DUST AND MOLECULES IN SPIRAL GALAXIES as seen with the JCMT - F.P. Israel, Sterrewacht Leiden
ATOMS and MOLECULES ...
... AND DUST
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 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
M83
NGC 6946, NGC 891 1
Origin of Subm/FIR emission: NGC 6822 Israel, Bontekoe & Kester, 1996
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 (model) α = 0.77
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 Galliano et al. 2003 dust cold 5-7 K most dust in small clumps gas/dust ratio 320-680 (740-1600)
Evidence for dust processing Spitzer: PAHs depleted in BCDGs 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
H2 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 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 H2 than expected from CO strength Yet molecular gas is >90% of the total gas mass On same curve as metal-poor galaxies?
What next? 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
JCMT LEGACY SURVEY Physical properties of dust Effects of galaxy morphology Low-metallicity Cluster environment Haloes, superwinds, and AGN Luminosity and dust mass functions of galaxies
Dostları ilə paylaş: |