Radio Observations at 1.4 GHz of Abell Clusters

Extract

We have observed with the Westerbork Synthesis Radio Telescope (WSRT) at 1.4 GHz the Abell clusters included in the HEAO-2 satellite observing program, for which radio information was not available. In practice we excluded the clusters south of 15°, in order to ensure an adequate angular resolution in declination; moreover we did not observe distance class (d.c.) 6 clusters for which better resolution and sensitivity would be necessary. The final list includes 61 clusters. These have been observed to a limiting peak flux density of about 5 mJy, corresponding to average minimum radio powers ranging from ∼5×10²¹ to ∼2×10²³ W/Hz for d.c. 1 to 5. By adding the present data to those already available in the literature, we have radio information about all the clusters of d.c. 1 and 2, north of 15°, except A1185. The sample of d.c. 3 clusters contains 60% of the clusters of this class, but seems unbiased both for richness criteria and for radio characteristics; therefore it is useful for statistical studies. The observed clusters of d.c. 4 and 5, instead, are richer than average. The list of the observed clusters is presented in table 1: the Abell name is given in column 1, the d.c. in column 2, the richness class in column 3, the number of radio detected cluster galaxies in column 4 (in parentheses the number of galaxies for which the membership of the cluster is doubtful or the radio identification is not certain is given). The identification of the radio sources with the cluster galaxies of d.c. 5 is still in progress. While a more complete discussion of the properties of radio sources in clusters will be performed later, using the data about all the clusters of the sample, here we summarize the results of the discussion on d.c. 1 and 2 clusters.