Galactic Structure

Dennis Zaritsky

Unlike the theory of stellar structure, which has a simple and intuitive outline, that of galactic structure is piecemeal and ad hoc. In fact, it has been difficult even to determine whether or not one should expect there to be such an analog. Numerical modeling of the problem grows ever more sophisticated and detailed in its efforts to match observations, suggesting that perhaps the problem is beyond any simple description. However, I will, using simple and general arguments, demonstrate that the global structure of galaxies of all sizes, masses, and morphological types can be described to a high degree using only two observational parameters. I will then explore the nature of those two parameters and ultimately present an attempt to tie those to basic physical parameters, thereby providing (perhaps) a simple and intuitive outline of galactic structure.