📄 Five-Year Wilkinson Microwave Anisotropy Probe Observations: Cosmolog…

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Komatsu, E. et al. (2009) · The Astrophysical Journal Supplement Series
Reads: 337 · Citations: 5408
DOI: 10.1088/0067-0049/180/2/330

🔗 https://ui.adsabs.harvard.edu/abs/2009ApJS..180..330K/abstract

#Astronomy #Astrophysics #Cosmology #CosmicMicrowaveBackground #CosmologyObservations

Five-Year Wilkinson Microwave Anisotropy Probe Observations: Cosmological Interpretation

The Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data provide stringent limits on deviations from the minimal, six-parameter Λ cold dark matter model. We report these limits and use them to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature. We also constrain models of dark energy via its equation of state, parity-violating interaction, and neutrino properties, such as mass and the number of species. We detect no convincing deviations from the minimal model. The six parameters and the corresponding 68% uncertainties, derived from the WMAP data combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO) in the distribution of galaxies, are: Ω<SUB> b </SUB> h <SUP>2</SUP> = 0.02267<SUP>+0.00058</SUP> <SUB>-0.00059</SUB>, Ω<SUB> c </SUB> h <SUP>2</SUP> = 0.1131 ± 0.0034, Ω<SUB>Λ</SUB> = 0.726 ± 0.015, n<SUB>s</SUB> = 0.960 ± 0.013, τ = 0.084 ± 0.016, and Δ_{R}^2 = (2.445± 0.096)× 10^{-9} at k = 0.002 Mpc<SUP>-1</SUP>. From these, we derive σ<SUB>8</SUB> = 0.812 ± 0.026, H <SUB>0</SUB> = 70.5 ± 1.3 km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, Ω<SUB> b </SUB> = 0.0456 ± 0.0015, Ω<SUB> c </SUB> = 0.228 ± 0.013, Ω<SUB> m </SUB> h <SUP>2</SUP> = 0.1358<SUP>+0.0037</SUP> <SUB>-0.0036</SUB>, z <SUB>reion</SUB> = 10.9 ± 1.4, and t <SUB>0</SUB> = 13.72 ± 0.12 Gyr. With the WMAP data combined with BAO and SN, we find the limit on the tensor-to-scalar ratio of r < 0.22(95%CL), and that n<SUB>s</SUB> > 1 is disfavored even when gravitational waves are included, which constrains the models of inflation that can produce significant gravitational waves, such as chaotic or power-law inflation models, or a blue spectrum, such as hybrid inflation models. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and the spatial curvature of the universe: -0.14 < 1 + w < 0.12(95%CL) and -0.0179 < Ω<SUB> k </SUB> < 0.0081(95%CL). We provide a set of "WMAP distance priors," to test a variety of dark energy models with spatial curvature. We test a time-dependent w with a present value constrained as -0.33 < 1 + w <SUB>0</SUB> < 0.21 (95% CL). Temperature and dark matter fluctuations are found to obey the adiabatic relation to within 8.9% and 2.1% for the axion-type and curvaton-type dark matter, respectively. The power spectra of TB and EB correlations constrain a parity-violating interaction, which rotates the polarization angle and converts E to B. The polarization angle could not be rotated more than -5fdg9 < Δα < 2fdg4 (95% CL) between the decoupling and the present epoch. We find the limit on the total mass of massive neutrinos of ∑m <SUB>ν</SUB> < 0.67 eV(95%CL), which is free from the uncertainty in the normalization of the large-scale structure data. The number of relativistic degrees of freedom (dof), expressed in units of the effective number of neutrino species, is constrained as N <SUB>eff</SUB> = 4.4 ± 1.5 (68%), consistent with the standard value of 3.04. Finally, quantitative limits on physically-motivated primordial non-Gaussianity parameters are -9 < f <SUP>local</SUP> <SUB>NL</SUB> < 111 (95% CL) and -151 < f <SUP>equil</SUP> <SUB>NL</SUB> < 253 (95% CL) for the local and equilateral models, respectively. <P />WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.

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📄 Measurements of Ω and Λ from 42 High-Redshift Supernovae

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Perlmutter, S. et al. (1999) · The Astrophysical Journal
Reads: 910 · Citations: 16874
DOI: 10.1086/307221

🔗 https://ui.adsabs.harvard.edu/abs/1999ApJ...517..565P/abstract

#Astronomy #Astrophysics #Cosmology #CosmologyObservations #CosmologyDistanceScale

Measurements of Ω and Λ from 42 High-Redshift Supernovae

We report measurements of the mass density, Ω<SUB>M</SUB>, and cosmological-constant energy density, Ω<SUB>Λ</SUB>, of the universe based on the analysis of 42 type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these supernovae, at redshifts between 0.18 and 0.83, are fitted jointly with a set of supernovae from the Calán/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All supernova peak magnitudes are standardized using a SN Ia light-curve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8Ω<SUB>M</SUB>-0.6Ω<SUB>Λ</SUB>~-0.2+/-0.1 in the region of interest (Ω<SUB>M</SUB><~1.5). For a flat (Ω<SUB>M</SUB>+Ω<SUB>Λ</SUB>=1) cosmology we find Ω<SUP>flat</SUP><SUB>M</SUB>=0.28<SUP>+0.09</SUP><SUB>-0.08</SUB> (1 σ statistical) <SUP>+0.05</SUP><SUB>-0.04</SUB> (identified systematics). The data are strongly inconsistent with a Λ=0 flat cosmology, the simplest inflationary universe model. An open, Λ=0 cosmology also does not fit the data well: the data indicate that the cosmological constant is nonzero and positive, with a confidence of P(Λ>0)=99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t<SUP>flat</SUP><SUB>0</SUB>=14.9<SUP>+1.4</SUP><SUB>-1.1</SUB>(0.63/h) Gyr for a flat cosmology. The size of our sample allows us to perform a variety of statistical tests to check for possible systematic errors and biases. We find no significant differences in either the host reddening distribution or Malmquist bias between the low-redshift Calán/Tololo sample and our high-redshift sample. Excluding those few supernovae that are outliers in color excess or fit residual does not significantly change the results. The conclusions are also robust whether or not a width-luminosity relation is used to standardize the supernova peak magnitudes. We discuss and constrain, where possible, hypothetical alternatives to a cosmological constant.

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📄 Nine-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: C…

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Hinshaw, G. et al. (2013) · The Astrophysical Journal Supplement Series
Reads: 483 · Citations: 5494
DOI: 10.1088/0067-0049/208/2/19

🔗 https://ui.adsabs.harvard.edu/abs/2013ApJS..208...19H/abstract

#Astronomy #Astrophysics #Cosmology #CosmicBackgroundRadiation #CosmologyObservations

Nine-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results

We present cosmological parameter constraints based on the final nine-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in conjunction with a number of additional cosmological data sets. The WMAP data alone, and in combination, continue to be remarkably well fit by a six-parameter ΛCDM model. When WMAP data are combined with measurements of the high-l cosmic microwave background anisotropy, the baryon acoustic oscillation scale, and the Hubble constant, the matter and energy densities, Ω<SUB> b </SUB> h <SUP>2</SUP>, Ω<SUB> c </SUB> h <SUP>2</SUP>, and Ω<SUB>Λ</SUB>, are each determined to a precision of ~1.5%. The amplitude of the primordial spectrum is measured to within 3%, and there is now evidence for a tilt in the primordial spectrum at the 5σ level, confirming the first detection of tilt based on the five-year WMAP data. At the end of the WMAP mission, the nine-year data decrease the allowable volume of the six-dimensional ΛCDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their ΛCDM parameter fits are consistent. New limits on deviations from the six-parameter model are presented, for example: the fractional contribution of tensor modes is limited to r < 0.13 (95% CL); the spatial curvature parameter is limited to \Omega _k = -0.0027^{+ 0.0039}_{- 0.0038}; the summed mass of neutrinos is limited to ∑m <SUB>ν</SUB> < 0.44 eV (95% CL); and the number of relativistic species is found to lie within N <SUB>eff</SUB> = 3.84 ± 0.40, when the full data are analyzed. The joint constraint on N <SUB>eff</SUB> and the primordial helium abundance, Y <SUB>He</SUB>, agrees with the prediction of standard big bang nucleosynthesis. We compare recent Planck measurements of the Sunyaev-Zel'dovich effect with our seven-year measurements, and show their mutual agreement. Our analysis of the polarization pattern around temperature extrema is updated. This confirms a fundamental prediction of the standard cosmological model and provides a striking illustration of acoustic oscillations and adiabatic initial conditions in the early universe.

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📄 Observational Evidence from Supernovae for an Accelerating Universe a…

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Riess, Adam G. et al. (1998) · The Astronomical Journal
Reads: 1212 · Citations: 17644
DOI: 10.1086/300499

🔗 https://ui.adsabs.harvard.edu/abs/1998AJ....116.1009R/abstract

#Astronomy #Astrophysics #Cosmology #CosmologyObservations #StarsSupernovaeGeneral

Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant

We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 <= z <= 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift supernovae and a set of 34 nearby supernovae are used to place constraints on the following cosmological parameters: the Hubble constant (H_0), the mass density (Omega_M), the cosmological constant (i.e., the vacuum energy density, Omega_Lambda), the deceleration parameter (q_0), and the dynamical age of the universe (t_0). The distances of the high-redshift SNe Ia are, on average, 10%-15% farther than expected in a low mass density (Omega_M = 0.2) universe without a cosmological constant. Different light curve fitting methods, SN Ia subsamples, and prior constraints unanimously favor eternally expanding models with positive cosmological constant (i.e., Omega_Lambda > 0) and a current acceleration of the expansion (i.e., q_0 < 0). With no prior constraint on mass density other than Omega_M >= 0, the spectroscopically confirmed SNe Ia are statistically consistent with q_0 < 0 at the 2.8 sigma and 3.9 sigma confidence levels, and with Omega_Lambda > 0 at the 3.0 sigma and 4.0 sigma confidence levels, for two different fitting methods, respectively. Fixing a ``minimal'' mass density, Omega_M = 0.2, results in the weakest detection, Omega_Lambda > 0 at the 3.0 sigma confidence level from one of the two methods. For a flat universe prior (Omega_M + Omega_Lambda = 1), the spectroscopically confirmed SNe Ia require Omega_Lambda > 0 at 7 sigma and 9 sigma formal statistical significance for the two different fitting methods. A universe closed by ordinary matter (i.e., Omega_M = 1) is formally ruled out at the 7 sigma to 8 sigma confidence level for the two different fitting methods. We estimate the dynamical age of the universe to be 14.2 +/- 1.7 Gyr including systematic uncertainties in the current Cepheid distance scale. We estimate the likely effect of several sources of systematic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these effects appear to reconcile the data with Omega_Lambda = 0 and q_0 >= 0.

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📄 Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: …

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Komatsu, E. et al. (2011) · The Astrophysical Journal Supplement Series
Reads: 451 · Citations: 8297
DOI: 10.1088/0067-0049/192/2/18

🔗 https://ui.adsabs.harvard.edu/abs/2011ApJS..192...18K/abstract

#Astronomy #Astrophysics #Cosmology #CosmicBackgroundRadiation #CosmologyObservations

Seven-year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation

The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H <SUB>0</SUB>) measurement, we determine the parameters of the simplest six-parameter ΛCDM model. The power-law index of the primordial power spectrum is n<SUB>s</SUB> = 0.968 ± 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison-Zel'dovich-Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, ∑m <SUB>ν</SUB> < 0.58 eV(95%CL), and the effective number of neutrino species, N <SUB>eff</SUB> = 4.34<SUP>+0.86</SUP> <SUB>-0.88</SUB> (68% CL), which benefit from better determinations of the third peak and H <SUB>0</SUB>. The limit on a constant dark energy equation of state parameter from WMAP+BAO+H <SUB>0</SUB>, without high-redshift Type Ia supernovae, is w = -1.10 ± 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Y<SUB>p</SUB> = 0.326 ± 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature-E-mode polarization cross power spectrum at 21σ, compared with 13σ from the five-year data. With the seven-year temperature-B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to Δ α =-1.1± 1.4° statistical ± 1.5 systematic (68% CL). We report significant detections of the Sunyaev-Zel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5-0.7 times the predictions from "universal profile" of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration. <P />WMAP is the result of a partnership between Princeton University and NASA's Goddard Space Flight Center. Scientific guidance is provided by the WMAP Science Team.

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