A Caltech Library Service

Quasars: cosmological evolution and x-ray background contribution

Schmidt, Maarten and Green, Richard F. (1986) Quasars: cosmological evolution and x-ray background contribution. In: Cosmic Radiation in Contemporary Astrophysics. NATO ASI Series. No.162. Springer Netherlands , Dordrecht, pp. 249-259. ISBN 9789401089227.

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item:


The luminosity function of quasars varies with redshift or cosmic epoch. We discuss how the luminosity function and its evolution can be determined from complete samples of quasars. We first concentrate on optical survey of quasars. For quasars of medium luminosity, the co-moving space density rises very steeply with redshift. Quasars of lower luminosity exhibit a slower increase of density with redshift, resulting in luminosity-dependent evolution of the space density. We also discuss evidence for a cutoff of quasar redshift and for a possible dependence of the cutoff on luminosity. We evaluate X-ray counts of quasars and show the need for negative X-ray luminosity evolution in order to explain the counts and the low average redshifts of X-ray quasars. As a consequence, the quasar contribution to the X-ray background is lower than originally suspected. We discuss other extragalac-tic contributors to the X-ray background and conclude that they, together with the quasars, contribute about 60 percent of the observed background. About half of this is contributed by active galactic nuclei with optical luminosities below those of quasars.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
Additional Information:© D. Reidel Publishing Compny 1986. This research was supported in part by the National Science Foundation under grants AST-8111754 and AST-8314134.
Funding AgencyGrant Number
Subject Keywords:Active Galactic Nucleus, Luminosity Function, Space Density, Cosmological Evolution, Seyfert Galaxy
Series Name:NATO ASI Series
Issue or Number:162
Record Number:CaltechAUTHORS:20201117-175541130
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106710
Deposited By: Rebecca Minjarez
Deposited On:18 Nov 2020 18:58
Last Modified:16 Nov 2021 18:56

Repository Staff Only: item control page