On the Determination of Star Formation Rates in Evolving Galaxy Populations

The redshift dependence of the luminosity density in certain wavebands (e.g. UV and Hα) can be used to infer the history of star formation in the populations of galaxies producing this luminosity. This history is a useful datum in studies of galaxy evolution. It is therefore important to understand the errors that attend the inference of star formation rate densities from luminosity densities. This paper explores the self-consistency of star formation rate diagnostics by reproducing commonly used observational procedures in a model with known galaxy populations, evolutionary histories and spectral emission properties. The study reveals a number of potential sources of error in the diagnostic processes arising from the differential evolution of different galaxy types. We argue that multi-wavelength observations can help to reduce these errors. Subject headings: cosmology: observations — galaxies: evolution — stars: formation