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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 clustersof galaxies: A262, Cancer, A1367, Coma and Virgo. With the aim ofdiscussing possible environmental dependences of the radio properties,we compare these results with those obtained for relatively isolatedobjects in the Coma supercluster. We find that the RLF of Cancer, A262and Virgo are consistent with that of isolated galaxies. Conversely weconfirm earlier claims that galaxies in A1367 and Coma have their radioemissivity enhanced by a factor ~ 5 with respect to isolated objects. Wediscuss this result in the framework of the dynamical pressure sufferedby galaxies in motion through the intra-cluster gas (ram-pressure). Wefind that the radio excess is statistically larger for galaxies in fasttransit motion. This is coherent with the idea that enhanced radiocontinuum activity is associated with magnetic field compression. TheX-ray luminosities and temperatures of Coma and A1367 imply that thesetwo clusters have significantly larger intracluster gas density than theremaining three studied ones, providing a clue for explaining the higherradio continuum luminosities of their galaxies. Multiple systems in theComa supercluster bridge (with projected separations smaller than 300kpc) have radio luminosities significantly larger than isolatedgalaxies. Table~1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html}
| Redshifts for Fainter Galaxies in the First CFA Slice. III. To the Zwicky Catalog Limit
We have measured redshifts for 241 galaxies selected from the Zwickycatalog with magnitudes 15.6 or 15.7 in the region (26.5^deg^ <=32.5^deg^, 8^h^<= α <= 17^h^, 1950). This region is theoriginal CfA "Slice of the Universe," which was complete to 15.5; nownearly all Zwicky-catalog galaxies in the region have measuredredshifts. These somewhat fainter galaxies outline the same structuresas the brighter ones. By examining a sample of 27 galaxies within themost prominent void we find (1) the fraction of absorption-line galaxiesis typical of regions outside the cores of rich clusters; and (2) thelocal morphology- density relation holds within the globally underdensevoid.
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