Forecasting constraints on the population distribution of black hole charge from binary black hole ringdown catalogs

The next generation of gravitational-wave observations will deliver both higher signal-to-noise ratios (SNRs) and a growing catalog of binary black hole detections, enabling unprecedented spectroscopic tests of remnant black holes and growing constraints on the population properties of any beyond Kerr behaviour. In particular, ringdown measurements can be used to constrain astrophysical black hole charge. We present forecasts for how these constraints will improve with increasing SNR and event counts. To this end, we perform charged ringdown parameter estimation on injected catalogs, followed by a hierarchical Bayesian analysis that simultaneously infers astrophysical charge and other population parameters, yielding population-level bounds on astrophysical black hole charge. We highlight methodological advances in hierarchical analyses that are central to obtaining robust results for bounded parameters, where standard sampling-based approaches can be biased near the negligible-charge hypothesis. Our results show how continued improvements in measurement precision and a growing catalog will steadily tighten population-level constraints on astrophysical charge.