ESO Very Large Telescope Optical Spectroscopy of BL Lacertae Objects. II. New Redshifts, Featureless Objects, and Classification Assessments

Sbarufatti, B.; Treves, A.; Falomo, R.; Heidt, J.; Kotilainen, J.; Scarpa, R.
Bibliographical reference

The Astronomical Journal, Volume 132, Issue 1, pp. 1-19.

Advertised on:
7
2006
Number of authors
6
IAC number of authors
0
Citations
91
Refereed citations
77
Description
We report on ESO Very Large Telescope optical spectroscopy of 42 BL Lacertae objects of unknown redshift. Nuclear emission lines were observed in 12 objects, while for another six we detected absorption features due to the host galaxy. The new high signal-to-noise ratio spectra therefore allow us to measure the redshift of 18 sources. Five of the observed objects were reclassified as either stars or quasars, and one is of uncertain nature. For the remaining 18 the optical spectra appear without intrinsic features in spite of our ability to measure rather faint (equivalent width ~0.1 Å) spectral lines. For the latter sources a lower limit to the redshift was set, exploiting the very fact that the absorption lines of the host galaxy are undetected in the observed spectra.