The unusual near-infrared morphology of the radio-loud quasar 4C + 09.17

Near-infrared images of the luminous, high redshift (z=2.1108) radio loudquasar 4C+09.17 reveal a complex structure. The quasar (K=15.76 mag) issurrounded by three "companion" objects having 17.9< K < 20.2 mag at radii of1.7" < r < 2.9", as well as bright, diffuse emission. The brightest companionhas a redshift of z=0.8384 (Lehnert & Becker 1997) and its optical-infraredcolors (Lehnert et al. 1997) are consistent with a late-type spiral galaxy atthis redshift with a luminosity of about 2L*. This object is likely the galaxyresponsible for the strongest MgII absorption line system seen in the spectrumof 4C+09.17 by Barthel et al. (1990). Redshifts are not available for theremaining two companions. The red colors of the second brightest companionappear most consistent with a high redshift star-forming galaxy at z > 1.5. Ifthis object is at the redshift of 4C +09.17 it has a luminosity of about 7L*.The faintest companion has colors which are unlike those expected from either aspiral or an E/S0 galaxy at any redshift associated with the 4C+09.17 system.Since this object lies along the same direction as the radio jet/lobe of4C+09.17, as well as the extended Ly-alpha emission mapped by Heckman et al.(1991) we suggest that this component can be explained as a combination ofstrong line emission and scattered QSO light. The resolved, diffuse emissionsurrounding 4C+09.17 is bright, K~17.0 mag, and about one magnitude redder inJ-K than the quasar. If this emission is starlight, a very luminous ellipticalhost galaxy is implied for 4C+09.17. Scattered and reddened AGN light, emissionline gas, and flux from absorbing galaxies along the line of sight may allcontribute to this emission.Comment: plain LaTex with 4 postscript figures, MNRAS, accepte