We present Magellan/IMACS spectroscopy of three recently discovered ultra-faint Milky Way satellites , Grus II , Tucana IV , and Tucana V. We measure systemic velocities of v _ { hel } = -110.0 \pm 0.5 \mathrm { km } ~ { } \mathrm { s } ^ { -1 } , v _ { hel } = 15.9 ^ { +1.8 } _ { -1.7 } \mathrm { km } ~ { } \mathrm { s } ^ { -1 } , and v _ { hel } = -36.2 ^ { +2.5 } _ { -2.2 } \mathrm { km } ~ { } \mathrm { s } ^ { -1 } for the three objects , respectively .
Their large relative velocity differences demonstrate that the satellites are unrelated despite their close physical proximity to one another .
We determine a velocity dispersion for Tuc IV of \sigma = 4.3 ^ { +1.7 } _ { -1.0 } \mathrm { km } ~ { } \mathrm { s } ^ { -1 } , but are unable to resolve the velocity dispersions of the other two systems .
For Gru II we place an upper limit at 90 % confidence on the dispersion of \sigma < 1.9 \mathrm { km } ~ { } \mathrm { s } ^ { -1 } , and for Tuc V we are not able to obtain any useful limits .
All three satellites have low mean metallicities below \mbox { [ Fe / H ] } = -2.1 , but none has a detectable metallicity spread .
Using the spectroscopic member stars , we determine proper motions for each satellite from the second Gaia data release .
We compute their orbits around the Milky Way , finding that all three objects are currently approaching pericenter .
Gru II is on a tightly bound orbit with a pericentric distance of 25 ^ { +6 } _ { -7 } kpc and orbital eccentricity of 0.45 ^ { +0.08 } _ { -0.05 } .
Tuc V has a significantly more extended orbit , with an apocenter likely beyond 100 kpc , and could be approaching the Milky Way for the first time .
The current orbital parameters of Tuc IV are similar to those of Gru II , with a pericenter of 25 ^ { +11 } _ { -8 } kpc and an eccentricity of 0.36 ^ { +0.13 } _ { -0.06 } .
However , a backward integration of the orbit of Tuc IV demonstrates that it collided with the Large Magellanic Cloud with an impact parameter of 4 kpc \sim 120 Myr ago , deflecting its trajectory and possibly altering its internal kinematics .
Based on their sizes , masses , and metallicities , we classify Gru II and Tuc IV as likely dwarf galaxies , but we are not able to draw strong conclusions about the nature of Tuc V .