Optical and radio properties of extragalactic radio sources with recurrent jet activity

TL;DR

This study investigates the optical and radio characteristics of 74 extragalactic radio sources with recurrent jet activity, revealing similarities and differences with typical FRII sources, and suggesting merger events influence host galaxy morphology.

Contribution

It provides a comprehensive analysis of the properties of recurrent jet activity sources, including black hole and stellar masses, and links galaxy morphology to merger history.

Findings

Black hole masses in restarting sources are similar to single-cycle FRII sources.

Stellar masses tend to be smaller in restarting sources.

Host galaxies show signs of frequent mergers, indicated by lower concentration indices.

Abstract

We present a sample of 74 radio sources with recurrent jet activity. The sample consists of 67 galaxies, 2 quasars and 5 unidentified sources, selected from the published data or are newly recognized. The sample's redshift range is 0.002 < z < 0.7 and the size of inner and outer structures varies from 0.02 to 4248 kpc. We analyse the optical and radio properties of the sample and compare them with the characteristics of ordinary one-off FRII radio sources. With the help of stellar population modelling, we derive black hole masses and stellar masses of host galaxies of 35 restarting radio sources, finding that the black hole masses in restarting radio sources are comparable to those of typical single-cycle FRII radio sources. The obtained median values of log M$_{BH}$ are 8.58 and 8.62 M$_{\odot}$ Unlike the black hole masses, the stellar masses in restarting radio sources tend to be smaller than in the FRII sources. Although the stellar populations of the hosts of recurrent activity sources are dominated by old stars, a significant fraction of young stars can be observed as well. Based on the Sloan Digital Sky Survey photometric observations, we also analyse the morphology of the host galaxies and obtained significantly smaller concentration indices for the restarting radio sources when compared to the classical FRII hosts. This effect can be interpreted as a result of frequent merger events in the history of host galaxies of restarting radio sources.