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General Relativity and Quantum Cosmology, gr-qc
Abstract:
We perform Bayesian analysis of gravitational-wave signals from non-spinning,
intermediate-mass black-hole binaries (IMBHBs) with observed total mass,
$M_{\mathrm{obs}}$, from $50\mathrm{M}_{\odot}$ to $500\mathrm{M}_{\odot}$ and
mass ratio $1\mbox{--}4$ 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 extrinsic parameter degeneracies. For low total
masses, $M_{\mathrm{obs}} \lesssim 50 \mathrm{M}_{\odot}$, the observed chirp
mass $\mathcal{M}_{\rm obs} = M_{\mathrm{obs}}\,\eta^{3/5}$ ($\eta$ being the
symmetric mass ratio) is better measured. In contrast, as increasing power
comes from merger and ringdown, we find that the total mass $M_{\mathrm{obs}}$
has better relative precision than $\mathcal{M}_{\rm obs}$. Indeed, at high
$M_{\mathrm{obs}}$ ($\geq 300 \mathrm{M}_{\odot}$), the signal resembles a
burst and the measurement thus extracts the dominant frequency of the signal
that depends on $M_{\mathrm{obs}}$. Depending on the binary's inclination, at
signal-to-noise ratio (SNR) of $12$, uncertainties in $M_{\mathrm{obs}}$ can be
as large as $\sim 20 \mbox{--}25\%$ while uncertainties in $\mathcal{M}_{\rm
obs}$ are $\sim 50 \mbox{--}60\%$ in binaries with unequal masses (those
numbers become $\sim 17\%$ versus $\sim22\%$ in more symmetric binaries).
Although large, those uncertainties will establish the existence of IMBHs. 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. (abridged)
