because the asymmetric drift is too large. Therefore, we reject models from scenario KG as being inconsistent with the data; however, see § 7.3 for a discussion of the issues involved in calculating the asymmetric drift. Finally, we test the hypothesis that the underlying disc scale length is given by the outer ( > 2 kpc) portion of the SB profile by only fitting the interior points and the external points of the SB profile with a MCMC chain corresponding to scenario E. The outer cut is made at 2 kpc; R$_{d}$ is subtly affected by the inclination and differences in scale height, and, moreover, the very tight correlation between M$_{d}$ and the disc M/L makes it difficult to obtain reasonable acceptance rates with MCMC. Therefore, we manually tested combinations of R$_{d}$ and M/L to produce the best fit; we adopt a value of R$_{d}$ = 1 . 3 kpc and fix the disc M/L to 0 . 53 M$_{d}$ . To avoid biasing the resulting value for z$_{d}$ , we do not include the external disc in our χ 2 calculations. The inner cut is trickier; we have found that small changes to the number of inner points fit may lead to large changes in the resulting bulge parameters. To rectify this issue, we plot the residuals of the surface brightness from a regression line fit of R$_{d}$ = 1 . 18 kpc (Fig. 11) and only fit the points that lie above the maximum of the Type II hump. At these points, the surface brightness is most assuredly bulge dominated. The stellar rotation is fit as in runs K and KL, along with the H I data in the outer part, and the velocity dispersion is fit as in the other three runs. For this run, we assume that the evolution of a disc would generate a ring of star formation that could reproduce the Type II hump. The process of generating this profile would alter the rotation and dispersions, however, and we caution that the kinematics that result may not fit the data as well as the direct fits presented here using MCMC. Accounting for this would require ad hoc selections of what points to fit, or excluding one or more data sets entirely; for example, excluding the stellar rotation and only fitting the H I data outside 3 kpc. Such a process is probably no more reliable than simply fitting the full data sets, evolving a test model from the PDFs and then determining how well the rotation curve and dispersion profile fit the observed data after evolution. Because we are assuming that a bar is supposed to form in this scenario, unstable models would not rule out this interpretation. However, models with Q < 1 must be tested separately. As in scenario KL, the stellar rotation curve is well fit while the circular velocity is larger than the H β curve (Fig. 5). The surface brightness fit is very good over the ranges we wish to fit; the inner eight points and outer exponential are well reproduced (Fig. 6). The velocity dispersion profile looks different from that for the previous scenarios since the 18 5.3. Testing the outer exponential fit