Crucial Factors for Ly{\alpha} Transmission in the Reionizing Intergalactic Medium: Infall Motion, HII Bubble Size, and Self-shielded Systems

Understand

Using the CoDa II simulation, we study the Ly$\alpha$ transmissivity of the intergalactic medium (IGM) during reionization.

• At $z>6$, a typical galaxy without an active galactic nucleus fails to form a proximity zone around itself due to the overdensity of the surrounding IGM.
• The gravitational infall motion in the IGM makes the resonance absorption extend to the red side of Ly$\alpha$, suppressing the transmission up to roughly the circular velocity of the galaxy.
• In some sight lines, an optically thin blob generated by a supernova in a neighboring galaxy results in a peak feature, which can be mistaken for a blue peak.