2023ApJ...955...13B

We report the discovery of four galaxy candidates observed 450-600 Myr after the Big Bang with photometric redshifts between z ∼ 8.3 and 10.2 measured using James Webb Space Telescope (JWST) NIRCam imaging of the galaxy cluster WHL0137-08 observed in eight filters spanning 0.8-5.0 μm, plus nine Hubble Space Telescope filters spanning 0.4-1.7 μm. One candidate is gravitationally lensed with a magnification of μ ∼ 8, while the other three are located in a nearby NIRCam module with expected magnifications of μ ≲ 1.1. Using SED fitting, we estimate the stellar masses of these galaxies are typically in the range $\mathrm{log}{M}_{\star }/{M}_{\odot }$ = 8.3-8.7. All appear young, with mass-weighted ages <240 Myr, low dust content A_V < 0.15 mag, and specific star formation rates sSFR ∼0.25-10 Gyr^–1 for most. One z ∼ 9 candidate is consistent with an age <5 Myr and an sSFR ∼10 Gyr^–1, as inferred from a strong F444W excess, implying [O III ]+H β rest-frame equivalent width ∼2000 Å, although an older z ∼ 10 object is also allowed. Another z ∼ 9 candidate is lensed into an arc 2.″4 long with a magnification of μ ∼ 8. This arc is the most spatially resolved galaxy at z ∼ 9 known to date, revealing structures ∼30 pc across. Follow-up spectroscopy of WHL0137-08 with JWST/NIRSpec will be useful to spectroscopically confirm these high-redshift galaxy candidates and to study their physical properties in more detail.