Modelling of Lyman-alpha emitting galaxies and ionized bubbles at the epoch of reionization

Abstract

Understanding Lyα emitting galaxies (LAEs) can be a key to reveal cosmic reionization and galaxy formation in the early Universe. Based on halo merger trees and Lyα radiation transfer calculations, we model redshift evolution of LAEs and their observational properties at z ≥ 6. We consider ionized bubbles associated with individual LAEs and IGM (integer-galactic medium) transmission of Lyα photons. We find that Lyα luminosity tightly correlates with halo mass and stellar mass, while the relation with star formation rate has a large dispersion. Comparing our models with the observed luminosity function by Konno et al., we suggest that LAEs at z ~ 7 have galactic wind of Vout ≳ 100 km s-1 and HI column density of NHI ≳ 1020 cm-2. Number density of bright LAEs rapidly decreases as redshift increases, due to both lower star formation rate and smallerHII bubbles. Our model predicts futurewide deep surveys with next-generation telescopes, such as James Webb Space Telescope, European Extremely Large Telescope, and Thirty Metre Telescope, can detect LAEs at z~10 with a number density of nLAE ~ a few × 10-6 Mpc-3 for the flux sensitivity of 10-18 erg cm-2 s-1.When giant HII bubbles are formed by clustering LAEs, the number density of observable LAEs can increase by a factor of few. By combining these surveys with future 21-cm observations, it could be possible to detect both LAEs with LLyα ≳ 1042 erg s-1 and their associated giant HII bubbles with the size ≳250 kpc at z ~ 10.