Detection of an oxygen emission line from a high redshift galaxy in the reionization epoch

TL;DR

This paper reports the first detection of an oxygen emission line from a galaxy during the reionization epoch, revealing low metallicity and dust content, which may facilitate photon escape into the intergalactic medium.

Contribution

First detection of an oxygen emission line at 88 micrometers from a high-redshift galaxy, providing insights into its interstellar medium during reionization.

Findings

Oxygen abundance is about one-tenth of the solar value.

Lack of far-infrared continuum suggests low dust content.

Non-detection of carbon line indicates minimal neutral gas.

Abstract

The physical properties and elemental abundances of the interstellar medium in galaxies during cosmic reionization are important for understanding the role of galaxies in this process. We report the Atacama Large Millimeter/submillimeter Array detection of an oxygen emission line at a wavelength of 88 micrometers from a galaxy at an epoch about 700 million years after the Big Bang. The oxygen abundance of this galaxy is estimated at about one-tenth that of the Sun. The non-detection of far-infrared continuum emission indicates a deficiency of interstellar dust in the galaxy. A carbon emission line at a wavelength of 158 micrometers is also not detected, implying an unusually small amount of neutral gas. These properties might allow ionizing photons to escape into the intergalactic medium.