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

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 μm, a flat continuum at 2-5 μm, and nondetections at <1.2 μm in the available photometric data sets, all of which are consistent with a z > 12 galaxy. An ALMA program targeting one of the candidates shows a tentative 4σ [O III] 88 μm 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 the James Webb Space Telescope, Nancy Grace Roman Space Telescope, and GREX-PLUS.