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Understanding Excitation Mechanisms in Star-Forming Regions and AGN Using ISM

This article discusses irradiated turbulent gas in star-forming regions and close to AGN. It delves into various excitation mechanisms such as PDRs, XDRs, MDRs, CRDRs, and photon excitation, covering topics like heating, cooling, energy fluxes, and specific examples in different galactic environments.

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Understanding Excitation Mechanisms in Star-Forming Regions and AGN Using 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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