Carniani, S.S.CarnianiMaiolino, R.R.MaiolinoPallottini, A.A.PallottiniVallini, L.L.ValliniPentericci, L.L.PentericciFerrara, A.A.FerraraCASTELLANO, MARCOMARCOCASTELLANOVANZELLA, ErosErosVANZELLAGRAZIAN, AndreaAndreaGRAZIANGallerani, S.S.GalleraniSANTINI, PaolaPaolaSANTINIWagg, J.J.WaggFONTANA, AdrianoAdrianoFONTANA2021-01-252021-01-2520170004-6361http://hdl.handle.net/20.500.12386/29986We present new ALMA observations of the [O III]88 μm line and high angular resolution observations of the [C II]158 μm line in a normal star forming galaxy at z = 7.1. Previous [C II] observations of this galaxy had detected [C II] emission consistent with the Lyα redshift but spatially slightly offset relative to the optical (UV-rest frame) emission. The new [C II] observations reveal that the [C II] emission is partly clumpy and partly diffuse on scales larger than about 1 kpc. [O III] emission is also detected at high significance, offset relative to the optical counterpart in the same direction as the [C II] clumps, but mostly not overlapping with the bulk of the [C II] emission. The offset between different emission components (optical/UV and different far-IR tracers) is similar to that which is observed in much more powerful starbursts at high redshift. We show that the [O III] emitting clump cannot be explained in terms of diffuse gas excited by the UV radiation emitted by the optical galaxy, but it requires excitation by in-situ (slightly dust obscured) star formation, at a rate of about 7 M<SUB>☉</SUB> yr<SUP>-1</SUP>. Within 20 kpc from the optical galaxy the ALMA data reveal two additional [O III] emitting systems, which must be star forming companions. We discuss that the complex properties revealed by ALMA in the z 7.1 galaxy are consistent with expectations by recent models and cosmological simulations, in which differential dust extinction, differential excitation and different metal enrichment levels, associated with different subsystems assembling a galaxy, are responsible for the various appearance of the system when observed with distinct tracers.STAMPAenArticle10.1051/0004-6361/2016303662-s2.0-85028950442000412231200031https://www.aanda.org/articles/aa/full_html/2017/09/aa30366-16/aa30366-16.html2017A&A...605A..42CFIS/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::PE9_6 Stars and stellar systems