Hubble tension or a transition of the Cepheid SnIa calibrator parameters?

Abstract

We re-analyze the Cepheid data used to infer the value of the Hubble constant H0 by calibrating Type Ia supernovae. We do not enforce a universal value of the empirical Cepheid calibration parameters RW (Cepheid Wesenheit color-luminosity parameter) and M W H (Cepheid Wesenheit Hband absolute magnitude). Instead we allow for variation of either of these parameters for each individual galaxy. We also consider the case where these parameters have two universal values: one for low galactic distances D < Dc and one for high galactic distances D > Dc where Dc is a critical transition distance. We find hints for a 3σ level mismatch between the low and high galactic distance parameter values. We then use model selection criteria (AIC and BIC) which penalize models with large numbers of parameters, to compare and rank the following types of RW and M W H parameter variations: Base models: Universal values for RW and M W H (no parameter variation), I: Individual fitted galactic RW with one universal fitted M W H , II: One universal fixed RW with individual fitted galactic M W H , III: One universal fitted RW with individual fitted galactic M W H , IV: Two universal fitted RW (near and far) with one universal fitted M W H , V: One universal fitted RW with two universal fitted M W H (near and far), VI: Two universal fitted RW (near and far) with two universal fitted M WH (near and far). We find that the AIC and BIC model selection criteria consistently favor model IV instead of the commonly used Base model where no variation is allowed for the Cepheid empirical parameters. The best fit value of the SnIa absolute magnitude MB and of H0 implied by the favored model IV is consistent with the inverse distance ladder calibration based on the CMB sound horizon H0 = 67.4 ± 0.5 km s −1 M pc −1 . Thus in the context of the favored model IV the Hubble crisis is not present. This model may imply the presence of a fundamental physics transition taking place at a time more recent than 100 M yrs ago.

A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km/s/Mpc Uncertainty from the Hubble Space Telescope and the SH0ES Team

“…We can combine all such constraints as shown in the figure with a result that is unsurprisingly not well defined. Mortsell et al (2021) and Perivolaropoulos & Skara (2021) did not include the color errors, which our analysis shows leads to an underestimate of the values of R and their uncertainties for nearly all SN hosts. From a Bayesian perspective, the addition of a free parameter, R, for each host (∼ 40 free parameters) is not justified by the improvement in the fit over the global R, as also suggested in the analysis from Mortsell et al (2021) and Follin & Knox (2017).…”

Constraining a late time transition of $G_{\rm eff}$ using low-z galaxy survey data

“…[1,3], where it is proposed that it would have the dual effect of solving both the Hubble and growth tensions. There have also been observational hints for such a transition at ≈ 20 Mpc in Cepheid [17,31] and Tully-Fisher data [18].…”

Late-transition versus smooth H(z) -deformation models for the resolution of the Hubble crisis

“…More specifically, in Refs. [172,173] hints were found for a transition of this parameter or at least for it having a different value for the anchor galaxies compared to the SnIa host galaxies. Even though the errors of the individual R E parameters for each host are consistent with the corresponding anchor (low distance) values (see Figs.…”

“…For example if the transition occurs at z = 0.01 then the calibrated value of M correctly obtained at z < 0.01 will not be the same as the value of M at z > 0.01 even though the value is assumed to be the same in the distance ladder methodology. Also, if the M transition takes place at z < 0.01 and the calibration analysis does not allow for such a transition then an incorrect value for M will be obtained by the calibration analysis [172]. Since in the Hubble flow (z > 0.01), the SnIa absolute magnitude M is degenerate with H 0 through the observable M = M − 5 log 10 (h) + 42.…”

“…Hints for such a late time transition may be seen in a recent re-analysis of the Cepheid SnIa calibration data where the Cepheid color-luminosity parameter is allowed to vary among galaxies [172,173]. More specifically, in Refs.…”