A resolved Lyman alpha profile with doubly peaked emission at z~7

Abstract

The epoch of reionization is a landmark in structure formation and galaxy evolution. How it happened is still not clear, especially regarding which population of objects was responsible for contributing the bulk of ionizing photons to this process. Doubly peaked Lyman-alpha profiles in this epoch are of particular interest since they hold information about the escape of ionizing radiation and the environment surrounding the source. We wish to understand the escape mechanisms of ionizing radiation in Ly alpha Lyalpha ts fi emitters during this time and the origin of a doubly peaked Lyman-alpha profile. We also wish to estimate the size of a potential ionized bubble. Using radiative transfer models, we fit the line profile of a bright Ly alpha Lyalpha ts fi emitter at $z 6.9$ using various gas geometries. The line modeling reveals significant radiation escape from this system. The studied source shows significant escape ($f_ esc Ly alpha Lyalpha ts fi as predicted by the best fitting radiative transfer model) and appears to inhabit an ionized bubble of radius b \,pMpc t_ age $. Radiative transfer modeling predicts the line to be completely redward of the systemic redshift. We suggest the line morphology is produced by inflows, by multiple components emitting Lyalpha , or by an absorbing component in the red wing. We propose that CDFS-1's profile has two red peaks produced by winds within the system. Its high $f_ esc Ly alpha Lyalpha ts fi ) and the low-velocity offset from the systemic redshift suggest that the source is an active ionizing agent. Future observations will reveal whether a peak is present blueward of the systemic redshift or if multiple components produce the profile.