The Borg Cube Simulation: Cosmological Hydrodynamics with CRK-SPH
  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 2x2304^3 cold dark matter plus
baryon particles in an 800 Mpc/h 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) Msun/h. We compute angular power spectra for the thermal and
kinematic Sunyaev-Zel'dovich effects and find good agreement with the low-l
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.
