Constraining high-redshift stellar-mass primordial black holes with next-generation ground-based gravitational-wave detectors

Understand

The possible existence of primordial black holes in the stellar mass window has received considerable attention because their mergers may contribute to current and future gravitational-wave detections.

• Primordial black hole mergers, together with mergers of black holes originating from Population~III stars, are expected to dominate at high redshifts ($z\gtrsim 10$).
• However the primordial black hole merger rate density is expected to rise monotonically with redshift, while Population~III mergers can only occur after the birth of the first stars.
• Next-generation gravitational-wave detectors such as Cosmic Explorer~(CE) and Einstein Telescope~(ET) can access this distinctive feature in the merger rates as functions of redshift, allowing for a direct measurement of the abundance of the two populations, and hence for robust constraints on the abundance of primordial black holes.