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For refcode 1990A&A...236..333H:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1990A&A...236..333H Environmental impact on the nuclear radio activity in spiral galaxies E. Hummel, J. M. van der Hulst, R. C. Kennicutt, and W. C. Keel Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire, SK11 9DL, UK Kapteyn Astronomical Institute, University of Groningen, Postbus 800, NL-9700 AV Groningen, The Netherlands Steward Observatory, University of Arizona, Tucson, AZ 85721, USA Department of Physics and Astronomy, University of Alabama, P.O. Box 1921, Tuscaloosa, AL 35486, USA Received February 9, accepted March 7, 1990 Abstract. We have analysed the properties of the radio continuum emission from the central region of a large sample of spiral galaxies (154 galaxies). This analysis focussed on four main themes: a comparison of interacting and non-interacting spiral galaxies, of barred and non-barred spirals, of early and late type spirals and of nuclei optically classified as HII region and Liner. The results can be summarized as follows: i) The central radio sources in interacting spiral galaxies are on average a factor 5 stronger than the ones in the more isolated galaxies. This difference is almost completely due to the activity in the H II region nuclei. The Liners in these subsamples are the same within a factor two. ii) The central radio sources in barred spirals are a factor 5 stronger than the ones found in non-barred spirals. This again is mainly due to the H II region nuclei. The Liners found in barred and non-barred spirals are similar. iii) The central radio sources associated with Liners in early type spirals are a factor 4 stronger than the ones in late type spirals. The ones associated with H II region nuclei in early type spirals are a factor 5 weaker than the ones in late type spirals. iv) The central radio sources found in nuclei classified as Liner are a factor 5 weaker than the ones found in H II region nuclei. The Liner nuclei are also smaller (~50 pc) when compared to the H II region nuclei (~400 pc). Radio core sources are found, almost exclusively, in nuclei classified as Liner. These results are consistent and underscore the results obtained from considerations how to feed a ''monster''. It is apparently relatively easy to enhance the star formation on a scale of ~1 kpc, while activating a compact core is much more difficult. In fact the latter seems to depend mostly on the mass distribution rather than on the presence or absence of a bar or companion. Key words: spiral galaxies - active nuclei - interacting galaxies - barred galaxies
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