Neutral hydrogen at high redshifts as a probe of structure formation .3. Radio maps from N-body simulations

Large inhomogeneities in neutral hydrogen in the Universe can be detected at redshifts z less than or equal to 10 using the redshifted 21-cm line emission. We use cosmological N-body simulations for dark matter and a simple model for baryonic collapse to estimate the signal expected from structures like protoclusters of galaxies at high redshifts. We study (i) the standard cold dark matter (CDM) model, (ii) a modified CDM model with less power at small scales, and (iii) a Lambda + CDM model in a universe with Omega(0), + Omega(Lambda), = 1. We show that it should be possible for the next generation of radio telescopes to detect such structures at a redshift of 3.34 with an integration of about 100 h. We also discuss possible schemes for enhancing signal-to-noise ratio to detect protocondensates at high redshifts.