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Search Results: 1 - 10 of 387983 matches for " Reinaldo R. de Carvalho "
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HCG 16 Revisited: Clues About Galaxy Evolution in Groups
Reinaldo R. de Carvalho,Roger Coziol
Physics , 1999, DOI: 10.1086/300816
Abstract: We present new spectroscopic observations of 5 galaxies, members of the unusually active compact group HCG 16, observed using the Palomar 5m telescope. The high signal to noise ratios (S/N $\sim 70$) of the spectra allow us to study the variation of the emission line characteristics and the stellar populations in the nucleus and the circumnuclear regions of the galaxies. The emission line characteristics of these galaxies are complex, varying between Seyfert 2 and LINERs or between LINERs and starbursts. All of the galaxies show traces of intermediate age stellar populations, supporting our previous result that post-starburst galaxies are common in compact groups. The galaxies HCG16--4 and HCG16--5 show double nuclei and therefore could be two cases of recent merger. Our observations support a scenario where HCG 16 was formed by the successive merger of metal poor, low mass galaxies. The galaxies HCG16--1 and HCG16--2, which are more evolved, form the old core of the group. Galaxies HCG16--4 and HCG16--5 are two more recent additions still in a merging phase. Galaxy HCG16--5 is a starburst galaxy which is just beginning to fall into the core. If HCG 16 is representative of compact groups in their early stage, the whole set of observations implies that the formation of compact groups is the result of hierarchical galaxy formation. HCG 16 could be one example of this process operating in the local universe.
The Relation Between Activity and Environment in Compact Groups of Galaxies
Roger Coziol,Angela Iovino,Reinaldo R. de Carvalho
Physics , 2000, DOI: 10.1086/301441
Abstract: We present the results of the classification of spectral activity types for 193 galaxies from a new sample of 49 compact groups of galaxies in the southern hemisphere (SCGs). This sample was selected in automated fashion from a digitized galaxy catalogue, covering an area of ~5200 sq deg, around the South Galactic Pole. It is complete up to m ~14.5 in b_j for the brightest galaxy of the group. The spectral analysis of the SCG galaxies confirms the results previously obtained for a smaller sample of Hickson's compact groups (HCG). We confirm the luminosity-activity and morphology-activity relations, as well as the predominance of AGNs (41% of SCGs galaxies). We verified also that the number of early-type non-emission-line galaxies increases with the number of members in the group. The SCGs contain more star-forming galaxies (SFGs) and less non-emission-line galaxies than HCGs, which suggests that they probe a wider range of physical properties. The SFGs are composed in majority of HII Nucleus Galaxies, which have less intense star formation than starburst galaxies. The star formation activity in SCGs is, consequently, remarkably low. The SFGs show also evidence for nuclear activity. If these results are further confirmed, 70% of the galaxies in SCGs would then have an active nucleus, making these systems remarkably rich in AGNs. Curiously, however, this characteristic of CGs generally excludes Seyfert 1 galaxies.(Abridged)
The Nature of the Activity in Hickson Compact Groups of Galaxies
Roger Coziol,André L. B. Ribeiro,Reinaldo R. de Carvalho,Hugo V. Capelato
Physics , 1997, DOI: 10.1086/305160
Abstract: We present the results of the spectral classification of the 82 brightest galaxies in a sample of 17 compact groups. We verify that the AGNs are preferentially located in the most early-type and luminous galaxies of the groups, as is usually observed in the field. But these AGNs also appear to be systematically concentrated towards the central parts of the groups. Our observations suggest a correlation between activity types, morphologies and densities of galaxies in the compact groups. This is consistent with a scenario in which galaxies of compact groups evolve by interacting with their environment and are currently in a quiet phase of their activity
Dissipationless Collapse of Spherical Protogalaxies and the Fundamental Plane
Christine C. Dantas,Hugo V. Capelato,Reinaldo R. de Carvalho,Andre L. B. Ribeiro
Physics , 2002, DOI: 10.1051/0004-6361:20020073
Abstract: Following on from the numerical work of Capelato, de Carvalho & Carlberg (1995, 1997), where dissipationless merger simulations were shown to reproduce the "Fundamental Plane" (FP) of elliptical galaxies, we investigate whether the end products of pure, spherically symmetric, one-component dissipationless {\it collapses} could also reproduce the FP. Past numerical work on collisionless collapses have addressed important issues on the dynamical/structural characteristics of collapsed equilibrium systems. However, the study of collisionless collapse in the context of the nature of the FP has not been satisfactorily addressed yet. Our aim in this paper is to focus our attention on the resulting collapse of simple one-component spherical models with a range of different initial virial coefficients. We find that the characteristic correlations of the models are compatible with virialized, centrally homologous systems. Our results strengthen the idea that merging may be a fundamental ingredient in forming non-homologous objects.
The Faint End of the Luminosity Function of Galaxies in Compact Groups
Stephen E. Zepf,Reinaldo R. de Carvalho,Andre L. B. Ribeiro
Physics , 1997,
Abstract: We study the luminosity function of galaxies in Hickson groups using our recent redshift survey of galaxies in and around 17 of these groups. We find that the galaxies in these regions have a luminosity function with M* = -19.5 + 5 log h, and alpha = -1.0, where M* and alpha are the usual parameters in the standard Schechter form of the luminosity function, and the magnitudes are measured in the B band. The formal 95% confidence intervals for M* and alpha range from (-19.3,-0.8), to (-19.7,-1.2) and are highly correlated as is usual for these fits. This luminosity function for galaxies in our Hickson group sample is very similar from that found in large surveys covering a range of environments. These values are also consistent with our earlier estimates based on a photometric analysis with statistical background correction, and do not support previous suggestions of an underabundance of intrinsically faint galaxies in compact groups. We confirm our earlier finding that the fainter galaxies are more diffusely distributed within individual groups than the brighter ones. This can be interpreted either as evidence for mass segregation within the groups or as the result of the selection procedure for Hickson groups.
"Fundamental-Plane"-Like Relations From Collisionless Stellar Dynamics: A Comparison of Mergers and Collapses
Christine C. Dantas,Hugo V. Capelato,Andre L. B. Ribeiro,Reinaldo R. de Carvalho
Physics , 2002, DOI: 10.1046/j.1365-8711.2003.06272.x
Abstract: We present a new set of dissipationless N-body simulations aiming to better understand the pure dynamical aspects of the ``Fundamental Plane'' (FP) of elliptical galaxies. We have extended our previous hierarchical merger scheme by considering the Hernquist profile for the initial galaxy model. Two-component Hernquist galaxy models were also used to study the effect of massive dark halos on the end-products characteristics. We have also performed new collapse simulations including initial spin. We found that the one-component Hernquist mergers give results similar to those found for the one-component King models, namely both were able to build-up small scatter FP-like correlations with slopes consistent with what is found for the near-infrared FP of nearby galaxies. The two-component models also reproduce a FP-like correlation, but with a significantly steeper slope. This is in agreement with what has been found for elliptical galaxies at higher redshift (0.1 $<$ z $<$ 0.6). We discuss some structural properties of the simulated galaxies and their ability to build-up FP-like correlations. We confirm that collapses generally do not follow a FP-like correlation regardless of the initial spin. We suggest that the evolution of gradients in the gravitational field of the merging galaxies may be the main ingredient dictating the final non-homology property of the end products.
The Two-Component Virial Theorem and the Physical Properties of Stellar Systems
Christine C. Dantas,Andre L. B. Ribeiro,Hugo V. Capelato,Reinaldo R. de Carvalho
Physics , 1999, DOI: 10.1086/312415
Abstract: Motivated by present indirect evidences that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem which explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the barionic or luminous component. Our analysis shows that the application of such a ``two-component virial theorem'' not only accounts for the scaling relations displayed, in particular, by elliptical galaxies, but also for the observed properties of all virialized stellar systems, ranging from globular clusters to galaxy clusters.
Evidence of Substructure in the Cluster of Galaxies A3558
Christine C. Dantas,Reinaldo R. de Carvalho,Hugo V. Capelato,Alain Mazure
Physics , 1997, DOI: 10.1086/304458
Abstract: We investigate the dynamical properties of the cluster of galaxies A3558 (Shapley 8). Studying a region of one square degree ($\sim$ 3 Mpc$^2$) centered on the cluster cD galaxy, we have obtained a statistically complete photometric catalog with positions and magnitudes of 1421 galaxies (down to a limiting magnitude of $B \sim 21$). This catalog has been matched to the recent velocity data obtained by Mazure et al. (1997) and from the literature, yielding a radial velocity catalog containing 322 galaxies. Our analysis shows that the position/velocity space distribution of galaxies shows significant substructure. A central bimodal core detected previously in preliminary studies is confirmed by using the Adaptive Kernel Technique and Wavelet Analysis. We show that this central bimodal subtructure is nevertheless composed of a projected feature, kinematically unrelated to the cluster, plus a group of galaxies probably in its initial merging phase into a relaxed core. The cD velocity offset with respect to the average cluster redshift, reported earlier by several authors, is completely eliminated as a result of our dynamical analysis. The untangling of the relaxed core component also allows a better, more reliable determination of the central velocity dispersion, which in turn eliminates the ``$\beta$-problem'' for A3558. The cluster also shows a ``preferential'' distribution of subclumps coinciding with the direction of the major axis position angle of the cD galaxy and of the central X-ray emission ellipsoidal distribution, in agreement with an anisotropic merger scenario.
The Evolution of Galaxies in Compact Groups
Roger Coziol,Reinaldo R. de Carvalho,Hugo V. Capelato,Andre L. B. Ribeiro
Physics , 1998, DOI: 10.1086/306270
Abstract: We present the analysis of the spectra of 62 galaxies in 15 compact groups. The galaxies were classified in four activity classes: galaxies without emission, starburst nucleus galaxies (SBNGs), luminous AGNs and low-luminosity AGNs (LLAGNs). The star formation in the HCG starbursts is more intense than in normal spirals, but comparable to those in the field SBNGs. Their mean gas metallicity is solar and they do not follow the metallicity-luminosity relation traced by the early-type SBNGs in the field, suggesting that most of them are late-type SBNGs. This morphology preference coupled to the observation that the HCG starbursts are predominantly in the halo of the groups is consistent with the idea that compact groups are embedded in sparser structures. The stellar metallicities of the non starburst galaxies are relatively high for their luminosities. In these galaxies the equivalent widths of the metal absorption lines are slightly narrower than normal while the Balmer absorption lines are relatively strong. All these galaxies could be ``post-starburst'' at an advanced stage of evolution. Our observations are supporting a scenario where the core of the groups are slowly collapsing evolved systems embedded in more extended structures (Ribeiro et al. 1998). In the core of the groups, the interactions were more frequent and the galaxies evolved at a more rapid rate than in their halos.
Incidência de episódios hipot?nicos-hiporresponsivos associados à vacina combinada DTP/Hib usada no Programa Nacional de Imuniza??es
Martins, Reinaldo M.;Camacho, Luiz A. B.;Lemos, Maria Cristina F.;Noronha, Tatiana G. de;Carvalho, Maria Helena C. de;Greffe, Nadja;Silva, Marli M. da;Périssé, André R.;Maia, Maria de Lourdes S.;Homma, Akira;
Jornal de Pediatria , 2007, DOI: 10.1590/S0021-75572007000800008
Abstract: objective:to evaluate the safety of a combined diphtheria-tetanus-whole cell pertussis-haemophilus influenzae type b vaccine used on the brazilian national immunizations program, chiefly the incidence of hypotonic-hyporesponsive episodes. method: follow-up of a cohort of 21,064 infants (20,925 or 99.7% adhered to the study protocol), within 48 hours of vaccination with diphtheria-tetanus-whole cell pertussis-haemophilus influenzae type b vaccine in health care units in the city of rio de janeiro, to ascertain and investigate spontaneous and solicited severe adverse events. each child was followed-up for one dose only. results: the rate of hypotonic-hyporesponsive episodes was 1/1,744 doses (confirmed cases) and 1/1,495 doses (confirmed plus suspect cases). the rate of convulsions was 1/5,231 doses. no cases of apnea were detected. these results are comparable to those found in the literature with diphtheria-tetanus-whole cell pertussis vaccine. conclusion: the diphtheria-tetanus-whole cell pertussis-haemophilus influenzae type b vaccine under study can be safely used in the national immunizations program, according to the current precautions and contraindications.
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