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Galaxies without dark matter halos?
John Baez wrote in message
... In article , Norm Dresner wrote: Since it's believed that there's a dark matter "halo" around or containing every normal matter galaxy, [...] Just to throw an interesting spanner in the works, the April 11th issue of Science reports that Aaron Romanowsky at the University of Nottingham claims to have found some galaxies *without* dark matter halos. Other astronomers are skeptical, so we should wait to see whether this gets confirmed or refuted. But if it were true, it would probably be a big deal. For one, it would probably kill all MOND-like theories in which dark matter is just an artifact of not understanding gravity well enough. For two, folks would have a lot of fun trying to explain such a thing could happen. It is suggested that it was stripped away through interaction with other galaxies. One characteristic of ellipticals is that they often do not have concentrated mass cores. Does anyone know if this is true for these? Another thing I am curious about is whether the motion of these galaxies with respect to others also indicates that they are not surrounded by dark matter. It seems to me that if it turns out that galaxies without concentrated cores do not contain dark matter within their visible limits but seem to still be surrounded by it could indicate a problem with our understanding of the gravitational dynamics around massive cores. I gather that some people think the dark matter problem could be associated with black holes and that would be ruled out. And explaining it with dark matter would at least get more complicated. -Ed Keane III |
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