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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, USAda et al. (2009), (3) Kirk et al. 4(2009),
Bellocheal. (2011),
Department of(4)Physics
and Astronomy,etUniversityof Victoria, 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada
5
Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada
uhäuser & Forbrich (2008), (6) Arzoumanian6 Department
et al. (2011),
Wilkingof Astronomy,(7)Universityof Massachusetts, Amherst, MA 01003, USA
7
Department of Physics, State University of New York at Fredonia, 280 Central Avenue, Fredonia, NY 14063, USA
2005), (8) Enoch et al. (2006), (9) Dzib
al.September(2010).
Receivedet
2018
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 (cyandots) objects overlaid. Contours represent the PS surface density, shown at 10%, 20%, 40%, and 80% of the peak value. The 20% contour is shown in red, while otherpositions of PS objects (redcontours are shown in green. Right: the Two Micron All Sky Survey AK extinction map of the region with the n =4 surface density andAbstractdots) overlaid.

We analyze high-quality stellar catalogs for 24 young and nearby (within 1 kpc) embedded clusters and present a
catalog of 32 groups which have a high concentration of protostars. The median effective radius of these groups is
0.17 pc. The median protostellar and pre-main-sequence star surface densities are 46 Me pc−2 and 11 Me pc−2,
respectively. We estimate the age of these groups using a model of constant birthrate and random accretion
stopping and ﬁnd a median value of 0.25 Myr. Some groups in Aquila, Serpens, Corona Australia, and Ophichus
L1688 show high protostellar surface density and high molecular gas surface density, and seem to be undergoing
vigorous star formation. These groups provide an excellent opportunity to study the initial conditions of clusteredstar formation. Comparisons of protostellar and pre-main-sequence stellar surface densities reveal continuous lowmass star formation of these groups over several Myr in some clouds. For groups with typical protostellar
highJeans
PS fragmentation
surface density
groups.
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 are always
fPS = NPS (NPS + NPMS).
larger than the associated Jeans length.
Key words: infrared: stars – stars: formation – stars: low-mass – stars: pre-main sequence – stars: protostars

0/I and Flat Class are referred to as PS stars, while Classd transition disk (TD) are referred to as PMS stars.
2.2. The Methodologies

order to select high PS fraction regions, an objective(3 )od is required to identify such regions. One simple method
h does not rely on the deﬁnition of stellar groups is to use The age of the groups, t, is derived using the model of Myers(2012):and the angular resolution to resolve high-density
Introduction
ocal surface density, Σ (Kirk1. &Myers 2011). If thelimit,groupings of stars (Allen et al. 2007). Furthermore, Spitzer
It is now commonly accepted that most stars form in clusters
1 - clusters
exp ( -int thea)
cted separation fromthe star to its nth nearest neighbor ishas been providing detailed imagesof youngof hundreds of stars (Lada & Lada 2003; Reipurth et al. 2014).
f=(4)
mid-IR, which for the ﬁrst timePS
allows us to identify young ,theprocess of isstars forming in clusters is oftaen the local stellarUnderstanding
surfacedensitystars with disks (pre-main-sequence (PMS) objects) andconsiderable importance. Although we have an increasingly
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 (redinfalling envelopes (PS objects) efﬁciently in clusters out todots) overlaid. The color scale is given in units of cm−2.

detailed picture of relatively isolated star formation in nearbya=0.2
Myr.
(2012) etdeveloped
a cluster evol1 kpcwhereand beyond(e.g., Evanset al.Myers
2009; Gutermuthal.
dark clouds, such as those in the Taurus complex, many gaps
2009; Kryukova et al. 2012; Dunham et al. 2015). In addition,column density map. In all ﬁgures,remain
the contours
thePS
PMS objects,
and the average
mass model for cluster age estimation. It assumed a constantution
in ourrepresent
understandingof andclusteredstar formation,suchsurface
as density
the and
Herschel
Space Observatory (Pilbratt et al. 2010) alsosurface 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 well as theprovidescolumn density
maps for accretion,
nearby star-forming
PSthatdustbirthrate,core–clump
and equally likely accretionoverlaid in red dots, blue dots, and yellow dots, respectively.
of 32 PS groups using this method. There are ﬁve
groups
2 We process
dominant fragmentation(e.g.,
Zhang
et al.Aquila-b5,
2015; Musca,
regionswithhighsensitivity
andangularresolution(Harvey
are interested in zones that have both a high PS fraction
and
a
have
only
PS
objects,
including
Perseus-b2,
n Pokhrel et al. 2018).
Busquetet surface
al. 2016;
themodel.
clusterhigh concentration of protostars. Using
the PS
density
Serpens-a1, and Serpens-b2. These clusters shouldvery Pokhrelin
et al.bestopping
2013;
et al.
2016),
making The
it possible
to studyages
the can be obtained from

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43

Catalog of High Protostellar Surface Density Regions in Nearby Embedded Clusters
Juan Li1,2, Philip C. Myers3
1, Helen Kirk4,5, Robert A. Gutermuth6, Michael M. Dunham3,7, and Riwaj Pokhrel3,6

Li etObservatory,al.
Shanghai Astronomical
Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030, People’s Republic of China; lijuan@shao.ac.cn
2
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, USA
4
Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada
5
Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada
6
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
7
Department of Physics, State University of New York at Fredonia, 280 Central Avenue, Fredonia, NY 14063, USA
Received 2018 September 20; revised 2018 December 2; accepted 2018 December 3; published 2019 January 29

Abstract
We analyze high-quality stellar catalogs for 24 young and nearby (within 1 kpc) embedded clusters and present a
catalog of 32 groups which have a high concentration of protostars. The median effective radius of these groups is
0.17 pc. The median protostellar and pre-main-sequence star surface densities are 46 Me pc−2 and 11 Me pc−2,
respectively. We estimate the age of these groups using a model of constant birthrate and random accretion
stopping and ﬁnd a median value of 0.25 Myr. Some groups in Aquila, Serpens, Corona Australia, and Ophichus
L1688 show high protostellar surface density and high molecular gas surface density, and seem to be undergoing
vigorous star formation. These groups provide an excellent opportunity to study the initial conditions of clustered
Figure 18. Surface densities of PS objects vs. gas column
densities. The Comparisonsredstar formation.
of protostellar and pre-main-sequence stellar surface densities reveal continuous lowcircles indicate clusters with PS ratios (ratioPS) higher than 0.8. The blue
mass
star
formationofthesegroups over several Myr in some clouds. For groups with typical protostellar
triangles indicate clusters with ratioPS ranging from 0.6 to 0.8. The green
triangles indicate clusters with ratioPS ranging from 0.4
to 0.6. The yellow
stars than 0.4 pc, we ﬁnd that these separations agree well with the thermal Jeans fragmentation scale.
separationsof less
indicate clusters with ratioPS ranging from 0.2 to 0.4. The diamonds indicate
On the other hand, for groups with typical protostellar separations larger than 0.4 pc, these separations are always
clusters with ratioPS below 0.2.
2. The median molecular gas column density of theselarger than the associated Jeans
groups length.
is 1.6×1022 cm−2, corresponding to 296 M pc−2.
elowestgas column
densitylow-massof these sub-clustersis
Keyofwords:
infrared: stars The– stars:formation– stars:– stars: pre-main
sequence– stars: protostars
sequence stars, and from the modal value
the protostar
sub-clusters with λPS0.4 pc, and λPS is always larger
about (2.75 ± 2.96)×1021 and (2.85 ± 1.76)×1021 cm−2,

luminosity.
than λJ for λPS 0.4 pc. These results support thecorresponding to 51±55 and 53±35 Me pc−2.
For a sphere of mean column density Σgas and radius R, thepicturethat the thermal Jeans fragmentation dominates at
3. We found a possible correlation between ΣPS and ΣPMS
freefall time τff is given by (Burkert & Hartmann 2004) 1. Introduction
limit,
andtheangularresolution
smallerscales. to resolve high-density(rcorr = 0.78), implying continuous and steady low-mass
6. Theetcalculated
gas Furthermore,
freefall time of Spitzer
these sub-clusters
groupings of stars (Allen
al. 2007).
star formation over several Myr.
moststarsa positive
form inpower-law
clusters correlation between theseems images
to correlatewiththe cluster
age inderivedpRIt is now commonly accepted that
4.
We
found
has
been
providingdetailedofyoung
clusters
the with thet ff »(5) & Lada 2003; Reipurth et al. 2014).
.
ofShundreds
of
stars
(Lada
theoretical
model
(r
=
0.65),
suggestingthat regions
YSO
surfacedensities
andthemoleculargascolumncorr
8G
gas
mid-IR, which for the ﬁrst time allows us to identify young
with shorter dynamical times have a greater PS fraction.
Understanding the process of starsdensities.
formingThein power-law
clusters indicesis of were 1.62±0.01 andstars with disks (pre-main-sequence(PMS)that objects)
This result also suggests
star clusterandformation isfor increasingly
PS and pre-main-sequence stars,
importance.
we have an
Table 4 presents the calculatedconsiderableτff value for theidentiﬁed PS Although1.42±0.01
infallingenvelopes(PS
objects)
efﬁciently
inclusters
out tolikely to be a relatively fast process.
A possible
respectively.
detailedofpicture
ofthe
relatively
isolated star formation in nearby
group
groups. Figure 24 shows a comparison
τff versus
andseems
beyond (e.g.,correlation
Evans etwas
al.found2009;between
Gutermuth
et al.
the group
age and τff:
5. The average separation between PS1 kpc
sourcesage, indicating a possible correlation
between them.
slope in the Taurus
dark clouds,
such Theas thosecomplex,many
gapsJeans fragmentationage=(1.31± 0.02)
τff (rto agreewell withthermalfor et al. 2012;2009; Kryukova
Dunhamet al.
2015).
In addition,corr = 0.78).
of the best-ﬁt line is 1.31, with remaina Pearsonincorrelation
coefﬁcient of clustered star formation, such as
our understandingthe
Herschel
Space
Observatory(Pilbrattetal.
2010) alsoof 0.78. This suggests that groups
shorter initial
dynamical
times
thewithelusiveconditions(Myers 2010), as well as theprovides dust column density maps for nearby star-forming
have a greater fraction of protostars, i.e., they are “younger.”dominant fragmentation process (e.g., Zhang et al. 2015;
regions with high sensitivity and angular resolution (Harvey
This result also suggests that star cluster formation is likely to
Busquet
et
al.
2016;
Pokhreletal.
2018).
et al. 2013; Pokhrel et al. 2016), making it possible to study the
be a relatively fast process, and favors the ﬁrst scenario. In this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

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

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 thebinary orbit of the moderate-temperature models. Because 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
are attributed to enhanced angular momentum, which is promoted by the gravitational torque of the stars. In a hotmodel (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 secularmotion of the ballistic particles. The asymmetry in the circumbinary disk does not depend on the mass ratio, but it
becomes less clear as the speciﬁc angular momentum of the infalling envelope increases. The relative accretion rate
onto the stars is sensitive to the angular momentum of the infalling envelope. For envelopes with constant angularmomentum, 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 thesecondary because gas with low speciﬁc angular momentum falls along the polar directions.
Key words: binaries: general – hydrodynamics – protoplanetary disks – stars: formation – stars: protostars
1. IntroductionMore than half of low-mass young stars are members ofhydrodynamics–
4youngcstars are members ofhydrodynamics–!

hydrodynamicsand4e 4(The4[(,)-ors:)-33

Structure of a Protobinary System: An Asymmetric Circumbinary Disk and Spiral Arms
1

Tomoaki Matsumoto1,2,3, Kazuya Saigo4, 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
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

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 byight panel) for the ﬁducial model with (q , jinf, c)=(0.2, 1.2, 0.1).binary orbit of the moderate-temperature models. Because of this asymmetry, the circumbinary disk has a density
a rotating frame with the same angular velocity as the binary. Allbump and a vortex, both of which continue to exist until the end of our calculation. The density bump and vortex
frame. The stage and region plotted here are the same as those inare attributed to enhanced angular momentum, which is promoted by the gravitational torque of the stars. In a hotmodel (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 secularmotion of the ballistic particles. The asymmetry in the circumbinary disk does not depend on the mass ratio, but it
becomes less clear as the speciﬁc angular momentum of the infalling envelope increases. The relative accretion rate
onto the stars is sensitive to the angular momentum of the infalling envelope. For envelopes with constant angularmomentum, 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 thesecondary because gas with low speciﬁc angular momentum falls along the polar directions.
Key words: binaries: general – hydrodynamics – protoplanetary disks – stars: formation – stars: protostars
1. IntroductionMore than half of low-mass young stars are members ofmultiple 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 compare
these high-resolution observations with numerical simulations,Price et al. 2018), and 3D grid-based simulations (Fateeva et al.
2011; Shi et al. 2012; Shi & Krolik 2015). There have also
been studies on disks surrounding black hole binaries (i.e.,
D’Orazio et al. 2013; Gómez de Castro et al. 2013; Farris et al.
2014; Miranda et al. 2017; Tang et al. 2017).
Although 2D simulations have the advantage of obtaining
high resolutions based on the assumption of a thin disk
approximation, circumbinary disks are not geometrically thin,
as shown in this paper, and 3D simulations are more
appropriate for reproducing such disks.
Several preceding 3D simulations (Shi et al. 2012; Shi &N

s po n di n g co l o r ed cu r v es i n th e u pper pa n el , s ca l ed b y th efi tted v a l u e o f zBlos f o r ea ch cu r v e, o b ta i n ed f r o m o u r fi tti n g
THE ZEEMAN EFFECT IN THE 44 GHz
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m a g en ta , b l u e, a n d g r e
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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
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onents are quite similar in intensity, withNational
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numerical frequency derivative of the Stokes I spectrum! LkL
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ABSTRACT
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1, 2 , 4 , 8 , 16 , 3 2 , 6 4 ) ⇥ 0 . 4 2 J y b ea mk m s
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3

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Intensity (Jy/beam)

1 [astro-ph.GA] 24 Dec 2018

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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

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in the thermal
CN line. They
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in
OH in
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line of milliGausstion of the 44
CH3fieldtral profilesinSiO
masers.
if thethe GHzmagnetic
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tem-THE) ⇠ 1.7⇥10
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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
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z
n
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(+
7l
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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
m a s er i n masers
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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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s
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en
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i
g
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r
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(a
n
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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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and
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2
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o)
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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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tted
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i
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re4=8=k3<
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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
factoraccounts
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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