Spatial segregation impact on star formation in nearby dwarf spheroidal
  galaxies
  Using our HST/ACS observations of the recently found isolated dwarf
spheroidal galaxies, we homogeneously measured their star formation histories.
We determined star formation rate as a function of time, as well as age and
metallicity of the stellar populations. All objects demonstrate complex star
formation history, with a significant portion of stars formed 10-13 Gyr ago.
Nevertheless, stars of middle ages (1-8 Gyr) are presented. In order to
understand how the star formation parameters influence the evolution of dSphs,
we also studied a sample of nearest dSphs in different environment: isolated (d
< 2 Mpc); beyond the Local Group virial radius (but within the Local Group zero
velocity sphere); and the satellites of M 31 located within the virial zone
(300 kpc). Using archival HST/ACS observations, we measured their star
formation histories. A comparative analysis of the parameters obtained allow us
to distinguish a possible effect of the spatial segregation on the dSphs
evolution scenario.
