All the work done by the DOC team members aimed at building up a reliable theory for the organic chemistry in nascent Solar type systems.
First, we investigated why some young protostars are enriched of iCOM while others are rather enriched of carbon chains. The first ones are called hot corinos while the second class of protostars are known as WCCC (Warm Carbon Chain Chemistry) sources. We found that the probability to form hot corinos is larger than that to form WCCC sources in a relatively quiet region, NGC1333, where only Solar type planetary systems are currently formed. However, the situation is inverted in the Orion Molecular Clouds, where also high-mass stars are formed. These results are intriguing because the comparison that we obtained between the measured iCOMs relative abundances in comets and hot corinos would suggest that the Solar System passed through a hot corino phase, whereas various evidences suggest that the Solar System was born in an environment similar to that of the Orion Molecular Clouds.
In fact, the situation is even more complicated, as we showed that the observations in the millimetre, where traditionally hot corinos are searched for and studied, are actually plagued by the dust in front of the embedded hot corinos. This dust absorbs the photons emitted by the hot corinos and can totally mask their presence or, at best, falsify the derivation of the iCOM abundances. Our studies paved the road for new searches and studies of hot corinos in the radio wavelengths, where we may harvest more of these sources.
Hot corinos are enriched of gaseous iCOMs. Thus, one crucial parameter to understand the real chemical composition of hot corinos is the iCOM binding energy (BE), which governs whether the molecule is in the gas-phase or frozen onto the dust grains. Following up our discovery of the heavy impact of the dust in the hot corino’s studies, we used the combination of multiwavelength observations with new calculated BEs and discovered that hot corinos have a chemical onion-like structure. This was possible thanks to the tight collaboration of the chemist and astronomer members of the DOC team. While the latter obtained amazingly sharp images of two hot corinos, SVS13A and HH212-mm, the former provided state-of-the-art quantum mechanical (QM) computations of the BEs on large clusters of water ice. More in general, our enlarged team provided the BEs of several species computed, for the first time, on large clusters of frozen water. With a few exceptions, these BEs were unknown and simply guessed in the astrochemical models.
We also developed a new methodology, based on the radio observations of methanol and ammonia to better understand how the chemical composition of a protostar depends on its pas history and, therefore, environment. Since methanol and ammonia are formed on the grain surfaces at different times, as showed by our astrochemical modelling which includes our latest QM chemistry calculations of the two species formation processes, their measured abundance ratio constrains the past history of the hot corino. In this way, we discovered the violent birth of the protostar called NGC1333-IRAS4A, which was born after (or because of) the crash of a bubble of gas, probably created by the explosion of a distant supernova, with the NGC1333 molecular cloud. Again, this opens up a new way to study the full history of a protostar since its incubation period.
Finally, we used state-of-the-art QM computations to fill up the huge gap in our knowledge of the reactions occurring on the gas-phase and on the grain surfaces in the interstellar conditions.
