A universal bilinear model for the dependence of void asymmetry distributions on Ω m and σ 8

Aims. We present a new, independent diagnostics based on void properties, which can be used to constrain the matter density parameter (Ω m ) and amplitude of the initial density field ( σ 8 ). This diagnostics utilizes coherent rotation of void galaxies, which can be observed as redshift asymmetry on opposite sides bisected by the projected spin axes of hosting voids. Methods. By identifying the voids and their member galaxies in the AbacusSummit of cosmological simulations and searching for their projected spin axes with an iterative method, we were able to numerically determine the void asymmetry distributions both in real and redshift spaces for three different classes of background cosmologies based on the cold dark matter (CDM): ΛCDM, w CDM, and w 0 w a CDM. Results. We find that the void asymmetry distributions in real and redshift spaces are well approximated by the generalized Gamma models characterized by the scale and shape parameters for all of the 33 background cosmologies considered. It turns out that the initial conditions affect only the scale parameter of the void asymmetry distributions that exhibits an almost linear dependence on each of Ω m and σ 8 , while being insensitive to w . Developing a bilinear model for the dependence of void asymmetry distributions on Ω m and σ 8 , we show that its coefficients are universal constants over the three cosmological classes. Conclusions. Given that the void asymmetry distributions in redshift space are readily measurable properties, we conclude that our universal model for the scale parameter of the void asymmetry distributions will contribute to breaking the Ω m - σ 8 degeneracy, regardless of w , when combined with standard large-scale structure diagnostics.