Triangulum Warp

The Triangulum Galaxy (M33) displays a pronounced warp in its outer disk that is difficult to reproduce in N-body simulations assuming a smooth NFW dark matter halo and the observed tidal field from M31. The warp amplitude, its specific orientation, and its radial extent all deviate from the predictions of tidal warp models, suggesting either that the dark matter halo is not well described by the assumed profile, that additional tidal sources are present, or that the warp has a non-tidal origin. Successive Collision Theory attributes M33's warp to angular momentum inheritance rather than external tidal forcing as the primary driver. The angular momentum axis of M33's outer disk gas is misaligned from the inner disk axis because the outer disk is being fed by accretion from the Local Group filament, which carries angular momentum with an orientation set by the large-scale collision geometry rather than the local orbital plane of M33 around M31.

The specific warp geometry of M33 encodes the orientation of the angular momentum delivered by the Local Group filament at M33's location, which is a function of the original collision axis, the impact parameter of the collision, and M33's position within the debris field. The warp is not a transient disturbance created by M31's tidal field but a quasi-steady structural feature maintained by ongoing misaligned accretion from the filamentary infall. This is consistent with the observation that the warp extends to very large radii — well beyond where M31's tidal field is effective — and that its orientation is not simply aligned with the M31 direction. Gravitational superposition from the Local Group's nested frame hierarchy also contributes to the effective potential shape at M33's outer disk radii, modifying the precession rate of any tidally excited warp mode and potentially stabilizing the warp in its observed orientation against differential rotation that would otherwise wind it up on a few orbital timescales.