paper

Baryonic acoustic oscillations from 21cm intensity mapping: the Square Kilometre Array case

arXiv:1609.00019 · doi:10.1093/mnras/stw3224

Abstract

We quantitatively investigate the possibility of detecting baryonic acoustic oscillations (BAO) using single-dish 21cm intensity mapping observations in the post-reionization era. We show that the telescope beam smears out the isotropic BAO signature and, in the case of the Square Kilometer Array (SKA) instrument, makes it undetectable at redshifts . We however demonstrate that the BAO peak can still be detected in the radial 21cm power spectrum and describe a method to make this type of measurements. By means of numerical simulations, containing the 21cm cosmological signal as well as the most relevant Galactic and extra-Galactic foregrounds and basic instrumental effect, we quantify the precision with which the radial BAO scale can be measured in the 21cm power spectrum. We systematically investigate the signal-to-noise and the precision of the recovered BAO signal as a function of cosmic variance, instrumental noise, angular resolution and foreground contamination. We find that the expected noise levels of SKA would degrade the final BAO errors by with respect to the cosmic-variance limited case at low redshifts, but that the effect grows up to at . Furthermore, we find that the radial BAO signature is robust against foreground systematics, and that the main effect is an increase of in the final uncertainty on the standard ruler caused by the contribution of foreground residuals as well as the reduction in sky area needed to avoid high-foreground regions. We also find that it should be possible to detect the radial BAO signature with high significance in the full redshift range. We conclude that a 21cm experiment carried out by the SKA should be able to make direct measurements of the expansion rate with competitive per-cent level precision on redshifts .

17 pages, 12 figures. MNRAS submitted

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