Insensitivity of the distance ladder Hubble constant determination to Cepheid calibration modelling choices

Abstract

Recent determination of the Hubble constant via Cepheid-calibrated supernovae by Riess et al. (2016) (R16) find ∼ 3σ tension with inferences based on cosmic microwave background temperature and polarization measurements from Planck. This tension could be an indication of inadequacies in the concordance ΛCDM model. Here we investigate the possibility that the discrepancy could instead be due to systematic bias or uncertainty in the Cepheid calibration step of the distance ladder measurement by R16. We consider variations in total-to-selective extinction of Cepheid flux as a function of line-of-sight, hidden structure in the period-luminosity relationship, and potentially different intrinsic color distributions of Cepheids as a function of host galaxy. Considering all potential sources of error, our final determination of H 0 = 73.3±1.7 km/s/Mpc (not including systematic errors from the treatment of geometric distances or Type Ia Supernovae) shows remarkable robustness and agreement with R16. We conclude systematics from the modeling of Cepheid photometry, including Cepheid selection criteria, cannot explain the observed tension between Cepheid-variable and CMB-based inferences of the Hubble constant. Considering a 'model-independent' approach to relating Cepheids in galaxies with known distances to Cepheids in galaxies hosting a Type Ia supernova and finding agreement with the R16 result, we conclude no generalization of the model relating anchor and host Cepheid magnitude measurements can introduce significant bias in the H 0 inference.

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].…”

Revisiting a Negative Cosmological Constant from Low-Redshift Data

“…The statistical significance of this discrepancy, currently at a level > ∼ 4σ, has steadily grown over recent year, owing also improvements in the distance ladder approach [32][33][34][35]. Additional (re)analyses of the local distance ladder [36][37][38][39][40][41][42][43][44][45][46], as well as independent estimates of H 0 from strong-lensing time delays [47][48][49] have independently supported the conclusion that local measurements favour a higher value of H 0 [8] (see, however, the study in [50]). Given that the Planck estimate of H 0 relies on the assumption of an underlying ΛCDM model, it is possible that the H 0 tension might be hinting towards new physics, possibly involving non-standard properties of dark matter or dark energy [51][52][53][54].…”

H0 tension and the string swampland

“…Far from it, when the sound horizon is calibrated using data from Baryon Acoustic Oscillations (BAO) and the all-sky map from the temperature fluctuations on the cosmic microwave background (CMB), the inferred value of the Hubble constant within ΛCDM is H 0 = 67.4 ± 0.5 km s −1 Mpc −1 [8][9][10][11]. The discrepancy is significant at 4.4σ level [7,11], and systematic effects do not seem to be responsible for this inconsistency [12][13][14][15][16]; see however [17].…”