PICASO 4.0: Clouds and Photochemistry in Climate Models of Brown Dwarfs and Exoplanets

TL;DR

PICASO 4.0 is an enhanced open-source atmospheric modeling tool for brown dwarfs and exoplanets, incorporating clouds, photochemistry, and non-equilibrium processes inspired by JWST observations.

Contribution

The paper introduces major new features in PICASO 4.0, including cloud modeling, photochemistry, and flexible volatile treatments, advancing the simulation capabilities for substellar atmospheres.

Findings

Validated against existing models and observations

Demonstrated ability to simulate non-equilibrium chemistry

Enhanced modeling of clouds and energy injection processes

Abstract

We present a major update to the open-source atmospheric modeling package \texttt{PICASO}, designed for simulating the thermal structure and spectra of hydrogen-rich atmospheres of brown dwarfs and exoplanets. This release, \texttt{PICASO 4.0}, expands upon the existing radiative-convective equilibrium model framework by incorporating several new capabilities. Key additions include the integration of \texttt{Virga} for self-consistent cloud modeling, new flexible treatments for rainout and cold trapping of volatile species, and support for photochemistry. We also introduce a parameterized energy injection scheme to simulate additional external or internal heating processes. These features are motivated by lessons from recent JWST observations that reveal the prevalence of non-equilibrium chemistry and clouds. We benchmark the new functionalities against previously published results in the literature, including the Sonora Diamondback grid, energy injected atmospheres, patchy cloud models, and other photochemical models of WASP-39b. \texttt{PICASO} continues to be actively developed as an open-source package aimed at enabling reproducible, community-driven atmospheric modeling of all substellar objects.