Polarização da radiação galáctica em 5 GHz: instrumentação, medidas e mapas / Polarization of the galactic emission at 5 GHz: instrumentation, measurements and maps

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The Galactic Emission Mapping (GEM) project was proposed in the late 1990 s, aiming to characterize the microwave emission of the Milk Way, in order to provide high quality data and models to allow a better foreground substraction of Cosmic Microwave Background maps. The project employs a 5.5 m - diameter antenna, currently operating at the Cachoeira Paulista s observational site (22°41 8.74"S, 44°59 54.34"W), where a 60° declination band, encompassing the Galactic Center and covering an arca of 47.14% of the sky, is scanned everyday. Since the beginning of this project, total power maps in 408, 1465 e 2300 MHz were produced. In this work, the developing of a new pseudo-correlation polarimetric receiver at 5 GHz is shown. Using a high-isolation Orthomode Transducer and a pair of FET cryogenic amplifiers, this polarimeter reaches a sensibility of 1.64 mK/√s, when the system temperature is about 25.5 K and the observation band is 400 MHz centered in 5 GHz. Computer simulations of different aspects of this instrument are exposed, including the thermal and clectromagnetic behavior of several components. We also show the results from bench tests and calibrations of the polarimeter. The data from the preliminary season of measurements, an amount of about 800 h, and from the first observation season, totalizing about 2500 h, are exhibited and analyzed. The data processing algorithms are shown, with emphasis given to the de-striping and cleaning tools. Maps of the polarized intensity and the U and Q components of the sky emission at 5 GHz are shown. These are the first maps at this frequency reported in the literature. Preliminary calculations of the spectral index were made, showing several synchrotron dominated regions in the sky. On the other hand, several regions in the Galactic plane are dominated by Faraday depolarization. An estimate of the power spectrum is calculated, showing that EE and BB polarization modes are equally produced.

ASSUNTO(S)

emissão síncrotron cosmologia observacional radioastronomy radioastronomia emissão galáctica galactic emission observational cosmology synchroton emission instrumentação:polarimetria instrumentation:polarimetry

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