Binary Black Hole Mergers in a Massive Scalar Field Cloud

Ultra-light bosonic fields arising from string theory stand as compelling candidates for wave dark matter, and their presence around a binary black hole (BBH) can alter the binary dynamics significantly through processes such as superradiance, accretion, and dynamical friction. In this work, we investigate the impact of a massive scalar field on the gravitational radiation emitted during the binary black hole coalescence. This is accomplished by performing numerical relativity simulations of the full Einstein-Klein-Gordon system, where we treat the back-reaction of the scalar field onto the spacetime consistently in both the initial data and evolution. In particular, we vary the scalar mass parameter and binary mass ratio in our simulations and investigate their impacts on the coalescence waveforms, carefully detangling the effects of orbital eccentricity to draw comparisons with the vacuum scenario. We then discuss the implications of our results for gravitational wave observations.