THE EVOLUTION OF THE ULTRAVIOLET LUMINOSITY FUNCTION FROM z {approx} 0.75 TO z {approx} 2.5 USING HST ERS WFC3/UVIS OBSERVATIONS
- Institute for Astronomy, ETH Zurich, 8092 Zurich (Switzerland)
- UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States)
- University of Colorado, Center for Astrophysics and Space Astronomy, 389-UCB, Boulder, CO 80309 (United States)
- Space Telescope Science Institute, Baltimore, MD 21218 (United States)
- Leiden Observatory, Leiden University, NL-2300 RA, Leiden (Netherlands)
- Carnegie Observatories, Pasadena, CA 91101 (United States)
We present UV luminosity functions (LFs) at 1500 A derived from the Hubble Space Telescope Early Release Science WFC3/UVIS data acquired over {approx}50 arcmin{sup 2} of the GOODS-South field. The LFs are determined over the entire redshift range z = 0.75-2.5 using two methods, similar to those used at higher redshifts for Lyman break galaxies (LBGs): (1) 13 band UV+optical+NIR photometric redshifts to study galaxies in the range z = 0.5-2 in three bins of dz = 0.5 and (2) dropout samples in three redshift windows centered at z {approx} 1.5, z {approx} 1.9, and z {approx} 2.5. The characteristic luminosity dims by 1.5 mag from z = 2.5 to z = 0.75, consistent with earlier work. However, the other Schechter function parameters, the faint-end slope and the number density, are found to be remarkably constant over the range z = 0.75-2.5. Using these LF determinations, we find the UV luminosity density to increase by {approx}1.4 dex according to (1 + z){sup 2.58{+-}0.15} from z {approx} 0 to its peak at z {approx} 2.5. Strikingly, the inferred faint-end slopes for our LFs are all steeper than {alpha} = -1.5, in agreement with higher-redshift LBG studies. Since the faint-end slope in the local universe is found to be much flatter with {alpha} {approx_equal} -1.2, this poses the question as to when and how the expected flattening occurs. Despite relatively large uncertainties, our data suggest {alpha} {approx_equal} -1.7 at least down to z {approx} 1. These new results from such a shallow early data set demonstrate very clearly the remarkable potential of WFC3/UVIS for the thorough characterization of galaxy evolution over the full redshift range z {approx} 0.5 to z {approx} 3.
- OSTI ID:
- 21454896
- Journal Information:
- Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 725; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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