2019ApJ...877..134S

Scattering processes in the atmosphere of a fast-rotating brown dwarf (BD) or self-luminous extrasolar giant planet (EGP) produce distinct polarimetric, in addition to spectrometric, signatures. An ability to unambiguously interpret these signals would improve our understanding of their atmospheric evolution, structure, and dynamics. To this end, we have incorporated molecular opacities to define the wavelength-dependent vertical structure of the atmosphere as a function of the internal energy, surface gravity, and metallicity of the BD. This allows us to use our recently developed semianalytic conics-based radiative transfer framework to generate realistic spectropolarimetric simulations. We have examined the simulated effects of the internal energy and surface gravity of BDs and of the grain size and atmospheric depth of clouds on polarized spectra in the J, H, and K near-infrared bands. We find that T-dwarf spectra can be fit more easily using cloudless atmospheres or high clouds, while fitting L-dwarf spectra requires an assumption of deep clouds. Polarimetry contains a wealth of information orthogonal to what can be obtained from photometry alone. However, under current limits of instrument sensitivity, the greatest benefits of polarimetry will apply to high clouds bearing small grains. Future work will examine the effect of gravitational darkening and disequilibrium chemistry on the spectropolarimetry of these BDs.