0 M ay 1 99 7 The Unusual Near - Infrared Morphology of the Radio Loud

Received ; accepted – 2 – ABSTRACT Near-infrared images of the luminous, high redshift (z = 2.1108) radio loud quasar 4C +09.17 reveal a complex structure. The quasar (K= 15.76 mag) is surrounded by three " companion " objects having 17.9 < K < 20.2 mag at radii of 1.7 ′′ < ∆r< 2.9 ′′ , as well as bright, diffuse emission. The brightest companion has a redshift of z = 0.8384 (Lehnert & Becker 1997) and its optical-infrared colors (Lehnert et al. 1997) are consistent with a late-type spiral galaxy at this redshift with a luminosity of about 2L *. This object is likely the galaxy responsible for the strongest MgII absorption line system seen in the spectrum of 4C +09.17 by Barthel et al. (1990). Redshifts are not available for the remaining two companions. The red colors of the second brightest companion appear most consistent with a high redshift star-forming galaxy at z > 1.5. If this 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 a spiral 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 of 4C +09.17, as well as the extended Lyα emission mapped by Heckman et al. (1991) we suggest that this component can be explained as a combination of strong line emission and scattered QSO light. The resolved, diffuse emission surrounding 4C +09.17 is bright, K∼ 17.0 mag, and about one magnitude redder in J-K than the quasar. If this emission is starlight, a very luminous elliptical host galaxy is implied for 4C +09.17. Scattered and reddened AGN light, emission line gas, and flux from absorbing galaxies along the line of sight may all contribute to this emission.