BEACON: JWST NIRCam Pure-parallel Imaging Survey. III. Constraints on the Ultraviolet Luminosity Function and the Clustering of z ~ 7-14 Galaxies
October 2026 • 2026ApJ..1009..134K
Abstract • The James Webb Space Telescope (JWST) has extended the frontier of galaxy detection to redshifts z > 11, finding a high abundance of UV-bright sources that challenge theoretical models. However, most current results come from just a few fields, introducing uncertainties due to cosmic variance. Here, we constrain z ~ 7--14 UV luminosity functions (LFs) over ~400 arcmin2 across 36 independent sight lines from Data Release 2 of BEACON, a JWST pure-parallel NIRCam multiband imaging survey. We identify 164 7 < z < 12 galaxy candidates: 150 F090W, 14 F115W, and no robust F150W dropouts. In the 11 pointings overlapping with public JWST spectroscopy, we find no contaminants, indicating a high purity in our sample. Our z ~ 7.5 UV LF agrees with previous bright-end measurements but yields lower number densities at -21 <= MUV <= -19. At z ~ 10, our measurements are lower than most photometric JWST results but match spectroscopic constraints, consistent with the high purity of our selection. The LFs at z ~ 7.5 and 10 are consistent with pre-JWST models, while our limits at z > 13 do not rule out a possible excess. We measure significant clustering of bright (MUV < -20.5) galaxies at 7 < z < 10. Fields hosting such sources are approximately 3 times more likely to be overdense relative to the full survey, implying that UV-bright galaxies preferentially reside in the most massive halos at these redshifts. Comparing with seminumerical simulations, we estimate that MUV < -20.5 galaxies inhabit halos ~0.8 dex less massive at z ~ 11 than at z ~ 8, consistent with a shift to higher star formation rates. However, their observed clustering exceeds predictions from pre-JWST luminosity--halo mass relations, suggesting these sources reside in more massive halos than previously modelled and/or multiple halo occupation.
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