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

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}^{\prime }> =24, down to {{log}}₁₀({M}_* /{M}_⊙ )≃ 8 and ≃ 3 {M}_⊙ yr^-1 at < {i}_{AB}^{\prime }> =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.