Significant increase in sensitive volume of a gravitational wave search upon including higher harmonics

TL;DR

Incorporating higher harmonics into gravitational wave search templates significantly enhances the detection volume for binary black hole mergers, especially for high mass ratio and high mass systems, challenging previous conclusions.

Contribution

This study demonstrates that including higher harmonics in search templates substantially improves sensitivity, particularly for certain binary black hole configurations, using the IAS-HM pipeline.

Findings

Sensitivity gains exceeding 100% for high mass ratio systems

IAS-HM performs comparably or better than LVK pipelines for equal mass mergers

Higher harmonics inclusion broadens detectable parameter space

Abstract

Most gravitational wave searches to date have included only the quadrupole mode in their search templates. Here, we demonstrate that incorporating higher harmonics improves the search sensitive volume for detecting binary black hole mergers, challenging the conclusion of previous studies. Using the $\tt{IAS-HM}$ detection pipeline, and the simulated (injection) signals from the LIGO-Virgo-Kagra (LVK) collaboration, we quantify the improvement in sensitivity due to the inclusion of higher harmonics. This improvement is significant for systems with higher mass ratios and larger total masses, with gains in sensitivity even exceeding $100\%$ at certain high masses. We also show that, due to using a marginalized detection statistic, the $\tt{IAS-HM}$ pipeline performs roughly as well as its quadrupole-mode-only counterpart even for equal mass-ratio mergers, and its sensitive volume is either better than or comparable to that of the individual LVK pipelines.