EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at $z\gtrsim 6$

Abstract

We expect luminous ($M_{1450}\lesssim -26.5$) high-redshift quasars to trace the highest density peaks in the early universe. Here, we present observations of four $z\gtrsim 6$ quasar fields using JWST/NIRCam in imaging and widefield slitless spectroscopy mode and report a wide range in the number of detected [OIII]-emitting galaxies in the quasars' environments, ranging between a density enhancement of $\delta \approx 65$ within a $2$ cMpc radius - one of the largest proto-clusters during the Epoch of Reionization discovered to date - to a density contrast consistent with zero, indicating the presence of a UV-luminous quasar in a region comparable to the average density of the universe. By measuring the two-point cross-correlation function of quasars and their surrounding galaxies, as well as the galaxy auto-correlation function, we infer a correlation length of quasars at $⟨z⟩=6.25$ of $r_0^{\mathrm{QQ}}=22.0_{-2.9}^{+3.0}\mathrm{cMpc}{h}^{-1}$, while we obtain a correlation length of the [OIII]-emitting galaxies of $r_0^{\mathrm{GG}}=4.1\pm 0.3\mathrm{cMpc}{h}^{-1}$. By comparing the correlation functions to dark-matter-only simulations we estimate the minimum mass of the quasars' host dark matter halos to be ${\log }_{10}(M_{\mathrm{halo},\min }/M_{\odot })=12.43_{-0.15}^{+0.13}$ (and ${\log }_{10}(M_{\mathrm{halo},\min }^{[\mathrm{OIII}]}/M_{\odot })=10.56_{-0.03}^{+0.05}$ for the [OIII]-emitters), indicating that (a) luminous quasars do not necessarily reside within the most overdense regions in the early universe, and that (b) the UV-luminous duty cycle of quasar activity at these redshifts is $f_{\mathrm{duty}}\ll 1$. Such short quasar activity timescales challenge our understanding of early supermassive black hole growth and provide evidence for highly dust-obscured growth phases or episodic, radiatively inefficient accretion rates.

ApJ accepted