The faint X-ray source population near 3C 295

We present a statistical analysis of the Chandra observation of the source field around the 3C 295 galaxy cluster (z = 0.46) to search for clustering of X-ray sources. We applied three different methods of analysis, all suggesting a strong clustering in the field on scales of a few arcmin. In particular 1) the log N-log S computed separately for the four ACIS-I chips reveals that there is a significant (3.2sigma in the 0.5-2 keV, 3.3sigma in the 2-10 keV and 4.0sigma in the 0.5-10 keV band) excess of sources to the North-North East and a void to the South of the central cluster; 2) the two point, two-dimensional Kolmogorov-Smirnov (KS) test, shows the probability that the sources are uniformly distributed is only a few percent; 3) a strong spatial correlation emerges from the study of the angular cot-relation function of the field: the angular correlation function (ACF) shows a clear signal on scales of 0.5 divided by 5 arcmin, correlation angle in the 0.5-7 keV band theta(0) = 8.5(-4.5)(+16.5), 90% confidence limit (assuming a power law ACF with slope gamma = 1.8). This correlation angle is 2 times higher than that of a sample of 8 ACIS-I field at the 2.5sigma confidence level. The above scales translate to 0.2 divided by 2 Mpc at the cluster redshift, higher than the typical cluster core radius, and more similar to the size of a "filament" of the large scale structure.