2008/03/31 by R. J. Bouwens, Rychard J. Bouwens, Garth D. Illingworth +4 · 5 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1086/590103
23 pages, 12 figures, accepted for publication in ApJ, updated to reflect accepted version
arxiv created 2008/05/12 · openalex publication_date 2008/10/07 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We use all available deep optical ACS and near-IR data over both the HUDF and the two GOODS fields to search for star-forming galaxies at z ≳ 7 and constrain the UV LF within the first 700 Myr. Our data set includes ~23 arcmin 2 of deep NICMOS J + H data and ~248 arcmin 2 of ground-based (ISAAC+MOIRCS) data, coincident with ACS optical data of greater or equal depths. In total, we find eight <z > ∼ 7.3 z -dropouts in our search fields, but no z ∼ 9 J -dropout candidates. A careful consideration of a wide variety of different contaminants suggest an overall contamination level of just ~12% for our z -dropout selection. After performing detailed simulations to accurately estimate the selection volumes, we derive constraints on the UV LFs at z ∼ 7 and z ∼ 9. For a faint-end slope α = − 1.74, our most likely values for M UV * and φ* at z ∼ 7 are –19.8 ± 0.4 mag and 1.1 + 1.7 −0.7 × 10 −3 Mpc −3 , respectively. Our search results for z ∼ 9 J -dropouts set a 1 σ lower limit on M UV * of –19.6 mag assuming that φ* and α are the same as their values at slightly later times. This lower limit on M UV * is 1.4 mag fainter than our best-fit value at z ∼ 4, suggesting that the UV LF has undergone substantial evolution over this time period. No evolution is ruled out at 99% confidence from z ∼ 7 to z ∼ 6 and at 80% confidence from z ∼ 9 to z ∼ 7. We find that the mass-to-light ratio of halos evolves as ~(1 + z) −1 if we require that the observed brightening in M UV * with redshift [i.e., M UV * = (− 21.02 ± 0.09) + (0.36 ± 0.08) (z − 3.8) ] be consistent with the expected evolution in the halo mass function. Finally, we consider the shape of the UV LF at z ≳ 5 and discuss the implications of the Schechter-like form of the observed LFs, particularly the unexpected abrupt cutoff at the bright end.