Improved Dynamical Constraints on the Mass of the central Black Hole in NGC 404

Understand

We explore the nucleus of the nearby 10$^9M_{\odot}$~early-type galaxy (ETGs), NGC~404, using Hubble Space Telescope (HST)/STIS spectroscopy and WFC3 imaging.

• We first present evidence for nuclear variability in UV, optical, and infrared filters over a time period of 15~years.
• This variability adds to the already substantial evidence for an accreting black hole at the center of NGC~404.
• We then redetermine the dynamical black hole mass in NGC~404 including modeling of the nuclear stellar populations.