Alignment of Radio Galaxy Axes using FIRST Catalogue

TL;DR

This study investigates the alignment of radio galaxy axes using the FIRST catalogue, finding significant alignment effects at small angular scales but limited evidence for three-dimensional alignment, with considerations of potential systematic biases.

Contribution

It provides the first large-scale analysis of radio galaxy axis alignment using the FIRST catalogue, highlighting the scale and significance of the effect.

Findings

Significant alignment within 1 degree angular separation.

Alignment distance scale estimated at roughly 28 Mpc.

Weak three-dimensional alignment signal at larger distances.

Abstract

We study the alignment of radio galaxies axes using the FIRST catalogue. we impose several cuts in order to select the candidates which are most likely to be free of systematic bias. In our study we primarily focus on testing for alignment among sources within a certain angular separation from one another since for most sources redshift information is not available. We find a very significant effect for angular distances less than 1 degrees. The distance scale of alignment is found to be roughly 28 Mpc, in agreement with earlier estimates, assuming that these sources are dominantly at redshift of 0.8. However we are not able to entirely rule out the possibility of systematic bias in data. We also perform a full three dimensional analysis using a smaller data sample for which redshift information is available. In this case we only find a very weak signal at much larger distances.