Possible Relic Lobes in Giant Radio Sources

TL;DR

This study uses low-frequency GMRT observations to analyze three giant radio sources with diffuse, hotspotless lobes, suggesting these lobes are relics from earlier activity cycles despite active cores.

Contribution

It provides new spectral age estimates and morphological analysis indicating that the lobes are relics, offering insights into the lifecycle of giant radio sources.

Findings

Lobes show no hotspots or jets, indicating relic status.

Spectral ages suggest these lobes are remnants of past activity.

Active cores imply ongoing central activity despite relic lobes.

Abstract

We present low-frequency observations with the GMRT of three giant radio sources (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 spectral ages of the lobes. All three sources have compact radio cores. Although the radio cores suggest that the sources are currently active, we suggest that the lobes in these sources could be due to an earlier cycle of activity.