A new (2+1)D cluster finding algorithm based on photometric redshifts: large scale structure in the Chandra Deep Field South

Aims. We study galaxy clustering and explore the dependence of galaxy properties on the the environment up to a redshift z similar to 1, on the basis of a deep multi-band survey in the Chandra Deep Field South. Methods. We have developed a new method which combines galaxy angular positions and photometric redshifts to estimate the local galaxy number-density. This allows both the detection of overdensities in the galaxy distribution and the study of the properties of the galaxy population as a function of the environmental density. Results. We detect two moderate overdensities at z similar to 0.7 and z similar to 1 previously identified spectroscopically. We find that the fraction of red galaxies within each structure increases with volume density, extending to z similar to 1 previous results. We measure red sequence slopes consistent with the values found in X-ray selected clusters, supporting the notion that the mass-metallicity relation hold constant up to z similar to 1. Conclusions. Our method based on photometric redshifts allows to extend structure detection and density estimates up to the limits of photometric surveys, i.e. considerably deeper than spectroscopic surveys. Since X-ray cluster detection at high redshift is presently limited to massive relaxed structures, galaxy volume density based on photometric redshift appears as a valuable tool in the study of galaxy evolution.