NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Quasar number density evolutionA simple model of quasar number density evolution is presented based on the occurrence of quasar-like radio galaxies (i.e., strong optical emission lines and type 2 radio morphology) exclusively in regions of low galaxy and intergalactic medium (IGM) density. This suggests a limit for the IGM density of 10 to the -4th (+ or - 1) per cu cm below which quasars are allowed to form and above which they are not allowed. In the recent past (z not greater than 1), the inferred quasar environments are the outskirts of clusters and near the centers of groups of galaxies. However, models of rich cluster evolution consistent with current X-ray observations predict gas densities of less than 10 to the -4th per cu cm in cluster cores in the more distant past (z between 1 and 5). This suggests that quasars were allowed to form in the cores of rich clusters at those epochs, which explains both the rich absorption spectra of high-redshift quasars and the absence of clusters surrounding quasars at lower redshift.
Document ID
19810050774
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Stocke, J. T.
(Steward Observatory Tucson, Ariz., United States)
Perrenod, S. C.
(Kitt Peak National Observatory Tucson, Ariz., United States)
Date Acquired
August 11, 2013
Publication Date
April 15, 1981
Publication Information
Publication: Astrophysical Journal
Subject Category
Astrophysics
Accession Number
81A35178
Funding Number(s)
CONTRACT_GRANT: NAS8-33351
Distribution Limits
Public
Copyright
Other

Available Downloads

There are no available downloads for this record.
No Preview Available