1,721,693 research outputs found
ROSAT HRI Investigation of the NGC 507 X-Ray Halo
No full textWe present an X-ray investigation of the elliptical galaxy NGC 507 in the Pisces cluster. We make use of archival ROSAT HRI and Chandra data, and of previously published PSPC data, to connect the large-scale structure of the halo to the core morphology. Our analysis, based on a bidimensional double beta model of the halo surface brightness, shows that the halo core (r 3r(e)) are characterized by different dynamical properties and suggests a different origin of the two components. The halo core has a complex morphology with a main X-ray emission peak, coincident with the center of the optical galaxy, and several secondary peaks. The spatial and spectral analysis of the central peak shows that this feature is produced by denser hot gas in the galaxy core. While both homogeneous and inhomogeneous cooling flow models predict a deposited mass exceeding the observed amount, our data support the scenario in which the gas is kinetically heated by stellar mass losses. Comparison with previously published studies suggests that the core of an X-ray extended galaxy is associated with the stellar distribution and has properties similar to the X-ray halos of compact galaxies. The secondary peaks are due instead to interactions between the radio-emitting plasma and the surrounding ISM, producing density fluctuations in the hot gas. We find that the energy input by the central radio source in the ISM is large enough to prevent gas cooling and may explain the failure of the cooling flow models. The total mass pro. le derived from the bidimensional model shows that a significant amount of dark matter is present at large radii. The dark halo extends on cluster scales and is likely associated with the whole cluster rather than with NGC 507. This structure is typical of many X-ray bright early-type galaxies and may explain the spatial and spectral differences with X-ray compact galaxies largely debated in the literature. The large-scale surface brightness distribution is irregular and more extended in the northeast direction. The displacement of the cluster halo from the optical galaxy and the filamentary structures observed in the halo core further suggest that the galaxy may be slowly moving within the group potential. Finally, we found that similar to20% of the sources detected by Kim & Fabbiano in the NGC 507 halo are due to point sources, while the nature of the remaining population is not clear. If associated with NGC 507, they could be either accreting binaries hosting a massive black hole or density clumps of the X-ray halo
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Deep ROSAT-HRI observation of the elliptical galaxy NGC 1399
No full textWe present the results of a deep (167 ks) observation of the NGC 1399/NGC 1404 field obtained from data collected between 1993 and 1996 with the ROSAT High Resolution Imager. We take advantage of the 5" resolution of the HRI to study in detail the structure of the galactic halo and to relate the results to those obtained at larger scales with poorer resolution instruments. We discuss possible non-equilibrium scenarios that may explain the global halo structure. We also find evidence of interactions between the nuclear radio source and the inner gaseous halo
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Deep ROSAT-HRI observation of the elliptical galaxy NGC 1399
No full textWe present the results of a deep (167 ks) observation of the NGC 1399/NGC 1404 field obtained from data collected between 1993 and 1996 with the ROSAT High Resolution Imager. We take advantage of the 5" resolution of the HRI to study in detail the structure of the galactic halo and to relate the results to those obtained at larger scales with poorer resolution instruments. We discuss possible non-equilibrium scenarios that may explain the global halo structure. We also find evidence of interactions between the nuclear radio source and the inner gaseous halo
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