We investigate the black hole mass function at z ∼5 using XQz5, our recent sample of the most luminous quasars between the redshifts 4.5 < z < 5.3. We include 72 quasars with black hole masses estimated from velocity-broadened emission-line measurements and single-epoch virial prescriptions in the footprint of a highly complete parent survey. The sample mean Eddington ratio and standard deviation is log λ ≈ -0.20 ± 0.24. The completeness-corrected mass function is modelled as a double power law, and we constrain its evolution across redshift assuming accretion-dominated mass growth. We estimate the evolution of the mass function from z = 5-4, presenting joint constraints on accretion properties through a measured dimensionless e-folding parameter, kef
CITATION STYLE
Lai, S., Onken, C. A., Wolf, C., Bian, F., & Fan, X. (2024). Supermassive black holes are growing slowly by z∼5. Monthly Notices of the Royal Astronomical Society, 531(2), 2245–2261. https://doi.org/10.1093/mnras/stae1301
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