1. CH+ and DIBs toward Herschel 36
Takeshi Oka
Department of Astronomy and Astrophysics and Department of Chemistry
The Enrico Fermi Institute, University of Chicago
DIBs group Jamuary 17, 2012

2. Two discoveries HD 204827 Treasure house of C3, C2 C2 DIBs HD 183143
Herschel J = 1 CH+, Radiative pumping
DIBs and dust emission

3. CH+ in the J = 1 excited rotational level
and radiative temperature of dust emission 2 1
R(0)
R(1)
Q(1)
Ted Dunham 1937 2
spontaneous emission J + 1 → J
Te ~ Tr ~ 17.5 K
Einstein’s coefficient
A = s-1
ncrit = 3 × 106 cm-3 1
Dirac 1927
ν = GHz ~ K μ = 1.7 Debye

4. AV ~ 60
AV ~ 40
Goto, Stecklum, Linz, Feldt, Henning, Pascucci, Usuda, 2006, ApJ, 649, 299

5. Two preliminaries Rotation of linear molecules Three temperatures2 1
Rotational constant
CH ,137 MHz cm K
HC5N 1,331 MHz cm K
Moment of inertia
HC11N MHz cm 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)
R(1)
R(0)
Q(J) J ← J ν = ν0 + B’J(J +1) – BJ(J + 1) = ν (B’ – B)J(J + 1)
Q(1)
P(J) J ˗ 1 ← J ν = ν0 + B’(J + 1)(J +2) – BJ(J + 1) = ν0 – 2B’J (B’ – B)J(J + 1)
Three temperatures
Kinetic temperature Tk Collision
Maxwell 1857
n(v) ~ v2exp(-mv2/kTk) 2
Excitation temperature Te Observed
Boltzmann 1860
n(J) ~ gJexp(-EJ/kTe) 1
Radiative temperature Tr Radiation
Planck 1900

6. Effect of dust emission on DIBs toward Her 36λ λ λ λ

7. Simulation of DIB velocity profiles
with 17.5 K dust emissiom and the 2.7 K background radiation
Collision only
Radiation and collision ,
Einstein 1916
Goldreich and Kwan 1974

8. Rotational distribution n(J)
B = K
μ = 5 Debye
C = 3 × s-1
B = 0.07 K
μ = 4 Debye
C = 10-7 s-1

9. Calculated spectra C12

10. Calculated spectra C6
B’ – B = 0.04B Δν