1,721,062 research outputs found
HI in the Dusty Elliptical Galaxy NGC5266
No full textRecent observations with the Australia Telescope Compact Array show that the elliptical galaxy NGC 5266 has a disk of neutral hydrogen extending to almost 10Re. This HI disk lies along the galaxy's major axis, at right angles to the inner minor-axis dust lane. The geometry and kinematics of the gas will allow us to determine both the intrinsic shape of the stellar galaxy and the mass distribution. The mass-to-light ratio M/L_B rises from about 2 in the central regions to ~12 at 9Re (H0=50 km/s/Mpc)
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
The HI-rich elliptical galaxy NGC 5266: an old merger remnant?
No full textWe present HI images for the dust-lane elliptical galaxy NGC 5266. This galaxy contains more than 10 billion solar masses of HI and our data show that the neutral hydrogen extends to about 8 arcmin each side of the nucleus, or 8 times the optical half-light radius. Surprisingly, the outer HI gas extends almost orthogonal to the optical dust lane. The overall HI kinematics can be successfully modeled by assuming that the gas lies in two orthogonal planes: in the plane of the dust lane in the central parts and perpendicular to this in the outer regions. The large amount of neutral gas observed and the HI morphology, suggest that this object may have formed from the merger of two gas rich spiral galaxies. If so, it probably represents a relatively old merger remnant since most of the HI appears settled. The mass-to-light ratio has also been derived with evidence for a dark matter halo around this galaxy
The HI-Rich Elliptical Galaxy NGC 5266
No full textWe present new HI images of the dust-lane elliptical galaxy NGC 5266 already known from single-dish observations to contain a large amount of HI. Our new data confirm that NGC 5266 contains ~2.4 x 10^10 m_sun (for H0 = 50 km/s/Mpc) of neutral hydrogen, i.e. more than most spiral galaxies of similar luminosity. The gas extends to ~8' each side of the nucleus, or 8 times the optical half-light radius R_e. Surprisingly, most of the HI extends almost orthogonal to the optical dust lane. A small fraction of the HI is associated with the dust lane and there are some hints of a faint warp connecting the two structures. The HI distribution is somewhat clumpy and asymmetric, but the overall velocity field in the inner 4' can be successfully modeled by assuming that the gas lies mainly in two perpendicular planes - in the plane of the dust lane in the central parts and orthogonal to this in the outer regions. Beyond the 4' radius, the gas has a different structure and may be in two tidal tails, or an edge-on ring. Measurement of the HI rotation curve is affected by asymmetries in the gas distribution, but the rotation velocity is at least 250 km/s at a radius of 4', and a flat rotation curve of ~270 km/s is consistent with the data. This would imply a value of M/L_B ~8 at ~4 R_e. If the outermost HI is in an edge-on ring, we estimate M/L_B ~16 at ~8 R_e. Comparing this with the value derived from optical observations for the inner region we find an increase of M/L_B by a factor ~2.7 at r~4 R_e, and by 5.3 at r~8 R_e. The large amount of neutral gas observed in NGC 5266 (M_HI/L_B~0.2) and the HI morphology, suggest that this object may have formed from the merger of two spiral galaxies. If so, NGC 5266 probably represents a relatively old merger remnant since most of the HI gas appears settled
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
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