Intrinsic selection biases of ground-based gravitational wave searches for high-mass BH-BH mergers

TL;DR

This paper analyzes how intrinsic selection biases in ground-based gravitational wave searches affect the detection volume for high-mass black hole mergers, especially considering black hole spins and their impact on detection sensitivity.

Contribution

It provides a spin-dependent fit for detection volume as a function of mass and spin, accounting for waveform harmonics and uncertainties, aiding interpretation of future IMBH merger detections.

Findings

Detection volume depends strongly on black hole spins.

Fits are reliable for specific mass and spin ranges for LIGO detectors.

Selection bias favors aligned spins, influencing detection interpretation.

Abstract

The next generation of ground-based gravitational wave detectors may detect a few mergers of comparable-mass M\simeq 100-1000 Msun ("intermediate-mass'', or IMBH) spinning black holes. Black hole spin is known to have a significant impact on the orbit, merger signal, and post-merger ringdown of any binary with non-negligible spin. In particular, the detection volume for spinning binaries depends significantly on the component black hole spins. We provide a fit to the single-detector and isotropic-network detection volume versus (total) mass and arbitrary spin for equal-mass binaries. Our analysis assumes matched filtering to all significant available waveform power (up to l=6 available for fitting, but only l<= 4 significant) estimated by an array of 64 numerical simulations with component spins as large as S_{1,2}/M^2 <= 0.8. We provide a spin-dependent estimate of our uncertainty, up to S_{1,2}/M^2 <= 1. For the initial (advanced) LIGO detector, our fits are reliable for $M\in[100,500]M_\odot$ ($M\in[100,1600]M_\odot$). In the online version of this article, we also provide fits assuming incomplete information, such as the neglect of higher-order harmonics. We briefly discuss how a strong selection bias towards aligned spins influences the interpretation of future gravitational wave detections of IMBH-IMBH mergers.