Interaction versus radio source generation - The properties of radio jet parent galaxies

This paper presents the first systematic survey at optical wavelengths of galaxies with detected radio jets using CCD imaging. About 50 percent of the sample of low-redshift galaxies with radio jets have a large nearby companion and/or show peculiar optical morphology not detected in isolated ellipticals. Forty-five percent of the objects have a companion galaxy at a distance shorter than 20 kpc. The multicomponent galaxies in the sample form a very homogeneous group with little gas and dust, while the isolated galaxies have more heterogeneous radio properties, with large amounts of gas and warm dust in a large fraction of these galaxies. Intrinsic differences between the multicomponent galaxies and the isolated ones are explained in terms of a different parent galaxy and interaction processes. It is concluded that, at least among galaxies with radio jets, the amount of gas available and the interactions could control the energy generation, producing a very well-defined type of radio source. 48 refs