The Demographics of Broad Line Quasars in the Mass-Luminosity Plane II. Black Hole Mass and Eddington Ratio Functions

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We employ a flexible Bayesian technique to estimate the black hole mass and Eddington ratio functions for Type 1 (i.e., broad line) quasars from a uniformly-selected data set of ~58,000 quasars from the SDSS DR7.

• We find that the SDSS becomes significantly incomplete at M_{BH} < 3 x 10^8 M_{Sun} or L / L_{Edd} < 0.07, and that the number densities of Type 1 quasars continue to increase down to these limits.
• Both the mass and Eddington ratio functions show evidence of downsizing, with the most massive and highest Eddington ratio black holes experiencing Type 1 quasar phases first, although the Eddington ratio number densities are flat at z < 2.
• We estimate the maximum Eddington ratio of Type 1 quasars in the observable Universe to be L / L_{Edd} ~ 3.