Lyman-break Galaxies at z ∼ 3 in the Subaru Deep Field: Luminosity Function, Clustering, and [O iii] Emission

Abstract

Abstract We combined deep U-band and optical/near-infrared imaging, in order to select Lyman Break Galaxies (LBGs) at z ∼ 3 using U − V and V − R c colors in the Subaru Deep Field. The resulting sample of 5161 LBGs gives a UV luminosity function (LF) down to M UV = − 18 , with a steep faint-end slope of α = − 1.78 ± 0.05 . We analyze UV-to-NIR energy distributions (SEDs) from optical photometry and photometry on IR median-stacked images. In the stacks, we find a systematic background depression centered on the LBGs. This results from the difficulty of finding faint galaxies in regions with higher-than-average surface densities of foreground galaxies, so we corrected for this deficit. Best-fit stellar population models for the LBG SEDs indicate stellar masses and star formation rates of log 10 ( M * / M ⊙ ) ≃ 10 and ≃ 50 M ⊙ yr−1 at 〈 i AB ′ 〉 = 24 , down to log 10 ( M * / M ⊙ ) ≃ 8 and ≃ 3 M ⊙ yr−1 at 〈 i AB ′ 〉 = 27 . The faint LBGs show a ∼1 mag excess over the stellar continuum in K-band. We interpret this excess flux as redshifted [O iii] λ λ 4959,5007 lines. The observed excesses imply equivalent widths that increase with decreasing mass, reaching EW 0 ( [ O iii ] 4959 , 5007 + H β ) ≳ 1500 Å (rest-frame). Such strong [O iii] emission is seen only in a miniscule fraction of local emission-line galaxies, but is probably universal in the faint galaxies that reionized the universe. Our halo occupation distribution analysis of the angular correlation function gives a halo mass of log 10 ( 〈 M h 〉 / h − 1 M ⊙ ) = 11.29 ± 0.12 for the full sample of LBGs, and log 10 ( 〈 M h 〉 / h − 1 M ⊙ ) = 11.49 ± 0.1 for the brightest half of the sample.