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

We investigate the stellar populations of Ly alpha 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(3 Sigma) = 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 similar to 108-108.5 M(circle dot), modest star formation rates (SFRs) of 1-100 M(circle dot) yr-1, and modest dust extinction of E(B - V)(star) < 0.2. The K-detected objects are massive, M(star) similar to 109-1010.5 M(circle dot), and have significant dust extinction with a median of E(B - V)(star) similar or equal to 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)(star) similar to 0.65, and their continua resemble those of some local ultraluminous infrared galaxies (ULIRGs). Interestingly, they have large Ly alpha equivalent widths similar or equal to 70-250 A. If these four are excluded, our sample has a weak anticorrelation between Ly alpha equivalent width and M(star). 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 z(phot) similar to 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 M(star) and sSFR similar to LBGs. Our reddest four LAEs have very high sSFRs in spite of large M(star), thus occupying a unique region in the M(star) versus sSFR space.