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

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 (but not all) past studies yield a local supermassive black hole mass density that is consistent with the range 4.4–5.9 × 10⁵f(H₀) M_⊙ Mpc⁻³ (when using H₀= 70 km s⁻¹ Mpc⁻¹). 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.