The nature of low-luminosity AGNs discovered by JWST based on clustering analysis: progenitors of low-z quasars?

Abstract

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 27 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 the angular and projected cross-correlation functions, we find that their typical DMH mass is log (Mhalo/h-1M⊙) = 11.46-0.25+0.19, and 11.53-0.20+0.15, respectively. This result implies that the host DMHs of these AGNs are ~1 dex smaller than those of luminous quasars. The DMHs of the JWST AGNs at 5 < z < 6 are predicted to grow to 1012-13h-1M⊙ at z ≲ 3, which is comparable to that of a more luminous quasar at the same epoch. Applying the empirical stellar-to-halo mass ratio to the measured DMH mass, we evaluate their host stellar mass as (M*M⊙)=9.48-0.41+0.31 and 9.60-0.33+0.24, which are higher than some of those estimated by the SED fitting. We also evaluate their duty cycle as fduty=0.37-0.15+0.19 per cent, corresponding to ~4/times 106 yr as the lifetime of the JWST AGNs. While we cannot exclude the possibility that the JWST AGNs are simply low-mass type-1 quasars, these results suggest that the JWST AGNs are a different population from type-1 quasars and the progenitors of quasars at z ≲ 3.