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Marco Spaans (Kapteyn) Rowin Meijerink (Leiden Obs)

Irradiated Dense Molecular Gas: from YSOs to AGN . Marco Spaans (Kapteyn) Rowin Meijerink (Leiden Obs). Photon- and X-ray Dominated Regions. Regions where photons dominate the thermal and chemical balance of gas

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Marco Spaans (Kapteyn) Rowin Meijerink (Leiden Obs)

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  1. Irradiated Dense Molecular Gas: from YSOs to AGN Marco Spaans (Kapteyn) Rowin Meijerink (Leiden Obs) Zwolle 2004

  2. Photon- and X-ray Dominated Regions • Regions where photons dominate the thermal and chemical balance of gas • Examples: - O & B stars (UC HII regions) and A & F stars - PNe and red giant outflows (AGB stars) - AGN, T Tauri stars and photo-evaporating PP disks Zwolle 2004

  3. References • Tielens & Hollenbach 1985 • Maloney et al. 1996 • Kaufman et al. 1999; Spaans 1996; Sternberg & Dalgarno 1995; Stőrzer et al. 1995; Spaans et al. 1994; Wolfire et al. 1993; le Bourlot et al. 1993; Tielens et al. 1993; van Dishoeck & Black 1988 Zwolle 2004

  4. Orion Bar • Generic high mass star-forming region • Template for starburst galaxies • Illuminated by Trapezium stars (θ¹ Ori) G, IUV, Χ~ 10^5 • Dense: nH ~ 3x10^4 - 6x10^6 cm-³ • Interface between HII region and OMC1 • 6cm --> PAHs --> H2* / C+ --> CO Zwolle 2004

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  6. PDRs: 6 < E < 13.6 eV • Heating: Photo-electric emission from grains and cosmic rays • Cooling: Fine-structure lines like [OI] 63, 145; [CII] 158 μm and emission by H2, CO, H2O • Chemical Transitions: H -> H2 C+ -> C -> CO Zwolle 2004

  7. XDRs: E > 1 keV • Heating: X-ray photo-ionization --> fast electrons; H and H2 vib excitation; UV emission (Ly α, Lyman-Werner) • Cooling: [FeII] 1.26, 1.64; [OI] 63; [CII] 158; [SiII] 35 μm; thermal H2 v=1-0 S(1) Zwolle 2004

  8. PDRsXDRs • Energetics: G0 =1.6x10^-3 erg cm^-2 s^-1 Galactic Habing flux FX = 84 L44 r2^-2 erg cm^-2 s^-1 Seyfert nucleus at 100 pc orTTauri star with 10^32 erg/s at 20AU • G/nH XDR ~ 5x10^-5 fUV FX N22^-1 n5^-1 ; G/nH PDR ~ 1 >> G/nH XDR Zwolle 2004

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  15. Diagnostics • Statistical equilibrium 2 level system: nlnHClu + nlBluJul = nunHCul + nuBulJul + nuAul global non-linear problem because Jul = 1/4π ƒ Iul[τul;Ω] dΩ Zwolle 2004

  16. Diagnostics • nCR ~ Σl<u Aul / Σl#u Cul • Clu = (gu/gl) Cul e^[-Eul/kT] • optically thin, two-level system: nu/nl=(gu/gl)e^[-Eul/kT] ———————— 1+nCR/n • Cul~T^½ (n-n), T^0 (e-n), T^-½ (e-i) • β=<e^-τ>Ω|τ ~ G (1-e^[-aτ] / τ) ; v dependent Zwolle 2004

  17. Diagnostics • Line ratios of: Isotopes; 12CO/13CO same for HCN, HCO+ Rotational transitions; CO, CS, HCN, HCO+, SO, CO+ H2CO, H2CS, CH3CN, NH3linear -> nH ; symmetric rotors ->T Ro-Vibrational; H2Information upto τ~1 Zwolle 2004

  18. Diagnostics • rotational H2 <--> temperature • [CII], [CI] <--> clumpiness • HCO+, H2O <--> kinematics • [OI] 6300 Å <--> 10^4 K gas [OIII], [NII] Zwolle 2004

  19. Diagnostics • H22-1 S(1)/1-0 S(1) <--> PDRs, XDRs, 0.1-0.5 shocks • [OI]/[CII] <--> nH, T (Tex, ncr) • [OI]+[CII] ————— <--> heating efficiency FIR 10^-3 -10^-2 — 0.1-1.0 • [FeII] 1.26; 1.64 ; HeH+ 149 <--> XDR Zwolle 2004

  20. Masers • Excitation: collisional, radiative or chemical pump • Molecules: e.g., H2O, OH, H2CO, CH3OH • Amplification: τ=αL < 0, I~e^τ, ΔΩsmall • Coherence: ΔV < Vturb, th ; geometry • Saturation: I~τ; maser limited by pump • Examples: NGC 4258, SF regions Zwolle 2004

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