SIMBAD references

We present sensitive submillimeter imaging of the Seyfert 1 galaxy NGC 7469 at 850 and 450 µm with the Submillimeter Common User Bolometer Array on the James Clerk Maxwell Telescope and ¹²CO J=3-2 line observations of 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 and 60 µm data, reveals a dominant warm dust component with a temperature of T_d∼35 K and a global molecular gas-to-dust ratio M(H₂)/M_d∼600. Including the atomic gas component yields a total gas-to-dust ratio of ∼830. Such high values are typical for IR-bright spiral galaxies, and in order to reconcile them with the significantly lower ratio of ∼100 obtained for the Milky Way, a cold dust reservoir, inconspicuous at far-infrared wavelengths, is usually postulated. However, while there is good evidence for the presence of cold gas/dust in NGC 7469 beyond its central region, our 450 µm map and available interferometric ¹²CO J=1-0 maps show the bright submillimeter/CO emission confined in the inner ∼2.5 kpc, where a high ¹²CO (J=3-2)/(J=1-0) ratio (∼0.85-1.0) is measured. This is consistent with molecular gas at T_kin≳30 K, suggesting that the bulk of the interstellar medium in the starburst center of NGC 7469 is warm. Nevertheless, the corresponding total gas-to-dust ratio there remains high, of the order of ∼500. We argue that, rather than unaccounted cold dust mass, this high ratio suggests an overestimate of M(H₂) from its associated ¹²CO J=1-0 line luminosity by a factor of ∼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 µm and ¹²CO J=1-0 emission has an estimated total gas-to-dust ratio of ∼50-160, closer to the Galactic value.