Towards a realistic population of simulated galaxy groups and clusters
  We present a new suite of large-volume cosmological hydrodynamical
simulations called cosmo-OWLS. They form an extension to the OverWhelmingly
Large Simulations (OWLS) project, and have been designed to help improve our
understanding of cluster astrophysics and non-linear structure formation, which
are now the limiting systematic errors when using clusters as cosmological
probes. Starting from identical initial conditions in either the Planck or
WMAP7 cosmologies, we systematically vary the most important `sub-grid'
physics, including feedback from supernovae and active galactic nuclei (AGN).
We compare the properties of the simulated galaxy groups and clusters to a wide
range of observational data, such as X-ray luminosity and temperature, gas mass
fractions, entropy and density profiles, Sunyaev-Zel'dovich flux, I-band
mass-to-light ratio, dominance of the brightest cluster galaxy, and central
massive black hole (BH) masses, by producing synthetic observations and
mimicking observational analysis techniques. These comparisons demonstrate that
some AGN feedback models can produce a realistic population of galaxy groups
and clusters, broadly reproducing both the median trend and, for the first
time, the scatter in physical properties over approximately two decades in mass
($10^{13} \lesssim M_{500} \lesssim 10^{15}~\textrm{M}_{\odot}$) and 1.5
decades in radius ($0.05 \lesssim r/r_{500} \lesssim 1.5$). However, in other
models, the AGN feedback is too violent (even though they reproduce the
observed BH scaling relations), implying calibration of the models is required.
The production of realistic populations of simulated groups and clusters, as
well as models that bracket the observations, opens the door to the creation of
synthetic surveys for assisting the astrophysical and cosmological
interpretation of cluster surveys, as well as quantifying the impact of
selection effects.
