Stellar Populations of Lyman-alpha Emitters at z=4.86: A Comparison to $z\sim5$ LBGs

TL;DR

This study analyzes the stellar populations of Lyman-alpha emitters at z=4.86, revealing their stellar masses, ages, and star formation rates, and compares these properties to Lyman-break galaxies at the same redshift.

Contribution

It provides the first detailed stellar population analysis of LAEs at z=4.86 using IRAC data and compares their properties to LBGs, highlighting similarities and differences.

Findings

LAEs have stellar masses from 10^8 to 10^10 Msun.

LAEs are generally less dusty and have lower star formation rates than LBGs.

Stellar properties of LAEs and LBGs are similar at fixed UV or optical luminosity.

Abstract

(abridged) We present a study of stellar population of LAEs at z=4.86 in GOODS-N and its flanking field. With the publicly available IRAC data in GOODS-N and further IRAC observations in the flanking fields, we select five LAEs which are not contaminated by neighboring objects in IRAC images and construct their observed SEDs with I_c, z', IRAC 3.6micron, and 4.5micron band photometry. The SEDs cover the rest-frame UV to optical wavelengths. We derive stellar masses, ages, color excesses, and star formation rates of five LAEs using SED fitting method. Assuming the constant star formation history, we find that the stellar masses range from 10^8 to $10^{10} Msun with the median value of 2.5x10^9 Msun. The derived ages range from very young ages (7.4 Myr) to 437 Myr with a median age of 25 Myr. The color excess E(B-V) are between 0.1-0.4 mag. Star formation rates are 55-209 Msun/yr. A comparison of the stellar populations is made between three LAEs and 88 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 among the whole LAE samples at z=4.86. The LAEs distribute at the relatively faint part of 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 lie on distributions of those of LBGs. On average, the LAEs show less dust extinction, and lower star formation rates than LBGs, while the stellar mass of LAEs nearly lies 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 Lya equivalent width.