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Mapping gravitational waves from collisions of black holes

Periodic Reporting for period 3 - BlackHoleMaps (Mapping gravitational waves from collisions of black holes)

Reporting period: 2018-10-01 to 2020-03-31

This project was conceived in 2014 to make it possible to extract as much scientific information as possible from upcoming gravitational-wave observations of merger of black holes. Breakthrough work had already lead to the first model of the signal from mergers of generic configurations of black-hole binaries, but the model was based on several approximations, and was not tuned to full numerical simulations through the crucial merger and ringdown phases. Making that next leap in understanding of binary mergers was the goal of this project, through a large-scale targeted campaign of numerical simulations, and progress in analytic modelling techniques. Accurate models are necessary to correctly and precisely measure the parameters of black holes, and this information in turn could revolutionise our understanding of how black holes form, how many of them are in the universe, their masses and spins, and in turn the formation of stars and galaxies, and the overall composition of our universe.
The beginning of the project coincided with the first direct detection of GWs in 2015. The preliminary model, intended as a prototype for a precise tuned model, was the only generic model available to rapidly estimate the parameters of the signal. The first year of the project was consumed with testing the accuracy of that model (it was fortunately far more accurate than we expected!) and verifying that the measurements of that first discovery signal were not biassed by systematic errors. Since then the numerical simulation campaign has continued, and full generic modelling is underway. In addition, to meet the needs of binary black hole observations that came much earlier than anticipated at the beginning of the project, we have also developed the first inspiral, merger and ringdown model to include higher waveform harmonics, which will be essential if binaries are observed with mass ratios higher that 1:2.
The first higher multipole model has dramatically extended the state of the art, and will play an important role not only in potential observations, but also in assessing the science potential of future detectors. A tuned higher-multipole model is in development, along with the tuned generic model that is the ultimate goal this project.