Subaru Deep Survey. V. A Census of Lyman Break Galaxies at<i>z</i> ≃ 4 and 5 in the Subaru Deep Fields: Photometric Properties

Abstract

(abridged) 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). The selection criteria for the LBG samples are examined with 85 spectroscopically identified objects and by Monte Carlo simulations. We find in the luminosity functions of LBGs (i) that the number density of bright galaxies (M_{1700}<-22; corresponding to SFR_{corr}>100 Msolar yr^{-1}) decreases significantly from z=4 to 5 and (ii) that the faint-end slope of the luminosity function may become steeper towards higher redshifts. We estimate dust extinction of z=4 LBGs with M<M^* from UV 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 luminosity. We find no evolution in dust extinction between LBGs at z=3 and 4. We investigate the evolution of UV-luminosity density at 1700A, rho, and find that rho does not significantly change from z=3 to z=5, i.e., rho(z=4)/rho(z=3)=1.0+/-0.2 and rho(z=5)/rho(z=3)=0.8+/-0.4, thus the cosmic star-formation rate (SFR) density remains constant. We find that the stellar mass density estimated from the cosmic SFR 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 Ly-a emitters (LAEs) to that of LBGs is ~60% at z=5, and thus about a half of the star formation at z=5 probably occurs in LAEs. We obtain a constraint on the escape fraction of UV-ionizing photons produced by LBGs, f_{esc}>~0.13.