Bright beacons? ALMA non-detection of a supposedly bright [OI] 63-um line in a redshift-6 dusty galaxy

TL;DR

This study reports a non-detection of the [OI] 63-um emission line in a z=6.03 galaxy using ALMA, challenging previous claims and indicating that detecting this line at high redshift is more difficult than expected.

Contribution

The paper provides the first ALMA non-detection of the [OI] 63-um line in a high-redshift galaxy, refuting earlier claims and highlighting observational challenges.

Findings

The [OI] 63-um line was not detected with ALMA, setting a new upper flux limit.

The non-detection suggests [OI] 63-um is harder to observe in z≥6 galaxies than previously thought.

Previous claims of detection with APEX are refuted by the new ALMA data.

Abstract

We report a non-detection of the [OI] 63-um emission line from the z = 6.03 galaxy G09.83808 using ALMA Band 9 observations, refuting the previously claimed detection with APEX by (Rybak et al. 2020); the new upper limit on the [OI] 63-um flux is almost 20-times lower. [OI] 63-um line could be a powerful tracer of neutral gas in the Epoch of Reionisation: yet our null result shows that detecting [OI] 63-um from z$\geq$6 galaxies is more challenging than previously hypothesised.