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

Brant Robertson, Benjamin D. Johnson, Sandro Tacchella, Daniel J. Eisenstein, Kevin Hainline, Santiago Arribas, William M. Baker, Andrew J. Bunker, Stefano Carniani, Courtney Carreira, Phillip A. Cargile, Stéphane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Francesco D'Eugenio, Eiichi Egami, Ryan Hausen, Jakob M. Helton, Peter Jakobsen, Zhiyuan Ji, Gareth C. Jones, Roberto Maiolino, Michael V. Maseda, Erica Nelson, Pablo G. Pérez-González, Dávid Puskás, Marcia Rieke, Renske Smit, Fengwu Sun, Hannah Übler, Lily Whitler, Christopher N. A. Willmer, Chris Willott, Joris Witstok

Published 2023-12-15Version 1

We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters spanning $0.4-0.9\mu\mathrm{m}$) and novel JWST images with 14 filters spanning $0.8-5\mu\mathrm{m}$, including 7 medium-band filters, and reaching total exposure times of up to 46 hours per filter. We combine all the imaging data at $>2\mu\mathrm{m}$ to construct the deepest imaging ever taken at these wavelengths, reaching as deep as $\approx31.4$ AB mag in the stack and 30.1-30.8 AB mag ($5\sigma$, $r=0.1"$ 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 $R_{1/2}\sim50-200$pc, stellar masses of $M_\star\sim10^7-10^8M_\odot$, and star-formation rates of $\mathrm{SFR}\sim0.1-1~M_\odot~\mathrm{yr}^{-1}$. 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 non-detections. 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 $\sim2.5$ 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.