Gravitational-wave population inference at past time infinity

Understand

Population studies of stellar-mass black-hole binaries have become major players in gravitational-wave astronomy.

• The underlying assumptions are that the targeted source parameters refer to the same quantities for all events in the catalog and are included when modeling selection effects.
• Both these points have so far been neglected when estimating the orientations of the black-hole spins.
• In particular, the detector-frame gravitational-wave frequency used to define frequency-dependent quantities (e.g., 20 Hz) introduces an inconsistent reference between events at the population level.