Astron. J., 120, 1626-1647 (2000/October-0)
The properties of the x-ray-selected EMSS sample of BL Lacertae objects.
RECTOR T.A., STOCKE J.T., PERLMAN E.S., MORRIS S.L. and GIOIA I.M.
Abstract (from CDS):
We present updated and complete radio, optical, and X-ray data for BL Lac objects in the Einstein Medium Sensitivity Survey (EMSS). The complete ``M91'' sample first presented in Morris et al. is updated to include 26 BL Lac objects in total, and we define a new, virtually complete sample consisting of 41 EMSS BL Lac objects (the ``D40'' sample). New high signal-to-noise ratio, arcsecond-resolution VLA observations are also presented for 11 EMSS BL Lac objects, completing VLA observations of the M91 sample. The addition of four new objects, as well as updated X-ray flux and redshift information, has increased the <Ve/Va> value for the M91 sample to 0.399±0.057 and <Ve/Va≥0.427±0.045 for the newly defined D40 sample. In conjunction with other studies of X-ray-selected BL Lac (XBL) samples, these results solidify negative evolution for XBLs, especially for more extreme high-energy-peaked BL Lac objects, for which we find <Ve/Va≥0.271±0.077. The observed <Ve/Va>, spectral, and radio properties of XBLs are completely consistent with being the beamed population of low-luminosity, FR-1 radio galaxies. However, our VLA observations do confirm that XBLs are too core dominated to be consistent with a beamed population of FR-1's seen at intermediate angles, as suggested by the unified model, if XBLs have moderate outflow velocities (γ∼5).
Galaxies: BL Lacertae Objects: General - Galaxies: Active
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