# Implications of a hot atmosphere/corino from ALMA observations towards NGC1333 IRAS 4A1

## TL;DR

This study presents high-resolution ALMA observations of the NGC1333 IRAS 4A protobinary, revealing complex organic molecules around A1 and A2 cores, with implications for understanding hot corino environments and disk/envelope structures.

## Contribution

First detection of complex organic molecules in absorption around the A1 core, suggesting a hot-corino-like atmosphere or layered envelope structure.

## Key findings

- COMs detected in absorption around A1 core
- A2 core exhibits complex molecules in emission as a hot corino
- Evidence supports a hot-corino atmosphere or layered envelope scenario

## Abstract

We report high angular resolution observations of NGC1333 IRAS4A, a protostellar binary including A1 and A2, at 0.84 mm with the Atacama Large Millimeter/submillimeter Array. From the continuum observations, we suggest that the dust emission from the A1 core is optically thick, and A2 is predominantly optically thin. The A2 core, exhibiting a forest of spectral lines including complex molecules, is a well known hot corino as suggested by previous works. More importantly, we report, for the first time, the solid evidence of complex organic molecules (COMs), including CH3OH, ^13CH3OH, CH2DOH, CH3CHO associated with the A1 core seen in absorption. The absorption features mostly arise from a compact region around the continuum peak position of the A1 core. Rather than originating from a larger common envelope surrounding the protobinary, the COM features are associated with individual cores A1 and A2. Considering the signatures observed in both continuum and spectral lines, we propose two possible scenarios for IRAS 4A1 - the COM absorption lines may arise from a hot-corino-like atmosphere at the surface of an optically-thick circumstellar disk around A1, or the absorption may arise from different layers of a temperature-stratified dense envelope.