Atmospheric Chemistry in Brown Dwarfs and Low Mass Stars

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Dr. Lodders will investigate the gas and condensation chemistry as a function of temperature, total pressure, and metallicity in the cool atmospheres of low-mass stars and brown (L and T) dwarfs. It is motivated by the need to understand molecular gas and cloud condensation chemistry in order to interpret the spectroscopic observations of these objects. A second major objective is to provide reliable abundance grids of gaseous, liquid, and solid compounds for such atmospheres derived from thermochemical equilibrium, and where necessary, thermochemical kinetic computations. This will provide the required chemistry inputs for atmospheric and spectral models of cool and low mass stars. The work is essential to address key questions about low-mass objects, including the following: What are the effective temperature scales of L and T dwarfs? What are their atmospheric compositions? How common are departures from chemical equilibrium due to vertical transport processes? How do clouds and weather affect the spectra of brown dwarfs? Dr. Lodders will also apply these results as part of a collaborative work to generate atmospheric models and high-resolution synthetic spectra of low-mass objects to determine spectral diagnostics of effective temperature, gravity, and composition as functions of mass and age. The project is complementary to observational studies of low-mass objects and provides a guide to interpret future observations from instruments such as HST, ISO, SIRTF, and SOFIA and from the ground-based observatories Gemini, Keck, Magellan, 2MASS, SDSS, and the LBT.The results of this work will be disseminated through refereed publications and meetings, with more popular/appealing results being presented to the public through press releases. The project will also benefit the existing interdisciplinary collaboration with other research groups working on spectral and evolutionary models. Undergraduates (to be supported here) and graduate students will be trained in this multidisciplinary field through participation in these projects.