SYSTEMATICS IN THE ORIENTATION OF GALAXIES

We examine possible systematic effects in the orientation of galaxies, with respect to their neighbors on different scales. For accomplishing this program we study different samples of the ESO catalog with redshifts taken from a compilation by A. P. Fairall. The samples are defined according to the morphology and the apparent flattening of the galaxies. In samples of spiral galaxies we find statistical evidence (2.8-sigma-level) for a preferred orientation of the major axis in the direction toward the nearest neighbors on scales of 3 Mpc/h. The redshift information is crucial in the detection of this effect, and when the nearest neighbors are considered in projection no systematics are detected. Elliptical galaxies are found preferentially oriented not only with the nearest but also with all neighbors on scales of 3 Mpc/h. This result is consistent with previous work that considered only projected angular separations [Lambas et al AJ, 95, 975 (1988)]. We analyze different cuts in the data in order to check the statistical confidence of the results and possible dependencies in the parameters. We briefly discuss the results obtained in the context of a hierarchical scenario where primeval angular momentum and velocity anisotropy were originated by tidal torques from the neighboring mass distribution.