Paper detail

HST Imaging of the BL Lacertae Object OJ 287

Hubble Space Telescope WFPC-2 I-band (F814W) images of the BL Lacertae object OJ 287 and the surrounding field are presented. We find evidence of associated extended nebulosity near OJ 287, as well as a small nebulosity to the West, which may be spatially coincident with the position of previously observed radio emission. The brightness of a host galaxy is difficult to determine due to the brightness of the active nucleus, but it lies in the range -21.5 > M_R > -23.1 (H_0 = 100 km s^{-1} Mpc^{-1}, q_0 = 0). No evidence is seen for the previously reported optical ``jet'' at position angle 220 degrees to a surface brightness limit of I = 24.3 mag arcsec^{-2}. There are several resolved and unresolved objects within 17'' of OJ~287 in the field to limits of I=25 (point source 5σdetections). The magnitudes and relative positions of these objects are reported. An offset in the centroid position between the OJ 287 point source and the underlying nebulosity reported by Wurtz, Stocke and Yee is confirmed and measured to be about 0.4 (1.2h^{-1} kpc at the redshift of OJ~287). This offset is tentatively interpreted as evidence for recent merger activity rather than a sign of gravitational microlensing.