The ionizing photon production efficiency of compactz~ 0.3 Lyman continuum leakers and comparison with high-redshift galaxies

Abstract

We have recently discovered five Lyman continuum leaking galaxies at z ~ 0.3 that were selected for their compactness, intense star formation, and high [O iii]λ5007/[O ii] λ3727 ratio. Here we derive their ionizing photon production efficiency, ξion, a fundamental quantity for inferring the number of photons available to reionize the Universe. This is the first time this is done for galaxies with confirmed strong Lyman continuum escape (fesc ~ 6–13%). We find an ionizing photon production per unit UV luminosity, ξion, that is higher by a factor 2–6 than the canonical value when reported to their observed UV luminosity. After correction for extinction, this value is close to the canonical value. The properties of our five Lyman continuum leakers are found to be very similar to those of the previously reported confirmed z = 3.218 leaker Ion2 and very similar to those of typical star-forming galaxies at z ≳ 6. Our results suggest that UV bright galaxies at high-z such as Lyman-break galaxies can be Lyman continuum leakers and that their contribution to cosmic reionization may be underestimated.