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 sub-sample of the ELAIS-S1 catalog covering approximately 4 deg ^ { 2 } and consisting of 148 objects selected at 15 \mu m with a flux > 0.5 mJy and redshift z < 0.5 .
We detected a positive signal in the correlation function that , in the range of separations 1 - 10 { \it h ^ { -1 } Mpc } is well approximated by a power law with a slope \gamma = 1.4 \pm 0.25 and a correlation length s _ { 0 } = 5.4 \pm 1.2 { \it h ^ { -1 } Mpc } , at the 90 % significance level .
This result is in good agreement with the redshift-space correlation function measured in more local samples of mid infrared selected galaxies like the IRAS PSC z 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 .