Clues about Disk Evolution from the Outermost Reaches of Galaxies
Rok Roskar (Washington)
Traditional theories of disk galaxy formation successfully predict that the light distribution in stellar disks
should roughly follow an exponential radial profile. However, an abundance of recent evidence suggests that
this is an oversimplification - many galaxies exhibit profiles, which deviate from a single exponential in the
outer parts. We investigate this phenomenon with an N-body/SPH approach. We simulate a suite of idealized
models representative of galaxy formation through dissipational collapse after the last major merger. We find
that the break is seeded by a drop in star formation density, while the outer exponential is populated almost
exclusively by stars that migrated there from the interior on surprisingly circular orbits. The degree of such
radial migrations is large and unexpected. I will discuss the theoretical basis for this phenomenon and present
observational evidence that lends support to the theory. I will also briefly chart out some far-reaching
implications of such migrations for studies ranging from the solar neighborhood to extragalactic stellar
populations.
