shutting down star formation, galaxy templates

At group meeting, Wu and Moustakas spoke about galaxies with very high star formation rates, and galaxies that have just shut down their star formation abruptly. Wu is looking for the trigger for the cessation in these galaxies, which look like a generic phase in galaxy evolution. Moustakas has been looking at incredibly high velocity (thousand km/s) outflows of gas, possibly driven by very strong star formation.

After lunch I spoke with Bovy about my ideas to replace a PCA space with a set of hard templates in redshift determination and outlier finding for galaxy spectra. Although you need many more templates to represent the galaxies than you would need basis spectra to represent the spectra at some level of precision, you don't have to do nearly as much work to match spectra to individual unmixed templates as you have to do to find the position of the spectrum in the n-dimensional PCA space, in principle. Whether that is true in practice too, I don't yet know.

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