New Determinations of the UV Luminosity Functions from z ∼ 9 to 2 Show a Remarkable Consistency with Halo Growth and a Constant Star Formation Efficiency

Abstract

Here we provide the most comprehensive determinations of the rest-frame UV luminosity function (LF) available to date with the Hubble Space Telescope (HST) at z ∼ 2–9. Essentially all of the noncluster extragalactic legacy fields are utilized, including the Hubble Ultra Deep Field, the Hubble Frontier Fields parallel fields, and all five CANDELS fields, for a total survey area of 1136 arcmin ². Our determinations include galaxies at z ∼ 2–3 leveraging the deep HDUV, UVUDF, and ERS WFC3/UVIS observations available over an ∼150 arcmin ² area in the GOODS-North and GOODS-South regions. All together, our collective samples include >24,000 sources, >2.3× larger than previous selections with HST. We identify 5766, 6332, 7240, 3449, 1066, 601, 246, and 33 sources at z ∼ 2, 3, 4, 5, 6, 7, 8, and 9, respectively. Combining our results with an earlier z ∼ 10 LF determination by Oesch et al., we quantify the evolution of the UV LF. Our results indicate that there is (1) a smooth flattening of the faint-end slope α from α ∼ −2.4 at z ∼ 10 to α ∼ −1.5 at z ∼ 2, (2) minimal evolution in the characteristic luminosity M* at z ≥ 2.5, and (3) a monotonic increase in the normalization ${\log }_{10}{\varphi }^{*}$ from z ∼ 10 to 2, which can be well described by a simple second-order polynomial, consistent with an “accelerated” evolution scenario. We find that each of these trends (from z ∼ 10 to 2.5 at least) can be readily explained on the basis of the evolution of the halo mass function and a simple constant star formation efficiency model.