Periodic Reporting for period 4 - S4F (Setting the Stage for Solar System Formation)
Reporting period: 2020-02-01 to 2021-01-31
The nexus of the work has been a large survey using ALMA of the complex chemistry of a system of solar-type young stars. The data show a wealth of molecular lines from different species that we identify through spectroscopic data obtained in laboratories on Earth. These observations have so far resulted in a number of discoveries of molecules – some that had never been seen in the interstellar medium before and some that had only been detected in more extreme environments, for example in the center of our Galaxy.
The high-quality data also allow us to make significant progress in making detailed and accurate inventories of molecular species in these regions and address their origin. A significant effort for the team has been on synthesising this information and study the more general trends in the abundances of different molecular species and their isotopic compositions – as well as comparing gas-phase inventories to knowledge about the ice chemistry in these regions. The results of these measurements support a picture where many of these species are formed during the densest cold phases in the evolution of young stars where most of the chemistry takes place on the surfaces of dust grains. The accurate measurements also pose new challenges with respect to mimicking these results in laboratory experiments as well as through detailed chemical models.
The results also pose new questions, e.g. whether this chemistry is ubiquitous - i.e. that all forming young stars are characterized by similar chemical processes and thereby have a chemical complexity that can be incorporated in their protoplanetary disks. We have carried out observations of a number of young protostars from different star-forming regions and in different evolutionary stages, focusing on the kinematics of the gas on the scales where disks form. In particular, we find that the physical structure is of great importance for the observed molecular signatures – but not necessarily that the physical evolution itself changes the chemistry significantly.
The final aspect of the action has been to put the observations of young stars in the earliest stages in the context of the understanding of our own Solar System and its origin. By comparing the chemical structures of Solar-type protostar to measurements of Solar System comets we show that there are significant similarities between the organic contents suggesting that a significant part of the chemistry occurring in the earliest stages of star formation is inherited to the protoplanetary disk and bodies formed within it. Interestingly, the same organic composition is also seen in different regions of the Galaxy – e.g. in its center where the physical conditions are significantly different. Other indications, e.g. the isotopic composition of water and organic molecules, lend support to the notion that the Sun in fact has formed in a clustered environment.
The results of the action has been published in a long range of publications in international peer-reviewed journals, through invited and contributed presentations at international conferences as well as in press-releases presenting particularly high profile results.