Context. Persistent tension between lowredshift observations and the cosmic microwave background radiation (CMB), in terms of two fundamental distance scales set by the sound horizon r d and the Hubble constant H 0 , suggests new physics beyond the Standard Model, departures from concordance cosmology, or residual systematics. Aims. The role of different probe combinations must be assessed, as well as of different physical models that can alter the expansion history of the Universe and the inferred cosmological parameters. Methods. We examined recently updated distance calibrations from Cepheids, gravitational lensing timedelay observations, and the tip of the red giant branch. Calibrating the baryon acoustic oscillations and type Ia supernovae with combinations of the distance indicators, we obtained a joint and selfconsistent measurement of H 0 and r d at low redshift, independent of cosmological models and CMB inference. In an attempt to alleviate the tension between latetime and CMBbased measurements, we considered four extensions of the standard ΛCDM model. Results. The sound horizon from our different measurements is r d = (137 ± 3 stat. ± 2 syst. ) Mpc based on absolute distance calibration from gravitational lensing and the cosmic distance ladder. Depending on the adopted distance indicators, the combined tension in H 0 and r d ranges between 2.3 and 5.1 σ , and it is independent of changes to the lowredshift expansion history. We find that modifications of ΛCDM that change the physics after recombination fail to provide a solution to the problem, for the reason that they only resolve the tension in H 0 , while the tension in r d remains unchanged. Prerecombination extensions (with early dark energy or the effective number of neutrinos N eff = 3.24 ± 0.16) are allowed by the data, unless the calibration from Cepheids is included. Conclusions. Results from timedelay lenses are consistent with those from distanceladder calibrations and point to a discrepancy between absolute distance scales measured from the CMB (assuming the standard cosmological model) and latetime observations. New proposals to resolve this tension should be examined with respect to reconciling not only the Hubble constant but also the sound horizon derived from the CMB and other cosmological probes.
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H0LiCOW XIII. A 2.4% measurement of H0 from lensed quasars: 5.3σ tension between early and lateUniverse probes
Abstract We present a measurement of the Hubble constant (H0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analyzed blindly with respect to the cosmological parameters. In a flat ΛCDM cosmology, we find $H_{0} = 73.3_{1.8}^{+1.7}~\mathrm{km~s^{1}~Mpc^{1}}$, a $2.4{{\ \rm per\ cent}}$ precision measurement, in agreement with local measurements of H0 from type Ia supernovae calibrated by the distance ladder, but in 3.1σ tension with Planck observations of the cosmic microwave background (CMB). This method is completely independent of both the supernovae and CMB analyses. A combination of timedelay cosmography and the distance ladder results is in 5.3σ tension with Planck CMB determinations of H0 in flat ΛCDM. We compute Bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. We explore extensions to flat ΛCDM using constraints from timedelay cosmography alone, as well as combinations with other cosmological probes, including CMB observations from Planck, baryon acoustic oscillations, and type Ia supernovae. Timedelay cosmography improves the precision of the other probes, demonstrating the strong complementarity. Allowing for spatial curvature does not resolve the tension with Planck. Using the distance constraints from timedelay cosmography to anchor the type Ia supernova distance scale, we reduce the sensitivity of our H0 inference to cosmological model assumptions. For six different cosmological models, our combined inference on H0 ranges from ∼73–78 km s−1 Mpc−1, which is consistent with the local distance ladder constraints.
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 NSFPAR ID:
 10175669
 Author(s) / Creator(s):
 ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
 Date Published:
 Journal Name:
 Monthly Notices of the Royal Astronomical Society
 ISSN:
 00358711
 Format(s):
 Medium: X
 Sponsoring Org:
 National Science Foundation
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