Peekaboo: the extremely metal poor dwarf galaxy HIPASS J1131-31

TL;DR

The paper reports the discovery and detailed analysis of HIPASS J1131-31, an extremely metal-poor dwarf galaxy, highlighting its low metallicity, recent star formation, and proximity to a bright star.

Contribution

It provides the first detailed characterization of HIPASS J1131-31, including its distance, metallicity, and stellar population, revealing it as one of the most metal-poor galaxies known.

Findings

Metallicity 12+log(O/H) ≈ 7.0, among the lowest known.

Distance estimate of 6.8 Mpc from Hubble observations.

Evidence suggests star formation began only in the last few Gyr.

Abstract

The dwarf irregular galaxy HIPASS J1131-31 was discovered as a source of HI emission at low redshift in such close proximity of a bright star that we call it Peekaboo. The galaxy resolves into stars in images with Hubble Space Telescope, leading to a distance estimate of 6.8+-0.7 Mpc. Spectral optical observations with the Southern African Large Telescope reveal HIPASS J1131-31 to be one of the most extremely metal-poor galaxies known with the gas-phase oxygen abundance 12+log(O/H) = 6.99+-0.16 dex via the direct [OIII] 4363 line method and 6.87+-0.07 dex from the two strong line empirical methods. The red giant branch of the system is tenuous compared with the prominence of the features of young populations in the color-magnitude diagram, inviting speculation that star formation in the galaxy only began in the last few Gyr.