GASEOUS MEAN OPACITIES FOR GIANT PLANET AND ULTRACOOL DWARF ATMOSPHERES OVER A RANGE OF METALLICITIES AND TEMPERATURES

Abstract

We present new calculations of Rosseland and Planck gaseous mean opacities\nrelevant to the atmospheres of giant planets and ultracool dwarfs. Such\ncalculations are used in modeling the atmospheres, interiors, formation, and\nevolution of these objects. Our calculations are an expansion of those\npresented in Freedman et al. (2008) to include lower pressures, finer\ntemperature resolution, and also the higher metallicities most relevant for\ngiant planet atmospheres. Calculations span 1 microbar to 300 bar, and 75 K to\n4000 K, in a nearly square grid. Opacities at metallicities from solar to 50\ntimes solar abundances are calculated. We also provide an analytic fit to the\nRosseland mean opacities over the grid in pressure, temperature, and\nmetallicity. In addition to computing mean opacities at these local\ntemperatures, we also calculate them with weighting functions up to 7000 K, to\nsimulate the mean opacities for incident stellar intensities, rather than\nlocally thermally emitted intensities. The chemical equilibrium calculations\naccount for the settling of condensates in a gravitational field and are\napplicable to cloud-free giant planet and ultracool dwarf atmospheres, but not\ncircumstellar disks. We provide our extensive opacity tables for public use.\n