The Star Formation Newsletter#325, 25-32
島 和宏

2019/09

ofUniversity
of! .Tokyo,2-21-1
Osawa,
181-0015,
Japan;
Kiso
Observatory,
SchoolofFormationsystemsaroundgiant
planets:ofplanetesimals
WeAstronomy,
provideda ofconsistent
spectraloftheMitaka,sampleintheCapture
opticalandandin outflow,
theablation
near-infrared.
We measuredtheanda total mass
ofmoon∼ 70 M
We classification
confirmthatRMon
drives Tokyoa bipolar
molecularwhich
is blue-shifted
north
4
A
GMC.
The
structurehierarchy
of
Orion
A
GMC
is
explored
with
the
DENDROGRAM
algorithm,
and
it
is
found
with
the UniversityNanŊay
radio
over
13
cycles.
All
these
maser
linesnorth
were
using
VLBI
arrays.
The
study
Science,oftheir
Tokyo,
Mitake-mura,
Kiso-gun,
NaganoJapan;
Kokugakuin
University,
asforatelescopepebbleaccretion
scenario
equivalent
widthsofalkalilines,
finding
that
they
have
a 397-0101,
moderate
correlation
with
age,
especiallyforHigashi,
objectsofRfoundation
Mon.
The
blue-shifted
outflowhas
excavatedthemolecular
cloud
ofimagedR Mon,
creatingthereflection
nebulathat theiscomposedofJapantwobranches.
All Atstructures
exceptone
inthe treehavevirialparameters
less than2,
confirms
alternating
flaresofthemethanolandwater
maserswithatheperiodof 34.4dand outflow
reveals
synchronised
Shibuya-ku,
150-8440,
1Tokyo1 We
withspectral
types
M8
and
later.
used spectral
indices
definedinliterature
toofestimate
surfacegravity,findingNGC
2261GMCandfilling
itJohansen
withhigh-velocity
gas.
“high’
velocities
theorientation
theistheapproximately
T.
RonnetandA.
indicating
self-gravity
isthe
importanton suggesting
theforspatialscalesfrom∼0.3
to∼4ispc.
power-laws
departures
behaviourofthe methanolandhydroxyl
masersthissource.
Theobserved
spatialdistribution
ofand
the
methanolthat
theirgravityassignmentis accurate
75% inofoursample.
We
investigatedthe correlation
betweenred
coloursn-s,
which
agreeswith
optical
jet,
that
the
accretion
disk
e-w.AlthoughThe
outflow
velocities
aremodest,E-mailcontact:
pandeyataries.res.in
1
Departmentof andAstronomy
andTheoretical
Physics,
Lund
Observatory,
Lund
University,
43,outflow
22100
Lund,
Swedenfrom
log-normal
distributions
are
found
at
the
high-density
endindividualof
N-PDFsofoutflow
activestar-forming
regions,
N-PDFsmaser
cloudlets
themeasuredtime
ofdoestheMnot
flaresoffeaturesimply
aBox
ring-likestructureofradiusandfinding
that
after
Myr,
thedelays
colourchangesignificantlyfor
oursamplewithspectral
types
M6.0–
±
9 age,
km/s.
The
outflowis∼10
rathermassive,∼0.56
theblue-shifted
lobe.
The
is thecompletely! inNew
observations
in
the
VI
bands
along
with
archival
data
from
the
2MASS
and
WISE
surveys
have
been
used
of
structures
in
the
Orion
A
GMC
are
predominantly
log-normalonscales
from
R∼0.4
to
4
pc.
240au
and
thickness
30au.
Internal
propermotions
indicatethatthevelocityofmethanolcloudlets
isdominatedbytoa<
E-mailcontact:
at
astro.lu.se
L3.0. In
this case,
red colours
might
be associatedring
structures, extinction, or viewing
optically
thickinthomas.ronnet
CO(3–2)
towards
R Mon,
indicatingwiththat circumstellar
it’s envelope isdisks,
2,000
E-mailcontact:
sonutabitha.15
atres.iist.ac.in∼◦ au.◦ The mass of the accretion disk
generateaby
catalogof young
stellarobjects(YSOs)
covering
anand
area
of is
about
6only
×
6one
in
the
Aurigaregioncentered
disc-windcomponent
ofinabout
5km/s.
The
methanolemission
detected
during
VLBI
observationislocatedangle.
Finally,
wecalculated
thebolometricluminosity,
andJK
bolometriccorrectionsforoursample.
We
found
Accepted
Research
Astronomy
andAstrophysics
andsurrounding
envelope
determinedfromanisothermal
graybody
fit
∼
0.34
M
.
We
estimate
a
mass
loss
rate
!
◦
◦ GHz
The
four
major
satellites
ofJupiter,
known
as
the
Galileanmoons,
andSaturn’s
mostmassivesatellite,
Titan,
are
Methanolmasers
at
6.7
are
the
brightest
of
class
II
methanolmasers
and
have
been
found
exclusively
towards
at
l
∼
173
and
b
∼
1.
5.
The
natureoftheidentified
YSOs
and
their
spatialdistribution
are
used
to
study
the
in
a∼region
about
550au
from
star, which
also
exhibitsOH
maser
flares.
Theofmethanol−5−1a central−6 erratic−1appearance
thatsix
objectsareoverluminouscomparedtoothermembersofthesame
association.
Thoseobjectsarealso
flagged
of
(1
3)
×
10
M
yr
,
correspondingtoanaccretion
rate
of
(1
9)
×
10
M
yr
.
We
find
that
R
Mon
!in a predominantly gaseous circum-planetary disk, during the last
! stages of formation of theirbelieved
to haveformedhttp://arxiv.org/pdf/1912.06984
massivestarforming
regions.
These
maserscanthusbealongusedasa thatuniquetoolionized
toduring
probe
the
early
phasesof massive
starformation
intheregion.
The
distribution
of
YSOs
with
of
the
and
molecular
gastherevealstwo
featurescanberelatedtoapowering
objectofrelatively
lowluminosity
which,
some
variability
cycles,canasbinarycandidates
by
the
Gaia
survey.
hasbolometricluminosity
of
<
1000
L
.
R
Mon
is
still
in
an
activeaccretionphase,
contributing
toobserved!
parentplanet.
Pebblesfromtheprotoplanetarydisk
areblockedfromflowing
intothecircumplanetary
disk
by
the
star formation.
We
present
here
a studyofthespectralenergyeach
distributionsof maser
320 name
6.7andGHzmethanolchosenring-likestructures
stretching
over
an
area
of aItfew
degreesin extent.
We
these
structures
as Auriga
excitemolecules
only
in thenearest
part
of
the
disc.
A
carefulanalysisof eventheinfrared
lightmasers
curvesrevealluminosity.
Hence
R
Mon
cannot
be
a
B0
star.
must
be
a
late
B
star
or
an
early
A
star.
◦
◦ drag assisted capture of planetesimals
positivepressure
gradient
at
the
outer
edge
of
the
planetary
gap,
so
the
gas
Acceptedby
MNRAS
the1correlation
MMB
inthelineHi-GAL
range(|l| ≤the60 Galactic,densities|b| ≤ 1mid-plane.
).supporting
The spectralenergy distributions
areBubblesand 2.catalogue,
Thebetween
centerwhich
ofthe
thefall
Bubblesappears
beinfrared
above
The
majorityofClass i YSOs
afromstrong
6.7
GHz
and totheflux
a radiative
pumpingof theSpectrallibraryofage-benchmark
low-mass
stars
and
brown
dwarfsshouldbethemaincontributor
tothedeliverysolidsonto
circum-planetarydisks.
a consistentframework
AcceptedbyThe
AstrophysicalJournalconstructedfrom
870–70µm using
data
from
the
ATLASGAL
andHi-GALsurveys.
Theemission
frommechanism
cold dustareassociatedwiththe Bubbles,
whereasthe ofrelatively
older
population,
i.e.,ClassHowever,iia common
objectsareratherrandomly
maser.
The
synchronised
behaviourofthehydroxyl
andmethanoltransitions
indicates
pumping
http://arxiv.org/pdf/1912.02806
1,2
3,4
3,4
5
6
7
for
the periodic
subsequentaccretionoftheremainsbuilt.
Here
we
use numericalintegrations
show
that mostE.modelled
Manjavacas, N.
Lodieu,moonsV.J.S.tree
Béjar
, be
M.R.
Zapatero-Osorio, S. Boudreault, M.
isby aflares
singlegrey
body
component
fit. toWe
estimatetheclump
properties
such
as mass,
FIRBonnefoy
luminosity
distributed.
Using
the
minimumspanning
analysis,wefound
26 probablesub-clusters
having5 toormore
members.
for
theof
G107.298+5.639.
planetesimals
being
captured
withindisk
arestrongly
ablateddue
to starthecriteria
frictional
1
andcolumndensity
thebest Mamalahoa
fit
the
SED
Considering
the2 Kauffman
for heating
massivethey
starThe
sub-clusters
are using
between∼0.5
pcaparameters–circum-planetary∼3 pc Highway,
in of
size
and
arefits.
somewhatelongated.
The
formation
efficiency
in
W.M.
Keck
Observatory,
65-1120
Kamuela,HI96743,
USA;
Departmentof Astronomy/Steward
Laboratory
Experimentsonthe
Motion
of
Dense
Dust
Clouds
Acceptedby
Astronomy
andAstrophysics
experience,thus
supplying
disk
with
small
dust
grains,whereas
only
aAZ,
small
fraction‘survives’
theircapture.
We
Long-term
multi-frequency
maser
observationsoftheintermediate-massyoungstellar3
formation,findthatregion
allthe
but
a few
maser
hosts
have
the
potentialtoharbourat USA;
least
one
mass
star.
The
most
of the we
sub-cluster
variesbetween5%– 20%
indicatingthatthesub-clusters
couldbehighboundregions.
The
Observatory,
The
UniversityofArizona,933
N.
CherryAvenue,Tucson,85721,
InstitutodeAstrofísica
11
thenconstructa simplemodelofa E38205,
circum-planetarydisk
supplied byablation,wherethefluxofof6.7
solidsthroughthedisk
NiclasSchneider
GerhardWurm
object
G107.298+5.639
https://arxiv.org/pdf/2001.01625
4
physicalproperties
ofand
the
methanolmaser
are also
discussed.
The
evolutionary
stagesGHz
maser
sources,radiiof these
sub-clusters
alsos/n,supportit. hosts
de Canarias,
C/
Vía
Láctea,La Laguna(Tenerife),
Spain;
Dpt.
de Astrofísica,
Univ.
de
La Laguna,is
at equilibriumwiththe luminosity
ablation
supplyrate, suggests
andinvestigate
formationindisks.
showthatstars
the
5 moonsassociated1
1Francisco
138206,
1 (Tenerife),
2 of
1(CSIC-INTA),
exploredusing
thediagram,
that
they
are
predominantly
withWe
high
mass
Avda.
Astrofísico
Sánchezs/n,
LaLotharstr.
LagunaSpain;
CentrodesuchAstrobiología
Faculty
ofOlechPhysics
Universityof Duisburg-Essen
1,the
47057
Duisburg,Germany
Mateusz, massMarianSzymczak, PawelWolak, EricGérardandAnna
Bartkiewicz
Acceptedby
MNRAS
growthofmajority
satellites
is E-28850
drivenmainlyby accretionofthe pebbles
thatthe ablatedmaterial.
The possibly
pebble6 coagulate
with
the
being
in
the
accretionphase.
However,
weaobserve
amolecularsmallfromnumberoffür
sources
that
could
Crta.
Ajalvir
km
4,
TorrejóndeArdoz,
Madrid,Spain;
Max-Planck-Institut
Sonnensystemforschung,
1
and
a
total
mass
of
∼
70
M
.
We
confirmthatRMon
drivesbipolaroutflow,which
isblue-shiftednorth!
E-mailcontact:
niclas.schneider
atofuni-due.de
Large
scale
star
formationin stars.
AurigaregionInstituteof Astronomy,
Faculty
Physics,
Astronomy
Informatics,
Nicolaus
Copernicus
University,
Grudziadzka
http://arxiv.org/pdf/1912.11789
accretingprotosatellites
rapidly
migrateinward
and
pile
up
in
resonant
chains
at
the
inner
edge
of
the
circum-planetary
7andberelatedtointermediateor
low-mass
Justus-von-Liebig-Weg
3, 37077,
Göttingen,Germany;
Université
Grenoble
CNRS,
IPAG,
38000 Grenoble,
of
R Mon. The1blue-shifted
outflowhas
excavatedthe molecular
cloud
north
ofAlpes,
R Mon,
creating
the reflection
nebula
1
2,3
3
4
disk.
We
proposethat
dynamical
instabilities
in
these
resonant
chainsareattheoriginofthedifferentarchitecturesofIn
laboratory
experiments,
we
study
the
motionoflevitated,
sedimenting
cloudsof
sub-mmgrainsatlowambient
A.K.
Pandey,Saurabh
Sharma,N.
Kobayashi,
Y.
Sarugaku
and
K.
Ogura
FranceNGC
2261byandfilling it with high-velocity gas. At “high’ velocities the orientation of the outflow is approximately
Accepted
MNRAS
Jupiter’sand
andat
Saturn’s
moon systems.
The
assemblyof moonsystems
throughpebbleofaccretion
can
be
seen
pressurehigh solid-to-gas
ratios!. Theexperimentsshow
a collective
behavior
particles,
i.e.therefore
grains2inInstituteclouds1
Aryabhatta
Research
InstituteofObservational
Sciences(ARIES),
ManoraPeak,
Nainital,
263velocities
002,
India;
n-s,
which
agreeswiththeopticaljet,suggestingthat
theaccretion
disk
is
e-w.
The
outflowaremodest,Probingtheearlyphases
of
high
mass
star
formation
with
6.7
GHz
methanolmasersE-mailcontact:
emanjavacas
atkeck.hawaii.edu
http://arxiv.org/pdf/1912.06973
asa down-scaled
manifestationof thesame process
thatclouds,
forms systemsof super-Earths
terrestrial-mass21
settlefaster than anisolated grain.
In2-21-1
collective
particle
the sedimentation
velocity
linearlydepends School
onplanets
! and
3 and
of
Tokyo,
Osawa,
Mitaka,Tokyo
181-0015,
Japan;
Kiso
of± 9Astronomy,
km/s. TheUniversity
outflow 1isofrather
massive,∼
0.56 Mblue-shifted
outflowlobe.
TheObservatory,
outflow is completely! in the1aroundsolar-type
stars
and
M-dwarfs.
Sonu
TabithaPaulson,JagadheepD.
PandianInthepastyears,
some
extremely
redbrown
dwarfswere
found.
They
werebelieved
to
have
low
surfacegravity,linearlydepends on of
theTokyo,particlecloseness C. Kiso-gun,
However, Nagano
collective397-0101,
behavior Japan;
only sets
in at a criticalvalue !critHigashi,
which
Science,
Mitake-mura,
Kokugakuin
University,
optically University
thick in CO(3–2)
towards
R Mon, indicating thatit’s envelope is <2,000 4au.
The mass of
the accretion
disk∼
1linearly
but
many
of
their
spectralcharacteristics
weresimilar
to
those
of
high
surfacegravitybrown
dwarfs,showing
that
increases
withtheexperiment
Stokesnumber
St.
For
St
<
0.003
particles
alwaysbehavecollectively.
For
Acceptedby Tokyo
A&A
Departmentof envelope
Earth
and
Space
IndianInstituteof Space&M
Technology,
Thiruvananthapuram
Shibuya-ku,
150-8440,
JapanSciences,andsurrounding
determinedfrom anisothermal
graybody
fit Scienceis ∼ 0.34. We estimate
a mass loss rate
Formationofmoon
systemsaroundgiant
planets:
Captureandablationofplanetesimals!
youthStokes(orlownumbers,
surface
spectral characteristics
are poorly
understood.
aim
surfacegravityindicatorslarge
large −1solid-to-gas
ratios are needed
to trigger
collectiveWe
behavior,
e.g. −1!crit = 0.04
at St
= 0.01.
−5 gravity)−6 to test
695547,
Kerala,
India
of
∼
(1
3)
×
10
M
yr
,
correspondingtoanaccretion
rate
of
(1
9)
×
10
M
yr
.
We
find
that
R Mon
as
foundationforapebbleaccretion
scenario!
!
http://arxiv.org/pdf/1912.04765
E-mailcontact:
pandeybrownat disks,
aries.res.inin late-M
early-L
dwarf
spectrausing environments
data obtainedwill
withthe faster.
X-shooter
spectrographat the gas
Very
Large
Appliedtoand
protoplanetary
particles
in dense
settleIn balancewith upward
motionshasbolometricluminosity
of
<
1000
L
1
1
! . R Mon is still in an active accretion phase, contributing to the observedT.
RonnetA.convection)
JohansenTelescope.
WeandselectedaVIbenchmarksample ofdwarfsmembers
of Chamaeleon
I (∼2
Myr),
Upper
Scorpius(turbulent
diffusion,
thealong
thicknessof brown
the midplaneparticlelayerwill be WISE
smallerthancalculatedNew
observations
the
bands
from
surveyshavebeenbasedusedontoluminosity.
Hence inR Mon
cannotbe a B0 withstar. archival
It must data
be a lateBthe
star2MASSor evenand
an
early
A
star.
◦
◦
1
(5–10
Myr),
Pleiades(132±27Myr),and(590–790
Myr)withsimilarmetallicities.
individual
especially
for
dust.
For
pebbles,largesolid-to-gas
ratiosare University,neededinstabilities
basedongeneratea grains,
catalog
ofoutflow
young andstellarobjects(YSOs)
covering
an area
ofwell-constrainedabout
6 × 6 toages,
intrigger
theandAurigacentered
Departmentof Astronomy
Theoretical
Physics,
Lund
Observatory,
Lund
Box
43,
22100region
Lund,
SwedenThemolecular
from
RPraesepeMon
Accepted
Journal◦ The
22 in the optical
Wel provided
a consistentclassification
the sample
and in the near-infrared. We measured the
back-reaction.
at∼ 173byandbAstrophysical∼ 1.◦ 5.spectral
The
natureof the of1
2
3identified YSOs and3 their spatial distribution are used to study theE-mailcontact:
thomas.ronnet
atastro.lu.se
GoranSandell
, of
W.
Vacca
, L. BouscasseandR.haveGüstenequivalent
widthstheiralkali
finding thatthey
moderate
especiallyfor objects
starformationin theregion.
Thelines,
distribution
of YSOs
along awith
that ofcorrelation
the ionizedwith
and age,molecular
gas reveals
two
Accepted
by
ApJL
1
2
The
four
major
satellites
oflater.
Jupiter,known
as atheGalileanandSaturn’s
mostmassivesatellite,
Titan,
arewithspectral
M8
and
Wean
used
indices
inintheliterature
estimatesurfacegravity,finding
University
oftypes
Hawaii,
Institutefor
Astronomy- Hilo,640defined
N.moons,
AohokuPlace,
Hilo,
HI
96720,USA;
SOFIA
ring-likestructures
stretchingoverareaspectralof
few
degrees
eachextent.
Weto
name
these
structuresas Science
AurigaLaboratory
Experimentsonthe
Motion
of
Dense
Dust
Cloudshttp://arxiv.org/pdf/1912.01714
believed
haveformedin a predominantly
gaseouscircum-planetarydisk, during
thelaststagesofformationof
theirthat theirgravityassignment
accurate
forappears
75%
our
WeGalactic
investigatedthebetweenred colours
Center,NASA
Ames
ResearchCenter,USRA,
MSof232-12,
Building
N232,
PO
Box
1,correlation
Moffett
Field,
CA
94035-0001,
Bubbles
1toand2.
ThecenterofistheBubblestobesample.
above
the
mid-plane.
Themajorityof Classi YSOs1
13
NiclasSchneiderandGerhardWurm
parentPebblesfromtheprotoplanetarydisk
areblockedfromflowing
intothecircumplanetarydisk
by theand associatedage,planet.
finding
thatthe
after
∼10
Myr,
the colourdoes
notchangesignificantlyfor
oursamplewith spectral
types
M6.0–
USA;
Max
PlanckInstitutfürRadioastronomie,
Auf
dem
Hügel
69, 53121
Bonn,
Germany
arewith
Bubbles,
whereasthe relatively
older
population,
i.e.,
Class
ii objects
are rather
randomly
1
positivepressure
gradienttheouter
theLotharstr.
planetary
thegassub-clusters
dragassisted
captureplanetesimals
L3.0.
In
this
case,
red
coloursmight
beedgeassociatedwithdisks,
ring
structures,
extinction,
ormembers.
viewing
distributed.
Using
the
minimumspanning
treeofanalysis,
wecircumstellar
found
26so
probablehaving5 orofmore
Facultyof Physics
University
Duisburg-Essen
1,gap,
47057
Duisburg,Germany
E-mailcontact:
gsandellatathawaii.edu
Theevolution
of
dust
inof
discs
influencedbyexternal
photoevaporation
shouldbe the main
contributor
tobolometrictheontodisks.
However,consistentangle.
Finally,
weare
calculated
andareJcircum-planetaryandK bolometriccorrections
for aoursample. framework
We foundThe
sub-clusters
betweenthe∼0.5
pc delivery– ∼31luminosity,
pcofinsolids
size andsomewhat
13 elongated. The star formation efficiency in
11
E-mailcontact:
niclas.schneideratuni-due.deWe
have
mappedHerbigBe starRotherMon
in
andwe
CO(3–2)
with integrations
APEX objects
in Chileandanalyzed
Andrew
D. Sellek, young
RichardA.
Booth
CathieJ. Clarkeforaccretionthemoons
remainsbeCO(3–2)
built.
use
numerical
to are
show
that
most
thatthesix
objects
aretheoverluminouscompared
toand
membersofHerethesameassociation.
Those
also
flaggedmostofsubsequentthesub-cluster
regionofvaries
between
5% – to20%
indicatingthatthesub-clusters
could be boundregions.
The
unpublished
Herschel
images.
We
find
that
R
Mon
is
embedded
in
a
small
cloud
with
a
gas
temperature
of
∼
20
K
1
In
laboratory
experiments,
westudy
motion ofMadingleylevitated,
sedimenting
cloudsofgrains at heating
low ambientplanetesimals
being
captured
withinathe
circum-planetary
disk arestrongly
ablatedduesub-mm
to thethey
asInstitutebinarycandidates
by theGaia
survey.
of Astronomy,
UniversityofCambridge,
Road,
Cambridge
CB30HA,
UKfrictionalradiiof these
sub-clusters
also
supportit.
pressure
and
at
high
solid-to-gas
ratios!. smallThe experiments
a collective
behaviorof particles,
i.e.their
grainsin clouds
experience,
supplying
the diskwithdust grains, show
whereasonly a small
fraction‘survives’
capture.
We
Accepted
bythus
MNRAS
E-mailcontact:
ads79 at cam.ac.uk
Acceptedby
MNRAS

The Star Formation Newsletter #325 (25-32)

25
26
27
28
29
30
31
32

as binary candidates by the Gaia survey.
Accepted by MNRAS

26
http://arxiv.org/pdf/1912.02806
Long-term multi-frequency maser observations of the intermediate-mass young stellar
object G107.298+5.639
Mateusz Olech1 , Marian Szymczak1 , Pawel Wolak1 , Eric Gérard2 and Anna Bartkiewicz1
1

Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka
5, 87-100 Torun, Poland; 2 GEPI, UMR 8111, CNRS and Observatoire de Paris, 5 Place J.Janssen, 92195 Meudon
Cedex, France
21
E-mail contact: olech at astro.umk.pl
Periodic flares of maser emission are thought to be induced either by variations of the seed photon flux in young
binary systems or the pump rate regulated by stellar and accretion luminosities. We seek to study the variability offour maser transitions of three different species in G107.298+5.639 to constrain the dominant mechanism of periodic
flares. Light curves of the 6.7 GHz methanol and 22.2 GHz water vapour maser were obtained with the Torun 32m
radio telescope over 39 and 34 cycles, respectively. The target was also monitored at the 1.6 GHz hydroxyl transitions
with the NanŊay radio telescope over 13 cycles. All these maser lines were imaged using VLBI arrays. The study
confirms alternating flares of the methanol and water masers with a period of 34.4d and reveals the synchronised
behaviour of the methanol and hydroxyl masers in this source. The observed spatial distribution of the methanol
maser cloudlets and the measured time delays of the flares of individual features imply a ring-like structure of radius
240au and thickness 30au. Internal proper motions indicate that the velocity of methanol cloudlets is dominated by adisc-wind component of about 5km/s. The methanol emission detected during only one VLBI observation is locatedin a region about 550au from a central star, which also exhibits OH maser flares. The erratic appearance of methanolfeatures can be related to a powering object of relatively low luminosity which, during some variability cycles, canexcite molecules only in the nearest part of the disc. A careful analysis of the maser and infrared light curves reveala strong correlation between the 6.7 GHz line and the infrared flux densities supporting a radiative pumping of themaser. The synchronised behaviour of the hydroxyl and methanol transitions indicates a common pumping mechanism
for the periodic flares of G107.298+5.639.
Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2001.01625

Large scale star formation in Auriga region
1

1

2,3

3

4

EVN(Jb,Ef,Mc,O8,Tr,Nt,Wb,Ys,Sr)
EVN(Jb,Ef,Mc,O8,Tr,Nt,Wb,Ys,Sr,T6,Ir)
EVN(Jb,Ef,Mc,O8,Tr,Nt,Wb,Ys,T6)
VLBA(BR,FD,HN,KP,LA,MK,NL,OV,PT,SC)

57444
57544
57681
57906

6668.519
6668.519
6668.519
22235.080

0.09
0.09
0.09
0.11

57600

57800

5.2⇥3.2; 61.38
4.2⇥2.8; 76.25
4.2⇥3.1; 79.75
0.6⇥0.5; -1.10

3.0
2.5
5.0
5.0

189
172
171
104

6.7GHz メタノールメーザー
Notes. No data were used from italicised stations
・ごく初期の大質量星形成領域にのみ付随 -> 大質量星形成のヒント？
・まれに周期的強度変動するメーザーがある
2000

H2O 22.2GHz

0
CH3OH 6.7GHz−1

Integrated flux density (Jy km s )

100

0
2

OH 1667MHz (RHC)02

OH 1665MHz (LHC)

0
57000

57200

57400

58000

58200

58400

MJD

Fig. 1. Time series of integrated flux densities in the I Stokes for water vapour and methanol maser transitions and in the RHC and LHC polarisation
for hydroxyl maser transitions of G107. The vertical dotted lines indicate the methanol peaks. The arrows below the time axes denote the dates of
VLBI observations (Table 1).

OH 1.667 GHz

10.03
0.44
> 5.9410.83 (1.06) 0.54 (0.15)
2.91 (0.44)
14.00
0.65
> 1.41
9.87 (1.94) 0.77 (0.38)
2.63 (0.53)
9.62
0.32
> 1.2511.10 (3.83) 1.10 (0.50)
1.02 (0.90)
18.83
42.00
22.49 (18.01) 15.61 (2.32) 1.29 (0.48)
0.19 (0.41)
16.40
218.60 146.51 (64.10) 17.62 (1.49) 1.19 (0.44)
07.85 M.36.59
15.79 (1.86)in G107.298+5.639
1.15 (0.49)
0.50 (0.64)
Olech et18.70
al.: (26.68)
Maser observations−1

Hydroxyl integrated flux density (Jy km s )約34日周期
H2 O 22 GHz
OHメーザーはちょっと遅れてる

3.0
2.5
2.0

1665MHz
1667MHzr = 0.677 (p<0.0001)
r = 0.405 (p<0.0004)

1.5
1.0
0.5
0.0
0.1

1

10

−1

Methanol integrated flux density (Jy km s )100

Fig. 3. Lomb-Scarglelines) calculated
the inFig. 6. periodograms
Correlation(black
betweenthe OHfor1.665/1.667
GHz and CH3 OH
tegrated flux time series in each of the observed transitions. The red
6.7 GHz maser integrated flux densities. The open symbols denote thedashed line represents a 0.01% false alarm probability level.

Fig. 2. Phased and normalised light curves of the integrated flux in each
upper limits for at least one transition. The solid lines show the best fitsobserved transition (grey points). Red points show binned light curves,
Fig. 5.
Propermotionsofthemethanolmaser
cloudlets
in
G107
as
meato the data.
with 0.05P and 0.1P bins for the 6.7, 22 GHz and both OH lines, respecsuredtively.
relativetotheircentreofmotiondenoted
by
small
black
cross.
The red line represents the best fit of asymmetric periodic powerfunction.
All thecurvesmotions
are foldedin
modulod, thelisted
variability
Cones represent
thelight
propereach 34.43
cloudletin Table A.2
The water maser emission was detected in two clusters
periodofthemethanolemission,andthedashedvertical
lines
show
the
and their colours and apertures correspond to the radial velocity (colour
placed within ⇠200 mas of each other just between the two
main
peaks of the 6.7 GHz flare.
OH cloudlets at about 12.2 km s 1 located ⇠250 mas north of

メタノールメーザーとOHメーザーの強度に相関bar) and uncertainty, respectively. The velocity scale is showngroups
at theof methanol masers (Fig. 4). These water maser clusters
the velocity
region of(Fig. 4) coincide withindi↵er in radial
in apersistentsimilar waymethanol
to those ofmasers
methanol
top right corner. The dashed ellipse displays the model of ring derived->
同じ励起機構によるもの？
masers.
interesting
theau)
relative
andat
radialve- the methanol maser
mas that(100
withpositions
an area
whichfrom the 3D structure analysis shown in Fig. 7, where the yellow
star It is<120
locities of thesewater maser
clusters between
are similar -15.6
to thoseand
seen-13.7 km s 1 appearedof velocity
shows the positionof fitted centre of the ring.
The grey star denotes
the emission
1
1
15.0 km s ) and SE ( 9.3 to 7.1 km s ) groups of methanol ten years ago (Hirota et al. 2008). However, the morphology ofpositionof themm well
continuum(Palauofetblueal. 2011).
the notsecondepoch(MJD 57444)
masersthat1.3
agreeswith thepeak
velocities
and red- the westernduring
cluster does
resemblethat observedby Hirotaof VLBI observations
shifted lobes of outflows observed in the CO lines (Palau et al.
2011).

A.4). Since
flux densities
of both masers are strongly
et al. (2008),(Fig.
who interpreted
it as thean expanding
shell. Moreover,at the epocha↵ectedof our observation(MJDfiltering
57901) no bywaterthemaser
was as Fig. A.4 depictsby spatial
VLBI,

M. Olech et al.: Maser observations in G107.298+5.639−1

Hydroxyl integrated flux density (Jy km s )A&A proofs: manuscript no. pap_g107_corr3 face-on 想像図
3.0

masers (Cragg et al. 2002) and the coincidence of these transi-2.5
disk common
wind?
tions in G107 supports
excitation processes which produce the population inversions simultaneously in both molecules2.0
and result in synchronised variability of maser flux densities.
4.2. Anti-correlated variability of CH3 OH and H2 O masers

1665MHz
1667MHzr = 0.677 (p<0.0001)
r = 0.405 (p<0.0004)

1.5
1.0

The present study reinforces our previous finding of alternating
variations of the methanol and water masers in the source (Szym-0.5
czak et al. 2016). The methanol maser flare exactly coincides
with the water maser minimum for all 33 cycles monitored over0.0
ring-like⇠3.5 yr (Figs. 1, 2). Furthermore, the water maser emission that
0.1
1
10
100
appeared outside the methanol velocity range, i.e. from 23 to−1
Methanol integrated flux density (Jy km s )17 km s 1 and greater than 5 km s 1 , also shows periodic variability. All the water maser cloudlets lie well within the methanolFig. 6. Correlation between the OH 1.665/1.667 GHz and CH3 OH
bounded region of projected size less than 200 au (Fig. 4). Thus,
6.7 GHz maser integrated flux densities. The open symbols denote theit is likely that the methanol and water masers operate in regions
upper limits for at least one transition. The solid lines show the best fits
Fig.of
5. similar
Proper motionsofthemethanolmaser
cloudlets
in
G107
as
meaphysical parameters, where a factor causing periodic
to the data.
sured
relativetotheircentreofmotiondenoted
by
small
black
cross.
changes is efficient.
Cones represent the proper motions in each cloudlet listed in Table A.2
excitation
mechanisms
6.7velocity
GHz (colourand 22 GHz
and theirThecolours
and apertures
correspond toofthetheradialOHiscloudlets at about 12.2 km s 1 located ⇠250 mas north ofbar)masers
and uncertainty,
respectively.
velocity
scale theis shown
at the line
are understoodin Thegeneralterms;
methanol
ディスクモデルが一番良さそう
the region of
persistent methanol masers (Fig. 4) coincide within
top likely
right corner.
The dashedellipse displays
modelSobolevof ring derived
invertedby infrared
photonsthe(e.g.
et al. 1997;<120 mas (100 au) with an area at which the methanol maser
fromthe 3Detstructure
analysisin Fig. line
7, where
the yellow star colliCragg
al. 2002)
whileshown
the water
is predominantly
between-15.6 and -13.7 km s 1 appearedshows the position of fitted centre of the ring. The grey star denotes the emission ofrvelocity=
240
AU
sionally(e.g. Elitzural. 1989;
Gray et al. 2016). Thepositionof thepumped
1.3 mm continuum
peaket(Palauet al. 2011).
during the second epoch (MJD 57444) of VLBI observations
oretical models generally indicate that the gas density and(Fig.
ki- A.4). Since the flux densities of both masers are strongly
h = 30 AU
netic temperature favouring both maser transitions do not overa↵ected by spatial filtering by the VLBI, as Fig. A.4 depictslap (Cragg
et al. 2002;
Grayproper
et al.motions
2016). in
However,modelling
powering
star. Somewhat
randomthis site may
the above discussed spatial di↵erences could be much smaller
resultfrom22
theGHzmethodof proper
motionstudies
we applied.
We forof themaser
excitation
withup-to-datemolecular
datalow brightness extended emission. Thus, the hydroxyl andcalculated
the properwithbarycentre(Nesterenok2013)motions
supports
therespect
view tothatthethe
inversionofis mostmethanol masers originate in basically the same gas volume at amethanol
distribution
the exciting
star. We
postponeof 200 420 au from the central protostar. We note that
efficientwhen therather
dust thantemperature
is muchlower
thanathedistancegas
detailed
analysisandof plausible
causesof theobserved
properreduces
mo- thetemperature
an increaseof theinfraredemission
theprojected size of ⇠450 au of the methanol maser region durtions
becausethemaser
exhibits
notonly
significant
variations
ining the three epochs is close to the lower limit of the disc sizes
maser gain (Yates et al. 1997).
the amplitude of flare and its profile, as the single dish monitor-

observed in intermediate-mass embedded protostars (Beltrán &distributed. Using the minimum spanning tree analysis, we found 26 probable sub-clusters having 5 or more members.
The sub-clusters are between ∼0.5 pc – ∼3 pc in size and are somewhat elongated. The star formation efficiency inmost of the sub-cluster region varies between 5% – 20% indicating that the sub-clusters could be bound regions. The
radii of these sub-clusters also support it.

28

Accepted by MNRAS
http://arxiv.org/pdf/1912.11789

Probing the early phases of high mass star formation with 6.7 GHz methanol masers
Sonu Tabitha Paulson1 , Jagadheep D. Pandian1
1

Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram
695547, Kerala, India
E-mail contact: sonutabitha.15 at res.iist.ac.in
Methanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards
22 as a unique tool to probe the early phases of massive
massive star forming regions. These masers can thus be usedstar formation. We present here a study of the spectral energy distributions of 320 6.7 GHz methanol masers chosenfrom the MMB catalogue, which fall in the Hi-GAL range (|l| ≤ 60◦ , |b| ≤ 1◦ ). The spectral energy distributions areconstructed from 870–70 µm using data from the ATLASGAL and Hi-GAL surveys. The emission from cold dust
is modelled by a single grey body component fit. We estimate the clump properties such as mass, FIR luminosityand column density using the best fit parameters of the SED fits. Considering the Kauffman criteria for massive starformation, we find that all but a few maser hosts have the potential to harbour at least one high mass star. The
physical properties of the methanol maser hosts are also discussed. The evolutionary stages of 6.7 GHz maser sources,
explored using the mass luminosity diagram, suggests that they are predominantly associated with high mass stars
with the majority being in the accretion phase. However, we observe a small number of sources that could possibly
be related to intermediate or low-mass stars.
Accepted by MNRAS
http://arxiv.org/pdf/1912.06973

Formation of moon systems around giant planets: Capture and ablation of planetesimals
as foundation for a pebble accretion scenario
T. Ronnet1 and A. Johansen1
1

Department of Astronomy and Theoretical Physics, Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden

E-mail contact: thomas.ronnet at astro.lu.se

6.7GHz メタノールメーザー-> 本当に大質量星形成領域に付随しているのか？
Methanol Multibeam survey: 972 sources のうち・Infraredの観測データがある
・距離が分かっている
320天体を調査
Figure 1. Source identification and apertures used by hyper for doing photometry. The two rows show the 160, 250 and 500 µm data
for G346.036+0.048 and G332.560 0.148 respectively, the latter showcasing a slightly crowded field.

Table 1. Flux densities of sources hosting 6.7 GHz methanol masers from 870 to 70 µm. The uncertainties in the measured flux densities
are given in parenthesis.

Name
G345.131-0.174
G345.576-0.225
G345.807-0.044
G345.824+0.044
G309.384-0.135
G5.618-0.082
G16.855+0.641
G010.724 0.334

870 µm500 µm

4.14 (0.11)
1.90 (0.06)
0.84 (0.05)
2.85 (0.09)
7.22(0.29)
4.31 (0.15)
1.80 (0.06)
4.05 (0.16)

17.52 (0.77)
6.71 (0.40)
3.92 (0.32)
5.40 (0.82)
34.35 (1.04)
20.19 (0.48)
8.25 (0.37)
18.46 (0.98)

Flux Values (Jy)350 µm
250 µm49.45 (1.56)
19.95 (0.80)
8.03 (0.48)
21.25 (2.15)
104.22 (2.65)
53.77 (1.19)
23.47 (0.78)
55.74 (1.99)

97.06 (2.64)
29.80 (1.02)
11.70 (0.65)
44.66 (2.92)
210.16 (5.33)
94.64 (2.18)
40.89 (1.05)
81.11 (2.97)

160 µm70 µm

125.80 (4.46)
33.28 (0.90)
9.75 (0.48)
61.32 (3.30)
376.29 (11.26)
98.20 (3.26)
55.24 (1.68)
112.08 (3.70)

60.30 (2.92)
3.85 (0.30)
0.54 (0.15)
44.96 (2.74)
270.82 (7.67)
17.61 (0.33)
18.91 (0.69)
39.01 (1.67)*The full table will be made available online.

tometry is elliptical and is determined by fitting a two-

aperture photometry since the resolution and morphol-

Paulson & Pandian
SED ﬁtting

2.2

Fitting the SEDof thedust from 870
We have fit temperature
the SED of thesources
160 µmusing a grey body to model the cold dus
solid
angle
optical depthsion:F⌫ = ⌦c B⌫ (Tc )(1✓ ◆⌫⌧ ⌫ = ⌧0⌫0e ⌧⌫ )
dust spectral index

Here, ⌦c is the deconvolved solid angle of thederived from the aperture used by hyper forphotometry (deconvolution
done using
the H
SEDs of 6.7 GHzis methanol
masersbeam size at 250 µm – i.e. 1800 ), Tc is the tempof the cold dust, ⌧0 is the optical depth at fre
Table 4. Summary of derived parameters⌫0 (chosen to be 500 µm wavelength) and is thParameter
MeanStandard
deviation index
MedianMaxemissivity
which is Min
assumed tobe 1 < <fitting
least sDust temperature (K)
21.54
5.29 was carried
20.86 out using
10.86 the nonlinear
47.59
Dust emissivity
1.83
0.29
1.83
1.00
2.85
Marquardt-Levenberg
algorithm.
E↵ective radius (pc)
0.69
0.41
0.61
0.07
1.99
The
emission
at
70
µm
is
not
2
Surface Density (g cm )
0.27
0.38
0.17
0.02
4.28 likely totributable
to 9.30
a single
component
Clump Mass (M )1.57 ⇥ 103
2.46
⇥ 103
⇥ 102 dust
11.07
1.62 ⇥ (Compiègn
104
Column Density (cm 2 )1.68 ⇥ 1024
2.29
⇥ 10241.15 ⇥ et1024al.7.95⇥ 1022 Rather,
2.50 ⇥ 1025
2010;
Battersby
2011).
the
70 µ
4
4
3
2
5
FIR luminosity (L )1.74 ⇥ 10
3.91 ⇥ 10
6.44 ⇥ 10
1.33 ⇥ 10
3.28 ⇥ 10
is expected to have contributions from both co
dust.
In orderto test ofthis
hypothesis,w
ure 3. Single component fits to the SEDs of characteristic sources. Thewarm
inset shows
the source
name, temperaturecold dust,
dust
cal depth at 500 µm and the dust spectral index.
compare the single component fit to the SED of ausing the following equation:with and without including the 70 µm flux. As
36

D 2 S⌫ R

Source Counts

Source Counts

Source Counts

Source Counts

Source Counts

SourceCounts
SourceCounts

Source Countsof
8usingPaulson& Pandian
the following
equation:
us
flu
60
36
D 2 S⌫ R
48
GA
M54= 48
(5)
B
(T
)
⌫
D ⌫
be
30
48
42
42
for
where
S⌫ is the integrated 870 µm flux, D is the distance
42
36
36
24
th
to36the source,
R is the gas-to-dust mass ratio (assumed
ing
to be 100),30
30 B⌫ is the Planck function for the cold dust
30
18
cotemperature
TD and ⌫ is the dust opacity which is
24
24
mi
taken
as241.85 cm2 g 1 at 870 µm. The clump masses
124(C
18 fromrange
18
18 11.07 M to 1.62⇥10 M , the median massra
being
approximately 930 M . The mass distribution of
126
12
12 is shown in Fig. 6 (left panel).
(2
the6 clumpsclu
The shapeof the mass distribution is similar to that
6
6
0
0
1
0
10
10
sia
observed
by10Urquhart20et al. (2013a)
although
there
0
30
40
50 are0
Effective Radius (pc)0
Tc (K) the14some key10di↵erences.
distribuits
102 While
103 peak of10the105
Clump mass
Mass (M)
tion is similar, the maximum
is wellbelow that oflen
Figure 4. Distribution of source size. The dashed red and blue
Figure5.
Distribution
of
cold
dust
temperature.
Urquhart et al. (2013a). We also see a larger fraction ofsolines show nominal boundaries between cores and clumps, andFigure6.
Distribution
of
mass
(left
panel)
andsources in the 100 to 1000 M range. These di↵erences
8 clumps
Paulson& PandianUr
and clouds
respectively.
are most likely due two reasons. First, the methodology
wasofobserved(Pandian etisal.
2012). This
doing photometrydi↵erent– thefurther
hypercorrobsoftware
en
48
48
stu
48
oratesthemoreevolvednatureof
6.7
GHz
methanoluses a Gaussian aperture to do photometry, while theetdua
maserscomparedtoinfrareddark
cloudswherelower
42 fluxes
4260
42 of Urquhart et al. (2013a) are from the ATLASop
obs
temperaturesaremeasured(e.g.
Pillaietal.
(2006)).
GAL compact source catalog where photometry has colu
54
th
36
36
36
been done by sextractor (Contreras et al. 2013). The
sec48
30 former
30
30 measures the flux of the compact source while
47
tion
42
3.3 theClump
Masses,Hcolumndensities
and2
latter measures the flux of the entire clump includ- sur
gr
24
24
24
36
surfacedensities
ing thedi↵useemission around the compact source. To thetio
30
corroborate
this,
we
have
comparedthefluxesdeter181818e↵e
The isothermalmasses of the sources can be computed
ing
24
mined
by
us
with
those
of
the
GAUSSCLUMP
catalogsamusing theth12
12 temperature values obtained from the best fit
12(Csengerietal.
2014).
Wefind
ourfluxestobecompa18
to 4
slightly larger than that of Csengeri et al. and6though
6 rable000,
126
MNRAS
1–15 (2019)(2014). This is because the latter fit the entire clump in- but
60
0
0
0
1
3
1
2
4
5
Fig
cludingdi↵usestructure
multiple10Gaus10 1
102310 2 the outer1024
102510with
10
10
10
10
10
0
2
2
H2 Column
Density(cm central) cm emission
Surface(gm)
Clumpsians, while
we only
fitDensity
thebased on by
0
10
20 Mass (M
30 )
40
50
Tc (K)
its morphology at 250 µm which is our reference wave- sity
Figure
7. Distributionof panel).
the surface density. The red and blue
Figure 6. Distribution of mass (left panel) and H
density(right2 column
length.
Thelargerfluxesin the ATLASGAL compact
dashed line show a threshold of 0.05 g cm 2 and 1.00 g cm 2
Figure 5. Distribution of cold dust temperature.
source catalog translate to larger masses in the work ofrespectively.
Urquhart et al. (2013a).
3.4

FI

C

2
10
103 mass (left panel) and (b) FIR luminosity (right panel)
Figure 9. Relationship of 6.7 GHz methanol maser luminosity with (a) clump

lationship:
102 10
10
10
10
10
10
10
10
10 9
10 8
10 7
10 6
10 5
✓ MMB
◆1.33Luminosity (L )MMB Luminosity (L )105
Re↵m(r) 580 M(91 pc
Figure 9. Relationship of 6.7 GHz methanol maser luminosity with (a) clump mass (left panel) and (b) FIR luminosity
where Re↵ is the e↵ective radius of the source. Fig. 1
shows the mass-radius relationship for our sample. W
104find that 295 out of 320 sources (92%) satisfy the cr
terionin the equation
above. The results are somelationship:
Kauﬀmann
et al. (2010)
what di↵erent from that of Urquhart et al. (2013a✓◆1.33fraction (⇠ 97%) o
52014b)
who
found
a
much
larger
10
Re↵
103
the
methanolmaserssatisfying
the criterion above. Thim(r) 580 M
pcbe due to two factors. First
discrepancy is most likely1 to
the photometry is di↵erent as explained in section 3.2
Thecompact
usedradius
by UrquhartawhereRe↵ sourceis thecataloge↵ectiveof theetsou
2(2013a)is thesensitive
to the entirerelationshipsubmillimeterforclump
in
92%がこの式を満たす
4
shows
mass-radius
our
10
10
cluding the di↵use emission, while the photometry usin
find that 295 out of 320 sources (92%) sat
hyper is sensitive only to the compact emission, simila
Low Mass Star Formationin theequationresulttoterionthe catalog
of Csengeri
et al.above.
(2014). The
A secondfac
from thatof Urquhart
torwhatis thatdi↵erent
we have determinede↵ectiveradii using et
th
1
10
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we haveusedfraction
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who maps
found(whicha muchlarger3
erencewavelength masers
for hyper)
rather than870 µm10
the methanol
satisfying
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ATLASGAL maps. The former typically has much bet
discrepancy is most likely to be due to two fa
ter signal to noise ratio leading to a better estimatiodi↵erent
as explained
ofthe
the photometry
source size. To isfurther
examinethis matter,in
w
1
0
1
10
10
10
The atcompact
sourceusedby satisf
Urqlookedthe sourcesin our catalog
sample that
do notEffective Radius (pc)theKau↵manncriterion andcomparede↵ective ra(2013a)is sensitive
to theentire thesubmillimet
102
dius
given incompact
source catalog
that ocludingthethedi↵useemission,while withthe photo
our work. We found that the e↵ective radius is liste
Figure 10. The clump mass as a function of source radius. The
hyper
issensitive
only tothecompact
emis
for
only
5
out
of
25
sources,theremaining
being
toshaded region represents
the
area
where
the
sourcesdoesn’tsatLow Mass Star Formation
to the forcatalogof Csengeri
et al.
isfy the Kau↵man criteria. The dashed green line is the powercompact
deconvolution.
We foundthe(2014).
e↵ective Ara
law fit to the data. The upper and lower solid red line shows thedius
the enclosed
fluxdetermined
to be larger inthe compac
torandis that
we havee↵ectiverad2
2
1
surface densities of 1 g cm
and 0.05 g cm , respectively.
10
sourcecatalog
comparedto thehyperweresults
250 µmHi-GALmaps(whichhaveleadin
usedClump Mass (M )101 10
10

9

8

7

6

5

4

Applied to protoplanetary disks, particles in dense environments will settle faster. In balance with upward gas motions(turbulent diffusion, convection) the thickness of the midplane particle layer will be smaller than calculated based on
individual grains, especially for dust. For pebbles, large solid-to-gas ratios are needed to trigger instabilities based on
back-reaction.

32

Accepted by ApJL
http://arxiv.org/pdf/1912.01714

The evolution of dust in discs influenced by external photoevaporation
Andrew D. Sellek1 , Richard A. Booth1 and Cathie J. Clarke1
1

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

E-mail contact: ads79 at cam.ac.uk
Protoplanetary discs form and evolve in a wide variety of stellar environments and are accordingly exposed to a wide
range of ambient far ultraviolet (FUV) field strengths. Strong FUV fields are known to drive vigorous gaseous flows
from the outer disc. In this paper we conduct the first systematic exploration of the evolution of the solid componentof discs subject to external photoevaporation. We find that the main effect of photoevaporation is to reduce thereservoir of dust at large radii and this leads to more efficient subsequent depletion of the disc dust due to radial drift.
Efficient radial drift means that photoevaporation causes no significant increase of the dust to gas ratio in the disc.
We show that the disc lifetime in both dust and gas is strongly dependent on the level of the FUV background andthat the relationship between these two lifetimes just depends on the Shakura-Sunyaev α parameter, with the similar
lifetimes observed for gas and dust in discs pointing to higher α values (∼ 10−2 ). On the other hand the distributionof observed discs in the plane of disc size versus flux at 850 µm is better reproduced by lower α (∼ 10−3 ). We find thatphotoevaporation does not assist rocky planet formation but need not inhibit mechanisms (such as pebble accretionat the water snow line) which can be effective sufficiently early in the disc’s lifetime (i.e. well within a Myr).
Accepted by MNRAS
https://arxiv.org/pdf/1912.06154

24

sibleh andthe heating (Kenyon & Hartmann 1987; Chiang & Goldreich 1997)
g inevoluWe model the viscous evolution of the gas and growth and radial- is supported by mean fits of the SED shape for q (Andrews &partialr, the Modelmigration of the dust as in Booth et al. (2017) for which the treatment
Williams
2005; Kenyon & Hartmann 1995) and the corresponding
ations) unof thedependence
dust followsofthatof Birnstieletal. (2012).
We employa midlinear
viscosityondiscradiusisalsoconsistent
withradial temperature proﬁle modeldnets;
dust mid-plane
planeradial temperature
profile T(R)modeledaccordingto:theobservedvariationofaccretion
rates
onto
T
Tauri
stars
as a
tetainii) to✓of age◆ q(Hartmann et al. 1998).
functionR
scsin(q=0.5) scale, we set the aspect ratio (the (1)2). ToT =T. a temperature
In
order
to
set
0
arietyR0
1/4starthese
R=1
au でT~279
K as
for
1M
ratio
of
scale
heightHoverradius,whichscales
H/R
/
R
) to
sun
7; Trion is
H/R⇠ 0.033
at R0 = 1 ↵auviscosity
such that Tprescription
a 1 M star.
As
Assuming
a constant& Sunyaev
0 ⇡ 279 K for(Shakura
affects
ourinitialwe viscosity
adopt the similarity
solution
Lynden-Bellonof1973),
thecondition
kinematic⌫ then scales
withofradiusaslatter& Pringle(1974)
forthesurfacedensity,⌃:ofthe surface
essingvisc / R3/2 q .
⌫ / R density
(2)

ement
2005)
ust inducttion.

at areon oflished012)
h018b)
andouter
volubackartialns (intions
been6)dustandii) to
simu-

✓

◆

✓

◆2

R spatially uniformR
We explore↵ values motivated by the range of
total disk
mass = 100⌃ = ⌃0
exp
,
(3)MJ
3
viscosities(Rafikov 2017) and
RC inferred from
RC observations: 10
2 (Hartmann et al. 1998). Following Clarke (2007) and Facchini
10
where = visc (Equation 2) and RC is the scale radius of the exet al. (2016)
we(i.e.
thenq = 0.5
suchthat⌫radiusisRlinearwithponential
cut off
RC choosesets theinitialextentof thedisc).
C was
exponential
cutoﬀ
radius.between
This dependence- whichresults
if stellarof dustvaried10 and 300 au.
The values
adoptedare irradiation
roughly in thein thederived
form ofthesubmm
blackbodyequilibrium
temperature
dominates
range
from
continuum
observationsof protoplanethe heating(Kenyon1987; Chiang& Goldreich
tary
discs (e.g.
Ansdell&etHartmannal. 2018; Tripathi
et al. 2017),
although1997)
accretion
following
the should
viscousmotionofthethiscoincidewith
the &- is observational
supportedbymeasuremean
fitsof notthenecessarily
SED shapefor qgas(Andrews
initial,mass-based
measureradiustherepresented
by theRC .corresponding
The denWilliams
2005;&ofHartmann
1995)+ radial
drift
dueKenyon
to dragfromgas andsity
normalisation,⌃ofis set by the
total
disc
mass.
Observational
0 , viscosity
lineardependenceon
discradiusisalsoconsistent with+ photoevaporation due to FUV irradiation
studiesmeasurevariation
dust massesof up to ⇠100ontoM T(e.g.
141stars
M as athe observedof accretion
rates
Tauri
in
Lupus, ofAnsdell
et al. 2016),
corresponding
to discs with & 30
functionage (Hartmann
et al.
1998).

Dust evolution in photoevaporating discs

0.2

10 8
400

80.0%
Ṁ
acc
90.0%
Ṁ
evap
RD

10 6
150

0.0

No Photoevaporation

67
10 125

100

10 8
75
50
10 9

180

350
10 9

300

4

10 9

3

9

250

10

200

140
10 7
120
100
10 8
80

10609

25
2

0

10 10

101.02Mass left in Disc
Mass lost to Wind
Mass lost to Star3
10 0.60.8
0.0110

Dust Mass Fraction Md/MD
Dust Mass Md / MJ

Dust Mass Fraction Md/MD
Dust Mass Md / MJ

10 2
0.8

40

10
1509

Dust Mass Fraction Md/MD
Dust Mass Md / MJ

10

10

0.8

0.0108
0.6

0.6
10 3

0.4
10 4
0.2

104

105

Time / years
10

0.01060.4

0.4

0.01040.2
0.0102

0.2
10 4

10 5
0.0
103

106

No Drift

101606

Ṁ / M yr 1
Dust Radius / AU

175

Ṁ / M yr 1
Dust Radius / AU

0.0

Full Model

1
Ṁ
/
M
yr
Dust Radius / AU

0.0

7

0.0
3
10 810

107

104

105

106

0.0100
0.0
103

107

Time / years

Ṁacc

10

6

6

104

105

106

107

Time / years

9

3

10 9

Ṁ / M yr 1

due to the small variation in the dust mass fraction.

Ṁ / M yr 1

Ṁ / M yr 1

evap including radial drift and photoevaporation, Model RD including radial drift but no photoevaporation and Model
Figure 5. From left to right: Model Ṁ
RDPE
Figure 5. PE
Fromleft to photoevaporationright: Model RDPE
includingradialdrift
andphotoevaporation,
Model
RD90including
radial drift
no cent
photoevaporation
andincludingbut noradial drift.
show,from top: the radiusof theper cent (orange)
and but
80 per(red) percentilesof Modelthe
96The
10 panels
7
7
10
PE including
but theno radius
radial ofdrift.
Thediscpanelsshow,
fromfortop:
the radiusof the90 perandlost80 to
perof themass distribution withthe gas(black,dashed)reference;
the massin dustleftcent
in the(orange)
disc (blue),thecent
wind(red)(red)percentiles
and lost to the
10 dustphotoevaporation(green); theglobaldust massfraction;
the gasmassdashed)loss ratefor
throughaccretion(solid)inandphotoevaporation
In addition,
the time
the lost
dust toat thedust mass star
distribution
withthe radiusof thegas disc(black,reference;
the mass
dust
left in the disc(dashed).
(blue), lostto the wind(red)ofand
thethewindbase beginningradially drift
in andhavingclearedthe discaccretionare shown(solid)
as the andtwo photoevaporation
black dotted lines. Notethe linear
scale on thestar (green);
globaldust masstofraction;
the gasmass
through(dashed).
In addition,
thebottom
time ofrightthe plot
dust at
94loss
10 rate8
10 8
10 duethe small tovariationin driftthe dust
masshaving
fraction.
the wind base tobeginningradially
in andcleared the disc are shown as the two black dotted lines. Note the linear scale on the bottom right plot9

Accepted by Research in Astronomy and Astrophysics

25http://arxiv.org/pdf/1912.06984
Spectral library of age-benchmark low-mass stars and brown dwarfs
E. Manjavacas1,2 , N. Lodieu3,4 , V.J.S. Béjar3,4 , M.R. Zapatero-Osorio5 , S. Boudreault6 , M. Bonnefoy7
1

W.M. Keck Observatory, 65-1120 Mamalahoa Highway, Kamuela, HI 96743, USA; 2 Department of Astronomy/Steward
Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ, 85721, USA; 3 Instituto de Astrofísica
de Canarias, C/ Vía Láctea, s/n, E38205, La Laguna (Tenerife), Spain; 4 Dpt. de Astrofísica, Univ. de La Laguna,Avda. Astrofísico Francisco Sánchez s/n, 38206, La Laguna (Tenerife), Spain; 5 Centro de Astrobiología (CSIC-INTA),
Crta. Ajalvir km 4, E-28850 Torrejón de Ardoz, Madrid, Spain; 6 Max-Planck-Institut für Sonnensystemforschung,
Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany; 7 Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble,
FranceE-mail contact: emanjavacas at keck.hawaii.edu
In the past years, some extremely red brown dwarfs were found. They were believed to have low surface gravity,
but many of their spectral characteristics were similar to those of high surface gravity brown dwarfs, showing thatyouth (or low surface gravity) spectral characteristics are poorly understood. We aim to test surface gravity indicatorsin late-M and early-L brown dwarf spectra using data obtained with the X-shooter spectrograph at the Very Large
Telescope. We selected a benchmark sample of brown dwarfs members of Chamaeleon I (∼2 Myr), Upper Scorpius(5–10 Myr), Pleiades (132±27 Myr), and Praesepe (590–790 Myr) with well-constrained ages, and similar metallicities.
We provided a consistent spectral classification of the sample in the optical and in the near-infrared. We measured theequivalent widths of their alkali lines, finding that they have a moderate correlation with age, especially for objects
with spectral types M8 and later. We used spectral indices defined in the literature to estimate surface gravity, findingthat their gravity assignment is accurate for 75% of our sample. We investigated the correlation between red colours
and age, finding that after ∼10 Myr, the colour does not change significantly for our sample with spectral types M6.0–
L3.0. In this case, red colours might be associated with circumstellar disks, ring structures, extinction, or viewing
angle. Finally, we calculated the bolometric luminosity, and J and K bolometric corrections for our sample. We foundthat six objects are overluminous compared to other members of the same association. Those objects are also flagged
as binary candidates by the Gaia survey.
Accepted by MNRAS
http://arxiv.org/pdf/1912.02806

Long-term multi-frequency maser observations of the intermediate-mass young stellar
object G107.298+5.639

a strong correlation between the 6.7 GHz line and the infrared flux densities supporting a radiative pumping of themaser. The synchronised behaviour of the hydroxyl and methanol transitions indicates a common pumping mechanism
for the periodic flares of G107.298+5.639.

27

Accepted by Astronomy and Astrophysics
https://arxiv.org/pdf/2001.01625

Large scale star formation in Auriga region
A.K. Pandey1 , Saurabh Sharma1 , N. Kobayashi2,3 , Y. Sarugaku3 and K. Ogura4
1

Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital, 263 002, India; 2 Instituteof Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan; 3 Kiso Observatory, School of
Science, University of Tokyo, Mitake-mura, Kiso-gun, Nagano 397-0101, Japan; 4 Kokugakuin University, Higashi,
Shibuya-ku, Tokyo 150-8440, Japan
E-mail contact: pandey at aries.res.in

New observations in the VI bands along with archival data from the 2MASS and WISE surveys have been used togenerate a catalog of young stellar objects (YSOs) covering an area of about 6◦ × 6◦ in the Auriga region centered
at l ∼ 173◦ and b ∼ 1.◦ 5. The nature of the identified YSOs and their spatial distribution are used to study thestar formation in the region. The distribution of YSOs along with that of the ionized and molecular gas reveals tworing-like structures stretching over an area of a few degrees each in extent. We name these structures as Auriga
Bubbles 1 and 2. The center of the Bubbles appears to be above the Galactic mid-plane. The majority of Class i YSOs
are associated with the Bubbles, whereas the relatively older population, i.e., Class ii objects are rather randomly
distributed. Using the minimum spanning tree analysis, we found 26 probable sub-clusters having 5 or more members.
The sub-clusters are between ∼0.5 pc – ∼3 pc in size and are somewhat elongated. The star formation efficiency inmost of the sub-cluster region varies between 5% – 20% indicating that the sub-clusters could be bound regions. The
radii of these sub-clusters also support it.
Accepted by MNRAS
http://arxiv.org/pdf/1912.11789

Probing the early phases of high mass star formation with 6.7 GHz methanol masers
Sonu Tabitha Paulson1 , Jagadheep D. Pandian1
1

Department of Earth and Space Sciences, Indian Institute of Space Science & Technology, Thiruvananthapuram
695547, Kerala, India

with the majority being in the accretion phase. However, we observe a small number of sources that could possibly
be related to intermediate or low-mass stars.

Accepted by MNRAS
29

http://arxiv.org/pdf/1912.06973

Formation of moon systems around giant planets: Capture and ablation of planetesimals
as foundation for a pebble accretion scenario
T. Ronnet1 and A. Johansen1
1

Department of Astronomy and Theoretical Physics, Lund Observatory, Lund University, Box 43, 22100 Lund, Sweden

E-mail contact: thomas.ronnet at astro.lu.se
The four major satellites of Jupiter, known as the Galilean moons, and Saturn’s most massive satellite, Titan, arebelieved to have formed in a predominantly gaseous circum-planetary disk, during the last stages of formation of theirparent planet. Pebbles from the protoplanetary disk are blocked from flowing into the circumplanetary disk by the
positive pressure gradient at the outer edge of the planetary gap, so the gas drag assisted capture of planetesimals
should be the main contributor to the delivery of solids onto circum-planetary disks. However, a consistent framework
for the subsequent accretion of the moons remains to be built. Here we use numerical integrations to show that mostplanetesimals being captured within a circum-planetary disk are strongly ablated due to the frictional heating theyexperience, thus supplying the disk with small dust grains, whereas only a small fraction ‘survives’ their capture. We
then construct a simple model of a circum-planetary disk supplied by ablation, where the flux of solids through the disk
is at equilibrium with the ablation supply rate, and investigate the formation of moons in such disks. We show that thegrowth of satellites is driven mainly by accretion of the pebbles that coagulate from the ablated material. The pebbleaccreting protosatellites rapidly migrate inward and pile up in resonant chains at the inner edge of the circum-planetary
disk. We propose that dynamical instabilities in these resonant chains are at the origin of the different architectures ofJupiter’s and Saturn’s moon systems. The assembly of moon systems through pebble accretion can therefore be seen
as a down-scaled manifestation of the same process that forms systems of super-Earths and terrestrial-mass planets
around solar-type stars and M-dwarfs.
Accepted by A&A
http://arxiv.org/pdf/1912.04765

The molecular outflow from R Mon
Goran Sandell1 , W. Vacca2 , L. Bouscasse3 and R. Güsten3
1

University of Hawaii, Institute for Astronomy - Hilo, 640 N. Aohoku Place, Hilo, HI 96720, USA; 2 SOFIA Sciencedisk. We propose that dynamical instabilities in these resonant chains are at the origin of the different architectures ofJupiter’s and Saturn’s moon systems. The assembly of moon systems through pebble accretion can therefore be seen
as a down-scaled manifestation of the same process that forms systems of super-Earths and terrestrial-mass planets
around solar-type stars and M-dwarfs.

30

Accepted by A&A
http://arxiv.org/pdf/1912.04765

The molecular outflow from R Mon
Goran Sandell1 , W. Vacca2 , L. Bouscasse3 and R. Güsten3
1

University of Hawaii, Institute for Astronomy - Hilo, 640 N. Aohoku Place, Hilo, HI 96720, USA; 2 SOFIA Science
Center, NASA Ames Research Center, USRA, MS 232-12, Building N232, PO Box 1, Moffett Field, CA 94035-0001,
USA; 3 Max Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
E-mail contact: gsandell at hawaii.edu
We have mapped the young Herbig Be star R Mon in CO(3–2) and 13 CO(3–2) with APEX in Chile and analyzed
unpublished Herschel images. We find that R Mon is embedded in a small cloud with a gas temperature of ∼ 20 K
and a total mass of ∼ 70 M! . We confirm that R Mon drives a bipolar molecular outflow, which is blue-shifted northof R Mon. The blue-shifted outflow has excavated the molecular cloud north of R Mon, creating the reflection nebula
NGC 2261 and filling it with high-velocity gas. At “high’23velocities the orientation of the outflow is approximatelyn-s, which agrees with the optical jet, suggesting that the accretion disk is e-w. The outflow velocities are modest,± 9 km/s. The outflow is rather massive, ∼ 0.56 M! in the blue-shifted outflow lobe. The outflow is completely
optically thick in CO(3–2) towards R Mon, indicating that it’s envelope is <∼ 2,000 au. The mass of the accretion disk
and surrounding envelope determined from an isothermal graybody fit is ∼ 0.34 M! . We estimate a mass loss rateof ∼ (1 - 3) × 10−5 M! yr−1 , corresponding to an accretion rate of (1 - 9) × 10−6 M! yr−1 . We find that R Mon
has bolometric luminosity of < 1000 L! . R Mon is still in an active accretion phase, contributing to the observed
luminosity. Hence R Mon cannot be a B0 star. It must be a late B star or even an early A star.
Accepted by The Astrophysical Journal

Laboratory Experiments on the Motion of Dense Dust Clouds
Niclas Schneider1 and Gerhard Wurm1
1

Faculty of Physics University of Duisburg-Essen Lotharstr. 1, 47057 Duisburg, Germany

E-mail contact: niclas.schneider at uni-due.de
In laboratory experiments, we study the motion of levitated, sedimenting clouds of sub-mm grains at low ambientn-s, which agrees with the optical jet, suggesting that the accretion disk is e-w. The outflow velocities are modest,± 9 km/s. The outflow is rather massive, ∼ 0.56 M! in the blue-shifted outflow lobe. The outflow is completely
optically thick in CO(3–2) towards R Mon, indicating that it’s envelope is <∼ 2,000 au. The mass of the accretion disk
and surrounding envelope determined from an isothermal graybody fit is ∼ 0.34 M! . We estimate a mass loss rateof ∼ (1 - 3) × 10−5 M! yr−1 , corresponding to an accretion rate of (1 - 9) × 10−6 M! yr−1 . We find that R Mon
has bolometric luminosity of < 1000 L! . R Mon is still in an active accretion phase, contributing to the observed
luminosity. Hence R Mon cannot be a B0 star. It must be a late B star or even an early A star.

31

Accepted by The Astrophysical Journal

Laboratory Experiments on the Motion of Dense Dust Clouds
Niclas Schneider1 and Gerhard Wurm1
1

Faculty of Physics University of Duisburg-Essen Lotharstr. 1, 47057 Duisburg, Germany

E-mail contact: niclas.schneider at uni-due.de
In laboratory experiments, we study the motion of levitated, sedimenting clouds of sub-mm grains at low ambientpressure and at high solid-to-gas ratios !. The experiments show a collective behavior of particles, i.e. grains in clouds
settle faster than an isolated grain. In collective particle clouds, the sedimentation velocity linearly depends on ! andlinearly depends on the particle closeness C. However, collective behavior only sets in at a critical value !crit which
linearly increases with the experiment Stokes number St. For St < 0.003 particles always behave collectively. For
large Stokes numbers, large solid-to-gas ratios are needed to trigger collective behavior, e.g. !crit = 0.04 at St = 0.01.
Applied to protoplanetary disks, particles in dense environments will settle faster. In balance with upward gas motions(turbulent diffusion, convection) the thickness of the midplane particle layer will be smaller than calculated based on
individual grains, especially for dust. For pebbles, large solid-to-gas ratios are needed to trigger instabilities based on
back-reaction.
Accepted by ApJL
http://arxiv.org/pdf/1912.01714

The evolution of dust in discs influenced by external photoevaporation
Andrew D. Sellek1 , Richard A. Booth1 and Cathie J. Clarke1
1

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

E-mail contact: ads79 at cam.ac.uk
Protoplanetary discs form and evolve in a wide variety of stellar environments and are accordingly exposed to a wide
range of ambient far ultraviolet (FUV) field strengths. Strong FUV fields are known to drive vigorous gaseous flows