Abstract

We present images taken with the Wide Field Planetary Camera (WFPC-2) on the Hubble Space Telescope (HST ) of 43 quasars selected from the 3CR radio catalog. The redshift range of the targets is large -- 0.3 <~ z <~ 2 -- and allows us to probe the nature of quasar hosts from about 20% to 80% of the age of the universe. These data were taken in the course of a large program that imaged 267 3CR radio galaxies and quasars using the HST in "snapshot" mode. Each quasar was centered on the Planetary Camera (PC1) and was imaged through the F702W filter (bandpass similar to Cousins R). Typical integration times were 5 and 10 minutes. For each quasar, we attempted to judge the contribution of the host galaxy to the total light from the quasar in two ways. The first method was to compare the radial light distributions of the quasars with that of both model point spread function and an empirical PSF constructed by summing individual observations of standard stars. Second, to provide morphological information we attempted to remove the contribution of the quasar nucleus from the extended emission by subtracting a point spread function constructed from observations of standard stars. This second method proved to be more sensitive in detecting marginally extended emission. Our analysis suggests that the quasar fuzz contributes from less than 5% to nearly 100% in the most extreme case (about 20% being typical) of the total light from the quasar, with 16 of the quasars (~40%) being unresolved according to the analysis of their light profiles (with only 7 being considered unresolved determined by PSF subtraction of the quasar images). The magnitudes of the hosts range from about 18 to more than 21 in the F702W filter and the sizes are typically 1" - 2" at a limiting surface brightness of ~21-22mF702W arcsec-2. Comparisons with the few ground-based images that are available of these sources suggest good overall morphological agreement with the HST images. The 0.1" resolution of the HST PC combination reveals a wide variety of structures in the host galaxies of these quasars. Most of the host galaxies show twisted, asymmetric, or distorted isophotes. About 1/4 of the quasar hosts have close (within a few arcseconds) companions seen in projection and about 1/10 show obvious signs of tidal interactions with a close companion. Finally, using radio images available from the literature, we find that in many of the resolved sources there is a correspondence between the radio and optical morphologies. We find that these sources exhibit a tendency for the principal axes of the radio and optical emission to align similar but perhaps weaker than that observed for radio galaxies. This correspondence also suggests that our methodology for removing the point source contribution from the resolved emission is sound. A more complete analysis of these data and new HST snapshot data will be presented in subsequent papers (Refer to PDF file for exact formulas).

Publication Date

1999

Comments

Also archived in: arXiv :astro-ph/9904106 v1 8 Apr 1999 This research is partially supported by HST GO grant number GO-5476.01-93A, by a program funded by the Dutch Organization for Research (NWO) and by a NATO research grant. M. D. L. would like to thank Chris Burrows, Tim Heckman, and Matt McMaster for useful suggestions. We would also like to thank an anonymous referee for her/his remarks that improved the presentation of our results.ISSN:1538-4365 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type

Article

Department, Program, or Center

School of Physics and Astronomy (COS)

Campus

RIT – Main Campus

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