No evidence that the binary black hole mass distribution evolves with redshift

¹ Universiteit Antwerpen, Prinsstraat 13, 2000 Antwerpen, Belgium
² Theoretische Natuurkunde, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
³ Kavli Institute for Cosmological Physics, The University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60615, USA

^⋆ Corresponding author: max.lalleman@uantwerpen.be

Received: 28 January 2025
Accepted: 15 April 2025

Abstract

Context. The mass distribution of merging binary black holes is generically predicted to evolve with redshift and to reflect systematic changes in their astrophysical environment, stellar progenitors, and/or dominant formation channels over cosmic time. Whether this effect is observed in gravitational-wave data remains an open question, however, and some contradictory results have been reported.

Aims. We study the ensemble of binary black holes within the latest GWTC-3 catalog released by the LIGO-Virgo-KAGRA Collaboration. We systematically searched for a possible evolution of their mass distribution with redshift.

Methods. We specifically focused on two key features in the primary mass distribution of a binary black hole: (1) an excess of 35 M_⊙ black holes, and (2) a broad power-law continuum ranging from 10 to ≳80 M_⊙. We determined whether one or both of these features were observed to vary with redshift.

Results. We found no evidence that either the Gaussian peak or power-law continuum components of the mass distribution change with redshift. In some cases, we placed somewhat stringent bounds on the degree of the allowed redshift evolution. Most notably, we found that the mean location of the 35 M_⊙ peak and the slope of the power-law continuum are constrained to remain approximately constant below redshift z≈1. The data remain more agnostic about other forms of a dependence on redshift, such as the evolution in the height of the 35 M_⊙ excess or the minimum and maximum black hole masses. We conclude that a redshift-dependent mass spectrum remains possible for all cases, but it is not required by the current data.