VAMANA: Modeling Binary Black Hole Population with Minimal Assumptions

TL;DR

VAMANA is a flexible mixture model approach for reconstructing the complex population distributions of binary black holes from gravitational wave data, capturing mass and spin variations with minimal assumptions.

Contribution

It introduces a novel mixture model framework that accurately reconstructs binary black hole populations, including mass and spin distributions, from gravitational wave observations.

Findings

Successfully reconstructs complex mass and spin distributions.

Demonstrates robustness with simulated data and real GW observations.

Provides estimates of merger rates for binary black holes.

Abstract

The population analysis of compact binaries involves the reconstruction of some of the gravitational wave (GW) signal parameters, such as, the mass and the spin distribution, that gave rise to the observed data. This article introduces VAMANA, which reconstructs the binary black hole population using a mixture model and facilitates excellent density measurement as informed by the data. VAMANA uses a mixture of weighted Gaussians to reconstruct the chirp mass distribution. We expect Gaussian mixtures to provide flexibility in modeling complex distributions and enable us in capturing details in the astrophysical chirp mass distribution. Each of the Gaussian in the mixture is combined with another Gaussian and a power-law to simultaneously model the spin component aligned with the orbital angular momentum and the mass ratio distribution, thus also allowing us to capture their variation with the chirp mass. Additionally, we can also introduce broadband smoothing by restricting the Gaussian mixture to lie within a threshold distance of a predefined reference chirp mass distribution. Using simulated data we show the robustness of our method in reconstructing complex populations for a large number of observations. We also apply our method to the publicly available catalog of GW observations made during LIGO's and Virgo's first and second observation runs and present the reconstructed mass, spin distribution, and the estimated merger rate of binary black holes.