Further Evidence for a Supermassive Black Hole Mass - Pitch Angle Relation

TL;DR

This paper strengthens the evidence for a correlation between spiral arm pitch angle and supermassive black hole mass in disk galaxies, proposing a new imaging-based method for SMBH mass estimation.

Contribution

It introduces an improved measurement technique for spiral pitch angles and confirms their relation to SMBH mass, offering a practical tool for mass estimation from imaging data.

Findings

Established a quantitative relation: log(M/M_sun) = 8.21 - 0.062P.

Validated the method's effectiveness compared to other SMBH mass estimation techniques.

Demonstrated the relation's consistency with spiral structure theories.

Abstract

We present new and stronger evidence for a previously reported relationship between galactic spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass M_BH of a disk galaxy's nuclear supermassive black hole (SMBH). We use an improved method to accurately measure the spiral arm pitch angle in disk galaxies to generate quantitative data on this morphological feature for 34 galaxies with directly measured black hole masses. We find a relation of log(M/M_sun) = (8.21 +/- 0.16) - (0.062 +/- 0.009)P. This method is compared with other means of estimating black hole mass to determine its effectiveness and usefulness relative to other existing relations. We argue that such a relationship is predicted by leading theories of spiral structure in disk galaxies, including the density wave theory. We propose this relationship as a tool for estimating SMBH masses in disk galaxies. This tool is potentially superior when compared to other methods for this class of galaxy and has the advantage of being unambiguously measurable from imaging data alone.