CONFRONTATION OF THE COLD PLUS HOT DARK-MATTER MODEL WITH OBSERVATIONAL DATA

A mixed cold-hot cosmological model with inflationary initial conditio ns (OMEGA(tot) = 1 and the flat, n = 1, spectrum of initial adiabatic perturbations) is compared with recent observational data. Results of the COBE DELTAT/T experiment are used to fix the normalization of the spectrum. The main restrictions on the model come from the clustering of galaxies at large scales, the value of the biasing parameter b for galaxies at R = 16(50/H0) Mpc and the conditions for quasar and galaxy formation. Under the most conservative assumptions (and neglecting so me tests), only a small region in the H0-OMEGA(nu) plane with H0 < 60 km s-1 Mpc-1, 0.1 less-than-or-equal-to OMEGA(nu) less-than-or-equal-t o 0.3 remains allowed (for H0 = 50, 0.17 less-than-or-equal-to OMEGA(n u) less-than-or-equal-to 0.28 is permitted). Natural additional requir ements that b greater-than-or-equal-to 1.7 and that large galaxies (M approximately 10(12) M.) formed at redshifts z greater-than-or-equal-t o 1 leave practically no allowed region for H0 greater-than-or-equal-t o 40. Therefore the HDM+CDM model is only marginally consistent with o bservations.