View
224
Download
0
Embed Size (px)
Citation preview
Thermalization of interstellar CO
Takeshi Oka
Department of Astronomy and Astrophysics and Department of ChemistryThe Enrico Fermi Institute, University of Chicago
Han Xiao and Phillip Lynch Department of Statistics, University of Chicago
OSU international symposium on molecular spectroscopy, June 24, 2009
Tomoharu Oka
Department of Physics, Keio University
: in diffuse clouds near the Galactic center
CO toward the Galactic center
Christian Andreas Doppler 1803-1853
(3,3) metastable
(1,1) ground
CO H3+
Oka, Geballe, Goto, Usuda, McCall, ApJ 632, 882 (2005)
CO
GC 14 % 76 %Spiral arms 86 % 24 %
H3+
IR absorption versus Radio CO emission
NHS 25
NHS 42
IRS1W
μ0 = 0.112 Debye
μ1-0 = 0.106 Debye
μ2-0 = 0.0093 Debye
150
1
Optical depth τ ∝ μ2n(CO)
GCS3-2
Critical density J = 1 → 0 700 cm-3
J = 3 → 2 3 × 104 cm-3
Radiation trapping
Wλ → N(CO)
J
7
6
5
3
4
210
Radiative processes
B = 57635.9687 MHz ≅ 2.766 K μ = 0.112 D
4 32
3
1 64
3ij ijAt hc
7.40 e-8 5.2 months
6.36 e-6 1.8 days
2.58 e-6 4.5 days
7.15 e-7 16 days
3.58 e-5 7.8 hours
2.23 e-5 12 hours
1.27 e-5 22 hours
)()( lulululu BnBAn
1
1
1
11
//
kThl
uullkThulu eg
gAn
eAn
1
1
12
32
1
11
/)1(2,1/)1(2,11
TJBJJJTJBJJJ eJ
JAn
eAn
T = 2.725 K
0.1512 J = 1 → 0 0.45360.0058 J = 2 → 1 0.0092
Collisional and radiative processes
' '
'
2 1exp( )
2 ' 1J J J J
J J
k E EJ
k J kT
Detailed balance
Steady State
1/21,/21,/)1(2,11/)1(2,1 1
1
12
12
1
11
1
1
12
32
1
11
JTBJJJJTBJJJTJBJJJTJBJJ n
eJ
JAn
eA
eJ
JAn
eA
0dt
dnJ
'
',',' 2J
HJJJJJJ nnknk
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)
CO J’
CO J
H2
H2