F. Pongetti

Multiple peaks in the angular power spectrum of the cosmic microwave background: Significance and consequences for cosmology

Multiple Peaks in the Angular Power Spectrum of the Cosmic Microwave Background: Significance and Consequences for Cosmology arXiv:astro-ph/0105296 v1 17 May 2001 P. de Bernardis 1 , P.A.R. Ade 2 , J.J. Bock 3 , J.R. Bond 4 , J. Borrill 5 , A. Boscaleri 6 , K. Coble 7 , C.R. Contaldi 4 , B.P. Crill 8 , G. De Troia 1 , P. Farese 7 , K. Ganga 9 , M. Giacometti 1 , E. Hivon 9 , V.V. Hristov 8 , A. Iacoangeli 1 , A.H. Jaffe 10 , W.C. Jones 8 , A.E. Lange 8 , L. Martinis 11 , S. Masi 1 , P. Mason 8 , P.D. Mauskopf 12 , A. Melchiorri 13 , T. Montroy 7 , C.B. Netterfield 14 , E. Pascale 6 , F. Piacentini 1 , D. Pogosyan 4 , G. Polenta 1 , F. Pongetti 15 , S. Prunet 4 , G. Romeo 15 , J.E. Ruhl 7 , F. Scaramuzzi 11 Dipartimento di Fisica, Universita’ La Sapienza, Roma, Italy Queen Mary and Westfield College, London, UK Jet Propulsion Laboratory, Pasadena, CA, USA Canadian Institute for Theoretical Astrophysics, University of Toronto, Canada National Energy Research Scientific Computing Center, LBNL, Berkeley, CA, USA IROE-CNR, Firenze, Italy Dept. of Physics, Univ. of California, Santa Barbara, CA, USA California Institute of Technology, Pasadena, CA, USA IPAC, California Institute of Technology, Pasadena, CA, USA Department of Astronomy, Space Sciences Lab and Center for Particle Astrophysics, University of CA, Berkeley, CA 94720 USA ENEA, Frascati, Italy Dept. of Physics and Astronomy, Cardiff University, Cardiff CF24 3YB, Wales, UK Nuclear and Astrophysics Laboratory, University of Oxford, Keble Road, Oxford, OX 3RH, UK Depts. of Physics and Astronomy, University of Toronto, Canada Istituto Nazionale di Geofisica, Roma, Italy ABSTRACT Three peaks and two dips have been detected in the power spectrum of the cosmic microwave background from the BOOMERANG experiment, at ∼ 210, 540, 840 and ∼ 420, 750, respec- tively. Using model-independent analyses, we find that all five features are statistically significant and we measure their location and amplitude. These are consistent with the adiabatic inflation- ary model. We also calculate the mean and variance of the peak and dip locations and amplitudes in a large 7-dimensional parameter space of such models, which gives good agreement with the model-independent estimates, and forecast where the next few peaks and dips should be found if the basic paradigm is correct. We test the robustness of our results by comparing Bayesian marginalization techniques on this space with likelihood maximization techniques applied to a sec- ond 7-dimensional cosmological parameter space, using an independent computational pipeline, and find excellent agreement: Ω tot = 1.02 +0.06 vs. 1.04±0.05, Ω b h 2 = 0.022 −0.003 vs. 0.019 +0.005 , and n s = 0.96 −0.09 vs. 0.90±0.08. The deviation in primordial spectral index n s is a consequence of the strong correlation with the optical depth. Subject headings: Cosmic Microwave Background Anisotropy, Cosmology

The BOOMERanG experiment and the curvature of the Universe

We describe the BOOMERanG experiment and its main result, i.e. the measurement of the large scale curvature of the Universe. BOOMERanG is a balloon-borne microwave telescope with sensitive cryogenic detectors. BOOMERanG has measured the angular distribution of the Cosmic Microwave Background on ∼ 3% of the sky, with a resolution of ∼ 10 arcmin and a sensitivity of ∼ 20μK per pixel. The resulting image is dominated by hot and cold spots with rms fluctuations ∼ 80μK and typical size of ∼ 1o. The detailed angular power spectrum of the image features three peaks and two dips at l = (213−13+10), (541−32+20), (845−25+12) and l = (416−12+22), (750−750+20), respectively. Such very characteristic spectrum can be explained assuming that the detected structures are the result of acoustic oscillations in the primeval plasma. In this framework, the measured pattern constrains the density parameter Ω to be 0.85 < Ω < 1.1 (95% confidence interval). Other cosmological parameters, like the spectral index of initial density fluctuations, the density parameter for baryons, dark matter and dark energy, are detected or constrained by the BOOMERanG measurements and by other recent CMB anisotropy experiments. When combined with other cosmological observations, these results depict a new, consistent, cosmological scenario.

First results from the BOOMERanG experiment

We report the first results from the BOOMERanG experiment, which mapped at 90, 150, 240 and 410 GHz a wide (3%) region of the microwave sky with minimal local contamination. From the data of the best 150 GHz detector we find evidence for a well defined peak in the power spectrum of temperature fluctuations of the Cosmic Microwave Background, localized at =197+/-6, with an amplitude of (68+/-8)μKCMB. The location, width and amplitude of the peak is suggestive of acoustic oscillations in the primeval plasma. In the framework of inflationary adiabatic cosmological models the measured spectrum allows a Bayesian estimate of the curvature of the Universe and of other cosmological parameters. With reasonable priors we find Ω=(1.07+/-0.06) and ns=(1.00+/-0.08) (68%C.L.) in excellent agreement with the expectations from the simplest inflationary theories. We also discuss the limits on the density of baryons, of cold dark matter and on the cosmological constant.

Three sun sensors for stratospheric balloon payloads

We describe three sun sensors which have been developed for balloon borne experiments. The sensors have different resolutions and sky coverage, and have been developed and used in the BOOMERanG project.

B2K: The polarization-sensitive BOOMERanG experiment

We describe the new BOOMERanG payload, which is being prepared for a new circum-antarctic flight, with the aim to detect the linear polarization of the Cosmic Microwave Background (CMB). In addition to polarization capabilities, obtained by means of special bolometers, the instrument has been improved in the attitude reconstruction system and in the calibration system.

Noise estimation in CMB time-streams and fast map-making

We describe here an iterative method for jointly estimating the noise power spectrum from a CMB experiments time-ordered data, together with the maximum-likelihood map. We test the robustness of this method on simulated Boomerang datasets with realistic noise.

Cosmic microwave background fluctuations

Several experiments have recently detected very low contrast, sub-horizon scale structures in the Cosmic Microwave Background (CMB). In the current cosmological model, these structures result from acoustic oscillations of the primeval plasma at recombination (

The new images of the microwave sky: a concordance cosmology ?

z \sim 1100

The Boomerang/ldb Instrument

). In the framework of the Hot Big Bang theory with the inflation hypothesis, the statistical properties of the image of the CMB allow us to measure most of the cosmological parameters.

l-space spectroscopy of the Cosmic Microwave Background with the BOOMERanG experiment

The existence and anisotropy of the cosmic microwave background (CMB), the large scale distribution of Galaxies, the expansion of the Universe and the abundance of light elements can be all be explained with a single cosmological model. In this paper we focus on the CMB anisotropy maps produced by the BOOMERanG experiment and on their impact on cosmology. The images are consistent with the result of acoustic oscillations of the photons-matter plasma in the pre-recombination Universe (z ≳ 1000). We show how the instrument and the observations have been optimized and how the basic parameters of the model are derived from the data. These observations of the CMB are gaussian and point to a low curvature Universe (ω ∼ 1), as expected in the inflation scenario. In order to fit these observations and other cosmological evidence, the composition of the Universe must have significant contributions from dark matter (ω m ∼ 0.3) and dark energy (ωΛ ∼ 0.7).