Temperature Of Background Radiation Research Articles

Anomalous CMB north-south asymmetry

Several accurate analyses have revealed a statistically significant north-south ecliptic asymmetry in the large-angle correlations strength of the cosmic microwave background (CMB) radiation temperature field data from the Wilkinson Microwave Anisotropy Probe (WMAP). This asymmetry is inconsistent with the statistical isotropy expected in the concordance cosmological model $\ensuremath{\Lambda}\mathrm{CDM}$. It has been suggested that a possible cause-effect relationship exists between this large-angle anisotropy and the anomalous CMB quadrupole-octopole planes alignment. In turn, this later phenomenon (or both) would be a consequence of one or more of the following undesired effects in CMB data: a systematic error in the data processing or in the instrument characterization, residual foregrounds, and large-angle correlations induced by the incomplete sky CMB data (cut-sky masks are needed to reject galactic foregrounds). Here, it is proved that the north-south asymmetry is unrelated to the quadrupole ($\ensuremath{\ell}=2$) and the octopole ($\ensuremath{\ell}=3$) properties because we find, at high confidence levels, such large-angle anisotropy in three- and five-year WMAP CMB maps containing only the multipole components $4\ensuremath{\le}\ensuremath{\ell}\ensuremath{\le}10$. The statistical significance depends on both, the CMB map analyzed as well as the cut-sky mask applied to exclude foregrounds. In general, we obtain that the significance level of the north-south asymmetry is less in five-year WMAP data with KQ75 ($\ensuremath{\gtrsim}90%\text{ }\text{ }\mathrm{CL}$) than it is in three-year data with Kp0 ($\ensuremath{\gtrsim}96%\text{ }\text{ }\mathrm{CL}$). For instance, in the WMAP internal linear combination (ILC)-five-year map with the KQ75 mask (a sky cut of 28.4%) this phenomenon is observed at 92.7% CL, whereas for the WMAP ILC-three-year map with the Kp0 mask (a sky cut of 23.5%) this phenomenon appears at 96.5% CL. Moreover, it is also shown that this hemispherical asymmetry is unlikely due to systematics or foreground contaminants, because it is present in single-frequency, multifrequency, and cleaned ILC-type CMB maps. Additionally, robustness tests show that the statistical significance of the north-south asymmetry is affected by the use of the KQ85 and KQ75 masks in five-year single-frequency WMAP CMB maps, whereas it is insensitive with respect to application of the Kp2 and Kp0 masks in three-year single-frequency WMAP CMB maps. The confidence levels were obtained using sets of Monte Carlo CMB maps produced according to the $\ensuremath{\Lambda}\mathrm{CDM}$ model.

Boltzmann babies in the proper time measure

After commenting briefly on the role of the typicality assumption in science, we advocate a phenomenological approach to the cosmological measure problem. Like any other theory, a measure should be simple, general, well defined, and consistent with observation. This allows us to proceed by elimination. As an example, we consider the proper time cutoff on a geodesic congruence. It predicts that typical observers are quantum fluctuations in the early universe, or Boltzmann babies. We sharpen this well-known youngness problem by taking into account the expansion and open spatial geometry of pocket universes. Moreover, we relate the youngness problem directly to the probability distribution for observables, such as the temperature of the cosmic background radiation. We consider a number of modifications of the proper time measure, but find none that would make it compatible with observation.

Spatial periodicity of galaxy number counts, CMB anisotropy, and SNIa Hubble diagram based on the universe accompanied by a non-minimally coupled scalar field

We have succeeded in establishing a cosmological model with a non-minimally coupled scalar field φ that can account not only for the spatial periodicity or the picket-fence structure exhibited by the galaxy N-z relation of the 2dF survey but also for the spatial power spectrum of the cosmic microwave background radiation (CMB) temperature anisotropy observed by the WMAP satellite. The Hubble diagram of our model also compares well with the observation of Type Ia supernovae. The scalar field of our model universe starts from an extremely small value at around the nucleosynthesis epoch, remains in that state for sufficiently long periods, allowing sufficient time for the CMB temperature anisotropy to form, and then starts to grow in magnitude at the redshift z of ∼1, followed by a damping oscillation which is required to reproduce the observed picket-fence structure of the N-z relation. To realize such behavior of the scalar field, we have found it necessary to introduce a new form of potential V(φ)∝ φ 2exp (−q φ 2), with q being a constant. Through this parameter q, we can control the epoch at which the scalar field starts growing.

A Quantum Mechanical Relation Connecting Time, Temperature, and Cosmological Constant of the Universe: Gamow’S Relation Revisited as a Special Case

Considering our expanding universe as made up of gravitationally interacting particles which describe particles of luminous matter and dark matter and dark energy which is described by a repulsive harmonic potential among the points in the flat 3-space, we derive a quantum mechanical relation connecting, temperature of the cosmic microwave background radiation, age, and cosmological constant of the universe. When the cosmological constant is zero, we get back the Gamow's relation with a much better coefficient. Otherwise, our theory predicts a value of the cosmological constant $2.0 10^{-56} {\rm {cm^{-2}}}$ when the present values of cosmic microwave background temperature of 2.728 K and age of the universe 14 billion years are taken as input.

Possibility of Observing Dark Matter via the Gyromagnetic Faraday Effect

If dark matter consists of cold, neutral particles with a nonzero magnetic moment, then, in the presence of an external magnetic field, a measurable gyromagnetic Faraday effect becomes possible. This enables direct constraints on the nature and distribution of such dark matter through detailed measurements of the polarization and temperature of the cosmic-microwave background radiation.

The Cosmic Microwave Background for Pedestrians: A Review for Particle and Nuclear Physicists

We intend to show how fundamental science is drawn from the patterns in the temperature and polarization fields of the cosmic microwave background (CMB) radiation, and thus to motivate the field of CMB research. We discuss the field's history, potential science and current status, contaminating foregrounds, detection and analysis techniques, and future prospects. Throughout the review we draw comparisons to particle physics, a field that has many of the same goals and that has gone through many of the same stages.

Cosmological Applications of a Geometrical Interpretation of “c”

We make the hypothesis that the velocity of light and the expansion of the universe are two aspects of one single concept connecting space and time in the expanding universe. We show that solving Friedman’s equations with that interpretation (keeping c = constant) could explain number of unnatural features of the standard cosmology. We thus examine in that light the flatness problem, the problem of the observed uniformity in term of temperature and density of the cosmological background radiation and the small-scale inhomogeneity problem. We finally show that using this interpretation of c leads to reconsider the Hubble diagram of distance moduli and redshifts as obtained from recent observations of type Ia supernovae without having to need an accelerating universe.

Spectral spatial fluctuations of CMBR: Strategy and concept of the experiment

Spectral spatial fluctuations (SSF) of the cosmic microwave background radiation (CMBR) temperature are considered as a result of an interaction of primordial atoms and molecules with CMBR in proto-objects moving with peculiar velocities relative to the CMBR. Expected optimistic values of Δ T/ T are 2 × 10 −5–2 × 10 −6 for SSF caused by HeH + at z = 20–30 which are possible redshifts of early reionization scenario. The bandwidth of the lines is 0.1–2% depending on the scale of proto-objects and redshifts. For the SSF search CMBR maps in different spectral channels are to be observed and then processed by the Difference method. Simulation of the experiment is made for MSRT (Tuorla Observatory, Finland) equipped with a 7 × 4 beam cryo-microbolometer array with a chopping flat and frequency multiplexer providing up to seven spectral channels in each beam (88–100 GHz). Expected Δ T/ T limit in the experiment is 2 × 10 −5 with 6′–7′ angular and 2% frequency resolution. Simulation shows that SSF may be recognized in the angular power spectrum when S/N in single frequency CMBR maps is as small as 1.17 or even something less for white noise. Such an experiment gives us a possibility to set upper limit of SSF in MM band and prepare future SSF observations.

The effect of modified dispersion relations on the thermodynamics of black-body radiation

In the study of loop quantum gravity and of models based on noncommutative geometry, there has been strong interest in some candidate modifications of the energy-momentum dispersion relation. In this paper we consider the effects of modified dispersion relation (MDR) on the thermodynamics of black-body radiation. We find a generalized Planck distribution and then apply it to find generalized Stefan–Boltzmann and generalized Wien’s law. As a consequence, we study the effects of these modifications on the entropy and specific heat of black-body radiation. We investigate also the relation between our findings and the results of E-infinity theory by considering distribution and temperature of cosmic microwave background radiation.

VLT UVES Observations of Interstellar Molecules and Diffuse Bands in the Magellanic Clouds

We discuss the abundances of interstellar CH, CH+, and CN in the Magellanic Clouds, derived from spectra of seven SMC and 13 LMC stars obtained (mostly) with the VLT UVES. CH and/or CH+ have now been detected toward three SMC and nine LMC stars; CN is detected toward Sk 143 (SMC) and Sk -67 2 (LMC). These data represent nearly all the optical detections of these molecular species in interstellar media beyond the Milky Way. In the LMC, the CH/H2 ratio is comparable to that found for diffuse Galactic molecular clouds in four sight lines but is lower by factors of 2.5-4.0 in two others. In the SMC, the CH/H2 ratio is comparable to the local Galactic value in one sight line but is lower by factors of 10-15 in two others. The abundance of CH in the Magellanic Clouds thus appears to depend on local physical conditions and not just on metallicity. In both the SMC and the LMC, the observed relationships between the column density of CH and those of CN, CH+, Na I, and K I are generally consistent with the trends observed in our Galaxy. Using existing data for the rotational populations of H2 in these sight lines, we estimate temperatures, radiation field strengths, and local hydrogen densities for the diffuse molecular gas. The inferred temperatures range from about 45 to 90 K, the radiation fields range from about 1 to 900 times the typical local Galactic field, and the densities (in most cases) lie between 100 and 600 cm-3. Densities estimated from the observed N(CH), under the assumption that CH is produced via steady state gas-phase reactions, are considerably higher than those derived from H2. Much better agreement is found by assuming that the CH is made via the (still undetermined) process(es) responsible for the observed CH+. A significant fraction of the CH and CH+ in diffuse molecular material in the SMC and LMC may be produced in photon-dominated regions. The excitation temperature obtained from the populations of the two lowest CN rotational levels toward Sk -67 2 is quite consistent with the temperature of the cosmic microwave background radiation measured with COBE. Toward most of our targets, the UVES spectra also reveal absorption at velocities corresponding to the Magellanic Clouds ISM from several of the strongest of the diffuse interstellar bands (DIBs; at 5780, 5797, and 6284 A). On average, the three DIBs are weaker by factors of 7-9 (LMC) and about 20 (SMC), compared to those typically observed in Galactic sight lines with similar N(H I), presumably due to the lower metallicities and stronger radiation fields in the LMC and SMC. The three DIBs are also weaker (on average, but with some exceptions), by factors of order 2-6, relative to E(B-V), N(Na I), and N(K I) in the Magellanic Clouds. The detection of several of the so-called C2 DIBs toward Sk 143 and Sk -67 2 with strengths similar to those in comparable Galactic sight lines, however, indicates that no single, uniform scaling factor (e.g., one related to metallicity) applies to all DIBs (or for all sight lines) in the Magellanic Clouds.

Deuterated hydrogen molecule and search for early structure-formation signatures in the Universe

Possible detection of signatures of structure formation at the end of the 'dark age' epoch (z ∼ 40-20) is examined. We discuss the spectral-spatial fluctuations in the cosmic microwave background radiation (CMBR) temperature produced by elastic resonant scattering of CMBR photons on deuterated hydrogen (HD) molecules located in protostructures moving with peculiar velocity. Detailed chemical kinematic evolution of HD molecules in the expanding homogeneous medium is calculated. Then, the HD abundances are linked to protostructures at their maximum expansion, whose properties are estimated by using the top-hat spherical approach and the A cold dark matter (ACDM) cosmology. We find that the optical depths in the HD three lowest pure rotational lines for high-peak protohaloes at their maximum expansion are much higher than those in LiH molecule. The corresponding spectral-spatial fluctuation amplitudes, however, are probably too weak to be detected by current and forthcoming millimetre telescope facilities. We extend our estimates of spectral-spatial fluctuations to gas clouds inside collapsed CDM haloes by using results from a crude model of HD production in these clouds. The fluctuations for the highest peak CDM haloes at redshifts ∼20-30 could be detected in the future. Observations will be important to test model predictions of early structure formation in the Universe.

Molecular Hydrogen in a Damped Lyα System at z abs = 4.224

We present a direct detection of molecular hydrogen at the highest redshift known today (zabs = 4.224) in a damped Lyα (DLA) system toward the quasar PSS J1443+2724. This absorber is remarkable for having one of the highest metallicities among DLA systems at zabs > 3, with a measured iron abundance relative to solar of -1.12 ± 0.10. We provide for the first time in this system accurate measurements of N I, Mg II, S II, and Ar I column densities. The sulfur and nitrogen abundances relative to solar, -0.63 ± 0.10 and -1.38 ± 0.10, respectively, correspond exactly to the primary nitrogen production plateau. H2 absorption lines are detected in four different rotational levels (J = 0, 1, 2, and 3) of the vibrational ground state in three velocity components with total column densities log N(H2) of 17.67, 17.97, 17.48, and 17.26, respectively. The J = 4 level is tentatively detected in the strongest component, with log N(H2) ~ 14. The mean molecular fraction is log f = -2.38 ± 0.13, with f = 2N(H2)/[2N(H2) + N(H I)]. We also measure log [N(HD)/N(H2)] < -4.2. The excitation temperatures T01 for the two main components of the system are 96 K and 136 K, respectively. We argue that the absorbing galaxy, whose star formation activity must have started at least (2-5) × 108 yr before z = 4.224, is in a quiescent state at the time of observation. The density of the gas is low, nH ≤ 50 cm-3, and the temperature is of the order of T ~ 90-180 K. The high excitation of neutral carbon in one of the components can be explained if the temperature of the cosmic microwave background radiation has the value expected at the absorber redshift, T = 14.2 K. These observations demonstrate the feasibility of studying H2 at the highest redshifts, provided high enough spectral resolution and good signal-to-noise ratio are achieved.

Recent Results from the Wilkinson Microwave Anisotropy Probe

The Wilkinson Microwave Anisotropy Probe (WMAP) is currently mapping temperature and polarization anisotropies of the cosmic microwave background radiation on the full sky in 5 microwave bands. We summarize major scientific results obtained from the first year data released on February 11, 2003: (1) precision determinations of the cosmological parameters, (2) discovery of early reionization of the universe, and (3) implications for the Inflationary paradigm.

First year Wilkinson Microwave Anisotropy Probe results: Implications for cosmology and inflation

The Wilkinson Microwave Anisotropy Probe (WMAP) is currently mapping the temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation on the full sky at five microwave frequencies. We summarize the major scientific results from the analysis of the first-year WMAP data, released on 11 February 2003: (1) the WMAP data alone fits a standard cosmological model, giving precise determinations of its six parameters; (2) the universe was reionized very early on in its history; (3) a joint analysis of WMAP data with smaller scale ground-based CMB experiments and large-scale structure data yields improved constraints on the geometry of the universe, the dark energy equation of state, the energy density in stable neutrino species and the inflationary paradigm.

C$^{\,\infty}$ perturbations of FRW models with a cosmological constant

Spatially homogeneous and isotropic cosmological models, with a perfect fluid matter source and non-vanishing cosmological constant, are studied. The equations governing linear perturbations of the space-time and the variation of energy density are given. The complete solution of the problem is obtained for $C^{\infty}$ perturbations, using a comoving time. The Sachs-Wolfe fluctuations of the temperature of the cosmic background radiation are obtained for the relatively growing density perturbations. It is found that the observable celestial microwave fluctuation pattern underwent a reversal approximately two billion years ago. What is observed today is a negative image of the last scattering surface with an attenuation of the fluctuations, due to the presence of the cosmological constant.

An Instrument to Measure the Temperature of the Cosmic Microwave Background Radiation at Centimeter Wavelengths

The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) is a balloon-borne instrument to measure the temperature of the cosmic microwave background at centimeter wavelengths. ARCADE uses narrow-band cryogenic radiometers to compare the sky to an external full-aperture calibrator. To minimize potential sources of systematic error, ARCADE uses a novel open-aperture design which maintains the antennas and calibrator at temperatures near 3 K at the mouth of an open bucket Dewar, without windows or other warm objects between the antennas and the sky. We discuss the design and performance of the ARCADE instrument from its 2001 and 2003 flights.

CN spectroscopy and cosmic background radiation measurements

A source of possible error, not previously considered, in the determination of the cosmic background radiation (CBR) temperature Tγ(CN) from interstellar CN absorption is proposed. This concerns the intrinsic assumption of the validity of using Hönl–London rotational line intensity factors to determine the rotational components of the oscillator strengths of the R(0), R(1), and P(1) lines of the CN B2Σ+–X2Σ+(0,0) transition. Published data on interstellar CN absorption shows that Tγ(CN) is slightly greater than the standard cosmological CBR temperature, Tγ(COBE) = 2.725 K, determined by the COBE satellite, even when local excitation effects of CN are taken into account. From this difference, an estimation was made of the maximum corrections, a few percent, to the ratio of the line strengths and to the ratio of the Hönl–London factors. Fluorescence lifetime data were shown to give similar values for the corrections as well as providing evidence for intramolecular coupling between the relevant B2Σ+state rotational levels and close-lying levels of the A2Π state, this being responsible for rendering the standard Hönl–London factors invalid. Key words: CN spectroscopy, cosmic background radiation, Hönl–London factors.

Relativistic corrections to the Sunyaev-Zeldovich effect for extremely hot clusters of galaxies

We present an accurate numerical table for the relativistic corrections to the thermal Sunyaev-Zeldovich effect for clusters of galaxies. The numerical results for the relativistic corrections have been obtained by numerical integration of the collision term of the Boltzmann equation. The numerical table is provided for the ranges 0.002 ≤ θ e ≤ 0.100 and 0 ≤ X < 20, where θ e ≡ k B T e /m e c 2 , X ≡ hω/k B T 0 , T e is the electron temperature, ω is the angular frequency of the photon and T 0 is the temperature of the cosmic microwave background radiation. We also present an accurate analytic fitting formula that reproduces the numerical results with high precision.

On a Property of Gravitational Systems

If one attributes to each component i of a gravitational system a dimensionless parameter ψi equal to the ratio of its relative mass (with respect to the mass of the system) to its relative position (with respect to a generally defined radius) and sums up the ψi values of all components outside the central core, one obtains a mass distribution index �ψ of the order of unity irrespective of the size or the type of the system. In the case of spiral galaxies (and probable other galactic systems) this property applies not only to the whole galaxy, but also to the matter inside any radius larger than the core radius. The mass distribution index in these systems has a maximum �ψ ∗ at a certain radius r∗, which strongly correlates with the surface brightness at r∗ in galaxies with similar mass to light ratio. The gravitational acceleration of all galaxies at r∗ divided by (�ψ ∗) 2 is constant and approximately equal to MOND acceleration parameter. Also, at this radius all galaxies have a surface temperature of the order of the temperature of the cosmic microwave background radiation.

Temperature of the Cosmic Microwave Background Radiation in Conformal Cosmology

A scheme is proposed for explaining the origin of the observed temperature of the cosmic microwave background (relict) radiation in which this radiation is treated as a product of the decay of primordial vector bosons in the framework of the Hoyle-Narlikar conformal cosmology.