1,720,969 research outputs found
Tidal stripping as a possible origin of the ultra diffuse galaxy lacking dark matter
No full textInternational audienceRecent observations revealed a mysterious ultra diffuse galaxy, NGC 1052-DF2, in the group of a large elliptical galaxy, NGC 1052. Compared to expectations from abundance matching models, the dark matter mass contained in NGC 1052-DF2 is smaller by a factor of ∼400. We utilize controlled N-body simulations of the tidal interaction between NGC 1052 and a smaller satellite galaxy that we suppose as the progenitor of NGC 1052-DF2, to test if tidal stripping can explain dark-matter deficiency at such levels. We find that when assuming a tightly bound and quite radial orbit and cored density structure for the dark halo of the satellite, our simulations reproduce well both the mass profile and the effective radius inferred from the observations of NGC 1052-DF2. Orbital parameters are in the tail, but still consistent with measurements of their distributions from cosmological simulations. Such strongly dark-matter deficient galaxies, in our scenario, are thus expected to be relatively rare in groups and clusters, and not present in the field
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
Formation of dense filaments induced by runaway supermassive black holes
Full text linkA narrow linear object extending from the centre of a
galaxy at redshift has recently been discovered and interpreted as
shocked gas filament forming stars. The host galaxy presents an irregular
morphology, implying recent merger events. Supposing that each of the
progenitor galaxies has a central supermassive black hole (SMBH) and the SMBHs
are accumulated at the centre of the merger remnant, a fraction of them can be
ejected from the galaxy with a high velocity due to interactions between SMBHs.
When such a runaway SMBH (RSMBH) passes through the circumgalactic medium
(CGM), converging flows are induced along the RSMBH path, and star formation
could eventually be ignited. We show that the CGM temperature prior to the
RSMBH perturbation should be below the peak temperature in the cooling function
to trigger filament formation. While the gas is temporarily heated due to
compression, the cooling efficiency increases, and gas accumulation becomes
allowed along the path. When the CGM density is sufficiently high, the gas can
cool down and develop a dense filament by . The mass and velocity of the
RSMBH determine the scale of filament formation. Hydrodynamical simulations
validate the analytical expectations. Therefore, we conclude that the
perturbation by RSMBHs is a viable channel to form the observed linear object.
Using the analytic model validated by simulations, we show that the CGM around
the linear object to be warm ().Comment: corrected typos, accepted for publication in MNRA
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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