Publication Date:
2018-05-28
Description:
Evidence presented by Yershov, Orlov, and Raikov apparently showed that the WMAP/Planck cosmic microwave background (CMB) pixel-temperatures (T) at supernovae (SNe) locations tend to increase with increasing redshift (|$z$|). They suggest this correlation could be caused by the Integrated Sachs–Wolfe effect and/or by some unrelated foreground emission. Here, we assess this correlation independently using Planck 2015 SMICA R2.01 data and, following Yershov et al., a sample of 2783 SNe from the Sternberg Astronomical Institute. Our analysis supports the prima facie existence of the correlation, but attributes it to a composite selection bias (high CMB T × high SNe |$z$|) caused by the accidental alignment of seven deep survey fields with CMB hotspots. These seven fields contain 9.2 per cent of the SNe sample (256 SNe). Spearman’s rank-order correlation coefficient indicates the correlation present in the whole sample (ρs = 0.5, p-value = 6.7 × 10−9) is insignificant for a sub-sample of the seven fields together (ρs = 0.2, p-value = 0.2) and entirely absent for the remainder of the SNe (ρs = 0.1, p-value = 0.6). We demonstrate the temperature and redshift biases of these seven deep fields, and estimate the likelihood of their falling on CMB hotspots by chance is at least ∼6.8 per cent (approximately 1 in 15). We show that a sample of 7880 SNe from the Open Supernova Catalogue exhibits the same effect and we conclude that the correlation is an accidental but not unlikely selection bias.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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