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
R. J. Bouwens, P. A. Oesch, M. Stefanon, G. Illingworth, I. Labbé, N. Reddy, H. Atek, M. Montes, R. Naidu, T. Nanayakkara, E. Nelson, S. Wilkins
Abstract
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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:msup> <mml:mrow> <mml:mi>ϕ</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msup> </mml:math> 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.