DUST AND MOLECULES IN SPIRAL GALAXIES as seen with the JCMT F.P. Israel, Sterrewacht Leiden

ATOMS and MOLECULES...

... AND DUST SCUBA 850 mu

M51 Line and Continuum

M51 J=3-2 CO depleted in center, enhanced in arms

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

Nuclear CO concentrations disk, torus or spiral?

12CO degeneracy resolved by 13co

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

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

The AGN in CENA

M83

NGC 6946, NGC 891 1

Origin of Subm/FIR emission: NGC 6822 Israel, Bontekoe & Kester, 1996 IRAS 60 microns I

Dust-to-gas ratios Dependent on metallicity, but how ? log [O]/[H] = α log M dust / M gas + cst Issa et al α = 0.85  Schmidt & Boller 1993 α = 0.63 Lisenfeld & Ferrara 1998 α = 0.52  Dwek 1998 (model) α = 0.77 

Interpretation of SEDs SED reflects: Big Grains nm (MRN, thermal) Very Small Grains (nonthermal) Polycyclic Aromatic Hydrocarbons (PAHs) at various temperatures with potentially varying size distributions

NGC 1569: ISO & SCUBA

Cold dust? Lisenfeld et al. 2002, 2005

Same observations, different views Galliano et al dust cold 5-7 K most dust in small clumps gas/dust ratio ( ) Lisenfeld et al. 2002/2005 dust warm 35 K processed dust VSG enhanced 7-12 times gas/dust ratio

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

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 (!)

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

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?

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 ( ) Christine Wilson (Canada) Stephen Serjeant (UK) Frank Israel (NL) (coordinators) and many others

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