GALAXY CLUSTERS AND THE COBE RESULT

The galaxy cluster temperature distribution function is calculated for several primordial power spectra, normalized to the amplitude of the COBE cosmic microwave background fluctuations. Using the Press-Schechter theory, we confirm that the standard cold dark matter model overproduces the abundance of X-ray clusters with this normalization (b approximately 1 in this case). Three possible resolutions are explored: (1) increasing the large-scale power of a CDM-dominated universe by changing the primeval power spectrum, (2) introducing models with a mixture of hot (approximately 30%) and cold dark matter, and (3) adopting a flat, low-density model (OMEGA = 0.2, LAMBDA = 0.8).