Cosmic Ray Chemistry
Relativistic charged particles, so-call cosmic rays, are the primary drivers of chemistry in molecular clouds in regions shielded from intense radiation. Cosmic rays affect molecular gas in numerous ways: charging dust grains, heating gas, and driving chemistry through ionizing molecular hydrogen (and other moleculars). Typically, astrochemical models make very simple assumptions about the cosmic ray flux. We are working on implementing more sophisticated treatments of cosmic rays into astrochemistry models, in-situ. These cosmic ray-chemistry models provide more sensitive and accurate predictions on the abundances of molecules in star-forming regions.
The gas accreting onto protostars heats to nearly a million degrees as it falls onto the surface, resulting in a shock near the surface of the forming protostar. The hot temperatures and high densities results in x-ray radiation and the acceleration of charged particles to relativistic energies. Modeling these high energy processes, and their transport through the protostellar envelope and cloud, is crucial to understanding the impact forming stars have on their natal environment. Prior work has quantified the acceleration of cosmic rays in the accretion shocks of cosmic rays. Current work is including protostellar x-ray emission in star-formation simulations.
Short-lived radioactive nuclei (radionuclides) have half-lives on order, or less, than a few million years. Excess amounts of certain isotopes measured in meteorites indicate the early solar system was contaminated by a wide-range of these nuclides. These isotopes provide fingerprints to the galactic and protostellar environment during the formation of the solar system. Theoretical models this enrichment by nearby supernova or high-mass stars, and we have recently proposed a novel local mechanism of isotope enrichment. We are currently investigating how these short-lived isotopes from supernova mix into cold, dense, star-forming gas.