Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic Star Formation Rate Density 300 Myr after the Big Bang

We characterize the earliest galaxy population in the JADES Origins Field, the deepest imaging field observed with JWST. We make use of ancillary Hubble Space Telescope optical images (five filters spanning $0.4-0.9\ \mu\mathrm{m}$ ) and novel JWST images with $14$ filters spanning $0.8-5.0\ \mu\mathrm{m}$ , including seven medium-band filters, and reaching total exposure times of up to $46\ \mathrm{hours}$ per filter. We combine all our data at $> 2.3\ \mu\mathrm{m}$ to construct an ultradeep image, reaching as deep as $\approx 31.4\ \mathrm{AB\ mag}$ in the stack and $30.3-31.0\ \mathrm{AB\ mag}$ ($5\sigma$ , $r = 0.1\ \mathrm{arcsec}$ circular aperture) in individual filters. We measure photometric redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts $z = 11.5-15$ . These objects show compact half-light radii of $R_{1/2} \sim 50-200\ \mathrm{pc}$ , stellar masses of $M_{\ast} \sim 10^{7}-10^{8}\ M_{\odot}$ , and star formation rates $\sim 0.1-1\ M_{\odot}/\mathrm{yr}$ . Our search finds no candidates at $15 < z < 20$ , placing upper limits at these redshifts. We develop a forward-modeling approach to infer the properties of the evolving luminosity function without binning in redshift or luminosity that marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the impact of nondetections. We find a $z = 12$ luminosity function in good agreement with prior results, and that the luminosity function normalization and UV luminosity density decline by a factor of $\sim 2.5$ from $z = 12$ to $z = 14$ . We discuss the possible implications of our results in the context of theoretical models for evolution of the dark matter halo mass function.

The Astrophysical Journal, Volume 970, Issue 1, id.31, 27 pages