The cluster environments of radio loud quasars

TL;DR

This study uses multi-colour imaging to analyze the environments of radio loud quasars at redshifts 0.6 to 1.1, revealing correlations between radio source size and environmental richness, and proposing a radio-based method for detecting high-redshift clusters.

Contribution

It demonstrates that radio source size correlates with environment richness and introduces a radio-based approach for efficiently identifying high-redshift galaxy groups and clusters.

Findings

Larger radio sources are found in less dense environments.

Smaller steep-spectrum sources are associated with richer environments.

Radio-based selection effectively detects high-redshift clusters.

Abstract

We have carried out multi-colour imaging of the fields of a statistically complete sample of low-frequency selected radio loud quasars at 0.6<z<1.1, in order to determine the characteristics of their environments. The largest radio sources are located in the field, and smaller steep-spectrum sources are more likely to be found in richer environments, from compact groups through to clusters. This radio-based selection (including source size) of high redshift groups and clusters is a highly efficient method of detecting rich environments at these redshifts. Although our single filter clustering measures agree with those of other workers, we show that these statistics cannot be used reliably on fields individually, colour information is required for this.