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Abstract:
We present observational evidence for the presence of black holes at the centers of the five nearest early-type galaxies with stellar masses between 1 and 10 billion M☉. Using adaptive optics kinematics from Gemini and VLT, we find that all five galaxies appear to host central massive black holes. To derive dynamical black hole masses in these galaxies, we developed a novel technique to use high-resolution HST spectroscopy to accurately model mass-to-light variations seen in these nuclei. We find that four of the five galaxies have central black holes dynamically with masses below 1 million M☉, with the lowest mass black hole being only ~10,000 M☉. This work provides a first glimpse of the demographics of black holes in this galaxy mass range and at velocity dispersions below 70 km/s, and thus provides an important extension to the bulge mass and galaxy dispersion scaling relations. The ubiquity of central black holes in these galaxies provides a unique constraint on massive black hole formation scenarios, favoring a formation mechanism that produces an abundance of low-mass seed black holes.
