Gravitational waves from binary black hole mergers surrounded by scalar field clouds: Numerical simulations and observational implications

We show how gravitational-wave observations of binary black hole (BBH) mergers can constrain the physical characteristics of a scalar field cloud parametrized by mass ˜μ and strength ϕ0 that may surround them. We numerically study the inspiraling equal-mass, nonspinning BBH systems dressed in such clouds, focusing especially on the gravitational-wave signals emitted by their merger-ringdown phase. These waveforms clearly reveal that larger values of ˜μ or ϕ0 cause bigger changes in the amplitude and frequency of the scalar-field-BBH ringdown signals. We show that the numerical waveforms of scalar-field-BBHs can be modeled as chirping sine-Gaussians, with matches in excess of 95%. This observation enables one to employ computationally expensive Bayesian studies for estimating the parameters of such binaries. Using our chirping sine-Gaussian signal model, we establish that observations of BBH mergers at a distance of 450 Mpc will allow to distinguish BBHs without any scalar field from those with a field strength ϕ0 ≳ 5.5 × 10−3, at any fixed value of ˜μ ∈ [0.3 , 0.8], with 90% confidence or better, in single detectors with Advanced LIGO/Virgo type sensitivities. This provides hope for the possibility of determining or constraining the mass of ultralight bosons with gravitational-wave observations of BBH mergers.