The anomalous DIBs in the spectrum of Herschel 36 II. Analysis of radiatively excited CH +, CH, and diffuse interstellar bands Takeshi Oka, Daniel E. Welty, Sean Johnson, Donald G. York, Julie Dahlstrom, and Lew Hobbs Department of Astronomy and Astrophysics, University of Chicago August 13, 2012, DIBs Meeting, O’Hare Hilton

1937 Birth of Molecular Astrophysics Theodore Dunham, Jr Walter Sydney Adams, 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) T r = 2.3 K A. E. Douglas and G. Herzberg, ApJ 94, 381 (1941) CH +

Andrew McKellar 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) T e = 2.3 K (= T r ) CN

Goto, Stecklum, Linz, Feldt, Henning, Pascucci, Usuda, 2006, ApJ, 649, 299 A V ~ 4 A V ~ 6

The three temperatures Kinetic temperature T k Collision Maxwell 1860 Phil. Mag. 4, 19 Excitation temperature T e Observed Boltzmann 1871 Wiener Berichte 63, 712 Radiative temperature T r Radiation Planck 1901 Ann. d. Physik 4, 564 If T k = T r, thermal, Boltzmann T e = T k = T r If T k > T r, collision dominated thermal T e = T k radiation dominated thermal T e = T r intermediate non-thermal −∞ < T e < ∞ α 2 = 2kT k /m θ = T r CH +, CH, CN DIBs

CH + in the J = 1 excited rotational level and radiative temperature of dust emission CH K μ = 1.7 Debye A = s -1 τ = 140 s n crit = 3 × 10 6 cm -3 T e = T r = 14.6 K R(0) R(1) Q(1) CN 4.9 K HD Bakker et at. A&A, 323, 469 (1997)

CH in the J = 3/2 excited fine structure level T e = T r = 6.7 K < 14.6 K ~ 25.6 K CHCH +

Effect of radiation on DIBs toward Her 36 Extended Tail toward Red ETR East Turkestan Republic (B’−B)J(J +1)

P. Thaddeus, M. C. McCarthy, Spectrochimica Acta A, 57, 757 (2001)

Collision dominated Radiation dominated A ~ ν 3

Simulation of DIB velocity profiles with high T r and the 2.7 K cosmic background radiation Collision only Radiation and collision Einstein 1916, Goldreich & Kwan 1974 Principle of Detailed Balancing Boltzmann, 1872 H-theorem Wiener Berichte 66, 275

Rotational distribution n(J)

Spectrum Rotation of linear molecules Rotational constant Moment of inertia CH + 417,568 MHz K HC 5 N 1,331 MHz K R(J) J + 1 ← J ν = ν 0 + B’(J + 1)(J +2) – BJ(J + 1) = ν 0 + 2B’(J + 1) + (B’ – B)J(J + 1) Q(J) J ← J ν = ν 0 + B’J(J +1) – BJ(J + 1) = ν 0 + (B’ – B)J(J + 1) P(J) J ˗ 1 ← J ν = ν 0 + B’(J + 1)(J +2) – BJ(J + 1) = ν 0 – 2B’J + (B’ – B)J(J + 1)

Simulated spectra T r, T k, 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 molecules A’ – A, B’ – B, C’ – C μ a, μ b, μ c Special group of molecules: Non-linear ← linear CH 2 (B 3 Σ u - - X 3 B 1 ), HCO (A 2 Π – XA’) and NO 2 (E 2 Σ u + - X 2 A 1 ) 100 % Vibrational excitation?

Conclusions Firm conclusions λ5780.5, λ5797.1, and λ6613.6, which show strong ETR are due to polar molecules. Non-polar molecules such as carbon chains (C n ) or symmetric hydrocarbon chains (HC n H, H 2 C n H 2, NC n N, etc.), symmetric PAHs (benzene, pyrene, coronene, ovalene etc.), or C60, C70 etc. and their cations and anions cannot be the carriers of those DIBs. λ5780.5, λ5797.1, and λ which show strong ETR and λ5849.8, λ , and λ which don’t, cannot be due to same molecules Likely conclusions λ5849.8, λ , and λ which do not show strong ETR are Most likely due to non-polar molecules although very large polar molecules with small β And many more

I am scared Short column length L ≤ 1000 AU High radiative temperature T r ~ 80 K

I am scared Short column length L ≤ 3000 AU High radiative temperature T r ~ 80 K 1 in 200

Something must be wrong about the subtraction

HD E(B-V) = 1.00 W(5780) = 70 ± 7