Molecular content of young disks revealed by JWST-MIRI: what is the carbon and oxygen budget available for planet formation?

The protostellar stage is a critical phase, early in stellar evolution (less than 0.5 Myr), during which a disk of gas and dust forms, setting the chemical budget for
planet formation.  However, unlike the older Class II disks, Class I protostars are deeply embedded in their natal envelopes. With the spectral range, sensitivity, and resolution of JWST-MIRI, we are now capable of characterizing these warm inner (< 10au) planet-forming regions for the first time for the young disks.
I will present new JWST-MIRI Cycle 4 observations of Class I protostars in the Ophiuchus, Taurus, and Corona Australis star-forming regions. Spectra show
a large variety of molecular emission and absorption features. We apply LTE slab models to determine the column densities and excitation temperatures of
detected species. By comparing the data with previous VLT-CRIRES observations that spectrally resolve CO emission, we can pinpoint the exact origin of the molecular emission. Only then can we assess the molecular content of the gas in the disks at the earliest stages of planet formation. I will show how we can use the fitted properties of the molecular lines to locate the emission and disentangle disks, outflows, hot corinos, and the range of excitation conditions present in each component. Preliminary results show the presence of H2O, CO2, HCN, and C2H2  species. RNO91, a Class I protostar, is particularly interesting as it is a clear example of a very prominent disk in a Class I system. Overall, our new data reveal the crucial transition between young embedded disks and mature T-Tauri disks.