Tidal dwarfs in the M81 group: the second generation? |
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| Authors: | L Makarova E Grebel I Karachentsev A Dolphin V Karachentseva M Sharina D Geisler P Guhathakurta P Hodge A Sarajedini P Seitzer |
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| Institution: | (1) Special Astrophysical Observatory, Russia;(2) Max-Planck Institute for Astronomy, Heidelberg, Germany;(3) Special Astrophysical Observatory, Russia;(4) Kitt Peak National Observatory, NOAO, USA;(5) Astronomical Observatory of Kiev University, Kiev, Ukraine;(6) Universidad de Concepción, Chile;(7) UCO/Lick Observatory, USA;(8) University of Washington, USA;(9) University of Florida, USA;(10) University of Michigan, USA |
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| Abstract: | We present a quantitative star formation history derivation of the four suspected tidal dwarf galaxies in the M 81 group:
Holmberg IX, BK3N,Arp-loop (A0952+69) and Garland using HST/WFPC2 images of these galaxies. We construct a library of synthetic
Colour-Magnitude Diagrams(CMDs) based on theoretical isochrones and data-derived determinations of photometric errors. These
synthetic CMDs were combined linearly andχ2-compared to observed photometry. All the galaxies show continuous star formation between about 20 and 200 Myr ago with star
formation rates between 7.5⋅10-3 M⊙/yr and 7.67⋅10-4 M⊙/yr. The metallicity of the detected stars is spanning rather a wide range, being lower than solar abundance. We suppose,
that all the galaxies were formed out of material from metal-poor outer part of the giant spiral galaxy M81after tidal interaction
about 200 Myr ago. However, this suggestion requires significantly more deep color-magnitude diagrams to be sure with the
scenario of the galaxy evolution.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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| Keywords: | dwarf galaxies photometry stellar content M81 group |
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