Gravitational radiation from first-order phase transitions in the presence of a fluid

First-order phase transitions are a source of stochastic gravitational radiation. Precision calculations of the gravitational waves emitted during these processes sourced by both the degrees of freedom undergoing the transition and the anisotropic stress of the ambient constituents have reached an age of maturity. Here we present numerical simulations of a scalar field coupled to a fluid for a set of models that represent different types of first-order phase transitions. We parametrize the final gravitational wave spectrum as a function of the ratio of the energies of the constituents and the coupling between the two sectors. In most of the cases we study, the field sector is the dominant source of gravitational radiation, but it is possible in certain scenarios for the fluid to have the most important contribution.