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Arxiv: 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: 4/16/2024 6:18:16 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 have suggested that PopIII starsmay form in pockets of pristine gas in the halo of more evolved galaxies. Wepresent NIRSpec integral field spectroscopy and micro-shutter arrayspectroscopic observations of the region around GN-z11, an exceptionallyluminous galaxy at z=10.6, that reveal a greater than 5 sigma detection of afeature consistent with being HeII1640 emission at the redshift of GN-z11. Thevery high equivalent width of the putative HeII emission in this clump(log(EW_rest(HeII)/A) = 1.79) and a lack of metal lines can be explained interms of photoionisation by PopIII stars, while photoionisation by PopII starsis inconsistent with the data. The high equivalent width would also indicatethat the putative PopIII stars likely have an initial mass function with anupper cutoff reaching at least 500 Msun. The PopIII bolometric luminosityinferred from the HeII line would be 7 x 10^9 Lsun, which would imply a totalstellar mass formed in the burst of about 2 x 10^5 Msun. We find thatphotoionisation by the active galactic nucleus (AGN) in GN-z11 cannot accountfor the HeII luminosity observed in the clump but can potentially beresponsible for an additional HeII emission observed closer to GN-z11. We alsoconsider the possibility of in situ photoionisation by an accreting directcollapse black hole hosted by the HeII clump. We find that this scenario isless favoured, but it remains a possible alternative interpretation. We alsoreport the detection of a Ly-alpha halo stemming out of GN-z11 and extendingout to about 2 kpc as well as resolved funnel-shaped CIII emission likelytracing the ionisation cone of the AGN.