1,721,001 research outputs found
AGN and starburst radio activity in the A3558 cluster complex
No full textWe present Very Large Array (VLA) 1.4 GHz (21 cm)
observations of the region between the centres of A3558 and A3562, in the major
cluster merger complex of the Shapley Concentration.
Our final catalogue includes a total of 174 radio sources above the
flux density limit of 0.25 mJy b-1. By cross-correlation with optical
and spectroscopic catalogues we found 33 optical counterparts
belonging to the Shapley Concentration.
We investigated the effects of cluster merger on the radio emission
properties of the galaxy population by means of the radio source
counts and the radio luminosity functions (RLF). We found that the radio
source counts are consistent with the field source counts.
The RLF of elliptical and S0 galaxies in the region surveyed,
is consistent with the “universal” RLF for early-type galaxies.
This result suggests that the deficit in radio galaxies found in our
previous work over the whole A3558 chain is entirely due to the
cluster A3558.
A population of faint radio
galaxies (log (W Hz-1) \la 22) is also found.
Half of these objects are also blue, suggesting that
starburst is the main mechanism driving the radio emission.
Finally, we detected 14 spiral radio galaxies, whose ratio between
radio and optical emission is similar to those found in galaxies located
in rich and dynamically evolved clusters.
Our results are briefly discussed in the light of the age and stage
of the merger in the A3558 cluster complex
The Complete Local-volume Groups Sample - II. A study of the central radio galaxies in the high-richness sub-sample
Full text linkWe present a study of the radio properties of the dominant early-type galaxies in 26 galaxy groups, the high-richness sub-sample of theComplete Local-volumeGroups Sample (CLoGS). Combining new 610 and 235 MHz observations of 21 groups from the Giant Metrewave Radio Telescope (GMRT) with archival GMRT and Very Large Array (VLA) survey data, we find a high detection rate, with 92 per cent of the dominant galaxies hosting radio sources. The sources have a wide range of luminosities, 1020-1024 WHz-1 in the 235 and 610 MHz bands. Themajority (54 per cent) are point-like, but 23 per cent have radio jets, and another 15 per cent are diffuse radio sources with no clear jet/lobe morphology. Star formation may dominate the radio emission in 2 of the point-like systems and may make a significant contribution to a further 1-3, but is unlikely to be important in the remaining 21 galaxies. The spectral index of the detected radio sources ranges from very flat values of ~0.2 to typical radio synchrotron spectra of ~0.9 with only two presenting steep radio spectra with α235610 > 1. We find that jet sources are more common in X-ray bright groups, with radio non-detections found only in X-ray faint systems. Radio point sources appear in all group environments irrespective of their X-ray properties or spiral fraction.We estimate the mechanical power (Pcav) of the jet sources in the X-ray bright groups to be 1041-1043 erg s-1, with the two large-scale jet systems (NGC 193 and NGC 4261) showing jet powers two orders of magnitude greater than the radiative losses from the cool cores of their groups. This suggests that central AGN are not always in balance with cooling, but may instead produce powerful periodical bursts of feedback heating
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
Extended Radio Emission in the Perhipheral Regions of the Shapley Concentration Core
Full text linkThe Shapley Concentration (SC) is a galaxy supercluster (few tens of degrees) in the Local Universe (<z>∼0.048) which is currently undergoing cluster mergers and group accretion. It is a diversified environment, with cluster complexes in advanced evolutionary stage, groups of clusters in the very early stages of merger, fairly massive clusters with ongoing accretion activity, and smaller groups located in filaments. These features make the SC an ideal place to observe the signatures of the formation of large-scale structures in the Universe. As a matter of fact, the SC has been observed over a broad range of frequencies with the most important observatories, allowing for a unique multiband study. In this paper, we will present new results from an ongoing study of the Shapley Concentration Core, which is being carried out with the Giant Metrewave Radio Telescope (GMRT). Our work confirms the role played by radio observations in disentangling the details of the accretion and merging processes, and delivers a wealth of information in regions well outside the cluster cores. In particular, we will report on the discovery of a relic in the region between the two clusters A 3558 and A 3562, and of the radio properties of the brightest galaxy in the peripheral cluster A 3556
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
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
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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