Searching For Transiting Planets Around Halo Stars. I. Sample Selection
  and Validation
  By measuring the elemental abundances of a star, we can gain insight into the
composition of its initial gas cloud -- the formation site of the star and its
planets. Planet formation requires metals, the availability of which is
determined by the elemental abundance. In the case where metals are extremely
deficient, planet formation can be stifled. To investigate such a scenario
requires a large sample of metal-poor stars and a search for planets therein.
This paper focuses on the selection and validation of a halo star sample. We
select ~17,000 metal-poor halo stars based on their Galactic kinematics, and
confirm their low metallicities ([Fe/H] < -0.5), using spectroscopy from the
literature. Furthermore, we perform high-resolution spectroscopic observations
using LBT/PEPSI and conduct detailed metallicity ([Fe/H]) analyses on a sample
of 13 previously known halo stars that also have hot kinematics. We can use the
halo star sample presented here to measure the frequency of planets and to test
planet formation in extremely metal-poor environments. The result of the planet
search and its implications will be presented and discussed in a companion
paper by Boley et al.
