ALMA Workshop 「系外銀河における微細構造線の観測とその理解」
2014年12月2-3日＠東大天文センター

Nearby Galaxiesでの[CI]の観測について• [CI]とは？
• 分子ガス質量のトレーサー• 輝線比を用いた種々の診断
Takuma Izumi
The Univ. of Tokyo(takumaizumi@ioa.s.u-tokyo.ac.jp)

[CI]とは？

1S

炭素原子輝線：[CI]1D• 電子基底（最安定な3P状態）はさC 1s22s22p2

Too high energy

らに3準位微細構造系に分裂。

• 3準位ゆえにモデル化が簡単

3P

2

3P

3P

1

FIR/submm

3P

0

}

→ LTEと背景温度を仮定すれ
ば、Texとτ(CI)が求まる。

• 周波数的に、ALMAでhigh-z天体を観測するのに適している。

ALMA Band 10
ALMA Band 8

1988ApJ...335..774Z[CI]輝線の励起を解く under LTE

3P

2

3P

3P

T3 P2 !3 P1 = (J(Tex )J(Tbg ))(1exp( ⌧3 P2 !3 P1 ))T3 P1 !3 P0 = (J(Tex )J(Tbg ))(1exp( ⌧3 P1 !3 P0 ))

1

3P

0

•

h⌫/kB
ただし、 J(T ) = exp(h⌫/k T )B1：submm/FIRなのでRJ近似は不可• また、LTE条件下では励起温度Texは1-0と2-1遷移で共通。τも互いに独立ではなく、励起温度の関数として決まる。

c2 (⌫)gu⌧ul =Nl Aul (1
2
8⇡⌫ul
gl

h⌫ul
exp(
))
kTex

• 以上を使うと全部解ける。

τ(2-1)/τ(1-0)

2Zmuidzinas et al. 1988, ApJ, 335, 774

1

0
0

50

Tex [K] 150200分子ガス質量のトレーサーとしての[CI]• 予想に反して[CI]は分子雲のどこからでも出ている。
• その分布はoptically-thinな13COと（ほぼ）完璧に一致。
• しかも、X(CI)/X(CO) abundance比も一様なようだ。
• その原因は…？

分子ガス質量のトレーサー• 空間分解した測定：- 位置の関数として柱密度を測定し、対象領域で積分• 一般的な水素分子柱密度のトレーサーとしては、- ダスト放射：○ 化学組成、励起に依存しない。 emissivity/
opacityがwell-determinedである必要、速度場の情報が得られない、
ダスト温度の精密測定が必要。
- 13CO：○ 速度場の測定も可能（複数成分への分離が容易）、ダス
トの詳細な性質が不要。 化学組成、励起に敏感。

• [CI]はどうなのか？
- 期待すること：Classical PDR（homogeneous, steady-statechemistry）の観点では、分子が解離されるlow-Av領域をトレースしているはず。。

分子ガス質量のトレーサー• 空間分解した測定：- 位置の関数として柱密度を測定し、対象領域で積分• 一般的な水素分子柱密度のトレーサーとしては、Hollenbach & Tielens 1997, ARAA, 35, 179- ダスト放射：○ 化学組成、励起に依存しない。 emissivity/
opacityがwell-determinedである必要、速度場の情報が得られない、
ダスト温度の精密測定が必要。
- 13CO：○ 速度場の測定も可能（複数成分への分離が容易）、ダス
トの詳細な性質が不要。 化学組成、励起に敏感。

• [CI]はどうなのか？
- 期待すること：Classical PDR（homogeneous, steady-statechemistry）の観点では、分子が解離されるlow-Av領域をトレースしているはず。。

分子ガス質量のトレーサー• 空間分解した測定：- 位置の関数として柱密度を測定し、対象領域で積分• 一般的な水素分子柱密度のトレーサーとしては、Hollenbach & Tielens 1997, ARAA, 35, 179- ダスト放射：○ 化学組成、励起に依存しない。 emissivity/
opacityがwell-determinedである必要、速度場の情報が得られない、
ダスト温度の精密測定が必要。
- 13CO：○観測と理論の両面から[CI]の有用性に迫るべきだが、速度場の測定も可能（複数成分への分離が容易）、ダス
いかんせん系外銀河での（高分解能）imaging例は皆無。。
トの詳細な性質が不要。
化学組成、励起に敏感。

• [CI]はどうなのか？
- 期待すること：Classical PDR（homogeneous, steady-statechemistry）の観点では、分子が解離されるlow-Av領域をトレースしているはず。。

13

CO J p 5 r 4 AND [C i] MAPPING OF ORION A

Vol. 539

系内天体観測からの示唆：空間分布(1)[CI](1-0)

13CO(1-0)

13CO(5-4)

Ori-A• [CI]と13COは基本的に同じ分布をしている 。
(e.g., Ikeda et al. 1999, ApJ, 527, L59;
Plume et al. 2000, ApJ, 539, L133;
Ojha et al. 2001, ApJ, 548, 253)

• しかも分子雲にubiquitous。
(e.g., Schilke et al. 1995; Kramer et al.
2008, A&A, 547, 555; Tatematsu et al.
1999, ApJ, 526, 295)

Plume et al. 2000, ApJ, 539, L133s
Observations and modeling results of the Orion A molecular cloud. Offsets are given with respect to the central position defined as a p 5h35m14.5,

H. Beuther et al.: Diﬀerent phases of ca
系内天体観測からの示唆：空間分布(2)A&A 571, A53 (2014)

IRDC: G11.11

IRDC: G48.66

Fig. 7. G48.66: the color scale shows from left to right the emission from C18 O(2–−1
C18 O(2–1)
and
[CI]
are
[32.0;
35.0]
and[32.0;
35.5]
kms. The integration ranges fo
IRDCからも、[CI]放射は強くでている。
show the ATLASGAL 870 µm emission starting at 3σ level of 150 mJy beam−1 andmark the positions of 70 µm sources.

•→ Classical-PDRの適用は難しそう。

without any clear association with the infrared dark filament. spatially i
13CO（やC
Interestingly,
two strong[CII] emission18
featureslie southeast the atomi
またしてもO）とほぼ同様のand northwest of the central peak in the filament in the direction and the 1of thetwo outflow lobes discussed in Fallscheer et al. (2009). gion. In th
空間分布。
While this is not conclusive, there is the possibility that these parably v[CII] emission features could be partly related to the outflow ponents ission show
from the embedded young protostar.
[CI] with•
Beuther et al. 2014, A&A, 571, 53

No. 1, 1999

IKEDA ET AL.

系内天体観測からの示唆：空間分布(3)[CI](1-0)/12CO(3-2)[CI](1-0)/13CO(1-0)

Tkin• [CI](1-0)/12CO(3-2)比は場所ごとに違う（Ori-Aの場合は南北のgradient）→ Ori-Aに付随するTkinの南
北gradientを反映して、τ(CI)が変化していることを反映？

τ(CI)?

Ikeda et al. 1999, ApJ, 527, L59
Fig. 2.—(a) Ratio of ∫ TMB(C i)dv to ∫ TMB [CO (J = 3–2)] dv. The contour
levels range
from 0.1 to 0.9 13
withintervals of 0.2. (b) Ratio of ∫ TMB(C i)dv to[CI](1-0)/
CO(1-0)比はほぼ一様！
∫ TMB [13CO (J = 1–0)] dv. The contour levels range from 0.3 to 0.9 with in-•13
tervals of →0.2. The
CO 13(J =COは同程度のopacity、かつabundance比がほぼ一様であ1–0) data was obtained from Bally et al. (1987).
[CI]とThe velocity range integrated was from 3 to 13 km s!1 for all lines.

ることを示唆。

served gradient suggests that t(C i) increases from the northern
C+/C/COとlayerに分かれるclassical-PDRの描像とは矛盾？
to theparts. The C i optical depth depends on the• southern
excitation temperature and on the column density N(C i). The
gas kinetic temperature is known to have a spatial gradient,parameters and line fluxes are summarized in Table 3. In thefollowing we briefly discuss the individual sources.

High-z天体の観測例：[CI]のabundanceThis source is one of the (apparently) brightest sources known
3.2.1. APM 08279+5255

to date, with a submillimeter flux of S850 µm = 75 ± 4 mJy(Lewis et al. 1998). The first CO detections by Downes et al.
(1999, J = 4, J = 9) already indicated the extreme excitation
conditions of the molecular gas (studied in detail in Weiß et
2.2 < z < 6.4の17個のQSO/SMG（観測+文献）
al. 2007a). One of the explanations for its apparent brightness! lensingand extreme excitation is that thegeometry is such that1
the central 100
pc of this source is magnified by a large factor
2.11) see also Egami et al. 2000).9
励起温度は、 Tex = 38.8 ⇥ ln((µ =0 60–100; Weiß et al. 2007,
The
C i(1–0) line has been detected by Wagg et al. (2006). The
LCI(21)/CI(1 0)sourceisnotdetected in C i(2–1) emission with an upper limit
ure 7. Left: C i(2–1) spectrum of APM 08279+5255; the line is not detected.
−1
of 1 Jy km s (Figure 7, left; upper limits are given in Table 3).

••• Optically-thinを仮定して、[CI]の質量は、4 GHz = 2.0 ± 0.22 mJy (Figure 6, right), in good agreementth the extrapolation from the SCUBA measurement (and con9 We note that Riechers et al. (2009a) derived a magnification factor of only
tent with the estimate of Tacconi et al. 2006,
4 of S233 GHz =23.6/T0ex
M[CI]
Q(Tex )e
∼4 forL
the molecular gas phase.
± 0.5 mJy, their
Table=
1). 1.9 ⇥ 10
[CI](1 0) [M ]Walter et al. 2011,
ApJ, 730, 18

High-z天体の観測例：[CI]のabundance• 励起温度は Tex ~ 30K：近傍銀河と同程度• Fractional abundanceは X(CI)/X(H2) ~ 8 10-5 程度でほぼ一定

Figure 14. Left: L′C i(1−0) /L′CO(3−2) ratio as a function of the cooling contribution of C i (LC i /LFIR ). Right: same L′C i(1−0) /L′CO(3−2) ratio, this time plotted as a
unction of LC i /L850 µm to take out the FIR luminosity dependence on the assumed dust temperatures. SMGs are plotted as circles, QSOs as stars in both panels.

•

See also, Weis et al. 2005, A&A, 429, L25; Alaghband-Zadeh et al. 2013,
Table 6MNRAS, 435, 1493
Derived Physical Properties

Walter et al. 2011, ApJ, 730, 18

Source
SMMJ02399-0136
APM08279+5255
RXJ0911+0551
F10214SDSSJ1148+5251
SMMJ123549+6215
GN20.2
GN20
BRI1335-0417
SMMJ14011+0252
Cloverleaf
SMMJ16359+6612
SMMJ163650+4057
SMMJ163658+4105
MM18423+5938
SMMJ213511-0102
PSSJ2322+1944

Tex a
(K)
21.6 ± 6.3
30.00
23.5 ± 3.0
42.0 ± 10.9
30.00
30.00
30.00
30.00
30.00
32.4 ± 5.2
26.7 ± 3.0
26.2 ± 4.0
30.00
30.00
34.1 ± 8.8
22.4 ± 0.6
32.8 ± 7.4

MC i(107 M⊙ )2.0 ± 0.2
0.050 ± 0.007
0.26 ± 0.04
0.36 ± 0.06...
1.8 ± 0.3
...
...
<11
0.15 ± 0.03
0.76 ± 0.12
0.16 ± 0.03
<1.4
1.8 ± 0.4
0.5 ± 0.1
0.91 ± 0.03
0.71 ± 0.11

MH2(1010 M⊙ )4.0 ± 0.5
0.154 ± 0.014
0.32 ± 0.04
0.95 ± 0.18
2.2 ± 0.5
3.4 ± 0.4
3.0 ± 1.2
4.7 ± 0.6
6.8 ± 1.4
0.31 ± 0.03
3.32 ± 0.05
0.34 ± 0.02
3.9 ± 0.5
4.6 ± 0.5
0.79 ± 0.08
0.95 ± 0.01
2.4 ± 0.3

X[C i]/X[H2 ]10−5

LC i(1−0) /LFIR
10−6

L′C i(1−0) /L′CO(3−2)

L′C i(2−1) /L′C i(1−0)

8.1 ± 1.4
5.4 ± 0.9
14 ± 36.4 ± 1.7
...
9 ± 2
...
...
<28
8.2 ± 1.6
3.8 ± 0.6
7.8 ± 1.5
<5.8
6.4 ± 1.5
11 ± 315.9 ± 0.5
4.9 ± 1.0

10 ± 41.3 ± 0.6
4.2 ± 1.8
1.4 ± 0.6...
12 ± 5...
...
<1314 ± 62.9 ± 1.3
12 ± 5
<9
9 ± 4
8 ± 4
14 ± 64.1 ± 1.8

0.30 ± 0.05
0.21 ± 0.03
0.52 ± 0.10
0.24 ± 0.06...
0.34 ± 0.08
...
...
<1.1
0.32 ± 0.06
0.15 ± 0.02
0.30 ± 0.06
<0.22
0.25 ± 0.06
0.41 ± 0.10
0.60 ± 0.02
0.19 ± 0.04

0.35 ± 0.18
<0.44
0.41 ± 0.08
0.8 ± 0.2
...
<0.34
...
...
<0.13
0.64 ± 0.12
0.49 ± 0.08
0.48 ± 0.11
<1.0
<0.82
0.7 ± 0.2
0.37 ± 0.02
0.65 ± 0.17

Z.-Y. Zhang et al.: Physical conditions of molecular gas in the Circinus galaxy[CI]に関する問題

Table 3. CO line intensities.

W line a
K km s−1

Beam = 18′′
F lineL′ line /L′CO3−2
Jy km s−1–

W lineK km s−1

Beam = 45′′
F lineL′ line /L′ CO3−2
Jy km s−1–––
310 ± 20240 ± 20140 ± 1555 ± 7––0.97 × 104
1.17 × 104
1.44 × 104
0.97 × 104

180 ± 35b
144 ± 25b
140 ± 2080 ± 1535 ± 519 ± 53.51 × 103
1.42 × 104
2.49 × 104
2.51 × 104
2.48 × 104
1.73 × 104

Transitions

•
•

12

CO J = 1 → 0
CO J = 2 → 1
12CO J = 3 → 2
12CO J = 4 → 3
12CO J = 6 → 5
12CO J = 7 → 6––
10.77 ± 0.2
0.45 ± 0.08
0.18 ± 0.03

113COと一致する、ほぼ分子雲の”どこにでもある”ことの原因は？
0.83 ± 0.20
1213

CO J = 1 → 0–––
13 ± 2.5
CO J = 2 → 1–––
12.5 ± 2.5
ほぼ一定のfractional abundanceの原因は？
CO J = 3 → 2
24 ± 5740
0.07 ± 0.02
9.5 ± 3.0
1313c

CI 1→0100 ± 25

5 × 10345 ± 10

230
1300
1850

1.4 × 104

0.79 ± 0.16
0.44 ± 0.09
0.19 ± 0.03
0.11 ± 0.03

0.07 ± 0.02
0.07 ± 0.02
0.05 ± 0.02!
Notes. (a) The integrated line intensities are calculated from Wline = T mb d! in the velocity range from 200 km s−1 to 700 km s−1 . (b) We takeaperture eﬃciencies of ηmb = 0.7 and 0.6 for 12 CO J = 1 → 0 and 12 CO J = 2 → 1 for SEST. (c) We convolve the 13 CO J = 3 → 2 emission to a
resolution of 45′′ , assuming that the distribution of 13 CO J = 3 → 2 is the same as that of 12 CO J = 3 → 2.

• これらが解明されると、気持ちに余裕をもってmassの推定に使える。。

A 568, A122 (2014)

ingle
d fit.
stud2012;
mule Lu
model

both
8 ×
T kin ,
ities.

onent
com-

32000
Integrated Line Flux Density [Jy km s-1]

→ 2
on of

12CO Total
12CO Low Excitation
12CO High Excitation
13CO Total

28000
24000

CO in 45'' beam

20000

12CO TotalalHighh Excitation
n

16000
12000

Zhang et al. 2014,
A&A, 568, 122

8000
Low Excitation
4000
013CO Total
al

0

2

4

6

8

10

12

Quantum
Number
Jup CO transitions. Big crosses
Fig.Rotational
3. Moment-zeroimagesof multiple-J
mark the central position of Circinus; small crosses in the upper panels
12 positions.13Upper left: 12 CO J = 3 → 2; upper
denote the sampled
right:
Fig. 8. Integrated flux densities
of
CO and CO in the central 45′′ re12
CO J = 4 → 3; lower left: 12 CO J = 6 → 5; lower right: 12 CO J =gion of the Circinus galaxy.
shadowed
7 → 6.The
Circlesin the lower regions
left of eachare
paneltheshowranges
the beam.ofThe
12
CO J = from
7 → 6 mapwasconvolved to an angularresolutionof 18′′ .
the best fitting results derived
thetwo-component
LVG
model−1
Contour levels are 20, 60, . . . , 180 K km s in steps of 40 K km s−1 for
12ing. The high- and low-excitation
CO J = 3 →components
2, J = 4 → 3, andandJ = 6the→ 5,totaland 10,integrated
20, 30 K km s−1
12
12
for 12 CO Jin= red,
7 → 6blue,(1σ = and
1.9, 3,green.
10, and 3The
K km total
s−1 for inteCO J =CO flux densities are plotted
3
→
2,
J
=
4
→
3,
J
=
6
→
5,
and
J
=
7
→
6).
Red
(thickdotted)13

Fig. 4. The 492 GHz C I 1 → 0 integrated intensity image of the central
part of the Circinus galaxy. Plotted contour levels are: 20 (6σ), 30, 40,
50, and 60 mK km s−1 . The red contour presents the half maximum levelof the C I emission. The beam size (FWHM) is 13.5′′ .

CircinusではCOのLVG解析からもとめたガス質量と、[CI]のLTE解析から求めたガス質量はほぼ一致。
of the map. The detected structure covers an angular distance of∼20′′ from northeast to southwest, corresponding to 400 pc onPossible interpretations (1): Clumpy-PDR

10

OKA ET AL.

Vol. 602• Classicalに想定されていた、”homogeneous medium”を変える (e.g., Oka et al. 2004, ApJ,
602, 803)。

• Turbulence etc.で密度構造にムOka et al. 2004,
ApJ, 602, 803

Fig. 8.—Column densities calculated from a steady state PDR model. (a) Total H column density. (b) Cþ column density map. (c) C0 column density map. (d) CO
lumn density map. The star symbol in each panel denotes the position of the UV source.

ラを作れば、想像以上に分子雲
内部にUV光が浸透し、[CI]が増えるだろう。

Possible interpretations (2):
C I lines as H
Non-equillibrium + Turbulence+2 gasCRmass tracer
1e5 yr• 星間化学は非平衡。
• 化学反応の（平衡状態までの）タイ

1e8 yrPapadopoulos et al. 2004,
MNRAS, 351, 147

ムスケール : O(1e7 yr) >Dynamical time：O(1e6-7 yr)• 従って、steady state abundance
ratioは実現できない。

• Turbulenceは領域ごとのabundanceの違いを均質化してしまう。
(e.g., Papadopoulos et al. 2004, MNRAS, 351, 147; Glover et al. 2014 in press.)• Cosmic-Rayは、分子雲深部に浸透し、COを解離。[CI]をenhance（c.f., M82中心部 Schilke et al. 1993, ApJ, 417, L67）。

8

Numerical Simulation (1)NH[CI](1-0) intensity
Glover et al. in press.

[CI](2-1) intensity

12CO(1-0) intensity

Figure 9. Two-dimensional PDF of the integrated intensity inthe 12 CO J = 1 ! 0 line, WCO , plotted as a function of thevisual extinction. The dashed line indicates a linear relationshipbetween WCO and AV and is there to guide the eye. The solidline shows the geometric mean of WCO as a function of AV . The
points are colour-coded according to the fraction of the total cloudarea that they represent.
12

Figure 11. As Figure 9, but for the [C i] 1 ! 0 line.

Numerical Simulation (2)13CO(1-0)

of AV at low extinctions than CO. To test this, we plot in
Figure 11 the 2D PDF of the integrated intensity of the[C i] 1 ! 0 line. We see that there is good linear correlation between WCI,1 0 and AV for visual extinctions in therange 1.5 < AV < 7. At higher extinctions, the correlation
becomes sub-linear, possibly because an increasing fractionof this high extinction gas consists of CO rather than C,
while at AV < 1.5, the correlation breaks down owing to
the photoionization of C. Comparing our results for C and
13
CO, we see that neutral atomic carbon is a better tracer oflow column density material, while 13 CO is to be preferredat high column densities. We also note that although thedi↵erence between AV = 1.5 and AV = 3 may seem minor,
it actually corresponds to approximately 20% of the total
mass of the cloud, consistent with our results in Section 3.2.
In the regime where WCI,1 0 scales linearly with AV ,the relationship between the two can be described by thefollowing empirical fit[CI](1-0)

WCI,1 0 = 0.7AV K km s 1 .

(18)

If we apply this fit to each pixel in our synthetic [C i] emission map, we can generate an estimate of AV and from thatcan estimate the cloud mass. The estimate that we obtainin this way is approximately 85% of the true mass of the“missing” 15% is the low AV material that is not
Glover et cloud;al. inthepress.
Figure 9.
of theintensity ofin
10.Two-dimensional
As Figure 9, butPDF
for theJ =integrated
1 ! 0 transition
As Figure 9, but for the [C i] 1 ! 0 line.
tracedFigure
well by11.
[C i].
12
13
13
theCO.COJ = 1 !the0 line,functionof theTo compute
COWemission
map, asweahaveassumeda
CO , plotted
Finally, we note that our finding here that [C i] emission
12
13
13
visualextinction.
Thebetween
dashed line
indicates
a linear relationshipconstant
ratio of 60:1
COand CO.
is a relatively good tracer of the column density over a sigbetween WCO and AV and is there to guide the eye. The solidof AV atlow ofextinctions
than CO.
To testto
this,weextentplot innificant
range
AV was alreadyanticipatedsomeline shows the geometric mean of WCO as a function of AV . The
Figure 11 the 2Dof thetheobservationally.
For PDF
example,in integrated
their studyintensityof NGC of891,
12cloudpointsare colour-coded
accordingthe fractionof thetotal
significantly
better tracerof thetocolumn
densitythanCO.
[C i] 1&!
0 line.(2000)
We seethata good
there spatial
is goodcorrelation
linear correlaGerin
Phillips
foundbeareathey represent.
The that
relationshipbetween W13CO and AV is extremely closetion between
WCI,1
in the0 and Aand
V for
tween
[C i] 1 !
0 emission
1.3visualmm extinctions
dust continuum-2
to linear for visualextinctions
in
the
range
3
<
A
<
10,
V
H2
range 1.5which< AVthey< 7.interpreted
At higheras
extinctions,the[Ccorrelation
emission,
evidence thati] emisalthough there are hints that opacity e↵ects are beginningbecomes
sub-linear,possibly
increasing fractionsion
is a good
tracer of
the gasbecause
column an
density.
to become important at AV ⇠ 10. However, as in the caseof this high extinction gas consists of CO rather than C,of 12 CO, the relationship breaks down at low AV owing towhile at AV < 1.5, the correlation breaks down owing to
the photodissociation of CO.
-2H2ofcolumn
the 21
photoionization
C. Comparing
results for C and
3.4.2
Tracing thedensity our-1[CI](1-0)
Since neutral atomic carbon is primarilyfound at lower
13
CO, we see that neutral atomic carbon is a better tracer ofgas densities and lower extinctions than CO, we might reaIn the previous section, we saw that oneof the main drawlow column density material, while 13 CO is to be preferredsonably expect [C i] emission emission to be a better tracer
backs with using [C i] to trace the structure of the cloud is
at high column densities. We also note that although thedi↵erence between AV = 1.5 and AV = 3 may seem minor,•

CO並み、low-Avに限ればそれ以上に高いlinearityを[CI]は示す。
→ 1.5 < Av < 7で[CI]が有用である。
→ N では、5e20-1e22 cm 程度の範囲。

• 上記の範囲で、X~ 1 10cm(K km/s)[CI]に関する問題

まとめ• これまでの研究をまとめると、おおむね[CI]を分子ガス質量のトレーサーとすること自体は大丈夫そうだ。

• ただし、なぜ分子ガスをトレースできるのか、観測的にはよく分かっていない。
→ Clumpy PDR, Turbulence, Non-equillibrium chemistry,
Cosmic-Ray• 空間分解できる近傍銀河（Milky Wayにはないvigorousな星形成環
境がある; NGC 253, M82, etc）で、[CI](1-0), (2-1)や、CO系を定量評価することが重要だろう。
→ 最終的にはHigh-z天体のガス質量、fractionの評価へ。

おまけ：輝線比を用いた診断：（1）星形成モード
The Astrophysical Journal, 757:157 (7pp), 2012 October 1
Milky Way disc

Milky Way centre

Papadopoulos & Geach

CO• [CI]がtotalmanner. However,gasを、HCNやhigh-J
given the small range of both CO
andCloverleaf

Tracersa = HCN,CO(4 − 3)

15

Disk / cloudb = CI(1 − 0),CO(1 − 0)

10Merger / nuclear

5

Number•0

Papadopoulos et al. 2012, ApJ, 757, 157
0.1

1

10

ra b 〈ra b〉
横軸はたとえばCO(4-3)/[CI](1-0)
Figure 2. Comparison of the ξSF proxies rHCN/CO , rHCN/[C i] , and rCO(4–3)/[C i]compiled for galaxy disks and clouds (representing our “disk mode”) andmergers and nuclear regions (representing our “burst mode”); data taken from
Gao & Solomon (2004), Israel et al. (1998), Israel & Baas (2001), Israel & Baas
(2003), Barvainis et al. (1997), White et al. (1994), and Petitpas & Wilson (1998).
To present the tracers on the same scale, we have normalized each proxy to theaverage value, ra/b /⟨ra/b ⟩, where a and b correspond to (e.g.,) HCN J(1 → 0)
and CO J(1 → 0). Although there is some overlap, due to the r

HCN r21 ∼ 0.6–1, the J = 2 → 1 transition of these two
がdensemolecules can gasを見ているとする。
also be used to the same effect. This allows
ALMA to survey rHCN/CO up to z ! 1 as the rest frequencies
of CO J(2 → 1) and HCN J(2 → 1) are at 230.538 GHz and177.264 GHz, respectively. HCN J(2 → 1) can be accessed(densegas)/(totalgas)の比を、そby ALMA out
to z ∼ 1 and HCN
J(3 → 2) out to z ∼ 2.
Given the order of magnitude differences expected for the
れらの輝線で代替するとして調べる
rHCN/CO -type of ratios between mergers and isolated disks,
it is very likely that even HCN J(3 → 2) and ratios suchと、バーストモードの星形成と
as HCN J(3 → 2)/CO J(1 → 0) or HCN J(3 → 2)/
CO J(2 → 1) will remain practical proxies of ξSF out toquiescentな星形成で輝線比に差がz ! 2 using ALMA. Moreover, given the tremendous sensitivity
boost at (sub)millimeter wavelengths that ALMA represents, the出る。
necessary calibration of such “hybrid” HCN/CO ratios in termsof ξSF will be trivial for large numbers of star-forming galaxies
in the local universe.

• [CI]で分子ガス質量を測りつつ、隣接
2.2.2. HCN J(1 → 0)/[C i]( P → P ),
3

3

1

3

3

HCN J(2 → 1)/[C i]( P1 → P0 )0

するCO(4-3)との輝線比をとって星This is a potentially powerful tracer of ξSF , with—as mentioned above—the HCN J(1 → 0) and HCN J(2 → 1) line
形成モードを調べる＠宇宙の古今

luminosities proportional to the dense star-forming gas mass,and [C i](3 P1 → 3 P0 ) scaling with total molecular gas mass,
but with many advantages over low-J CO lines (see Paper I).
The higher rest frequency of [C i](3 P1 → 3 P0 ) (ν0 = 492 GHz),
compared to HCN J(1 → 0) means that the correspondingおまけ：輝線比を用いた診断：（2）熱源診断~10万!!!

Meijerink et al. 2007, A&A, 793, 811• Cosmic-RayにCOが解離されたように、X線でも同様にCOは解離、[CI]を著しくenhanceするという予測もある。

• ただし、これはhomogeneous, steady stateなgas-phase modelである点に注意。

Z.-Y. Zhang et al.: Physical conditions of molecular gas in the Circin

おまけ：輝線比を用いた診断：
the literature, including

redshift galaxies (e.g., W
C I and 12 CO J = 3 →（2）熱源診断the ratios lies within an olines). The correlation de
なぜかhigh-z天体でbasically follows the sam~10万!!! （微妙に）比が高い。
We find that the C I
tios RCI/CO32 in nearby
QSOの影響（XDR）？
those found in the highing galaxies (i.e., Circi
RCI/CO32 = 0.17 ± 0.03
NearbyでAGN近傍だけを
about
half
the average
Meijerink et al. 2007,
A&A,
793,of811
空間分解して観測すべし。
2011, 0.32 ± 0.13). In themostly close to 0.1. In thethe RCI/CO32
ratiosc.f. Takano,
Izumi
et areal. bthose in quiescent galaxi
Cosmic-RayにCOが解離されたように、X線でも同様にCOは解離、[CI]
ALMA
Cycle
2
caused by
the enhancedgを著しくenhanceするという予測もある。
Zhang et al. 2014, A&A, 568, 122••

5. Summary and con
ただし、これはhomogeneous, steady stateなgas-phase modelでWe present new APEX m
ある点に注意。
2, 4 → 3, 6 → 5, 7 → 6
the Circinus galaxy. Thes′′