VLBA polarization observations of BL Lac objects and passive elliptical galaxies

• Published in: Monthly notices of the Royal Astronomical Society Vol. 352; no. 1; pp. 112 - 124
• Main Authors: Bondi, M., Marchã, M. J. M., Polatidis, A., Dallacasa, D., Stanghellini, C., Antón, S.
• Format: Journal Article
• Language: English
• Published: 23 Ainslie Place , Edinburgh EH3 6AJ , UK . Telephone 226 7232 Fax 226 3803 Blackwell Science Ltd 01.07.2004; Blackwell Science
• Subjects: Active and peculiar galaxies (including bl lacertae objects, blazars, seyfert galaxies, markarian galaxies, active galactic nuclei); Astronomy; BL Lacertae objects: general; Earth, ocean, space; Exact sciences and technology; polarization; Quasars. Active or peculiar galaxies, objects, and systems; radio continuum: galaxies; Stellar systems. Galactic and extragalactic objects and systems. The universe; Continuum; Polarization; Elliptical galaxies; Radio galaxies; Morphology; Cosmic radio sources; Jets; Spectral index; BL Lacertae objects: general; Magnetic fields; BL Lacertae objects; radio continuum: galaxies
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2004.07903.x

ABSTRACT We present Very Long Baseline Array (VLBA) 5‐GHz polarimetric observations of 23 BL Lacertae (BL Lac) objects and radio galaxies selected from the 200‐mJy sample. BL Lac objects have core polarization values lower than those found in previous samples. The magnetic field geometry in the jets is not unique: both parallel and perpendicular geometries are observed, even in the same sources. The parsec‐scale morphology of radio galaxies is clearly divided in two classes: one‐sided core‐jet sources, which show polarized emission in the core and/or jet, and two‐sided symmetric objects which are not polarized. We discuss and compare the parsec‐scale polarization properties of the radio cores and jets for the BL Lac objects and the radio galaxies in relation to their parsec‐scale morphology and high‐frequency integrated spectral index.