A first look at quasar-galaxy clustering at $z\simeq 7.3$

Abstract

We present JWST observations of the environments surrounding two high-redshift quasars, J0252$-$0503 at $z=7.0$ and J1007$+$2115 at $z=7.5$, which enable the first constraints on quasar-galaxy clustering at $z\sim 7.3$. Galaxies in the vicinity of the quasars are selected through ground-based and JWST/NIRCam imaging and then spectroscopically confirmed with JWST/NIRSpec using the multi-shutter assembly (MSA). Over both fields, we identified 51 $z>5$ galaxies, of which eight are found within a $\hat{I}”v_{\text{LOS}}=\pm 1500\mathrm{km}{\mathrm{s}}^{-1}$ line-of-sight velocity window from the quasars and another eight in the background. The galaxy J0252\_8713, located just $7\mathrm{pkpc}$ and $\hat{I}”v_{\text{LOS}}\approx 360\mathrm{km}{\mathrm{s}}^{-1}$ from quasar J0252$-$0503, emerges as a compelling candidate for one of the most distant quasar-galaxy mergers. Combining the galaxy discoveries over the two fields, we measure the quasar-galaxy cross-correlation and obtain a correlation length of $r_0^{\mathrm{QG}}\approx 7.6_{-1.6}^{+1.7}{h}^{-1}\mathrm{cMpc}$, based on a power-law model with a fixed slope of ${\hat{I}}_{\mathrm{QG}}^3=2.0$. Under the assumption that quasars and galaxies trace the same underlying dark matter density fluctuations, we infer a minimum dark matter halo mass for $z\simeq 7.3$ quasars of ${\log }_{10}(M_{\text{halo, min}}/{\text{M}}_{\odot })=11.6_{-0.7}^{+0.6}$ in a halo model framework. Compared to measurements from EIGER at $⟨z⟩=6.25$ and ASPIRE at $⟨z⟩=6.7$ (where ${\log }_{10}(M_{\text{halo, min}}/{\text{M}}_{\odot })\gtrsim 12.3$), our clustering results provide tentative evidence for a non-monotonic redshift evolution of quasar clustering properties. We further estimate a quasar duty cycle of $f_{\mathrm{duty}}\approx 0.05\%$, consistent with constraints from quasar proximity zones and IGM damping wings. (abridged)

16 pages, 7+2 figures; accepted by A&A