Astronomy and Astrophysics – Astronomy
Scientific paper
Mar 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995a%26a...295..317c&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 295, no. 2, p. 317-329
Astronomy and Astrophysics
Astronomy
50
Cosmic Dust, Emission Spectra, Far Infrared Radiation, Infrared Astronomy, Infrared Spectra, Interstellar Matter, Spiral Galaxies, Luminosity, Markarian Galaxies, Mass Distribution, Star Formation, Temperature Distribution
Scientific paper
We have mapped 32 non-active spirals at 1300 micrometers and measured 7 of them at 450 and 800 micrometers. We determine gas masses, dust temperatures and IR luminosities. From a detailed analysis we find: (1) The spatial extent of the cold dust is comparable to the optical size of the galaxies. About 70% of the mass is contained within half the optical radius; there the gas surface density decreases inversely proportional to the galactocentric radius. (2) The new submm data set limits on the decomposition of the FIR spectra into dust components of different temperatures. The flux ratios of 450 to 1300 micrometers suggest two kinds of nonactive spirals: those with S450 micrometers/S1300 micrometers approximately equal to 40, like the Milky Way, where the coldest dust is approximately 20K and accounts for most of the emission between 100 and 1300 micrometers; on the other hand, there are galaxies with S450 micrometers/S1300 micrometers approximately 20 which implies that most of the interstellar dust is extremely cold (approximately 10 K). (3) The ratio of infrared luminosity to gas mass, LIR/Mgas, equals 5 +/- 2 in solar units. For active galaxies from the Markarian catalog this ratio is 20 times larger. Therefore LIR/Mgas gives a clear signature for the activity stage.
Chini Rolf
Kruegel Endrick
Lemke Roland
Ward-Thompson Derek
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