Transcript 09ColumbusC.ppt

Thermalization of interstellar CO
: in diffuse clouds near the Galactic center
Takeshi Oka
Department of Astronomy and Astrophysics and Department of Chemistry
The Enrico Fermi Institute, University of Chicago
Han Xiao and Phillip Lynch
Department of Statistics, University of Chicago
Tomoharu Oka
Department of Physics, Keio University
OSU international symposium on molecular spectroscopy, June 24, 2009
CO toward the Galactic center
H3+
CO
(1,1) ground
Christian Andreas Doppler
1803-1853
(3,3) metastable
Oka, Geballe, Goto, Usuda, McCall,
ApJ 632, 882 (2005)
GC
Spiral arms
CO
H3+
14 %
86 %
76 %
24 %
IR absorption versus Radio CO emission
NHS 25
NHS 42
μ0 = 0.112 Debye
150
μ1-0 = 0.106 Debye
IRS1W
GCS3-2
μ2-0 = 0.0093 Debye
1
Optical depth τ ∝ μ2n(CO)
Critical density J = 1 → 0 700 cm-3
J = 3 → 2 3 × 104 cm-3
Radiation trapping
Wλ → N(CO)
Radiative processes
J
1 64 4 3
Aij  
ij
3
t
3hc
7
3.58 e-5
7.8 hours
B = 57635.9687 MHz ≅ 2.766 K μ = 0.112 D
nu Aul  Bul  ( )  nl Blu  ( )
6
2.23 e-5
12 hours
g
1
1


nu Aul 1  h / kT   nl Aul u h / kT
 1
gl e
1
 e
5
1.27 e-5
22 hours
4
6.36 e-6 1.8 days
1
2J  3
1


nJ 1 AJ 1, J 1  2 B ( J 1) / T   nJ AJ 1, J
 1
2 J  1 e 2 B ( J 1) / T  1
 e
T = 2.725 K
3
2.58 e-6 4.5 days
2
1
0
2
7.15 e-7 16 days
7.40 e-8 5.2 months
0.1512
0.0058
J=1→0
J=2→1
0.4536
0.0092
Collisional and radiative processes
Steady State
dnJ
0
dt

1
2J  3
1
1
2J 1
1




AJ 1, J 1  2 B ( J 1) / T  nJ 1   AJ 1, J

A
1

n

A
nJ 1

J
,
J

1
J
J
,
J

1
2 B ( J 1) / T
2 BJ / T
2 BJ / T


e

1
2
J

1
e

1
e

1
2
J

1
e

1





  k J ', J nJ '  k J , J ' nJ nH 2
CO J’
H2
CO J
H2
J'
k J ' J
E  EJ '
2J  1

exp(  J
)
k J  J ' 2 J ' 1
kT
Detailed balance
Green & Chapman, ApJS 37, 169 (1978)
D. R. Flower, J. Phys. B: At. Mol. Opt. Phys. 34, 2731 (2001)
Wernli, Valiron, Faure, Wiesenfeld, Jankowski, Swalewicz, A&A, 446, 367 (2006)
Schöier, van der Tak, van Dishoeck, Black, A&A 432, 369 (2005) LAMDA
Yang, Stancil, Balakrishnan, Forrey, J. Chem. Phys. 124, 104304 (2006)
Polynomial fitting is dangerous
n(1)/n(0)
Cubic spline
FMM
Some combinations are not useful
n(1)/n(0)
n(2)/n(0)
Some combinations are more useful
n(1)/n(0)
n(3)/n(2)
Galactic C.
Spiral arms
Understanding a monster
X-ray
HII region
Radio recomb.
Fine structure
γ-ray
Radio continuum
H3+ IR abs.
CO IR abs
H2 FIR
H2 IR emission
Radio CO, CS, HCN, CH emission