Probing high-redshift galaxies with Lyα intensity mapping

Abstract

We present a study of the cosmological Lya emission signal at z > 4. Our goal is to predict the power spectrum of the spatial fluctuations that could be observed by an intensity mapping survey. The model uses the latest data from the Hubble Space Telescope (HST) legacy fields and the abundance matching technique to associate UV emission and dust properties with the haloes, computing the emission from the interstellar medium (ISM) of galaxies and the intergalactic medium (IGM), including the effects of reionization, self-consistently. The Lya intensity from the diffuse IGM emission is 1.3 (2.0) times more intense than the ISM emission at z = 4(7); both components are fair tracers of the star-forming galaxy distribution. However the power spectrum is dominated by ISM emission on small scales (k>0.01 h Mpc-1)with shot noise being significant only above k = 1 h Mpc-1. At very large scales (k < 0.01 h Mpc-1) diffuse IGM emission becomes important. The comoving Lya luminosity density from IGM and galaxies, ρ IGMLyα = 8.73(6.51) × 1040 erg s-1 Mpc-3 and ρ IGMLyα = 6.62(3.21) × 1040 erg s-1 Mpc-3 at z=4(7), is consistent with recent Sloan Digital Sky Survey determinations.We predict a power k3PLyα(k, z)/2π2 = 9.76 × 10-4(2.09 × 10-5)nW2m-4 sr-2 at z = 4(7) for k = 0.1 h Mpc-1.