2022MNRAS.509.5416T

Supermassive black hole masses (M_BH) can dynamically be estimated with various methods and using different kinematic tracers. Different methods have only been cross-checked for a small number of galaxies and often show discrepancies. To understand these discrepancies, detailed cross-comparisons of additional galaxies are needed. We present the first part of our cross-comparison between stellar- and gas-based M_BH estimates in the nearby fast-rotating early-type galaxy NGC 6958. The measurements presented here are based on ground-layer adaptive optics-assisted Multi-Unit Spectroscopic Explorer (MUSE) science verification data at around 0_.^′′6 spatial resolution. The spatial resolution is a key ingredient for the measurement and we provide a Gaussian parametrization of the adaptive optics-assisted point spread function for various wavelengths. From the MUSE data, we extracted the stellar kinematics and constructed dynamical models. Using an axisymmetric Schwarzschild technique, we measured an M_BH of (3.6^+2.7_–2.4) ×10⁸M_☉ at 3σ significance taking kinematical and dynamical systematics (e.g. radially varying mass-to-light ratio) into account. We also added a dark halo, but our data do not allow us to constrain the dark matter fraction. Adding dark matter with an abundance matching prior results in a 25 per cent more massive black hole. Jeans anisotropic models return M_BH of (4.6^+2.5_–2.7) ×10⁸ and (8.6^+0.8_–0.8) ×10⁸M_☉ at 3σ confidence for spherical and cylindrical alignments of the velocity ellipsoid, respectively. In a follow-up study, we will compare the stellar-based M_BH with those from cold and warm gas tracers, which will provide additional constraints for the M_BH for NGC 6958, and insights into assumptions that lead to potential systematic uncertainty.