confusion in angle-spectrum space, and search

At Galaxy Coffee, Trevor Mendel (MPE) showed discussed resolved stellar populations as observed with the MUSE integral-field spectroscopy instrument. They extract spectra using spatial priors based on HST imaging, which is not unlike the forced photometry we did with WISE. This is obviously a good idea in confused fields. That led to a bus conversation with Mendel about the confusion limit as applied to spectroscopic (or multi-band imaging data). The confusion limit is a function (in this case) of the spectral diversity, as well as spatial resolution; indeed a band with low angular resolution but in which there is strong spectral diversity could help enormously with confusion. This is a fundamental astronomy point which (to my limited knowledge of the literature) may be unexplored. We also discussed what the data-analysis problems would look like if we had models of stellar spectra that we believed.

In the afternoon, Price-Whelan and I pair-coded a search algorithm for stellar structures that hew close to one orbit, given noisy phase-space measurements. We chased the problem for a while and then decided we have to suck it up and do some real engineering. Brute-force search is slow! Our usual mode is play first, profile later, but this problem is slow enough that we need to profile before playing. In particular, we have to apply some engineering know-how to the discretization of our model (computed) orbits and to our comparison of data to models (where we probably need a kd-tree or the like).

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