1,721,033 research outputs found
Dust and Nebular Emission in Star Forming Galaxies
No full textIn Chapter 2 we describe how we modelled the nebular emission produced by H II
regions. We start with an introduction on the ionized gas physics and on the basic
assumptions of the library. Then we describe of the adopted ionizing sources, the role of
the ionizing parameter and the geometry of gas. We also discuss the accuracy and the
limitations of the method and compare the results 'Yith observed H II galaxies
In Chapter 3 we firstly summarize the main features of the GRASIL code and
how galaxies are schematized in it. Then we introduce the method that we propose to
correctly compute the nebular emission for a galaxy using the library described in the
previous chapter, and compare the method to other models in literature.
In Chapter 4 we apply the model to discuss several methods to estimate the attenuation
in normal star forming galaxies by considering the UV, optical emission lines and
FIR properties. In particular, we compare the attenuation suffered by the ionized gas
with the one suffered by the stellar continuum. We show that observations require the
extinction of different stellar populations to vary with age.
In Chapter 5 we study the attenuation in starburst galaxies. In particular we
examine the correlation between the FIR/UV ratio and the UV spectral index in the Wu
et al. (2002) sample of starbursts. We also discuss the observed attenuation law and,
by using our model, we explore its origin, and the effect of the age selective extinction.
Furthermore we apply our model to explain some UV, FIR and optical properties of Very Luminous IR galaxies.
Chapter 6 is dedicated to the measure of the star formation rate. We compare the
different SFR estimators, namely the UV luminosity, the dust SED, the emission lines
and the radio continuum. In the case of normal spiral galaxies, we provide our best
calibrations for them and underline the different robustness of each estimator.
In Chapter 7 we discuss some applications of IR nebular lines. In particular, we
present a method to derive the metallicity of galaxies from IR nitrogen lines and radio
emission. We also used the model to interpret the excitation diagram of galactic H II
regions and starburst galaxies. Finally, we discuss the possibility to study the formation
phase of elliptical galaxies with spectroscopical observations carried with SIRTF.
Appendix A collects some observational data extracted from the Wu et al. (2002)
sample of starburst galaxies
Drift removal by means of alternating least squares with application to Herschel data
No full textWe consider the problem of reconstructing an image observed with a linear, noisy instrument, the output of which is affected by a drift too, causing a slowly varying deviation of the readouts from the baseline level. Since the joint estimation of the image and the drift, which is the optimal approach, is demanding for large data, we consider an alternative approach, where we remove the drift and the noise in two separate steps. In particular, we remove the drift by means of Least Squares (LS) and the noise by means of Generalised Least Squares (GLS). Moreover, we introduce an efficient drift removal algorithm, based on Alternating Least Squares (ALS), and carry out an analysis which proves convergence and gives geometrical insight. Finally, we apply the approach to the Herschel satellite data, discussing the performance and showing that nearly optimal results are achieved.We consider the problem of reconstructing an image observed with a linear, noisy instru-
ment, the output of which is affected by a drift too, causing a slowly varying deviation of
the readouts from the baseline level. Since the joint estimation of the image and the drift,
which is the optimal approach, is demanding for large data, we consider an alternative
approach, where we remove the drift and the noise in two separate steps. In particular, we
remove the drift by means of Least Squares (LS) and the noise by means of Generalised
Least Squares (GLS). Moreover, we introduce an efficient drift removal algorithm, based on
Alternating Least Squares (ALS), and carry out an analysis which proves convergence and
gives geometrical insight. Finally, we apply the approach to the Herschel satellite data,
discussing the performance and showing that nearly optimal results are achieved
Discovery of a dormant 33 solar-mass black hole in pre-release Gaia astrometry
No full textGaia Collaboration: P. Panuzzo et al.[Context]. Gravitational waves from black-hole (BH) merging events have revealed a population of extra-galactic BHs residing in short-period binaries with masses that are higher than expected based on most stellar evolution models – and also higher than known stellar-origin black holes in our Galaxy. It has been proposed that those high-mass BHs are the remnants of massive metal-poor stars.[Aims] Gaia astrometry is expected to uncover many Galactic wide-binary systems containing dormant BHs, which may not have been detected before. The study of this population will provide new information on the BH-mass distribution in binaries and shed light on their formation mechanisms and progenitors.[Methods] As part of the validation efforts in preparation for the fourth Gaia data release (DR4), we analysed the preliminary astrometric binary solutions, obtained by the Gaia Non-Single Star pipeline, to verify their significance and to minimise false-detection rates in high-mass-function orbital solutions.[Results] The astrometric binary solution of one source, Gaia BH3, implies the presence of a 32.70 ± 0.82 M
BH in a binary system with a period of 11.6 yr. Gaia radial velocities independently validate the astrometric orbit. Broad-band photometric and spectroscopic data show that the visible component is an old, very metal-poor giant of the Galactic halo, at a distance of 590 pc.[Conclusions] The BH in the Gaia BH3 system is more massive than any other Galactic stellar-origin BH known thus far. The low metallicity of the star companion supports the scenario that metal-poor massive stars are progenitors of the high-mass BHs detected by gravitational-wave telescopes. The Galactic orbit of the system and its metallicity indicate that it might belong to the Sequoia halo substructure. Alternatively, and more plausibly, it could belong to the ED-2 stream, which likely originated from a globular cluster that had been disrupted by the Milky Way.This work presents results from the European Space Agency (ESA) space mission Gaia. Gaia data are being processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC is provided by national institutions, in particular the institutions participating in the Gaia MultiLat eral Agreement (MLA). The Gaia mission website is https: //www.cosmos.esa.int/gaia. The Gaia archive website is https://archives.esac.esa.int/gaia. The Gaia mission and data processing have financially been supported by, in alphabetical order by country:...... the European Commission’s Sixth Framework Programme through the European Leadership in Space Astrometry (ELSA) Marie Curie Research Training Network (MRTN CT-2006-033481), through Marie Curie project PIOF GA-2009-255267 (Space AsteroSeismology & RR Lyrae stars, SAS-RRL), and through a Marie Curie Transfer of-Knowledge (ToK) fellowship (MTKD-CT-2004-014188); the European Commission’s Seventh Framework Pro gramme through grant FP7-606740 (FP7-SPACE-2013-1) for the Gaia European Network for Improved data User Ser vices (GENIUS) and through grant 264895 for the Gaia Research for European Astronomy Training (GREAT-ITN) network;...the European Research Council (ERC) through grants 320360 (The Gaia-ESO Milky Way Survey), 647208 (Do intermediate-mass black holes exist?), 687378 (Small Bod ies: Near and Far), 682115 (Using the Magellanic Clouds to Understand the Interaction of Galaxies), 695099 (A sub percent distance scale from binaries and Cepheids – Cep Bin), 745617 (Our Galaxy at full HD – Gal-HD), 834148 (Accelerating Galactic Archeology), 895174 (The build-up and fate of self-gravitating systems in the Universe), 947660 (Measuring Hubble’s Constant to 1% with Pulsating Stars – H1PStars), 951549 (Sub-percent calibration of the extra galactic distance scale in the era of big surveys – Uni verScale), 101004214 (Innovative Scientific Data Explo ration and Exploitation Applications for Space Sciences – EXPLORE), 101004719 (OPTICON-RadioNET Pilot), 101055318 (The 3D motion of the Interstellar Medium with ESO and ESA telescopes – ISM-FLOW), 101063193 (Evo lutionary Mechanisms in the Milky waY: the Gaia Data Release 3 revolution – EMMY), 101093572 (StarDance: the non-canonical evolution of stars in clusters) and 101135205 (HORIZON-CL4-2023-SPACE-01-71 SPACIOUS project);....the Spanish Ministry of Economy (MINECO/FEDER, UE), the Spanish Ministry of Science and Innovation (MCIN), the Spanish Ministry of Education, Culture, and Sports, and the Spanish Government through grants BES-2016-078499, BES-2017-083126, BES-C-2017-0085, ESP2016-80079-C2-1-R, FPU16/03827, RTI2018-095076- B-C22, PID2021-122842OB-C22, PDC2021-121059-C22, and TIN2015-65316-P (‘Computación de Altas Prestaciones VII’), the Juan de la Cierva Incorporación Programme (FJCI-2015-2671 and IJC2019-04862-I for F. Anders), the Severo Ochoa Centre of Excellence Programme (SEV2015-0493) and MCIN/AEI/10.13039/501100011033/ EU FEDER and Next Generation EU/PRTR (PRTR C17.I1 and CNS2022-135232); the European Union through European Regional Development Fund ‘A way of mak ing Europe’ through grants PID2021-122842OB-C21 and PID2021-125451NA-I00, the Institute of Cosmos Sciences University of Barcelona (ICCUB, Unidad de Excelen cia ‘María de Maeztu’) through grant CEX2019-000918- M, the University of Barcelona’s official doctoral pro gramme for the development of an R+D+i projec through an Ajuts de Personal Investigador en Forma ció (APIF) grant, the Spanish Virtual Observatory project funded by MCIN/AEI/10.13039/501100011033/ through grant PID2020-112949GB-I00; the Centro de Investi gación en Tecnologías de la Información y las Comunica ciones (CITIC), funded by the Xunta de Galicia through the collaboration agreement to reinforce CIGUS research centers, research consolidation grant ED431B 2021/36 and scholarships from Xunta de Galicia and the EU - ESF ED481A-2019/155 and ED481A 2021/296; the Red Española de Supercomputación (RES) computer resources at MareNostrum, the Barcelona Supercomputing Cen tre - Centro Nacional de Supercomputación (BSC-CNS) through activities AECT-2017-2-0002, AECT-2017-3-0006, AECT-2018-1-0017, AECT-2018-2-0013, AECT-2018-3- 0011, AECT-2019-1-0010, AECT-2019-2-0014, AECT 2019-3-0003, AECT-2020-1-0004, and DATA-2020-1-0010, the Departament d’Innovació, Universitats i Empresa de la Generalitat de Catalunya through grant 2014-SGR-1051 for project ‘Models de Programació i Entorns d’Execució Parallels’ (MPEXPAR), and Ramon y Cajal Fellowships RYC2018-025968-I, RYC2021-031683-I and RYC2021- 033762-I, funded by MICIN/AEI/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR and the European Science Foundation (‘Investing in your future’); the Port d’Informació Científica (PIC), through a collaboration between the Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT) and the Institut de Física d’Altes Energies (IFAE), supported by the grant EQC2021-007479-P funded by MCIN/AEI/ 10.13039/501100011033 and by the "European Union NextGenerationEU/PRTR), and also by MICIIN with funding from European Union NextGenerationEU(PRTR C17.I1) and by Generalitat de Catalunya……With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (CEX2019-000918-M)Peer reviewe
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
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