Measuring and Replicating the 1–20 μm Energy Distributions of the Coldest Brown Dwarfs: Rotating, Turbulent, and Nonadiabatic Atmospheres

Cold, low-mass, field brown dwarfs are important for constraining the terminus of the stellar mass function, and also for optimizing atmospheric studies of exoplanets. In 2020 new model grids for such objects were made available: Sonora-Bobcat and ATMO 2020. Also, new candidate cold brown dwarfs were announced, and new spectroscopic observations at lambda approximate to 4.8 mu m were published. In this paper we present new infrared photometry for some of the coldest brown dwarfs, and put the new data and models together to explore the properties of these objects. We reconfirm the importance of mixing in these atmospheres, which leads to CO and NH3 abundances that differ by orders of magnitude from chemical equilibrium values. We also demonstrate that the new models retain the known factor greater than or similar to 3 discrepancy with observations at 2 less than or similar to lambda mu m less than or similar to 4, for brown dwarfs cooler than 600 K. We show that the entire 1 less than or similar to lambda mu m less than or similar to 20 energy distribution of six brown dwarfs with 260