Localizing Gravitational-wave Signals with Pulsar Timing Arrays: From the Worst To Best Case Scenario

The origin of the nanohertz-frequency gravitational-wave (GW) background discovered by several PTA collaborations is likely to be a population of inspiraling supermassive black hole binary systems, formed through the mergers of galaxies over cosmic time. A key milestone for PTA efforts will be resolving individual systems out of this confusion background signal to allow single-event characterization in tandem with the population signal. But how well can PTAs resolve the origin of a signal, and how is this localization capability tethered to the three-dimensional geometry of the pulsar network, the precision with which the pulsar distances are known, the noise in each pulsar, and the timespan over which a pulsar has been monitored? In this talk, I will explore these factors to present a geometric understanding of the PTA signal localization problem, with the goal of developing scaling relationships that may guide future expectations.