Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry
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 temperatu...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2023-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/acc8cb |
| _version_ | 1797698296154685440 |
|---|---|
| author | Brianna Lacy Adam Burrows |
| author_facet | Brianna Lacy Adam Burrows |
| author_sort | Brianna Lacy |
| collection | DOAJ |
| description | 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 CH _4 –CO and NH _3 –N _2 chemistry and the presence of water clouds can bring models and observations into better, though still not complete, agreement. |
| first_indexed | 2024-03-12T03:52:06Z |
| format | Article |
| id | doaj.art-ff2ef1542df74c38b7f38bb09ddf5bca |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:52:06Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-ff2ef1542df74c38b7f38bb09ddf5bca2023-09-03T12:19:43ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-019501810.3847/1538-4357/acc8cbSelf-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium ChemistryBrianna Lacy0https://orcid.org/0000-0002-9420-4455Adam Burrows1https://orcid.org/0000-0002-3099-5024Department of Astronomy, University of Texas at Austin , Austin, TX 78712, USA ; brianna.lacy@utexas.eduDepartment of Astrophysical Sciences, Princeton University , Princeton, NJ 08544, USAY 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 CH _4 –CO and NH _3 –N _2 chemistry and the presence of water clouds can bring models and observations into better, though still not complete, agreement.https://doi.org/10.3847/1538-4357/acc8cbBrown dwarfsY dwarfsAtmospheric structureExoplanet atmospheres |
| spellingShingle | Brianna Lacy Adam Burrows Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry The Astrophysical Journal Brown dwarfs Y dwarfs Atmospheric structure Exoplanet atmospheres |
| title | Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry |
| title_full | Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry |
| title_fullStr | Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry |
| title_full_unstemmed | Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry |
| title_short | Self-consistent Models of Y Dwarf Atmospheres with Water Clouds and Disequilibrium Chemistry |
| title_sort | self consistent models of y dwarf atmospheres with water clouds and disequilibrium chemistry |
| topic | Brown dwarfs Y dwarfs Atmospheric structure Exoplanet atmospheres |
| url | https://doi.org/10.3847/1538-4357/acc8cb |
| work_keys_str_mv | AT briannalacy selfconsistentmodelsofydwarfatmosphereswithwatercloudsanddisequilibriumchemistry AT adamburrows selfconsistentmodelsofydwarfatmosphereswithwatercloudsanddisequilibriumchemistry |