FRIPRO-Fri prosjektstøtte

Stars at the late stages of their life play a crucial role in the chemical evolution of galaxies by ejecting synthesized heavy elements and dust particles into the interstellar medium (ISM). With advancements in observational facilities offering high sensitivity and resolution, we can now measure the abundances and spatial distributions of various molecules in the outflows of evolved stars, particularly solar-type stars in their final phases of life. This allows us to better understand the last stages of stellar evolution, the origin of different atoms and their isotopes, and the recycle material from stars to the ISM. In this project, we are using high-resolution ALMA observations to study molecular gas around a sample of nearby evolved stars. Specifically, we investigated the extended atmosphere of the AGB star R Dor, which is key to understanding dust formation and how stellar winds drive mass loss. Our analysis revealed complex, uneven gas motions, with some layers falling toward the star and others flowing outward, and identified dense "blobs" that may play a significant role in the star’s mass-loss process.

Solar-type stars eject a substantial amount of heavy elements and dust particles to the interstellar medium through strong stellar winds at late phases of stellar evolution, known as the asymptotic giant branch (AGB) phase. They, therefore, significantly influence the chemical composition of galaxies. To trace the enrichment of the interstellar medium by outflows of evolved stars, it is critical to understand the chemical networks active in them. In this research proposal, I target two main gaps in our knowledge that can be significantly advanced with the current observational facilities, new laboratory molecular data, and upgraded chemical models. These concern the role of AGB stars in the production of fluorine, the essential element for the maintenance of solidity of our bones and teeth, in our Galaxy and the impact of a chromospheric UV radiation field on the chemistry and dust-formation process around AGB stars. This project aims to make a more realistic picture of the recycled materials and stardust from evolved stars by considering the impact of internal UV radiation in the chemical models. The great novelty of this project is the use of new promising high-spectral and -spatial Atacama large millimetre array (ALMA) observations towards a well-selected sample and upgraded radiative transfer and chemical models.