James Webb Space Telescope Feed Post

UNCOVER: The growth of the first massive black holes from JWST/NIRSpec -- spectroscopic confirmation of an X-ray luminous AGN at z=10.1 Published: 8/5/2023 3:05:44 AM Updated: 8/5/2023 3:05:44 AM

Paper abstract: The James Webb Space Telescope is now detecting early black holes (BHs) asthey transition from "seeds" to supermassive BHs. Recently Bogdan et al. (2023)reported the detection of an X-ray luminous supermassive black hole, UHZ-1,with a photometric redshift at z > 10. Such an extreme source at this very highredshift provides new insights on seeding and growth models for BHs given theshort time available for formation and growth. Harnessing the exquisitesensitivity of JWST/NIRSpec, here we report the spectroscopic confirmation ofUHZ-1 at z = 10.073 +/- 0.002. We find that the NIRSpec/Prism spectrum istypical of recently discovered z~10 galaxies, characterized primarily bystar-formation features. We see no clear evidence of the powerful X-ray sourcein the rest-frame UV/optical spectrum, which may suggest heavy obscuration ofthe central BH, in line with the Compton-thick column density measured in theX-rays. We perform a stellar population fit simultaneously to the new NIRSpecspectroscopy and previously available photometry. The fit yields a stellar massestimate for the host galaxy that is significantly better constrained thanprior photometric estimates (M* ~ 1.4 x 10^8 Msun). The resulting ratio ofM_BH/M* remains two to three orders of magnitude higher than local values, thuslending support to the heavy seeding channel for the formation of supermassiveBHs within the first billion years of cosmic evolution.