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arXiv · 2603.20362

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

Roberto Maiolino·Hannah Übler·Michele Perna·Joris Witstok·Gareth C. Jones·Pablo G. Perez-Gonzalez·Kimihiko Nakajima·Elka Rusta·Stefania Salvadori·Sandro Tacchella·Piero Madau·James A. A. Trussler·Francesco D'Eugenio·Xihan Ji·Jan Scholtz·Stefano Carniani·Yuki Isobe·Harley Katz·Santiago Arribas·William M. Baker·Torsten Böker·Volker Bromm·Andrew J. Bunker·Stephane Charlot·Jacopo Chevallard·Mirko Curti·Emma Curtis-Lake·Daniel Eisenstein·Eiichi Egami·Andrea Ferrara·Luca Graziani·Kevin Hainline·Jakob M. Helton·Lucy Ivey·Benjamin Jonson·Maria Koller·Nimisha Kumari·Alessandro Marconi·Giovanni Mazzolari·Nicolas Laporte·Eleonora Parlanti·Robert Pascalau·Laura Pentericci·Pierluigi Rinaldi·Brant Robertson·Bruno Rodríguez Del Pino·Raffaella Schneider·Alessandra Venditti·Giacomo Venturi·Christopher N. A. Willmer·Callum Witten·Sandra Zamora
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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.

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Roberto Maiolino, Hannah Übler, Michele Perna, Joris Witstok, Gareth C. Jones, Pablo G. Perez-Gonzalez, Kimihiko Nakajima, Elka Rusta, Stefania Salvadori, Sandro Tacchella, Piero Madau, James A. A. Trussler, Francesco D'Eugenio, Xihan Ji, Jan Scholtz, Stefano Carniani, Yuki Isobe, Harley Katz, Santiago Arribas, William M. Baker, Torsten Böker, Volker Bromm, Andrew J. Bunker, Stephane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Daniel Eisenstein, Eiichi Egami, Andrea Ferrara, Luca Graziani, Kevin Hainline, Jakob M. Helton, Lucy Ivey, Benjamin Jonson, Maria Koller, Nimisha Kumari, Alessandro Marconi, Giovanni Mazzolari, Nicolas Laporte, Eleonora Parlanti, Robert Pascalau, Laura Pentericci, Pierluigi Rinaldi, Brant Robertson, Bruno Rodríguez Del Pino, Raffaella Schneider, Alessandra Venditti, Giacomo Venturi, Christopher N. A. Willmer, Callum Witten, Sandra Zamora. 2026-03-20. The search for Population III: Confirmation of a HeII emitter with no metal lines at z=10.6. https://arxiv.org/abs/2603.20362

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