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