TY - JOUR
T1 - Demographics of z ∼ 6 quasars in the black hole mass–luminosity plane
AU - Wu, Jin
AU - Shen, Yue
AU - Jiang, Linhua
AU - Bañados, Eduardo
AU - Fan, Xiaohui
AU - Ho, Luis C.
AU - Vestergaard, Marianne
AU - Wang, Feige
AU - Wang, Shu
AU - Wu, Xue Bing
AU - Yang, Jinyi
N1 - Funding Information:
We thank the anonymous referee for useful comments that improved the manuscript, C. Willott and Y. Matsuoka for providing the selection functions in the CFHQS and SHELLQs surveys, and W. He for helpful discussions. We acknowledge support from the National Key R&D Program of China (2016YFA0400703), the National Science Foundation of China (11721303, 11890693), and the science research grants from the China Manned Space Project with NO. CMSCSST-2021-A05. YS acknowledges support from NSF grants AST-1715579 and AST-2009947. MV gratefully acknowledges financial support from the Independent Research Fund Denmark via grant number DFF 8021-00130. FW thanks the support provided by NASA through the NASA Hubble Fellowship grant #HF2-51448 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.
Publisher Copyright:
© 2022 The Author(s)
PY - 2022/12/1
Y1 - 2022/12/1
N2 - 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 MBH > 108.5 M, with a median 1σ uncertainty of ∼0.5 dex in abundance. The intrinsic Eddington ratio distribution of MBH > 108.5 M quasars can be approximated by a mass-dependent Schechter model, with a broad peak around log (Lbol/LEdd) ∼ −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.
AB - 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 MBH > 108.5 M, with a median 1σ uncertainty of ∼0.5 dex in abundance. The intrinsic Eddington ratio distribution of MBH > 108.5 M quasars can be approximated by a mass-dependent Schechter model, with a broad peak around log (Lbol/LEdd) ∼ −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.
KW - galaxies: active
KW - methods: statistical
KW - quasars: supermassive black holes
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U2 - 10.1093/mnras/stac2833
DO - 10.1093/mnras/stac2833
M3 - Article
AN - SCOPUS:85145263804
SN - 0035-8711
VL - 517
SP - 2659
EP - 2676
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -