CORINOS. I. JWST/MIRI Spectroscopy and Imaging of a Class 0 Protostar IRAS 15398–3359

<jats:title>Abstract</jats:title> <jats:p>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. Mid-infrared emission from disks and outflows provide complementary constraints on the protostellar systems. We present an overview of JWST/Mid-Infrared Instrument (MIRI) Medium Resolution Spectroscopy (MRS) and imaging of a young Class 0 protostar, IRAS 15398−3359, and identify several major solid-state absorption features in the 4.9–28 <jats:italic>μ</jats:italic>m wavelength range. These can be attributed to common ice species, such as H<jats:sub>2</jats:sub>O, CH<jats:sub>3</jats:sub>OH, NH<jats:sub>3</jats:sub>, and CH<jats:sub>4</jats:sub>, and may have contributions from more complex organic species, such as C<jats:sub>2</jats:sub>H<jats:sub>5</jats:sub>OH and CH<jats:sub>3</jats:sub>CHO. In addition to ice features, the MRS spectra show many weaker emission lines at 6–8 <jats:italic>μ</jats:italic>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 <jats:sc>ii</jats:sc>], [Ne <jats:sc>ii</jats:sc>], [S <jats:sc>i</jats:sc>], and H<jats:sub>2</jats:sub>, tracing a bipolar jet and outflow cavities. MIRI imaging serendipitously covers the southwestern (blueshifted) outflow lobe of IRAS 15398−3359, showing four shell-like structures similar to the outflows traced by molecular emission at submillimeter wavelengths. This overview analysis highlights the vast potential of JWST/MIRI observations and previews scientific discoveries in the coming years.</jats:p>