Galaxy Cluster Environments of Radio Sources

TL;DR

This study uses SDSS and FIRST data to analyze the environments of radio sources, revealing that bent and FR I sources are more often in galaxy clusters, especially at higher redshifts.

Contribution

It provides a large-scale classification of galaxy clusters associated with different types of radio sources, highlighting the environmental differences based on radio morphology and optical properties.

Findings

Bent radio sources are found in clusters 78% of the time.

FR I sources are more likely in clusters than FR II.

Single-component sources are less associated with clusters.

Abstract

Using the Sloan Digital Sky Survey (SDSS) and the FIRST (Faint Images of the Radio Sky at Twenty Centimeters) catalogs, we examined the optical environments around double-lobed radio sources. Previous studies have shown that multi-component radio sources exhibiting some degree of bending between components are likely to be found in galaxy clusters. Often this radio emission is associated with a cD-type galaxy at the center of a cluster. We cross-correlated the SDSS and FIRST catalogs and measured the richness of the cluster environments surrounding both bent and straight multi-component radio sources. This led to the discovery and classification of a large number of galaxy clusters out to a redshift of z ~ 0.5. We divided our sample into smaller subgroups based on their optical and radio properties. We find that FR I radio sources are more likely to be found in galaxy clusters than FR II sources. Further, we find that bent radio sources are more often found in galaxy clusters than non-bent radio sources. We also examined the environments around single-component radio sources and find that single-component radio sources are less likely to be associated with galaxy clusters than extended, multi-component radio sources. Bent, visually-selected sources are found in clusters or rich groups ~78% of the time. Those without optical hosts in SDSS are likely associated with clusters at even higher redshifts, most with redshifts of z > 0.7.