CH + spectrum and diffuse interstellar bands toward Herschel 36 excited by dust emission

1. CH+ spectrum and diffuse interstellar bands toward Herschel 36 excited by dust emission Julie Dahlstrom,Takeshi Oka, Sean Johnson,Daniel E. Welty, Lew Hobbs andDonald G. York Department of Astronomy and Astrophysics, University of Chicago June 20, 2012, Columbus meeting WH07

2. 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) • 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+

3. CN and the cosmic blackbody radiation CN P(1) R(1) R(0) Te = 2.3 K (= Tr) Andrew McKellar 1910 -1960 A. McKellar, PASP, 51, 233 (1940) A. McKellar, PDAO, 7, 251 (1941) W.S. Adams, ApJ, 93, 11 (1941)

4. AV ~ 6 AV ~ 4 Goto, Stecklum, Linz, Feldt, Henning, Pascucci, Usuda, 2006, ApJ, 649, 299

5. The three temperatures Kinetic temperature TkCollision Maxwell 1860 Phil. Mag. 4, 19 α2 = 2kTk/m Radiative temperature TrRadiation Planck 1901 Ann. D. Physik 4, 564 θ = Tr Excitation temperature Te Observed Boltzmann 1871 Wiener Berichte 63, 712 If Tk = Tr, thermal, Boltzmann Te = Tk = Tr If Tk > Tr, collision dominated thermal Te = Tk radiation dominated thermal Te = Tr intermediatenon-thermal −∞ < Te < ∞

6. CH+ in the J = 1 excited rotational level and radiative temperature of dust emission 2 1 0 Te = Tr = 14.6 K R(0) R(1) Q(1) μ = 1.7 Debye A = 0.0070 s-1τ = 140 s ncrit = 3× 106 cm-3 2 1 CN 4.9 K CH+ 40.1 K 0 HD 213985 Bakker et at. A&A, 323, 469 (1997)

7. CH in the J = 3/2 excited fine structure level ~ 25.6 K Te = Tr = 6.7 K < 14.6 K CH+ CH

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

9. Simulation of DIB velocity profiles with high Tr and the 2.7 K cosmic background radiation Collision only Radiation and collision , Einstein 1916 Goldreich Kwan 1974 ΔJ > 1 Principle of Detailed Balancing Boltzmann, 1872 H-theorem Wiener Berichte 66, 275

10. Rotational distribution n(J)

11. Spectrum Rotation of linear molecules Rotational constant CH+ 417,568 MHz 20.04 K Moment of inertia 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) R() 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)

12. Simulated spectra Tr, Tk, B, μ, C, β, Γ CH+ CH DIBs

13. Reservation λ6613 Sarre et al. 1995, MNRAS 277, L41 Kerr et al. 1996, MNRAS 283, L105

14. Other possible mechanisms Linear molecules B’ – B μ General molecules A’ – A, B’ – B, C’ – C μa, μb, μc Special group of molecules: Non-linear ← linear CH2 (B3Σu- - X3B1), HCO (A2Π – XA’) and NO2 (E2Σu+ - X2A1) 100 % Vibrational excitation?

15. I am scared Short column length L ≤ 1000 AU High radiative temperature Tr ~ 80 K