Abstract

Evolutionary population synthesis models describing the energetic emission and stellar mass distribution of galaxies and star clusters are the essential interpretative tool in astrophysics and cosmology. They are used to infer key properties of stellar systems (age, chemical composition, stellar mass, dark matter fraction) from data, to predict the spectral energy distribution of simulated galaxies, to trace galaxy ages as a function of cosmic time for constraining cosmology, to predict the number, mass and location of stellar remnants rooting gravitational waves. Given their widespread use, the accuracy of population synthesis models affects directly our understanding of galaxy formation and evolution in a cosmological context. I shall review progress and difficulties and discuss key applications of these models over cosmic time.