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

TL;DR

ASPIRE delivers the first statistically robust view of the environments of $z>6.5$ quasars by combining JWST/NIRCam WFSS [OIII] surveys (487 emitters across 25 fields) with coordinated ALMA [CII] observations (15–17 candidates), enabling a quasar–galaxy cross-correlation analysis. The measured cross-correlation length $r_0^{QG}$ is $8.68^{+0.51}_{-0.55}$ h$^{-1}$ cMpc (fixed slope $\ \gamma_{QG}=2.0$) and $12.20^{+3.47}_{-2.30}$ h$^{-1}$ cMpc when the slope is free, implying quasar host halos with $\log(M_{halo,min}/M_\odot)=12.27^{+0.21}_{-0.26}$. The auto-correlation of quasars is $r_0^{QQ}=15.76^{+2.48}_{-2.70}$ h$^{-1}$ cMpc, and seven protocluster fields ($δ_{gal,[OIII]}>5$) reveal substantial field-to-field variance and complex, filamentary structures with $|v_{los}|$ up to $\sim800$ km s$^{-1}$. Overall, ASPIRE shows that the earliest luminous quasars trace massive overdensities at $z\sim7$ but with pronounced environmental diversity, offering key constraints on SMBH growth pathways and the relation between quasars and their host galaxies during 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 WFSS data, we identified 487 galaxies at $5.3 \lesssim z \lesssim 7.0$ exhibiting [OIII] emission. Among these, 122 [OIII] emitters lie within $|Δv_{\rm los}| < 1000~{\rm km~s^{-1}}$ of the quasars, corresponding to a $\sim9.4$-fold enhancement relative to the average galaxy density at other redshifts. Furthermore, we identified 16 [CII]-emitting galaxies at the quasar redshifts from ALMA mosaic observations. A cross-correlation function (CCF) analysis between quasars and [OIII]+[CII] emitters yields a cross-correlation length of $r_0^{\rm QG} = 8.68^{+0.51}_{-0.55}~h^{-1}~\mathrm{cMpc}$ and a auto-correlation of $r_0^{\rm{QQ}}=15.76^{+2.48}_{-2.70}~h^{-1}~{\rm cMpc}$, indicating that $z \sim 7$ quasars reside in dark matter halos with $M_{\rm halo} = 10^{12.27^{+0.21}_{-0.26}}~M_\odot$. Notably, the number of [OIII]-emitting galaxies at quasar redshifts varies significantly from field to field, ranging from zero to twenty, highlighting a diverse quasar environment. Remarkably, seven quasars trace significant galaxy overdensities (i.e., protoclusters), with $δ_{\rm gal} > 5$ within a volume of $V \sim 500~{\rm cMpc^3}$. We also find that $|Δv_{\rm los}|$ 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 overdensities, albeit with substantial field-to-field variation.

Figures (18)

• Figure 1: The redshift and absolute magnitude distribution of ASPIRE quasars. We selected a flux-limited sample of 25 quasars at $6.5<z\lesssim6.8$ with $M_{1450}<-25.0$ (orange asterisks). To ensure all ASPIRE quasars can be observed with ALMA, we excluded known quasars with $\rm Decl. > 30^\circ$. This sample also includes a radio-loud quasar (red asterisk, $z=6.82$). The triangles denote three quasars satisfy our luminosity cut but were published after JWST Cycle 1 proposal deadline and therefore were not included in ASPIRE.
• Figure 2: ASPIRE NIRCam dither pattern. We used 3-point INTRAMODULEX primary dither pattern with two sub-pixel dithers at each primary positions for ASPIRE observations except for J0910--0414. The orange lines highlight the WFSS dithers, while the blue lines highlight the dithers for short wavelength channel observations with F200W filter. The red lines denote the direct imaging and the out-of-field imaging dithers with F356W filter. The magenta circle on module A highlights the position of the quasar J0109--3047. The background image is the calibrated F356W image of this quasar field.
• Figure 3: The average 5$\sigma$ limiting magnitudes measured in 0.32 apertures for each ASPIRE field. These are measured by placing 1000 random apertures across each NIRCam mosaic image (including both module A and module B) and measuring the median absolute deviation of flux measured in the fixed aperture size.
• Figure 4: ALMA mosaic pattern. We used a 23-pointings ALMA mosaic observation to cover a $\sim1.3$ arcmin$^2$ sky area (highlighted by red circles) for each quasar field. This region falls into the full wavelength coverage footprint of the NIRCam module A slitless spectroscopic observation (blue shaded region). Note that the actual NIRCam observations have different position angles for different fields, while all ALMA mosaic were observed at position angle zero. The black cross marks the position of the central quasar.
• Figure 5: [O3] emitter searching strategy. The left panel shows the [O3] emitter detection algorithm based on 1D spectra, while the right panel illustrates the algorithm based on 2D spectra. We visually inspected all [O3] emitter candidates identified by both algorithms and compiled the final [O3] emitter catalog.