A high-resolution cosmological simulation of a strong gravitational lens
  We present a cosmological hydrodynamical simulation of a 10^13 Msun galaxy
group and its environment (out to 10 times the virial radius) carried out using
the EAGLE model of galaxy formation. Exploiting a novel technique to increase
the resolution of the dark matter calculation independently of that of the gas,
the simulation resolves dark matter haloes and subhaloes of mass 5x10^6 Msun .
It is therefore useful for studying the abundance and properties of the haloes
and subhaloes targeted in strong lensing tests of the cold dark matter model.
We estimate the halo and subhalo mass functions and discuss how they are
affected both by the inclusion of baryons in the simulation and by the
environment. We find that the halo and subhalo mass functions have lower
amplitude in the hydrodynamical simulation than in its dark matter only
counterpart. This reflects the reduced growth of haloes in the hydrodynamical
simulation due to the early loss of gas by reionisation and galactic winds and,
additionally, in the case of subhaloes, disruption by enhanced tidal effects
within the host halo due to the presence of a massive central galaxy. The
distribution of haloes is highly anisotropic reflecting the filamentary
character of mass accretion onto the cluster. As a result, there is significant
variation in the number of structures with viewing direction. The median number
of structures near the centre of the halo, when viewed in projection, is
reduced by a factor of two when baryons are included.
