ALMA detection of extended [CII] emission in Himiko at z=6.6

Abstract

Himiko is one of the most luminous Lyα emitters at z = 6.595. It has three star forming clumps detected in the rest-frame UV, with a total SFR = 20 M${}_{\odot }$/yr. We report the ALMA detection of the [CII]158$\hat{I}¼$m line emission in this galaxy with a significance of 9$\ddot{I}ƒ$. The total [CII] luminosity (L[CII]= (1.2$\pm$0.2)$\times$10${}^8$ L${}_{\odot }$) is fully consistent with the local L[CII]-SFR relation. The ALMA high-angular resolution reveals that the [CII] emission is made of two distinct components. The brightest [CII] clump is extended over 4 kpc and is located on the peak of the Lyα nebula, which is spatially offset by 1 kpc relative to the brightest UV clump. The second [CII] component is spatially unresolved (size $<$2 kpc) and coincident with one of the three UV clumps. While the latter component is consitent with the local L[CII]-SFR relation, the other components are scattered above and below the local relation. We shortly discuss the possible origin of the [CII] components and their relation with the star forming clumps traced by the UV emission.

6 pages, 3 figures, 2 tables; submitted to ApJL