Demographics of z ∼ 6 quasars in the black hole mass-luminosity plane

Jin Wu, Yue Shen, Linhua Jiang, Eduardo Bañados, Xiaohui Fan, Luis C Ho, Marianne Vestergaard, Feige Wang, Shu Wang, Xue-Bing Wu, Jinyi Yang

Research output: Contribution to journalArticlepeer-review

Abstract

We study the demographics of z ∼ 6 broad-line quasars in the black hole (BH) mass–luminosity plane using a sample of more than 100 quasars at 5.7 < z < 6.5. These quasars have well-quantified selection functions and nearly one-third of them also have virial BH masses estimated from near-IR spectroscopy. We use forward modelling of parametrized intrinsic distributions of BH masses and Eddington ratios, and account for the sample flux limits and measurement uncertainties of the BH masses and luminosities. We find significant differences between the intrinsic and observed distributions of the quantities due to measurement uncertainties and sample flux limits. There is also marginal evidence that the virial BH masses are susceptible to a positive luminosity-dependent bias (BH mass is overestimated when luminosity is above the average), and that the mean Eddington ratio increases with BH mass. Our models provide reliable constraints on the z ∼ 6 BH mass function at M BH > 10 8.5 M, with a median 1σ uncertainty of ∼0.5 dex in abundance. The intrinsic Eddington ratio distribution of M BH > 10 8.5 M quasars can be approximated by a mass-dependent Schechter model, with a broad peak around log (L bol/L Edd) ∼ −0.9. We also find that, at 4.5 ≾ z ≾ 6, the number densities of more massive BHs tend to decline more rapidly with increasing redshift, contrary to the trend at 2.5 ≾ z ≾ 4.5 reported previously.

Original languageEnglish (US)
Pages (from-to)2659-2676
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Volume517
Issue number2
Early online dateOct 4 2022
DOIs
StatePublished - Dec 1 2022

Keywords

  • galaxies: active
  • methods: statistical
  • quasars: supermassive black holes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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