Evolution of the Quasar Distribution, Cosmology, and the Accretion Disk Model of AGN.
Abstract
The relationship between the observed statistical distribution of extragalactic objects, the physical evolution of individual objects, and the cosmological model is discussed. Three simple forms of statistical evolutionpure luminosity evolution (PLE), pure density evolution (PDE), and generalized luminosity evolution (GLE)are discussed in detail and it is shown that these evolutions imply specific forms of physical evolution. Parametric and nonparametric analyses of the redshift luminosity distribution for combined samples are developed. The parametric method relies on the moments of the data and can simultaneously determine the evolution of the distribution and the cosmological parameters based on a minimum number of assumptions. The nonparametric method determines the shape of the distribution assuming a cosmological model. The nonparametric method is modified to produce smooth distributions instead of histogram distributions which are sensitive to random fluctuations in the data. Both methods are applied to a combined sample of 265 QSO's with 0.2 < z < 2.2 and B < 21.1. It is found that PLE and PDE are inconsistent with the data, independent of the choice of cosmological model. GLE may be an adequate description with luminosity evolution of the form L ~ exp (tau /0.12) where tau is the fractional lookback time, and density decreasing with redshift. QSO physical evolution is predicted using the massive black hole accretion disk model. It is shown that PLE and GLE require a steepening of the UV spectral index, alpha_{rm UV}, with redshift, if this spectral region is dominated by thermal emission from a hot accretion disk. With reasonable assumptions about the mass accretion rate and initial mass distribution, the statistical evolution may be predicted. It is shown that the spectral steepening may be the cause of the well known kink or break in the slope observed in the quasar luminosity function and that the characteristic double power law shape of the QSO luminosity function is predicted by the accretion disk model.
 Publication:

Ph.D. Thesis
 Pub Date:
 1990
 Bibcode:
 1990PhDT.........8C
 Keywords:

 Physics: Astronomy and Astrophysics;
 Accretion Disks;
 Active Galactic Nuclei;
 Astronomical Models;
 Cosmology;
 Mass Distribution;
 Quasars;
 Statistical Distributions;
 Black Holes (Astronomy);
 Histograms;
 Luminosity;
 Red Shift;
 Spectral Bands;
 Thermal Emission;
 Ultraviolet Spectra;
 Astrophysics