bootstrap and jackknife, Arcturus

I wrote words about bootstrap and jackknife in my nascent line-fitting document. Bovy made some fake data for demos.

I read the Navarro et al paper on Arcturus, the moving group that is in the Solar Neighborhood but lagging the Solar motion (and the Local Standard of Rest) by 100 km/s. Navarro et al base their conclusions—that the stream is a disrupting galaxy that has contributed stars to the disk—on a number of things which are not at all consistent with Bovy and my reconstruction of the local velocity field. That is, most of the stars that Navarro et al associate with the moving group are not part of the moving group found in our analysis, though they certainly are lagging stars, and the group we find has a velocity dispersion way too small to be the remnant of anything massive. Then again, we do find a large population of lagging stars outside the Arcturus group, many of which may be interesting.