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

Two discoveries HD 204827 Treasure house of C3, C2 C2 DIBs HD 183143 Herschel 36 J = 1 CH+, Radiative pumping DIBs and dust emission

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 = 0.0070 s-1 ncrit = 3 × 106 cm-3 1 Dirac 1927 ν = 835.137 GHz ~ 40.08 K μ = 1.7 Debye

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

Two preliminaries Rotation of linear molecules Three temperatures 2 1 Rotational constant CH+ 835,137 MHz 27.86 cm-1 40.08 K HC5N 1,331 MHz 0.04441 cm-1 0.06390 K Moment of inertia HC11N 169 MHz 0.005639 cm-1 0.008117 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) = ν0 + (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

Effect of dust emission on DIBs toward Her 36 λ 5780.5 λ 5797.1 λ 6196.0 λ 6613.6

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

Rotational distribution n(J) B = 0.008 K μ = 5 Debye C = 3 × 10-8 s-1 B = 0.07 K μ = 4 Debye C = 10-7 s-1

Calculated spectra C12

Calculated spectra C6 B’ – B = 0.04B Δν