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We explore the possibility that an intrinsic correlation between galaxyellipticities arising during the galaxy formation process may account for partof the shear signal recently reported by several groups engaged in weak lensingsurveys. Using high resolution N-body simulations we measure the projectedellipticities of dark matter halos and their correlations as a function of pairseparation. With this simplifying, but not necessarily realistic assumption(halo shapes as a proxy for galaxy shapes), we find a positive detection ofcorrelations up to scales of at least 20 h^-1mpc (limited by the box size). Thesignal is not strongly affected by variations in the halo finding technique, orby the resolution of the simulations. We translate our 3d results into angularmeasurements of ellipticity correlation functions and shear variance which canbe directly compared to observations. We also measure similar results fromsimulated angular surveys made by projecting our simulation boxes onto theplane of the sky and applying a radial selection function. Interestingly, theshear variance we measure is a small, but not entirely negligible fraction(from ~10-20 %) of that seen by the observational groups, and the ellipticitycorrelation functions approximately mimic the functional form expected to becaused by weak lensing. The amplitude depends on the width in redshift of thegalaxy distribution. If photometric redshifts are used to pick out a screen ofbackground galaxies with a small width, then the intrinsic correlation maybecome comparable to the weak lensing signal. Although we are dealing withsimulated dark matter halos, whether there is a signal from real galaxies couldbe checked with a nearby sample with known redshifts.Comment: 12 pages, 11 ps figures, emulateapj.sty, submitted to Ap

Weak‐Lensing Surveys and the Intrinsic Correlation of Galaxy Ellipticities