We use deep Gemini/GMOS-S g,r photometry to study the stellar populations of the recently discovered Milky Way satellite candidates Horologium I , Pictor I , Grus I , and Phoenix II .
Horologium I is most likely an ultra-faint dwarf galaxy at D _ { \odot } = 68 \pm 3 kpc , with r _ { h } = 23 ^ { +4 } _ { -3 } pc and \langle [ Fe/H ] \rangle = -2.40 ^ { +0.10 } _ { -0.35 } dex .
It ’ s color-magnitude diagram shows evidence of a split sub-giant branch similar to that seen in some globular clusters .
Additionally , Gaia DR2 data suggests it is , or was , a member of the Magellanic Cloud group .
Pictor I with its compact size ( r _ { h } = 12.9 ^ { +0.3 } _ { -0.2 } pc ) and metal-poor stellar population ( \langle [ Fe/H ] \rangle = -2.28 ^ { +0.30 } _ { -0.25 } ) closely resembles confirmed star clusters .
Grus I lacks a well-defined centre , but has two stellar concentrations within the reported half-light radius ( r _ { h } = 1.77 ^ { +0.85 } _ { -0.39 } arcmin ) and has a mean metallicity of \langle [ Fe/H ] \rangle = -2.5 \pm 0.3 .
Phoenix II has a half-light radius of r _ { h } = 12.6 \pm 2.5 pc and an \langle [ Fe/H ] \rangle = -2.10 ^ { +0.25 } _ { -0.20 } and exhibits S-shaped tidal arms extending from its compact core .
Great circles through each of these substructures intersect at the Large Magellanic Cloud ( LMC ) .
This suggests that these objects are , or once were , satellites of the LMC .