The Sonora Substellar Atmosphere Models. IV. Elf Owl: Atmospheric Mixing and Chemical Disequilibrium with Varying Metallicity and C/O Ratios

Sagnick Mukherjee, Jonathan J. Fortney, Caroline V. Morley, Natasha E. Batalha, Mark S. Marley, Theodora Karalidi, Channon Visscher, Roxana Lupu, Richard Freedman, Ehsan Gharib-Nezhad

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Disequilibrium chemistry due to vertical mixing in the atmospheres of many brown dwarfs and giant exoplanets is well established. Atmosphere models for these objects typically parameterize mixing with the highly uncertain Kzz diffusion parameter. The role of mixing in altering the abundances of C-N-O-bearing molecules has mostly been explored for atmospheres with a solar composition. However, atmospheric metallicity and the C/O ratio also impact atmospheric chemistry. Therefore, we present the Sonora Elf Owl grid of self-consistent cloud-free 1D radiative-convective equilibrium model atmospheres for JWST observations, which includes a variation in Kzz across several orders of magnitude and also encompasses subsolar to supersolar metallicities and C/O ratios. We find that the impact of Kzz on the T(P) profile and spectra is a strong function of both Teff and metallicity. For metal-poor objects, Kzz has large impacts on the atmosphere at significantly higher Teff than in metal-rich atmospheres, where the impact of Kzz is seen to occur at lower Teff. We identify significant spectral degeneracies between varying Kzz and metallicity in multiple wavelength windows, in particular, at 3-5 μm. We use the Sonora Elf Owl atmospheric grid to fit the observed spectra of a sample of nine early to late T-type objects from Teff = 550-1150 K. We find evidence for very inefficient vertical mixing in these objects, with inferred Kzz values lying in the range between ∼101 and 104 cm2 s−1. Using self-consistent models, we find that this slow vertical mixing is due to the observations, which probe mixing in the deep detached radiative zone in these atmospheres.

Original languageEnglish (US)
Article number73
JournalAstrophysical Journal
Volume963
Issue number1
DOIs
StatePublished - Mar 1 2024

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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