Testing Cold Dark Matter Models at Moderate to High Redshift

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Abstract
The Cosmic Background Explorer (COBE) microwave background temperature fluctuations and the abundance of local rich clusters of galaxies provide the two most powerful constraints on cosmological models. When all variants of the standard cold dark matter (CDM) model are subject to the combined constraints, the power spectrum of any model is fixed to ~10% accuracy in both the shape and overall amplitude. These constrained models are not expected to differ dramatically in their local large-scale structure properties. However, their evolutionary histories differ, with the differences being dramatically larger toward higher redshifts. In particular, it should be true that any statistical measure that probes a rapidly diminishing tail of some distribution should provide a sensitive test at some sufficiently high redshift, when the objects in question are rare and hence in the tail. We examine in detail six standardized, COBE- and cluster-normalized CDM models with respect to a large set of independent observations. The observations include the correlation function of rich clusters of galaxies, the galaxy power spectrum, the evolution of the rich cluster abundance, the gravitational lensing by moderate- to high-redshift clusters, the Lyα forest, the damped Lyα systems, the high-redshift galaxies, the reionization of the universe, and future cosmic microwave background experiments. It seems that each of the independent observations examined is potentially capable of distinguishing among at least some of the models. The combined power of several or all of these observations is tremendous. Thus, we appear to be on the verge of being able to make dramatic tests of all the models in the near future using a rapidly growing set of observations, mostly at moderate to high redshift. Consistency or inconsistency among different observed phenomena on different scales and/or at different epochs with respect to the models will have profound implications for the theory of the growth of cosmic structure.