Accretion Discs in Realistic Potentials

Summary

Abstract

A realistic stellar cluster potential may have an observable effect on the thermal structure of an AGN accretion disc. Optimization of model parameters has found an extremely good fit to the broad-band spectrum of 3C 273 for reasonable assumptions about the central black hole and surrounding cluster.

Introduction

Various authors have shown that compact stellar clusters around AGN Black Holes are important in determining the properties and evolution of Active Galactic nuclei, e.g.. We describe a way of directly determining the mass and size of such clusters in certain cases.

Radiation from an AGN accretion disc derives, at least in part, from the local release of binding energy through viscosity. Here we assume that accretion is the sole energy source: the spectrum of the disc is determined by the potential into which it is falling. We derive an estimate of the disc spectrum by assuming black-body emission.

In a forthcoming paper, we find the spectrum expected from this model AGN, in which a dense, young stellar cluster surrounds a massive Black Hole. Here, we show a fit of this model to the continuum of 3C 273 (in its low state).

A Model of 3C 273

In Perry & Williams, we derive cluster parameters from the parameters of the fit given by. We have optimized the fit of our model to the data, (Fig. 1). In this figure, the different symbols identify different observations; the points near 10²¹ Hz are upper limits.