Accidental deep field bias in CMB T and SNe $z$ correlation

Abstract

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 $\times$ 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 (${\rho }_s=0.5$, p-value $=6.7\times 10^{-9}$) is insignificant for a sub-sample of the seven fields together (${\rho }_s=0.2$, p-value $=0.2$) and entirely absent for the remainder of the SNe (${\rho }_s=0.1$, 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 $\sim$ 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.

arXiv comment12 pages, 6 figures, 7 tables (+ appendices: 7 pages, 8 figures, 1 table), accepted for publication in MNRAS

References in corpus (27)

• Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
• Measurements of Omega and Lambda from 42 High-Redshift Supernovae
• Planck 2015 results. XIII. Cosmological parameters
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• The Supernova Legacy Survey: Measurement of Omega_M, Omega_Lambda and w from the First Year Data Set
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• Planck 2013 results. I. Overview of products and scientific results
• Dark Energy Survey Year 1 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing
• The Hubble Deep Field: Observations, Data Reduction, and Galaxy Photometry
• The Dark Energy Survey: more than dark energy - an overview
• LSST Science Book, Version 2.0
• A Measurement of the Cosmic Microwave Background Damping Tail from the 2500-square-degree SPT-SZ survey
• The ESSENCE Supernova Survey: Survey Optimization, Observations, and Supernova Photometry
• Joint Bayesian component separation and CMB power spectrum estimation
• A full sky, low foreground, high resolution CMB map from WMAP
• Cosmological parameters from supernova observations: A critical comparison of three data sets
• Planck 2015 results. IX. Diffuse component separation: CMB maps
• The Atacama Cosmology Telescope: Two-Season ACTPol Spectra and Parameters
• CMB lensing tomography with the DES Science Verification galaxies
• Results from the High-Z Supernova Search Team
• Tension and Systematics in the Gold06 SnIa Dataset
• Multi-resolution internal template cleaning: An application to the Wilkinson Microwave Anisotropy Probe 7-yr polarization data
• An Intensive HST Survey for z>1 Supernovae by Targeting Galaxy Clusters
• Testing the mutual consistency of different supernovae surveys
• Correlation of supernova redshifts with temperature fluctuations of the Cosmic Microwave Background
• Possible signature of distant foreground in the Planck data
• Chandra Deep Field South: The 1Msec Catalog