Resolving the black hole sphere of influence in a hyper-luminous obscured quasar at redshift 4.6

2025/04/18 by Mai Liao, Liao, Mai, Roberto J. Assef +37
Physics and Astronomy · #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #astro-ph.GA

paper · pdf · doi:10.48550/arxiv.2504.13409

96 pages, 43 figures, 7 tables, resubmitted, comments welcome

arxiv created 2026/07/29 · arxiv updated 2026/07/30

Abstract

Supermassive black holes (SMBHs) imprint gravitational signatures on the matter within their sphere of influence (SoI). Nuclear gas dynamics can hence be used to accurately measure the mass of an SMBH, yet such measurements remain elusive in the early Universe. We report the first dynamical measurement of an SMBH mass at z > 2, based on high spatial resolution observations of the [C II]157.7um and CO (12-11) 216.93um emission lines that resolve the SoI in an obscured quasar at z = 4.6. The radial profile of the velocity dispersion reveals a clear Keplerian rise, requiring the presence of an approximately 6 × 10⁹~\rm M_\odot SMBH. We propose that obscured quasarsallow tracers like [C II] to survive in the inner regions, and may be ideal targets for increasing dynamical SMBH mass estimates in the early Universe.

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