Mon. Not. R. Astron. Soc., 406, 1152-1165 (2010/August-1)
Star formation history of KDG61 and KDG64 from spectroscopy and colour-magnitude diagrams.
MAKAROVA L., KOLEVA M., MAKAROV D. and PRUGNIEL P.
Abstract (from CDS):
A study of two dE/dSph members of the nearby M81 group of galaxies, KDG61 and UGC5442 = KDG64, has been made. Direct Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images and integrated-light spectra of 6-m telescope of Special Astrophysical Observatory of Russian Academy of Sciences have been used for quantitative star formation history analysis. The spectroscopic and colour-magnitude diagrams analysis gives consistent results. These galaxies appear to be dominated by an old population (12-14Gyr) of low metallicity ([Fe/H] ∼ -1.5). Stars of ages about 1-4Gyr have been detected in both galaxies. The later population shows marginal metal enrichment. We do not detect any significant radial gradients in age or metallicity in these galaxies. Our radial velocity measurement suggests that the HII knot on the line-of-sight of KDG61 is not gravitationally attached to the galaxy.