Cosmology with active galactic nuclei

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This proposal is for $20200 pa over 4 years to trace the largest-scale structures in the Universe using quasars and radio galaxies. These luminous objects, known as 'Active Galactic Nuclei' can be seen to the limits of the observable universe, now to redshifts > 6. Radio emission is unaffected by dust so that unlike optically-selected objects, their true distribution may be mapped. We now have vast surveys at radio and optical wavelengths (FIRST, NVSS, 2dF, SDSS) producing catalogues of millions of objects. My colleagues and I have taken first steps in demonstrating how to exploit these data to use AGN as large-scale tracers of galaxy organization. In the process we assumed the 'unified model' relation between quasars and radio galaxies - and this is crucial if they are to be used as cosmic probes. Accordingly this interrelation between quasars and radio galaxies now requires critical examination, with optimum statistical techniques. Development of these is in progress. The current proposal describes three further investigations in which my students and I are engaged  - an examination of the Integrated Sachs-Wolfe effect, an improved definition of the discrete-galaxy cosmic dipole first measured by Blake and myself in 2002, and the analysis of a limited sky survey at the extreme radio frequency of 43 GHz. If newly-developed statistical techniques agree that unified models work, we have the ability to work out galaxy distributions independently of the optical, IR, and X-ray findings, all challenged by dust obscuration. We shall therefore be able to lend independent verification or otherwise to the strange 'consensus' model of the universe now prevelant, the one in which the Energy Density is 2 percent baryons that we know and love, while the rest is 30 per cent  Dark Matter of unknown form combined with 70 per cent Dark Energy of unknown type.