Large-Scale Intrinsic Alignment of Galaxy Images

Understand

We compute the two-point image correlation function for bright galaxies in the seventh data release of the Sloan Digital Sky Survey (SDSS) over angular scales 0.01' <= \theta <= 120' and projected separations 0.01 Mpc <= r <= 10 Mpc.

• We restrict our analysis to SDSS galaxies with accurate spectroscopic redshifts, and we find strong evidence for intrinsic alignment of the galaxy images.
• On scales greater than r ~ 40 kpc, the intrinsic alignment of the SDSS galaxy images compares well with the intrinsic alignment of galaxy images in a Lambda-CDM universe, provided we impose Gaussian-random errors on the position angles of the theoretical galaxies with a dispersion of 25 degrees.
• Without the inclusion of these errors, the amplitude of the two-point image correlation function for the theoretical galaxies is a factor of ~2 higher than it is for the SDSS galaxies.