2001MNRAS.327L..15B

We present wide-field 33x34arcmin² multiband (BVI) CCD photometry (down to I≤20.5 of the very low surface brightness dwarf spheroidal galaxy Sextans. In the derived colour-magnitude diagrams we find evidence suggesting the presence of multiple stellar populations in this dwarf spheroidal. In particular, we discover (i) a blue horizontal branch tail that appears to lie on a brighter sequence with respect to the prominent red horizontal branch and the RR Lyrae stars, very similar to what was found by Majewski et al. for the Sculptor dwarf spheroidal, (ii) hints of a bimodal distribution in colour of the red giant branch stars, (iii) a double red giant branch bump. All of these features suggest that (at least) two components are present in the old stellar population of this galaxy: the main one with [Fe/H]~-1.8 and a minor component around [Fe/H]≲-2.3. The similarity to the Sculptor case may indicate that multiple star formation episodes are also common in the most nearby dwarf spheroidals that ceased their star formation activity at very early epochs.