1,721,038 research outputs found
Measuring the high redshift space density of FRI radio galaxies: investigating the nature of the FRI/II divide
Get PDFThe results are presented here of multi-wavelength observations
centred on two fields of the Leiden-Berkeley Deep Survey, which form the basis
for a study of the population and cosmic evolution of the high
redshift, low power, Fanaroff & Riley class I (FRI) radio galaxies.
These fields, Hercules.1 and Lynx.2, contain a complete sample of 81
radio sources with S_1.4GHz > 0.5 mJy within 0.6 square
degrees. Wide-field, ~1.5 arcsec resolution, radio observations,
along with near infra-red and optical imaging, and some multi-object
spectroscopy, are used to select the best high-redshift FRI
candidates, giving 37 in total. Currently, the host galaxy
identification fraction is 86% with 11
sources remaining unidentified at a level of r > 25.2
(Hercules; 4 sources) or r > 24.4 (Lynx; 7 sources) and
K > 20. Spectroscopic redshifts are determined for
49% of the sample and photometric redshift estimates are presented for the
sample sources without spectra or previously published results.95% of the 37 best FRI high-redshift candidate sources were then observed using
sub-arcsecond radio resolution, with the aim of detecting extended
emission with respect to compact core features - vital for
unambiguous morphological classification. The nature of the radio
observations meant that 10 extra sample sources could also be included
in the data. Lower resolution data were also taken
for the Lynx.2 field sources to provide a comparison with the
1.5 arcsec data.The classification of the entire radio sample is done in two
stages. Sources which showed clear extension are classified by
morphology alone, whereas sources with no obvious or weak extension
were classified using a combination of morphology and flux density
loss in the higher resolution data indicative of resolved out extended emission. Five
groups are used for this - `Certain FRIs', `Likely FRIs', `Possible FRIs', `Unclassifiable
sources' (for those not included in the higher resolution
observations) and `Not FRIs'. The final group numbers are 8, 10, 24,
33 and 6 for groups 1-5 respectively.The space densities of the maximum, probable and minimum FRIs are then
calculated and compared to two previously published measurements of the
local value, and with the behaviour of the strongest FRII sources. The results
for all three groups show density enhancements of factors of 5-9 at
z ~ 1.0 which implies cosmic evolution of the FRI population; this
enhancement is also in very good agreement with that predicted by previous
models. The behaviour of the FRI/FRII dividing luminosity, as a
function of host galaxy absolute magnitude, at the different cosmic
epochs of the sample, and for two different star formation histories,
is also investigated. A shift to brighter absolute magnitudes is found
to be inconsistent with the data but this conclusion is weak due to
the lack of knowledge of the host galaxy stellar populations, and the
small number of sources in the sample
En route to finding extraterrestrial life
No full textThe last decade has seen an enormous leap forward in the characterization of extrasolar planet atmospheres, with ground-based telescopes playing a unique and increasingly important role. The prospects for the ELT are extremely exciting, and characterizing rocky exoplanets will be at the heart of its science. The detection of potential biomarker gases, such as molecular oxygen, can provide the first evidence of extraterrestrial life before the end of the next decade
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
Characterization of exoplanet atmospheres using high-dispersion spectroscopy with the E-ELT and beyond
No full textGround-based high-dispersion (R ∼ 100,000) spectroscopy provides unique information on exoplanet atmospheres, inaccessible from space - even using the JWST or other future space telescopes. Recent successes in transmission- and dayside spectroscopy using CRIRES on the Very Large Telescope prelude the enormous discovery potential of high-dispersion spectrographs on the E-ELT, such as METIS in the thermal infrared, and HIRES in the optical/near-infrared. This includes the orbital inclination and masses of hundred(s) of non-transiting planets, line-by-line molecular band spectra, planet rotation and global wind patterns, longitudinal spectral variations, and possibly isotopologue ratios. Thinking beyond the E-ELT, we advocate that ultimately a systematic search for oxygen in atmospheres of nearby Earth-like planets can be conducted using large arrays of relatively low-cost flux collector telescopes equipped with high-dispersion spectrographs
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
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