Oral Presentation

The Icy Chemical Origin of Protostellar Disks Probed by JWST

Author(s): Yao-Lun Yang (RIKEN)

Presenter: Yao-Lun Yang (RIKEN)

Protostellar disks mediate the infalling materials from the surrounding envelopes and the accretion onto the protostars. At the same time, outflows driven by the disks continuously shape the envelope structures and process the materials therein via shocks. More importantly, recent studies suggest that planet formation may already start during the embedded phase of star formation. Thus, understanding the chemistry of protostellar disks and its origin not only constrains ongoing dynamical processes but also explores the initial chemical conditions of planet formation. While ALMA provides excellant characterization of the gaseous disks, most chemical reactions that occur in ice mantle remain ill-constrained at the comparable level of details. In this talk, I will try to answer whether the gas-phase signatures represent the chemical evolution in ice using JWST spectroscopy. In the CORINOS program, we identified icy COMs regardless of the presence of gaseous COMs.  Supported by insights from laboratory experiments, these identifications provide a foundation for further constraining the ice compositions in protostellar envelopes. We measured the abundances of both simple and complex ice species in an embedded protostar, IRAS 15398-3359. We also find similar ice abundances of SO2 and COMs across sources with diverse gas-phase appearances. Using radiative transfer modeling, we further disentangled the interplay between protostellar structure and the ice compositions, which led to a surprisingly high CO2 abundance of 76% compared to water. These findings depict a complex chemical evolution of protostellar disks. Finally, I will discuss the synergy between gas and ice characterization to understand the chemistry of protostellar disks.