Rinaldi, P.P.RinaldiCaputi, K. I.K. I.CaputiCOSTANTIN, LUCALUCACOSTANTINGillman, S.S.GillmanIani, E.E.IaniPérez-González, P. G.P. G.Pérez-GonzálezÖstlin, G.G.ÖstlinColina, L.L.ColinaGreve, T. R.T. R.GreveNoorgard-Nielsen, H. U.H. U.Noorgard-NielsenWright, G. S.G. S.WrightAlonso-Herrero, A.A.Alonso-HerreroÁlvarez-Márquez, J.J.Álvarez-MárquezEckart, A.A.EckartGarcía-Marín, M.M.García-MarínHjorth, J.J.HjorthIlbert, O.O.IlbertKendrew, S.S.KendrewLabiano, A.A.LabianoLe Fèvre, O.O.Le FèvrePye, J.J.PyeTikkanen, T.T.TikkanenWalter, F.F.Waltervan der Werf, P.P.van der WerfWard, M.M.WardAnnunziatella, M.M.AnnunziatellaAzzollini, R.R.AzzolliniBik, A.A.BikBoogaard, L.L.BoogaardBosman, S. E. I.S. E. I.BosmanCrespo Gómez, A.A.Crespo GómezJermann, I.I.JermannLangeroodi, D.D.LangeroodiMelinder, J.J.MelinderMeyer, R. A.R. A.MeyerMoutard, T.T.MoutardPeissker, F.F.PeisskerTOPINKA, MartinMartinTOPINKAvan Dishoeck, E.E.van DishoeckGüdel, M.M.GüdelHenning, Th.Th.HenningLagage, P. -O.P. -O.LagageRay, T.T.RayVandenbussche, B.B.VandenbusscheWaelkens, C.C.WaelkensNavarro-Carrera, R.R.Navarro-CarreraKokorev, V.V.Kokorev2025-03-082025-03-0820230004-637Xhttp://hdl.handle.net/20.500.12386/36555We make use of JWST medium-band and broadband NIRCam imaging, along with ultradeep MIRI 5.6 μm imaging, in the Hubble eXtreme Deep Field to identify prominent line emitters at z ≃ 7-8. Out of a total of 58 galaxies at z ≃ 7-8, we find 18 robust candidates (≃31%) for (Hβ + [O III]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW<SUB>0</SUB>(Hβ +[O III]) ≃87-2100 Å. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at 5.6 μm, indicating the simultaneous presence of a prominent Hα emission line with EW<SUB>0</SUB>(Hα) ≃200-3000 Å. This is the first time that Hα emission can be detected in individual galaxies at z > 7. The Hα line, when present, allows us to separate the contributions of Hβ and [O III] to the (Hβ +[O III]) complex and derive Hα-based star formation rates (SFRs). We find that in most cases [O III]/Hβ > 1. Instead, two galaxies have [O III]/Hβ < 1, indicating that the NIRCam flux excess is mainly driven by Hβ. Most prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density ${\mathrm{log}}_{10}({\rho }_{{\mathrm{SFR}}_{{\rm{H}}\alpha }}/({M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}))\simeq -2.35$ , which is about a quarter of the total value ( ${\mathrm{log}}_{10}({\rho }_{{\mathrm{SFR}}_{\mathrm{tot}}}/({M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{Mpc}}^{-3}))\simeq -1.76$ ) at z ≃ 7-8. Therefore, the strong Hα emitters likely had a significant role in reionization.STAMPAenArticle10.3847/1538-4357/acdc272-s2.0-85166237032https://api.elsevier.com/content/abstract/scopus_id/85166237032https://iopscience.iop.org/article/10.3847/1538-4357/acdc272023ApJ...952..143RFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation