The visibility of Lyman α emitters during reionization

We present the first Lyman α emitter (LAE) study that combines: (i) cosmological smoothed particle hydrodynamic (SPH) simulations run using GADGET-2, (ii) radiative transfer simulations (CRASH) and (iii) a previously developed LAE model. This complete LAE model accounts for the intrinsic LAE, Lyα/continuum luminosity, dust enrichment and Lyα transmission through the intergalactic medium (IGM) to quantify the effects of reionization, dust and velocity fields on the Lyα and UV luminosity functions (LFs). We find that a model neglecting dust sorely fails to reproduce either the slope or the magnitude of the observed Lyα and UV LFs. Clumped dust is required to simultaneously fit the observed UV and Lyα LFs, such that the intrinsic Lyα-to-continuum luminosity is enhanced by a factor fα/fc˜ 1.5 (3.7) excluding (including) peculiar velocities. The higher value including velocity fields arises since LAEs reside in large potential wells and inflows decrease their Lyα transmission. For the first time, a degeneracy is found between the ionization state of the IGM and the clumping of dust inside high-redshift galaxies. The Lyα LF z ˜ 5.7 can be well reproduced (to within a 5σ error) by a wide range of IGM average neutral hydrogen fraction, 3.4 × 10-3 < <χH I> < 0.16, provided that the increase in the Lyα transmission through a more ionized IGM is compensated by a decrease in the Lyα escape fraction from the galaxy due to dust absorption. The physical properties of LAEs are presented along with a discussion of the assumptions adopted.