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

TL;DR

This study measures the ionizing photon production efficiency of five confirmed Lyman continuum leakers at z~0.3, revealing their potential role in cosmic reionization and similarities to high-redshift galaxies.

Contribution

First measurement of ionizing photon production efficiency in galaxies with confirmed strong Lyman continuum escape, linking local leakers to high-redshift reionization sources.

Findings

Ionizing photon production efficiency is 2-6 times higher than canonical values before extinction correction.

Properties of local leakers are similar to high-redshift star-forming galaxies.

Results imply high-z UV-bright galaxies could significantly contribute to reionization.

Abstract

We have recently discovered five Lyman continuum leaking galaxies at z~0.3, selected for their compactness, intense star-formation, and high [OIII]/[OII] ratio (Izotov et al. 2016ab). Here we derive their ionizing photon production efficiency, a fundamental quantity for inferring the number of photons available to reionize the Universe, for the first time for galaxies with confirmed strong Lyman continuum escape (fesc~6-13%). We find an ionizing photon production per unit UV luminosity, which is a factor 2-6 times higher 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 confirmed z=3.218 leaker Ion2 from de Barros et al. (2016) 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.