The search for Population III: Confirmation of a HeII emitter with no metal lines at z=10.6

TL;DR

This paper confirms the detection of a high-redshift HeII emitter at z=10.6 near galaxy GN-z11, supporting the presence of Population III stars with no metal lines, using JWST spectroscopy.

Contribution

First spectroscopic confirmation of a metal-free HeII emitter at z=10.6, indicating Population III stars in the early universe.

Findings

HeII emission is spectrally resolved in two components separated by 120 km/s.

Equivalent Width of HeII emission exceeds 20 Å.

No metal lines detected in the spectrum.

Abstract

We report the confirmation of a HeII$\lambda$1640 emitter located at 3 pkpc from the galaxy GN-z11, at z=10.6. The detection, based on JWST NIRSpec-IFU high-resolution spectroscopy, confirms a previous claim based on medium-resolution spectroscopy. The HeII$\lambda$1640 identification is further supported by the independent detection of H$\gamma$ obtained by \"Ubler et al. (2026) at the same location. The HeII emission is spectrally resolved in two components separated by 120 km/s. The Equivalent Width of the HeII emission is extremely high ($>$20 A). No metal lines are detected. We argue that Population III stars are the most plausible explanation for the observed He II emission, with no satisfactory alternative from other classes of sources or mechanisms.