2018MNRAS.479.1137F -
Mon. Not. R. Astron. Soc., 479, 1137-1153 (2018/September-1)
Accidental deep field bias in CMB T and SNe z correlation.
FRIDAY T., CLOWES R.G., RAGHUNATHAN S. and WILLIGER G.M.
Abstract (from CDS):
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 x 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 x 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.
Abstract Copyright:
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
Journal keyword(s):
methods: statistical - surveys - supernovae: general - cosmology: cosmic background radiation - cosmology: observations
Simbad objects:
5
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