def rho_crit(self):
        """
        critical density
        :return: value in M_sol/Mpc^3
        """
        h = self.cosmo.H(0).value / 100.
        return 3 * h ** 2 / (8 * np.pi * const.G) * 10 ** 10 * const.Mpc / const.M_sun
def rho_crit ( self ) : h = self . cosmo . H ( 0 ) . value / 100. return 3 * h ** 2 / ( 8 * np . pi * const . G ) * 10 ** 10 * const . Mpc / const . M_sun
critical density
        :return: value in M_sol/Mpc^3