Emissão anômala de micro-ondas na Via Láctea

In this work, it is presented a brief review of the phenomenon known as Anomalous Microwave Emission (AME) in the Milky Way. AME represents an interesting challenge for modern astrophysics. Since the identification of this emission in 1996, and despite several studies dedicated to this subject, no definite explanation has yet been given about the physical mechanisms responsible for such emission.É apresentada uma revisão sucinta do fenômeno conhecido como Emissão Anômala de Micro-ondas na Via Láctea (AME, da sigla em inglês para Anomalous Microwave Emission), que representa um desafio interessante para a astrofísica moderna. Desde a identificação dessa emissão, em 1996, ainda não foi dada uma explicação definitiva sobre os mecanismos físicos responsáveis por tal emissão, apesar dos vários estudos dedicados ao tema

Alignment tests for low CMB multipoles

We investigate the large scale anomalies in the angular distribution of the cosmic microwave background radiation as measured by WMAP using several tests. These tests, based on the multipole vector expansion, measure correlations between the phases of the multipoles as expressed by the directions of the multipole vectors and their associated normal planes. We have computed the probability distribution functions for 46 such tests, for the multipoles l=2-5. We confirm earlier findings that point to a high level of alignment between l=2 (quadrupole) and l=3 (octopole), but with our tests we do not find significant planarity in the octopole. In addition, we have found other possible anomalies in the alignment between the octopole and the l=4 (hexadecupole) components, as well as in the planarity of l=4 and l=5. We introduce the notion of a total likelihood to estimate the relevance of the low-multipoles tests of non-gaussianity. We show that, as a result of these tests, the CMB maps which are most widely used for cosmological analysis lie within the ~ 10% of randomly generated maps with lowest likelihoods.Comment: References added, updated discussion on alignment with Ecliptic Plane. 12 Pages, 6 Figures. Results for additional maps, the normalized frequencies for the tests and a Mathematica Notebook that computes the tests can be found on http://fma.if.usp.br/~abramo/MVA.htm

Mapa da Galáxia em 408 MHz

Este artigo procura mostrar como foi obtido um mapa da emissão da Galáxia em 408 MHz. Os mapas da emissão da Galáxia nas frequências de rádio do espectro eletromagnético são de grande importância para o estudo da radiação cósmica de fundo em micro-ondas (RCFM). Para confeccionar o mapa deste trabalho, foram utilizados os dados obtidos com o radiotelescópio do projeto Galactic Emission Mapping (GEM) na cidade de Bishop – Califórnia – EUA.Inicialmente é apresentada uma introdução sobre a descoberta da emissão em radiofrequência por fontes extraterrestres. Em seguida, a importância dos mapas no estudo da RCFM é apresentada. O experimento GEM em si, seu funcionamento e o processo de aquisição e tratamento de dados é abordado de maneira sucinta. Em especial, como a superação do problema na leitura de posição do azimute deste radiotelescópio foi resolvida é tratada. O artigo é finalizado com as conclusões e as referências bibliográficas

A high performance cost-effective digital complex correlator for an X-band polarimetry survey

The detailed knowledge of the Milky Way radio emission is important to characterize galactic foregrounds masking extragalactic and cosmological signals. The update of the global sky models describing radio emissions over a very large spectral band requires high sensitivity experiments capable of observing large sky areas with long integration times. Here, we present the design of a new 10 GHz (X-band) polarimeter digital back-end to map the polarization components of the galactic synchrotron radiation field of the Northern Hemisphere sky. The design follows the digital processing trends in radio astronomy and implements a large bandwidth (1 GHz) digital complex cross-correlator to extract the Stokes parameters of the incoming synchrotron radiation field. The hardware constraints cover the implemented VLSI hardware description language code and the preliminary results. The implementation is based on the simultaneous digitized acquisition of the Cartesian components of the two linear receiver polarization channels. The design strategy involves a double data rate acquisition of the ADC interleaved parallel bus, and field programmable gate array device programming at the register transfer mode. The digital core of the back-end is capable of processing 32 Gbps and is built around an Altera field programmable gate array clocked at 250 MHz, 1 GSps analog to digital converters and a clock generator. The control of the field programmable gate array internal signal delays and a convenient use of its phase locked loops provide the timing requirements to achieve the target bandwidths and sensitivity. This solution is convenient for radio astronomy experiments requiring large bandwidth, high functionality, high volume availability and low cost. Of particular interest, this correlator was developed for the Galactic Emission Mapping project and is suitable for large sky area polarization continuum surveys. The solutions may also be adapted to be used at signal processing subsystem levels for large projects like the square kilometer array testbeds