Abstract
Retrieval of L dwarfs is challenging due to poor thermal profile constraints arising from limited pressure layers probed with low resolution NIR spectra, the effects of rainout on abundance profiles of prominent opacity sources, and the presence of clouds. We determined how the first two challenges affect retrieved L dwarf properties by conducting atmospheric retrievals on synthetic cloud-free L dwarf spectra derived from the Sonora Bobcat models at SpeX resolution using a variety of thermal and chemical abundance profile parameterizations. We determined that low resolution NIR spectra alone are not sufficient to constrain the thermal profile beyond the photosphere in objects earlier than L5, even in the absence of clouds. We also find that a nonuniform abundance profile for iron hydride (FeH) is needed to accurately retrieve bulk properties like surface gravity, radius, effective temperature, C/O ratio, and metallicity in early- to mid- L dwarfs. Nonuniform prescriptions for other gases in NIR retrievals may also be warranted near the L/T transition (CH$_{4}$) and early Y dwarfs (Na and K).
