barak.virial.deltavir¶

barak.virial.deltavir(redshift, cosmo=None)[source]¶

The Virial overdensity as a function redshift.

This is an approximation parameterized by Bryan & Norman 98, ApJ, 495, 80. Good to 1% for omega(z) = 0.1-1, requires either omega = 1 (flat universe) or omega_lambda = 0.

This is given by dissipationless spherical top-hat models of gravitational collapse (Peebles 1990 ‘The Large Scale structure of the Universe’, Eke et al. 1996 MNRAS, 282, 263).