Search results for: the-cosmic-web

The Cosmic Web

Author : J. Richard Gott
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Semi-autobiographical discussion of astronomy and astronomers, and history of astronomy and cosmology.--

The Cosmic Web and the Local Universe

Author : M.A.M. van de Weijgaert
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The Cosmic Web

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The Cosmic Web

Author : N. Katherine Hayles
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From the central concept of the field—which depicts the world as a mutually interactive whole, with each part connected to every other part by an underlying field— have come models as diverse as quantum mathematics and Saussure’s theory of language. In The Cosmic Web, N. Katherine Hayles seeks to establish the scope of the field concept and to assess its importance for contemporary thought. She then explores the literary strategies that are attributable directly or indirectly to the new paradigm; among the texts at which she looks closely are Robert Pirsig’s Zen and the Art of Motorcycle Maintenance, Nabokov’s Ada, D. H. Lawrence’s early novels and essays, Borges’s fiction, and Thomas Pynchon’s Gravity’s Rainbow.

Dark Matter and Cosmic Web Story

Author : Jaan Einasto
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The concepts of dark matter and the cosmic web are some of the most significant developments in cosmology in the past century. They have decisively changed the classical cosmological paradigm, which was first elaborated upon during the first half of the 20th century but ran into serious problems in the second half. Today, they are integral parts of modern cosmology, which explains everything from the Big Bang to inflation to the large scale structure of the Universe. Dark Matter and Cosmic Web Story describes the contributions that led to a paradigm shift from the Eastern point of view. It describes the problems with the classical view, the attempts to solve them, the difficulties encountered by those solutions, and the conferences where the merits of the new concepts were debated. Amidst the science, the story of scientific work in a small country occupied by the Soviet Union and the tumultuous events that led to its breakup are detailed as well. This book is accompanied by a website which contains additional material: copies of the originals of some crucial papers, astronomical movies, and movies which showcase the private life of the author. The link is given below: http://www.aai.ee/~einasto/DarkMatter/ Contents:PrologueClassical Cosmological ParadigmGalactic Models and Dark Matter in the Solar VicinityGlobal Dark MatterThe Cosmic WebThe Nature of Dark MatterThe Structure of the Cosmic WebCosmic Inflation, Dark Energy and the Evolution of the UniverseEpilogue Readership: Students and professionals in astrophysics, cosmology and physics; non-experts interested in the history of science, and the life and social activity of scientists in a country occupied by Soviet Union for 50 years. Keywords:Dark Matter;Cosmic Web;Large-Scale Structure of the UniverseKey Features:The development of the concepts of dark matter and the cosmic web as a change in the worldview (paradigm) in cosmology is describedA personal view of the development of dark matter and cosmic web concepts as seen by a non-Western scientistDescription of scientific work and social activity in a small country occupied by the Soviet Union; the participation of scientists in processes which led to the collapse of the Soviet Empire, and to the end of the Cold WarReviews: “A deeply humane but also political account, the book offers a fascinating insider tour into one of the most important processes of cosmology. Einasto a pioneer of dark matter research offers a thorough scientific description of the discovery of dark matter.” Anne Liljeström Editor Stars and Universe “A fascinating combination of the scientific history of dark matter with personal recollections, by an author who was there both for the discovery of DM and for the (singing revolution) in Estonia.” Virginia Trimble Professor of Astronomy University of California, Irvine

Disentangling the Cosmic Web

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The Cosmic Web and the Role of Environment in Galaxy Evolution

Author : Ryan Cybulski
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The Universe, on extra-galactic scales, is composed of a vast network of structures dubbed the "cosmic web". One of the most fundamental discoveries about the evolution of galaxies is that their properties have a dependence on their location relative to this cosmic web (i.e., their environment). However, detailed studies of the environmental dependence on galaxy evolution have been extremely challenging due to the inherent complexity of the structures on the largest scales, a plethora of techniques being used to try to map the cosmic web, and other confounding factors, such as the masses of galaxies, that also affect their evolution. In this work, we will present a technique for characterizing the environments of galaxies in the cosmic web, which is comprised of two separate, but complementary, methods that together provide a more complete measure of environment. After some introductory background in Chapter 1, we will demonstrate these mapping techniques on the Coma Supercluster, and present an analysis of the star-formation activity of about 4,000 galaxies in the supercluster environment in Chapter 2. Next, in Chapter 3 we present a greatly expanded application of our mapping techniques encompassing about 60,000 galaxies within 200 Mpc that addresses several outstanding questions from the Coma Supercluster study, and also leads to new intriguing insights into the evolution of galaxies as a function of environment. Then, in Chapter 4 we present a pilot study focusing on galaxy evolution as traced by the gas content around two galaxy clusters. We also expand upon this pilot study in Chapter 5, whereupon we examine more closely the resiliency of molecular gas content, compared to the atomic gas, to the effects of the cluster environment. And finally, in Chapter 6 we present some concluding remarks and explore some promising avenues for future study.

Galaxies and Gas in Dark Matter Halos and the Cosmic Web

Author : Seunghwan Lim
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In the current understanding of galaxy formation, galaxies are believed to form and evolve in dark matter halos. The dark matter halos are collapsed objects that form and grow via gravitational instability of small initial density fluctuation in the cosmic field. They are not only the hosts of galaxies but are tracers of the cosmic web of the Universe. They are thus crucial components for understanding how galaxies form and evolve within the cosmic web. This dissertation is a systematic investigation of the galaxies and gas in the dark matter halos and the cosmic web, using observation data of large galaxy surveys such as the Sloan Digital Sky Survey (SDSS), and of the Cosmic Microwave Background (CMB) survey such as the Planck, together with simulations and modellings for comparison and interpretation. Specifically, we have identified dark matter halos in the low-redshift Universe, and constructed the largest to date all-sky group catalog. We also investigated correlations between many of the galaxy and halo properties, particularly finding, for the first time, an observational proxy of halo age. Then, I developed a series of novel approaches to maximize the detection of the Sunyaev-Zel'dovich effect (SZE), and from it explored the gas properties in halos to find that the gas mass fraction even in Milky Way-size halos is about the cosmic mean fraction. The analysis identified the baryons in a warm-hot medium on halo scales. We also show that the thermal SZE can be used to constrain the mean relationship between thermal energy of IGM gas and local total matter density for the first time. We support the reliability of our methods and results with tests where the methods are applied to the mock CMB maps constructed from simulations. Finally, we present comparisons with simulations of the SZE, and discuss the implications for its constraining power of galaxy formation models.

The Zeldovich Universe IAU S308

Author : Rien van de Weygaert
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On megaparsec scales, matter and galaxies have aggregated into a complex network of interconnected filaments, wall-like structures and compact clusters surrounded by large near-empty void regions. Dubbed the 'Cosmic Web', theoretical and observational studies have led to its recognition as a key aspect of structure in the Universe, representing a universal phase in the gravitationally driven emergence and evolution of cosmic structure. IAU Symposium 308 marked the centenary of the birth of the Russian physicist and cosmologist Yakov B. Zeldovich (1914-87), who was instrumental in the development of this view of structure formation. His seminal work paved the way towards an understanding of the complex web-like structure observed in our Universe. This volume synthesizes the insights obtained from many different observational and theoretical studies, and helps prepare researchers and students working in this vibrant field for the many upcoming surveys.

X ray Spectroscopy of Clusters of Galaxies and of the Cosmic Web

Author : Norbert Werner
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How filaments of galaxies are woven into the cosmic web

Author : J. Richard Bond
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Clusters Voids and Reconstructions of the Cosmic Web

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Mapping the Cosmic Web

Author : Zeynep Pirin Erdoǧdu
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Galaxy Formation in the Cosmic Web

Author : Oliver Jens Hahn
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Cosmology with Underdensities of the Cosmic Web

Author : Vasiliy Grigoriyvich Demchenko
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Geometric Graphs the Cosmic Web and Hypergraphs

Author : Bruno Coutinho
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First, we show how network science can be applied to study the cosmic web and we explore a hypothetical spreading process at the cosmic level using concepts from network science. The concept of the cosmic web, viewing the Universe as a set of discrete galaxies held together by gravity, is deeply engrained in cosmology. Yet, little is known about the most effective construction and the characteristics of the underlying network. We explore seven network construction algorithms that use various galaxy properties, from their location to their size and relative velocity. We find that a model relying only on spatial proximity offers the best correlations between the physical characteristics of the connected galaxies. We show that the properties of the networks generated from simulations and observations are identical, unveiling a deep universality of the cosmic web. Second, we explore a generalization of graphs, called hypergraphs, which offer a much more faithful representation of many complex systems. We find that in most real-world hypergraphs two key combinatorial problems, the edge and the vertex cover problems, can be solved in polynomial time.

A Void Perspective of the Cosmic Web

Author : Erwin Platen
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Structure Formation Within the Cosmic Web

Author : Elizabeth Eardley
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Evolution of Galaxies in the Cosmic Web

Author : Behnam Darvish Sarvestani
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We study the effects of environment on the evolution of galaxies, with an emphasis on two different approaches towards the definition of environment: (1) environment defined based on the local surface density of galaxies and (2) environment defined based on the major components of the cosmic web; i.e., filaments, clusters and the field. In the first approach, surface density field is estimated using a variety of estimators and tested with simulations. Using the estimated surface densities assigned to galaxies, we observe a strong environmental dependence on the properties of galaxies (e.g., SFR, sSFR and the quiescent fraction) at z ≤ 1. We explore the fractional role of stellar mass and environment in quenching the star-formation. In the second approach, we use the Multi-scale Morphology Filter algorithm to disentangle the density field into its component. We apply this method to a sample of star-forming galaxies for a large-scale structure at z ∼0.84 in the HiZELS-COSMOS field. We show that the observed median SFR, stellar mass, sSFR, the mean SFR$-$mass relation and its scatter for star-forming galaxies do not strongly depend on the cosmic web. However, the fraction of H[Alpha] star-forming galaxies varies with environment and is enhanced in filaments. Furthermore, we study the physical properties of a spectroscopic sample of star-forming galaxies in a large filament in the COSMOS field at z ∼0.53, with spectroscopic data taken with the Keck/DEIMOS spectrograph, and compare them with a control sample of field galaxies. We spectroscopically confirm the presence of a large galaxy filament (∼ 8 Mpc). We show that within the uncertainties, the ionization parameter, EW, EW versus sSFR relation, EW versus stellar mass relation, line-of-sight velocity dispersion, dynamical mass, and stellar-to-dynamical mass ratio are similar for filament and field star-forming galaxies. However, we show that on average, filament star-forming galaxies are more metal-enriched (∼ 0.1-0.15 dex) and the electron densities are significantly lower (a factor of ∼17) in filament star-forming systems compared to those in the field. Our results highlight the potential role of galaxy filaments and intermediate-density environments on the evolution of galaxies, which has been poorly investigated.

Capturing the Cosmic Web for Cosmology

Author : Krishna Naidoo
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