Cosmology with HI intensity mapping: effect of higher order corrections

Abstract

One of the main challenges of cosmology is to unveil the nature of dark energy and dark matter. They can be constrained with baryonic acoustic oscillations (BAO) and redshift space distortions, amongst others. Both have characteristic signatures in the dark matter power spectrum. Biased tracers of dark matter, such as neutral hydrogen, are used to quantify the underlying dark matter density field. It is generally assumed that on large scales the bias of the tracer is linear. However, there is a coupling between small and large scales of the biased tracer which gives rise to a significant non-linear contribution on linear scales in the power spectrum of the biased tracer. The Hydrogen Intensity and Real-time eXperiment (HIRAX) will map the brightness temperature of neutral hydrogen (HI) over BAO scales thanks to the intensity mapping technique. We forecasted cosmological parameters for HIRAX taking into account non-linear corrections to the HI power spectrum and compared them to the linear case. We used methods based on Fisher matrices. We found values for the bias to error ratio of the cosmological parameters as high as 1 or 7, depending on the noise level. We also investigated the change in peaks location on the baryonic acoustic oscillations signal. The value of the shift goes up to Δk = 10-2h/Mpc with a reduction of amplitude of the BAO features from 16:33% to 0:33%, depending on the scales.