A stochastic background of g.w. may also be of astrophysical origin. In fact the emission of g.w. from a large number of unresolved astrophysical sources can create a stochastic background of g.w. The work done by the Rome group (prof. V. Ferrari and collaborators) on the study of the stochastic background of gravitational radiation is focused on the contributions given by cosmological populations of astrophysical sources, i.e. sources distributed throughout the universe from the onset of the galaxy formation up to the present time. In collaboration with Raffaella Schneider and Sabino Matarrese they have elaborated a general method to evaluate the spectral properties of the stochastic background generated by astrophysical sources, whose rate of formation can be deduced from the rate of formation of the corresponding stellar progenitor. The star formation rate they use is based on observations collected by the Hubble space Telescope, Keck and other large telescopes on the UV emission of stars forming galaxies up to redshifts of about
For reviews on the subject refers to Refs.[7,8,9].