CORINOS I: JWST/MIRI Spectroscopy and Imaging of a Class 0 protostar IRAS 15398-3359

TL;DR

This study uses JWST/MIRI spectroscopy and imaging to analyze a young Class 0 protostar, revealing ice features, warm gas emissions, and outflow structures, advancing understanding of early star formation and organic molecule formation.

Contribution

First JWST/MIRI observations of a Class 0 protostar revealing ice, gas, and outflow features, providing new insights into early star formation processes.

Findings

Detection of ice absorption features of H2O, CH3OH, NH3, CH4

Identification of warm CO and water vapor emission lines

Observation of bipolar jet and outflow cavity structures

Abstract

The origin of complex organic molecules (COMs) in young Class 0 protostars has been one of the major questions in astrochemistry and star formation. While COMs are thought to form on icy dust grains via gas-grain chemistry, observational constraints on their formation pathways have been limited to gas-phase detection. Sensitive mid-infrared spectroscopy with JWST enables unprecedented investigation of COM formation by measuring their ice absorption features. We present an overview of JWST/MIRI MRS spectroscopy and imaging of a young Class 0 protostar, IRAS 15398-3359, and identify several major solid-state absorption features in the 4.9-28 $\mu$m wavelength range. These can be attributed to common ice species, such as H$_2$O, CH$_3$OH, NH$_3$, and CH$_4$, and may have contributions from more complex organic species, such as C$_2$H$_5$OH and CH$_3$CHO. The MRS spectra show many weaker emission lines at 6-8 $\mu$m, which are due to warm CO gas and water vapor, possibly from a young embedded disk previously unseen. Finally, we detect emission lines from [Fe II], [Ne II], [S I], and H$_2$, tracing a bipolar jet and outflow cavities. MIRI imaging serendipitously covers the south-western (blue-shifted) outflow lobe of IRAS 15398-3359, showing four shell-like structures similar to the outflows traced by molecular emission at sub-mm wavelengths. This overview analysis highlights the vast potential of JWST/MIRI observations and previews scientific discoveries in the coming years.