High-redshift Galaxy Candidates at z=9-10 as Revealed by JWST Observations of WHL0137-08

We report the discovery of four galaxy candidates observed 450-600 Myr after the Big Bang with photometric redshifts between z similar to 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 mu m, plus nine Hubble Space Telescope filters spanning 0.4-1.7 mu m. One candidate is gravitationally lensed with a magnification of mu similar to 8, while the other three are located in a nearby NIRCam module with expected magnifications of mu less than or similar to 1.1. Using SED fitting, we estimate the stellar masses of these galaxies are typically in the range logM(circle dot) M-circle star = 8.3-8.7. All appear young, with mass-weighted ages <240 Myr, low dust content AV < 0.15 mag, and specific star formation rates sSFR similar to 0.25-10 Gyr(-1) for most. One z similar to 9 candidate is consistent with an age <5 Myr and an sSFR similar to 10 Gyr(-1), as inferred from a strong F444W excess, implying [O III]+H beta rest-frame equivalent width similar to 2000 A, although an older z similar to 10 object is also allowed. Another z similar to 9 candidate is lensed into an arc 2 4 long with a magnification of mu similar to 8. This arc is the most spatially resolved galaxy at z similar to 9 known to date, revealing structures similar to 30 pc across.

Automated summary

The discovery of four galaxy candidates observed 450-600 Myr after the Big Bang is reported. Using the James Webb Space Telescope (JWST) and the Hubble Space Telescope (HST), the redshifts and masses of these galaxies were estimated, revealing that they are overall young.