BL Lac objects with optical jets: PKS 2201+044, 3C 371 and PKS 0521-365

TL;DR

This study examines three BL Lac objects with optical jets, using high-resolution near-IR imaging and multi-wavelength comparisons, revealing similarities in jet morphology and unique spectral features that differentiate them from typical BL Lacs and NLS1s.

Contribution

The paper provides high-resolution near-IR images of optical jets in BL Lac objects and compares their multi-wavelength properties, highlighting their unique spectral and structural characteristics.

Findings

Optical jets show morphological similarities across bands.

Presence of broad emission lines in spectra contrasts typical BL Lacs.

Differences in black hole masses and radio structures from NLS1s.

Abstract

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.