Uncertainties of Synthetic Population Models

This paper investigates the uncertainties in the synthetic integrated colours of simple stellar populations, currently the most popular method of estimating the ages of unresolved stellar systems. Three types of uncertainties studied here originate from the stellar models, the population synthesis techniques, and from the stellar spectral libraries. Despite some skepticism, synthetic colours appear to be reliable age indicators as long as they are used for select age ranges. This revised version was published online in September 2006 with corrections to the Cover Date.