Cosmic Microwave Background CMB Cold Spot Controversy

by Tommy on 28/04/2017

Even with all the recent post deletions, I seem to be stuck on post number 666. That’s very bad.

Since I am definitely afflicted with a very mild case of small positive integer factoring numerology neurosis (AKA Number Theory), that is an unacceptable situation to be in for very long. People might start to talk. Rumors may arise as to my true motivations. Therefore I recently ran across this. I was vaguely aware there was a minor temperature anomaly hidden in there but I never really researched it. So when it showed up in the popular press along with the multiverse mania I decided to investigate it. And then of course I had a crackpot idea. And crackpot ideas are meant to be shared. You never know what might come out of that. Certainly not the Multiverse.

Evidence against a supervoid causing the CMB Cold Spot, Ruari Mackenzie, Tom Shanks, Malcolm N. Bremer, Yan-Chuan Cai, Madusha L.P. Gunawardhana, András Kovács, Peder Norberg and Istvan Szapudi, Submitted to MNRAS (12 April 2017)

We report the results of the 2dF-VST ATLAS Cold Spot galaxy redshift survey (2CSz) based on imaging from VST ATLAS and spectroscopy from 2dF AAOmega over the core of the CMB Cold Spot. We sparsely surveyed the inner 5 radius of the Cold Spot to a limit of iAB ≤ 19.2, sampling ∼ 7000 galaxies at z < 0.4. We have found voids at z = 0.14, 0.26 and 0.30 but they are interspersed with small over-densities and the scale of these voids is insufficient to explain the Cold Spot through the ΛCDM ISW effect. Combining with previous data out to z ∼ 1, we conclude that the CMB Cold Spot could not have been imprinted by a void confined to the inner core of the Cold Spot. Additionally we find that our 'control' field GAMA G23 shows a similarity in its galaxy redshift distribution to the Cold Spot. Since the GAMA G23 line-of-sight shows no evidence of a CMB temperature decrement we conclude that the Cold Spot may have a primordial origin rather than being due to line-of-sight effects.

See also: An Alternative View

Could multiple voids explain the Cosmic Microwave Background Cold Spot anomaly, Krishna Naidoo, Aurélien Benoit-Lévy and Ofer Lahav, Mon Not R Astron Soc Lett 459 (1): L71-L75. (20 March 2016), DOI:10.1093/mnrasl/slw043

Understanding the observed Cold Spot (CS) (temperature of ~ -150 μK at its center) on the Cosmic Microwave Background (CMB) is an outstanding problem. Explanations vary from assuming it is just a > 3 sigma primordial Gaussian fluctuation to the imprint of a supervoid via the Integrated Sachs-Wolfe and Rees-Sciama (ISW+RS) effects. Since single spherical supervoids cannot account for the full profile, the ISW+RS of multiple line-of-sight voids is studied here to mimic the structure of the cosmic web. Two structure configurations are considered. The first, through simulations of 20 voids, produces a central mean temperature of ~ -50 μK. In this model the central CS temperature lies at ~ 2 sigma but fails to explain the CS hot ring. An alternative multi-void model (using more pronounced compensated voids) produces much smaller temperature profiles, but contains a prominent hot ring. Arrangements containing closely placed voids at low redshift are found to be particularly well suited to produce CS-like profiles. We then measure the significance of the CS if CS-like profiles (which are fitted to the ISW+RS of multi-void scenarios) are removed. The CS tension with the LCDM model can be reduced dramatically for an array of temperature profiles smaller than the CS itself.

So what is my crackpot theory? Sorry, I already killed it off. It’s not the multiverse, though.

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