Hans-Walter Rix (MPIA) has been kicking around ideas for observationally testing the process of radial migration of orbits in the Milky Way disk. It is a slippery problem, because stars aren't tagged with their birth locations in the disk! His idea has been to assume that stellar surface metallicity is a nearly deterministic function of time and radius, and then look at explaining all of the variance in abundances we see at any radius today as being the result of radial migration. This is like a maximal approach to the problem. Maximal in the sense that it attributes all variance (in the age-metallicity relationship) to migration.
Today, on the plane home from undislo, I read a very nice draft by Neige Frankel (MPIA) that executes these ideas, and beautifully (and probabilistically). She uses stellar ages from the C and N dredge-up analysis of Melissa Ness (MPIA), which are imprecise but do seem to be ages. Frankel finds sensible parameters for the migration, in terms of radius variance as a function of time. It all hangs together, because the Milky Way data (from APOGEE in this case) really do show a broadening of scatter in metallicity as a function of radius as age increases. That is, there does seem to be at least qualitative support for this picture of radial migration.
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