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NASA NTRS2013

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 Lambda-CDM 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 Omega(sub b)h(exp 2), Omega(sub c)h(exp 2)and Omega(sub Lambda), are each determined to a precision of approx. 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 5 sigma 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 Lambda-CDM parameter space by a factor of 68,000 relative to pre-WMAP measurements. We investigate a number of data combinations and show that their Lambda-CDM 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(sub kappa) = (0.0027 (sub +0.0039) (sup −0.0038;) the summed mass of neutrinos is limited to Sigma M(sub nu) < 0.44 eV (95% CL); and the number of relativistic species is found to lie within N(sub eff) = 3.84 +/- 0+/-40, when the full data are analyzed. The joint constraint on N(sub eff) and the primordial helium abundance, Y(sub He), 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.

cosmology↗

NASA NTRS1982

Observational tests of Baryon symmetric cosmology

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of pi(0)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the amma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurement of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed.

Stecker, F. W.↗

NASA NTRS1983

Observational tests of baryon symmetric cosmology

Observational evidence for Baryon symmetric (matter/antimatter) cosmology and future observational tests are reviewed. The most significant consequences of Baryon symmetric cosmology lie in the prediction of an observable cosmic background of gamma radiation from the decay of Pi(O)-mesons produced in nucleon-antinucleon annihilations. Equations for the prediction of the gamma ray background spectrum for the case of high redshifts are presented. The theoretical and observational plots of the background spectrum are shown to be in good agreement. Measurements of cosmic ray antiprotons and the use of high energy neutrino astronomy to look for antimatter elsewhere in the universe are also addressed. Previously announced in STAR as N83-10996

Stecker, F. W.↗

NASA NTRS1974

Confrontation of Lemaitre models and the cosmological constant with observations

The history of the cosmological constant and the Lemaitre models is reviewed briefly. Using recent cosmological observations, it is found that the cosmological constant if nonzero must be in absolute value less than 2 times 10 to the negative 56th power per sq cm. The predictions of the Lemaitre models are compared with modern observations. It is shown that Lemaitre models without evolution fail to reproduce the observed radio source counts. The existence of quasars with large redshift (z greater than 2.5) is shown to be strong evidence against the Lemaitre models.

Petrosian, V.↗

NASA NTRS1994

Testing the gravitational instability hypothesis?

We challenge a widely accepted assumption of observational cosmology: that successful reconstruction of observed galaxy density fields from measured galaxy velocity fields (or vice versa), using the methods of gravitational instability theory, implies that the observed large-scale structures and large-scale flows were produced by the action of gravity. This assumption is false, in that there exist nongravitational theories that pass the reconstruction tests and gravitational theories with certain forms of biased galaxy formation that fail them. Gravitational instability theory predicts specific correlations between large-scale velocity and mass density fields, but the same correlations arise in any model where (a) structures in the galaxy distribution grow from homogeneous initial conditions in a way that satisfies the continuity equation, and (b) the present-day velocity field is irrotational and proportional to the time-averaged velocity field. We demonstrate these assertions using analytical arguments and N-body simulations. If large-scale structure is formed by gravitational instability, then the ratio of the galaxy density contrast to the divergence of the velocity field yields an estimate of the density parameter Omega (or, more generally, an estimate of beta identically equal to Omega(exp 0.6)/b, where b is an assumed constant of proportionality between galaxy and mass density fluctuations. In nongravitational scenarios, the values of Omega or beta estimated in this way may fail to represent the true cosmological values. However, even if nongravitational forces initiate and shape the growth of structure, gravitationally induced accelerations can dominate the velocity field at late times, long after the action of any nongravitational impulses. The estimated beta approaches the true value in such cases, and in our numerical simulations the estimated beta values are reasonably accurate for both gravitational and nongravitational models. Reconstruction tests that show correlations between galaxy density and velocity fields can rule out some physically interesting models of large-scale structure. In particular, successful reconstructions constrain the nature of any bias between the galaxy and mass distributions, since processes that modulate the efficiency of galaxy formation on large scales in a way that violates the continuity equation also produce a mismatch between the observed galaxy density and the density inferred from the peculiar velocity field. We obtain successful reconstructions for a gravitational model with peaks biasing, but we also show examples of gravitational and nongravitational models that fail reconstruction tests because of more complicated modulations of galaxy formation.

Babul, Arif↗

NASA NTRS1990

Cosmology from the moon

The effective investigation of observational cosmological parameters is considered with attention given to the shielding provided by the lunar environment. The present measurements of the microwave and IR backgrounds are discussed, and reference is given to IR, microwave, and X- and gamma-ray investigations away from the earth to protect from terrestrial interferences. The most promising lunar investigations of cosmology are found to be studies of the microwave background and the X-ray and gamma-ray backgrounds from a hole in the lunar surface of 10 meters in depth.

Mather, John C.↗

NASA NTRS1991

The best-fit universe

Inflation provides very strong motivation for a flat Universe, Harrison-Zel'dovich (constant-curvature) perturbations, and cold dark matter. However, there are a number of cosmological observations that conflict with the predictions of the simplest such model: one with zero cosmological constant. They include the age of the Universe, dynamical determinations of Omega, galaxy-number counts, and the apparent abundance of large-scale structure in the Universe. While the discrepancies are not yet serious enough to rule out the simplest and most well motivated model, the current data point to a best-fit model with the following parameters: Omega(sub B) approximately equal to 0.03, Omega(sub CDM) approximately equal to 0.17, Omega(sub Lambda) approximately equal to 0.8, and H(sub 0) approximately equal to 70 km/(sec x Mpc) which improves significantly the concordance with observations. While there is no good reason to expect such a value for the cosmological constant, there is no physical principle that would rule out such.

Turner, Michael S.↗

NASA NTRS2004

Space-Based Gravitational-Wave Observations as Tools for Testing General Relativity

We continued a project, to analyse the ways in which detection and study of gravitational waves could provide quantitative tests of general relativity, with particular emphasis on waves that would be detectable by space-based observatories, such as LISA. This work had three foci: 1) Tests of scalar-tensor theories of gravity that, could be done by analyzing gravitational waves from neutron stars inspiralling into massive black holes, as detectable by LISA; 2) Study of alternative theories of gravity in which the graviton could be massive, and of how gravitational-wave observations by space-based detectors, solar-system tests, and cosmological observations could constrain such theories; and 3) Study of gravitational-radiation back reaction of particles orbiting black holes in general relativity, with emphasis on the effects of spin.

Will, Clifford M.↗

NASA NTRS1983

CCD photometry of Abell clusters. II - Surface photometry of 249 cluster galaxies

The luminosity of the brightest cluster galaxies remains the best standard candle for observational cosmology. Studies of over 250 relatively nearby clusters show that the luminosity of these objects within an aperture of constant metric diameter has a dispersion of only 0.35 mag. The observations considered by Schneider et al. (1983) were acquired to measure the aperture luminosities of the brightest cluster galaxies. However, the data base, because of its high signal-to-noise ratio and large spatial coverage, allows several other investigations to be performed. In the present investigation, surface photometry of the brightness three galaxies within approximately 250 kpc of the cluster center is presented, taking into account the cores of 83 Abell clusters. The relevance of the photometry to cosmological studies is also discussed. It is found that dynamical friction does play an extremely important role in determining properties of brightest cluster galaxies and cluster morphology.

Schneider, D. P.↗

NASA NTRS2013

Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results

We present the final nine-year maps and basic results from the Wilkinson Microwave Anisotropy Probe (WMAP) mission. The full nine-year analysis of the time-ordered data provides updated characterizations and calibrations of the experiment. We also provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate cosmic microwave background (CMB) anisotropy from foreground emission, and both types of signals are analyzed in detail.We provide new point source catalogs as well as new diffuse and point source foreground masks. An updated template-removal process is used for cosmological analysis; new foreground fits are performed, and new foreground reduced are presented.We nowimplement an optimal C(exp -1)1 weighting to compute the temperature angular power spectrum. The WMAP mission has resulted in a highly constrained Lambda-CDM cosmological model with precise and accurate parameters in agreement with a host of other cosmological measurements. When WMAP data are combined with finer scale CMB, baryon acoustic oscillation, and Hubble constant measurements, we find that big bang nucleosynthesis is well supported and there is no compelling evidence for a non-standard number of neutrino species (N(sub eff) = 3.84 +/- 0.40). The model fit also implies that the age of the universe is (sub 0) = 13.772 +/- 0.059 Gyr, and the fit Hubble constant is H(sub 0) = 69.32 +/- 0.80 km/s/ Mpc. Inflation is also supported: the fluctuations are adiabatic, with Gaussian random phases; the detection of a deviation of the scalar spectral index from unity, reported earlier by the WMAP team, now has high statistical significance (n(sub s) = 0.9608+/-0.0080); and the universe is close to flat/Euclidean (Omega = −0.0027+0.0039/−0.0038). Overall, the WMAP mission has resulted in a reduction of the cosmological parameter volume by a factor of 68,000 for the standard six-parameter Lambda-CDM model, based on CMB data alone. For a model including tensors, the allowed seven-parameter volume has been reduced by a factor 117,000. Other cosmological observations are in accord with the CMB predictions, and the combined data reduces the cosmological parameter volume even further.With no significant anomalies and an adequate goodness of fit, the inflationary flat Lambda-CDM model and its precise and accurate parameters rooted in WMAP data stands as the standard model of cosmology.

dark matter↗

NASA NTRS2011

The Beginning and End of the Universe

Cosmology is the scientific study of how the Universe began more than 13 billion years ago, how its properties have changed from that time to the present, and what its eventual fate might be. Observational cosmology uses telescopes like the Hubble to reach back in time to find the faint echoes of the Big Bang. In this lecture, I will give an overview of cosmology, highlighting the very rapid progress this field has made in the last decade, and the role that NASA space telescopes have played and will continue to play in the years to come. I will then focus on two of the most intriguing of those recent discoveries: inflation and dark energy. Our universe began in an extremely rapid accelerated expansion, called inflation, which removed all traces anything that may have existed before, flattened the geometry of space-time, and turned microscopic quantum fluctuations into the largest structures in the universe. At the present time, more than 70% of the mass-energy in the Universe consists of a mysterious substance called dark energy. The dark energy causes the expansion of the Universe to accelerate, and he will discuss the ways that we might be able to measure that acceleration more accurately, revealing the nature of the dark energy and learning the eventual fate of the Universe.

Gardner, Jonathan P.↗

NASA NTRS2012

The Beginning and End of the Universe

Gardner, Jonathan P.↗

NASA NTRS2007

The Beginning and End of the Universe

Cosmology is the scientific study of how the Universe began more than 13 billion years ago, how its properties have changed, and what its future might be. The balance of forces and energy cause the Universe to expand, first accelerating, then decelerating and then accelerating again. Within this overall structure, the interplay of atoms and light with the mysterious dark matter and dark energy causes stars and galaxies to form and evolve, leading to galaxies like our own home, the Milky Way. Observational cosmology uses telescopes on Earth and in space to reach back in time to find the faint remaining echoes of the Big Bang and to trace the formation and evolution of the galaxies and structures that fill the Universe. In this lecture, Dr. Gardner will give an overview of cosmology, outlining the 13-billion year history of the Universe, and highlighting the very rapid progress this field has made in the last decade. He will discuss the role that NASA space telescopes have played in this progress and will continue to play in the years to come. He will give a time-based history of the Universe, discussing the successive processes that formed matter, particles, atoms, stars and galaxies. In particular, he will focus on cosmological inflation, the rapid accelerated expansion that marks the beginning of the Universe, and dark energy, a tenuous substance that overcomes gravity and whose properties will determine its final fate.

Gardner, Jonathan P.↗

NASA NTRS2008

The Beginning and End of the Universe

Cosmology is the scientific study of how the Universe began more than 13 billion years ago, how its properties have changed, and what its future might be. The balance of forces and energy cause the Universe to expand, first accelerating, then decelerating and then accelerating again. Within this overall structure, the interplay of atoms and light with the mysterious dark matter and dark energy causes stars and galaxies to form and evolve, leading to galaxies like our own home, the Milky Way. Observational cosmology uses telescopes on Earth and in space to reach back in time to find the faint remaining echoes of the Big Bang and to trace the formation and evolution of the galaxies and structures that fill the Universe. In this lecture, Dr. Gradner will give an overview of cosmology, outlining the 13-billion year history of the Universe, and highlighting the very rapid progress this field has made i the last decade. He will discuss the role that NASA space telescopes have played in this progress and wil continue to play in the years to come. He will give a time-based history of the Universe, discussing the successive processes that formed matter, particles, atoms, stars and galaxies. In particular, he will focus on cosmological inflation, the rapid accelerated expansion that marks the beginning of the Universe, and dark energy, a tenuous substance that overcomes gravity and whose properties will determine its final fate.

Gardner, Jonathan↗

NASA NTRS1985

Discovery of a probable galaxy with a redshift of 3.218

The discovery of a narrow emission line object, probably a galaxy, with a redshift of 3.218, is reported. The object is a companion to the quasar PKS 1614 + 051, which is at a redshift of 3.209. This is the most distant non-QSO, nongravitationally lensed object presently known by a large margin. Its properties are consistent with those expected of a high-redshift galaxy. This object has an age of only a few percent of the present age of the universe. The object was discovered with a novel technique, which promises to push studies of distant galaxies to redshifts as high as those of the most distant quasars known, and which may eventually lead to the discovery of primeval galaxies. This discovery opens the way for studies of galaxies beyond redshift three, which should prove invaluable for observational cosmology.

Djorgovski, S.↗

NASA NTRS1989

A coasting cosmology

A Friedmann-Robertson-Walker cosmology with energy density decreasing in expansion as 1/R-squared, where R is the Robertson-Walker scale factor, is studied. In such a model the universe expands with constant velocity; hence the term coasting cosmology. Observational consequences of such a model include the age of the universe, the luminosity distance-redshift relation (the Hubble diagram), the angular diameter distance-redshift relation, and the galaxy number count as a function of redshift. These observations are used to limit the parameters of the model. Among the interesting consequences of the model are the possibility of an ever-expanding closed universe, a model universe with multiple images at different redshifts of the same object, a universe with Omega - 1 not equal to 0 stable in expansion, and a closed universe with radius smaller than 1/H(0).

Kolb, Edward W.↗

NASA NTRS1990

Astrophysics and cosmology closing in on neutrino masses

Massive neutrinos are expected in most grand unified theories that attempt to unify the strong and electroweak interactions. So far, heroic laboratory experiments have yielded only upper bounds on the masses of the elusive neutrinos. These bounds, however, are not very restrictive and cannot even exclude the possibility that the dark matter in the universe consists of neutrinos. The astrophysical and cosmological bounds on the masses of the muon and tau neutrinos, m(nu sub mu) and m(nu sub tau), which already are much more restrictive than the laboratory bounds, and the laboratory bound on the mass of the electron neutrino, m(nu sub e) can be improved significantly by future astrophysical and cosmological observations that perhaps will pin down the neutrino masses. Indeed, the recent results from the solar neutrino experiments combined with the seesaw mechanism for generating neutrino masses suggest that m(nu sub e) of about 10 to the -8th electron volts, m(nu sub mu) of about 0.001 electron volts, and m(nu sub tau) of about 10 electron volts, which can be tested in the near future by solar neutrino and accelerator experiments.

Dar, Arnon↗

NASA NTRS1992

Visualizing the universe, part 2

It is now possible to create animated views of the universe that are realistic, physically relevant, and breathtaking. To demonstrate the point, we describe our efforts to navigate the CfA redshift survey. For our project, we selected several CCD images of spiral and elliptical galaxies, and placed them at their observed positions in redshift space. We demonstrate how, by choreographing aesthetically pleasing trajectories, we are able to develop our own and the viewer's intuition about the large-scale structures found in the CfA redshift survey. We show for instance that three-dimensional motion enhances significantly our perception of voids and sheets in the distribution of galaxies. Such sophistication happily has become possible with the 'coming of age' of observational cosmology, as data have grown to drive the field.

Falco, Emilio E.↗