1,721,272 research outputs found
Dynamics of high redshift disk galaxies
Full text linkThis thesis discusses the dynamical properties of high redshift infrared selected and morphologically large disk selected galaxies at redshifts between 0.7 and 2.4 and their Tully-Fisher relations. Most observations were done using the near infrared integral field spectrograph SINFONI of the Very Large Telescope (VLT).UBL - phd migration 201
Spectroscopy and nuclear dynamics of starburst galaxies
Full text linkThe aim of this work is to study starbursts and the dynamical processes involved, both from gas and stellar components. For this purpose, one nearby galaxy with a nuclear starburst was selected, as well as a sample of 6 ultraluminous infrared galaxies (ULIRGs). Observations of these sources were carried out with SINFONI, the spectrograph for integral field observations in the near-infrared, an instrument that is mounted on the VLT in Chile. The thesis contains a study of the spectral features that are characteristic for starbursts, and a comparison of dynamical masses and mass-to-light ratios of the ULIRGs, calculated with different methods both from stellar dynamics and gas dynamics.UBL - phd migration 201
Orion's Dragon and other stories: Feedback by massive stars
Full text linkStellar feedback is a crucial ingredient in the evolution of galaxies. Massive stars disrupt their natal molecular clouds and perturb the ambient interstellar medium, not only when they explode as supernovae but also during their lifetimes by stellar winds and radiation. The irradiated, heated, and stirred gas cools through the emission of fine-structure lines. The far-infrared fine-structure line of ionized carbon is the dominant coolant of warm neutral gas and has been suggested as a powerful tracer of the star-formation rate (a derivative of stellar feedback) in distant galaxies. This thesis aims to explore the origins of the [CII] emission and to quantify stellar feedback observationally in local samples. I have used high-resolution (both spectral and angular) observations of the [CII] line obtained with the upGREAT instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) of the Horsehead Nebula and the Orion Nebula at the surface of the Orion molecular cloud. This nearby template star-forming region allows to study physical properties of the irradiated gas and to precisely determine the amount of kinetic energy deposited in the expanding bubbles surrounding the massive stars.Interstellar matter and star formatio
Gas, dust, and star formation in distant radio galaxies
Full text linkIn this thesis I discuss recent observations of distant (z > 2) radio galaxies. There is strong evidence that radio galaxies are the progenitors of the brightest cluster ellipticals and are among the most luminous and massive galaxies at any epoch, allowing relatively detailed studies of their formation process out to large distances. Submillimeter emission has been detected in many, implying star formation rates of order 1000 Msun/yr over scales of tens of kpc, consistent with a scenario in which these galaxies are currently forming the bulk of their eventual stellar population. Many radio galaxies also host giant (~ 150 kpc) emission line nebulae. We obtaind very deep narrow-band Ly-a images for a select few of these. The observations show spectacular detail with a wealth of morphological structure, such as extended (~ 80 kpc) filamentary structures, giving insight in feedback processes during their formation. I discuss the possible origin and the ionization source of these halos in connection with the sub-mm results, and discuss possible implications for theories of galaxy formation.Interstellar matter and star formatio
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
- …
