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Session 4 - Low Luminosity AGN and Starburst Galaxies.
Display session, Monday, June 10
Tripp Commons,
A composite AGN/starburst picture has been conjectured to explain the class of AGNs that are highly luminous IRAS sources. We are performing observations designed to investigate the physical conditions in the inner regions of a sample of a dozen IRAS-selected radio-bright southern Seyferts 2 galaxies. We are particularly interested in correlations between radio morphology and the properties of any associated emission-line gas in the circumnuclear environment. Our data consists of optical spectra obtained with the AAT and 13, 6 and 3 cm radio continuum observations made with the ATCA. The sample was found to contain a variety of different radio morphologies, ranging from well defined linear triples sources to more diffuse, knotty radio emitting regions. In the majority of cases where long-slit spectra were obtained, we found significantly extended emission lines. An analysis of the line ratios in the nuclear regions often showed a transition from AGN-dominated to star-formation-dominated emission consistent with the composite picture described above. In one example of a galaxy with diffuse and knotty radio emission, IC 3639, the radio knots were found to correspond to optical gas with line ratios indicative of massive star formation over a 4kpc scale. There is a strong east-west asymmetry, with the star forming knots on the western side and shocked gas, devoid of radio emission, on the eastern side. Kinematic data from various lines, including very extended [OI]\lambda6300, is also presented for some of the galaxies. Near IR spectra show the detection of molecular hydrogen and [FeII] emission in the nuclei of 4 of the galaxies, supporting the view that many of these galaxies contain vigorous nuclear star-formation.
