Dark matter is classified as "cold", "warm", or "hot" according to its velocity (more precisely, its free streaming length). Many experiments to directly detect and study dark matter particles are being actively undertaken, but none have yet succeeded. The primary candidate for dark matter is some new kind of elementary particle that has not yet been discovered, in particular, weakly interacting massive particles (WIMPs). Most dark matter is thought to be non-baryonic in nature it may be composed of some as-yet undiscovered subatomic particles. Thus, dark matter constitutes 85% of total mass, while dark energy plus dark matter constitute 95% of total mass–energy content.īecause dark matter has not yet been observed directly, if it exists, it must barely interact with ordinary baryonic matter and radiation, except through gravity. In the standard Lambda-CDM model of cosmology, the total mass–energy of the universe contains 5% ordinary matter and energy, 27% dark matter and 68% of a form of energy known as dark energy. Other lines of evidence include observations in gravitational lensing and in the cosmic microwave background, along with astronomical observations of the observable universe's current structure, the formation and evolution of galaxies, mass location during galactic collisions, and the motion of galaxies within galaxy clusters. Primary evidence for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter. Dark matter is called dark because it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect or emit electromagnetic radiation, and is therefore difficult to detect. For this reason, most experts think that dark matter is abundant in the universe and that it has had a strong influence on its structure and evolution. Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained by accepted theories of gravity unless more matter is present than can be seen. When we allow σ v to vary and marginalize over it, the growth rate constraint becomes |$f\sigma _8=0.494^$| for FOV A.Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total mass–energy density or about 2.241×10−27 kg/m3. Our constraint is consistent with the prediction of general relativity fσ 8 ∼ 0.392 within the 1 σ confidence level. This corresponds to 4.2 σ detection of RSD. Adopting a ΛCDM cosmology with the fixed expansion history and no velocity dispersion (σ v = 0), and using the RSD measurements on scales above 8 h −1 Mpc, we obtain the first constraint on the growth rate at the redshift, f ( z)σ 8( z) = 0.482 ± 0.116 at z ∼ 1.4 after marginalizing over the galaxy bias parameter b( z)σ 8( z). RSD has been extensively used to test general relativity on cosmological scales at z < 1. We detect clear anisotropy due to redshift-space distortions (RSD) both in the correlation function as a function of separations parallel and perpendicular to the line of sight and its quadrupole moment. The survey, which uses the Subaru Telescope and covers a redshift range of 1.19 < z < 1.55, is the first cosmological study at such high redshifts. We measure the redshift-space correlation function from a spectroscopic sample of 2783 emission line galaxies from the FastSound survey.
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