A Supermassive Black Hole Mass Measurement in NGC 5102 with Schwarzschild Orbit-superposition Modeling

Abstract

We present a stellar-dynamical mass measurement of the central black hole in the lenticular galaxy NGC~5102 (SA0$^-$). Our analysis combines high-quality integral-field spectroscopy from the VLT Multi Unit Spectroscopic Explorer with high-spatial- and high-spectral-resolution Hubble Space Telescope Imaging Spectrograph observations, using the Ca II triplet as a stellar kinematic tracer. We constrain the black hole mass with axisymmetric, three-integral Schwarzschild orbit-superposition models, incorporating surface brightness measurements from HST F547M WFPC2 imaging. Assuming a distance of $3.66\,\mathrm{Mpc}$, we find a black hole mass of $(1.30^{+0.19}_{-0.18})\times10^6\,\mathrm{M_{\scriptscriptstyle\odot}}$, which is within $1.7\sigma$ of a previous CO band-head-based Jeans Anisotropic Modeling result ($M_{\bullet}=(9.1^{+1.8}_{-1.5})\times10^5\,\mathrm{M_{\scriptscriptstyle\odot}}$). Our measurement is also consistent with literature extrapolations of the $M_{\bullet}$-$\sigma_e$ relation into the currently under-sampled low-mass regime. The close agreement between these independent dynamical approaches provides external validation of the Jeans Anisotropic Modeling framework and supports the robustness of our Schwarzschild orbit-superposition result, bolstering confidence in future black hole mass measurements with this framework.