Heidelberg Joint Astronomical Colloquium

Speaker Timothy C. Beers
Title The metallicity distribution function(s) of halo stars as revealed by SDSS/SEGUE

The lowest metallicity stars in the Galaxy preserve our best snapshots of the chemical elements formed in the Big Bang, and in the very first generations of (presumably) massive stars that theory tells us formed shortly thereafter. Over the past several decades, dedicated searches for these objects have identified at least a handful of stars with metallicities [Fe/H] less than one hundred thousandth the solar abundance, and approaching one millionth solar. Astronomers are also learning how better to identify and mine these fossils of creation in the future, based on the apparent association of the lowest metallicity stars with the outer-halo component of the newly recognized inner/outer structure of our Galaxy. I summarize the current state of affairs, consider multiple lines of evidence for the complex metallicity distribution function of the dual halos, and point toward new survey efforts to begin in the near future.