Elevated ionizing photon production efficiency in faint high-equivalent-width Lyman-α emitters. Issue 4 (4th March 2020)

• Record Type: Journal Article
• Authors: Maseda, Michael V; Bacon, Roland; Lam, Daniel; Matthee, Jorryt; 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
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 493:Issue 4(2020)
• Page Start: 5120
• Page End: 5130
• Publication Date: 2020-03-04
• Subjects: Galaxies: evolution -- Galaxies: high-redshift -- Galaxies: ISM; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa622
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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.