ASPIRE: The Environments and Dark Matter Halos of Luminous Quasars in the Epoch of Reionization

Abstract We present a systematic study of the environments of 25 luminous quasars at z > 6.5 from the ASPIRE program. Using JWST/NIRCam wide-field slitless spectroscopy data, we identified 487 galaxies at 5.3 ≲ z ≲ 7.0 exhibiting [O iii ] emission. Among these, 122 [O iii ] emitters lie within ∣Δ v los ∣ < 1000 km s −1 of the quasars, corresponding to a ∼9.4-fold enhancement relative to the average galaxy density at other redshifts. Furthermore, we identified 16 [C ii ]-emitting galaxies at the quasar redshifts from Atacama Large Millimeter/submillimeter Array (ALMA) mosaic observations. A cross-correlation function analysis between quasars and [O iii ]+[C ii ] emitters yields a cross-correlation length of r 0 QG = 8.6 8 − 0.55 + 0.51 h − 1 cMpc and an autocorrelation of r 0 QQ = 15.7 6 − 2.70 + 2.48 h − 1 cMpc , indicating that z ∼ 7 quasars reside in dark matter halos with M halo = 1 0 12.2 7 − 0.26 + 0.21 M ⊙ and have a quasar lifetime of t Q = 1 0 7.05 − 1.01 + 0.95 yr . Notably, the number of [O iii ]-emitting galaxies at quasar redshifts varies significantly from field to field, ranging from 0 to 20, highlighting a diverse quasar environment. Remarkably, seven quasars trace significant galaxy overdensities (i.e., protoclusters), with δ gal > 5 within a volume of V ∼ 500 cMpc 3 . We also find that ∣Δ v los ∣ increases rapidly toward smaller galaxy–quasar separations in protocluster fields, consistent with galaxy kinematics around extremely massive halos in cosmological simulations. By combining JWST and ALMA data, we reveal the complex and diverse environments of these early quasars, providing robust evidence that the earliest luminous quasars are effective tracers of galaxy overdensiti