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cougar wrote: Without getting into the details, this does NOT seem to be a slam dunk for your position.
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I think I've defined my position pretty clearly. Evidence is now accumulating that many ellipticals may not have dark matter halos. Since CDM models predict that they all should have dark matter halos this creates problems with those models and they will need closer scrutiny.
There are at least 10 ellipticals indicated among the papers I've cited which show no evidence for dark matter halos. Ever paper I cited with the exception of the NGC 404 paper was cited by the authors of the new study. As for the abstract you refer to - if you go into the paper you find it says this in section 4:
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Therefore dark halos are not required to explain the decreasing velocity dispersion profiles of NGC 1400, 4946, 5812, 6721, and 7507, even if the best-fit models selected by the 2C method would include a sizable dark component (see Table 4).
NGC 7796 stands out as a different case. In the 2C analysis a satisfactory fit is found only by considering the presence of a sizable secondary component; ..."
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and this in section 5 after eliminating three galaxies with significant amounts of rotation thus reducing the sample to the 3 galaxies which their modeling tool appears most valid:
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In the previous section we have concluded that no evidence for dark matter is found for NGC 5812 and 7507, while NGC 7796 appears to possess a dark halo, much like two other galaxies (NGC 4472 and IC 4296) studied in the same program (SKP). We should try to find a way to interpret such apparently discordant results.
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Thus using their method they find that 2 of the 5 galaxies that best fit their model do not require dark matter halos and 3 others excluded because of rotation velocity do not require dark matter halos either. Using the newer planetary nebula method 4 of 5 galaxies are indicated not to have dark matter halos. NGC 404 was shown to lack dark matter as well.
Now I'm not sure what you mean by "slam dunk" in this instance because the point is that all ellipticals are supposed to have dark matter halos and it appears that less than 50% of the ellipticals for which such measurements are possible actually indicate the presence of a dark halo. If a sizeable fraction of ellipticals lack dark matter halos you have a problem that requires the attention of CDM theorists. That is my position and its supported by these new results as well as the older studies.
In fact its not even a position so much as pointing out what the observational results are!