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The three-rung distance ladder, which calibrates Type Ia supernovae (SNe Ia) through stellar distances linked to geometric measurements, provides the highest precision direct measurement of the Hubble constant. In light of the Hubble tension, it is important to test the individual components of the distance ladder. For this purpose, we report a measurement of the Hubble constant from 35 extragalactic Cepheid hosts measured by the SH0ES team, using their distances and redshifts at cz ≤ 3300 km sâˆ'1, instead of any more distant SNe Ia, to measure the Hubble flow. The Cepheid distances are calibrated geometrically in the Milky Way, NGC 4258, and the Large Magellanic Cloud. Peculiar velocities are a significant source of systematic uncertainty at z ∼ 0.01, and we present a formalism for both mitigating and quantifying their effects, making use of external reconstructions of the density and velocity fields in the nearby universe. We identify a significant source of uncertainty originating from different assumptions about the selection criteria of this sample, whether distance or redshift limited, as it was assembled over three decades. Modeling these assumptions yields central values ranging from H 0 = 71.7 to 76.4 km sâˆ'1 Mpcâˆ'1. Combining the four best-fitting selection models yields H 0 = 72.9 âˆ' 2.2 + 2.4 as a fiducial result, at 2.4 σ tension with Planck. While SNe Ia are essential for a precise measurement of H 0, unknown systematics in these supernovae are unlikely to be the source of the Hubble tension. [ABSTRACT FROM AUTHOR]

We present a calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC) on the Hubble Space Telescope (HST)/ACS F814W system. We use archival HST observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the Magellanic Clouds. We show that these surveys are biased bright by up to ∼0.1 mag in the optical due to blending, and that the bias is a function of local stellar density. We correct the LMC TRGB magnitudes from Jang & Lee and use the geometric distance from Pietrzyński et al. to obtain an absolute TRGB magnitude of. Applying this calibration to the TRGB magnitudes from Freedman et al. in SN Ia hosts yields a value for the Hubble constant of H0 = 72.4 ± 2.0 km s−1 Mpc−1 for their TRGB+SNe Ia distance ladder. The difference in the TRGB calibration and the value of H0 derived here and by Freedman et al. primarily results from their overestimate of the LMC extinction, caused by inconsistencies in their different sources of TRGB photometry for the Magellanic Clouds. Using the same source of photometry (OGLE) for both Clouds and applying the aforementioned corrections yields a value for the LMC I-band TRGB extinction that is lower by 0.06 mag, consistent with independent OGLE reddening maps used by us and by Jang & Lee to calibrate TRGB and determine H0. [ABSTRACT FROM AUTHOR]

The giant spiral galaxy M101 is host to the nearest recent Type Ia supernova (SN 2011fe) and thus has been extensively monitored in the near-infrared to study the late-time light curve of the SN. Leveraging this existing baseline of observations, we derive the first Mira-based distance to M101 by discovering and classifying a sample of 211 Miras with periods ranging from 240–400 days in the SN field. Combined with new Hubble Space Telescope (HST) WFC3/IR channel observations, our data set totals 11 epochs of F110W (HST YJ) and 13 epochs of F160W (HST H) data spanning ∼2900 days. We adopt absolute calibrations of the Mira period–luminosity relation based on geometric distances to the Large Magellanic Cloud and the water megamaser host galaxy NGC 4258, and find μ M101 = 29.10 ± 0.06 mag. This distance is in 1 σ agreement with most other recent Cepheid and tip of the red giant branch distance measurements to M101. Including the previous Mira SN Ia host, NGC 1559, and SN 2005df, we determine the fiducial SN Ia peak luminosity, M B 0 = − 19.27 ± 0.09 mag. With the Hubble diagram of supernovae Ia, we derive H 0 = 72.37 ± 2.97 km s−1 Mpc−1, a 4.1% measurement of H 0 using Miras. We find excellent agreement with recent Cepheid distance ladder measurements of H 0 and confirm previous indications that the local universe value of H 0 is higher than the early universe value at ∼95% confidence. Currently, the Mira-based H 0 measurement is still dominated by the statistical uncertainty in the SN Ia peak magnitude. [ABSTRACT FROM AUTHOR]

The tip of the red giant branch (TRGB) is a standard candle that can be used to help refine the determination of the Hubble constant. Gaia Data Release 3 (DR3) provides synthetic photometry constructed from low-resolution BP/RP spectra for Milky Way field stars that can be used to directly calibrate the luminosity of the TRGB in the Johnson–Cousins I band, where the TRGB is least sensitive to metallicity. We calibrate the TRGB luminosity using a two-dimensional maximum likelihood algorithm with field stars and Gaia synthetic photometry and parallaxes. For a high-contrast and low-contrast break (characterized by the values of the contrast parameter R or the magnitude of the break β), we find M TRGB I = −4.02 and −3.92 mag respectively, or a midpoint of −3.970 − 0.024 + 0.042 (sys) ± 0.062 (stat) mag. This measurement improves upon the TRGB measurement from Li et al., as the higher precision photometry based on Gaia DR3 allows us to constrain two additional free parameters of the luminosity function. We also investigate the possibility of using Gaia DR3 synthetic photometry to calibrate the TRGB luminosity with ω Centauri, but find evidence of blending within the inner region for cluster member photometry that precludes accurate calibration with Gaia DR3 photometry. We instead provide an updated TRGB measurement of m TRGB I = 9.82 ± 0.04 mag in ω Centauri using ground-based photometry from the most recent version of the database described in Stetson et al., which gives M TRGB I = −3.97 ± 0.04 (stat) ± 0.10 (sys) mag when tied to the Gaia EDR3 parallax distance from the consensus of Vasiliev & Baumgardt, Soltis et al., and Maíz Apellániz. [ABSTRACT FROM AUTHOR]

A correction to the article "A 3% Solution: Determination of the Hubble Constant With the Hubble Space Telescope and Wide Field Camera," by Adam G. Riess and colleagues, is presented.

The simplest ΛCDM model provides a good fit to a large span of cosmological data but harbors large areas of phenomenology and ignorance. With the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the model have emerged. The most statistically significant tension is the 4σ to 6σ disagreement between predictions of the Hubble constant, H0, made by the early time probes in concert with the 'vanilla' ΛCDM cosmological model, and a number of late time, model-independent determinations of H0 from local measurements of distances and redshifts. The high precision and consistency of the data at both ends present strong challenges to the possible solution space and demands a hypothesis with enough rigor to explain multiple observations—whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. A thorough review of the problem including a discussion of recent Hubble constant estimates and a summary of the proposed theoretical solutions is presented here. We include more than 1000 references, indicating that the interest in this area has grown considerably just during the last few years. We classify the many proposals to resolve the tension in these categories: early dark energy, late dark energy, dark energy models with 6 degrees of freedom and their extensions, models with extra relativistic degrees of freedom, models with extra interactions, unified cosmologies, modified gravity, inflationary models, modified recombination history, physics of the critical phenomena, and alternative proposals. Some are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within 1–2σ between Planck 2018, using the cosmic microwave background power spectra data, baryon acoustic oscillations, Pantheon SN data, and R20, the latest SH0ES Team Riess, et al (2021 Astrophys. J. 908 L6) measurement of the Hubble constant (H0 = 73.2 ± 1.3 km s−1 Mpc−1 at 68% confidence level). However, there are many more unsuccessful models which leave the discrepancy well above the 3σ disagreement level. In many cases, reduced tension comes not simply from a change in the value of H0 but also due to an increase in its uncertainty due to degeneracy with additional physics, complicating the picture and pointing to the need for additional probes. While no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along. [ABSTRACT FROM AUTHOR]