Molecular line emission from 1000 au scales outflows to <30 au compact structures in NGC1333 IRAS4A2

Abstract

Aims. Studying protostellar objects in their earliest stages, particularly during the Class 0 phase, provides key insight into the beginnings of planet formation and dust evolution. Disentangling the various components, however, is particularly challenging. High spatial and spectral resolution observations of molecular line emission with the Atacama Large Millimeter/submillimeter Array (ALMA) are therefore crucial for probing their complex environments. Methods. In this work, we present high-resolution ($\sim$30 au) ALMA observations at 1.3 millimeters of the Class 0 protostellar system IRAS4A2. Results. We detected large, well-traced outflows in HCN (3-2), H$_{2}$CO$(2_{1~2}-1_{1~1})$, and HCO$^{+}$ (3-2), along with numerous complex organic molecules (COMs) tracing central, more compact regions. Using moment maps, we analyzed the kinematics and spatial distributions of the molecular emission, revealing a wide range of spatial scales, from compact structures within the IRAS4A2 core at $\sim$8 au in radius, to extended $\sim$5000 au outflow emission. Specifically, we find that CH$_{3}$CDO and CH$_{3}$OCHO could be both good tracers of the disk, possibly tracing its rotation. Lines of OCS (22-21), SO$_{2}~(13_{3~11}-13_{2~12})$, HCN, H$_{2}$CO, and HCO$^{+}$, show more extended structures around IRAS4A2, likely tracing the envelope, disk, accretion shocks, the base of an outflow, and the outflow itself. Conclusions. Most COMs appear to trace distinct inner regions near the central protostar, while other molecules trace more extended structures, such as the envelope or outflows. The kinematics, emission patterns, and position-velocity diagrams suggest that individual molecules trace multiple components simultaneously, making it challenging to disentangle their true origins. Altogether, these findings highlight the complex spatial distribution within the IRAS4A2 system. Abridged.