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

TL;DR

The paper reports the discovery and spectroscopic confirmation of the Little Cub, an extremely metal-poor star-forming galaxy in the local universe, providing insights into early galaxy evolution and interactions.

Contribution

This study presents the first high-quality spectroscopic confirmation of the Little Cub as one of the most metal-poor galaxies known locally, highlighting its potential as a near-pristine galaxy undergoing environmental effects.

Findings

Confirmed extremely low metallicity with 12 + log(O/H) = 7.13

Identified as a companion to NGC 3359 with signs of gas stripping

Provides a rare example of a near-pristine galaxy in the local universe

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] 4363 Angstrom 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.