REDSHIFT SPACE CLUSTERING OF GALAXIES AND COLD DARK MATTER MODEL

The distortion,effect of peculiar velocities on the power spectrum and correlation function of galaxies in redshift space is investigated ov er a large range of scales, from approximately 1 to 400 h-1 Mpc, using large-scale computer simulations of cold dark matter models. The resu lts are compared with observations of optical and IRAS galaxies. The d istortion effect is observed to be large; it significantly changes the shape of the power spectrum. For OMEGA = 1, the redshift space power spectrum is enhanced by a factor of nearly 2 over the real space spect rum on large scales, and is decreased by a factor of about 5 on small scales, resulting in a considerably steeper spectrum in redshift space than in real space. A direct comparison of observations and simulatio ns in redshift space reveals that, contrary to previous suggestions, t he power spectrum of IRAS galaxies, as well as optical galaxies, is co nsistent with the spectrum of the standard cold dark matter (CDM) mode l. The problems that an OMEGA = 1 CDM model currently faces, such as t oo large perculiar velocities on small scales, may be related more to the high value of OMEGA in the model rather than to the shape of the s pectrum. A low-density CDM model is also investigated and found to be consistent with the data. It appears that the redshift-space power spe ctrum alone is rather insensitive to OMEGA for CDM models for scales l ess-than-or-equal-to 200 h-1 Mpc.