An Ultra-faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey

We report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644-5953 (Pictor II or Pic II) is a low surface brightness (μ ={28.5}_-1⁺¹ {mag} {arcsec}{}^-2 within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of {45}_-4⁺⁵ {kpc}. The physical size ({r}_1/2={46}_-11⁺¹⁵ {pc} ) and low luminosity ({M}_V=-{3.2}_-0.5^+0.4 {mag} ) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644-5953 (Pic II) is located {11.3}_-0.9^+3.1 {kpc} from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644-5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.