Concerns about the reliability of publicly available SNe Ia data

Abstract

I highlight several concerns regarding the consistency of Type Ia supernova data in the publicly available Pantheon and JLA compilations. The measured heliocentric redshifts (zhel) of $\sim$150 SNe Ia as reported in the Pantheon catalogue are significantly discrepant from those in JLA - with 58 having differences amounting to between 5 and 137 times the quoted measurement uncertainty. The discrepancy seems to have been introduced in the process of rectifying a previously reported issue. The Pantheon catalogue until very recently had the redshifts of all SNe Ia up to z $\sim$ 0.3 modified under the guise of 'peculiar velocity corrections' - although there is no information on peculiar velocities at such high redshifts. While this has reportedly been rectified on Github by removing peculiar velocity corrections for z > 0.08, the impact of this on the published cosmological analysis of the Pantheon catalogue is not stated. In JLA, the effect of these 'corrections' is to significantly bias the inferred value of ${\Omega }_{\Lambda }$ towards higher values, while the equivalent effect on Pantheon cannot be ascertained due to the unavailability of the individual components of the covariance matrix in the public domain. I provide Jupyter notebooks and URLs in order to allow the reader to ascertain the veracity of these assertions.

arXiv commentCode for verifying the claims can be found at https://github.com/rameez3333/PantheonvsJLAcrosschecks

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