Warm gas in central regions of nearby galaxies. Extended mapping of CO(3-2) emission

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Abstract
We have mapped the CO(3-2) line emission from several nearby galaxies, using the Heinrich-Hertz-Telescope. Our investigation includes twelve galaxies of various types and in different stages of star forming activity. The main results of this CO(3-2) survey are: 1. In none of the observed objects the emission is confined to the nucleus, as claimed in some earlier publications. CO(3-2) emission can be detected for some objects to the same extent as the CO(2-1) and the CO(1-0) lines. 2. The emission is more concentrated to the vicinity of star forming structures than the lower CO transitions. This is shown by decreasing line ratios from the very centres towards larger radii. 3. The CO(3-2) luminosity is stronger in objects that contain a nuclear starburst or morphological peculiarities. 4. The line ratios seem to be independent of Hubble type, color or luminosity. Most galaxies with enhanced central star formation show line ratios of ~1.3 in the very centre and \~1.0 at a radius of about 1kpc. Objects with a ring-like molecular gas distribution or normal galaxies show lower ratios. 5. Starburst galaxies show CO(3-2) emission also in their disks. The line intensities there are higher than that of normal galaxies.

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