James Webb Space Telescope Feed Post

EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at z >= 6

Observations of four z>= 6 quasar fields. Top panels show the RGB images constructed from NIRCam imaging data (F115W, F200W and F356W) of each quasar field. Bottom panels show the optical and NIR spectra of the quasars observed with X-Shooter/VLT and FIRE/Magellan (J0100+2802, J0148+0600, J1030+0524), or MOSFIRE+ESI/Keck (J1148+5251). The colored data points show the redshifts and projected distances of all [O III]-emitting galaxies detected in the NIRCam grism spectra above a luminosity of L[O III],5008 = 1042 erg s-1 ; their color corresponds to their velocity offset with respect to the quasars’ redshifts and their size correlates with the logarithm of their luminosity, log10 L[O III],5008. The grey shaded area denotes the velocity interval of |?v| = vmax around the redshift of the quasar. All galaxies that fall within this velocity range are also circled in the respective RGB images to show the spatial distribution around the quasar (indicated by a red arrow). Abstract: We expect luminous (M1450?-26.5) high-redshift quasars to trace the highest density peaks in our universe, and therefore to reside in proto-clusters encompassing an abundance of galaxies in close vicinity. Here, we present observations of four z?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 d>100 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 rQQ0=21.3+2.7-2.6 cMpch-1, while we obtain a correlation length of the [OIII]-emitting galaxies of rGG0=4.2±0.1 cMpch-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 log10(Mhalo,min/M?)=12.30±0.14 (and log10(M[OIII]halo,min/M?)=10.72±0.03 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 fduty«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.