Optical and X-Ray Selected Samples of Quasars: Evolution of the Luminosity Distributions.

Spectroscopic and X-ray observations were obtained of quasar candidates in the 1.72 deg.('2) region centered on 13('h) 36(DEGREES) which were selected on the basis of ultraviolet excess. A complete sample totalling 35 quasars with B < 19.8 is produced. Quasars make up 81% of the candidates but 96% of the those fainter than B = 19.2. About half of the quasar sample is detected in X -rays by deep exposures with the Einstein Observatory. The X-ray fluxes and upper limits for the 35 quasars are used to show that quasars with B < 19.80 and z < 2.2 contribute. (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI). of the observed X-ray background at 2 keV. The completion of identifications of quasar candidates with B < 18.25 yields 22 quasars in a separate survey of 37.2 deg.('2). A parametric likelihood analysis of the joint redshift-luminosity distribution is developed and applied to the composite sample of 57 quasars with 17.0 < B < 19.8. Best estimates and joint confidence regions are determined for the parameters of several models of the luminosity and evolution functions. The luminosity function, (PHI)(> L), is found to be described well by a steep power law, L('-3.5) , verified by non-parametric estimation. The PG quasar sample, consisting of 114 quasars with B < 16.6 in (TURN) 10('4) deg('2), is added to the data set and fitted with pure luminosity evolution (LE) models. The characteristic quasar luminosity is found to evolve as (1+z)('3.4) or e('6(tau)), consistent with the results of the fits before the PG sample addition. LE models fit the data, after accounting for incompleteness in the data set, while a specific luminosity-dependent density evolution model is tested and rejected. The evolution models are extrapolated to fainter magnitudes and compared with the optical number counts and independently with the observed 2 keV X-ray background. Pure density evolution models are rejected in both comparisons but LE models produce very good fits to the observed N(< B) data and predict that quasars contribute a substantial fraction to the observed X-ray background at 2 keV. These data indicate that the luminosity function is shallower at luminosities corresponding to Seyfert galaxies. The models are used to test alternatives to quasar evolution and a stellar collision theory (SCT) of mass supply. The SCT is consistent with most of the data but the predicted evolution rate is weaker than observed. Several ways of reconciling the SCT and models of the quasar emission mechanism are suggested and tested.