Discovery of ultra-steep spectrum giant radio galaxy with recurrent radio jet activity in Abell 449

TL;DR

This paper reports the discovery of an ultra-steep spectrum giant radio galaxy with fading lobes near Abell 449, revealing a rare relic structure and evidence of new jet activity, providing insights into active galactic nuclei evolution.

Contribution

It presents the first detailed analysis of a rare ultra-steep spectrum giant radio galaxy with recurrent jet activity near Abell 449, including new low-frequency radio observations.

Findings

Diffuse radio lobes are bright only at low frequencies.

Synchrotron age of lobes is about 160 Myr.

The parent galaxy shows signs of new jet activity.

Abstract

We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.