Missing [CII] emission from early galaxies

Understand

ALMA observations have revealed that [CII] 158$\mu$m line emission in high-z galaxies is ~2-3$\times$ more extended than the UV continuum emission.

• Here we explore whether surface brightness dimming (SBD) of the [CII] line is responsible for the reported [CII] deficit, and the large $L_{\rm [OIII]}/L_{\rm [CII]}$ luminosity ratio measured in early galaxies.
• We first analyse archival ALMA images of nine z>6 galaxies observed in both [CII] and [OIII].
• After performing several uv-tapering experiments to optimize the identification of extended line emission, we detect [CII] emission in the whole sample, with an extent systematically larger than the [CII] emission.