2002/05/23 by Zoltán Haiman, Zoltan Haiman · 7 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Dark Ages #Emission spectrum #Emissivity #Galaxies: Formation, Evolution, Phenomena #Galaxy #Intergalactic medium #Line (geometry) #Luminosity #Radio Astronomy Observations and Technology #Redshift #Reionization #astro-ph
paper · pdf · doi:10.1086/343101
published as Astrophys.J. 576 (2002) L1-L4 · Submitted to ApJL, 4 figures included
arxiv created 2002/05/23 · openalex publication_date 2002/09/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
For a source of Lyα radiation embedded in a neutral intergalactic medium (IGM) prior to the reionization epoch, the Lyα emission line is strongly suppressed by the intervening IGM. The damping wing of the so-called Gunn-Peterson trough can extend to the red side of the emission line and erase a significant fraction of the total line flux. However, the transmitted fraction increases with the size of the local cosmological H II region surrounding the source, and therefore with the ionizing luminosity and age of the source. Motivated by the recent discovery of a Lyα-emitting galaxy at a redshift z = 6.56 (Hu et al.), possibly prior to the reionization of the IGM, we revisit the effects of a neutral IGM on the Lyα emission line. We show that for faint sources with little or even no ionizing continuum, a sufficiently broad (Δ v ≳ 300 km s -1 ) emission line can still remain observable. In particular, the line detected by Hu et al. is consistent with a source embedded in a neutral IGM. We provide characterizations of the asymmetry and total transmitted flux of the Lyα line as functions of the ionizing emissivity of its source. We argue that a statistical sample of Lyα emitters extending beyond the reionization redshift can be a useful probe of reionization.