The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe

Hsyu, Tiffany; Cooke, Ryan J.; Prochaska, J. Xavier; Bolte, Michael

Abstract

We report the discovery of the Little Cub, an extremely metal-poor star-forming galaxy in the local universe, found in the constellation Ursa Major (a.k.a. the Great Bear). We first identified the Little Cub as a candidate metal-poor galaxy based on its Sloan Digital Sky Survey photometric colors, combined with spectroscopy using the Kast spectrograph on the Shane 3 m telescope at Lick Observatory. In this Letter, we present high-quality spectroscopic data taken with the Low Resolution Imaging Spectrometer at Keck Observatory, which confirm the extremely metal-poor nature of this galaxy. Based on the weak [O III] λ4363 Å emission line, we estimate a direct oxygen abundance of 12 + log(O/H) = 7.13 ± 0.08, making the Little Cub one of the lowest-metallicity star-forming galaxies currently known in the local universe. The Little Cub appears to be a companion of the spiral galaxy NGC 3359 and shows evidence of gas stripping. We may therefore be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way–like galaxy.

Citation

Hsyu, T., Cooke, R. J., Prochaska, J. X., & Bolte, M. (2017). The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe. Astrophysical Journal, 845(2), Article L22. https://doi.org/10.3847/2041-8213/aa821f

• Journal Article Type: Article
• Acceptance Date: Jul 24, 2017
• Online Publication Date: Aug 22, 2017
• Publication Date: Aug 22, 2017
• Deposit Date: Sep 20, 2017
• Publicly Available Date: Sep 20, 2017
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 845
• Issue: 2
• Article Number: L22
• DOI: https://doi.org/10.3847/2041-8213/aa821f
• Public URL: https://durham-repository.worktribe.com/output/1344687