After carefully writing down a likelihood function for velocity differences between stellar pairs, Price-Whelan (Flatiron) and I had the Duh realization that the maximum-likelihood velocity difference is just the precise velocity difference you would have computed by plugging the ESA Gaia DR2 catalog entries into the most straightforward formula. Oh well! But of course the likelihood function is still useful, because it can be evaluated at alternative hypotheses (such as: velocity difference vanishes) and it can be integrated in Bayes to make evidences (for what those are worth).
The short-term consequence of all this is that it is extremely easy to make a good comoving-star catalog from Gaia DR2. So easy it is barely a publication! Should we do it anyway?
No comments:
Post a Comment