Astro Lunch

Galactoseismology in the Age of Gaia

Recent analyses of astrometric data from the SDSS, RAVE, and LAMOST surveys suggest that the stellar disk of the Milky Way is in a state of disequilibrium.  In particular, the disk appears to exhibit bending and breathing waves normal to its midplane in the Solar Neighbourhood and corrugation-like bending waves at larger Galactocentric radii. These waves may be linked to other time-dependent disk phenomena such as the bar, spiral structure, and the warp.  They may also be the result of a passing dark matter subhalo or dwarf galaxy. I will review the observational evidence for these waves, the theory of bending and breathing waves in stellar disks, and implications of disequilibrium for attempts to determine the local gravitational potential. Gaia-DR2, now just a few months away, should provide a significantly clearer picture of "waves in the disk".