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UV Luminosity Functions at redshifts z∼z \sim4 to z∼z \sim10: 10000 Galaxies from HST Legacy Fields

Mar 17, 2014
49 pages
Published in:
  • Astrophys.J. 803 (2015) 1, 34
  • Published: Apr 13, 2015
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Abstract: (IOP)
The remarkable Hubble Space Telescope (HST) data sets from the CANDELS, HUDF09, HUDF12, ERS, and BoRG/HIPPIES programs have allowed us to map the evolution of the rest-frame UV luminosity function (LF) from z∼10z\sim 10 to z∼4z\sim 4. We develop new color criteria that more optimally utilize the full wavelength coverage from the optical, near-IR, and mid-IR observations over our search fields, while simultaneously minimizing the incompleteness and eliminating redshift gaps. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy candidates at z∼4z\sim 4, z∼5z\sim 5, z∼6z\sim 6, z∼7z\sim 7, z∼8z\sim 8, and z∼10z\sim 10, respectively, from the ∼1000 arcmin(2) area covered by these data sets. This sample of >10,000 galaxy candidates at z⩾4z\geqslant 4 is by far the largest assembled to date with HST. The selection of z ∼z\,\sim 4–8 candidates over the five CANDELS fields allows us to assess the cosmic variance, the largest variations are at z⩾7z\geqslant 7. Our new LF determinations at z∼4z\sim 4 and z∼5z\sim 5 span a 6 mag baseline and reach to –16 AB mag. These determinations agree well with previous estimates, but the larger samples and volumes probed here result in a more reliable sampling of >L∗\gt {{L}^{*}} galaxies and allow us to reassess the form of the UV LFs. Our new LF results strengthen our earlier findings to 3.4σ3.4\sigma significance for a steeper faint-end slope of the UV LF at z>4z\gt 4, with α evolving from α=−1.64±0.04\alpha =-1.64\pm 0.04 at z∼4z\sim 4 to α=−2.06±0.13\alpha =-2.06\pm 0.13 at z∼7z\sim 7 (and α=−2.02±0.23\alpha =-2.02\pm 0.23 at z∼8z\sim 8), consistent with that expected from the evolution of the halo mass function. We find less evolution in the characteristic magnitude M(*) from z∼7z\sim 7 to z∼4,z\sim 4, the observed evolution in the LF is now largely represented by changes in ϕ∗{{\phi }^{*}}. No evidence for a non-Schechter-like form to the z ∼ 4–8 LFs is found. A simple conditional LF model based on halo growth and evolution in the M/L ratio (∝(1+z)−1.5)(\propto {{(1+z)}^{-1.5}}) of halos provides a good representation of the observed evolution.
Note:
  • 53 pages, 28 figures, 11 tables, accepted for publication in the Astrophysical Journal
  • galaxies: evolution
  • galaxies: high-redshift