Reconsidering the consistent use of precessing, higher order multipole models for gravitational wave analyses

The growing number of gravitational-wave (GW) observations allows for constraints to be placed on the underlying population of black holes; current estimates show that black hole spins are small, with binaries more likely to have comparable component masses. Since general relativistic effects, such as spin-induced orbital precession and higher order multipole moments, are more likely to be observed for asymmetric binary systems, a direct measurement remains unlikely. Nevertheless, we continue to consistently probe these effects by performing Bayesian inference with our most accurate and computationally expensive models. As the number of GW detections increases, it may soon become infeasible to consistently use these models for analyses. In this paper, we provide a selection criterion that determines when less accurate and computationally cheaper models can be used without giving biased estimates for the population properties of black holes in the Universe. We show that when using our selection criterion, comparable estimates can be obtained for the underlying mass and spin distribution of black holes for a simulated ‘worst-case’ scenario population, while reducing the overall cost of performing Bayesian inference on our population by ⁠~20 per cent. We anticipate a reduction of up to 78 per cent in the overall cost for an astrophysically motivated population, since there are fewer events with observable spin-precession and higher order multipole power.