EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at $z\gtrsim6$ (2403.07986v2)

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 $z\gtrsim6$ 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 $\delta\approx65$ 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 $\langle z\rangle=6.25$ of $r_0^{\rm QQ}=22.0^{+3.0}_{-2.9}~{\rm cMpc}\,h^{-1}$, while we obtain a correlation length of the [OIII]-emitting galaxies of $r_0^{\rm GG}=4.1\pm0.3~{\rm cMpc}\,h^{-1}$. By comparing the correlation functions to dark-matter-only simulations we estimate the minimum mass of the quasars' host dark matter halos to be $\log_{10}(M_{\rm halo, min}/M_\odot)=12.43^{+0.13}_{-0.15}$ (and $\log_{10}(M_{\rm halo, min}^{\rm [OIII]}/M_\odot) = 10.56^{+0.05}_{-0.03}$ 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 $f_{\rm duty}\ll1$. 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.

• The paper quantifies the quasar-galaxy clustering signal, reporting a cross-correlation length of approximately 9.1 cMpc h⁻¹ and significant environmental variation.
• It employs JWST NIRCam imaging and slitless spectroscopy to derive precise host dark matter halo masses, estimating log10(M_halo/min) ≈ 12.43.
• The study finds a low duty cycle of around 0.4% of the Hubble time, challenging existing models of early supermassive black hole growth.

Clustering of Luminous Quasars at High Redshifts: A Detailed Analysis

The paper "EIGER VI. The Correlation Function, Host Halo Mass and Duty Cycle of Luminous Quasars at $z\gtrsim6$" provides a comprehensive examination of the clustering properties of high-redshift luminous quasars ($z \gtrsim 6$). The authors utilized observations from the James Webb Space Telescope (JWST) and associated advanced analysis techniques to paper the environments of these quasars, with particular focus on their host dark matter halo masses and duty cycles.

Overview and Methodology

The paper investigates four quasar fields at redshifts greater than six, employing both imaging and widefield slitless spectroscopy using JWST's NIRCam. The goals were to assess galaxy density enhancements near quasars and to calculate two-point correlation functions from which clustering strengths can be derived. Particularly, the paper leverages data on O-emitting galaxies to provide insights into the environment of these early Universe quasars.

The methodology centers around analyzing the two-point cross-correlation function of quasars with surrounding galaxies and the auto-correlation function of galaxies themselves. The research applies state-of-the-art cosmological simulations and empirical models to interpret the clustering signals, aiming to estimate the host halo masses and duty cycles of these quasars.

Key Findings

1. Quasar Environments: The paper reveals significant variations among quasar environments. For example, one quasar, J0148+0600, resides in a highly dense environment with an estimated overdensity ($\delta$) of approximately 65 within a 2 cMpc radius—one of the most significant proto-cluster detections to date. On the other hand, J1030+0524 resides in an environment with no significant density enhancement, displaying a density contrast close to zero.
2. Correlation Functions: The quasar-galaxy cross-correlation function demonstrates a length scale of $$r_0^{\rm QG} = 9.1^{+0.5}_{-0.6} \,{\rm cMpc}\,h^{-1}$$, while the galaxy-galaxy auto-correlation function yields $r_0^{\rm GG} = 4.1 \pm 0.3 \,{\rm cMpc}\,h^{-1}$.
3. Host Dark Matter Halo Masses: By comparing observational data with simulations (notably Flamingo-10k), the research estimates the minimum halo mass for quasars as $$\log_{10}(M_{\rm halo, min}/M_\odot) = 12.43^{+0.13}_{-0.15}$$. The halo mass for O-emitters is reported as $$\log_{10}(M_{\rm halo, min}^{\rm [OIII]}/M_\odot) = 10.56^{+0.05}_{-0.03}$$.
4. Duty Cycle and Lifetime: The findings suggest a surprisingly low duty cycle, with luminous quasars being active for only about 0.4% of the Hubble time at this redshift. This indicates shorter active periods than previously thought, challenging conventional models of black hole growth, which require longer durations for consistent accretion.

Implications and Future Directions

The findings have several implications for the understanding of early supermassive black hole growth and the evolution of galaxy structures in the early Universe. The divergence in quasar environments could suggest that while some high-redshift quasars do indeed trace significant overdensities, others do not, perhaps due to differences in host halo properties or quasar activity phases.

The low duty cycle raises questions about the mechanisms governing black hole accretion in the early Universe. The results suggest either pursuit of super-Eddington accretion scenarios or an increased role for obscured, radiatively inefficient phases in quasar evolution.

Future work should continue to explore the environmental factors influencing quasar activity and investigate whether similar findings are evident with a broader range of quasar luminosities and host properties. Further observational surveys and refined simulations could yield deeper insights into the cosmological contexts of quasar activity and the role of feedback processes in galaxy evolution.