The evolution of the galaxy UV luminosity function at redshifts z ~ 8-15 from deep JWST and ground-based near-infrared imaging

Abstract

We reduce and analyse the available James Webb Space Telescope (JWST) ERO and ERS NIRCam imaging (SMACS0723, GLASS, CEERS) in combination with the latest deep ground-based near-infrared imaging in the COSMOS field (provided by UltraVISTA DR5) to produce a new measurement of the evolving galaxy UV luminosity function (LF) over the redshift range $z=8-15$. This yields a new estimate of the evolution of UV luminosity density ($\ddot{I}{}_{\mathrm{UV}}$), and hence cosmic star-formation rate density ($\ddot{I}{}_{\mathrm{SFR}}$) out to within $<300$\, Myr of the Big Bang. Our results confirm that the high-redshift LF is best described by a double power-law (rather than a Schechter) function up to $z\sim 10$, and that the LF and the resulting derived $\ddot{I}{}_{\mathrm{UV}}$ (and thus $\ddot{I}{}_{\mathrm{SFR}}$), continues to decline gradually and steadily up to $z\sim 15$ (as anticipated from previous studies which analysed the pre-existing data in a consistent manner to this study). We provide details of the 61 high-redshift galaxy candidates, 47 of which are new, that have enabled this new analysis. Our sample contains 6 galaxies at $z\ge 12$, one of which appears to set a new redshift record as an apparently robust galaxy candidate at $z\simeq 16.4$, the properties of which we therefore consider in detail. The advances presented here emphasize the importance of achieving high dynamic range in studies of early galaxy evolution, and re-affirm the enormous potential of forthcoming larger JWST programmes to transform our understanding of the young Universe.

28 pages, 4 figures in main manuscript, accepted for publication in MNRAS. Updated zero-point corrections noted in Appendix C