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Thread: Hubble Observations Suggest a Missing Ingredient in Dark Matter Theories

  1. #1
    Join Date
    Aug 2003
    The Wild West

    Hubble Observations Suggest a Missing Ingredient in Dark Matter Theories

    This recent release by NASA's Hubblesite is interesting in its possible implications.

    A recent study of 11 hefty galaxy clusters found that some small-scale clumps of dark matter are so concentrated that the lensing effects they produce are 10 times stronger than expected. These concentrations are associated with individual cluster galaxies.
    The finding is that "Dark matter in clusters is therefore distributed on both large and small scales," the small scales being individual galaxies, which apparently harbor a much higher concentration of dark matter than previously thought. (Of course, the cluster itself harbors its own concentration.)

    The implication being, how have these "small-scale clumps of dark matter" come to be? Running the clock back, what particular circumstance, what change in the current theory, would have been necessary to yield these results after 12-13 billion years?
    Everyone is entitled to his own opinion, but not his own facts.

  2. #2
    Join Date
    Feb 2005
    I thought that oxygen might be some dark matter, IIRC

  3. #3
    Join Date
    Mar 2008
    Assuming tidal stripping can not close the gap, there may be a missing parameter for Dark Matter Intensity. There have been suggestions about dark matter self-interactions usually leading to some kind of destruction into gamma rays. The conservative Intensity interaction would make some dark matter darker or more intense at the expense of other dark matter brighter and weaker.

  4. #4
    Join Date
    Apr 2005
    They also measured the rotation speeds of some of the massive individual galaxies in the cluster.

    The article neglects to mention whether or not these rotation speeds are within expectations of the mass as measured by gravitational lensing:

    Follow-up spectroscopic observations added to the study by measuring the velocity of the stars orbiting inside several of the cluster galaxies. "Based on our spectroscopic study, we were able to associate the galaxies with each cluster and estimate their distances," said team member Piero Rosati of the University of Ferrara in Italy.

    "The stars' speed gave us an estimate of each individual galaxy's mass, including the amount of dark matter," added team member Pietro Bergamini of the INAF-Observatory of Astrophysics and Space Science in Bologna, Italy.

  5. #5
    Join Date
    Apr 2007
    Nowhere (middle)
    Quote Originally Posted by publiusr View Post
    I thought that oxygen might be some dark matter, IIRC
    Oxygen has known physical properties which do not match those observed in dark matter.
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