Observations Of Cosmic Microwave Background Anisotropies Research Articles

Comparing inflationary models in extended Metric-Affine theories of gravity

We study slow-roll inflation as a common feature in Metric-affine Theories of Gravity. In particular, we take into account extended metric, teleparallel and symmetric-teleparallel theories of gravity, based on different geometric invariants, discussing analogies and differences. The analysis for each model is performed in two approaches. First, we focus on the potential-slow-roll approach by studying the reconstructed potentials for different forms of the extended models related to the considered gravitational theory in the Einstein frame. Secondly, we investigate the Hubble-slow-roll approach for some conventional inflationary potentials related to the specific extended model in the Jordan frame. We compare all results with cosmic microwave background anisotropy observations coming from Planck 2018 and BICEP2/Keck array satellites in order to find the observational constraints on the parameters space of the models as well as their prediction from the spectral parameters. Eventually, we attempt to present a qualitative comparison between three classes of considered modified gravities using the obtained inflationary results. The aim is to select, in principle, cosmological signatures capable of discriminating among concurrent models in view to point out the representation of gravity, according with geometric invariants, which better addresses the early universe dynamics.

First study of reionization in the Planck 2015 normalized closed ΛCDM inflation model

We study reionization in two non-flat $\Lambda$CDM inflation models that best fit the Planck 2015 cosmic microwave background anisotropy observations, ignoring or in conjunction with baryon acoustic oscillation distance measurements. We implement a principal component analysis (PCA) to estimate the uncertainties in the reionization history from a joint quasar-CMB dataset. A thorough Markov Chain Monte Carlo analysis is done over the parameter space of PCA modes for both non-flat $\Lambda$CDM inflation models as well as the original Planck 2016 tilted, spatially-flat $\Lambda$CDM inflation model. Although both flat and non-flat models can closely match the low-redshift ($z\lesssim6$) observations, we notice a possible tension between high-redshift ($z\sim8$) Lyman-$\alpha$ emitter data and the non-flat models. This is solely due to the fact that the closed models have a relatively higher reionization optical depth compared to the flat one, which in turn demands more high-redshift ionizing sources and favors an extended reionization starting as early as $z\approx14$. We conclude that as opposed to flat-cosmology, for the non-flat cosmology models (i) the escape fraction needs steep redshift evolution and even unrealistically high values at some redshifts and (ii) most of the physical parameters require to have non-monotonic redshift evolution, especially apparent when Lyman-$\alpha$ emitter data is included in the analysis.

An introduction to the Planck mission

The Cosmic Microwave Background (CMB) is the oldest light in the universe. It is seen today as black body radiation at a near-uniform temperature of 2.73 K covering the entire sky. This radiation field is not perfectly uniform, but includes within it temperature anisotropies of order . Physical processes in the early universe have left their fingerprints in these CMB anisotropies, which later grew to become the galaxies and large scale structure we see today. CMB anisotropy observations are thus a key tool for cosmology. The Planck mission was the European Space Agency’s probe of the CMB. Its unique design allowed CMB anisotropies to be measured to greater precision over a wider range of scales than ever before. This article provides an introduction to the Planck mission, including its goals and motivation, its instrumentation and technology, the physics of the CMB, how the contaminating astrophysical foregrounds were overcome, and the key cosmological results that this mission has so far produced.

PRIMORDIAL GRAVITATIONAL WAVES AND INFLATION: POSSIBILITIES FOR DETECTION

The curl-modes of Cosmic Microwave Background (CMB) polarization probe horizon-scale primordial gravitational waves related to inflation. A significant source of confusion is expected from a lensing conversion of polarization related to density perturbations to the curl mode, during the propagation of photons through the large scale structure. Either high resolution CMB anisotropy observations or 21 cm fluctuations at redshifts 30 and higher can be used to delens polarization data and to separate gravitational-wave polarization signature from that of cosmic-shear related signal. Separations based on proposed lensing reconstruction techniques for reasonable future experiments allow the possibility to probe inflationary energy scales down to 1015GeV . Beyond CMB polarization, at frequencies between 0.01 Hz to 1 Hz, space-based laser interferometers can also be used to probe the inflationary gravitational wave background. The confusion here is related to the removal of merging neutron star binaries at cosmological distances. Given the low merger rate and the rapid evolution of the gravitational wave frequency across this band, reliable removal techniques can be constructed. We discuss issues related to joint constraints that can be placed on the inflationary models based on CMB polarization information and space-based interferometers such as the Big Bang Observer.

Effects of cosmological magnetic helicity on the cosmic microwave background

Cosmological magnetic fields induce temperature and polarization fluctuations in the cosmic microwave background (CMB) radiation. A cosmological magnetic field with current amplitude of order 10{sup -9} G is detectable via observations of CMB anisotropies. This magnetic field (with or without helicity) generates vector perturbations through vortical motions of the primordial plasma. This paper shows that magnetic field helicity induces parity-odd cross correlations between CMB temperature and B-polarization fluctuations and between E- and B-polarization fluctuations, correlations which are zero for fields with no helicity (or for any parity-invariant source). Helical fields also contribute to parity-even temperature and polarization anisotropies, canceling part of the contribution from the symmetric component of the magnetic field. We give analytic approximations for all CMB temperature and polarization anisotropy vector power spectra due to helical magnetic fields. These power spectra offer a method for detecting cosmological helical magnetic fields, particularly when combined with Faraday rotation measurements which are insensitive to helicity.

Polarized CMB: Reionization and Primordial Tensor Modes

We discuss upcoming opportunities with cosmic microwave background (CMB) observations during the post-WMAP era. The curl-modes of CMB polarization probe inflationary gravitational waves (IGWs). While a significant source of confusion is expected from cosmic shear conversion of polarization related to density perturbations, higher resolution observations of CMB anisotropies can be used for a lensing reconstruction and to separate gravitational-wave polarization signature from that of lensing. Separations based on current lensing reconstruction techniques allow the possibility to probe inflationary energy scales below 1015GeV in a range that includes grand unified theories. The observational detection of primordial curl-modes is aided by rescattering at late times during the reionized epoch with optical depth to electron scattering at the level of 0.1 and above. An improved measurement of this optical depth is useful to optimize experimental parameters of a post-WMAP mission attempting to target the IGW background.

Trade-off between angular resolution and straylight contamination in the PLANCK Low Frequency Instrument

The study of cosmic microwave background (CMB) anisotropies represents one of the most powerful cosmological tools. After the great success of the two NASA satellite missions COBE and WMAP, PLANCK is the third generation of mm-wave instruments designed for space observations of CMB anisotropies within the new Cosmic Vision 2020 ESA Science Programme. PLANCK will map the whole sky with unprecedented sensitivity, angular resolution and frequency coverage, using two instruments that share the focal region of a 1.5 m off-axis dual reflector telescope: the Low Frequency Instrument (LFI) and the High Frequency Instrument (HFI). In the optimisation of the optical interfaces of the LFI two concurrent demands have to be satisfied: the very good angular resolution (which affects the ability to reconstruct the angular power spectrum of the CMB anisotropies at high multipoles) and a very low level of straylight contamination (which may be one of the most serious sources of systematic effects). We present the results of the optical simulations aimed at establishing the trade-off between angular resolution and straylight rejection, carried out for the 100 GHz channel of the PLANCK LFI. Antenna patterns of different models of dual profiled corrugated conical feed horns have been simulated using advanced simulation techniques, considering the whole spacecraft geometry in order to obtain reliable sidelobe predictions. We show the optical computation accuracy necessary to provide strong straylight evaluation in reasonable computational time and demonstrate the inadequacy of a Gaussian feed model in realistic far beam predictions.

High‐Resolution Observations of the Cosmic Microwave Background Power Spectrum with ACBAR

We report the first measurements of anisotropy in the cosmic microwave background (CMB) radiation with the Arcminute Cosmology Bolometer Array Receiver (ACBAR). The instrument was installed on the 2.1 m Viper telescope at the South Pole in 2001 January; the data presented here are the product of observations up to and including 2002 July. We present two deep differential maps produced by subtracting leading and trailing observations from the main field. The differential maps cover approximately 24 deg2 of sky selected for low dust contrast. These results represent the highest signal-to-noise ratio observations of CMB anisotropy to date; in the deepest 150 GHz band map, we reached an rms of ~8.0 ?K per 5' beam. The 3

Cosmic Microwave Background observations and cosmology

Observations of the Cosmic Microwave Background (CMB) play a pivotal role in the development of modern cosmology. Most of the predictions of the Hot Big Bang model are now experimentally confirmed, and the parameters of the model have recently been constrained to good accuracy. The so-called Concordance cosmology, derived from observations of the CMB spectrum and anisotropy, from measurements of the large-scale distribution of galaxies, of the expansion of the Universe and of the abundance of light elements, requires significant contributions from dark matter (Ω m ∼ 0.3) and dark energy (Ω Λ ∼ 0.65). Also, an initial inflation phase is required for the model to be self consistent. Here we focus on CMB anisotropy and CMB polarization observations and on their role in constraining the model.

A New Exactly Solvable Inflation Model and its Power Spectrum

We present a new exactly solvable inflation model inwhich inflation can stop automatically, and in the approximately de Sitter limit, we give its power spectrum which can be tested in thefuture observations of cosmic microwavebackground anisotropy.

Cross correlation of the cosmic microwave background with radio sources: constraints on an accelerating universe.

We present a new limit on the cosmological constant based on the absence of correlations between the cosmic microwave background (CMB) and the distribution of distant radio sources. In cosmological constant, cold dark matter ( LambdaCDM) models, such correlations should have been produced via the integrated Sachs-Wolfe effect, assuming that radio sources trace the local ( z approximately 1) matter density. We find no evidence of correlations and obtain a 95% C.L. upper limit on the cosmological constant of Omega(Lambda)< or =0.74. If 0.6<Omega(Lambda)<0.7 as suggested by recent CMB anisotropy and supernovae observations, then the integrated Sachs-Wolfe effect should be detectable with upcoming CMB maps and radio surveys.

Contribution of Bright Extragalactic Radio Sources to Microwave Anisotropy

We estimate the contribution of extragalactic radio sources to fluctuations in sky temperature over the range of frequencies (10-300 GHz) used for cosmic microwave background (CMB) anisotropy measurements. CMB anisotropy observations at high resolution and low frequencies are especially sensitive to this foreground. Our catalog of 2207 bright radio sources includes 758 sources with flux measurements at 90 GHz. We develop a method to extrapolate the source spectra and predict skymaps of extragalactic radio sources at instrument resolutions of 10'-10° FWHM. Our results indicate that the brightest radio sources will dominate microwave anisotropy for a wide range of resolutions and frequencies. We predict the location and flux of the brightest radio sources at each frequency, making it straightforward to develop a template for masking the pixels containing them. This masking should be sufficient to protect most CMB anisotropy observations from unacceptable radio source confusion.

CMB anisotropy experiments

Anisotropies in the cosmic microwave background (CMB) encode information about the evolution and development of the universe. Quality observations of CMB anisotropies can provide a very strong test of cosmological models and provide high precision determination of major cosmological parameters. This paper provides a review of the COBE DMR results, the current status of the measurements of the CMB anisotropy power spectrum and then focuses current and future programs including both suborbit al observations and the two selected satellite missions: the NASA MidEX mission MAP and the ESA M3 mission Max Planck Surveyor. This review includes both a description of the experimental programs and the expected quality level of results.

Cosmic entropy from the bosonic string

In Kaluza-Klein models, the compactification ofa high number of extra spatial dimensions generatesentropy in the observable four-dimensional universe. AKaluza–Klein cosmological model recently derived from the bosonic string theory in the limit ofan infinite number of extra dimensions is compared withthe available data from the observations of cosmicmicrowave background anisotropies.

Cosmic microwave background measurements can discriminate among inflation models

Quantum fluctuations during inflation may be responsible for temperature anisotropies in the cosmic microwave background (CMB). Observations of CMB anisotropies can be used to falsify many currently popular models. In this paper we discuss the prospectus for observations of CMB anisotropies at the accuracy of planned satellite missions to reject currently popular inflation models and to provide some direction for model building.

Cosmic Microwave Background Anisotropy inCOBEDMR‐normalized Open and Flat‐Λ Cold Dark Matter Cosmogonies

We compute the cosmic microwave background (CMB) anisotropy in open and flat-Λ cold dark matter (CDM) cosmogonies which are normalized to the two-year DMR sky maps. Presently available CMB data are consistent with Ω0 ~ 0.3-0.4 open models but do not strongly disfavor open models with either Ω0 ~ 0.1 or Ω0 ~ 1. There are indications that old (t0 ≳ 15-16 Gyr), high baryon density (ΩB ≳ 0.0175 h-2), low-density (Ω0 ~ 0.2-0.4), spatially flat Λ models have more intermediate-scale power than is suggested by presently available CMB anisotropy observations. Accumulating CMB data should strengthen the observational discriminative power; however, a better understanding of systematic effects will be needed before it will be possible to draw robust conclusions about model viability.

Contribution of Extragalactic Infrared Sources to Cosmic Microwave Background Foreground Anisotropy

We estimate the level of confusion to cosmic microwave background (CMB) anisotropy measurements caused by extragalactic infrared sources. CMB anisotropy observations at high resolution and high frequencies are especially sensitive to this foreground. We use data from the COBE satellite to generate a Galactic emission spectrum covering millimeter and submillimeter wavelengths. Using this spectrum as a template, we predict the microwave emission of the 5319 brightest infrared galaxies seen by IRAS. We simulate sky maps of extragalactic infrared sources over the relevant range of frequencies (30-900 GHz) and instrument resolutions (10'-10° FWHM). An analysis of the temperature anisotropy of these sky maps shows that a reasonable observational window is available for CMB anisotropy measurements.

Monte Carlo Simulations of Medium-Scale Cosmic Microwave Background Anisotropy

Recent detections of cosmic microwave background (CMB) anisotropy at half-degree angular scales show considerable scatter in the reported amplitude, even at similar angular resolution. We use Monte Carlo techniques to simulate the current set of medium-scale CMB observations, including all relevant aspects of sky coverage and measurement technique. The scatter in the reported amplitudes is within the range expected for the standard cold dark matter (CDM) cosmological model and results primarily from the restricted sky coverage of each experiment. Within the context of standard CDM, current observations of CMB anisotropy support the detection of an acoustic peak in the CMB power spectrum consistent with baryon density 0.005 < Ωb < 0.078 (95% confidence) for Hubble constant H0 = 50 km s-1 Mpc-1. Flat models (Ωb = 0) are rejected at more than 5 standard deviations. The uncertainties are approximately evenly divided between instrument noise and sample variance arising from the limited sky coverage.

Thermal history constraints on the isocurvature baryon model

view Abstract Citations (45) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Thermal History Constraints on the Isocurvature Baryon Model Hu, Wayne ; Sugiyama, Naoshi Abstract We present a thorough and detailed investigation of baryon isocurvature models including realistic thermal histories, \ie, late or partial reionization of the universe and compact object formation after standard recombination. Constraints on these models are imposed from spectral distortion in the cosmic microwave background (CMB), number fluctuations in galaxy counts $\sigma_8$, and recent CMB anisotropy observations. Since the status of degree scale anisotropies is as yet unclear, the lack of spectral distortions is the most serious constraint on the spectral index of initial fluctuations: $-1.2 \simlt n \simlt -0.5$ in partially ionized models and $-1.2 \simlt n \simlt -0.9$ in compact object dominated universes in order to avoid significant bias in galaxy formation. Full ionization of the universe before $z = 300$ is also forbidden by this constraint. Intermediate scale CMB fluctuations which are significantly larger than standard CDM is a {\it robust} prediction of these models. Many models are consequently in conflict with the recent degree scale detections by Python, ARGO, and MSAM, \eg, compact object dominated models with $\Omega_0 \simlt 0.2$. Moreover, {\it all} models will be ruled out if the low CMB fluctuations on degree scales as detected by the SP91 13 point scan are confirmed. On the other hand, most models fare well compared with the high Tenerife and MAX detections. Publication: The Astrophysical Journal Pub Date: December 1994 DOI: 10.1086/174921 arXiv: arXiv:astro-ph/9403031 Bibcode: 1994ApJ...436..456H Keywords: Astronomical Models; Background Radiation; Baryons; Cosmology; Extraterrestrial Radio Waves; Galactic Evolution; Thermal Analysis; Universe; Anisotropy; Cosmic Background Explorer Satellite; Dark Matter; Galactic Clusters; Mathematical Models; Radio Astronomy; Spaceborne Astronomy; Astrophysics; COSMOLOGY: COSMIC MICROWAVE BACKGROUND; COSMOLOGY: LARGE-SCALE STRUCTURE OF UNIVERSE; COSMOLOGY: THEORY; Astrophysics E-Print: 18pgs, uuencoded tarred postscript, CfPA-TH-94-16, UTAP-178 full text sources arXiv | ADS |

Gauge Invariant Cosmological Perturbations with Cold Dark Matter

In the gauge-invariant formalism, the evolution of adiabatic and baryonic isocurvature density perturbations in a universe dominated by cold dark matter (CDM) is thoroughly investigated. We evaluate anisotropies in the cosmic microwave background (CMB) and large scale peculiar velocities. From the recent observations of CMB fluctuations, we find new and stringent constraint is obtained for adiabatic CDM models as S20h>0.3. As for baryonic isocurvature perturbations, though the constraint is required as .G!hI :<:;0.6, we find these baryonic isocurvature models are more viable than axion isocurvature models. However it is difficult for both adiabatic and baryonic isocurvature CDM models to explain the observed large scale velocity field at :<:; 50 hI Mpc while being consistent with the observations of CMB anisotropies.