Evidence for the evolution of the black hole mass function with redshift

by Stefano Rinaldi (Istituto Nazionale di Fisica Nucleare)

Tuesday 31 Oct 2023, 15:00 → 16:00 Europe/Rome

Abstract: The astrophysical graveyard is populated by black holes and neutron stars: these are the remains of the most massive stars, and studying them will teach us about the physics that governs the stars' lives and deaths. GW observations are now revealing the population of black holes via the detection of binary black hole mergers, and the numbers are set to grow rapidly in the coming years. The mass function and redshift distribution of binary black holes provide a key to interpret their formation channels, which depend on the not-well-understood physics of massive binary evolution.

In this talk, after a brief overview of the most recent LIGO-Virgo-KAGRA collaboration results, I will present our contribution to this problem: making use of Bayesian non-parametric methods, which are data-driven models able to infer arbitrary probability densities under minimal mathematical assumptions, we find evidence for the evolution with redshift of both the primary mass and mass ratio distribution. I will then discuss some possible astrophysical interpretations of our findings, namely a trend in metallicity with redshift and/or the presence of multiple, redshift-dependent formation channels.