Impact of Spin Priors on the Population Inference of Merging Binary Black Holes

Abstract Gravitational waves generated by the merger of binary black holes (BBHs) provide valuable information about the BBHs themselves. In particular, the spin distribution is a crucial parameter for investigating the formation processes of BBHs. However, the LIGO-Virgo-KAGRA group’s population analysis may potentially be affected by systematic errors due to the spin prior. This study examines whether such errors introduce bias into the population analysis. The results show that no bias is introduced in estimating the effective spin distribution for BBH events up to O2. However, when posterior samples are derived from prior samples that significantly deviate from the population, population analysis may be affected. Therefore, when considering a subpopulation model for large spins, attention must be paid to the choice of spin prior to each event.