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InterCat Webinars

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Measuring the chemical evolution of ices from molecular clouds to protoplanetary disks

Melissa McClure (Leiden Observatory, Leiden University, The Netherlands)

Planets form at the midplane of the protoplanetary disks surrounding newborn stars. The habitability of a planet is determined in part by the relative amounts of CHON elements at the planet's surface, and these CHONs are most likely delivered through incorporation or delivery of astronomical ices during planet formation. These ices originate in cold, dense molecular cloud cores and chemically evolve as the cores collapse to form protostars surrounded by protoplanetary disks. To understand the relative amounts and degree of complexity of the ices incorporated into comets and planets, we need observational constraints on both the chemical evolution of ices from where they form in clouds to the locations in disks where planets are being formed.


In the first part of the talk, I will describe a cutting-edge Early Release Science (ERS) program, Ice Age (P.I. McClure, over 50 team members world wide) with the upcoming James Webb Space Telescope (JWST) to measure the chemical evolution of ices entering disks. This ERS program will provide the star and planet formation and astrochemistry communities with a non-proprietary dataset of JWST spectra, laboratory data, and chemical models within the 5 months of JWST's science operations. With this dataset, and other GTO JWST programs, we will be able to confirm the amount and complexity of ice formed non-energetically within molecular clouds and test the degree to which energetic processing increases its complexity prior to its incorporation into the disk. These programs will also be able to determine the radial distribution of ices in these disks. Time permitting, in the last part of the talk I will demonstrate a new method for identifying specific locations where ices are "left behind" in protoplanetary disks (McClure 2019; McClure, Dominik, and Kama 2020), possibly by formation of planetesimals. By combining these direct JWST studies of the icy dust input into protoplanetary disks with the direct measurement of material moving out of the disk onto the central star, we can map out where icy material is being retained in a given disk, which is a first, critical step to forming planets.

Prestellar Formation of Glycine via Dark Chemistry

Sergio Ioppolo (Queen Mary University of London, United Kingdom)

An international team of laboratory astrophysicists, in part active within INTERCAT, have shown that glycine, the simplest amino acid and an important building block of life, can form under the harsh conditions that govern chemistry in space. The results, recently published in Nature Astronomy, show that glycine and very likely other amino acids are formed in dense interstellar clouds, well before these transform into new stars and planets. 

Action gas phase spectroscopy of superhydrogenated PAHs, using the free electron laser FELIX

Frederik Doktor Skødt Simonsen (IFA, Aarhus University)  

Fragmentation of polycyclic aromatic hydrocarbons: a possible route for ethylene formation in interstellar medium

Zeyuan Tang (IFA, Aarhus University)  

The fragmentation of polycyclic aromatic hydrocarbons (PAHs) is important for understanding the survivability of PAHs under harsh interstellar environment and the formation of small molecules like H2, C2H2, C2H4. It is a challenge for current computational technology to explain the complex rearrangements of chemical bonds during the fragmentation in a comprehensive manner. This work combines molecular dynamics (MD) and density functional theory (DFT) to investigate the fragmentation of PAHs and propose a possible route for ethylene (C2H4) formation caused by fragmentation. MD simulations have successfully revealed the fragmentation pattern of two hydrogenated pyrenes and confirmed the structure of fragments. We have found that the edge of PAHs having three connected hydrogenated carbon atoms is the active site for ethylene formation. A more general rule for ethylene formation is introduced based on DFT calculations of other PAHs with similar edge structures.