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Astron. Astrophys. 357, 91-100 (2000)

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Optical imaging and spectroscopy of BL Lac objects *

R. Falomo 1 and M.-H. Ulrich 2

1 Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy (falomo@pd.astro.it)
2 ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany (mhulrich@eso.org)

Received 23 November 1999 / Accepted 9 March 2000


We present optical images and spectroscopy for a dozen of BL Lac objects. Most of these objects were not previously studied and we give for the first time the properties of their host galaxies. The properties of the new host galaxies are generally consistent with those derived in previous optical studies. We found a case (1101-23) where the external isophotes of the galaxy are clearly boxy.

In addition we gathered spectroscopy for several BL Lac objects with unknown redshift and for companion galaxies. This allowed us to derive a tentative redshift for two new BL Lacs and to investigate the environment around PKS 0829+04. These data complement existing data available in the literature on host galaxies of BL Lacs and their (close) environments.

Key words: galaxies: active – galaxies: BL Lacertae objects: general – galaxies: interactions – galaxies: nuclei – galaxies: photometry – galaxies: structure

* Based on observations collected at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: R. Falomo

© European Southern Observatory (ESO) 2000

Online publication: May 3, 2000