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We perform Bayesian analysis of gravitational-wave signals from nonspinning, intermediate-mass black-hole binaries (IMBHBs) with observed total mass, M₎₁ₒ, from 50M_ to 500M_ and mass ratio 1--4 using advanced LIGO and Virgo detectors. We employ inspiral-merger-ringdown waveform models based on the effective-one-body formalism and include subleading modes of radiation beyond the leading (2, 2) mode. The presence of subleading modes increases signal power for inclined binaries and allows for improved accuracy and precision in measurements of the masses as well as breaking of degeneracies in distance, orientation and polarization. For low total masses, M₎₁ₒ50M_, for which the inspiral signal dominates, the observed chirp mass M₎₁ₒ=M₎₁ₒ^3/5 (being the symmetric mass ratio) is better measured. In contrast, as increasing power comes from merger and ringdown, we find that the total mass M₎₁ₒ has better relative precision than M₎₁ₒ. Indeed, at high M₎₁ₒ (300M_), the signal resembles a burst and the measurement thus extracts the dominant frequency of the signal that depends on M₎₁ₒ. Depending on the binary's inclination, at signal-to-noise ratio (SNR) of 12, uncertainties in M₎₁ₒ can be as large as 20--25% while uncertainties in M₎₁ₒ are 50--60% in binaries with unequal masses (those numbers become 17% vs. 22% in more symmetric mass-ratio binaries). Although large, those uncertainties in M₎₁ₒ will establish the existence of IMBHs. We find that effective-one-body waveforms with subleading modes are essential to confirm a signal's presence in the data, with calculated Bayesian evidences yielding a false alarm probability below 10^-5 for SNR9 in Gaussian noise. Our results show that gravitational-wave observations can offer a unique tool to observe and understand the formation, evolution and demographics of IMBHs, which are difficult to observe in the electromagnetic window.
Graff et al. (2015) studied this question.