The Borg Cube Simulation: Cosmological Hydrodynamics with CRK-SPH

Abstract

A challenging requirement posed by next-generation observations is a firm theoretical grasp of the impact of baryons on structure formation. Cosmological hydrodynamic simulations modeling gas physics are vital in this regard. A high degree of modeling flexibility exists in this space making it important to explore a range of methods in order to gauge the accuracy of simulation predictions. We present results from the first cosmological simulation using Conservative Reproducing Kernel Smoothed Particle Hydrodynamics (CRK-SPH). We employ two simulations: one evolved purely under gravity and the other with non-radiative hydrodynamics. Each contains 2 × 2304 3 cold dark matter plus baryon particles in an 800 h −1 Mpc box. We compare statistics to previous non-radiative simulations including power spectra, mass functions, baryon fractions, and concentration. We find self-similar radial profiles of gas temperature, entropy, and pressure and show that a simple analytic model recovers these results to better than 40% over two orders of magnitude in mass. We quantify the level of non-thermal pressure support in halos and demonstrate that hydrostatic mass estimates are biased low by 24% (10%) for halos of mass 10 15 (10 13 ) h −1 M . We compute angular power spectra for the thermal and kinematic Sunyaev-Zel'dovich effects and find good agreement with the low-Planck measurements. Finally, artificial scattering between particles of unequal mass is shown to have a large impact on the gravity-only run and we highlight the importance of better understanding this issue in hydrodynamic applications. This is the first in a simulation campaign using CRK-SPH with future work including subresolution gas treatments.

Map Applications to Target Exascale Architecture with Machine-Specific Performance Analysis, Including Challenges and Projections

“…All of these error controls must be satisfied when running the challenge problem simulations at the >50× FOM requirement. For a recent exploration of cosmological simulation errors in hydrodynamic simulations by ExaSky, see Emberson, Frontiere, Habib, Heitmann, Larsen, Finkel, and Pope [32]; this paper uses the ExaSky-developed CRK-HACC code that implements the recently developed CRK-SPH method [33] in a cosmological setting. The final challenge problem runs will be carried out with a new set of subgrid models for gas cooling, UV heating, star formation, and supernova and AGN feedback, which are now under active development.…”

Higher-order initial conditions for mixed baryon-CDM simulations

“…While the cosmological baryon bias is a robust prediction of our cosmological model, the latest generation of cosmological galaxy formation simulations in large-scale structure context (e.g. Dubois et al 2014;Schaye et al 2015;Springel et al 2018;Emberson et al 2019, for the Horizon-AGN, Eagle, Illustris-TNG, and Borg-Cube simulations) still do not model it due to multiple reasons that we discuss below. At the same time, the precision determination of the matter power spectrum has now reached the level at which baryonic effects must be included in predictions from collisionless 'total matter' N-body simulations (cf.…”

Simulating Hydrodynamics in Cosmology with CRK-HACC

“…This study is devoted to the application of CRK-SPH in a cosmology framework, capitalizing on the accuracy of the solver, and serving as a basis for future work modeling numerous baryonic probes -such as Sunyaev-Zel'dovich maps, gravitational weak lensing measurements, gas-evolved synthetic sky catalogs, and the Lyman-α forest, to name a few. The Borg Cube simulation, described in Emberson et al (2019), was the first application of the CRK-HACC solver utilized in this manner, specifically in a non-radiative setting.…”