Lyman continuum escape fraction in Ly α emitters at z ? 3.1

We measure the Lyman continuum (LyC) escape fraction in 54 faint Lyman-alpha emitters (LAEs) at $z$ ? 3.1 in the GOODS-South field. With the average magnitude of R = 26.7 AB (M_UV = -18.8 and L ? 0.1L∗), these galaxies represent a population of compact young dwarf galaxies. Their properties are likely to resemble those in the galaxies responsible for reionizing the Universe at $z$ > 6. We do not detect LyC emission in any individual LAEs in the deep HST F336W images, which covers the rest-frame 820 Å. We do not detect the LyC emission of these LAEs in the stacked F336W images either. The 3σ upper limit of LyC escape fractions is $f-{\rm esc}\lt 14\!-\!32{{\ \rm per\ cent}}$. However, the high Ly α rest-frame equivalent width (EW), low stellar mass, and UV luminosity of these LAEs suggest that they should have $f-{\rm esc}\gt 50{{\ \rm per\ cent}}$. The low LyC escape fraction from this work and other stacking analyses suggests that the LyC-leaking galaxies with $f-{\rm esc}\gt 50{{\ \rm per\ cent}}$ at $z$ = 2-3 do not follow the relation between f_esc and UV luminosity and Ly α EW derived from typical galaxies at similar redshifts. Therefore, the UV luminosity and Ly α EW are not the best indicators for the LyC escape fraction.