galaxy structure, detecting stars

In the morning's Galaxy Coffee at MPIA, Rix talked about (among other things) Bovy's results on the structure of the Milky Way as a function of metallicity (from SEGUE data). Rix has the view that the results qualitatively confirm the view that vertical structure is set by radial mixing, where vertical action is sort-of conserved. Rix was followed by David Fisher (UMD) who spoke about bulges and pseudo-bulges. I challenged Fisher on whether his subjects of study were in fact bulgy, since he finds them by fitting two-dimensional images of near-face-on galaxies. He admitted that many of them may not be; his interest is in the action at the centers of disks, whatever the three-dimensional morphology.

In the afternoon, Lang and I worked on testing our optimal detection ideas in Stripe 82 data. It looks like we can beat what astronomers think of as optimal coadds (signal-to-noise-squared-weighted co-add images) by nearly ten percent in signal-to-noise-squared. That is like a ten-percent discount on observing time or total cost, so I am pretty pleased. We crush normal methods like exposure-time-weighted, unweighted, and (gasp) stacks where all contributing images have been smoothed to the same PSF.