The mass of spiral galaxy halos

A discussion is presented of previous and current work on the determination of the mass distribution of spiral galaxy halos. The two most common tools utilized to determine the mass of spiral galaxies, i.e., companion galaxies and rotation curves are discussed. The most recent research of companion galaxies, which probes the potential to larger distances and utilizes more accurate dynamic modeling, demonstrates that isolated late-type galaxies do have very large dark-matter halos.