Investigating Chemical Evolution of Complex Molecules in Massive Hot Cores Using Astrochemical Modeling

Barger, Christopher, Chemistry - Graduate School of Arts and Sciences, University of Virginia
Garrod, Rob, AS-Chemistry, University of Virginia

Hot cores represent an intermediate stage of massive star formation. These objects are the result of collapsing dark clouds in the interstellar medium (ISM) prior to the formation of new stars and star systems that may eventually harbor life. A salient feature of these cores is their strong millimeter/sub-millimeter molecular line emission, indicating the presence of myriad terrestrial molecules including alcohols, aldehydes, carboxylic acids, esters, and nitriles (Herbst & van Dishoeck 2009; Garrod & Widicus Weaver 2013). As such, these sources are compelling to study and model. Astrochemical modeling of objects including hot cores has evolved from relatively simple gas-phase steady-state calculations (Herbst & Klemperer 1973), to gas-grain models (e.g. Viti & Williams 1999), to robust three-phase modeling accounting for gas-phase, grain-surface, and ice-mantle-chemistry (e.g. Garrod 2013). We use the three-phase astrochemical modeling code MAGICKAL to investigate the chemical dependence of cosmic-ray ionization rate and warm-up timescale in hot cores. We then compare our chemical and spectroscopic modeling results to observational data (Bisschop et al. 2007) to constrain the cosmic-ray ionization rate and warm-up timescale in four well-studied sources: NGC 6334 IRS 1, NGC 7538 IRS 1, W3(H2O), and W33A. Furthermore, we advance our hot-core modeling technique to incorporate one-dimensional radiation hydrodynamics, which includes explicit spatial structure, physical histories of gas parcels, and temperature treatment. These additions allow for a more robust and self-consistent treatment of hot core chemistry, and we briefly discuss chemical behavior for this new regime, and address how our results compare to observational data toward Sgr B2(N2), a chemically-rich source located near the Galactic Center.

MS (Master of Science)
All rights reserved (no additional license for public reuse)
Issued Date: