Stellar populations of Ly[alpha] emitters at z = 4.86: A comparison to z ∼ 5 Lyman break galaxies

Abstract

We present a study of a stellar population of Ly[alpha] emitters (LAEs) at z = 4.86 in the Great Observatories Origins Deep Survey North (GOODS-N) field and its flanking field. The LAEs are selected based on optical narrowband (NB711) and broadband (V, I[subscript c], and z') observations by the Suprime-Cam attached to the Subaru Telescope. With the publicly available Infrared Array Camera (IRAC) data in GOODS-N and further IRAC observations in the flanking fields, we select five LAEs that are not contaminated by neighboring objects in IRAC images and construct their observed spectral energy distributions (SEDs) with I[subscript c], z', IRAC 3.6 [micron]m, and 4.5 [micron]m band photometries. The SEDs cover the rest-frame UV-to-optical wavelengths. We derive the stellar masses, ages, color excesses, and star formation rates (SFRs) of the five LAEs using an SED fitting method. Assuming a constant star formation history, we find that the stellar masses range from 10[superscript 8] to 10[superscript 10] M[subscript circled dot] with the median value of 2.5 × 10[superscript 9] M[subscript circled dot]. The derived ages range from very young (7.4 Myr) to 437 Myr, with a median age of 25 Myr. The color excess E(B − V ) is between 0.1 and 0.4 mag. SFRs are 55–209 M[subscript circled dot] yr[superscript −1]. A comparison of the stellar populations is made between 3 LAEs and 88 Lyman break galaxies (LBGs) selected at the same redshift, in the same observed field, and down to the same limit of the rest-frame UV luminosity. These three LAEs are the brightest and reddest samples of all the LAE samples at z = 4.86. The LAEs are distributed at the relatively faint part of the UV-luminosity distribution of LBGs. Deriving the stellar properties of the LBGs by fitting their SEDs with the same model ensures that model difference does not affect the comparison. It is found that the stellar properties of the LAEs are located in the region where the properties of LBGs are distributed. On average, the LAEs show less dust extinction and lower SFRs than LBGs, while the stellar mass of LAEs lies nearly in the middle part of the mass distribution of LBGs. However, the stellar properties of LAEs and LBGs are similar at the fixed UV or optical luminosity. We also examine the relations between the output properties from the SED fitting and the rest-frame Ly[alpha] equivalent width, but cannot find any significant correlation.