Six new supermassive black hole mass determinations from adaptive-optics assisted SINFONI observations

Different massive black hole mass - host galaxy scaling relations suggest that the growth of massive black holes is entangled with the evolution of their host galaxies. The number of measured black hole masses is still limited and additional measurements are necessary to understand the underlying physics of this apparent coevolution. We add six new black hole mass (M_BH) measurements of nearby fast rotating early-type galaxies to the known black hole mass sample, namely NGC 584, NGC 2784, NGC 3640, NGC 4570, NGC 4281, and NGC 7049. Our target galaxies have effective velocity dispersions (σ_e) between 170 and 245 km s^-1, and thus this work provides additional insight into the black hole properties of intermediate-mass early-type galaxies. We combined high-resolution adaptive-optics SINFONI data with large-scale MUSE, VIMOS and SAURON data from ATLAS^3D to derive two-dimensional stellar kinematics maps. We then built both Jeans Anisotropic Models and axisymmetric Schwarzschild models to measure the central black hole masses. Our Schwarzschild models provide black hole masses of (1.3 ± 0.5) × 10⁸ M_⊙ for NGC 584, (1.0 ± 0.6) × 10⁸ M_⊙ for NGC 2784, (7.7 ± 5) × 10⁷ M_⊙ for NGC 3640, (5.4 ± 0.8) × 10⁸ M_⊙ for NGC 4281, (6.8 ± 2.0) × 10⁷ M_⊙ for NGC 4570, and (3.2 ± 0.8) × 10⁸ M_⊙ for NGC 7049 at 3σ confidence level, which are consistent with recent M_BH-σ_e scaling relations. NGC 3640 has a velocity dispersion dip and NGC 7049 a constant velocity dispersion in the center, but we can clearly constrain their lower black hole mass limit. We conclude our analysis with a test on NGC 4570 taking into account a variable mass-to-light ratio (M/L) when constructing dynamical models. When considering M/L variations linked mostly to radial changes in the stellar metallicity, we find that the dynamically determined black hole mass from NGC 4570 decreases by 30%. Further investigations are needed in the future to account for the impact of radial M/L gradients on dynamical modeling.