The Uchuu Simulations: Data Release 1 and Dark Matter Halo Concentrations

TL;DR

The Uchuu simulations provide an extensive set of high-resolution cosmological N-body data, enabling detailed study of dark matter halo evolution and properties across a vast range of scales and redshifts.

Contribution

This paper introduces the Uchuu suite of large, high-resolution cosmological simulations and provides initial data including statistics, power spectra, and halo concentration models.

Findings

Simulations accurately reproduce power spectra from BAO scale to small scales.

Mass-concentration relation fits within 5% across eight orders of magnitude in halo mass.

Detected an upturn in the mass-concentration relation for halos at z>0.5.

Abstract

We introduce the Uchuu suite of large high-resolution cosmological $N$-body simulations. The largest simulation, named Uchuu, consists of 2.1 trillion ($12800^3$) dark matter particles in a box of side-length 2.0 Gpc/h, with particle mass $3.27 \times 10^{8}$ Msun/h. The highest resolution simulation, Shin-Uchuu, consists of 262 billion ($6400^3$) particles in a box of side-length 140 Mpc/h, with particle mass $8.97 \times 10^{5}$ Msun/h. Combining these simulations we can follow the evolution of dark matter halos and subhalos spanning those hosting dwarf galaxies to massive galaxy clusters across an unprecedented volume. In this first paper, we present basic statistics, dark matter power spectra, and the halo and subhalo mass functions, which demonstrate the wide dynamic range and superb statistics of the Uchuu suite. From an analysis of the evolution of the power spectra we conclude that our simulations remain accurate from the Baryon Acoustic Oscillation scale down to the very small. We also provide parameters of a mass-concentration model, which describes the evolution of halo concentration and reproduces our simulation data to within 5 per cent for halos with masses spanning nearly eight orders of magnitude at redshift 0<z<14. There is an upturn in the mass-concentration relation for the population of all halos and of relaxed halos at z>0.5, whereas no upturn is detected at z<0.5. We make publicly available various $N$-body products as part of Uchuu Data Release 1 on the Skies & Universes site. Future releases will include gravitational lensing maps and mock galaxy, X-ray cluster, and active galactic nuclei catalogues.