Inferring the Spins of the Black Hole Binary Population with Next-Generation Ground-Based Gravitational Wave Detectors

Precisely measuring the spins of black holes in binaries remains a significant challenge in gravitational wave astronomy. This spin information is crucial to address fundamental questions about the nature of astrophysical black holes, their formation pathways and the environments in which they form. But current measurements of back hole spins from gravitational waves are mostly uninformative, obfuscated by limited signal-to-noise ratios (SNRs) and short signal lengths. Future ground-based interferometers will alleviate these barriers, as better low-frequency sensitivity will allow us to more accurately infer spin parameters of individual binaries with longer inspirals and higher SNRs, and consequently constrain the spin distribution of the binary black hole population. However, the exact minimum frequency sensitivity cutoff for planned future instruments such as Cosmic Explorer and Einstein Telescope remains uncertain. In this talk, I will demonstrate how accurate spin inference is dependent upon minimum frequency cutoff in these future instrument networks. I will show how parameter estimation of spins for individual binary mergers improves with more low frequency content, and the consequent improvements for constraining spin distributions across the population of binary black holes.