ch + spectrum and diffuse interstellar bands toward herschel 36 excited by dust emission
DESCRIPTION
CH + spectrum and diffuse interstellar bands toward Herschel 36 excited by dust emission. Julie Dahlstrom , Takeshi Oka , Sean Johnson, Daniel E. Welty, Lew Hobbs and Donald G. York Department of Astronomy and Astrophysics, University of Chicago. June 20, 2012, Columbus meeting WH07. - PowerPoint PPT PresentationTRANSCRIPT
CH+ spectrum and diffuse interstellar bands toward Herschel 36 excited by dust emission
Julie Dahlstrom, Takeshi Oka, Sean Johnson, Daniel E. Welty, Lew Hobbs and Donald G. York
Department of Astronomy and Astrophysics, University of Chicago
June 20, 2012, Columbus meeting WH07
1937 Birth of Molecular Astrophysics
Theodore Dunham, Jr. 1897-1984 Walter Sydney Adams, 1876-1956
T. Dunham, Jr. PASP 49, 29 (1937) PAAS 9, 5 (1937)
W. S. Adams, ApJ, 93, 11 (1941)
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) Tr = 2.3 K
A. E. Douglas and G. Herzberg, ApJ 94, 381 (1941) CH+
Andrew McKellar 1910 -1960
CN and the cosmic blackbody radiation
W.S. Adams, ApJ, 93, 11 (1941)
A. McKellar, PASP, 51, 233 (1940)
R(0)
R(1) P(1)
A. McKellar, PDAO, 7, 251 (1941)
Te = 2.3 K (= Tr)
CN
Goto, Stecklum, Linz, Feldt, Henning, Pascucci, Usuda, 2006, ApJ, 649, 299
AV ~ 4
AV ~ 6
The three temperaturesKinetic temperature Tk Collision Maxwell 1860 Phil. Mag. 4, 19
Excitation temperature Te Observed Boltzmann 1871 Wiener Berichte 63, 712
Radiative temperature Tr Radiation Planck 1901 Ann. D. Physik 4, 564
If Tk = Tr, thermal, Boltzmann Te = Tk = Tr
If Tk > Tr, collision dominated thermal Te = Tk
radiation dominated thermal Te = Tr
intermediate non-thermal −∞ < Te < ∞
''
( ')exp ( ) /
( )J
J J eJ
gn JE E kT
n J g
2
22
3
4v
dn N v e dv
3
5
8 1
1ch
k
hE
e
α2 = 2kTk/m
θ = Tr
CH+ in the J = 1 excited rotational level and radiative temperature of dust emission
CH+ 40.1 K
μ = 1.7 DebyeA = 0.0070 s-1 τ = 140 sncrit = 3 × 106 cm-3
Te = Tr = 14.6 K
0
2
1
2
1
0
R(0)R(1) Q(1)
CN 4.9 K
HD 213985
Bakker et at. A&A, 323, 469 (1997)
CH in the J = 3/2 excited fine structure level
Te = Tr = 6.7 K < 14.6 K
~ 25.6 K
CHCH+
Effect of radiation on DIBs toward Her 36
Extended Tail toward Red ETREast Turkestan Republic
(B’−B)J(J +1)
Simulation of DIB velocity profiles with high Tr and the 2.7 K cosmic background radiation
1 1( ) ( 1)J Jn J C n J C
11
11
( ) 2 1 2exp( ) exp( )
( 1) 2 1J e J
J Je J kJ
C n J g J hBJE E
n J g J kTC
1
1 1
( 1)( ) (0) (2 1)exp
Jm
m k km
C NhB hBJ Jn J n J
kT kTC
Collision only
Radiation and collision
1 1 1 1( )( ) ( 1)( )JJ J J Jn J A B C n J B C Einstein 1916
,
1 1/ /
1 2 1 1( ) 1 ( 1)
1 2 1 1r r
J JJ Jh kT h kT
Jn J A C n J A C
e J e
4/3 2
2 /
41 /3 2
2 /
1 2 1
2 1 1 2 1( ) (0)1 2 1
12 1 1 2 1
k
r
k
r
hBm kTJ hBm kT
m hBm kThBm kT
m mB C e
m e mn J nm m
B C em e m
Goldreich Kwan 1974
Principle of Detailed Balancing Boltzmann, 1872 H-theorem Wiener Berichte 66, 275
ΔJ > 1
4/3 2
2 /
41 /3 2
2 /
1 2 1
2 1 1 2 1( ) (0)1 2 1
12 1 1 2 1
k
r
k
r
hBm kTJ hBm kT
m hBm kThBm kT
m mB C e
m e mn J nm m
B C em e m
Rotational distribution n(J)
Spectrum Rotation of linear molecules
)1(ˆ2
ˆˆ
2
222
JhBJJHJEI
JH
I
PE
I
hB
28
i
ii zmI 2
Rotational constant
Moment of inertia
R()
CH+ 417,568 MHz 20.04 K
HC5N 1,331 MHz 0.06390 K
R(J) J + 1 ← J ν = ν0 + B’(J + 1)(J +2) – BJ(J + 1) = ν0 + 2B’(J + 1) + (B’ – B)J(J + 1)
Q(J) J ← J ν = ν0 + B’J(J +1) – BJ(J + 1) = ν0 + (B’ – B)J(J + 1)
P(J) J ˗ 1 ← J ν = ν0 + B’(J + 1)(J +2) – BJ(J + 1) = ν0 – 2B’J + (B’ – B)J(J + 1)
1
2 t
Simulated spectra
Tr, Tk, B, μ, C, β, Γ CHCH+DIBs
Reservation λ6613
Sarre et al. 1995, MNRAS 277, L41
Kerr et al. 1996, MNRAS 283, L105
Other possible mechanisms
Linear molecules B’ – B μ
General moleculesA’ – A, B’ – B, C’ – C μa, μb, μc
Special group of molecules: Non-linear ← linearCH2 (B3Σu
- - X3B1), HCO (A2Π – XA’) and NO2 (E2Σu+ - X2A1)
100 %
Vibrational excitation?
I am scared
Short column length L ≤ 1000 AU
High radiative temperature Tr ~ 80 K