A Comprehensive Measurement of the Local Value of the Hubble Constant with 1 km s−1 Mpc−1 Uncertainty from the Hubble Space Telescope and the SH0ES Team

By A. Riess, W. Yuan, Lucas Macri, D. Scolnic, D. Brout, S. Casertano, David O. Jones, Y. Murakami, G. Anand, L. Breuval and 9 more. Astrophysical Journal Letters, 2021

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We report observations from the Hubble Space Telescope (HST) of Cepheid variables in the host galaxies of 42 Type Ia supernovae (SNe Ia) used to calibrate the Hubble constant (H 0). These include the complete sample of all suitable SNe Ia discovered in the last four decades at redshift z ≤ 0.01, collected and calibrated from ≥1000 HST orbits, more than doubling the sample whose size limits the precision of the direct determination of H 0. The Cepheids are calibrated geometrically from Gaia EDR3 parallaxes, masers in NGC 4258 (here tripling that sample of Cepheids), and detached eclipsing binaries in the Large Magellanic Cloud. All Cepheids in these anchors and SN Ia hosts were measured with the same instrument (WFC3) and filters (F555W, F814W, F160W) to negate zero-point errors. We present multiple verifications of Cepheid photometry and six tests of background determinations that show Cepheid measurements are accurate in the presence of crowded backgrounds. The SNe Ia in these hosts calibrate the magnitude–redshift relation from the revised Pantheon+ compilation, accounting here for covariance between all SN data and with host properties and SN surveys matched throughout to negate systematics. We decrease the uncertainty in the local determination of H 0 to 1 km s−1 Mpc−1 including systematics. We present results for a comprehensive set of nearly 70 analysis variants to explore the sensitivity of H 0 to selections of anchors, SN surveys, redshift ranges, the treatment of Cepheid dust, metallicity, form of the period–luminosity relation, SN color, peculiar-velocity corrections, sample bifurcations, and simultaneous measurement of the expansion history. Our baseline result from the Cepheid–SN Ia sample is H 0 = 73.04 ± 1.04 km s−1 Mpc−1, which includes systematic uncertainties and lies near the median of all analysis variants. We demonstrate consistency with measures from HST of the TRGB between SN Ia hosts and NGC 4258, and include them simultaneously to yield 72.53 ± 0.99 km s−1 Mpc−1. The inclusion of high-redshift SNe Ia yields H 0 = 73.30 ± 1.04 km s−1 Mpc−1 and q 0 = −0.51 ± 0.024. We find a 5σ difference with the prediction of H 0 from Planck cosmic microwave background observations under ΛCDM, with no indication that the discrepancy arises from measurement uncertainties or analysis variations considered to date. The source of this now long-standing discrepancy between direct and cosmological routes to determining H 0 remains unknown.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2d9c241d121b7fb7d7afad3537a15b8f269aad58

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Citations in the corpus

The Atacama Cosmology Telescope: DR6 Gravitational Lensing Map and Cosmological Parameters (2023, methodology): “A local measurement of the expansion rate, calibrated using Cepheid variable stars, is 7% higher than the prediction from Planck assuming the ΛCDM model (Riess et al. 2022), at quoted 5σ significance.”
The Pantheon+ Analysis: The Full Data Set and Light-curve Release (2021, background): “2 paper by Brout et al. (2022b), and the determination of H0 is discussed by Riess et al. (2022).”
The Pantheon+ Analysis: Cosmological Constraints (2022, background): “As shown in the top Pantheon+ and SH0ES section of Table 3, for ΛCDM, flat wCDM, and flat w0waCDM, we find H0= 73.4± 1.1, 73.5± 1.1, and 73.3± 1.1 km s−1Mpc−1, respectively.”
Validation of the Scientific Program for the Dark Energy Spectroscopic Instrument (2023, background): “However, several local measurements of the Hubble constant find higher values (e.g. Freedman et al. 2019; Wong et al. 2020; Riess et al. 2022), albeit with varying degrees of tension.”
Rock ‘n’ roll solutions to the Hubble tension (2019, background): “[26–30]) has become stronger with time and is currently at a very high statistical significance level [21].”
Hubble Tension: The Evidence of New Physics (2023, result): “It is interesting that the H0 values measured by TRGB have small errors and are between the SH0ES results and the CMB results.”