Speaker
Description
After four observing runs, the LVK collaboration has estimated a local binary black hole (BBH) merger rate density of $R_0=14-26\, \textrm{Gpc}^{-3}\,\textrm{yr}^{-1}$. In this talk, I will show that current theoretical predictions systematically overestimate the BBH local merger rate when a realistic model of the metallicity-dependent star formation rate is adopted. Specifically, I will present an empirical framework for the evolution of cosmic star formation and metallicity, which has enough flexibility to bracket the whole range of observational uncertainties. I will show that, even under the most conservative assumptions, the predicted local BBH merger rate is overestimated by more than an order of magnitude. This finding indicates that revisions to the treatment of stellar and binary evolution are necessary to achieve consistency between theoretical predictions and observations.