Multiplicative and additive systematics in galaxy density fluctuations and clustering measurements
arxiv(2024)
摘要
Galaxy clustering measurements are a key probe of the matter density field in
the Universe. With the era of precision cosmology upon us, surveys rely on
precise measurements of the clustering signal for meaningful cosmological
analysis. However, the presence of systematic contaminants can bias the
observed galaxy number density, and thereby bias the galaxy two-point
statistics. As the statistical uncertainties get smaller, correcting for these
systematic contaminants becomes increasingly important for unbiased
cosmological analysis. We present and validate a new method for understanding
and mitigating these systematics in galaxy clustering measurements (two-point
function) by identifying and characterizing contaminants in the galaxy
overdensity field (one-point function) using a maximum-likelihood estimator
(MLE). We test this methodology with KiDS-like mock galaxy catalogs and
synthetic systematic template maps. We estimate the cosmological impact of such
mitigation by quantifying uncertainties and possible biases in the inferred
relationship between the observed and the true galaxy clustering signal. Our
method robustly corrects the clustering signal to the sub-percent level and
reduces numerous additive and multiplicative systematics from 1.5σ to
less than 0.1σ for the scenarios we tested. In addition, we provide an
empirical approach to identifying the functional form (additive,
multiplicative, or other) by which specific systematics contaminate the galaxy
number density. Even though this approach is tested and geared towards
systematics contaminating the galaxy number density, the methods can be
extended to systematics mitigation for other two-point correlation
measurements.
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