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Published byKendal Latham Modified over 9 years ago
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DUST AND MOLECULES IN SPIRAL GALAXIES as seen with the JCMT F.P. Israel, Sterrewacht Leiden
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ATOMS and MOLECULES...
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... AND DUST SCUBA 850 mu
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M51 Line and Continuum
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M51 J=3-2 CO depleted in center, enhanced in arms
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ISM in Spiral Galaxies Atomic gas avoids center Molecular gas often concentrated in center Dust emission follows total gas Metallicity & excitation gradients Center: exclusively molecular Inner disk: molecules dominant Outer disk: atoms dominant
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Nuclear CO concentrations disk, torus or spiral?
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12CO degeneracy resolved by 13co
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Molecules in galaxy centers Concentrated within R = 0.5 kpc High contrast with disk CO CO pollutes broadband continuum! Physical parameters only from several line transitions! At least two components: Lukewarm and dense Hot and tenuous Hot and tenuous gas >50% of mass
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Dust in galaxy centers heating/cooling depends on: dust grain composition dust grain size (distribution) Radiation, shocks, turbulence Size distribution and other properties affected radiatively and dynamically active circumnuclear environment
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The AGN in CENA
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M83
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NGC 6946, NGC 891 1
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Origin of Subm/FIR emission: NGC 6822 Israel, Bontekoe & Kester, 1996 IRAS 60 microns I
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Dust-to-gas ratios Dependent on metallicity, but how ? log [O]/[H] = α log M dust / M gas + cst Issa et al. 1990 α = 0.85 Schmidt & Boller 1993 α = 0.63 Lisenfeld & Ferrara 1998 α = 0.52 Dwek 1998 (model) α = 0.77
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Interpretation of SEDs SED reflects: Big Grains 5-250 nm (MRN, thermal) Very Small Grains (nonthermal) Polycyclic Aromatic Hydrocarbons (PAHs) at various temperatures with potentially varying size distributions
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NGC 1569: ISO & SCUBA
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Cold dust? Lisenfeld et al. 2002, 2005
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Same observations, different views Galliano et al. 2003 dust cold 5-7 K most dust in small clumps gas/dust ratio 320-680 (740-1600) Lisenfeld et al. 2002/2005 dust warm 35 K processed dust VSG enhanced 7-12 times gas/dust ratio 1500-2900
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Evidence for dust processing Spitzer: PAHs depleted in BCDGs weak relation radiation field hardness strong relation energy density Wu et al. 2006, Rosenberg et al 2006, Higdon et al 2006 IRAS: PAH depletion sequence f 25 / f 12: Im 4.5 Sm 2.9 Sc 1.8 Melisse & Israel 1994a, b ANS-UV: behaviour 2175A bumps
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H 2 from FIR or submm independent from CO measurements FIR or subm maps tracing dust column densities Flux ratios tracing dust temperatures HI maps tracing atomic gas Assumption dust-to-gas ratio proportional to metallicity (!)
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X-factor as function of metallicity Filled symbols: large beam Open symbols: resolved log X = -α log [O]/[H] + c α = -2.3 (+/-0.3) Israel 1997, 2000
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Molecular gas in galaxy centers (Much) less H 2 than expected from CO strength Yet molecular gas is >90% of the total gas mass On same curve as metal-poor galaxies?
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What next? JCMT Legacy Survey Physical Processes in Galaxies in the Local Universe 299 galaxies randomly selected from an HI-flux- limited sample, plus 32 remaining SINGS galaxies, using HARP-B and SCUBA2 (2007- 2009) Christine Wilson (Canada) Stephen Serjeant (UK) Frank Israel (NL) (coordinators) and many others
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JCMT LEGACY SURVEY Physical properties of dust Molecular gas and gas-to-dust ratios Effects of galaxy morphology Low-metallicity Cluster environment Haloes, superwinds, and AGN Luminosity and dust mass functions of galaxies
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