UC Santa Cruz

My dissertation combines the detailed atmospheric characterization of brown dwarfs using mid-infrared spectroscopy with the development of next generation mid-infrared detector technology. Brown dwarfs have similar compositions, atmospheric physics, and chemistry to gas giant exoplanets, but they are much easier to observe because they do not suffer from obscuration from a host star. Brown dwarfs are thus high-quality testing grounds for atmospheric models, optimizing requirements for exoplanet-focused instrumentation, and making the most out of future observations with the James Webb Space Telescope. I led two mid-infrared observational projects to characterize the atmospheres of brown dwarfs. First, I took 3-4 micron spectra of VHS 1256b and PSO 318.5, two analogs of the HR 8799 gas giants using Keck/NIRSPEC. I detected methane, a molecular species that was previously thought to be non-existent in both objects. These methane measurements provide evidence of chemical disequilibrium. It is likely that the atmospheres of gas giant exoplanets will also exhibit chemical disequilibrium. For my second project, I acquired 50 hours of Gemini/GNIRS 4.5 - 5 micron spectra of four ultra-cool brown dwarfs. I combined the data with previously existing mid-infrared spectra of four additional brown dwarfs and Jupiter to show that gaseous objects with effective temperatures of 700 K and below have carbon monoxide absorption due to disequilibrium chemistry. For my last project, I am testing a 10 micron detector that will be photon-noise-limited, unlike the previous generation of mid-infrared detectors currently used in astronomical instruments. My detector test setup shows that the 10 micron detector can be operated cryogenically and fast enough to overcome the mid-infrared sky background.