IS THE BL-LACERTAE OBJECT AO-0235+164 BEING LENSED BY ITS INTERVENING MG-II ABSORBER

We report the results of deep CFHT imaging of the BL Lac object AO 0235 + 164. This object exhibits Mg II absorption features and has been considered to be the best candidate for a microlensed BL Lac on the basis of its multiple redshift systems, decentered host, and extreme apparent superluminal motion. We test the microlensing hypothesis by modeling our images with a two-dimensional image fitting routine. The resulting best-fit models allow us to put strong constraints on lensing scenarios for this object, and to put limits on the mass-to-light ratio of the foreground Mg II absorbing galaxy. We conclude that while AO 0235 + 164 is almost certainly being weakly amplified by macrolensing, microlensing by stars in the foreground lens is unnecessary in order to explain the observed properties of AO 0235 + 164. These results are combined with the work of previous authors to suggest that the (probably lensing) Mg II absorbing galaxy in the foreground of AO 0235 + 164 is embedded in a cooling flow.