Date: 9/11/2024
Harvard ADS: JWST PRIMER: a new multifield determination of the evolving galaxy UV luminosity function at redshifts z ≃ 9 - 15
Paper abstract: We present a new determination of the evolving galaxy ultraviolet (UV) luminosity function (LF) over the redshift range 8.5< z< 15.5 using a combination of several major Cycle-1 JWST imaging programmes - Public Release IMaging for Extragalactic Research, JWST Advanced Deep Extragalactic Survey, and Next Generation Deep Extragalactic Exploratory Public Survey. This multifield approach yields a total of ~eq 370 arcmin2 of JWST/NIRCam imaging, reaching (5-\sigma) depths of ~eq 30 AB mag in the deepest regions. We select a sample of 2548 galaxies with a significant probability of lying at high redshift (p(z> 8.5)> 0.05) to undertake a statistical calculation of the UV LF. Our new measurements span ~eq 4 mag in UV luminosity at z=9-12.5, placing new constraints on both the shape and evolution of the LF at early times. Our measurements yield a new estimate of the early evolution of cosmic star-formation rate density (\rho _{\rm {SFR}}) confirming the gradual decline deduced from early JWST studies, at least out to z ~eq 12. Finally we show that the observed early evolution of the galaxy UV LF (and \rho _{\rm {SFR}}) can be reproduced in a {\rm \Lambda }cold dark matter Universe, with no change in dust properties or star-formation efficiency required out to z ~eq 12. Instead, a progressive trend towards younger stellar population ages can reproduce the observations, and the typical ages required at z ~eq 8, 9, 10, and 11 all converge on ~eq 380-330 Myr after the big bang, indicative of a rapid emergence of early galaxies at z ~eq 12 - 13. This is consistent with the first indications of a steeper drop-off in \rho _{\rm {SFR}} we find beyond z ~eq 13, possibly reflecting the rapid evolution of the halo mass function at earlier times.
