A photometrically and kinematically distinct core in the Sextans dwarf spheroidal galaxy

We present the line-of-sight radial velocity dispersion profile of the Sextans dwarf spheroidal galaxy (dSph), based on a sample of 88 stars extending to about 1° (∼1.5 kpc). Like the Draco and Ursa Minor dSphs, Sextans shows some evidence of a fall-off in the velocity dispersion at large projected radii, with significance p= 0.96. Surprisingly, the dispersion at the very centre of Sextans is close to zero (with significance p= 0.96). We present evidence which suggests that this latter change in the stellar kinematics coincides with changes in the stellar populations within the dSph. We discuss possible scenarios which could lead to a kinematically and photometrically distinct population at the centre of Sextans.