From astrobites: “Dark Matter in the Milky Way: ‘A Matter of Perspective’ “

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Astrobites

Jul 25, 2017
Nora Shipp

Title: The core-cusp problem: A matter of perspective
Authors: Anna Genina, Alejandro Benitez-Llambay, Carlos S. Frenk, Shaun Cole, Azadeh Fattahi, Julio F. Navarro, Kyle A. Oman, Till Sawala, Tom Theuns
First Author’s Institution: Institute for Computational Cosmology,University, UK

Status: Submitted to the Monthly Notices of the Royal Astronomical Society, Open Access

Dark matter dominates the Universe around us, far exceeding the amount of everyday baryonic matter that makes up humans, the Earth, and the entire visible Milky Way. Our galaxy is embedded in an invisible cloud of dark matter, which contains smaller dark matter clouds that orbit around us like satellites. These satellites do not contain big spiral galaxies like the Milky Way and, although they may contain smaller galaxies, they are made up of almost entirely dark matter, which means that they are very sensitive to the precise nature of the dark matter particle.

Today’s paper investigates whether two of the Milky Way’s largest satellite galaxies (Fornax and Sculptor, Figure 1) conflict with the leading theory of Cold Dark Matter (CDM), potentially requiring a complete reconsideration of our understanding of the evolution of the Universe.

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Projected density plot of a redshift {\displaystyle z=2.5} dark matter halo from a cosmological N-body simulation. The visible part of the galaxy (not shown in the image) lies at the dense centre of the halo and has a diameter of roughly 20 kiloparsecs. There are also many satellite galaxies, each with its own subhalo which is visible as a region of high dark matter density in the image. http://en.wikipedia.org/wiki/User:Cosmo0

Don’t get too excited, though. I will break the suspense and say that, as usual, the answer is “not yet” – we don’t know enough about these mini galaxies to throw away CDM. There is still a lot of work to be done if we want to break this paradigm.

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Figure 1. The Fornax (left) and Sculptor (right) galaxies. (Source: ESO)

See the full article here .

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