Vol 21, No 3

Measurement of Hubble constant: were differences in secondary distance indicators apparent as early as the HST Key Project?

Rahul Kumar Thakur, Shashikant Gupta, Rahul Nigam, PK Thiruvikraman


Abstract Different measurements of the Hubble constant (H0) are not consistent, and a tension between the CMB based methods and cosmic distance ladder based methods has been observed. Measurements from various distance based methods are also inconsistent. To aggravate the problem, the same cosmological probe (Type Ia SNe for instance) calibrated through different methods also provides different values of H0. We compare various distance ladder based methods through the already available unique data obtained from the Hubble Space Telescope (HST). Our analysis is based on parametric (t-test) as well as non-parametric statistical methods such as the Mann-Whitney U test and Kolmogorov-Smirnov test. Our results show that different methods provide different values of H0 and the differences are statistically significant. The biases in the calibration would not account for these differences as the data have been taken from a single telescope with a common calibration scheme. The unknown physical effects or issues with the empirical relations of distance measurement from different probes could give rise to these differences.


Keywords Cosmology — Supernovae — Hubble constant

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