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Cloudless Atmospheres for Young Low-Gravity Substellar ObjectsAtmospheric modeling of low-gravity (VL-G) young brown dwarfs remains challenging. The presence of very thick clouds is a possible source of this challenge, because of their extremely red near-infrared (NIR) spectra, but no cloud models provide a good fit to the data with a radius compatible with the evolutionary models for these objects. We show that cloudless atmospheres assuming a temperature gradient reduction caused by fingering convection provide a very good model to match the observed VL-G NIR spectra. The sequence of extremely red colors in the NIR for atmospheres with effective temperatures from approx. 2000 K down to approx. 1200 K is very well reproduced with predicted radii typical of young low-gravity objects. Future observations with NIRSPEC and MIRI on the James Webb Space Telescope (JWST) will provide more constraints in the mid-infrared, helping to confirm or refute whether or not the NIR reddening is caused by fingering convection. We suggest that the presence or absence of clouds will be directly determined by the silicate absorption features that can be observed with MIRI. JWST will therefore be able to better characterize the atmosphere of these hot young brown dwarfs and their low-gravity exoplanet analogs.
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Document Type
Reprint (Version printed in journal)
Tremblin, P. (Paris XI Univ. Orsay, France)
Chabrier, G. (Exeter Univ. United Kingdom)
Baraffe, I. (Exeter Univ. United Kingdom)
Liu, Michael C. (Hawaii Univ. Honolulu, HI, United States)
Magnier, E. A. (Hawaii Univ. Honolulu, HI, United States)
Lagage, P.-O. (Saclay Research Centre Gif-sur-Yvette, France)
De Oliveira, C. Alves (Space Telescope Science Inst. Baltimore, MD, United States)
Burgasser, A. J. (California Univ. La Jolla, CA, United States)
Amundsen, D. S. (Columbia Univ. New York, NY, United States)
Drummond, B. (Exeter Univ. United Kingdom)
Date Acquired
January 18, 2018
Publication Date
November 15, 2017
Publication Information
Publication: The Astrophysical Journal
Volume: 850
Issue: 1
ISSN: 2041-8205
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