Presentation #102.344 in the session Poster Session.
Y dwarfs are the coolest spectral class of brown dwarf, with effective temperatures less than 500 K and a detection as low as 250 K. They are the tail end of the star formation process, and a valuable analogue for the atmospheres of giant gaseous exoplanets. Understanding their atmospheric compositions and processes will inform our understanding of planet and star formation, and provide a stepping stone in the effort to characterize other substellar bodies, especially those with water clouds. In addition to water clouds, their spectra are shaped predominantly by gaseous water, methane, and ammonia, and, in some regimes, by collision-induced absorption and carbon-monoxide. Published self-consistent model grids do not accurately replicate all the current observations. Considering dis-equilibrium carbon and nitrogen chemistry and the presence of water clouds rather than simple clear chemical-equilibrium atmospheres can bring models and observations into better agreement, but not full agreement. In this talk, we present a new suite of 1-d radiative-convective equilibrium models for Y dwarf atmospheres and spectra. We compute clear and cloudy, equilibrium-chemistry and disequilibrium-chemistry models and systematically compare them against current observations to identify what changes might explain the observed discrepancies. We further explore how JWST-quality observations can constrain the nature of atmospheric mixing and cloud formation in Y dwarf atmospheres.