THE OPTICAL COUNTERPARTS AND THE ENVIRONMENTS OF ULTRA-STEEP-SPECTRUMRADIO-SOURCES

We present the results of a study of the optical morphologies of dista nt ultra-steep spectrum (USS) radio galaxies and their environments. T he alignment between the optical and radio axes previously noted for h igh redshift radio galaxies is also found for the radio sources in our sample. The strength of the alignment effect is found not to depend s trongly on the size of the radio source. Clustering around the radio g alaxies is investigated by examining the galaxy number density as a fu nction of projected distance from the radio galaxy. No excess of brigh t galaxies (R less than or similar to 21.5) near the positions of the radio galaxies is found, suggesting that gravitational lensing by fore ground clusters as has been previously suggested to occur for some sam ples of quasars - is not as important for USS radio galaxies. Furtherm ore no excess of faint galaxies (R similar to 23) was found. However, we cannot rule out the possibility that distant radio galaxies reside in clusters, as the magnitude limit of our sample is sufficiently brig ht that it would be difficult to detect normal cluster galaxies at z > 1 if their luminosity function and sizes are similar to those of near by clusters. An excess of companion galaxies is detected along the axe s of the radio sources. The angular separations involved range from 3. 1 '' to 10 '' which corresponds to 25 - 80 kpc at z = 2. This ''compan ion alignment'' could be due to the luminosity of a merging dwarf gala xy being enhanced by scattering and/or jet-induced star formation. Alt ernatively, this alignment could find its origin in a galaxy distribut ion that is elongated in the direction of the radio axis.