ALMA Detection of Extended [C ii] Emission in Himiko at z = 6.6

Himiko is one of the most luminous Ly α emitters at z = 6.595. It has three star-forming clumps detected in the rest-frame UV, with a total SFR = 20 M ⊙ yr −1 . We report the Atacama Large Millimeter/submillimeter Array (ALMA) detection of the [C ii ]158 μ m line emission in this Galaxy with a significance of 8 σ . The total [C ii ] luminosity ( L [C ii ] = 1.2 × 10 8 L ⊙ ) is fully consistent with the local L [C ii ] –SFR relation. The ALMA high-angular resolution reveals that the [C ii ] emission is made of two distinct components. The brightest [C ii ] clump is extended over 4 kpc and is located on the peak of the Ly α nebula, which is spatially offset by 1 kpc relative to the brightest UV clump. The second [C ii ] component is spatially unresolved (size <2 kpc) and coincident with one of the three UV clumps. While the latter component is consistent with the local L [C ii ] –SFR relation, the other components are scattered above and below the local relation. We shortly discuss the possible origin of the [C ii ] components and their relation with the star-forming clumps traced by the UV emission.