# A low-frequency study of recently identified double-double radio galaxies

## TL;DR

This study uses low-frequency GMRT observations to confirm the episodic jet activity in 21 double-double radio galaxies, revealing their ages and identifying a new candidate quasar DDRG.

## Contribution

It provides high-sensitivity low-frequency imaging of DDRGs, confirming their episodic nature and estimating their age limits, including the discovery of a new DDRG with a quasar candidate.

## Key findings

- None of the suspected hot-spots are flat-spectrum cores.
- Estimated age limits range from 11 to 52 million years.
- A new DDRG with a quasar candidate was identified.

## Abstract

In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time scales of episodic activity. Here we present high-sensitivity 607-MHz Giant Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio galaxies (DDRGs) identified from the FIRST survey to confirm their episodic nature. These GMRT observations show that none of the inner compact components suspected to be hot-spots of the inner doubles are cores having a flat radio spectrum, confirming the episodic nature of these radio sources. We have indentified a new DDRG with a candidate quasar, and have estimated the upper spectral age limits for eight sources which showed marginal evidence of steepening at higher frequencies. The estimated age limits (11 $-$ 52 Myr) are smaller than those of the large-sized ($\sim$ 1 Mpc) DDRGs.

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Source: https://tomesphere.com/paper/1905.00677