The Physical Properties of Star-Forming Galaxies with Strong [O III] Lines at z=3.25

We present an analysis of physical properties of 34 [O III] emission-line galaxies (ELGs) at z=3.254\(\pm\)0.029 in the Extended Chandra Deep Field South (ECDFS). These ELGs are selected from deep narrow H2S(1) and broad Ks imaging of 383 arcmin\(^{2}\) obtained with CFHT/WIRCam. We construct spectral energy distributions (SEDs) from U to Ks to derive the physical properties of ELGs. These [O III] ELGs are identified as starburst galaxies with strong [O III] lines of L([O III]) ~ 10\(^{42.6}\) - 10\(^{44.2}\) erg s\(^{-1}\), and have stellar masses of M* ~ 10\(^{9.0}\)-10\(^{10.6}\) M\(_\odot\) and star formation rates of ~ 10-210 M\(_\odot\) yr\(^{-1}\). Our results show that 24% of our sample galaxies are dusty with Av > 1 mag and EW(OIII)\(_{rest}\) ~ 70-500 \(\AA\), which are often missed in optically selected [O III] ELG samples. Their rest-frame UV and optical morphologies from HST/ACS and HST/WFC3 deep imaging reveal that these [O III] ELGs are mostly multiple-component systems (likely mergers) or compact. And 20% of them are nearly invisible in the rest-frame UV owing to heavy dust attenuation. Interestingly, we find that our samples reside in an overdensity consisting of two components: one southeast (SE) with an overdensity factor of \(\delta_{gal}\) ~ 41 over a volume of 13\(^{3}\) cMpc\(^{3}\) and the other northwest (NW) with \(\delta_{gal}\) ~ 38 over a volume of 10\(^{3}\) cMpc\(^{3}\). The two overdense substructures are expected to be virialized at z=0 with a total mass of ~ 1.1 x 10\(^{15}\) M\(_\odot\) and ~ 4.8 x 10\(^{14}\) M\(_\odot\), and probably merge into a Coma-like galaxy cluster.