A Comprehensive JWST/NIRSpec Census of Broad-Line Active Galactic Nuclei: Faint, Tiny, but Highly Accreting Sources in the Remote Universe

TL;DR

This study uses JWST/NIRSpec data to identify and analyze 252 broad-line AGNs across a wide redshift range, revealing that high-redshift BLAGNs are faint, low-mass, yet highly accreting, shedding light on early black hole growth.

Contribution

First comprehensive JWST/NIRSpec survey of BLAGNs from z=0.8 to 7.2, including 171 new sources, demonstrating their properties and growth during early cosmic epochs.

Findings

High-redshift BLAGNs are fainter and less massive than low-redshift counterparts.

Most high-redshift BLAGNs have Eddington ratios between 0.1 and 1.0.

Detection rate of BLAGNs remains consistent across redshifts.

Abstract

We present a sample of 252 broad-line Active Galactic Nuclei (BLAGNs), incorporating 171 newly identified sources, spanning a redshift interval from $z$ = 0.8 to 7.2. We have analyzed spectroscopic data from the NIRSpec instrument aboard the James Webb Space Telescope, using the G140H, G140M, G235H, G235M, G395H, and G395M gratings to survey N $\sim$ 80,000 galaxies for BLAGNs. Through emission-line fitting, using a sum of Gaussian models for {H$\alpha$}, {H$\beta$}, [N II] $\lambda\lambda6548, 6584$, and [O III] $ \lambda\lambda4959, 5007$, we separate AGN broad-line components from narrow-line emission. We find the detection rate of BLAGNs to be relatively consistent across our redshift range. Compared to typical low-$z$ AGNs ($z$ $\lesssim$ 1), the high-$z$ BLAGNs are systematically fainter and less massive, yet they accrete more efficiently, with most showing Eddington ratios between 0.1 and 1.0. This confirms the rapid black hole growth during the early cosmic epochs. The detection of faint, low-mass BLAGNs at high redshift also helps bridge the observational gap between local supermassive black holes and remote luminous quasars, providing a more complete view of black hole-galaxy coevolution across cosmic time.