The angular power spectrum of NVSS radio galaxies

We measure the angular power spectrum C-l of radio galaxies in the NRAO VLA Sky Survey (NVSS) using two independent methods: direct spherical harmonic analysis and maximum likelihood estimation (MLE). The results are consistent and can be understood using models for the spatial matter power spectrum and for the redshift distribution of radio galaxies at mJy flux density levels. A good fit to the angular power spectrum can only be achieved if radio galaxies possess high bias with respect to mass fluctuations; by marginalizing over the other parameters of the model we derive a 68 per cent confidence interval 1.53 < b(0) x sigma(8) < 1.87, where b(0) is the linear bias factor for radio galaxies and sigma(8) describes the normalization of the matter power spectrum. Our models indicate that the majority of the signal in the NVSS C-l spectrum is generated at low redshifts z less than or similar to 0.1. Individual redshifts for the NVSS sources are thus required to alleviate projection effects and probe directly the matter power spectrum on large scales.