Ross Fadely arrived in Heidelberg today for a short visit. We discussed how to demonstrate success in and set the scope for our paper on star–galaxy classification using hierarchical Bayesian methods with (known bad) template SEDs. We are going to start by visualizing a few of the correct and incorrect classifications and see why they went that way.
Joe Hennawi consulted with me about a problem he is working on with Suzuki and Prochaska, to estimate the mean attenuation by the Lyman-alpha-absorbing IGM in large samples of quasars. The idea, roughly, is to assume that there is reasonable or modelable variations among quasars intrinsically, and then model the cosmological IGM attenuation and the proximity effects directly with a probabilistic model. We figured out how to do it on averages (stacks) of spectra, and we have a rough idea of how to do it on non-coadded individual quasars, but the latter is harder. I learned something important: Though I am consistently against stacking your data, it has the great advantage of employing the central limit theorem to make your noise Gaussian!
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