Abstract

The radio properties of radio quiet active galaxies are revisited and considered under the starburst without black hole model. These radio properties are consistent with the luminosity, compactness and spectral index expected from a massive starburst process, where bright and compact radio supernovae and supernova remnants, i.e. radio hypernovœ, generate the radio emission.

Introduction

Since the discovery of quasars, theoretical and observational work has been done in order to characterize the variety of active galactic nuclei (AGNs), and to understand the physical mechanisms operating in these regions. The most popular scenario considers the presence of an accretion disc around a massive black hole. Under this scenario, different regimes of accretion and/or black hole masses plus some anisotropy in the radiation field could account for the whole variety of AGNs. Alternatively, a different model based on the evolution of a central compact star cluster, has been proposed and worked out in some detail (Terlevich, 1990 and references).

A natural way to ascertain the true nature of the compact objects in AGNs, is to look at the central regions of galaxies with the highest spatial resolution available, i.e. radio observations. High resolution VLBI and VLA observations with 5 and 250 mas resolution, respectively, allow the nuclei and cores of nearby active galaxies to be mapped with typical resolutions of a few parsecs. In this paper I briefly discuss the radio properties, absolute luminosity, spectral index, morphology and compactness of radio quiet active galaxies and compare these properties with the predictions of the starburst model.