New Dark Energy Constraints from Supernovae, Microwave Background, and Galaxy Clustering

Using supernova, cosmic microwave background, and galaxy clustering data, we make the most accurate measurements to date of the dark energy density ${\rho }_X$ as a function of cosmic time, constraining it in a rather model-independent way, assuming a flat universe. We find that Einstein’s simplest scenario, where ${\rho }_X(z)$ is constant, remains consistent with these new tight constraints and that a big crunch or big rip is more than 50 Gyr away for a broader class of models allowing such cataclysmic events. We discuss popular pitfalls and hidden priors.