314 research outputs found
O estatuto da sintaxe no sujeito histórico gramatical: entre a regra e a transgressão
No full textGesualda Rasia examines historically from a discursive perspective the approach to syntactic facts by their regularities or their irregularities in linguistic and grammatical studies. After that, she analyses utterances in Brazilian grammarsfrom the 1930's, in which she observes the emergency of transgression in the very proposition of rigid rules. According to Rasia, such utterances illustrate the tense con viviality that materializes the contradiction inherent to the grammatical historical subject between the homogeneity of the theoretical object and the heterogeneity of the real object.Gesualda Rasia examina historicamente, sob o olhar da Análise de Discurso, a abordagem dos fatos sintáticos por suas regulari dades ou por suas irregularidades nos estudos lingüísticos e gramaticais. Em seguida, a autora analisa enunciados de gramáticas brasileiras da década de 1930, nos quais observa o aparecimento da transgressão justamente na proposta de rigidez da regra. De acordo com ela, tais enunciados ilustram o convívio tenso que materializa a contradição inerente ao sujeito-histórico gramatical entre a homogeneidade do objeto teórico e a heterogeneidade do objeto real.Gesualda Rasia examina historicamente, sob o olhar da Análise de Discurso, a abordagem dos fatos sintáticos por suas regulari dades ou por suas irregularidades nos estudos lingüísticos e gramaticais. Em seguida, a autora analisa enunciados de gramáticas brasileiras da década de 1930, nos quais observa o aparecimento da transgressão justamente na proposta de rigidez da regra. De acordo com ela, tais enunciados ilustram o convívio tenso que materializa a contradição inerente ao sujeito-histórico gramatical entre a homogeneidade do objeto teórico e a heterogeneidade do objeto real
Catalogo e analisi delle singole sepolture
No full textAnalytical description and material culture catalogue of all graves and grave goods from the Lombard necropolis of Andrazza, Forni di Sopra (UD
Systematics in the X-ray cluster mass estimators
No full textWe examine the systematics affecting the X-ray mass estimators applied
to a set of five galaxy clusters resolved at high resolution in
hydrodynamic simulations, including cooling, star formation and feedback
processes. These simulated objects are processed through the X-ray Map
Simulator, X-MAS, to provide Chandra-like long exposures that are
analysed to reconstruct the gas temperature, density and mass profiles
used as input. These clusters have different dynamic state: we consider
a hot cluster with temperature T = 11.4keV, a perturbed cluster with T =
3.9keV, a merging object with T = 3.6keV, and two relaxed systems with T
= 3.3keV and T = 2.7keV, respectively. These systems are located at z =
0.175 so that their emission fits within the Chandra ACIS-S3 chip
between 0.6 and 1.2 R500.
We find that the mass profile obtained via a direct application of the
hydrostatic equilibrium (HE) equation is dependent upon the measured
temperature profile. An irregular radial distribution of the temperature
values, with associated large errors, induces a significant scatter on
the reconstructed mass measurements. At R2500, the actual
mass is recovered within 1σ, although we notice this estimator
shows high statistical errors due to high level of Chandra background.
Instead, the poorness of the β-model in describing the gas density
profile makes the evaluated masses to be underestimated by ~40 per cent
with respect to the true mass, both with an isothermal and a polytropic
temperature profile. We also test ways to recover the mass by adopting
an analytic mass model, such as those proposed by Nvarro, Frenk &
White and Rasia, Tormen & Moscardini, and fitting the temperature
profile expected from the HE equation to the observed one. We conclude
that the methods of the HE equation and those of the analytic fits
provide a more robust mass estimation than the ones based on the
β-model. In the present work, the main limitation for a precise
mass reconstruction is to ascribe to the relatively high level of the
background chosen to reproduce the Chandra one. After artificially
reducing the total background by a factor of 100, we find that the
estimated mass significantly underestimates the true mass profiles. This
is manly due (i) to the neglected contribution of the gas bulk motions
to the total energy budget and (ii) to the bias towards lower values of
the X-ray temperature measurements because of the complex thermal
structure of the emitting plasma
ON THE DISCREPANCY BETWEEN THEORETICAL AND X-RAY CONCENTRATION-MASS RELATIONS FOR GALAXY CLUSTERS
No full textIn the past 15 years, the concentration-mass relation has been investigated diffusely in theoretical studies. On the other hand, only recently has this relation been derived from X-ray observations. When that happened, the results caused a certain level of concern: the X-ray normalizations and slopes were found significantly dissimilar from those predicted by theory. We analyzed 52 galaxy clusters and groups, simulated with different descriptions of the physical processes that affect the baryonic component, with the purpose of determining whether these discrepancies are real or induced by biases in the computation of the concentration parameter or in the determination of the selection function of the cluster sample for which the analysis is carried out. In particular, we investigate how the simulated concentration-mass relation depends (1) on the radial range used to derive the concentration; (2) on the presence of baryons in the simulations, and on the effect of star formation and feedback from supernovae and active galactic nuclei (AGNs). Finally, we evaluate (3) how the results differ when adopting an X-ray approach for the analysis and (4) how the selection function based on X-ray luminosity can impact the results. All effects studied go in the direction of alleviating the discrepancy between observations and simulations, although with different significance: while the choice of the radial range to fit the profiles and the inclusion of the baryonic component play only a minor role, the X-ray approach to reconstruct the mass profiles and the selection of the cluster sample have a strong impact on the resulting concentration-mass relation. Extending the fit to the most central regions or reducing the fitting radius from the virial boundary to the typical X-ray external radius causes an increase of the normalization in radiative simulations by 5%-10%. In the second case, we measure a slope that is up to twice steeper than that derived by using the typical theoretical radial range. Radiative simulations including only supernova feedback produce 30% higher concentrations than the dark matter case. Such a difference is largely reduced when including the effect of AGN feedback. The concentration-mass relation derived from the X-ray synthetic catalog is significantly steeper due to the combination of several different effects, such as environment, dynamical state and dynamical history of the clusters, bias in mass and temperature measurements, and their dependence on the radius and on the mass of the system. Finally, selecting clusters according to their X-ray luminosity produces a net increase in both normalization and slope of the relation, since at fixed mass, the most luminous clusters are also the most concentrated
Simulating Chandra observations of galaxy clusters
No full textAlthough trivial in principle, direct comparison of galaxy clusters
X-ray observations to numerical hydro-N-body simulations is not always
simple, because of many possible artefacts introduced by the instrument
response, sky background and instrumental noise. To address these
problems, we constructed the software package X-MAS (X-ray Map
Simulator), a tool devoted to simulate X-ray observations of galaxy
clusters obtained from hydro-N-body simulations. One of the main
features of X-MAS is the ability to generate event files following the
same standards used for real observations. This implies that its
simulated observations can be analysed in the same way as - and with the
same tools of - real observations. In this paper we present how the
X-MAS package works, and discuss its application to the simulation of
Chandra ACIS-S3 observations. Using the results of high-resolution
hydro-N-body simulations, we generate fake Chandra observations of a
number of simulated clusters. We then compare some of the main physical
properties of the input data to those derived from the simulated
observations after performing a standard imaging and spectral analysis.
We find that, because of the sky background, the lower surface
brightness spatial substructures, which can be easily identified in the
simulations, are no longer detected in the simulated observations. We
also show that, when a cluster has a complex (i.e. not isothermal)
thermal structure along the line of sight, then the projected
spectroscopic temperature obtained from the observation is significantly
lower than the emission-weighed value inferred directly from
hydrodynamical simulation. This implies that much attention should be
paid in the theoretical interpretation of observed temperatures
O OLHAR DO COLABORADOR ACERCA DA AVALIAÇÃO DE DESEMPENHO NA UNIJUÍ/RS
No full textEste artigo teve como proposta analisar a avaliação de desempenho desenvolvida na UNIJUÍ e conhecer a percepção dos técnicos administrativos e gestores acerca deste processo. Metodologicamente a pesquisa configura-se como de natureza aplicada, de abordagem qualitativa, de acordo com os objetivos exploratórios e descritivos, e por fim, de acordo com os procedimentos técnicos como: bibliográfica, documental, de campo e de levantamento. Concluiu-se que a avaliação de desempenho na UNIJUÍ está consolidada uma vez que ocorre há alguns anos e os seus colaboradores entendem como importante e necessária, havendo comprometimento de todos os envolvidos neste processo. Contudo para ser um processo de avaliação que deve ser orientado pela preparação, envolvimento e comprometimento dos avaliadores e avaliados, primando pela clareza, transparência, imparcialidade e profissionalismo, é imprescindível, melhorar algumas práticas de gestão, a análise e encaminhamentos a partir dos resultados. Conclui-se que é necessário rever o instrumento aplicado e sua forma de avaliação no que se refere aos quesitos: acompanhamento, desempenhando, aperfeiçoando e empreendendo, bem como, melhorar a forma de apresentação dos objetivos desta avaliação por parte do Setor de Recursos Humanos
Weighing simulated galaxy clusters using lensing and X-ray
No full textContext. Measuring the mass of galaxy clusters is a key issue in cosmology. Among the methods employed to achieve this goal, the techniques based on lensing and X-ray analyses are perhaps the most widely used. However, the comparison between these mass estimates is often difficult and, in several clusters, the results apparently are inconsistent. Aims. We aim at investigating potential biases in lensing and X-ray methods to measure the cluster mass profiles. Methods. We do so by performing realistic simulations of lensing and X-ray observations that are subsequently analyzed using observational techniques. The resulting mass estimates are compared among them and with the input models. Three clusters obtained from state-of-the-art hydrodynamical simulations, each of which has been projected along three independent lines-of-sight, are used for this analysis. Results. We find that strong lensing models can be trusted over a limited region around the cluster core. Extrapolating the strong lensing mass models to outside the Einstein ring can lead to significant biases in the mass estimates, if the BCG is not modeled properly for example. Weak lensing mass measurements can be largely affected by substructures, depending on the method implemented to convert the shear into a mas
The origin of ICM enrichment in the outskirts of present-day galaxy clusters from cosmological hydrodynamical simulations
No full textThe uniformity of the intra-cluster medium (ICM) enrichment level in the outskirts of nearby galaxy clusters suggests that chemical elements were deposited and widely spread into the intergalactic medium before the cluster formation. This observational evidence is supported by numerical findings from cosmological hydrodynamical simulations, as presented in Biffi et al. (2017), including the effect of thermal feedback from active galactic nuclei. Here, we further investigate this picture, by tracing back in time the spatial origin and metallicity evolution of the gas residing at z = 0 in the outskirts of simulated galaxy clusters. In these regions, we find a large distribution of iron abundances, including a component of highly-enriched gas, already present at z = 2. At z > 1, the gas in the present-day outskirts was distributed over tens of virial radii from the the main cluster and had been already enriched within high-redshift haloes. At z = 2, about 40% of the most Fe-rich gas at z = 0 was not residing in any halo more massive than 10^{11} h^{-1}{ M_{\odot }} in the region and yet its average iron abundance was already 0.4, w.r.t. the solar value by Anders and Grevesse (1989). This confirms that the in situ enrichment of the ICM in the outskirts of present-day clusters does not play a significant role, and its uniform metal abundance is rather the consequence of the accretion of both low-metallicity and pre-enriched (at z > 2) gas, from the diffuse component and through merging substructures. These findings do not depend on the mass of the cluster nor on its core properties
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