On the surface density of X-ray selected BL Lacertae objects.
Abstract
Only a handful of BL Lac objects have been found as a result of systematic optical identification of serendipitous Einstein X-ray sources. By combining the data from two flux-limited complete X-ray surveys (the HEAO 1 A-2 and the Einstein Observatory Medium Sensitivity Survey) the surface density of X-ray emitting BL Lac objects is evaluated as a function of their X-ray flux. It is found that a single power law is not an acceptable representation of the BL Lac objects' X-ray log N-log S. The number-flux relationship is consistent with the Euclidean slope at 'high' flux levels but shows a drastic flattnring below fluxes of the order of 10 to the -12th ergs per sq cm/s. The implications of this result are briefly discussed with respect to the luminosity function, the cosmological evolution, and the X-ray to optical flux ratio in BL Lac objects.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 1984
- DOI:
- 10.1086/184345
- Bibcode:
- 1984ApJ...284L..23M
- Keywords:
-
- Bl Lacertae Objects;
- X Ray Sources;
- Cosmology;
- Luminosity;
- Radiant Flux Density;
- Astrophysics