Observatorio Nacional

Rio de Janeiro, Brazil

Observatorio Nacional

Rio de Janeiro, Brazil
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Agency: European Commission | Branch: FP7 | Program: CSA | Phase: INFRA-2007-1.2.3;INFRA-2007-1.2-03 | Award Amount: 5.11M | Year: 2008

EELA-2 aims to build, on the current EELA e-Infrastructure, a high capacity, production-quality, scalable Grid Facility providing round-the-clock, worldwide access to distributed computing, storage and network resources for a wide spectrum of applications from European and Latin American scientific communities. The project will provide an empowered Grid Facility with versatile services fulfilling application requirements and ensure the long-term sustainability of the e-Infrastructure beyond the term of the project. The specific EELA-2 objectives are: - Build a Grid Facility by: Expanding the current EELA e-Infrastructure to consist of more production sites mobilising more computing nodes and more storage space, at start of the project and to further grow storage over the duration of the project; Providing, in collaboration with related projects (e.g. EGEE), the full set of Grid Services needed by all types of scientific applications; Supporting applications various types (from classical off-line data processing up to control and data acquisition of scientific instruments), selected against well defined criteria (including grid added value, suitability for Grid deployment, outreach/potential impact); - Ensure the Grid Facility sustainability: Through the already established and new contacts with policy/decision makers, collaborating with RedCLARA and NRENs and supporting the ongoing creation of e-Science Initiatives and/or National Grid initiatives (NGI). Building the support of the e-Infrastructure to provide a complete set of Global Services from a Central Operation Centre and to pave the way for the creation of Regional Operation Centres in Latin America: Attracting new applications; Making available knowledge of EELA-2 Grid Facility to all potential users, developers, and decision makers through an extensive Training and Dissemination program; Creating knowledge repositories federated with the EGEE ones.

Bordalo V.,Observatorio Nacional | Telles E.,Observatorio Nacional
Astrophysical Journal | Year: 2011

For the first time we present a new data set of emission line widths for 118 star-forming regions in H II galaxies (HIIGs). This homogeneous set is used to investigate the L-σ relation in conjunction with optical spectrophotometric observations. We were able to classify their nebular emission line profiles due to our high-resolution spectra. Peculiarities in the line profiles such as sharp lines, wings, asymmetries, and in some cases more than one component in emission were verified. From a new independent homogeneous set of spectrophotometric data, we derived physical condition parameters and performed statistical principal component analysis. We have investigated the potential role of metallicity (O/H), Hβ equivalent width (W Hβ), and ionization ratio [O III]/[O II] to account for the observational scatter of the L-σ relation. Our results indicate that the L-σ relation for HIIGs is more sensitive to the evolution of the current starburst event (short-term evolution) and dated by W Hβ or even the [O III]/[O II] ratio. The long-term evolution measured by O/H also plays a potential role in determining the luminosity of the current burst for a given velocity dispersion and age as previously suggested. Additionally, galaxies showing Gaussian line profiles present tighter correlations indicating that they are the best targets for the application of the parametric relations as an extragalactic cosmological distance indicator. Best fits for a restricted homogeneous sample of 45 HIIGs provide us with a set of new extragalactic distance indicators with an rms scatter compatible with observational errors of δlog L Hα = 0.2dex or 0.5mag. Improvements may still come from future optimized observational programs to reduce the observational uncertainties on the predicted luminosities of HIIGs in order to achieve the precision required for the application of these relations as tests of cosmological models. © 2011. The American Astronomical Society. All rights reserved..

Pereira F.I.M.,Observatorio Nacional
Nuclear Physics A | Year: 2011

We calculate the strange star properties in the framework of the Field Correlator Method. We find that for gluon condensate values G2 in the range 0.006-0.007 GeV4, which give a critical temperature Tc∼170 MeV at μc=0, the sequences of strange stars are compatible with some of the semi-empirical mass-radius relations and data obtained from astrophysical observations. © 2011 Elsevier B.V.

Pinheiro G.,Observatorio Nacional | Chan R.,Coordenacao de Astronomia e Astrofisica
General Relativity and Gravitation | Year: 2011

A new model is proposed to a collapsing star consisting of an initial inhomogeneous energy density and anisotropic pressure fluid with shear, radial heat flow and outgoing radiation. In previous papers one of us has always assumed an initial star with homogeneous energy density. The aim of this work is to generalize the previous models by introducing an initial inhomogeneous energy density and compare it to the initial homogeneous energy density collapse model. We will show the differences between these models in the evolution of all physical quantities that characterizes the gravitational collapse. The behavior of the energy density, pressure, mass, luminosity and the effective adiabatic index is analyzed. The pressure of the star, at the beginning of the collapse, is isotropic but due to the presence of the shear the pressure becomes more and more anisotropic. The black hole is never formed because the apparent horizon formation condition is never satisfied, in contrast of the previous model where a black hole is formed. An observer at infinity sees a radial point source radiating exponentially until reaches the time of maximum luminosity and suddenly the star turns off. In contrast of the former model where the luminosity also increases exponentially, reaching a maximum and after it decreases until the formation of the black hole. The effective adiabatic index is always positive without any discontinuity in contrast of the former model where there is a discontinuity around the time of maximum luminosity. The collapse is about three thousand times slower than in the case where the energy density is initially homogeneous. © 2010 Springer Science+Business Media, LLC.

Holanda R.F.L.,Observatorio Nacional
International Journal of Modern Physics D | Year: 2012

Constraints on the Hubble parameter, H0, via X-ray surface brightness and SunyaevZel'dovich effect (SZE) observations of the galaxy clusters depend on the validity of the cosmic distance duality relation (DD relation), η = DL(z)(1+z)-2/DA(z) = 1, where DL and DA are the luminosity distance and angular diameter distance (ADD), respectively. In this work, we argue that if the DD relation does not hold, the X-ray plus SZE technique furnishes a H 0* = H0η2. We use 25 ADD of galaxy clusters to obtain simultaneous constraints on H0 and possible violation of the DD relation in a flat ΛCDM model. Such a violation is parametrized by two functions: η(z) = 1 + η0z and η(z) = 1 + η0z/(1+z), where η0 is a constant parameter quantifying possible departures from the strict validity. Finally, by marginalizing on the η0 in both parametrizations, we obtain constraints on H0 regardless of the validity of the DD relation. For the linear and nonlinear η(z) functions, we obtain H0 = 75 -7 +7 km/s/Mpc and 75-7 +10 km/s/Mpc, respectively (without systematic errors). Our results support recent H 0 measurements by using X-ray and SZE observations of galaxy clusters which have taken the distance duality as valid. © World Scientific Publishing Company.

Oliveira V.C.,Observatorio Nacional | Barbosa V.C.F.,Observatorio Nacional
Geophysical Journal International | Year: 2013

We have presented a joint inversion of all gravity-gradient tensor components to estimate the shape of an isolated 3-D geological body located in subsurface. The method assumes the knowledge about the depth to the top and density contrast of the source. The geological body is approximated by an interpretation model formed by an ensemble of vertically juxtaposed 3-D right prisms, each one with known thickness and density contrast. All prisms forming the interpretation model have a polygonal horizontal cross-section that approximates a depth slice of the body. Each polygon defining a horizontal cross-section has the same fixed number of vertices, which are equally spaced from 0° to 360° and have their horizontal locations described in polar coordinates referred to an arbitrary origin inside the polygon. Although the number of vertices forming each polygon is known, the horizontal coordinates of these vertices are unknown. To retrieve a set of juxtaposed depth slices of the body, and consequently, its shape, our method estimates the radii of all vertices and the horizontal Cartesian coordinates of all arbitrary origins defining the geometry of all polygons describing the horizontal cross-sections of the prisms forming the interpretation model. To obtain a stable estimate that fits the observed data, we impose constraints on the shape of the estimated body. These constraints are imposed through the well-known zeroth- and first-order Tikhonov regularizations allowing,for example, the estimate of vertical or dipping bodies. If the data do not have enough in-depth resolution, the proposed inversemethod can obtain a set of stable estimates fitting the observed data with different maximum depths. To analyse the data resolution and deal with this possible ambiguity, we plot the ℓ2-norm of the residuals (s) against the estimated volume (vp) produced by a set of estimated sources having different maximum depths. If this s × vp curve (s as a function of vp) shows a well-defined minimum of s, the data have enough resolution to recover the shape of the body entirely. Conversely, if the observed data do not have enough resolution,some estimates with different maximum depths produce practically the same minimum value of s on the s × vp curve. In this case, the best estimate among a suite of estimates producing equally data fits is the one fitting the gravity-gradient data and producing the minima of both the source's bottom depth and volume. The histograms of the residuals can be used to quantify and remove systematic errors in the data. After removing these errors, we confirmed the ability of our method to recover the source geometry entirely (or its upper part only), if the data have suffcient (or insufficient) in-depth resolution. By inverting the gravity-gradient data from a survey over the Vinton salt dome (Louisiana, USA) with a density contrast of 0.55 g cm-3,we estimated a massive cap rock whose maximum depth attains 460 ± 10m and its shallowest portion is elongated in the northeast-southwest direction. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.

Pereira F.I.M.,Observatorio Nacional
Nuclear Physics A | Year: 2013

By using the recent nonperturbative equation of state of the quark-gluon plasma derived in the formalism of the Field Correlator Method, we investigate the bulk properties of the strange quark matter in β-equilibrium and with charge neutrality at T = p = 0. The results show that the stability of strange quark matter with respect to Fe56 is strongly dependent on the model parameters, namely, the gluon condensate G2 and the qq- interaction potential V1. A remarkable result is that the width of the stability window decreases as V1 increases, being maximum at V1 = 0 and nearly zero at V1 = 0.5GeV. For V1 in the range 0 ≤ V1 ≤ 0.5GeV, all values of G2 are lower than 0.006-0.007GeV4 obtained from comparison with lattice data at Tc(μ = 0) ~ 170MeV. Our results do not favor the possibilities for the existence of (either nonnegative or negative) absolutely stable strange quark matter. © 2012 Elsevier B.V..

Costa F.E.M.,Observatorio Nacional
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We discuss some cosmological consequences of a general model of coupled quintessence in which the phenomenological coupling between the cold dark matter and dark energy is a function of the cosmic scale factor ?(a). This class of models presents cosmological solutions in which the Universe is currently dominated by an exotic component, but will eventually be dominated by cold dark matter in the future. This dynamical behavior is considerably different from the standard ΛCDM evolution, and may alleviate some conflicts in reconciling the idea of the dark energy-dominated universe with observables in String/M theory. Finally, we investigate some observational features of this model and discuss some constraints on its parameters from current Type Ia supernovae (SNe Ia), baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) data. © 2010 The American Physical Society.

Costa F.E.M.,Observatorio Nacional | Alcaniz J.S.,Observatorio Nacional
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We propose a general class of interacting models in which the interaction between the cold dark matter component and Λ is parametrized by an arbitrary function of the cosmic scale factor (a). Differently from other dynamical Λ scenarios in which the final stage of cosmic expansion is a de Sitter phase, we find solutions of transient acceleration, in which the Λ-dark matter interaction will drive the Universe to a new dark matter-dominated era in the future. We investigate some cosmological consequences of this model and discuss some constraints on its parameters from current Type Ia aupernovae, baryonic acoustic oscillations, CMB, and H0 data. © 2010 The American Physical Society.

Gomes R.S.,Observatorio Nacional
Icarus | Year: 2011

Numerical integrations of the equations of motion of the giant planets and scattering particles show that there is a possible orbital itinerary that a particle may follow from a scattering mode up to a stable position near the orbit of 2004 XR190. This orbital evolution requires that the particle gets trapped in a mean motion resonance with Neptune coupled with the Kozai resonance. Imposing migration on Neptune while a particle is experiencing both resonances can entail an escape from resonance at a low particle's eccentricity. This eccentricity and the associated inclination are always similar to those of 2004 XR190. I conclude that 2004 XR190 was most likely a scattered object that went through those resonance processes and was eventually deposited at its current position. By the same argument, it is expected that there must exist several other objects with similar semimajor axis, eccentricity and inclination as those of 2004 XR190. © 2011 Elsevier Inc.

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