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The Irradiated and Stirred ISM of Active Galaxies

The Irradiated and Stirred ISM of Active Galaxies. Marco Spaans, Rowin Meijerink (Leiden), Frank Israel (Leiden), Edo Loenen (Leiden), Willem Baan (ASTRON), Dominik Schleicher (Leiden/ESO), Ralf Klessen (Heidelberg) Juan Pablo Perez Beaupuits (Groningen).

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The Irradiated and Stirred ISM of Active Galaxies

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  1. The Irradiated and Stirred ISM of Active Galaxies Marco Spaans, Rowin Meijerink (Leiden), Frank Israel (Leiden), Edo Loenen (Leiden), Willem Baan (ASTRON), Dominik Schleicher (Leiden/ESO), Ralf Klessen (Heidelberg) Juan Pablo Perez Beaupuits (Groningen)

  2. 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

  3. XDRs: E > 1 keV • Heating: X-ray photo-ionization --> fast electrons; H and H2vibexcitation; UV emission (Ly α, Lyman-Werner) • 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

  4. 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

  5. 107 M๏BH at 3% Eddington forh G0=10 and 1-100 keV powerlaw of slope -1 (with 10% L) A comment on AGN: Relative Size PDR/XDR

  6. 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

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

  8. g • E.g., P cygni profiles in Arp220: 100 km/s outflow (100 pc scale)

  9. changes in high density tracers normal mechanical • temperature increases • E.g., HNC, HCN, HCO+ affected

  10. Sample of ULIRGs • combined PV, SEST and literature • low density gas: CO(1-0) & CO(2-1) • high density gas: HCN(1-0), HNC(1-0), HCO+(1-0), CN(1-0), CN(2-1), CS(3-2) • total of 117 sources, but incomplete: • 110 CO(1-0), but 32 CO(2-1) • 84 HCN • only 33 have HCN, HNC and HCO+ • Note: single dish, so integrated properties

  11. Relation with LFIR • relation LFIR – Lmolecule reflects Kennicutt-Schmidt laws: ΣSFR~ Σgasα , α=1.4 • Krumholz & Thompson (2007): • if ncrit < nave: α ≈ 1.5 (KS law) • if ncrit > nave: α ≤ 1 • Note: slope in fits = 1/α

  12. A few fits 2e3 3e6 4e5 1e4 3e6 2e7 CO(1-0) α~ 1.4 CO(2-1) closer to 1 Others α≤ 1; black squares OH-MM 2e5 1e6

  13. Relation with LFIR • Kennicutt-Schmidt laws: ΣSFR~ Σgasα , α=1.4 • Krumholtz & Thompson (2007): • if ncrit < nave: α ≈ 1.5 (K-S law) • if ncrit > nave: α ≤ 1 • Note: slope in fits = 1/α • Our data follow the K&T predictions, but can we learn more?

  14. Toy model: starburst that decays; deplete dense gas and go from SF -> SNe

  15. For some ULIRGs, dense gas tracers that correlate with IR may trace more SN than UV exposure, see Loenen et al. (2008)

  16. Lowering the metallicity to 1% Zo: CO no longer dominant molecular gas coolant

  17. Summary • In addition to fine structure lines, CO, HCN, HNC, HCO+ lines are good diagnostics to get to SF properties • Turbulence (and cosmic rays) matter!

  18. so IR response of the ISM may not be tracing star formation directly; [CII] en [CI] lines probe this directly

  19. 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

  20. In fact, CRs can dominate the thermodynamics of molecular gas for star formation rates > 100 Mo/yr; think of Arp220

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