A multifrequency study of possible relic lobes in giant radio sources

TL;DR

This study uses low-frequency GMRT and VLA observations to analyze three giant radio sources with diffuse lobes, investigating their ages and activity cycles to identify potential relic lobes from previous activity.

Contribution

It provides new age estimates and spectral analysis of giant radio sources, exploring the relic nature of their lobes and their possible origin from earlier activity cycles.

Findings

Lobes are likely relics from past activity cycles.

Radio cores indicate current activity despite relic lobes.

Age estimates support the relic hypothesis.

Abstract

We present low-frequency observations with the Giant Metrewave Radio Telescope (GMRT) of three giant radio sources (GRSs, J0139+3957, J0200+4049 and J0807+7400) with relaxed diffuse lobes which show no hotspots and no evidence of jets. The largest of these three, J0200+4049, exhibits a depression in the centre of the western lobe, while J0139+3957 and J0807+7400 have been suggested earlier by Klein et al. and Lara et al. respectively to be relic radio sources. We estimate the ages of the lobes. We also present Very Large Array (VLA) observations of the core of J0807+7400, and determine the core radio spectra for all three sources. Although the radio cores suggest that the sources are currently active, we explore the possibility that the lobes in these sources are due to an earlier cycle of activity.