ch + , ch, and cn emission from the red rectangle
DESCRIPTION
CH + , CH, and CN Emission from the Red Rectangle. Lewis M. Hobbs, Julie A. Thorburn, D. G. York, Takeshi Oka, Department of Astronomy and Astrophysics, the University of Chicago, Theodore P. Snow, Center for Astrophysics and Space Astronomy, University of Colorado, and John Barentine, - PowerPoint PPT PresentationTRANSCRIPT
CH+, CH, and CN Emission from the Red Rectangle
Lewis M. Hobbs, Julie A. Thorburn,
D. G. York, Takeshi Oka,Department of Astronomy and Astrophysics, the University of Chicago,
Theodore P. Snow,Center for Astrophysics and Space Astronomy, University of Colorado,
and John Barentine, New Mexico State University and Apache Point Observatory
59th Ohio State University International Symposium on Molecular SpectroscopyWI02, 2:05 pm, June 23, 2004
1937 Birth of Molecular Astrophysics
Theodore Dunham, Jr. 1897-1984 Walter Sydney Adams, 1876-1956
T. Adams, Jr. PASP 49, 29 (1937) PAAS 9, 5 (1937)
P. Swings & L. Rosenfeld, ApJ 86, 483 (1937)
A. McKellar, PASP 52, 187, 312 (1940) 53, 233 (1941) CH CN Pub. Dom. Astroph. Obs. 7, 251 (1941)
A. E. Douglas and G. Herzberg, ApJ 94, 381 (1941) CH+
Men’shchikov et al. A & A 393, 867 (2002)
12 3,max
710
1.2
0.57
6000
7750
0.01
2.5 10
g
d
H
D pc
M M
M M
L L
T K
n cm
• Apache Point Observatory 3.5-meter• 3,800–10,000 Å ; / ~ 38,000 (8 km/s)• S/N ~ 1000• 7 nights, from Feb. 2001 to Feb. 2004• 134 emission lines detected. 57 atomic, 76 molecular
1 1A X
2 2A X
2 2B X
CH+
CH
CN
(0 - 0) 4236 Å
Waelkens, van Winckel, Trams, Waters, A & A 256, L15 (1992)
Balm and Jura, A & A 261, L25 (1992)
Hall, Miles, Sarre, Fossey, Nature 358, 629 (1992)
Bakkers, van Dishoeck, Waters, Schoenmaker, A & A 323, 469 (1997)
(1 0) 3969 Å, (2-1) 4177 Å, (1-1) 4443 Å, (0- 1) 4793 Å, (1-2) 5029 Å, 52 lines up to J = 6
4307 Å 3 lines
3875 Å 24 lines up to N = 14
f = 5.45 × 10-3
f = 1.08 × 10-3
CH+ (0 - 0)CH (0 - 0)
CH+ and CH are in different regions
2 2B X CN up to N = 14
CH+ Spontaneous emission time τ
A → X τ ~ 1 μs Larsson, Siegbahn, CP 76, 175 (1983)
v = 1→0 τ ~ 1 s Ornellas, Machado, JCP 84, 1296 (1985)
J = 6→5 τ ~ 2.15 s Sun, Freed, JCP 88, 2659 (1988)
μA→X = 0.47 Debye
μ1→0 = 0.0105 Debye
μ0 = 1.656 Debye
B0 = 13.9302 cm-1
32
3
4| |
3if ifAc
Critical density
nc ~ 108 cm-3 !
NGC 7072 up to J = 6 Cernicharo, Liu, Gonzalez-Alfonso, Cox, Barlow, Lim, Swinyard, ApJ 483, L65 (1997)
Collisional thermalization ??
What is the collision partner ??
H, H2, (He), (e-)
The Enigma of CH+ Chemistry
Production
C+ + H → CH+ + hν 10-17 cm3 s-1
C+ + H2 → CH+ + H Endothermic by 0.4 eV
C + H3+ → CH+ + H2
Destruction
CH+ + H → C+ + H2
Exothermic by 0.4 eV
CH+ + H2→ CH2+ + H
Exothermic by 1.7 eV
CH+ + e- → C + H
No way to thermalize CH+ by collisions!!
Lambert, Danks, ApJ, 303, 401(1986)
1 2 2
1 2 2 2
( ) ( ) ( )
( ) ( ) ( ) ( ) ( )
n k n H n H
n C k n H k n H n H
C
H
H
n
C+ + H2* ↔ CH+ + H v = 1 0.517 eV
CH+ + H2→ CH2+ + H
k1n(C+)n(H2*) = k-1n(CH+)n(H) + k2n(CH+)n(H2)
The critical density should still be high > 108 cm-3
CN Spontaneous emission time τ
A → X τ ~ 0.2 μs Bauschlicher, Langhoff, Taylor
(1988)
J = 14 → 13 τ ~ 12 s Langhoff, Bauschlicher(1989)
μ0 = 1.351 Debye
B0 = 1.89109 cm-1
32
3
4| |
3if ifAc
Critical density
nc ~ 108 cm-3 !
Hertzprung-Russell Diagram
R ~ 300R