Two Remarkably Luminous Galaxy Candidates at z ≈ 10–12 Revealed by JWST

The first few hundred Myrs at $z>10$ mark the last major uncharted epoch in history of Universe, where only a single galaxy (GNz11 $z\approx11$) is currently spectroscopically confirmed. Here we present search for luminous galaxies with $JWST$/NIRCam photometry spanning $\approx1-5\mu$m and covering 49 arcmin$^{2}$ from public Early Release Science programs (CEERS GLASS). Our most secure candidates are two $M_{\rm{UV}}\approx-21$ systems: GLASS-z12 GLASS-z10. These display abrupt $\gtrsim1.8$ mag breaks their spectral energy distributions, consistent complete absorption flux bluewards Lyman-$\alpha$ that redshifted to $z=12.4^{+0.1}_{-0.3}$ $z=10.4^{+0.4}_{-0.5}$. Lower redshift interlopers such as quiescent strong Balmer would be comfortably detected $>5\sigma$ multiple bands instead find no flux. From SED modeling infer these have already built up $\sim 10^9$ solar masses stars over $\lesssim300-400$ after Big Bang. brightness sources enable morphological constraints. Tantalizingly, GLASS-z10 shows clearly extended exponential light profile, potentially disk $r_{\rm{50}}\approx0.7$ kpc. sources, if confirmed, join GNz11 defying number density forecasts based on Schechter UV luminosity functions, which require survey area $>10\times$ larger than studied here high redshifts. They extend evidence lower redshifts little or evolution bright end function into cosmic dawn epoch, implications just how early began forming. This, turn, suggests future deep $JWST$ observations may identify relatively much earlier epochs might been anticipated.