Absence of spectroscopically confirmed galaxies beyond redshift 14.5

Determine why no galaxy beyond approximately redshift 14.5 has yet been spectroscopically confirmed, distinguishing observational limitations from a possible drastic change in the properties of galaxies at higher redshift.

Background

MoM-z14 at redshift 14.44 is identified as the most distant confirmed galaxy known in the paper, while several candidates at higher redshift remain unconfirmed or have been identified as lower-redshift interlopers.

The authors explicitly frame the absence of confirmed galaxies beyond this record as an unresolved question. They distinguish two possibilities: insufficient spectroscopic follow-up and target faintness on the observational side, or a genuine rapid change in galaxy properties at earlier cosmic times.

References

The most intriguing question is why we have not (yet) confirmed any galaxy beyond $z\sim 14.5$ (the current record holder is MoM-z14 at $z=14.44$; \citealt{Naidu2025}), despite the presence of relatively bright galaxies up to this redshift and the high success rate of spectroscopic confirmation for candidates up to this redshift. Is this a purely observational limitation, due to the small number of spectroscopic follow-up observations and the faintness of the targets, or does it signal a drastic change in galaxy properties?

— Too many or too bright? Status and perspectives in the study of the UV Luminosity Function at z>10  (2610.12121 - Fontana et al., 8 Oct 2026) in Section 1, Introduction