Identification and photometric redshifts for type-I quasars with medium- and narrow-band filter surveys

• Autor(a) principal: Silva, Carolina Queiroz de Abreu
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06012016-185554/
• topic: AGNs; AGNs; Bayesian statistics; Cosmologia; Cosmology; Estatística Bayesiana; J-PAS; J-PAS; Quasares; Quasars

Quasars are valuable sources for several cosmological applications. In particular, they can be used to trace some of the heaviest halos and their high intrinsic luminosities allow them to be detected at high redshifts. This implies that quasars (or active galactic nuclei, in a more general sense) have a huge potential to map the large-scale structure. However, this potential has not yet been fully realized, because instruments which rely on broad-band imaging to pre-select spectroscopic targets usually miss most quasars and, consequently, are not able to properly separate broad-line emitting quasars from other point-like sources (such as stars and low resolution galaxies). This work is an initial attempt to investigate the realistic gains on the identification and separation of quasars and stars when medium- and narrow-band filters in the optical are employed. The main novelty of our approach is the use of Bayesian priors both for the angular distribution of stars of different types on the sky and for the distribution of quasars as a function of redshift. Since the evidence from these priors convolve the angular dependence of stars with the redshift dependence of quasars, this allows us to control for the near degeneracy between these objects. However, our results are inconclusive to quantify the efficiency of star-quasar separation by using this approach and, hence, some critical refinements and improvements are still necessary.