The main purpose of this project, undertaken by Dr. Matthew Bershady of the University of Wisconsin at Madison, is to determine independently the mass distributions of the disk and halo components of nearby, low surface-brightness spiral galaxies through direct, kinematic measurements. The scientific motivation is to understand if such systems are truly dark-matter dominated at all radii, to measure precisely the mass-to-light ratios of their disks, and to determine what implications this has for their stellar populations. Dr. Bershady also seeks to place limits on the disk stellar initial mass function and test the viability of the hypothesis of non-Newtonian limit of modified Newtonian gravity. Tests will be carried out via rotation-curve decompositions that use the measured disk mass-to-light ratios, and by using the measured disk vertical acceleration to see if disk light traces disk mass. The technical approach uses observed stellar line-of-sight velocity dispersions (LOSVDs) to implement a surrogate method of estimating LOSVDs in 10-15 low surface-brightness galaxies via gas and stellar tangential velocities. The observations will be carried out at several large telescopes, with new and upgraded integral-field spectroscopic instruments developed by Dr. Bershady.
The program includes (1) graduate and undergraduate training, extended to under represented groups in South Africa, (2) course development on galaxy formation and spectrograph instrumentation will intertwine with the research work, (3) commissioning science programs on new instruments, and (4) public outreach lectures on Dr. Bershady's research. The program design and execution involve data collection, modeling and analysis over a three-year period.
