Downsizing of supermassive black holes from the SDSS quasar survey (II). Extension to z~4

TL;DR

This study analyzes SDSS quasar data to determine how the maximum mass of active black holes evolves with redshift up to z~4, revealing a significant increase during the peak quasar activity epoch.

Contribution

It extends previous analyses to higher redshifts using CIV lines, providing a comprehensive view of black hole mass evolution up to z~4.

Findings

Maximum black hole mass increases as (1+z)^{1.64} from z=0.1 to 4

Method overcomes Malmquist bias issues in mass estimation

Results include the epoch of maximum quasar activity

Abstract

Starting from the quasar sample of the Sloan Digital Sky Survey (SDSS) for which the CIV line is observed, we use an analysis scheme to derive the z-dependence of the maximum mass of active black holes, which overcomes the problems related to the Malmquist bias. The same procedure is applied to the low redshift sample of SDSS quasars for which Hbeta measurements are available. Combining with the results from the previously studied MgII sample, we find that the maximum mass of the quasar population increases as (1+z)^(1.64+/-0.04) in the redshift range 0.1<z<4, which includes the epoch of maximum quasar activity.