Determination of the intrinsic scatter in the M-sigma and M-L relations

TL;DR

This paper refines the M-sigma and M-L relations for supermassive black holes, revealing larger intrinsic scatter than previously thought, which impacts understanding of black hole demographics and evolution.

Contribution

It provides improved estimates of the intrinsic scatter in the M-sigma and M-L relations based on a larger sample, highlighting the importance of this scatter in black hole studies.

Findings

Intrinsic scatter is larger than previously estimated.

Large scatter affects the black hole mass function and evolutionary studies.

Scatter decreases when considering only elliptical galaxies.

Abstract

We report on recently derived improved versions of the relations between supermassive black hole mass (M_BH) and host-galaxy bulge velocity dispersion (sigma) and luminosity (L) (the M-sigma and M-L relations), based on ~50 M_BH measurements and ~20 upper limits. Particular attention is paid to recovery of the intrinsic scatter (epsilon_0) in both relations. The scatter was found to be significantly larger than estimated in most previous studies. The large scatter requires revision of the local black hole mass function, and it implies that there may be substantial selection bias in studies of the evolution of the M-sigma and M-L relations. When only considering ellipticals, the scatter appears to decrease. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We also report on the effects on the fits of culling the sample according to the resolution of the black hole's sphere of influence.