Over lunch, Bovy, Hennawi, Myers, and I discussed the next projects
for the XDQSO project. We
figured out how to do XD photometric redshifts, which is an amusing
problem on which we might get excellent performance (by my definition
of performance
). We also discussed variability and the
production, from our probabilistic results, a hard-cut catalog.
I went to the Milky Way session in the afternoon, which included very nice talks by Kevin Schlaufmann (UCSC) and, of course, Zolotov. Schlaufmann showed that there is significant substructure in radial-velocity space, and that the overdensities in radial velocity also show chemical-abundance differences from the smooth component. Some of his ECHOS (what he calls the substructures) did not look to me at first glance to be statistically significant on their face, but then they do show chemical-abundance offsets from the field that do, taken as a whole, look highly significant. So I guess Schlaufmann is right and I am wrong!
Zolotov followed with a highly relevant theory talk, showing that you expect chemical-abundance differences between halo stars that fell in and halo stars that were kicked out of an early central bulge or disk. In the question period, it came up that the in-situ stars (as she calls them) should be on nearly-radial orbits. Furthermore, if they are kicked out in a set of short-duration events, there could be very strong non-trivial structure in phase-space for these stars. Gotta think about that, and then convince Zolotov and her team to find the strongest signatures in the simulations.
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