Spectral Ages of Giant Radio Sources

TL;DR

This study uses multifrequency radio observations to estimate the spectral ages of giant radio sources, revealing they are significantly older than smaller sources and providing insights into particle acceleration and spectral properties.

Contribution

The paper presents new spectral age estimates for a sample of giant radio sources using multifrequency data, highlighting their older ages and correlations with luminosity and size.

Findings

Median spectral age of ~20 Myr for giant radio sources

Spectral age increases with distance from hotspots in most sources

Injection spectral index correlates with luminosity, redshift, and size

Abstract

Multifrequency observations with the GMRT and the VLA are used to determine the spectral breaks in consecutive strips along the lobes of a sample of selected giant radio sources (GRSs) in order to estimate their spectral ages. The maximum spectral ages estimated for the detected radio emission in the lobes of our sample of ten sources has a median value of $\sim$20 Myr. The spectral ages of these GRSs are significantly older than smaller sources. In all but one source (J1313+6937) the spectral age gradually increases with distance from the hotspot regions, confirming that acceleration of the particles mainly occurs in the hotspots. Most of the GRSs do not exhibit zero spectral ages in the hotspots. This is likely to be largely due to contamination by more extended emission due to relatively modest resolutions. The injection spectral indices range from $\sim$0.55 to 0.88 with a median value of $\sim$0.6. We show that the injection spectral index appears to be correlated with luminosity and/or redshift as well as with linear size.