MINDS. The Detection of 13CO2 with JWST-MIRI Indicates Abundant CO2 in a Protoplanetary Disk

We present JWST-MIRI Medium Resolution Spectrometer (MRS) spectra of the protoplanetary disk around the low-mass T Tauri star GW Lup from the MIRI mid-INfrared Disk Survey Guaranteed Time Observations program. Emission from (CO2)-C-12, (CO2)-C-13, H2O, HCN, C2H2, and OH is identified with (CO2)-C-13 being detected for the first time in a protoplanetary disk. We characterize the chemical and physical conditions in the inner few astronomical units of the GW Lup disk using these molecules as probes. The spectral resolution of JWST-MIRI MRS paired with high signal-to-noise data is essential to identify these species and determine their column densities and temperatures. The Q branches of these molecules, including those of hot bands, are particularly sensitive to temperature and column density. We find that the (CO2)-C-12 emission in the GW Lup disk is coming from optically thick emission at a temperature of similar to 400 K. (CO2)-C-13 is optically thinner and based on a lower temperature of similar to 325 K, and thus may be tracing deeper into the disk and/or a larger emitting radius than (CO2)-C-12. The derived NCO2 NH2O 2O and CO2 snowlines and/or an overall lower disk temperature. This paper demonstrates the unique ability of JWST to probe inner disk structures and chemistry through weak, previously unseen molecular features.