In Milky Way Group Meeting at MPIA today we discussed this paper on spiral structure as observed by Gaia. The paper shows that the spiral arms appear not just in the density of young stars but in their metallicities (at very low amplitude). What does this mean? I think maybe it's just the response of a smoother disk population to a perturbation: If you have a smooth disk with a metallicity gradient in it, and you perturb it, you wind up a spiral in the disk and that spiral appears as a low-amplitude abundance feature, because the spiral involves synchronizing the radial oscillations of stars at different guiding radii (and hence, given the gradient, different abundances). It is easy to work out quantitatively though. Maybe I should do that? Reminds me of what I have been working on with Neige Frankel (CITA), but in the vertical (rather than azimuthal) dynamics.
No comments:
Post a Comment