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18:30:24
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429
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18:29:24Catalog of00:36:00
429 Surface 9Density Regions in Nearby Embedded Clusters
High Protostellar
Juan Li1,2, Philip C. Myers3
1, Helen Kirk4,5, Robert A. Gutermuth6, Michael M. Dunham3,7, and Riwaj Pokhrel3,6

Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China; lijuan@shao.ac.cn
2 quoted in this work: (1) Maury et al. (2011),
References for the distances
Key laboratory for Radio Astronomy, Chinese Academy of Science, 2 West Beijing Road, Nanjing, JiangSu 210008, People’s Republic of China
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USAØr 4(2009),
c University
Y O OIda et al. (2009),(3) Kirk et al.
Bellocheal. (2011),
Department of(4)Physics
and Astronomy,etof Victoria, 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada
5
Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canadac
H Universitylsß 3 C c. B=I
6 etO
uhäuser & ØForbrich (2008), (6) Arzoumanianal. (2011),
Wilking
Departmentof Astronomy,(7)of Massachusetts, Amherst, MA 01003, USA
7
Department of Physics, State University of New York at Fredonia, 280 Central Avenue, Fredonia, NY 14063, USAs
H2018al.September~yHohHk~zyH
Hoh dr2005), (8) ØEnoch etual. (2006),(9) Dzib(2010).
Receivedet
20; revised 2018 December 2; accepted 2018 December 3; published 2019 January 29
Figure 1. Maps of the Aquila-a region. Left: the n =4 surface density of PS objects for the clusters with positions of PS (red dots), Class II (blue dots), and TD (cyanØ Contours
T represent the PS surface density, shownBat C10%, 20%,
8 B<B
=C contour
lis shown in red,pwhile otherzdOdots) objects overlaid.
40%, and 80% of the D=8
peak value. The 20%
positions of PS objects (redcontours are shown in green. Right: the Two Micron All Sky Survey A extinction map of the region with the n =4 surface density andAbstractdots) overlaid. Ø
d M O 2~nGI
We analyze high-quality stellar catalogs for 24 young and nearby (within 1 kpc) embedded clusters and present a

~t
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K

catalog of 32 groups which have a high concentration of protostars. The median effective radius of these groups isnyI
0/I and Flat Class are referred
to asprotostellar
PS stars,
while Class
0.17 pc. The medianand pre-main-sequencestar surfaceØ
densities are 46 M pc and 11 M pc ,Figure10. Mapsof theandIC random5146-baccretion
region.
Contours represent
the PS surface den
respectively. We estimate the age of these groups using a modelof constantbirthrateØaà
OId transition disk (TD) arereferredtoasPMS
stars.
stopping and ﬁnd a median value of 0.25 Myr. Some groups in Aquila,
Serpens,
CoronaAustralia,
Herschelcolumndensitymapandof Ophichus
the region with the n =4 surface density an
e

−2

e

−2

L1688 show high protostellar surface density and high molecular gasØsurface density,nand seem yto be undergoingi~vigorous star formation. These groups provide an excellent opportunity to study the initial conditions of clusteredH densities
B reveal continuous1low.
star formation. Comparisons of protostellar and pre-main-sequence stellar surface
mass star formation of these groups over several Myr in some clouds.
For groups S
with typical protostellarØ
The 532
Astrophysical Journal,
871:163 (18pp), 2019 February 1
highJeans
PS fragmentation
surfacedensitygroups. Y
separations of less than 0.4 pc, we ﬁnd that these separations agreewithinwell with thethe thermal
scale.
On the other hand, for groups with typical protostellar separations larger than 0.4 pc, these separations
Table are4 alwaysfPS =NPSof (Identiﬁed
NPS +NPMS).
larger than the associated Jeans length.
Derived Physical
Properties
Clumps
Key words: infrared: stars – stars: formation – stars: low-mass – stars:
pre-main sequence
ΣPMS
fPS
age
τff
RegionΣPS – stars: protostars

2.2. The Methodologies

Oe
OI
OeI

order to select high PS fraction regions, an objective(3 )od is required to identify such regions. One simple method
t, is
using
the
pc )
(M
pc derived)(Myr)(Myr) model of Myersh does not rely on the deﬁnition of stellar groups is to use The age of the (Mgroups,
Aquila-a
2.3
5.7
0.30
0.64
0.53
(2012):
andAquila-b1
the angular resolution
to 64resolve high-density
Introduction
ocal surface density, Σ (Kirk1. &Myers 2011). If thelimit,
95
0.6
0.22
0.10
groupings Aquila-b2of stars (Allen etal. 2007).276Furthermore,
Spitzer
1382
0.83
0.08
0.04
It is now commonly accepted that most stars form in clusters
1
exp
(
t
a
)
cted separation from
the
star
to
its
nth
nearestneighbor
is
has
been
providingdetailed
imagesofyoungclustersintheAquila-b3
1169
0
1
L
The2003;
Astrophysical871:163 (18pp), 2019 February 1of hundreds of stars (Lada & Lada
ReipurthJournal,
et al. 2014).
=0 us to identify, 0.110 Li et al.(4)mid-IR, which
for the ﬁrst329
timefPS
allowsyoung
Aquila-b4
1
L
0.06
Understanding
theprocess of isstars .
forming
t 0.46a anden the local stellar
surfacedensity
B in clusters= 1. is ofstars withAquila-b5
disks (pre-main-sequence(PMS) objects)
Table
398 2
464
0.37
0.10
= BBconsiderable
4, importance.
Although we have an increasingly
e

−2

e

−2

Figure 2. Maps of the Aquila-b region. Left: the n =4 surface density of PS objects for the clusters with positions of PS (red dots), Class II (blue dots), and TD(yellow dots) objects overlaid. Contours represent the PS surface density, shown at 2.5%, 5%, 10%, 20%, 40%, and 80% of peak value. The 20% contour is shown inred, while other contours are shown in green. Right: the Herschel column density map of the region with the n =4 surface density and positions of PS objects (redPropertiesof 688
Identiﬁed
Clumpsinfalling envelopes(PS objects)
efﬁciently
in clusters
out toAquila-b6
01Ldots) overlaid. The color scale is given in units of cm−2.

0.09

detailed picture of relatively
isolated star formation in nearby
4.1
9.9
0.29 etdeveloped
0.66
0.39
a=0.2
Myr.
(2012)
a clusterevolN
1 kpcwhere
and Aquila-c
beyond(e.g., Evanset al.Myers
2009;
Gutermuth
al.
NPS c
a
b
b
a
a
a
a
dark clouds, such as those in theRegion
Tauruscomplex, many
gaps
R.A.
Σpeak
contouretreffb In
NPS
N
TDb
Aquila-det al.
66Dunham
11al. 2015).
0.86
0.06
0.17
II
2009;Decl.
Kryukova
2012;
addition,
NtotalPS−2
column density map. In all
the contours
thePS
PMS objects,
and the average
mass
ution
model
for
estimation.
assumed a constantin ourrepresent
understandingof andclusteredstar formation,suchsurface
as density
Iﬁgures,remain(J2000)(J2000)) 20 cluster
Aquila-e
15age
0.57
0.25 It 0.27
the and
Herschel
Space(degObservatory(Pilbrattet (pc)al. 2010)
also
surface density of the PS stars. The thePS, Class
II
and
TD
stars
are
of
gas
contained
withintheidentiﬁed
regions.
We
identifyatotal
elusive initial conditions (Myers
2010), as wellas the18:39:20.001
00:33:59.93
20% for
0.53 star-forming
40.32equally
0.29 likely7 accretion
3
providescolumn 120
density
nearbyPSthatdustbirthrate,core–clump
overlaid in red dots, blue dots, and yellow dots, respectively.
of 32Aquila-a
PS groups using this method.
There are ﬁve
groups
2 We process
Auriga/CMC-1
0.9 maps
0.9accretion,
0.50 and
0.82
dominant
fragmentation(e.g.,
Zhang
et
al.
2015;
Aquila-b1
18:29:37.989−01:51:02.99
123120
1.25%
0.10
6
L
4
0
regionswithhighsensitivity
andangularresolution(Harvey
are interested in zones that have both a high PS fraction
and
a
have
only
PS
objects,
including
Aquila-b5,
Musca,
Perseus-b2,
Auriga/CMC-2
1.3
3.0
0.30
0.63
0.60
n Pokhrel et al.
Busquetet surface
al. 2016;
2018).
themodel.
The
clustercanfrom
Aquila-b2
20%
0.024
5
Lbe obtained
10high concentration of protostars. Using
the PS
density
Serpens-a1,
and Serpens-b2. 18:29:58.999
These clusters shouldvery Pokhrelinet −02:01:18.00
al.bestopping
2013;
et L
al.
2016),
makingit possible
to studyages
the

B

S=

n-1
.
pr

(1)

Auriga/CMC-3

1.8

14

0.11

1.81

0.59

The AstrophysicalSurface
Journal, 871:163Density(18pp), 2019 February
1
Li et al.
Catalog of High Protostellar
Regionsin Nearby Embedded Clusters
Figure 20. Maps of Corona Australis (left) and Chameleon I (right) for n=3 (right). Contours represent the PS surface density, shown at 1.25%, 2.5%, 5%, 10%,Figure 20%,
20. Maps
Corona(left) and Chameleon I (right) for n=3 (right). Contours
PS surface
density,showntheat 1.25%,
40%,ofand
80% Australisof peak value.
availablerepresent
on thetheweb.
We alsothankreferee2.5%,
for 5%,
the 10%,very

4,540%, andKirk
80% of peak,value.
Juan Li1,2, Philip C. Myers3 20%,
, HelenRobert A. Gutermuth6
1

f

yr)

3
0
4
1
6
0
9
9
7
7

2
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6

3

8

68

7

2
8
68
8

7
0
1
2
3

0
3
0
36
43

3,7
3,6
, Michael M.
Dunham, and
Riwaj Pokhrel
helpfulreport which
improved
our paper. This work was

Li etObservatory,al.
Shanghai Astronomical
Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030,supported
People’s in
Republic
China;
lijuan@shao.ac.cn
part byofthe
National
Natural Science Foundation
2
Key laboratory for Radio Astronomy, Chinese Academy of Science, 2 West Beijing Road, Nanjing, of
JiangSu
210008,People’sRepublicof China and U1731237),
China(11590780,
11590784,
11773054,
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge,
MA02138,
USA
and Key Laboratory for Radio Astronomy, CAS. R.A.G.’s
4
Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria,
BC, V8P
5C2,project
Canadaparticipationin thiswas supported by NASA ADAP
5
Department of Physics and Astronomy, University of Victoria, Victoria, BC,grants
V8P 1A1,
Canada
NNX11AD14G,
NNX15AF05G,
and NNX17AF24G,
6
Department of Astronomy, University of Massachusetts, Amherst, MANASA
01003,JPL/Caltech
USA
contract 1489384, and NSF grant AST
7
Department of Physics, State University of New York at Fredonia, 280 Central Avenue,
Fredonia,
NY 14063,
USA the next generation mm-wave
1636621in supportof TolTEC,
Received 2018 September 20; revised 2018 December 2; accepted 2018 December 3;camera
publishedfor 2019
LMT.January 29

Abstract

ORCID iDs

C. Myers
https://orcid.org/0000-0002-2885-1806
We analyze high-quality stellar catalogs for 24 young and nearby (within 1 kpc)Philip
embeddedclusters
andpresent a
Helen
Kirk
https://orcid.org/0000-0002-5779-8549
catalog of 32 groups which have a high concentration of protostars. The median effective radius of these groups is−2
0.17 pc. The median protostellar and pre-main-sequence star surface densities Robert
are 46A.MGutermuthpc−2 andhttps:/
11 M/orcid.org/0000-0002e pc ,6447-899Xe
respectively. We estimate the age of these groups using a model of constantMichaelbirthrate
and random
M. Dunhamhttps:/accretion/orcid.org/0000-0003stopping and ﬁnd a median
value
of
0.25
Myr.
Some
groupsin
Aquila,Serpens,
CoronaAustralia,
andOphichus
0749-9505
Figure 23. Mean spacing of PS objects vs. Jeans length. The blue dashed line
Riwaj Pokhrel
https://orcid.org/0000-0002-0557-7349
0.008 ± 0.001)+(1.017±
represents surface
the best ﬁtdensity
to the data:
L1688 show high protostellar
andλhigh
molecular
gas surface
density,and seemto beundergoingPS=( −(rcorr = 0.92). The red solid line represents λPS=λJ.
vigorous star formation.0.007)λThese
groups provide an excellent opportunity to study the initial conditions of clustered
Figure 21. Surface densities of PS objects vs. PMS stars. The blue dashed line
Figure 18. Surface densities of PS objects vs. gas column
densities. The Comparisonsredstar8formation.
protostellar
andpre-main-sequencestellarcontinuous
Figure 22.reveal
Surface densities
of PS andlowPMS vs. gas column densities. The red
Figure represents
21.of
Surfacedensities
objects
PMS stars. The blue dashedlinesurface densities
thebest ﬁt of
to PS
the
data:
Σvs.
Ø
14
4
>
2
<
<
2
PMS=(0.236 ± 0.001) ΣPS (rcorr = 0.78).
22.
Surfacedensities
of PSReferences
and PMSvs.dashedgas column
densities.
redﬁtFhcircles indicate clusters with PS ratios (ratioPS) higher than 0.8. The blue
circles
indicatePSobjects,while
the redline indicatestheThebest± 0.001)ΣPS (rcorrclouds.
=o0.78). ForFigure
represents
thegroups
best ﬁt to thedata: several
ΣPMS=(0.236
Ø
C
Ø
h
mass
star
formation
of
these
over
Myr
in
some
groupswith
typicalprotostellar
0 to the 62
1.40red0.01
circles indicate
objects,
dashedline indicatesbest ﬁt1
to thetriangles indicate clusters with ratioPS ranging from 0.6 to 0.8. The green
SPS =while
log Sthe- (2.050.12) (rthePS data:PSlog
corr = 0.82). The bluegas
The
AstrophysicalJournal,871:163(18pp),
2019
February
1
Li
et
al.
1.40
0.01
A 2with8 ratioPS.ranging from,0.4separations
triangles indicate clusters
to 0.6. The yellow
stars than 0.4 pc, we ﬁnd that these separations agree well with the PS
Allen,
L.,log
Meteath,T.,
Gutermuth,R., theetscale.
al.
2007,
and
Planetsof less
thermalJeans
fragmentation
SPS = S.
log
Sgas
(2.05
0.12
)dasheddata:(rin= 0.82).
Thetheblue
corrProtostars
circles
indicate
PMS
objects,-while
blue
line
indicates
best ﬁt toØcRMindicate clusters with ratioPS ranging from 0.2 to 0.4. The diamonds indicate
V, indicate
ed.
B. PMS
Reipurth,
D. while
Jewitt,&SblueK. dashed
Keil
AZ:
Univ.
Arizona
1.13
0.02 (Tucson,
circles
objects,
theline
indicates
the
best
ﬁt
to
log
S
=
log
(
1.31
0.12
)
(r
=
0.66).
the
PMS
data:
2.
The
medianmoleculargascolumndensity
of
these
On
the
other
hand,
for
groupswith
typicalprotostellar
separations
larger
than
0.4
pc,
these
separations
are
PMS
corr
gasalways
available
on
the
web.
We
also
thank
the
referee
for
the
very
1.13
0.02
clusters with ratioPS below 0.2.
Press),
361log SPMS = log Sgas
−2 the PMS- (1.31 0.12) (rcorr = 0.66).
data:
2. The groups
medianis 1.6×10
molecular22 cm
gas−2column
density toof296these,
correspondingMpc.
helpfulreportwhich improved
our paper. Thislarger than the associatedJeans
length.
22−2eAndré, Ph., Men’shchikov, A., Bontemps, S., et al. 2010, A&A, 518, L102
cm−2, corresponding
to 296work
M pcwas.
groupsis 1.6×10eThe
columnNaturaldensityScienceof these
sub-clusters
is Arzoumanian, D., André, Ph., Didelon, P., et al. 2011, A&A, 529, L6
supported inpartlowest
by thegas
National
Foundation

21 low-mass
21
The
lowestgas column
densityof (2.85
these ±sub-clusters
is −2 Belloche,and535,λPS2 is always larger
with
λPSet0.4
Keyofwords:
infrared: stars– stars:formation–21stars:–U1731237),stars:
pre-mainsequence– stars:
protostars
A.,sub-clusters
Parise,B., Schuller,F.,
al. 2011,pc,
A&A,
and
about
(2.75
±
2.96)×10
sequence stars, and from the modal value
the protostar
of China(11590780,
11590784,
11773054,
and1.76)×10
21−2 cm ,
sub-clusters with λ 0.4 pc, and λ is always largerØØ 2 A A2 <
o

SA

L

PS
PSA&A,and (2.85± 1.76)×10cm. ,about corresponding(2.75 ± 2.96)×10
Benedettini, M.,
S., Schisano,E., etpc.
al. 2018,
619, 52λPS 0.4
These
results
support the
thanPezzuto,
λJ forpc−2
51±55
and 53±35
M
and Key
Laboratory
fortoRadio
Astronomy,CAS.
−2e R.A.G.’sluminosity.
for
λ

0.4
pc.
These
results
supportthethan
λBoogert,A.
C.
A.,
Chiar,
J.
E.,
Knez,
C.,
et
al.
2013,
ApJ, 777,
73 dominates
J
PS
pc
.
corresponding
to51±55
and
53±35M
picturethat
thethermalJeans
fragmentation
at
e
3.
We
found
a
possiblecorrelation
betweenΣandΣ
PS
PMS Burkert,
participationin
thisprojectwas
supported
by
NASA
ADAP
For a sphere of mean column density Σgas and radius R, theA.,&
Hartmann,
L.
2004,
ApJ,
616,
288
picturethat
thethermalJeans
fragmentation
dominates
at
3. We founda possible
correlation
betweenandΣPSsteadyand Σlow-mass
smallerscales.
PMS(r=0.78),
implying
continuous
corr
Busquet,G.,
Estalella,R.,
Palau,
A.,
et
al.
2016,
ApJ,
819,
139
grants
NNX11AD14G,
NNX15AF05G,
and
NNX17AF24G,
freefall time τff is given by (Burkert & Hartmann 2004) 1. Introduction
and the angularsmaller
resolution
high-density
scales. to resolve(r =0.78),
implying
and limit,
steady low-massgas298,freefall
time of these sub-clusters
Casertano,6.S., The& Hut,calculated
P. 1985, ApJ,
80
star
formation
overcontinuous
several Myr.
NASA corr
JPL/Caltech
contract
1489384,
and groupings
NSF grant AST
6.
The
calculated
gas
freefalltimeof Spitzer
these
of
stars
(Allenetal.
2007).
Furthermore,
star4.formationover
severalMyr.
Currie,M.
J.,Berry,
D.
S.,
Jenness,
T.,
et
al.
2014,
in
ASP
Conf.
Ser. with
485, theseems
tocorrelatewiththeclusterage sub-clusters
derivedWe
foundapositive
power-lawcorrelation
between
the
that
most
starsa positiveform
inpower-law
clusters
in supportof TolTEC,
the next generation mm-wave
seemstheoreticalto DatacorrelatewiththeclusteragederivedthepRIt is now commonly accepted1636621
Astronomical
Analysis
Softwareand
Systems
XXIII,
ed. N.with
Manset
&
4.
We
found
correlation
between
the
has
been
providingdetailed
imagesofyoungclusters
in
the
model
(r
=
0.65),
suggestingthat
regions
YSO
surfacedensities
andthemoleculargascolumncorr
t ff »().
5
camerafor LMT.
ofShundreds
of
stars
(Lada
&
Lada
2003;
Reipurthetal.
2014).
P. theoretical
Forshay (San Francisco,
CA:
ASP),
391 suggesting that regions
model
(r
=
0.65),
YSO
surfacedensities
andthemoleculargascolumncorr
8G
with
dynamical
times
haveyounga greater
PS fraction.
gaswhich forﬁrst
timeshorter
allowsus toD.,identify
densities. The power-law indices mid-IR,
were 1.62±0.01
and theRio,N., shorter
Robberto,
M., Soderblom,
et al. 2009,
ApJS,
183,fraction.
261
withdynamical
times havea greater
PS
Understanding the process of starsdensities.
formingin power-law
clusters
is ofThe
indiceswere
1.62±0.01 and stars, DaThis
resultalso
suggeststhat
starclusterformationis
1.42±0.01
for
PS
and
pre-main-sequence
DeGioia-Eastwood,K.,
Throop,H.,
Walker,G.,&
Cudworth,
K.
M.
2001,
stars
with
disks
(pre-main-sequence(PMS)
objects)
and
ORCID
iDs
This
resultalso
suggeststhat starfast
clusterformationis
1.42±0.01
for
PS
and
pre-main-sequencestars,
considerable
importance.
Althoughwehave
anincreasingly
ApJ,
549,
578
likelytobearelatively
process.
A
possible
respectively.
Table 4 presents the calculated τff value for the identiﬁed PS
infalling envelopes Dunham,(PSlikely
objects)
efﬁciently
inN. clusters
out toto Allen,bea wasrelatively
fastA220,possible
M. correlation
M.,
L.
E.,
Evans,
J.,
et al.process.
2015,
11 and τ :Philiprespectively.
C.star
https://orcid.org/0000-0002-2885-1806
found
betweentheApJS,groupage
5.Myers
The
average
PS sources seems
detailedofpicture
ofthe
relatively
isolatedformation
inseparation
nearby between
ffgroupgroups. Figure 24 shows a comparison
τff versus
Dzib, correlation
S.,Evans
Linard, L.,
Mioduszewski,
A.GutermuthJ., et al.the
2010,
ApJ,
718,
610
1
kpc
and
beyond(e.g.,
et
al.
2009;
et
al.
was
found
between
group
age
and
τff:
5. Kirk
The toaverageseparation
betweenPSsourcesseems
Helen
https://orcid.org/0000-0002-5779-8549
±668,
0.02)
τff (rcorr = 0.78).
agree wellwith gaps
thermal Jeans fragmentation for Elmegreen, B.age=(1.31
age, indicating a possible correlation
between them.
slope in the Taurus
dark clouds,
such Theas thosecomplex,
many
G.
2007,
ApJ,
1064
age=(1.31 ± 0.02)
τff (rto A.agree
well withthermalJeans fragmentationfor et al. 2012;2009; Kryukova
etGlenn,al.
2015).
In addition,corr = 0.78).
https://orcid.org/0000-0002Robert
Gutermuth
Enoch, M. L.,Dunham
Young, K. E.,J.,et al. 2006,
ApJ, 638, 293of the best-ﬁt line is 1.31, with remaina Pearsonincorrelation
coefﬁcient of clustered star formation, such as
our understanding6447-899X
Evans,
N. J., II, Allen, (Pilbratt
L. E., Blake, et
G. A.,
et al.
2003, PASP,the
Herschel
Space
Observatory
al.
2010)
also115, 965
of 0.78. This suggests that groups
shorter initial
dynamical
times
Figure 24.M.
Ageof PSasgroups
vs. asgas freefall
The blue dashed line
thewithelusiveconditions(Myers2010),
well
the time. provides
Evans, N. J., II, Dunham, M. M., Jorgensen, J. K., et al. 2009, ApJS, 181, 321
MichaelDunhamhttps://orcid.org/0000-0003dust column
density maps for nearby star-forming
represents the best ﬁt to the data: age=(1.31 ± 0.02) τff (rcorr = 0.78).
have a greater fraction of protostars, i.e., they are “younger.”
Fazio, G. G., Hora, J. L., Allen, L. E., et al. 2004, ApJS, 154, 100749-9505
dominant
fragmentation(e.g., Zhang et al. 2015;16
Figure 23. Mean spacing of PS objects
vs. Jeans length.
The blue dashed lineprocess
Friesen,R. K., Bourke,
T. L., Di Francesco,J., Gutermuth,
R., & Myers, P. C.
regionswithhighsensitivity
and angularresolution(HarveyThis
resultthealso
starλPScluster
formationis likely to±
16
1ﬁt to thethat
Riwaj
Pokhrel https://orcid.org/0000-0002-0557-7349
=( − 0.008± 0.001)+(1.017
represents
bestsuggests
data:
2016, ApJ, 833, 204
Busquet
et
al.
2016;
Pokhreletal.
2018).
etal.
2013;
Pokhreletal.
2016),
makingitpossible
to
study
the
be
a relatively
fast process,andlinefavorsthe ﬁrst
scenario.
In thisThe red solid
represents
λPS=λ0.007)λ(rcorr = 0.92).
J.
Gutermuth, R. A., Bourke, T. L., Allen, L. E., et al. 2008, ApJL, 673, 151

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Structure of a P rotobinary System: An Asymmetric Circumbinary D isk and Sp iral Arms
1

Tomoaki Matsumoto1,2,3, Kazuya Saigo4, and Shigehisa Takakuwa5,6

The Astrophysical Journal, 871:36 (17pp), 2019 January 20

Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan; matsu@hosei.ac.jp
2
Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
3
RIKEN Center for Computational Science (R-CCS), 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
4
Chile Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan
5
Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan
6
Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Received 2018 O ctober 18; revised 2018 November 28; accepted 2018 D ecember 4; published 2019 January 21

!
! g

s
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DECD B.0
DECD B -58 OR0O .0 OdrlqnT [bAbstract
!
N 0
0= We
M investigate
N 0 0=
0
the gas structures around young binary stars using three-dimensional numerical simulations. Eachmodel exhibits
circumstellar disks, spiral arms, and a circumbinary disk with an inner gap or cavity. The
I
T FE L t
circumbinary disk has an asymmetric pattern rotating at an angular velocity of approximately one-fourth of the!
i
2 5- binary orbit
0 of thexmoderate-temperatureO x models.
‒ Because
O of this asymmetry, the circumbinary disk has a density
bump
and a vortex, both of which
continue to exist until the end of our calculation. The density bump and vortex) -58OgreO
are attributed to enhanced angular momentum, which is promoted by the gravitational torque of the stars. In a hot
!

3
U

4

model (c 2.0), the asymmetry rotates considerably more slowly than in the moderate-temperature models. The
cold models (c  0.02) exhibit eccentric circumbinary disks, the precession of which is approximated by a secular))motion61b
F The, asymmetry in the circumbinary disk does not depend on the mass ratio, but itof the ballistic I
particles.
becomes less clear as the speciﬁc angular momentum of the infalling envelope increases. The relative accretion rate
onto Saigo,
the stars
is sensitive to the angular momentum of theTheinfallingenvelope.
Forenvelopes
constant
angularMatsumoto,& Takakuwa
AstrophysicalJournal,871:36(17pp), 2019with
January
20
Matsumoto, Saigo
momentum, the secondary tends to have a higher accretion rate than the primary, except in very low angularmomentum cases. For envelopes with a constant angular velocity, the primary has a higher accretion rate than the circumsecondary disk. The gas stream along the prconnected to the bridge between the two circum
secondary because gas with low speciﬁc angular momentum falls along the polar directions.
These streams along the spiral arms cause the accretU]acircumbinary disk to the circumstellar disks.
Key words: binaries: generalT – hydrodynamics.0 O – protoplanetary disks – stars: formation – stars: protostars

T
EACB
1. jcgIntroduction heMore than half of low-mass young stars are members of4( )multiple systems, and multiple star formation is considered to

be a major mode of low-mass star formation (Reipurth et al.
2014). Recent high-resolution observations taken with the
Atacama Large Millimeter/Submillimeter Array (ALMA) haverevealed the early phases of low-mass binary and multiple starformation (e.g., Dutrey et al. 2014; Takakuwa et al. 2014;
Tokuda et al. 2014; Tobin et al. 2016). In order to comparethesehigh-resolution observations with numerical simulations,for the ﬁducial model with (q , j inf, c)=(0.2, 1.2, 0.1). The temporal average is taken in the

The streamlines show eddy-like streams aroundL5 points in the gap of the circumbinary disk. Th
are similar to a tadpole orbit, which is one of the cPrice et al. 2018), and 3D grid-based simulations(Fateeva
et ofal.
in therestricted
three-bodyproblem.
Fig ure 1. A snapshot
the simulation
for the ﬁducial
model with The(q , j i n f eddy, c )=(ona logarithmic
scale in thetoz =0plane,in
while
lower pan
2011; Shi et al. 2012; Shi & Krolik 2015). density
Theredistributions
have
also
are smoothly
connected
thosethethespiralarpanels. The squares with the black horizontal and vertical lines depict the AMR
circumbinary
Note levels
that forthere
areL2,twostagnbeen studies on disks surrounding black holebinaries(i.e.,levels aredisk.
comparison.
The
contourthe potential
the L1,and L3Lag
nearetthe
D’Orazio et al. 2013; Gó mez de Castro et al. 2013; Farris
al. L2 and L3 points, at (x , y);(−1.2(0.9,−0.6),
respectively.
witha threshold density (Machida et al.
2014; Miranda et al. 2017; Tang et al. 2017).SFUMATO: accretion
Figure 5 typeshows
the gasﬂow1952;
moreKrumholz
quantitative
2010) and Bondi–Hoyle
accretion(BondiAlthough 2D simulations have the advantageof obtaining
spiralarmsthehave
rotation
velocityfasterhere.
than thet al. 2004).
We adopt
lattera typeof accretion
methodhigh resolutions based on the assumption The
of detailed
a thindisk(Figure of
implementation
particles
given
in sp
velocity
5, theleftsink
panel).
The isgasof theMatsumoto accelerated
et al.thin,(2015a).
particles accretegasfromwithinbyThethesinkgravitational
torquethe oapproximation, circumbinary disks are not geometrically−2a sink radiusof rshowing, which issink=4Δxfast
min=2.34×10
therebyrotation.
as shown in this paper, and 3D simulations
are smaller
morethan the binary separation. The masses
considerably
Along thespiral arms, the radial velocity indicate
appropriate for reproducing such disks.
of the sink particles are ﬁxed in the course of the calculation.
andoutﬂow(Figure5, middle panel). The inner po
Fig ure 3 . Masses of the circumbinary disk (CBD) and the circumstellar disks
simulationsarein the rest frame in this study,
Several preceding 3D simulations (Shi et al.The2012;
Shi arm& performed
spiralexhibits inﬂow, while the outer port
(CSDs) for the primary and secondary as a function of time for the ﬁducial

.0

0,
S

Structure of a Protobinary System: An Asymmetric Circumbinary Disk and Spiral Arms
Matsumoto, Saigo, & Takakuwa

The Astrophysical Journal, 871:36 (17pp), 2019 January 20

1

Tomoaki Matsumoto1,2,3

N

The Astrophysical Journal, 871:36 (17pp), 2019 January 20

4Matsumoto, Saigo,& Takakuwa, Kazuya
Saigo, and Shigehisa Takakuwa5,6

Faculty of Sustainability Studies, Hosei University, Fujimi, Chiyoda-ku, Tokyo 102-8160, Japan; matsu@hosei.ac.jp
2
Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA
3
RIKEN Center for Computational Science (R-CCS), 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan
4
Chile Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan
6
5
Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065, Japan
6
Academia Sinica Institute of Astronomy and Astrophysics, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
Received 2018 October 18; revised 2018 November 28; accepted 2018 December 4; published 2019 January 21

5

N

N

9

Abstract

We investigate the gas structures around young binary stars using three-dimensional numerical simulations. Eachmodel exhibits circumstellar disks, spiral arms, and a circumbinary disk with an inner gap or cavity. The
circumbinary disk has an asymmetric pattern rotating at an angular velocity of approximately one-fourth of thevelocity, vj−vkep, where the Keplerian velocity is deﬁned by
Figure 9. Temporal average of thecircumbinary
disk
in the periodof 80–100
revolutionsof the binary for the model with
(q ,S9jinf, c)=(0.2,
1.2, 0.1).
temporalp
9
binaryorbit
of 756
themoderate-temperaturemodels.
BecauseofThethisasymmetry, the circumbinary disk has a density
ight panel) for M
the average
ﬁducialismodel
with
(q
,
j
,
c)=(0.2,
1.2,
0.1).
calculated in theinfrotating frame with the angular velocity of 0.266Ωå, which is the mean pattern speed of the asymmetry mode of the circumbinary disk ina rotatingwiththe sameangularrevolutions.
velocity
asThethecolor
binary.
Allbump
Theframe
Astrophysical871:36 (17pp),
2019
January
Saigo,& Takakuwa
the periodofJournal,
80–100scalesdepict20the andcolumnadensity
distribution
and thecontinue
density distributions
inMatsumoto,the z=0(middlepanel)
vortex,both(leftofpanel)which
to exist
untilplanetheendof our calculation. The density bump and vortex
frame. The stage andplottedarepanel).
the samethose in indicate the density-weighted velocity distribution (left panel) and the velocity distributions in the z=0 planeand region
the y=0
planehere(right
The asstreamlines
enhanced
momentum,promoted(middle panel) and the y=0 plane (right panel). In are
all theattributed
panels, the frametois rotated
so that theangularmaximal surface
density lies on thewhich
x-axis. Theisangularvelocity of by
the the gravitational torque of the stars. In a hotframe is different from those of the binary, and two
circumstellar
are showna central disk and rotatesa ring in theconsiderablyedge-on views.
model(c disks2.0),
theasasymmetry
more slowly than in the moderate-temperature models. The
cold models (c  0.02) exhibit eccentric circumbinary disks, the precession of which is approximated by a secularwith jinf=2.0, and the circumsecondary disk is more massive
decrease in Γ is mainly attributed to an increase in M˙ 1, as
motionofal.theballisticthan
particles.
The asymmetry
in the circumbinary disk does not depend on the mass ratio, but it
observed in the ﬁducial model (Figure 6).
Young et(2015)
the circumprimarydisk.
reported a model with hot gas (c = 0.25) becomes
showing variability
in as theThespeciﬁc
asymmetryof the momentum
circumbinary disk
is qualitatively
less clear
angularof theinfalling envelope increases. The relative accretion rateaccretion rates, the timescale of which wast∼90.
model
different
jinf 1.8.momentum
In these models,ofthere
several mth
onto
the Ourstars
is sensitive
to whenthe angulartheareinfallingenvelope. For envelopes with constant angularwith c=0.2 also exhibits variability mainly in the accretion
modes with considerable amplitudes, and the m=1 mode does
Figurelow
8. Angularvelocity of the m=1 mode, Ωp (top), amplitude of the
momentum,thesecondary
tends
to
have
a
higheraccretionrate
than
the primary, except in very
angularrate of the secondary, and the timescale is longer (t ∼ 100–200)
not have the largest amplitude (see also Figure 17 for the modelm=1 mode, ∣a1∣ ∣a 0∣ (middle), and mean surface density ∣a 0∣ (bottom) as a
momentum cases. Forwith
envelopeswith aanalysis
constant
angularvelocity,∣athe
rate
thanThethered, green, and blue lines are for the values that arethan that of Young et al. (2015).
jinf = 1.8). Fouriershowsthat the amplitudesm∣ primary has a higher accretionfunctionof time.
Ø
756N
Eupper abscissa
oscillatethe largest
modemomentum
with m 1 fallschanges
=2, 4, and 6. The
secondary because gas
with andlowthat
speciﬁcangularalong the polar
directions. measured in the cylindrical shells with RringC
with time.
shows the time in units of the rotation period of the binary.
4.7. Dependence on Angular Momentum of Infalling Gas
M – stars: protostars
9
Key words: binaries: general – hydrodynamics – protoplanetary disks – stars: formation
Figure 16 shows representative models with different

4.8. Dependence on Mass Ratio
This structure is observed clearly when we take a temporal
speciﬁc angular momenta for the infalling gas. We observe
average of the disk (Figure 10, right panel). The center of the
Figure 18 compares models with different mass ratios q . The
that the models with jinf - 0.8do not have circumbinary disks,models with q =0 and 1 correspond to a single star
andetanal. 2018), and 3D grid-based simulations
vortex (black (Fateeva
streamlines)
nearly coincides with the density
while the models with jinf 0.9 have circumbinary disks. This
1. IntroductionPriceet al.
equal-mass binary, respectively. In the binary cases (q ¹ 0),
bump (red contours). It is located at the corotation radius withis in agreement with the results of the SPH simulations by Bate
2011; Shi et al. 2012; Shi & Krolikthe2015).
have
also
the structures
the circumbinarydisks are
& Bonnell (1997). They implicitly
the halfconditionforangularTherevelocityof theasymmetry Wp for the Keplerian
Moreusedthanof low-mass
young ofstars
are members
ofnot very sensitive tothe mass ratio q . All the binary models examinedbeen
here show
studies on disks surrounding blackhole
binaries(i.e.,
circumbinary disk formation, in which the centrifugal radius ofrotation(see
whitecircle).
Wealso ﬁnd that the peak of themultiplesystems,
andmultiplestarformationisconsideredto2asymmetry in their circumbinary disks, with almost
the same et al. 2013; Gómez de Castro(GMtot ), is larger than the orbital radius of
the gas, Rcent = jinf
D’Orazio
et
al.
2013;
Farrisetal.
speciﬁcangularmomentumj (blue contours) is located inamplitude
and angular(Reipurthvelocity Ωp irrespectiveof q (see also
be+ aq ),major
star formation
et al.
yieldingmode of low-mass
the secondary star, a2=D/(1almostthe same orientation as the density peak and the center
2014; Miranda et al. 2017; Tang et al.
2017).
Table 1).
2014).1 2Recent high-resolution
observations
taken
with
the
of
the
vortexto the origin, and conﬁrm that this
For
all
the
binarymodels,theradialextentof
each
Although 2D simulations have the advantagewithof respectobtaining⎛ GMtot D ⎞conﬁguration is maintained in the other periods, i.e., the 30–50
Array(ALMA)
circumbinary disk
oscillates
as seenhavein the ﬁducial
model.
jinf . ⎜ Atacama(3)⎟ . Large Millimeter/Submillimeterhigh resolutions based on the assumptionof a thinperiods.
disk This indicates that the density⎝ 1revealed+q⎠
and 50–70 revolutions
The radial extent
is moreto thestage than to the mass
the early phases of low-mass
binaryandsensitive
multiplestarapproximation,
circumbinary
disks
are
not
geometricallythin,bump and vortex are caused by the locally enhanced angularratio because of this oscillation.
formation(e.g.,
2014;
Takakuwa et al. 2014;
For q =0.2, Equation (3) gives
jinf 0.91,
which Dutrey
is in goodet al. The
model with q =0 corresponds to the case asof a shown
singlewhichareresultsin this paper, and 3Dmomentum,
simulations
morefrom the gravitational torque.
Tokuda et al. 2014; Tobin etstar
al.(the2016).
Inpanelorder
to compare
leftmostof Figure18). The disk has
a narrow
agreement with our simulations.
Further discussion of the asymmetry is made in Section 5.1.
appropriate
for reproducing such disks.
ring shape
almost constantspeciﬁc angular momentum
The models with circumbinarydisks ( jinf 0.9) showthese high-resolution
observations
withwith
numerical
simulations,jinf. The central star does not cause gravitational torque,Several
and the preceding 3D simulations (Shi et al. 2012; Shi &M˙ 2 > M˙ 1 throughout the evolution. On the other hand, the

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THE ZEEMAN EFFECT IN THE 44 GHz
pr o cedu r e des cr i b ed i n S ecti o n 3 .

m a g en ta , b l u e, a n d g r e
o f F i g u r e 2 ; th a t i s , i t
o f th e G a u s s i a n co m po
are shown by green and blue profiles in the upperCLASS I METHANOL (CH3 OH) MASER LINE TOWARD DR21W
w h er e ea ch o f th e th r eeanel of Figure 4, and their composite profile is shown
1
2
E. Momj i an and A . P . S arma
ogether with the observed Stokes I profile of maser Ba ppr o pr i a tel y b y th e fi t
Todeterminethemagnetic
field
strength,wefittedan the upper panel in Figure 5. The two fitted comth e ca pti o n to F i g u r e 2 .
1Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA, emomjian@nrao.edu
onents are quite similar in intensity, withNational
the stronger

ci a ted des cr i pti o n ).

numerical frequency derivative of the Stokes I spectrum! LkL
V‒ Stokes V spectrum. Thisc is now standard proceto the
! 2A=
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L
LkL
l o
c
Our procedure to fidure, and has been described in detail in many sources;! )) 56F mLs
0
( B
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3
<
D
using equation (1) wa
see, e.g., Momjian & Sarma (2017). The key point is
ABSTRACT
MAN in AIP S (Greisthat
the
StokesV
profileisfitsimultaneouslytothe5!detection
0
1Zeeman e↵ect in thel44 GHz Classop
We
reporttheoftheI methanol
towardtheis that it allow
this
task
4
derivativeof the I profile anda scaled
replicaof the maser
I . line
!
b
op
.
29
29
29
H
29
high mass star forming region DR21W. There are two prominent maser spots
in DR21W inat theI toends
be fitted simulta
4 1982;
Momj i an
3
profileitselfvia
theequation(Troland&Heiles!
”LVa=of a northwest-southeast linear arrangement. For the maser at the northwestern end (maser A), we fit
component fitted for a
2> F1
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F
Sault
et ACal. 1990):
three Gaussian!
components.
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the strongest
we obtain b
a significant Zeeman detection,
magnetic field value.
1with zBlos = 23.4 ± 3.2 Hz. If we use z = 0.920 Hz mG 1 for the F = 5 ! 4 hyperfine transition,b d I
0lower panel
this corresponds to a magnetic field |BlosV| ==25.4
mG;
Blos would be higher if a (1)di↵erent hyperfine
was of Figurea I +2 d rule⌫ out some hyperfines, since fields-1
curve
in the upper pan
responsible for the 44 GHz maser, but our results also
in these-2
regions cannot The
be hundreds
ofreplica
mG. ClassI methanol
masers isformin outflows
where shocks
compresstedvalue of b , and likescaledlof theI spectrum
includedin the!
op-3
magnetic fields in proportion to gas density. Designating our detected Blos = 25 mG as themagnetic
respectively.
The sum
fit F1
toACaccount forsmall0calibration
errors!
cR
sm( in RCP versus
3
2
1
0
-1
-2
-3
-4
Relative Right Ascension
field(arcsec)
in the post-shock gas, we find that Blos in the pre-shock gas should be 0.1–0.8
mG.
Althoughcurve within the lower pan!
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Fthis. Hpaper,, 6F
LCP ; forZeeman
all results
reported
a .are10in 3good. agreement
there
are
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thermal-line
detections
DR21W,
such
valuesigure 1 . V el o ci ty - i n teg r a ted i m a g e o f th e 4 4 G H z C l a s sH
B5information
G1CN. about
B5
the black
AC G thermal
C H O H m a se r s i n D R 2 1W , s h o Zeeman
w i n g th e m a s measurements
er s A a n d The
B
magnetic
is containedin gas histogram-li
in thelinetheof 0.36
and 0.71 fieldmG about
3.50 away in DR21(OH)w a r d w h i ch w e r epo r t th e detecti o n o f th e Z eem a n e↵ect.
thelower panel of thate v el o ci ty r a n g e i s
0 . 3 to3 . 0 ofk m comparables. C o n to u r s a r e density
a int
the pre-shockgas density
DR21W.
Comparison
magnetic, derived
the tootherfit parameter,b , inwhich
is equal
to zBoflosour
1, 2 , 4 , 8 , 16 , 3 2 , 6 4 ) ⇥ 0 . 4 2 J y b ea mk m s
. T h e po s i ti o n
to the kinetic
energydensityin DR21W
indicates
thatmoleculemagnetic fields likely
play wea require tha
tection,, 0 ) i n th e fi g u r e co r r es po n ds to ↵=energy
2 0 3 85 density
4 . 9 , = + 4 2 wherez is theZeemansplittingfactorfor the
2 0 (J 2 0 0 0 ). A h i g h er a n g u l a significant
r r es o l u ti o n i m a g rolee w i th ina
LSR Velocity (km/s)
shaping the dynamics of the post-shocked gas in DR21W.
error
in the fit be at thetter v i ew o f th e w ea k er m a s er s l o ca ted b etw een A a n d beingBobserved, and Blos is the line of sight magnetic
3

0

00

Maser An b efo u n din K o g a n &90

Maser A

I=(RCP+LCP)/2

80
70

Component 1

60
50

Maser B

Intensity (Jy/beam)

1 [astro-ph.GA] 24 Dec 2018

Relative Declination (arcsec)

2 Physics
ne being about 1.4 times the other.
Their velocities
atDepartment,
DePaul University, 2219 N. Kenmore Ave., Chicago, IL 60614, USA; asarma@depaul.edu
ne center are separated by only 0.17 km s 1 , and both
omponents are very narrow, with velocity linewidths(Accepted 2018 December 22 )omparable to the fitted component in maser A thatas the least velocity width.

40

Component 3

30

Component 2

20
10
0

0.04

V=(RCP-LCP)/2

0.02
0

-0.02

1

1

1

h

S l y s h (19 9 8 ).

m

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s

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-3.5

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-2.5

-2.0

-1.5

-1.0

-0.5

0.0

in the thermal
CN line. They
measuredthesefields Thus,
in
OH in
maser
line of milliGausstion of the 44
CH3fieldtral profilesinSiO
masers.
if thethe GHzmagnetic
the tens
are expected53
gas
particledensity
is suchthe maserbrightness
tem-THE) ⇠ 1.7⇥10
cmbe entirely, similardue
to to the Ze
al. 2018), Tb inZEEMANEFFECT
IN THEn(H
44 GHz2weredeemedtoregions.
Given that
the F
= 5of!
4 hyperfine
5 DR21W
3
CLASS I For
METHANOL(CH
LINE
TOWARD
3 OH) MASER
cm
we’ larger
ve usedd ⌦ is the yields
maserabeaming
angle.
thepre-shockdensity
of
3.3
⇥
10
k
would obtain athat
muchvalue for thlower limit for Blos , it is also worth asking if
1
2
in ourabove for
DR21W.
Both
mag-This seems
9.488 MHz methanol
maser
in whichweotherE. hyperfines
Momj
i ancalculations
andP . S armatracedby these
SiOthese
masers.
we
can ruleout someof theforA . which
44 GHz Methanol Maser Zeeman Effect toward DR21W
5
netic
field values
detected methanol
in USA,the thermalline about since field
Zeeman e↵ect
in DR21W,
findcalculated
that Observatory,
1 etNational
Radio Astronomy
P.O. Box O,
Socorro, NM 87801,
emomjian@nrao.edu
maserCNobservations,
Lankhaar
al. we(2018)the
Zeemansplitting0! (2009),78 University,
3H NN 3.5xkl60614,GE
R . the predictedV
2 Physics
K, and based factors,
on Slysh&
Kalenskii
away
in DR21(OH)
well
with
Department,
DePaul2219
N.
KenmoreAve.,
Chicago,compareILUSA;
asarma@depaul.edu
tected
in
maser
A
are
expected in such rz. For example,
if
the
F
=
7
!
6
hyperfine
were
!
k
k6
1
+
V
⌦ ' 0.03. responsible
Using theseforvalues,
find
range
0.1-0.8
mG for theline-of-sight
pre-shockfield
asdescribed
inV
lemmings
et al. (2011),
maser,ofour
detectedthe 44 we
GHz
CH3 OH(Accepted2018 December 22 )31
n (2) that Rfield⇡ in10maser
in DR21W basedon our observations.
s A. would
Therefore,of symmetrymG,! 2lbe 60 times higher than 25 )h axis+ I7i
I7V for the molecular quantFinally,
we atcandetectedvalue for
Blos in if the mlying that it oris unlikely
thata !rotation
ABSTRACT
cause circularpolarization
1500 mG.
Fieldsas large
this areunlikely
theusek ofaslkk ouralsoVtothemagnetic
energydensityin than g⌦
mmetry for thedensities
molecularstatesis+therate
Rbecomeslargerin quantum
regions
where
GHz
CHs
masersaregClassWe report
the !
detection
Zeemane↵ectthecompare
44 GHzI emission
methanollinep
toward1 %(of44
8
I7DR21Wcrm
l,+
I7h maser
Vthe
3 OH intheTherepost-shocked
regionstothekinetic
bserved splitting
responsible
the2016).
shapehigh(Leurini
mass starfor
regionIfDR21W.
are two
spots
into
DR21W
at thedensity.
ends
!al.
lprominenth maserV
shiftduetheenergy
Zeemane↵ect. In our dformedetforming
we arrange
the
eight
hy2
of a lines
northwest-southeast
linear
For the maser
at thenorthwestern(maserA),
wefit
The magnetic
energydensity
is given
B /8⇡,
V profile. Moreover,suchaofrotation
would
where
g⌦ ⇡
25 ends 1by. The
stimulated
emission
perfinethe 44 GHz
CHarrangement.
3 OH maser transition in
2
2
three
Gaussiancomponents.
In
thestrongest
component,
weobtainasignificant
Zeemandetection,k
V =four
3Blos(Crutcher1999).
For Blos = 25 mG fromnsity-dependent
polarization,
but value
the comB
decreasing
absolute
of
z,
the
first
give
plauby1± 3.2 Hz. If
we use z = 0.920 Hz mG
for theF = 5 ! 4 hyperfine transition,with zBlos = 23.4
!
"
k
V
our
observations,themagnetic
energy density is thenigher intensity
in
maser
B
shows
a
smaller
LSR
Velocity(km/s)
LSR
Velocity(km/s)
siblethisvaluesof thetofield(tens fieldof mG)
for
maser
A;
the
A k Tb ⌦correspondsamagnetic
|B
|
=
25.4
mG;
B
would
be
higherifal(di↵erent hyperfine
was
los
los
5
3
!
k
k
"
:
<h
V
R
'
erg
cmout.some
If B
due into thesea difthan that detected
ino g maserA.
los is larger
5. mG
S maser,
to k es Iand(u p butp er 7.5
p a n ourel — ⇥
bl a results
ck 10
h on
i s t o g rathe
ml i k erealml i rulen e)⇠Figure120
bordergure 4. S to k es I (u p p ernext
p a n el — responsiblebltwo
a ck h i s t yieldra m- l i k fore|B
l i n e)the| 44GHz
also
hyperfines,
since fields
los
4⇡h ⌫
!
z
n
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(+
7l
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el
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o
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hundreds
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form in outflows
where shocks compress
to w a r dlastththee m ofa twos ermG.
i n D give
R Class
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etransition
possible,thees Ito w CHa r d th 3e OH
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ed
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r
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r
een
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etas al.
2011),
wheremagnetic
fieldsinproportiontogas
density.
Designating
ourdetected
=
25
mG
the
magnetic
epo regions
likelyamplifythemagnetic
field
GHz
CH
OH
maser,
themagnetic
energydensity
will
los
3
b
l
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e
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a
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s
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en
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n
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i
g
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r
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(a
n
d
l
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s
ted
i
n
and can be ruled out. Sincen en ts th a t w e fi ttedandto th e 1500
S to k es I prmGo fi l e (corespectively,
m po T a b l egas,
2 ) th a wet w e findfi tted tothat
th e S B
to k es I inl e. T pre-shockh e r edts 1 a n d 2 f o r m a s er B i n T a b fieldl e 2 , r esin
pectithev el y ).post-shockT h eis thebeEinsteincoefficient
gas should
0.1–0.8 mG.
Although
C IFforD theDHCF
los pr o fi the
toa n thecu r v e s u per po s ed o n th e S tobe
k es V evenpr o fi l e i n larger.
th e l o w er pa n el Next, the kinetic energy density, ineen
d b l u e gas
cu r v es i density,n th e l o w er pa n so
el a r ethat
th e der i v a ti v es
arepa nno
suchvaluesin good agreement withi s th e s u m Zeemano f th e tw o codetections
l o r ed cu r v es s h o towardw n i n th e l o w DR21W,
er pa n el
th e co r r es po n di n g co l o r ed cu r v es there
i n th e u pper
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cluding
thecontributionofbothand turbulent!
LKNOl3HNNxao f F i g u r e 4 ; th a t i s , i t i s th e s u m o f th e s ca l ed der i v a ti v es
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2
i
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given
mn of. ouri v a tigasv e pr o density
fi l es h a iss b eenins caDR21W.
l ed by (3/2)= of comparable density(3)
to thepre-shockComparison
magnetic
a
ppr
o
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i
a
tel
y
b
y
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e
fi
tted
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a
l
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e
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s
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cr
i
b
ed
i
n
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re4=8=k3<
i!
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Bboth
nenergyted. Certainly,
components
p r e the fitted
p Gaussian
r e
mass
m
2.8
mp , where
mp isVthe protonmass,
densityto thedensityin( DR21W
indicatesthat magnetic
fieldslikely playath e kinetico n to F energy
i g u r e 4 . ther maser B show a formally significant detection,
with
+
+
)
! 5role5GFdynamics%+ andC Dpost-shockedBI#
zof 2.8 also
ʼ k
‒forV
I D in-%+significant
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in DR21W.
thenumerical
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component (compoHaystack 37 m telescope with a velocity resolution ofndpost-shockedandprent 1 prein Tablerefer2), and b to
= the
10.5 ± 3.1
Hz for the other
1/2
0.014 km s .
Maser B

1 [astro-ph.GA] 24 Dec 2018

120

120

I=(RCP+LCP)/2

80

Component 1

Component 2

60

40
20

0
0.06
0.04

V=(RCP-LCP)/2

Intensity (Jy/beam)

Intensity (Jy/beam)

60

40
20

0
0.06
0.04

0

0

-0.02

-0.02

-0.04

-0.04

-4.0

V=(RCP-LCP)/2

0.02

0.02

-0.06
-4.5

I=(RCP+LCP)/2

100

100
80

Maser B

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

-0.06
-4.5

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

-1.0

los

los

1

-0.5

0.0

6

Centre for Astrophysics and Planetary Science, University of Kent, Canterbury CT2 7NH, UK
School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
Characterising the high-mass star forming filament
8
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748, Garching bei München, Germany
9
G351.776–0.527
andINAF – Osservatorio Astrofisico
di Arcetri, L.go E.with
Fermi Herschel
5, 50125 Firenze,
ItalyAPEX dust
10
Excellence Cluster Universe, Boltzmannstr. 2, 85748, Garching bei München, Germany? , ??
7

continuum and gas observations

Received 11 S.
June
2018 / Accepted 20 November 2018
Leurini1 , E. Schisano2,3 , T. Pillai4,5 , A. Giannetti3,4 , J. Urquhart6,4 , T. Csengeri4 , S. Casu1 , M. Cunningham7 ,D. Elia2 , P. A. Jones7 , C. König4 , S. Molinari2 , T. Stanke8 , L. Testi8,9,10 , F. Wyrowski4 , and K. M. Menten4

ABSTRACT

1

INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italye-mail: silvia.leurini@inaf.it
G351.776-0.5272 Istitutois among
the most
massive,closest,andfilaments
theRoma,inner
Galactic plane and therefore it is an idealdi Astrofisica
e Planetologia
Spaziali– INAF,
Viayoungest
Fosso del Cavaliere
100, in
00133
Italy
3
INAF
–
IstitutodiRadioastronomia,
andItalian
ALMA
Regional
Centre,Via
P.
Gobetti
101,
40129,
laboratory to study
the kinematics of dense gas and mass replenishment on a large scale. Bologna,
In thisItaly
paper, we present far-infrared and
418
Max-Planck-Institut
fürRadioastronomie,
Auf
dem
Hügel
69,
53121
Bonn,
Germanysubmillimetre 5wavelength
continuum
observations
combinedwith
spectroscopic
C
O
(2–1)
data
of the entire region to study its
Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave, Boston, MA 02215, USA
6temperature, mass
distribution,
and
TheUniversity
structure
is composedof 7NH,a mainCentrefor Astrophysics
andkinematics.
Planetary Science,of Kent,
Canterbury CT2
UK elongated region with an aspect ratio of ⇠23,
7
Schoolwith
of Physics,
Universityofof NewSouth Wales,
Sydney, NSW
2052,main
Australia
which is associatedanetworkfilamentary
structures.
Thefilament
has a remarkably constant width of 0.2 pc. The
8EuropeanSouthern
Observatory,Karl-Schwarzschild-Str.
2,85748,
Garchingbei
München,Germany
total mass of the
network (including the main filament) is 2600 M , while we estimate
a mass of ⇠2000 M for the main structure.
9
INAF – Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy
Therefore, the10networka largeBoltzmannstr.
reservoir 2,of85748,
gas anddustbeithat
couldGermany
still be accreted onto the main structure. From the analysis
Excellenceharbours
Cluster Universe,
Garching
München,of the gas kinematics, we detect two velocity components in the northern part of the main filament. The data also reveal velocity
June 2018 / Accepted 20 November 2018
oscillations inReceived
C18 O 11along
the spine in the main filament and in at least one of the branches. Considering the region as a single
structure, we find that it is globally close to virial equilibrium indicating that the entire structure is approximately in a stable state.
ABSTRACT

Key words. ISM: kinematics and dynamics – ISM: clouds – stars: formation

G351.776-0.527 is among the most massive, closest, and youngest filaments in the inner Galactic plane and therefore it is an ideal
laboratory to study the kinematics of dense gas and mass replenishment on a large scale. In this paper, we present far-infrared andsubmillimetre wavelength continuum observations combined with spectroscopic C18 O (2–1) data of the entire region to study its
a mainregionwith an aspect ratioof ⇠23,
thatof its
gaselongatedcontent
is continuously
replenished
via sub-filaments.
1. Introductiontemperature, mass distribution, and kinematics. The structure is composed
which is associated with a network of filamentary structures. The main filament has a remarkably constant width of 0.2 pc. The
In the case of intermediate-mass clouds, Kirk et al. (2013) identotal mass of the network (including the main filament) is 2600 M , while we estimate a mass of ⇠2000 M for the main structure.
In recent years increasing
evidencehas
beencollectedthathightified
motions
the filament
along defined structures andTherefore, the network harbours a large reservoir of gas and dust that could
still begas
accreted
onto theonto
main structure.
From the analysisof thegas kinematics,
we detect
twoformation
velocity components
in the northern
part
of
the
main
filament.
The
data
also
revealvelocity
mass star formation
is tightly
linkedtotheofmassivefrom the filament onto the central cluster in the Serpens region.
oscillations in C18 O along the spine in the main filament and in at least one of the branches. Considering the region as a single
clumps and massive
clusters.
Observations
inmolecular
tracRecently,
Motte isetapproximatelyal. (2018)in proposed
structure, we find that it is globally close to virial equilibrium indicating thatthe entire structure
a stable state. an evolutionary scenario

2

8
1 0

5

O

0

.8

5
8

6

3

M

G
7
c
M G0 c
8
8
O

C1

p

0

2

8
0

M

G

8

0

ers (e.g. Schneider et al. 2010; Peretto et al. 2013, 2014; Hacar in which global collapse of massive clouds and hubs generates
Key words. ISM: kinematics and dynamics – ISM: clouds – stars: formation
et al. 2017) have revealed global collapse in several massive gas flow streams. In this picture, such flows would efficiently
clouds and havesuggested that clumps build up their mass as thatconcentrateon smallscales,helping to increase the mass
its gas content ismatter
continuously
replenished
via sub-filaments.
1. Introductiona result of the supersonic global collapse of their surrounding In thecaseofintermediate-massclouds,Kirk
etal.
(2013)
of low-mass prestellar seeds present in
the idencloud. With time theseIn recent years increasing evidence has been collected that high- tified gas motions onto the filament along defined structures andcloud. For instance,
Perettoetal.
(2014)
suggestedthatorganeventually
high-mass
protostars.
mass star formation is tightly linked to the formation of massive fromseeds
the filament
onto thebecome
central clusterin the Serpens
region. Numerical simuised velocity gradientsinthefilaments
of
SDC13
are
the
resultclumps and massive clusters. Observations in molecular trac- Recently,
lations
also
supportthis scenario(e.g. Vázquez-Semadeni
et al.
Motte
et al.
(2018) proposedan evolutionary
scenarioers (e.g. Schneider
et al. 2010;
al. 2013, 2014;
Hacar in which global collapse of massive clouds and hubs generatesof large-scale longitudinalcollapse
andPeretto
couldetgenerate
kinematic
2017). Observational evidence of gas streams inflowing on small

0
G
7

2

Sterrewacht Leiden, Huygens Laboratory, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
Institut für Astronomie und Astrophysik, Eberhard Karls Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
4
Evolutionarymodelsof cold and6, low-massplanets:
Center for Space andHabitability, Universityof Bern, Gesellschaftsstrasse
CH-3012, Bern, Switzerland
5
Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
Cooling curves, magnitudes, and detectability
6
Department of Astronomy, University of Michigan, 1085 S. University, Ann Arbor MI 48109, United States
Esther F. Linder1 , Christoph Mordasini1 , Paul Mollière2 , Gabriel-Dominique Marleau3,1 , Matej Malik4 ,Received 16.07.2018 / Accepted 04.12.2018
Sascha P. Quanz5 , Michael R. Meyer63ABSTRACT

1

Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
2
Sterrewacht Leiden, Huygens Laboratory, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
3
Context. Future
instruments
likeund
NIRCamandEberhard
MIRI onJWSTor METIS
at theELTwill be able
to image
exoplanets
Institutfür Astronomie
Astrophysik,
Karls
UniversitätTübingen,
Auf derMorgenstelle
10, 72076
Tübingen,Germanythat are too
4
faint (becauseCenterof a forlowSpacemass,
hence aUniversity
small size
or lowe↵ective temperature)
current
direct imaging instruments. On the
andandHabitability,of Bern,
Gesellschaftsstrasse
6, CH-3012,for
Bern,
Switzerland
5
Institute
Particle Physics
and Astrophysics,
ETH a
Zurich,Wolfgang-Pauli-Strasse
CH-8093and/or
Zurich, cool
Switzerland
theoretical side,
coreforaccretionformationmodels predictsignificant
population of 27,
low-massplanets at orbital distances
6of Astronomy, University of Michigan, 1085 S. University, Ann Arbor MI 48109, United Statesof ⇠ 10–100 Departmentau.

1812.02027v1 [astro-ph.EP] 5 Dec 2018

iv:1812.02027v1 [astro-ph.EP] 5 Dec 20183

Aims. Evolutionarymodels /predicting
the planetary intrinsic luminosity as a function of time have traditionally concentrated on
Received 16.07.2018
Accepted 04.12.2018
gas-dominated giant planets. We extend these cooling curves to Saturnian and Neptunian planets.
Methods. We simulate the cooling of isolated core-dominatedABSTRACT
and gas giant planets with masses of 5 M to 2 MX . The planets consistof a core made of iron, silicates, and ices, surrounded by a H/He envelope, similar to the ice giants in the solar system. The luminosity
Context. Future instruments like NIRCam and MIRI on JWST or METIS at the ELT will be able to image exoplanets that are too
includes thefaintcontribution
anda small
contractionof thecoretemperature)and of thefor
H/He
envelope,
as wellas radiogenic(because of froma low themass,coolingand hence
size or lowe↵ectivecurrent
direct imaging
instruments.
On the decay. For
the atmosphere
we
use
grey,
AMES-Cond,
petitCODE,andHELIOSmodels.
We
considersolar
andnon-solar
metallicities
theoretical side, core accretion formation models predict a significant population of low-mass and/or cool planets at orbital distances as well as
cloud-free and
The most important initial conditions, namely the core-to-envelope ratio and the initial (i.e., postof ⇠cloudy
10–100 atmospheres.
au.
Aims. Evolutionarymodelsthe planetary
intrinsic luminosity
as athefunctionof time havetraditionally concentrated onformation) luminosity
are taken
frompredicting
planet formation
simulations
based oncore accretion
paradigm.
gas-dominatedgiant
planets.
We
extendthese
cooling
curvesto
SaturnianandNeptunianplanets.
Results. We first compare our cooling curves for Uranus, Neptune, Jupiter, Saturn, GJ 436b, and a 5 M planet with a 1% H/He
Methods. We simulate the cooling of isolated core-dominated and gas giant planets with masses of 5 M to 2 MX . The planets consist
envelope withevolutionarymodels.
We thenpresent
temporalof iceplanets
between
5 M and 2 MX inof aothercore madeof iron, silicates,
and ices,surroundedby atheH/Heenvelope,evolution
similar to thegiants within the masses
solar system.
The luminosity
terms of theirluminosity,e↵ectivetemperature,radius,and entropy.
Weanddiscussof asdi↵erent
post formation
entropies. For
includesthe contribution
fromthe cooling andcontractionof the coreof the the
H/Heimpact
envelope,well as radiogenic
decay. For
atmosphere weuse grey,
AMES-Cond,
petitCODE,
and HELIOS
considersolar
and non-solar
metallicities
as well aswavelength
the di↵erenttheatmospheretypes
and initialconditions
magnitudes
in models.
variousWe
filterbands
between
0.9 and
30 micrometercloud-free and cloudy atmospheres. The most important initial conditions, namely the core-to-envelope ratio and the initial (i.e., post
are provided.
formation)
are fluxes
taken fromformation
simulations
based on theaccretion paradigm.
Conclusions.
Using luminosity
black body
andplanet
non-grey
spectra,we estimate
thecoredetectabilityof such planets with JWST. It is foundResults. We first compare our cooling curves for Uranus, Neptune, Jupiter, Saturn, GJ 436b, and a 5 M planet with a 1% H/He
that a 20 (100)M
planetcanbedetected
with
JWST
in
the
background
limit
up
to
an
age
of
aboutbetween
10 (100)
andenvelope with other evolutionary models. We then present the temporal evolution of planets with masses
5 MMyrand with
2 MX NIRCamin
MIRI, respectively.
terms of their luminosity, e↵ective temperature, radius, and entropy. We discuss the impact of di↵erent post formation entropies. For
the di↵erent atmosphere types and initial conditions magnitudes in various filter bands between 0.9 and 30 micrometer wavelength

Key words.arePlanetsand satellites: physical evolution – atmospheres – detection
provided.

u

e

N
H

1

Conclusions. Using black body fluxes and non-grey spectra, we estimate the detectability of such planets with JWST. It is foundthat a 20 (100) M planet can be detected with JWST in the background limit up to an age of about 10 (100) Myr with NIRCam and
MIRI, respectively.

Ma

C

3

3

3

0
.I

R

1. Introduction
lutionhistory of the planets. Finally, Jin & Mordasini (2017)– detection
N Key words. Planets and satellites: physical evolution – atmospheres93
3 photoevaporation
3 a certain
3Iplanetary compostudied if through
During the last few years, the Kepler satellite has detected nu- sition is revealed.
1 exoplanets
2/ of which m, /,merous
1. Introduction many are in the sub-Neptunian or lution history of⨁the planets. Finally, Jin & Mordasini (2017)super-Earth mass range (e.g., Batalha et al. 2012; Burke et al. studied
In ifthethroughliterature,
evolutionary
calculations
for gas giants arephotoevaporationa certain
planetary compoDuring
the
last
few
years,
theKeplersatellite
has
detected
nu2014; Fressin et al. 2013; Petigura et al. 2013). Di↵erent from sition
is revealed.
abundant(e.g., Burrows et al. 1997; Bara↵e et al. 2003; Podolak
merous exoplanets of which many are in the sub-Neptunian or3

4

Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
National Astronomical Observatory of Japan, Subaru Telescope, National Institutes of Natural Sciences, Hilo, HI 96720, USA
ALMA 5Detection
ofScience
Extendedin the MD,
HD21218,
32297
Space Telescope
Institute, Millimeter
3700 San MartinHalos
Drive, Baltimore,
USAand6
Exoplanets and Stellar Astrophysics
Lab,
NASA
GoddardSpace
FlightCenter,Greenbelt,
MD
20771, USA
HD 61005 Debris Disks
7
Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
1,8 5; revised 2018 October1 23; accepted 2018 October
4
2018 July
26;J.published
December
MeredithReceived
A. MacGregor, Alycia J. Weinberger , A. Meredith Hughes2, D.
Wilner3 2018
, Thayne
Currie13
,
5
1
2
6
7
John H. Debes , Jessica K. Donaldson , Seth Redﬁeld , Aki Roberge , and Glenn Schneider
1

Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road NW, Washington, DC 20015, USA
2
Abstract
Department of Astronomy, Wesleyan University, Van Vleck
Observatory, 96 Foss Hill Drive, Middletown, CT 06457, USA
3
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
We present4 National
Atacama
LargeObservatory
Millimeter/submillimeter
Array Institutes(ALMA)
1.3Sciences,
mm (230
GHz)of theAstronomicalof Japan, Subaru Telescope, Nationalof Natural
Hilo, HI
96720, observations
USA
5
Space
Telescope
Science
Institute,
3700
San
MartinDrive,
Baltimore,MD,
21218,
USA
HD32297 and HD61005
debris disks, two of the most iconic debris disks because of their dramatic swept-back6
Exoplanets and Stellar Astrophysics Lab, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
wings seen in scatteredlight
images. These observations achieve sensitivities of 14 and 13μJybeam−1 for
7
Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
Received 2018 July
5; revised 2018 andOctoberprovide
23; accepted2018highest
October 26;
published 2018images
December of
13 these two systems at
HD32297 and HD61005,
respectively,theresolution

millimeter wavelengths to date. By adopting a Markov Chain Monte Carlo modeling approach, we determine thatboth disks are best described by a two-componentAbstract
model consisting of a broad (ΔR/R>0.4) planetesimal belt
We
present
Atacama
Large
Millimeter/submillimeter
Array(ALMA)
1.3 mm (230
observationsof disk.
the The innerwith a rising surface density gradient and a steeply fallingouterhalo aligned
withGHz)the scatteredlight
HD32297
andHD61005
debrisdisks,
two
of
the
most
iconicdebrisdisks
becauseof
theirdramatic
swept-backand outer edges of the planetesimal belt are located at 78.5±8.1au and 122±3au for−1HD32297, andwings seen in scattered light images. These observations achieve sensitivities of 14 and 13μJybeam for
41.9±0.9auandfor HD61005.
The thehalos
extendto 440±32au
and 188±8au,HD32297
and67.0±0.5auHD61005, respectively,
and provide
highestresolution
images of these
two systems atrespectively.
12
We alsomillimeter
detect wavelengths
CO J=2–1
from HD32297
withthe dust
continuum.
to date.gas
By emission
adopting a Markov
Chain Monte co-located
Carlo modelingapproach,
we determinethat These new
ALMAbothimagesobservational
evidence thatmodel
larger,millimeter-sizedgrains may also
populate
disksprovide
are best describedby a two-component
consistingof a broad (ΔR/R>0.4)
planetesimalbeltthe extended
a rising
gradientthought
and a steeply
fallingbeouter
halo aligned
the scattered
light disk.
The inner
halos ofwith
thesetwosurface
disksdensity
previously
to only
composedof withsmall,
micron-sizedgrains.
We discuss the
and
outer
edges
of
the
planetesimalbelt
arelocatedat78.5±8.1auand
122±3auforHD32297,
implications of these results for potential shaping and sculpting mechanisms of asymmetric debrisanddisks.

,01,41.9±0.9au and 67.0±0.5au for HD61005. The halos extend to 440±32au and 188±8au, respectively.
We alsodetect 12CO matter
J=2–1–gas
emissionfrom HD32297
co-locatedwith the –dust
continuum. Thesenew
Key words:
circumstellarstars:
individual(HD 32297,
HD 61005)
submillimeter:planetarysystems
ALMA images provide observational evidence that larger, millimeter-sized grains may also populate the extended
halos of these two disks previously thought to only be composed of small, micron-sized grains. We discuss theimplications of these results for potential shaping and sculpting mechanisms of asymmetric debris disks.

44 M

.
.
7 complicated
A since
7 structure Aa
7 u
in debris disks can be created
Key words: circumstellarstars: individual(HD 32297,
HD 61005)alternative,– submillimeter:planetary systems
Hu matter – DHO
8 through
M 7
CH -2
.
non-planetarymechanisms
including
Debris disks are often seen as a sign of previous successful
stellarﬂybys, interactions
medium (ISM;
A formation
7O in 835reviews
A including
H A6
Awith the interstellar
L 9H7Mplaneta system (see recent
complicatedsincestructureindebrisdisks
canbecreated
1. Introduction
e.g., Artymowicz & Clampin 1997), recent massive collisions
al. 2018;
Wyatt 2018). Planetesimals, larger bodies throughmHughes et Debris
7
non-planetarymechanisms
including(e.g., alternative,
Mazoyer et
al. 2014), or
instabilities
from dust and gas
disks are often seen as a sign of previous successful
1. Introduction

leftover from the planet formation process, collide within thesein a system (see recent reviews including
disks andplanet
grindformation
down into
smaller and smaller dust grains that
Hughes et al. 2018; Wyatt 2018). Planetesimals, larger bodies
are observablevia
scatteredlight orprocess,thermalemission.
It isleftover from the planet formation
collidewithin these
expecteddisksthat andanygrindinterior
planets
shouldwithgrains
this dusty
down
into smaller
andinteract
smaller dustthatareobservablevia
scatteredlightorthermalemission.
It
is amaterial, sculpting it through gravitational perturbations. In
expectedthatanyinterior
planets
shouldinteract
with
this
dusty
few systems, we can link the geometry and location of a dust
sculpting it through gravitational perturbations. In abelt backmaterial,
to known
planets. For example, the presence of afew systems, we can link the geometry and location of a dust
giant planeta warpin the theβ Pictoris
belt wasback inferred
to known fromplanets.
For example,
presence debris
of adisk and later conﬁrmed through direct imaging (Mouillet et al.

stellarﬂybys, interactions
with &
the Kuchnerinterstellar2013).
medium (ISM;interactions(e.g., Lyrae.g., Artymowicz & Clampin 1997), recent massive collisions
Scatteredlight
imaginghas revealed
a populationof edge-on(e.g., Mazoyer
et al.
2014),or instabilities
from dust
and gasdebrisdisks
thatexhibitdramatic
asymmetricstructuresinteractions (e.g., Lyra & Kuchner 2013).
Scatteredlightbowedimaging disk
has revealed
a populationedge-on such as HD
including
midplanes(e.g., of“wings”
debrisdisks
thatexhibitdramatic
asymmetricstructures
32297 and HD 61005) and extensions (e.g., “needles” such as
includingbowed disk
midplanes(e.g., “wings”
such as HD
HD 15115).
To date,the dominantmechanismat work shaping
32297 and HD 61005) and extensions (e.g., “needles” such asthesesystems
remainsthesubjectofdebate.
HD 15115). To date, the dominant mechanism at work shaping The leading
theories
disk leadingmaterial and either
thesesystemsinvolve
remains interactions
the subject ofbetween
debate. The

Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatﬁeld AL10 9AB, UK
5
Kavli Institute for Astronomy and Astrophysics, Peking University, Yiheyuan Lu 5, Haidian Qu, 100871 Beijing, Peoples Republic of China
6
Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
The JCMTNRC
Transient
Survey: An Extraordinary Submillimeter Flare in the T Tauri
7
Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2, Canada
8
BinarySystem JWGiheung-gu
566
School of Space Research, Kyung Hee University,
1732, Deogyeong-Daero,
Yongin-shi, Gyunggi-do 17104, Republic of Korea
9
Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands
1
2
4
1
5
Steve MairsReceived, Bhavana
Lalchand, Geoffrey
Bower3 23;, Jan
Forbrich, Graham 24;
S. Bell, GregoryJ. Herczeg,
2018 August
31; revised
2018 C.
November
accepted2018 November
published2019 January
23
6,7
2
8
9
, Wen-Ping Chen , Jeong-Eun Lee , and Alvaro Hacar
Doug Johnstone1

East Asian Observatory, 660 N. A’ohoku Place, Hilo, HI 96720, USA; s.mairs@eaobservatory.org
Abstract
Graduate Institute of Astronomy, National Central University,
300 Jhongda Road, Zhongli, Taoyuan 32001, Taiwan
3
Academia Sinica Institute of Astronomy and Astrophysics, 645 N A’ohoku Place, Hilo, HI 96720, USA
The4 Centre
binaryT TauriResearch,systemJWof 566
the Orion
Molecular
Cloudunderwent
anLane,energetic,
short-lived
ﬂare
for Astrophysics
SchoolPhysics,inAstronomy
and Mathematics,
University
of Hertfordshire,College
Hatﬁeld AL10
9AB, UK
5
Kavli
Institutefor
Astronomy
andAstrophysics,
PekingUniversity,
YiheyuanLu
5,
HaidianQu,
100871
Beijing,
Peoples
RepublicofChina
observed at submillimeter
wavelengths by the SCUBA-2 instrument on 2016 November 26 (UT). The emission
6
NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada
faded by nearly 50%7 Department
during ofthe
31andminuteintegration.
The Victoria,
simultaneous
sourcePhysics
Astronomy,
University of Victoria,
BC, V8P 5C2,
Canada ﬂuxes averaged over the
8
1
1
SchoolofSpace
Research,
Kyung
Hee
University,
1732,
Deogyeong-Daero,
Giheung-gu
Yongin-shi,
Gyunggi-doof Korea
observation are 500 9 107 mJy beam at 450 μm and 466 47 mJy beam at17104,
850Republic
μm. The
850 μm ﬂux
Leiden Observatory, Leiden University,19P.O. Box-9513,
2300-RA
Leiden,The
Netherlands
1
1
L n 2018= 8November´ 10 23;erg
s 2018Hz November
corresponds to aReceived
radio 2018
luminosity, approximately
oneJanuaryorder23of magnitude brighter
August 31; ofrevisedaccepted
24; published 20192

(in terms of nL n ) than that of a ﬂare of the young star GMR-A, detected in Orion in 2003 at 3mm. The event may
Abstract
be the most luminous known ﬂare associated witha young stellar object and is also the ﬁrst coronal ﬂarediscoveredat submillimeter
wavelengths.
The
spectralindex
between
450 anand
850 μmofα=0.11
The binary
T Tauri system
JW 566 in theOrion
Molecular
Cloudunderwent
energetic,
short-lived
ﬂare is broadly
4K
observed
submillimeteremission.
wavelengths
by brightness
the SCUBA-2temperature
instrument onwas
2016inNovember
26 6(UT).
The
emission´ 10
consistent
with atnonthermal
The
excess of. We interpret this
faded
50% reconnection
during the 31 minuteintegration. charged
The simultaneous
ﬂuxesgyrosynchrotron/synchrotron
averaged over the
event tobe by
a nearlymagneticthat energizedparticlessource
to emitobservation are 500 107 mJy beam-1 at 450 μm and 466 47 mJy beam-1 at 850 μm. The 850 μm ﬂux
radiation.
corresponds to a radio luminosity of L = 8 ´ 1019 erg s-1 Hz-1, approximately one order of magnitude brighternTWL n ) thanof a ﬂare–ofstars:
the youngstar GMR-A,
detectedin Oriongeneralin 2003 –at surveys
3mm. The event may(in termsof njets
Key words:
ISM:
andthatoutﬂows
formation– stars:
variables:
be the most luminous known ﬂare associated with a young stellar object and is also the ﬁrst coronal ﬂarediscovered at submillimeter wavelengths. The spectral index between 450 and 850 μmof α=0.11 is broadly
consistent with nonthermal emission. The brightness temperature was in excess of 6 ´ 10 4 K . We interpret thisformingtostar
activity: Forbrich et al. (2008) reported aevent to1.beIntroductiona magnetic reconnection that energized chargeda particles
emitshowgyrosynchrotron/synchrotron
strong ﬂare at 22GHz toward a very deeply embedded
Young stellarradiation.
objects (YSOs) host a range of high-energy

T K4 S
-6
L
JW
G
O 3 5
C
K J
A stars: formation
J 88G
T BN/KL
T K
02protostargeneralin the– surveys
Orion
region.
In all Mof these cases, B
Key words:
ISM:
jets and outﬂows
phenomena, pointing
towardmagnetic
activity– (e.g.,
Feigelson– stars: variables:
as nonthermal L
radiation.
311999; Benz & Güdel 2010). Of the variability of 8 the radio emission
8K is interpretedU& GK
Montmerle
Giant ﬂares from young stars are important both for
YSOs across the
spectrum, radio
a forming Y
star show
Forbrich U
et al. (2008) reported a
Lelectromagnetic. 1. Introduction
U and X-ray
JMO
Ractivity:munderstanding
magnetic reconnection
as well as for evaluating
variability Young
are most
closely
to magnetic
andstellarobjects related(YSOs) hosta range of activity,
high-energy
indeed YSOs
show
strong,
very
short
lived
ﬂares
in
these
phenomena, pointing toward magnetic activity (e.g., Feigelson
wavelength
ranges. 1999;
X-ray
ﬂares
of 2010).
this nature
have been& MontmerleBenz& GüdelOf the variabilityof
YSOs
acrosstheelectromagnetic
spectrum,
radio
and
X-ray
comparatively well-studied (e.g., Getman et al. 2008a, 2008b),
are most
closely related
to magnetic
activity, radio
andwhereas variability
observationsof greaternumbersof nonthermal
indeed YSOs show strong, very short lived ﬂares in theseﬂares on wavelength
timescales ranges.
of hours
or less
onlynaturerecently
X-ray
ﬂareshaveof thishavebecomebeenpossible comparatively
with sensitivity
improvements,
andthuscomparably
well-studied(e.g., Getman
et al.
2008a,
2008b),
few sources
suchobservations
as these areknown
at thisof time.
So far,whereasof greaternumbers
nonthermal
radiotheon timescalesofof radio
hours orless have only
becomeon
majority ﬂaresof observations
variability
haverecently
been madestrong ﬂare at 22GHz toward a very deeply embedded
the impactof high-energy
photons
disks andprotostarin the Orion
BN/KL region.
In allonof protoplanetarythese cases,(e.g.,
Güdel etradiation.
al. 2014). The X-ray
the atmosphericradio emission isescapeinterpreted
as nonthermal
Giantﬂares fromfrom ﬂares,
young producedstars are importantemissionby hotterboth
gasforthan quiescent
understanding
magnetic
reconnection
as
well
as
for
evaluating
X-ray emission, emits energetic photons that penetrate deep
the impact of high-energy photons on protoplanetary disks andinto the disk
et al.
therebyaffecting midplaneatmosphericescape(Glassgold(e.g., Güdel
et 2004),al. 2014).
The X-rayionizationand chemistry(e.g.,
Rab
al. quiescent
2017; Fraschetti et al.
emissionfrom ﬂares,
produced byhottergasetthan+2018).
Variability
has been
detectedin H13CO
X-ray
emission,emits energetic
photons
that penetrate
deep emission andintoattributed
the disk (Glassgold
et al.(Cleeves
2004), thereby
affectingto ﬂareset al.
2017).midplane
Flash-heating fromionization and chemistry (e.g., Rab et al. 2017; Fraschetti et al.

Hertzsprung–Russell diagram

D. M.-A. Meyer ,1 L. Haemmerlé,2 and E. I. Vorobyov3,4
1 Astrophysics Group, School of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, UK

2 Observatoire de Genève, Université de Genève, chemin des Maillettes 51, CH-1290 Sauverny, Switzerland

ABSTRACT

3 Research Institute of Physics, Southern Federal University, Stachki 194, Rostov-on-Don 344090, Russia
4 Department of Astrophysics, The University of Vienna, Vienna A-1180, Austria!"#$%"&'(')*+",)-../0122&3&'(,435"6/53",2,$+&02&+.43%(7&80.+&3.29:92;2;9:;2<;:=>::)8?)@$0.4.6.()"*)A.&.40.43&%)A34($3()60(+)"$

ceived 2018 December 19; in original form 2018 August 27$%"&'(')*+",)-../0122&3&'(,435"6/53",2,$+&02&+.43%(7&80.+&3.29:92;2;9:;2<;:=>::)8?)@$0.4.6.()"*)A.&.40.43&%)A34($3Physics and Astronomy, University of Exeter, Exeter EX4 4QL, UK
Advance Access publication 2019 January 10
rsité de Genève, chemin des Maillettes 51, CH-1290 Sauverny, Switzerland
outhern Federal University, Stachki 194, Rostov-on-Don 344090, Russia
On the episodic excursions of massive protostars in thee University of Vienna, Vienna A-1180, Austria

Massive protostars grow and evolve under the effect of rapid accretion of circumstellar gas
n
lI t
−1
2018
December
27.
Received
2018
December19;
inoriginalform
2018
August27
and dust, falling at high rates (≥10−4 −10−3 MAccepted
yr
).
This
mass
infallhas
beenshown,⊙y mboth numerically and observationally, to be episodically interspersed by accretion of denseo dgaseous clumps migrating through the circumstellar disc to the protostellar
A B Ssurface,
T R A C T causing
Massive protostars growof circumstellar gas O
sudden accretion and luminous bursts. Using numerical gravitoradiation-hydrodynamics
and and evolve under the effect
I of rapid accretionp
and dust, falling at high rates (≥10−4 −10−3 M⊙ yr−1 ). This mass infall has been shown,stellar evolution calculations, we demonstrate that, in addition to the known bloating ofboth numerically and observationally, to be episodicallyinterspersed by accretionMof dense
cbsrYIlmassive protostars, variable episodic accretion further influences their evolutionary
tracksof through the circumstellar disc to the protostellar surface, causing
gaseous clumps
migratingaUsing numerical gravitoradiation-hydrodynamics
esuddenaccretion andluminous bursts.
andmassive young stellar objects (MYSOs). For each accretion-driven flare, theyexperience
rapid
stellar evolution calculations, we demonstrate that, in addition to the known bloating of
excursions towards more luminous, but colder regions of the Hertzsprung–Russell diagram.
O Hlt umassive protostars, variable episodic accretion further influences their evolutionary tracks ofDuring these excursions, which can occur up to the end of the pre-main-sequence
evolution,
massive youngstellar objects (MYSOs).
S For each accretion-driven flare, they experience rapid
towards
more luminous, but colder regions of the Hertzsprung–Russell diagram.
the photosphere of massive protostars can episodically release much lessexcursions
energetic
photons
During theseexcursions, which can occur up to the end of the pre-main-sequence evolution,and MYSOs surreptitiously adopt the same spectral type as evolved massive(supergiants)
the photosphere of massive protostars can episodically release much less energetic photons
stars. Each of these evolutionary loop brings the young high-mass stars close
the forbidden
and toMYSOs
surreptitiously adopt the same spectral type as evolved massive (supergiants)
stars. Eachof these
evolutionary loop brings the young high-mass stars close to the forbidden
Hayashi region and might make their surrounding H II regions occasionally
fainter,
beforeHayashiregionandmight make their surrounding H II regions occasionally fainter, before
they recover their quiescent, pre-burst surface properties. We interpret such cold, intermittent
they recover their quiescent, pre-burst surface properties. We interpret such cold, intermittent
pre-main-sequence stellar evolutionary excursions, and the dipping variabilityof H II regions
pre-main-sequencestellar evolutionary excursions, and the dipping variability of H II regions
the signatureof the presence of a fragmenting circumstellar accretion disc surrounding
as the signature of the presence of a fragmenting circumstellar accretionas discsurrounding
MYSOs.
We conjecture
the MYSOs. We conjecture that this mechanism might equivalently affecttheyoungstars
in the that this mechanism might equivalently affect young stars in theintermediate-mass regime.
intermediate-mass regime.
Key words: methods: numerical – stars: circumstellar matter – stars: evolution – stars: flares.

Key words: methods: numerical – stars: circumstellar matter – stars: evolution – stars: flares.
1 I N T RO D U C T I O NGravitationally collapsing pre-stellar cores give birth to new young

Basu 2005, 2010, 2015;
Machida& Matsumoto
Nayakshin&stars, which
grow bymass accretion 2011;of surrounding
molecular

Basu 2005, 2010, 2015; Machida & Matsumoto 2011; Nayakshin &Lodato 2012; Vorobyov & Elbakyan 2018; Zhao et al. 2018)
The disc fragmentation scenario equivalently applies to starformation in the high-mass regime. Numerical simulations pre-liR