Decoding the gravitational evolution of dark matter halos

Decoding the gravitational evolution of dark matter halos

Researchers at Kavli IPMU and their collaborators have revealed that considering environmental effects such as a gravitational tidal force spread over a scale much larger than a galaxy cluster is indispensable to explain the distribution and evolution of dark matter halos around galaxies. A detailed comparison between theory and simulations made this work possible. The results of this study, which are published in Physical Review D as an Editors' Suggestion, contribute to a better understanding of fundamental physics of the universe.

In the standard scenario for the formation of a cosmic structure, , which has an energy budget in the universe that is approximately five times greater than ordinary matter (e.g., atoms), first gathers gravitationally to form a crowded region, the so-called . Then these dark attract atomic gas and eventually form stars and galaxies. Hence, to extract cosmological information from a three-dimensional galaxy map observed in SDSS BOSS, the SuMIRe project, etc., it is important to understand how clustering of dark matter halos has gravitationally evolved throughout cosmic history. (This is referred to as the bias problem.)

"Various studies have described the halo bias theoretically," said Teppei Okumura, a project researcher involved in the study from Kavli IPMU. "However, none of them reproduced simulation results well. So, we extended prior studies motivated by a mathematical symmetry argument and examined if our extension works."

The authors demonstrate that higher-order nonlocal terms originating from such as gravitational tidal force must be taken into account to explain the halo bias in simulations. They also confirm that the size of the effect agrees well with a simple theoretical prediction.

"The results of our study allow the distribution of dark matter halos to be more accurately predicted by properly taking into account higher-order terms missed in the literature," said Shun Saito, the principal investigator of the study from Kavli IPMU. "Our refined model has been already applied to actual data analysis in the BOSS project. This study certainly improves the measurement of the nature of dark energy or neutrino masses. Hence, it has led to a better understanding of the of the universe."

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A warm dark matter search using XMASS: Editors' suggestion of Physical Review Letters

More information: Understanding higher-order nonlocal halo bias at large scales by combining the power spectrum with the bispectrum, Shun Saito*, Tobias Baldauf, Zvonimir Vlah, UroŇ° Seljak, Teppei Okumura, and Patrick McDonald, Physical Review D 90, 123522. DOI: 10.1103/PhysRevD.90.123522
Journal information: Physical Review D

Provided by Kavli Institute for the Physics and Mathematics of the Universe
Citation: Decoding the gravitational evolution of dark matter halos (2015, January 13) retrieved 16 September 2019 from
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Jan 14, 2015
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Jan 16, 2015
Dark matter has mass. Dark matter physically occupies three dimensional space. Dark matter is physically displaced by the particles of matter which exist in it and move through it.

The Milky Way's halo is not a clump of stuff anchored to the Milky Way. The Milky Way is moving through and displacing the dark matter.

The Milky Way's halo is the state of displacement of the dark matter.

The Milky Way's halo is the deformation of spacetime.

What is referred to geometrically as the deformation of spacetime physically exists in nature as the state of displacement of the dark matter.

A moving particle has an associated dark matter displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the dark matter passes through both.

Jan 19, 2015
Are Black holes made of DM?
Acceptable thought and a good question. The answer is that we don't really know. What we do know is that both normal and dark matter should fall inwards, but what both end up to be is a mystery.

Note that the 'black" in a black hole is not the same as the "dark" in DM. DM is dark because it doesn't interact with our familiar matter thus we have no way of trying to detect it (yet). A black hole is "black" because the gravity is so strong that even light will fall in.

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