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NaCl is a diatomic molecule with a large dipole moment, which allows for itsdetection even at relatively small abundances. It has been detected towardsseveral evolved stars, among which is the AGB star IK Tau, around which it isdistributed in several clumps that lie off-center from the star. We aim tostudy the three-dimensional distribution of NaCl around the AGB star IK Tau,and to obtain the abundance of NaCl relative to H$_2$ for each of the clumps.First, a new value for the maximum expansion velocity is determined. Theobserved ALMA channel maps are then deprojected to create a three-dimensionalmodel of the distribution of NaCl. This model is then used as input for theradiative transfer modelling code magritte, which is used to obtain the NaClabundances of each of the clumps by comparing the observations with the resultsof the magritte simulations. Additionally, the rotational temperature of theclumps is determined using population diagrams. We derive an updated value forthe maximum expansion velocity of IK Tau $\upsilon_\mathrm{exp}$ = 28.4 km/s. Aspiral-like shape can be discerned in our three-dimensional distribution modelof the NaCl. This spiral lies more or less in the plane of the sky. Thedistribution is also flatter in the line-of-sight direction than in the planeof the sky. We find clump abundances between $9 \times 10^{-9}$ and $5 \times10^{-8}$ relative to H$_2$, where the relative abundance is typically lower forclumps closer to the star. For the first time, we used deprojection tounderstand the three-dimensional environment of an AGB star and calculated thefractional abundance of NaCl in clumps surrounding the star.

The unusual 3D distribution of NaCl around the AGB star IK Tau