MULTICOLOR IMAGES OF SPATIALLY RESOLVED STRUCTURES AROUND HIGH-REDSHIFT QUASARS

We present multicolor, optical, and near-IR imaging of spatially resolved continuum-emitting structures ("fuzz") around six high-redshift (z = 2-3) radio-loud quasars selected from the earlier imaging survey of Heckman et al. We argue that this fuzz is most plausibly interpreted as the stellar population of the host galaxy of the quasar. All six quasars are well resolved in the near-IR images (corresponding to emission at almost-equal-to 6000 to 7000 angstrom in the quasar rest frame). The implied K-corrected absolute visual magnitudes for the fuzz are -24 to -26 (for H0 = 75 km s-1 Mpc-1 and q0 = 0). This is several magnitudes brighter than the most luminous galaxies in the present-day universe (namely, the "first-ranked" giant ellipticals in rich clusters and host galaxies of low-z radio-loud quasars). In four of the six cases the fuzz is at least 1.5 mag redder in (B-K) than the central quasar, so that it is unlikely that the near-IR fuzz is generally quasar light scattered by either dust or electrons in the quasar halo. In two cases, the fuzz is well resolved in the optical images (almost-equal-to 1400 angstrom in the QSR rest frame), in two other cases the optical fuzz is possibly resolved and in the last two cases the optical fuzz is unresolved. The measured spectral energy distributions in the two best-resolved cases are similar to those of the most actively star-forming present-day galaxies (e.g., Magellanic Irregular and Markarian starburst galaxies). If the rest-frame UV fuzz is indeed starlight, the fuzz luminosities imply starformation rates of several hundred solar masses per year in these two objects. The apparent K magnitudes for the fuzz lie along the remarkably tight K versus redshift "IR Hubble diagram" for radio galaxies discovered by Lilly in 1989. The available data are also consistent with the fuzz around high-z radio-loud quasars having spectral energy distributions that are similar to those of high-z radio galaxies. These data imply that radio-loud quasars and radio galaxies at high redshift are intimately related phenomena and are consistent with some recent efforts to "unify" the two AGN classes.