Lyman Continuum Emission from Spectroscopically Confirmed Lyα Emitters at z ∼ 3.1

Abstract

We present a study of Lyman continuum (LyC) emission in a sample of ∼150 Lyα emitters (LAEs) at z ≈ 3.1 in the Subaru-XMM Deep Survey field. These LAEs were previously selected using the narrowband technique and spectroscopically confirmed with Lyα equivalent widths (EWs) ≥ 45 Å. We obtain deep UV images using a custom intermediate-band filter U J that covers a wavelength range of 3330 ∼ 3650 Å, corresponding to 810 ∼ 890 Å in the rest frame. We detect five individual LyC galaxy candidates in the U J band, and their escape fractions (f esc) of LyC photons are roughly between 40% and 80%. This supports a previous finding that a small fraction of galaxies may have very high f esc. We find that the f esc values of the five LyC galaxies are not apparently correlated with other galaxy properties such as Lyα luminosity and EW, UV luminosity and slope, and star formation rate (SFR). This is partly due to the fact that these galaxies only represent a small fraction (∼3%) of our LAE sample. For the remaining LAEs that are not detected in U J, we stack their U J-band images and constrain their average f esc. The upper limit of the average f esc value is about 16%, consistent with the results in the literature. Compared with the non-LyC LAEs, the LyC LAEs tend to have higher Lyα luminosities, Lyα EWs, and SFRs, but their UV continuum slopes are similar to those of other galaxies.