Recovering physical parameters from galaxy spectra using MOPED

We derive physical parameters of galaxies from their observed spectra using MOPED, the optimized data compression algorithm of Heavens, Jimenez & Laha v. Here we concentrate on parametrizing galaxy properties, and apply the me thod to the NGC galaxies in Kennicutt's spectral atlas. We focus on derivin g the star formation history, metallicity and dust content of galaxies. The method is very fast, taking a few seconds of CPU time to estimate similar to 17 parameters, and is therefore specially suited to studying large data sets, such as the Anglo-Australian two-degree-field (2dF) galaxy survey and the Sloan Digital Sky Survey (SDSS). Without the power of MOPED, the recov ery of star formation histories in these surveys would be impractical. In K ennicutt's atlas, we find that for the spheroidals a small recent burst of star formation is required to provide the best fit to the spectrum. There i s clearly a need for theoretical stellar atmospheric models with spectral r esolution better than I A if we are to extract all the rich information tha t large redshift surveys contain in their galaxy spectra.