THE CORRELATION-FUNCTION OF RADIO-SOURCES

We investigate the large-scale clustering of radio sources in the Gree n Bank and Parkes-MIT-NRAO 4.85-GHz surveys by measuring the angular t wo-point correlation function w (theta). Excluding contaminated areas, the two surveys together cover 70 per cent of the whole sky. We find both surveys to be reasonably complete above 50 mJy. On the basis of p revious studies, the radio sources are galaxies and radio-loud quasars lying at redshifts up to z similar to 4, with a median redshift z sim ilar to 1. This provides the opportunity to probe large-scale structur es in a volume far larger than that within the reach of present optica l and infrared surveys. We detect a clustering signal w (theta)approxi mate to 0.01 for theta = 1 degrees. By assuming an evolving power-law spatial correlation function in comoving coordinates xi(r(c), z)=(r(c) /r(0))(-gamma) (1+z)(gamma-(3+epsilon)), where gamma=1.8, and the reds hift distribution N(z) of the radio galaxies, we constrain the r(0)-ep silon parameter space. For 'stable clustering' (epsilon=0). We find th e correlation length r(0) approximate to 18 h(-1) Mpc, larger than the value for nearby normal galaxies and comparable to the cluster-cluste r correlation length.