Low-redshift measurement of the sound horizon through gravitational time-delays

Abstract

Context. The Cosmic Microwave Background (CMB) yields an inference on the matter sound horizon, within the Standard Model. Independent, direct measurements of the sound horizon are then a probe of possible deviations from the Standard Model. Aims. We aim at measuring the sound horizon r s from low-redshift indicators, completely independent from CMB inference. Methods. We use the measured product H(z)r s from Baryon Acoustic Oscillations (BAO), plus Supernovae Ia to constrain H(z)/H 0 and time-delay lenses analysed by the H0LiCOW collaboration to anchor cosmological distances (∝ H −1 0 ). Additionally, we investigate the influence of adding a sample of higher-redshift quasars with standardisable UV-Xray luminosity distances. We adopt polynomial expansions in H(z) or in comoving distances, so that our inference is completely independent of any underlying cosmological model. Our measurements are independent of Cepheids and systematics from peculiar motions, to whithin percent-level accuracy. Results. The inferred sound horizon r s varies between (133 ± 8) Mpc and (138 ± 5) Mpc across different models. The discrepancy with CMB measurements is robust against model choice. Statistical uncertainties are comparable to systematics. Conclusions. The combination of time-delay lenses, supernovae and BAO yields a cosmology-independent (and Cepheid-calibrationindependent) distance ladder, and a CMB-independent measurement of r s . These cosmographic measurements are then a competitive test of the Standard Model, regardless of hypotheses on the underlying cosmology.

Resolving the Hubble tension with new early dark energy

“…[34]. 30 As a cross-check, note that this is compatible with the value found in Ref. [34], H 0 ¼ 71.49 AE 1.20 km s −1 Mpc −1 , using the same datasets with the exception of Planck 2018 data (instead of 2015 data) and the helium abundance.…”

“…where we used (30). As expected, the main dependence is due to m, but also f NEDE (and x −1 Ã ¼ H Ã =m) go into its determination.…”

“…This is an extremely small coupling bounded from above by ∼10 −50 when using the estimates suggested in ( 27) and (30). While this ensures that our assumptionλ ≪ λ can be easily justified, it also raises concerns about the effectiveness of our trigger mechanism.…”

“…However, so far, all of these attempts have been plagued by creating a tension with BAO measurements (or by introducing a lot of free parameters) [13,28,29]. The sound horizon r s , which characterizes oscillations in the primordial plasma before recombination, is key to understanding this failure [12,30]: BAO measurements are anchored at early times through their dependence on r s . Used in combination with the Pantheon dataset, they constrain the combination r s H 0 and, therefore, require us to lower r s if we want to increase H 0 in order to have agreement with the local measurement.…”

Holismokes

“…The dependence of H 0 inference on the cosmological model can When the dark energy equation-of-state parameter w is allowed to vary, significant parameter degeneracy between H 0 and w exists, which weakens the constraint on H 0 . be reduced by making use of the type Ia SN relative distance scale and anchoring the distance scale with the D ∆t and D d measurements, as recently illustrated by, for example Jee et al (2019), Arendse et al (2019), andTaubenberger et al (2019).…”