Simulations of Chemistry in Star-Forming Regions and Cometary Ices

Astrochemical models have long been used in the study of the chemistry of interstellar space (Herbst & Klemperer 1973). Over the past decades, several advancements have been made to these models, including the incorporation of grain-surface chemistry (Hasegawa et al. 1992), the incorporation of warm-ups to simulate nascent star formation (Garrod et al. 2008), and more recently adaption of these models to study cometary ice chemistry (Garrod 2019). Here we present several studies which utilize state-of-the-art astrochemical models (MAGICKAL; Garrod 2013a, MIMICK; Garrod 2013b). First, we use MIMICK to study the effect of grain-surface back-diffusion on reaction rates for the H + H -> H2 reaction system (Willis & Garrod 2017). Then we incorporate this correction into MAGICKAL to study several organic molecules in star-forming regions. These include methoxymethanol (CH3OCH2OH), cyanamide (NH2CN), methyl isocyanide (CH3NC), and propyne (CH3CCH). We then develop a new chemical network for the study of isocyano species in the star-forming region Sagittarius B2(N2) (Willis et al. 2020). In this study, we also present a new method of modeling the chemistry of the star-formation process, transitioning from the simple two-stage methods of past models to a simultaneous collapse/warm-up model. Finally, we present ongoing work that builds on the cometary ice simulations of Garrod (2019). Here we include heat-transfer simulations to model the effects of solar radiation on the temperature of the cometary ice, as well as a new backdiffusion treatment for the movement of particles between layers in the cometary ice.