Radius-Luminosity and Mass-Luminosity Relationships for Active Galactic Nuclei; Koratkar and Gaskell

Radius-Luminosity and Mass-Luminosity Relationships for Active Galactic Nuclei
Koratkar and Gaskell
The Astrophysical Journal, 370:L61-L64, 1991 April 1

In this paper, Koratkar and Gaskell study ten active galactic nuclei in an attempt to find a independant direct relationship between mass and bolometric luminosity of interior objects, i.e. the central black hole. Given any trend or solution is simple and calculable, they could then find a way to discern properties of distant galaxies based on a single observable. Though the paper touches lightly on raiud-luminosity relationships, I will focus more on the development of a mass-luminosity relationship and the verification of previous derivations in existence.

This paper centers around data collected by the authors regarding the active galactic nuclei, herein referred to as AGNs, of ten individual galaxies. These AGNs represent the core element of each galaxy and are expected to produce and radiate the majority of energy of the galaxy over most, if not all wavelengths of our observable range. The accepted model physics at that time of publishing favored the idea that any energy radiated would be the result of accretion from the Broad-Line Region onto the central object, or black hole. if we accept this model as correct, then it would make sense that the bolometric luminosity, a measure of the expected energy generation across all measurable wavelenghts, would correlate to the total mass of this region, the core AGN.

To produce working data for the mass is familiar and quite simple. Analyzing the Doppler width of the emission spectra provides velocity information for the gasses of the broad-line region surrounding the core. If we assume that the movement of gasses is dominated by gravitational forces, then we can calculate a value for the mass of the AGN by integrating over the core radius. Calculation can be done using any number of available methods, but was done using Monte Carlo methods for this paper.

This study resulted in producing a tested relationship between the bolometric luminosity and a calculated mass of AGNs. Since real astronomical data was used, this paper was a big step on the side of observational astronomy. In addition, it proved to solidify belief in the previously derived theoretical relationship suggested by previous researchers like Dibai, Joly, and Reshetnikov years earlier.