Reoriented Memory of Galaxy Spins for the Early Universe
First author: Jun-Sung Moon
Galaxy spins are believed to retain initially acquired tendency of being aligned with the intermediate principal axes of the linear tidal field, which disseminates a prospect of using them as a probe of the early universe physics. This roseate prospect, however, is contingent upon the key assumption that the observable stellar spins of the present galaxies measured at inner radii have the same alignment tendency toward the initial tidal field as their dark matter counterparts measured at virial limits. We test this assumption directly against a high-resolution hydrodynamical simulation to find that the present galaxy stellar spins have strong but {\it reoriented} memory for the early universe. An analytic single-parameter formula for this reorientation is derived and found to be in good accord with the numerical results.