Observations and properties of candidate high frequency GPS radio sources in the AT20G survey

TL;DR

This study used high-frequency radio observations and optical spectra to analyze candidate GPS sources from the AT20G survey, revealing their variability, youth, and potential for being restarted radio galaxies, thus enhancing understanding of their evolution.

Contribution

It provides new high-frequency radio data and optical spectra for candidate GPS sources, identifying their nature and potential for being young or restarted radio galaxies.

Findings

Approximately 60% of the sources are genuinely young radio galaxies.

Three sources show evidence of being restarted radio galaxies.

Up to 25% of the candidate GPS sources may be restarted radio galaxies.

Abstract

We used the Australia Telescope Compact Array (ATCA) to obtain 40 GHz and 95 GHz observations of a number of sources that were selected from the Australia Telescope Compact Array 20 GHz (AT20G) survey . The aim of the observations was to improve the spectral coverage for sources with spectral peaks near 20 GHz or inverted (rising) radio spectra between 8.6 GHz and 20 GHz. We present the radio observations of a sample of 21 such sources along with optical spectra taken from the ANU Siding Spring Observatory 2.3m telescope and the ESO-New Technology Telescope (NTT). We find that as a group the sources show the same level of variability as typical GPS sources, and that of the 21 candidate GPS sources roughly 60% appear to be genuinely young radio galaxies. Three of the 21 sources studied show evidence of being restarted radio galaxies. If these numbers are indicative of the larger population of AT20G radio sources then as many as 400 genuine GPS sources could be contained within the AT20G with up to 25% of them being restarted radio galaxies.