TY - JOUR
T1 - Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry
AU - Lacy, Brianna
AU - Burrows, Adam
N1 - Funding Information:
The authors would like to acknowledge support for this research under NASA WFIRST-SIT award # NNG16PJ24C and NASA Grant NNX15AE19G, and from the Heising-Simons Foundation via the 51 Pegasi b Fellowship. Work presented here made use of the SVO Filter Profile Service ( http://svo2.cab.inta-csic.es/theory/fps/ ) supported from the Spanish MINECO through grant AYA2017-84089. The authors would also like to thank Dr. Nicole Allard for providing data and an interpolation code used to incorporate Na i and K i absorption cross sections into our models. This research was expedited and improved thanks to fruitful conversations with Dr. Caroline Morley and her research group at UT Austin, in particular Ph. D. student James Mang.
Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.
PY - 2023/6/1
Y1 - 2023/6/1
N2 - Y dwarfs are the coolest spectral class of brown dwarf. They have effective temperatures less than 500 K, with the coolest detection as low as ∼250 K. They make up the low-mass tail of the star formation process, and are a valuable analog to the atmospheres of giant gaseous exoplanets in a temperature range that is difficult to observe. Understanding Y dwarf atmospheric compositions and processes will thus deepen our understanding of planet and star formation and provide a stepping stone toward characterizing cool exoplanets. Their spectra are shaped predominantly by gaseous water, methane, and ammonia. At the warmer end of the Y-dwarf temperature range, spectral signatures of disequilibrium carbon monoxide have been observed. Cooler Y dwarfs could host water clouds in their atmospheres. JWST spectral observations are anticipated to provide an unprecedented level of detail for these objects, and yet published self-consistent model grids do not accurately replicate even the existing Hubble Space Telescope and ground-based observations. In this work, we present a new suite of 1D radiative-convective equilibrium models to aid in the characterization of Y-dwarf atmospheres and spectra. We compute clear, cloudy, equilibrium chemistry and disequilibrium chemistry models, providing a comprehensive suite of models in support of the impending JWST era of panchromatic Y-dwarf characterization. Comparing these models against current observations, we find that disequilibrium CH4-CO and NH3-N2 chemistry and the presence of water clouds can bring models and observations into better, though still not complete, agreement.
AB - Y dwarfs are the coolest spectral class of brown dwarf. They have effective temperatures less than 500 K, with the coolest detection as low as ∼250 K. They make up the low-mass tail of the star formation process, and are a valuable analog to the atmospheres of giant gaseous exoplanets in a temperature range that is difficult to observe. Understanding Y dwarf atmospheric compositions and processes will thus deepen our understanding of planet and star formation and provide a stepping stone toward characterizing cool exoplanets. Their spectra are shaped predominantly by gaseous water, methane, and ammonia. At the warmer end of the Y-dwarf temperature range, spectral signatures of disequilibrium carbon monoxide have been observed. Cooler Y dwarfs could host water clouds in their atmospheres. JWST spectral observations are anticipated to provide an unprecedented level of detail for these objects, and yet published self-consistent model grids do not accurately replicate even the existing Hubble Space Telescope and ground-based observations. In this work, we present a new suite of 1D radiative-convective equilibrium models to aid in the characterization of Y-dwarf atmospheres and spectra. We compute clear, cloudy, equilibrium chemistry and disequilibrium chemistry models, providing a comprehensive suite of models in support of the impending JWST era of panchromatic Y-dwarf characterization. Comparing these models against current observations, we find that disequilibrium CH4-CO and NH3-N2 chemistry and the presence of water clouds can bring models and observations into better, though still not complete, agreement.
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U2 - 10.3847/1538-4357/acc8cb
DO - 10.3847/1538-4357/acc8cb
M3 - Article
AN - SCOPUS:85162141378
SN - 0004-637X
VL - 950
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 8
ER -