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Scale Structure

The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Scale Structure - Free Register to Access Experts & Abstracts

Athina Brintaki - One of the best experts on this subject based on the ideXlab platform.

Lawrence M Widrow - One of the best experts on this subject based on the ideXlab platform.

  • Magnetic Fields in the Large-Scale Structure of the Universe
    Space Science Reviews, 2012
    Co-Authors: D. Ryu, D. R. G. Schleicher, Rudolf A. Treumann, Christos G Tsagas, Lawrence M Widrow
    Abstract:

    Magnetic fields appear to be ubiquitous in astrophysical environments. Their existence in the intracluster medium is established through observations of synchrotron emission and Faraday rotation. On the other hand, the nature of magnetic fields outside of clusters, where observations are scarce and controversial, remains largely unknown. In this chapter, we review recent developments in our understanding of the nature and origin of intergalactic magnetic fields, and in particular, intercluster fields. A plausible scenario for the origin of galactic and intergalactic magnetic fields is for seed fields, created in the early universe, to be amplified by turbulent flows induced during the formation of the large Scale Structure. We present several mechanisms for the generation of seed fields both before and after recombination. We then discuss the evolution and role of magnetic fields during the formation of the first starts. We describe the turbulent amplification of seed fields during the formation of large Scale Structure and the nature of the magnetic fields that arise. Finally, we discuss implications of intergalactic magnetic fields.

D. Ryu - One of the best experts on this subject based on the ideXlab platform.

  • Magnetic Fields in the Large-Scale Structure of the Universe
    Space Science Reviews, 2012
    Co-Authors: D. Ryu, D. R. G. Schleicher, Rudolf A. Treumann, Christos G Tsagas, Lawrence M Widrow
    Abstract:

    Magnetic fields appear to be ubiquitous in astrophysical environments. Their existence in the intracluster medium is established through observations of synchrotron emission and Faraday rotation. On the other hand, the nature of magnetic fields outside of clusters, where observations are scarce and controversial, remains largely unknown. In this chapter, we review recent developments in our understanding of the nature and origin of intergalactic magnetic fields, and in particular, intercluster fields. A plausible scenario for the origin of galactic and intergalactic magnetic fields is for seed fields, created in the early universe, to be amplified by turbulent flows induced during the formation of the large Scale Structure. We present several mechanisms for the generation of seed fields both before and after recombination. We then discuss the evolution and role of magnetic fields during the formation of the first starts. We describe the turbulent amplification of seed fields during the formation of large Scale Structure and the nature of the magnetic fields that arise. Finally, we discuss implications of intergalactic magnetic fields.

  • Shock Waves in the Large-Scale Structure of the Universe
    Astrophysics and Space Science, 2008
    Co-Authors: D. Ryu, Hyesung Kang
    Abstract:

    Cosmological shock waves are induced during hierarchical formation of large-Scale Structure in the universe. Like most astrophysical shocks, they are collisionless, since they form in the tenuous intergalactic medium through electromagnetic viscosities. The gravitational energy released during Structure formation is transferred by these shocks to the intergalactic gas as heat, cosmic-rays, turbulence, and magnetic fields. Here we briefly describe the properties and consequences of the shock waves in the context of the large-Scale Structure of the universe.

  • turbulence and magnetic fields in the large Scale Structure of the universe
    Science, 2008
    Co-Authors: D. Ryu, Hyesung Kang, Jungyeon Cho, Santabrata Das
    Abstract:

    The nature and origin of turbulence and magnetic fields in the intergalactic space are important problems that are yet to be understood. We propose a scenario in which turbulent-flow motions are induced via the cascade of the vorticity generated at cosmological shocks during the formation of the large-Scale Structure. The turbulence in turn amplifies weak seed magnetic fields of any origin. Supercomputer simulations show that the turbulence is subsonic inside clusters and groups of galaxies, whereas it is transonic or mildly supersonic in filaments. Based on a turbulence dynamo model, we then estimated that the average magnetic field strength would be a few microgauss (μG) inside clusters and groups, approximately 0.1 μG around clusters and groups, and approximately 10 nanogauss in filaments. Our model presents a physical mechanism that transfers the gravitational energy to the turbulence and magnetic field energies in the large-Scale Structure of the universe.

Natalia Porqueres - One of the best experts on this subject based on the ideXlab platform.

  • Inferring high-redshift large-Scale Structure dynamics from the Lyman-$\alpha$ forest
    Astron.Astrophys., 2019
    Co-Authors: Natalia Porqueres, Jens Jasche, Guilhem Lavaux, Torsten Enßlin
    Abstract:

    One of the major science goals over the coming decade is to test fundamental physics with probes of the cosmic large-Scale Structure out to high redshift. Here we present a fully Bayesian approach to infer the three-dimensional cosmic matter distribution and its dynamics at z > 2 from observations of the Lyman-α forest. We demonstrate that the method recovers the unbiased mass distribution and the correct matter power spectrum at all Scales. Our method infers the three-dimensional density field from a set of one-dimensional spectra, interpolating the information between the lines of sight. We show that our algorithm provides unbiased mass profiles of clusters, becoming an alternative for estimating cluster masses complementary to weak lensing or X-ray observations. The algorithm employs a Hamiltonian Monte Carlo method to generate realizations of initial and evolved density fields and the three-dimensional large-Scale flow, revealing the cosmic dynamics at high redshift. The method correctly handles multi-modal parameter distributions, which allow constraining the physics of the intergalactic medium with high accuracy. We performed several tests using realistic simulated quasar spectra to test and validate our method. Our results show that detailed and physically plausible inference of three-dimensional large-Scale Structures at high redshift has become feasible.Key words: large-Scale Structure of Universe / dark matter

  • Imprints of the large-Scale Structure on AGN formation and evolution
    Astron.Astrophys., 2018
    Co-Authors: Natalia Porqueres, Jens Jasche, Torsten A. Enßlin, Guilhem Lavaux
    Abstract:

    Black hole masses are found to correlate with several global properties of their host galaxies, suggesting that black holes and galaxies have an intertwined evolution and that active galactic nuclei (AGN) have a significant impact on galaxy evolution. Since the large-Scale environment can also affect AGN, this work studies how their formation and properties depend on the environment. We have used a reconstructed three-dimensional high-resolution density field obtained from a Bayesian large-Scale Structure reconstruction method applied to the 2M++ galaxy sample. A web-type classification relying on the shear tensor is used to identify different Structures on the cosmic web, defining voids, sheets, filaments, and clusters. We confirm that the environmental density affects the AGN formation and their properties. We found that the AGN abundance is equivalent to the galaxy abundance, indicating that active and inactive galaxies reside in similar dark matter halos. However, occurrence rates are different for each spectral type and accretion rate. These differences are consistent with the AGN evolutionary sequence suggested by previous authors, Seyferts and Transition objects transforming into low-ionization nuclear emission line regions (LINERs), the weaker counterpart of Seyferts. We conclude that AGN properties depend on the environmental density more than on the web-type. More powerful starbursts and younger stellar populations are found in high densities, where interactions and mergers are more likely. AGN hosts show smaller masses in clusters for Seyferts and Transition objects, which might be due to gas stripping. In voids, the AGN population is dominated by the most massive galaxy hosts.Key words: large-Scale Structure of Universe / galaxies: active / galaxies: evolution / galaxies: formation / galaxies: Seyfert

Guilhem Lavaux - One of the best experts on this subject based on the ideXlab platform.

  • Inferring high-redshift large-Scale Structure dynamics from the Lyman-$\alpha$ forest
    Astron.Astrophys., 2019
    Co-Authors: Natalia Porqueres, Jens Jasche, Guilhem Lavaux, Torsten Enßlin
    Abstract:

    One of the major science goals over the coming decade is to test fundamental physics with probes of the cosmic large-Scale Structure out to high redshift. Here we present a fully Bayesian approach to infer the three-dimensional cosmic matter distribution and its dynamics at z > 2 from observations of the Lyman-α forest. We demonstrate that the method recovers the unbiased mass distribution and the correct matter power spectrum at all Scales. Our method infers the three-dimensional density field from a set of one-dimensional spectra, interpolating the information between the lines of sight. We show that our algorithm provides unbiased mass profiles of clusters, becoming an alternative for estimating cluster masses complementary to weak lensing or X-ray observations. The algorithm employs a Hamiltonian Monte Carlo method to generate realizations of initial and evolved density fields and the three-dimensional large-Scale flow, revealing the cosmic dynamics at high redshift. The method correctly handles multi-modal parameter distributions, which allow constraining the physics of the intergalactic medium with high accuracy. We performed several tests using realistic simulated quasar spectra to test and validate our method. Our results show that detailed and physically plausible inference of three-dimensional large-Scale Structures at high redshift has become feasible.Key words: large-Scale Structure of Universe / dark matter

  • A rigorous EFT-based forward model for large-Scale Structure
    JCAP, 2019
    Co-Authors: Fabian Schmidt, Jens Jasche, Franz Elsner, Nhat Minh Nguyen, Guilhem Lavaux
    Abstract:

    Conventional approaches to cosmology inference from galaxy redshift surveys are based on n-point functions, which are under rigorous perturbative control on sufficiently large Scales. Here, we present an alternative approach, which employs a likelihood at the level of the galaxy density field. By integrating out small-Scale modes based on effective-field theory arguments, we prove that this likelihood is under perturbative control if certain specific conditions are met. We further show that the information captured by this likelihood is equivalent to the combination of the next-to-leading order galaxy power spectrum, leading-order bispectrum, and BAO reconstruction. Combined with MCMC sampling and MAP optimization techniques, our results allow for fully Bayesian cosmology inference from large-Scale Structure that is under perturbative control. We illustrate this via a first demonstration of unbiased cosmology inference from nonlinear large-Scale Structure using this likelihood. In particular, we show unbiased estimates of the power spectrum normalization σ8 from a catalog of simulated dark matter halos, where nonlinear information is crucial in breaking the b1−σ8 degeneracy.

  • Imprints of the large-Scale Structure on AGN formation and evolution
    Astron.Astrophys., 2018
    Co-Authors: Natalia Porqueres, Jens Jasche, Torsten A. Enßlin, Guilhem Lavaux
    Abstract:

    Black hole masses are found to correlate with several global properties of their host galaxies, suggesting that black holes and galaxies have an intertwined evolution and that active galactic nuclei (AGN) have a significant impact on galaxy evolution. Since the large-Scale environment can also affect AGN, this work studies how their formation and properties depend on the environment. We have used a reconstructed three-dimensional high-resolution density field obtained from a Bayesian large-Scale Structure reconstruction method applied to the 2M++ galaxy sample. A web-type classification relying on the shear tensor is used to identify different Structures on the cosmic web, defining voids, sheets, filaments, and clusters. We confirm that the environmental density affects the AGN formation and their properties. We found that the AGN abundance is equivalent to the galaxy abundance, indicating that active and inactive galaxies reside in similar dark matter halos. However, occurrence rates are different for each spectral type and accretion rate. These differences are consistent with the AGN evolutionary sequence suggested by previous authors, Seyferts and Transition objects transforming into low-ionization nuclear emission line regions (LINERs), the weaker counterpart of Seyferts. We conclude that AGN properties depend on the environmental density more than on the web-type. More powerful starbursts and younger stellar populations are found in high densities, where interactions and mergers are more likely. AGN hosts show smaller masses in clusters for Seyferts and Transition objects, which might be due to gas stripping. In voids, the AGN population is dominated by the most massive galaxy hosts.Key words: large-Scale Structure of Universe / galaxies: active / galaxies: evolution / galaxies: formation / galaxies: Seyfert

  • Probabilistic cartography of the large-Scale Structure
    arXiv: Cosmology and Nongalactic Astrophysics, 2015
    Co-Authors: Florent Leclercq, Jens Jasche, Guilhem Lavaux, Benjamin D. Wandelt
    Abstract:

    The BORG algorithm is an inference engine that derives the initial conditions given a cosmological model and galaxy survey data, and produces physical reconstructions of the underlying large-Scale Structure by assimilating the data into the model. We present the application of BORG to real galaxy catalogs and describe the primordial and late-time large-Scale Structure in the considered volumes. We then show how these results can be used for building various probabilistic maps of the large-Scale Structure, with rigorous propagation of uncertainties. In particular, we study dynamic cosmic web elements and secondary effects in the cosmic microwave background.