Prospects for measuring off-axis spins of binary black holes with Plus-era gravitational-wave detectors

TL;DR

This study evaluates how upcoming gravitational-wave detectors can better measure the spins of binary black holes, especially off-axis spins, to understand their formation channels, showing significant improvements over current designs.

Contribution

The paper assesses the enhanced spin measurement capabilities of Plus-era detectors compared to previous designs using simulated gravitational-wave signals.

Findings

Plus upgrades improve spin estimation for unequal mass and high-spin systems.

Plus detectors yield better spin estimates for hierarchical BBH mergers.

Significant improvements in off-axis spin measurement with Plus detectors.

Abstract

The mass and spin properties of binary black holes (BBHs) inferred from their gravitational-wave signatures reveal important clues about how these systems form. BBHs originating from isolated binary evolution are expected to have spins preferentially aligned with their orbital angular momentum, whereas there is no such preference in binaries formed via dynamical assembly. The fidelity with which near-future gravitational-wave detectors can measure off-axis spins will have implications for the study of BBH formation channels. In this work, we examine the degree to which the Advanced LIGO Plus (A+) and Advanced Virgo Plus (AdV+) interferometric detectors can measure both aligned and misaligned spins. We compare spin resolution between the LIGO-Virgo network operating at either A+/AdV+ ("Plus") sensitivity or Advanced-era design ("Design") sensitivity using simulated BBH gravitational-wave signals injected into synthetic detector noise. The signals are distributed over the mass-spin parameter space of likely BBH systems, accounting for the effects of precession and higher-order modes. We find that the Plus upgrades yield significant improvements in spin estimation for systems with unequal masses and moderate or large spins. Using simulated signals modelled after different types of hierarchical BBH mergers, we also conclude that the Plus detector network will yield substantially improved spin estimates for 1G+2G binaries compared to the Design network.