On the local radio luminosity function of galaxies II. Environmental dependences among late-type galaxies

Using new extensive radio continuum surveys at 1.4 GHz (FIRST and NVSS), we derive the distribution of the radio/optical and radio/NIR luminosity (RLF ) of late-type (Sa-Irr) galaxies (m(p) < 15.7) in 5 nearby clusters of gala xies: A262, Cancer, A1367, Coma and Virgo. With the aim of discussing possi ble environmental dependences of the radio properties, we compare these res ults with those obtained for relatively isolated objects in the Coma superc luster. We fmd that the RLF of Cancer, A262 and Virgo are consistent with t hat of isolated galaxies. Conversely we confirm earlier claims that galaxie s in A1367 and Coma have their radio emissivity enhanced by a factor simila r to 5 With respect to isolated objects. We discuss this result in the fram ework of the dynamical pressure suffered by galaxies in motion through the intra-cluster gas (ram pressure). We find that the radio excess is statisti cally larger for galaxies in fast transit motion. This is coherent with the idea that enhanced radio continuum activity is associated with magnetic fi eld compression. The X-ray luminosities and temperatures of Coma and A1367 imply that these two dusters have significantly larger intracluster gas den sity than the remaining three studied ones, providing a clue for explaining the higher radio continuum luminosities of their galaxies. Multiple system s in the Coma supercluster bridge (with projected separations smaller than 300 kpc) have radio luminosities significantly larger than isolated galaxie s.