Spinning Dust Peak Shift

The anomalous microwave emission from spinning dust grains peaks at a frequency determined by the characteristic rotation rate of the grain population, which depends sensitively on the local interstellar conditions: radiation field intensity, gas temperature and density, ionic fraction, and magnetic field strength. Observations across different regions of the sky find the AME peak shifting between approximately 15 and 30 GHz, with no single set of environmental parameters consistently explaining the full range of observed peak frequencies in the standard spinning dust framework. The most significant tension involves environments where the AME peak is found at anomalously low frequencies inconsistent with theoretical predictions for the local radiation field and density, or where the peak shifts in a direction opposite to that expected when moving from diffuse ISM to denser molecular environments.

Successive Collision Theory explains the AME peak shift anomalies through the hereditary time transmission mechanism applied to grain rotation dynamics. In SCT, spinning dust grains embedded within the Galactic interstellar medium experience a proper time rate modified by the accumulated time-dilation corrections from the nested frame hierarchy — solar potential, Galactic potential, Local Group potential, and higher parent frames. The physical rotation rate of a grain is set by the balance of driving and damping torques in proper time, but an observer measuring the AME frequency in coordinate time will see a slightly shifted peak compared to what pure ISM physics predicts, because the relationship between proper time and coordinate time carries the hereditary correction factor. This correction shifts the observed peak frequency systematically across all environments at the level of a fraction of a percent, which when accumulated over regions with different depths of gravitational embedding produces a coherent pattern of peak frequency offsets.

Additionally, the angular momentum field inherited from the collision debris imprints a preferred rotation direction on grains along the collision axis. Grains in regions where the inherited angular momentum field is aligned with the grain's electric dipole moment are more efficiently spun up by the local radiation and gas coupling, raising the characteristic rotation rate and shifting the peak to higher frequencies. In regions where the inherited angular momentum field is misaligned, the driving efficiency is lower and the peak shifts down. The observed AME peak frequency map across the Galactic plane should therefore show a coherent large-scale pattern aligned with the collision axis — the same axis encoded in the CMB quadrupole-octupole alignment — superimposed on the local environmental variation. This large-scale pattern is testable with the full-sky AME maps from the C-BASS, QUIJOTE, and SKA-MID surveys.