Hunting for Supermassive Black Holes in Nearby Galaxies with the Hobby-Eberly Telescope

TL;DR

This study conducted a spectroscopic survey of over a thousand nearby galaxies using the Hobby-Eberly Telescope to identify suitable candidates for precise supermassive black hole mass measurements, highlighting biases in current data.

Contribution

It presents a large, targeted galaxy sample with detailed kinematic data, enabling future black hole mass measurements and revealing biases in existing black hole mass samples.

Findings

Black hole mass measurements are biased towards dense galaxies.

Large disk and low dispersion galaxies are under-represented.

The dataset provides high-resolution spectra and kinematic measurements.

Abstract

We have conducted an optical long-slit spectroscopic survey of 1022 galaxies using the 10m Hobby-Eberly Telescope (HET) at McDonald Observatory. The main goal of the HET Massive Galaxy Survey (HETMGS) is to find nearby galaxies that are suitable for black hole mass measurements. In order to measure accurately the black hole mass, one should kinematically resolve the region where the black hole dominates the gravitational potential. For most galaxies, this region is much less than an arcsecond. Thus, black hole masses are best measured in nearby galaxies with telescopes that obtain high-spatial resolution. The HETMGS focuses on those galaxies predicted to have the largest sphere-of-influence, based on published stellar velocity dispersions or the galaxy fundamental plane. To ensure coverage over galaxy types, the survey targets those galaxies across a face-on projection of the fundamental plane. We present the sample selection and resulting data products from the long-slit observations, including central stellar kinematics and emission line ratios. The full dataset, including spectra and resolved kinematics, is available online. Additionally, we show that the current crop of black hole masses are highly biased towards dense galaxies and that especially large disks and low dispersion galaxies are under-represented. This survey provides the necessary groundwork for future systematic black hole mass measurement campaigns.