Efficient high mass ratio binary black holes simulations using new gauges and initial data

We need more high mass ratio binary black hole merger simulations for better surrogate models and comparison with analytical waveforms. One of the primary issues with the current high mass ratio simulations is the large difference in the coordinate radius of the horizons. The coordinate radius of the horizon depends on the initial data and the gauge used during the simulation. Commonly used gauge choices lead to a very small coordinate radius for the horizon of the smaller black hole, which strains the mesh refinement and control systems used in the code, reducing its efficiency. We present a new gauge based on the rescaled Kerr metric that allows us to control the coordinate radius of a black hole's horizon irrespective of its mass. Simulations using this new gauge require a simpler grid structure reducing the strain on the other parts of the code and increasing its efficiency. We are also exploring using these rescaled Kerr metrics as our background metric for the initial data, which could allow us to generate initial data for higher mass ratio systems.