Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters Maseda, Michael V Bacon, Roland Lam, Daniel Matthee, Jorryt J ; https://orcid.org/0000-0003-2871-127X Brinchmann, Jarle Schaye, Joop Labbe, Ivo Schmidt, Kasper B Boogaard, Leindert Bouwens, Rychard Cantalupo, Sebastiano Franx, Marijn Hashimoto, Takuya Inami, Hanae Kusakabe, Haruka Mahler, Guillaume Nanayakkara, Themiya Richard, Johan Wisotzki, Lutz Space and Planetary Science Astronomy and Astrophysics Galaxies: evolution Galaxies: high-redshift Galaxies: ISM While low-luminosity galaxies dominate number counts at all redshifts, their contribution to cosmic reionization is poorly understood due to a lack of knowledge of their physical properties. We isolate a sample of 35 z ≈ 4–5 continuum-faint Lyman-α emitters from deep VLT/MUSE spectroscopy and directly measure their H α emission using stacked Spitzer/IRAC Ch. 1 photometry. Based on Hubble Space Telescope imaging, we determine that the average UV continuum magnitude is fainter than −16 (≈ 0.01 L⋆), implying a median Lyman-α equivalent width of 259 Å. By combining the H α measurement with the UV magnitude, we determine the ionizing photon production efficiency, ξion, a first for such faint galaxies. The measurement of log10 (ξion [Hz erg−1]) = 26.28 (⁠+0.28−0.40⁠) is in excess of literature measurements of both continuum- and emission line-selected samples, implying a more efficient production of ionizing photons in these lower luminosity, Lyman-α-selected systems. We conclude that this elevated efficiency can be explained by stellar populations with metallicities between 4 × 10−4 and 0.008, with light-weighted ages less than 3 Myr. Oxford University Press 2020 info:eu-repo/semantics/article doc-type:Article Article http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/11531 Maseda MV, Bacon R, Lam D, et al. Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters. <i>Monthly Notices of the Royal Astronomical Society</i>. 2020;493(4):5120-5130. doi:<a href="https://doi.org/10.1093/mnras/staa622">10.1093/mnras/staa622</a> eng info:eu-repo/semantics/altIdentifier/doi/10.1093/mnras/staa622 info:eu-repo/semantics/altIdentifier/issn/0035-8711 info:eu-repo/semantics/altIdentifier/e-issn/1365-2966 info:eu-repo/semantics/altIdentifier/arxiv/2002.11117 info:eu-repo/semantics/openAccess