The redshift-space two-point correlation function of ELAIS-S1 galaxies

We investigate the clustering properties of galaxies in the recently completed ELAIS-S1 redshift survey through their spatial two-point autocorrelation function. We used a subsample of the ELAIS-S1 catalogue covering approximately 4 deg(2) and consisting of 148 objects selected at 15 mu m with a flux > 0.5 mJy and a redshift < 0.5. We detected a positive signal in the correlation function that in the range of separations 1-10 h(-1) Mpc is well approximated by a power law with a slope gamma = 1.4 +/- 0.25 and a correlation length s(0)= 5.4 +/- 1.2 h(-1), at the 90 per cent significance level. This result is in good agreement with the redshift-space correlation function measured in more local samples of mid-infrared-selected galaxies such as the IRAS Point Source Catalog (PSCz) redshift survey. This suggests a lack of significant clustering evolution of infrared-selected objects out to z = 0.5 that is further confirmed by the consistency found between the correlation functions measured in a local (z < 0.2) and a distant (0.2 < z < 0.5) subsample of ELAIS-S1 galaxies. We also confirm that optically selected galaxies in the local redshift surveys, especially those of the SDSS sample, are significantly more clustered than infrared objects.