BL Lac objects with optical jets: PKS 2201+044, 3C 371 and PKS 0521-365
  We investigate the properties of the three BL Lac objects, PKS 2201+044, 3C
371 and PKS 0521-365, that exhibit prominent optical jets. We present high
resolution near-IR images of the jet of the first two, obtained with an
innovative adaptive-optics system (MAD) at ESO VLT telescope. Comparison of the
jet in the optical, radio, NIR and X-ray bands reveals strong similarities in
the morphology. A common property of these sources is the presence of broad
emission lines in their optical spectra at variance with the typical
featureless spectrum of the nearby BL Lac objects. Despite some resemblances
(e.g. in the radio type), significant differences (e.g. in the central black
hole masses and radio structures) with radio-loud NLS1s are found.
