for convergence over different binning grids), and only very large differences, which are unlikely in the K band, would produce significantly different values of $\sigma$.

$\bullet$ We do not include the disk contribution to $\sigma$. The disk is modeled as fully rotationally supported, so the disk stars are dispersion-free. In addition, we find that the disk contribution to the total gravitational potential inside the bulge radius is negligible and its effect on the calculated $\sigma$ is marginal. Observationally the inner disk would add to the signal coming from the bulge, depending on inclination. The model galaxies do not suffer from inclination effects, and rather than attempting to model them, we choose to use data that have been corrected for inclination. In addition we argue that, since we are restricting ourselves to the K band, the disk contribution to the estimate of $\sigma$ in observed galaxies is not likely to be significant.

Results
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The observational sample we use is not a Tully-Fisher dedicated sample, and galaxies were not selected based on the quality of their rotation curves or their morphological type. The goal in this work is to characterise the physical properties of the galaxies in this sample so that 