A Semi-automatic Search for Giant Radio Galaxy Candidates and their Radio-Optical Follow-up

TL;DR

This study developed a computational method to identify giant radio galaxy candidates from the NVSS survey, followed by optical spectroscopy and high-resolution radio imaging, resulting in the discovery of 39 new GRGs.

Contribution

The paper introduces a semi-automatic algorithm for detecting GRG candidates and combines it with follow-up observations to significantly expand known GRG samples.

Findings

Discovered 39 new giant radio galaxies.

Developed an effective semi-automatic candidate selection method.

Confirmed redshifts and structures of several candidates.

Abstract

We present results of a search for giant radio galaxies (GRGs) with a projected largest linear size in excess of 1 Mpc. We designed a computational algorithm to identify contiguous emission regions, large and elongated enough to serve as GRG candidates, and applied it to the entire 1.4-GHz NRAO VLA Sky survey (NVSS). In a subsequent visual inspection of 1000 such regions we discovered 15 new GRGs, as well as many other candidate GRGs, some of them previously reported, for which no redshift was known. Our follow-up spectroscopy of 25 of the brighter hosts using two 2.1-m telescopes in Mexico, and four fainter hosts with the 10.4-m Gran Telescopio Canarias (GTC), yielded another 24 GRGs. We also obtained higher-resolution radio images with the Karl G. Jansky Very Large Array for GRG candidates with inconclusive radio structures in NVSS.