Cold chemistry in hot cores: exploring the early origins of chemical complexity in nascent stellar systems

Abstract: The interstellar medium provides an enormous laboratory for the exploration of chemistry of various kinds. But it is not a laboratory that we control, and its results - while resting on processes that individually may occur very rapidly - unfold on timescales that are typically much longer than a human lifetime. Our observations of the molecular compositions of interstellar clouds and star-forming regions represent only snapshots of a process of chemical evolution that must be pieced together through various means. Computational kinetics models provide a powerful tool for understanding the time-dependent evolution of chemical complexity in the universe, and the pathways that lead to potentially pre-biotic molecules in space.
 
Some of the most molecule-rich interstellar objects - known as "hot molecular cores" - are accretions of warm gas and dust that surround young protostars, which ultimately evolve into high-mass stellar systems. Along with their low-mass (solar-type) analogs, "hot corinos", they are characterized by rich rotational emission spectra that exhibit a wealth of organic molecules of varying degrees of complexity. But the formation of these "hot" (>100 K), gas-phase molecules is closely related to an earlier stage of chemistry that occurs on the surfaces of microscopic dust grains at much lower temperatures. Recent observational, experimental and modeling evidence indicates that some of the most complex molecules that we detect in highly evolved protostellar systems may have a much earlier origin than previously thought. These molecules, if preserved throughout the star- and planet-formation process, may ultimately feed the compositions of planetary and/or cometary bodies.
 
I will discuss new modeling treatments that we have developed to allow accurate kinetic simulations of some of the coldest chemistry in the universe, producing some of the largest molecules yet identified in space. I will also explore recent interstellar molecular detections that we have made with collaborators, including propanol and urea, and what the models can tell us about their origins.