Science

High energy (E>13.6 eV) ionizing agents play a central role in both the physical and chemical properties of the bulk, cold (T<50 K) gas. Ionization regulates magnetically-driven turbulence in low mass protoplaentary disks and powers both cold gas-phase chemistry and ice chemistry on the surfaces of cold dust grains.  

The ionization properties of disks are poorly understood, both at baseline values and under extreme conditions, such as may occur during extreme energetic events, like X-ray flares originating from the central star. Fortunately, the abundances of molecular ions are sensitive probes that can be used to constrain and even map out ionization physics in disks. Through submillimeter wavelength observations, such as those provided by the Atacama Large Millimeter Array (ALMA), we are working to constrain this crucial parameter spatially and over time.

It is important to understand how the bulk gas and solid composition(s) of disks get initially incorporated into forming planetesimals. The solid materials in the disk, like silicates and ice, get incorporated into the rocky planetesimals/cometesimals, while the gas is incorporated into forming gas giant planets' atmospheres, under the assumption of planet formation by the core accretion mechanism. Using sensitive observations from ALMA coupled with chemical models, we aim to map how observed molecular abundances trace the underlying bulk composition of the disk (especially the forms of C/N/O bearing molecules), to better understand what the typical chemical outcome of planet-formation may look like.

Where do the materials that make up the disk (and eventually planets) initially come from? How much memory of the original interstellar material from which the Sun formed survived and was incorporated into our disk? How much was reprocessed by later phase chemical evolution within the disk itself? These questions are central toward understanding our solar system's chemical inheritance, but also in addressing the broader question of how much the local environment (e.g., stellar type, disk mass, etc) matters in determining the final outcome(s) of the planet formation process.