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

Aayush Saxena, Andrew J. Bunker, Gareth C. Jones, Daniel P. Stark, Alex J. Cameron, Joris Witstok, Santiago Arribas, William M. Baker, Stefi Baum, Rachana Bhatawdekar, Rebecca Bowler, Kristan Boyett, Stefano Carniani, Stephane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Daniel J. Eisenstein, Ryan Endsley, Kevin HainlineJakob M. Helton, Benjamin D. Johnson, Nimisha Kumari, Tobias J. Looser, Roberto Maiolino, Marcia Rieke, Hans-Walter Rix, Brant E. Robertson, Lester Sandles, Charlotte Simmonds, Renske Smit, Sandro Tacchella, Christina C. Williams, Christopher N. A. Willmer, Chris Willott

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We present the properties of 17 faint Ly$\alpha$ emitting galaxies (LAEs) at $z>5.8$ from the JWST Advanced Deep Extragalactic Survey (JADES) in the Hubble Ultra Deep Field/GOODS-S. These LAEs span a redshift range $z\approx5.8-8.0$ and a UV magnitude range $M_{UV}\approx-17$ to $-20.6$, with the Ly$\alpha$ equivalent width (EW) in the range $\approx 25-350$ \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 measured an average ionizing photon production efficiency, log($\xi_\rm{ion}$/erg$^{-1}$ Hz) $\approx25.57$ across our LAEs, which does not evolve strongly with redshift. We report an anti-correlation between the Ly$\alpha$ escape fraction (f_\rm{esc}) and the velocity offset from systemic redshift, consistent with model expectations. We further find that the strength and velocity offset of Ly$\alpha$ are neither correlated with galaxy spectroscopic properties nor with $\xi_\rm{ion}$. We find a decrease in $f_\rm{esc}$(Ly$\alpha$) with redshift, indicative of decreasing sizes of ionized bubbles around LAEs at high redshifts. We used a range of galaxy properties to predict Lyman continuum $f_\rm{esc}$ for our LAEs, finding that the ionizing photon output into the intergalactic medium remains roughly constant across the observed Ly$\alpha$ EW, showing a mild increase at fainter M$_{UV}$ and at higher redshifts. We derived correlations between the ionizing photon output from LAEs and $M_{UV}$, Ly$\alpha$ EW and redshifts, which can be used to constrain the ionizing photon contribution of LAEs at $z > 6$ towards cosmic reionization.
Original languageEnglish
JournalAstronomy & Astrophysics
Publication statusAccepted/In press - 25 Jan 2024


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