Presentation #544.01 in the session “Extrasolar Planets: Formation of Planets and Protoplanetary Disks”.
Understanding the chemistry of protoplanetary disks is essential to understanding planetary formation and composition. Many protoplanetary disks are depleted in CO compared to the interstellar medium from which they form. A possible explanation of this phenomena is CO gas condensing onto grains as CO2 ice in the cold outer disk. As these grains move into the hotter inner disk via radial drift, the CO2 ice would sublimate into gas. This should result in an anti-correlation between CO emission in the outer disk and CO2 emission in the inner disk. To test this hypothesis we reimage archival Atacama Large Millimeter/Submillimeter Array observations of 13CO and C18O 3-2 emission towards several protoplanetary disks and compare the resulting fluxes to archival CO2 data from Spitzer. Only the relationship between 13CO and CO2 is analyzed, as C18O emission was detected towards too few sources to create a sizable C18O data set. When first analyzing the relationship between 13CO and CO2, no significant trend is discovered. However, when disks around M-type stars were removed from analysis, a positive (albeit somewhat weak) correlation is observed between 13CO and CO2 fluxes. The lack of an inverse trend contradicts the possibility of CO being converted to CO2. The positive trend may simply be a result of disks with higher carbon content having higher abundances of multiple carbon based species. More observations are needed to confirm this trend.