Quasar Formation and Evolution and Cosmological Constraints

Mathematics – Logic

Scientific paper

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Cosmology: General, Quasar: Formation, Evolution, Luminosity Function, Multi-Colour Selection

Scientific paper

This thesis is a contribution to the understanding of the phenomenon of quasar formation and evolution. It approaches several theoretical and observational aspects as well as the problem of the construction of large quasar samples, in the long-term aim of combining everything in a geometrical cosmological test, in order to determine the values of the cosmological parameters, Omega and Lambda. During this thesis, the V/Vmax test was applied on the Large Bright Quasar Survey sample, showing that 1) the sample was biased due to the selection criteria and 2) the (simple) Pure Luminosity Evolution law was not a good approximation for all redshifts but that it described in a good way the phenomenon of quasar evolution, up to a redshift of ~2. For these two reasons a quasar candidate selection technique, efficient at all redshifts, was established and some theoretical models on quasar formation and evolution were developed. The quasar candidate selection technique, developed for the needs of the VIRMOS (Visible and InfraRed Multi-Object Spectroscopy) project, consists in comparing the observed spectral energy distribution to the one calculated for some quasar model spectra and a series of real stellar spectra. The best fit allows the classification of an object either as a star candidate or as a quasar candidate, providing, at the same time, en estimation of the photometric redshift. For the theoretical part of this PhD, two quasar formation and evolution models have been developed. An analytical model that has been developed in collaboration with the University of Barcelona, is about to be operational. In this code, initially created in order to study the formation and evolution of galaxies, a model of accretion around the central black holes, was instroduced, inspired by the Dopita "truly Unified Model" (1997). In parallel, an analytical model was developed, that brings together the large scale structure formation theory and the phenomenon of accretion disk instabilities. The hypothesis of a linear relation between the black hole mass and the dark matter halo mass was rejected and constraints on the exponent, n, of the power spectrum, P(k), were imposed.

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