Really Large Mergers

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Science  29 Aug 2003:
Vol. 301, Issue 5637, pp. 1154
DOI: 10.1126/science.301.5637.1154a

Our galaxy contains an interesting stream of stars that may represent the disruption of a previous small satellite galaxy as it merged with the Milky Way. Forbes et al. (p. 1217) used the Keck 10-meter telescope and the Hubble Space telescope to obtain direct evidence for such merger processes in the Tadpole Galaxy UGC 10214. They observed the stretching of the colliding dwarf galaxy into a characteristic ellipse and the formation of tidal tails on the rotating galaxy arising from the gravitational forces induced from the dark-matter halo of the larger galaxy. These observations imply that this process is ongoing and likely happens fairly quickly in the universe, and may also explain the high abundance of small elliptical galaxies.

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