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Chaotic Milky Way and Dark Matter distribution

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  1. Apr 9, 2004 #1

    hellfire

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    This paper:
    http://www.edpsciences.org/papers/aa/pdf/press-releases/aa0959.pdf

    ...press release:
    http://www.eso.org/outreach/press-rel/pr-2004/pr-08-04.html

    suggests that the kinematic heating (statistical dispersion of velocities in the perpendicular plane to the galactic plane) of the Milky Way disk, may be due to massive compact objetcs (but must not; three other sources are mentioned: spiral arms effects, satellite galaxies and gas clouds).

    Besides from the fact that the paper is quite interesting, my question is how far such an hypothesis could question the constraints put on the distribution and nature of dark matter in spiral galaxies. Lets say: what is the influence of dark matter on kinematic heating of the disk, if any?

    Regards.
     
    Last edited: Apr 9, 2004
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  3. Apr 9, 2004 #2

    marcus

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    Hi hellfire, I scanned the press release and part of the article but couldnt find the part referring to dark matter or massive compact halo objects. If you have a page reference and want to point us at the spot, that would help.

    My impression is that they spent 20 years measuring the dispersion of star velocities perpendicular to the galactic plane and so they can say
    for the first time how much the stars are bobbing up and down thru the plane.

    My impression is that now that there is a statistical handle on the up/down dispersion people will rush to find explanations to account for it and all kinds of mechanisms will be proposed for why the dispersion is whatever it is and not something else.

    But it seems early to guess.

    BTW this bobbing up and down thru the plane, like a ball on a rubberband, is something astronomers have been aware of for a long time----and they must have had a rough idea of how much other stars do it, just not measured as accurately as these people have now done.

    I remember someone was speculating that periodic mass extinctions on earth could be explained by the sun bobbing up and down thru the galactic plane and taking the earth thru regions where there were clouds of bad stuff. Did you happen to see that speculation, I dont remember more detail unfortunately and did not see any followup on it.

    Did you get any idea from the article, or elsewhere, of what can have damped the up and down oscillations of stars thru the galactic plane?
    since the whole thing contracted into a plane there must have been a lot of infalling stars and originally a lot of up and down velocity, where did it go?
    must be some standard explanation for this but I dont know it
     
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