Blue straggler stars in dwarf spheroidal galaxies II: Sculptor and
  Fornax
  The existence of blue straggler stars (BSSs) in dwarf spheroidal galaxies
(dSphs) is still an open question. In fact, many BSS candidates have been
observed in the Local Group dSphs, but it is unclear whether they are real BSSs
or young stars. Shedding light on the nature of these BSS candidates is
crucial, in order to understand the star formation history of dSphs. In this
paper, we consider BSS candidates in Sculptor and Fornax. In Fornax there are
strong hints that the BSS population is contaminated by young stars, whereas in
Sculptor there is no clear evidence of recent star formation. We derive the
radial and luminosity distribution of BSS candidates from wide field imaging
data extending beyond the nominal tidal radius of these galaxies. The
observations are compared with the radial distribution of BSSs expected from
dynamical simulations. In Sculptor the radial distribution of BSS candidates is
consistent with that of red horizontal branch (RHB) stars and is in agreement
with theoretical expectations for BSSs generated via mass transfer in binaries.
On the contrary, in Fornax the radial distribution of BSS candidates is more
concentrated than that of all the considered stellar populations. This result
supports the hypothesis that most of BSS candidates in Fornax are young stars
and is consistent with previous studies.
