Kavli Affiliate: Gregory J. Herczeg
| First 5 Authors: Andrea Banzatti, Klaus M. Pontoppidan, John Carr, Evan Jellison, Ilaria Pascucci
| Summary:
Previous analyses of mid-infrared water spectra from young protoplanetary
disks observed with the Spitzer-IRS found an anti-correlation between water
luminosity and the millimeter dust disk radius observed with ALMA. This trend
was suggested to be evidence for a fundamental process of inner disk water
enrichment, used to explain properties of the Solar System 40 years ago, in
which icy pebbles drift inward from the outer disk and sublimate after crossing
the snowline. Previous analyses of IRS water spectra, however, were very
uncertain due to the low spectral resolution that blended lines together. We
present new JWST-MIRI spectra of four disks, two compact and two large with
multiple radial gaps, selected to test the scenario that water vapor inside the
snowline is regulated by pebble drift. The higher spectral resolving power of
MIRI-MRS now yields water spectra that separate individual lines, tracing upper
level energies from 900 K to 10,000 K. These spectra clearly reveal excess
emission in the low-energy lines in compact disks, compared to the large disks,
establishing the presence of a cooler component with $T approx$ 170-400 K and
equivalent emitting radius $R_{rm{eq}}approx$ 1-10 au. We interpret the cool
water emission as ice sublimation and vapor diffusion near the snowline,
suggesting that there is indeed a higher inwards mass flux of icy pebbles in
compact disks. Observation of this process opens up multiple exciting prospects
to study planet formation chemistry in inner disks with JWST.
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