The Pristine Survey – VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates★

Abstract

We present the results of a 3-year long, medium-resolution spectroscopic campaign aimed at identifying very metal-poor stars from candidates selected with the CaHK, metallicity-sensitive Pristine survey. The catalogue consists of a total of 1007 stars, and includes 146 rediscoveries of metal-poor stars already presented in previous surveys, 707 new very metal-poor stars with [Fe/H]<−2.0⁠, and 95 new extremely metal-poor stars with [Fe/H]<−3.0⁠. We provide a spectroscopic [Fe/H] for every star in the catalogue, and [C/Fe] measurements for a subset of the stars (10% with [Fe/H]<−3 and 24% with −3<[Fe/H]<−2⁠) for which a carbon determination is possible, contingent mainly on the carbon abundance, effective temperature and S/N of the stellar spectra. We find an average carbon enhancement fraction ([C/Fe] ≥ +0.7) of 41 ± 4% for stars with −3<[Fe/H]<−2 and 58 ± 14% for stars with [Fe/H]<−3⁠, and report updated success rates for the Pristine survey of 56 % and 23 % to recover stars with [Fe/H]<−2.5 and [Fe/H]<−3⁠, respectively. Finally, we discuss the current status of the survey and its preparation for providing targets to upcoming multi-object spectroscopic surveys such as WEAVE