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

¹ Observatoire de Genève, Université de Genève, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
e-mail: daniel.schaerer@unige.ch
² CNRS, IRAP, 14 Avenue E. Belin, 31400 Toulouse, France
³ Main Astronomical Observatory, Ukrainian National Academy of Sciences, 27 Zabolotnoho str., Kyiv 03680, Ukraine
⁴ Astronomical Institute, Czech Academy of Sciences, Boční II 1401, 141 00, Prague, Czech Republic
⁵ Astronomy Department, University of Virginia, PO Box 400325, Charlottesville, VA 22904-4325, USA
⁶ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received: 17 May 2016
Accepted: 31 May 2016

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, ξ_ion, 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 (f_esc ~ 6–13%). We find an ionizing photon production per unit UV luminosity, ξ_ion, 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.