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

Abstract

We report the confirmation of a HeII$\hat{I}»$1640 emitter located at 3 pkpc from the galaxy GN-z11, at z=10.6. The detection, based on JWST NIRSpec-IFU high-resolution spectroscopy, confirms a previous claim based on medium-resolution spectroscopy. The HeII$\hat{I}»$1640 identification is further supported by the independent detection of H${\hat{I}}^3$ obtained by Übler 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.

Submitted to MNRAS, 12 pages, 9 figures; revised metadata