THE FIRST HUNDRED BROWN DWARFS DISCOVERED BY THE <i>WIDE-FIELD INFRARED SURVEY EXPLORER</i> ( <i>WISE</i> )

Abstract

We present ground-based spectroscopic verification of six Y dwarfs (see\nCushing et al), eighty-nine T dwarfs, eight L dwarfs, and one M dwarf\nidentified by the Wide-field Infrared Survey Explorer (WISE). Eighty of these\nare cold brown dwarfs with spectral types greater than or equal to T6, six of\nwhich have been announced earlier in Mainzer et al and Burgasser et al. We\npresent color-color and color-type diagrams showing the locus of M, L, T, and Y\ndwarfs in WISE color space. Near-infrared classifications as late as early Y\nare presented and objects with peculiar spectra are discussed. After deriving\nan absolute WISE 4.6 um (W2) magnitude vs. spectral type relation, we estimate\nspectrophotometric distances to our discoveries. We also use available\nastrometric measurements to provide preliminary trigonometric parallaxes to\nfour our discoveries, which have types of L9 pec (red), T8, T9, and Y0; all of\nthese lie within 10 pc of the Sun. The Y0 dwarf, WISE 1541-2250, is the closest\nat 2.8 (+1.3,-0.6) pc; if this 2.8 pc value persists after continued\nmonitoring, WISE 1541-2250 will become the seventh closest stellar system to\nthe Sun. Another ten objects, with types between T6 and &gt;Y0, have\nspectrophotometric distance estimates also placing them within 10 pc. The\nclosest of these, the T6 dwarf WISE 1506+7027, is believed to fall at a\ndistance of roughly 4.9 pc. WISE multi-epoch positions supplemented with\npositional info primarily from Spitzer/IRAC allow us to calculate proper\nmotions and tangential velocities for roughly one half of the new discoveries.\nThis work represents the first step by WISE to complete a full-sky,\nvolume-limited census of late-T and Y dwarfs. Using early results from this\ncensus, we present preliminary, lower limits to the space density of these\nobjects and discuss constraints on both the functional form of the mass\nfunction and the low-mass limit of star formation.\n