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JWST-JADES. Possible Population III signatures at z=10.6 in the halo of GN-z11 Published: 6/1/2023 8:50:00 PM Updated: 6/3/2023 2:16:58 PM

Paper abstract: Finding the first generation of stars formed out of pristine gas in the earlyUniverse, known as Population III (PopIII) stars, is one of the most importantgoals of modern astrophysics. Recent models suggest that PopIII stars may formin pockets of pristine gas in the halo of more evolved galaxies. Here wepresent NIRSpec-IFU and NIRSpec-MSA observations of the region around GN-z11,an exceptionally luminous galaxy at z=10.6, which reveal a >5\sigmadetection of a feature consistent with being HeII\lambda1640 emission at theredshift of GN-z11. The very high equivalent width of the putative HeIIemission in this clump (170 A), and the lack of metal lines, can be explainedin terms of photoionisation by PopIII stars, while photoionisation by PopIIstars is inconsistent with the data. It would also indicate that the putativePopIII stars likely have a top-heavy initial mass function (IMF), with an uppercutoff reaching at least 500 M_\odot. The PopIII bolometric luminosityinferred from the HeII line would be ~ 2\times 10^{10}~L_\odot, which(with a top-heavy IMF) would imply a total stellar mass formed in the burst of~ 6\times 10^{5}~M_\odot. We find that photoionisation by the ActiveGalactic Nucleus (AGN) in GN-z11 cannot account for the HeII luminosityobserved in the clump, but can potentially be responsible for additional HeIIemission observed closer to GN-z11. We also consider the possibility of in-situphotoionisation by an accreting Direct Collapse Black Hole (DCBH) hosted by theHeII clump; we find that this scenario is less favoured, but it remains apossible alternative interpretation. We also report the detection of aLy\alpha halo stemming out of GN-z11 and extending out to ~2 kpc, aswell as resolved, funnel-shaped CIII] emission, likely tracing the ionisationcone of the AGN.