The synchrotron foreground and CMB temperature-polarization cross correlation power spectrum from the first year WMAP data

We analyse the temperature-polarization cross-correlation in the Galactic synchrotron template that we have recently developed, and between the template and CMB temperature maps derived from WMAP data. Since the polarized synchrotron template itself uses WMAP data, we can estimate residual synchrotron contamination in the CMB $C_\ell^{TE}$ angular spectrum. While $C_2^{TE}$ appears to be contamined by synchrotron, no evidence for contamination is found in the multipole range which is most relevant for the fit of the cosmological optical depth.Comment: Accepted for pubblication on MNRAS Lette

PC1643+4631A,B: The Lyman-Alpha Forest at the Edge of Coherence

This is the first measurement and detection of coherence in the intergalactic medium (IGM) at substantially high redshift (z~3.8) and on large physical scales (~2.5 h^-1 Mpc). We perform the measurement by presenting new observations from Keck LRIS of the high redshift quasar pair PC 1643+4631A, B and their Ly-alpha absorber coincidences. This experiment extends multiple sightline quasar absorber studies to higher redshift, higher opacity, larger transverse separation, and into a regime where coherence across the IGM becomes weak and difficult to detect. We fit 222 discrete Ly-alpha absorbers to sightline A and 211 to sightline B. Relative to a Monte Carlo pairing test (using symmetric, nearest neighbor matching) the data exhibit a 4sigma excess of pairs at low velocity splitting (<150 km/s), thus detecting coherence on transverse scales of ~2.5 h^-1 Mpc. We use spectra extracted from an SPH simulation to analyze symmetric pair matching, transmission distributions as a function of redshift and compute zero-lag cross-correlations to compare with the quasar pair data. The simulations agree with the data with the same strength (~4sigma) at similarly low velocity splitting above random chance pairings. In cross-correlation tests, the simulations agree when the mean flux (as a function of redshift) is assumed to follow the prescription given by Kirkman et al. (2005). While the detection of flux correlation (measured through coincident absorbers and cross-correlation amplitude) is only marginally significant, the agreement between data and simulations is encouraging for future work in which even better quality data will provide the best insight into the overarching structure of the IGM and its understanding as shown by SPH simulations.Comment: 15 pages, 11 figures; accepted for publication in Astronomical Journa

Estimativa de parâmetros biofísicos em plantio de sorgo com aplicação de técnicas de sensoriamento remoto.

Atualmente, o sorgo é um dos grãos mais produzidos no mundo, superado apenas pela soja, milho, trigo e arroz (Simões, 2008). No Brasil, a área cultivada com sorgo tem se expandido, com plantio em sucessão à soja, principalmente quando é maior o risco climático da escolha pela cultura de milho (Casela, 2002). Segundo o IBGE (2009), a safra de sorgo 2009/10 terá acréscimo de 1,1%, com produção estimada em 1.869.419 toneladas. Ao considerar a análise espacialmente explícita de parâmetros biofísicos da cultura, torna-se fundamental a aplicação de técnicas de sensoriamento remoto nas quais possuem como vantagem a possibilidade de extração de informações da produção agrícola de forma rápida e menos onerosa (Papa, 2009). Informações de sensores remotos têm alimentado diversos modelos e algoritmos para obtenção de parâmetros biofísicos da superfície da terra (Andrade et al., 2009). O SEBAL (Surface Energy Balance Algorith for Land) é um algoritmo que tem como vantagem a obtenção de alguns parâmetros biofísicos com poucos dados observacionais de forma efetiva e econômica. Diante do exposto, este trabalho objetivou estimar parâmetros biofísicos em plantio de sorgo com aplicação do algoritmo SEBAL e imagem do sensor TM do satélite Landsat 5