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Dust and Molecules in Spiral Galaxies: Insights from JCMT

Explore dust, molecules, and gas distribution in spiral galaxies using JCMT data. Discover metallicity gradients, nuclear gas concentrations, and more. Learn about physical processes impacting circumnuclear environments.

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Dust and Molecules in Spiral Galaxies: Insights from JCMT

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  1. F.P. Israel, Sterrewacht Leiden DUSTAND MOLECULES IN SPIRAL GALAXIESas seen with the JCMT

  2. ATOMS and MOLECULES ...

  3. ... AND DUST • SCUBA 850 mu

  4. M51 Line and Continuum

  5. M51 J=3-2 COdepleted in center, enhanced in arms

  6. ISMinSpiralGalaxies • 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

  7. Nuclear CO concentrationsdisk, torus or spiral?

  8. 12CO degeneracyresolved by 13co

  9. 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

  10. Dust in galaxy centers Size distribution and other properties affected radiatively and dynamically active circumnuclear environment heating/cooling depends on: • dust grain composition • dust grain size (distribution) • Radiation, shocks, turbulence

  11. The AGN in CENA

  12. M83

  13. NGC 6946, NGC 891 1

  14. IRAS 60 microns I OriginofSubm/FIRemission: NGC6822 Israel, Bontekoe & Kester, 1996

  15. Dust-to-gasratios Dependent on metallicity, but how ? log [O]/[H] = α logMdust / Mgas+ 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

  16. 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 sizedistributions

  17. NGC 1569: ISO & SCUBA

  18. Colddust? Lisenfeld et al. 2002, 2005

  19. Lisenfeld et al. 2002/2005 dust warm 35 K processed dust VSG enhanced 7-12 times gas/dust ratio 1500-2900 Sameobservations, differentviews Galliano et al. 2003 dust cold 5-7 K most dust in small clumps gas/dust ratio 320-680 (740-1600)

  20. Evidence for dust processing Spitzer: PAHsdepletedinBCDGs • 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 f25 / f12: Im 4.5 Sm 2.9 Sc 1.8 Melisse & Israel 1994a, b ANS-UV: behaviour 2175A bumps

  21. H2 from FIR or submmindependent 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 (!)

  22. 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

  23. Moleculargasingalaxy centers • (Much) less H2 than expected from CO strength • Yet molecular gas is >90% of the total gas mass • On same curve as metal-poor galaxies?

  24. 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 What next?

  25. 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 JCMT LEGACY SURVEY

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