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We have begun an optical-IR imaging survey of the fields of radio-loud quasars (RLQs) at z$>$0.6 in order to extend our knowledge of RLQ environments out to z=2, to expand the sample of known high-redshift galaxy clusters, to study cluster galaxies at high redshift, and to study the origins of `associated' CIV absorption.
At z=0.5--0.7 bright RLQs are often found in rich clusters, but at z$<$0.5 only faint RLQs reside in rich clusters. This indicates that quasars in rich environments have undergone rapid evolution, but almost nothing is known about how this evolution extends to higher redshift. Acquiring such knowledge will help constrain models of quasar formation and evolution, as well as models of large-scale structure formation.
In addition, at z$>$1.3 some quasars show possible evidence for residing in cluster environments, in the form of excess z$_{abs}$$\sim$z$_{em}$ `associated' CIV absorption systems in their spectra. Our deep R, I, and K$_s$ images will allow us to confirm or constrain the cluster hypothesis for the origin of this absorption. We will present some preliminary results from the data we have obtained to date.
