Gaseous probes of the universe can be explored in detail at low redshift and provide insight into how galaxies form and evolve throughout time. Dr. Mary Putman (University of Michigan) will address key unknowns of galaxy formation and evolution by examining gas dynamics and ionization in the Galactic halo and gas enrichment in nearby dwarf galaxies. The hot diffuse halo may still harbor a substantial amount of a galaxy's baryons and fuel galaxy disks. This halo medium can be probed with high-velocity clouds (HVCs) in the Galactic halo that show a "head-tail" structure, or a high column density head trailed by a diffuse tail. Simulations of these clouds moving through the halo will be compared to the observations, and by combining these comparisons with HVC distance constraints, the elusive density distribution, size, and mass of the diffuse Galactic halo will be probed. The origin and role of the diffuse halo will subsequently be assessed. The amount of ionizing radiation escaping from spiral galaxy disks will be investigated with H-alpha observations of Galactic halo clouds. The radiation in the Galactic halo will be investigated with H-alpha maps of HVCs at a range of distances. This will include the Magellanic Stream, a gaseous halo feature that is intriguingly bright in H-alpha emission. Gaseous flows within the building blocks of galaxies will be probed with metallicity measurements of H-II regions found in the outer gaseous disks of dwarf galaxies (well beyond an existing stellar component). This will address how dwarfs evolve and where the metals produced by the stars in these galaxies have gone.
As a part of this work, Dr. Putman will extend this research on galaxy evolution to middle schools throughout the Detroit-area through presentations done by University of Michigan undergraduate and graduate students. The impact of this program is two-fold. First, middle-school students in diverse school districts will experience an engaging, interactive program designed to trigger or maintain their interest in the sciences at a key stage of their development. Second, college students, and the future science educators, will reap the benefits of service learning by being trained to do the presentations.
