Active Galactic Nuclei and Nuclear Starbursts

Summary

Abstract

The Starburst model for radio-quiet Active Galactic Nuclei (AGN) postulates that the activity seen in most AGN is powered solely by young stars and compact supernova remnants (cSNR) in a burst of star formation at the time when the metal rich core of the spheroid of normal early type galaxies was formed. In this model, the broad permitted lines characteristic of the Broad Line Region (BLR) and their variability are originated in these cSNR. Combined analytic and numerical hydrodynamic simulations, with static photoionization computations have shown that cSNR can reproduce most of the basic properties of the BLR in low luminosity AGN.

We have explored the hypothesis that QSOs are the young metal rich cores of massive elliptical galaxies forming at z ≳ 2.0. Only a small fraction (∼ 5%) of the total mass of a normal spheroid, the core mass, is needed to participate in a burst to explain the observed luminosities and luminosity function of Quasars at z ≳ 2.0. We predict that the progenitors of QSOs should look as dusty starbursts and about 4 times more luminous than QSOs themselves.

Introduction

The hypothesis that a Starburst can power the most extreme forms of nuclear activity has been proposed several times in the past (Shklovskii 1960, Field 1964, McCrea 1976), but was not favoured mainly because it failed to explain satisfactorily the observed large luminosity and variability of quasars, their radio emission, unresolved images, the presence of extremely broad permitted emission lines in the spectrum and their observed intensity ratios.