The CLASS blazar survey – II. Optical properties |
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| Authors: | A Caccianiga MJ Marchã S Antón K-H Mack MJ Neeser |
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| Institution: | 1CAAUL, Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa, Portugal;2ASTRON/NFRA, Postbus 2, NL-7990 AA Dwingeloo, the Netherlands;3Istituto di Radioastronomia del CNR, Via P. Gobetti 101, I-40129 Bologna, Italy;4Radioastronomisches Institut der Universität Bonn, Auf dem Hügel 71, D-53121 Bonn, Germany;5Kapteyn Astronomical Institute Postbus 800, NL-9700 AV Groningen, the Netherlands;6Universitäts-Sternwarte München, Scheinerstrasse 1, D-81679 München, Germany |
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| Abstract: | This paper presents the optical properties of the objects selected in the CLASS blazar survey. Because an optical spectrum is now available for 70 per cent of the 325 sources present in the sample, a spectral classification, based on the appearance of the emission/absorption lines, is possible. A wide variety of optical spectral types is found. Besides 'classical' BL Lacs (42), BL Lac candidates (5) and high-power  flat spectrum radio quasars (67), a significant number of 'passive' elliptical galaxies (41) is also found. Moreover, 33 broad emission line objects with a low radio power  are discovered, suggesting that at least a fraction (∼  per cent) of low-power blazars have a broad line region. Finally, 34 objects showing only narrow emission lines, either as a result of some starburst activity in the host galaxy or as a result of the presence of an active galactic nucleus, appear in the sample. |
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| Keywords: | surveys galaxies: active BL Lacertae objects: general quasars: general |
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