Following the Chemical History of Stellar Ejecta through Molecular Observations and Laboratory Spectroscopy

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This project seeks to unravel how matter in our Galaxy is transferred from stars, which create the majority of the chemical elements, to interstellar space. The PI and her students and collaborators will examine the chemical composition of material that eventually will create new solar systems. This will provide insight into what becomes of the elements ejected from stars, including elements that are essential for life. The research is highly interdisciplinary, involving both observational and laboratory studies that interrelate astronomy, chemistry, planetary science, and physics. This research will be almost entirely conducted by graduate students, and this lab has been a fruitful training ground for future scientists. The PI is also involved in the development of interdisciplinary courses in the physical sciences. Mass loss from circumstellar envelopes of evolved stars and the more advanced, planetary nebulae (PNe) stage, is a major avenue by which the interstellar medium (ISM) is enriched in gas, dust, and the heavier elements. The chemical and physical characteristics of circumstellar shells and subsequent PNe thus have major impact on the overall life cycle of dense material in the ISM. The goals of this project are (1) to probe the physical and chemical properties of circumstellar envelopes and planetary nebulae to determine the extent of their molecular composition, and (2) to examine their morphological structures through radio/millimeter-wave astronomical observations. A further aim is to identify new molecules in these objects, in particular refractory species possibly linked to dust grains such as TiOH or FeC2, using laboratory spectroscopy followed by additional observations. The O-rich circumstellar shells to be studied include those of the supergiant S Persei and the Asymptotic Giant Branch (AGB) stars TX Cam and R Cas, which will be investigated using the highly sensitive ALMA-type receivers at the Sub-millimeter Telescope (SMT) of the Arizona Radio Observatory (ARO), and the new ARO 12 meter ALMA-prototype antenna. Other molecules will be sought with the ARO facilities, with the purpose of examining the revolutionary concept that diffuse clouds are being populated with remnant molecular material from PNe.