tokens: that the near-isothermal density profiles were found to be broadly consistent with MOdified Newtonian Dynamics (MOND). With this greater sample of total- mass profiles that cover a greater stellar mass range, new tests of MOND and the general mass-discrepancy–acceleration relations can be made. In order to make useful comparisons between simulations and observations, it is necessary that exactly the same measurements are made for each. Currently, there is great difficulty in achieving this, since observational measurements are best constrained in the inner regions of galaxies, while the resolution limitations of cosmological simulations mean that measurements for simulated galaxies are best constrained at radii greater than ∼0.5 R e . This means that while care can be taken to make measurements in the same way, the underlying data are fundamentally different. 8 SUMMARY AND CONCLUSIONS We measure total-mass density slopes for 21 fast-rotator ETGs of the SLUGGS survey (Brodie et al. 2014 ), including a greater number of galaxies in the low-mass range than the previous study by Cappellari et al. ( 2015 ). These measurements are made by conducting dynamical mass modelling on 2D kinematics that extend to large radii. We apply the jam mass-modelling technique (Cappellari 2008 ), using two different parametrizations of mass distribution to recover the total-mass density profiles for individual galaxies. We determine that the best fits of the model kinematics to the input kinematics of each galaxy are produced by the model in which the total mass is separated into its stellar and DM components, where the DM distribution is parametrized as a double power law (as given by equation 2 ). We find that the measured total-mass density slope values are robust to slight variations within the applied modelling, whereas the separation of stellar and DM is much more degenerate, and susceptible to such variations in the modelling. In order to be consistent with Cappellari et al. ( 2015 ), we measure γ tot values for each galaxy by fitting a power-law slope to the stellar plus DM profile in the radial range 0.1–4 R e , and find an average total-mass density slope of γ tot = −2.24 ± 0.05 for our sample of 21 galaxies, identifying no discernable trend with stellar mass. We collate measurements of total-mass density slopes from multiple observational studies, for a comprehensive overview of the γ tot behaviour across a broad range of stellar masses, utilizing an array of data-types and measurement techniques. Overwhelmingly, the studies all tend to produce consistent results when including the central regions, as shown in Fig. 6 . This is despite the fact that the data utilized have varying radial extents for individual galaxies – an indication that these slopes do not display much variation with radius. We find that there tends to be very little trend with stellar mass, and that the slight shallowing of total-mass density slopes we see at lower stellar masses may not
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