The Archival Discovery of a Strong Lyensuremathα and [C II] Emitter at z = 7.677


We report the archival discovery of Lyensuremathα emission from the bright ultraviolet galaxy Y002 at z = 7.677, spectroscopically confirmed by its ionized carbon [C II] 158 ensuremathμm emission line. The Lyensuremathα line is spatially associated with the rest-frame UV stellar emission (M $_UV$ åisebox-0.5ex~ -22, 2× brighter than $M_mathrmUV^⋆ $ ), and it appears offset from the peak of the extended [C II] emission at the current i̊sebox-0.5ex~1″ spatial resolution. We derive an estimate of the unobscured SFR$_UV$ = (22 ensuremath± 1) M $_ensuremathødot$ yr$^-1$ and set an upper limit of SFR$_IR$ < 15 M $ensuremathødot$ yr$^-1$ from the far-infrared (FIR) wavelength range, which globally places Y002 on the SFR(UV+IR)-L $[C II]$ correlation observed at lower redshifts. In terms of velocity, the peak of the Lyensuremathα emission is redshifted by ensuremathΔv $_Lyensuremathα $ rs̊ebox-0.5ex~ 500 km s$^-1$ from the systemic redshift set by [C II] and a high-velocity tail extends up to rae̊box-0.5ex~1000 km s$^-1$. The velocity offset is up to raib̊ox-0.5ex~3.5× higher than the average estimate for similarly UV-bright emitters at z raiso̊x-0.5ex~ 6-7, which might suggest that we are witnessing the merging of two clumps. A combination of strong outflows and the possible presence of an extended ionized bubble surrounding Y002 would likely facilitate the escape of copious Lyensuremathα light, as indicated by the large equivalent width EW$0$(Lyensuremathα) $,=,24-6^+5$ rAÅssuming that [C II] traces the neutral hydrogen, we estimate a H I gas fraction of M $_H I$/M $_ensuremath⋆$ ensuremathgtrsim 8 for Y002 as a system and speculate that patches of high H I column densities could contribute to explaining the observed spatial offsets between Lyensuremathα- and [C II]-emitting regions. The low dust content, implied by the nondetection of the FIR continuum emission at rest frame raiseb̊-0.5ex~160 ensuremathμm, would be sufficient to absorb any potential Lyensuremathα photons produced within the [C II] clump as a result of large H I column densities.