A Search for H-Dropout Lyman Break Galaxies at z~12-16

TL;DR

This study reports the discovery of bright galaxy candidates at redshifts around 12-13, challenging existing models and suggesting a higher abundance of early universe galaxies than previously thought.

Contribution

First identification of bright z~12-13 galaxy candidates using H-dropout selection and near-infrared imaging, with tentative spectroscopic confirmation and implications for galaxy evolution models.

Findings

Candidates' number density aligns with a double power-law luminosity function.

Models fail to reproduce the bright end of UV luminosity functions at z~10-13.

Existence of star-forming galaxies at z>10 supported by observations.

Abstract

We present two bright galaxy candidates at z~12-13 identified in our H-dropout Lyman break selection with 2.3 deg2 near-infrared deep imaging data. These galaxy candidates, selected after careful screening of foreground interlopers, have spectral energy distributions showing a sharp discontinuity around 1.7 um, a flat continuum at 2-5 um, and non-detections at <1.2 um in the available photometric datasets, all of which are consistent with z>12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4sigma [OIII]88um line at z=13.27, in agreement with its photometric redshift estimate. The number density of the z~12-13 candidates is comparable to that of bright z~10 galaxies, and is consistent with a recently proposed double power-law luminosity function rather than the Schechter function, indicating little evolution in the abundance of bright galaxies from z~4 to 13. Comparisons with theoretical models show that the models cannot reproduce the bright end of rest-frame ultraviolet luminosity functions at z~10-13. Combined with recent studies reporting similarly bright galaxies at z~9-11 and mature stellar populations at z~6-9, our results indicate the existence of a number of star-forming galaxies at z>10, which will be detected with upcoming space missions such as James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.