Reasons from Physical Considerations why the Evolution of Quasars is Probably not Pure Luminosity Evolution

Details Reasons from Physical Considerations why the Evolution of Quasars is Probably not Pure Luminosity Evolution Reasons from Physical Considerations why the Evolution of Quasars is Probably not Pure Luminosity Evolution

Sep 1989

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1989baas...21.1226g&link_type=abstract

Bulletin of the American Astronomical Society, Vol. 21, p.1226-1226

Mathematics

Probability

Scientific paper

The significance of three recent observational results pertaining to AGNs is considered in term of accretion disk models. The results are (i) the Dibai mass-luminosity relationship, (ii) the luminosity independence of the shape of the UV spectrum, and (iii) the correlation between the luminosities of AGNs and their host galaxies. All three are shown to be incompatible with pure luminosity evolution in an accretion-disk model. "Statistical Density Evolution" (SDE), where AGNs always radiate at a luminosity proportional to their mass when they are "on", but have a probability of being "on" which is a function of mass and cosmic epoch, is offered as a solution to the observational constraints. A physical model giving such evolution is suggested. The accretion has to be self-limiting to a rate close to the Eddington limit. The gas accreted is identified with the BLR gas. The ubiquity of BLRs and the constancy of their covering factors suggest that the BLR is generated by the AGN, probably by stimulated mass loss from the stars. The instability provided by the feedback provides an abrupt cutoff mechanism when the fuel supply runs low. The trigger to start or restart the AGN is probably an input of gas to the nucleus. Encounters with companions galaxies probably provide this.

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