The constant stability disk model

My project was born from my supervisor hypothesizing the controversial mass discrepancy acceleration relation (MDAR) could be explained by the constant stability disk model. The model claims a galaxy’s gas distribution adjusts to its stellar distribution to maintain a constant value for the Toomre stability parameter, Q. To test the hypothesis, we built a set of “typical” or “template” galaxies built from the model in the hope together, they would trace out the observed MDAR. In short, constant stability is not the enlightening physical insight underlying MDAR. However, we showed it may serve such a purpose in explaining other galaxy scaling relations - namely a correlation between MHI/LR and Vmax in Hi selected galaxies. As an aside, I realised if MDAR held strictly, as it must in MOND, then the implied dark matter profiles take forms starkly different from those predicted by dark matter simulations. Kinematical studies of real galaxies with highly extended disks could therefore finally settle the debate between MOND and dark matter.

Note added in retrospect: A fact that was not well emphasised in the original report I have presented here is that unlike the local applications of constant Q in other work, I am applying it quite globally here and then integrating. Because constant Q is known not to hold everywhere in a galaxy, the models are potentially unreliable even once accounting for my efforts to smooth profiles in the inner and outermost parts of the galaxy.

My project report can be downloaded from here and the associated computer programs are available here.