Hi IM correlation function from UNIT simulations: BAO and observationally induced anisotropy

We study the clustering of Hi intensity maps (IM) produced from simulations with a focus on baryonic acoustic oscillations (BAOs) and the effects induced by telescope beam smoothing and foreground cleaning. We start by creating an Hi catalogue at z = 1.321 based on the Semi-Analytic Galaxy Evolution (SAGE) model applied to the UNIT simulations. With this catalogue, we investigate the relation between model Hi and the dark matter haloes and we also study the abundance of Hi, Omega(HI) predicted by this model. We then create synthetic Hi IM with a nearest-grid-point approach. In order to simulate the telescope beam effect, a Gaussian smoothing is applied on the plane perpendicular to the line of sight. The effect of foreground removal methods is simulated by exponentially damping the largest wavelength Fourier modes on the radial direction. We study the anisotropic 2-point correlation function (2PCF) xi(r(perpendicular to), r(parallel to)) and how it is affected by the aforementioned observational effects. In order to better isolate the BAO signal, we study several 2PCF mu-wedges (with a restricted range of orientations mu) tailored to address the systematics effects and we compare them with different definitions of radial 2PCFs. Finally, we discuss our findings in the context of an SKA-like survey, finding a clear BAO signal in most of the estimators here proposed.

Automated summary

The study focuses on clustering of Hi intensity maps, particularly on baryonic acoustic oscillations (BAOs) and effects induced by telescope beam smoothing and foreground cleaning. A Hi catalogue is created using the Semi-Analytic Galaxy Evolution (SAGE) model in UNIT simulations at z = 1.321. Synthetic Hi intensity maps are generated to simulate telescope effects and foreground removal methods, and the 2-point correlation function and BAO signal are analyzed accordingly. Various 2-point correlation function mu-wedges are studied to effectively isolate the BAO signal and compare different radial 2-point correlation functions definitions.