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JADES: The production and escape of ionizing photons from faint Lyman-alpha emitters in the epoch of reionization

Paper abstract: We present the properties of 16 faint Lyman-\alpha emitting galaxies (LAEs) at z>5.8 from the JWST Advanced Deep Extragalactic Survey (JADES) spectroscopic data in the Hubble Ultra Deep Field/GOODS-S. These LAEs span a redshift range z~5.8-8.0 and UV magnitude range M_{\textrm{UV}} ~ -17 to -20.6, with Ly\alpha equivalent width (EW) in the range ~ 25-350 \AA. The detection of other rest-optical emission lines in the spectra of these LAEs enables the determination of accurate systemic redshifts and Ly\alpha velocity offsets, as well as the physical and chemical composition of their stars and interstellar media. These faint LAEs are consistent with metal-poor systems with high ionization parameters, similar to the general galaxy population at z>6. We measure an average ionizing photon production efficiency, log(\xi_{\textrm{ion}}/erg^{-1} Hz) ~ 25.56 across our LAEs, which does not evolve strongly with redshift. We report an anti-correlation between Ly\alpha escape fraction and velocity offset from systemic, consistent with model expectations. We further find that the strength and velocity offset of Ly\alpha are not correlated with galaxy spectroscopic properties nor with \xi_{\textrm{ion}}. We find a decrease in Ly\alpha escape fractions with redshift, indicative of decreasing sizes of ionized bubbles around LAEs at high redshifts. We use a range of galaxy properties to predict Lyman continuum escape fractions for our LAEs, finding that the ionizing photon output into the intergalactic medium from our LAEs remains roughly constant across the observed UV magnitude and Ly\alpha equivalent width, showing a mild increase with redshift. We derive correlations between the ionizing photon output from LAEs and UV magnitude Ly\alpha strengths and redshift, which can be used to build realistic reionization models.