253 research outputs found
Telescope search for decaying relic axions
No full textA search for optical line emission from the two-photon decay of relic axions was conducted in the galaxy clusters Abell 2667 and 2390, using spectra from the VIMOS (Visible MultiObject Spectrograph) integral field unit at the Very Large Telescope. New upper limits to the two-photon coupling of the axion are derived, and are at least a factor of 3 more stringent than previous upper limits in this mass window. The improvement follows from a larger collecting area, integration time, and spatial resolution, as well as from improvements in signal to noise and sky subtraction made possible by strong-lensing mass models of these clusters. The new limits either require that the two-photon coupling of the axion be extremely weak or that the axion mass window between 4.5 eV and 7.7 eV be closed. Implications for sterile-neutrino dark matter are discussed briefly also
The Dark Matter Density Profile in Brightest Cluster Galaxies
No full textThe inner dark matter (DM) density slope is an important test of our understanding of DM and its interplay with baryons during galaxy formation. Two of the main challenges in comparing to numerical simulations are measuring the mass profile over a wide radial range, and separating the contributions of the baryons and DM. I will show that the cores of galaxy clusters are an opportune place to make progress on these fronts due to the several precise observational tools that are available. By combining strong and weak gravitational lensing with spatially-resolved stellar kinematic measures within the centrally-located brightest cluster galaxies (BCGs), we have measured the total and DM density profiles in 7 relaxed galaxy clusters from radii of ~3 kpc to 3 Mpc. Surprisingly, we found that the slope of the total density profile follows that seen in CDM-only simulations quite closely, even at small radii where the contribution of stellar mass in the BCG is significant. Correspondingly, when the DM is isolated, its inner density slope is systematically shallower than a CDM-type cusp. Furthermore, the inner DM slope appears to correlate with properties of the BCG, providing a clue that DM in the cluster core is affected by the assembly history of the central galaxy. I will briefly discuss several physical scenarios that might explain these findings and evaluate their likelihood in light of our observations
Strong Lensing Modeling in Galaxy Clusters as a Promising Method to Test Cosmography. I. Parametric Dark Energy Models
No full textIn this paper we probe five cosmological models for which the dark energy equation of state parameter, w(z), is parameterized as a function of redshift using strong lensing data in the galaxy cluster Abell 1689. We constrain the parameters of the w(z) functions by reconstructing the lens model under each one of these cosmologies with strong lensing measurements from two galaxy clusters, Abell 1689 and a mock cluster, Ares, from the Hubble Frontier Fields Comparison Challenge, to validate our methodology. To quantify how the cosmological constraints are biased due to systematic effects in the strong lensing modeling, we carry out three runs considering the following uncertainties for the multiple image positions: 0.′′25, 0.′′5, and 1.′′0. With Ares, we find that larger errors decrease the systematic bias on the estimated cosmological parameters. With real data, our strong-lensing constraints on w(z) are consistent with those derived from other cosmological probes. We confirm that strong lensing cosmography with galaxy clusters is a promising method to constrain w(z) parameterizations. A better understanding of galaxy clusters and their environment is needed, however, to improve the SL modeling and hence to estimate stringent cosmological parameters in alternative cosmologies
Juventude e televisão: apropriações e representações de uma identidade local
No full textEste artigo discute a representação da cidade de Cataguases (MG) transmitida pelo telejornal MGTV, da TV Integração de Juiz de Fora. A partir de discussões em grupos focais com estudantes da cidade, nosso objetivo é analisar quais elementos da identidade local são focalizados pela TV regional e como eles são interpretados pelos estudantes. Fundamentamos nossas discussões teóricas em conceitos como representações sociais, identidades e diferenças e detectamos duas formas diferentes de reconhecimento de Cataguases na TV: de um lado, jovens da escola pública não se sentem representados pelo telejornal; por outro lado, jovens da escola particular se mostram familiarizados com tradições da cultura local difundidas pela elite da cidade
Testing gravity with galaxy-galaxy lensing and redshift-space distortions using CFHT-Stripe 82, CFHTLenS, and BOSS CMASS datasets
No full textThe combination of galaxy-galaxy lensing (GGL) and redshift space distortion of galaxy clustering (RSD) is a privileged technique to test general relativity predictions and break degeneracies between the growth rate of structure parameter f and the amplitude of the linear power spectrum sigma(8). We performed a joint GGL and RSD analysis on 250 sq. deg using shape catalogues from CFHTLenS and CFHT-Stripe 82 and spectroscopic redshifts from the BOSS CMASS sample. We adjusted a model that includes non-linear biasing, RSD, and Alcock-Paczynski effects. We used an N-body simulation supplemented by an abundance matching prescription for CMASS galaxies to build a set of overlapping lensing and clustering mocks. Together with additional spectroscopic data, this helps us to quantify and correct several systematic errors, such as photometric redshifts. We find f (z = 0.57) = 0.95 +/- 0.23, sigma(8)(z = 0.57) = 0.55 +/- 0.07 and Omega(m) = 0.31 +/- 0.08, in agreement with Planck cosmological results 2018. We also estimate the probe of gravity E-G = 0.43 +/- 0.10, in agreement with Lambda CDM-GR predictions of E-G = 0.40. This analysis reveals that RSD efficiently decreases the GGL uncertainty on Omega(m) by a factor of 4 and by 30% on sigma(8). We make our mock catalogues available on the Skies and Universe database
THE CASSAVA (MANIHOT-ESCULENTA, C) CV PIONEIRA .3. COOKING CHARACTERISTICS
No full textThe edible parts of cassava cultivar Pioneira roots after 12 and 24 months of cultivation were analysed for human consum. The yield was 63% when the roots were harvested at the right time (12 months), and lower (58%) for older roots, with 24 months. Total cyanide contents were 62,0 - 61,8 and 58,0 - 63,4 ppm, respectively. Cooking time was 13,5 min and 19,5 min, respectively, although the cooked mass quality was similar good. The edible part of the roots was processed in french fries or tholes, submited to two treatment: blanching for three minutes and boiling for ten minutes. Treated and in natura tholes were fried in vegetable oil at 190-degrees-C. The effect of freezing (-20-degrees-C for 60 days) on the cooking quality was also evaluated. The frozen storage reduced the total cyanid content in all treatment. The rate of cyanid decrease were 45%, 84% and 88% with frying, blanching and frying, and boiling and frying, respectively. Blanching followed by frying assured a safe cyanid level for human consum as well as a good acceptance in sensorial analysis. The influence of the age of the roots in cooking quality was a decrease in softness. Frozen storage softened the 24 month old roots and worsened the flavor of 12 month old root. For table purposes cassava roots should be processed in french fries and blanching, what would allow frozen storage of edible part.UNIV ESTADUAL PAULISTA JULLO MESQUITA FILHO,FAC CIENCIAS AGRON,DEPT TECNOL PROD AGROPECUARIOS,BR-18600 BOTUCATU,SP,BRAZILUNIV ESTADUAL PAULISTA JULLO MESQUITA FILHO,FAC CIENCIAS AGRON,DEPT TECNOL PROD AGROPECUARIOS,BR-18600 BOTUCATU,SP,BRAZI
Concepções de uma estética materialista para uma arte transformadora: a superação do caráter abstrato na particularidade do trabalho artístico
No full textEste artigo tem como objetivo resgatar as bases de uma estética materialista - principalmente, as desenvolvidas por György Lukács - que lance luz sobre a produção artística como elaboração da própria realidade, e que, por consequência, se configure num instrumento de auxílio à superação das contradições materiais. Partimos do pressuposto de que a dominação cultural representa uma extensão do poder que o capital exerce sobre o trabalho, reduzindo as possibilidades de transformação a partir das elaborações artísticas. A partir do movimento dialético entre base e superestrutura, a produção artística como reflexo da realidade pode estabelecer um caráter transformador da vida social, desde que a obra de arte represente de maneira efetiva possibilidades de contrapor e superar as contradições existentes no capital quando recobra seu caráter objetivo na própria vida humana.This article aims to rescue the principles of a materialist aesthetic - mainly those ones developed by György Lukács - that focuses on the artistic production as an elaboration of its own reality, and as a consequence, becomes an aid instrument that supports the overcoming of material contradictions. We assumed here that cultural domination is an extension of the power of capital over labor, reducing the possibility of transformation through artistic elaborations. From the dialectic movement between basis and superstructure, the artistic production as a reflection of reality may become a transformative force in society, considering that the masterpiece represents in an effective way possibilities to oppose and overcome the contradictions in capital when it regains its objective character in human life
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