James Webb Space Telescope Feed Post

Harvard ADS: The nature of low-luminosity AGNs discovered by JWST at 5 < z < 6 based on clustering analysis: ancestors of quasars at z\lesssim3?

Paper abstract: James Webb Space Telescope (JWST) has discovered many faint AGNs at high-z by detecting their broad Balmer lines. However, their high number density, lack of X-ray emission, and overly high black hole masses with respect to their host stellar masses suggest that they are a distinct population from general type-1 quasars. Here, we present clustering analysis of 28 low-luminosity broad-line AGNs found by JWST (JWST AGNs) at 5 < z < 6 based on cross-correlation analysis with 679 photometrically-selected galaxies to characterize their host dark matter halo (DMH) masses. From angular and projected cross-correlation functions, we find that their typical DMH mass is \log (M_\mathrm{halo}/h^{-1}\mathrm{M}_\odot) = 11.61_{-0.24}^{+0.19}, and 11.72_{-0.20}^{+0.17}, respectively. This result implies that the host DMHs of these AGNs are ~1 dex smaller than that of luminous quasars. The DMHs of JWST AGNs at 5 < z < 6 are predicted to grow to 10^{12\unicode{x2013}13}\,h^{-1}\mathrm{M}_\odot, a typical mass of quasar at z<~3. Applying the empirical stellar-to-halo mass ratio to the measured DMH mass, their host stellar mass is evaluated as \log(M_*/\mathrm{M}_\odot)=9.72_{-0.39}^{+0.31}, and 9.90_{-0.33}^{+0.27}, which are higher than some of those estimated by the SED fitting. We also evaluate their duty cycle as f_\mathrm{duty}=0.36_{-0.14}^{+0.18} per cent, namely ~7\times10^6 yr as the lifetime of JWST AGNs. While we cannot exclude the possibility that JWST AGNs are simply low-mass type-1 quasars, these results suggest that JWST AGNs are a different population from type-1 quasars, and may be the ancestors of quasars at z<~3.