A Multifrequency Study of Double-Double Radio Galaxies

TL;DR

This study uses multi-frequency radio observations to analyze the spectral properties, ages, and activity cycles of double-double radio galaxies, providing insights into episodic activity in active galactic nuclei.

Contribution

It demonstrates how combined GMRT and VLA observations can determine spectral ages and activity timescales in DDRGs, highlighting their rarity.

Findings

Spectral ages of inner and outer lobes estimated

Episodic activity timescales derived

DDRGs are relatively rare phenomena

Abstract

One of the striking examples of episodic activity in active galactic nuclei are the double-double radio galaxies (DDRGs) with two pairs of oppositely-directed radio lobes from two different cycles of activity. We illustrate, using the DDRG J1453+3308 as an example, that observations over a wide range of frequencies using both the GMRT and the VLA can be used to determine the spectra of the inner and outer lobes, estimate their spectral ages, estimate the time scales of episodic activity, and examine any difference in the injection spectra in the two cycles of activity. Low-frequency GMRT observations also suggest that DDRGs and triple-double radio galaxies are rather rare.