re-doing spectroscopic distances in EDR3 with high-alpha too

Christina Eilers (MIT) and I discussed our ESA Gaia EDR3 projects today. Our top priority is to re-do our machine-learning (linear regression, really) spectrophotometric distance estimates for very luminous red-giant stars, and then re-map the Milky Way disk in abundances and kinematics. We think that even a small improvement in the parallaxes (as we expect to get on Thursday) might make a big difference to our inferred spectroscopic distances. We discussed the point that in our DR2 work we only used stars on the “low-alpha sequence”; we want to generalize if we are going to make complete abundance maps. But also the stars with different abundance trends might want very different distance estimation parameters. That suggests doing the EDR3 regression in a more “abundance-aware” way.