Accretion Shocks in Clusters of Galaxies and their SZ Signature from
  Cosmological Simulations
  Cold dark matter (CDM) hierarchical structure formation models predict the
existence of large-scale accretion shocks between the virial and turnaround
radii of clusters of galaxies. Kocsis et al. (2005) suggest that the
Sunyaev-Zel'dovich (SZ) signal associated with such shocks might be observable
with the next generation radio interferometer, ALMA. We study the
three--dimensional distribution of accretion shocks around individual clusters
of galaxies drawn from adaptive mesh refinement (AMR) and smoothed particle
hydrodynamics (SPH) simulations of LCDM (dark energy dominated CDM) models. In
relaxed clusters, we find two distinct sets of shocks. One set ("virial
shocks"), with Mach numbers of 2.5-4, is located at radii 0.9-1.3 Rvir, where
Rvir is the spherical infall estimate of the virial radius, covering about
40-50% of the total surface area around clusters at these radii. Another set of
stronger shocks ("external shocks") is located farther out, at about 3 Rvir,
with large Mach numbers (~100), covering about 40-60% of the surface area. We
simulate SZ surface brightness maps of relaxed massive galaxy clusters drawn
from high resolution AMR runs, and conclude that ALMA should be capable of
detecting the virial shocks in massive clusters of galaxies. More simulations
are needed to improve estimates of astrophysical noise and to determine optimal
observational strategies.
