Stringent limits on the masses of the supermassive black holes in seven nearby galaxies

TL;DR

This study provides new, stringent upper limits on supermassive black hole masses in seven nearby galaxies using Hubble Space Telescope data, supporting the nebular line width as a reliable tracer of nuclear gravitational potential.

Contribution

It introduces a method to derive tight black hole mass limits from nebular emission line widths, expanding the sample to 114 galaxies for scaling relation studies.

Findings

Black hole mass limits are above the M-sigma relation.

Nebular line width effectively traces nuclear potential.

Sample size of galaxies with limits increased to 114.

Abstract

We present new stringent limits on the mass $M_{bh}$ of the central supermassive black hole for a sample of 7 nearby galaxies. Our $M_{bh}$ estimates are based on the dynamical modeling of the central width of the nebular emission lines measured over subarcsecond apertures with the Hubble Space Telescope. The central stellar velocity dispersion $\sigma_c$ of the sample galaxies is derived from new long-slit spectra from ground-based observations and the bulge effective radius is obtained from a two-dimensional photometric decomposition of the i-band images from the Sloan Digital Sky Survey. The derived stringent $M_{bh}$ limits run parallel and above the $M_{bh}-\sigma_c$ relation with no systematic trend depending on the galaxy distance or morphology. This gives further support to previous findings suggesting that the nuclear gravitational potential is remarkably well traced by the width of the nebular lines when the gas is centrally peaked. With our investigation, the number of galaxies with stringent $M_{bh}$ limits obtained from nebular-line width increases to 114 and can be used for studying the scaling relations between $M_{bh}$ and properties of their host galaxies.