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The Southern Hemisphere component

PKS 0518-458 (Pictor A) is a low red shift (z=0.035) Fanaroff-Riley type II radio galaxy. At pc-scale resolution a one-sided jet-like structure is orientated so that the jet is directed at the hot spot in the north-west radio lobe. From the SHEVE observations, and simulations, it was found that there is some difficulty accepting that the optical jet suggested from sub-arcsecond imaging with the HST is real.

PKS 0521-365 (2EG J0524-3630) is the second closest extragalactic (z=0.055) radio source to be identified as a source of greater than 100 MeV gamma-rays by the EGRET instrument. With multi frequency SHEVE observations, the core of the radio source was identified and with multi epoch observations evolution was searched for. Some evidence for motion in the pc-scale jet was obtained but the period over which the source was observed was not sufficient to show significant change. The pc-scale radio jet aligns accurately with a kpc-scale radio and optical jet. The brightness temperature of the radio core is approximately tex2html_wrap_inline5912 K, well below the nominal limit for synchrotron radiation. As such, PKS 0521-365 is not likely to be a highly beamed source. PKS 0521-365 is thus an example of a gamma-ray source which does not fit the paradigm of Salamon & Stecker [1994], in which gamma-ray sources have a relativistic jet aligned with our line of sight.

PKS 1322-427 (Centaurus A, NGC 5128) is the closest active extragalactic radio galaxy to us, at a distance of approximately 3.5 Mpc. The extensive SHEVE observations presented here have unambiguously identified the core of the radio source for the first time and have followed over a period of approximately 4.3 years the evolution in the sub-pc-scale jet. The evolution in Centaurus A consists of the steady linear motion of one component close to the core, C2, as well as irregular and dramatic changes in the internal structure of a more complicated component further from the core, C1. High resolution and high quality VLBI images from the combination of SHEVE and VLBA data have revealed for the first time a sub-pc-scale radio counterjet. The dual frequency observations used to identify the core support the possible existence of a free-free absorbing structure which surrounds the core and may take the form of a pc-scale disk or torus of ionised material.

PKS 1514-241 (AP Libræ) is a low red shift (z=0.049) BL Lac type object which hosts a core dominated radio source. The SHEVE observations have revealed a slightly resolved pc-scale jet which is misaligned with the kpc-scale radio structure as seen with the VLA. Higher angular resolution observations will be required to determine more detail. The VLBI data on PKS 1514-241 was used in the investigation of gamma-ray emission from AGN as an example of a beamed radio source at low red shift which has not been identified as a gamma-ray source.

PKS 1718-649 (NGC 6328) is likely to be the lowest red shift (z=0.014) member of the GHz Peaked-Spectrum (GPS) class of radio sources found to date. Evidence for this comes from the pc-scale morphology as seen with the SHEVE observations, the kpc-scale radio structure and radio polarisation as seen with the ATCA, and the radio spectrum over almost 3 orders of magnitude in frequency, from 408 MHz to 230 GHz. Evidence that the radio source is not the typical core-jet source observed in many radio galaxies comes from optical imaging and optical spectroscopy. There is also some evidence from optical spectroscopy and HI imaging observations supporting suggestions that GPS radio sources are confined by an unusually dense or confused AGN environment which could possibly be caused by merger activity.

PKS 2152-699 (z=0.028) is a radio source which appears to be morphologically intermediate between the FR I and FR II classes, but above the FR I/FR II luminosity break. It is associated with a host galaxy which has the unusual property of nuclear-like optical emission some 5 kpc from the galaxy nucleus. There is a direct connection between the kpc-scale radio and optical structures, although they are misaligned. The SHEVE observations show that the inner radio jet in this galaxy is highly aligned with the extra-nuclear optical structure, strengthening the evidence supporting previous suggestions that the jet and a cloud of gas interact at the site of the extra-nuclear optical emission, the jet being deflected in the interaction. A model has been developed and presented which describes the deflection of the jet, showing that such an interaction is plausible, given the data from radio and optical observations.


next up previous contents
Next: The Northern Hemisphere component Up: Concluding remarks Previous: Concluding remarks

Steven Tingay
Tue Nov 26 15:27:29 PST 1996