scholarly journals Cosmic String Wakes and Large-Scale Structure

1988 ◽  
Vol 130 ◽  
pp. 562-562
Author(s):  
A. Stebbins ◽  
S. Veeraraghavan ◽  
R. Brandenberger ◽  
J. Silk ◽  
N. Turok
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Ambient Medium ◽  
Unit Length ◽  
Long Strings ◽  
Topological Defects ◽  
Two Dimensional ◽  
Order Unity ◽  
The Galaxy ◽  
Redshift Survey

Cosmic Strings are one-dimensional topological defects that may be formed in the early universe during a phase transition, and which may be the source of all inhomogeneities in our universe. Their mass per unit length, μ, gives us a dimensionless parameter, μ6 ≡ 106Gμ/c2, which must be of order unity for strings to seed galaxy formation. Results to date from the ongoing CfA redshift survey suggest that galaxies are distributed on two-dimensional surfaces, whose typical separation is about 50h50−1 Mpc. The loop distribution is unlikely to imprint such large-scale patterns in the galaxy positions so we have examined whether this structure could be caused by infinite strings. Because an infinite string typically moves at a substantial fraction of the speed of light, it will leave behind a very large accretion wake in the ambient medium. Gravitational instablity causes these wakes to continue to accrete matter long after the string has moved elsewhere. These wakes form around the two-dimensional surfaces swept out by the long strings.

scholarly journals N-body Simulations to Test the Reliability of Two-point Correlation Functions of Galaxies

1992 ◽  
Vol 9 ◽  
pp. 703-704
Author(s):  
Yasushi Suto
Keyword(s):  
Correlation Functions ◽  
Large Scale ◽  
Sample Volume ◽  
Limited Data ◽  
Observable Universe ◽  
Large N ◽  
The Galaxy ◽  
Point Correlation ◽  
Systematic Biases ◽  
Redshift Survey

The shape and amplitude of the galaxy – galaxy correlation functions, ξgg(r), are among the most widely used measures of the large-scale structure in the universe (Totsuji & Kihara 1969). The estimates, however, might be seriously affected by the limited size of the sample volume, or equivalently, the limited number of available galaxies. In fact, while the observable universe extends c/H0 ~ 3000h-1Mpc, most observational works to map the distribution of galaxies so far have been mainly applied to samples within ~ 100h-1Mpc from us. Thus a CfA redshift survey slice, for example, of 8h < α < 17h, 26.5° < δ < 32.5°, and cz ≾ 15000km/sec (de Lapparent et al. 1986, 1988) represents merely ~ 2 x 10-5 of the total volume of the observable universe. This clearly illustrates the importance of examining possible systematic biases and variations in the estimates of two-point correlation functions from instrinsically limited data. We studied such sample-to-sample variations by analysing subsamples extracted from large N-body simulation data.

scholarly journals Three-dimensional Visualization of Cosmological and Galaxy Formation Simulations

2010 ◽  
Vol 6 (S277) ◽  
pp. 263-266
Author(s):  
Bruno Thooris ◽  
Daniel Pomarède
Keyword(s):  
Galaxy Formation ◽  
Adaptive Mesh Refinement ◽  
Large Scale ◽  
Multiple Scales ◽  
Three Dimensional ◽  
Adaptive Mesh ◽  
Ray Casting ◽  
Parallel Simulations ◽  
The Galaxy ◽  
Isosurface Reconstruction

AbstractOur understanding of the structuring of the Universe from large-scale cosmological structures down to the formation of galaxies now largely benefits from numerical simulations. The RAMSES code, relying on the Adaptive Mesh Refinement technique, is used to perform massively parallel simulations at multiple scales. The interactive, immersive, three-dimensional visualization of such complex simulations is a challenge that is addressed using the SDvision software package. Several rendering techniques are available, including ray-casting and isosurface reconstruction, to explore the simulated volumes at various resolution levels and construct temporal sequences. These techniques are illustrated in the context of different classes of simulations. We first report on the visualization of the HORIZON Galaxy Formation Simulation at MareNostrum, a cosmological simulation with detailed physics at work in the galaxy formation process. We then carry on in the context of an intermediate zoom simulation leading to the formation of a Milky-Way like galaxy. Finally, we present a variety of simulations of interacting galaxies, including a case-study of the Antennae Galaxies interaction.

scholarly journals Disordered hyperuniformity in two-dimensional amorphous silica

2020 ◽  
Vol 6 (16) ◽  
pp. eaba0826 ◽  
Author(s):  
Yu Zheng ◽  
Lei Liu ◽  
Hanqing Nan ◽  
Zhen-Xiong Shen ◽  
Ge Zhang ◽  
...  
Keyword(s):  
Amorphous Silica ◽  
Density Functional ◽  
Large Scale ◽  
Single Layer ◽  
Topological Defects ◽  
Density Functional Theory Calculations ◽  
Density Fluctuations ◽  
Atomic Scale ◽  
Two Dimensional ◽  
Wave Localization

Disordered hyperuniformity (DHU) is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems. DHU systems are characterized by vanishing infinite-wavelength normalized density fluctuations and are endowed with unique novel physical properties. Here, we report the discovery of disordered hyperuniformity in atomic-scale two-dimensional materials, i.e., amorphous silica composed of a single layer of atoms, based on spectral-density analysis of high-resolution transmission electron microscopy images. Moreover, we show via large-scale density functional theory calculations that DHU leads to almost complete closure of the electronic bandgap compared to the crystalline counterpart, making the material effectively a metal. This is in contrast to the conventional wisdom that disorder generally diminishes electronic transport and is due to the unique electron wave localization induced by the topological defects in the DHU state.

scholarly journals Probing the accelerating Universe with redshift-space distortions in VIPERS

2014 ◽  
Vol 11 (S308) ◽  
pp. 617-622
Author(s):  
Sylvain de la Torre
Keyword(s):  
Growth Rate ◽  
Large Scale ◽  
Large Scale Structure ◽  
Einstein Gravity ◽  
Accelerating Universe ◽  
Data Release ◽  
The Galaxy ◽  
Redshift Survey ◽  
Galaxy Redshift ◽  
Clustering Pattern

AbstractWe present the first measurement of the growth rate of structure at z=0.8. It has been obtained from the redshift-space distortions observed in the galaxy clustering pattern in the VIMOS Public Redshift survey (VIPERS) first data release. VIPERS is a large galaxy redshift survey probing the large-scale structure at 0.5 < z < 1.2 with an unprecedented accuracy. This measurement represents a new reference in the distant Universe, which has been poorly explored until now. We obtain σ8 = 0.47 ± 0.08 at z = 0.8 that is consistent with the predictions of standard cosmological models based on Einstein gravity. This measurement alone is however not accurate enough to allow the detection of possible deviations from standard gravity.

scholarly journals Barred galaxies in cosmological zoom-in simulations: the importance of feedback

2019 ◽  
Vol 488 (2) ◽  
pp. 1864-1877 ◽  
Author(s):  
Tommaso Zana ◽  
Pedro R Capelo ◽  
Massimo Dotti ◽  
Lucio Mayer ◽  
Alessandro Lupi ◽  
...  
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Stellar Content ◽  
Barred Galaxies ◽  
Stellar Feedback ◽  
The Galaxy ◽  
Key Factor ◽  
Formation And Evolution ◽  
Zoom In ◽  
Statistical Sample

Abstract Bars are a key factor in the long-term evolution of spiral galaxies, in their unique role in redistributing angular momentum and transporting gas and stars on large scales. The Eris-suite simulations are cosmological zoom-in, N-body, smoothed-particle hydrodynamic simulations built to follow the formation and evolution of a Milky-Way-sized galaxy across the build-up of the large-scale structure. Here we analyse and describe the outcome of two particular simulations taken from the Eris suite – ErisBH and Eris2k – which mainly differ in the prescriptions employed for gas cooling, star formation, and feedback from supernovae and black holes. Our study shows that the enhanced effective feedback in Eris2k, due to the collective effect of the different micro-physics implementations, results in a galaxy that is less massive than its ErisBH counterpart till z ∼ 1. However, when the stellar content is large enough so that global dynamical instabilities can be triggered, the galaxy in Eris2k develops a stronger and more extended bar with respect to ErisBH. We demonstrate that the structural properties and time evolution of the two bars are very different. Our results highlight the importance of accurate sub-grid prescriptions in cosmological zoom-in simulations of the process of galaxy formation and evolution, and the possible use of a statistical sample of barred galaxies to assess the strength of the stellar feedback.

COSMIC STRINGS, HOT DARK MATTER AND THE LARGE-SCALE STRUCTURE OF THE UNIVERSE

1990 ◽  
Vol 05 (09) ◽  
pp. 1633-1651 ◽  
Author(s):  
ROBERT H. BRANDENBERGER ◽  
LEANDROS PERIVOLAROPOULOS ◽  
ALBERT STEBBINS
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Large Scale ◽  
Cosmic Strings ◽  
Unit Length ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Rotation Curves ◽  
The Universe

A review of recent results on large-scale structure and galaxy formation in a model with hot dark matter and cosmic strings is given. With cosmic strings seeding perturbations, many of the arguments against hot dark matter disappear. It is shown that spherical accretion about loops leads to dark matter haloes with flat velocity rotation curves. Velocity perturbations due to wakes behind long, moving strings lead to a network of planar overdensities with a distinguished scale of slightly less than 40×40 Mpc2. If the mass per unit length μ exceeds a certain bound, then the wakes become nonlinear by the present time. In this case, their thickness can be calculated.

scholarly journals Optical Redshift Surveys

1992 ◽  
Vol 9 ◽  
pp. 681-683
Author(s):  
L. Nicolaci da Costa
Keyword(s):  
Large Scale ◽  
Current Status ◽  
Redshift Surveys ◽  
Galaxy Distribution ◽  
The Galaxy ◽  
Redshift Survey ◽  
Different Depths ◽  
Source Of Information ◽  
The Universe

Redshift surveys of galaxies have been over the past decade the major source of information for studies of the large-scale structure of the Universe. Following the completion of the original CfA Redshift Survey, several groups have joined the endeavor, probing different regions of the sky to different depths in a remarkable long-term effort to study the nature of the galaxy distribution and its statistical properties at different scales. Here I summarize the current status of the ongoing surveys drawn from optical galaxy catalogs. The review is not intended to be complete but rather to demonstrate the vitality of the area and to point out that exciting new data should be forthcoming in the next few years.

scholarly journals Large Scale Galactic Structure

1995 ◽  
Vol 148 ◽  
pp. 258-266
Author(s):  
Gerard Gilmore ◽  
Rodrigo Ibata
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Scale Effects ◽  
Essential Feature ◽  
Chemical Abundance ◽  
Small Satellites ◽  
The Galaxy ◽  
Moving Groups ◽  
Scale Properties

AbstractModern models of Galaxy formation make fairly specific predictions which are amenable to detailed tests with galactic kinematic and chemical abundance data. For example, popular Cold Dark Matter models ‘predict’ growth of the Galaxy about a central core, which should contain the oldest stars. Later accretion of material forms the outer halo and the disks, while continuing accretion will continue to affect the kinematic structure of both the outer halo and the thin disk. This picture, which contains aspects of both the monolithic (‘ELS’) and the multifragment (‘Searle-Zinn’) pictures often discussed in chemical evolution models, makes some specific predictions which can be tested. The essential feature of these predictions is that they are believable only for the largest scale effects. Large scale properties of the Galaxy must be measured to test them. It is these studies which need large angular scale data. One specific example of current interest is the ‘prediction’ that mergers of small satellites are an essential feature of galactic evolution. This leads one to look for kinematic and spatial structures, and ‘moving groups’, as a primary test of such models.

scholarly journals Detecting multi-scale filaments in galaxy distribution

2014 ◽  
Vol 10 (S306) ◽  
pp. 45-47
Author(s):  
Elmo Tempel
Keyword(s):  
Point Process ◽  
Large Scale ◽  
Three Dimensional ◽  
Sloan Digital Sky Survey ◽  
Point Distribution ◽  
Multi Scale ◽  
Galaxy Distribution ◽  
Sky Survey ◽  
The Galaxy ◽  
Redshift Survey

AbstractThe main feature of the spatial large-scale galaxy distribution is its intricate network of galaxy filaments. This network is spanned by the galaxy locations that can be interpreted as a three-dimensional point distribution. The global properties of the point process can be measured by different statistical methods, which, however, do not describe directly the structure elements. The morphology of the large-scale structure, on the other hand, is an important property of the galaxy distribution. Here, we apply an object point process with interactions (the Bisous model) to trace and extract the filamentary network in the presently largest galaxy redshift survey, the Sloan Digital Sky Survey (SDSS data release 10). We search for multi-scale filaments in the galaxy distribution that have a radius of about 0.5, 1.0, 2.0, and 4.0h−1Mpc. We extract the spines of the filamentary network and divide the detected network into single filaments.

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