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arXiv · 1610.09385

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

Dieu D. Nguyen·Anil C. Seth·Mark den Brok·Nadine Neumayer·Michele Cappellari·Aaron J. Barth·Nelson Caldwell·Benjamin F. Williams·Breanna Binder
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Abstract

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. We combine HST/STIS spectroscopy with WFC3 images to create a local color-$M/L$~relation derived from stellar population modeling of the STIS data. We then use this to create a mass model for the nuclear region. We use Jeans modeling to fit this mass model to adaptive optics (AO) stellar kinematic observations from Gemini/NIFS. From our stellar dynamical modeling, we find a 3$σ$ upper limit on the black hole mass of $1.5\times10^5M_{\odot}$. Given the accretion evidence for a black hole, this upper limit makes NGC~404 the lowest mass central black hole with dynamical mass constraints. We find that the kinematics of H$_2$ emission line gas show evidence for non-gravitational motions preventing the use of gas dynamical modeling to constrain the black hole mass. Our stellar population modeling also reveals that the central, counter-rotating region of the nuclear cluster is dominated by $\sim$1~Gyr old populations.

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Dieu D. Nguyen, Anil C. Seth, Mark den Brok, Nadine Neumayer, Michele Cappellari, Aaron J. Barth, Nelson Caldwell, Benjamin F. Williams, Breanna Binder. 2016-11-03. Improved Dynamical Constraints on the Mass of the central Black Hole in NGC 404. https://doi.org/10.3847/1538-4357%2Faa5cb4

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