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Astron. Astrophys. 343, 93-99 (1999)

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On the local radio luminosity function of galaxies *

II. Environmental dependences among late-type galaxies

G. Gavazzi 1 and A. Boselli 2

1 Universitá degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy
2 Laboratoire d'Astronomie Spatiale, Traverse du Siphon, B.P. 8, F-13376 Marseille Cedex 12, France

Received 11 September 1998 / Accepted 5 November 1998

Abstract

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 ([FORMULA]) in 5 nearby clusters of galaxies: A262, Cancer, A1367, Coma and Virgo. With the aim of discussing possible environmental dependences of the radio properties, we compare these results with those obtained for relatively isolated objects in the Coma supercluster. We find that the RLF of Cancer, A262 and Virgo are consistent with that of isolated galaxies. Conversely we confirm earlier claims that galaxies in A1367 and Coma have their radio emissivity enhanced by a factor [FORMULA] with respect to isolated objects. We discuss this result in the framework of the dynamical pressure suffered by galaxies in motion through the intra-cluster gas (ram-pressure). We find that the radio excess is statistically larger for galaxies in fast transit motion. This is coherent with the idea that enhanced radio continuum activity is associated with magnetic field compression. The X-ray luminosities and temperatures of Coma and A1367 imply that these two clusters have significantly larger intracluster gas density than the remaining three studied ones, providing a clue for explaining the higher radio continuum luminosities of their galaxies. Multiple systems in the Coma supercluster bridge (with projected separations smaller than 300 kpc) have radio luminosities significantly larger than isolated galaxies.

Key words: galaxies: clusters: general – galaxies: fundamental parameters – galaxies: interactions – galaxies: intergalactic medium – galaxies: luminosity function, mass function – radio continuum: galaxies

* Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: Gavazzi (Gavazzi@trane.uni.mi.astro.it)

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© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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