Ideal scales for weighing the Universe

Abstract

We investigate the performance of a large class of cosmic microwave background experiments with respect to their ability to measure various cosmological parameters. We pay special attention to the measurement of the total cosmological density, $Ω$. We consider interferometer experiments, all-sky single-dish experiments, and also single-dish experiments with a deep-patch technique. Power spectrum estimates for these experiments are studied, and their induced errors in cosmological parameter estimates evaluated. Given this motivation we find various promising corners in the experiment parameter space surveyed. Low noise all-sky satellite experiments are the expensive option, but they are best suited for dealing with large sets of cosmological parameters. At intermediate noises we find a useful corner in high-resolution deep patch single-dish experiments. Interferometers are limited by sample variance, but provide the best estimates based on the very small angular scales. For all these experiments we present conservative, but still promising estimates of the accuracy of the measurement of $Ω$. In these estimates we consider a variety of possible signals not necessarily in the vicinity of standard cold dark matter.