VANZELLA, ErosErosVANZELLALoiacono, F.F.LoiaconoBergamini, P.P.BergaminiMESTRIC, UrosUrosMESTRICCASTELLANO, MarcoMarcoCASTELLANORosati, P.P.RosatiMENEGHETTI, MASSIMOMASSIMOMENEGHETTIGrillo, C.C.GrilloCALURA, FrancescoFrancescoCALURAMIGNOLI, MarcoMarcoMIGNOLIBradač, M.M.BradačAdamo, A.A.AdamoRihtaršič, G.G.RihtaršičDickinson, M.M.DickinsonGronke, M.M.GronkeZANELLA, AnitaAnitaZANELLAANNIBALI, FrancescaFrancescaANNIBALIWillott, C.C.WillottMessa, M.M.MessaSani, E.E.SaniAcebron, A.A.AcebronBolamperti, A.A.BolampertiCOMASTRI, AndreaAndreaCOMASTRIGILLI, RobertoRobertoGILLICaputi, K. I.K. I.CaputiRicotti, M.M.RicottiGRUPPIONI, CarlottaCarlottaGRUPPIONIRavindranath, S.S.RavindranathMERCURIO, AmataAmataMERCURIOStrait, V.V.StraitMartis, N.N.MartisPascale, R.R.PascaleCaminha, G. B.G. B.CaminhaAnnunziatella, M.M.AnnunziatellaNONINO, MarioMarioNONINO2025-02-192025-02-1920230004-6361http://hdl.handle.net/20.500.12386/36058We present JWST/Near Infrared Spectrograph (NIRSpec) integral field spectroscopy (IFS) of a lensed Population III candidate stellar complex (dubbed Lensed And Pristine 1, LAP1), with a lensing-corrected stellar mass of ≲10<SUP>4</SUP> M<SUB>⊙</SUB> and an absolute luminosity of M<SUB>UV</SUB> > −11.2 (m<SUB>UV</SUB> > 35.6), confirmed at redshift 6.639 ± 0.004. The system is strongly amplified (μ ≳ 100) by straddling a critical line of the Hubble Frontier Field galaxy cluster MACS J0416. Although the stellar continuum is currently not detected in the Hubble and JWST/Near Infrared Camera (NIRCam) and Near Infrared Imager and Slitless Spectrograph (NIRISS) imaging, arclet-like shapes of Lyman and Balmer lines, Lyα, Hγ, Hβ and Hα are detected with NIRSpec IFS with signal-to-noise ratios (S/N) of approximately 5 − 13 and large equivalent widths (> 300 − 2000 Å), along with a remarkably weak [O III]λλ4959, 5007 at S/N ≃ 4. LAP1 shows a large ionizing photon production efficiency, log(ξ<SUB>ion</SUB>[erg Hz<SUP>−1</SUP>]) > 26. From the metallicity indexes R23 = ([O III] + [O II])/Hβ ≲ 0.74 and R3 = ([O III]/Hβ) = 0.55 ± 0.14, we derive an oxygen abundance of 12 + log(O/H)≲6.3. Intriguingly, the Hα emission is also measured in mirrored subcomponents where no [O III] is detected, providing even more stringent upper limits on the metallicity if in situ star formation is ongoing in this region (12 + log(O/H) < 6). The formal stellar mass limit of the subcomponents would correspond to ∼10<SUP>3</SUP> M<SUB>⊙</SUB> or M<SUB>UV</SUB> fainter than −10. Alternatively, this metal-free, pure line-emitting region could be the first case of a fluorescing H I gas region induced by transverse escaping ionizing radiation from a nearby star complex. The presence of large equivalent-width hydrogen lines and the deficiency of metal lines in such a small region make LAP1 the most metal-poor star-forming region currently known in the reionization era and a promising site that may host isolated, pristine stars. <P />Based on observations collected with the James Webb Space Telescope (JWST) and Hubble Space Telescope (HST). These observations are associated with JWST GO program n.1908 (PI: E. Vanzella) and GTO n.1208 (CANUCS, PI: C. Willot).STAMPAenArticle10.1051/0004-6361/2023469812-s2.0-85176111714https://www.aanda.org/articles/aa/full_html/2023/10/aa46981-23/aa46981-23.htmlhttp://arxiv.org/abs/2305.14413v12023A&A...678A.173VFIS/05 - ASTRONOMIA E ASTROFISICA