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Arxiv: JWST ice band profiles reveal mixed ice compositions in the HH 48 NE disk Published: 9/12/2024 6:08:15 PM Updated: 9/12/2024 6:08:15 PM

Paper abstract: Planet formation is strongly influenced by the composition and distributionof volatiles within protoplanetary disks. With JWST, it is now possible toobtain direct observational constraints on disk ices, as recently demonstratedby the detection of ice absorption features towards the edge-on HH 48 NE diskas part of the Ice Age Early Release Science program. Here, we introduce a newradiative transfer modeling framework designed to retrieve the composition andmixing status of disk ices using their band profiles, and apply it to interpretthe H2O, CO2, and CO ice bands observed towards the HH 48 NE disk. We show thatthe ices are largely present as mixtures, with strong evidence for CO trappingin both H2O and CO2 ice. The HH 48 NE disk ice composition (pure vs. polar vs.apolar fractions) is markedly different from earlier protostellar stages,implying thermal and/or chemical reprocessing during the formation or evolutionof the disk. We infer low ice-phase C/O ratios around 0.1 throughout the disk,and also demonstrate that the mixing and entrapment of disk ices candramatically affect the radial dependence of the C/O ratio. It is thereforeimperative that realistic disk ice compositions are considered when comparingplanetary compositions with potential formation scenarios, which willfortunately be possible for an increasing number of disks with JWST.