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

TL;DR

This study reports the ALMA detection of extended [CII] emission in the high-redshift galaxy Himiko, revealing complex spatial structures and their relation to star-forming regions, advancing understanding of early galaxy properties.

Contribution

First ALMA detection of [CII] emission in Himiko showing multiple spatial components and their relation to UV star-forming clumps at z=6.6.

Findings

[CII] emission is extended and spatially offset from UV clumps.

The total [CII] luminosity aligns with local L[CII]-SFR relation.

Different [CII] components show varied relation to star formation.

Abstract

Himiko is one of the most luminous Ly{\alpha} 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$\mu$m line emission in this galaxy with a significance of 9$\sigma$. 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 Ly{\alpha} 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.