KiDS: The Universe Is More Homogeneous Than Expected

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bystander
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KiDS: The Universe Is More Homogeneous Than Expected

Post by bystander » Sat Aug 01, 2020 4:12 pm

The Universe Is More Homogeneous Than Expected
Kilo-Degree Survey (KiDS) | 2020 Jul 31
kids1000-massmap-zoom-hires[1].jpeg
A zoom-in on a part of the KiDS map, showing a patch of the Universe approximately
1.5 x 1 billion light years across. In this false-colour image high-density regions of
the Universe are shown in yellow, and low-density regions in pink. The grey square
shows the size of an individual KiDS image, with a full moon for scale. Over 1000
images make up the KiDS map. Credit: B.Giblin, K.Kuijken and the KiDS team.

New results from the Kilo-Degree Survey (KiDS) show that the universe is nearly 10 percent more homogeneous than the Standard Model of Cosmology (Λ-CDM) predicts. The latest KiDS map was made with the OmegaCAM on ESO's VLT Survey Telescope at Cerro Paranal in Northern Chile. A group of astronomers led from institutes in the Netherlands, Scotland, England and Germany have described the KiDS-1000 result in five articles ...

The new KiDS map covers about 1000 square degrees, which equates to 5% of the extragalactic sky. 31 million galaxies were used for the analysis. The galaxies are up to 10 billion light years away, which means their light was emitted when our Universe was less than half its present age.

KiDS uses the galaxies to map the distribution of matter in the Universe. This is done through weak gravitational lensing, where the light from distant galaxies is slightly deflected by the gravitational effect of large amounts of matter, such as galaxy clusters. That effect is used to determine the "clumpiness" of the distribution of the galaxies. This concerns all matter in the universe, of which more than 90 percent consists of invisible dark matter plus invisible tenuous gas.

Over time, the gravity of matter in the Universe makes it less and less homogeneous; areas with a little more mass than average attract matter from their surroundings, so increasing the contrast. Meanwhile the expansion of the Universe counteracts this growth. Both of these processes are gravity driven and are therefore of great importance for testing the Standard Model of Cosmology (Λ-CDM), which fairly accurately predicts how density variations increase with the age of the universe.

However, the new KiDS results show a discrepancy: the universe is nearly 10 percent more homogeneous than the standard model predicts. ...

Universe is more uniform than theory predicts
University College, London | 2020 Jul 31

KiDS-1000 Methodology: Modelling and inference for joint weak gravitational
lensing and spectroscopic galaxy clustering analysis
~ B. Joachimi et al KiDS-1000 catalogue: weak gravitational lensing shear measurements ~ Benjamin Giblin et al KiDS-1000 catalogue: Redshift distributions and their calibration ~ H. Hildebrandt et al KiDS-1000 Cosmology: Cosmic shear constraints and comparison
between two point statistics
~ Marika Asgari et al KiDS-1000 Cosmology: Multi-probe weak gravitational lensing and
spectroscopic galaxy clustering constraints
~ Catherine Heymans et al
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neufer
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Re: KiDS: The Universe Is More Homogeneous Than Expected

Post by neufer » Sat Aug 01, 2020 4:18 pm

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Art Neuendorffer