Zooming In on Dark Matter Haloes

Dark Matter Haloes

An artist’s impression of dark matter haloes with various mass in the Universe. Credit: YU Jingchuan, Beijing Planetarium

Most matter in the Universe is dark and completely different in nature from the matter that makes up stars, planets and people. Galaxies form and grow when gas cools and condenses at the center of enormous clumps of this dark matter, the so-called dark matter haloes.

An international research team led by Prof. WANG Jie from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) used supercomputers in China and Europe to zoom in on a typical region of a virtual universe as if zooming in on an image of the Moon to see a flea on its surface.

The study was published in Nature on September 2, 2020.

The biggest dark matter haloes in today’s universe contain huge galaxy clusters, collections of hundreds of bright galaxies. The properties of such clusters, which weigh over a quadrillion (a million billion) times as much as our Sun, are well studied.

On the other hand, the masses of the smallest dark matter haloes are unknown. They are hypothesized to be about the mass of the Earth, according to currently popular theories.

Such small haloes would be extremely numerous, containing a substantial fraction of all the dark matter in the universe. However, they would remain dark throughout cosmic history because stars and galaxies grow only in haloes more than a million times as massive as the Sun.

“These small haloes can only be studied by simulating the evolution of the Universe in a large supercomputer,” said Prof. WANG.

Projected Dark Matter Density

Simulations of formation of dark matter haloes ranging in size from Earth mass to clusters of galaxies find a universal halo density structure spanning 20 orders of magnitude in mass. Credit: Dr. Sownak Bose, Center for Astrophysics, Harvard University

The research team, based at the National Observatory of the Chinese Academy of Sciences in China, Durham University in the UK, the Max Planck Institute for Astrophysics in Germany, and the Center for Astrophysics in the USA, took five years to develop, test and carry out their cosmic zoom.

It enabled them to study the structure of dark matter haloes of all masses between that of the Earth and that of a big galaxy cluster. In number, the zoom covers a mass range of 10 to the power 30 (that is a one followed by 30 zeroes), which is equivalent to the number of kilograms in the Sun.

By zooming-in on the virtual universe in such microscopic detail, the researchers were able to study the structure of dark matter haloes ranging in mass from that of the Earth to a big galaxy cluster.

“Surprisingly, we find that haloes of all sizes have a very similar internal structure, i.e., they are extremely dense at the center, become increasingly spread out, and have smaller clumps orbiting in their outer regions,” said Prof. WANG. “Without a measure scale it was almost impossible to tell an image of a dark matter halo of a massive galaxy from one whose mass is a fraction of the Sun.”

Particles of dark matter can collide near the centers of haloes, and may, according to some theories, annihilate in a burst of energetic (gamma) radiation.

Co-author, Prof. Carlos Frenk from Durham University said: “By zooming in on these relatively tiny dark matter haloes, we can calculate the amount of radiation expected to come from different sized haloes.”

Most of this radiation would be emitted by dark matter haloes too small to contain stars and future gamma-ray observatories might be able to detect these emissions, making these small objects individually or collectively “visible.”

“This would confirm the hypothesized nature of the dark matter, which may not be entirely dark after all,” said co-author Simon White from the Max Planck Institute of Astrophysics. “Our research sheds light on these small haloes as we seek to learn more about what dark matter is and the role it plays in the evolution of the universe.”

Read Zooming In Tight on Dark Matter for more on this research.

Reference: “Universal structure of dark matter haloes over a mass range of 20 orders of magnitude” by J. Wang, S. Bose, C. S. Frenk, L. Gao, A. Jenkins, V. Springel and S. D. M. White, 2 September 2020, Nature.
DOI: 10.1038/s41586-020-2642-9

The simulations were carried out in the Cosmology Machine supercomputers in Guangzhou, China, Durham, England of the UK, and Munich, Germany.

8 Comments on "Zooming In on Dark Matter Haloes"

  1. But why is it called dark matter, isn’t it a form of energy in a certain vibrational frequency we didn’t know

  2. No Emi, it isn’t.
    It’s a form of bullshit.

  3. … in the words of a famous physicist, which one I don’t remember now, ” one should only do calculations when it knows the results it needs to get”.
    In the world of book keeping it is called “book cooking”, not nice practice, but also possible…
    … it is like the math is the language of the Universe, but does it have to be. No, I don’t think it needs to be the language of the Universe.
    It is just a cover story, that clicks sometimes and sometimes it doesn’t…

  4. Torbjörn Larsson | September 7, 2020 at 8:33 am | Reply

    That they see cusped clumps like the early dark matter halo models is no surprise. For galactic halos the dark matter models were complemented with normal matter circulation, which is driven by supernovae feedback say, and then became smooth in the core and fitted our observations best.

    More surprising is the large clump size cut off. Observations of clump distributions in galactic strong lensing has spoken of “structures ranging from hundreds of thousands of times the mass of the Milky Way galaxy to clumps no more massive than the heft of a commercial airplane.” [NASA website.]

    @No, Emi, King rocker, it isn’t – and what does any of that mean, and why would it be any of that?

    Dark matter is a cold (massive particle) gas.

    It is seen by many independent means. [Starting with the cosmic background spectra over imprints in galaxy positions (so called baryonic acoustic oscillation imprints) to structures on all scales. (From cosmic filaments that harbor galaxy clusters over the clusters themselves to galaxies down to dwarf galaxy size.)]

    It seems dark matter is only interacting by gravity, so even less perceptible in daily life than the once seen-as-bullshit neutrinos*. But it is – since it is on average 5 times more mass within the universe than easily seen matter – an important part of modern cosmology which lends it its name: Lambda (dark energy Cold Dark Matter model [ https://en.wikipedia.org/wiki/Lambda-CDM_model ]. That is also the only model that explains what we see at the large statistics and high precision we now can resolve observations!

    * For instance, the clump that should be weakly associated with our solar system should mass about an average sized asteroid worth. That is 100,000 times less mass disturbance than we could notice with our best orbit models (say).

    On the other hand anyone can pull out a cosmic background spectra and easily identify the dark matter dominated peaks by sight – don’t even need a ruler – see for instance PBS Space Time free programs with an astrophysicist explaining how [youtube “Secrets of the Cosmic Microwave Background” @PBS Space Time.

    • Torbjörn Larsson | September 7, 2020 at 8:40 am | Reply

      Some dropped closing parentheses, but I think it is readable.

      Note also that when I say “gas” I mean in the astronomer/cosmologist sense, a cloud of particles. Dark matter is not found with in the standard particle models (where for example neutrinos sits). It is something new and so exciting!

  5. Martin Másílko | September 10, 2020 at 3:27 pm | Reply

    Great work! @Harvard & Smithsonian Center for Astrophysics (Jie Wang, Sownak Bose, Carlos S. Frenk, Liang Gao, Adrian Jenkins, Volker Springel, Simon D. M. White)

    So called Dark Matter is in fact the Noosphere.

    We can imagine it as following:
    * Collapse our entire 3D / 4D world into a TV screen – a 2D world
    * Now, we are making various experiments on the screen (2D collapsed Universe)
    * We don’t “consider” the remaining “hardware” producing the image – there are multiple wires and chips, processing the image behind the screen
    * The Dark Matter is these chips and wires
    * Happily, we can “see” on your pictures some of these
    * As the Universe is more living than a thing, thus, we can see more organic structures in your simulation

    Let’s focus on how the Noosphere really works.

    The Noosphere is an “interface”, forming our reality. It follows certain laws as well, which are still waiting to be explored. An initial research was performed here: http://noosphere.princeton.edu/.

    An enabling idea for this option is Princeton PEAR research: (https://web.archive.org/web/*/https://www.princeton.edu/~pear/ and https://www.amazon.com/Consciousness-Source-Reality-Robert-Jahn/dp/1936033038) – i.e. “Our thoughts and emotions are creating the Universe in physical means.”

    @skanda42

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