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

TL;DR

This study compares dense large-scale structures and voids in the HectoMAP galaxy survey with cosmological simulations, finding strong agreement that supports the standard $\\Lambda$CDM model.

Contribution

It provides the first detailed comparison of observed large-scale structures with high-resolution cosmological simulations at intermediate redshift.

Findings

Observed and simulated structures have similar size and richness distributions.

Largest structures in observations are consistent with simulation predictions.

Overall large-scale structure properties support the $\\Lambda$CDM model.

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.