Introduction

Pictor A is the seventh brightest radio galaxy in the sky at 408 MHz. It has a redshift, z= 0.036, and a nuclear, optical spectrum which has broad, permitted emission lines (Hydrogen, Helium), and relatively narrow optical forbidden emission lines ([OI], [SII], [OIII], [NII], etc.) superimposed on a featureless continuum. A ground-based image of the galaxy in the light of H is shown in Fig. 1 for comparison with the HST images.

The goal of our observations was to study the physics of the energy generation in this object's nucleus by measuring the size of the narrow-emission-line region (NLR), and searching for morphological features (such as a compact, double nucleus, or an optical jet related to the radio emission) which would provide clues as to the energy's source. At the redshift of Pictor A, 1" pc (where is the scale of the Hubble constant). Current physical models predicted that the nucleus of this object should be a point source and contain roughly 90%of the total flux observed from the ground within 1"while the NLR should be 0."1 in size (roughly 2.5 PC pixels at 43 mas pixel, the scale of the Planetary Camera).