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 \pm 0.44 ) \times 10 ^ { 16 } M _ { \odot } 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 \pm 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 .
The SSC contributes only a minor portion ( 9.0 \% \pm 2.1 \% ) of the peculiar velocity of the local group .