Low-Temperature Gas Opacities with AESOPUS 2.0

TL;DR

This paper presents AESOPUS 2.0, a comprehensive update to low-temperature gas opacity calculations, incorporating expanded molecular data and revised physics, providing improved opacity tables and a web tool for custom calculations.

Contribution

AESOPUS 2.0 introduces updated molecular absorption, revised physics, and a web interface, enhancing low-temperature gas opacity modeling compared to previous versions.

Findings

Updated molecular absorption with 80 species from ExoMol and HITRAN.

Revised H- photodetachment cross section and added free-free absorption.

Provided new opacity tables and a web tool for custom calculations.

Abstract

This work introduces new low-temperature gas opacities, in the range 3.2 <= log(T/K) <= 4.5, computed with the AESOPUS code under the assumption of thermodynamic equilibrium (Marigo &_Aringer_2009). In comparison to the previous version AESOPUS 1.0, we updated and expanded molecular absorption to include 80 species, mostly using the recommended line lists currently available from the ExoMol and HITRAN databases. Furthermore, in light of a recent study, we revised the H- photodetachment cross section, added the free-free absorption of other negative ions of atoms and molecules, and updated the collision-induced absorption due to H2/H2, H2/H, H2/He, and H/He pairs. Using the new input physics, we computed tables of Rosseland mean opacities for several scaled-solar chemical compositions, including Magg et al. (2022)'s most recent one, as well as alpha-enhanced mixtures. The differences in opacity between the new AESOPUS 2.0 and the original AESOPUS 1.0 versions, as well as other sets of calculations, are discussed. The new opacities are released to the community via a dedicated web-page that includes both pre-computed tables for widely used chemical compositions, and a web-interface for calculating opacities on-the-fly for any abundance distribution.