A Measurement of the Hubble Constant by the Megamaser Cosmology Project

2017 ◽  
Vol 13 (S336) ◽  
pp. 86-91 ◽  
Author(s):  
James Braatz ◽  
James Condon ◽  
Christian Henkel ◽  
Jenny Greene ◽  
Fred Lo ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Hubble Constant ◽  
Final Analysis ◽  
Direct Test ◽  
Microwave Background ◽  
Distance Measurements ◽  
Standard Cosmological Model ◽  
Geometric Measurement ◽  
Hubble Flow

AbstractThe Megamaser Cosmology Project (MCP) measures the Hubble Constant by determining geometric distances to circumnuclear 22 GHz H2O megamasers in galaxies at low redshift (z < 0.05) but well into the Hubble flow. In combination with the recent, exquisite observations of the Cosmic Microwave Background by WMAP and Planck, these measurements provide a direct test of the standard cosmological model and constrain the equation of state of dark energy. The MCP is a multi-year project that has recently completed observations and is currently working on final analysis. Based on distance measurements to the first four published megamasers in the sample, the MCP currently determines H0 = 69.3 ± 4.2 km s−1 Mpc−1. The project is finalizing analysis for five additional galaxies. When complete, we expect to achieve a ~4% measurement. Given the tension between the Planck prediction of H0 in the context of the standard cosmological model and astrophysical measurements based on standard candles, the MCP provides a critical and independent geometric measurement that does not rely on external calibrations or a distance ladder.

scholarly journals Decaying Dark Energy in Light of the Latest Cosmological Dataset

Symmetry ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 372 ◽  
Author(s):  
Ivan de Martino
Keyword(s):  
Dark Energy ◽  
Cosmic Microwave Background ◽  
Parameter Space ◽  
Hubble Constant ◽  
Two Dimensions ◽  
Matter Density ◽  
Microwave Background ◽  
Energy Models ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature

Decaying Dark Energy models modify the background evolution of the most common observables, such as the Hubble function, the luminosity distance and the Cosmic Microwave Background temperature–redshift scaling relation. We use the most recent observationally-determined datasets, including Supernovae Type Ia and Gamma Ray Bursts data, along with H ( z ) and Cosmic Microwave Background temperature versus z data and the reduced Cosmic Microwave Background parameters, to improve the previous constraints on these models. We perform a Monte Carlo Markov Chain analysis to constrain the parameter space, on the basis of two distinct methods. In view of the first method, the Hubble constant and the matter density are left to vary freely. In this case, our results are compatible with previous analyses associated with decaying Dark Energy models, as well as with the most recent description of the cosmological background. In view of the second method, we set the Hubble constant and the matter density to their best fit values obtained by the Planck satellite, reducing the parameter space to two dimensions, and improving the existent constraints on the model’s parameters. Our results suggest that the accelerated expansion of the Universe is well described by the cosmological constant, and we argue that forthcoming observations will play a determinant role to constrain/rule out decaying Dark Energy.

scholarly journals First cosmological results using Type Ia supernovae from the Dark Energy Survey: measurement of the Hubble constant

2019 ◽  
Vol 486 (2) ◽  
pp. 2184-2196 ◽  
Author(s):  
E Macaulay ◽  
R C Nichol ◽  
D Bacon ◽  
D Brout ◽  
T M Davis ◽  
...  
Keyword(s):  
Dark Energy ◽  
Hubble Constant ◽  
Type Ia Supernovae ◽  
Distance Measurements ◽  
Dark Energy Survey ◽  
Systematic Uncertainties ◽  
Type Ia ◽  
Ia Supernovae ◽  
Energy Survey ◽  
Inverse Distance

ABSTRACT We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) at redshift 0.018 &lt; z &lt; 0.85 to existing distance measurements of 122 low-redshift (z &lt; 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations (BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement makes minimal assumptions about the underlying cosmological model, and our analysis was blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the Cosmic Microwave Background assuming a ΛCDM universe.

scholarly journals Cosmological evolution with interaction between dark energy and dark matter

2015 ◽  
Vol 24 (03) ◽  
pp. 1530007 ◽  
Author(s):  
Yuri L. Bolotin ◽  
Alexander Kostenko ◽  
Oleg A. Lemets ◽  
Danylo A. Yerokhin
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Model ◽  
Holographic Dark Energy ◽  
Main Task ◽  
Nonlinear Interactions ◽  
Dark Sector ◽  
Standard Cosmological Model ◽  
Linear And Nonlinear ◽  
The Universe

In this review we consider in detail different theoretical topics associated with interaction in the dark sector. We study linear and nonlinear interactions which depend on the dark matter and dark energy densities. We consider a number of different models (including the holographic dark energy and dark energy in a fractal universe), with interacting dark energy and dark matter, have done a thorough analysis of these models. The main task of this review was not only to give an idea about the modern set of different models of dark energy, but to show how much can be diverse dynamics of the universe in these models. We find that the dynamics of a universe that contains interaction in the dark sector can differ significantly from the Standard Cosmological Model.

scholarly journals CMB anisotropy science: a review

2012 ◽  
Vol 8 (S288) ◽  
pp. 42-52 ◽  
Author(s):  
Anthony Challinor
Keyword(s):  
Dark Matter ◽  
Cosmological Model ◽  
Cosmic Microwave Background ◽  
Gravitational Waves ◽  
Early Universe ◽  
Critical Role ◽  
Microwave Background ◽  
Fundamental Physics ◽  
Standard Cosmological Model

AbstractThe cosmic microwave background (CMB) provides us with our most direct observational window to the early universe. Observations of the temperature and polarization anisotropies in the CMB have played a critical role in defining the now-standard cosmological model. In this contribution we review some of the basics of CMB science, highlighting the role of observations made with ground-based and balloon-borne Antarctic telescopes. Most of the ingredients of the standard cosmological model are poorly understood in terms of fundamental physics. We discuss how current and future CMB observations can address some of these issues, focusing on two directly relevant for Antarctic programmes: searching for gravitational waves from inflation via B-mode polarization, and mapping dark matter through CMB lensing.

scholarly journals A fake interacting dark energy detection?

2020 ◽  
Vol 500 (1) ◽  
pp. L22-L26
Author(s):  
Eleonora Di Valentino ◽  
Olga Mena
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmic Microwave Background ◽  
Hubble Constant ◽  
Energy Detection ◽  
Microwave Background ◽  
Planck Data ◽  
Cosmological Constraints ◽  
Data Analyses ◽  
Constant Tension

ABSTRACT Models involving an interaction between the dark matter and the dark energy sectors have been proposed to alleviate the long-standing Hubble constant tension. In this paper, we analyse whether the constraints and potential hints obtained for these interacting models remain unchanged when using simulated Planck data. Interestingly, our simulations indicate that a dangerous fake detection for a non-zero interaction among the dark matter and the dark energy fluids could arise when dealing with current cosmic microwave background (CMB) Planck measurements alone. The very same hypothesis is tested against future CMB observations, finding that only cosmic variance limited polarization experiments, such as PICO or PRISM, could be able to break the existing parameter degeneracies and provide reliable cosmological constraints. This paper underlines the extreme importance of confronting the results arising from data analyses with those obtained with simulations when extracting cosmological limits within exotic cosmological scenarios.

scholarly journals Measuring the Hubble constant with observations of water-vapor megamasers

2012 ◽  
Vol 8 (S289) ◽  
pp. 255-261 ◽  
Author(s):  
James Braatz ◽  
Mark Reid ◽  
Cheng-Yu Kuo ◽  
Violette Impellizzeri ◽  
James Condon ◽  
...  
Keyword(s):  
Precise Measurement ◽  
Hubble Constant ◽  
Microwave Background ◽  
Distance Measurements ◽  
The Past ◽  
Systematic Effort ◽  
Type Ia ◽  
Cepheid Variables ◽  
Ia Supernovae ◽  
Green Bank Telescope

AbstractTo constrain models of dark energy, a precise measurement of the Hubble constant, H0, provides a powerful complement to observations of the cosmic microwave background. Recent, precise measurements of H0 have been based on the ‘extragalactic distance ladder,’ primarily using observations of Cepheid variables and Type Ia supernovae as standard candles. In the past, these methods have been limited by systematic errors, so independent methods of measuring H0 are of high value. Direct geometric distance measurements to circumnuclear H2O megamasers in the Hubble flow provide a promising new method to determine H0. The Megamaser Cosmology Project (MCP) is a systematic effort to discover suitable H2O megamasers and determine their distances, with the aim of measuring H0 to a few percent. Based on observations of megamasers in UGC 3789 and NGC 6264, and preliminary results from Mrk 1419, the MCP has so far measured H0 = 68.0 ± 4.8 km s−1 Mpc−1. This measurement will improve as distances to additional galaxies are incorporated. With the Green Bank Telescope, we recently discovered three more excellent candidates for distance measurements, and we are currently acquiring data to measure their distances.

scholarly journals Possible Modification of the Standard Cosmological Model to Resolve a Tension with Hubble Constant Values

2021 ◽  
Vol 66 (9) ◽  
pp. 739
Author(s):  
S.L. Parnovsky
Keyword(s):  
Dark Energy ◽  
Hubble Constant ◽  
Baryonic Matter ◽  
Astronomical Observations ◽  
Significant Challenge ◽  
Λcdm Model ◽  
Modern Cosmology ◽  
Standard Cosmological Model ◽  
The One ◽  
The Universe

The tensions concerning the values of Hubble constant obtained from the early and the late Universe data pose a significant challenge to modern cosmology. Possible modifications of the flat homogeneous isotropic cosmological ΛCDM model are considered, in which the Universe contains the dark energy, cold baryonic matter, and dark matter. They are based on general relativity and satisfy two requirements: (1) the value of the Hubble constant calculated from the value of the Hubble parameter at the recombination by formulas of the flat ΛCDM model, should be equal to 92% of the one based on low-redshift observations; (2) deviations from the ΛCDM model should not lead to effects that contradict astronomical observations and estimations obtained thereof. The analysis showed that there are few opportunities for the choice. Either we should consider DM with negative pressure −pdmc2 ≪ pdm < 0, which weakly affects the evolution of the Universe and the observed manifestations of DM, or we should admit the mechanism of generation of new matter, for example, by the dark energy decay.

scholarly journals Clustering and halo abundances in early dark energy cosmological models

2021 ◽  
Vol 504 (1) ◽  
pp. 769-781
Author(s):  
Anatoly Klypin ◽  
Vivian Poulin ◽  
Francisco Prada ◽  
Joel Primack ◽  
Marc Kamionkowski ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Power Spectra ◽  
Hubble Constant ◽  
Cosmological Models ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Linear Evolution ◽  
James Webb Space Telescope ◽  
Non Linear

ABSTRACT Cold Dark Matter with cosmological constant (ΛCDM) cosmological models with early dark energy (EDE) have been proposed to resolve tensions between the Hubble constant $H_0=100\, h$ km ṡ−1Ṁpc−1 measured locally, giving h ≈ 0.73, and H0 deduced from Planck cosmic microwave background (CMB) and other early-Universe measurements plus ΛCDM, giving h ≈ 0.67. EDE models do this by adding a scalar field that temporarily adds dark energy equal to about 10 per cent of the cosmological energy density at the end of the radiation-dominated era at redshift z ∼ 3500. Here, we compare linear and non-linear predictions of a Planck-normalized ΛCDM model including EDE giving h = 0.728 with those of standard Planck-normalized ΛCDM with h = 0.678. We find that non-linear evolution reduces the differences between power spectra of fluctuations at low redshifts. As a result, at z = 0 the halo mass functions on galactic scales are nearly the same, with differences only 1–2 per cent. However, the differences dramatically increase at high redshifts. The EDE model predicts 50 per cent more massive clusters at z = 1 and twice more galaxy-mass haloes at z = 4. Even greater increases in abundances of galaxy-mass haloes at higher redshifts may make it easier to reionize the universe with EDE. Predicted galaxy abundances and clustering will soon be tested by the James Webb Space Telescope (JWST) observations. Positions of baryonic acoustic oscillations (BAOs) and correlation functions differ by about 2 per cent between the models – an effect that is not washed out by non-linearities. Both standard ΛCDM and the EDE model studied here agree well with presently available acoustic-scale observations, but the Dark Energy Spectroscopic Instrument and Euclid measurements will provide stringent new tests.

scholarly journals A common explanation of the Hubble tension and anomalous cold spots in the CMB

2020 ◽  
Vol 499 (1) ◽  
pp. 320-333
Author(s):  
A Kovács ◽  
R Beck ◽  
I Szapudi ◽  
I Csabai ◽  
G Rácz ◽  
...  
Keyword(s):  
Dark Energy ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Hubble Constant ◽  
Cold Spot ◽  
Microwave Background ◽  
Spot Area ◽  
Dark Energy Component ◽  
Repeated Observation ◽  
Temperature Maps

ABSTRACT The standard cosmological paradigm narrates a reassuring story of a universe currently dominated by an enigmatic dark energy component. Disquietingly, its universal explaining power has recently been challenged by, above all, the ∼4σ tension in the values of the Hubble constant. Another, less studied anomaly is the repeated observation of integrated Sachs–Wolfe (ISW) imprints ∼5× stronger than expected in the Lambda cold dark matter (ΛCDM) model from $R_{\rm v}\gtrsim 100\,\rm {\mathit{ h}^{-1}Mpc }$ superstructures. Here, we show that the inhomogeneous AvERA (Average Expansion Rate Approximation) model of emerging curvature is capable of telling a plausible albeit radically different story that explains both observational anomalies without dark energy. We demonstrate that while stacked imprints of $R_{\rm v}\gtrsim 100\,\rm {\mathit{ h}^{-1}Mpc }$ supervoids in cosmic microwave background (CMB) temperature maps can discriminate between the AvERA and ΛCDM models, their characteristic differences may remain hidden using alternative void definitions and stacking methodologies. Testing the extremes, we then also show that the CMB Cold Spot can plausibly be explained in the AvERA model as an ISW imprint. The coldest spot in the AvERA map is aligned with multiple low-z supervoids with $R_{\rm v}\gtrsim 100\,\rm {\mathit{ h}^{-1}Mpc }$ and central underdensity δ0 ≈ −0.3, resembling the observed large-scale galaxy density field in the Cold Spot area. We hence conclude that the anomalous imprint of supervoids may well be the canary in the coal mine, and existing observational evidence for dark energy should be reinterpreted to further test alternative models.

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