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Pegasus III (Peg III) is one of the few known ultra-faint stellar systems in the outer halo of the Milky Way. We present the results from a follow-up campaign with Magellan/IMACS and Keck/DEIMOS. Deep stellar photometry down to $r_0approx 25$ mag at 50% completeness level has allowed accurate measurements of its photometric and structural properties. The color-magnitude diagram of Peg III confirms that the stellar system is well described by an old ($gtrsim12$ Gyr) and metal-poor ([Fe/H]$lesssim-2.0$ dex) stellar population at a heliocentric distance of $215pm12$ kpc. The revised half-light radius $r_{h}=53pm14$ pc, ellipticity $epsilon=0.38^{+0.22}_{-0.38}$, and total luminosity $M_{V}=-3.4pm0.4$ are in good agreement with the values quoted in our previous paper. We further report on the spectroscopic identification of seven, possibly eight member stars of Peg III. The Ca II triplet lines of the brightest member stars indicate that Peg III contains stars with metallicity as low as [Fe/H]=$-2.55pm0.15$ dex. Peg III has a systemic velocity of $-222.9 pm 2.6$ km s$^{-1}$ and a velocity dispersion of $5.4^{+3.0}_{-2.5}$ km s$^{-1}$. The inferred dynamical mass within the half-light radius is $1.4^{+3.0}_{-1.1} times 10^6rm{M_{odot}}$ and the mass-to-light ratio $rm{M/L}$$_{V} = 1470^{+5660}_{-1240}$ $rm{M_{odot}/L_{odot}}$, providing further evidence that Peg III is a dwarf galaxy satellite. We find that Peg III and another distant dwarf satellite Pisces II lie relatively close to each other ($Delta d_{spatial}=43pm19$ kpc) and share similar radial velocities in the Galactic standard-of-rest frame ($Delta v_{GSR}=12.3pm3.7$ km s$^{-1}$). This suggests that they may share a common origin.
We use new kinematic data from the ultra-faint Milky Way satellite Segue 1 to model its dark matter distribution and derive upper limits on the dark matter annihilation cross-section. Using gamma-ray flux upper limits from the Fermi satellite and MAG
We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and mar
We present the star formation histories (SFHs) of 20 faint M31 satellites ($-12 lesssim M_V lesssim -6$) that were measured by modeling sub-horizontal branch (HB) depth color-magnitude diagrams constructed from Hubble Space Telescope (HST) imaging. R
[abridged] We present MMT/Megacam imaging in Sloan $g$ and $r$ of the extremely low luminosity Bootes II Milky Way companion. We use a bootstrap approach to perform robust measurements of, and uncertainties on, Bootes IIs distance, luminosity, size,
We present the results of a comprehensive Keck/DEIMOS spectroscopic survey of the ultra-faint Milky Way satellite galaxy Segue 1. We have obtained velocity measurements for 98.2% of the stars within 67 pc (10 arcmin, or 2.3 half-light radii) of the c