High-Resolution Radio Imaging of Gravitational Lensing Candidates in the 1 Jansky BL Lacertae Sample

Abstract

While BL Lacertae objects are widely believed to be highly beamed, low-luminosity radio galaxies, many radio-selected BL Lac objects have extended radio power levels and optical emission lines that are too luminous to be low-luminosity radio galaxies. In addition, Stocke & Rector discovered an excess of Mg II absorption systems along BL Lac sight lines compared with quasars, suggesting that gravitational lensing may be another means of creating the BL Lac phenomenon in some cases. We present a search for gravitationally lensed BL Lac objects with deep, high-resolution, two-frequency VLA radio maps of seven lensing candidates from the 1 Jy BL Lac sample. We find that none of these objects are resolved into an Einstein ring like B0218+357, nor do any show multiple images of the core. All of the lensing candidates that were resolved show a flat-spectrum core and very unusual, steep-spectrum extended morphology that is incompatible with a multiply lensed system. Thus, while these observations do not rule out microlensing, no macrolensing is observed.