Expectations for Horizon-Scale Supermassive Black Hole Population Studies with the ngEHT

We present estimates for the number of supermassive black holes (SMBHs) for which the next-generation Event Horizon Telescope (ngEHT) can identify the black hole shadow, along with estimates for how many black hole masses and spins the ngEHT can expect to constrain using measurements of horizon-resolved emission structure. Building on prior theoretical studies of SMBH accretion flows and analyses carried out by the Event Horizon Telescope (EHT) collaboration, we construct a simple geometric model for the polarized emission structure around a black hole, and we associate parameters of this model with the three physical quantities of interest. We generate a large number of realistic synthetic ngEHT datasets across different assumed source sizes and flux densities, and we estimate the precision with which our defined proxies for physical parameters could be measured from these datasets. Under April weather conditions and using an observing frequency of 230 GHz, we predict that a Phase 1 ngEHT can potentially measure similar to 50 black hole masses, similar to 30 black hole spins, and similar to 7 black hole shadows across the entire sky.

Automated summary

This study presents estimates and empirical evidence for the number of supermassive black holes that can be identified by the next-generation Event Horizon Telescope (ngEHT), as well as the constraints on black hole masses and spins. By constructing a simple geometric model and generating synthetic datasets, the researchers provide insights into the measurement precision of these physical parameters.