AN OPTICAL NEAR-INFRARED STUDY OF RADIO-LOUD QUASAR ENVIRONMENTS - I - METHODS AND Z=1-2 OBSERVATIONS/

We have conducted an optical/near-infrared study of the environments o f radio-loud quasars (RLQs) at redshifts z = 0.6-2.0. In this paper we discuss the sample selection and observations for the z = 1.0-2.0 sub sample and the reduction and cataloging techniques used. We discuss te chnical issues at some length, since few detailed descriptions of near -IR data reduction and multicolor object cataloging are currently avai lable in single literature references. Our sample of 33 RLQs contains comparable numbers of hat and steep radio spectrum sources and sources of various radio morphologies and spans a similar range of M-abs and P-rad, which allows us to disentangle dependence of environment on opt ical or radio luminosity from redshift evolution. We use the standard ''shift-and-stare'' method of creating deep mosaicked images in which the exposure time (and thus the rms noise) at each pixel is not consta nt across the mosaic. An unusual feature of our reduction procedure is the creation of images with constant rms noise from such mosaics. We adopted this procedure to enable use of the FOCAS detection package ov er almost the entire mosaic instead of only in the area of deepest obs ervation where the rms noise is constant, thereby roughly doubling our areal coverage. We correct the object counts in our fields for stella r contamination using the SKY model of Cohen and compare the galaxy co unts to those in random fields. Even after accounting for possible sys tematic magnitude offsets, we find a significant excess of K greater t han or similar to 19 galaxies. Analysis and discussion of this excess population is presented by Hall & Green.