Aspects of multimode Kerr ringdown fitting

A black hole that is ringing down to quiescence emits gravitational radiation of a very specific nature that can inform us of its mass and angular momentum, test the no-hair theorem for black holes, and perhaps even give us additional information about its progenitor system. This paper provides a detailed description of, and investigation into the behavior of, multimode fitting of the ringdown signal provided by numerical simulations. We find that there are at least three well-motivated multimode fitting schemes that can be used. These methods are tested against a specific numerical simulation to allow for comparison to prior work.