The impact of baryons, massive neutrinos and intrinsic alignments on weak lensing void statistics

Abstract We investigate the impact of baryonic physics, massive neutrinos, and galaxy intrinsic alignments (IA) on weak lensing (WL) void statistics using high-resolution convergence maps from the MillenniumTNG simulations. Full-sky and octant-sky maps are produced via ray-tracing from simulation mass shells and realistic mock galaxy catalogues that self-consistently include intrinsic galaxy shapes and alignments. WL voids are identified in the smoothed convergence field using the tunnel algorithm and characterized through their abundance and stacked radial convergence profiles. We explore the dependence of these observables on source redshift, angular smoothing scale, and convergence peak threshold. Baryonic physics has an impact of up to ≈30 % on void abundance, suppressing small voids, likely due to feedback processes, and enhancing large ones, consistent with stronger matter evacuation from underdense regions driven by radiative cooling. Stacked profiles are suppressed at all radii at the ≈10 % level. Massive neutrinos, through free-streaming, enhance the abundance of small voids and suppress large ones, with a strong dependence on the void peak threshold and the neutrino mass. They also modify void profiles by enhancing void centres and suppressing void edges. IA primarily affect the tails of the void size distribution, enhancing both small and large voids at the ≈20 % level, and inducing coherent,percnt-level changes in stacked profiles. Our results show that all three systematics leave measurable and partially degenerate signatures in WL void statistics, underscoring the importance of accurate modeling in upcoming Stage-IV surveys.