The Rise of the Galactic Empire: Ultraviolet Luminosity Functions at <i>z</i> ∼ 17 and <i>z</i> ∼ 25 Estimated with the MIDIS+NGDEEP Ultra-deep JWST/NIRCam Data Set
Pablo G. Pérez‐González, Göran Östlin, Luca Costantin, Jens Melinder, Steven L. Finkelstein, Rachel S. Somerville, Marianna Annunziatella, Javier Álvarez-Márquez, L. Colina, Avishai Dekel, Henry C. Ferguson, Zhaozhou Li, L. Y. Aaron Yung, Micaela B. Bagley, Leindert Boogaard, D. Burgarella, Antonello Calabrò, K. I. Caputi, Y. Cheng, Mark Dickinson, A. Eckart, Mauro Giavalisco, Steven Gillman, T. R. Greve, M. Hamed, Nimish P. Hathi, J. Hjorth, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Vasily Kokorev, Á. Labiano, Danial Langeroodi, Gene C. K. Leung, Priyamvada Natarajan, Casey Papovich, Florian Peißker, L. Pentericci, Nor Pirzkal, Pierluigi Rinaldi, P. van der Werf, Fabian Walter
Abstract
Abstract We present a sample of six F200W and three F277W dropout sources identified as 16 < z < 25 galaxy candidates using the deepest JWST/NIRCam data to date (5 σ depths ∼31.5 mag at ≥2 μ m), provided by the MIRI Deep Imaging Survey and the Next Generation Deep Extragalactic Exploratory Public survey. We estimate ultraviolet (UV) luminosity functions and densities at z ∼ 17 and z ∼ 25. The number density of galaxies with absolute magnitudes of −19 < M UV < −18 at z ∼ 17 ( z ∼ 25) is a factor of 4 (25) smaller than at z ∼ 12; the luminosity density presents a similar evolution. Compared to state-of-the-art galaxy simulations, we find the need for an enhanced UV-photon production at z = 17–25 in M DM = 10 8.5−9.5 M ⊙ dark matter halos, provided by an increase in the star formation efficiency at early times and/or by intense compact starbursts with enhanced emissivity linked to strong burstiness, low or primordial gas metallicities, and/or a top-heavy initial mass function. There are a few robust theoretical predictions for the evolution of galaxies above z ∼ 20 in the literature; however, the continuing rapid drop in the halo mass function would predict a more rapid evolution than we observe if photon production efficiencies remained constant. Our z > 16 candidates present mass-weighted ages around 30 Myr, and attenuations A ( V ) < 0.1 mag. Their average stellar mass is M ⋆ ∼ 10 7 M ⊙ , implying a stellar-to-baryon mass fraction around 10% if the emissivity increases with redshift, or significantly higher otherwise. Three candidates present very blue UV spectral slopes ( β ∼ −3) compatible with Population III young (≲10 Myr) stars and/or high escape fractions of ionizing photons; the rest have β ∼ −2.5 similar to the z = 10–12 samples.