Stellar Populations of Lyman Alpha Emitters at z = 3 - 4 Based on Deep
  Large Area Surveys in the Subaru-SXDS/UKIDSS-UDS Field
  We investigate the stellar populations of Lyman alpha emitters (LAEs) at
z=3.1 and 3.7 in 0.65 deg^2 of the Subaru/XMM-Newton Deep Field, based on
rest-frame UV-to-optical photometry obtained from the Subaru/XMM-Newton Deep
Survey, the UKIDSS/Ultra Deep Survey, 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(3sigma)=24.1 mag. Eight of
the 11 K-detected LAEs are spectroscopically confirmed. We find that the
K-undetected objects, which should closely represent the LAE population as a
whole, have low stellar masses of ~ 10^8 - 10^8.5 Msun, modest SFRs of 1 - 100
Msun yr^-1, and modest dust extinction of E(B-V) < 0.2. The K-detected objects
are massive, Mstar ~ 10^9 - 10^10.5 Msun, and have significant dust extinction
with a median of E(B-V) ~= 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) ~ 0.65, and their continua resemble those of
some local ULIRGs. Interestingly, they have large Lyman alpha equivalent widths
~= 70 - 250 A. If these four are excluded, our sample has a weak
anti-correlation between EW(Lya) and Mstar. We compare the stellar masses and
the specific star formation rates (sSFR) of LAEs with those of Lyman-break
galaxies, distant red galaxies, submillimetre galaxies, and I- or K-selected
galaxies with z_phot ~ 3. We find that the LAE population is the least massive
among all the galaxy populations in question, but with relatively high sSFRs,
while 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. (abridged)
