Observational impact of intra-halo velocity contributions

Establish the observational impact of intra-halo velocity contributions to the connected trispectrum of the moving-lens signal, including whether these contributions should be interpreted as part of the more general Rees–Sciama effect.

Background

The analytical framework defines the moving-lens velocity field using large-scale linear modes and therefore omits nonlinear and intra-halo velocity contributions. This omission breaks the symmetry between the two Gaussian contractions and leaves the connected trispectrum contribution to the signal unquantified.

The unresolved issue is both interpretive and observational: it is unclear whether the omitted contribution should be classified as part of the moving-lens effect or as a Rees–Sciama contribution, and its impact on searches for the moving-lens signal has not yet been established. The paper identifies hydrodynamical simulations as the natural tool for addressing this question as future CMB measurements become more precise.

References

Whether that contribution is best regarded as part of the more general Rees--Sciama effect is partly a matter of convention, but its observational impact on ML searches remains to be established.

— The moving lens effect: analytical modelling and foreground suppression  (2609.04133 - Wayland et al., 3 Sep 2026) in Section 6, Conclusions