Gradients of Metallicity and Age of Stars in the Dwarf Spheroidal Galaxies KKs 3 and ESO 269-66

We compare the properties of the stellar populations of the globular clusters and field stars in two dwarf spheroidal galaxies (dSphs): ESO 269-66, a near neighbor of the giant S0 galaxy NGC 5128, and KKs 3, one of the few extremely isolated dSphs within 10 Mpc. The histories of star formation in these galaxies are known from previous work on deep stellar photometry of images from the Hubble Space Telescope (HST). The age and metal content for the nuclear globular clusters in KKs 3 and ESO 269-66 are known from published spectroscopic studies: T = 12.6 billion years, Fe/H] = -1.5, and -1.55 dex. We use the Sersic function to construct and analyze the profiles of the surface density of the stars with high and low metallicities (red and blue) in KKs 3 and ESO 269-66, and show that (1) the profiles of the density of red stars are steeper than those of blue stars, which is indicative of gradients of metallicity and age in the galaxies, and (2) the globular clusters in KKs 3 and ESO 269-66 contain roughly 4 and 40%, respectively, of all the old stars in the galaxies with metallicities [Fe / H] ~ -1.5 ÷ -1.6 dex and ages of 12-14 billion years. The globular clusters are, therefore, relicts of the first, most powerful bursts of star formation in the central regions of these objects. It is probable that, because of its isolation, KKs 3 has lost a smaller fraction of old low-metallicity stars than ESO 269-66. Keywords: galaxies: dwarf- galaxies: star clusters- galaxies: KKs 3, ESO 269-66