Abstract
We use data from the ESA Gaia mission Early Data Release 3 (EDR3) to measure the trigonometric parallax of
ω
Cen, the first high-precision parallax measurement for the most massive globular ...cluster in the Milky Way. We use a combination of positional and high-quality proper motion data from EDR3 to identify over 100,000 cluster members, of which 67,000 are in the magnitude and color range where EDR3 parallaxes are best calibrated. We find the estimated parallax to be robust, demonstrating good control of systematics within the color–magnitude diagram of the cluster. We find a parallax for the cluster of 0.191 ± 0.001 (statistical) ±0.004 (systematic) mas (2.2% total uncertainty) corresponding to a distance of 5.24 ± 0.11 kpc. The parallax of
ω
Cen provides a unique opportunity to directly and geometrically calibrate the luminosity of the tip of the red giant branch (TRGB) because it is the only cluster with sufficient mass to provide enough red giant stars, more than 100 one magnitude below the tip, for a precise, model-free measurement of the tip. Combined with the preexisting and most widely used measurements of the tip and foreground Milky Way extinction, we find
M
I
,TRGB
=−3.97 ± 0.06 mag for the
I
-band luminosity of the blue edge. Using the TRGB luminosity calibrated from the Gaia EDR3 parallax of
ω
Cen to calibrate the luminosity of Type Ia supernovae results in a value for the Hubble constant of
H
0
= 72.1 ± 2.0 km s
−1
Mpc
−1
. We make the data for the stars in
ω
Cen available electronically and encourage independent analyses of the results presented here.
We present an improved determination of the Hubble constant from Hubble Space Telescope (HST) observations of 70 long-period Cepheids in the Large Magellanic Cloud (LMC). These were obtained with the ...same WFC3 photometric system used to measure extragalactic Cepheids in the hosts of SNe Ia. Gyroscopic control of HST was employed to reduce overheads while collecting a large sample of widely separated Cepheids. The Cepheid period-luminosity relation provides a zero-point-independent link with 0.4% precision between the new 1.2% geometric distance to the LMC from detached eclipsing binaries (DEBs) measured by Pietrzy ski et al. and the luminosity of SNe Ia. Measurements and analysis of the LMC Cepheids were completed prior to knowledge of the new DEB LMC distance. Combined with a refined calibration of the count-rate linearity of WFC3-IR with 0.1% precision, these three improved elements together reduce the overall uncertainty in the geometric calibration of the Cepheid distance ladder based on the LMC from 2.5% to 1.3%. Using only the LMC DEBs to calibrate the ladder, we find H0 = 74.22 1.82 km s−1 Mpc−1 including systematic uncertainties, 3% higher than before for this particular anchor. Combining the LMC DEBs, masers in NGC 4258, and Milky Way parallaxes yields our best estimate: H0 = 74.03 1.42 km s−1 Mpc−1, including systematics, an uncertainty of 1.91%-15% lower than our best previous result. Removing any one of these anchors changes H0 by less than 0.7%. The difference between H0 measured locally and the value inferred from Planck CMB and ΛCDM is 6.6 1.5 km s−1 Mpc−1 or 4.4 (P = 99.999% for Gaussian errors) in significance, raising the discrepancy beyond a plausible level of chance. We summarize independent tests showing that this discrepancy is not attributable to an error in any one source or measurement, increasing the odds that it results from a cosmological feature beyond ΛCDM.
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 Pietrzy ski 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.
The Hubble Tension and Early Dark Energy Kamionkowski, Marc; Riess, Adam G
Annual review of nuclear and particle science,
09/2023, Volume:
73, Issue:
1
Journal Article
Peer reviewed
Open access
Over the past decade, the disparity between the value of the cosmic expansion rate determined directly from measurements of distance and redshift and that determined instead from the standard Lambda ...cold dark matter (ΛCDM) cosmological model, calibrated by measurements from the early Universe, has grown to a level of significance requiring a solution. Proposed systematic errors are not supported by the breadth of available data (and unknown errors are untestable by lack of definition). Simple theoretical explanations for this Hubble tension that are consistent with the majority of the data have been surprisingly hard to come by, but in recent years, attention has focused increasingly on models that alter the early or pre-recombination physics of ΛCDM as the most feasible. Here, we describe the nature of this tension and emphasize recent developments on the observational side. We then explain why early-Universe solutions are currently favored and the constraints that any such model must satisfy. We discuss one workable example, early dark energy, and describe how it can be tested with future measurements. Given an assortment of more extended recent reviews on specific aspects of the problem, the discussion is intended to be fairly general and understandable to a broad audience.
We present new measurements of the parallax of seven long-period (≥10 days) Milky Way (MW) Cepheid variables (SS CMa, XY Car, VY Car, VX Per, WZ Sgr, X Pup, and S Vul) using one-dimensional ...astrometric measurements from spatial scanning of Wide-Field Camera 3 on the Hubble Space Telescope (HST). The observations were obtained at ∼6 month intervals over 4 years. The distances are 1.7-3.6 kpc, with a mean precision of 45 as (signal-to-noise ratio (S/N) 10) and a best precision of 29 as (S/N = 14). The accuracy of the parallaxes is demonstrated through independent analyses of >100 reference stars. This raises to 10 the number of long-period Cepheids with significant parallax measurements, 8 obtained from this program. We also present high-precision mean F555W, F814W, and F160W magnitudes of these Cepheids, allowing a direct, zeropoint-independent comparison to >1800 extragalactic Cepheids in the hosts of 19 SNe Ia. This sample addresses two outstanding systematic uncertainties affecting prior comparisons of MW and extragalactic Cepheids used to calibrate the Hubble constant (H0): their dissimilarity of periods and photometric systems. Comparing the new parallaxes to their predicted values derived from reversing the distance ladder gives a ratio (or independent scale for H0) of 1.037 0.036, consistent with no change and inconsistent at the 3.5 level with a ratio of 0.91 needed to match the value predicted by Planck cosmic microwave background data in concert with ΛCDM. Using these data instead to augment the Riess et al. measurement of H0 improves the precision to 2.3%, yielding 73.48 1.66 km s−1 Mpc−1, and the tension with Planck + ΛCDM increases to 3.7 . The future combination of Gaia parallaxes and HST spatial scanning photometry of 50 MW Cepheids can support a <1% calibration of H0.
We present year-long, near-infrared Hubble Space Telescope (HST) WFC3 observations used to search for Mira variables in NGC 1559, the host galaxy of the Type Ia supernova (SN Ia) SN 2005df. This is ...the first dedicated search for Miras, highly evolved low-mass stars, in an SN Ia host, and subsequently the first calibration of the SN Ia luminosity using Miras in a role historically played by Cepheids. We identify a sample of 115 O-rich Miras with P < 400 days based on their light-curve properties. We find that the scatter in the Mira period-luminosity relation (PLR) is comparable to Cepheid PLRs seen in SN Ia host galaxies. Using a sample of O-rich Miras discovered in NGC 4258 with HSTF160W and its maser distance, we measure a distance modulus for NGC 1559 of (statistical) (systematic) mag. Based on the light curve of the normal, well-observed, low-reddening SN 2005df, we obtain a measurement of the fiducial SN Ia absolute magnitude of mag. With the Hubble diagram of SNe Ia we find km s−1 Mpc−1. Combining the calibration from the NGC 4258 megamaser and the Large Magellanic Cloud detached eclipsing binaries gives a best value of km s−1 Mpc−1. This result is within 1 of the Hubble constant derived using Cepheids and multiple calibrating SNe Ia. This is the first of four expected calibrations of the SN Ia luminosity from Miras that should reduce the error in H0 via Miras to ∼3%. In light of the present Hubble tension and JWST, Miras have utility in the extragalactic distance scale to check Cepheid distances or calibrate nearby SNe in early-type host galaxies that would be unlikely targets for Cepheid searches.
We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to reduce the uncertainty in the local value of the Hubble constant from 3.3% to 2.4%. The bulk of this improvement comes ...from new near-infrared (NIR) observations of Cepheid variables in 11 host galaxies of recent type Ia supernovae (SNe Ia), more than doubling the sample of reliable SNe Ia having a Cepheid-calibrated distance to a total of 19; these in turn leverage the magnitude-redshift relation based on ~300 SNe Ia at z< 0.15. All 19 hosts as well as the megamaser system NGC 4258 have been observed with WFC3 in the optical and NIR, thus nullifying cross-instrument zeropoint errors in the relative distance estimates from Cepheids. Other noteworthy improvements include a 33% reduction in the systematic uncertainty in the maser distance to NGC 4258, a larger sample of Cepheids in the Large Magellanic Cloud (LMC), a more robust distance to the LMC based on late-type detached eclipsing binaries (DEBs), HST observations of Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW) Cepheids. We consider four geometric distance calibrations of Cepheids: (i) megamasers in NGC 4258, (ii) 8 DEBs in the LMC, (iii) 15 MW Cepheids with parallaxes measured with HST/FGS, HST/WFC3 spatial scanning and/or Hipparcos, and (iv) 2 DEBs in M31. The Hubble constant from each is 72.25 + or - 2.51, 72.04 + or - 2.67, 76.18 + or - 2.37, and 74.50 + or - 3.27 km s super(-1) Mpc super(-1), respectively. Our best estimate of H sub(0)= 73.24 + or - 1.74 km s super(-1) Mpc super(-1) combines the anchors NGC 4258, MW, and LMC, yielding a 2.4% determination (all quoted uncertainties include fully propagated statistical and systematic components). This value is 3.4sigma higher than 66.93 + or - 0.62 km s super(-1) Mpc super(-1) predicted by LambdaCDM with 3 neutrino flavors having a mass of 0.06 eV and the new Planck data, but the discrepancy reduces to 2.1sigma relative to the prediction of 69.3 + or - 0.7 km s super(-1) Mpc super(-1) based on the comparably precise combination of WMAP+ACT+SPT+BAO observations, suggesting that systematic uncertainties in CMB radiation measurements may play a role in the tension. If we take the conflict between Planck high-redshift measurements and our local determination of H sub(0) at face value, one plausible explanation could involve an additional source of dark radiation in the early universe in the range of DeltaN sub(eff)approximate 0.4-1. We anticipate further significant improvements in H sub(0) from upcoming parallax measurements of long-period MW Cepheids.
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