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 \mathrm { [ Fe / H ] } \lesssim - 3.0 .
Our follow-up campaign has revealed that 3.8 ^ { +1.3 } _ { -1.1 } % of our candidates have \mathrm { [ Fe / H ] } \lesssim - 3.0 and 32.5 ^ { +3.0 } _ { -2.9 } % have -3.0 \lesssim \mathrm { [ Fe / H ] } \lesssim - 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 ] \lesssim - 2.7 are within about 2 kpc of the Galactic Center .
They are among the most metal-poor stars known in the bulge .