Exploration of features in the black hole mass spectrum inspired by non-parametric analyses of gravitational wave observations

Abstract: Current gravitational-wave data reveal structures in the mass function of binary compact objects. Properly modelling and deciphering such structures is the ultimate goal of gravitational-wave population analysis: in this context, non-parametric models are a powerful tool to infer the distribution of black holes from gravitational waves without committing to any specific functional form. Here, we aim to quantitatively corroborate the findings of non-parametric methods with parametrised models incorporating the features found in such analyses. We propose two modifications of the currently favoured PowerLaw+Peak model, inspired by non-parametric studies, and use them to analyse the third Gravitational Wave Transient Catalogue. Our analysis marginally supports the existence of two distinct, differently redshift-evolving subpopulations in the black hole primary mass function, and suggests that, to date, we are still unable to robustly assess the shape of the mass ratio distribution for symmetric ($q>0.7$) binaries.