What’s the best model of galaxy surface brightness distribution?

From the experiments that we have done over the last few years, my advisors and I were convinced that Sersic-based galaxy surface brightness model is not good for model selection. Simply speaking, it is impossible to tell whether a galaxy data is supported by single Sersic profile or bulge-disc profile, which consists of Sersic bulge and exponential disc (i.e. specific case of Sersic profile with n=1) if the galaxy is truly generated from single Sersic profile. Although this has been perceived by the experts of galaxy image modeling, it was a bit surprising to note that reliable Bayes factor estimation from accurate marginal likelihood computation of each model also tells the same.

More detail studies on this subject including practical choice of Bayes factor and hierarchical prior elicitation to improve a reliability of Bayes factor model selection for galaxy bulge-disc decomposition will be ready for submitting to a journal very soon.

However, if possible, we believe that one should find a better model with minimal parameter degeneracy for the best analysis result. One candidate for better model is a set of orthogonal basis function for modeling galaxy light distribution as suggested by some people.

Bayesian goodness-of-fit test for a galaxy surface brightness distribution model is possible using the Verdinelli and Wasserman algorithm implemented in the BIE for finding the best model supported by galaxy data. This would be an interesting study.


~ by ilsangyoon on March 12, 2012.

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