A Steep Decline in the Galaxy Space Density beyond Redshift 9 in the CANUCS UV Luminosity Function

Abstract

We present a new sample of 158 galaxies at redshift z > 7.5 selected from deep James Webb Space Telescope (JWST) NIRCam imaging of five widely separated sight lines in the CANUCS survey. Two-thirds of the pointings and 80% of the galaxies are covered by 12–14 NIRCam filters, including seven to nine medium bands, providing accurate photometric redshifts and robustness against low-redshift interlopers. A sample of 28 galaxies at z > 7.5 with spectroscopic redshifts shows a low systematic offset and scatter in the difference between photometric and spectroscopic redshifts. We derive the galaxy UV luminosity function at redshifts 8–12, finding a slightly higher normalization than previously seen with the Hubble Space Telescope at redshifts 8–10. We observe a steeper decline in the galaxy space density from z = 8 to 12 than found by most JWST Cycle 1 studies. In particular, we find only eight galaxies at z > 10 and none at z > 12.5, with no z > 10 galaxies brighter than F277W AB = 28 or M UV = −20 in our unmasked, delensed survey area of 53.4 arcmin2. We attribute the lack of bright z > 10 galaxies in CANUCS compared to GLASS and CEERS to intrinsic variance in the galaxy density along different sight lines. The evolution in the CANUCS luminosity function between z = 8 and 12 is comparable to that predicted by simulations that assume a standard star formation efficiency without invoking any special adjustments.

Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic Star Formation Rate Density 300 Myr after the Big Bang

“…In agreement with previous determinations of the UV luminosity function in extragalactic JWST fields (Pérez-González et al 2023a;Donnan et al 2023b;Harikane et al 2023Harikane et al , 2024Adams et al 2024;Finkelstein et al 2024;McLeod et al 2024;Willott et al 2024), we find that the luminosity function of galaxies has smoothly declined from z ∼ 8, as first established by HST observations (e.g., McLure et al 2013), to z ∼ 12. Our results for the abundance of galaxies at z ∼ 12 are in broad agreement with the literature values, as shown in Figures 16 and 17.…”

“…Shown are 16%-84% (jade-shaded region) and 2024) agree with our results, but their z ∼ 14 point lies above our constraints albeit with large uncertainties. If we extrapolate the UV luminosity evolution inferred by our model, we find good agreement with the literature measurements back to z ∼ 8 (e.g., Ishigaki et al 2018;Bouwens et al 2022;Pérez-González et al 2023a;Adams et al 2024;Willott et al 2024). Also shown in Figure 17 is the corresponding evolution in the cosmic SFR density ρ SFR , using the approximate conversion from ρ UV of κ UV = 1.15 × 10 −28 M ☉ yr −1 erg −1 s Hz from Madau & Dickinson (2014).…”