The Pristine survey III: Spectroscopic confirmation of an efficient search for extremely metal-poor stars

• Published in: arXiv.org 2017-08
• Main Authors: Youakim, K, Starkenburg, E, Aguado, D S, Martin, N F, Fouesneau, M, González Hernández, J I, C Allende Prieto, Bonifacio, P, Gentile, M, Kielty, C, Côté, P, Jablonka, P, McConnachie, A, R Sánchez Janssen, Tolstoy, E, Venn, K
• Format: Article
• Language: English
• Subjects: Infrared photometry; Iron; Metallicity; Photometry; Searching; Spectroscopy; Stars
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1708.01264

The Pristine survey is a narrow-band, photometric survey focused around the wavelength region of the Ca II H & K absorption lines, designed to efficiently search for extremely metal-poor stars. In this work, we use the first results of a medium-resolution spectroscopic follow-up to refine the selection criteria for finding extremely metal-poor stars (\(\textrm{[Fe/H]} \leq -3.0\)) in the Pristine survey. We consider methods by which stars can be selected from available broad-band and infrared photometry plus the additional Pristine narrow-band photometry. The spectroscopic sample presented in this paper consists of 205 stars in the magnitude range \(14 < V < 18\). Applying the photometric selection criteria cuts the sample down to 149 stars, and from these we report a success rate of 70% for finding stars with \(\textrm{[Fe/H]} \leq -2.5\) and 22% for finding stars with \(\textrm{[Fe/H]} \leq -3.0\). These statistics compare favourably with other surveys that search for extremely metal-poor stars, namely an improvement by a factor of \(\sim 4-5\) for recovering stars with \(\textrm{[Fe/H]} \leq -3.0\). In addition, Pristine covers a fainter magnitude range than its predecessors, and can thus probe deeper into the Galactic halo.