scholarly journals Determining Ω0 and λ0 from Cosmological Redshift Distortion of Galaxies and Quasars

1999 ◽  
Vol 183 ◽  
pp. 235-240
Author(s):  
Yasushi Suto
Keyword(s):  
Large Scale ◽  
Collaborative Work ◽  
Cosmological Parameters ◽  
Three Dimensional ◽  
Density Parameter ◽  
Cosmological Redshift ◽  
Peculiar Velocity ◽  
Dimensional Distribution ◽  
Space Distortion ◽  
The Universe

The three-dimensional distribution of galaxies in the redshift surveys differ from the true one since the distance to each galaxy cannot be determined by its redshift z only; for z ≪ 1 the peculiar velocity of galaxies, typically ∼ (100–1000)km/sec, contaminates the true recession velocity of the Hubble flow, while the true distance for objects at z ≳ 1 sensitively depends on the (unknown and thus assumed) cosmological parameters. This hampers the effort to understand the true distribution of large-scale structure of the universe. Nevertheless such redshift-space distortion effects are quite useful since through the detailed theoretical modeling, one can derive the peculiar velocity dispersions of galaxies as a function of separation, and also can infer the cosmological density parameter Ω0, the dimensionless cosmological constant λ0, and the spatial biasing factor b of galaxies and/or quasars, for instance. In this talk, I discuss the importance of such redshift distortion induced by the geometry of the universe, which summarizes the recent results of my collaborative work in this topic (Matsubara & Suto 1996; Nakamura, Matsubara, & Suto 1998; Magira, Matsubara, Jing, & Suto 1998).

Cosmology

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Galaxy Formation ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Big Bang ◽  
Newtonian Gravity ◽  
Microwave Background ◽  
Cosmological Redshift ◽  
Frw Model ◽  
The Big Bang ◽  
The Universe

This chapter is about the large-scale structure of the universe, how it is described in general relativity and recent advances in determining the cosmological parameters. The Hubble distance–redshift relationship is discussed. The assumptions of the FRW cosmologies are presented and the FRW solutions of Einstein equation are derived. The FRW model is interpreted in terms of Newtonian gravity. Cosmological redshift is explained. The evidence for dark matter and its possible origin are discussed. The evidence for the Big Bang is presented, including the cosmic microwave background and the latest measurements of the CMB by the Planck probe. The evidence for dark energy is discussed, along with its interpretation as an FRW cosmology with a non-zero cosmological constant. Computer models of galaxy formation are discussed. Outstanding cosmological puzzles are presented along with their possible solution by inflationary models.

scholarly journals Measuring the cosmic bulk flow with 6dFGSv

2014 ◽  
Vol 11 (S308) ◽  
pp. 336-339 ◽  
Author(s):  
Christina Magoulas ◽  
Christopher Springob ◽  
Matthew Colless ◽  
Jeremy Mould ◽  
John Lucey ◽  
...  
Keyword(s):  
Velocity Field ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Distortion Parameter ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Redshift Surveys ◽  
Luminous Matter ◽  
The Galaxy ◽  
Space Distortion

AbstractWhile recent years have seen rapid growth in the number of galaxy peculiar velocity measurements, disagreements remain about the extent to which the peculiar velocity field - a tracer of the large-scale distribution of mass - agrees with both ΛCDM expectations and with velocity field models derived from redshift surveys. The 6dF Galaxy Survey includes peculiar velocities for nearly 9 000 early-type galaxies (6dFGSv), making it the largest and most homogeneous galaxy peculiar velocity sample to date. We have used the 6dFGS velocity field to determine the amplitude and scale of large-scale cosmic flows in the local universe and test standard cosmological models. We also compare the galaxy density and peculiar velocity fields to establish the distribution of dark and luminous matter and better constrain key cosmological parameters such as the redshift-space distortion parameter.

scholarly journals The AAO 2DF QSO Redshift Survey

1999 ◽  
Vol 183 ◽  
pp. 178-184 ◽  
Author(s):  
B.J. Boyle ◽  
R.J. Smith ◽  
T. Shanks ◽  
S.M. Croom ◽  
L. Miller
Keyword(s):  
Large Scale ◽  
Cosmological Parameters ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Redshift Survey ◽  
The Universe

The study of large-scale structure through QSO clustering provides a potentially powerful route to determining the fundamental cosmological parameters of the Universe (see Croom & Shanks 1996). Unfortunately, previous QSO clustering studies have been limited by the relatively small sizes of homogeneous QSO catalogues that have been available. Although approximately 10,000 QSOs are now known (Veron-Cetty & Veron 1997), the largest catalogues suitable for clustering studies contain only 500–1000 QSOs (Boyle et al. 1990, Crampton et al. 1990, Hewett et al. 1994). Even combining all such suitable catalogues, the total number of QSOs which can be used for clustering studies is still only about 2000.

scholarly journals Clustering, Isotropy, and Redshift Cutoff

1986 ◽  
Vol 119 ◽  
pp. 447-454
Author(s):  
Patrick S. Osmer
Keyword(s):  
Optical Depth ◽  
Three Dimensional ◽  
Radial Distance ◽  
Specific Question ◽  
Dimensional Distribution ◽  
Steep Decline ◽  
Age Of The Universe ◽  
Short Time ◽  
The Universe ◽  
Luminosity Evolution

The topics of clustering, isotropy, and redshift cutoff are in reality just different aspects of the problem of the three-dimensional distribution of quasars, assuming, of course that the redshifts are cosmological and therefore an indication of radial distance. The distribution in redshift has additional interest because of the substantial lookback times involved, up to four fifths of the age of the universe. The radial variation of quasar density between redshift zero and two, and the attendant questions of density and luminosity evolution, are discussed elsewhere in this symposium by Green and shall not be treated here. Rather we shall concern ourselves with the behavior at redshifts larger than two and the specific question of a steep decline of quasar density at redshifts near three. For simplicity we may characterize the problem as one of studying either the formation of quasars as we normally see them in a cosmologically short time or of the properties of the universe and its optical depth, should intergalactic absorption contribute significantly to blocking our view at redshift three. Of course other hypotheses are also possible.

scholarly journals Shifting fish distributions in warming sub-Arctic oceans

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Steven E. Campana ◽  
Ragnhildur B. Stefánsdóttir ◽  
Klara Jakobsdóttir ◽  
Jón Sólmundsson
Keyword(s):  
Fish Species ◽  
Climate Warming ◽  
Large Scale ◽  
Linear Models ◽  
Three Dimensional ◽  
Species Abundance ◽  
Time Frame ◽  
Thermal Limits ◽  
Dimensional Distribution ◽  
Distribution Shifts

Abstract The distributional response of marine fishes to climate warming would be expected to be very different than that of homeothermic birds and mammals, due both to more direct thermal effects on poikilothermic fish physiology and on reduced habitat fragmentation. In this study, we use a combination of linear models and graphical tools to quantify three-dimensional distribution shifts in 82 fish species caught in 5390 standardized groundfish survey tows over a 22-year time frame in the highly-productive sub-Arctic waters around Iceland. Over a 1 °C range, temperature significantly modified the distributional centroids of 72% of all fish species, but had relatively little effect on diversity. Most of the geographic shifts were to the northwest, and there was no overall tendency to move to deeper waters. A doubling of species abundance significantly influenced the distribution of 62% of species, but lacked the poleward orientation observed with temperature increases. Stenothermal species, those near their upper or lower thermal limits, and those with restricted spatial ranges were most likely to shift their distribution in response to climate warming, while deepwater species were not. A 2–3 °C warming of marine waters seems likely to produce large-scale changes in the location of many sub-Arctic fisheries.

Observational and astrophysical cosmology: 1980–2018

2019 ◽  
pp. 375-423
Author(s):  
Malcolm S. Longair
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Constant ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Semiconductor Detectors ◽  
Empirical Knowledge ◽  
Global Geometry ◽  
The Universe ◽  
Large Scale Structure Formation

Since 1980, our empirical knowledge of the universe has advanced tremendously and precision cosmology has become a reality. These developments have been largely technology-driven, the result of increased computer power, new generations of telescopes for all wavebands, new types of semiconductor detectors, such as CCDs, and major investments by many nations in superb observing facilities. The discipline also benefitted from the influx of experimental and theoretical physicists into the cosmological arena. The accuracy and reliability of the values of the cosmological parameters has improved dramatically, many of them now being known to about 1%. The ΛCDM model provides a remarkable fit to all the observational data, demonstrating that the cosmological constant is non-zero and that the global geometry of the universe is flat. The underlying physics of galaxy and large-scale structure formation has advanced dramatically and demonstrated the key roles played by dark matter and dark energy.

Three-dimensional simulation of large-scale structure in the Universe

Nature ◽  
1983 ◽  
Vol 305 (5931) ◽  
pp. 196-198 ◽  
Author(s):  
Joan Centrella ◽  
Adrian L. Melott
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Dimensional Simulation ◽  
The Universe

scholarly journals The flatness problem and the age of the Universe

2020 ◽  
Vol 495 (4) ◽  
pp. 3571-3575
Author(s):  
Phillip Helbig
Keyword(s):  
Early Universe ◽  
Time Scale ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Fine Tuning ◽  
Density Parameter ◽  
Age Of The Universe ◽  
Short Time ◽  
The Universe ◽  
Flatness Problem

ABSTRACT Several authors have made claims, none of which has been rebutted, that the flatness problem, as formulated by Dicke and Peebles, is not really a problem but rather a misunderstanding. Nevertheless, the flatness problem is still widely perceived to be real. Most of the arguments against the idea of a flatness problem are based on the change with time of the density parameter Ω and normalized cosmological constant λ and, since the Hubble constant H is not considered, are independent of time-scale. An independent claim is that fine-tuning is required in order to produce a Universe which neither collapsed after a short time nor expanded so quickly that no structure formation could take place. I show that this claim does not imply that fine-tuning of the basic cosmological parameters is necessary, in part for similar reasons as in the more restricted flatness problem and in part due to an incorrect application of the idea of perturbing the early Universe in a gedankenexperiment; I discuss some typical pitfalls of the latter.

Statistical studies of the spatial distribution of galaxies

1996 ◽  
Vol 28 (02) ◽  
pp. 337-338
Author(s):  
Vicent J. Martínez ◽  
María Jesús Pons-Bordería
Keyword(s):  
Spatial Distribution ◽  
Structure Formation ◽  
Statistical Study ◽  
Three Dimensional ◽  
Dimensional Distribution ◽  
Statistical Studies ◽  
The Universe ◽  
Clustering Patterns

The statistical study of the clustering patterns formed by the three-dimensional distribution of galaxies is one of the most important observational clues to discriminate between rival theories of structure formation in the Universe.

scholarly journals A kinematic confirmation of the hidden Vela supercluster

2019 ◽  
Vol 490 (1) ◽  
pp. L57-L61 ◽  
Author(s):  
Hélène M Courtois ◽  
Renée C Kraan-Korteweg ◽  
Alexandra Dupuy ◽  
Romain Graziani ◽  
Noam I Libeskind
Keyword(s):  
Excellent Agreement ◽  
Mass Concentration ◽  
Large Scale ◽  
Milky Way ◽  
Large Scale Structure ◽  
Peculiar Velocity ◽  
The Galaxy ◽  
Zone Of Avoidance ◽  
First Time ◽  
The Universe

ABSTRACT The Universe region obscured by the Milky Way is very large and only future blind large H i redshift, and targeted peculiar surveys on the outer borders will determine how much mass is hidden there. Meanwhile, we apply for the first time two independent techniques to the galaxy peculiar velocity catalogue CosmicFlows−3 in order to explore for the kinematic signature of a specific large-scale structure hidden behind this zone: the Vela supercluster at cz ∼18 000 km s−1. Using the gravitational velocity and density contrast fields, we find excellent agreement when comparing our results to the Vela object as traced in redshift space. The article provides the first kinematic evidence of a major mass concentration (knot of the Cosmic Web) located in the direction behind Vela constellation, pin pointing that the Zone of Avoidance should be surveyed in detail in the future.

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