Forecasting the impact of linear 3x2pt systematics on constraints of neutrino mass

Abstract

Neutrinos are fundamental particles that are millions of times more abundant than the baryons that make up all the visible matter in the Universe. Nevertheless, their extremely weak interaction with matter makes their detection particularly challenging. Recent particle physics experiments have confirmed that at least two of the three neutrino species have mass. However, these experiments can only determine the quadratic mass differences between the species, not their absolute individual values. Due to their abundance, neutrinos compose a significant fraction of the energy density of the Universe. Their physical effects on the background evolution of the Universe and on the growth of cosmic structures leave measurable impacts on cosmological observables. Among them, measurements of galaxy correlation are some of the main observables that provide a way to place upper limits on the sum of the masses of the three neutrino species. In this work, we investigate the correlation between the sum of neutrino masses, constrained using photometric galaxy data (3 × 2pt analysis), and some of the main linear systematics affecting these measurements, such as galaxy bias and intrinsic alignments. Through a Fisher matrix forecast analysis, we also verify that the Rubin LSST survey has constraining power on the sum of neutrino masses comparable to that of other surveys with more sensitive probes. Finally, by combining results from recent surveys with Rubin LSST synthetic measurements, the information on the neutrino parameter does not saturate, indicating that Rubin LSST can significantly contribute to joint cosmological analysis of the neutrino mass.