2021ApJ...908...25B

We present multi-color high-resolution imaging of the host galaxy of the dwarf Seyfert UGC 06728. As the lowest-mass black hole to be described with both a direct mass constraint and a spin constraint, UGC 06728 is an important source for comparison with black hole evolutionary models, yet little is known about the host galaxy. Using Hubble Space Telescope imaging in the optical and near-infrared, we find that UGC 06728 is a barred lenticular (SB0) galaxy with prominent ansae at the ends of the bar. We cleanly separated the active galactic nucleus (AGN) from the resolved galaxy with two-dimensional image decompositions, thus allowing accurate surface brightness profiles to be derived in all filters from the outer edge of the galaxy all the way into the nucleus. Based on a sample of 51 globular cluster candidates identified in the images, the globular cluster luminosity function predicts a distance to UCG 06728 of 32.5 ± 3.5 Mpc. Combining the galaxy photometry with the distance estimate, we derive a starlight-corrected AGN luminosity, the absolute magnitude of the galaxy, and a constraint on the galaxy stellar mass of logM_*/M_☉=9.9±0.2.