Dr Zaritsky will use deep optical imaging and spectroscopy with the Large Binocular Telescope to study the stellar content, history, and motions in the outer parts of galaxy disks. These regions were long known to contain gas, but until recently were thought to be making no new stars. Clumps of new stars will be mapped out using deep images in blue light, to investigate the history of starbirth in the outer galaxy, and find the true edge of the stellar disk. The motions of the stellar clumps will be measured from the Doppler shift of their spectral lines. The averaged motion will show how fast the outer parts of the galaxy rotate about its center, and the mass density of the outer disk can be inferred from the way that the motion of individual clumps of stars deviates from that mean. Dr Zaritsky will use his results to test key concepts in models for galactic evolution, such as whether the thin disks can survive the repeated mergers through which large galaxies are expected to grow; what the tightness of scaling relations implies for the development of galaxy disks; and how disk sizes could be related to the angular momentum distribution of the protogalaxy.
This proposal will fund the training of a graduate student. Dr Zaritsky will use his deep galaxy images to develop laboratory exercises for his undergraduate observational astronomy class, a Vatican summer school that he has proposed for 2010, and a Study Abroad course in Ghana scheduled for winter 2009. The labs will also be made available over the internet.
