Yesterday Eilers (MPIA) and I thought that splitting the stars into many populations would help us: Every stellar population would have its own kinematic distribution, but every population would share the same gravitational potential. We were right on the first part: The velocity dispersion and scale length are both a strong function of chemical abundances (metallicity or alpha enhancement). We even made a bin-free model where we modeled the dependences continuously! But for each stellar population, the degeneracy between circular velocity of the potential and scale-length of the distribution function remains. And it is exact. So splitting by stellar sub-population can't help us! Durn. And Duh.
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