Earliest Galaxy Evolution in the CANUCS+Technicolor fields: Galaxy Properties at $z\sim10-16$ seen with the Full NIRCam Medium and Broad Band Filters

TL;DR

This study identifies galaxies at redshifts 10-16 using JWST NIRCam data, revealing moderate evolution in the UV luminosity function and emphasizing the importance of medium-band filters for accurate high-redshift galaxy characterization.

Contribution

First comprehensive analysis of $z ext{=}10 ext{-}16$ galaxies using full NIRCam medium and broad band filters, highlighting the impact of filter choice on galaxy property measurements.

Findings

Eight candidate galaxies at $z ext{=}10 ext{-}16$ identified.

UV luminosity function shows moderate evolution from $z ext{=}11$ to $z ext{=}15$.

Medium-band filters improve galaxy detection and reduce contamination.

Abstract

We present a sample of $z_{\rm phot}\sim10-16$ galaxies by exploiting one of the richest JWST NIRCam imaging data, taken in the CANUCS survey in Cycle 1 and the Technicolor (TEC) survey in Cycle 2. The combination of the CANUCS+TEC provides multi-epoch, deep NIRCam images in all medium bands (MBs) and broad bands (BBs) onboard NIRCam (22 filters in total), over $\sim23\ {\rm arcmin}^2$ in three independent lines of sight. We select high-$z$ galaxy candidates based on photometric redshifts, and obtain eight candidates at $z\sim10-16$, including a very robust candidate at $z\sim15.4$. The ultraviolet (UV) luminosity function (LF) from our sample is consistent with previous JWST studies showing a scatter of $\sim0.6$ dex across the literature, marking the significance of the field-to-field variance in interpreting galaxy abundance measurements at $z>10$. We find that the UV LF moderately evolves at $z>10$, and the LF normalization and the luminosity density decline by a factor of $\sim7$ from $z\sim11$ to $z\sim15$, indicating less steep evolution than $z<11$. We highlight the importance of MB filters, not only to minimize the contamination by low-$z$ interlopers but also to maximize the completeness. In particular, faint and less blue galaxies could be missed when the sample is built solely on BB data. The contamination and incompleteness of BB-only selected samples can bias our views of earliest galaxy evolution at $z>10$, including the UV LF by $\sim0.6$ dex, the size-magnitude relation by $\sim0.6$ dex, and the UV slope-magnitude relation by $\Delta\beta_{\rm UV}\sim-0.3$.