The morphology of the Milky Way and spiral galaxies
Alex Pettitt (Hokkaido University)
March 26, 2015
Abstract: The arm structure of the Milky Way remains somewhat of an unknown, with observational studies hindered by our location within the Galactic disk. We present the results of a project aimed at constraining the global structure of the Milky Way through numerous numerical simulations and synthetic observations. We subject Galactic interstellar medium gas, simulated using smoothed particle hydrodynamics, to many different stellar potentials representing different arm and bar morphologies. We then use a 3D radiative transfer code to simulate the emission from the simulation output, allowing for the construction of synthetic longitude-velocity (l-v) emission maps as viewed from the Earth. By constraining these to observational data we are able to reverse engineer a top-down view of the our Galaxy. The best fitting maps have implications for the origin of spiral structure; is it caused by steady density waves, swing-amplified local instabilities, the rotation of inner bars or tidal interactions with nearby bodies? We will end with discussion of ongoing work looking into the sensitivity of disk galaxies to the latter of these processes, to discern the limits at which spiral arms are either tidally induced or formed by the disk itself.