1999ApJ...514L..95P -
Astrophys. J., 514, L95-L98 (1999/April-1)
Extended dust emission and atomic hydrogen: a reservoir of diffuse H2 in NGC 1068.
PAPADOPOULOS P.P. and SEAQUIST E.R.
Abstract (from CDS):
We report on sensitive submillimeter imaging observations of the prototype Seyfert 2/starburst galaxy NGC 1068 at 850 and 450 µm using the Submillimeter Common-User Bolometer Array on the James Clerk Maxwell Telescope. We find clear evidence of dust emission associated with the extended H I component that, together with the very faint 12CO J=1-0 emission, gives a gas-to-dust ratio of Mgas/Mdust∼70-150. This contrasts with the larger ratio Mgas/Mdust∼330 that is estimated within a galactocentric radius of r≤1.36 kpc, where the gas is mostly molecular and starburst activity occurs. The large gas-to-dust ratio that is found for the starburst region is attributed to a systematic overestimate of the molecular gas mass in starburst environments when the luminosity of the 12CO J=1-0 line and a standard Galactic conversion factor are used. On the other hand, submillimeter imaging proves to be a more powerful tool than conventional CO imaging for revealing the properties of the diffuse H2 that coexists with H I. This molecular gas phase is characterized by low densities [n(H2)<103 cm–3], very faint emission from subthermally excited CO, and contains more mass than H I, namely, M(H2)/M(H I) ∼ 5.
Abstract Copyright:
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Journal keyword(s):
ISM: Dust, Extinction - Galaxies: Individual: NGC Number: NGC 1068 - ISM: Atoms - ISM: Molecules
Simbad objects:
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