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 Ly α 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 Ly α 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 Ly α 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 Ly α luminosities, Ly α EWs, and SFRs, but their UV continuum slopes are similar to those of other galaxies.

Keywords

• High-redshift galaxies
• Galaxy properties
• Star formation