1,720,977 research outputs found
Digging into the Galactic Bulge: Stellar Population and Structure of the Poorly Studied Cluster NGC 6316
Full text linkHigh-resolution Hubble Space Telescope optical observations have been used to analyze the stellar population and the structure of the poorly investigated bulge globular cluster NGC 6316. We constructed the first high-resolution reddening map in the cluster direction, which allowed us to correct the evolutionary sequences in the color–magnitude diagram (CMD) for the effects of differential reddening. A comparison between the CMDs of NGC 6316 and 47 Tucanae revealed strikingly similar stellar populations, with the two systems basically sharing the same turnoff, subgiant branch, and horizontal branch morphologies, indicating comparable ages. The red giant branch in NGC 6316 appears slightly bluer than in 47 Tucanae, suggesting a lower metal content. This has been confirmed by the isochrone fitting of the observed CMD, which provided us with updated values of the cluster age, distance, average color excess, and metallicity. We estimated an absolute age of 13.1 ± 0.5 Gyr, consistent with the age of 47 Tucanae, an average color excess E ( B − V ) = 0.64 ± 0.01, and a true distance modulus ( m − M ) _0 = 15.27 ± 0.03 that sets the cluster distance at 11.3 kpc from the Sun. In addition, the photometric estimate of the cluster metallicity suggests [Fe/H] ≈ −0.9, which is ∼0.2 dex smaller than that of 47 Tucanae. We also determined the gravitational center and the density profile of the system from resolved stars. The latter is well reproduced by a King model. Our results confirm that NGC 6316 is another extremely old relic of the assembly history of the Galaxy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Empirical measurement of the dynamical ages of three globular clusters and some considerations on the use of the dynamical clock
Full text linkWe have used the ``dynamical clock'' to measure the level of dynamical
evolution reached by three Galactic globular clusters (namely, NGC 3201, NGC
6316 and NGC 6440). This is an empirical method that quantifies the level of
central segregation of blue stragglers stars (BSSs) within the cluster
half-mass radius by means of the parameter, defined as the area
enclosed between the cumulative radial distribution of BSSs and that of a
lighter population. The total sample with homogeneous determinations of
now counts a gran-total of 59 clusters: 52 old GCs in the Milky Way
(including the three investigated here), 5 old clusters in the Large Magellanic
Cloud, and 2 young systems in the Small Magellanic Cloud. The three objects
studied here nicely nest into the correlation between and the
central relaxation time defined by the previous sample, thus proving and
consolidating the use of the dynamical clock as an excellent tracer of the
stage of star cluster dynamical evolution in different galactic environments.
Finally, we discuss the advantages of using the dynamical clock as an indicator
of star cluster dynamical ages, compared to the present-day central relaxation
time.Comment: 16 pages and 8 figures, in press in the Ap
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Discovery of a double sequence of blue straggler stars in the core-collapsed globular cluster NGC 6256
Full text linkWe used a combination of high-resolution optical images acquired with the
Hubble Space Telescope and near-IR wide-field data to investigate the stellar
density profile and the population of blue straggler star (BSS) in the Galactic
globular cluster NGC6256, with the aim of probing its current stage of internal
dynamical evolution. We found that the inner stellar density profile
significantly deviates from a King model while is well reproduced by a steep
cusp with a power-law slope alpha=-0.89, thus implying that the cluster is
currently in the post core-collapse (PCC) phase. This is also confirmed by the
very high segregation level of the BSS population measured through the A+
parameter. We also found that the distribution of BSSs in the color-magnitude
diagram is characterized by a collimated blue sequence and a red more sparse
component, as already observed in other three PCC clusters. The comparison with
appropriate collisional models demonstrates that the vast majority of the BSSs
lying along the collimated blue sequence is consistent with a generation of
coeval (1 Gyr-old) stars with different masses originated by an event that
highly enhanced the collisional rate of the system (i.e. the core collapse).
This study confirms that the segregation level of BSSs is a powerful dynamical
diagnostic also of star cluster in a very advanced stage of dynamical
evolution. Moreover, it pushes forward the possibility of using the morphology
of the BSS in the color-magnitude diagram as a tracer of the core-collapse and
subsequent dynamical evolutionary phases.Comment: Accepted for publication in Ap
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
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