We present a new sample of 158 galaxies at redshift z>7.5 selected from deep \jwst\ NIRCam imaging of five widely-separated sightlines in the CANUCS survey. Two-thirds of the pointings and 80\% of the galaxies are covered by 12 to 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 to 12, finding a slightly higher normalization than previously seen with \hst\ at redshifts 8 to 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 MUV=−20 in our unmasked, delensed survey area of 53.4 square arcminutes. 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 sightlines. 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.
@article{arxiv.2311.12234,
title = {A Steep Decline in the Galaxy Space Density Beyond Redshift 9 in the CANUCS UV Luminosity Function},
author = {Chris J. Willott and Guillaume Desprez and Yoshihisa Asada and Ghassan T. E. Sarrouh and Roberto Abraham and Maruša Bradač and Gabe Brammer and Vince Estrada-Carpenter and Kartheik G. Iyer and Nicholas S. Martis and Jasleen Matharu and Lamiya Mowla and Adam Muzzin and Gaël Noirot and Marcin Sawicki and Victoria Strait and Gregor Rihtaršič and Sunna Withers},
journal= {arXiv preprint arXiv:2311.12234},
year = {2024}
}