1,720,963 research outputs found
GALAXY KINEMATICS WITH VIRUS-P: THE DARK MATTER HALO OF M87
Full text linkWe present two-dimensional stellar kinematics of M87 out to R = 238 '' taken with the integral field spectrograph VIRUS-P. We run a large set of axisymmetric, orbit-based dynamical models and find clear evidence for a massive dark matter halo. While a logarithmic parameterization for the dark matter halo is preferred, we do not constrain the dark matter scale radius for a Navarro-Frenk-White (NFW) profile and therefore cannot rule it out. Our best-fit logarithmic models return an enclosed dark matter fraction of 17.2(-5.0)(+5.0)% within one effective radius (R-e congruent to 100 ''), rising to 49.4(-8.8)(+7.2)% within 2 R-e. Existing SAURON data (R <= 13 ''), and globular cluster (GC) kinematic data covering 145 '' <= R <= 554 '' complete the kinematic coverage to R = 47 kpc (similar to 5R(e)). At this radial distance, the logarithmic dark halo comprises 85.3(-2.4)(+2.5)% of the total enclosed mass of 5.7(-0.9)(+1.3) x 10(12) M-circle dot making M87 one of the most massive galaxies in the local universe. Our best-fit logarithmic dynamical models return a stellar mass-to-light ratio (M/L) of 9.1(-0.2)(+0.2) (V band), a dark halo circular velocity of 800(-25)(+75) km s(-1), and a dark halo scale radius of 36(-3)(+7) kpc. The stellar M/L, assuming an NFW dark halo, is well constrained to 8.20(-0.10)(+0.05) (V band). The stars in M87 are found to be radially anisotropic out to R congruent to 0.5 R-e, then isotropic or slightly tangentially anisotropic to our last stellar data point at R = 2.4 R-e where the anisotropy of the stars and GCs are in excellent agreement. The GCs then become radially anisotropic in the last two modeling bins at R = 3.4 R-e and R = 4.8 R-e. As one of the most massive galaxies in the local universe, constraints on both the mass distribution of M87 and anisotropy of its kinematic components strongly inform our theories of early-type galaxy formation and evolution in dense environments.Astronom
Dynamical Measurements Of Black Hole Masses In Four Brightest Cluster Galaxies At 100 Mpc
Full text linkWe present stellar kinematics and orbit superposition models for the central regions of four brightest cluster galaxies, based upon integral-field spectroscopy at Gemini, Keck, and McDonald Observatories. Our integral-field data span radii from <100 pc to tens of kiloparsecs, comparable to the effective radius of each galaxy. We report black hole masses, M-circle, of 2.1(-1.6)(+1.6) x 10(10) M-circle dot for NGC 4889, 9.7(-2.5)(+3.0) x 10(9) M-circle dot for NGC 3842, and 1.3(-0.4)(+0.5) x 10(9) M-circle dot for NGC 7768, with errors representing 68% confidence limits. For NGC 2832, we report an upper limit of M-circle < 9.0 x 10(9) M-circle dot. Our models of each galaxy include a dark matter halo, and we have tested the dependence of M-circle on the model dark matter profile. Stellar orbits near the center of each galaxy are tangentially biased, on comparable spatial scales to the galaxies' photometric cores. We find possible photometric and kinematic evidence for an eccentric torus of stars in NGC 4889, with a radius of nearly 1 kpc. We compare our measurements of M-circle to the predicted black hole masses from various fits to the relations between M-circle and stellar velocity dispersion (sigma), luminosity (L), or stellar mass (M-star). Still, the black holes in NGC 4889 and NGC 3842 are significantly more massive than all sigma-based predictions and most L-based predictions. The black hole in NGC 7768 is consistent with a broader range of predictions.NSF AST-1009663Miller Institute for Basic Research in Science, University of California, BerkeleyW. M. Keck FoundationCynthia and George Mitchell Foundation NSF-0908639GN-2003A-Q-11Astronom
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
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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