Spectro-Polarimetry of Brown Dwarfs
Since my arrival at Caltech, about half of my time has been spent on an exciting new project using the Wide-Field Infrared Camera (WIRC) at the prime focus of the Hale telescope. The instrument was upgraded with a science-grade H2 detector and optics for spectro-polarimetry in the fall of 2016. A survey with the new WIRC+Pol mode commenced in early 2017, with the goal of studying the atmospheric composition and cloud structure of many nearby brown dwarfs. Clouds induce polarization in the near-infrared thermal radiation from these targets, and non-uniform emission over the observed projected disk, from patchy clouds, hot-spots, or rotation-induced oblateness will create a measurable polarization signal (on the order of 0.1–0.5%). Although cloudy atmospheres have been suggested by modeling of the spectral energy distributions (SEDs) and photometric variabilities of many brown dwarfs, a detected polarization signal would constitute a first solid confirmation of clouds, and would also provide an independent diagnostic of cloud properties. WIRC+Pol combines polarimetry with time-resolved photometry and spectroscopy to greatly enhance our understanding of cloudy substellar (brown dwarf and gas giant exoplanet) atmospheres.
My role on this project is as project scientist, co-managing all aspects of the project together with PI, Dr Dimitri Mawet.