New simulations and observations of highly-complex molecules in star-forming regions

Dr Robin Garrod, Department of Chemistry, University of Virginia. Part of the Astrophysics Research Seminar series.

Title: New simulations and observations of highly-complex molecules in star-forming regions

Abstract: Interstellar space is replete with molecules, ranging from the very simple (e.g. molecular hydrogen), to more complex and exotic species such as the cyanopolyynes (e.g. HC9N). However, certain high-mass star-forming cores (i.e. "hot cores") in particular demonstrate some of the richest chemistry observed outside the solar system, and are host to many molecules that are familiar from the terrestrial chemistry lab, including alcohols, aldehydes, esters and ethers. Our recent 3-mm ALMA line survey ("EMoCA") of the chemically-rich Galactic Center high-mass star-forming source Sagittarius B2(N) has identified a selection of new, and yet more complex molecules, whose formation mechanisms are just beginning to be fully explored. These include a new class of molecule for interstellar chemistry: branched aliphatic species, here represented by iso-propyl cyanide (i-C3H7CN), whose straight-chain form (n-C3H7CN) was also detected. The production of many such molecules seems to be strongly dependent on diffusive chemistry on cold dust-grain surfaces, followed by the energetic processing and heating of the resultant ice mantles. Here, I will outline the chemical and physical processes that take place in interstellar clouds and star-forming cores, and will discuss new astronomical detections of organic molecules. I will show how new gas- and solid-phase chemical kinetics simulations, combined with astrophysical spectral-emission models, can help us understand the chemistry of star formation. I will also present recent work that uses complex molecule abundances to constrain the cosmic-ray ionization rates and chemical timescales within individual star-forming objects.

Host: Dr Catherine Walsh

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