In this paper we present Very Large Array ( VLA ) 1.4 GHz ( 21 cm ) observations of the region between the centres of A3558 and A3562 , in the major cluster merger complex of the Shapley Concentration .
Our final catalogue includes a total of 174 radio sources above the flux density limit of 0.25 mJy b ^ { -1 } .
By cross-correlation with optical and spectroscopic catalogues we found 33 optical counterparts belonging to the Shapley Concentration . We investigated the effects of cluster merger on the radio emission properties of the galaxy population by means of the radio source counts and the radio luminosity functions ( RLF ) .
We found that the radio source counts are consistent with the field source counts .
The RLF of elliptical and S0 galaxies in the region surveyed here , is consistent with the “ universal ” RLF for early–type galaxies .
This result suggests that the deficit in radio galaxies found in our previous works over the whole A3558 chain , is entirely due to the cluster A3558 .
A population of faint radio galaxies ( logP _ { 1.4 ~ { } GHz } ( W Hz ^ { -1 } ) < \sim 22 ) is also found .
Half of these objects are also blue , suggesting that starburst is the main mechanism driving the radio emission .
Finally , we detected 14 spiral radio galaxies , whose ratio between radio and optical emission is similar to those found in galaxies located in rich and dynamically evolved clusters . Our results are briefly discussed in the light of the age and stage of the merger in the A3558 cluster complex .