Impact of higher harmonics of gravitational radiation on the population inference of binary black holes

TL;DR

This study assesses whether ignoring higher harmonics in gravitational wave templates biases the inferred population properties of binary black holes, finding minimal bias but improved precision when including these modes.

Contribution

It demonstrates that neglecting subdominant modes does not significantly bias population inference, but including them enhances measurement accuracy.

Findings

Neglecting subdominant modes does not cause significant bias in population inference.

Including higher harmonics improves the precision of parameter estimates.

Better measurement of maximum black hole mass constrains the upper mass gap.

Abstract

Templates modeling just the dominant mode of gravitational radiation are generally sufficient for the unbiased parameter inference of near-equal-mass compact binary mergers. However, neglecting the subdominant modes can bias the inference if the binary is significantly asymmetric, very massive, or has misaligned spins. In this work, we explore if neglecting these subdominant modes in the parameter estimation of non-spinning binary black hole mergers can bias the inference of their population-level properties such as mass and merger redshift distributions. Assuming the design sensitivity of advanced LIGO-Virgo detector network, we find that neglecting subdominant modes will not cause a significant bias in the population inference, although including them will provide more precise estimates. This is primarily due to the fact that asymmetric binaries are expected to be rarer in our detected sample, due to their intrinsic rareness and the observational selection effects. The increased precision in the measurement of the maximum black hole mass can help in better constraining the upper mass gap in the mass spectrum.