#GaiaSprint, day 4

Each day at the Sprint, we have a check-in, in which daily results are discussed. Today Cecilia Mateu (UdelaR) showed improvements she has made to the database or list she maintains of known or reported stellar streams in the Milky Way halo. With the encouragement of Ana Bonaca (Harvard) and the help of Adrian Price-Whelan (Princeton), she made an astropy-compatible data file that delivers coordinate transformations into the stellar stream reference frames (great-circle coordinates). This will make it much, much easier for people to perform analyses on streams and compare new detections to known objects.

At lunch, a subset of the group that discussed the ESA Gaia selection function yesterday met again to discuss the possibility of putting together a large funding proposal to create what's needed. Many interesting things came up in this discussion. One is that many more projects are enabled by the selection function. So a small investment here greatly increases the impact of Gaia. Another is that we need to have a set of clearly defined example problems that illustrate the relevant issues. Another is that many of these possible example projects need not just an observational selection function but also a 3-d dust map in the Milky Way. Is that the same project or a different one? Another is that there aren't a lot of possible funding avenues that would be appropriate in both scale and international scope. It was a valuable discussion, but I don't know where we are at the end.

The highlight of the day was a long discussion of the kinematics of the Milky Way bar with Larry Widrow (Queen's) and Ortwin Gerhard (MPE) and Christina Eilers (MPIA) and Sarah Pearson (Flatiron). We almost became convinced that we are seeing the bar at the center of the Galaxy kinematically. It appears as a quadrupole in the velocity field. But if we are seeing it, we are seeing it at the wrong angle! So there is work to do. And many of the simple ideas about what we see depend on some kind of steady-state assumption, when in practice the bar evolves on a time-scale comparable to it's rotation period. More soon!