The Density Contrast of the Shapley Supercluster

Understand

We calculate the density contrast of the Shapley Supercluster (SSC) based on the enhanced abundance of X-ray clusters in it using the extended Press-Schechter formalism.

• We derive a total SSC mass of M_tot=(4.4+-0.44)x10^{16} M_sun within a sphere of 50 Mpc centered at a distance of about 160 Mpc.
• The nonlinear fractional density contrast of the sphere is (1+delta)=1.76+-0.17 relative to the mean matter density in the Universe, but the contrast increases in the interior of the SSC.
• Including the cosmological constant, the SSC region is found to be gravitationally unbound.