The first involves a systematic study of the properties of a newly discovered class of galaxies that are distinguished by their large but very low surface mass density disks. These low surface brightness galaxies have been missed by previous surveys of the sky because they are very difficult to discern against the night sky background. Nonetheless, their existence offers us a new window into galaxy evolution and provides us with examples of galaxies that form stars rather inefficiently.
The second area of study is concerned with a multi-wavelength analysis of the radiation emitted by normal galaxies in order to understand how their stellar populations evolve. Key to this is the understanding of how dust obscuration hinders and biases our view about the kinds of stars that make up galaxies. Only by making a proper stellar census in galaxies as a function of time can we begin to understand the enigmatic processes that produced them in the first place.
The latter two aspects of Bothun's research are concerned with the formation and evolution of large scale structure in the Universe. While it is already difficult to understand how galaxies form, it is even more challenging to understand how galaxies managed to form themselves into very large coherent structures (e.g., clusters, superclusters, great walls, filaments, voids). To shed light on this, Bothun has been engaging in a systematic study of the properties of clusters of galaxies in order to empirically assess their rate of dynamical evolution. In addition, Bothun is part of a large collaboration that uses the Tully-Fisher relation to estimate distances to spiral galaxies and hence the expansion parameter of the universe. More interesting than the determination of this parameter, however, is the demonstration that the expansion motion of nearby galaxies is strongly perturbed. If this perturbation is gravitational in origin, then an all-sky survey of these deviant motions will provide an accurate reflection of the local distribution of mass in the Universe. This distribution might be quite different than the distribution of light (e.g., galaxies) and provides a strong observational constraint on competing cosmogenic models.