Orateur
Description
Despite the tremendous number of exoplanets detected, planet-forming scenarios are not yet able to fully explain the large diversity of planets. They form and obtain their composition from gas and dust in protoplanetary disks. The elemental composition of disks is known to vary spatially due to physical (ex: pebble drift) and chemical (chemical reactions, sublimation) processes. Thus, the elemental composition of planetary atmospheres is expected to give valuable insight about their formation, in particular the C/O ratio. However, the chemical composition of planet-forming regions of disks is still poorly constrained, making it difficult to link exoplanetary atmospheres and planet formation history. In this context, the James Webb Space Telescope opens an unprecedented observation window on the inner disks (<10 au), by detecting plenty of new molecules, especially hydrocarbons. In particular, the JWST spectra show a large dispersion of H₂O and C₂H₂ emission in TTauri disks (Grant et al. 2025), potentially highlighting chemical processes at stake. We now need thermo-chemical models to understand these observations and quantify fundamental parameters of disks. I will present an overview of my work based on the thermo-chemical model Dust And LInes (DALI) to investigate the relationship between the observed variation of H₂O and C₂H₂ emission and the C/O ratio. After mentioning several modelling improvements, especially a refined Carbon chemistry, I will show that the C₂H₂/H₂O line flux ratio is very sensitive to the C/O ratio, but also other parameters such as the elemental abundances O/H and C/H, or the dust size distribution. These results could put strong constraints on our understanding of the structure and evolution of protoplanetary disks.