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Title: Water UV-shielding in the Terrestrial Planet-forming Zone: Implications from Water Emission
Abstract Mid-infrared spectroscopy is one of the few ways to observe the composition of the terrestrial planet-forming zone, the inner few astronomical units, of protoplanetary disks. The species currently detected in the disk atmosphere, for example, CO, CO 2 , H 2 O, and C 2 H 2 , are theoretically enough to constrain the C/O ratio on the disk surface. However, thermochemical models have difficulties in reproducing the full array of detected species in the mid-infrared simultaneously. In an effort to get closer to the observed spectra, we have included water UV-shielding as well as more efficient chemical heating into the thermochemical code Dust and Lines. We find that both are required to match the observed emission spectrum. Efficient chemical heating, in addition to traditional heating from UV photons, is necessary to elevate the temperature of the water-emitting layer to match the observed excitation temperature of water. We find that water UV-shielding stops UV photons from reaching deep into the disk, cooling down the lower layers with a higher column. These two effects create a hot emitting layer of water with a column of 1–10 × 10 18 cm −2 . This is only 1%–10% of the water column above the dust τ = 1 surface at mid-infrared wavelengths in the models and represents <1% of the total water column.  more » « less
Award ID(s):
1907653
PAR ID:
10356081
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
The Astrophysical Journal Letters
Volume:
930
Issue:
2
ISSN:
2041-8205
Page Range / eLocation ID:
L26
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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