by Emil Lenc (CAASTRO, SIfA, University of Sydney)
A study of deep observations of Pictor A in
radio with the Australia Telescope Compact Array (ATCA) and in X-rays with the
Chandra X-ray observatory over a time span of 15 years has just been accepted for publication in Monthly Notices: Hardcastle et al. (2015). The new observations build on earlier observations with the ATCA and Chandra and allow this powerful Fanaroff-Riley class II radio source, the nearest known, to be studied in great detail spatially, temporally and spectrally. This has provided further evidence of time variability in the jet and confirmed previous tentative evidence of a counter-jet. Futhermore, the new observations have, for the first time, provided tentative evidence of variability in the bright western hotspot linking back to earlier evidence of small-scale structure in the hotspot based on high-resolution radio observations (Tingay et al. 2008). Spectrally, the data confirms predictions of an inverse-Compton model and favours models in which filaments in the radio images are predominantly the result of spatial variation of magnetic fields in the presence of a relatively uniform electron distribution. The greyscale image above shows the 0.5 - 5.0 keV X-ray emission from Pictor A observed with the Chanda X-ray observatory and the red contours show the 5.5 GHz radio emission mapped with the ATCA.