Imaging the water snowline in a protostellar envelope with H13 CO+?
Merel L.R. van ’t Ho↵1 , Magnus V. Persson2 , Daniel Harsono1 , Vianney Taquet1, 3 , Jes K. Jørgensen4 , Ruud Visser5 ,Edwin A. Bergin6 , and Ewine F. van Dishoeck1, 7
1

A&A proofs: manuscript no. H13CO+_paper_arxiv
Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands
e-mail: vthoff@strw.leidenuniv.nl
2
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala,SwedenA&A
proofs:manuscript
no.Italy
H13CO+_paper_arxiv
3
INAF, Osservatorio Astrofisico di Arcetri, Largo E.
Fermi
5, 50125
Firenze,
4
Centre for Star and Planet Formation, Niels Bohr Institute & Natural History Museum of Denmark, University of Copenhagen,Øster Voldgade 5–7, 1350 Copenhagen K., Denmark5
European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
6
Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109-1107, USA
7
Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
13+

背景：スノーラインの位置を観測的に制限することは、惑星形成メカニズムの解明に不可欠
最も重要な水のスノーラインは、原始惑星円盤での直接観測することがとても難しい

Fig. 3. Integ
shaped H13 C
transfer codeand simulated(right panel).
served due tocontinuum pelower left cor

arXiv:1801.02636v1 [astro-ph.SR] 8 Jan 2018

目的：HCO＋は水のスノーラインの良いトレーサーなのか。

低質量星NGC1333-IRAAS2Aのエンベロープに対し、光学的に薄いH CO でマップピング。
Fig. 3. Integrated intensity maps for a spherically symmetric ringH218O観測結果との比較で、本当にこれがよいトレーサーかどうかわかる。
ABSTRACT
shaped H CO distribution. Emission simulated with the radiative
13

A&A proofs: manuscript no. H13CO+_paper_arxiv+

transfer code Ratran is convolved with the observed beam (left panel),simulatedwith the (u, v) coverage of the NOEMA observations
Context. Snowlines are key ingredients for planet formation. Providing observational constraints on the locations of theandmajor
snowTable
1.
Overviewof themolecular
towardIRAS2A.
(rightimportantpanel).
The
southern line
peakobservationsin the simulations
is probably
not obtiallycompositions
resolve the snowline.
the only thermal
waterlines is therefore crucial for fully connecting planet
to their Furthermore,formation mechanism.
Unfortunately,
the most
served due to presence of water in the outflow (see text for details). The
lines
that
can
be
observedfromtheground(except
fortheHO
2 to the central star.
snowline, that of water, is very difficult to observe directly in protoplanetary disks due to its close proximityacontinuum peakis denoted withcross, andthe beam is shownin theTransition
Frequency
Eupa/kBeamv
at 183 GHz)
arealines
the lesstracer
abundant
isotopologue
Aims. Based on chemical considerations, HCO+ line
is18predicted
to begoodfromchemicalof thewater snowline, because
parlower it
leftiscorner.
00
1

観測：NOrthern Extended Millimeter Array (NOEMA) @ ~0.9ʼʼ 分解能

(GHz)

(K)

H O. As such, even ALMA will have great difficulty locating
A&Aabundant
proofs: manuscript
no. H13CO+_paper_arxiv
ticularly
in dense clouds
when water isthefrozenout. This work aims to map
the optically thin isotopologue H CO toward
H13CO+ J=3-2@
260.255
GHz
water snowline in protoplanetaryFig. disks.
3. atIntegrated
intensityfrom
mapsthea spherically
HforstarCOJ = 3in disks.
2 symmetric260.255 ring25
the envelope of the low-mass protostar NGC1333-IRAS2A, where the snowline
islarger distance
than
2

13
+

+

( )
(km s )
0.93⇥0.68
0.09
0.87⇥0.72 0.115
2.1⇥1.7
4.06

18
An alternative approachis to
use chemical
as hasEmission
shapedH13 CO+imaging,
distribution.
simulated
the radiative
22,0 with203.408
204
13
2 O 31,3
Comparison with previous observations of H18
will showwhether
CO+ isDue
indeeda goodtracerof the waterHsnowline.
+ observed beam (left panel),
2 O been
done forthe COHsnowline.
to CO
being
highlytransfer
code
Ratranis volatile,
convolved00 with
DCOtheJ=2 1
144.068
10
Methods. NGC1333-IRAS2A was observed using
NOrthern
Extended
Array(NOEMA)at ⇠ 0 . 9 resolution, targeting
itsthesnowline
is locatedtens Millimeterof AU
the central
andfromsimulatedwithstarthe(around(u, v) coverage of the NOEMA observations(a)the H13 CO+ J = 3 2 transition at 260.255 GHz.⇠20
TheK;
integrated
emission
profilewasanalyzedusing
1D
radiative
transfermodeling
see e.g. Burke & Brown
2010).
Althoughthis is peakfar inNotes.
Velocity resolution.
(rightpanel).
The southern
the simulations
is probably not ob+
of a spherical envelope with a parametrized abundancefor H13 CO. Thisprofilevalidatedwitha fullchemicalmodel.
enoughprofile
to be spatiallyresolved
with
ALMA,
it of
directly
servedduewastolocatingpresence
water
in theoutflow (seetext for details). The
13
+
00
18
remainsofdifficult;since COpeak,
linecontinuum
emission
optically
Results. The H CO emission peaks ⇠2 northeast
the continuum
whereasispeak
Hgenerallycompact
emissionon source.
2 Oisshowsdenotedwith a cross,and thebeam is shown in theit +does
not revealbytheatcold
disk
midplane.
Reactions
within the inner ⇠360 AU to
Quantitative modeling shows that a decrease in thick,
H13 CO
abundanceleast
a factorof sixisneededlower
left corner.
++
higheraccretion
rates) and the lower vapor pressure, the snow+ N2 H
CO predicts
are the main
destruction
route forinNHCO
2 H , so
reproduce the observed emission profile. Chemicalgaseousmodeling
indeeda steep increase
just outside
water snowline;
linetheis locatedfurther away from the star than in protoplanetaryis
expected
tobeabundant
only+ when CO is frozen out. Taking
the 50% decrease in gaseous H2 O at the snowline is not enough to allow HCO to be abundant. This places the disks
water(10s–100
snowlineAU
at 225instead of a few AU,
Harsono et al. 2015;
simple chemical considerations into account, an upper limit for
Fig. 2. Integrated
intensity map for
the H13 CO+ J = 3 2 transition
AU, further away from the star than expected based
on
the
1D
envelope
temperature
structurefor
NGC1333-IRAS2A.
In
contrast,
+
Cieza
et
al.
2016).
In addition,
H18
O has
already
been overlaid
observed
the CO snowline location can therefore be derived from N2 H
(color scale) toward
IRAS2A, with
1.2 mmcontinuum
in
2 the
+
DCO observations show that the CO snowline isemission
at the expected
location,makinganHo↵outburst
scenario
unlikely.
towardfourof these(Jørgensen
& van
2010;
white
contours(topobjects
panel) andthe H18
22,0Dishoeck
transition inblue(Aikawa
et
al.
2015;
van
’t
et
al.
2017),ashas
2 O 31,313+
18
13+contours (middle panel). The continuum contours are 1.8 (1 ) ⇥ [3, 10,
et al.
2013).
Conclusions. The spatial anticorrelation of the Hbeen
COdoneandforH2theO emission
providea proofconcept
CO canbe 2012,
used asa The only thing lacking are thus highdisks around
TW Hyaand ofHD
163296that(QiH Persson
13 H18 O+ contours are 9.8 (1 ) ⇥ [3, 8, 15,
25, 50, 75] mJy beam 1 , ofandHtheCO. Here, we present NOEMA
2
tracer of the water snowline.
et al. 2013, 2015), and several protostellar envelopes (Jørgensen spatial resolution images
1
1

Fig. 4. Spectr(left panels) a
peak, right pa
and the botto
for each spec
velocity is ma+ s . The beams are depicted in the lower left
25, 35] mJy
observationsof beam
H13 COkm
toward one source, IRAS2A, and com2004; Anderl et al. 2016).
corners.
The position
18 of the continuum peak is marked by a black cross
Key words. ISM: individual objects: NGC1333-IRAS2A–
ISM:
molecules–
astrochemistry–stars:
protostars–
submillimeter:
pare
these
to
the
H
O
emissionpresented
et byal.
For youngthe emissionof complex(the close binary is2 unresolvedin thesedata) andby
the Persson
outflow axes
Fig. 3. Integrated intensity
mapsprotostars,
for a sphericallysymmetric
ring- organic (2012).
planetary systems
is a deeply
embeddedClass
0 protostar
the along the so
red IRAS2A
and blue arrows.
The integrated
intensities
along
the dashedin
white
13+ molecules (COMs) has been used as tracer of the inner region
shaped H CO distribution. Emission simulated with the radiative
ofthe
thebottom
Perseusmolecular
quadruple
line areregion
shown inpanel,
normalizedcloud.
to their The
maximum
value. tensity maps
warm
enough to sublimate
water ice,beam
the so(leftcalledhot core, be- NGC1333
transfer code Ratranis convolved
with the observed
panel),The zeroflux level
andsourcepositionare(Jørgensen
marked by dottedlines.
outflows
suggest
that
it
is
a
close
binaryetal.
2004a), H13 CO+ em
cause
these
speciesareexpectedtobetrapped
in
water
ice.
How00
and simulated with the (u, v) coverage of the NOEMA observations
ever, the exact binding energy, and thus spatial extent, will di↵er which has recently been confirmed (0 . 6 separation, Tobin et al. northeast of(right panel). The southern peak in thesimulations
is probably
not (e.g.,ob- Öberg et
1. Introduction
freeze-out
of wateral. 2011;
SimilarMadhusudhan
to Persson et al. (2012) we adopt a distance of
The asyfor di↵erent molecules.
Compactradius
COM emission
has beende- 2015).
13The+
served due to presence
of
water
in
the
outflow
(see
text
for
details).
250
pc(Enochetal.the2006).
Fig.
2.
Integrated
intensity
map
for
the
H
CO
J
=
3
2
transition
et
al.
2014;
Ali-Dib
et
al.
2014;
Ali-Dib
2017;
Walsh
et
al.
2015;in a beamisbrightestfor
red-shiftedvelocities.
of thepeak
chanemission isFig.
4.
Spectraextracted
towardIn
thenonecontinuum
position
tected toward NGC1333-IRAS2A (hereafter IRAS2A) extend13
+
00
13
+
scale)
IRAS2A,the 1.2mm
in observations
continuum
isingdenotedwitha00. 4cross,
beam
shown
in2005;
thecontinuum(left panels)
andtheresults
H CO arepeak
positionNEof 2theandcontinuum
Water is probably the molecule thatappealspeakmostto
our imagiTheandpresented
in2 Sects.
3, ulating emis
00
nels
does
the
CO
emissionpeakat the (⇠sourceposition.
InMordasini
etJørgensen
al.iswith
2016;
Eistrupetal.overlaid
2016;
Booth
etHal.
2017).
between⇠ 0(colorand⇠and
1toward. 0the(e.g.,
et O
al.
Maret
+
18 topwhite contours (top panel) and the H18
31,3 22,0transitionandin bluerightpanels showthe
H13(RA,Dec)
COJ = 3 ofet
2 transition
2
stead,peak,emissionpeaks
areat o↵sets
aplower
left corner.
compared
withpanels).
the HThe
Oobserved
observations
from
Perssonal. like H13 CO+
00
nation, as it is essential for life as weknow
it. In star-forming
reet al. 2014; Mauryetal.
2014),
similar
to
the
size
(⇠
0
.
8)
of
2
18
In(middle
addition,formation
tocontours
panel).planetesimal
The continuum contours
are 1.8 (1is )thought⇥ [3, 10,00 panels00
andbe
the significantly
bottomO003)1,3
22,0red-shifted
transition. The
two spectra
proximately(-2the,1.5integrated) andthe(3H002,-3
in +theerage as the18(2012).
InforSect.
4,
H13theCOis channels,
analyzed(Perssonet al.in12012).
The
exact
relationship25, 50,75] mJy beam
, thisand theregionH18
are9.8 (1 ) ⇥ [3,8, 15,
gions, water plays an important role as coolant of thetheHwarmgas,
areshown onsameemission
verticalThesystemic
00 1988;
2 O contours
2 O emission
enhanced(e.g.,
Stevenson&
LunineSchooandatradiative(1each,-600species) intransfer
theblue-shiftedchannels.
H18
O,scale.
on envelope
the
other
east and sou
1
1
1
2
using
1D
modelingofaspherical
25,
mJy
beamsnowline
km s . remains
The beamsunclear
are depictedin the lower left velocity is marked by the vertical dotted line at vlsr ⇡ 7 km s .
between COMs
and35]thewater
though.
as dominant carrier of oxygen, and as major constituentof icyhand,
on source (located by Persson sion pattern
13 emission+
nenberg&ofOrmel2017).
The
exact
andshows
timecompact
evolutionThethecontinuum
is marked
by alocation
black
cross
with
a
parametrizedHCOabundance
profile.
In
addition,
For example, thecorners.
extentof position
methanolemission
inpeakIRAS2Ais half00
et al. 2012 ⇠0 . 1 southwest of the continuum peak) and extends peak in the dgrain mantles deep inside a planet-forming disk (seee.g., Mel-H18close
binarywateris (Maretunresolveddata)protostellar
and theitoutflow
axes abundancebythesnowlineinsystems
is thusa crucialprofileis validated against the outcome of athe size of the (theOofemission
et inal.these2014),
while
is this18 2009; Bergin & van Dishoeck 2012; van Dishoeck
red2 and blue arrows. The integrated intensities along the dashed white along the southern outflow axis. Overlaying
the integrated innick
et
al.
full
chemical
network
low-resolution
DCO+ observations.
2
Article number,
page 4andof 10
twice the size in(Anderl
et al. to2016).
In
in planet
formation.
18
lineNGC1333-IRAS4A
areingredientshown in the bottom
panel,
normalized
their maximum
value.
maps forincluding
H13 CO+ andHwe(see Fig.the2) predicted
shows that the
2 Oconfirm
The maintensity
conclusions,that
2013, for reviews). The transition from water being
frozenout
addition,
Perssonal.flux(2012)
concludethat C2are
H5marked
CN is bylikelyTheetzerolevel andsource position
dotted lines.
+
00
13
+
18
H13 CObetween
emissionsurrounds
thewater
emissionand peaks
anticorrelation
H
CO
and
H
O,
are
summarized
in ⇠2
not
relatedtosublimation
of
water
ice.
Since
the
detectionofonto dust grains to being predominantly present in the gas phase
Unfortunately, the water snowline is verynortheast
hard toobserveof thecontinuum peak. 2
Sect.
5.
is verydifficult in mature protoplanetary disks, with only
13+
occurs at the water snowline: the midplane radius COMs
at which
50%

H13CO+のemission peak：
一方、H

13

continuum peakの北~2ʼʼ

Oはコンパクトなemission

asymmetryin the spatial distribution of the H CO
directly in protoplanetary disks. Because of theThelargebinding

.: Imaging the water snowline in a protostellar envelope with H COe↵ect of the threeauses the H13 CO+y, it could perhaps
entary structure at=> 定量的モデル：

oward the continted in Fig. 4. Alnt on source, it iswhere water emis⇡ 0.8 km s 1 ) of
that the emission
on, the H18
2 O lineshown in Persson
he H182 O emission
ct component. The
spectrum is due to2).
d the systemic vege-scale envelope
channel maps inound the systemic
MT single dish obs that only ⇠7% ofervations, demond on larger scales.
n shows that somen the central changht at scales larger

このずれは、360AU以内でのH13CO+のabundanceの減少で説明できる。

A&A proofs: manuscript no. H13CO+_paper_arxiv

CO+O+ emission at thephysical-chemical
tive transfer code
the physical strucofiles for IRAS2A
he 1D spherically
Y (Ivezić & Elitzur
ameters were fitand the spatial exed on the chemiabundant when its
lest H13 CO+ disabundance insidend a higher abuner abundances arentegrated intensity
ence of the southannot be modelede restrict the comt. For a first analyi↵erence between
not be reproduced
ong the radial cut
fted channels arencluding all chand integrated radiale required to reach
wever, deriving thehis work. Finally,u, v) coverage are

Fig. 6. Left panels: Temperature (gray) and density (blue) profiles for the IRAS2A envelope from Kristensen et al. (2012) (top), and the corresponding H2 O (light blue), CO (blue) and HCO+ (purple) abundances predicted by the GRAINOBLE model (bottom). The dashed green line
shows the empirically inferred abundance profile for H13 CO+ (scaled down by a factor 100). Right panels: As left panels, but with the temperature
increased by a factor 2.2. The vertical dotted lines mark the H2 O and CO snowlines.

13>90 AU can roughly reproduce the observed integrated
intensity +20,000 AU radial extent of the model. An increased temperature
水スノーラインの丁度外側でH
CO が増加：(Fig. 5, second row). However, independent of the inner abun- is thus required to set the inner radius of the H CO abundance
13

Fig. 5. Di↵erent H13 CO+ abundance profiles (left panels) and the resulting simulated integrated emission along the northeastern part of the radial cut shown in Fig. 2 (right panels). The observed emission is shownin purple. The location of the abundance jumps (in Kelvin and AU) is
indicated in the top right corners. Bottom panel: Temperature (gray) anddensity (blue) profiles for the IRAS2A envelope from Kristensen et al.
(2012) used in the top two models. The location of the H2 O and CO
snowlines (at 100 K and 20 K, resp.) are marked by the dotted red andblue lines, respectively. The temperature profile increased by a factorof 2.2, used in the bottom two models, is shown in black. The resulting
H2 O snowline is indicated by the dashed red line while the CO snowline
now falls outside the adopted radial range. For IRAS2A, 100 corresponds
to ⇠250 AU.

produced from the Ratran images in GILDAS by creating a (u, v)
table with the function uv_fmodel.
Di↵erent H13 CO+ abundance profiles with their corresponding integrated emission profiles are presented in Fig. 5. For the
13physical+structure, the18
adopted
2 temperature drops below 100 K
around 90 AU. An H13 CO+ abundance of 1 ⇥ 10 10 at radii

H CO とH

dance, the emission always peaks on source, as in the case of
a constant H13 CO+ abundance at all radii (Fig. 5, top row). Although a large fraction (⇠90%) of the emission is already being resolved out with the (u, v) coverage of the observations, thisthus does not result in a dip in the H13 CO+ emission toward thesource position.
To13
reproduce +the location of the emission peak, the abundance jump has to be shifted outward to a radius of ⇠360 AU.
To move the 100 K radius, representing the water snowline, thisfar out, the temperature profile has to be multiplied by a factor of 2.2 (Fig. 5, third row). However, the observed integrated
intensity cannot be reached with this abundance profile, as the
H13 CO+ emission becomes optically thick for outer abundanceshigher than 3 ⇥ 10 10 . Varying the abundance does not a↵ect theposition of the emission peak.
The best match to the observed H13 CO+ radial profile canbe reached by introducing an additional drop in the abundancearound ⇠4000 AU (Fig. 5, fourth row). An increase in abundance of at least a factor of six is required around 360 AU to
get the emission peak at the observed location, but the exact radius of the outer drop does not influence the peak position. Sucha decrease in the H13 CO+ abundance can be expected around the
CO snowline because formation of HCO+ will be limited in thisregion due to a reduction in the parent gaseous CO molecules.

+at the water snowline, while the original temperature places theouter radius around the CO snowline. This discrepancy will befurther discussed in Sects. 4.2 and 4.3. The main result of thesemodels is that the observed position of the H13 CO+ emission
peak can only be reproduced by a reduction in the abundance ofat least a factor 6 in the inner ⇠360 AU.

化学モデルの予測と一致（水スノーラインが225AU付近で、一方H CO のabundanceピークは360AUからさらに135AU外側）
4.2. Comparison with a full chemical model

To inspect the legitimacy of the simple abundance profile, we
水スノーラインは225AUに置かれる。
compare it to the outcome of the astrochemical code GRAINO-

BLE (Taquet et al. 2012a,b, 2013, 2014). In short, GRAINOBLE
uses the rate equations approach (Hasegawa et al. 1992) considering three types of reactions (a so-called three-phase model
based on Hasegawa & Herbst 1993): reactions for gas-phase
species, reactions for species on the ice surface, and reactions forbulk ice species. The gas-phase chemical network is taken fromthe KIDA dabatase (Wakelam et al. 2015) supplemented by ionneutral reactions described in Taquet et al. (2016). A cosmic ray
ionization rate of 5 ⇥ 10 17 s 1 is used. In addition to thermal
desorption, UV-photodesorption and chemical desorption upon
formation of an exothermic surface reaction have been included
as desorption processes. The surface chemical network follows
the results of recent laboratory experiments in order to form the

1Dエンベロープの温度構造から予測される距離よりも、かなり遠い

Oの空間的不一致：

Article number, page 5 of 10「H13CO+は水スノーラインのトレーサーとして使える」ことを示す。

The Near-Infrared Outflow and Cavity of the proto-Brown Dwarf
Candidate ISO-Oph 200?
Whelan, E.T.1 , Riaz, B.2 , and Rouzé, B.1
1

Maynooth University Department of Experimental Physics, National University of Ireland Maynooth, Maynooth Co. Kildare,
proto-brown dwarf候補天体のNIR観測論文。
Ireland2

Max-Planck-Institut fr Extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching, Germany

天体：ISO-Oph 200（0,06+-0.01 Msun）。SEDからClass Iと考えられている（Evans+09）
ABSTRACT

arXiv:1801.08749v1 [astro-ph.SR] 26 Jan 2018

In this lettera near-infrared integral fieldstudy of a proto-brown dwarf candidate is presented. A ⇠ 0.00 5 blue-shifted outflow is detected
観測：integral ﬁeld
spectrograph
SINFONIを使ってVLTで観測。
1
1
1
Whelan, E.T. et al.: The ISO-Oph 200 NIR Outflow
in both H2 and [Fe II] lines at V sys = (-35 ± 2) km s and V sys = (-51 ± 5) km s respectively. In addition, slower (⇠ ± 10 km s ) H2
emission is detected out to < 5.00 4, in the Outflow
direction of
the blue
V sysbothO↵set
PA and red-shifted outflow lobes but along a di↵erent position angle
00
to the more compact faster emission. It isargued(kmthatemission is a jet and the extended H2 emission is tracing
Features 1 )the (more)(compact)
H2 Jet0.00 7± 1230
a cavity. The source extinction is estimatedat Av -35
= ±2
18 magmag and the outflow extinction at Av = 9 mag ± 0.4 mag. The H200
Fe II Jet
-51 ± 50. 5
215
outflow temperature is calculated to be 1422
density of the [Fe II] outflow is measured at ⇠ 10000 cm 3 .
F1 K ± 255
4 ± 3K and
4.00 0the electron
67
10
00
F2
3
2.=6 3.8 80
Furthermore, the mass outflow rate is estimated
at10Ṁ±out[H2]⇥ 10 M yr 1 and Ṁout[FeII] = 1 ⇥ 10 8 M yr 1 . Ṁout[FeII] takes-14 ±is5 investigated
5.00 4248 using the ratio of the [FeII] 1.257 µm and [PII] 1.188 µm lines.
a Fe depletion of ⇠ 88% into account. TheF3depletion
Outflowfeaturescorresponding
Using the Pa and Br lines Table
and a1.range
in emission
stellar mass
andandradiusṀacc is propercalculated to be (3 - 10) ⇥ 10 8 M yr 1 . Comparing theseties. O↵sets are with respect to the source position and along therates puts the jet efficiency inlinePA.
with
ofofmagneto-centrifugalmodelsof jet launching in low mass protostars. This is agiven
PAs predictions
are measured E
N. It is argued that F1, F2
andfurther case of a brown dwarfF3outflow
analogous
form partexhibitingof a cavity aroundthe jet. properties to protostellar jets.

コンパクトなblueシフトoutﬂow：

全てのラインで見えている

Key words. stars: brown dwarfs - stars:jets - stars:formation

solved H2 emission is seen at distance of 2.00 6 to 5.00 4 and along adi↵erent PA to the faster emission. The main emission features
here are marked F1, F2 and F3 in Figure 2. Theinvelocity,mor1. Introduction
protostellar
HH jets (Riaz et al., 2017). Here we present thephology and PA of this emission would suggest that it is tracing
resultsofanear-infrared
study of an outflow from a proto-BDa cavityaroundthe formation
collimated jet. processThis emission is not detected
Outflows play an important rolein thestarin [Fe II] and is discussed further in Section 4. candidate, which also shows characteristics similar to protosteland are driven by young stellar objects(YSOs)
in theClass
0 lar
A H2 excitation
diagramcan beconstructedby plotting
the driving source of the outflow is a YSO named ISOjets. The
loget
of al.,
the column
the statisticalto Class II evolutionary stages natural(Frank2014).densities
Thus,(divided
they byOph
200(↵ = 16:31:43.8, = - 24:55:24.5). The near- to midweight),
of a200
numberof H2 lines against the upper energy levelal.: Therange
ISO-OphinNIR Outflow
can be observed Whelan,acrossE.T.
a etlarge
wavelength(Whelan, infraredµm) spectral slope of the SED for ISO-Oph 200of the line. This can be used to derive the temperatureand(2-24
to2014a). Also, as di↵erent wavelengthcanconstrainregimes
the extinctionof o↵erthe linecompleregion
et al., with a Class I classification (Evans et al., 2009).
is(Davisconsistent
Outflow
Vemitting
O↵set
PA
sys
1 temperature2011).toIn launchinga thermalised
gas at a(kmsinglementary observational constraints
models,Featuresmulti)(00 ) We( )the points
Fig. 2. Continuum subtracted spectro-images of the ISO-Oph will lie along a straightH2line,00
the -35
slopeof which
is 230the havetempera-conducted physical and chemical modelling of subJet±2
0.
7
studieshave
proventureimportant(Nisiniet al.,
2016).
200 outflow in the H2 wavelength
1-0 S(1) and [FeII] 1.257µm lines.
(Caratti o Garatti
et al.,
is215
constrained
continuum and molecular line data for thisFe
II Jet2006).
-51The± 5 extinction
0.00 5 millimeter/millimeter
Velocities have been corrected
for the systemic
velocityof thefield
Near-infrared(NIR)
integralobservations
areby investigating
the scatterthe 4points
straight
line. find the results to be consistent with an early StageF1 aofparticularly± 3 about
4.00 0this67
object,and00source. Top panels: Herethe emission
in a studies
mainly blue-shifted
10 ±which
3 should
2. 6 reduce
80 the scatCorrecting
line fluxes
for extinction
usefultool forof jet launchingintheClass
0/IF2sources
0+I
stage (Riaz et al. in prep). The total (dust +55.00 4 varying
248 evolutionary
velocity range is shown to highlight the blue-shifted jet emission ter of the points about F3
a linear -14
fit. ±Therefore,
Av and
are
still
very
much
embedded
in
their
natal
clouds(Davisetal.,only. Black contours begin at 3 and increase in multiples of 1.5. analysing
the1.goodness
ofemission
the fit leads
to an andestimateof Amassv (Toddgas)
for
ISO-Oph
200 as derived from the sub-millimeter
Table
Outflowfeaturescorresponding
proper2
1
1 = 4.5 ⇥ 10 15 erg cm2011).
s 1 µm The. TheJ,H,
blue contours& RamsayHowat,
2006).
H2 excitation
for theand K show
NIRthebands
cover
Fe IIareforbidden
andHdiagramties. O↵sets
withArespect
tothe source
andISOalongthe
2 position
850
µm
flux
is
0.06±0.01
M with a bolometric luminosity ofcontinuum emission and they correspond to 50%, 75% and 95% Oph 200
jetPA.
wasPAsconstructed
Figureusing theare measured
Eof N. A.1)
It is argued
thatfluxes
F1, F2 andro-vibrational emission lines that aregiven
strongtracersof9 (see
jets.
These
⇠
0.09±0.02
L
.
The
mass
of the central object in this Class Iof the peak flux of the continuum. The black stars marks the po- given F3
in Table
1.
For
A
=
mag,
T
=
1442
±
255
K
is
meav
form part of a cavity
around the jet.
linesandcan
usedPA
toisinfer
jet properties
suchisas
temperatureandsition of the emission peaks
the beemissiondelineatedsured. This resultin agreementwith thetemperatures
reportedsystemcan be constrained to within the sub-stellar mass regime
by the dashed line). Bottom
panels:emission in
the extinction
by Garcia Lopezet al. (2013)
the very low mass protostar
densityandHeretothe
measurethetowards
the jetfor (Garcia
theofmeasured bolometric luminosity and numerical simvelocity ranges -80 km s 1 to 128 km s 1 (H2 ) and -96 km s 1 to IRS54. By varying the extinction it is found that using
the analysis
Lopez
et
al.,
2013).
Integralfield
spectroscopy
providesspectro1
114 km s ([Fe II]) is shown. This range was chosen to show si- the excitation diagrams is in a agreement with theAestimates
stellarevolution, as discussed in Riaz et al. (2016).
00ulations
00v
solved H2 emission is seen at distance of 2. 6 to 5. 4 andofalongamultaneously the extended
blue andred-shifted
low velocity
H2 presented
imageswhich
allow
the properties
of
the
jets
mappedasThea mainin Section
3.1.
di↵erent
PA totothebe
fasteremission.
emission features
Consideringthevery
low mass reservoir in the (envelope+disk)
emission which it is argued
traces the
The chosen
range
Using
the
lines
and
the models
ofvelocity,
Takami morfunction
ofcavity.
velocityand distance(Davisetratiosal.,of2011).
Such
herethearemarked
F1,[FeF2II]
andF3 studin Figure
2.
The
for
this
system,andthepresence of an outflow that will further
also shows that there is no red-shifted counterpart to the blue- et al. (2006), the electron density (ne ) can be estimated.
Studies
phologyandbe
PA tracingof this emission
would suggest that it is tracing
found
theis[FeII] andH2 foundlinesthattodi↵erent
shifted jet emission andies
that havethe cavity
emission
not seenin havethe 1.600µm / 1.644µm,This1.664µm/ 1.644dissipate
the envelope material, ISO Oph-200 will likely have aa cavityaroundthe collimatedjet.
emission
is notµm,
detected[FeII]. Contours start at components
3 and increase inof 1.5.
1 theandforbidden
1.677µmII]/ and1.644
ratiosassociatedaremoreinaccurate
tracers of theofmultiples
the jet,withemissionin [Feis µm
discussed
further
Sectionfinal
4.
massto below the sub-stellar limit, and can be considered as= 5 ⇥ 10 15 erg cm 2 s 1 µm 1 . The continuum emission is plot- density than the 1.534 µm / 1.644 µm ratio. However,withfaster,hot
densematerial
andtheAmolecular
H2 excitationemission
diagram cantracbe constructed
bydueplotting
theastrongcandidate
proto-BD.
ted in the same way as for the top panels.
the non-detection
of
the
1.600
µm,
1.664
µm
and
1.677
µm
naturallog (Carattiof the column
densitieset(divided by thelines
statisticaling lower excitation, slower moleculargasoGarattihere we are limited to using the 1.534 µm / 1.644 µm ratio. From

速度の遅い（~ +-10km/s）red&blueシフトの広がったemission：
H2のみで見える

方向は、速いコンパクトなemissionとは異なるPAを持っている。

コンパクトemission => jet

広がったH2 emission => cavityをトレースSourceの減光量：

Av = 18 mag +- 1 mag

Outﬂowの減光量：

Av = 9 mag +- 0.4 mag

H2 outﬂowの温度：[Fe II]の電子密度：with color-color diagram (Davis+11)

Whelan, E.T. et al.: The ISO-Oph

1422 K +- 255 K~10000 cm-3

mass outﬂow rate：
For H2,

M = 3.8 x 10-10 Msun/yr

For FeII,M = 1.0 x 10-8 Msun/yr

PaβとBrγ線のLuminosity、星の質量（0.06 - 0.1 Msun）、
半径（0.9 - 0.5 Rsun ）を用いて：

Fig. 3. Colour map of the full H2 1-0 S(1) emission. The colours
are shown to highlight the di↵erence intensity between the H2
jet emission along a PA of 230 (dashed line) and the extended
emission which likely delineates a cavity. A cavity with open広がったH2 emissionが、H2・[Fe II]の両方で見られる ing angle 40 is overlain here and well represents the extended
fainter emission.

Macc ~ (3-10) x 10-8 Msun/yr

ものと違うgeometryを持っている＝

我々が見ているものはwind-swept cavity

Opening angle ~40 にﬁttingできる：and [PII]Davis+02のClass
1.188 µm lines it is foundI天体の値の範囲内
that 88% ± 14 % of the Fe is
still in dust grains in the jet (Garcia Lopez et al., 2010). Taking
this value of the dust depletion into account places Ṁout[FeII] at⇠ 1 ⇥ 10 8 M yr 1 . Overall our results put the jet efficiency
proto-BDのNIR観測は、BD質量天体のjetを調べるには良いツール。
( Ṁout / Ṁacc ) within the limits of magneto-centrifugal jet launch広い角度のwindのようなoutﬂow成分の証拠を探すことができ、ing models (Frank et al., 2014). Also note that as the mass outflow rate is higher in the [Fe II] than H2 component of the jet,
jetの減光が調べられ、jetの効率が測定できる。
our results support the argument of Garcia Lopez et al. (2013),
that most of the outflow material is transported in the component
近い将来、JWST/NIRSPECを使ったより高分解能でのjetのcollimationやstructureの観測が可能になる。
traced by the atomic rather than molecular lines.

in theresult
(Fran
wind
range
angle
is shoexten
lar carange
the exto thethe ar
A slo
hydro
evide
2014)
Tu
would
than
al., 20its of
some
II BD
date.
Class
consi
to a bI 217
date bwith etinctiounder
the acGravity drives the evolution of infrared dark hubs:
JVLA observations of SDC13
G. M. Williams1 , N. Peretto1 , A. Avison2,3 , A. Duarte-Cabral1 , and G. A. Fuller2
1

School of Physics and Astronomy, Cardi↵ University, Queens Buildings, The Parade, Cardi↵ CF24 3AA, UK
email: williamsgwen12@gmail.com
2
Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL, UK
背景：フィラメントが集中している箇所（hub）は、星団・大質量星形成と深い関わり。
3
UK ALMA Regional Centre Node

ハブの進化とそこでの星形成の関係の理解は重要。

iv:1801.07253v1 [astro-ph.GA] 22 Jan 2018

Received Month Day, Year; accepted Month Day, Year

ABSTRACT
目的：SDC13の運動・密度構造を調べ、進化やfragmentationの駆動源を決める
Context. Converging networks of interstellar filaments, i.e. hubs, have been recently linked to the formation of stellar clusters andmassivethe relationshipbetween the evolutionof these systems
and theGreen
formation ofBankcores/stars
inside them is (0.07 pc)
観測：NH3(1,1)& stars.
NHUnderstanding
with Jansky
Very Large
Array,
Telescope3(2,2) 輝線

at the heart of current star formation research.
Aims. The goal is to study the kinematic and density structure of the SDC13 prototypical hub at high angular resolution to determine
G. M. Williams et al.: Gravity drives the evolution of infrared dark hubs: JVLA observations of SDC13
what drives its evolution and fragmentation.
Methods. We have mapped SDC13, a ⇠1000 M infrared dark hub, in NH3 (1,1) and NH3 (2,2) emission lines, with both the Jansky
Very Large Array and Green Bank Telescope. The high angular resolution achieved in the combined dataset allowed us to probe scales
down to 0.07pc. After fitting the ammonia lines, we computed the integrated intensities,
velocities and line widths, along
全てのcentroid
hubフィラメントはsupercriticalwith gas temperatures and H2 column densities.
Results. The mass-per-unit-lengths of all four hub filaments are thermally super-critical,
consistent with the presence of tens of（transonicの非熱的な速度分散を持つ）
gravitationally bound cores identified along them. These cores exhibit a regular separation of ⇠ 0.37 ± 0.16 pc suggesting gravitational
instabilities running along these super-critical filaments are responsible for their fragmentation. The observed local increase of thedense gas velocity dispersion towards starless cores is believed to be a consequence of such fragmentation process. Using energy
コアの間隔：
フィラメントに沿って~0.37pc
conservation arguments, we estimate that the gravitational to kinetic energy conversion
efficiency in the SDC13
cores is ⇠ 35%. We
see velocity gradient peaks towards ⇠ 63% of the cores as expected during the early stages of filament fragmentation. Another clear
observational signature is the presence of the most massive cores at the filaments’ junction, where the velocity dispersion is the largest.
We interpret this as the result of the hub morphology generating the largest acceleration gradients near the hub centre.
Conclusions. We propose a scenario for the evolution of the SDC13 hub in which filaments first form as post-shock structures in afew
Myer（非平衡
supersonic turbulent flow. As a result of the turbulent energy dissipation in theフィラメントの年齢：ashock, the dense gas within the filaments
is initiallymostly sub-sonic. Then gravity takes over and starts shaping the evolution of the hub, both fragmenting filaments and pulling the gas
towards the centre of the gravitational well. By doing so, gravitational energy is フィラメントの半解析的モデル（Clarke+16,
converted into kinetic energy in both local (cores) andglobal (hub centre) potential well minima. Furthermore, the generation of larger gravitational acceleration gradients at the filament
junctions promotes the formation of more massive cores.
17）を使用）Fig. 5. Left: Spitzer 8 µm flux Key
densitywords.
in units of
MJy/sr, overlaid with
IRAM 30m MAMBO
1.2mm dust
continuum contours andin dynamics – ISM:structurestars:formation– stars:massive– ISM:clouds– ISM:kinematics
steps of 5mJy/beam, from 3mJy/beam to 88mJy/beam. Crosses denote the positions of identified 1.2mm MAMBO compact sources(white for starless and blue for protostellar, Peretto et al. 2014) and two 1.3mm SMA continuum sources (in black crosses, McGuireet al. 2016). Middle: H2 column density map in units of 1022 cm 2 , derived from the NH3 integrated intensity. Overlaid contours areplaced in 1 ⇥1022 cm 2 steps, from 2 ⇥1022 cm 2 to 12 ⇥1022 cm 2 . Right: Plot showing the extracted cores (black crosses, numbered
1. Introduction
according to Table 2) andfilaments (labelled coloured lines). The extraction of these structures are discussed in Section While
4. Extra a lot of e↵ort has focused on the properties of individcores at the outskirts of the North-East and South-East arms are in the more di↵use regions of the cloud where the spines
did not
ual filaments
in nearby star-forming regions (Arzoumanian et al.
extend through. Spine colours match those in subsequent figures.

<= Peretto+14の力学的タイムスケールとconsistent2011; Peretto et al. 2012; Palmeirim et al. 2013; Panopoulou
The star formation process can be perceived as the mechanism et al. 2014; Salji et al. 2015), here we focus on hub filament
procedure used. However, because of the relatively large peak this column density map to that calculated with a non-uniform
systems(HFS), i.e. a small network of spatially converging inleading
concentrationdi↵use interstellar
intoa constant
NH3 (1,1) main line opacityof 4.7,to
we theindependently
performed oftemperature,
we are satisfied clouds
that assuming
temperterstellar
a Gaussian fit of the opticallythinnerof the hyperfine
compoacrossWhilethe entire
cloud
does not introduce
significantfilaments (Myers 2009). The converging nature of suchcompact,
nuclearburning,ballsatureof gas.
theimportanceof anynents. By doing so, we observe the same increase of the line

changes to the morphology of features in the map, whilst extend-

FWHM

V (km/s) N(H2 ) (1022 cm 2 )vir as discussed in Section 5.2.
are associated to the filament lengths and mean core separations. Inclination angle a↵ects the timescales quoted,
equilibrium, those with ↵vir < 1 are likely to be gravitationallyunstable, while structures with ↵vir > 2 are unbound and either
14
dispersing or held together by external pressure. Figure 18 shows
23 18
8
7 6 2
17
24 25 20
19 14 1228
21
22 15 structures. Based on this12 27
the map of virial ratios for26all SDC1310map, it is clear that as we go from large to small scale, the virial
8
ratio increases from ↵vir ⇠ 0.1 towards 1. Such low-values sug6
gests that SDC13 is gravitationally unstable on all scales, and4that the transfer of gravitational to kinetic energy could be the2process responsible for the increase of the virial ratios on small
1.4
scales.
1.2
Such an evolution of the viral ratio can be analytically de1.0
scribed by the following equation:
0.8
!
0.6
|Eg,0 |
Ek,0↵vir = 2+ 2✏ 1
(8)
0.4
|Eg |
|Eg |
0.2

Trot (K)| V| (km/s/pc)|V| (km/s)

1.2
1.0
0.8
0.6
0.4
0.2
0.06
5
4
3
2
1
200
18
16
14
12
10
8
0.0

NW

0.5

1.0
1.5
2.0
2.5
Length from origin (pc)

3.0

NE

where Ek and Eg are the kinetic and gravitational energies, respectively, the 0 index indicates the initial value, i.e. at the startof the collapse/fragmentation, and ✏ is the fraction of the gravitational energy which is converted into kinetic energy. Note that
as |Eg | becomes increasingly larger during the collapse, ✏ = 1
translates into ↵vir ! 2, which is expected if all the gravitational energy were to be converted into kinetic energy. A meanae f f,0 ⇠ 0.26 ± 0.02 km s 1 is evaluated from Figure 17 (as discussed in Section 5.1). By estimating each energy term of equation 8 for every core showing an increase of velocity dispersion
one can determine which value of ✏ is required to reproduce
the observed ↵vir value. Assuming that the cores of initial diN the fragmentation of a uniform densitySEameter core result fromtransonic filament of initial velocity dispersion ae f f,0 , one canrewrite equation 8 as:!
2
3 Rae f f,0
2 0 R↵vir =+ 2✏ 1
(9)
G M
core

重力に起因するものではなく、HII領域からの圧縮の可能性が高い
・同定コアの73%で速度分散が増加：
フィラメントの分裂過程に起因する物質の蓄積の結果と解釈
Fig. 18.
Virial ratio map of all identified dendrogram structures.
1.0

コアでの重力エネル
0.8

ギーから運動エネル
ギーへ変換効率を求

0.6

3 k

where = 5 2k⇢⇢ is a factor depending on the power law index k⇢ of the density profile of the collapsing core, and 0 is
Fig. 8. Profiles along the spines, where each column denotes a di↵erent filament(North-Westin thered,onset
North-Eastin (seeblue,
North inits initialvalue beforeof collapse
Appendix
F forgreen and South-East in grey). The origin of each spine was centred at the huba region.
The first
row plots
columnwe
densityof an
H2inimore detailed
derivation).
Forthesimplicity,
assumedflat density(i.e.while
3/5),
androwk⇢ =plots
2 oncecalculated from the fitted NH3 integrated intensity. The second row plots the tially
FWHM
velocityprofile
width,
third
thecol0 = the1begins= 1).also
Figure19theplots
the energy
conversion
absolute centroid line-of-sight velocity (o↵set from the cloud systemic velocitylapseof 37
km s(i.e.
), both
fromhyperfinestructureefficiency✏
againstthevirial
ratio
for
every
core
for
both
fitting. The fourth row plots the absolute velocity gradient evaluated over the mean core size of ⇠0.1 pc. The fifth row plots the the
combined
and JVLA–only
thisofplot,
rotational temperature derived from the NH3 emission (see Appendix B.2) which
has JVLA/GBT
a standard data
deviationof 1.8 K. data.
The Ondrops
only starless cores are included, as protostellar cores, or cores attemperature below 8 K are artificial and due to missing NH3 (2,2) detections at filament
these particularlocations.
The
verticalshadedregionsjunctions are subject to extra energy sources that willin each panel correspond to the peak N(H2 ) positions of the cores along the spine,are ⇠0.1ofpc
a↵ectandthe estimate✏. wide.
One can see that a conversion efficiency
between 20–50% can explain most of the observed velocity dispersion increases towards starless cores. The JVLA–only data
note that similarities emerge in the large scale morphology of all the common
physicaloriginof theSDC13
evolution,
points(orangecircles),believed
to befilament
less contaminatedbyas
foreground/backgroundemission
to 5.
the cores, are clustered around a
profiles between pairs of filaments (the North-West and North- discussed indetail throughout
Sectionmedian efficiency of 35%.
East filaments on one side, and the North and South-East filaKlessen & Hennebelle (2010) proposed a theory according
ments on the other). Overall, such similarities are suggestive ofto which accretion is capable of driving turbulent motions ingalaxies on all scales, finding an ✏ value of a few percent when
considering both galaxy and molecular cloud sized structures.
Clarke et al. (2017) evaluate the efficiency required to reproduce
10
a given velocity dispersion due to accretion driven turbulence infilament structures. They find an ✏ = 5 10 % is sufficient todrive a 1D ⇠ 0.23 km s 1 , a consistent efficiency to that foundby Heitsch (2013). While these are theoretical estimates, our observationally derived value of ⇠ 40% is somewhat larger. This

フィラメントの結合部に最もmassiveなコアが付随（速度分散は最も大きい）

・2つのフィラメントでの大きな視線速度勾配：0.4めた（ε~ 35 %）

0.2

0.0
0.0

<= 理論値よりも大き
0.5

1.0

1.5

2.0

vir

Fig. 19. Observed virial ratio plotted against the energy conversion efficiency of gravitational energy into kinetic energy for the
combined JVLA/GBT data (in blue), and the JVLA–only data(in orange). Only starless along the filaments are plotted, as protostellar or hub centre cores are subject to extra energy sourcethat will e↵ect the estimate of ✏. Errors were propagated using aMonte Carlo error propagation method.

いG. M. Williams et al.: Gravity drives the evolution of infrared dark hu<= ハブ形状によって生まれる加速度勾配に起因すると考えられる
could point towards an even more important role of gravitydriven turbulence than previously thought (see also Traficante
et al. 2018; Ballesteros-Paredes et al. 2017, submitted).

SDC13の進化シナリオ：
超音速乱流でのpost shock構造として、フィラメントが形成
乱流エネルギーの散逸の結果、高密度コアは亜音速に重力が優位になり、hubの進化を促す。
それによって、重力エネルギーは運動エネルギーへと変換される

17

フィラメント連結部でのより大きな重力加速度勾配の発生が、大質量コア形成を促進

Fig. 20. Map of gravitational acceleration in SDC13 in units of1 ⇥ 10 12 km s 2 . Mass was calculated from the H2 column density map in the middle panel of Figure 5. Contours are of the H2column density in Figure 5, plotted in 1 ⇥1022 cm 2 steps, from2 ⇥1022 cm 2 to 12 ⇥1022 cm 2 .
constructed acceleration profiles along each filament. These are

to identify bo
us to characte
are supercritic
ity dispersion
them (⇠ 0.37
equilibrium fithat the filame
dynamical tim
that the large rament cannot
to the comprethat the veloci
fied cores, whof matter due
derive an averficiency withivalues publish
presence of m
the large acceogy.
All elemenlution of the S
form as post-s
result of the tu
gas within the
ity takes overfragmenting fi
the gravitation
verted into kincentre) potenti
the hub centre

Acknowledgemen
postgraduate stud
der grant number