The Bright-end Galaxy Candidates at z ∼ 9 from 79 Independent HST Fields

Abstract

We present a full data analysis of the pure-parallel Hubble Space Telescope ( HST ) imaging observations in the Brightest of Reionizing Galaxies Survey (BoRG[z9]) in Cycle 22. The medium-deep exposures with five HST /WFC3IR+UVIS filter bands from 79 independent sightlines (∼370 arcmin 2 ) provide the least biased determination of number density for z  ≳ 9 bright galaxies against cosmic variance. After a strict two-step selection for candidate galaxies, including dropout color and photometric redshift analyses, and revision of previous BoRG candidates, we identify one source at z  ∼ 10 and two sources at z  ∼ 9. The z  ∼ 10 candidate shows evidence of line-of-sight lens magnification ( μ  ∼ 1.5), yet it appears surprisingly luminous ( mag), making it one of the brightest candidates at known (∼0.3 mag brighter than the z  = 8.68 galaxy EGSY8p7, spectroscopically confirmed by Zitrin and collaborators). For z  ∼ 9 candidates, we include previous data points at fainter magnitudes and find that the data are well fitted by a Schechter luminosity function with , mag, and Mpc −3 mag −1 , for the first time without fixing any parameters. The inferred cosmic star formation rate density is consistent with unaccelerated evolution from lower redshift.