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Fig. 5


Sulphur isotope 32S/34S ratio variation when accounting for different carbon 12C/13C ratios as a function of galactocentric radius, DGC (e.g. Wilson & Rood 1994; Halfen et al. 2017; Milam et al. 2005; Yan et al. 2019) (for the implemented 13C32S/C34S ratios, see Chin et al. 1996). The 32S/34S to DGC relations obtained from a linear least-squares fit to weighted data (taken as 1/σ, see Sect. 5) are shown and plotted as lines with different styles (see legend). The 32S/34S ratios from this work are shown in orange, cyan, and light green. All ratios were gleaned from integrated intensity ratios except for Sgr B2(N) (see Fig. 3), where our derived integrated column density ratios are used. Possible differences between integrated column density ratios and line intensity ratios for the mean values in Sgr B2(N) fall inside the error bars. For the case of the GC l.o.s. clouds towards Sgr B2(N), their distances are uncertain and they are believed to be located within 1 kpc from the GC (see Sect. 3). As described in Sect. 5, the purple and yellow hatched-shaded loci are derived from [Fe/H] vs DGC relationsobtained by Bovy et al. (2014) and Genovali et al. (2014), after accounting for the models of Kobayashi et al. (2011); hatched-only loci correspond to an extrapolation of those relations, following Inno et al. (2019). Using the same models, two 32S/34S ratios are included. These ratios are derived from iron abundances measured in the central 30 pc of the Galaxy by Davies et al. (2009) and Najarro et al. (2009). A zoom on the results of our study displayed in the left part of the figure is shown in Fig. C.1.

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