The Phoenix radio survey: The angular correlation function

Using the Phoenix radio survey, a homoge- neous survey selected at 1.4 GHz and covering an area of 3d eg 2 , we analyse the clustering of the sub-mJy ra- dio population using angular correlation function analy- sis. Extensive simulations are carried out to investigate the signicance of the estimated angular correlation am- plitudes. Our analysis show that for the S1:4 > 0: 5m Jy sub-samples the radio source distribution is anisotropic at the 2 signicance level. Additionally, we estimate up- per limits for the angular correlation amplitudes that, de- spite the large uncertainties, are in good agreement with the amplitude estimates for sources brighter than 1 mJy, detected in the FIRST radio survey (Cress et al. 1997). Adopting a radio luminosity function and assuming an evolving spatial correlation function of the form (r )= (r=r0) (1 + z) (3+) , with the evolution parametrised by , we nd an upper limit for the angular correlation length r0 9h 1 Mpc for S1:4 > 0: 5m Jy and =2 :1. This agrees well with the value r0 6 8h 1 Mpc esti- mated from the FIRST radio survey for sources brighter than 1 mJy. Additionally, we quantify the characteristics, in terms of areal coverage and limiting flux density, of fu- ture deep radio surveys to yield a signicant correlation amplitude detection and to explore possible changes of the correlation amplitude with flux density.