1,721,004 research outputs found
Lights and Shadows on Galaxies Understanding
No full textWith this book we neither aimed at tracing a history, even concise, of extragalactic
astronomy nor at summarizing the vast panorama of scientific successes in this
field of astrophysics. Our wish was to stimulate some distinguished researchers, via
interviews in specific fields of extragalactic studies, at expressing their own convictions
and perplexities about the progresses achieved in our understanding of galaxies
across one century of research, if necessary emphasizing the scientific problems that
still remain open. After about fifty interviews, we try in this chapter to delineate a
picture underlying the facts and the views emerged from the presentations.
The US of the second decade of XXth century has been the cradle where a bunch
of scientists triggered a debate about the nature of spiral nebulæ, and put into discussion
the size of The Galaxy set by Jacobus Kapteyn. The new research field,
extragalactic astronomy, very soon reached the rank of a mature scientific branch
of astrophysics “on the shoulder of giants” of the caliber of Hubble, Zwicky and
Baade. However, it was only after WWII that the growth of extragalactic astronomy
was overwhelming thanks to big investments in US and later on, for the worse economic
conditions, also in some European countries and in Japan. In the last decade
of the XXth century extragalactic astronomy assumed the today physiognomy of
highly developed science branch in most of the advanced and emerging economies.
The national level institutions and observing facilities characterizing the 1960-1980s
decades boosted huge international collaborations and consortia, with hundreds of
researchers involved with ground based telescopes located in the best observing
sites. Space facilities with a complete wavelength coverage bypassed the limitations imposed by the Earth atmosphere providing a panchromatic view of galaxies. We
refer to this as the Big Science era of extragalactic astronomy
From the realm of the nebulae to populations of galaxies: dialogues on a century of research
Full text linkIn order to outline possible future directions in galaxy research, this book wants to be a short stopover, a moment of self-reflection of the past century of achievements in this area. Since the pioneering years of galaxy research in the early 20th century, the research on galaxies has seen a relentless advance directly connected to the parallel exponential growth of new technologies. Through a series of interviews with distinguished astronomers the editors provide a snapshot of the achievements obtained in understanding galaxies. While many initial questions about their nature have been addressed, many are still open and require new efforts to achieve a solution. The discussions may reveal paradigms worthwhile revisiting. With the help of some of those scientists who have contributed to it, the editors sketch the history of this scientific journey and ask them for inspirations for future directions of galaxy research
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
Early-type galaxies across the UV-optical color magnitude diagram
No full textWith the aim to clarify the mechanisms driving the evolution of galaxies in nearby groups, we focus on Early-Type galaxies (ETGs) of two groups in the Leo cloud. Using SPH simulations with chemo-photometric implementation, we match kinematical, photometric and morphological properties of ETGs to trace back their evolution. We follow ETG evolution in the rest-frame UV-optical color magnitude diagram (CMD), from the blue cloud (BC) to the red sequence (RS), through the green valley (GV). ETGs brighter than Mr ~ -21 mag are old (13-14 Gyr) and spend up to 10 Gyr in the BC before they reach the RS. ETGs fainter than Mr=-21 mag are slightly younger (11-12 Gyr), and spend about 7-8 Gyrs in the BC. All ETGs cross the GV in about 3-4 Gyr, the turn-off occurs at z~ 0.3-0.4. For UGC 6324, the faintest ETG in our sample, simulations predict strong oscillations in the GV. We conclude that ETGs evolution in the two groups is driven by gravitational mechanisms such as merging and/or interactions which may happen before or during the collapse phase of groups
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