HectoMAP and Horizon Run 4: Dense Structures and Voids in the Real and Simulated Universe

Abstract

HectoMAP is a dense redshift survey of red galaxies covering a 53 \(deg^{2}\) strip of the northern sky. HectoMAP is 97\% complete for galaxies with \(r<20.5\), \((g-r)>1.0\), and \((r-i)>0.5\). The survey enables tests of the physical properties of large-scale structure at intermediate redshift against cosmological models. We use the Horizon Run 4, one of the densest and largest cosmological simulations based on the standard \(\Lambda\) Cold Dark Matter (\(\Lambda\)CDM) model, to compare the physical properties of observed large-scale structures with simulated ones in a volume-limited sample covering 8\(\times10^6\) \(h^{-3}\) Mpc\(^3\) in the redshift range \(0.22<z<0.44\). We apply the same criteria to the observations and simulations to identify over- and under-dense large-scale features of the galaxy distribution. The richness and size distributions of observed over-dense structures agree well with the simulated ones. Observations and simulations also agree for the volume and size distributions of under-dense structures, voids. The properties of the largest over-dense structure and the largest void in HectoMAP are well within the distributions for the largest structures drawn from 300 Horizon Run 4 mock surveys. Overall the size, richness and volume distributions of observed large-scale structures in the redshift range \(0.22<z<0.44\) are remarkably consistent with predictions of the standard \(\Lambda\)CDM model.