Aims: The determination of elusive redshifts of bright BL Lac objects Methods: We use the capabilities of newly available spectrograph X-Shooter at European Southern Observatory (ESO) Very Large Telescope, that combines high resolution and a large wavelength range, to obtain UVB to near-IR spectra of BL Lacs. Results: Our observations of PKS 0048-097 detect three emission lines that permit to derive a redshift z = 0.635. Moreover, a Mg II absorption system at z = 0.154 that is associated with a foreground spiral galaxy at 50 Kpc projected distance is found. Conclusions: The obtained redshift allows us to comment about the optical beaming factor and the absorption of the high energy spectrum by the Extragalactic Background Light.
@article{arxiv.1205.1215,
title = {On the redshift of the bright BL Lac object PKS 0048-097},
author = {Marco Landoni and Renato Falomo and Aldo Treves and Boris Sbarufatti and Roberto Decarli and Fabrizio Tavecchio and Jari Kotilainen},
journal= {arXiv preprint arXiv:1205.1215},
year = {2015}
}
Comments
5 pages, 6 figures; Accepted for publication by A&A; AA/2012/19114