Decoding the molecular complexity of the solar-type protostar NGC 1333 IRAS 4A

The characterisation of the molecular inventory of solar-type protostars is of crucial importance for a deep understanding of the chemical complexity underlying our cosmic origins. In this context, we present here the full millimetre line survey of the Class 0 protostellar object NGC 1333 IRAS 4A in the spectral bands at 3, 2 and 1.3 mm. In recognition of the powerful tool that unbiased spectral studies provide for investigating the chemistry and physics of star-forming regions, we provide a detailed description of the survey and the results of the analysis. We describe the identification of 1474 spectral lines belonging to 97 different molecular species, including complex organic molecules (COMs), which together cover the most ubiquitous chemical elements of life on Earth, namely carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur (CHNOPS). The abundances obtained herein are compared with the Class 0 protostellar objects L483 and L1527, and selected molecular ratios are used as tracers of physicochemical properties of the sources. Particularly, the dominance of oxygen-bearing species and the presence of distinct excitation temperature regimes support the attribution of NGC 1333 IRAS 4A as a hot corino featuring three physical components with distinguished and diverse chemical composition.