The Line-of-Sight Analysis of Spatial Distribution of Galaxies in the COSMOS2015 Catalogue

New observations of high-redshift objects are crucial for the improvement of the standard ΛCDM cosmological model and our understanding of the Universe. One of the main directions of modern observational cosmology is the analysis of the large-scale structure of Universe, in particular, in deep fields. We study the large-scale structure of the Universe along the line of sight using the latest version of the COSMOS2015 catalogue, which contains 518,404 high quality photometric redshifts of galaxies selected in the optical range of the COSMOS field (2×2 deg2), with depth up to the redshift z∼6. We analyze large-scale fluctuations in the number of galaxies along the line of sight and provide an estimate of the average linear sizes of the self-correlating fluctuations (structures) in independent redshift bins of Δz=0.1 along with the estimate of the standard deviation from homogeneity (the observed cosmic variance). We suggest a new method of the line-of-sight analysis based on previous works and formulate further prospects of method development. For the case of the theoretical form of approximation of homogeneity in the ΛCDM framework, the average standard deviation of detected structures from homogeneity is σmeanΛCDM=0.09±0.02, and the average characteristic size of structures is RmeanΛCDM=790±150 Mpc. For the case of the empirical approximation of homogeneity, the average standard deviation of detected structures from homogeneity is σmeanempiric=0.08±0.01, and the average characteristic size of structures is Rmeanempiric=640±140 Mpc.

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Origin and evolution of the large-scale structure of the universe

Canadian Journal of Physics ◽

10.1139/p90-117 ◽

1990 ◽

Vol 68 (9) ◽

pp. 799-807

Author(s):

Joseph Silk

Keyword(s):

Large Scale ◽

Background Radiation ◽

Building Blocks ◽

Large Scale Structure ◽

Big Bang ◽

Scale Structure ◽

Observational Cosmology ◽

Spontaneous Breaking ◽

Fluctuation Spectrum ◽

The Universe

Ever since the epoch of the spontaneous breaking of grand unification symmetry between the nuclear and electromagnetic interactions, the universe has expanded under the imprint of a spectrum of density fluctuations that is generally considered to have originated in this phase transition. I will discuss various possibilities for the form of the primordial fluctuation spectrum, spanning the range of adiabatic fluctuations, isocurvature fluctuations, and cosmic strings. Growth of the seed fluctuations by gravitational instability generates the formation of large-scale structures, from the scale of galaxies to that of clusters and superclusters of galaxies. There are three areas of confrontation with observational cosmology that will be reviewed. The large-scale distribution of the galaxies, including the apparent voids, sheets and filaments, and the coherent peculiar velocity field on scales of several tens of megaparsecs, probe the primordial fluctuation spectrum on scales that are only mildly nonlinear. Even larger scales are probed by study of the anisotropy of the cosmic microwave background radiation, which provides a direct glimpse of the primordial fluctuations that existed about 106 years or so after the initial big bang singularity. Galaxy formation is the process by which the building blocks of the universe have formed, involving a complex interaction between hydrodynamical and dynamical processes in a collapsing gas cloud. Both by detection of forming galaxies in the most remote regions of the universe and by study of the fundamental morphological characteristics of galaxies, which provide a fossilized memory of their past, can one relate the origin of galaxies to the same primordial fluctuation spectrum that gave rise' to the large-scale structure of the universe.

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Spatial Distribution of Quasars

Symposium - International Astronomical Union ◽

10.1017/s0074180900159650 ◽

1987 ◽

Vol 124 ◽

pp. 627-638

Author(s):

Yaoquan Chu ◽

LiZhi Fang

Keyword(s):

Spatial Distribution ◽

Large Scale ◽

Large Scale Structure ◽

Scale Structure ◽

Observational Cosmology ◽

Small Scale ◽

Large Scale Systems ◽

Isothermal Case ◽

The Universe ◽

Adiabatic Case

The distribution of quasars has become one of the most interesting problems in observational cosmology. This is due mainly to the development of theory of the formation of large scale structure in the universe. In recent years, several scenarios of clustering have been proposed. In the adiabatic case, the clustering process is from larger scales to smaller ones, i.e., the first systems to form out would be on the scale of superclusters, then these systems fragment to form smaller scale systems such as galaxies. In the isothermal case, the clustering is from smaller scales to larger ones, namely, galaxies condense out at first and larger scale systems, such as clusters and superclusters, then form later via hierachical build-up processes. In the universe contain two components, the scenario of clustering might be different from both standard adiabatic and isothermal cases(1). According to this new scenario, there should be two kinds of small scale objects, one is formed due to fragment of larger scale systems, another is formed before large scale systems form.

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Gravitational lensing in cosmology

International Journal of Modern Physics D ◽

10.1142/s0218271815300116 ◽

2015 ◽

Vol 24 (05) ◽

pp. 1530011 ◽

Cited By ~ 1

Author(s):

Toshifumi Futamase

Keyword(s):

Gravitational Lensing ◽

Large Scale ◽

Cosmological Parameters ◽

Galaxy Cluster ◽

Large Scale Structure ◽

Research Field ◽

Scale Structure ◽

Observational Cosmology ◽

Law Of Gravity ◽

The Universe

Gravitational lensing is a unique and direct probe of mass in the universe. It depends only on the law of gravity and does not depend on the dynamical state nor the composition of matter. Thus, it is used to study the distribution of the dark matter in the lensing object. Combined with the traditional observations such as optical and X-ray, it gives us useful informations of the structure formation in the universe. The lensing observables depend also on the global geometry as well as large scale structure of the universe. Therefore it is possible to withdraw useful constraints on the cosmological parameters once the distribution of lensing mass is accurately known. Since the first discovery of the lensing event by a galaxy in 1979, various kinds of lensing phenomena caused by star, galaxy, cluster of galaxies and large scale structure have been observed and are used to study mass distribution in various scales and cosmology. Thus, the gravitational lensing is now regarded as an indispensable research field in the observational cosmology. In this paper, we give an instructive introduction to gravitational lensing and its applications to cosmology.

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Gravitational Lenses as Tools in Observational Cosmology

Symposium - International Astronomical Union ◽

10.1017/s0074180900159844 ◽

1987 ◽

Vol 124 ◽

pp. 729-746 ◽

Cited By ~ 2

Author(s):

Claude R. Canizares

Keyword(s):

Large Scale ◽

Computer Time ◽

Scale Structure ◽

Gravitational Lens ◽

Observational Cosmology ◽

Line Of Sight ◽

Small Scale ◽

Gravitational Lenses ◽

Single Object ◽

The Universe

The study of gravitational lenses is intimately tied to observational cosmology. When we observe a gravitationally lensed quasar, we are viewing a single object along two or more neighboring paths (null geodesics) of cosmological dimensions (Figure 1). What we see depends on bulk properties of the universe, such as Ho and qo, on the large scale structure and inhomogeneities along the paths, and on the small scale structure in and around the primary deflector. Furthermore, the deflection of light depends on the gravitational field along the line of sight, so it is sensitive to all forms of matter: luminous or dark, baryonic or exotic. Thus the images of gravitationally lensed quasars contain an imprint of the universe that is virtually inaccessible by any other means. The hope of decoding this imprint has stimulated observers and theorists to expend many thousands of hours of telescope time, computer time and cogitation on the elucidation of gravitational lens properties.

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Simulations of Large-Scale Structure in the New Millennium

Symposium - International Astronomical Union ◽

10.1017/s0074180900196548 ◽

2005 ◽

Vol 216 ◽

pp. 105-119 ◽

Cited By ~ 1

Author(s):

Yasushi Suto

Keyword(s):

Large Scale ◽

Large Scale Structure ◽

Vital Role ◽

Scale Structure ◽

Observational Cosmology ◽

Initial Condition ◽

The Galaxy ◽

The Universe ◽

Quasar Distribution ◽

New Millennium

Simulations of large-scale structure in the universe have played a vital role in observational cosmology since the 1980's in particular. Their important role will definitely continue to be true in the 21st century; indeed the requirements for simulations in the precision cosmology era will become more progressively demanding as they are supposed to fill the missing link in an accurate and reliable manner between the “initial” condition at z=1000 revealed by WMAP and the galaxy/quasar distribution at z=0 − 6 surveyed by 2dF and SDSS. In this review, I will summarize what we have learned so far from the previous cosmological simulations, and discuss several remaining problems for the new millennium.

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