Lyman Continuum Emission from Spectroscopically Confirmed Ly$\alpha$ Emitters at $z\sim 3.1$

Abstract

We present a study of Lyman continuum (LyC) emission in a sample of $\sim$150 Ly$\alpha$ emitters (LAEs) at $z\approx 3.1$ in the Subaru-XMM Deep Survey field. These LAEs were previously selected using the narrowband technique and spectroscopically confirmed with Ly$\alpha$ equivalent widths (EWs) $\ge 45$ Å. We obtain deep UV images using a custom intermediate-band filter $U_{\mathrm{J}}$ that covers a wavelength range of $3330\sim 3650$ Å, corresponding to 810$\sim$890 Å in the rest frame. We detect 5 individual LyC galaxy candidates in the $U_{\mathrm{J}}$ band, and their escape fractions ($f_{\mathrm{esc}}$) of LyC photons are roughly between 40% and 80%. This supports a previous finding that a small fraction of galaxies may have very high $f_{\mathrm{esc}}$. We find that the $f_{\mathrm{esc}}$ values of the 5 LyC galaxies are not apparently correlated with other galaxy properties such as Ly$\alpha$ 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 ($\sim 3$%) of our LAE sample. For the remaining LAEs that are not detected in $U_{\mathrm{J}}$, we stack their $U_{\mathrm{J}}$-band images and constrain their average $f_{\mathrm{esc}}$. The upper limit of the average $f_{\mathrm{esc}}$ 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$\alpha$ luminosities, Ly$\alpha$ EWs, and SFRs, but their UV continuum slopes are similar to those of other galaxies.

13 pages, 9 figures. Accepted for publication in ApJ