arXiv subjects

J. F. Macias-Perez

Publications and source records attributed to J. F. Macias-Perez.

44 records · Page 3Linked to original sources

arXiv2003

First Detection of Polarization of the Submillimetre Diffuse Galactic Dust Emission by Archeops

We present the first determination of the Galactic polarized emission at 353 GHz by Archeops. The data were taken during the Arctic night of February 7, 2002 after the balloon--borne instrument was launched by CNES from the Swedish Esrange base near Kiruna. In addition to the 143 GHz and 217 GHz frequency bands dedicated to CMB studies, Archeops had one 545 GHz and six 353 GHz bolometers mounted in three polarization sensitive pairs that were used for Galactic foreground studies. We present maps of the I, Q, U Stokes parameters over 17% of the sky and with a 13 arcmin resolution at 353 GHz (850 microns). They show a significant Galactic large scale polarized emission coherent on the longitude ranges [100, 120] and [180, 200] deg. with a degree of polarization at the level of 4-5%, in agreement with expectations from starlight polarization measurements. Some regions in the Galactic plane (Gem OB1, Cassiopeia) show an even stronger degree of polarization in the range 10-20%. Those findings provide strong evidence for a powerful grain alignment mechanism throughout the interstellar medium and a coherent magnetic field coplanar to the Galactic plane. This magnetic field pervades even some dense clouds. Extrapolated to high Galactic latitude, these results indicate that interstellar dust polarized emission is the major foreground for PLANCK-HFI CMB polarization measurement.

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arXiv2003

Cosmological constraints from Archeops

We analyze the cosmological constraints that Archeops places on adiabatic cold dark matter models with passive power-law initial fluctuations. Because its angular power spectrum has small bins in l and large l coverage down to COBE scales, Archeops provides a precise determination of the first acoustic peak in terms of position at multipole l_peak=220 +- 6, height and width. An analysis of Archeops data in combination with other CMB datasets constrains the baryon content of the Universe, Omega(b)h^2 = 0.022 (+0.003,-0.004), compatible with Big-Bang nucleosynthesis and with a similar accuracy. Using cosmological priors obtainedfrom recent non-CMB data leads to yet tighter constraints on the total density, e.g. Omega(tot)=1.00 (+0.03,-0.02) using the HST determination of the Hubble constant. An excellent absolute calibration consistency is found between Archeops and other CMB experiments, as well as with the previously quoted best fit model.The spectral index n is measured to be 1.04 (+0.10,-0.12) when the optical depth to reionization, tau, is allowed to vary as a free parameter, and 0.96 (+0.03,-0.04) when tau is fixed to zero, both in good agreement with inflation.

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arXiv2003

The Cosmic Microwave Background Anisotropy Power Spectrum measured by Archeops

We present a determination by the Archeops experiment of the angular power spectrum of the cosmic microwave background anisotropy in 16 bins over the multipole range l=15-350. Archeops was conceived as a precursor of the Planck HFI instrument by using the same optical design and the same technology for the detectors and their cooling. Archeops is a balloon-borne instrument consisting of a 1.5 m aperture diameter telescope and an array of 21 photometers maintained at ~100 mK that are operating in 4 frequency bands centered at 143, 217, 353 and 545 GHz. The data were taken during the Arctic night of February 7, 2002 after the instrument was launched by CNES from Esrange base (Sweden). The entire data cover ~ 30% of the sky.This first analysis was obtained with a small subset of the dataset using the most sensitive photometer in each CMB band (143 and 217 GHz) and 12.6% of the sky at galactic latitudes above 30 degrees where the foreground contamination is measured to be negligible. The large sky coverage and medium resolution (better than 15 arcminutes) provide for the first time a high signal-to-noise ratio determination of the power spectrum over angular scales that include both the first acoustic peak and scales probed by COBE/DMR. With a binning of Delta(l)=7 to 25 the error bars are dominated by sample variance for l below 200. A companion paper details the cosmological implications.

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arXiv2001

Bayesian blind component separation for Cosmic Microwave Background observations

We present a technique for the blind separation of components in CMB data. The method uses a spectral EM algorithm which recovers simultaneously component templates, their emission law as a function of wavelength, and noise levels. We test the method on Planck HFI simulated observations featuring 3 astrophysical components.

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arXiv2001

COSMOSOMAS: A Circular Scanning Instrument to Map the Sky at Centimetric Wavelengths

We describe the first instrument of a Cosmic Microwave Background experiment for mapping cosmological structures on medium angular scales (the COSMOSOMAS experiment) and diffuse Galactic emission. The instrument is located at Teide Observatory (Tenerife) and is based on a circular scanning sky strategy. It consists of a 1 Hz spinning flat mirror directing the sky radiation into a 1.8 m off-axis paraboloidal antenna which focuses it on to a cryogenically cooled HEMT-based receiver operating in the frequency range 12--18 GHz. The signal is split by a set of three filters, allowing simultaneous observations at 13, 15 and 17 GHz, each with a 1 GHz bandpass. A 1-5 degree resolution sky map complete in RA and covering 20 degrees in declination is obtained each day at these frequencies. The observations presented here correspond to the first months of operation, which have provided a map of ~9000 square degrees on the sky centred at DEC = +31 degrees with sensitivities of 140, 150 and 250 microK per beam area in the channels at 13, 15 and 17 GHz respectively. We discuss the design and performance of the instrument, the atmospheric effects, the reliability of the data obtained and prospects of achieving a sensitivity of 30 microK per beam in two years of operation.

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arXiv2000

A measurement at the first acoustic peak of the CMB with the 33 GHz interferometer

This paper presents the results from the Jodrell Bank-IAC two-element 33 GHz interferometer operated with an element separation of 32.9 wavelengths and hence sensitive to 1 deg scale structure on the sky. The level of CMB fluctuations, assuming a flat CMB spatial power spectrum over the range of multipoles l = 208 +- 18, was found using a likelihood analysis to be ΔT_l = 63^{+7}_{-6} mu K at the 68% confidence limit, after the subtraction of the contribution of monitored point sources. Other possible foreground contributions have been assessed and are expected to have negligible impact on this result.

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arXiv1999

Gravitational lensing statistics with extragalactic surveys. IV. Joint constraints from gravitational lensing statistics and CMB anisotropies

We present constraints on the cosmological constant lambda_0 and the density parameter Omega_0 from joint constraints from the analyses of gravitational lensing statistics of the Jodrell Bank-VLA Astrometric Survey (JVAS), optical gravitational lens surveys from the literature and CMB anisotropies. This is the first time that quantitative joint constraints involving lensing statistics and CMB anisotropies have been presented. Within the assumptions made, we achieve very tight constraints on both lambda_0 and Omega_0. These assumptions are cold dark matter models, no tensor components, no reionisation, CMB temperature T_CMB=2.728, number of neutrinos n_nu=3, helium abundance Y_He=0.246, spectral index n_s=1.0, Hubble constant H_0=68km/s/Mpc, baryonic density Omega_b=0.05. All models were normalised to the COBE data and no closed models (k=+1) were computed. Using the CMB data alone, the best-fit model has lambda_0=0.60 and Omega_0=0.34 and at 99% confidence the lower limit on lambda_0+Omega_0 is 0.8. Including constraints from gravitational lensing statistics doesn't change this significantly, although it does change the allowed region of parameter space. A universe with lambda_0=0 is ruled out for any value of Omega_0 at better than 99% confidence using the CMB alone. Combined with constraints from lensing statistics, lambda_0=0 is also ruled out at better than 99% confidence. As the region of parameter space allowed by the CMB is, within our assumptions, much smaller than that allowed by lensing statistics, the main result of combining the two is to change the range of parameter space allowed by the CMB along its axis of degeneracy.

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arXiv1999

Measuring Cosmological Parameters with the JVAS and CLASS Gravitational Lens Surveys

The JVAS (Jodrell Bank-VLA Astrometric Survey) and CLASS (Cosmic Lens All-Sky Survey) are well-defined surveys containing about ten thousand flat-spectrum radio sources. For many reasons, flat-spectrum radio sources are particularly well-suited as a population from which one can obtain unbiased samples of gravitational lenses. These are by far the largest gravitational (macro)lens surveys, and particular attention was paid to constructing a cleanly-defined sample for the survey itself and for the underlying luminosity function. Here we present the constraints on cosmological parameters, particularly the cosmological constant, derived from JVAS and combine them with constraints from optical gravitational lens surveys, `direct' measurements of $Ω_{0}$, $H_{0}$ and the age of the universe, and constraints derived from CMB anisotropies, before putting this final result into the context of the latest results from other, independent cosmological tests.

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