Angular systematics-free cosmological analysis of galaxy clustering in
  configuration space
  Galaxy redshift surveys are subject to incompleteness and inhomogeneous
sampling due to the various constraints inherent to spectroscopic observations.
This can introduce systematic errors on the summary statistics of interest,
which need to be mitigated in cosmological analysis to achieve high accuracy.
Standard practices involve applying weighting schemes based on completeness
estimates across the survey footprint, possibly supplemented with additional
weighting schemes accounting for density-dependent effects. In this work, we
concentrate on pure angular systematics and describe an alternative approach
consisting in analysing the galaxy two-point correlation function where angular
modes are nulled. By construction, this procedure removes all possible known
and unknown sources of angular observational systematics, but also part of the
cosmological signal.We use a modified Landy-Szalay estimator for the two-point
correlation function that relies on an additional random catalogue where
angular positions are randomly drawn from the galaxy catalogue, and provide an
analytical model to describe this modified statistic. We test the model by
performing an analysis of the full anisotropic clustering in mock catalogues of
luminous red and emission-line galaxies at 0.43 < z < 1.1. We find that the
model fully accounts for the modified correlation function in redshift space,
without introducing new nuisance parameters. The derived cosmological
parameters from the analysis of baryon acoustic oscillations and redshift-space
distortions display slightly larger statistical uncertainties, mostly for the
growth rate of structure parameter fs8 that exhibits a 50% statistical error
increase, but free from angular systematic error.
