DeterminingH₀with Bayesian hyper-parameters

Abstract

Abstract. We re-analyse recent Cepheid data to estimate the Hubble parameter H 0 by using Bayesian hyper-parameters (HPs). We consider the two data sets from Riess et al 2011 and 2016 (labelled R11 and R16, with R11 containing less than half the data of R16) and include the available anchor distances (megamaser system NGC4258, detached eclipsing binary distances to LMC and M31, and MW Cepheids with parallaxes), use a weak metallicity prior and no period cut for Cepheids. We find that part of the R11 data is down-weighted by the HPs but that R16 is mostly consistent with expectations for a Gaussian distribution, meaning that there is no need to down-weight the R16 data set. For R16, we find a value of H 0 = 73.75 ± 2.11 km s −1 Mpc −1 if we use HPs for all data points (including Cepheid stars, supernovae type Ia, and the available anchor distances), which is about 2.6 σ larger than the Planck 2015 value of H 0 = 67.81±0.92 km s −1 Mpc −1 and about 3.1 σ larger than the updated Planck 2016 value 66.93 ± 0.62 km s −1 Mpc −1 . If we perfom a standard χ 2 analysis as in R16, we find H 0 = 73.46 ± 1.40 (stat) km s −1 Mpc −1 . We test the effect of different assumptions, and find that the choice of anchor distances affects the final value significantly. If we exclude the Milky Way from the anchors, then the value of H 0 decreases. We find however no evident reason to exclude the MW data. The HP method used here avoids subjective rejection criteria for outliers and offers a way to test datasets for unknown systematics.

Quantifying the evidence for the current speed-up of the Universe with low and intermediate-redshift data. A more model-independent approach

“…Other works that make use of the cosmic distance ladder find very similar results to the one reported by [92], see e.g. [93][94][95][96], and are also consistent with preceding studies, as e.g. [97,98].…”

Local resolution of the Hubble tension: The impact of screened fifth forces on the cosmic distance ladder

“…The first is to modify the statistical framework to refine the measure of the tension (e.g. [8][9][10][11]). While a range of estimates for the probability of distance ladder and CMB concordance are derivable from plausible methodologies, the magnitude of the raw discrepancy (derived simply by combining errorbars in quadrature) has been growing, and is now sufficiently large that almost all statistical approaches suggest strong disagreement.…”

SU(2)cmband the cosmological model: angular power spectra

“…In particular, the ac-celerated expansion of the universe at late times due to the dominance of dark energy as well as the spatial flatness of the universe de Bernadis et al (2000) can be considered secured facts. However, recent results reveal a considerable tension between the high value of the present expansion rate H0 = 73.48 ± 1.66 km s −1 Mpc −1 extracted from calibrated distances to SNe Ia (local observation Riess et al (2018); Cardona et al (2017)) and the low values H0 = 66.93 ± 0.62 km s −1 Mpc −1 obtained from the 2015 Planck data or H0 = 69.1 +0.4 −0.6 km s −1 Mpc −1 from the clustering of galaxies (global observations ; Abbott et al (2017)). An independent distance estimator, appealing to time delays from gravitational lensing, extracts a high value of H0 = 72.8 ± 2.4 km s −1 Mpc −1 (local observation Bonvin et al (2017)).…”