The Absence of [CII] 158$\mu$m Emission in Spectroscopically-Confirmed Galaxies at $z>8$

Understand

The scatter in the relationship between the strength of [CII] 158$\mu$m emission and the star formation rate at high-redshift has been the source of much recent interest.

• Although the relationship is well-established locally, several intensely star-forming galaxies have been found whose [CII] 158$\mu$m emission is either weak, absent or spatially offset from the young stars.
• Here we present new ALMA data for the two most distant, gravitationally-lensed and spectroscopically-confirmed galaxies, A2744\_YD4 at $z=$8.38 and MACS1149\_JD1 at $z=$9.11, both of which reveal intense [OIII] 88$\mu$m emission.
• In both cases we provide stringent upper limits on the presence of [CII] 158$\mu$m with respect to [OIII] 88$\mu$m.