1,720,961 research outputs found
Insight about induced SFR in the shell system of early-type galaxies from UV observations.
No full textCurrent views consider shell structures as a debris of recent minor/major merging event though also weak interaction models could produce long lasting shells on host galaxies possessing a stellar thick disc. Recent optical observations suggest an external origin of the matter, as predicted by merging models. At the same time, a set of observations showing a clear association between cold (HI/CO) gas and stars challenges present merging models In this framework we will present Galex observations of a well selected sample of shell galaxies chosen among those with detected HI and/or CO both in the main body of the galaxy and interleaved with shells. With these data we will show whether the HI/CO gas rich shells host ongoing star formation processes and we will give independent indications: (1) about the present day star formation; (2) if their presence or absence is consistent with the kinematics of the ionised gas, (3) address merging models which fails in reproducing a coupling between stellar and gaseous shells
The GALEX UV emission in shell galaxies
No full textShell galaxies are widely considered the debris of recent accretion/merging episodes. Their high frequency in low density environment suggests that such episodes could be among the driver of the early-type galaxy secular evolution. We present far and near UV GALEX photometric properties of a sample of shell galaxies
Tracing Galaxy Evolution in the Field: the UV Emission in Shell Galaxies Mapped by GALEX
No full textWe studied with GALEX images three nearby shell galaxies whose optical line strength indices suggest that they host recent (<2 Gy) star formation
Insights About Induced SFR in the Shell Systems of Early-Type Galaxies from UV (GALEX)
No full textCurrent views consider shell structures as a debris of recent minor/major merging event though also weak interaction models could produce long lasting shells on host galaxies possessing a stellar thick disc. Recent optical observations suggest an external origin of the matter, as predicted by merging models. At the same time, a set of observations showing a clear association between cold (HI/CO) gas and stars challenges present merging models In this framework we will present Galex observations of a well selected sample of shell galaxies chosen among those with detected HI and/or CO both in the main body of the galaxy and interleaved with shells. With these data we will show whether the HI/CO gas rich shells host ongoing star formation processes and we will give independent indications: (1) about the present day star
formation; (2) if their presence or absence is consistent with the kinematics of the ionised gas, (3) address merging models which fails in
reproducing a coupling between stellar and gaseous shells
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
Spectro-Photometric Evolution of Elliptical Galaxies. III. Infall models with gradients in mass density and star formation
Full text linkIn this study we present a simple model of elliptical galaxies aimed at interpreting the gradients in colours and narrow band indices observed across these systems. Salient features of the model are the gradients in mass density and star formation and infall of primordial gas aimed at simulating the collapse of a galaxy into the potential well of dark matter. Adopting a multi-zone model we follow in detail the history of star formation, gas consumption, and chemical enrichment of the galaxy and also allow for the occurrence of galactic winds according to the classical supernova (and stellar winds) energy deposit. The outline of the model, the time scale of gas accretion and rate of star formation as a function of the galacto-centric distance in particular, seek to closely mimic the results from Tree-SPH dynamical models. Although some specific ingredients of the model can be questioned from many points of view (of which we are well aware), the model has to be considered as a gross tool for exploring the consequences of different recipes of gas accretion and star formation in which the simple one-zone scheme is abandoned. With the aid of this model we discuss the observational data on the gradients in metallicity, colours, and narrow band indices across elliptical galaxies. Tables~4 and 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http:// cdsweb.u-strasbg.fr/Abstract.htm
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
- …
