  Sophisticated analysis of modern large-scale structure surveys requires mock
catalogs. Mock catalogs are used to optimize survey design, test reduction and
analysis pipelines, make theoretical predictions for basic observables and
propagate errors through complex analysis chains. We present a new method,
which we call "quick particle mesh", for generating many large-volume,
approximate mock catalogs at low computational cost. The method is based on
using rapid, low-resolution particle mesh simulations that accurately reproduce
the large-scale dark matter density field. Particles are sampled from the
density field based on their local density such that they have N-point
statistics nearly equivalent to the halos resolved in high-resolution
simulations, creating a set of mock halos that can be populated using halo
occupation methods to create galaxy mocks for a variety of possible target
classes.
