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  • 2110.11967v1

    Rights statement: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version Jorryt Matthee, Rohan P Naidu, Gabriele Pezzulli, Max Gronke, David Sobral, Pascal A Oesch, Matthew Hayes, Dawn Erb, Daniel Schaerer, Ricardo Amorín, Sandro Tacchella, Ana Paulino-Afonso, Mario Llerena, João Calhau, Huub Röttgering, (Re)Solving reionization with Lyα: how bright Lyα Emitters account for the z ≈ 2–8 cosmic ionizing background, Monthly Notices of the Royal Astronomical Society, Volume 512, Issue 4, June 2022, Pages 5960–5977 is available online at: https://academic.oup.com/mnras/article/512/4/5960/6553844

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(Re)Solving Reionization with Lyα: How Bright Lyα Emitters account for the $z\approx2-8$ Cosmic Ionizing Background

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  • Jorryt Matthee
  • Rohan P. Naidu
  • Gabriele Pezzulli
  • Max Gronke
  • David Sobral
  • Pascal A. Oesch
  • Matthew Hayes
  • Dawn Erb
  • Daniel Schaerer
  • Ricardo Amorín
  • Sandro Tacchella
  • Ana Paulino-Afonso
  • Mario Llerena
  • João Calhau
  • Huub Röttgering
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<mark>Journal publication date</mark>30/06/2022
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number4
Volume512
Number of pages18
Pages (from-to)5960–5977
Publication StatusAccepted/In press
<mark>Original language</mark>English

Abstract

The cosmic ionizing emissivity from star-forming galaxies has long been anchored to UV luminosity functions. Here we introduce an emissivity framework based on Ly$\alpha$ emitters (LAEs), which naturally hones in on the subset of galaxies responsible for the ionizing background due to the intimate connection between the production and escape of Ly$\alpha$ and LyC photons. Using constraints on the escape fractions of bright LAEs ($L_{\rm{Ly\alpha}}>0.2 L^{*}$) at $z\approx2$ obtained from resolved Ly$\alpha$ profiles, and arguing for their redshift-invariance, we show that: (i) quasars and LAEs together reproduce the relatively flat emissivity at $z\approx2-6$, which is non-trivial given the strong evolution in both the star-formation density and quasar number density at these epochs and (ii) LAEs produce late and rapid reionization between $z\approx6-9$ under plausible assumptions. Within this framework, the $>10\times$ rise in the UV population-averaged $f_{\rm{esc}}$ between $z\approx3-7$ naturally arises due to the same phenomena that drive the growing Ly$\alpha$ emitter fraction with redshift. Generally, a LAE dominated emissivity yields a peak in the distribution of the ionizing budget with UV luminosity as reported in latest simulations. Using our adopted parameters ($f_{\rm{esc}}=50\%$, $\xi_{\rm{ion}}=10^{25.9}$ Hz erg$^{-1}$ for half the bright LAEs), we find that a highly ionizing minority of galaxies with $M_{\rm UV}5$. We conclude with proposed observational tests to further develop our suggested Ly$\alpha$-anchored formalism.

Bibliographic note

This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version Jorryt Matthee, Rohan P Naidu, Gabriele Pezzulli, Max Gronke, David Sobral, Pascal A Oesch, Matthew Hayes, Dawn Erb, Daniel Schaerer, Ricardo Amorín, Sandro Tacchella, Ana Paulino-Afonso, Mario Llerena, João Calhau, Huub Röttgering, (Re)Solving reionization with Lyα: how bright Lyα Emitters account for the z ≈ 2–8 cosmic ionizing background, Monthly Notices of the Royal Astronomical Society, Volume 512, Issue 4, June 2022, Pages 5960–5977 is available online at: https://academic.oup.com/mnras/article/512/4/5960/6553844