Observations Constraining the Relative Masses of the Disk, Bulge and Halo of the Milky Way

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Dr. Schechter, at the Mount Wilson and Las Campanas Observatories of the Carnegie Institution of Washington, is conducting an observational research project which consists of three separate but related components, all of which will aid the construction of three dimensional models of the mass of the Milky Way Galaxy. The project focuses on using three different tracers of mass to determine the relative contributions to the mass of our Galaxy from the disk, the bulge, and the halo. It has proven especially difficult to determine the relative contributions of a disk, a bulge, and a dark halo to the total masses of external galaxies. A better understanding of the relative importance of dark and luminous matter in a galaxy is a prerequisite to understanding how galaxies formed. The premise underlying Dr. Schechter's research efforts is that projection effects make it virtually impossible to construct well constrained models of the mass for external galaxies. However, in the Milky Way one can measure all three components of position and velocity for a wide variety of tracers of mass. Our knowledge of the mass distribution in our Galaxy can then be applied to understanding the structure of other galaxies.