Creating mock catalogues of stellar haloes from cosmological simulations
  We present a new technique for creating mock catalogues of the individual
stars that make up the accreted component of stellar haloes in cosmological
simulations and show how the catalogues can be used to test and interpret
observational data. The catalogues are constructed from a combination of
methods. A semi-analytic galaxy formation model is used to calculate the star
formation history in haloes in an N-body simulation and dark matter particles
are tagged with this stellar mass. The tags are converted into individual stars
using a stellar population synthesis model to obtain the number density and
evolutionary stage of the stars, together with a phase-space sampling method
that distributes the stars while ensuring that the phase-space structure of the
original N-body simulation is maintained. A set of catalogues based on the
$\Lambda$CDM Aquarius simulations of Milky Way mass haloes have been created
and made publicly available on a website. Two example applications are
discussed that demonstrate the power and flexibility of the mock catalogues. We
show how the rich stellar substructure that survives in the stellar halo
precludes a simple measurement of its density profile and demonstrate
explicitly how pencil-beam surveys can return almost any value for the slope of
the profile. We also show that localized variations in the abundance of
particular types of stars, a signature of differences in the composition of
stellar populations, allow streams to be easily identified.
