Irradiated Dense Molecular Gas from YSOs to AGN

Photon- and X-ray Dominated Regions where photons dominate thermal and chemical balance of gas

References Tielens & Hollenbach 1985 n Maloney et al. 1996 n Kaufman et al.

Orion Bar Generic high mass star-forming region n Template for starburst galaxies n Illuminated

PDRs: 6 < E < 13. 6 e. V Heating: Photo-electric emission from grains

XDRs: E > 1 ke. V n Heating: X-ray photo-ionization --> fast electrons; H

PDRs XDRs n Energetics: G 0 = 1. 6 x 10^-3 erg cm^-2 s^-1

Diagnostics n Statistical equilibrium 2 level system: nln. HClu + nl. Blu. Jul =

Diagnostics n. CR ~ Σl<u Aul / Σl#u Cul n Clu = (gu/gl) Cul

Diagnostics n Line ratios of: Isotopes; 12 CO/13 CO same for HCN, HCO+ Rotational

Diagnostics n rotational H 2 <--> temperature n [CII], [CI] n HCO+, H 2

Diagnostics n n H 2 2 -1 S(1)/1 -0 S(1) <--> PDRs, XDRs, 0.

Masers Excitation: collisional, radiative or chemical pump n Molecules: e. g. , H 2

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

Photon- and X-ray Dominated Regions where photons dominate thermal and chemical balance of gas n 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 n Zwolle 2004

References Tielens & Hollenbach 1985 n Maloney et al. 1996 n 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 n Zwolle 2004

Orion Bar Generic high mass star-forming region n Template for starburst galaxies n Illuminated by Trapezium stars (θ¹ Ori) G, IUV, Χ~ 10^5 n Dense: n. H ~ 3 x 10^4 - 6 x 10^6 cm-³ n Interface between HII region and OMC 1 n 6 cm --> PAHs --> H 2* / C+ --> CO n Zwolle 2004

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PDRs: 6 < E < 13. 6 e. V Heating: Photo-electric emission from grains and cosmic rays n Cooling: Fine-structure lines like [OI] 63, 145; [CII] 158 μm and emission by H 2, CO, H 2 O n Chemical Transitions: H -> H 2 C+ -> CO n Zwolle 2004

XDRs: E > 1 ke. V n Heating: X-ray photo-ionization --> fast electrons; H and H 2 vib excitation; UV emission (Ly α, Lyman-Werner) n Cooling: [Fe. II] 1. 26, 1. 64; [OI] 63; [CII] 158; [Si. II] 35 μm; thermal H 2 v=1 -0 S(1) Zwolle 2004

PDRs XDRs n Energetics: G 0 = 1. 6 x 10^-3 erg cm^-2 s^-1 Galactic Habing flux FX = 84 L 44 r 2^-2 erg cm^-2 s^-1 Seyfert nucleus at 100 pc or TTauri star with 10^32 erg/s at 20 AU n G/n. H XDR ~ 5 x 10^-5 f. UV FX N 22^-1 n 5^-1 ; G/n. H PDR ~ 1 >> G/n. H XDR Zwolle 2004

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Diagnostics n Statistical equilibrium 2 level system: nln. HClu + nl. Blu. Jul = nun. HCul + nu. Bul. Jul + nu. Aul global non-linear problem because Jul = 1/4π ƒ Iul[τul; Ω] dΩ Zwolle 2004

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

Diagnostics n Line ratios of: Isotopes; 12 CO/13 CO same for HCN, HCO+ Rotational transitions; CO, CS, HCN, HCO+, SO, CO+ H 2 CO, H 2 CS, CH 3 CN, NH 3 linear -> n. H ; symmetric rotors -> T Ro-Vibrational; H 2 Information upto τ~1 Zwolle 2004

Diagnostics n rotational H 2 <--> temperature n [CII], [CI] n HCO+, H 2 O <--> kinematics n [OI] 6300 Å <--> 10^4 K gas [OIII], [NII] <--> clumpiness Zwolle 2004

Diagnostics n n H 2 2 -1 S(1)/1 -0 S(1) <--> PDRs, XDRs, 0. 1 -0. 5 shocks [OI]/[CII] <--> n. H, T (Tex, ncr) [OI]+[CII] ————— <--> heating efficiency FIR 10^-3 -10^-2 — 0. 1 -1. 0 [Fe. II] 1. 26; 1. 64 ; He. H+ 149 <--> XDR Zwolle 2004

Masers Excitation: collisional, radiative or chemical pump n Molecules: e. g. , H 2 O, OH, H 2 CO, CH 3 OH n Amplification: τ=αL < 0, I~e^τ, ΔΩ small n Coherence: ΔV < Vturb, th ; geometry n Saturation: I~τ; maser limited by pump n Examples: NGC 4258, SF regions n Zwolle 2004