Linking the Binary SMBH Population to PTA Data with a Self-Consistent Synthesis Framework

Pulsar timing arrays (PTAs) are galactic-scale gravitational wave observatories that are sensitive to the gravitational wave background (GWB) from the cosmic population of binary supermassive black holes (SMBH), which form following massive galaxy mergers. Due to a lack of direct observations, there remain many open questions about how to model the binary SMBH population that is producing the GWB detectable by PTAs. Currently, there are a wide variety of models commonly used to predict the GWB, including models based on cosmological simulations, semi-analytic models which can be built on top of observations of galaxies, and quasar-based models. Given the variety of assumptions that are included in each of these models, it is difficult to link the results derived from them individually into a single astrophysical inference. In this talk, I will present on-going work happening within the NANOGrav Astrophysics Working Group to create a self-consistent binary SMBH population synthesis framework that bridges these disparate modeling approaches. I will also show how we combine these new predictions for the GWB with a Gaussian Process emulator to extract a self-consistent astrophysical inference from NANOGrav's pulsar timing data.