We present MMT/Megacam imaging in Sloan g and r of the extremely low luminosity Bo?tes II Milky Way companion. We use a bootstrap approach to perform robust measurements of, and to calculate uncertainties on, Bo?tes II's distance, luminosity, size, and morphology. Comparisons with theoretical isochrones and empirical globular cluster fiducials show that Bo?tes II's stellar population is old and metal-poor ([Fe/H] ? 2). Assuming a stellar population like that of M92, Bo?tes II is at a distance of 42 ± 2 kpc, closer than the initial published estimate of 60 ± 10 kpc. This distance revision, combined with a more robust measurement of Bo?tes II's structure with both a Plummer model and an exponential model, results in more compact inferred physical half-light sizes of rh 36 ± 9 and 33 ± 10 pc, respectively, and lower-limit inferred luminosities of MV ? 2.4 ± 0.7 and -2.2 ± 0.7 mag, respectively. Our revised size and luminosity calculations move Bo?tes II into a region of size-luminosity space not previously known to be occupied by old stellar populations, but also occupied by the recently discovered Milky Way satellites Willman 1 and Segue 1. We show that the apparently distorted morphology of Bo?tes II is not statistically significant given the present data. We use a tidal argument to support a scenario in which Bo?tes II is a dwarf galaxy (dark matter-dominated) rather than a globular cluster (not dark matter-dominated), although our inferred uncertainty on the M/L for Bo?tes II is substantial. Moreover, we cannot rule out the possibility that Bo?tes II is a star cluster on the verge of disruption like Palomar 5.
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