Discovery and Photometry of Low Metallicity and Horizontal Branch Stars in the Galactic Halo

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Dr. Beers will complete an objective prism survey of the northern and southern hemispheres of our Galaxy and then follow up on selected stars which have extremely low metal abundances and stars on the horizontal branch of their evolutionary track. The final database of candidates should include about 16,000 stars with relatively low abundances of iron, and about 25,000 horizontal branch stars will be identified. The halo of our Galaxy contains less than 1 percent of the luminous stars in the entire Galaxy. Yet the halo is fundamental for revealing crucial issues of stellar evolution, the processes of galaxy formation and evolution, and for constraining the distribution of matter throughout the Galaxy. To understand the halo, one must first find it and characterize it. Ideally, complete spectroscopic and photometric information for the approximately one billion luminous stars which populate the halo would allow the observer to draw a picture of the halo which is untainted by sampling bias. Short of this, one can only attempt to minimize the effects of any selection criteria which must be imposed to make the problem tractable. In its broadest sense, the purpose of Dr. Beers' survey is to discover the objects which will, eventually, allow for a much more complete understanding of the halo of our Galaxy.