Invited Presentation

Evolution of Organic Chemistry from Ice to Gas: The Synergy between ALMA and JWST

Author(s): Yao-Lun Yang and the CORINOS team

Presenter: Yao-Lun Yang (RIKEN)

In recent years, the increasing detection of complex organic molecules (COMs) in Class 0/I protostars highlights the extensive chemical evolution at the onset of star formation. However, the formation pathways of COMs and whether most protostars undergo similar chemical evolution remain open questions with little observational constraints. Most COMs form in the ice mantles covering dust grains. While ALMA provides sub-100 au resolution for studying gaseous COMs in nearby embedded protostars, measurements of the chemical composition in ices had been limited by low resolution and limited sensitivity until JWST, which can probe ices at a spatial scale comparable to that by ALMA with unprecedented sensitivity. In this talk, I will present the JWST/MIRI observations of a Class 0 protostar, IRAS 15398-3359, from the CORINOS program and discuss the prospect of ice identification and modeling in the JWST era. The MIRI spectrum robustly characterizes the shape of ice features, including the fine details of broad absorption features. Besides the common ice species, which are definitively identified, the spectrum shows potential evidence of organic ice species, such as ethanol and acetaldehyde. The well-calibrated spectrum also provides strong constraints on ice modeling and enables direct comparison with synthetic spectra from radiative transfer calculation. Moreover, line and continuum emission in our MIRI observations gives us the most crisp view of the outflows and jets in mid-IR. The ionized lines, such as [Fe II] and [Ne II], trace collimated bipolar jets, while the H2 lines come from the shocked gas in the wide-angle outflow cavity. I will also discuss the potential of a holistic view of COM chemistry learned from both JWST and ALMA observations. The JWST observations of IRAS 15398-3359 show striking details on the ice absorption as well as the protostellar structure, demonstrating the prospect of understanding organic chemical evolution from protostars to planets.