1,721,002 research outputs found
The Dark Energy Spectroscopic Instrument: one-dimensional power spectrum from first Ly α forest samples with Fast Fourier Transform
No full textFull list of the authors: Ravoux, Corentin; Abdul Karim, Marie Lynn; Armengaud, Eric; Walther, Michael; Karaçaylı, Naim Göksel; Martini, Paul; Guy, Julien; Aguilar, Jessica Nicole; Ahlen, Steven; Bailey, Stephen; Bautista, Julian; Beltran, Sergio Felipe; Brooks, David; Cabayol-Garcia, Laura; Chabanier, Solène; Chaussidon, Edmond; Chaves-Montero, Jonás; Dawson, Kyle; de la Cruz, Rodrigo; de la Macorra, Axel; Doel, Peter; Fanning, Kevin; Font-Ribera, Andreu; Forero-Romero, Jaime; Gontcho A Gontcho, Satya; Gonzalez-Morales, Alma X.; Gordon, Calum; Herrera-Alcantar, Hiram K.; Honscheid, Klaus; Iršič, Vid; Ishak, Mustapha; Kehoe, Robert; Kisner, Theodore; Kremin, Anthony; Landriau, Martin; Le Guillou, Laurent; Levi, Michael; Lukić, Zarija; Magneville, Christophe; Meisner, Aaron; Miquel, Ramon; Moustakas, John; Mueller, Eva-Maria; Muñoz-Gutiérrez, Andrea; Napolitano, Lucas; Nie, Jundan; Niz, Gustavo; Palanque-Delabrouille, Nathalie; Percival, Will; Pérez-Ràfols, Ignasi; Pieri, Matthew; Poppett, Claire; Prada, Francisco; Ramírez Pérez, César; Rossi, Graziano; Sanchez, Eusebio; Schlegel, David; Schubnell, Michael; Seo, Hee-Jong; Sinigaglia, Francesco; Tan, Ting; Tarlé, Gregory; Wang, Ben; Weaver, Benjamin; Yèche, Christophe; Zhou, ZhiminWe present the one-dimensional Ly α forest power spectrum measurement using the first data provided by the Dark Energy Spectroscopic Instrument (DESI). The data sample comprises 26 330 quasar spectra, at redshift z > 2.1, contained in the DESI Early Data Release and the first 2 months of the main survey. We employ a Fast Fourier Transform (FFT) estimator and compare the resulting power spectrum to an alternative likelihood-based method in a companion paper. We investigate methodological and instrumental contaminants associated with the new DESI instrument, applying techniques similar to previous Sloan Digital Sky Survey (SDSS) measurements. We use synthetic data based on lognormal approximation to validate and correct our measurement. We compare our resulting power spectrum with previous SDSS and high-resolution measurements. With relatively small number statistics, we successfully perform the FFT measurement, which is already competitive in terms of the scale range. At the end of the DESI survey, we expect a five times larger Ly α forest sample than SDSS, providing an unprecedented precise one-dimensional power spectrum measurement. © 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.The authors acknowledge support from Agence National de la Recherche (grant ANR-16-CE31-0021). The project leading to this publication has received funding from Excellence Initiative of Aix-Marseille University - A*MIDEX, a French 'Investissements d'Avenir' programme (grant AMX-20-CE-02-DARKUNI). This material is based upon work supported by the US Department of Energy (DOE), Office of Science, Office of High-Energy Physics, under Contract No. DE-AC02-05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract. Additional support for DESI was provided by the U.S. National Science Foundation (NSF), Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF's National Optical-Infrared Astronomy Research Laboratory; the Science and Technology Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/collaborating-institu tions. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. National Science Foundation, the U.S. Department of Energy, or any of the listed funding agencies
One-dimensional power spectrum from first DESI Lyman-{\alpha} forest
Get PDFThe Lyman-alpha forest is a unique probe of large-scale matter density
fluctuations at high redshift z > 2. We measure the one-dimensional Lyman-alpha
forest power spectrum using the first data provided by the Dark Energy
Spectroscopic Instrument (DESI), with a fast Fourier transform estimator. The
data sample contains quasar spectra included in the DESI Early Data Release and
the first two months of the main survey. This first set of data already
provides an improvement in terms of spectroscopic resolution with respect to
the previous measurements. We investigated methodological and instrumental
contaminants associated with DESI and used synthetic data to validate and
correct our measurement. Coupling our measurement with theoretical predictions
from hydrodynamical simulations will yield strong constraints on the primordial
matter power spectrum, neutrino masses, and dark matter properties. A quadratic
maximum likelihood estimator was applied to the same data set on a companion
paper and agrees with our measurement.Comment: 4 pages, 3 figures, contribution to the 2024 Cosmology session of the
58th Rencontres de Morion
Mesures unidimensionnelle et tridimensionnelle de la distribution de la matière à partir des forêts Lyman-α d'eBOSS et de DESI
No full textThe distribution of matter on cosmological scales can be predicted in the framework of the LambdaCDM model. It depends, among other things, on the properties of dark matter and neutrinos. Large spectroscopic surveys, such as eBOSS and DESI, aim to provide a map of this matter distribution. This thesis is a contribution to the study of Lyman-alpha forest samples from these surveys. The Lyman-alpha forest measures the absorption of light from distant sources by the intergalactic medium. As of now, it is the best probe for the distribution of matter at high redshift and small cosmological scale (of the order of a megaparsec). In this thesis, I use some eBOSS and DESI Lyman-alpha forest samples associated with quasars located at a redshift z>2, to study both their one- and three-dimensional properties. On the one hand, I carry out the first measurement of the one-dimensional power spectrum of Lyman-alpha forest with DESI data. Since DESI is a new instrument, I evaluate the instrumental systematics, contributing to the improvement of the instrument's noise modeling. This 1D power spectrum will be used to constrain the LambdaCDM model, the sum of neutrino masses, and the properties of dark matter. On the other hand, I create a three-dimensional tomographic map, by interpolating the Lyman-alpha forests from the eBOSS survey. With a volume approaching one gigaparsec cube, this map is the largest 3D tomographic reconstruction created from a Lyman-alpha forest sample. It traces the fluctuations of matter density, smoothed on a scale of 13 megaparsecs, in the redshift range 2.1 2, pour étudier leurs propriétés uni- et tri-dimensionnelles. D'une part, je présente la première mesure du spectre de puissance unidimensionnel de la forêt Lyman-alpha avec les données DESI. Comme DESI est un nouvel instrument, je me concentre sur les systématiques instrumentales, contribuant ainsi à l'amélioration de la modélisation du bruit de l'instrument. Ce spectre de puissance 1D sera utilisé pour contraindre le modèle LambdaCDM, la somme des masses des neutrinos, et les propriétés de la matière noire. D'autre part, cette thèse présente une carte tomographique tridimensionnelle, interpolant les forêts Lyman-alpha du relevé eBOSS. Avec un volume proche d'un gigaparsec cube, cette carte est la plus grande reconstruction tomographique 3D créée à partir des forêts Lyman-alpha. Elle retrace les fluctuations de la densité de matière, lissées sur une échelle de 13 mégaparcs, dans la plage de décalage vers le rouge 2.1 < z < 3.2. Je développe un algorithme pour rechercher des candidats proto-amas et vides cosmiques à partir de cette carte. Je mesure ensuite la corrélation entre les positions des vides détectés et l'échantillon de forêt Lyman-alpha utilisé pour construire la carte. Cette mesure fournit la première observation des vitesses particulières du gaz intergalactique (RSD) autour des vides à un redshift aussi élevé. En ajustant un modèle linéaire à cette mesure, je mesure le paramètre associé au RSD beta = 0.52
One-dimensional power spectrum from first DESI Lyman-α forest
No full textInternational audienceThe Lyman-alpha forest is a unique probe of large-scale matter density fluctuations at high redshift z > 2. We measure the one-dimensional Lyman-alpha forest power spectrum using the first data provided by the Dark Energy Spectroscopic Instrument (DESI), with a fast Fourier transform estimator. The data sample contains quasar spectra included in the DESI Early Data Release and the first two months of the main survey. This first set of data already provides an improvement in terms of spectroscopic resolution with respect to the previous measurements. We investigated methodological and instrumental contaminants associated with DESI and used synthetic data to validate and correct our measurement. Coupling our measurement with theoretical predictions from hydrodynamical simulations will yield strong constraints on the primordial matter power spectrum, neutrino masses, and dark matter properties. A quadratic maximum likelihood estimator was applied to the same data set on a companion paper and agrees with our measurement
One-dimensional power spectrum from first DESI Lyman-α forest
No full textInternational audienceThe Lyman-alpha forest is a unique probe of large-scale matter density fluctuations at high redshift z > 2. We measure the one-dimensional Lyman-alpha forest power spectrum using the first data provided by the Dark Energy Spectroscopic Instrument (DESI), with a fast Fourier transform estimator. The data sample contains quasar spectra included in the DESI Early Data Release and the first two months of the main survey. This first set of data already provides an improvement in terms of spectroscopic resolution with respect to the previous measurements. We investigated methodological and instrumental contaminants associated with DESI and used synthetic data to validate and correct our measurement. Coupling our measurement with theoretical predictions from hydrodynamical simulations will yield strong constraints on the primordial matter power spectrum, neutrino masses, and dark matter properties. A quadratic maximum likelihood estimator was applied to the same data set on a companion paper and agrees with our measurement
Lyman-alpha forest tomography and cross-correlation with cosmic voids
No full textInternational audienceThe Lyman-alpha forest is a unique probe of large-scale matter density fluctuations at high redshift (z > 2). It is possible to obtain 3D maps of the matter distribution from Lyman-alpha data, using tomographic reconstruction methods. Here, we present the largest tomographic map of matter fluctuations at z > 2, over the Gpc^3 volume covered by Lyman-alpha forest from SDSS-IV quasar spectra in the Stripe 82 field. We present a catalog of high-redshift voids constructed from this map. The measurement of the cross-correlation between these voids and the Lyman-alpha forest provides the first observation of the matter velocity flow around voids, through the RSD effect, at such high redshift. The data is in good agreement with simulations and is well adjusted with a linear, Kaiser velocity model
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
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
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
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