THE ASTRONOMICAL JOURNAL    VOLUME 109, NUMBER 3, PAGE 853           MARCH 1995

    A 20 cm VLA SURVEY OF ABELL CLUSTERS OF GALAXIES. IV. THE RADIO SAMPLE
                            AND CLUSTER PROPERTIES

                     MICHAEL J. LEDLOW AND FRAZER N. OWEN

        National Radio Astronomy Observatory, Socorro, New Mexico 87801
         Electronic mail: mledlow@nmsu.edu, fowen@pilabo.aoc.nrao.edu


                                   ABSTRACT

    This is the fourth in a series of papers describing an in depth study
    of a large statistical sample of radio galaxies in Abell clusters.
    This sample forms the basis of a detailed optical and radio study of
    the host galaxy properties, environments, and evolutionary models for
    radio galaxies as a class of objects.  In this paper, we examine the
    radio detection statistics as a function of cluster morphological type,
    galaxy richness, and spatial location within the cluster galaxy
    distribution.  These relationships are also parameterized as a function
    of radio power.  The spatial distributions of the radio sources as a
    function of distance from the cluster center indicate that radio
    galaxies are preferentially located at small radii from the center of
    the cluster potential.  This is observed as a factor of 2-3 excess over
    that predicted by a King-model surface-density distribution.  The
    excess is higher in the upper radio power bin.  This result is easily
    explained, however, from the spatial distribution of the brightest
    galaxies and the relationship between radio and optical luminosity.
    The sample is divided into richness classes 0, 1, and 2, according to
    Abell's criterion, and in two radio power ranges.  While simple
    counting shows that richer clusters have more radio galaxies in both
    radio power bins, when the detections are scaled to the number of
    galaxies surveyed in each cluster, no significant correlations are
    found.  This result implies that the number of radio galaxies detected
    simply scales with the number of galaxies surveyed.  The higher galaxy
    density (and presumably higher ICM gas density) in richer clusters does
    not appear to affect the rate of radio source formation.  The clusters
    are divided into Rood-Sastry and Bautz-Morgan morphological types.
    While it would appear that the more regular clusters have higher radio
    detection rates, when the classes are normalized to the number of
    galaxies, the radio detection rates are found to be identical
    regardless of cluster morphology.  In conclusion, it is the optical
    properties of the host galaxy which most influence both the radio
    detection rate and the radio source properties.  The cluster
    properties, galaxy density, and spatial location of the galaxy do not
    significantly affect the observed radio statistics.