S21A0091

The atmospheric characterization of brown dwarfs have been mostly conducted by low/mid-resolution observation despite the obvious importance of high-resolution observation. Given the fact that brown dwarf atmospheres share many dynamical, physical, and chemical processes with those of gas giant exoplanets, atmospheric characterization of brown dwarfs by high-resolution spectroscopy is urgently needed prior to the observation of exoplanet atmospheres by next-decade telescopes such as the James Webb Space Telescope. In this proposal, we propose AO-assisted, Subaru/IRD observations to obtain spatially resolved spectra of the best characterized brown dwarfs observable from Mauna Kea with highest-ever spectral resolution (R∼70,000). Our targets span a wide range of spectral type and includes both field and companion brown dwarfs. The aim of this proposal is to 1. Detect absorption features of several molecules such as H₂O, NH₃, CH₄, H₂S, and HCN to constrain the metallicity, elemental abundances, and the strength of vertical mixing in the atmospheres and 2. Constrain the rotation velocity using the line broadening, which would lead to the understanding of the formation and evolution mechanism of brown dwarfs via comparison between field and companion brown dwarfs.

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