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The galaxy UV luminosity function at z≃ 2–4; new results on faint-end slope and the evolution of luminosity density

Parsa, Shaghayegh and Dunlop, James S. and McLure, Ross J. and Mortlock, Alice (2016) The galaxy UV luminosity function at z≃ 2–4; new results on faint-end slope and the evolution of luminosity density. Monthly Notices of the Royal Astronomical Society, 456 (3). pp. 3194-3211. ISSN 0035-8711. doi:10.1093/mnras/stv2857.

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We present a new, robust measurement of the evolving rest-frame ultraviolet (UV) galaxy luminosity function (LF) over the key redshift range from z ≃ 2 to z ≃ 4. Our results are based on the high dynamic range provided by combining the Hubble Ultra Deep Field (HUDF), CANDELS/GOODS-South, and UltraVISTA/COSMOS surveys. We utilize the unparalleled multifrequency photometry available in this survey ‘wedding cake’ to compile complete galaxy samples at z ≃ 2, 3, 4 via photometric redshifts (calibrated against the latest spectroscopy) rather than colour–colour selection, and to determine accurate rest-frame UV absolute magnitudes (M1500) from spectral energy distribution (SED) fitting. Our new determinations of the UV LF extend from M1500 ≃ −22 (AB mag) down to M1500 = −14.5, −15.5 and −16 at z ≃ 2, 3 and 4, respectively (thus, reaching ≃ 3–4 mag fainter than previous blank-field studies at z ≃ 2,3). At z ≃ 2, 3, we find a much shallower faint-end slope (α = −1.32 ± 0.03) than reported in some previous studies (α ≃ −1.7), and demonstrate that this new measurement is robust. By z ≃ 4, the faint-end slope has steepened slightly, to α = −1.43 ± 0.04, and we show that these measurements are consistent with the overall evolutionary trend from z = 0 to 8. Finally, we find that while characteristic number density (ϕ*) drops from z ≃ 2 to z ≃ 4, characteristic luminosity (M*) brightens by ≃ 1 mag. This, combined with the new flatter faint-end slopes, has the consequence that UV luminosity density (and hence unobscured star formation density) peaks at z ≃ 2.5–3, when the Universe was ≃ 2.5 Gyr old.

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Additional Information:© 2016 The Authors. Published for the Royal Astronomical Society by Oxford University Press.
Issue or Number:3
Record Number:CaltechAUTHORS:20170628-143424767
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78670
Deposited By: Joy Painter
Deposited On:28 Jun 2017 21:44
Last Modified:15 Nov 2021 17:42

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