Populating the Low-mass End of the M BH –${\sigma }_{* }$ Relation

We present high-resolution spectroscopy taken with the Keck Echellete Spectrograph and Imager to measure stellar velocity dispersions for eight active dwarf galaxies (M* < 3 × 109 M⊙) with virial black hole masses. We double the number of systems in this stellar mass regime with measurements of both black hole mass (MBH) and stellar velocity dispersion (σ*), and place them on the MBH–σ* relation. The tight relation between MBH and σ* for higher mass galaxies is a strong piece of evidence for the coevolution of BHs and their host galaxies, but it has been unclear whether this relation holds in the dwarf galaxy regime. Our sample is in good agreement with the extrapolation of the MBH–σ* relation to low BH/galaxy masses, suggesting that the processes that produce MBH–σ* can also operate in dwarf galaxies. These results provide important constraints for massive black hole seed formation models and models exploring the impact of active galactic nucleus feedback in dwarf galaxies.