Lyman-α transmission properties of the intergalactic medium in the CoDaII simulation

Journal Article · Sat Sep 25 00:00:00 EDT 2021 · Monthly Notices of the Royal Astronomical Society

DOI:https://doi.org/10.1093/mnras/stab2762· OSTI ID:1826821

Gronke, Max ; Ocvirk, Pierre ; Mason, Charlotte ; Matthee, Jorryt ; Bosman, Sarah E. I. ; Sorce, Jenny G.; Lewis, Joseph ; Ahn, Kyungjin; Aubert, Dominique; Dawoodbhoy, Taha ; Iliev, Ilian T. ; Shapiro, Paul R.; Yepes, Gustavo

ABSTRACT The decline in abundance of Lyman-α (Lyα) emitting galaxies at z ≳ 6 is a powerful and commonly used probe to constrain the progress of cosmic reionization. We use the CoDaII simulation, which is a radiation hydrodynamic simulation featuring a box of ∼94 comoving Mpc side length, to compute the Lyα transmission properties of the intergalactic medium (IGM) at z ∼ 5.8 to 7. Our results mainly confirm previous studies, i.e. we find a declining Lyα transmission with redshift and a large sightline-to-sightline variation. However, motivated by the recent discovery of blue Lyα peaks at high redshift, we also analyse the IGM transmission on the blue side, which shows a rapid decline at z ≳ 6 of the blue transmission. This low transmission can be attributed not only to the presence of neutral regions but also to the residual neutral hydrogen within ionized regions, for which a density even as low as $$n_{\rm HI}\sim 10^{-9}\, \mathrm{cm}^{-3}$$ (sometimes combined with kinematic effects) leads to a significantly reduced visibility. Still, we find that $$\sim 1{{\ \rm per\ cent}}$$ of sightlines towards M1600AB ∼ −21 galaxies at z ∼ 7 are transparent enough to allow a transmission of a blue Lyα peak. We discuss our results in the context of the interpretation of observations.

• Sponsoring Organization: USDOE
• OSTI ID: 1826821
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 508 Journal Issue: 3; ISSN 0035-8711
• Publisher: Oxford University Press
• Country of Publication: United Kingdom
• Language: English