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A Comprehensive Analysis of the UV Spectral Properties of Dwarf Galaxies at
Get PDFGalaxy evolution is concerned with the mechanisms that determine the distributions of gas, dust, and metals, and with the efficiency with which galaxies produce stars. These components are the primary visible building blocks of a galaxy. Throughout cosmic history the escape of ionizing radiation from a galaxy out into the intergalactic medium has been a notoriously difficult measurement to make, and one that informs the ionizing background radiation. This is relevant for the development of galaxies generally, but also plays a significant role in understanding the last great phase change of the universe, reionization (). It is unclear whether it is massive galaxies or dwarf galaxies which are able to expel sufficient amounts of ionizing radiation to ionize neutral hydrogen in the intergalactic medium during this epoch of the universe. Any attempts to measure the ionizing escape fraction during reionization is untenable even for newer instruments like the James Webb space telescope due to the neutral intergalactic medium obscuring large amounts of ionizing radiation. As such, lower redshift galaxies are studied both for the sake of constraining the ionizing background throughout cosmic history and as benchmarks for understanding reionization. Often, studies will select galaxies based on their Ly emission as it has a possible connection with Lyman continuum escape. However, since Ly is a resonant line transition it is absorbed and scattered by even small amounts of neutral hydrogen. Because of this, it is unclear what galaxy properties may be correlated with Ly escape. To understand the biases behind selecting on Ly we need to better understand what causes Ly to escape and the distribution of Ly properties in galaxy samples. Ly also serves as a proxy of the neutral fraction in the intergalactic medium at high redshift. Finally, outflows and feedback are best understood by comparing empirical measures of outflows and covering fractions with models from simulations. These models can be better constrained when including empirical markers in the dwarf regime. Many studies have looked into these measurements at higher masses (\rm log(M^*/M_\odot)>9), or for samples biased towards strong line emitters. There has yet to be a complete sample of low mass galaxies studied at .In this work we present a sample of 32 galaxies at during the peak of star-formation in the history of the universe. We focus on low-UV luminosity (\rm M_{UV} > -19) and low mass (\rm log(M^*/M_\odot)<9) sub-samples of this parent sample. A unique characteristic of this sample is the complete spectroscopy of the galaxies. Each galaxy has rest-UV and rest-optical spectra from the Keck/LRIS and keck/MOSFIRE instruments respectively. This allows us to confirm the redshift of galaxies for which we do not observe any apparent spectral features in the rest-UV spectra. This, along with improved S/N from gravitational lensing, allows us to to produce a complete sample of dwarf galaxies from which to measure proxies of the ionizing escape fraction of galaxies. The primary proxies used in the literature and in this work are the Ly EW, the Ly escape fraction, and the low-ionization interstellar absorption line EW \citep{Saldana-Lopez2023}. The Ly EW we measure for individual galaxies and find that generally dwarf galaxies tend to have Ly in emission in contrast to higher mass samples which show Ly EWs have Ly in absorption on average \citep{Du2018}. The volumetric escape fraction of dwarf galaxies at is consistent with the literature value of \citep{Hayes2010,Ciardullo2014,Sobral2017,Weiss2021}, placing an upper limit on the volumetric escape fraction of ionizing photons. The LIS absorption lines show about a factor of 2 weaker EWs for low mass galaxies when compared with higher mass samples \citep{jones2012,Du2018}. A lower EW of LIS absorption lines implies a lower covering fraction of neutral hydrogen and therefore greater avenues of escape on average for ionizing photons. Collectively, our measurements imply greater amounts of ionizing radiation escaping from dwarf galaxies on average when compared with higher mass samples of star-forming galaxies
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
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
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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