Exploring Features in the Binary Black Hole Population

TL;DR

This paper analyzes the distribution and features of binary black hole populations using gravitational wave data, revealing multiple peaks in mass distribution, spin-mass correlations, and redshift evolution patterns, which inform astrophysical formation theories.

Contribution

The study extends a mixture model framework to include redshift evolution and identifies detailed features in the binary black hole population using GWTC-3 data.

Findings

Chirp mass distribution has multiple peaks and lacks mergers with 10-12 M_sun.

Aligned spins increase with binary mass.

Redshift evolution varies across mass distribution peaks.

Abstract

Vamana is a mixture model framework that infers the astrophysical distribution of chirp mass, mass ratio, and spin component aligned with the orbital angular momentum for the binary black hole population. We extend the mixing components in this framework to also model the redshift evolution of merger rate and report all the major one and two-dimensional features in the Binary Black Hole population using the 69 gravitational wave signals detected with a false alarm rate $<1\mathrm{yr}^{-1}$ in the third Gravitational-Wave Transient Catalog (GWTC)-3. Endorsing our previous report and a corroborating recent report from LIGO Scientific, Virgo, and KAGRA Collaborations, we observe the chirp mass distribution has multiple peaks and a lack of mergers with chirp masses $10 \textrm{--} 12M_\odot$. In addition, we observe aligned spins show mass dependence with heavier binaries exhibiting larger spins, mass ratio shows a dependence on the chirp mass but not on the aligned spin, and the redshift evolution of the merger rate for the peaks in the mass distribution is disparate. These features possibly reflect the astrophysics associated with the binary black hole formation channels. However, additional observations are needed to improve our limited confidence in them.