5214

36

Megan Reiter ,1,2‹
Omnarayani Nayak,33 Margaret Meixner3,4
and Olivia Jones
1,2‹
3,4
1MeganOmnarayani
Nayak,Margaret
Meixner
Jones
Department Reiterof Astronomy, ,Universityof Michigan, 311 West
Hall, 1085 South
University Avenue,
Ann Arbor, MIand48109,Olivia
USA

2
2

21 UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University Avenue, Ann Arbor, MI 48109, USA
32 Department of Physics & Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

43 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
Department of Physics & Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
4 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

Accepted 2018 November 27. Received 2018 November 27; in original form 2018 August 31
Accepted 2018 November 27. Received 2018 November 27; in original form 2018 August 31

LMCとSMCの大質量YSO（6天体）に対し、ABSTRACTABSTRACTAs nearby neighbours to the Milkywith
Way, the Large
and Small（R=4800）
Magellanic Clouds (LMC and近赤外中分散分光観測
FIRE
As nearbyneighbours
to opportunity
the Milky Way,
the Large
and SmallinMagellanic
Clouds
(LMC
and
SMC)
providea uniqueto study
star formation
the context
of theirgalactic

10-12

10-14

SMC) provide
a unique ofopportunity
to study
starformation
the characterized
context of theirecosystems.
Thousands
young stellar
objects(YSOs)
have inbeen
withgalactic
largeecosystems.
Thousandsof surveys.
young stellar
objectshave
beencharacterizedwith oflargescale
Spitzerand Herschel
In thispaper, (YSOs)
we
present
newnear-IR
spectroscopy
fiveMC
candidatehigh-mass
YSOs:
near-IR
spectra5217
Figure 2. Approximate location of the YSOs targeted in this programme shown on three-colour Spitzer images of the Large (left; Meixner et al. 2006) andscale Spitzer
and inHerschelsurveys.
Ininthis
new near-IR
spectroscopyof fivehigh-mass
YSOs
the LMCand onethepaper,
SMC.weWepresent
detect multiplehydrogenrecombination
Small (right; Gordon et al. 2011) Magellanic Clouds. White boxes and labels indicate the regions targeted for near-IR spectroscopy. Most regions contain one
high-mass
YSOs
in
the
LMC
and
one
in
the
SMC.
We
detectmultiplehydrogenrecombinationlines, as well as He I 2.058 µm, H2 , [Fe II], and [S III] in these highly excited sources. We
object, except for N159 where we target three YSOs.
Paβ
[Fe
II]
HeI
H
Brγ
CO
bandhead22.058 µm,ofHeachII], and
III] thatin thesehighly excitedsources.
lines, as thewellinternal
as He Iextinction
2 , [Feestimatesourceand[Sfind
it is highest
for sources
with Wetheestimate theinternal extinctionof eachUsing
sourceline
andratios,
find thatis highest
for sourcesexcitation
with theyoungest
evolutionaryclassifications.
weitassessthe dominant
Table 3. FIRE observations of high-mass star-forming regions in the LMC and SMC.
youngest evolutionaryline ratios,
assess the dominant excitation
mechanismin the threeclassifications.
sources whereUsing
we detectboth Hwe2 2.12 µm and [Fe II] 1.64 µm. Inµm we
anddetect[Fe II]CO
1.64µm. Inmechanismin the three sourceswhere
we
detectboth H2 2.12
eachcase, photoexcitation
dominates
over
shock
excitation.
Finally,
bandhead
TargetRegion
RA
Dec.
Ka
tint
30
Dor YSO
J2000
J2000
[mag]
[s]
each case, photoexcitation
dominates
overWhileshockthisexcitation.
Finally,
we detect COabsorption
in one of our LMC
sources.
feature isoften associatedwithbandhead
evolvedabsorption
in oneisoflikely
our LMC
While
this feature
is oftenassociated withevolvedstars,
this object
youngsources.
with strong
polycyclicaromatichydrocarbons(PAHs)
andJ84.703995–69.079110
LMC/30 Dor
05h 38m 48.s 96–69◦ 04′ 44.′′ 8
14.07
4 × 60stars, this object
is likely
young
with
polycyclicaromatichydrocarbons
andJ72.971176–69.391112
LMC/N79
04h 51m 53.s 08–69◦ 23′ 28.′′ 0
12.39
4 × 60detected
at longer
wavelengths.(PAHs)
Comparedfine-structure
emissionlines
tracing
an strong
H II region
J84.906182–69.769472
LMC/N15905h 39m 37.s 53–69◦ 46′ 09.′′ 8
12.57
4 × 300
detected
longer wavelengths.
Comparedfine-structure
emissionlines
tracingour
an sources
H II regiontohigh-mass YSOs
in theGalaxy,havehigher atbolometricand line luminosities,
J84.923542–69.769963
LMC/N15905h 39m 41.s 89–69◦ 46′ 11.′′ 9
12.16
4 × 600
H72.97-69.39
to high-mass
YSOs
the Galaxy,
our ofsourceshave higher
bolometricand andlineSMC.
luminosities,
consistentwiththeirinselection
as somethebrightest
sourcesin the LMC
J85.018918–69.743288
LMC/N15905h 40m 04.s 54–69◦ 44′ 35.′′ 8
11.73
4 × 300
consistent with their selection as some of the brightest sources in the LMC and SMC.
J16.280250–71.995194
SMC/N7601h 05m 07.s 26–71◦ 59′ 42.′′ 7
14.12
5 × 600
Key words: stars: formation – stars: massive – stars: pre-main-sequence – stars: protostars.
5218
M. Reiter
et al.– stars: massive – stars: pre-main-sequence – stars: protostars.
Note.a K magnitudes from Kato et al. (2007).
Key words:
stars: formation

全てで多数の水素再結合線（とHe I 2.058 µm）
Downloaded from https://academic.oup.com/mnras/article-abstract/483/4/5211/5284997 by National AstronomicalObservatory, Japan user on 27 Feを示す

比Paβ/Brγを使って、internal減光量を見積もった：1 <= Av <= 12 mag
Table 5. Extinction estimates.
of ionizing radiation precedes the end of accretion (e.g. Klaassen
To improve the signal in these cases, we bin the data to a spectral

resolution R ≈ 1200 to improve line identification and fitting. All
N159:theJ84.906182-69.769472
et al. 2011, 2018). Therefore,of LMCemissionlines
frommany sources at a uniform
etpresence
al. 2016). The
and SMC
providelines detected with ≥3σ
are rγlisted in Table
4. V)
1 I N T RO D U C T I O N
NamePa β/B
E(B −
AV a
et
al.
2016).
The
LMC
and
SMC
providemany
sourcesatauniform(∼50 kpc,
Pietrzyński
et al. 2013 and ∼60 kpc, Scowcroftnecessarily
signalthat accretionan emerging H II region does notdistance
1 I N T RO D U C T I O N
distance(∼50
kpc, Pietrzyński
et al.galaxies
2013 and∼60
kpc, Scowcroft
The formation and evolution ofhas
high-mass
stars remains an openetal. 2016,
respectively)in irregularwithfavourable
orienfinished.
30
DorandYSO
4.24 ± 0.41 0.72 ± 0.16
2.46 ± 0.57
The
formationand evolutionof high-mass
remainsplane
an openet al. 2016,
respectively)in irregularlaboratories,
galaxies withorienquestionin astrophysics.
The recent
explosionstarsof Galactic
surtations.
Unlikeother extragalactic
thefavourable
LMC
SMC
5 S P E C T R A L F E AT U R E S-16dominatetheother
spectra,likelytrac10veys
1.56 ± 0.01 3.09 ± 0.05
10.5 ± 0.15
questionastrophysics.
The recentHydrogen
explosionof recombination
Galacticofplanesur- lines aretations.
extragalacticlaboratories,
theH72.97–69.39
LMC and SMC
has inprovidedan unprecedented
view of thousands
activelycloseUnlike
enoughto resolve
individual
high-mass
star-forming
reBinnedand smoothed
spectraare shown
3. The most
II Multi-wavelength
regions.
Most
sourcesalso
ing
emissiontheassociatedveys has provided
unprecedented
view ofactivelyareHcloseenough toresolve
individual
high-mass
star-forming
restar-forming
cloudsanthroughout
the planeof thousands
thefrom
Milky ofWay
(e.g.
gions.
surveysparticularly
with J84.906182–69.769472
Spitzerand Her5.18± 0.230.25in±Fig.
0.05
0.84 promi± 0.15
N159:
J84.923542-69.769963
nent emission lines in each source are hydrogen recombination
star-forming
cloudsthroughout
the
plane
the etMilky
WayMoli(e.g.
gions.
Multi-wavelength
surveys
Spitzer
HerHoareet al. 2005;
Urquhart
et al.
2008;
Schulleral. 2009;
schel
have
uncovereda wealth
ofparticularly
candidate withyoung
stellarand
objects
Iofemission(fiveout of six).
Hard
UV
photons
are required
haveHe
J84.923542–69.769963
1.40 ± 0.38 3.34 ± 0.59
11.4 ± 2.05
and higher excitation species are seen in a few
Hoare
et al.
2005;
Urquhartal.
Schulleral.
2009; obserMolischelhigh-luminosity
have
uncovereda wealthof candidate
stellar objects
nari
et al.
2010;
Aguirreet al.et2011).
Unlikeprevioustargeted(YSOs)
in bothgalaxies(e.g.
Meixner
et al. young
2006;
Whitney
et lines,
al. although rarer3.20
hinting thatsourcesmay
to2008;
exciteHe I etemission,
Papillon
YSO± 0.31 1.39 ± 0.16
4.73 ± 0.56
nari et al.these
2010;surveys
Aguirredid
et al.
previous targeted
obser(YSOs)Meixner
in both etgalaxies(e.g.
Meixneral. 2006;
Whitney
et cases.
al. Lines detected in each source are listed in Table 4. We briefly
vations,
not2011).
selectUnlike
for a particularstar-formation2008;
al. 2013;
Sewiłoet al.et2013;
Seale
et al. 2014).
N76
YSO
0.88
± 0.65
4.43± below.
0.11 12.13 ± 0.30
excitetheline.
However,
there
does
not
appeartobealuminosity
N159:
Papillon
YSO
describetherelevant
featuresofeach
objectvations,these
surveysdid
notselectforaparticularstar-formation
2008;
Meixner
et
al.
2013;
Sewiło
et
al.
2013;
Seale
et
al.
2014).
indicator, instead providing an unbiased sample. This large populaHundreds of candidate YSOs have been targeted for follow-up ob-18
a Assuming
YSOs(Cooperthresholdfor
He I in Galactic
indicator,
insteadan unbiased
This large
populaHundredshigh-massofcandidate
YSOsInfraRed
have
beenSpectrographtargeted forfollow-up
ob- RV = 3.41 and RV = 2.74 for the LMC and SMC, respecof clumps
hasproviding
enabled construction
ofsample.
an required
evolutionary
sequenceservations
withthe Spitzer(Spitzer
IRS;
10tionNote.
tion massof clumps
has enabledconstructionof anSvoboda
evolutionary
servations
the around
Spitzeret InfraRed
Spectrograph(SpitzerIRS;
andfunctionfor high-mass
al.sequence2016).
Oliveira
et withal. 2009;
Sealeal.
2009;and
Oliveira et tively.
al. 2011;
Woods
in emission
lowetstars
al. (e.g.
2013)
and etindeedHe I is seen
5.1 30 Dor YSO
andGalaxy-widemass function
for high-massstarsthose(e.g. Svoboda
al.
2016).
Oliveira
et al.
2009;Seale
al. Fischer
2009;
Oliveiraal. 2011;
surveys,particularlythat targetetgalaxies
ex- Edwards
etal. 2011;
Oliveira
et 2006;
al.et2013;
Ruffleet al. et2015;
JonesWoods
et al.
intermediate-mass
stars
(e.g.
et
al.
2003,
Galaxy-wide
surveys,thosethat target
exet al. 2011;
Oliveira etal.reveal
2013;absorption
Ruffle et al.
Jones etices
al. most massive and luminous YSOs in the LMC reside in the
ternalto the MilkyWay, particularly
allow detailed
studiesof thegalaxies
association
2017).
Spectroscopic
data
due2015;
to molecularThe
etdetailedal. 2008;
Cauley&galaxies
Johns-Krulland
2014;
Reiteret al.
Inprotostars
H II due
Our targets
haveof internal
extinction
ternal to star
the formation
Milky Way,
studiesof closest
the association
2017).
Spectroscopic
data2018).
reveal absorption
to molecularices
betweenandallowenvironment.
Twoof thesilicate
dust in theyoungestwhile
more
evolved
R136
SSCa atrange
the heartof 30 Dor.
The YSOvalues.
that weTwo
targetofinthe
regions
as of
well
as
low-mass
photoexcibetween
star formationand environment.
Twothe closest
galaxiesand silicate
in stars,
the youngest
protostars
while
moreheavily
evolvedtothe Milky
Way, the Large
andSmall Magellanic
Clouds(LMC pre-main-sequencesources
showdust
fine-structure
emissionlines andUV-pumped
poly! 5) also
have theevomostthisextincted
programmeobjects
lies ∼11(ApcV outside
the central
SSCyoungest
where strong
N76
YSO
to-20
the
MilkyareWay,
the Largeprime
and
Small
Magellanic
Cloudssourcesaromaticshow
fine-structure
emission
andtypically
UV-pumped
polySMC),
particularly
for observational
scrutiny(LMC(e.g. collisional
cyclichydrocarbons(PAHs) linesthat areexcitedinwinds
and turbulencefrom R136 impact ongoingtationlikelydominates
overexcitation(see Osterbrock10andv
lutionaryclassifications(J84.923542–69.769963
andstartheformation.
N76 YSO;and SMC),
are2008;
particularly
for observational(e.g.Fischer
cyclicaromatichydrocarbons(PAHs)that
that are typically excitedJ84.703995–69.079110,
in
II regions.
Whitney
et al.
Dobbs etprime
al.&2010;
Louie,2006;
Koda &scrutiny
Egusa 2013;
H
which we refer to as the 30 Dor YSO, isFerland
Kwan
&
2011,
respectively).
Given
see Table 1). Our extinction estimate
for the N76 YSO is intermediregions.
Whitneyetetal.al.
2008;Choi
Dobbs
et al.
2010;
Louie,
Koda& Egusa
2013; 2.0
H IINew
observations with2.5
the Atacama Large Millimeter/subSewiło
2013;
et al.
2015;
Lewis
et al.
2015;
Ochsendorf
the most massive YSO within the footprint of ALMA observations
1.0
1.5
I
emission
is
seen
in
young
embeddedsources
(e.g.
Covey
et
al.
He
ate
betweenthevaluesdetermined
Ward
al. (2017)
whoinfoundNew observations
with provide
the Atacama
Sewiło et al. 2013; Choi et al. 2015; Lewis et al. 2015; Ochsendorf
millimeter
Array (ALMA)
maps Largeof the Millimeter/subcontinuum andof 30 Dor (Nayak et al. 2016).byThis
sourceetremains
embeddedits
λ [µm]
2011; Connelley& Greene 2014)molecular
as well as
more
evolvedregions,
millimeter
Array(ALMA)
providemapsof theandemissionwithcomparable
sensitivity
to= 0.81and± 0.35
maggas,(optical)
and
AV =
± by
9.3fitting
magthe(KAcontinuum
natal
molecular
with a massof ∼24M⊙19.5(derived
V resolution⋆ E-mail: megan.reiter@stfc.ac.uk
molecular
with comparable
andtoemission
observationsof evolutionary
Galactic
clouds.stage.
For sensitivity
the first time,itresolution
is using
possible
Robitailleet al.
2006
modelsto theSED;
see Nayak
et al. 2016).
it is not clearly an indicator of source
massemission
or
band)
line
ratioswiththe
Galactic
extinction
curve⋆ E-mail:Figure 3. Spectra of
the high-massstar-forming regions in the LMC and SMC observed with FIRE. Source demographics
are listed
in Tables 1,clouds.
2 and 3 whileobservationsof Galactic
For the first time, it is possibleThe spectrum of the 30 Dor YSO shows a few of the brighter
megan.reiter@stfc.ac.uk
Wedetectalargernumberofnear-IRemissionlines
fromsources=
3.1.
(Cardelli,
Clayton&Mathis
1989)
and
R
⃝
V
C 2019lines detected in eachobjectThe
are listed
in Table 4.
Author(s)hydrogen recombination lines (Paβ, Brγ) as well as He I emission at
II classification.
two sources in the LMC with the
⃝
with
the H
C 2019 The
PublishedbyAuthor(s)Oxford University Presson behalfof theRoyal AstronomicalThe
Society
We detect both the 1.26 µm and 1.64 µm lines of [Fe II] in
Section3). However,young
sourcesluminosities
emit the bulk of theirstar-forming regionsin the Galaxy
in theRed MSX
Source(RMS)
Publishedby Oxford
University
Press
on behalfof theRoyal
Astronomical
Society
fewestlines
detected
also
have
the
lowest(seeemission
Table 3).
twosources, the H72.97–69.39 candidate SSC and J84.906182–
3
at longer wavelengths where large beam sizes make contamination
survey (L⋆ ∼ 10 L⊙ ). The FIRE spectra presented in this paper
MNRAS 483, 5211–5222 (2019)
J84.923542–69.769963
has the youngest
source classificationof our
69.769472. These two [Fe II] lines originate from the same upperprovide simultaneous coverage over ∼0.8–2.5 µm. Overall,hydrofrom the environment
more likely, especiallyfor distant sources likegen recombination lines dominate the detected emission
lines,
withourtargets
intheMagellanic
Clouds
(at
500
µm,
the
Herschelbeamsources in the LMC, YSO2, and is the only source with rising conlevel, so a deviation of their observed flux compared to the intrinsic
many sources also showing H2 , He I 2.058 µm, and [Fe II] emission
is 36 arcsec corresponding to 8.7 pc at the distance of the LMC).
tinuum in the near-IR
spectrum. Deeper integrations would provide
value (1.49; see Smith & Hartigan 2006) provides an independent(see Table 4). We now examine how emission lines detected in most
New ALMA data obtained with ∼1 arcsec resolution provide a
bettersignal-to-noise
data, allowing
line detections,of our sources may be used to diagnose their physicalproperties.
better qualitative
assessment offor
the moresource evolution
via indicatorsand
estimate of the reddening. Following the same procedure as for

高いA を持つ天体：

2.058 µm. We also detect high ionization lines like [S III] 0.9533 µm
in the 30 Dor YSO spectrum.
The 30 Dor YSO is the only source in the sample that shows theCO bandhead in absorption. Molecules readily form in the cooler
envelopes of evolved stars, making CO bandhead absorption a usefulprobe of their extended atmospheres (e.g. Förster Schreiber 2000;
Bieging, Rieke & Rieke 2002). In young sources, CO bandhead
emissionhas been shown to trace circumstellar discs in some highmass young stellar objects (e.g. Ilee et al. 2013). The CO bandhead
has been seen in absorption in a few lower-mass stars, particularly
those with high accretion rates (typically members of the FU Orionis
class of objects; see e.g. Calvet et al. 1991; Hartmann & Kenyon
1996; Connelley & Reipurth 2018).

Downloaded from https://academic.oup.com/mnras/article-abstrac

Flux + offset [erg s-1 cm-2 A-1]

10-10

M. Reiter et al.

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AstronomicalObservatory,
Japan
user
February
2019
Downloadedfromhttps://academic.oup.com/mnras/article-abstract/483/4/5211/5284997
by byNational
AstronomicalObservatory,
Japan
user
on on
27 27
February
2019

Unveiling the nature of candidate high-mass young stellar objects in theUnveiling the nature of candidate high-mass young stellar objects in the
Magellanic Clouds with near-IR spectroscopy
Magellanic Clouds with near-IR spectroscopy

5.2 Super star cluster H72.97–69.39 in N79
H72.97–69.39 is a young SSC candidate located in the N79 regionof the LMC. It is the most luminous site of star formation in the
LMC, with physical characteristics that suggest that it is a younger
analogue of the R136 SSC in the heart of 30 Dor (see Ochsendorf
et al. 2017). ALMA observations of H72.97–69.39 suggest that thesource is young as it is still associated with a significant amountof dense molecular gas. At the same time, the mass of ionized gas
is small compared to other YSOs in the LMC, suggesting that thehighest-mass sources are just beginning to ionize the surrounding

他の天体よりも若い進化分類になり、星形成の初期フェーズを意味

3つ：[Fe II] 1.64 µm emissionを示す
4つ：H2 2.12 µm emissionを示す

両輝線：ショックのトレーサーと見なされるが、HII領域に付随しているので強いUVによる光励起
かも[Fe II]と水素再結合の比 <1：３天体全てで、光励起が卓越していることを示す
しかしながら、
0.01 <= H2/Brγ <= 1.3：４天体のうち２天体の励起にショックが寄与していることを示す
H2/Brγが高い天体は若い進化分類を持ち、その内部のsourceは降着・アウトフロー
を駆動していることを意味する

30 Dor YSO：CO bandhead 吸収を検出
若いはず
Spitzer IRS：PAHの特徴やHII領域で励起される典型的なemission lineを示す
ALMA：母分子雲に付随していることを示す
銀河系内の大質量YSOsでの検出の多くはemissionでのCO bandheadを示す（Cooper+13）
30 Dor YSOでのCO bandhead吸収の起源はよくわからない

The Astrophysical Journal Letters, 871:L12 (5pp), 2019 January 20

Evidence
Evidence ofof Hubble
Hubble Flow-like
Flow-like Motion
Motion ofof Young
Young Stellar
StellarPopulations
away
from
the
Perseus
Populations away from the Perseus ArmArmperpendicular to the plane of thprescription of Gaia Collaboration etan expansion center at (l, b ) =
1,2
2,3
1,2
Section 3), located near the young
1,2 ,Carlos
Tapia
Carlos G.
G. Román-Zúñiga
Román-Zúñiga1,2 ,,1Alexandre
Alexandre Roman-Lopes
Roman-Lopes2,3 ,, Mauricio
Mauricio
Tapia,
We then derived a new set of o
1 , and Valeria Ramírez-Preciado11
Jesús
Hernández
Jesús
Hernández,
andValeria
Ramírez-Preciado
11
positions ( xp , yp), and proper motion
Instituto
Institutode
deAstronomía,
Astronomía,Universidad
UniversidadNacional
NacionalAutónoma
AutónomadedeMéxico,
México,Unidad
UnidadAcadémica
Académicaen
enEnsenada,
Ensenada,Ensenada
Ensenada22860
22860Mexico;
Mexico;croman@astro.unam.mx
croman@astro.unam.mx
2
2Programa de Estancias de Investigación (PREI), DGAPA-UNAM, Mexico
center. Assuming that rotation and
Programa de Estancias de Investigación (PREI), DGAPA-UNAM, Mexico
33
Departamento
Departamentode
deFísica
FísicayyAstronomía,
Astronomía,Universidad
UniversidadLa
LaSerena,
Serena,La
LaSerena,
Serena,Chile
Chile
PsAm
The Astrophysical Journal Letters, 871:L12 (5pp), 2019 January 20
Román-Zúñiga
et al. are negligible, the variation
Received
Received2018
2018AugustAugust19;
19;revised
revised2018
2018December
December12;
12;accepted
accepted2018
2018December
December26;
26;publishedpublished2019
2019January
January22
22
motions as a function of the projectwill only keep the bulk motion comp
Abstract
Abstractline of sight: ¶mx ¶x » ¶my ¶y »In
In thisthis Letter
Letter we
we present
present evidence
evidence ofof thethe coherent
coherent outward
outward motion
motion ofof aa sample
sample ofof young
young stars
stars (t(t<<3030Myr)
Myr) inin thetheto either of the m xp versus xp or m yp v
Perseus
W3/W4/W5
PerseusArm,
Arm,whose
whoseapparent
apparentorigin
originisislocatedlocatedin
inthe
thevicinity
vicinityof
ofthe
the
W3/W4/W5complex.
complex.Using
Usingastrometricastrometricand
andﬁrst order, a direct estimate of◦photometricradius ﬁeld
ﬁeld centeredcentered near
near W4,
W4, wewe selected
selected aa
photometric data
data fromfrom thethe Gaia
Gaia Data
Data Release
Release 22 catalog
catalog ofof anan 88◦ radiuscorrection. In our case, thesampleofyoungintermediatetohigh-massstar
candidates.
Thesampleislimitedtosourceswithparallax
sample of young intermediate- to high-mass star candidates. The sample is limited to sources with parallax
cml, b » 5.4 (xp , yp) mas yr-1, applie
uncertainties
below
20%
and
Bayesiandistanceestimates
within
1800
and
3100
pc.
The
selection
includesuncertainties below 20% and Bayesian distance estimates within 1800 and 3100 pc. The selection includes
projected positions, which we ﬁnallyembeddedembedded stellar
stellar populations
populations as
as wellwell asas young
young open
open clusters.
clusters. Projected
Projected velocities
velocities derived
derived fromfrom perspectiveperspectiveproper motions. This accounts forcorrected
corrected proper
proper motions
motions clearlyclearly suggest
suggest thatthat thethe youngyoung star
star population
population emerged
emerged fromfrom thethe Perseus
Perseus Arm,Arm, with
with aacorrection by the unknown line of s
possiblezone
near
W3/W4/W5
region,tracingaa front
that
expandsaway
atat aa rateofpossible convergence
convergence
zone
near
W3/W4/W5
region,tracing
front
that
expands
away
rate
of
Now, it is important to consider t
-1
-1
about
15km
kmss-1kpc
kpc-1..
about15
data, it is impossible to determin
Key
Key words:
words: Galaxy:
Galaxy: kinematics
kinematics andand dynamics
dynamics –– open
open clusters
clusters andand associations:associations: generalgeneral –– stars:
stars: kinematics
kinematics andandexpansion is due to purely persp
dynamics
dynamics –– stars:
stars: massive
massiveeffects. In order to quantify this, w
and Wright & Mamajek (2018; theira system in linear expansion withH
II
regions
(W4
and
W5),
a
massivemolecular
ridge
with
1.1. Introduction
H II regions (W4 and W5), a massive molecular ridge with
Introduction
predict the required radial velocitie
The Astrophysical Journal Letters, 871:L12 (5pp), 2019
January
20 (W3), and several embedded star clusters (e.g.,
Román-Zúñiga etFigureal. 1. Gaia color-absolute magnitude diagram showing the selection of aactiveformation
active formation (W3), and several embedded star clusters (e.g.,
velocities measured from the sy
Star
Star clusters
clusters areare formed
formed within
within giant
giant molecularmolecular clouds
cloudssamplecontainingOBstars.
Gray
symbolsareGaiasourcesinthemaincatalog
Carpenter
et
al.
2000;
Koenigetal.
2008;
Román-Zúñiga
etal.
Carpenter et al. 2000; Koenig et al. 2008; Román-Zúñiga et al.
expansion age term8 kd = (1.0227t(GMCs)(GMCs) with
with aa large
large diversity,
diversity, likely
likely related
related toto thethe early
earlywith parallax errors under 20%. Green symbols indicate the PsAm sample.
2015;
Jose
et
al.
2016;
Sung
et
al.
2017)
possibly
hostinga
2015; Jose et al. 2016; Sung et al. 2017) possibly hosting aroutine, we found that for stars w
organization
Yellow and cyan symbols show the control samples. The color/brightnessorganization ofof thethe clouds
clouds andand environmental
environmental factors
factors (Lada(Lada &&
large
large number
number ofof OB
OB stars.
stars. AroundAround W345,
W345, this
this region
region ofof thetheconstraints (Section 2) are indicated with dotted lines. The solid color lines are
Section 3), the expected distribution
Lada
Lada 2003;
2003; Longmore
Longmore etet al.
al. 2014).
2014). In
In aa recent
recent review,
review,
PsAm
PsAm hosts
hosts several
several OB
OB associations
associations like
like PerPer OB1,
OB1, which
which
3 Myr isochrones from the PARSEC 1.2 s models (Bressan et al. 2012; Tangpeak around 100 km s−1. We are a
Gouliermis
Gouliermis(2018,(2018,and
andreferencesreferencestherein)
therein)discussed
discussedthe
thecasecaseofofcontains
theopenclusters
NGC
884
and
869,
and
the
et al. 2014).
contains
theopenclusters
NGC
884
and
869,
and
the
distribution
by providing our sample
gravitationallyunboundyoung
stellarsystems,
representing
gravitationally unbound young stellar systems, representing
Cassiopeia
Cassiopeia OB8,
OB8, which
which includes
includes thethe cluster
cluster NGC
NGC 663.
663. HereHerein the range -15 < vR < -65 km
GMC
GMC complex-scaled
complex-scaled multiplex
multiplex associations
associations thatthat may
may be
be
we
show
that
a
sampleofintermediatetohigh-massyoung
we show that a sample of intermediate- to high-mass young
and dhigh. We extracted sources within 1.8 < (d kpc) < 3.1,
standard of rest velocity for the W34
considered
considered to
to bebe thethe open
open end
end ofof an
an intricate,
intricate, hierarchicalhierarchicalstars
stars in
inW345
W345 andand nearby
nearby associations
associations traces
traces what
what looks
looks like
like aa
which we deﬁne as a “full” sample expected to contain sources
1998; Bieging & Peters 2011). We
process
process thatthat scales
scales down
down toto thethe formation
formation ofof compact,
compact, boundboundcoherent
expanding
front
of
young
(t
<
30
Myr)
stars
and
coherent expanding front of young (t < 30 Myr) stars andacross the entire girth of the PsAm. We limited the sample to
distribution when we increased theclusters.
clusters.In
Inthatthatscenario,
scenario,large
largeGMC
GMCcomplexes
complexesmay
mayproduce
produceaa
6clusters,
clusters, likely
likely born
born atat thethe PsAm
PsAm close
close toto thethe W345
W345 region.
region.
sv<
0.2
parallaxaccuracy
andcontained
sources
withv
over 100 km s−1. Radial velocity
large
large number
number ofof starstar clusters
clusters born
born with
with aa variety
variety ofof energy
energyFigure 2. Perspective-corrected projected velocity map for the full withinsample, in
Galactic coordinates.
The backgroundingrayscale
is
a
WISE
WSSA
12
μm
infrared
(
d
d
)
<
1.2
d
+
20
.
a
distance
range
deﬁnedbyhighlowphysicallyunreasonable as a solely
distributions(Blaauw
1964)
that,
in
most
cases:(a)expandanddistributions (Blaauw 1964) that, in most cases: (a) expand andemission map. The orange-red hue indicates regions of strong CO emission
from theof Dameof the CO emission
Gaia
As shown
in composite
Figure survey
1, using
the etMal.RP(2001).
versusNotice
BP -thatRPmost
2.
Data
SampleSelection
andAnalysisfore,
we can safely consider our sam
disperse,
(b)
can
be
tracedthroughtheirmassive(OB)
2. Data Sample Selection andabove
Analysisb∼3° corresponds to clouds in the Local Arm, not Perseus. The contours indicate H I column density (EBHIS+GASS surveys HI4PI Collaboration et al.
disperse, (b) can be traced through their massive (OB)color-absolutemagnitude
we selected
a The
locus
expansion.
members,
Myr-1 for visualization
2016) in levels of 50–200 cm−2/healpix. The arrows indicate projectedvelocities scaled tounits of 500 pcdiagram,
purposes.
colors of thearrowsmembers, andand (c)(c) may
may containcontain crucial
crucial information
information about
about their
their
Our
of
intermediateto
Our mainmain goal
goal isis toto study
study thethe kinematics
kinematics
ofmap
intermediate
to by cos q . The region delimited by the yellow
containing
sourcesthanextension
1.547 ´
(BPHB-3- Rsupernova
P ) - 1.2
dashed line
indicatesbrighter
the approximateof theremnant nearFinally,W3.
in thisare parametrized
we applied the same cformationformation process.
process. In
In general,
general, thethe expansion
expansion andand dispersal
dispersal ofofmassive
(OB)
stars
as
tracers
of
the
young
stellarpopulationinopenclusters in themassive (OB) stars as tracers of the youngYoungstellarpopulationin region are indicated with labels.
(the slope follows the reddening vector using the extinction
sampleswithin the same cone: one (fyoungyoung star
star systems
systems may
may bebe related
related toto complex
complex dynamical
dynamical
W345
and
its
surroundings.
Using
the
Gaia
Table
AccessW345
andits
surroundings.
Using
the
Gaia
Table
Accesscoefﬁcients
from
Evans
et
al.
2018)
and
colorswithinlimited to sources with distances d<interactions
interactions between
between clusters
clusters andand sub-clusters
sub-clusters during
during their
their
Protocolextraction
Protocol (TAP)(TAP) services
services andand 4catalog
catalogbetween
extraction
tool atat projected velocity, vl,pc , and a0.3purely< BP - RP < 1.2 mag. This locus minimizes contaminathe toolcorrected
the PsAm) and a second one (coformation
4 we retrieved a catalog
formation process,process, andand also
also toto thethe rapid
rapid removal
removal ofof gasgas duedue totoAstronomisches
Rechen-Institut,
weretrievedacatalog
Astronomisches
Rechen-Institut,0), fromhorizontal unit proper motion vector vl,pc = (1,tion
as ﬁeld giant and dwarf stars, and is expected to containcontaining stars in the same distan
massivemassive star
star winds
winds andand moremore violent
violent events
events like
like Wolf–Rayet
Wolf–Rayetcomprisingcone
centered
comprising all
all DR2DR2 entries
entries within
within an
an 8°-radius
8°-radius
cone
centeredcos q =55 vl,pc ∣vl,pc∣. The most striking feature in thismostly
map isbright intermediate to massive members of young stellar
older population dominated by ﬁ
outbursts
outbursts oror supernova
supernova explosions.
explosions. The
The current
current availability
availability ofofThe
catalogontheW345
complexat(α,δ)=(40°,61°).
The catalog
on the W345 complex at (α, δ)=(40°,the61°).
groupsonwith average extinctions within AV=1 and 3 mag. We
high degreeof coherence in the orientation of the vectors(
BP - RP ) < 2.4. The resultant s
precisepreciseastrometricastrometricparametersparameters(distances,(distances,proper
propermotions)motions)from
from
,
and
R
magnitudes)contains
a
full
set
of
photometric
(G,
B
, and
Rpp magnitudes)contains a full set of photometric (G, Bppthe
estimateplaneof the sky, pointing away from W345, increasing
in around 10% of contamination in this sample due to2468 stars, respectively. The purpos
thetheGaia
Gaiasatellite
satelliteData
DataRelease
Release22(DR2;(DR2;see
seeGaia
GaiaCollaboration
Collaborationϖparallaxandparallaxes,
ϖandandwithparallaxandastrometricastrometric(proper(propermotions,motions,μμPP,,parallaxes,
ﬁeld
stars
with
anomalouscolors,withadistribution
affected
magnitude
distance.
On
the
other
hand,
the
selected
is to apply a similar analysis to t
etet al.
roughlyfromtoerrors,al. 2016,
2016, 2018)2018) allows
allows thethe exploration
exploration ofof starstar kinematics
kinematics ininparameters. This
Thisconeconeextends
extendssample
roughlycovers
from250250
toerrors, σσϖϖ))parameters.
by patchy
the current
star-forming regions in W345,
and extinction. Finally, we also restricted the projected
observed behavior (see Section 3
this420
direction
from
this context,
context, andand itit has
has provided
provided evidence
evidence ofof coherent
coherent motion
motion420pc
pc (depending(depending on
on distance)
distance) inin eacheachhighlights
directionseveral
from thethe221source overdensities that correspondraw
to wellvelocity moduli to vl + vb = ∣v∣ < 60 km s . The total
candidates in the PsAm is not a dataand
W345
of
the
PsAm
and
and expansion
expansion ofof stellar
stellar populations
populations inin certain
certain stellar
stellar systems,
systems,
W345complex,
complex,covering
coveringthe
theprojected
projectedwidth
width
of
the
PsAm
and
known young open clusters (see also Figure 4). For instance,
number of sources in this restricted PsAm sample is 1100.
in the whole Gaia DR2 sample in th
fromprovidingformedatat GMC
from star-forming
star-forming complexes
complexes (e.g.,(e.g., Kounkel
Kounkel etet al.
al. 2018;
2018; Kuhn
Kuhn
providing aa good
good sampling
sampling ofof thethe populations
populations
formedGMC
the overdensity near (l, b ) = (135, -0.4) corresponds toFrom
NGC the distances and proper motions, we calculated
etet al.
complexesal. 2019)
2019) toto moremore evolved
evolved young
young cluster
cluster associations
associations (e.g.,(e.g.,
complexes inin thethe region.
region.
884 and forNGC
869
in the Per OB1 association, also known
as velocities over the plane of the sky on galactic
projected
Wright3. Results
The
star
Wright && Mamajek
Mamajek 2018)2018) andand OBOB associations
associations with
with driven
drivenThe TAPTAP tool
tool also
also provides
provides distancedistance estimatesestimatesfor eacheachstarMyr old, d = 2.5 0.2 kpc Currie et al.
Persei(10–13h + cthatcoordinates as vl, b = 4.74dml, b , where ml and μb are directly
expansion
by
using
a
Galactic
stellardensitymodel
prior
varieswith
expansion (e.g.,(e.g., Cantat-Gaudin
Cantat-Gaudin etet al.
al. 2019).
2019).
by using a Galactic stellar density model 2010).
prior thatvarieswith
7
In
Figure2
weshow
the persp
We
can
also
distinguish
two
clear
groupsinthetransformed from the μα and μδ values provided in the DR2.
The
each
2018)
The goal
goal ofof thisthis Letter
Letter isis toto report
report aa discovery
discovery about
about thetheeach position
position (l,(l, b)b) (Bailer-Jones(Bailer-Jones etet al.
al.westernmost
2018) andand provides
providesvelocities vl,pc, vb, pc (scaled to unit
edged corresponding to NGC 663 and NGC
654angular
of
The
size
of
the
region
of
study
is
quite
large,
thus
globalpictureofstarcluster
evolutioninaregionofthePerseusconﬁdence
intervals,deﬁned
by
lower
and
upper
limits,global picture of star cluster evolution in a region of the Perseus
conﬁdence intervals, deﬁned by lower andupper
limits,dlow
low
Gaia DR2 stars present in the full di
the CasOB8
association(20 Myr old, d = 2.4 0.2 kpc
Tapia a correction by perspective expansion/contraction
requiringArm
Arm (hereafter(hereafter PsAm),
PsAm), aroundaround thethe W3/W4/W5
W3/W4/W5 complex
complex
9that traces star-forming regions, as
44
Anothervery
important
et
al.
1991;
Pandeyetal.
2005).
(Brown
et
al.
1997)
to
take
into
account
theeffectofthemotion(hereafter
http://gaia.ari.uni-heidelberg.de/(hereafter W345).
W345). W345,
W345, locatedlocated onon thethe Galactic
Galactic plane,
plane, isis aa
http://gaia.ari.uni-heidelberg.de/molecular and neutral gas near W345
5featurethat emerges
fromisFigureis that 12
for μmthe infrared
perspectiveWe
conﬁrmedlargerdoes
well-studied
region,two
FigurePerspective-corrected
projected velocity
map for 5thefullsample,that
inaaGalactic
coordinates.
Thebackgroundin grayscalea WISE2 WSSA
We
conﬁrmedthatlargeropening
opening
doesnot
notalteralterourourresults
resultssigniﬁcantly.
signiﬁcantly.
well-studied massive
massive2.star-forming
star-forming
region,containing
containing
twogiant
giant
well as H I and CO integrated intens
motionsfor Noticethe control
sample,identify
emission map. The orange-red hue indicates regions of strong CO emission from the composite surveycorrectedof Dame etal. (2001).
that mostof theweCOcannotemission
we use an orientation parameter bygrouping
and the vectors
present
net null trend,et6withthe constraint of σϖ/ϖ0.1 does not signiﬁcantly alter our results.
density(EBHIS+GASS
surveys
HI4PIa Collaboration
al.A tighter
above b∼3° corresponds to clouds in the Local Arm,11not Perseus. The contours indicate H I columnany7
majorityof visualization
the sources purposes.
moving inparallelFigureand3. Perspective-corrected
propermotions
the andfull sample (color
All theproper motions
velocities are expressedunits
of masfor
yr−1
Myr-1 for2016) in levels of 50–200 cm−2/healpix. The arrows indicate projected velocities scaled to units of 500 pc
Thedirections
colors of thearrowsto
8
Plus a redshift/blueshift correction, whichkms−1, respectively.
parametrized by cos θ) and the control sample (blue X symbols). The average
Galactic extension
disk. Thisof conﬁrms
the aboveeffectactually
the HB-3 thatsupernova
remnant
nearisW3.
in this map are parametrized by cos q . The region delimited by the yellow dashed line indicates the approximate
valuesforclustermembercandidatesareindicatedwiththeblack dots andassociated to the PsAm population.
Young open clusters in the region are indicated with labels.
labels.
In Figure 3 we show the perspective-corrected proper2
motions (a dot-vector plot) for the full and the control sample.
between the corrected projected velocity, vl,pc , and a purely
well with the larger groups), the control sample sources appear
We clearly see that while the PsAm stars form a tight, well-40

W3/W4/W5領域のGaia DR2 dataを使用
W4付近から半径8 カタログ

若い（<30 Myr）中・大質量候補天体をセレクト(+control sample)

若い星はPsAmの位置から離れているというシナリオにThe Astrophysical Journal Letters, 871:L12 (5pp), 2019 January 20

Román-Zúñiga et al.

For instance, the Gaia DR2 parallaxes provide distances thatare still uncertain in the 102 pc scale for the PsAm, impeding an
accurate analysis of the distribution of young stellar populations within this part of the Arm. Also, the lack of radial
velocity measurements for most of the stars in our sample
prevents a full six-dimensional position–velocity analysis at
this Galactic region. From the observed expanding motion andthe available theories in the literature, we propose threepossible scenarios.

ベクトルを戻すとW345近くの収束領域に行き着く
現在は1.5 Myrの若い埋もれたpopulationがある←10-20s-1と、他の系でのunboundグループの1. The presencekmof the HB-3
supernova (SN) remnant nearW3, along with the presence of tens of OB stars in theW345 complex (see the top panel Figure 2), suggest thatSN explosions could be one possible driving mechanism in
the region, which could transfer the mechanical energy to
the cluster-gas systems. Indeed, it is known that a single SN
can imprint momentum of the order of 10 5M: km s-1 (Kim
& Ostriker 2015), providing up to 1050 erg in 10 Myr(Thornton et al. 1998). Super-bubble-type expansions via
SN often pierce and surpass the disk, depending on thehomogeneity of the local medium (Mac Low et al. 1989).
-1-1
Also, most of the mechanical energy from SN events andmassive star winds is carried by ionizing radiation, which
could provide impulse for the stellar system expansion.
Gaia DR2 data could provide evidence of a champagneﬂow-type expansion of gas layers (Tenorio-Tagle 1979),
with the stars moving along with the gas.
2. Recently, Tchernyshyov et al. (2018) presented detailed gas
velocity maps and compared them to the Stationary Density
Wave model of the Milky Way spiral structure (Lin &Shu 1964), particularly near the PsAm. The study suggeststhat a spiral arm can be fed from one side by diffuse gas
causing a net outward ﬂow toward its trailing edge. The
main effect is a concentration of the dense gas where ﬂows
converge, and a dissipation of those centers after starformation, forming a divergence of the velocity ﬁeld. Thismechanism can provide a direct explanation of theobserved effect in our sample. Moreover, if gas and stars
are expelled away from the arm, aided by this mechanism,
then we should expect a net torque in the arm. If this is true,
our study presents actual evidence of the action of spiraldensity waves near the co-rotation radius in the PsAm.
3. Another possibility is that all the groups that we areconsidering are all part of a much larger association of2clusters that is expanding away as a massive unboundyoung stellar system with an age spread of about 30 Myr(considering the estimated ages of the older clusters in thesample). The driving mechanisms behind the expansion
could be directly related to the star formation process,along with gas dispersal and the dynamic evolution of thesystem, similar to what is observed in star-forming
complexes like Orion, Vela OB2, or Scorpio–Centaurus.
However, it would be necessary to determine how toadjust such proposed scenarios to the spiral arm widthscale that we report in this Letter.

典型的な膨張速度よりも十分大きい
YSO populationが銀河面から実際に膨張しているのは明らか
Fitting：15.4 km s

Figure 4. Perspective-corrected projected velocity moduli ∣v∣ as a function ofprojected distance, d cen from an estimated convergence point (l = 137°. 8,
b = 1°. 3). The top and bottom panels show the result for the PsAm and thecontrol sample, respectively. The positions of known young open clusters areshown as large polygon-shaped symbols with error bars.

kpc のハッブルタイプの膨張

結果の解釈＆現在受け入れられている銀河系での星形成シナリオへの影響：(l, b ) = (137.8, 1.3), which was estimated by projecting
backwards the vl , vb vectors of candidate members of known
open clusters, (deﬁned as sources within a small vicinity
around published centers and distances and limited tosv v < 0.1). We can see how the corrected velocity moduli
for most of the sources are in the range of 10–20 km s−1, which
is signiﬁcantly larger than the typical expansion velocities forunbound groups in other systems (e.g., Cantat-Gaudin et al.
2019; Kuhn et al. 2019; Wright & Mamajek 2018). It is clearthat the young stellar population is actually expanding away fromthe Galactic plane: a linear ﬁt to the data suggests a (projected)
Hubble-type expansion of about 15.4 km s-1 kpc-1. The
additional panel of the Figure 4 shows the equivalent plot forthe control sample, where we conﬁrm a null expansion trend,with a correlation coefﬁcient near zero. The results for the codistant control sample are equivalent, with a null expansion trend
and little or no coherence in the dot-vector plot.

=> このレターの範囲を超えている（より正確なデータが必要なので）例えば・・・

Gaia DR2の視差は10 pc scaleで不確定性が未だあり、正確な分布解析が難しい

また、radial velocityの測定がないため、6次元の位置速度解析ができていない
4. Discussion and Summary

今回観測された広がる動きと現在ある理論から、可能性のある３つシナリオを提案
The analysis of the Gaia DR2 data described above reveals ascenario where young stellar populations are moving awayfrom a location in the PsAm. Tracing back the (v , v ) vectors

While eloquent, our analysis is just a starting point. Future

1：W3付近のHB-3超新星残骸の存在：超新星爆発が駆動メカニズム
力学的エネルギーを星団-ガス系へ移す
実際、単一SNは105 Msun km s-1の運動量（Kim&Ostriker 15）、
最大1050 erg in 10 Myrを与える（Thompson+98）
SNによるSuper-bubbleタイプの膨張は、ディスクを貫く（Mac Low+89）
また、SNと大質量星風からの力学的エネルギーの多くは、
ionizing radiatoinによって運ばれ、恒星系膨張への要因となる
Gaia DR2 dataはシャンパン流型のガス層の膨張の証拠（Tenorio-Tagle 79）であり、星はガスに沿って動いている。
2：Tchernyshyov+18：
詳細なガスの速度マップを示し、銀河系spiral構造の密度波モデル（Lin & Shu 64）と比較を行なっている（特にPrAm付近の）。
主な効果は高密度ガスの集中（そこに流れが収束）と、星形成後の中心ガスの散逸。
それが速度場の発散を生み出している
今回の観測結果はこのメカニズムによるものと解釈できる

更に、このメカニズムによって星とガスがarmから追い出されるとすると、armでのnet torqueを
これが本当ならば我々の研究は、PsAmでのspiral密度波の作用の実際の証拠を与えている。
3：全てのグループが、かなり大きな星団アソシエーションである可能性。
約30Myrで広がっている、巨大なunboundな若い恒星系のような膨張をしている
膨張の駆動メカニズム：ガスの散逸・系の力学的進化の変化による星形成過程と直接関係している（OrionやVela OB2、Scorpio-Centaurusのような星形成領域で観測されるものと似ている）=> But このシナリオをspiral armスケールにどのように適合させるかが問題である

Advance Access publication 2018 December 6

Evolution of Hubble wedges in episodic protostellar outflows

39 Evolution of Hubble wedges in episodic protostellar outflows
21School
I. Physikalisches
Universitätzu Köln,
Zülpicher
Str. CF24
77, D-50937
Köln, Germanyof Physics Institut,and Astronomy,
Cardiff
University,
Cardiff
3AA, UK
32 School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK

Universitäts-Sternwarte München, Scheinerstraße 1, D-81679 München, Germany

3 Universitäts-Sternwarte München, Scheinerstraße 1, D-81679 München, Germany

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1‹
1
2
1
P. F. Rohde,1‹1‹ S. Walch, 1‹ D. Seifried , 1 A. P. Whitworth, 2 S. D. Clarke 1 and D.
P. F. Rohde,
S. Walch, D. Seifried , A. P. Whitworth, S. D. Clarke and D.
3
A. Hubber 3
HubberInstitut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
1A.
I. Physikalisches

若い低質量星からのアウトフローの最近の研究：降着とアフトフローは一時的なもの
Accepted 2018 November 30. Received 2018 November 30; in original form 2018 August 23
Accepted 2018 November 30. Received 2018 November 30; in original form 2018 August 23

ABSTRACTABSTRACT

Young low-mass protostars undergo short phases of high accretion and outburst activity leading
新たに開発したsub-gridアウトフローモデル：一時的な振る舞いを考慮
Young
low-mass
protostars
short phasesof highthat
accretionand outburst activity
tolumpy
outflows.
Recent undergo
observations
have shown
the position–velocity
and leading
mass–
to lumpy
outflows.
Recentobservations
have shownthat thefeatures;
position–velocity
and bullets
mass–velocity
diagramsof suchoutflows
exhibit individualbullet-likesome of thesevelocity diagramsof suchoutflows
exhibitindividualbullet-likefeatures;assomeof thesebullets
subscribe
to a ‘Hubble
Law’
velocity
relation,and others
are manifest‘Hubblewedges’.
subscribea ‘Hubble
Law’ velocity
are manifest
as ‘Hubble
Inorder totoexplore
the originof these relation,
features,and
we others
have developed
a newepisodicwedges’.
outflow
In orderexplorethe originof these features, we have developed a new episodic outflow
GANDALF, which mimics the accretion and ejection behaviour ofmodel
fortotheSPH codeGANDALF, which mimics the accretion and ejection behaviour ofmodel for the
SPHWe
code
FU-Ori-typestars.
apply
this model to simulations of star formation, invoking two types
FU-Ori-typestars. We
apply thissymmetricmodel to simulationsof star formation,
invoking,typesandofinitial conditions:sphericallycores in solid-bodyrotation withρ ∝ twor−2
of initial conditions:symmetric
cores proportionalin solid-bodytorotation
withofρan∝Bonnor–r−2 , andsphericallysymmetricsphericallyturbulent coreswith density
the density
sphericallyturbulentcores
withparameters,
density proportional
to thedensityof an Bonnor–
Ebert
sphere.symmetric
For a wide
range ofmodel
we find that
episodicoutflows
lead toEbert sphere. Fora widerange
of andmodel
parameters,that episodic
outflows
toself-regulationof theejectedmass
momentum,andwewefindachieve
acceptable
results,leadevenself-regulationoftheejectedmass
andmomentum,andweachieve
acceptable
results,evenwith relatively low resolution. Using this model, we find that recently ejected outflow bullets
with relatively
lowwedge’
resolution.
Using
this model, werelation.
find thatHowever,recently once
ejectedoutflowbullets
producea ‘Hubble
in theposition–velocity
sucha bullethitsproducea ‘Hubble
wedge’
in the position–velocity
relation.
a bullet hitstheleading
shock front,
it decelerates
and aligns witholder However,bullets to once
form sucha ‘Hubble-law’.
the leading
shock
front, itasdecelerates
with older
bulletswhich
to forma ‘Hubble-law’.
Bullets
can beidentified
bumps in andthe aligns
mass–velocity
relation,canbe fit with a
Bullets candM/dυbe identified
asbumps
in the mass–velocity relation, which can be fit with a
−1.5
∝
υ
.
power-law,
RAD
RAD
−1.5
power-law, dM/dυRAD ∝ υRAD .
wedges in protostellar outflows
Key words: stars: formation – stars: protostars – stars:Hubble
winds, outflows.
Key words: stars: formation – stars: protostars – stars: winds, outflows.

アウトフローをモデリングするのに必要なmass-resolutionを減少させる（連続的なアウトフローよりもアウトフローバーストで、ガスがより高密度になるので）と同時に、要求される計算量を減らす（アウトフローparticuleは短いoutburstで発射されるので）。
2567

MIN
cores form protostars, and these protostars are usually surrounded
instabilities (MRI; Balbus& Hawley 1991) in the disc (e.g. Zhu,
rLAUNCH
0.07
AU disc (e.g.Whit′′ thesecores
form protostars,
protostars
usually
instabilities
Balbus& Zhu
Hawleyin Stamatellos,
theZhu, 0.047 AU to 0.140 AU
byaccretion
discs& Adams
1987;areTan
et al. surrounded
2014, andHartmann& (MRI;
Gammie2009a;
et al.1991)
2010a;
= and
rShu
(18)
υ ′′ROT.1(e.g.
1 × ω(t) ,θWIND
0.4 radby accretion
discs (e.g.
Shu &theAdams
1987;luminosities
Tan et al. 2014,
andHartmann& Gammie
2009a;
Zhu etetal.
Stamatellos,
Whitreferences
therein).
However,observedof suchworth& Hubber
2011b;
Kuffmeieral.2010a;2018).
Using a large
en- 0.2 rad to 0.4 radθJET Kuffmeier et al. 2018).
0.01 Using a large en- 0.005 to 0.05
references andtherein).
However,the observed
luminosities
such
worth &ofHubber
2011b;
withprotostars,
therefore
by implication
also theiraccretionofrates,
sembleSmoothed
Particle Hydrodynamics(SPH) simulations
f Particle Hydrodynamics
0.1
0.05 to 0.2
protostars,
therefore
byℓ implication
also theiraccretion
rates,
semble Whitworthof Smoothed
simulationsaretypicallyand
much
lower than
one would expect,
given
their masses
Lomax,&EJECT
Hubber (2016a,b) conclude(SPH)that episodicac√
SPH (t)f&
0.9 that episodic ac- —AngMomution, P (θ ), giving the probability
are formation
typically much
lower
one
would
expect,massesLomax,is(19)Whitworth
Hubber(2016a,b)concludeω(t)= thanêsteady, given theirandtime-scales,andassuming
thismiscretion
necessarytoreproducetheobserved
stellarinitialmass
IAD (t) accretion;
2
2
mSPHandsinassuming(θ ) r steady accretion; this mis0.025stellarM⊙ initial mass —MMINθ (equation (14)), for three different
and formation
cretion isandnecessarythe observed
match
is called time-scales,‘the luminosity
problem’ (Kenyon
et al. 1990, 1994;
function
the ratioto
ofreproduce
brown dwarfs
to hydrogen-burningstars.
ted line shows the default value
foris called ‘the luminosity problem’ (Kenyon et al. 1990, 1994;
match
functionand the ratioof brownprotostars
dwarfs to hydrogen-burningandtheadditional
constraint
that
Kenyon& Hartmann1995).
The luminosity
problemcan be mitiMost, possibly
all, forming
launch fast bipolarstars.
out.
Kenyon& Hartmann1995).
luminosity
problem can be mitiMost,
all, forming
protostars
launchfastetbipolarout! theThe
"onto
gated
if theaccretion from
disc
flows
(see,possibly
e.g., the reviewsof Arceet al. (2007);Frank
al. (2014);
1/2 the protostar is episodic,GM(t)gateda large
if thefraction
accretionfrom the⋆ discoccuring
onto theinprotostar
is episodic,
flows (2016),(see, e.g.,
the reviews ofArce fromet al. (2007);etFrank(2018)).
et al. (2014);
′′
with
of
short intense
eventsBally
results
The(N(t) > 1, equation 11),
υROT.1≤the accretion,(20) or the recent
If morethan fourSamalparticlesal.areinjected
with a large
fractionof the&raccretionin short intense
eventsBally (2016),
or therecentfrom
Samal et al.
(2018)).
The
calledoutbursts(Offner
McKee occuring2011; Dunham& Vorobyov
inferenceis that,duringthe results
collapse,
gravitational
is conLAUNCH
ly in order to cancel unwanted
this process
is repeateduntil energy
thepositionsand velocities of all thecalledCesaroni
outburstset (Offner
McKee
Vorobyovinference
that, during
the collapse,
gravitationalenergyis conal. 2018;&Hsieh
et al.2011;2018;Dunham
Ibryamov,&Semkov&
vertedintoiskinetic
and magnetic
energy,which thendrivesandmomentum that is not 2012;
parallelnew
SPH particles
in whichthe outflow
have been
computed. Finally, if
toetensure
thatHsieh
the outflow
velocity
field isSemkov
not dominatedby rotation.
2012;
Cesaroni
al.
2018;
et
al.
2018;
Ibryamov,&vertedintokinetic
andmagnetic
energy,thendrivesandet al. 2018). Such outbursts are observed
collimates the outflow, either through magnetic pressure or magneherical–polar coordinate Peneva
system, 2018; Kuffmeier
SPH
particles
havebeen injected> 0), the masses and angular
the resulting
momentumthatbe carried awayby thePeneva2018; IfKuffmeier
et al.angular2018).
Such
outbursts
arecanobserved
collimates
theforces
outflow,eitherthroughmagneticpressure(N(t)
or magnein
FU-Orionis-typestars(FUors),which
undergoarapidincrease
tocentrifugal(Blandford
&
Payne
1982;
Lynden-Bell2003;
gin and the polar axis is parallel
momentaof&thesink
particleand
its two2003;
constituent parts (the central, theremainsIAD
and
is forcesMachida,outflowis∼ (FUors),
smallerthan−1−4 arestin accretion
FU-Orionis-type
stars
increasein the Pudritz
tocentrifugal(Blandford
Payne
1982;
Lynden-Bell
IAD
yr−1 L
toundergo∼10
Mrapidinrate, from10−7 M⊙which
et al. 2007;
Inutsuka& Matsumoto
2008; Seifried⊙ yr , for ajected SPH particle in a groupof−7 next time-step.
−1
protostarandthe2016).
IAD)
mustoutflow
be2008;adjusted,according toavailable
for10theThevelocitytheinjectedM
to ∼10−4M
yr−1 ,1985;
for a of etin accretion
rate,
from (Herbig∼
Pudritz
et al.Frank2007;etMachida,
Inutsuka&
Matsumoto
Seifried⊙ yr Hartmann⊙totalperiod
of
order
10
years
1966;
&
Kenyon
al.
2012;
al.
2014;
Bally
The
removesh radius r ∈ [rMIN , rMIN + 2 AU],
period of order
10 years(Herbig
SPH
particleis 1966; Hartmann & Kenyon 1985;
etsignificant
al. 2012; fraction
Frank etofal.the
2014;
Bally
2016). Thefrom
outflow
removesaangularmomentumthestar–discmuthal angle φ ∈ [0, 2π ]. (All(t)angular→ MSINK(t) −4N(t)mSPHstar–disc
,
(29)
Mof
SINK
a significant
fractionthemomentumsystem,the gasin theaccretion
disc tofrom
reachthethe central′′
Figure2.′′ Sketch of′′ the outflow configuration, in the spherical polarcoor- enablingors in this coordinate system are(21)υ
1 = υ OUT.1 + υ ROT.1 .
system,enabling
the
gas
in
the
accretion
disc
to
reach
the
centralprotostar(Konigl&Pudritz
2000;
Pudritzetal.
2007).
Sincethe⋆ E-mail: rohde@ph1.uni-koeln.de
dinate system where
the sink
particle is at rest at theorigin and the polar(PFR);
seifired@ph1.uni-koel.de(SW)
g. r ′′1 .)protostar (Konigl & Pudritz 2000; Pudritz et al. 2007). Since the⋆ E-mail: rohde@ph1.uni-koeln.de (PFR); seifired@ph1.uni-koel.de (SW)axisTois parallelto L IADfor. the fact that part of the injected angularcompensate
mometer, giving the smallest radiusM⋆ (t) → M⋆ (t) −4N (t)mSPH ,(30)
C 2018 The Author(s)(t),
weinjectasecondSPH
particlementumisnotparalleltoê
resenting the outflow can⃝
be
inIAD
⃝
C 2018 The Author(s)Published by Oxford University′′ Press on behalf of the Royal Astronomical Society
ely short time-steps. It has Publisheddefault by Oxford= (r,onθ,behalf
φ + ofπ),theand
weAstronomical
compute itsSociety
velocity, analoat positionr 2 Press
University
Royal
see Section 3.3.5) and must be
gously to the first particle, i.e.
MIAD (t) = MSINK (t) −M⋆ (t) ,(31)higher velocities,
makingstronger with respectis the much smaller – and un!
"1/2 the jet component
to′′the low-velocity
wind component(seeGM⋆ (t)r ′′2 Section 3.3.3). Increasing
outflow is assumed to originate
1/4
,
(22)
=
P (θ )
υOUT.2leads to a wider outflow, affecting ′′θWIND
gle of the wide-angle wind, withrLAUNCH|r 2a|larger volume, with moreparticles being injected in the low-velocity wind component (seeL (t) → L (t) −&L
(t) ,
(32)
Section 3.3.1). r and φ are drawn

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Downloaded from https://academic.oup.com/mnras/article-abstract/483/2/2563/5232391 by Na

Table 1. The model parameters, with their default values, and the ranges
where fAngMom = 0.9. This ensures that the angular momentum ofover which we vary them in Section 3.3.
the protostar is a few per cent of the break-up angular momentum
Hartmann
et al. 1989; Audard et al. 2014; Safron et al. 2015; Fehérvelocity
1 I N T RO Dfor
U CaT 10I OR
N⊙ protostar of the same mass. The rotational
Hartmann
et al. 1989;
Audardal. 2014; Safron
et valueal. 2015;
Model
al. 2017).
of parameter
thisetbehaviour
isDefault
still debated,
butFehér
one Range
et al. The cause
1 I N T RO Dcomponent
U C T I O N in the outflow (e.g. Launhardt et al. 2009;etChen
et al. 2017).
Theinterplay
cause of ofthisgravitational
behaviour isandstillmagnetorotational
debated, but one
In the core accretion
scenarioforstar Tabone
formation,
collapsingdense
possibility
is the
2016;
Lee
et
al.
2017;
et
al.
2017)
is
then
given
by
r
In the core accretion scenario for star formation, collapsing dense
possibility is the interplayof gravitational 20
andAU
magnetorotational 10 AU to 30 AU

1. Rotating setup
一時的な降着とprotostarからのアウトフローの効果を調査
安定した、剛体回転の球対称コア（ρr-2）の中心で形成
Hubble wedges in protostellar outflows
2569
2570
P. F. Rohde et al.
Table 2. Parameters for the runs performed with the Rotating Setup (Section 2.4). Reading left to right, the columns give the run number, the run ID, thefeedback mechanism, the number of particles in the core (NCORE ), the sink formation density (ρSINK ), the wind opening angle (θWIND ), the launching radius(rLAUNCH ), the jet opening angle (θJET ), the fraction of the gas accreted by a protostar that is ejected in bipolar outflows (fEJECT ), the minimum radius at which
the SPH particles representing the outflow are injected (rMIN ), and the Shakura–Sunyaev viscosity parameter for MRI viscosity (αMRI ).

Hubble wedges in protostellar outflows

2573

Feedback

NCORE
103

ρSINK
g cm−3

θWIND
radianrLAUNCH
AU

θJET
radianfEJECT

rMIN
AU

αMRI

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

CONT:100
CONT:200
CONT:400
EPISODIC:25
EPISODIC:50
EPISODIC:100
EPISODIC:200
EPISODIC:400
RHOSINK:11
RHOSINK:12
THETAWIND:0.6
THETAWIND:0.2
RLAUNCH:14
RLAUNCH:047
THETAJET:0.05
THETAJET:0.005
FEJECT:0.2
FEJECT:0.05
RMIN:30
RMIN:10
ALPHAMRI:0.2
ALPHAMRI:0.05

Continuous
Continuous
Continuous
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic
Episodic

100
200
400
25
50
100
200
400
100
100
100
100
100
100
100
100
100
100
100
100
100
100

10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−11
10−12
10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−10
10−10

0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.6
0.2
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4

0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.14
0.047
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07

0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.05
0.005
0.01
0.01
0.01
0.01
0.01
0.01

0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.05
0.1
0.1
0.1
0.1

20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
20
30
10
20
20

0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.05

3.2 Comparison between episodic and continuous outflows

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Run

therefore are very numerous, specificallyHere, we compare and contrast episodic outflow feedback withṀ f
(4π/3) rMIN
(41)
mSPH < ⋆ EJECT 2
continuous outflow feedback. The continuous feedback runs (Runs
4 N̄NEIB πθJET υLAUNCH
1–3, Table 2) equate the accretion rate onto the protostar (dM⋆ /dt)!
"!
"−1
to the accretion rate onto the sink particle (dMSINK /dt) – rather
Ṁ⋆υLAUNCH
than using the sub-grid model of Stamatellos, Hubber & Whitworth.
(42)< 7 × 10−6 M⊙−1−6 M yr−1
Figure 3. False-colour images of the column-density in run EPISODIC:400 at times t = 2.4 kyr, t = 4 kyr and t = 16 kyr. The spatial scale increases from top
10
100
km
s
⊙
(2011a) and obtaining episodic accretion rate onto the protostar;to bottom, and the circle in the bottom panel shows the initial radius of the dense core (0.015 pc). The first panel shows the outflow cavity shortly after the first
we reiterate that in the episodic approach particles are only ejected
To obtain the second expression, we have substituted the default valoutflow event. In the second panel, the outflow breaks outHubbleof the wedges
dense core.
Multipleoutflows
bullets forming
in protostellar
2573 a chain of Herbig–Haro-like objects are seen in the third
during an outburst (see Section 2.3). The continuous feedback runs
ues for fEJECT = 0.1, rMIN = 20 AU, and θJET = 0.01 rad. The factor
panel.
use NCORE ≃ 105 (Run 1), NCORE ≃ 2 × 105 (Run 2), and NCORE ≃4 in the denominator derives from the fact that we launch outflow
4 × 105 (Run 3); all other parameters have their default values. The
SPH particles in groups of four. N̄NEIB is the mean number of neighresults are compared with the episodic accretion Runs 6 and 7.
bours, and we have substituted N̄NEIB = 50. In the runs with continescaping from the core and its envelope, MTOTAL (t), varies by at
3.1.2 Sink creation
Fig. 5 shows the evolution of MSINK (t) and MTOTAL (t) (top panel),uous outflow, Ṁ⋆ is usually much smaller than 10−6 M⊙ yr−1 , andmost 10 per cent; and the total momentum escaping, PTOTAL (t), by
In Runs 6, 9 and 10 (see Table 2), the number of SPH particles inand POUTFLOW (t) and PTOTAL (t) (bottom panel), obtained with conthe launch speed, υLAUNCH is usually ! 100 km s−1 . Consequently,
at
most
20
per
cent.
the core is held constant (at NCORE = 105 ; hence mSPH = 10−5 M⊙tinuous and episodic outflows. There is no evidence that the runs
convergence requires NCORE ! 106 SPH particles per M⊙ .
and MRES = 10−3 M⊙ ) and the sink creation density is decreased
with continuous outflows have converged with increasing NCORE –A further issue affecting the runs with continuous outflow is that
−10
−3
−11
−3
from ρSINK = 10 g cm (Run 6) through ρSINK = 10 g cm
particularly as regards the momentum carried away from the core
the high velocity of the launched SPH particles greatly reduces the(Run 9) to ρSINK = 10−12 g cm−3 (Run 10). Along this sequence, the(blue, , and black lines on the bottom panel of Fig. 5) – and there3.1.3 Synopsis
time-step for these particles and for all those with which they insink radius increases from rSINK = 0.9 AU (Run 6) through rSINK =fore we cannot safely draw any conclusions regarding the physics
teract, even indirectly – in particular, those that get entrained in the
Low NCORE means not having to follow so many SPH particles
2.0 AU (Run 9) to rSINK = 4.3 AU (Run 10).
of continuous outflows. The reason for non-convergence is that theoutflow early on. Even though the code uses individual particle time
(but at the price of coarser mass resolution), and low ρSINK means
Fig. 4 shows the evolution of MSINK (t) and MTOTAL (t) (top rightcontinuous outflows are not properly resolved.
steps, many particles have short time steps, throughout the simulanot having to follow the SPH particles to such high densities, andhand panel), and POUTFLOW (t) and PTOTAL (t) (bottom right-handTo be properly resolved, the SPH particles near the axis of thetion, and hence the computing requirements are very demanding.
hence with such short timesteps (but at the price of excising thepanel), obtained with different ρSINK . There are some systematic
outflow must have neighbour-lists which contain exclusively SPH
In contrast, the runs with episodic outflow only require these shortdetailed dynamics at these high densities). On both counts this rechanges with increasing ρSINK , and the results are therefore notparticles that are also in the outflow (and all SPH particles in thetimesteps for brief periods during and immediately after an outburst.
duces computing requirements. Since our outburst model produces
strictly converged, even at the highest ρSINK . In particular, the downoutflow must have neighbour-lists which contain at least a signifiapproximately converged results with low NCORE and low ρSINK –time between outbursts is longer with lower ρSINK . However, thecant fraction of SPH particles that are also in the outflow). In othermodulo slightly longer downtimes between outburst events – we
3.3 Varying the physical parameters
overall behaviour is not strongly dependent on ρSINK . (i) At allwords, the SPH particles in the outflow must interact hydrodynamconclude that it can be used in larger scale simulations of star fortimes, the mass of the sink particle, MSINK (t) varies by less thanicallywithone
another.
With
continuous
outflow,
the
rate
at
which
The Outflow Feedback Model involves six physical parameters, andmation (e.g. Clarke et al. 2017), where the computing requirementsa few per cent. (ii) In all the simulations, the downtime between
outflow SPH particles are launched may be so low that this requiretheir values are poorly constrained by observation or theory. In thiswith higher NCORE and/or higher ρSINK = 10−10 g cm−3 might not be
successive outburst events increases with time. (iii) At late times
ment is not met; successively ejected outflow SPH particles may
section, we explore how the results change when these parameters
feasible.
(t ! 30 kyr), as ρSINK changes by a factor of 100, the total mass
be
too
far
apart.
The
SPH
particlesintheoutflowwill
onlyinteract
are increased
decreasedfrom their default values (i.e. those in the
Figure 6. The evolution of the sink mass (MSINK (t), dashed lines) and the total mass carried away by all the escaping SPH particles(MTOTALor(t),solid lines),hydrodynamicallywithone
another
if
they
have
very
low-mass,
and:100: θWIND = 0.4 rad, rLAUNCH = 0.07 AU,
6, EPISODIC
for different values of the model parameters. Top left: the wind opening angle, θWIND = 0.2 radian, 0.4 radian (default) and 0.6fiducial
radian. Run
Top right:
the launchradius, rLAUNCH =MNRAS
0.047 AU,AU (default),
483,0.07
2563–2580(2019)and 0.14 AU. Middle left: the jet opening angle, θJET = 0.005 radian, 0.01 radian (default), and 0.05 radian.
Middle right: the ejected fraction, fEJECT = 0.05, 0.1 (default), and 0.2. Bottom left: the minimum injection radius, rMIN = 10 AU, 20 AU (default) and 30 AU.
MNRAS
2563–2580(2019)
Bottom right: the Shakura–Sunyayev viscosity parameter,
αMRI =483,
0.05,
0.1 (default),
and 0.2.

RUN11以下で、パラメータを一つだけ変化させた

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主要なproperty（protostarの成長速度・アウトフローによって運ばれる質量や運動量）は、数値パラメータにほとんど依存しない

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2. Turbulent Setup
一時的な降着とprotostarからのアウトフローの効果を調査
turbulentで球対称なコア（Bonnor-Ebert球に比例する密度proﬁle）の中心付近で誕生
Hubble wedges in protostellar outflows
2575
2576
P. F. Rohde2576
et al. P. F. Rohde et al.

(2001); Tafalla et al. (2004);
Santiago-Garcı́a
et al. (2009);
Wang(2001);
Tafalla et al. (2004);
Santiago-Garcı́aet4.2
al. Mass–velocity(2009); Wang Relation
4.2 Mass–velocity Relation
et al. (2014), we constructetPV-diagrams,
false-colour
plots of i.e. false-colour plots ofal. (2014), wei.e.
construct
PV-diagrams,
The left-hand panels of Fig.
show MV-diagramsfor10theleft MV-diagrams
lobe
The10left-handpanels of Fig.
show
for the left lobeof the simulated outflow, ofi.e.theplotsofsimulated
outflow, i.e. plots of"MPIXEL =

d 2M
d 2M
"r"M
"υPIXEL"r "υRADRAD =dr dυRADdr dυRAD

(46)

"M =

dM
(46)
"υRAD
dυRAD

"M =

dM
"υRAD
dυRAD

(47)

(47)

against υRAD , at the sameagainst
times υasRADthein the, atPV-diagrams
the same times
as rightthe PV-diagrams in the rightEach point hand
represents
masspoint
in arepresents
radial velocity
panels.theEach
the mass in a radial velocity
on the (r, υRAD ) plane. Here,r is(r,radialand υrRAD
is radialon theυRADdistance,) plane. Here,is radialdistance,handand υpanels.
isradialRAD−1−1, and only
pointsto points≥22 that correspond to ≥22interval"υvelocity= 2thatkmcorresponds , and only"υRAD
RAD = 2 km s intervalvelocity, both measured fromthe centreof mass. from
For thevelocity,
both measured
thevelocity
centre of mass.
For the−4−4
are considered.
At low
υRAD ! At low velocities, υRAD !
10 M⊙ )SPH
M⊙velocities,) are considered.
articles (≥ 10
0.56akms−1 .ofFor
axis we take 180 bins withwidth"υbins
0.56articles
km
s−1(≥
. For
axisa wetakeof180
with
width
"υRAD =SPH
RAD =
−1
−1
plots can bewitha single
power80 kmshellss , the, theplots
can beshallow
fitted wellwith a single shallow power80fitted
km s well
the spatial axis, we take the180spatial
sphericallyaround symmetricaxis, symmetric
we take 180shells
sphericallyaroundlaw,
law,
the centre of mass with athewidthof of"rmass= 0.0056
and consider
centrewith apcwidthof "r = 0.0056
pc and consider
only particles with radialonly
outflow
velocities
than the velocities
escape largerdM
particleswith larger
radial outflow
than the −γ
escape
dM
−γ
∝
,
(48)
∝ υRAD,(48)
RADM⊙ ,
3.9inMthis
velocity (equation (37)). velocity
Note that(equationin this case
MTOTAL= υ3.9(37)).
Note =
that⊙ , case M
dυTOTAL
dυRAD
RAD
−1
−1
effectively
so the escape velocity atso0.1
is 0.58velocity
km s .atThis
thepcescape
0.1 pcis 0.58 km s . This effectively≃ 1.5,
good agreement
observed
simulatedwith γ with
≃ 1.5,
in good andagreement
withvalues
observed and simulated values
constrains our analysis toconstrains
the outflowour
cones.
As atofinal
step, wecones.
use As awith
analysisthe outflow
finalγ step,
weinuseet al. 1981; Lada(Kuiper& Fichet1996;
Bachiller
1999;Bachiller & Tafalla 1999;
al. 1981;
Lada&&Tafalla
Fich 1996;smoothinga kernel density estimatora tocompute"M
with a smoothingkerneldensityestimator
to acompute"MPIXEL ,(Kuiper
PIXEL , with
Richer et al. 2000; Keegan& Downes
2005;Keegan
Arce et&al.Downes
2007; Liu
Richeret al. 2000;
2005; Arce et al. 2007; Liulength obtained using ”Scott’s(Scott1992).
lengthRule”
obtainedusing”Scott’s Rule” (Scott 1992).
et
Li etofal. 2018).
et al. 2017; Li et al. 2018).
Fig. 10 (right-hand side) Fig.
shows
diagramsside)
for theleft lobeof
10PV(right-handshows
PV diagrams
foral.the2017;
left lobe
Someassociatedobservers have reported
knee, at havehigh velocities,
Some aobservers
reported a aboveknee, at high velocities, above
Figure 8. Column density images of the Turbulent Setup, at t = 115, 117, 120 and 122 kyr. The circle indicates the initial radiusof the core,andsamethe viewing
the outflow
at thetimes
shownaton
8. Featuresassociatedthe asoutflow
theFig.
sametimes as shown
on Fig. 8. Features
which
the slopeabruptlywhichbecomes
steeper. We
find nomuch
evi- steeper. We find no evithe muchslope abruptly
becomesangle is chosen so that the outflow axis is approximately horizontal. The bullets are labelled AL/R through EL/R for the corresponding
left and rightlobe,within marked
with the individualbullets
are
A, B, C,etc., arein both
figures.
the individualbullets
markedA, B, C, etc.,
in both
figures.
dence
for this,panel
possibly because
ourthis,simulation
unable todence forpossiblyisbecause
ourresolve
simulation is unable to resolveorder of increasing age (see Fig. 9). The time series, from top to bottom, shows the end of a cycle of a bullet, here bullet DL , whenhits the leadingshock
The itPV-diagramat 115kyr
shown in theattop
panel
Theis PV-diagram
115right-handkyr is shownin the top
right-handfront. Bullet DL hits the leading shock front with high velocity, overtakes the older bullets and decelerates. In the last panel, theofnewly
aFig. 10.
small
theinvolved.
small amounts of mass involved.
L is inFig. ejected
10. Atbullet
this Estage,
A, At
B, thisand stage,
C define
the Hubble
ofbulletsbullets
A, B, and C thedefinetheamounts
Hubble of masscomparable position as former bullet DL in the first frame.
the bullets
asthe
small
localarepeaks.
On theare
MVmanifest
diagram,bullets
manifest as small local peaks.
has at ∼25On
Law. The oldest bullet, A,
moves
at ∼25s−1 andanddiagram,has
Law.
The slowest,
oldest bullet,
A,km
moves
slowest,
kmthe
s−1MV
The oldest
lowestandtheyoungest
bullet, and the youngest bullet,Theoldestvelocity,bullet, A,
has
thelowest velocity,
only reached ∼0.3 pc. Bullets
B and C∼0.3
appearareCinappear merged,
only reached
pc. merged,
Bullets Bbut
andbutbullet,
are inA, has the−5
F,fasterhas thethan
highest.
twothereasons
for There
this. (a)The
F, hashighest.
are
twoprotostellar
reasons for this. (a) The protostellar
The first two bullets interact with the collapsing dense core material∼2 × 10andt = 150 kyr. ṀSINK is relatively constant,factbetween
kinematicallyseparate.
moves outwards
fasterB thanA, outwards
atfact Bkinematicallyseparate.
moves
A, atThere are−1andmass,
so theMlaterbullets are launched at highermass,M⋆ (t) increases,
and are thus not visible in Fig. 8. The timespan from 115 kyr to 122
tends
tosdecrease
overreachedtime.
∼5 × 10−6 M⊙ yr−1 . The accretion rate∼30⋆ (t) increases, and so the later bullets are launched at higher, and has
∼0.46
moves
outwardskm
andChasreached∼0.46fasterpc. C moves
outwards
faster
∼30 kms−1 ,pc.
−1
velocityequation (16)).
(b) (see
The laterbullets
encountervelocityequation(16)).
(b) Thelesslater bullets encounter lesskyr is chosen to capture the end of a cycle of an outflow bullet, here
It drops briefly, following an outburst, because
outburst
thehasB,reached, andBulletD moves∼0.52 pc.
than B, theat ∼40km sheats, andhas reached
Bullet (seeD movesthan
at ∼40 ∼0.52
km s−1pc.
−1 ofresistancebecausebullets haveclearedthe way
for them.
becauseearlierbullets
have cleared the way for them.
bullet D, when it hits the leading shock front. This cycle happens
accretion disc (cf. Lomax et al. 2014, outwards2015). The, outwards
but has only
beenkmgoing
it going
at accretion∼80 km sratebut ∼6haskyr,onlysobeen
for ∼6 kyr,so it earlierresistanceat ∼80s−1 , for−1
−7
in a similar fashion for all other bullets, except the first bullet A.
10hit
M
, but
the protostar is low in the quiescent phase,⊙ yr
has Ṁ
notyettheleadingandhitbeen
decelerated.
E decelerated. Bullet E
hasshock
not yetthe leading
shockBullet
and been⋆ =This is the first bullet that breaks out of the core and survives as a
Notethelaunched,time resapproaches 10−3 M⊙ yr−1 during an outburst.
has only
justthat
been
thebeenlast launched,∼1 kyr; thewithin
outburst
has within
only justthe atlast ∼1 kyr; the outburst at
5 DISCUSSION
5 DISCUSSION
coherent structure. Bullets B and C have higher velocity and haveolution in Fig. 9 is too coarse to resolve ∼114
the verykyrshortthat outbursts.
launches EThecan bekyr
seenFig. 9. E can be seen on Fig. 9.
∼114
thatonlaunches

一時的アウトフロー：
pcスケールの長いS字型のbulletのchain
を生む=> HH天体と同一であると見なした

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Figure 9. Evolution of the accretion
onto theparticle, Ṁ(t) (green),
the protostar,labels, A–F,
to theoutflow
Figure 9.rates
Evolution
ofsinkthe accretionrates
the sinkand
particle,
ṀSINK (t)Ṁ(green),andThethe protostar,Ṁ⋆correspond(t) (blue). The
labels,
A–F, correspond to the outflow⋆ (t) (blue).
SINK ontobullets formed in the individual
outbursts
Figs.
8 and 10).
Note thattheFigs.
time8resolution
in thisfigureis tooresolution
coarse toin
fully
very
shorttooutbursts.
bullets
formed(seein theindividual
outbursts(see
and 10). Notethatthe time
thisresolve
figure isthetoo
coarsefully resolve the very short outbursts.

2577

bulletのPV図は２つの特徴を示す：
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・初期に排出されたbulletは低視線速度で放出、
leading shockで減速されている。bulletはradial
distanceに比例するradial velocityを持つ（ハッブル則に従う）
・最近に放たれたbulletは速い視線速度を持ち、shock frontで未だに減速していない。
bulletsはハッブルwedgeを形作る

Figure 10. MV- and PV-diagrams for the lefthand outflow lobe, at the same four times illustrated in Fig. 8, and using the same labels (A through F) to identify
features associated with the individual bullets. Left Panels: MV-diagrams showing power-law behaviour with slope γ ∼ 1.5. The locations of individual bullets
are marked by small jumps on this plot. Right panels: PV-diagram. The black line shows the best-fit Hubble law (υRAD ∼ υO + υO′ r), and marks the locationof bullets that have already been decelerated at the leading shock; those bullets that have not yet been decelerated lie above this line.

increases. They are also launched into a cavity that has been cleared

Figure 10. MV- and PV-diagrams for the lefthand outflow lobe, at the same four times illustrated in Fig. 8, and using the same labels (A through F) to identify
out bybullets
earlier bullets (Wang et al. 2014), and therefore they tendfeatures associated with the individual bullets. Left Panels: MV-diagrams showing power-law behaviour with slope γ ∼ 1.5. The locations of individual
are marked by small jumps on this plot. Right panels: PV-diagram. The black line shows the best-fit Hubble law (υRAD ∼ υO + υO′ r), and marks
location
tothe
travelfurther before they run into the ambient medium and areof bullets that have already been decelerated at the leading shock; those bullets that have not yet been decelerated lie above this line.

アウトフロー中のガスの質量-速度の関係（左図）：dM/dv
RAD
decelerated. As a result the later bullets leave wakes pointing
backtowards the star – these are the Hubble Wedges – and the earlier
The main difference between the prescriptions for ejection
bulletsused
define an approximately linear Hubble-like velocity field. In
by e.g. Federrath et al. 2014; Offner & Arce 2014; Offner& Chaour simulations,the individual outflow events also produce bumps
ban 2017 and our model is such that the ejection rate is not deintheMV
relationthat are similar to those observed by Qiu &termined directly by the accretion rate onto the sink, but by the
Zhang
accretion rate onto the central protostar within the sink,and (2009)
this=> 観測値によく合う。

increases. They are also launched into a cavity that has been clearedout by earlier bullets (Wang et al. 2014), and therefore they tend
to travel further before they run into the ambient medium and are
decelerated. As a result the later bullets leave wakes pointing backtowards the star – these are the Hubble Wedges – and the earlier
bullets define an approximately linear Hubble-like velocity field. In
our simulations, the individual outflow events also produce bumps
in the MV relation that are similar to those observed by Qiu &Zhang (2009)

The main difference between the prescriptions for ejection usedby e.g. Federrath et al. 2014; Offner & Arce 2014; Offner & Chaban 2017 andour model is such that the ejection rate is not de-1.5RADtermined
directly by the accretion rate onto the sink, but by theaccretion rate onto the central protostar within the sink, and thisrate is moderated by an episodic cycle. Nonetheless, like Federrath
et al. (2014) we find that the feedback is self-regulated, in the sensethat the outflow properties do not depend strongly on the ejection
fraction fEJECT .

v

でだいたいﬁtできる

個々のbullet：この関係に従う小さなbumpとして現れる
rate is moderated by an episodic cycle. Nonetheless, like Federrath
et al. (2014) we find that the feedback is self-regulated, in the sensethat the outflow properties do not depend strongly on the ejection
fraction fEJECT .

MNRAS 483, 2563–2580 (2019)

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Hubble wedges in protostellar outflowsDepartment of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8551, Japan
4
Graduate School of Natural Sciences, Nagoya City University, Yamanohata 1, Mizuho-cho, Mizuho-ku, Nagoya 467-8501, Japan
Received 2018 August 21; revised 2018 October 31; accepted 2018 December 9; published 2019 January 25© 2019.©The
AmericanAstronomical
Society. Society.
All rights
2019.
The American
Astronomical
Allreserved.
rights reserved.

Planetesimals
Perturbed
by abyGiant
Planetin ainGas
Disk
Shock-generating
Planetesimals
Perturbed
a Giant
Planeta Gas
Disk
33Shock-generating
1

1
2
2
3
3
4
M. Nagasawa, 1K. K.
, H.2Tanaka, H.2Nomura, 3T. Nakamoto, and3, H.
M. Nagasawa, K.Tanaka
K. Tanaka, H. Tanaka, H. Nomura, T. Nakamoto
andMiura
H. Miura4
Abstract1
Departmentof Physics,
SchoolSchoolof Medicine,
KurumeUniversity,
67 Asahi-machi,
Kurume-city,
Fukuoka
830-0011,
Japan;Japan;
nagasawa_makiko@med.kurume-u.ac.jp
Departmentof Physics,of Medicine,
KurumeUniversity,
67 Asahi-machi,
Kurume-city,
Fukuoka
830-0011,
nagasawa_makiko@med.kurume-u.ac.jp
22
AstronomicalInstitute,
TohokuUniversity,
6-3 Aramaki,
Aoba-ku
Sendai,
MiyagiMiyagi
980-8578,
Japan Japan
AstronomicalInstitute,
TohokuUniversity,
6-3 Aramaki,
Aoba-ku
Sendai,
980-8578,
33Departmentof EarthandPlanetary
Sciences,TokyoTokyo
Instituteof Technology,
2-12-1,
Ookayama,
Meguro-ku,
TokyoTokyo
152-8551,
Japan Japan
Departmentof Earthand Planetary
Sciences,
InstituteofTechnology,
2-12-1,
Ookayama,
Meguro-ku,
152-8551,
The AstrophysicalJournalLetters,
869:L33(6pp),
2018
December20
4
4Graduate
SchoolSchoolof Natural
Sciences,
NagoyaCity University,
Yamanohata
1, Mizuho-cho,
Mizuho-ku,
Nagoya467-8501,
Japan Japan
Graduateof Natural
Sciences,
NagoyaCity University,
Yamanohata
1, Mizuho-cho,
Mizuho-ku,
Nagoya467-8501,
Received
2018
August21;
revised2018
October
31;
accepted
2018
December
9;
published
2019
January25© 2018. The American Astronomical
Society.
rightsreserved.
Received 2018 August
21; Allrevised2018
October 31; accepted 2018 December 9; published 2019 January 25

We examined the excitations of planetesimals caused by the resonances of a giant planethttps://doi.org/10.3847/2041-8213/aaf6ad
in a protoplanetary gas
disk. The highly excited planetesimals generate bow shocks, the mechanism of which results in chondrule
formation, crystallization of silicate dust, and evaporation of icy planetesimals. The planetesimals beyond 2:1
Abstract
Abstract
resonance
migrateowing caused
to causedthegasdrag andobtaintheinmaximum
eccentricity around 3:1 resonance, which is
We examinedthe excitationsof planetesimals
by theof a giant
planetplanet
in a protoplanetarygas gasWe examinedthe excitationsof planetesimals
byresonances
the resonancesof a gianta protoplanetary
locatedat excited
approximately
halftheplanetary
distance.
Theeccentricity
depends
on the parametersof thedisk. disk.
Thehighlyexcitedplanetesimals
generate
bow bow
shocks,the mechanismof which
results
in chondruleThehighlyplanetesimals
generateshocks,the mechanismof which
results
in chondrule
Gaia-DR2
Conﬁrms
VLBA
ParallaxesinOphiuchus,
Serpens,
andAquilaformation,
crystallizationof silicate
dust, dust,
and evaporationof icyof planetesimals.
The Theplanetesimals
beyond
2:1 2:1
formation,
crystallizationof silicate
and evaporation
icy planetesimals.
planetesimals
beyondplanetesimals
andtheJovianplanet,
such
as
size
and
location,
and
the
gas
density
of
the
disk.
The
maximum
resonance
migrateowing
to thetogas
and obtainthe maximum
eccentricity
around3:1 resonance,
whichwhich
is isresonance
migrateowing
the draggas dragand obtainthe maximum
eccentricity
around3:1 resonance,
1half of
2,3
4
locatedat approximately
the aplanetary
distance.
Theeccentricity
depends
onrespectthethecaseJ.ofTobin6,7 ,relative
velocity
100
km
sized
planetesimalwiththeofgas
up to ∼12
kmGallis−1 5in thelocatedat approximately
halftheplanetary
distance.
Theeccentricity
depends
on1 parameters
the toparametersof disk
the reaches
GiselaN.
Ortiz-León,
Laurent
Loinard,SergioA.
Dzib,
MarinaKounkel,PhillipA.
B.
, Johnplanetesimals
andtheJovianplanet,
such
as
size
and
location,
and
the
gas
density
of
the
disk.
The
maximum
planetesimals and the Jovian planet, such as size and location, and the gas density of the disk. The maximum
Jupitertosecularresonance,
occursbecausethethedisk’s
gravity.
We ﬁnd that11if a Jovian-mass planet
8 100sized
9 with1012relative
ofowinga II
100planetesimalwithrespect
towhich
theto
gas
disk
up 2toup
∼12
kmof
s−1
incasethe ofcase of, Rosa M. Torres , and Amy J. Mioduszewski
relative
velocityof a,kmkm sizedplanetesimal
respect
theRodríguez
gas reaches
disk reaches
to∼12
kmins−1
Neal
J.velocity
Evans
Lee
Hartmann, LuisF.
, CesarBriceño
1 within
Jupiterowing
to secularresonance,whichoccursbecauseof theofdisk’s
gravity.
We ﬁndthat
ifthata100
Jovian-massplanetplanet
Jupiterowing
to secularresonance,whichoccursbecausethedisk’sgravity.
We
ﬁnd
if
a
Jovian-massislocated10
au,theplanetesimals
largerthankm
gain
sufﬁcientvelocity
to
cause
the
meltingofMax
Planck Institut
fürRadioastronomie,
Auf
dem
Hügel
69,
D-53121Bonn, Germany; gortiz@mpifr-bonn.mpg.de
is locatedwithin10 au,102thelargerlarger
than than
100 kmsufﬁcientvelocity
to cause
the meltingof ofis locatedwithinau, planetesimals
the planetesimals
100gainkm gainsufﬁcientvelocity
to cause
the melting
chondruleprecursors
crystallizationofthesilicate.
ThemaximumhigherMorelia
for large
planetesimals
andInstituto
deandy Astrofísica,
Universidad
Nacional
Autónomade is
Mexico,58089,
Mexicochondruleprecursors
andcrystallizationofRadioastronomía
theofsilicate.
The maximum
velocityishigherfor large
planetesimals
and velocity
chondruleprecursors
andcrystallization
thesilicate.
Themaximum
velocityishigherforlarge
planetesimals
and3
eccentric
planets.
Planetesimals
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icy planetesimals
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15
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canLeidenObservatory,
P.O.
Box
9513,
RA, Leiden, The Netherlands
Key words:
meteorites,
meteors,
meteoroids– minorplanets,
asteroids:
general– planets
and satellites:
dynamical
Key words:
meteorites,
meteors,
meteoroids– minorplanets,
asteroids:
general– planets
andNL-2300
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dynamical
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evolution
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shock
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Department
ofsatellites:
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andsatellites:
formation– shockwaves
9Departmentof Astronomy,
Universityof Michigan,
500 Church
Street, Ann Arbor, MI 48105, USA
The AstrophysicalThe
Letters, 869:L33
2018 869:L33
December
20 2018 December
https://doi.org/10.3847/2041-8213/aaf6ad
AstrophysicalJournal(6pp),
Letters,
20
https://doi.org/10.3847/2041-8213/aaf6ad
10 (6pp),meteoroids
Key Journal
words:
meteorites,
meteors,– minor Observatory,
planets,
asteroids:
general– planets
Cerro
TololoInteramerican
Casilla603,
Serena,Chile and satellites: dynamical
1. Introduction
system,whichwhich
is normallysimilarto theto rotational
speedspeedofLa of
1. Introduction
system,is normallysimilarthe rotational
11
evolutionandstability–
planetsandsatellites:
formation
–
shock
waves
Centro Universitario de Tonalá, Universidad de Guadalajara,
Avenida
Nuevo
Periférico
No.
555,
the ascending
nodesnodesof planets,
it allows
the inclinationof Ejido
theof theSan José Tatepozco, C.P. 48525, Tonalá, Jalisco, México
the ascendingof planets,
it allowstheinclination© 2018. The American Astronomical
Society.
All rights
reserved.Society. All rights reserved.
© 2018. The
AmericanAstronomical

The observationof anasteroid
belt shows
depletionor piling
The observation
an asteroid
belt shows
depletionor piling
12of
asteroidtooscillatewithlargelarge
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asteroid
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Domenici
Science
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up ofupmaterials
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dependingontheRadiolocationofConﬁrms
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The Theresonanceswith with
Jupiterare Received
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oids oids
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Loinard, Laurent, Sergio
A. Dzib of,theMarinaKounkel,Phillip
A.
B.
Galli
,
John
J.
Tobin
,
Gisela N.
Ortiz-León
Loinard,SergioA.
Dzib,
MarinaKounkel,Phillip
A.
B.
Galli
,
John
J. Tobin6,7 ,and andascendingnodesystem,of Saturncausedby is
1.
Introduction
whichof periastronthe 2periastronascendingof Saturncaused92 in
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Neal
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,
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WhenWhenthe primordialgas disk
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Planck of
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69, D-53121
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InstitutodeAstronomía,
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materials
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of Physics
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Street,WA
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7Department
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situation,
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relatedJupiterisBellingham,mosteffective
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situation,
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preserved
for–105
Laboratoire d’astrophysiquede Bordeaux,Univ. Bordeaux,
CNRS,
B18N,
allée Geoffroy
Saint-Hillaire,
F-33615
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the
main
belt
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current
asteroids(∼2compareau) is mainly
Laboratoired’astrophysiquedeBordeaux,
Univ.
Bordeaux,
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allée
Geoffroy
Saint-Hillaire,
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oftheasteroids.
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6 South/W40
thehadexcitation
the eccentricities
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the73019,
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disk
inWeidenschilling
thePhysics
Aquila
Rift,
which
been
mainlyidentiﬁedby USA
theirThe
infraredexcess with
Spitzer. We
6Weidenschilling
resonances
with
Jupiterareespecially
noticeable.
AsterLinThe
1996;
Marzari
et al.
1997;
et
Lin 1996;
Marzarial.
1997;
et1998;
al.
1998;
Homer
L.etDodge
Department
andal.
Astronomy,
UniversityofOklahoma,
440 ofW.
Street,Norman,Homer
L.ofDodge
Departmentof Physics
and Astronomy,
University
ofBrooks
Oklahoma,
440
W. Brooks
Street, Norman,
OK 73019, USA
7
7 P.O. Box 9513,
self-gravity
not Netherlandsbeneglected
when
we consider
the theself-gravity
shouldnotbeneglected
when
we consider
the secular resonances related to the rotation
determinedbyLeidenObservatory,
NL-2300
RA,should
Leiden,The
Marzari& Weidenschilling2002).
Duringthemigration,
theLeidenObservatory,
P.O.
Box
9513,
NL-2300
RA,
Leiden,The
Netherlands
Marzari&Weidenschilling2002).
Duringthemigration,thethe
Gaia-DR2
parallaxes
againstpublished
andnewparallaxes
obtainedfrom our Very Long Baseline Array
88oids
betweenthe
Jovian2:1(3.3
au)
Jupiter
DepartmentofAstronomy,
The
University
of
Texas
at
Austin,2515
Speedway,
C1400,
Austin,
TX 78712-1205,
USA
evolution
ofatandplanetesimals
experiencing
gasAustin,
drag.
Nagasawa
evolutionof Stopplanetesimals
experiencing
gas
drag.
Nagasawa
Departmentof resonanceAstronomy,
The
UniversityofTexas
Austin,2515
Speedway,
Stop
C1400,
TX
78712-1205,
USA
planetesimals
pass passthroughmany
Jovianresonances,which
planetesimals
throughmany
Jovianwhich
99 resonances,oftheperiastronandascendingnode
SaturnbyDepartmentof Astronomy,
Universityof Michigan,
500
ChurchStreet,Ann
Arbor,
MI
48105,
USA
DepartmentofAstronomy,
UniversityofMichigan,
500
ChurchStreet,Ann
Arbor,
MI
48105,
USAetal.
(2014)
showedthat
theJoviansecularresonance,
which
et
al.
(2014)
showedthat
theJoviansecularresonance,
which(VLBA)
program
Gould’s
Belt
Distances
Survey.
We
obtainconsistent
results
betweenGaia andthe of
VLBA
for caused
the10
excitetheau)
eccentricitiesof theeccentri(5.2currently
dispersed
exceptforobjects
trappedinexcitethe haveeccentricitiesof planetesimals.
the planetesimals.
These
10eccentriCerroThese
TololoInteramerican
Observatory,
Casilla Observatory,
603,
La Serena,
Chile603, La Serena, Chile
Cerro Tololo
Interamerican
Casillaarises
owing
to
the
gas
disk
gravity,excites
the
300
km
sized
11
arises
owing
to
the
gas
disk
gravity,excites
the
300
km
sized
11
Jupiter.
Whentheprimordial
theofeigenfrequencitiescities
arefurtherboosted
the
ofin
2:1
resonance,
andareUniversitario
furtherboostedatlocation
the location
ofeach2:1
resonance,andCentrodeat
Tonalá,UniversidaddeGuadalajara,
Nuevo
Periférico
No.Nuevo
555, Ejido
San
José
C.P.
48525,
Tonalá,Jalisco,MéxicoCentroUniversitariodeTonalá,Universidad
de Guadalajara,
Avenida
Periférico
No. Tatepozco,
555,
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San
José
Tatepozco,
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−1 seemean
parallaxes
ofAvenidatheregions
analyzed
here.
We
small
offsets,when
comparingmeanexists,
values,a few
12resonances(e.g.,
Trojans
andHildas).
Migrationofasteroids
12
planetesimals
up
toup
vrelto20
km
sSocorro,(Figure1). 1).
planetesimals
vCenter,km
s−1NM(FigureNational
Radio
Astronomy
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Science Operations
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they
normally
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cies
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systemalmostcoincidewiththerotationalof−1−1Received
October
26;
revised2018
December3; accepted2018supersonicDecember5; planetesimals,
published2018
December
19
The
supersonicplanetesimals,
which
appearfollowing
the
The
which
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ofacausedmicroarcseconds
theparallaxes,
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accepted
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s km
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velocityof8vrel8(planetesimals)
by
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accounts
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loss
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formationof a of
Jovianplanet,causecause
severalinteresting
effects.
formationa Jovianplanet,severalinteresting
effects.
to the(Marzari&
Weidenschilling2002).
Secularto gasthe diskgas disk(Marzari&
Weidenschilling2002).
Seculartheperiastraofplanets
causedbygravity
of
the
disk.
In
such
a
selectioneffectbyon Gaia
towardthelessstars.
Gaia-DR2
data alone conclusively placestheregionbeyond
2:1
resonance
if asteroidal
the protoplanetarydisk
is theobscured
The
shock
wave
generatedbyis wellknown
Abstract
Thebrightest,
shock
wave
generatedbyplanetesimals
the planetesimals
is wellknown
Abstract
resonance
is known
to havea strong
effecteffecttheresonance
is known
to havea strong
on asteroidal
the
6 disk7 andtheresonance
related to Jupiter is most effective inas oneofthemechanismschondrules,
which
are
one
offormation
theOphiuchus,formationof chondrules,
which
arefrom
Main
SerpensSouth
same
distance,asofsituation,
weﬁrst
inferredorbit
in thegas(e.g.,
Heppenheimer
1980;
orbit
in primordial
the Serpens
primordialgas(e.g.,
Heppenheimer
1980;
We
present
Gaia-DR2
astrometryofof YSO
candidatesin
Serpens
Main,
andSerpens
–10
yr
after
thea sample
formation
ofasthe
Jupiter(Ida&mechanisms
preservedfor10
We diskpresent
Gaia-DR2
astrometryof aatsampleof
YSO
candidates
in Ophiuchus,
Serpens
Main,
andSerpensVLBA data alone in a previous
0.1–10.1–1
mmbysized
spherical
grainsgrains
commonly
foundin primitivemm
sized
spherical
commonly
foundin primitive
WardWard
1981;1981;
Lecar& Franklin
1997).
The
secularresonances
Lecar&
Franklin1997).
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secularresonances
South/W40
inthe
Aquila
Rift,
which
had
been
mainlyidentiﬁed
theirinfraredexcesswith
Spitzer.
We
comparetheexcitationoftheeccentricities
the asteroids.
The diskSouth/W40
inthe
Aquila
Rift,
which
had
been
mainlyidentiﬁedbytheir
infraredexcesswith
Spitzer.
We
comparepublication.
Thus,
Serpens
Main,meteorites.
SerpensandW40of the same complex ofofmolecular
clouds,
1996;
Marzarial.
1997;
Weidenschilling
et
al.
1998;
In South,theasteroid
beltVeryregionofare
theminimum-massmeteorites.
In
theasteroid
belt Long
regionofall
the part
minimum-mass
areLinrelatedto thethetoGaia-DR2
motionsof parallaxes
thepericenterandtheare relatedthemotions
ofet
thepericenterandascending
the against
ascendingagainstpublished
and new
parallaxes
obtainedfrom
ourBaseline
Array
the
Gaia-DR2
parallaxes
publishedand−10new−10parallaxes
ourVeryLong Baseline Array−3−1−3 obtained from−1self-gravity
shouldbe neglected
when weconsider the
disk
(∼10
cm gOphiuchus,),consistent
athe
ofand
10
km
sGaia
would
disk
(∼10
cm
),velocity
a Gaiavelocity
of
kmfor
s and
be fornot
nodesof theobjects.
Periastranodesofobjects
rotateat(VLBA)
aandmeandistanceofDistances
436±
9
pc.
both
Gaia
and
VLBA
suggesta small parallax
gradientnodesof(VLBA)theobjects.
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rotateprogram
Gould’s
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Distances
Survey.
We
obtainconsistent
results
betweenthe 10
VLBA
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Marzari&located
Weidenschilling2002).
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program
Gould’s
Belt
Survey.
WegInobtainresults
betweenthebeVLBA
thenecessaryforthemeltingof 1 mm
sized
dust
(Iida
for complete
thecompletemelting
ofcomparing
1 mm
dust
(Iidaof a few
owing
to thetomean
gravityof otherplanets
and
disk.
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the
owing
the gravity
of otherplanets
and
disk.
When
theWe
parallaxes
in
each
of
thetheregions
analyzed
here.
seenecessary
small
offsets,when
comparingmean
values,ofsized
amean
few
mean
parallaxes
intheeachofdistancethe
regions
analyzed
here.
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see
small
offsets,
whenvalues,evolutionofplanetesimals
experiencing
gas
drag.
Nagasawa
acrossthecloud,
andthechangesfrom
144.2±1.3
to138.4±
2.6
pc
when
going
from
L1689
to
L1688.
planetesimals
passthroughmany
Jovianetresonances,al.etwhich2001).
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1,Gaiawe1,showtherequired
to ortodue to aal. 2001).
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Figure
we by
show
the
conditions
rotational
speed
ofoftheof microarcseconds
anoftheasteroid
is closeto parallaxes,
rotational
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asteroidiswhichclose
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microarcseconds
inareintroducedbythezero-point
error
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due
torequired
aerrortens ofintheareeitherintroduced
theconditions
Gaia
zero-point
cause
the
meltingofchondruleprecursors
(1900
K)
and
the
et
al.
(2014)
showedthat
theJoviansecularresonance,
which
cause
the
meltingofchondruleprecursors
(1900
K)
and
the
theexcite
eigenfrequenciesofthesystem,which
isnormallysimilartothe eigenfrequenciesof thebysystem,isby
normallysimilarto obscured
selectioneffectGaia which
towardthebrightest,
lessstars.
Gaia-DR2
data alone
conclusively
placesselectioneffectGaia
towardthebrightest,
lessobscuredstars.
Gaia-DR2
data
alone
conclusively
placestheeccentricitiesof theplanetesimals.
These
eccentriKeywords:
astrometry
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individual
objects(AquilaRiftcomplex,
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theIn outerregion,theof cities
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corresponds
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oscillates
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corresponds
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Serpens
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Thus,
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velocities
becomehigherbecausethegasdensityisplanetesimals
uptovrel20 km s−1 (Figure 1).
the transferoftheangularmomentumoftheplanettothelocatedatamean
distance
of
436±
9
pc.
In
Ophiuchus,
both
Gaia
and
VLBA
suggestasmall
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distance
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436±
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pc.
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both
Gaia
and
VLBA
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normally
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high
as
e∼0.3–0.6
atsmall.
approximately
small.
maximum
relative
velocities
of
300
km
sized
asteroid.
Similarly,
when
the rotational
speed
ofchanges
theoftheascendingThemaximum
relative
velocities
of
300
km
sized
acrossthe cloud,androtational
thethedistancefrom
144.2±1.3from
toThe
138.4±
2.6
pc
when
going
from
L1689
to
L1688.
asteroid.
Similarly,
when
the
speed
thedistanceascendingacrosscloud,
andchanges144.2±1.3
to138.4±
2.6
pc
when
going
from
L1689
to
L1688.
Thebysupersonickm
s−1
relative
2–3
that
is,
they
velocity
planetesimals
excitedby Jupiterare indicatedcircles.
To To planetesimals, which appear following thenodeof au,
anofasteroid
is close
toobtain
the
of of
the
planetesimals
excitedby– Jupiterareindicatedbycircles.
node
anasteroid
is close
to– eigenfrequencies
the aeigenfrequencies
ofvtherel8
Key
words:
astrometry
ISM:
individual– objects(AquilaRiftcomplex,
Ophiuchus)radiationmechanisms:
nonKey words:
astrometry
ISM: individual
objects(AquilaRift complex,
Ophiuchus)– radiation
mechanisms: nonformationof a Jovian
planet,cause
interesting
thermaldisk– radio(Marzaricontinuum:stars– Weidenschilling
techniques:interferometricto the gas&continuum:2002).
Secularthermal –1.
radio
stars
–1 techniques:interferometric
the star-forming
regionsstudiedbyseveralour program
haveeffects.
parallax
Introduction
1

34

The
wave
generatedby the planetesimals
known
resonance is known to have a strong effect on the asteroidal
andshockpropermotionsmeasurements
availableis wellin theDR2
Observationsofnearbyregionsrichinextremelyyoung
thestar-forming
regionsstudiedbyourprogramhave
parallax
1.
Introduction
as
one
of
the
formationmechanismsofchondrules,
which
are
the star-forming regions
studied Therefore,
by our program haveparallax
orbit in the primordial gas1. Introduction
disk (e.g., Heppenheimer 1980;
catalog.
wecannow
comparethe
VLBI
astrometry
andTaurus,
proper motions
measurements
availablein theavailable
DR2
andpropermotionsmeasurementsin the DR2
objects(forofLecar
examplePerseus,
Orion,
Observations
nearbyregionsrich
in regions
extremely
young
0.1–1
sized
grainscommonly
foundin primitive
Observationsof Ophiuchus,
nearbyrich
in extremely
young
Ward
1981;
&
Franklin1997).
The
secularresonances
catalog.
Therefore,
we cannow compare
themm
VLBI
astrometry
againstGaia
tothesphericalvalidate
the accuracyof ourmeasurements.
catalog.
Therefore,
we cannow
compareVLBI astrometry

INAF-Osservatorio Astroﬁsico di Arcetri, Largo Enrico Fermi 5, I-50125, Firenze, Italia; rivilla@arcetri.astro.it
Departamento de Astronomía, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago, Chile; gejixing666@gmail.com
Received 2018
February
2; revisedtoward2018 December
accepted 2018 December 5; published 2019 February 5
ALMA Observationsof Ethyl
FormateOrion4;KL© 2019. The American Astronomical Society. All rights reserved.

4

35

ALMA Observations of Ethyl Formate toward Orion KL
1,2
Yaping Peng
Peng1,2
YapingV. M.
M. Rivilla
Rivilla33,, Li
Li Zhang
Zhang11
,, V.

1,2
J. X.
X. Ge
Ge44,, andand Bing
Bing Zhou
Zhou1,2,, J.
Abstract11
Department of Astronomy, Yunnan University, and Key Laboratory of Astroparticle Physics of Yunnan Province, Kunming, 650091, Peopleʼs Republic of China

Department of Astronomy, Yunnan University, and Key Laboratory of Astroparticle Physics of Yunnan Province, Kunming, 650091, Peopleʼs Republic of China
pyp893@163.com, lizhang@ynu.edu.cn,
lizhang@ynu.edu.cn, bingzhoukm@126.com
bingzhoukm@126.com
pyp893@163.com,
2
2
College ofof Science,
Science, Yunnan
Yunnan Agricultural
Agricultural University,
University, Kunming,
Kunming, 650201,
650201, Peopleʼs
Peopleʼs Republic
Republic ofof China
China
College
3
3 INAF-Osservatorio Astroﬁsico di Arcetri, Largo Enrico Fermi 5, I-50125, Firenze, Italia; rivilla@arcetri.astro.it
INAF-Osservatorio Astroﬁsico di Arcetri, Largo Enrico Fermi 5, I-50125, Firenze, Italia; rivilla@arcetri.astro.it
44
Departamento dede Astronomía,
Astronomía, Universidad
Universidad dede Chile,
Chile, Camino
Camino elel Observatorio
Observatorio 1515,
1515, Las
Las Condes,
Condes, Santiago,
Santiago, Chile;
Chile; gejixing666@gmail.com
gejixing666@gmail.com
Departamento
Received 20182018 February
February 2;
2; revised
revised 20182018 December
December 4;4; accepted
accepted 20182018 December
December 5;5; publishedpublished 20192019 February
February 55
Received

Downloaded from https://academic.oup.com/mnras/article-abstract/482/4/5349/5146468 by National Astronomical Observatory

Orion KL is one of the prime templates of astrochemical and prebiotic chemical studies. We wish to explore moreorganic molecules with increasing complexity in this region. In particular, we have searched for one of the mostcomplex organic molecules detected in space so far, ethyl formate(C2H5OCHO). This species is the next step in
49–5361 (2019)
doi:10.1093/mnras/sty2901
ss publication 2018 October29
chemicalcomplexity afterAbstract
the simplest member of esters (methyl formate, CH3OCHO). The mechanisms leading to
Abstract
formation
are ofstill
poorly andknown.
havestudies.
usedWehighresolution (∼1 5) ALMA observations covering
Orion KL
KL is
is oneoneitsof thetheprime templates
templatesofastrochemical
andprebioticWe
chemicalstudies.
We
wish angular
to explore
explore more
more
Orion
of
prime
astrochemical
prebiotic
chemicalwish
toorganic molecules
molecules
with increasing
increasing
complexity
in thisthisregion.
In particular,
particular,
wehavesearched
for oneone ofoftheunblended
mostorganicwithcomplexity
inregion.
In
wehavesearched
for
the
most
a
large
bandwidth
from
214
to
247
GHz.
We
have
detected
82
lines of C2H5OCHO (49 and 33 of the
H55OCHO).
OCHO).
This species
species isis thethezonenext step
step inincomplex organicorganic molecules
molecules
detectedin space
space so
soof
far, ethyl
ethyl
formate
(C22H
This
next
complexdetectedinfar,formate(C
Hz methanol
maser
surveythecentralmoleculartransandgauche-conformers,
respectively).
The
line
imagesshowedthat
C2H5OCHO arises mainly from theOCHO).
The
mechanisms
leadingtochemicalcomplexity
after
the
simplest
memberofesters(methylformate,CH3chemical complexity after the simplest member of esters (methyl formate, CH3OCHO). The mechanisms leading to5) ALMA
ALMA observations
observations
coveringrotational temperatures and column densities
its formation
formation are
arecompact
still poorly
poorly known.
known.
We
havetheused hothigh angularangularresolution (∼1(∼1 regions.
5)covering
its
still
have
used
high
resolution
ridgeWeandcore-southwest
The derived
H55OCHOOCHO (49(49 andand 3333 ofof thethelarge bandwidth
bandwidth fromfrom 214
214 toto 247247 GHz.
GHz. WeWe havehave detected
detected 82
82 unblended
unblendedlines of
of C
C22H
16
−2lines16−2
aa large
1,2‹
2showedcmthathotcore-SW,andfor theare
122±34
K, 1‹(0.9and± 0.3)×10
H55theOCHO
arisesmainly fromfromthe 103±13 K, (0.6 ± 0.3)×10 cm
transand gauche-conformers,
gauche-conformers,
respectively).
The
line
imagesshowedthat for
C22H
OCHO
arisesmainlythetransand
respectively).
The
line
imagesC
Rickert,F.
Yusef-Zadeh
J.
Ottcompact ridge
ridge andandthe hot
hot core-southwest
core-southwest
regions.
The derived
derivedrotationaltemperaturesand column
columndensities
compact
ridge.
The
comparisonofspatialdistribution
andabundance
ratioswithchemicallyrelatedmolecules
compact
theregions.
The
rotationaltemperatures
anddensities
16
−2
16
−2
artment ofare
Physics
and Astronomy,
Northwestern
University,
SheridanEvanston,
IL 60208-3112,
USA
16
cm−2
for thethe hot
hot2145
core-SW,
andRd,
103±13
K, (0.6(0.6± 0.3)×100.3)×1016
cm−2
for thethe122±34
K, (0.9(0.9 ±± 0.3)×100.3)×10cm
forcore-SW,and103±13
K,
±
cm
for
are 122±34
K,
OCHO
is likely
formed on the surface of dust grains(methylformate,ethanol,andformicacid)
thatrelated
C2H
Astronomycompact
Observatory,
Lopezville
NM 87801,
USA
5molecules
compact
ridge.1003
The MNRAS
comparisonof Socorro,
spatialdistribution
andabundance
ratiosindicateswith chemicallychemicallyrelatedmolecules
482, Rd,
5349–5361(2019)
doi:10.1093/mnras/sty2901
ridge.
The
comparisonofspatialdistribution
andabundance
ratioswith
MNRAS 482, 5349–5361 (2019)
doi:10.1093/mnras/sty2901
H
OCHO
is
likelyformedonthesurfaceof
dust
grains(methyl formate,formate,ethanol,andformicacid)
indicates
that
C
Advance
Accesspublication2018
October29
tofunctional-groupradicals(CH
OCHO)
derivedfrom
methylformate (CH3OCHO).
byaddition
of
CH
2
5
H
OCHO
is
likelyformedonthesurfaceof
dust
grains(methylethanol,andformicacid)
indicatesthat
C
3 October 29 2 52Advance Access publication 2018

37

A GHz
6.7 GHzmethanolmaser
surveyof central
the central
molecular
A 6.7
methanolmaser
surveyof themolecularzonezone
1 CIERA and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208-3112, USA
1 CIERA and
Department of Physics and Astronomy, Northwestern University, 214533 Sheridan Rd, Evanston,
IL 60208-3112, USA◦
2
Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801, USA
2 NationalNational
Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801, USA

Downloaded from https://academic.oup.com/mnras/article-abstract/482/4/5349/5146468 by National Astronomical Observatory J

Matthew
Rickert,F.(7pp),Yusef-Zadeh
and
The Astrophysical871:1722019 February
1J. Ott
Matthew
F. Yusef-Zadeh
and J.
Ott
A B S T R A Rickert,
CJournal,
T

Downloaded from https://academic.oup.com/mnras/article-abstract/482/4/5349/5146468 by National Astronomical Observatory

to functional-groupfunctional-group radicals
radicals (CH(CH22OCHO)OCHO) derived
derived fromfrom methyl
methyl formate
formate (CH(CH33OCHO).
OCHO).
by addition
addition ofof CH
CH33 tobyKeywords:
ISM:
abundances–
ISM:
individual
objects(OrionKey
words:
ISM:
abundances–
ISM:
individual
objects(OrionKL)–
ISM:
molecules–
radiolines:
ISM –– KL)stars: – ISM: molecules – radio lines: ISM – stars:
Keywords:
ISM:
abundances–
ISM:
individual
objects(OrionKL)–
ISM:
molecules–
radiolines:
ISM
stars:
October 18. Received 2018 October 11; in original form 2018 August 11
formationformationformation
Supporting material:material: ﬁgure
ﬁgure sets,
sets, machine-readable
machine-readable tables
tablesSupporting
Supporting
material:
ﬁguresets, machine-readable
tables2
1,2‹ 1,2‹
1‹ 1‹2

https://doi.org/10.3847/1538-4357/aaf9a6

1. Introduction
Introduction
OCHO, hereafter
hereafter MF),
which isis relatively
relatively
methyl formate
formate (CH(CH OCHO,© 2019. The American
Astronomical
Society.
All (CMZ)
rights reserved.
1.
which
methylThecentralmolecular
zone
spans
the
inner
∼450
pc
(∼3
) MF),
ofourGalaxy.
Thisregionabundant inin many
many high-mass
high-mass (e.g.,(e.g., Favre
Favre etet al.
al. 2011;
2011; Rivilla
Rivilla etet al.
al.
abundant
Almost200
molecules
have
been
detectedintheinterstellar
Almost 200 molecules
havebeen bydetectedin theinterstellar
1.
Introduction
methylformateisdefineditsenhancedmolecularemissionandcontains
5
per
cent
of
the
entireGalaxy’s
2017a, 2017b)
2017b) andand low-mass
low-mass star-forming
star-forming regions
regions (e.g.,(e.g., Cazaux
Cazaux (CH3OCHO, hereafter MF), which is relatively
2017a,
medium (ISM)(ISM) andand circumstellar
circumstellar environments,
environments, ofof whichwhich more
more
mediumetal.
2003).
Ethyl
formate(C
H
OCHO,
hereafter
EF)
is
the
next
2
5
et
al.
2003).
Ethyl
formate(C
H
OCHO,
hereafter
EF)
is
the
abundantinmanyhigh-mass (e.g., Favre et al. 2011; Rivilla et al.
2
5
gas
mass.
However,numberdetectedstar-forming
sites towardsnext
the CMZ
than 65
65 areare considered
consideredmolecularcomplexorganic
molecules(COMs),
Accepted2018 October
18.
Received
2018the
October
11; in originalform 2018 August
11
thancomplexorganic
molecules(COMs),
Accepted
2018
October 18.
Received
2018
October 11;
insteporiginalform
2018
August11
200
molecules
have
been
detected
inoftheinterstellar
stepin thethechemicalcomplexityof esters,
esters, with
with 11
11 atoms.
atoms. EF
EF hashasinchemicalcomplexityofmolecules with
with Almost
atoms
containing
carbon.
The
formationofmolecules
66 atoms
containing
carbon.
The
formationof2017a,
2017b)
low-mass star-forming regions (e.g., Cazaux
may be low for the amount of molecular
gas thatispresent, andsurveys andof startwo conformers:
conformers:thetrans-conformer(alsoimproved
calledanti-conformer)
twothetrans-conformer
calledanti-conformer)
these COMs
COMs medium
in thethe ISMISM isis(ISM)
still poorly
poorlyandunderstoodand isis subject
subjectenvironments,ofcircumstellarof atoms
whichmore (also
these
in
still
understood
and
of
where
the
heavytheC-C-O-C=O
form
a planarplanarzigzagchain,etal.
2003).
Ethyl
formate(C2H5OCHO, hereafter EF) is the next
formation
indicatorscanhelp
clarify
this.
With
Karl
G.
Jansky
Very
Large
Array
(VLA),
where
the
heavy
atoms
C-C-O-C=O
formazigzagchain,
intensedebate.
Twogeneraltheorieshave
been
proposed:gasintense debate.
Two 65generalhave been complex
proposed: gas-organic
A B S Tand
R A theCmolecules
Tgauche-conformer
than
are theories
considered(COMs),
produced byby anan out-of-plane
out-of-plane rotation
rotation ofof
B S T R A C Tand◦thegauche-conformer
producedphase chemistrychemistry (e.g.,(e.g., Millar
Millaret al.
al. 1991;
1991; Balucani
Balucani
etsurvey
al.A2015;
2015;◦chemical
phase
et
al.
OH)
masersspanning
the
inner
3
we conducteda blindof
6.7
GHz
methanol
(CH
step
in
the
complexityof esters,4 with 11 atoms. EF has 5
1,2 et1
1,3
3
The
centralmolecular
zone
(CMZ)
spans
the
inner
∼450
pc
(∼3
)
of
our
Galaxy.
This◦the ethyl
ethyl The
group(CMZ)(C22H
H55))spansaroundthe
O-Cbondpc(Medvedev(Medvedev
et Galaxy.
al.
centralcarbon.
molecular
zone
theof
inner
∼450
(∼3 ) of ourThis region region
the
group
(C
around
the
O-C
bond
et
al.
6 chemistryatoms containing
formation
Taquet etet al.
al. molecules2016), andand dust
dustwithgrain surface
surfacechemistry(e.g., The
GarrodTaquet2016),
grain(e.g.,
Garrodis definedby Theits
enhancedmolecularemissionandcontains
5 Several
perofcentofthe Galaxy’s
entireGalaxy’s2009).
The
formationroutes
of EF
EF
are
still
poorlyknown.
Several×40
arcmin
(450
pc
×
100
pc)
of
the
Galaxy.
We
detected
43
CHOH
maserstowards
two
conformers:thetrans-conformer(also called anti-conformer)
32009).
formationroutesofarestillpoorlyknown.
isdefinedbyitsenhancedmolecularemissionandcontains
5
per
cent
the
entire&Herbst2006;
Fedoseev
et
al.
2015;
Chuangetal.
2016).
5& Herbst 2006;
Fedoseev
et al.in2015;
et al.
2016).
theseCOMs
theChuang
ISM isstill
poorlymolecularunderstoodandHowever,is havesubjectof of detectedchemicalpathwayshave
been
proposed,
includingreactions
ontowards
gas mass.
the number
star-forming
sites aretowards
the CMZ
chemicalpathways
been
proposed,
includingreactionsonOrion KLKL is
is aa high-mass
high-mass
star-forming ∼16
region ofthatwhichprovidesa newmolecular
gas
mass.
However,thenumberofdetectedstar-forming
sites
the
CMZ
28
locations,aredetections.
Thevelocities
of
most
of
these
masers
where
the
heavy
atoms
C-C-O-C=O
form a planar zigzag chain,Orionstar-forming
regionthat
providesa1
thelow
surfaceofproposed:
dust
grainsandreactionsin thatthe gasgas
phase.
Onone
intensedebate.
Twogeneraltheorieshave
been
gasfortheamountof andmolecular
gasin
is de
present,
andoneimproved
surveysof3-72star (Xangari), 58089 Morelia, Michoacán, México
surfaceof
dust
grainsreactions
phase.
On
superb template
templatefor constraining
constraining
the chemicalchemicalmodels(e.g.,
Instituto
de Radioastronomía
y may
Astrofísica,
Universidad
Nacional
Autónoma
México,Apdo.
Postalsuperbforthemodels(e.g.,
bemay
lowbethefortheamountofmoleculargas
thatis thepresent,
andimproved
surveysof starproducedOH
masersareconsistent
with
being
locatedwithinthe
CMZ.
AmajorityofthedetectedCHandthegauche-conformerbyan out-of-plane rotation of
hand,
Charnleyetal.
(1995)
usedgas-phasereactionsstarting
with
3
hand,
Charnley
et etal.help(1995)
usedgas-phasereactionsstarting
indicators
can
this.
With
the
G.
JanskyVery Array
Large Array
Brouillet et
et al.
al.
2013; Crockett
Crockett
et al.
al. 2015;
2015;
FengMillar
et al.
al. 2015;
2015;
Carrollphase
chemistry(e.g.,
etformation
al. formation
1991;
Balucanial.clarify
2015;
Brouillet
2013;
et
Feng
et
Carrollindicators
canHhelp
clarify
this.
With
Karl
G.KarlJanskyVerywith
Large(VLA),(VLA),◦l.rodriguez@irya.unam.mx
ethanol(COH,
hereafterET)
tothe
produceEF.
Recently,
the spanning
2H5
5OH,
ethanol(ChereafterET)
toproduceEF.
Recently,
thedistributed
positive
Galactic
longitudes,
similartotwo-thirdsofthemoleculargas
et al.
al. 2017;
2017; Favre
Favre
et al.
al. 2017;
2017;
Friedel &&towards
Looney 2017).
2017).
Orion KLKL
OH)
masers
the
inner
3
we
conductedablindsurveyof
6.7GHz
methanol
(CH
2
the
ethyl
group
(C
H
)
aroundthe
O-C
bonddel(Medvedev
et al.
2◦etetFriedelLooneyOrion
3
2 inner5OH) masers
spanning Emiliano
the
3 Zapata Km.4, Real
we conducteda blindsurveyof 6.7GHz
methanol(CH
Taquetet al.andand
grain
surfacechemistry
Garrod3gas-phaseMesoamerican
CenterfordustTheoretical
Physics,
Universidad
Autónoma
Chiapas,Carretera
Bosque (Terán), 29050 Tuxtla
formationof EF
EF (e.g.,has
been
includedin aadenewchemicalformation
of
has
been
includedinnewgas-phasechemicalconsists ofof different
different
spatialand2016),chemicalcomponentsy:
theGalactic
hot× 40 arcmin(450
pc The
×
100
pc)
of
theCH
Galaxy.
We
detected
43
CHmasers
towards
consists
spatialchemicalcomponentsy:
thehot
3 OH masers
OH
maser
is
an
exclusive
mass
distributed
atpositive
longitudes.
6.7GHz2009).
The
formationroutes
of
EF
are
still
poorlyknown.
Several3
×40
arcmin
(450
pc
×
100
pc)
of
the
Galaxy.
We
detected
43
CHOH
towards
network (Taquet(Taquetal. 2016),
2016), ininGutiérrez,
which formic
formicChiapas,
acid (HCOOH)(HCOOH)
3and
network
al.
which
acid
core, thethe compact
compact
ridge, 2006;
the extended
extendedridge, andandtheplateau& Herbst
Fedoseev
et theal.plateau
2015;
Chuanget ofal. etet2016).
Méxicocore,
ridge,
theridge,
arenewdetections.
The
ofand
most
of masers
these masersare28 8locations,∼16 formation,
of∼16
which
are
new
The
velocities
of
most
of
these
are
ammonia(NH33))whichfavor
thedetections.
formationof EF.
EF.
On velocities
the
other
hand,
) starwith
newdetections
indicating
sites
ofindicator
high-mass(>
M28⊙ locations,ammonia
(NH
favor
the
formation
of
On
the
other
hand,
(Blake etet al.
al. 1987).
1987). In
In particular,
particular,
two3 ofregions,
the hot
hot
core
and
the
chemicalpathwayshave
been
includingreactions(Blaketwo
regions,
the
core
and
the
InstitutodeAstronomía,
Universidad
Nacional
AutónomadeMéxico,Apartado
Postal70-264,
CdMx,
CP 04510,
México on
masersareproposed,
consistent
with
being
locatedwithinthe
CMZ.
Amajorityofthedetected
CH
Orion
KL
is
a
high-mass
star-forming
regionthat
providesa
3 OH
The
AstrophysicalJournal,871:172(7pp),
2019
February1
https://doi.org/10.3847/1538-4357/aaf9a6
Garrodetal.
(2008)
proposedanalternative
scenario
based
on
OH
masersareconsistent
with
being
locatedwithinthe
CMZ.
Amajorityofthedetected
CH
The
AstrophysicalJournal,871:172(7pp),
2019
February1
https://doi.org/10.3847/1538-4357/aaf9a6
Garrod et al. (2008) proposed an alternative scenario based on 3
compact ridge,
ridge, have
have received
received
specialattention
becausetheyare4attention
compact
specialbecausetheyaremassivestarformation
in
the
CMZ.
surfacedust
grainsreactionsin the gas
phase.
On onedistributed
towards
positive
Galactic
longitudes,
similarto two-thirds
themoleculargas
The Americantemplate
Astronomical
Society.
Allrightsreserved. Nacional
Instituto
deOpticayin
Electrónica,
Luis
EnriqueErro#1,
CPgasand
72840,
Tonantzintla,
Puebla,Méxicograin-surface
chemistry,
inlongitudes,which
EF cancanbetheformed
from
ETof
and
superbfortheAstrofísica,
chemicalmodels(e.g.,©(e.g.,
2019. The
AmericanAstronomicalAllrightsreserved.
very richrich ©inin2019.
organic
speciesBlake
etal.constraining
1987;Society.
Favre
et al.
al.
grain-surface
chemistry,
which
EF
be
formedfromETanddistributed
towards
positive
Galactic
similarto two-thirdsofthe ofmolecularveryorganic
species(e.g.,
Blake
et
al.
1987;
Favre
et
5
maser
is an exclusive
mass
distributedat positive
Galactic
longitudes.
The
6.7CH
GHz
CHmaser
MF atvia
cosmicray-induced
photodissociation.
3 OHethand,
Charnleyal.
(1995)
usedgas-phasereactionsstartingwith
2011; Wang
WangBrouillet
et al.
al. 2011).
2011).
While
the
hot
core
is
rich
in
nitrogenMF
via
cosmicray-induced
photodissociation.
National
Radio
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Observatory,
520
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Road,
Charlottesville,
VA
22903,
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isan
exclusive
mass
distributed
positive
Galactic
longitudes.
The
6.7
GHz
2011;
et
While
the
hot
core
is
rich
in
nitrogenKey
words:
catalogues–
surveys–
Galaxy:centre–Galaxy:nucleus–galaxies:
starforma3
etal.2013,
2013;
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CarrollThe
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compared)formation,
starproposed
formation,
withdetections
detections
indicatingofof high-mass(> )8 starM⊙routes
2017;Received
Pagani etet al.
2017;indicator
bearing molecules
molecules (Peng(Peng etet al.
al. 2013,
The
different
shouldbecompared
2017;
Pagani2017;
bearingwith
newindicatingsites ofsites
indicatorof high-mass(> 8 M
2018
June
10;
revised2018
December
17;
accepted
2018
December
17;
published
2019
January30
ethanol(C
H
OH,
hereafterET)
toproduceEF.
Recently,
the
⊙
2
5
tion.
et al.the
2017;
Favre
etricheral.
2017;Friedel&Looney2017).
Orion
KLits
with
observations
of
EF
and
its chemicallychemicallyrelatedwith
species.
Flat-spectrum
RadioContinuum
Emission
Associatedwithò Eridani
massivestarformation
in of
the
CMZ.
Rizzo etet al.
al. 2017),
2017),
thecompact
ridge isisricherinoxygen-bearing
withobservations
EFandrelatedspecies.
Flat-spectrum
RadioContinuum
Emission
Associatedò Eridani
Rizzo
compactridgeinoxygen-bearing
massivestar formationin the CMZ.
However,
because
EF
is
a
very
complexmolecule
that
therefore
formation
of
EF
has
been
includedinanewgas-phasechemicalspecies(Blakeetal.
1987;
Beuther
et
al.
2005;
Friedel&SnyderHowever,
because
EF
is
a
very
complexmolecule
that
therefore
species (Blake
et al. 1987;ofBeutherFriedel& Snyderconsists
different
spatialandchemicalcomponentsy:
theso– hot
1,2 et al. 2005;
4centre – Galaxy: 4
5
KeyLoinard
words:
catalogues–Chávez-Dagostino
surveys
Galaxy:nucleusgalaxies:
star5 forma1,2 1 , Laurent
1 a 1,3
F. Rodríguez
, Susana
Lizano, Miguel
TimothyS.toward
Bastianhas
lowabundance,
it–1,3has sofarcentre
beenChávez-Dagostino
detected
only
towardfour ,– andKey bywords:
catalogues– surveys
Galaxy:–, Galaxy:nucleusgalaxies:
forma2008; Gong
Gong etetLuisal. 2015).
2015).
The hot
hot
core
regionmay
be heatedheatedby
Luis
F.
Rodríguez, Susana
LizanoLaurent
Loinard, Miguel,–Timothy
Bastian, andhasa, lowabundance,
it
has
far
been
detected
only
four
2008;
al.
The
core
regionmaybe
network(TaquetetS.staral.
2016),
in which formic acid (HCOOH) and5 the plateau5
tion.
core,
the
compact
ridge,
theextendedridge,
andAnthonyJ.
Beasleysources:thethreemassivestar-forming
regions
Sgr
B2(N)shocksfrom
sourceI
outﬂow(e.g.,
Goddi
et
al.
2011)
or
by
an
sources: the Anthony
three massive
star-forming regions Sgr B2(N)J. Beasleyshocks from1 source I outﬂow 1(e.g., Goddi et al. 2011) ortion.
by anInstitutodeRadioastronomíayAstrofísica,
Universidad
Nacional
AutónomadeMéxico,Apdo.
Postal
3-72(Xangari),
58089
Morelia,
Michoacán,
Méxicoammonia
(NH
)
favor
the
formationof EF. On the other hand,(Bellocheetal.
2009),
W51
e2(Rivillaetal.
2017b),
andOrion
InstitutodeRadioastronomíayAstrofísica,
Universidad
Nacional
AutónomadeMéxico,Apdo.
Postal
3-72(Xangari),
58089
Morelia,
Michoacán,
Méxicoexplosive event
event
that occurredoccurredaround500In
yr agoago(e.g., Bally
Ballytwo
et al.
al. regions,(Bellocheal. 2009),
W51(Rivilla et al. 2017b), and Orion3(Blakeet al.around1987).
particular,
theethotcore
andise2theexplosive
that
500
yr
(e.g.,
etl.rodriguez@irya.unam.mx
to(Tercero
addressl.rodriguez@irya.unam.mx
issue2015),
to andbetterconstrain
the molecular gas
KL(Terceroet thisal. Emiliano
2013,2015),
andthelow-massstar-forming
2011,
2017;
Zapata etet al.
al.Center
2011;
Rivillaet Physics,
al. 2013;
2013;
Wright Autónoma
& ways
KL
et
al.
2013,
the
low-massstar-forming
2 for Rivilla
Zapata2011;
etal.
Wright&Garrodetal.
(2008)
proposedanalternative
scenario based on
U2011,C T I 2017;
O N2 compact
Mesoamerican
Theoretical
Universidad
deChiapas,Carretera
Zapata
Km.4,
Real
del
Bosque(Terán),29050
Tuxtlaridge,
have received
specialattention
becausetheyinstead
areMesoamerican
Theoretical
Physics,
Universidad Autónoma
de Chiapas,
Carretera
Emiliano Zapata Km.4, Real del Bosque (Terán), 29050 Tuxtla
regionBarnard1b we(Marcelino
etal. 2018).
2018).
Bellocheet al.
al. (2009),(2009),
mass
inChiapas,
the
CMZ,
have
chosento address
this issue by
Plambeck 2017).
2017). Whether
Whether this
this
explosive Center
eventforimpacted
impactedthe
Gutiérrez,
MéxicoregionBarnard
1b(Marcelino
etal.
BellocheetPlambeck
explosive
event
the
Gutiérrez,
Chiapas,México3
ways
toaddress
this
issue
is
to
betterconstrainthemoleculargasgrain-surface
chemistry,
in
which
EF
can
be
formedfrom ET and
3U C T
InstitutodeUniversidad
Nacional
AutónomadeMéxico,Apartado
Postal70-264,CP 04510,
MéxicoTerceroet1987;al. (2013),(2013),
andRivillaetApartado
al.CdMx,(2017b)allusedsingle-dish
very
rich
in
organic
speciesBlake
et al.
Favre
al.
release zoneof complex
complexmolecules
the
gasD
phase
is
under
debateways
toet
address
this
issue
is
tousedbetterconstrainthemolecular
gas
1into
Ithe
N
TAstronomía,
RO
I OunderN(e.g.,
Terceroetal.
andRivillaetal.
(2017b)allsingle-dishInstitutodeAstronomía,
Universidad
Nacional
AutónomadeMéxico,Postal70-264,
CdMx,
CP 04510,
Méxicolecular(CMZ)
occupies
inner∼pc(∼debate
obtaining
improvedcountsofthestar-forming
sites
in thisreleaseofmolecules
the
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is
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Tinto
RO
D
U
C T phase
Ide
O
N450
mass
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thenumber
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have
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issue by
4 Astrofísica,
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Nacional
Opticadey Electrónica,
Luis30
Enrique
ErroSingle-dish
#1,
CP in
72840,
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observations
give
the
line
intensity
mass
the
CMZ,
we
have
insteadchosentoaddress
this
issue
by
(e.g.,
Favre
et
al.
2017;
Friedel&Looney2017).
Instituto
Nacional
Astrofísica,
OpticayElectrónica,
Luis
EnriqueErro#1,
CP
72840,
Tonantzintla,
Puebla,MéxicoMFvia
cosmicray-induced
photodissociation.
IRAM
30
m
data.
Single-dishobservations
give
the
line
intensity
5 2011).
etal.is 2017;Friedel& central
Looney2017).
2011;
Wang
et
al.
the
hot
core
ispc
rich
in
nitrogenxy.(e.g.,
ThisFavre
regiondefinedbyTheenhancedmoleculartheAstronomy
CMZ.
5gas
National
RadioWhile
Astronomy
Observatory,
520inner
Edgemont
Charlottesville,
VA 22903,
USAcounts
molecular
zone
(CMZ)
occupies
the∼over450Road,pclarge(∼obtaining
improved
ofthe
thespatial
numberof star-forming sites in
National
Radio
520
Edgemont
Road,
Charlottesville,
VA
22903,
USA
integrated
beam
area
and
do
not
provideThe central
zone
(CMZ)
occupies
the inner∼ 450Observatory,(∼obtaining
improvedcountsof thenumberofstar-forming sites in
The ester
ester familyfamily ofof molecules
molecules
ismolecularessential
for10;
many
prebiotic
integrated
over
aa December
large
beam
area
and
do
not
providethe
spatial
The
for
many
prebiotic◦ is essential
Received2018
June
revisedDecember17; accepted201817;
published
2019
January
30indifferent) oftheGalaxy’s
Galaxy.
Thisregionis2018
definedbyenhancedmolecular
gas
the
CMZ.
chemicalroutes proposed should be compared
Received
2018
June
10;
revised2018
December
17;
accepted
2018
December
17;Thepublished
2019
January
30 of◦cent 3ofe processes.
being lessThe
than
1
per
the
volume,Dueto30
magnitudes
ofvisualextinction
thedirection
2017;
Paganietal.
2017;
bearingmolecules
(Peng
et
al.
2013,
3
)
of
the
Galaxy.
Thisregionisdefinedbyenhancedmolecular
gas
the
CMZ.
distribution
of
EF,
nor
do
they
provideanaccurate
value
of
the
processes.
The
simplest
representativeisthe
8-atommoleculeEF, nor do they
providean accurate ofvalueof extinction
thesimplest representativeis thebeing
8-atommoleculeemission. Whileless than
1 per cent ofdistribution
the Galaxy’sofvolume,Due
to 30 magnitudes
visualin the direction ofemission.
While
being
less
than
1
per
cent
of
the
Galaxy’s
volume,Dueto30
magnitudes
ofvisualextinction
inthedirectionofto contain 5Rizzo
per centetof
theGalaxy’smolecular
gas
the
CMZ,
masersareusefulprobesofstarformation
in
the
CMZ.
with observations of EF and its chemically related species.
al. 2017),
thetocompact
is Galaxy’s
richerin oxygen-bearing
Abstract
it is estimatedcontain 5 perridgecent of themoleculargas
the CMZ, masers are useful probes of star formation in the CMZ.
Abstract
it is estimatedto contain 5 percent of the Galaxy’s
molecular gasthe first
the CMZ,
masersare useful probesof starof
formationin the CMZ.
11 Theet al. 1998; Xuet al. 2015).
The
interstellar
We
conducted
blindinterferometricsurvey6.7 GHz−11−1
However,
becauseEF
isofGHz
a6.7verymass(Dahmenet al. medium
1998;
Xu et al. et2015).
interstellar
mediumWe
conducted
theblindinterferometricsurveyGHz complex molecule that therefore
species(Blakeetal.
1987;
Beutheral.
2005;
Friedel&SnyderWe present
Very
Large
Array
observations
at
33.0
GHz
that
detectemissioncoincident
withòfirstEridanitowithinmass (DahmenWe
et al.present
1998; Xuet al.Large2015).Array
The interstellar
mediumWe conducted
theemission
first blindinterferometricof to
6.7withinVeryobservationsat33.0 GHz
that detect
coincident
withòsurvey
Eridani:3aOH)
towardsCMZ
usingunique in its physicalproperties,
containingamethanol(CHmaserssupports
towardsthe
theKarl
CMZ G.
using the Karl G.
in theCMZ
is uniqueof
inhigherits physicalproperties,
containing
highermasers
methanol(CHthe
3 OH)
0
07
(0.2
au
at
the
distance
thisstar),
withapositional
accuracy
of
0
05.
This
resultstrongly
the
a
low
has
maserstheabundance,
CMZ
using supports
the itKarl
G.
in the CMZ
is 0uniquein itsauphysicalproperties,
containinga highermethanolaccuracy(CH
07 (0.2
at thehot
distanceofthis star),with abepositional
0 has
05.towards
This
resultstrongly
the so far been detected only toward four3 OH)of
2008;
Gong
et
al.
2015).
The
core
regionmayheatedby
Jansky
Very
Large
Array
(VLA).
This maser
is a strong indicamoleculargasauthors
densitythat(Ao
et al.
2013),Jansky
highertemperature(MorLarge
Array(VLA).
This
strongdensity (Ao et al.suggestion2013),
highertemperature(Morof previous
thequiescentcentimeteremissioncomes
star
and masernotfroma aproposed
Janskyfrom
VerytheLarge
Array(VLA).
maser
isindicaa strong
indicamolecular
gas suggestion
density(Aoof
et previousal.
2013),
higher temperature(Morauthors
thattheVeryquiescentcentimeteremissioncomesfromtheisThis
star
and
not
from
a massive
proposedsources:thethree
star-forming regions Sgr B2(N)formation(van Dishoeck& Blaketorofhigh-mass(>
8 M⊙ ) starris
& Serabyn
1996;
Martinaxis
et al. of
2004;
Oka
et et
al.au).
2005;
Ao centimeter
et al. or byfromsourceIaexoplanet
outﬂow(e.g.,
Goddi
al.
2011)
an
(3.4
emissionisremarkably
ﬂat
and
is
giant
with
semimajor∼1)starformation(van
Dishoeck
Blakeis
torMofhigh-mass(>
8
M
risexoplanet& Oka
Serabyn
1996;
Martinet al.
2004;
ettor
al.0of
2005;
Ao
al.
)
star
formation(van
Dishoeck&Blakehigh-mass(>
8
1996; Martinshocks
et al.
2004;
et
al.
2005;
Ao
et
al.
0 (3.4au).
The
centimeteremissionisremarkably
ﬂat& and
giant
with
a Oka
semimajor
axis
ofetThe∼1⊙⊙ 1998; Minier et al. 2003). Unlike other CH OH
masers(i.e.e236, (Rivilla et al. 2017b), and Orion
2013),
andincreased
turbulentvelocity(Ballyetal.
1987;
Morris&3
consistentwithoptically
thinwith
free–free
emission.
In1987;
particular,
it&canbemodeledasaetstellar
wind
with
aothermass-loss(Bellocheetal.
2009),
W51
OH
masers
(i.e.
36,
1998;
Minieral.
2003).
UnlikeCH2013),
andincreased
turbulentvelocity(Ballyetal.
Morrisexplosive
event
that
occurredaround500
yrago(e.g.,
Ballyetal.
consistent
opticallythin
free–free
emission.
In
particular,
it
can
be
modeledasastellarwind
withamass-loss
3
1998; Minier et al. 2003). Unlike other CH OH masers (i.e. 36,
eased turbulent velocity (Bally et al. 1987; Morris&−1−11

Flat-spectrum Radio Continuum Emission Associated with ò Eridani

Luis F. Rodríguez

, Susana Lizano, Laurent Loinard, Miguel Chávez-Dagostino , Timothy S. Bastian
Anthony J. Beasley38

Abstract

We present Very Large Array observations at 33.0 GHz that detect emission coincident with ò Eridani to within
0 07 (0.2 au at the distance of this star), with a positional accuracy of 0 05. This result strongly supports thesuggestion of previous authors that the quiescent centimeter emission comes from the star and not from a proposed
giant exoplanet with a semimajor axis of ∼1 0 (3.4 au). The centimeter emission is remarkably ﬂat and isconsistent with optically thin free–free emission. In particular, it can be modeled as a stellar wind with a mass-loss
rate of the order of 6.6×10
M yr , which is 3300 times the solar value, exceeding other estimates of thisstar’s wind. However, interpretation of the emission in terms of other thermal mechanisms like coronal free–freeand gyroresonance emission cannot be discarded.

, and