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  • 1
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    Noncosmological signal contributions to the COBE DMR anisotropy maps (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We examine the COBE Differential Microwave Radiometer (DMR) data for evidence of noncosmological source contributions. The DMR maps are cross-correlated with maps of rich clusters, extragalactic IRAS sources, HEAO 1 A-2 X-ray emission, and 5 GHz radio sources. We limit the rms contributions from these sources on a 7 deg angular scale to less than 10 micro-K (95 percent confidence level) in the DMR maps, although the LMC probably contributes about 50 micro-K to a limited region of the sky. Thus, our previous interpretation that the fluctuations in the COBE DMR data are most likely due to cosmic fluctuations at the surface of last scattering remains intact. The Comptonization parameter for hot electrons traced by rich clusters is limited to delta(y) less than 2 x 10 exp -6 (95 percent confidence level) averaged over the 7 deg DMR beam.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 414; 2; p. L77-L80.
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  • 2
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    Limits on Gaussian fluctuations in the cosmic microwave background at 19.2 GHz (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The Northern Hemisphere data from the 19.2 GHz full sky survey are analyzed to place limits on the magnitude of Gaussian fluctuations in the cosmic microwave background implied by a variety of correlation functions. Included among the models tested are the monochromatic and Gaussian-shaped families, and those with power law spectra for n from -2 to 1. We place an upper bound on the quadrupole anisotropy of DeltaT/T less than 3.2 x 10 exp -5 rms, and an upper bound on scale-invariant (n = 1) fluctuations of a2 less than 4.5 x 10 exp -5 (95 percent confidence level). There is significant contamination of these data from Galactic emission, and improvement of our modeling of the Galaxy could yield a significant reduction of these upper bounds.
    Keywords: SPACE RADIATION
    Type: In: After the first three minutes; Proceedings of the 1st Astrophysics Workshop, Univ. of Maryland, College Park, Oct. 15-17, 1990 (A93-23605 07-90); p. 107-112.
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  • 3
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    A preliminary measurement of the cosmic microwave background spectrum by the Cosmic Background Explorer (COBE) satellite (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A preliminary spectrum is presented of the background radiation between 1 and 20/cm from regions near the north Galactic pole, as observed by the FIRAS instrument on the COBE satellite. The spectral resolution is 1/cm. The spectrum is well fitted by a blackbody with a temperature of 2.735 + or - 0.06 K, and the deviation from a blackbody is less than 1 percent of the peak intensity over the range 1-20/cm. These new data show no evidence for the submillimeter excess previously reported by Matsumoto et al. (1988) in the cosmic microwave background. Further analysis and additional data are expected to improve the sensitivity to deviations from a blackbody spectrum by an order of magnitude.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 354; L37-L40
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  • 4
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    Structure in the COBE differential microwave radiometer first-year maps (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Results of the first year of data from the differential microwave radiometers on the Cosmic Background Explorer are presented. Statistically significant structure that is well described as scale-invariant fluctuations with a Gaussian distribution is shown. The rms sky variation, smoothed to a total 10-deg FWHM Gaussian, is 30 +/-5 micro-K for Galactic latitude greater than 20-deg data with the dipole anisotropy removed. The rms cosmic quadrupole amplitude is 13 +/-4 micro-K. The angular autocorrelation of the signal in each radiometer channel and cross-correlation between channels are consistent and give a primordial fluctuation power-law spectrum with index of 1.1 +/-0.5, and an rms-quadrupole-normalized amplitude of 16 +/-4 micro-K. These features are in accord with the Harrison-Zel'dovich spectrum predicted by models of inflationary cosmology.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 396; 1, Se; L1-L5
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  • 5
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    Limits of Gaussian fluctuations in the cosmic microwave background at 19.2 GHz (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The Northern Hemisphere data from the 19.2 GHz full sky survey are analyzed to place limits on the magnitude of Gaussian fluctuations in the cosmic microwave background implied by a variety of correlation functions. Included among the models tested are the monochromatic and Gaussian-shaped families, and those with power-law spectra for n values between -2 and 1. An upper bound is placed on the quadrupole anisotropy of Delta T/T less than 3.2 x 10 exp -5 rms, and an upper bound on scale-invariant (n = 1) fluctuations of a2 less than 4.5 x 10 exp -5 (95 percent confidence level). There is significant contamination of these data from Galactic emission, and improvement of the modeling of the Galaxy could yield a significant reduction of these upper bounds.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 391; 2, Ju; L49-L52
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  • 6
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    Interpretation of the cosmic microwave background radiation anisotropy detected by the COBE Differential Microwave Radiometer (1992)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The large-scale cosmic background anisotropy detected by the COBE Differential Microwave Radiometer (DMR) instrument is compared to the sensitive previous measurements on various angular scales, and to the predictions of a wide variety of models of structure formation driven by gravitational instability. The observed anisotropy is consistent with all previously measured upper limits and with a number of dynamical models of structure formation. For example, the data agree with an unbiased cold dark matter (CDM) model with H0 = 50 km/s Mpc and Delta-M/M = 1 in a 16 Mpc radius sphere. Other models, such as CDM plus massive neutrinos (hot dark matter (HDM)), or CDM with a nonzero cosmological constant are also consistent with the COBE detection and can provide the extra power seen on 5-10,000 km/s scales.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 396; 1, Se; L13-L18
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  • 7
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    A search for anisotrophy in the cosmic microwave background on intermediate angular scales (1992)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The results of a search for anisotropy in the cosmic microwave background on angular scales near 1 deg are presented. Observations were simultaneously performed in bands centered at frequencies of 6, 9, and 12 per cm with a multifrequency bolometric receiver mounted on a balloon-borne telescope. The statistical sensitivity of the data is the highest reported to date at this angular scale, which is of critical importance for understanding the formation of structure in the universe. Signals in excess of random were observed in the data. The experiment, data analysis, and interpretation are described.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 395; 2 Au
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