The radio galaxy PictorA { a study with the VLA

Detailed multi-frequency VLA observations of the prominentsouthernradiogalaxyPictorAaredescribed.Thera- diostructureisfoundtocompriseverydim,nearlycircularlobes with an extraordinarily bright and compact hot spot located at thewesternextremityofthewesternlobe.Afaintjetisobserved to connect this hot spot with the radio nucleus. No counter-jet is seen. The eastern lobe contains two hot spots of much lesser brightness and compactness. The radio lobes have signicantly differentspectralindices,withtheeastern(un-jetted)lobebeing 'steeper'. Enhanced spectral steepening is found in the central regions surrounding the radio nucleus, and around the periph- eriesofbothradiolobes.Theeasternlobedepolarizesatahigher frequencythanthewesternlobe,andalsodisplaysamuchhigher rms scatter in the derived rotation measure, although the mean rotation measure is very similar in both lobes. Steepening of the high frequency spectral index (6cm to2cm) is seen in the lobe near to the western hot spot. From the similarity in the structure of the western hot spot { including the extended lament { between radio and optical wavelengthrangesitisconcludedthatalloftheextendedoptical emission is due to the synchrotron process. The implications of these ndings are discussed.