Sagittarius Stream Warp

The Sagittarius dwarf galaxy is being actively disrupted by the Milky Way and has deposited a vast tidal stream that wraps multiple times around the Galaxy, extending from near the Galactic center to distances beyond 100 kpc in the halo. Detailed mapping of the stream's multiple wraps has revealed that the stream does not follow a single great-circle plane; instead, successive wraps are systematically offset from each other in a pattern called the stream warp or precession signature. In ΛCDM, the precession rate and warp pattern of the Sagittarius stream serve as a sensitive probe of the Milky Way's dark matter halo shape, with stream modeling requiring a nearly spherical or mildly prolate halo at intermediate radii transitioning to a different shape at large radii. However, attempts to fit the full multi-wrap morphology with a single consistent halo model have failed, leaving a systematic residual warp that does not match any smooth CDM halo shape.

In Successive Collision Theory, the Sagittarius stream warp arises from the spatially varying gravitational potential produced by the nested comoving frame hierarchy. The effective gravitational potential of the Milky Way at large halo radii includes contributions not only from the Milky Way's own mass distribution but also from the gravitational superposition of the Local Group, the Virgo Supercluster, and higher parent frames. This superposition contribution varies smoothly as a function of direction within the halo, being stronger toward the Local Group barycenter and weaker in the opposite direction. As the Sagittarius stream extends to large radii on successive wraps, different portions of the stream experience different effective potentials, causing them to precess at slightly different rates and producing the observed warp pattern that cannot be fit with a single smooth axisymmetric halo model.

The SCT framework therefore predicts that the Sagittarius stream warp encodes the large-scale structure of the nested frame hierarchy rather than the intrinsic shape of the Milky Way's dark matter halo. The direction and magnitude of the warp should correlate with the direction toward the Local Group barycenter and the axis of the Virgo Supercluster, providing a specific observational test. The fact that no single CDM halo shape fits the full multi-wrap stream is a natural consequence of the fact that the relevant potential is genuinely non-axisymmetric due to the superposition of surrounding parent frames — a feature absent from all CDM-only halo models but intrinsic to SCT's hierarchical frame structure.