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W.-H. Sun (National Central University), Xu Zhou (National Astronomical Observatories), W.-P. Chen (National Central University), D. Burstein, R.A. Windhorst (Arizona State University), J. Ma (National Astronomical Observatories), Y.-I. Byun (Yonsei University), Z.-J. Jiang, J.-S. Chen (National Astronomical Observatories)
Previous HI observations of the M81/M82/NGC3077 system clearly show widespread HI distribution within this galaxy group. While the gas is vulnerable to tidal disruption of a galaxy encounter, are there also stars imbedded in this HI distribution? Our deep exposures of the M81+M82 group in 10 optical bands using the Beijing-Arizona-Taipei-Connecticut (BATC) filter set clearly reveal, for the first time, widespread stellar distributions that coincide with the atomic hydrogen clouds - considered to be the relics of the merging process of the galaxies - splayed over the region. The spectral energy distributions of the stellar groups to the east and west of M81 (including the "Arp" Loop) are similar to that measured at the southeast edge of the optical disk of M82. This similarity in stellar radiation, combined with the observed peculiar rotational velocity of M82, suggests that the diffuse stellar population in the intergalactic space around M81 is mainly the relic of the tidally-disrupted disk of M82 during the last close encounter. Recent measurements of distances to and CBR radial velocities of M81 (3.63 Mpc and 48 km/s) and M82 (3.9 Mpc and 296 km/s) lend further support to the notion of a close passage between these two galaxies several hundred million years ago.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.