The Relationship between Stellar Light Distributions of Galaxies and Their Formation Histories

A major problem in extragalactic astronomy is the inability to distinguish in a robust, physical, and model independent way how galaxy populations are related to each other and to their formation histories. A similar, but distinct, and also long standing question is whether the structural appearances of galaxies, as seen through their stellar light distributions, contain enough physical information to offer this classification. We argue through the use of 240 images of nearby galaxies that three model independent parameters measured on a single galaxy image reveal its major ongoing and past formation modes, and can be used as a robust classification system. These parameters quantitatively measure: the…