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Dark flow

  1. Aug 12, 2010 #1
    Anybody out there with info? What part of the expandable universe have the galaxys been observed to be flowing to a pecticular direction. Been looking for information site on topic. Thanks
  2. jcsd
  3. Aug 12, 2010 #2


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    skepticism about "dark flow" is still advisable.
    Here was Ned Wright's comment when Kashlinsky's paper came out:
    =quote http://www.astro.ucla.edu/~wright/cosmolog.htm =
    Dark Flow Detected - Not!

    24 Sep 2008 - Kashlinsky et al. (2008) have claimed a detection of a bulk flow in the motion of many distant X-ray emitting clusters of galaxies. Unfortunately this paper and the companion paper have several errors so their conclusions cannot be trusted. A technical discussion of these errors can be found here.

    Only academic sources are to be trusted because they have some self-critical ethic. Popularization and public relations media ("discovery channel") will say unbalanced hype, omitting reservations, and quote scientists' oversimple soundbites, if they think it will excite viewers and boost ratings.

    I think if you look at academic sources on "dark flow" (a jazzy name for a possible drift in a large but limited patch of galaxies) you will find it has NOT gained a lot of adherents since 2008. The jury is still out, so to speak. That is my take. But I could be wrong! You can judge for yourself by looking at Kashlinsky's publication record and checking to see how many other people have cited his papers on this alleged drift.

    Here are the 4 papers by Kashlinsky that are about the alleged drift. Two in 2008 and then two more around January 2010 with a "new measurement" of the "dark flow".

    1. arXiv:1001.1261 [pdf, ps, other]
    The error budget of the Dark Flow measurement
    F. Atrio-Barandela, A. Kashlinsky, H. Ebeling, D. Kocevski, A. Edge
    Comments: ApJ, in press
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

    2. arXiv:0910.4958 [pdf, ps, other]
    A new measurement of the bulk flow of X-ray luminous clusters of galaxies
    A. Kashlinsky (GSFC), F. Atrio-Barandela (U Salamanca, Spain), H. Ebeling (IfA, Hawaii), A. Edge (U of Durham, UK), D. Kocevski (UCD)
    Comments: Ap.J. (Letters), Mar 20/2010. Replaced with published version
    Journal-ref: ApJ, (2010), 712, L81-l85
    Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

    5. arXiv:0809.3734 [pdf, ps, other]
    A measurement of large-scale peculiar velocities of clusters of galaxies: results and cosmological implications
    A. Kashlinsky (GSFC), F. Atrio-Barandela (U of Salamanca), D. Kocevski (UC Davis), H. Ebeling (U of Hawaii)
    Comments: Ap.J. (Letters), in press. 20 Oct issue (Vol. 686)
    Subjects: Astrophysics (astro-ph)

    6. arXiv:0809.3733 [pdf, ps, other]
    A measurement of large-scale peculiar velocities of clusters of galaxies: technical details
    A. Kashlinsky (GSFC), F. Atrio-Barandela (U of Salamanca), D. Kocevski (UC Davis), H. Ebeling (U of Hawaii)
    Comments: Minor changes to match the published version - Ap.J., 1 Feb 2009 issue
    Subjects: Astrophysics (astro-ph)

    Here is the list of all his publications with live links to the PDF (and the html summaries called "abstracts")

    You have to judge for yourself. A key factor is the "cited by" link on the HTML abstract page. You can see how many other scientists have cited his two recent "dark flow" papers: the "new measurement" one labeled 0910.4958 and the "error budget" one labeled 1001.1261
    If there is a big dropoff in citations, then probably the scientific community is not buying it. If citations remain high then there is a chance the idea is going somewhere (other than out into the popular media.)
    Last edited: Aug 12, 2010
  4. Aug 12, 2010 #3


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    I second that motion, marcus. Bold claims require bold evidence. The OP needs citations to assert this claim.
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