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Blind and pointed Sunyaev-Zel'dovich observations with the Arcminute Microkelvin Imager
Full text linkIn this thesis I discuss my work on the Arcminute Microkelvin Imager (AMI). I focus on the detection of Sunyaev-Zel’dovich (SZ) signatures at 14-18GHz.
Once the background science and operation of the instrument are described I proceed to present my contribution to the calibration of AMI, including: primary beam measurements; refinements to the known antenna geometry and flagging geostationary satellite interference. This is followed by an outline of the software that I have developed to subtract sources from visibilities, concatenate data from multiple observations, simulate data, and perform jack-knife tests to evaluate the magnitude of systematic errors.
The Bayesian analysis that I use to obtain parameter estimates and to quantify the significance of putative SZ detections is described. I perform realistic simulations of clusters and use these to characterise
the analysis. I then, for the first time, apply the analysis to data from the AMI blind cluster survey. I identify several previously unknown
SZ decrements.
Finally, I conduct pointed observations towards a high luminosity subsample of eight clusters from the Local Cluster Substructure Survey
(LoCuSS). For each of these I provide probability distributions of parameters such as mass, radius, and temperature. I compare my
results to those in the literature and find an overall agreement
Investigating the Source of Planck-Detected AME: High-Resolution Observations at 15 GHz
Full text linkThe Planck 28.5 GHz maps were searched for potential Anomalous Microwave Emission (AME) regions on the scale of ~3° or smaller, and several new regions of interest were selected. Ancillary data at both lower and higher frequencies were used to construct spectral energy distributions (SEDs), which seem to confirm an excess consistent with spinning dust models. Here we present higher resolution observations of two of these new regions with the Arcminute Microkelvin Imager Small Array (AMI SA) between 14 and 18 GHz to test for the presence of a compact (~10 arcmin or smaller) component. For AME-G107.1+5.2, dominated by the Hii region S140, we find evidence for the characteristic rising spectrum associated with either the spinning dust mechanism for AME or an ultra- /hypercompact Hii region across the AMI frequency band; however, for AME-G173.6+208 we find no evidence for AME on scales of ~2–10 arcmin
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
Signal and Data Transport for the SKA
No full textThe SKA will be a transformative radio telescope that will address fundamental unanswered questions about our Universe. The SKA will require high precision timing and will then generate unprecedented volumes of data. The Signal and Data Transport (SADT) Consortium has design the systems that address these requirements. I will discuss the design work undertaken by the SADT Consortium to address these challenges through three separate networks:
• A network to transport the astronomical data (tens of Terabits per second), first from the receivers to a Central Signal Processor and then secondly transport the resultant data out of the telescope site to the Science Data Processor
• A clock ensemble that provides a high accuracy timescale that can be tied to global UTC and a network that then distributes a reference frequency and absolute time to each antenna
• A network that passes control, monitor and service data throughout the telescope
Signal and Data Transport for the SKA
No full textThe SKA will be a transformative radio telescope that will address fundamental unanswered questions about our Universe. The SKA will require high precision timing and will then generate unprecedented volumes of data. The Signal and Data Transport (SADT) Consortium has design the systems that address these requirements. I will discuss the design work undertaken by the SADT Consortium to address these challenges through three separate networks: • A network to transport the astronomical data (tens of Terabits per second), first from the receivers to a Central Signal Processor and then secondly transport the resultant data out of the telescope site to the Science Data Processor • A clock ensemble that provides a high accuracy timescale that can be tied to global UTC and a network that then distributes a reference frequency and absolute time to each antenna • A network that passes control, monitor and service data throughout the telescope
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
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