THE ANGULAR-CORRELATION FUNCTION OF GALAXIES IN COLD DARK-MATTER AND COLD PLUS HOT DARK-MATTER MODELS

We estimate the angular correlation functions, w(theta), for the stand ard CDM, tilted n = 0.7 CDM and hybrid (CHDM) models, and compare with observations. When compared with the APM observational results scaled to the Lick depth, them appears to be fair agreement with the estimat e from the CHDM model. But a more detailed comparison using the unscal ed APM data for the five magnitude slices with DELTAb(j) = 0.5 shows t hat, in fact, none of the models can actually fit w(theta) for all the slices simultaneously. The CDM and tilted CDM models are then seen to fall below the APM data by a factor approximately 2 at theta = 1-degr ees, where the observed w(theta) is still relatively large (approximat ely 0.1) and, thus, probably less affected by any possible residual sy stematic errors. As n = 0.7 tilted CDM and SCDM bracket all possible t ilted models, we conclude that none of the tilted models is consistent with the APM results. With CHDM, a w(theta) amplitude that is 30%-40% too high on scales theta < 0.5-degrees is predicted for the deepest s lices (b(j) almost-equal-to 20). We find that no reasonable simple var iation of the parameters for the luminosity function or for the evolut ion of the correlation function with redshift could change the situati on. Thus, the discrepancy between the APM data and the CHDM model, tho ugh small seems to be real.