The effect of undetected gravitational lenses on statistical measures of quasar evolution
Abstract
Brightness amplifications by undetected gravitational lenses could be responsible in part for the apparent evolution of quasars, particularly for those which appear to be of high luminosity. It is shown that values of the evolution parameter greater than or equal to 0.6 and numbermagnitude slopes greater than or equal to 0.9 need not necessarily imply source density evolution if lensing events are common. Quasar samples which are defined by flux limits and minimum luminosities will preferentially include gravitational lens systems. Even if lensing events are quite rare, a large fraction of the lensed quasars will appear more luminous than the most luminous unlensed quasar.
 Publication:

The Astrophysical Journal
 Pub Date:
 December 1980
 DOI:
 10.1086/183418
 Bibcode:
 1980ApJ...242L.135T
 Keywords:

 Cosmology;
 Gravitational Lenses;
 Luminous Intensity;
 Quasars;
 Brightness Temperature;
 Mathematical Models;
 Space Density;
 Statistical Analysis;
 Astrophysics