Pop III binary black holes detections using the next generation gravitational-wave detectors

Future gravitational-wave (GW) detector networks will detect binary-black-hole mergers (BBHs) up to redshift of ~20, which provides a direct measurement of the formation history of BBHs in the “early” universe. Here we show how GW detections of BBHs made by proposed third-generation detectors can be used to search for the Population III binaries at redshift >~10. To identify these Pop III binaries, we perform a mock data analysis based on the redshift distribution predicted by cosmological simulation, and infer its characteristic peak using Gaussian process regression with minimal model assumptions. With one month of observations at the predicted rate of ~400 Pop III BBHs per month, parameters describing its volumetric merger rate can be constrained at the O(10%) level.