Analysis of Anomalous DIBs in the Spectrum of Herschel 36

1. Analysis of Anomalous DIBs in the Spectrum of Herschel 36 arXiv:1304.2842 Takeshi Oka, Daniel E. Welty, Sean Johnson, Donald G. York, Julie Dahlstrom, and Lew Hobbs Department of Astronomy andAstrophysics, University of Chicago May 20, 2013, IAU 297 The Diffuse Interstellar Band, Noordwijkerhout

2. Spectra toward two Stars: d ~ 1.5 kpc Tr ~ 2.7 K Tr >> 2.7 K 9 SgrHerschel 36 > 200 Ordinary Extraordinary E(B – V) = 0.33 0.87

3. High radiative Temperature, Tr=14.6 K CH+ Direct Evidence Tr=14.6 K, CH+ 9 Sgr Her 36 CH+ CH Tex = 2.3 K A. McKellar, PASP, 53, 233 (1941) Tex = 14.6 K = Tr Tex = Tr = 3.22 K Field & Hitchcock, PRL (1966) Tex = Tr = 3.75 K Thaddeus & Clauser, PRL (1966) Tex = Tr = 2.73 K Meyer & Jura, ApJ (1984) 2 120.3 K μ = 1.7 Debye A = 0.0070 s-1 τ = 140 s ncrit ~ 3× 106 cm-3 40.1 K μ = 1.48 Debye A = 1.24 × 10-5s-1 τ = 0.93 days ncrit ~ 104 cm-3 1 CN 0

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

5. Spectacular Effect of high Tr on DIBs 30 2 20 1 Huge difference 10 Huge Effect Many J levels are radiatively pumped 0 High contrast Polar non-polar CH+ B = 417.7 GHz μ = 1.7 D HCCCCCN B = 1.3 GHz μ = 4.33 D Spectroscopically makes sense!

6. Spectroscopically makes sense Extended Tail toward Red (ETR) East Turkestan Republics R(J) J + 1 ← J ν= ν0+ 2B’(J + 1) +(B’ – B)J(J + 1) Q(J) J ← J ν= ν0+ (B’ – B)J(J + 1) P(J) J ˗ 1 ← J ν= ν0– 2B’J+ (B’ – B)J(J + 1) B’ < B HCCCCCN HCCCCCN

7. The Crucial Parameter β = (B’ – B)/B HC3N μ = 3.6 Debye HC5N μ = 4.3 Debye HC9N μ = 5.6 Debye C8H-μ = 11.9 Debye

8. Rotational Distribution at high Tr Collision dominated Radiation and collision , Einstein 1916 Goldreich & Kwan 1974 Principle of Detailed Balancing Boltzmann, 1872 H-theorem Wiener Berichte 66, 275

9. Calculated Rotational Distribution n(J)

10. Spectral Simulation Radiation dominated T = 2.73 K T = 80 K T = 2.73 K T = 80 K Collision dominated

11. Comparison of Simulated ETR with Observed Tr, Tk, B, μ, C, β, Γ CH+ CH DIBs Her 36 Her 36 SE

12. Other possible mechanisms Linear molecules J B’ – B μ General molecules J, Ka, Kc 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) A’ – A = A’ 100 % Vibrational excitation?

13. 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 (Cn) or symmetric hydrocarbon chains (HCnH, H2CnH2, NCnN, etc.), symmetric PAHs (benzene, pyrene, coronene, ovalene etc.), or C60, C70 etc. and their cations and anions cannot be the carriers of those DIBs. Likely conclusions λ5849.8, λ 6196.0, and λ6379.3 which do not show strong ETR are Most likely due to non-polar molecules. Carriers of λ5780.5, λ5797.1, and λ6613.6, which show strong ETR are probably not very large, otherwise βis too small.

14. I am scared Short column length L ≤ 1000 AU High radiative temperature Tr ~ 80 K High column density required > 1014 cm-2 Professor John Maier Professor Peter Sarre Sarre et al. 1995, MNRAS 277, L41 Kerr et al. 1996, MNRAS 283, L105 P. Thaddeus, M. C. McCarthy, Spectrochimica Acta A, 57, 757 (2001)

15. Herschel 36 Trad >> 2.73 K 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 Tex Observed Boltzmann 1871 Wiener Berichte 63, 712 If Tk = Tr, thermal, Boltzmann Tex = Tk = Tr Tk > Tr, collision dominated thermal Tex = Tk radiation dominated thermal Tex = Tr intermediatenon-thermal −∞ < Tex < ∞ CH+, CH, CN DIBs

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

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

18. I am scared Short column length L ≤ 3000 AU High radiative temperature Tr ~ 80 K 1 in 200

19. HD 29647 E(B-V) = 1.00 W(5780) = 70 ± 7

20. 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 (1949) W.S. Adams, ApJ, 93, 11 (1941)