2022MNRAS.516.1032H

The atmospheric chemical composition of a hot Jupiter can lead to insights into where in its natal protoplanetary disc it formed and its subsequent migration pathway. We use a 1D chemical kinetics code to compute a suite of models across a range of elemental abundances to investigate the resultant abundances of key molecules in hot Jupiter atmospheres. Our parameter sweep spans metallicities between 0.1x and 10x solar values for the C/H, O/H, and N/H ratios, and equilibrium temperatures of 1000 and 2000 K. We link this parameter sweep to the formation and migration models from previous works to predict connections between the atmospheric molecular abundances and formation pathways, for the molecules H₂O, CO, CH₄, CO₂, HCN, and NH₃. We investigate atmospheric H₂O abundances in eight hot Jupiters reported in the literature. All eight planets fall within our predicted ranges for various formation models; however, six of them are degenerate between multiple models and hence require additional molecular detections for constraining their formation histories. The other two planets, HD 189733 b and HD 209458 b, have water abundances that fall within ranges expected from planets that formed beyond the CO₂ snowline. Finally, we investigate the detections of H₂O, CO, CH₄, CO₂, HCN, and NH₃ in the atmosphere of HD 209458 b and find that, within the framework of our model, the abundances of these molecules best match with a planet that formed between the CO₂ and CO snowlines and then underwent disc-free migration to reach its current location.