Influence of major mergers on the radio emission of elliptical galaxies

TL;DR

This study examines how major mergers influence the radio emission of elliptical galaxies, finding that mergers have minimal impact compared to optical luminosity and that isolated galaxies show higher radio activity.

Contribution

It provides a comprehensive analysis using large samples from SDSS, FIRST, and NVSS, demonstrating that major mergers do not significantly trigger radio emission in elliptical galaxies.

Findings

Radio fraction of merging galaxies is about 6%.

Radio emission is mainly dependent on optical luminosity.

Merging has little effect on radio emission compared to luminosity.

Abstract

We investigate the influence of major mergers on the radio emission of elliptical galaxies. We use a complete sample of close pairs, which contains 475 merging and 1828 non-merging paired elliptical galaxies of M_r<-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. 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 as that of isolated galaxies, which is less than 3%. Radio emission of elliptical galaxies is only slightly affected by major mergers, but predominantly depends on their optical luminosities. Therefore, merging is not important in triggering the radio emission of elliptical galaxies.