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We study the anisotropy signature which is expected if the sources of ultrahigh energy, >10^{19} eV, cosmic-rays (UHECRs) are extragalactic and trace thelarge scale distribution of luminous matter. Using the PSCz galaxy catalog as atracer of the large scale structure (LSS), we derive the expected all skyangular distribution of the UHECR intensity. We define a statistic, thatmeasures the correlation between the predicted and observed UHECR arrivaldirection distributions, and show that it is more sensitive to the expectedanisotropy signature than the power spectrum and the two point correlationfunction. The distribution of the correlation statistic is not sensitive to theunknown redshift evolution of UHECR source density and to the unknown strengthand structure of inter-galactic magnetic fields. We show, using this statistic,that recently published >5.7x10^{19} eV Auger data are inconsistent withisotropy at ~98% CL, and consistent with a source distribution that traces LSS,with some preference to a source distribution that is biased with respect tothe galaxy distribution. The anisotropy signature should be detectable also atlower energy, >4x10^{19} eV. A few fold increase of the Auger exposure islikely to increase the significance to >99% CL, but not to >99.9% CL (unlessthe UHECR source density is comparable or larger than that of galaxies). Inorder to distinguish between different bias models, the systematic uncertaintyin the absolute energy calibration of the experiments should be reduced to wellbelow the current ~25%.

Searching for a Correlation Between Cosmic-Ray Sources Above 10^{19} eV and Large-Scale Structure