THE POWER SPECTRA OF DARK HALOS IN A COLD DARK-MATTER UNIVERSE

Using an N-body simulation in which individual dark halos can be resolved, the evolution of the power spectrum, P(k), of halos in a standard cold dark matter (CDM) universe is investigated in both real and red-shift space. Three minimum overdensities of halos are chosen (similar to 2000, similar to 500, and similar to 70) and the power spectra of these objects are determined at various epochs in the simulation. In both redshift space and real space, the shapes and amplitudes of the power spectra of the halos and the degree to which the power spectra of the halos agree with the power spectrum of the mass particles depend upon both the minimum overdensity and mass of the halos. The power spectra of the mass particles in both real and redshift space show much more evolution than the power spectra of the halos. Later than b=6, the evolution of the power spectra of the mass particles is not well described by linear theory. Over the scales investigated (0.1 Mpc(-1) less than or similar to kh-1 less than or similar to 3 Mpc(-1)), at the end of the simulation (b=1) the ratio of P(k) in redshift space to P(k) in real space is considerable less than the linear theory prediction of 28/15, both in the case of the halos and in the case of the mass particles. The redshift space power spectra of the halos are compared to the power spectra of IRAS and CfA galaxies. For a universe normalized to the observed microwave background fluctuations, good agreement between the power spectra of the CfA galaxies and high-mass, high-overdensity halos is found. At the same epoch, the power spectrum of high-mass, moderate-overdensity halos agrees well with the power spectrum of IRAS galaxies.