Running Late: The observable implications of delayed supermassive black hole growth.

Despite the vast amount of processes that depend on the co-evolution of supermassive black holes (SMBHs) and their host galaxies, their physical relationship is still not fully understood. Observations have revealed a well-constrained scaling relation between SMBH mass and galaxy bulge mass in the local universe. In galaxy formation simulations, a different form of SMBH growth behavior emerges at high redshift: prolonged slow growth in the early universe that is then compensated for by a rapid increase in mass. After this "catch-up" period of rapid growth, the SMBH growth resembles the observed local scaling relation. We conduct an in-depth study of this SMBH growth behavior to explore implications it has on the early universe scaling relation. We construct a simple model, using said behavior, to predict the quasar luminosity function which can be compared to well-documented observable quantities. To combine the simulation behaviors with a mock catalog of galaxies, we employ mathematical convolution techniques. This involves numerical integration methods over a population of dark matter halos and models relating the dark matter halo population to quasar luminosity. Alongside the mathematical approach that constructs our model, we employ Markov Chain Monte Carlo techniques to find the parameters that best fit our predicted function to observational data. These results allow us to systematically quantify the range of allowed scenarios for the emergence of the scaling relation between SMBH mass and galaxy bulge mass observed in the local universe.