article published yes Michael V Maseda author Roland Bacon author Daniel Lam author Jorryt J Matthee author 7439a258-f3c0-11ec-9501-9df22fe067200000-0003-2871-127X Jarle Brinchmann author Joop Schaye author Ivo Labbe author Kasper B Schmidt author Leindert Boogaard author Rychard Bouwens author Sebastiano Cantalupo author Marijn Franx author Takuya Hashimoto author Hanae Inami author Haruka Kusakabe author Guillaume Mahler author Themiya Nanayakkara author Johan Richard author Lutz Wisotzki author 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 Press2020 eng Space and Planetary ScienceAstronomy and AstrophysicsGalaxies: evolutionGalaxies: high-redshiftGalaxies: ISM 0035-8711 1365-2966 2002.1111710.1093/mnras/staa622 49345120-5130 yes Maseda, Michael V., et al. “Elevated Ionizing Photon Production Efficiency in Faint High-Equivalent-Width Lyman-α Emitters.” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 493, no. 4, Oxford University Press, 2020, pp. 5120–30, doi:<a href="https://doi.org/10.1093/mnras/staa622">10.1093/mnras/staa622</a>. Maseda, M. V., Bacon, R., Lam, D., Matthee, J. J., Brinchmann, J., Schaye, J., … Wisotzki, L. (2020). Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters. <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press. <a href="https://doi.org/10.1093/mnras/staa622">https://doi.org/10.1093/mnras/staa622</a> Maseda, Michael V, Roland Bacon, Daniel Lam, Jorryt J Matthee, Jarle Brinchmann, Joop Schaye, Ivo Labbe, et al. “Elevated Ionizing Photon Production Efficiency in Faint High-Equivalent-Width Lyman-α Emitters.” <i>Monthly Notices of the Royal Astronomical Society</i>. Oxford University Press, 2020. <a href="https://doi.org/10.1093/mnras/staa622">https://doi.org/10.1093/mnras/staa622</a>. 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> Maseda MV, Bacon R, Lam D, Matthee JJ, Brinchmann J, Schaye J, Labbe I, Schmidt KB, Boogaard L, Bouwens R, Cantalupo S, Franx M, Hashimoto T, Inami H, Kusakabe H, Mahler G, Nanayakkara T, Richard J, Wisotzki L. 2020. Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters. Monthly Notices of the Royal Astronomical Society. 493(4), 5120–5130. M.V. Maseda, R. Bacon, D. Lam, J.J. Matthee, J. Brinchmann, J. Schaye, I. Labbe, K.B. Schmidt, L. Boogaard, R. Bouwens, S. Cantalupo, M. Franx, T. Hashimoto, H. Inami, H. Kusakabe, G. Mahler, T. Nanayakkara, J. Richard, L. Wisotzki, Monthly Notices of the Royal Astronomical Society 493 (2020) 5120–5130. M. V. Maseda <i>et al.</i>, “Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters,” <i>Monthly Notices of the Royal Astronomical Society</i>, vol. 493, no. 4. Oxford University Press, pp. 5120–5130, 2020. 115312022-07-07T10:46:41Z2022-08-18T11:23:27Z