Zeeman Doppler mapping deconstructed

Abstract

Aims. Magnetic and abundance maps of chemically peculiar (CP) stars, derived with the help of Zeeman Doppler mapping, have invariably been used as arguments against theories, in particular atomic diffusion theory. We intend to expose the fallacy of these claims. Methods. We have identified in the literature those (5) CP stars for which multiple maps have been published, all based on the same Zeeman Doppler mapping strategy. For each of these stars we have then carried out inter comparisons between the recovered distributions of magnetic field and of abundances. Results. Agreement between maps often turns out to be quite poor in regard to both abundances, field topology and absolute field strengths. Maps based on the same set of observations can differ considerably, even when they are coming from the same authors. Conclusions. It becomes clear that Zeeman Doppler mapping cannot be guaranteed to yield unique results. When a number of physically impossible magnetic geometries all provide good fits to the observed Stokes $IQUV$ profiles, these solutions must necessarily be spurious and cannot be used as constraints to diffusion theory.