Dr. Brandt A. L. Gaches

Astrochemistry Discussions

Astronomy on Tap ATX #55

Astronomy on Tap ATX #42

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 molecules). Typically, astrochemical models make very simple assumptions about the cosmic ray flux. I am working on implementing more sophisticated treatments of cosmic rays physics into astrochemical models. These cosmic ray-chemistry models provide more sensitive and accurate predictions on the abundances of molecules in star-forming regions.

Protostellar Feedback

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 result 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 young stars have on their natal environment. Prior work has quantified the acceleration of cosmic rays in the accretion shocks of accreting protostars. I am currently implementing protostellar x-ray emission in star-formation simulations.

Short-Lived Radionuclides

Short-lived radioactive nuclei (radionuclides) have half-lives of less than a few million years. Excess amounts of specific radioactive isotopes measured in meteorites indicate the early solar system was contaminated by a wide-range of radionuclides. These isotopes provide fingerprints of the galactic and protostellar environment during the formation of the solar system. Theoretical models typically explain this enrichment by supposing the existence nearby supernova or high-mass stars. I have recently proposed a novel local mechanism of isotope enrichment. My student and I are currently investigating how radioactive isotopes from supernova mix into cold, dense, star-forming gas.