2022ApJ...933L..14L

Coalescing binary black hole (BBH) systems are likely formed via several channels, and it is challenging to understand their formation/evolutionary processes. Some features in the mass function of the primary components (m₁), such as the distinct Gaussian-like peak located at ∼34 M_☉, have been previously found. In this work, we investigate the possible dependence of the mass ratio (q = m₂/m₁) distribution on the primary mass. We find a Bayesian odds ratio of 18.1 in favor of divergence in the mass ratio distributions between the low- and high-mass ranges over an invariable mass ratio distribution. BBHs with m₁ >= 29 M_☉ have a stronger preference of being symmetric compared to those with m₁ <= 29 M_☉ at a 97.6% credible level. Additionally, we find mild evidence that BBHs with m₁ located in the Gaussian-like peak have a mass ratio distribution different from that of other BBHs. Our findings may favor some formation channels, such as chemically homogeneous evolution and dynamical assembly in globular clusters/nuclear star clusters, which are more likely to provide symmetric BBHs in the high-mass range.