Presentation #207.06 in the session “Extrasolar Planets II”.
Planet formation via the accretion of mm to cm size particles, often called pebbles, has been recently invoked to explain the diversity of planetary types and systems, as well as our own Solar System. However, this formation mechanism heavily relies on the availability of pebbles in the outer disk (beyond tens of au) and the pebble inward flux. Previous work using the IRS spectrograph on board the Spitzer space telescope has shown that there is a positive correlation between the millimeter dust mass and the infrared H₂O/HCN flux ratio from protoplanetary disks around young T Tauri stars . Banzatti et al (2020) has recently found that disks with smaller millimeter dusk disk radii measured with ALMA had a larger H₂O/HCN ratio while disks with larger radii had a smaller ratio. These results hint that small disks could contain more water vapor because, lacking large planets, their millimeter grains experienced a greater degree of inward drift. We have selected three disks with pebbles imaged by ALMA that extend from 15 to 159 au. We then use an adapted version of the CLIcK fitting tool (Liu, Pascucci, and Henning 2019) to model their water infrared spectra and retrieve water column densities. We find that smaller dust disks have higher water column densities inside the snowline as expected from more efficient inward drift of pebbles and speculate on the pebble inward influx using current and upcoming JWST spectra.