Dr. R. Michael Rich, of the University of California - Los Angeles, will undertake a large scale radial velocity study of the Galactic bulge using M giants selected from the Two Micron All-sky Imaging Survey (2MASS) and observed using the Hydra multifiber spectrograph at Cerro Tololo Inter-American Observatory. The investigator has shown that the M giants make excellent kinematic probes that can be studied over the entirety of the Galactic bulge, even in high extinction regions; the ultimate sample of 10,000 radial velocities is a factor of ten greater than previous studies. Dr. Rich has developed techniques that give a precision of 3 km/s for radial velocity measurements, making it possible to discover cold kinematic features in the bulge, if present. Comparison of the resulting longitude-velocity diagrams, minor axis rotation curves, and other velocity data with self-consistent models of the Galactic bulge/bar, will allow for insight into the formation of the Galactic bulge. In addition, Dr. Rich will obtain detailed abundances for stars in the bulges of the Milky Way and M31 using infrared spectroscopy. For the Milky Way bulge, he will observe at least 150 stars ranging from 30 to 300 pc from the nucleus using the NIRSPEC echelle spectrograph at the Keck observatory. This program will extend detailed abundance measurements into regions of the Galaxy that are near the nucleus and are obscured by dust. The presence or absence of an abundance gradient constrains models of secular evolution of the bar, while measurements of composition (e.g. oxygen abundance) can constrain the formation timescale and the initial mass function of the primordial stellar population.
Dr. Rich will contribute to the training of the next generation of astronomers by supporting a Ph.D. student whose thesis is in progress and also research by an undergraduate student and a postdoctoral scientist through this program. The Galactic bulge radial velocity survey and the resulting models will be made available to the Hayden Planetarium, which is building a virtual Milky Way Galaxy that can be observed by the public in a simulated fly-through, and he will explore other visualizations of the data to bring the results to the public. The entire database of ~10,000 stars with spectroscopy and radial velocities will be made available to the astronomical community.
