The local supermassive black hole mass density: corrections for dependencies on the Hubble constant

TL;DR

This paper revises previous measurements of the local supermassive black hole mass density by accounting for dependencies on the Hubble constant, leading to more accurate estimates and suggesting ways to improve future measurements.

Contribution

It introduces corrections for Hubble constant dependencies in black hole density estimates and provides updated ranges and methods for better future estimations.

Findings

Corrected black hole mass density range: 4.4-5.9 x 10^5 M_Sun/Mpc^3

Past estimates underestimated density by factors of ~2 without correction

Provides tabulated bulge-to-total flux ratios for improved mass estimation

Abstract

We have investigated past measurements of the local supermassive black hole mass density, correcting for hitherto unknown dependencies on the Hubble constant, which, in some cases, had led to an underestimation of the mass density by factors of ~2. Correcting for this, we note that the majority of past studies yield a local supermassive black hole mas density that is consistent with the range 4.4-5.9 x 10^5 f(H_0) M_Sun / Mpc^3 (when using H_0 = 70 km/s/Mpc). In addition, we address a number of ways in which these past estimates can be further developed. In particular, we tabulate realistic bulge-to-total flux ratios which can be used to estimate the luminosity of bulges and subsequently their central black hole masses.