What governs the efficiency of radial migration?

Transient spiral arms likely drive several dynamical processes that evolve galactic disks over long time-scales. One such process, commonly called radial migration, could cause a substantial fraction of disk stars to move large radial distances over the lifetime of the disk without kinematically heating. Should radial migration be efficient, it could have a significant impact on the disk’s kinematic, structural and chemical evolution. Observational studies resulting from large surveys such as RAVE, APOGEE and Gaia, suggest that episodes of efficient radial migration have occurred; however the development of a theoretical framework for those results is ongoing. I will first demystify the physics that governs radial migration and present an analytic criterion used to determine which stars could migrate. Based on this foundation I will present scaling relations that constrain the efficiency of radial migration for a given stellar population. I will argue that a higher fraction of stars will migrate in kinematically colder populations. I will also show that although higher amplitude spirals could in principle induce larger radial excursions, there is a fundamental upper limit to this distance which is smaller toward the inner disk.

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