Galaxy Cluster Environments of Radio Sources
  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.
