Tidal dwarfs in the M81 group: The second generation?

Details Tidal dwarfs in the M81 group: The second generation? Tidal dwarfs in the M81 group: The second generation?

Dec 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002a%26a...396..473m&link_type=abstract

Astronomy and Astrophysics, v.396, p.473-487 (2002)

Astronomy and Astrophysics

Astrophysics

54

Galaxies: Dwarf, Galaxies: Photometry, Galaxies: Stellar Content, Galaxies: Interactions, Galaxies: Individual: M 81, Galaxies: Evolution

Scientific paper

We derive quantitative star formation histories of the four suspected tidal dwarf galaxies in the M 81 group, Holmberg IX, BK3N, Arp-loop (A0952+69), and Garland, using Hubble Space Telescope/Wide Field Planetary Camera 2 images in F606W and F814W obtained as part of a Snapshot survey of dwarf galaxies in the Local Universe. We consider the spatial distribution and ages of resolved stellar populations in these dwarf irregular galaxies. We use synthetic color-magnitude diagrams to derive the ages of the major star formation episodes, star formation rates, and approximate metallicity ranges. All the galaxies show evidence of continuous star formation between about 20 and 200 Myr ago with star formation rates in the range 7.5*E-3-7.6*E-4 Msun yr-1. The metallicity of the detected stars spans a wide range, and have lower than solar abundance. A possible scenario is that all four dwarf galaxies were formed from material in the metal-poor outer part of the giant spiral galaxy M 81 after the tidal interaction between M 81, M 82, and NGC 3077 ~ 200 Myr ago. While we do not directly detect pronounced old stellar populations, the photometric limits of our data are such that the presence of such a population is not entirely ruled out. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal ID GO-8192. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/396/473

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