The ionizing photon production efficiency at z ∼6 for Lyman-Alpha emitters using JEMS and MUSE

C. Simmonds, S. Tacchella, M. Maseda, C. C. Williams, W. M. Baker, C. E.C. Witten, B. D. Johnson, B. Robertson, A. Saxena, F. Sun, J. Witstok, R. Bhatawdekar, K. Boyett, A. J. Bunker, S. Charlot, E. Curtis-Lake, E. Egami, D. J. Eisenstein, Z. Ji, R. MaiolinoL. Sandles, R. Smit, H. Übler, C. J. Willott

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


We study the ionizing photon production efficiency at the end of the Epoch of Reionization (z ∼5.4-6.6) for a sample of 30 Ly α emitters. This is a crucial quantity to infer the ionizing photon budget of the universe. These objects were selected to have reliable spectroscopic redshifts, assigned based on the profile of their Ly α emission line, detected in the MUSE deep fields. We exploit medium-band observations from the JWST Extragalactic Medium-band Survey (JEMS) to find the flux excess corresponding to the redshifted Hα emission line. We estimate the ultraviolet (UV) luminosity by fitting the full JEMS photometry, along with several HST photometric points, with Prospector. We find a median UV continuum slope of, indicating young stellar populations with little-To-no dust attenuation. Supported by this, we derive ζion,0 with no dust attenuation and find a median value of log. If we perform dust attenuation corrections and assume a Calzetti attenuation law, our values are lowered by ∼0.1 dex. Our results suggest Ly α emitters at the Epoch of Reionization have slightly enhanced ζion,0 compared to previous estimations from literature, in particular, when compared to the non-Ly α emitting population. This initial study provides a promising outlook on the characterization of ionizing photon production in the early universe. In the future, a more extensive study will be performed on the entire data set provided by the JWST Advanced Deep Extragalactic Survey (JADES). Thus, for the first time, allowing us to place constraints on the wider galaxy populations driving reionization.

Original languageEnglish (US)
Pages (from-to)5468-5486
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Aug 1 2023


  • galaxies: evolution
  • galaxies: general
  • galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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