Influence of major mergers on the radio emission of elliptical galaxies (Research Note)

Aims. We investigate the influence of major mergers on the radio emission of elliptical galaxies. Methods. We use a complete sample of close pairs, which contains 475 merging and 1828 non-merging paired elliptical galaxies of Mr < −21.5 selected from the Sloan Digital Sky Survey. In addition, a control sample of 2000 isolated field galaxies is used for comparison. We cross-identify the optical galaxies with the radio surveys of FIRST and NVSS. Results. We find that the radio fraction of merging paired galaxies is about 6%, which is slightly higher than the 5% obtained for non-merging paired galaxies, although these values are consistent with each other owing to the large uncertainty caused by the limited sample. The radio fraction is twice that of isolated galaxies, which is less than 3%. Conclusions. Radio emission of elliptical galaxies is only slightly affected by major mergers, but depends predominantly on their optical luminosities. We therefore conclude that merging is unimportant in triggering the radio emission of elliptical galaxies.