Stellar populations of Lyα emitters at z = 3-4 based on deep large area surveys in the Subaru-SXDS/UKIDSS-UDS Field

Abstract

We investigate the stellar populations of Lyα emitters (LAEs) at z = 3.1 and 3.7 in 0.65 deg2 of the Subaru/XMM-Newton Deep Field, based on rest-frame ultraviolet-to-optical photometry obtained from the Subaru/XMM-Newton Deep Survey, the UKIRT Infrared Deep Sky Survey/Ultra Deep Survey (UKIDSS/UDS), and the Spitzer legacy survey of the UKIDSS/UDS. Among a total of 302 LAEs (224 for z = 3.1 and 78 for z = 3.7), only 11 are detected in the K band, i.e. brighter than K(3σ) = 24.1 mag. Eight of the 11 K-detected LAEs are spectroscopically confirmed. In our stellar population analysis, we treat K-detected objects individually, while K-undetected objects are stacked at each redshift. We find that the K-undetected objects, which should closely represent the LAE population as a whole, have low stellar masses of ∼108-108.5 M⊙, modest star formation rates (SFRs) of 1-100 M⊙ yr-1, and modest dust extinction of E(B - V){black star} < 0.2. The K-detected objects are massive, Mstar ∼ 109-1010.5 M⊙, and have significant dust extinction with a median of E(B - V){black star} ≃ 0.3. Four K-detected objects with the reddest spectral energy distributions, two of which are spectroscopically confirmed, are heavily obscured with E(B - V){black star} ∼ 0.65, and their continua resemble those of some local ultraluminous infrared galaxies (ULIRGs). Interestingly, they have large Lyα equivalent widths ≃70-250 Å. If these four are excluded, our sample has a weak anticorrelation between Lyα equivalent width and Mstar. We compare the stellar masses and the specific SFRs (sSFRs) of LAEs with those of Lyman-break galaxies (LBGs), distant red galaxies, submillimetre galaxies, and I- or K-selected galaxies with photometric redshifts of zphot ∼ 3. We find that the LAE population is the least massive among all the galaxy populations in question, but with relatively high sSFRs, while near-infrared (NIR)-detected LAEs have Mstar and sSFR similar to LBGs. Our reddest four LAEs have very high sSFRs in spite of large Mstar, thus occupying a unique region in the Mstar versus sSFR space. © 2009 The Authors. Journal compilation © 2009 RAS.