星形成ゼミ
担当：SFN#345 24-29
2021/10/22
総研大 D2 竹村英晃

SFN#345 24-29
24. Physical Properties and Real Nature of Massive Clumps in the Galaxy

25. Discovery of a Highly Collimated Flow from the High-Mass Protostar
ISOSS J23053+5953 SMM2
26. Dynamical effects of the radiative stellar feedback on the H I-to-H2
transition
27. Characterization of the dust content in the ring around Sz 91: indications
for planetesimal formation?
28. Signatures of UV radiation in low-mass protostars I. Origin of HCN
and CN emission in the Serpens Main region

29. The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages(ASHES). IV. Star formation signatures in G023.477

arXiv:2108.08981v1 [astro-ph.GA] 20 Aug 2021

Physical
Properties
Accepted XXX. Received
YYY; in original form ZZZand Real Nature of Massive Clumps
in the Galaxy

•
•
•
•
•
•

ABSTRACT
Zu-Jia Lu, Veli-Matti Pelkonen, Mika Juvela, Paolo Padoan, Troels Haugbølle, Åke Nordlund

Systematic surveys of massive clumps have been carried out to study the conditions leading to the formation of massive
stars. These clumps are typically at large distances and unresolved, so their physical properties cannot be reliably derived fromthe observations alone. Numerical simulations are needed to interpret the observations. To this end, we generate synthetic
Herschel observations using our large-scale star-formation simulation, where massive stars explode as supernovae driving theinterstellar-medium turbulence. From the synthetic observations, we compile a catalog of compact sources following the exact
same procedure as for the Hi-GAL compact source catalog. We show that the sources from the simulation have observational
properties with statistical distributions consistent with the observations. By relating the compact sources from the synthetic
observations to their three-dimensional counterparts in the simulation, we find that the synthetic observations overestimate theclump masses by about an order of magnitude on average due to line-of-sight projection, and projection effects are likely to beeven worse for Hi-GAL Inner Galaxy sources. We also find that a large fraction of sources classified as protostellar are likely to
be starless, and propose a new method to partially discriminate between true and false protostellar sources.
Key words: MHD – radiative transfer – methods: numerical – stars: formation – catalogues
大質量クランプ（大質量星形成領域）のサーベイ観測が行われてきたが、距離が遠いため分解できず、物理量はよく分かっていない。
1 INTRODUCTION
we compile the first synthetic catalog of massive clumps that can be
観測のみでは限界があるため、数値シミュレーションを行う。
compared statistically to the Hi-GAL compact source catalog, based
Massivestars are essential constituents of the ecosystem of galaxies,
3D
MHDシミュレーション＋Herschelの模擬観測を行い、Herschelの観測結果（Hi-GAL）の結果と比較した。
on a star-formation simulation of a 250 pc region of the ISM driven
driving the thermodynamical and chemical evolution of their interby supernova (SN) explosions.
模擬観測の結果から同定したコンパクトな構造の質量は、視線方向に射影する効果により、1桁程度質量を過大評価している。
stellar medium (ISM). Understanding their formation process is aUsing earlier evolutionary stages of the same simulation, we haveprerequisite
for modeling Galaxyの天体ではより質量を過大評価しているかも。
the evolution of galaxies and investigating•
Hi-GALのInner
previously
shown that SNe alone can drive the observed turbulence
the high-redshift universe. A complete theory of star formation is notin MCs (Padoan et al. 2016a; Pan et al. 2016) and can explain bothProtostellarに分類されていた構造の中にstarlessが多く混ざっていた。
available yet, massive-star formation being perhaps the main hurdle
the formation and dispersion of MCs (Lu et al. 2020). The star forto overcome. An important limitation in the study of massive stars
mation rate per free-fall time in the clouds was also found to beis the difficulty to test our theoretical models against observational
consistent with the observations (Padoan et al. 2017). The simulaHi-GALのサンプルは高空間分解能では、fragmentationしているはずなので、今後ALMAで観測していく必要がある。
data, because massive stars are more rare and shorter lived than lowtion was then used to study the formation of massive stars in Padoanmass stars. Regions of massive star formation tend to be at relatively
et al. (2020), where it was also shown that observations could grossly
large distances, obscured by high extinction levels, and confused byoverestimate the mass of protostellar
cores, depending on distancecomplex gas and stellar dynamics, as massive stars form in stellar
https://arxiv.org/pdf/2109.01243.pdf

シミュレーション（3D MHD + AMR）•

𝐿!"# = 250 pc（グリッド：0.24 ‒ 0.0076 pc）、 𝑀!"# = 1.9×10$ 𝑀⨀。

•

乱流の起源はSNのみ (Padoan et al. 2016a; Pan et al. 2016)。

•

初期条件：𝑛&,( = 5 cm)* 、𝑇( = 10+ K、𝐵( = 4.6 µG（自己重力なしで45 Myr計算）••

70 µm, 160 µm, 250 µm
𝑡 = 34.2 Myr, 𝐷 = 2 kpc

SNをランダムに起こす（6.25 SNe Myr-1）。

𝑛 > 10$ cm)* など (Haugbølle et al. 2018) の条件でsink（星）を作り、7.5 M◉を超え
かつ星の寿命 (Schaller et al. 1992) を迎えたものたところでSNを起こす。
•星の質量とモーメント、1051 ergのエネルギーをガウシアン分布でその場に残す (Padoan et al. 2016a)。

•4283個の星（>2 M◉）が形成され、~415回のSNeが発生。
•

大質量側（ >8 M◉ ）の質量分布は、SalpeterのIMFを再現。

模擬観測•

自己重力を入れてから15.4、23.3、34.2 Myr後のスナップショットをHershcelで模擬観測（70、160、250、350、500 μm）。
•

距離は2、4、8、12 kpc→各波長ごとに36マップ

構造同定•

Hi-GAL (Elia et al. 2017, 2021) と同じ手法を適用。
•

CuTEx (Moli- nari et al. 2011)：画像の2階微分を用いて構造同定（Curvature-based source detection）

Real Nature of Massive Clumps

3Real Nature of Massive Clumps

7

discussed in § 6.1 must be even larger in the Inner Galaxy survey thanin the synthetic observations. Finally, the bottom panels of Figure 4
show that the observed clump temperatures are well reproduced by
the synthetic catalog, except for slightly larger values in the case of
protostellar sources at 2 and 4 kpc in the Outer Galaxy, and at all distances in the Inner Galaxy. This temperature difference is discussed
below in the context of Figure 5. The temperature of starless sources
is instead perfectly reproduced in both median values and dispersion
at all distances for both the Outer and the Inner Galaxy.
Figure 5

Figure 4. Source classification and derived source parameters as a function of
distance. Top panels: fraction of protostellar sources in the synthetic catalog(solid line) and in the Hi-GAL catalogs (dashed lines) for the Outer Galaxy(left) and the Inner Galaxy (right). Second row: median values of the synthetic
source diameters, separated into starless (red) and protostellar (blue) sources.
Error bars are between the 2.5 and 97.5 percentiles. The median values for
the Hi-GAL sources are shown by the dashed lines, while the shaded regions
correspond to the same percentile range as for the error bars. Third row: thesame as the second row of panels, but for the source mass derived from theSED fitting. Fourth row: the same as the previous row, but for the source
temperature.

Hi-GALクランプと本研究のクランプの質量

Figure 6. Left four panels: mass versus diameter and mass versus temperature for starless (upper panels) and protostellar (lower panels) synthetic sources(solid contour lines). The black line is Larson’s mass-size relation, " (r) = 460 M (r/pc) 1.9 (Larson 1981). Source number density isocontours representing
the starless and protostellar sources from the Hi-GAL Outer Galaxy catalog are also displayed with dashed lines. The number densities have been computed
subdividing the area of the plot with a grid of 70 ⇥ 70 cells in logarithmic intervals. Once the global maximum of both distributions in the same panel (starlessor protostellar) has been found, the plotted contours are chosen to show the number density of 5%, 20% and 70% of the maximum, as in Figure 7 of Elia et al.
(2017). Right four panels: the same as in left four panels, but comparing with the sources from the Hi-GAL Inner Galaxy survey. In this case the number ofsynthetic sources at distances 3 > 2 kpc has been rescaled by a factor (3/2 kpc) 2 /2, to mimic the distance distribution of the sources in the Inner Galaxy, as in
Figure 5.

•

視線方向の密度プロファイル（シミュレーション結果）。
•

密度のピークをもつmainのクランプの他にも複数のクランプが存在する。

•

星がmainのクランプに付随している（左）こともあれば、そうではない場合（右）こともある。

105

105

star in column
star in clump

104

100

10

2

•

10

1

質量を過大評価している。

100

Z.-J.Mmain
Lu :et79.40,
al. Mall : 1613.20, Nc : 68
10 1
Mtot : 1719.81, MSED : 1037.00
diameter (the size on the plane of the sky). The position of the
0
50
100
150
200
250 maximum
0 density is50
100vertical transparent
150
200 in Figure250
shown by theline
7,
Lbox [pc]Lbox [pc]whose thickness corresponds to the diameter of the synthetic source
and thus
main
Wea also
defineas independent
3Dthe
Figure 7. Density profile along the line of sight for two example sources (the sametwo asofinthe
Figure3):3D
oneclump.
source has
dominant
clump(left panel) andclumpsall othermaximathanhighest
1% ofdensity
theother has many clumps of approximately the same peak density (right panel). The
red verticallinedensity
shows thepositionwithof thevalue
main larger
clump (the•t=34.2 Myrでの密度分布。
absolute
maximumthat defines
the main
3D clump(see the horizontalpeak), with the thickness of the line corresponding to the source diameter (we assumethatthe 3D clump
has the same
diameteras the corresponding
source).
The open cyan diamonds are the stars located inside the main clump. The open red
circles
are thelocated inare
theassumed
column ofsourcefootprint,
but outsidedashedline).
Allstars
3D clumps
tothe
have
a sizein the direction• The
若い星は高密度領域に分布している。
of the dominant clump.
green dashed horizontal line shows the 1% of the maximum
density,which
is minimum
density diameter
we have chosen
to define secondaryof the lineof sight
equal
to the source
as well.
clumps.
With these definitions of main and secondary 3D clumps, we can•
進化が進んだ星は高密度領域（原始星コア）に付随せず、ランダムに分布
then associate three different mass values to each line of sight, thetotal mass of the column, "tot , the sum of the 3masses of all clumps,
6.1 Observational versus
Intrinsic Clump Massmean density around the star in a (0.12 pc) volume. While in theするようになる。
"all , and the mass of the main clump, "main , and compare them with
example dominated by the main 3D clump (left panel) one star isthe mass of the corresponding synthetic source, "SED . In the twofound inside the mainclump,and several
more in its
vicinity, only11
Figure 7 shows the density profile along the lines of sight of two examples
Real
NatureofinMassive
Clumpsof Figure 7, themain
3D clump
left panel>the8thevalueM<has
5a massM
are found in the line of sight
of
the
other
(right◉ example
sources of similar mass (618 and 1037 M ) at 12 kpc, both classified " two stars
=
305.7
M
,
approximately
half
of
the
estimated◉mainpanel) and at relatively low densities, and none inside the main 3D
as protostellar in the synthetic catalog, chosen to be an example of a source
mass, "SED , while the main 3D clump in the right panel has aclump.
line of sightdominatedby aagerealclump (left panel) and of a line of 1 massstellar
<3D
1 Myr
5 Myr
> 5 Myr"main = 79.4 M , approximately 13 times
smaller than "SED .
103sight without a dominant 3D clump (right panel). The gas density is
profilesshown within Figure
7 arefor all
TheDensity
comparison
oflike"allthose
and "
"SED
for computed
all the sources
maincomputed within a column of size equal to the source diameter. The in our
the catalog
sources isinshown
our synthetic
catalog,
and
are
then
used
to
identify
in Figure 8, where the black solid line marks
open cyan diamonds mark the positions of stars located inside the thethe
main 3Drelation.
clump The
corresponding
to fits
eachto synthetic
source.
The
one-to-one
least-squares
the medianvalue of210星近傍
main 3D clump, while the open red circles are for the stars located in each
main
3Dtwo
clump
in eachline of ofsight
is defined
as intheFigurefractionof themassesas a function"SED
are shown
8 asofthe column of the source footprint, but outside of the main 3D clump. dashedthe corresponding
columnat theresult
highestdensitymaximumand dotted lines.
The centered
most strikingof thiscomparison
The y-axis coordinate of the diamonds and circles corresponds to the is thatand with
along the line
sight
equal
to thesynthetic
source" a sizeoverestimatesthe oftrue
massof themain
3D clump,
Mmain : 305.71, Mall : 653.55, Nc : 13
Mtot : 717.21, MSED : 618.48

10

N

10 1

101

100

SED

星近傍（各時間ごと）
10 3 10 2 10 1 100

101

102

103

104

105

"main , by a factor greater than 10, on average (dashed contour lines
MNRAS 000, 1–17 (2021)
and dotted least-squares fit). Because the median
relation given by(0.587±0.020)
the fit is rather shallow, "main = (0.230 ± 0.014)"SEDfor

10 3 10 2 10 1 100

101

観測では視線方向のemission
をすべて足し合わせるため、

102

103

104

105

10 3 10 2 10 1 100

101 (0.838±0.015)
102 103 104

3the Outern [cm] Galaxy and "main = (0.137 ± 0.009)"SED

105

(the

•

密度も過大評価している。
all clumps
main clump

103

Mall, Mmain [M ]101

MSEDとmainのクランプの質量。

102

101

100

Outer Galaxy

10 1
103

Mall, Mmain [M ]

10

•

103

n [cm 3]n [cm 3]103
2star in column

104

102

101

100

Inner Galaxy

10 1
100

101

102

MSED [M ]103Galaxy’s distance distribution shown in the upper panel). However,there is also a considerable overlap between the two types of sources.
To partially separate true from false protostellar sources, we propose
to separate the protostellar sources in two groups using theas due to protostellar
medianrelation for the true sources (cyan line). We first obtain an•
Protostellar（70μm検出あり）のサンプルには原始星が付随しているものと、そうではない“誤検出”が含まれている。
e two denser peaks in3
3
analytical
fit to the cyan line for the Outer Galaxy distance distribut ⇠ 10 cm , can be•
真のProtostellarの70μmの超過を温度の関数でフィットすることで、真のProtostellarの同定条件を設定。
tion,
nsity distribution andthe density threshold
2877
367
+
+ 1.3 ,
(6)
Outer:
Inner:
70,ob / 70,gb =d thus to discriminate
15()/10 K)()/10 K) 5

do not correspond too completely random

Protostellar クランプの同定

101
0.4

Protostellarでは、 MSED/Mmain ~4であり、 70 μmの超過からサンプルを分
MNRAS 000, 1–17 (2021)
類した場合でも、似た傾向が得られている。

0•Real Nature of Massive Clumps

0.0

Inner Galaxy

103

0.8

0.6

102
101

0.4

100
0.2

10 1
10 2
10

15

20

25

T [K]

30

35

0.0
40

Ntrue/Ntot

103

Mmain [M ]

104

102

starless
Outer Galaxy

Falsehigh 70µm excess

True

13
104
103

101

102

100

N

10 2

Protostellarはstarlessに比べて射影の影響を受けにくい。

101

10 1
103

100

102

Inner Galaxy

101

102

100

103

104
103

101

102

100

101

10 1
100

101 102 103
MSED [M ]100

101 102 103
MSED [M ]100

101 102 103
MSED [M ]100

101 102 103
MSED [M ]10 1 100 101 102 103
MSED/Mmain

100

N

0.2

10 1

F70,ob/F70,gb•

Mmain [M ]10

Ntrue/Ntot

F70,ob/F70,gb

and for the Inner Galaxy case,an be partially differ•上の条件よりも超過が大きい場合には、平均のprotstellarの検出率はouterとinnerで64%と66%なのに対し、超過が小さい
on purely observable
2051
365
+
+ 0.5 ,
(7)
m excess ontheir tem70,ob / 70,gb =場合にはそれぞれ14%と21%になる。
()/10 K) 15 ()/10 K) 5
the synthetic sources,
m excess and temperwhich is shown by the solid black lines in Figure 10. The dashedduces well that of theblack lines connecting the diamond symbols show the ratio between𝐹
he ratioof the 70 `mtrue protostellar 𝑁
sources
total protostellar sources found above
78, :;<=>?@AB:C
A>G=,and
H>:A:<A=II@>`m flux, 70,gb , thatthe analytical fits. The values of this ratio are shown in the y-axis
𝑁A:A@I,78,fluxes
D>@E;:FE
fit of𝐹theat theon the right-handside of H>:A:<A=II@>the plots. The lower black dotted lines,
0 shows that the temconnecting the circle symbols,
1.0 show the same ratio for sources below
True protostellar
protostellar
sources
the analytical Outer
fit to themedian line. One
see that, in the case of the104
Galaxy• canStarlessのサンプルでは、M
SED>>Mmain（ MSED/Mmain ~20）。
False
protostellar
as approximately
the
Outer
Galaxy,approximately
0.8 80% of the protostellar sources are true
103
i-GAL sources in theones in the approximate temperature range between
21 K and
33 K,
•
False
protostellarでも同様。
ith the Inner
Galaxy,while below the lines the fractionof true protostellar sources is always
102
0.6

arXiv:2109.06793v1 [astro-ph.GA] 14

Nicolaus Copernicus Astronomical Center, ul. Rabiańska 8, 87-100 Toruń, Poland
University of Le Havre, Laboratoire Ondes et Milieux Complexes, UMR CNRS 6294,75 Rue Bellot, 76600 Le Havre, France
12
Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) – UMR 6251, F-35000 Rennes, France
11

Signatures of UV radiation in low-mass protostars

Received March
2021; accepted
September13, 2021
I. Originof19,HCN
and
CN
emission in the Serpens Main region••

Agnieszka Mirocha, Agata Karska, Marcin Gronowski et al.
ABSTRACT

Context. Ultraviolet radiation (UV) influences the physics and chemistry of star-forming regions, but its properties and significancein the immediate surroundings of low-mass protostars are still poorly understood.
Aims. We aim to extend the use of the CN/HCN ratio, already established for high-mass protostars, to the low-mass regime to trace
and characterize the UV field around low-mass protostars on ⇠ 0.6 ⇥ 0.6 pc scales.
Methods. We present 50 ⇥ 50 maps of the Serpens Main Cloud encompassing 10 protostars observed with the EMIR receiver at the
IRAM 30 m telescope in CN 1-0, HCN 1-0, CS 3-2, and some of their isotopologues. The radiative-transfer code RADEX and thechemical model Nahoon are used to determine column densities of molecules, gas temperature and density, and the UV field strength,
G0 .
Results. The spatial distribution of HCN and CS are well-correlated with CO 6-5 emission that traces outflows. The CN emission isextended from the central protostars to their immediate surroundings also tracing outflows, likely as a product of HCN photodissociation. The ratio of CN to HCN total column densities ranges from ⇠1 to 12 corresponding to G0 ⇡ 101 103 for gas densities andtemperatures typical for outflows of low-mass protostars.
Conclusions. UV radiation associated with protostars and their outflows is indirectly identified in a significant part of the Serpens
Main low-mass star-forming region. Its strength is consistent with the values obtained from the OH and H2 O ratios observed with
Herschel and compared with models of UV-illuminated shocks. From a chemical viewpoint, the CN to HCN ratio is an excellent
tracer of UV fields around low- and intermediate-mass star-forming regions.
Key words. astrochemistry – stars: formation – ISM: molecules – ISM: individual objects: Serpens Main – ISM: jets and outflows–Submillimeter: ISM

小質量星形成領域（Serpens Main）において、分子組成や温度へのUVの影響を調べた。
• Introduction
大質量星形成領域では観測例があり (Cesaroni 2005;cal
Zinnecker2007)、CNとHCNの比がUVの有無を調
1.
conditions &andYorkechemicalcomposition in star-forming regions
dependonthecharacteristicsof the above processes.
べるのによく使われる手法のひとつ (Doty & Neufeld 1997; Stäuber et al. 2005)。
The formation of low-mass stars is associated with many physThe importance of UV radiation for star formation was iniical
The inside-out collapse of dense cores is ac- tially considered only in the context of massive stars, where the• phenomena.
UV（X線）によってHCNがCNに電離され、CNの電離よりも10倍速く進む。→CN/HCNが大きくなる。
companied by the ejection of bipolar outflows and the formation central stars are the main source of UV photons from early stages
10個の原始星をCN、HCNなど（IRAMof embedded disks (e.g. Frank et al. 2014; 30
Li etm）で観測し、RADEX、Nahoonを用いてUV強度などを求めた。
al. 2014). Ul- (Cesaroni 2005; Zinnecker & Yorke 2007). In dense star-forming
traviolet (UV) radiation can be produced in mass accretion on environments, the far-UV radiation is revealed by the chemithe central object or bow shocks, and it irradiates the outflow cal composition of the material, since it dissociates and ionizes
cavities in the envelopes (Spaans et al. 1995; van Kempen et al. molecules and atoms with ionization potentials below 13.6 eV
2009a; Visser et al. 2012; Drozdovskaya et al. 2015). The physi- (Benz et al. 2016). More energetic photons are easily absorbed
in the surrounding interstellar medium (Draine 2003). Among?
the most useful diagnostics of UV radiation is the ratio of CN to
Corresponding author: Agata Karska
e-mail: agata.karska@umk.pl
HCN (Doty & Neufeld 1997; Stäuber et al. 2005). In the pres-http://arxiv.org/abs/2109.06793v1

観測結果

A. Mirocha et al. 2021: Signatures of UV radiation around low-mass protostars

RADEX for nH = 105 cm 3 and T kin = 50 K for a range of SMM9, and to a lesser extent toward Ser SMM8 and SMM10.
line intensity ratios (orange line). The observed line intensity ra- The former source drives a large outflow, where bright emission
CNとHCNの柱密度の比を求める。
tio is shown as a rectangle: light green color corresponding to in HCN likely results from its high abundance in the warm gas
the values observed at the protostar position, blue color for the (similarly to o↵-source position 3). The latter sources are charac8 color
8
weak
emission in general (Figure 2).
outflow
positions and dark green
for both regions. Column terized6 by•
HNCの柱密度を10cm-2 に固定し、CNの柱密度を10cma-2veryから
10molecular
cm-2 まで変化させる。
Ser
SMM8
is
a
low
luminosity
sources(Lbol of 0.2 L , see Table
density ranges are marked with black and navy emdashed lines
46 1), which-3
is located on the map edge in CO 6-5. Ser SMM10 is
温度 Tandは 50 -positions,
100 K、数密度nH は 10 - 10 cm の範囲で変化させる。
kin outflow
for• protostars
respectively.
associated with CO 6-5 peak, but is clearly very weak in both
CN and HCN.
Table 3: Model-dependent column density ratios of CN to HCN
The median value of the CN to HCN intensity ratio at theA&A proofs: manuscript no. a
at protostar and o↵-source
positions
柱密度比の計算結果
protostellar positions is 0.63 ± 0.19. Taking into account the
輝線強度比
emission in the line wings, the ratio is slightly lower and equals
In su
nH2
T kin NCN /NHCN NCN /NHCN
CN / IHCN
0.40 ± 0.18. It is Igenerally
consistent with the ratios measured
and CN3(cm ) (K) Protostars O↵-sourcefor each source using the full profile. The ratio calculated for the
influence
10450
1.57-5.55
0.85-3.79
selected o↵-source positions equals 0.43 ± 0.18 and 0.20 ± 0.18,
their rati
104
100 1.40-4.98
0.76-3.40
for the full profile and wings, respectively.
104
200 1.33-4.70
0.72-3.21
The CN/HCN intensity ratio for
the Class 0 protostars is
原始星
4
10
300 1.32-4.66
0.71-3.18
観測結果 3.3.2. Ra
0.61 ± 0.23 and for the Class I protostars is 0.67 ± 0.17, indicat104
400 1.45-5.13
0.78-3.50
ing that the evolutionary stage does not strongly a↵ect the meaLine rati
104
500 1.56-5.53
0.85-3.77
sured ratios. A slightly higher CN/HCN ratio for Class I protolocal abu
stars is consistent with increasing opening angles of the outflows
105
50
1.85-6.55
1.00-4.67
sity ratio
for more evolved sources and larger areas a↵ected by UV radia105
100 1.87-6.23
1.01-4.52
Prototion (see Discussion). The opacity e↵ects overestimate the ratioアウトフロー
105
200 2.01-7.12
1.09-4.86
theimpaof CN and HCN, and could have a slightly stronger impact on
105
300 2.14-7.60
1.16-5.18
east subc
5
the more massive envelopes of Class 0 sources (Section 3.3.1). (Off-sourse)
10
400 2.22-7.87
1.20-5.37
close to S
105
500 2.27-8.02
1.23-5.47
outflows
10650
2.52-8.93
1.37-6.10
Figure C
106
100 2.84-10.04 1.54-6.85
4. Analysis
is on the106
200 3.17-11.22 1.72-7.65
average oIn this section, we calculate column densities of the molecules
柱密度比o↵-sourc
106
300 3.33-11.80 1.80-8.05
with the radiative-code RADEX (van der Tak et al. 2007) and
106
400 3.01-10.67 1.63-7.28
NCN with/ NHCN The
Fig.
The ratio
to HCN column
densities
obtained
compare them tothe5:results
fromoftheCN
chemical-code
Nahoon,run
6
10
500 2.75-9.73
1.49-6.64
53
for ndensities
cm UV
and
T kin =fields.
50 K for a range of SMM9, a
H = 10 and
for a set of gas RADEX
temperatures,radiationline intensity ratios (orange line). The observed line intensity ra- The form
tio is shown as a rectangle: light green color corresponding to in HCN
protostars (Mottram et al. 2014), we find optical depth of CS 3-2 4.1. Column densitiesof observed
molecules
observations
the values
at from
the protostar
position, blue color for the (similarly
132line as 2.1, assuming column densities of 5 ⇥ 10 cm . Using
outflow positions and dark green color for bothregions. Column terized b•
柱密度比（CN/HCN）は、原始星の位置で1.3‒
11.8、アウトフローの位置（Off-sourse）で0.7
‒
8.1。
In
case
of
optically
thin
lines
and
LTE
conditions,thecolumna revised collisional rates for HCN adopted from Mullins et al.
density ranges are marked with black and navy emdashed lines Ser SMM
level of aandgiven
molecule,
Nu , canbe calcu1), which
2016, the optical depth calculated for HCN 1-0 is 2.9, assuming density of the upper
for protostars
outflow
positions,
respectively.
associatecolumn densities of 3 ⇥ 1014 cm 2 . This value is in agreement lated using Equation 2, where = 8⇡k/hc3 is a constant equal
CN and H
with the optical depth calculated from F=2!1 to F=1!1 ratio. toR 1937 cm 2 , W is the integrated intensity of the emission line
Table
Model-dependent
columnratios of CN to HCN
Similar optical depths (within a factor of 2) are found for gas ( T mb dV), A isthe 3:
Einsteincoefficient and⌫ is density
the transition
The m
at protostar
andando↵-source
positionstemperatures of 300 K and number densities of 104 cm 3 .
frequency between
the upper
lower level
expressed in GHz

輻射輸送（RADEX）

化学モデル（Nahoon） 柱密度比を使って、G0の値を求める。

A&A proofs: manuscript no. amirocha

Table 4: Dominant processes in CN and HCN chemistry at 50 K•

物理状態とUVの強度から、分子の存在量を求めるコード。

•

UV（星形成）なしで各分子のアバンダンス比が安定するまで
A. Mirocha et al. 2021: Signatures of UV radiation around low-mass protostars
計算し、その後UVを入れて計算。

CN、HCNが関係する反応

Molecule

CN

HCN

Weak UV fields(G0 = 10 3 10 1 )O + CN ! N + CO
CN + N ! C + N2
N + CH ! H + CN
CNC+ + e ! C + CN
N + C2 ! C + CN
HCN + C+ ! H + CNC+
HCN + H+ ! H + HNC+
HCN + h⌫ ! H + CN
N + CH2 ! H + HCN
H + CCN ! C + HCN
HCNH+ + e ! H + HCN

Medium UV fields(G0 = 10 1 101 )Destruction
CN + h⌫ ! C + N
O + CN ! N + CO
Production
N + C2 ! C + CN
H + CN+ ! CN + H+
Destruction
HCN + C+ ! H + CNC+
Production
H + CCN ! C + HCN
HCNH+ + e ! H + HCNStrong UV fields(G0 = 101 106 )CN + h⌫ ! C + N
HCN+ + e ! H + CN
N + CH ! H + CN
H + CN+ ! CN + H+
N + C2 ! C + CN
HCN + h⌫ ! H + CN

HCNH+ + e ! H + HCN
H + CCN ! C + HCN

value of G0 . The ratio increases with G0 until it equals
sequently, the NCN /NHCN decreases for higher G0 . S
culations performed at 300 K show a very similar p
Fig. F.1).
The NCN /NHCN ratios obtained from observations
tive transfer models are ⇠ 1 12 (see Section 4.1).
models are consistent with the observed column dens
CN to HCN for UV fields that are 103 larger than tinterstellar value (Figure 8). The observations are atent with models with significantly lower UV fields
10 2 times the average interstellar UV field. For thr
observed with Herschel, gas densities at 1000 AU an
dent signatures of UV fields were found (Kristensen e
2017; Karska et al. 2018). Using Figure 8, we estim
ward Ser SMM1, SMM3 and SMM4 of 103 104 thevalue. We discuss these values and compare them tosurements
Section 5.3.
A. Mirocha et al. 2021: Signatures of UV radiation
aroundinlow-mass
protostars
In order to understand the chemistry leadin
CN/HCN>1
inthepresenceof UV fields, both prod
Fig. 8: The column density ratio of CN to HCN from Nahoon
for a range of hydrogen densities and UV field strengths assum- destruction of each molecule need to be investigate
ing T = 50 K. The corresponding range of ratios from observa- shows the dominant reactions at 50 K for three UV fie
3
10 1 ), medium (G0 = 10 1 101 ),tions and radiative transfer models are shown in green (see Table - weak (G0 = 10164). Yellow stars show the positions of Ser SMM1, SMM3, and (G0 = 10 10 ). These reactions account for more th
SMM4 assuming their gas number densities at 1000 AU from accumulated total flux of all reactions, where the reacdefined as reactants’ abundances multiplied by the re
Kristensen et al. (2012).
coefficient. Additional reactions, where CN or HCN
or destruction is greater than 30%, are listed in Appen
In the regime of strong UV fields (G0 > 101 ), theare run for a temperature range between 10 and 200 K and a total
destruction route of both HCN and CN is photodissohydrogen densities from 104 cm 3 to 106 cm 3 .
Figure 7 shows the model results assuming a visual extinc- UV photons. Similarly, in medium UV fields CN is altion of 5 mag which corresponds to a lack of UV radiation. In destroyed by UV photons, and HCN is removed by ththat case, HCN is more abundant than CN by about 2-3 orders with C+ , which production also requires UV radiatio
of magnitude. The column density ratio of CN to HCN weakly temperature of 300 K, corresponding to the bulk of
depends on the gas temperature until & 100 K, so we fix the gas outflows from low-mass protostars (Karska et al. 201
pact of photodissociation of HCN becomes dominanttemperature at 50 K.

Class 0/I 天体の違い•

CN/HCNのluminosity比と原始星の温度やluminosityの間に相関関
係はない。
•

•

Class 0/Iの間はCN/HCNの比は変化しない。

Herschel/PACSの観測でサンプル間に[OI]の強度に大きな差がな
いこととconsistent (Karska et al. 2018)。

UV radiation around low-mass protostars

アウトフローのショックによるUV放射

e

,
-

a
,
n
n
e
x
r
e

ショック前後•アウトフローのショック由来のUV放射による分子の存在量をモデル化(Lehmann et al. 2020).

•

アウトフローのショックでUVが放射されるのは、HerschelのH2OとOHの存在量の観測結果から示唆されている (Wampfler et al. 2013;
Kristensen et al. 2017)。

Post-shock•

観測結果のうち、CN/HCN比がもっとも高い領域に関しては、
Vsh=35 km/sのモデルとconsistent。
•

Fig. 13: The observed CN/HCN column density ratio comparedwith shock models with UV for a preshock density of 104 cm 3

モデルのよりも、 CN/HCN比が小さい傾向にある。