1,721,007 research outputs found
Focusing on warm dark matter with lensed high-redshift galaxies
No full textWe propose a novel use of high-redshift galaxies, discovered in deep Hubble Space Telescope (HST) fields around strong lensing clusters. These fields probe small comoving volumes (~103 Mpc3) at high magnification (μ ≳ 10) and can detect otherwise inaccessible ultrafaint galaxies. Even a few galaxies found in such small volumes require a very high number density of collapsed dark matter (DM) haloes. This implies significant primordial power on small scales, allowing these observations to rule out popular alternatives to standard cold dark matter (CDM) models, such as warm dark matter (WDM). In this work, we analytically compute WDM halo mass functions at z = 10, including the effects of both particle freestreaming and residual velocity dispersion. We show that the two z ≈ 10 galaxies already detected by the Cluster Lensing And Supernova survey with Hubble (CLASH) survey are sufficient to constrain the WDM particle mass to mx < 1 (0.9) keV at 68 per cent (95 per cent) confidence limit (for a thermal relic relativistic at decoupling). This limit depends only on the WDM halo mass function and, unlike previous constraints on mx, is independent of any astrophysical modelling. The forthcoming HST Frontier Fields can significantly tighten these constraints. © 2013 The Authors
JWST CEERS and JADES Active Galaxies at z = 4-7 Violate the Local M •-M ⋆ Relation at >3σ: Implications for Low-mass Black Holes and Seeding Models
Full text linkJWST is revolutionizing our understanding of the high-z Universe by expanding the black hole horizon, looking farther and to smaller masses, and revealing the stellar light of their hosts. By examining JWST galaxies at z = 4-7 that host Hα-detected black holes, we investigate (i) the high-z M •-M ⋆ relation and (ii) the black hole mass distribution, especially in its low-mass range (M • ≲ 106.5 M ⊙). With a detailed statistical analysis, our findings conclusively reveal a high-z M •-M ⋆ relation that deviates at >3σ confidence level from the local relation. The high-z relation is log ( M • / M ⊙ ) = − 2.43 − 0.83 + 0.83 + 1.06 − 0.09 + 0.09 log ( M ⋆ / M ⊙ ) . Black holes are overmassive by ∼10-100× compared to their low-z counterparts in galactic hosts of the same stellar mass. This fact is not due to a selection effect in surveys. Moreover, our analysis predicts the possibility of detecting in high-z JWST surveys 5-15× more black holes with M • ≲ 106.5 M ⊙, and 10-30× more with M • ≲ 108.5 M ⊙, compared to local relation’s predictions. The lighter black holes preferentially occupy galaxies with a stellar mass of ∼107.5-108 M ⊙. We have yet to detect these sources because (i) they may be inactive (duty cycles 1%-10%), (ii) the host overshines the active galactic nucleus (AGN), or (iii) the AGN is obscured and not immediately recognizable by line diagnostics. A search of low-mass black holes in existing JWST surveys will further test the M •-M ⋆ relation. Current JWST fields represent a treasure trove of black hole systems at z = 4-7; their detection will provide crucial insights into their early evolution and coevolution with their galactic hosts
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
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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