The chemical abundances of large samples of extremely metal-poor (EMP) stars
can be used to investigate metal-free stellar populations, supernovae, and
nucleosynthesis as well as the formation and galactic chemical evolution of the
Milky Way and its progenitor halos. However, current progress on the study of
EMP stars is being limited by their faint apparent magnitudes. The acquisition
of high signal-to-noise spectra for faint EMP stars requires a major telescope
time commitment, making the construction of large samples of EMP star
abundances prohibitively expensive. We have developed a new, efficient
selection that uses only public, all-sky APASS optical, 2MASS near-infrared,
and WISE mid-infrared photometry to identify bright metal-poor star candidates
through their lack of molecular absorption near 4.6 microns. We have used our
selection to identify 11,916 metal-poor star candidates with V < 14, increasing
the number of publicly-available candidates by more than a factor of five in
this magnitude range. Their bright apparent magnitudes have greatly eased
high-resolution follow-up observations that have identified seven previously
unknown stars with [Fe/H] <~ -3.0. Our follow-up campaign has revealed that
3.8^{+1.3}_{-1.1}% of our candidates have [Fe/H] <~ -3.0 and
32.5^{+3.0}_{-2.9}% have -3.0 <~ [Fe/H] <~ -2.0. The bulge is the most likely
location of any existing Galactic Population III stars, and an infrared-only
variant of our selection is well suited to the identification of metal-poor
stars in the bulge. Indeed, two of our confirmed metal-poor stars with [Fe/H]
<~ -2.7 are within about 2 kpc of the Galactic Center. They are among the most
metal-poor stars known in the bulge.Comment: 28 pages, 6 figures, and 4 tables in emulateapj format; accepted for
publication in Ap
