Long troughs in the Lyman-α forest below redshift 6 due to islands of neutral hydrogen
Authors: Laura Keating, Lewis Weinberger, Girish Kulkarni, Martin G Haehnelt, Jonathan Chardin, Dominique Aubert
Journal: Monthly Notices of the Royal Astronomical Society, Volume 491, Issue 2, January 2020, Pages 1736-1745
Abstract: A long (110 cMpc/h) and deep absorption trough in the Lyα forest has been observed extending down to redshift 5.5 in the spectrum of ULAS J0148+0600. Although no Lyα transmission is detected, Lyβ spikes are present which has led to claims that the gas along this trough must be ionized. Using high resolution cosmological radiative transfer simulations in large volumes, we show that in a scenario where reionization ends late z ~ 5.2, our simulations can reproduce troughs as long as observed. In this model, we find that the troughs are caused by islands of neutral hydrogen. Small ionized holes within the neutral islands allow for the transmission of Lyβ. We have also modelled the Lyα emitter population around the simulated troughs, and show that there is a deficit of Lyα emitters close to the trough as is observed.