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A flat Universe from high-resolution maps of the cosmic microwave background radiation


The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole lpeak = (197 ± 6), with an amplitude ΔT200 = (69 ± 8) µK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.

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Figure 1: Boomerang sky maps (equatorial coordinates).
Figure 2: Angular power spectrum measured by Boomerang at 150 GHz.
Figure 3: Observational constraints on Ωm and ΩΛ.

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  1. Sachs,R. K. & Wolfe,A. M. Perturbations of a cosmological model and angular variations of the microwave background. Astrophys. J. 147, 73–90 ( 1967).

    Article  ADS  Google Scholar 

  2. Weinberg, S., Gravitation and Cosmology (Wiley & Sons, New York, 1972).

    Google Scholar 

  3. Hu,W., Sugiyama,N. & Silk,J. The physics of cosmic microwave background anisotropies. Nature 386, 37–43 (1997).

    Article  ADS  CAS  Google Scholar 

  4. Bond,J. R., Efstathiou,G. & Tegmark, M. Forecasting cosmic parameter errors from microwave background anisotropy experiments. Mon Not. R. Astron. Soc. 291 , L33–L41 (1997).

    ADS  Google Scholar 

  5. Hinshaw,G. et al. Band power spectra in the COBE-DMR four-year anisotropy map. Astrophys. J. 464, L17– L20 (1996).

    Article  ADS  Google Scholar 

  6. Scott,P. F. et al. Measurement of structure in the cosmic background radiation with the Cambridge cosmic anisotropy telescope. Astrophys. J. 461, L1–L4 (1996).

    Article  ADS  Google Scholar 

  7. Netterfield,C. B. et al. A measurement of the angular power spectrum of the anisotropy in the cosmic microwave background. Astrophys. J. 474 , 47–66 (1997).

    Article  ADS  Google Scholar 

  8. Leitch,E. M. et al. A measurement of anisotropy in the cosmic microwave background on 7-22 arcminute scales. Astrophys. J. (submitted); also as preprint astro-ph/9807312 at 〈〉 ( 1998).

  9. Wilson,G. W. et al. New CMB power spectrum constraints from MSAMI. Astrophys. J. (submitted); also as preprint astro-ph/9902047 at 〈〉 (1999).

  10. Baker,J. C. et al. Detection of cosmic microwave background structure in a second field with the cosmic anisotropy telescope. Mon Not. R. Astron. Soc. (submitted); also as preprint astro-ph/9904415 at 〈〉 (1999).

  11. Peterson,J. B. et al. First results from Viper: detection of small-scale anisotropy at 40 GHZ. Preprint astro-ph/9910503 at 〈〉 (1999).

  12. Coble,K. et al. Anisotropy in the cosmic microwave background at degree angular scales: Python V results. Astrophys. J. 519, L5–L8 (1999).

    Article  ADS  Google Scholar 

  13. Torbet,E. et al. A measurement of the angular power spectrum of the microwave background made from the high Chilean Andes. Astrophys. J. 521, 79–82 (1999).

    Article  ADS  Google Scholar 

  14. Miller,A. D. et al. A measurement of the angular power spectrum of the CMB from l = 100 to 400. Astrophys. J. (submitted); also as preprint astro-ph/9906421 at 〈〉 (1999 ).

  15. Mauskopf,P. et al. Measurement of a peak in the CMB power spectrum from the test flight of BOOMERanG. Astrophys. J. (submitted); also as preprint astro-ph/9911444 at 〈〉 (1999 ).

  16. Melchiorri,A. et al. A measurement of Ω from the North American test flight of BOOMERanG. Astrophys. J. (submitted); also as preprint astro-ph/9911445 at 〈〉 (1999 ).

  17. de Bernardis,P. et al. Mapping the CMB sky: the BOOMERanG experiment. New Astron. Rev. 43, 289–296 (1999).

    Article  ADS  Google Scholar 

  18. Mauskopf,P. et al. Composite infrared bolometers with Si3N4 micromesh absorbers. Appl. Opt. 36, 765– 771 (1997).

    Article  ADS  CAS  Google Scholar 

  19. Bock,J. et al. Silicon nitride micromesh bolometer arrays for SPIRE. Proc. SPIE 3357, 297–304 (1998).

    Article  ADS  Google Scholar 

  20. Masi,S. et al. A self contained 3He refrigerator suitable for long duration balloon experiments. Cryogenics 38, 319–324 (1998).

    Article  ADS  CAS  Google Scholar 

  21. Masi,S. et al. A long duration cryostat suitable for balloon borne photometry. Cryogenics 39, 217–224 (1999).

    Article  ADS  CAS  Google Scholar 

  22. Schlegel,D. J., Finkbeiner,D. P. & Davis, M. Maps of dust IR emission for use in estimation of reddening and CMBR foregrounds. Astrophys. J. 500, 525–553 (1998).

    Article  ADS  Google Scholar 

  23. Delabrouille,J., Gorski,K. M. & Hivon, E. Circular scans for CMB anisotropy observation and analysis. Mon. Not. R. Astron. Soc. 298, 445– 450 (1998).

    Article  ADS  Google Scholar 

  24. Cheung, L. H. et al. 1.0 millimeter maps and radial density distributions of southern HII/molecular cloud complexes. Astrophys. J. 240, 74– 83 (1980).

    Article  ADS  Google Scholar 

  25. Kogut,A. et al. Dipole anisotropy in the COBE DMR first-year sky maps. Astrophys. J. 419, 1–6 ( 1993).

    Article  ADS  Google Scholar 

  26. Tegmark,M. CMB mapping experiments: a designer's guide. Phys. Rev. D 56, 4514–4529 (1997).

    Article  ADS  CAS  Google Scholar 

  27. Bond,J. R., Crittenden,R., Jaffe,A. H. & Knox,L. E. Computing challenges of the cosmic microwave background. Comput. Sci. Eng. 21, 1–21 ( 1999).

    Google Scholar 

  28. Borrill,J. in Proc. 3K Cosmology EC-TMR Conf. (eds Langlois, D., Ansari, R. & Vittorio, N.) 277 (American Institute of Physics Conf. Proc. Vol. 476, Woodbury, New York, 1999).

    Book  Google Scholar 

  29. Prunet,S. et al. in Proc. Conf. Energy Density in the Universe (eds Langlois, D., Ansari, R. & Bartlett, J.) (Editiones Frontieres, Paris, 2000).

    Google Scholar 

  30. Gorski,K. M., Hivon,E. & Wandelt,B. D. in Proc. MPA/ESO Conf. (eds Banday, A. J., Sheth, R. K. & Da Costa, L.) (European Southern Observatory, Garching); see also 〈〉.

  31. Kogut,A. in Microwave Foregrounds (eds de Oliveira Costa, A. & Tegmark, M.) 91–99 (Astron. Soc. Pacif. Conf. Series. Vol 181, San Francisco, 1999).

    Google Scholar 

  32. Toffolatti,L. et al. Extragalactic source counts and contributions to the anisotropies of the CMB. Mon. Not. R. Astron. Soc. 297, 117–127 (1998).

    Article  ADS  Google Scholar 

  33. Wright,A. E. et al. The Parkes-MIT-NRAO (PMN) surveys II. Source catalog for the southern survey. Astrophys. J. Supp. Ser. 91, 111–308 (1994); see also 〈〉.

    Article  ADS  Google Scholar 

  34. Borrill,J. in Proc. 5th European SGI/Cray MPP Workshop (CINECA, Bologna, 1999); Preprint astro-ph/9911389 at 〈〉 ( 1999); see also 〈〉.

    Google Scholar 

  35. Durrer,R., Kunz,M. & Melchiorri, A. Phys. Rev. D 59, 1– 26 (1999).

    Article  Google Scholar 

  36. Seljak,U. & Zaldarriaga,M. A line of sight approach to cosmic microwave background anisotropies. Astrophys. J. 437 , 469–477 (1996).

    Google Scholar 

  37. Lewis,A., Challinor,A. & Lasenby, A. Efficient computation of CMB anisotropies in closed FRW models. Preprint astro-ph/9911177 at 〈〉 (1999).

  38. Efstathiou,G. & Bond,R. Cosmic confusion: degeneracies among cosmological parameters derived from measurements of microwave background anisotropies. Mon Not. R. Astron. Soc. 304, 75–97 (1998).

    Article  ADS  Google Scholar 

  39. Wright,E. et al. Comments on the statistical analysis of excess variance in the COBE-DMR maps. Astrophys. J. 420, 1– 8 (1994).

    Article  ADS  Google Scholar 

  40. Perlmutter,S. et al. Measurements of and Λ from 42 high-redshift supernovae. Astrophys. J. 517, 565– 586 (1999).

    Article  ADS  Google Scholar 

  41. Schmidt,B. P. et al. The high-Z supernova search: measuring cosmic deceleration and global curvature of the Universe using type Ia supernovae. Astrophys. J. 507, 46–63 (1998).

    Article  ADS  Google Scholar 

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The Boomerang experiment was supported by Programma Nazionale di Ricerche in Antartide, Universita' di Roma “La Sapienza”, and Agenzia Spaziale Italiana in Italy, by the NSF and NASA in the USA, and by PPARC in the UK. We thank the staff of the National Scientific Ballooning Facility, and the United States Antarctic Program personnel in McMurdo for their preflight support and an effective LDB flight. DOE/NERSC provided the supercomputing facilities.

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Correspondence to P. de Bernardis.

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de Bernardis, P., Ade, P., Bock, J. et al. A flat Universe from high-resolution maps of the cosmic microwave background radiation. Nature 404, 955–959 (2000).

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