Stellar populations in Luminous Red Galaxies: cosmic chronometers?

The expansion rate of the Universe can potentially be measured using age-dating of Luminous Red Galaxies (LRGs). Here, we explore the validity of the assumptions implicit in this method using LRGs identified in the Millenium Simulation (MS). We use stellar population modelling and spectral synthesis to estimate the errors on ages that can be expected and discuss optimization of such an experiment. We find that H(z) using simulated galaxies from MS can be recovered with high accuracy. Using single stellar populations (SSPs) to age-date LRGs is not sufficient but if the MS star formation histories of galaxies are used, accurate ages are obtainable. We discuss an observing program to carry out this experiment using SALT (Southern African Large Telescope).