DUST AND MOLECULES IN SPIRAL GALAXIES as seen

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

ATOMS and MOLECULES. . .

. . . AND DUST SCUBA 850 mu

M 51 Line and Continuum

M 51 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?

12 CO degeneracy resolved by 13 co

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 gas >50% of mass

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

The AGN in CENA

M 83

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 Mdust / Mgas + cst Issa et al. 1990 α = 0. 85 Schmidt & Boller 1993 α = 0. 63 Lisenfeld & Ferrara 1998 α = 0. 52 Dwek 1998 α = 0. 77 (model)

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

NGC 1569: ISO & SCUBA

Cold dust? Lisenfeld et al. 2002, 2005

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

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 Melisse & Israel 1994 a, b ANS-UV: behaviour 2175 A bumps 1. 8

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 SCUBA 2 (20072009) 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