We present a spectroscopic survey of 2046 red giant stars , distributed over the central 4 kpc \times 2 kpc of the Small Magellanic Cloud ( SMC ) .
After fitting and removing a small velocity gradient across the SMC ( 7.9 km s ^ { -1 } deg ^ { -1 } oriented at 10 ^ { \circ } E of N ) , we measure an rms velocity scatter of 27.5 \pm 0.5 km s ^ { -1 } .
The line of sight velocity distribution is well-characterized by a Gaussian and the velocity dispersion profile is nearly constant as a function of radius .
We find no kinematic evidence of tidal disturbances .
Without a high-precision measurement of the SMC ’ s proper motion , it is not possible to constrain the SMC ’ s true rotation speed from our measured radial-velocity gradient .
However , even with conservative assumptions , we find that v < \sigma and hence that the SMC is primarily supported by its velocity dispersion .
We find that the shape of the SMC , as measured from the analysis of the spatial distribution of its red giant stars , is consistent with the degree of rotational flattening expected for the range of allowed v / \sigma values .
As such , the properties of the SMC are consistent with similar low luminosity spheroidal systems .
We conclude that the SMC is primarily a low luminosity spheroid whose irregular visual appearance is dominated by recent star formation .
A simple virial analysis using the measured kinematics implies an enclosed mass within 1.6 kpc of between 1.4 and 1.9 \times 10 ^ { 9 } M _ { \odot } , and a less well constrained mass within 3 kpc of between 2.7 and 5.1 \times 10 ^ { 9 } M _ { \odot } .