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B Cold spot still baffles scientists

  1. Oct 19, 2016 #1


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    October 12, 2016
    University of Portsmouth
    Astrophysicists have created the largest ever map of voids and superclusters in the Universe, which helps solve a long-standing cosmological mystery.

    So what is causing this cold spot?
  2. jcsd
  3. Oct 19, 2016 #2


    Staff: Mentor

    Have you googled "Integrated Sachs-Wolfe effect" (the effect that the article you linked to says causes the difference in CMB temperature)? If not, do so. If you have, what don't you understand about it?
  4. Oct 25, 2016 #3
    I think the O.P. may have been thinking that this text from the article (quoting one of the authors) suggested that the ISW is not the cause of the cold spot:

  5. Oct 25, 2016 #4


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    On page 5 of the subject paper, the authors note "The value of AISW we obtain is larger than the [lambda]CDM expectation but consistent with it at 1.2[sigma] similar to other results using luminous red galaxies in cross-correlation (e.g. Giannantonio et al. 2012). This is in contrast to the high-signifcance detections of the stacked ISW signal reported by Granett et al. (2008); Planck Collaboration et al. (2015b), which exceed the CDM expectation by a factor of ~5 or more, corresponding to a 3[sigma] discrepancy (see Nadathur et al. 2012; Flender et al. 2013; Cai et al. 2014; Hotchkiss et al. 2015; Aiola et al. 2015). Such a large discrepancy has been hard to explain in any alternative theoretical models. Our result is therefore an important step towards the resolution of this apparent anomaly." This appears to defeat any claim of an anomalous ISW effect, as suggested by the article. An off hand remark by the author may have merely been cut and pasted on the editor's table in the spirit of journalistic license.
  6. Oct 25, 2016 #5
    Ouch, thank you. So the article essentially states the opposite of what the paper says, even though they quoted the author. I hadn't had a chance to go through it properly but I didn't expect the pop-sci version to be that far off.
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