Finding the Elusive Substellar Members of Young Moving Groups

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2016-12

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University of Hawaii at Manoa

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Young moving groups (YMGs) consist of coeval, comoving stars, with ages between 10–100 Myrs, that have migrated from their origins after formation. They provide a valuable link between ongoing star formation in molecular clouds (~ 1 Myr) and old field stars (� 1 Gyr). However, previous searches based on optical surveys such as Hipparcos and the Palomar Sky Survey were insensitive to these very faint cool dwarfs. More recent surveys with GALEX have begun to reveal the nearby (< 25 pc) low-mass members (� 0.1 M8) but the cool, substellar members have remained elusive. We have increased the search volume by a factor of ~ 10 using a novel combination of photometry and proper motions from Pan-STARRS, WISE, and 2MASS in order to uncover the missing substellar members down to ~ 0.01 M8 (at 10 Myr). We have obtained NIR low-resolution spectroscopy and confirmed the youth of 65 new ultracool dwarf YMG candidates. We also obtained high-resolution NIR spectroscopy to determine radial velocities for our young brown dwarfs. With our RVs and PS1 parallaxes, we have nearly doubled the number of confirmed bona fide substellar YMG members, which are also brown dwarf age benchmarks. Our new young brown dwarfs empirically define the substellar spectral evolution with age and provide us with a snapshot of brown dwarf evolution. Finally, our resulting young brown dwarfs will be valuable targets for future surveys of brown dwarf binarity and young exoplanet characterization.

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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Physics & Astronomy

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