gr photometry of Sextans A and Sextans B

Both galaxies have HI discs as massive as their respective stellar components. In both cases the HI discs display solid-body rotation with maximum amplitude of ~50km/s (albeit with significant uncertainty due to the poorly constrained inclination), implying a dynamical mass ~10^9^~M_{sun}_, a mass-to-light ratio M/L_V_~25 and a dark to-barionic mass ratio of ~10. The distribution of the stellar components is more extended than the gaseous disc in both galaxies.

We find that the main, approximately round-shaped, stellar body of Sex A is surrounded by an elongated low-SB stellar halo that can be interpreted as a tidal tail, similar to that found in another member of the same association (Antlia). We discuss these, as well as other evidences of tidal disturbance, in the framework of a past passage of the NGC3109 association close to the Milky Way, that has been hypothesized by several authors and is also supported by the recently discovered filamentary configuration of the association itself