JWST COSMOS-3D [OIII] census and luminosity func.

We leverage the 0.33deg^2^ covered by COSMOS-3D using NIRCam/WFSS F444W to perform the largest spectroscopic search for [OIII] emitters at 6.75<z<9.05. We present our catalogue of 249 [OIII] emitters and their associated completeness function.

The inferred constraints on the [OIII] LF enable us to characterise the knee of the [OIII] 5008{AA} LF, resulting in improved [OIII] 5008{AA} LF constraints at z~7, 8. Notably, we find evidence for a decline of the [OIII] luminosity density between z~6-8, which could be expected if the metallicity of [OIII] emitters, as well as the cosmic star-formation rate density, is declining at these redshifts. We find that theoretical models that reproduce the z~7,8 [OIII] 5008{AA} LF do not reproduce well the [OIII] equivalent width distribution, pointing to potential challenges in the modelling of [OIII] and other nebular lines in the early Universe.