Journal Article

Star formation history of KDG 61 and KDG 64 from spectroscopy and colour–magnitude diagrams

Lidia Makarova, Mina Koleva, Dmitry Makarov and Philippe Prugniel

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 406, issue 2, pages 1152-1165
Published in print August 2010 | ISSN: 0035-8711
Published online July 2010 | e-ISSN: 1365-2966 | DOI:
Star formation history of KDG 61 and KDG 64 from spectroscopy and colour–magnitude diagrams

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A study of two dE/dSph members of the nearby M81 group of galaxies, KDG 61 and UGC 5442 = KDG 64, 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 (12–14 Gyr) of low metallicity ([Fe/H]∼−1.5). Stars of ages about 1–4 Gyr 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 H ii knot on the line-of-sight of KDG 61 is not gravitationally attached to the galaxy.

Keywords: galaxies: dwarf; galaxies: evolution; galaxies: formation; galaxies: individual: KDG 61; galaxies: individual: KDG 64; galaxies: stellar content

Journal Article.  9598 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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