Water UV-shielding in the Terrestrial Planet-forming Zone: Implications for Carbon Dioxide Emission

Carbon Dioxide is an important tracer of the chemistry and physics in terrestrial planet forming zone. Using a thermo-chemical model that has been tested against mid-infrared water emission we re-interpret CO2 as observed with Spitzer. We find both UV-shielding extra chemical heating significantly reduce total column emitting layer. Water more efficient effect, reducing by $\sim$ 2 orders magnitude. These lower abundances lead to CO2-to-H2O flux ratios are closer values, but still too bright, especially relative terms. Invoking depletion elemental oxygen outside mid-plane iceline strongly impacts than it does H2O emission, bringing line values. conclude Spitzer-IRS coming from thin layer photo-sphere disk, similar strong lines. Below this layer, expect not be present except when replenished physical process. This would visible $^{13}$CO2 spectrum well certain $^{12}$CO2 features can JWST-MIRI.