SHELLQs. Black Hole Mass and Eddington Ratio Distributions of Intermediate-Luminosity Quasars at 6

Year: 2026

Type: preprint

Abstract: We present near-infrared spectroscopy of 21 quasars at 6.07 < z < 6.90 obtained with JWST/NIRSpec and Subaru/MOIRCS. These targets have absolute ultraviolet magnitudes of -25 < M_1450 < -22 and are drawn from a sample of z>6 quasars identified in the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project. These quasars occupy the intermediate-luminosity regime between luminous quasars and the faint high-redshift AGNs uncovered by JWST. We detect broad Balmer emission lines and MgII 2798 with underlying continua from the NIRSpec and MOIRCS targets, respectively. The virial black hole masses of this sample span a wide range of 7.2 < log M_BH/M_sun < 9.4, with Eddington ratios of -1.3 < log L_bol/L_Edd < 0.4. Combining these measurements with our previous mass estimates for other SHELLQs quasars, we construct a sample of 27 quasars with M_BH estimates at 6 < z < 7 and derive the distributions of M_BH and L_bol/L_Edd. When compared with luminosity-matched quasars at z ~ 1.3, we find median offsets of delta log M_BH/M_sun = -0.4 and Delta log L_bol/L_Edd = 0.2 in the high-redshift sample. In addition, 11% of the high-redshift quasars are accreting near or above the Eddington limit. As a systematic check, adopting the Eddington-ratio-dependent calibration of single-epoch M_BH estimates increases the inferred super-Eddington fraction to 22%. These results indicate that a representative population of distant supermassive black holes undergo a rapid accretion phase, although not as extreme as that seen in the most luminous quasar population, consistent with the anti-hierarchical growth scenario of supermassive black holes.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.09266

Institutions: Waseda University, Kavli Institute for the Physics and Mathematics of the Universe, Waseda Institute for Advanced Study, Ehime University, Wuhan University, Princeton University, The University of Tokyo, National Institutes of Natural Sciences, National Astronomical Observatory of Japan, Research Center for the Early Universe, Ludwig-Maximilians-Universität München, Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Massachusetts Institute of Technology, University of Toronto, National Tsing Hua University, The Graduate University for Advanced Studies, SOKENDAI, Peking University, Max Planck Institute for Astronomy, University of Toyama, Institut de Ciències del Cosmos, Universitat de Barcelona, The University of Texas at Austin, Kagoshima University, Institute of Astronomy and Astrophysics, Academia Sinica, Academia Sinica, Nagoya University Institute for Advanced Research, Nagoya University, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Sorbonne Université, University of Michigan

Language: English

Topic: Galaxies: Formation, Evolution, Phenomena

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Aeronautics and Space Administration, Space Telescope Science Institute, Ministry of Education, Culture, Sports, Science and Technology, National Natural Science Foundation of China, Japan Society for the Promotion of Science

Awards: G103270039, Reconstruction of the climatic changes from borehole temperature and tree rings in the Kamchatka Peninsula, G1338664626, G256731684, Subaru, Euclid, and JWST reveal the formation of supermassive black holes in the cosmic dawn, Multi-scale investigation of the environments of the first supermassive black holes: from host galaxies to large-scale structure, G5568641063, Probing the origin of supermassive black holes with Subaru Telescope, JWST, and Euclid, G6877934016, G7328853082, Wide-field survey for supermassive black holes in the cosmic dawn, G89351655

OpenAlex ID: W7212143382