Inference on gravitational waves from coalescences of stellar-mass compact objects and intermediate-mass black holes

TL;DR

This paper assesses how accurately gravitational wave signals from coalescences involving intermediate-mass black holes can be measured, highlighting the importance of detector sensitivity and waveform models for understanding these cosmic events.

Contribution

It provides a detailed analysis of parameter measurement accuracy for intermediate-mass black hole mergers, emphasizing the role of low-frequency sensitivity and waveform uncertainties.

Findings

IMBHs above 130 solar masses can be identified with 95% confidence.

Mass and spin parameters are measurable with varying accuracy depending on source mass.

Low-frequency sensitivity enhances measurement of the inspiral phase for massive sources.

Abstract

Gravitational waves from coalescences of neutron stars or stellar-mass black holes into intermediate-mass black holes (IMBHs) of $\gtrsim 100$ solar masses represent one of the exciting possible sources for advanced gravitational-wave detectors. These sources can provide definitive evidence for the existence of IMBHs, probe globular-cluster dynamics, and potentially serve as tests of general relativity. We analyse the accuracy with which we can measure the masses and spins of the IMBH and its companion in intermediate-mass ratio coalescences. We find that we can identify an IMBH with a mass above $100 ~ M_\odot$ with $95\%$ confidence provided the massive body exceeds $130 ~ M_\odot$. For source masses above $\sim200 ~ M_\odot$, the best measured parameter is the frequency of the quasi-normal ringdown. Consequently, the total mass is measured better than the chirp mass for massive binaries, but the total mass is still partly degenerate with spin, which cannot be accurately measured. Low-frequency detector sensitivity is particularly important for massive sources, since sensitivity to the inspiral phase is critical for measuring the mass of the stellar-mass companion. We show that we can accurately infer source parameters for cosmologically redshifted signals by applying appropriate corrections. We investigate the impact of uncertainty in the model gravitational waveforms and conclude that our main results are likely robust to systematics.