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Excitation Mechanisms: The Irradiated and Stirred ISM

Excitation Mechanisms: The Irradiated and Stirred ISM. Marco Spaans (Groningen)

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Excitation Mechanisms: The Irradiated and Stirred ISM

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  1. Excitation Mechanisms:The Irradiated and Stirred ISM Marco Spaans (Groningen) Rowin Meijerink (Leiden), Frank Israel (Leiden), Edo Loenen (Leiden), Willem Baan (ASTRON), Juan-Pablo Perez-Beaupuits (Groningen) Dominik Schleicher (Leiden/ESO), Ralf Klessen (Heidelberg), Padelis Papadopoulos (Bonn), Paul van der Werf (Leiden)

  2. Concentrate on irradiated turbulent gas in star-forming regions and close to AGN • PDRs (UV/SB) • XDRs (X-ray/AGN) • MDRs (turbulence/flows) • CRDRs (CRs/SNe) • Photon excitation (pumping/dust)

  3. Energetics G0 =1.6x10-3 erg cm-2 s-1is the Habing flux over 6-13.6 eV Orion Bar has 105 G0 FX= 84 L44 r2-2erg cm-2 s-1 is the X-ray flux over 1-100 keV with a power law E-0.9 Think of Seyfert nucleus at 100 pc or TTauri star with 1032 erg/s at 20 AU

  4. 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 • 10 eV photon penetrates 0.5 mag of dust • Heating efficiency ~ 0.1 – 1.0 %

  5. Orion Bar (van der Werf 1993)

  6. XDRs: E > 1 keV • Heating: X-ray photo-ionization --> fast electrons - Coulomb heating H and H2vibexcitation - UV • Cooling: [FeII] 1.26, 1.64; [OI] 63; [CII] 158; [SiII] 35 μm; thermal H2vib; gas-dust • 1 keV photon penetrates 1022 cm-2 of NH • Heating efficiency ~ 10 – 50 %

  7. 30 Doradus (Brandl et al. 2007)

  8. Maloney et al. (1996)

  9. PDR (left) with n=105 cm-3 and G=103.5 • XDR with n=105 cm-3 and FX = 5.1 erg s-1 cm-3 • Note NH dependence H2, C+, C, CO, OH, H2O: FIR lines of species trace different regions

  10. Fine-structure lines (Kaufman et al. 1999; Meijerink et al. 2007

  11. J=16-15 at 1841 GHz (0.16 mm) redshifted into ALMA window (Spaans & Meijerink 2008)

  12. Mrk 231 SPIRE (see Loenen presentation; van der Werf et al. 2010)CO SLED has not yet turned down at J=13-12

  13. 107 M๏BH at 3% Eddington for G0=100 and 1-100 keV powerlaw of slope -1 (with 10% Lbol; Schleicher et al. 2010) Check out poster Pérez-Beaupuits! A comment on AGN: Relative Size PDR/XDR

  14. Metallicity and Multi-Phase ISM: Lower metallicity yields smaller molecular clouds Atomic cooling dominates by mass X-factor: Mihos et al. (1999) Bolatto et al. (1999), Roellig et al. (2006)

  15. Multi-Phase Medium; atomic vs molecular(Wolfire et al. 2003; Spaans & Norman 1997)

  16. MDRs: how about kinetics? • Mechanically Dominated Regions • Turbulent dissipation heats the gas, which leads to IR emission • UV only heats cloud surface • Cosmic rays also heat deep inside cloud, but strongly affect HCO+ • E.g., at T>100K: HNC + H  HCN + H

  17. Sources of Turbulence • YSOs • SNe • Sloshing motions (accretion) • If 1-10% efficiency through a turbulent cascade -> mechanical heating competes with normal CR heating for SF rates of 10 – 100 Mo/yr

  18. M82, shock tracer SiO 2-1 + 4.8 GHz radio (García-Burillo et al. 2001, IRAM PdB)

  19. g • E.g., P cygni profiles in Arp220: 100 km/s outflow (100 pc scale; Sakamoto et al. 2009)

  20. Mrk 231, SPIRE, outflow in OH upto 103 km/s (Fischer et al. 2010)

  21. Turbulent dissipation causes changes in high density tracers (Loenen et al. 2008) normal mechanical • Temperature increases • E.g., HNC, HCN, HCO+ affected

  22. For some ULIRGs, dense gas tracers that correlate with IR may trace more SN than UV exposure

  23. How about CRs? • PDR model with CR rate = 5x10-15 s-1; so SN rate for ~100 M0/yr • Note small changes in C, OH and H2O

  24. CRs can dominate gas heating for SFR > 100 Mo/yr; think of Arp220 and IMF through MJeans(Papadopoulos 2010)

  25. CRs ≠ X-rays; only very high CR rates boost OH+ and H2O+ (fine-structure lines little affected by CRs)

  26. Pumping of high density tracers • HNC (HCN) rotational lines pumped by mid-IR photons at 21.5 (14) μm that are absorbed by the degenerate bending mode (1st vibrational level) and decay via the P branch (Aalto et al. 2007). • A=5.2 (1.7) s-1 for HNC (HCN); requires TIR~50 K (τ>1) and n<ncr • Appears relevant for Arp 220, Mrk 231, NGC 4418, where HNC outshines HCN, and can dominate upto 106 (103) cm-3 for TIR=85 (55) K

  27. Mrk 231; SPIRE, IR pumping of water lines by dust emission(Gonzalez-Alfonso 2010)

  28. Summary • PDRs, XDRs, MDRs and CRDRs are likely to be present simultaneously, but are also distinguishable • For the future, ALMA will be crucial to provide spatial information to separate the XDR and thus constrain properties of accreting supermassive black holes and feedback effects

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