21-cm foregrounds and polarization leakage: cleaning and mitigation strategies

ABSTRACT The success of H i intensity mapping is largely dependent on how well 21-cm foreground contamination can be controlled. In order to progress our understanding further, we present a range simulated data from two different ∼3000 deg2 sky regions, with varying effects polarization leakage. Combining these cosmological simulations creates test cases that require treatments. This allows us conduct the most generalized study date into foregrounds and their cleaning techniques for post-reionization era. We first provide pedagogical review commonly used blind removal [principal component analysis (PCA)/singular value decomposition (SVD), fast independent (FASTICA), morphological (GMCA)]. also trial non-blind parametric fitting technique discuss potential hybridization methods. highlight similarities differences in finding methods produce near equivalent results, explain fundamental reasons this. Our results demonstrate polarized residuals should generally subdominant small scales ($k\gtrsim 0.1\, h\, \text{Mpc}^{-1}$). However, larger scales, are more case dependent. some cases, aggressive cleans severely damp power but still leave dominant residuals. find changing fraction has little impact within realistic (0.5–2 per cent); however, higher level Faraday rotation does cleaning. gain cross-correlations optical galaxy surveys, where extreme levels residual circumvented. contribute errors optimal balance between overcleaning undercleaning.