The Coyote Universe Extended: Precision Emulation of the Matter Power
  Spectrum
  Modern sky surveys are returning precision measurements of cosmological
statistics such as weak lensing shear correlations, the distribution of
galaxies, and cluster abundance. To fully exploit these observations, theorists
must provide predictions that are at least as accurate as the measurements, as
well as robust estimates of systematic errors that are inherent to the modeling
process. In the nonlinear regime of structure formation, this challenge can
only be overcome by developing a large-scale, multi-physics simulation
capability covering a range of cosmological models and astrophysical processes.
As a first step to achieving this goal, we have recently developed a prediction
scheme for the matter power spectrum (a so-called emulator), accurate at the 1%
level out to k~1/Mpc and z=1 for wCDM cosmologies based on a set of
high-accuracy N-body simulations. It is highly desirable to increase the range
in both redshift and wavenumber and to extend the reach in cosmological
parameter space. To make progress in this direction, while minimizing
computational cost, we present a strategy that maximally re-uses the original
simulations. We demonstrate improvement over the original spatial dynamic range
by an order of magnitude, reaching k~10 h/Mpc, a four-fold increase in redshift
coverage, to z=4, and now include the Hubble parameter as a new independent
variable. To further the range in k and z, a new set of nested simulations run
at modest cost is added to the original set. The extension in h is performed by
including perturbation theory results within a multi-scale procedure for
building the emulator. This economical methodology still gives excellent error
control, ~5% near the edges of the domain of applicability of the emulator. A
public domain code for the new emulator is released as part of the work
presented in this paper.
