We perform an autocorrelation study of the Auger data with the aim to constrain the number density n _ { s } of ultrahigh energy cosmic ray ( UHECR ) sources , estimating at the same time the effect on n _ { s } of the systematic energy scale uncertainty and of the distribution of UHECR .
The use of global analysis has the advantage that no biases are introduced , either in n _ { s } or in the related error bar , by the a priori choice of a single angular scale .
The case of continuous , uniformly distributed sources is nominally disfavored at 99 % C.L .
and the fit improves if the sources follow the large-scale structure of matter in the universe .
The best fit values obtained for the number density of proton sources are within a factor \sim 2 around n _ { s } \simeq 1 \times 10 ^ { -4 } / Mpc ^ { 3 } and depend mainly on the Auger energy calibration scale , with lower densities being preferred if the current scale is correct .
The data show no significant small-scale clustering on scales smaller than a few degrees .
This might be interpreted as a signature of magnetic smearing of comparable size , comparable with the indication of a \approx 3 ^ { \circ } magnetic deflection coming from cross-correlation results .
The effects on the above results of some approximations done is also discussed .