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Abstract
The discovery of brown dwarfs of the new Y spectral type by the NASA Wide-field Infrared Survey Explorer (WISE) has allowed astronomers to study the physics of the coolest brown dwarfs and determine their prevalence in the Milky Way. This thesis exploits the high resolution and wide field–of–view of Gemini Multi–Conjugate Adaptive Optics System (GeMS) to perform diffraction-limited imaging to explore the binary properties of a sample of five WISE Y-dwarfs and measure astrometric distances. Regarding binarity, I report no evidence for binary companions in these data, which suggests these systems are not equal–luminosity (or equal–mass) binaries with separations larger than 0.5–1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e. 1011 erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs. Regarding GeMS astrometric performance, I report the first parallaxes and proper motion measurements for the Y0 dwarf WISEA J071322.55–291752.0 and the Y1 dwarf WISEP J154151.65–225025.2 measured with a Multi–Conjugate Adaptive Optics System (MCAO). Parallaxes measurements for both objects are consistent with those delivered in previous studies while proper motion precisions are at least comparable (4.2 mas) with that delivered from the no-adaptive optics camera FourStar, installed in Magellan. Imaging and astrometric results presented in this thesis demonstrate the potential of GeMS to perform high– resolution and high–precision astrometric studies for sparse fields, and conclude that the high astrometric potential can be best exploited by targeting crowded fields.