A hybrid cosmological hydrodynamic/N-body code based on a weighted essentially nonoscillatory scheme

We present a newly developed cosmological hydrodynamics code based on weighted essentially non-oscillatory (WENO) schemes for hyperbolic conservation laws. WENO is a higher order accurate finite difference scheme designed for problems with piecewise smooth solutions containing discontinuities and has been successfully applied for problems involving both shocks and complicated smooth solution structures. We couple hydrodynamics based on the WENO scheme with the standard Poisson solver-particle-mesh (PM) algorithm for evolving the self-gravitating system. The third-order low-storage total variation diminishing (TVD) Runge-Kutta scheme has been used for the time integration of the system. To test the accuracy and convergence rate of the code, we subject it to a number of typical tests, including the Sod shock tube in multiple dimensions, the Sedov blast wave, and formation of the Zel'dovich pancake. These tests validate the WENO hydrodynamics with a fast convergence rate and high accuracy. We also evolve a low-density flat cosmological model (LambdaCDM) to explore the validity of the code in practical simulations.