Simulating the shocks in the dissociative galaxy cluster Abell 1758N
  Major mergers between massive clusters have a profound effect in the
intracluster gas, which may be used as a probe of the dynamics of structure
formation at the high end of the mass function. An example of such a merger is
observed at the northern component of Abell 1758, comprised of two massive
sub-clusters separated by approximately 750 kpc. One of the clusters exhibits
an offset between the dark matter and the intracluster gas. We aim to determine
whether it is possible to reproduce the specific morphological features of this
cluster by means of a major merger. We perform dedicated SPH (smoothed particle
hydrodynamics) N-body simulations in an attempt to simultaneously recover
several observed features of Abell 1758, such as the X-ray morphology and the
separation between the two peaks in the projected galaxy luminosity map. We
propose a specific scenario for the off-axis collision of two massive clusters.
This model adequately reproduces several observed features and suggests that
Abell 1758 is seen approximately 0.4 Gyr after the first pericentric passage,
and that the clusters are already approaching their maximum separation. This
means that their relative velocity is as low as 380 km/s. At the same time, the
simulated model entails shock waves of ~4500 km/s, which are currently
undetected presumably due to the low-density medium. We explain the difference
between these velocities and argue that the predicted shock fronts, while
plausible, cannot be detected from currently available data.
