The Influence of High-Density Environment on the Radio--Far-Infrared Correlation of Spiral Galaxies

It is found that the far-infrared and radio luminosities of a sample of spirals in high-density environments from the Hickson Compact Group Catalogue 1982 (Hickson 1982) are highly correlated even though the radio radiation originates almost entirely in extranuclear regions for most of the spirals. A comparison of the above correlation with that for a sample of isolated spirals shows that, statistically, the total radio emission from the group spirals is lower by about a factor of 2 than the isolated spirals. These results can be interpreted on the basis of a model in which interactions among group galaxies produce inflow of gas toward the centers, resulting in enhanced star formation, which in turn produces enhancement of far-infrared and radio radiation from those regions. At the same time removal of gas and magnetic fields from the disk of the galaxies results in a decrease of total radio emission from those galaxies. It is interesting that, except for one Seyfert galaxy, the radio luminosities of all the group galaxies are less than about 10^22^ W Hz^-1 ^at 20 cm, which suggests that the high-density environment is not conducive for the development of powerful radio sources at the present epoch.