SATMC: Spectral energy distribution Analysis Through Markov Chains

We present the general purpose spectral energy distribution (SED) fitting tool SED Analysis Through Markov Chains (satmc). Utilizing Monte Carlo Markov Chain (MCMC) algorithms, satmc fits an observed SED to SED templates or models of the user's choice to infer intrinsic parameters, generate confidence levels and produce the posterior parameter distribution. Here, we describe the key features of satmc from the underlying MCMC engine to specific features for handling SED fitting. We detail several test cases of satmc, comparing results obtained from traditional least-squares methods, which highlight its accuracy, robustness and wide range of possible applications. We also present a sample of submillimetre galaxies (SMGs) that have been fitted using the SED synthesis routine grasil as input. In general, these SMGs are shown to occupy a large volume of parameter space, particularly in regards to their star formation rates which range from similar to 30 to 3000 M-circle dot yr(-1) and stellar masses which range from similar to 10(10) to 10(12) M-circle dot. Taking advantage of the Bayesian formalism inherent to satmc, we also show how the fitting results may change under different parametrizations (i.e. different initial mass functions) and through additional or improved photometry, the latter being crucial to the study of high-redshift galaxies.