Gas and dust in NGC 7469: Submillimeter imaging and CO J=3-2

We present sensitive submillimeter imaging of the Seyfert 1 galaxy NGC 7469 at 850 and 450 mu m with the Submillimeter Common User Bolometer Array on the James Clerk Maxwell Telescope and (CO)-C-12 J = 3-2 line observations o f its central starbursting region. The global dust spectrum, as constrained by the new set of submillimeter data and available 1.30 mm and IRAS 100 an d 60 mu m data, reveals a dominant warm dust component with a temperature o f T-d similar to 35 K and a global molecular gas-to-dust ratio M(H-2)/M-d s imilar to 600. Including the atomic gas component yields a total gas-to-dus t ratio of similar to 830. Such high values are typical for IR-bright spira l galaxies, and in order to reconcile them with the significantly lower rat io of similar to 100 obtained for the Milky Way, a cold dust reservoir, inc onspicuous at far-infrared wavelengths, is usually postulated However, whil e there is good evidence for the presence of cold gas/dust in NGC 7469 beyo nd its central region, our 450 mu m map and available interferometric (CO)- C-12 J = 1-0 maps show the bright submillimeter/CO emission confined in the inner similar to 2.5 kpc, where a high (CO)-C-12 (J = 3-2)/(J = 1-0) ratio (similar to 0.85-1.0) is measured. This is consistent with molecular gas a t T-kin greater than or similar to 30 K, suggesting that the bulk of the in terstellar medium in the starburst center of NGC 7469 is warm. Nevertheless , the corresponding total gas-to-dust ratio there remains high, of the orde r of similar to 500. We argue that, rather than unaccounted cold dust mass, this high ratio suggests an overestimate of M(H-2) from its associated (CO )-C-12 J = 1-0 line luminosity by a factor of similar to 5 when a Milky Way value for this conversion is used. Finally, the diffuse cold gas and dust that is the likely source of the observed faint extended 450 mu m and (CO)- C-12 J = 1-0 emission has an estimated total gas-to-dust ratio of similar t o 50-160, closer to the Galactic value.