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

Abstract

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 $5\lt z\lt 6$ 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 $\log (M_{\mathrm{halo}}/h^{-1}\, \mathrm{M_\odot }) = 11.46_{-0.25}^{+0.19},$ and $11.53_{-0.20}^{+0.15}$, respectively. This result implies that the host DMHs of these AGNs are ${\sim} 1$ dex smaller than those of luminous quasars. The DMHs of the JWST AGNs at $5\lt z\lt 6$ are predicted to grow to $10^{12-13}\, h^{-1}\, \mathrm{M_\odot }$ at $z\lesssim 3$, 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 $\log (M_*/\mathrm{M_\odot })=9.48_{-0.41}^{+0.31},$ 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 $f_{\mathrm{duty}}=0.37_{-0.15}^{+0.19}$ per cent, corresponding to ${\sim} 4\times 10^6$ 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 $z\lesssim 3$.

Topics & Concepts