1,721,201 research outputs found
Evolution of 3D Galaxy Sizes with CANDELS
No full textAlthough present-day telescopes provide fabulous images of galaxies up to very high redshift, they have a strong limitation: we can see just the 2D projection on the sky of the galaxy's profile.
In this work, we present the evolution of the 3D structure of galaxies out to z=3 by deprojecting Sersic profile fits (Nedkova et al. 2021) to optical+near-IR HST/ACS imaging from CANDELS (Koekemoer et al. 2011; Grogin et al. 2011) and stellar mass estimate inferred via fitting the UV-to-mid-IR spectral energy distribution (Leja et al. 2020). We compare the 2D and 3D evolution of the Mass-size relation with redshift showing that, although the half-light radius is barely affected by the deprojection, the overall galaxy's structure deeply changes. Since central density is thought to play a key role in the star-formation histories of galaxies, our work provides a crucial link with those theoretical models that explain the 'quenching' of galaxies.
The main results summarised in this poster are:
We publish the 3D light profiles at a common rest-frame wavelength of 5000Å for more than 40000 galaxies in the redshift range 0.5<z<3
The Size-Stellar Mass distribution (and its evolution) is nearly identical in 2D and 3D: projected size measurements are excellent proxies for intrinsic galaxy sizes
An accurate estimate of the central density depends strongly on deprojection, with a significant impact on the empirical relationship between central density and star-formation activity (quenching
Realistic multi-wavelength mock observations for the Auriga cosmological simulations
No full textDit proefschrift presenteert een studie naar het genereren en analyseren van synthetische waarnemingen voor Melkwegachtige gesimuleerde sterrenstelsels. In het bijzonder richt het proefschrift zich op het geavanceerd modelleren van stof en het implementeren van observabelen aangedreven door stellaire terugkoppeling in simulaties van nabewerking van melkwegstelsels, bereikt door gebruik te maken van de nieuwe emissiebibliotheek TODDLERS (Time evolution of Observables including Dust Diagnostics and Line Emission from Regions containing young Stars), met de radiatieve overdrachtscode SKIRT
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
The hunt for quasars at cosmic dawn : insights into redshift > 6 weak-line active galaxies and deep learning for discovering lensed sources
No full textSynthetic spectroscopic observations : methods and applications in stellar kinematics of simulated galaxies
No full textDit proefschrift presenteert een studie naar het genereren en analyseren van synthetische ruimtelijk opgeloste spectroscopische waarnemingen van gesimuleerde sterrenstelsels. Het proefschrift richt zich op de ontwikkeling van een raamwerk om realistische spectroscopische schijnwaarnemingen te bouwen voor state-of-the-art hydrodynamische simulaties, gebruikmakend van stellaire populatiemodellen met hoge spectrale resolutie en volledige stralingsoverdrachtsbehandeling met SKIRT. resolutie stellaire populatiemodellen en volledige behandeling van radiatieve overdracht met SKIRT. Met behulp van deze synthetische waarnemingen bestudeert het proefschrift het vermogen van kosmologische simulaties om de kinematische structuur van sterrenstelsels waargenomen in het lokale heelal en in vroegere tijden te reproduceren en onderzoekt het ook de vertekeningen in de gemeten kinematica
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
First results from the TNG50 simulation: the evolution of stellar and gaseous discs across cosmic time
Get PDFWe present a new cosmological, magnetohydrodynamical simulation for galaxy formation: TNG50, the third and final instalment of the Illustris TNG project. TNG50 evolves 2 x 2160(3) dark matter particles and gas cells in a volume 50 comoving Mpc across. It hence reaches a numerical resolution typical of zoom-in simulations, with a baryonic element mass of 8.5 x 10(4) M-circle dot and an average cell size of 70-140 pc in the star-forming regions of galaxies. Simultaneously, TNG50 samples similar to 700 (6500) galaxies with stellar masses above 10(10) (10(8)) M-circle dot at z = 1. Here we investigate the structural and kinematical evolution of star-forming galaxies across cosmic time (0 less than or similar to z less than or similar to 6). We quantify their sizes, disc heights, 3D shapes, and degree of rotational versus dispersion-supported motions as traced by rest-frame V-band light (i.e. roughly stellar mass) and by H alpha light (i.e. star-forming and dense gas). The unprecedented resolution of TNG50 enables us to model galaxies with sub-kpc half-light radii and with less than or similar to 300-pc disc heights. Coupled with the large-volume statistics, we characterize a diverse, redshift- and mass-dependent structural and kinematical morphological mix of galaxies all the way to early epochs. Our model predicts that for star-forming galaxies the fraction of disc-like morphologies, based on 3D stellar shapes, increases with both cosmic time and galaxy stellar mass. Gas kinematics reveal that the vast majority of 10(9-11.5) M-circle dot star-forming galaxies are rotationally supported discs for most cosmic epochs (V-rot/sigma > 2-3, z less than or similar to 5), being dynamically hotter at earlier epochs (z greater than or similar to 1.5). Despite large velocity dispersion at high redshift, cold and dense gas in galaxies predominantly arranges in disky or elongated shapes at all times and masses; these gaseous components exhibit rotationally dominated motions far exceeding the collisionless stellar bodies
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
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
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