Dr. Jennifer Johnson (Ohio State University), Dr. Gillian Knapp (Princeton University), & Dr. Timothy Beers (Michigan State University) will identify and analyze up to several thousand carbon-enhanced stars in the Milky Way galaxy, based on medium-resolution stellar spectroscopy and broadband ugriz photometry obtained with the Sloan Digital Sky Survey (SDSS). These data will allow these investigators to derive estimates of both [Fe/H] and [C/Fe] for all stars in this sample. Accurate radial velocities will also enable detailed investigations of the kinematics of these stars. These data will be used to constrain (1) the frequency of carbon enhancement among stars as a function of declining metallicity, which provides information on the nature of the initial mass function for early-generation stars, (2) the distribution of carbon enhancement among low-metallicity stars - e.g., whether it is continuous or multi-modal, and (3) the separation of carbon-enhanced, metal-poor stars into (at least) the two main categories that are presently recognized, those that exhibit the presence of s-process elements, and those that do not, based on the detection (or not) of the strong barium and strontium features that are associated with production in the s-process.
The results of this research will have impact on a wide range of research activities in astronomy, nuclear physics, and chemistry, since knowledge of the astrophysical origins of the elements provides the basis for understanding the chemical evolution of the Milky Way, as well as for detailed investigations of the nature of neutron-capture processes, which are of great interest to the nuclear physics community. This research will provide opportunities for the training of graduate and undergraduate students in the areas of both astronomy and nuclear physics, and will become part of the extensive education and outreach program being undertaken by SDSS-II.
