Abundances of Iron-Peak Elements in Very Metal-Poor Stars

We have derived new detailed abundances of Mg, Ca, and the Fe-group elements Sc to Zn (Z = 21–30) for 37 very metal-poor main-sequence-turnoff stars ([Fe/H < -2.1). High signal-to-noise spectra from Keck HIRES optical and near-UV, originally gathered for a beryllium abundance survey, were utilized to make the abundance determinations. Combined with new experimental atomic laboratory data, we obtained precise LTE abundance ratios for both neutral and ionized species for the 10 Fe-group elements and the alpha elements Mg and Ca. The neutral/ion abundance values agree well for the 6 elements that have detectable transitions in our stars in the wavelength range 3100–5800 Å. We confirm previous findings of correlations among the elements Sc, V and Ti, and find that they show increasing, relative overabundances with decreasing metallicity. We further find that Zn appears correlated with these other elements, and it also appears to be increasingly overabundant at the lowest metallicity values. Likewise, Co appears to mimic the behavior of Zn, but the abundance reliability of Co makes this interpretation difficult.