Hubble Space Telescope photometry of the dwarf spheroidal galaxy ESO 410-G005

We present Hubble Space Telescope WFPC2 imaging of the nearby low surface b rightness dwarf spheroidal galaxy ESO 410-G005, which has been resolved int o stars for the first time. The resulting color-magnitude diagram for about 2500 stars shows a red giant branch with a tip at I = 22.4 +/- 0.15 mag, w hich yields a distance of D-MW = 1.9 +/- 0.2 Mpc. ESO 410-G005 is found to be metal-poor with a mean metallicity of < [Fe/H]> = (-1.8 +/- 0.4) dex est imated from its red giant branch. Upper asymptotic giant branch stars appea r to be present near the center of the galaxy, indicative of a substantial, centrally concentrated intermediate-age population, unless these objects a re artifacts of crowding. Previous studies did not detect ESO 410-G005 in K alpha or in H I. Based on our distance estimate, ESO 410-G005 is a probabl e member of the Sculptor group of galaxies. Its linear separation from the nearest spiral, NGC 55, is 230 kpc on the sky. The deprojected separation r anges from 340 to 615 kpc depending on the assumed distance of NGC 55. The deprojected distance from the Sculptor group spiral NGC 300 is (385 +/- 200 ) kpc. ESO 410-G005 appears to be a relatively isolated dSph within the Scu lptor group. Its absolute magnitude, M-V,M-0 = -12.1 +/- 0.2 mag, its centr al surface brightness, mu (V,0) = 22.7 +/- 0.1 mag arcsec(-2), and its mean metallicity, [Fe/H] = (-1.8 +/- 0.4) dex follow the trend observed for dwa rf galaxies aries in the Local Group.