Subaru Deep Survey. V. A Census of Lyman Break Galaxies atz ≃ 4 and 5 in the Subaru Deep Fields: Photometric Properties

Abstract

We investigate photometric properties of Lyman Break Galaxies (LBGs) at z = 3.5 − 5.2 based on large samples of 2,600 LBGs detected in deep (i ′ 27) and wide-field (1,200 arcmin 2 ) images taken in the Subaru Deep Field (SDF) and the Subaru/XMM Deep Field (SXDF) using broad band B, V , R, i ′ , and z ′ filters. The selection criteria for the LBG samples are examined with 85 spectroscopically identified objects, and the completeness and contamination of the samples are estimated from Monte Carlo simulations based on a photometric-redshift catalog of the Hubble Deep Field-North. We find that these LBG samples are nearly rest-frame UV magnitude-limited samples, missing systematically only 10% of red high-z galaxies (in number) which are a dusty population with E(B − V ) 0.4. We calculate luminosity functions of the LBGs with the estimated completeness and contamination, and find (i) that the number density of bright galaxies (M 1700 < −22 ; corresponding to SFR 100h −2 70 M ⊙ yr −1 with extinction correction) decreases significantly from z = 4 to 5 and (ii) that the faint-end slope of the luminosity functions of LBGs may become steeper towards higher redshifts. We estimate dust extinction of z ≃ 4 LBGs with M < M * (≃ −21) from UV-continuum slopes, and obtain E(B − V ) = 0.15 ± 0.03 as the mean value. The dust extinction remains constant with apparent luminosity, but increases with intrinsic (i.e., extinction-corrected) luminosity. We find no evolution in dust extinction between LBGs at z = 3 and 4. We investigate the evolution of UV-luminosity density by integrating the luminosity functions of LBGs, and find that the UV-luminosity density at 1700Å, ρ UV does not significantly change from z = 3 to z = 5, i.e., ρ UV (z = 4)/ρ UV (z = 3) = 1.0 ± 0.2 and ρ UV (z = 5)/ρ UV (z = 3) = 0.8 ± 0.4, thus the cosmic star-formation rate (SFR) density (with correction for dust extinction) remains constant within the error bars, or possibly a slight decline, from z = 3 to z = 5. We estimate the stellar mass density from the cosmic SFR thus obtained, and find that this stellar mass density is consistent with those derived directly from the stellar mass function at z = 0 − 1, but exceeds those at z ∼ 3 by a factor of 3. We find that the ratio of the UV-luminosity density of Lyman α emitters (LAEs) to that of LBGs is ≃ 60% at z ≃ 5, and thus about a half of star formation probably occurs in LAEs at z ≃ 5. We obtain a constraint on the escape fraction of UV-ionizing photons (i.e., UV continuum in 900Å) produced by LBGs, f esc 0.13. This implies that the escape fraction of LBGs may be larger than that of star-forming galaxies at z = 0.

The environments of Ly α blobs – I. Wide-field Ly α imaging of TN J1338−1942, a powerful radio galaxy at z ≃ 4.1 associated with a giant Ly α nebula★

“…Both of them agree with the R − i colours of our SXDS control sample within the errors. We then extracted 11 sources with i < 26.0 from our sample (R − i colours of 0.08 ± 0.4), and found that 10 of them satisfy the LBG selection criteria by Ouchi et al (2004). The remaining one source has slightly red R − i colour, but fainter than 1σ level in B band, which is consistent with the Lyman-break feature.…”

“…The raw data were reduced with SDFRED20080620 (Yagi et al 2002;Ouchi et al 2004) and IRAF. We flat-fielded using the median sky image after masking sources.…”

The Metal Abundances Across Cosmic Time (     ) Survey. I. Optical Spectroscopy in the Subaru Deep Field

“…In brief, data were obtained mostly under photometric conditions with average seeing of 0 9-1 0 for all five narrowband and two intermediate-band filters. These data were reduced following standard reduction procedures using SDFRED (Yagi et al 2002;Ouchi et al 2004), a software package designed especially for Suprime-Cam data.…”

Lyα EMISSION FROM HIGH-REDSHIFT SOURCES IN COSMOS

“…To achieve this goal, a set of continuum-selected objects brighter than z + < 25 or IRAC [4.5 μm] < 23.5 were selected to satisfy the above magnitude and mass limits, respectively. From this flux-limited sample, B J , g + , V J , r + , i + , and z + LBGs were selected using known criteria (Ouchi et al 2004;Capak et al 2004Capak et al , 2011aIwata et al 2003;Hildebrandt et al 2009). Objects with a probability greater than 50% of being at z > 4, based on the Ilbert et al (2010) photo-z catalog, were also included if they met the flux limit.…”

“…The study of the high-redshift universe and the early evolution of galaxies has primarily relied on two techniques to obtain large samples of high-redshift galaxies, the Lyman break technique (LBGs; Steidel et al 1999;Ouchi et al 2004;Bouwens & Illingworth 2006, and references therein) and narrowband surveys targeting Lyα emitting galaxies (LAEs; Hu & McMahon 1996;Rhoads & Malhotra 2001;Ajiki et al 2003;Hu et al 2004Hu et al , 2010Taniguchi et al 2005;Murayama et al 2007;Gronwall et al 2007;Ouchi et al 2008, and references therein). Studying the difference in the nature and properties of the two populations, selected by these two techniques, helps to understand early stages of galaxy formation and provides constraints on reionization.…”