Spin Filament Alignment

Galaxy spins are not randomly oriented relative to the cosmic filaments in which galaxies reside; they show a statistical tendency to align either parallel or perpendicular to the local filament axis depending on galaxy mass. Low-mass galaxies tend to spin with their rotation axes parallel to the filament axis, while high-mass galaxies tend to have their rotation axes perpendicular to the filament — a mass-dependent transition that has been robustly detected in large galaxy surveys. This mass-dependent spin-filament alignment has been partially reproduced in ΛCDM simulations through tidal torque theory, but the observed alignment amplitude is systematically stronger than simulated predictions, and the mass scale of the parallel-to-perpendicular transition does not precisely match simulation predictions across all simulation codes and resolution levels.

Successive Collision Theory predicts spin-filament alignments as a fundamental, first-principles consequence of angular momentum inheritance, with an amplitude that naturally exceeds ΛCDM tidal torque predictions. In SCT, galaxy spins are set by the inherited angular momentum of the collision debris stratum from which each galaxy formed — not by the stochastic torque from neighboring dark matter halos as tidal torque theory posits. The filaments themselves are organized along the same angular momentum field: they trace the preferred collapse directions set by the collision geometry, which defines a coherent axis throughout each filamentary structure. Since both the galaxy spin and the filament orientation arise from the same underlying angular momentum field, their alignment is exact at the level of the debris field coherence — far stronger than the statistical correlation produced by tidal torque theory, which requires a specific geometry of neighboring mass distributions.

The mass-dependent transition from parallel to perpendicular alignment follows naturally in SCT from the competition between inherited angular momentum and angular momentum acquired through subsequent mergers and accretion. Low-mass galaxies in filaments retain their primordial spin direction aligned with the filament because their low merger rates and small angular momentum budgets from accretion have not significantly perturbed the inherited orientation. High-mass galaxies, which have undergone more mergers and accreted more material, have had their spin axes torqued by the net angular momentum of infalling material, which arrives preferentially along the filament axis and therefore torques massive galaxy spins toward perpendicular alignment with the filament. The mass scale of the transition reflects the threshold above which merger-acquired angular momentum overcomes the primordial inherited component — a physically determined threshold in SCT rather than an adjustable parameter as in tidal torque models.