =theEq. (10)5−3clouds.
Here wedetermine
thediscphysicalparametersof the central molecular zone (CMZ) cloud G0.2
Critical number density
ncritshow= n0 exp(s) disc around
1.0 (1.4)
× 10Hya,cm the closest(Ref. 10)the star. In this Letter wethatcrittheTW
protoplanetary
to Earth,
may be theturbulence,magneticfield
andfilamentary
structure.
Using column-density 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)
objecttime
where a photoevaporative
imagedaroundthe timewhich
is being
created.
Indeed the−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
detected gap in the ALMA images is consistent22with−2the expectations of X-ray photoevaporation models, thus not and show that at least one dense core isNotes. All physical parameters are derived for pixels that fall within the 5 × 10 cm(10 σ sensitivity)
column densitythe
contourshown inthem. Wefilament
width Wfil = 0.17 ± 0.08 pc and the sonic scale λsonic = 0.15 ±the presence ofvelocity
a planet.
The
photoevaporation
alsomeasureconsistent
a (1)
broad
Figure 1 and where requiring
the HNCO intensity-weighted
has validmeasurements(see Figuremodel4). Thisisdefinesthefixed areawith
A = 17
pc2 range of properties
findonset≈
λsonic. A strong
velocity
is seen in the HNCO intensity-weighted
fil ofwithin which we deriveand TW
reportHya
all physicalparametersof G0.253+0.016.
Alltheuncertainties
were
propagatedonW
each
independentof thesystem,e.g. accretion
rate andlocationturbulence,of thegap andatbasedthedispersal.
We showthat gradienttheparameter. The standard deviation of each parameter is provided in brackets; we note that someof the parameters
do not have Gaussian
obtained
ALMA+Mopra.
The
gradient is likely caused by large-scale shearing of G0.253+0.016, pro
central,870whichµm continuum
sourceproducedby withfreeemissionfromtheprobability distributions,e.g.,unresolved
β = 0.34(0.35),
must not be readas βmight
havingbea finiteprobability
to befreenegative(by definition
it gas and/or residual
double-peaked
subtracting the gradient to isolate the turbulent motions, we find a nemust not), instead thisa consequenceof the skewed distribution of β. Nevertheless, the standard
deviation isvelocity
always aPDF.
useful Aftermeasuredustis inside
the gap.
of 8.3 (0.3)
kpc typical(Malkin for2013;
Zhu & Shen We measure the total and turbulent velocity dispersion, 8.8 ± 0.2 kmof the uncertainty in each parameter (D’Agostini 2004). References: (1) assuming a distancevelocity
PDF
turbulence.
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
0.1 kmrespectively.
Using magnetohydrodynamical
turbulence simulations, we find that G0.253+0.0(2013), Ao et al. (2013), Bally et al. (2014), Ginsburg et al. (2016), (5) Pillai et al. (2015); notethatsthe, magnetic
field measurement
of
−3 B
field
= 130 ± because
50 µG is only <5.4 (0.5) mG in Pillai
et al. (2015) was adjusted to reflect the correct volume density n0 = 1.3magnetic(0.7) × 104 cm
of turb
G0.253+0.016,
http://arxiv.org/pdf/1609.03903∼1/10 of the ordered field component. Combining these mthe volume density reported in Longmore et al. (2012) is incorrect. We further propagatedwe
thereconstructuncertainty of
n
into
the
uncertainty
the dominant turbulence driving mode in G0.253+0.016 and find a driving parameter bof Btot . (6) Kauffmann et al. (2008). (7) Price et al. (2011). (8) Federrath & Klessen (2012), Federrath (2016). (9) Federrath et al.
indicating
solenoidal(2008b), Federrath et al. (2010), Padoan & Nordlund (2011), Molina et al. (2012), Federrath &Banerjee (2015),
Nolan (divergence-free)
et al. (2015). (10) driving. We compare this to spiral-arm clouds, which typically hav
a Note that the mass of 1.3 × 105 M
Federrath & KlessenThe(2012).
by Longmore
et al.
(2012) is a factorof 1.8star
higherthanour" derived
link
betweenturbulence,magnetic
fields,filaments,
andformationinCencompressive(curl-free)drivingcomponent(b the> 0.4).
Motivated by previous reports of strong shearing m
16
Federrathetal.
estimate, because Longmore
et al. (2012) computed
thecloudmass in anarea of 1.3×105 M" /(1023 cm−2 µmol mH ) = 58 pc2 , which is significantly
tral
Molecular
Zone
G0.253+0.016
CMZ,
we
speculate
that
shear
the solenoidal driving in G0.253+0.016 and show that this red(2012)causes
also
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.
rate
(SFR)
by4,5a,Lfactorof 6.9nearby clouds.
1
3 effective
6 compared to typicaldominating
the cloudpossiblygalaxy-centerWe
theestimate.
cloud
diameter=Ballycorresponds
to aandsignificantly
smallerarea(25 M.
pc2 )clouds
compared to the2 ,8.
area
used
for
their mass
Here
we Kruijssen
deriveall physicalquantities
C.
Federrath, J.
RathborneS.
N.measureLongmore,formation
J. M.
D.
J.
, Y. Contreras7 ,b The average volume density of 8 × 104 cm−3 reported in Longmore et al. (2012) isin a fixed area A= 17(1) pc12 (seeabove).
in general.consistently
Our measurements
andresultsaresumma4.7 ± 0.1
num8
9 pc and combine
10,11,12 it with the Mach 13
R.
M.
Crocker
,
G.
Garay
,
J.
M.
Jackson
,
L.
Testi
and
A.
J.
Walsh
Accepted
by
ApJ
4
−3
incorrect
becausean errorthe scriptfrom whichthat value was derived.
Theplasmacorrectedβvalue
derivedtheheresonic
is n0 =
1.3 (0.7)
× 10ofcm .
rized in Table
1. Hereweoflist
the inmost
importantresults
ber andto derivescale
λsonic1and conclusions:the turbulencein G0.253+0.016.
We find Canberra,
λsonic = ACT 2611, Australia
http://adsabs.harvard.edu/pdf/2016arXiv160905911F
Research School of Astronomy and Astrophysics,
Australian
National University,
−1
2
LM−2
(1 +
) = 0.15± 1710,0.11 pc,
in agreement
CSIRO Astronomy and Space Science, P.O.
Box76,βEpping
NSW,
Australia
with
our Moores
measurementof theIC2,
filament
width,Science
Wfil = Park, 146 Brownlow Hill,
1. Using the DisPerSE3 filament
detection
algorithm,
Astrophysics
Research
Institute, Liverpool
John
University,
Liverpool
0.17 ± 0.08 pc. This
supports
the idea that theSpitzer
Observationsof Long Term Infrared Variability Among Young Stella
we find 11 high-S/NLiverpool
filamentsL3
in 5RF,the dense
gasKingdomof
Unitedfilament
width
isdetermined
by
the
sonic
scale,
G0.253+0.016 (see Fig.
1).
Located
along
some
of
inUniversität
Chamaeleon
I Mönchhofstraße
4
Astronomisches Rechen-Institut, Zentrum
für AstronomiederHeidelberg,
12-14, 69120 HeiEquation(5), bothin the CMZ andin spiral-arm
these filaments are three over-dense regions with1
Kevin We
M. caution
Flaherty
Lindsay DeMarchi2,8 , James Muzerolle3 , Zoltan Balog4 , William
delberg, Germany
clouds (Federrath 2016).
that, Equaa column density exceeding
2.5 × 1023 cm−2 . As
5
6
5
ThomasMegeath, Elise
Furlan , Robert Gutermuth7
tion (5) strictly
only
applies tothefilament
popuMax-Planckfür Astronomie,Königstuhl
17, 69117
Heidelberg,
Germany
shown in previous studies,
one of Institut
these coreshas
6
lations
perpendiculartheorderedmagnetic
field;
1 toUSAa water maser, which
may University
indicate local
active 389-UCB,CASA,
of Colorado,
Boulder,
CO 80309,
Van Vleck Observatory, Astronomy Dept., Wesleyan University, 96 Foss Hill Drive, Middletown, CT
we findsimilarwidthsfor paralleland perstar formation. We7 findthatthe filling Leiden
fractionUniversity, however,2
LeidenObservatory,
PO Box 9513,
NL-2300
RAofLeiden,theNetherlands
Dept.
Physics
andAstronomy, Colgate University, 13 Oak Drive, Hamilton, NY 13346, USA
pendicular filaments(see Fig.
2).
of these cores is only 0.1% of the total area of3
Space
Telescope
Science
Institute, 3700 San Martin Drive, Baltimore, Maryland, 21218, USA
G0.253+0.016, indicating inefficient dense-core and4 that the filament width in9.
Our
results
imply
Max-Planck-InstitutfürAstronomie, Königstuhl 17, 69117 Heidelberg, Germany
star formation.
5
G0.253+0.016 is14similar
to Astrophysicalthe filament widthin Center, Dept. of Physics and Astronomy, University of Toledo, Toled
RitterResearch
nearby clouds, despite
the orders-of-magnitude difUSA
2. We construct the average radial profile of the filaferenceinsomephysicalparametersofnearby6ments and find a typical filament column density of
Infrared Processing and Analysis Center, California Institute of Technology, 770 S. Wilson Ave, Pasade
clouds compared to the CMZ. The reason behind∼ 1023 cm−2 , which is an order of magnitude higher
USA is the sonic scale, Equathe similarity in W
than the average filament column density observed
7 fil
Astronomy,
Universityof Massachusetts, Amherst, MA 01003, USAtion (5). It dependsDepartment
only on L,ofM= σv,3D /csin nearby spiral-arm clouds. We measure an aver8
Department
Physics,
University, Syracuse, NY, 13244, USAand β = pthermal /pmagnetic. Whileofthe
thermalSyracuse
andage width of Wfil = 0.17 ± 0.08 pc (see Fig. 2).
magnetic pressure arebothcontact:
an orderkflahertyof magnitude
E-mailat wesleyan.edu
higher in G0.253+0.016 compared to clouds in so3. We find that the filament width does not signifiInfraredvariability
iscommonlarneighborhood,
the
ratio
(plasmaβ∼
0.3)
is among young stellar objects, with surveys finding daily to weekly flu
cantly depend on the orientation of the filaments
similar in both environments.
same applies
few tenths of Thea magnitude.
Space-based observations can produce highly sampled infrared light curves,
with respect to the ordered magnetic field compofor the sonic Mach limited
number—both
v,3D and cofs areto totalσbaselines
about a month due to the orientation of the spacecraft. Here we presen
nent in G0.253+0.016.
individually enhancedin G0.253+0.016
by factorsof theChameleon I cluster
whose low declination makes it observable by the Spitzer space telescope o
of
a
few,
but
their
ratio
(M
∼
10)
is
again
similar
4. Based on the column density PDF analyzed inperiod. We observe 30 young stellar objects with a daily cadence to better sample variability on timesca
to nearby clouds (Schneider et al. 2013).
Rathborne et al. (2014b) and combined with theWe find such variability is common, occurring in ∼80% of the detected cluster members. The change
column density power spectrum, we reconstruct thecolor
200density
days fordispersion
many of the sources falls between that expected for extinction and fluctuations in
10. Using the reconstructed overvolumevolume density dispersion, σρ/ρ0 = 1.3 ± 0.5, usingWith
cadenceusandσρ/ρ0 together withM ourandhighβ allows
to longde- baseline we can derive power spectral density curves covering two orders
the method developed in Brunt et al. (2010b).
rive the driving modeparameterb ofturbu- power at low frequencies, up to the boundaries of our 200 day surv
in frequency
andfindthesignificant
lence, following Equations (7) and (8). We find
5. Analyzing the spatial distribution of the HNCO
b = σρ/ρ0 M−1 (1 + β −1 )1/2 = 0.22 ± 0.12, indicatintensity-weighted velocity, we see a strong large15
ing solenoidal driving in G0.253+0.016.
scale velocity gradient across the whole cloud,which is likely associated with strong shearing mo11. We argue that the solenoidal driving in thistions (Kruijssen et al., in preparation). We subGalactic-Center cloud is caused by strong shear,tract the large-scale gradient in order to obtainin agreement with the strong large-scale velocity
the distribution of turbulent velocities. From thegradient (c.f. Fig. 4) and with detailed numerical
Gaussian shape of the velocity PDF (Fig. 4), we
simulations of CMZ clouds. We speculate thatfind a turbulent velocity dispersion of σv,1D =this solenoidal mode of turbulence driving might
3.9 ± 0.1 km s−1 , which is significantly smaller thanbe the typical driving mode in the centers of galax−1
the total velocity dispersion (8.8 ± 0.2 km s ).
ies, because of the enhanced shear in such environments. The solenoidal (shearing) mode of tur6. Using magnetohydrodynamical turbulence simulabulence might explain the low SFRs observed intions that take the measured turbulent velocity
the CMZ compared to spiral-arm clouds, where thedispersion and the total (ordered+turbulent) magdriving appears to have a significantly more comnetic field strength Btot = 2.2 (0.9) mG adaptedpressive component, b > 0.4 (see Fig. 6). Usingfrom Pillai et al. (2015) as input, we determine the
SFR theory based on MHD turbulence, we find that
turbulent magnetic field component Bturb = 130 ±b = 0.22 yields a factor of 6.9 lower SFR compared2

4/4