Space number density of bright quasars in the halo model of galaxy formation

TL;DR

This paper models the space density evolution of bright quasars within the halo model of galaxy formation, fitting observational data and estimating quasar lifetimes in a Lambda-CDM universe.

Contribution

It introduces a halo model-based approach to explain quasar number density evolution and estimates quasar lifetimes consistent with observational data.

Findings

Model fits observational data well for specific protogalaxy masses.

Estimated quasar lifetime is approximately 6 million years.

Results support the halo model within the Lambda-CDM framework.

Abstract

We analyse the redshift dependence of space number density of quasars assuming that they are the short-lived active stages of the massive galaxies and arise immediately after the collapse of homogeneous central part of protogalaxy clouds. Obtained dependence fits the observational data ChaMP+CDF+ROSAT (Silverman et al. 2005) very well for protogalaxy clouds of mass $M\approx 8\cdot 10^{11}$ $h^{-1}M_{\odot}$ and ellipticity $e<0.4$. The lifetime of bright X-ray AGNs or QSOs with $L_X>10^{44.5}$ erg$\cdot s^{-1}$ in the range of energies $0.3-8$ keV is $\tau_{QSO}\sim 6\cdot10^6$ years when the mass of supermassive black hole is $M_{SMBH}\sim 10^{9}$ $M_{\odot}$ and the values of other quasar parameters are reasonable. The analysis and all calculations were carried out in the framework of $\Lambda$CDM-model with parameters determined from 5-years WMAP, SNIa and large scale structure data (Komatsu et al. 2009). It is concluded, that the halo model of galaxy formation in the $\Lambda$CDM cosmological model matches well observational data on AGNs and QSOs number density coming from current optical and X-ray surveys.