HI intensity mapping correlation function from UNIT simulations: BAO and
  observationally induced anisotropy
  We study the clustering of HI intensity maps produced from simulations with a
focus on baryonic acoustic oscillations (BAO) and the effects induced by
telescope beam smoothing and foreground cleaning. We start by creating a 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, $\Omega_{\rm HI}$, predicted by this model. We then create
synthetic HI intensity maps 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) $\xi(r_\perp,r_\parallel)$ 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.
