Very large scale structure in an open cosmology of cold dark matter and baryons

The standard cosmology of cold dark matter (CDM) in a flat universe with Gaussian, scale-invariant fluctuations, which is so successful in explaining the major properties of galaxies and their clustering on moderate scales, fails to account for the observed clustering of clusters and streaming velocities on scales of 30-100/h Mpc. Assuming that these observations are being interpreted correctly, an open Friedmann model where CDM and baryons contribute comparably to the mean mass density is considered. In this model the CDM is responsible for galaxy formation, while the presence of the baryons induces a large-scale feature in the spectrum of fluctuations at the precombination Jeans mass, giving rise to structure on very large scales. Using linear analysis and simulations based on the Zeldovich approximation, the resultant cluster-cluster correlation function and mean streaming velocity are found to be compatible with the observations. 71 references.