The Best and Brightest Metal-Poor Stars

Abstract

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.

28 pages, 6 figures, and 4 tables in emulateapj format; accepted for publication in ApJ

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Cited by in corpus (13)

• The Radial Velocity Experiment (RAVE): Fifth Data Release
• High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the SkyMapper Survey
• A box full of chocolates: The rich structure of the nearby stellar halo revealed by Gaia and RAVE
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• The R-process Alliance: First Magellan/MIKE Release from the Southern Search for R-Process-enhanced Stars
• The oldest and most metal poor stars in the APOSTLE Local Group simulations
• The Pristine survey III: Spectroscopic confirmation of an efficient search for extremely metal-poor stars
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• The COMBS survey I: Chemical Origins of Metal-Poor Stars in the Galactic Bulge
• The Most Metal-poor Stars in the Inner Bulge
• Keck HIRES Spectroscopy of SkyMapper Commissioning Survey Candidate Extremely Metal-Poor Stars
• The universality of the rapid neutron-capture process revealed by a possible disrupted dwarf galaxy star
• An Impacting Descent Probe for Europa and the other Galilean Moons of Jupiter