Multi-catalog comparison of post-Newtonian and numerical relativity mode amplitudes

The gravitational wave signal from a binary black hole merger carries information about its orbital dynamics. While the post-Newtonian (PN) expansion accurately models the early inspiral phase of a waveform, numerical relativity (NR) simulations are necessary near the merger. Nevertheless, the leading-order dependence of PN mode amplitudes on the binary parameters can motivate fitting functions for the NR amplitudes near the merger. This work studies whether PN-inspired fits can describe NR amplitudes across multiple publicly available NR catalogs, including SXS, RIT, and MAYA. We find that PN fits capture the dependence of NR mode amplitudes on the mass ratio of non-spinning systems. However, we observe significant discrepancies in the behavior of mode amplitudes for aligned spin simulations from different NR catalogs. These discrepancies highlight the need to ensure consistency across NR catalogs, essential for developing reliable waveform models. Furthermore, the results suggest that modes poorly represented by PN expressions could carry information about the strong-field dynamics of the merger, making them valuable for tests of general relativity.