A Candidate for the Least-massive Black Hole in the First 1.1 Billion Years of the Universe

We report a candidate of a low-luminosity active galactic nucleus (AGN) at z = 5 that was selected from the first near-infrared images of the JWST CEERS project. This source, named CEERS-AGN-z5-1 at absolute 1450 angstrom magnitude M (1450) = -19.5 +/- 0.3, was found via a visual selection of compact sources from a catalog of Lyman break galaxies at z > 4, taking advantage of the superb spatial resolution of the JWST/NIRCam images. The 20 photometric data available from CFHT, Hubble Space Telescope, Spitzer, and JWST suggest that the continuum shape of this source is reminiscent of that for an unobscured AGN, and there is a clear color excess in the filters where the redshifted H beta+[O iii] and H alpha are covered. The estimated line luminosity is L (H beta+[O III]) = 10(43.0) erg s(-1) and L (H alpha ) = 10(42.9) erg s(-1) with the corresponding rest-frame equivalent width EWH beta+[O III] = 1100 angstrom and EWH alpha = 1600 angstrom, respectively. Our spectral energy distribution fitting analysis favors the scenario that this object is either a strong broad-line emitter or even a super-Eddington accreting black hole (BH), although a possibility of an extremely young galaxy with moderate dust attenuation is not completely ruled out. The bolometric luminosity, L (bol) = 2.5 +/- 0.3 x 10(44) erg s(-1), is consistent with those of z < 0.35 broad-line AGNs with M (BH) similar to 10(6) M (circle dot) accreting at the Eddington limit. This new AGN population in the first 1.1 billion years of the universe may close the gap between the observed BH mass range at high redshift and that of BH seeds. Spectroscopic confirmation is awaited to secure the redshift and its AGN nature.

Automated summary

We report the discovery of a low-luminosity active galactic nucleus (AGN) candidate at a redshift of z = 5 using the near-infrared images from the JWST CEERS project. This AGN, named CEERS-AGN-z5-1, was identified as a compact source in a catalog of Lyman break galaxies at z > 4, taking advantage of the high spatial resolution of the JWST/NIRCam images. Photometric data from various telescopes suggest that CEERS-AGN-z5-1 has the properties of an unobscured AGN, with clear signs of emission lines and a high bolometric luminosity.