Understanding JWST results: What thermochemical models tell us about the cold H2O content in disks

JWST is allowing us to characterize the chemical composition of the inner, planet-forming regions of protoplanetary disks in more detail than even before. One particularly interesting finding is a prominent cold H2O reservoir seen in compact, drift-dominated disks that may trace ice sublimation near the H2O snowline, a site where planets may form. We investigate the origin of this cold emission using DALI thermochemical models. Interestingly, models with H2O abundances set by a chemical network do not show this cold emission inherently. Instead, an enhancement in abundance at the snow surface of 1-2 orders of magnitude is needed. We investigate what conditions or processes can produce such an enhancement in abundance, and thus how the presence or absence of this cold H2O reservoir can inform us of the conditions under which planets form in the inner regions of the disk.