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

doi:10.3847/2041-8213/aa821f

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

Authors

Tiffany Hsyu

Dr Ryan Cooke ryan.j.cooke@durham.ac.uk
Associate Professor

J. Xavier Prochaska

Michael Bolte

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