http://arxiv.org/abs/1706.09723
The current >3 sigma tension between the Hubble constant H0 measured from local distance indicators and from cosmic microwave background is one of the most highly debated issues in cosmology, as it possibly indicates new physics or unknown systematics. In this work, we explore whether this tension can be alleviated by the sample variance in the local measurements, which use a small fraction of the Hubble volume. We use a large-volume cosmological N-body simulation to model the local measurements and to quantify the variance due to local density fluctuations and sample selection. We explicitly take into account the inhomogeneous spatial distribution of type Ia supernovae. Despite the faithful modeling of the observations, our results confirm previous findings that sample variance in local Hubble constant measurements is small; we find sigma(local H0)=0.31 km/s/Mpc, a nearly negligible fraction of the ~ 6 km/s/Mpc necessary to explain the difference between the local and the global H0 measurements. While the H0 tension could in principle be explained by our local neighborhood being a underdense region of radius ~150 Mpc, the extreme required underdensity of such a void (delta ~ -0.8) makes it very unlikely in a LCDM Universe, and it also violates existing observational constraints. Therefore, sample variance in a LCDM Universe cannot appreciably alleviate the tension in H0 measurements even after taking into account the inhomogeneous selection of type Ia supernovae.
H. Wu and D. Huterer
Fri, 30 Jun 17
6/65
Comments: 10 pages, 6 figures, 1 table; main result in Figure 3
You must be logged in to post a comment.