The Fundamental Plane of Black Hole Activity in the Optical Band

TL;DR

This study explores an alternative Fundamental Plane of Black Hole activity using optical [OIII] emission, confirming its universality across supermassive black holes and X-ray binaries, and analyzing radio loudness in low-luminosity AGN.

Contribution

It introduces a new version of the Fundamental Plane using optical luminosity, demonstrating its applicability across different black hole masses and accretion states.

Findings

The optical-based Fundamental Plane is consistent with the X-ray-based one.

The plane applies to both supermassive black holes and X-ray binaries.

Radio loudness varies among low-luminosity AGN within the plane.

Abstract

Black hole accretion and jet formation have long been thought to be scale invariant. One empirical relation suggesting scale invariance is the Fundamental Plane of Black Hole activity, which is a plane in the space given by black hole mass and the radio/X-ray luminosities. We search for an alternative version of this plane using the luminosity of [OIII] emission line instead of X-ray luminosity. We use a complete sample of 39 supermassive black holes selected from the Palomar Spectroscopic Survey with available radio and optical measurements and information on black hole mass. A sample of stellar mass X-ray binaries has also been included to examine if physical processes behind accretion is universal across the entire range of black hole mass. We present the results of multivariate regression analysis performed on the AGN sample and show that the sample stretches out as a plane in the 3D logarithmic space created by bolometric luminosity, radio luminosity and black hole mass. We reproduce the established Fundamental Plane of Black Hole activity in X-rays. We show that this plane can be obtained with the supermassive black hole sample alone and the X-ray binaries agrees to the found relation. We also discuss radio loudness of various classes of low-luminosity AGN in view of our fundamental plane.