Temperature Of Background Radiation Research Articles

The Primeval Radiation Spectrum Longward of 3 mm

Ground based measurements of the temperature of the microwave background radiation show good agreement with a (2.72 ± 0.08) K black-body spectrum for wavelengths longer than 3.3 mm. The techniques and problems associated with absolute, ground based, radiometry are reviewed, and the prospects for improvement assessed. The prospects of finding spectral distortions anticipated by theory, and new measurements of the spectrum shortward of 3.3 mm, have renewed interest in this dormant area of experimental cosmology.

Towards the absolute zero

Low-temperature physicists are constantly trying to extend the temperature range accessible to experimental investigations closer and closer to the absolute zero. While the third law of thermodynamics prevents their ever reaching 0 K, they have long since surpassed Nature herself. The temperature of the cosmic background radiation is 3 K; below 3 K, we are creating new physics, hitherto unknown to the universe. And this has been done without any large expenditures of manpower or equipment—the most sophisticated weapons at the cold frontier of physics are inexpensive indeed.

The Sunyaev-Zel'dovich effect in the millimetric region

We analyse the spectral shape and possible spurious distortions of the Sunyaev-Zel'dovich effect, arising from the interaction of the cosmic background radiation with hot gases of rich clusters, in the millimetric region. We show that one can measure this effect with high accuracy with present-day infrared detectors, obtaining a larger amount of information than by using radio systems. In particular, one can accurately measure the temperature of the cosmic background radiation without the usual absolute calibration of the detector.

The influence of strong interactions on the early stages of the Universe

It is shown that the singularity of space-time in Einstein-Friedmann's cosmology can be avoided, if one takes into account the strong interaction of the elementary particles in the earliest stage of the Universe. Under the additional assumption that there exists a maximum temperature of particles and radiation (Tmax≃1.9×1012 K) in consequence of which the number of hadrons (nucleons) in the early Universe has been greater than today by a factor of about 107, the Friedmann equation is integrated numerically where the integration constant is fitted by the present values of the massdensity, the Hubble-constant and the temperature of the background radiation. The minimum radius of curvature of the Universe becomes 1.4×1011 km; the density in its neighbourhood remains within reasonable limits of the magnitude of the nuclear density. The early evolution of the Universe with time will be discussed in detail.

Interstellar H2CO. I - Absorption studies, dark clouds, and the cosmic background radiation

view Abstract Citations (150) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Interstellar H2CO. I. Absorption studies, dark clouds, and the cosmic background radiation. Evans, N. J., II ; Zuckerman, B. ; Morris, G. ; Sato, T. Abstract The 2ii 212 transition at 2-cm wavelength of interstellar formaldehyde has been observed in absorption against galactic continuum sources and the 2.7 K cosmic background radiation. In addition, the 110 lii transition at 6-cm wavelength of the rare isotopic species H213C06O has been detected in absorption against the cosmic background radiation in at least two clouds. These observations are used to distinguish among the various models for cooling the 6-cm doublet of H212C16O below 2.7 K, and a collisional pumping model is found to be in the best agreement with the observations. In the dark clouds that display this cooling, calculations indicate that the H2 densities are between 102 and 106 , 2 < 10-6, and the value of H213C16O( H212C16O is similar to the terrestrial 12Ct12C ratio. Estimates of the H2CO/H2 ratio in several diverse clouds indicate values of the order of 2-4 x 10-6 Observations toward Cas A indicate that the temperature of the cosmic background radiation at 2-mm wavelength is %< 2.9 K. Subject headings: cosmic background radiation - molecules, interstellar - nebulae Publication: The Astrophysical Journal Pub Date: March 1975 DOI: 10.1086/153424 Bibcode: 1975ApJ...196..433E Keywords: Astronomical Models; Background Radiation; Formaldehyde; Interstellar Matter; Absorption Spectra; Astronomical Catalogs; Clouds; Density Distribution; Electron Transitions; Line Spectra; Molecular Spectra; Optical Pumping; Radial Velocity; Temperature Distribution; Astrophysics full text sources ADS | data products SIMBAD (8)

Limit on the rest masses from big bang cosmology

The age of the Universe and the Hubble deceleration of galaxies depends upon the average mass density. The temperature of the electromagnetic background radiation determines also the neutrino particle density. These empirical informations put an upper limit on the rest masses of the neutrinos, which are more restrictive than the laboratory values.

On the Temperature of the Microwave Background Radiation at a Large Redshift

view Abstract Citations (18) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Temperature of the Microwave Background Radiation at a Large Redshift Bahcall, John N. ; Joss, Paul C. ; Lynds, Roger Abstract It is shown that the temperature of the microwave background radiation at a redshift of the order of 2.5 is certainly less than 200 K and probably less than 45 K. Further detailed studies of the absorption spectra of large-redshift quasars can improve these limits. Subject headings: cosmic background radiation - quasi-stellar sources or objects Publication: The Astrophysical Journal Pub Date: June 1973 DOI: 10.1086/181227 Bibcode: 1973ApJ...182L..95B full text sources ADS |

X-ray Survey of Centaurus A

An x-ray survey of Centaurus A has given marginal evidence of its x-ray flux. If taken as an upper limit on inverse Compton x-rays generated by scattering interactions between relativistic electrons and cosmological background photons, the observation implies an upper limit of close to 3 degrees K for the background radiation temperature.

Density perturbations in cosmological models

Differential equations are derived, following the methods ofLifshitz (1946) andLifshitz andKhalatnikov (1963), for density perturbations in isotropic, spatially homogeneous cosmological models of arbitrary space curvature. The unperturbed models contain both matter and radiation. An explicit third-order equation is obtained for the time development of the perturbations, and it is shown that one of the solutions is not covariantly defined. The two remaining solutions are compared with existing solutions for the limiting cases of radiation-filled and dust-filled models. The results ofBonnor's (1957) Newtonian analysis are shown to be a valid limiting case of our equation when the pressurep is finite, but small compared with the densityp timesc 2. A detailed analysis is given of a model containing coupled radiation (p=pc 2/3) and dust (p=0). It is shown that density perturbations with long wavelengths are unstable (with slow growth rate) for all time. The instability exists because for a long-wavelength disturbance, the time scale governing the propagation of pressure effects (which stabilize perturbations) is longer than the time scale for which pressure falls to the point of ineffectiveness. The present value of the critical wavelength is ∼60 Mpc in models based on flat space sections in which the present background radiation temperature is 3 °K.

Measurement of cosmic background radiation at 3.2-cm wavelength

A measurement of the equivalent temperature of the cosmic microwave background radiation at 3.2 cm wavelength is described. The result, T BG = (3.0 ± 0.5)°K, has already been reported and discussed [ Phys. Rev. Letters 16, 405 1966]. This paper describes the apparatus and technique used for the measurement with particular emphasis on the sources of error. After a summary of the general requirements on a radiometer used for background measurements, we discuss the Dicke-type radiometer which was designed and built especially for this measurement. The design and testing of the critical components—the antenna, the reference termination, and the switch—are dealt with in some detail. It was necessary to measure and subtract off the radiation due to oxygen and water vapor in the atmosphere and this technique is discussed. Also, some techniques used in making precision measurements of wave-guide and antenna loss are described. The result is discussed briefly.