1,724,372 research outputs found
A multi-wavelength study of the starburst galaxy NGC 7673
No full textHST/WFPC2 images resolve NGC 7673 into a large number of star clusters. Among these, 31 fall inside the IUE large aperture, which was used to acquire an integrated ultraviolet spectrum of the galaxy. We have fitted Starburst99 evolutionary synthesis models to the observed colours of these clusters and derived ages, reddenings, and masses of the clusters. Then a simple sum of the clusters synthetic UV spectra was compared to the observed IUE spectrum, in order to investigate the star-formation history of NGC 7673
[Hawaii Railway Company., Limited, Hawaii, Engine Drawing Card, Sketch No. 7673]
No full textThis engine drawing card was created for Hawaii Railway Company, Class 8-14 1/4 C. Section N-8 1/4 C. Sketch 7673. Copy Spec. 25F92
Biomimetics—Prospects and Developments
No full textSince its inaugural issue published in 2016, the scientific journal Biomimetics (ISSN 2313-7673), published by MDPI, has developed into a robust scientific journal that is appreciated in the field [...
Dissecting the star formation history of starburst galaxies: the case of NGC 7673
No full textWe have collected archival data on NGC 7673 to constrain the star formation history that produced the young star clusters and the field stellar population in this galaxy during the last 2 Gyr. We have considered the sample of 50 star clusters detected by Hubble Space Telescope/WFPC2 in the UV,V and I bands and estimated their age, intrinsic reddening and mass via comparison of their colours with STARBURST99 models. We have found two prominent epochs of cluster formation occurred about 20 and 2 Myr ago, with somewhat minor events between 3 and 6 Myr ago. The star clusters are characterized by an intrinsic reddening E(B - V) < 0.4 mag and a mass lower than 2 Ã 106Msolar. Out of the 50 star clusters, we have selected 31 located within the boundaries of the (IUE) large slit that was employed to obtain the spectrum of NGC 7673 between 1150 and 3350 Ã
. For each cluster, we have built a synthetic spectrum corresponding to the age, mass and intrinsic reddening derived from the cluster colours, properly redshifted to NGC 7673. The spectra have then been added together in a final, clusters integrated spectrum. This and the IUE, FUSE spectra of NGC 7673 have allowed us to describe the star formation history of the unresolved stars in the field as either exponentially decaying or multiburst. In the first case, we have derived an e-folding time of 700 (900) Myr and an initial star formation rate of 16 (13) Msolaryr-1 when the Fitzpatrick's (Calzetti's) extinction law is used. In the case of a multiburst star formation history, we have assumed that the same bursts which produced the star clusters built up also the field population. In this way, the field population turns out to be composed by a young (<40 Myr) component three (two) times brighter than the star clusters, and a component as old as ~850 (450) Myr, about 200 (100) times more massive than the star clusters together. These star formation histories fit equally well the observed UV spectrum of NGC 7673
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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 star cluster system of the NGC 7673 starburst
No full textWe investigate the star cluster system
in the starburst galaxy NGC 7673 using archival Hubble Space Telescope
WFPC2 broad-band images. For the first time we are able
to examine the internal structures of the prominent optical clumps
in this galaxy. The clumps are composed of young stars, 16–33% of which
are in bright star clusters. We identify 268 star cluster
candidates in both the F555W and
F814W images, and 50 clusters with the F255W
filter. These data allow us to estimate ages and masses using color-magnitude
and two-color diagrams for our sample. We find a population
of young, <6 Myr clusters located throughout
the galaxy with concentrations in the clumps. Star cluster mass estimates
are 5–50 10 for the brightest objects. The
starburst remains active in physically well-separated
regions, indicating a widespread starburst trigger. We discuss clump
lifetimes, their implications for the future evolution of NGC 7673, and
possible relationships to high redshift starbursts
Variations on the Author
Get PDF“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
Get PDFWe 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
Get PDFWe 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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