1,720,958 research outputs found
The evolution of blue and red quasars at cosmic noon and beyond
No full textObservations show that allmassive galaxies contain a supermassive black hole (SMBH) at their centre and,despite their vastly different spacial scales, SMBHs and their host galaxiesappear to co-evolve. While most descriptions of this phenomenon invoke energyfeed back from the SMBH during an active accretion phase, the exact nature ofthese feedback mechanisms are not fully understood. Accreting SMBHs or activegalactic nuclei (AGN) come in many flavours - ranging in mass, luminosity, accretionrate and colour. The most luminous AGN are known as quasars, and given theirimmense power, quasars are the ideal laboratory for studying the role of AGN feedbackin massive galaxy assembly. The primary aim of this thesis is to understand therole of energetic quasar-driven winds in depositing energy into their hosts,and hence, how these winds impact galaxy evolution at the peak epoch of bothSMBH and galaxy growth - 1.0 ≲ zsys ≲ 4.0. Byharnessing the power of large statistical samples from the Sloan Digital SkySurvey, I therefore investigate the redshift evolution of the outflowproperties of luminous blue quasars. I leverage advanced spectroscopic analysistechniques to show that the primary driver of quasar-driven outflows is the massand the accretion rate of the SMBH. The strongest outflows occur inquasars with MBH > 109 M⊙ and L/LEdd > 0.2 at allredshifts, hence, there is no evidence to suggest a redshift evolution in theoutflow properties of luminous blue quasars. This thesis also addresses thecrucial question of whether dust enhances the efficiency of AGN feedback. Iconduct a detailed investigation of the rest-UV/optical emission from aluminous, heavily reddened quasar (HRQ) at cosmic noon, with bolometric luminosityLBol = 1048.16 erg s−1 and E(B − V)= 1.55 mag. The HRQ hosts strong multi-phase, multi-scale winds consistent withthe trends identified in blue quasars between SMBH mass, accretion rate andoutflow velocity - making it unclear whether dusty quasars host stronger windsthan their blue counterparts. However, a full rest-UV to infrared SED analysisof 60 additional HRQs shows that their hot dust emission is suppressed. Thissuggests that strong AGN feedback processes are active in the red quasar phaseand have cleared the inner regions of dust. Given also that excess rest-UVemission - likely scattered quasar light - is very common in HRQs, they likelymark a key evolutionary stage in SMBH and host galaxy growth. The results of thisthesis cement the fact that studying AGN feedback is crucial to ourunderstanding of galaxy evolution and highlight that only by studying diversepopulations can we gain a complete understanding of the physics that drivesthese phenomena.<div/
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
A big red dot: scattered light, host galaxy signatures, and multiphase gas flows in a luminous, heavily reddened quasar at cosmic noon
Full text linkWe present a deep X-Shooter rest-frame ultraviolet (UV) to optical spectral analysis of the heavily reddened quasar, ULASJ2315 + 0143 at z = 2 . 566, known to reside in a major-merger host galaxy. The rest-frame optical is best fit by a dust- reddened quasar ( E ( B -V ) QSO = 1 . 55) with black-hole mass log 10 (H β, M BH [M ⊙]) = 10 . 26 ±0 . 05, bolometric luminosity L Bol = 10 48 . 16 erg s -1 and Eddington-scaled accretion rate log 10 ( λEdd ) = -0 . 19. We find remarkable similarities between ULASJ2315 + 0143 and the high-redshift little red dots (LRDs). The rest-frame UV cannot be explained by a dusty quasar component alone and requires an additional blue component consistent with either a star-forming host galaxy or scattered AGN light. We detect broad high-ionization emission lines in the rest-UV, supporting the scattered light interpretation for the UV excess. The scattering fraction represents just 0.05 per cent of the total luminosity of ULASJ2315 + 0143 . Analysis of the mid-infrared SED suggests an absence of hot dust on torus-scales similar to what is observed for LRDs. The obscuring medium is therefore likely on galaxy scales. We detect narrow, blueshifted associated absorption-line systems in C IV , N V , Si IV, and Si III . There is evidence for significant high-velocity ( > 1000 km s -1 ) outflows in both the broad- and narrow-line regions as traced by C IV and [O III ] emission. The kinetic power of the [O III ] wind is ϵion k = 10 44 . 61 erg s -1 ∼0 . 001 L Bol . ULASJ2315 + 0143 is likely in an important transition phase where star formation, black-hole accretion and multiphase gas flows are simultaneously occurring.</p
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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