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The phenomenon of multiple populations in globular clusters is still far fromunderstood, with several proposed mechanisms to explain the observed behaviour.The study of elemental and isotopic abundance patterns are crucial forinvestigating the differences among candidate pollution mechanisms. We derivemagnesium isotopic ratios for 13 stars in the globular cluster 47 Tucanae (NGC104) to provide new, detailed information about the nucleosynthesis that hasoccurred within the cluster. For the first time, the impact of 3D model stellaratmospheres on the derived Mg isotopic ratios is investigated. Using bothtailored 1D atmospheric models and 3D hydrodynamical models, we derivemagnesium isotopic ratios from four features of MgH near 5135{\AA} in 13 giantsnear the tip of the RGB, using high signal-to-noise, high-resolution spectra.We derive the magnesium isotopic ratios for all stars and find no significantoffset of the isotopic distribution between the pristine and the pollutedpopulations. Furthermore, we do not detect any statistically significantdifferences in the spread in the Mg isotopes in either population. No trendswere found between the Mg isotopes and [Al/Fe]. The inclusion of 3D atmosphereshas a significant impact on the derived 25Mg/24Mg ratio, increasing it by afactor of up to 2.5, compared to 1D. The 26Mg/24Mg ratio, on the other hand,essentially remains unchanged. We confirm the results seen from other globularclusters, where no strong variation in the isotopic ratios is observed betweenstellar populations, for observed ranges in [Al/Fe]. We see no evidence for anysignificant activation of the Mg-Al burning chain. The use of 3D atmospherescauses an increase of a factor of up to 2.5 in the fraction of 25Mg, resolvingpart of the discrepancy between the observed isotopic fraction and thepredictions from pollution models.

The chemical composition of red giants in 47 Tucanae. II. Magnesium isotopes and pollution scenarios