HOST GALAXY AND ENVIRONMENT OF THE BL-LACERTAE OBJECT PKS-0548-322 - OBSERVATIONS WITH SUBARCSECOND RESOLUTION

We report on direct, subarcsecond resolution imaging of the nebulosity and spectroscopy of galaxies in the field of the BL Lacertae object PKS 0548-322. Surface photometry of the nebulosity is used to derive the properties of the host galaxy (M(v) = -23.4), which exhibits signs of interaction with a close companion galaxy at similar to 25 kpc. The radial brightness profile of the nebulosity is well fitted by the contribution of a bulge (r(1/4)) plus a point source and a small internal disk. An analysis of the galaxies in the field shows that the source is located in a rich cluster of galaxies. Spectra of five galaxies in the field indicate that they are at the same redshift as the BL Lac object, thus supporting the imaging result of a surrounding cluster associated with the BL Lac. This cluster is most likely Abell S0549.