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The anomalous DIBs in the spectrum of Herschel 36 II. Analysis of radiatively excited CH + , CH,

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.

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The anomalous DIBs in the spectrum of Herschel 36 II. Analysis of radiatively excited CH + , CH,

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  1. 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 andAstrophysics, University of Chicago August 13, 2012, DIBs Meeting, O’Hare Hilton

  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 < ∞ CH+, CH, CN DIBs

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

  10. A ~ ν3 Radiation dominated Collision dominated

  11. 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 Principle of Detailed Balancing Boltzmann, 1872 H-theorem Wiener Berichte 66, 275

  12. Rotational distribution n(J)

  13. 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) 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)

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

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

  16. 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?

  17. 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. λ5780.5, λ5797.1, and λ6613.6which show strong ETR and λ5849.8, λ 6196.0, and λ6379.3 which don’t, cannot be due to same molecules Likely conclusions λ5849.8, λ 6196.0, and λ6379.3 which do not show strong ETR are Most likely due to non-polar molecules although very large polar molecules with smallβ And many more

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

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

  20. Something must be wrong about the subtraction

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

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