Intensity mapping of neutral hydrogen ( HI ) is a promising observational probe of cosmology and large-scale structure .
We present wide field simulations of HI intensity maps based on N-body simulations of a 2.6 { Gpc / h } box with 2048 ^ { 3 } particles ( particle mass 1.6 \times 10 ^ { 11 } { M _ { \odot } / h } ) .
Using a conditional mass function to populate the simulated dark matter density field with halos below the mass resolution of the simulation ( 10 ^ { 8 } { M _ { \odot } / h } < M _ { halo } < 10 ^ { 13 } { M _ { \odot } / h } ) , we assign HI to those halos according to a phenomenological halo to HI mass relation .
The simulations span a redshift range of 0.35 \lesssim z \lesssim 0.9 in redshift bins of width \Delta z \approx 0.05 and cover a quarter of the sky at an angular resolution of about 7 ^ { \prime } .
We use the simulated intensity maps to study the impact of non-linear effects and redshift space distortions on the angular clustering of HI .
Focusing on the autocorrelations of the maps , we apply and compare several estimators for the angular power spectrum and its covariance .
We verify that these estimators agree with analytic predictions on large scales and study the validity of approximations based on Gaussian random fields , particularly in the context of the covariance .
We discuss how our results and the simulated maps can be useful for planning and interpreting future HI intensity mapping surveys .