Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres over a Range of Metallicities and Temperatures

TL;DR

This paper provides new, detailed calculations of gaseous mean opacities across a wide range of conditions, improving models of giant planet and ultracool dwarf atmospheres with higher metallicities and finer resolution.

Contribution

It expands previous opacity calculations to include lower pressures, higher metallicities, and finer temperature resolution, offering comprehensive tables and analytic fits for atmospheric modeling.

Findings

Opacities calculated from 1 microbar to 300 bar and 75 K to 4000 K.

Includes metallicities from solar to 50 times solar.

Provides analytic fits for mean opacities over the parameter grid.

Abstract

We present new calculations of Rosseland and Planck gaseous mean opacities relevant to the atmospheres of giant planets and ultracool dwarfs. Such calculations are used in modeling the atmospheres, interiors, formation, and evolution of these objects. Our calculations are an expansion of those presented in Freedman et al. (2008) to include lower pressures, finer temperature resolution, and also the higher metallicities most relevant for giant planet atmospheres. Calculations span 1 microbar to 300 bar, and 75 K to 4000 K, in a nearly square grid. Opacities at metallicities from solar to 50 times solar abundances are calculated. We also provide an analytic fit to the Rosseland mean opacities over the grid in pressure, temperature, and metallicity. In addition to computing mean opacities at these local temperatures, we also calculate them with weighting functions up to 7000 K, to simulate the mean opacities for incident stellar intensities, rather than locally thermally emitted intensities. The chemical equilibrium calculations account for the settling of condensates in a gravitational field and are applicable to cloud-free giant planet and ultracool dwarf atmospheres, but not circumstellar disks. We provide our extensive opacity tables for public use.