This project takes a combined observational and theoretical approach to understanding the role of carbon monoxide (CO) in the formation of the comae of comets. Using both new millimeter-wave CO data to be acquired under this award, and an extensive array of millimeter data for a variety of molecules acquired under a previous award, the PI and undergraduate students will constrain the CO production rates and physical state of the gas. The excitation and collisional parameters will be constrained using maps of the CO, hydrogen cyanide, and methanol emission of comet Hale-Bopp and a hydrodynamic model developed by a collaborator on the project. CO production rates will then be obtained for different types of comets over a large range of heliocentric distances, using mm-wavelength spectra and the parameters obtained from Hale-Bopp. The PI will search for CO emission in short-period comets and analyze the role of solar heating and other energy sources on the depletion of CO in comet nuclei. CO production and outbursts in distant comets will also be analyzed and modeled. This work, carried out at an undergraduate institution, will involve undergraduate students in data acquisition, reduction, and analysis and provide the PI with material for the upper-level astrophysics courses that she teaches.
