“A new dark force?” | The daily galaxy

"A new dark force?"

Everything we know about the universe and all the laws of physics apply to four percent of the universe. The other 96 percent are unknown incidents of dark matter and dark energy. Neil Degrese Tyson says, “If we know all of the matter and energy we’re familiar with,” and measure how much gravity there must be, that’s one-sixth of the gravity that actually works on the universe. Used to be. We call that dark matter. It really should be called Dark Gravity. And we don’t know what that is. ”

Now, a new theory about the nature of dark matter as a “dark force” helps to explain that a pair of galaxies about 65 million light-years from Earth contains very few mysterious substances, a physicist According to the study led by University of California, Riverside.

Insane Search for Dark Matter Signals – “Where Are They Hidden?”

Dark matter is non-juminous and cannot be directly observed. Thought to make up 85% of matter in the universe, its nature is not well understood. Unlike ordinary matter, it does not absorb, reflect or emit light, making it difficult to detect.

New Theory-A Dark Force

The prevailing Dark Matter theory, known as cold dark matter or CDM, holds that particles of dark matter are non-collision, which are separated by gravity. A new second theory, called Self-Interacting Dark Matter or SIDM, proposes to self-interact Dark Matter particles through a dark dark force. Both theories explain how the overall structure of the universe emerges, but they predict different dark matter distributions in the inner regions of a galaxy. SIDM suggests that dark matter particles collide with each other in the inner halo of a galaxy, which is close to its center.

NGC 1052 dF2

Typically, a visible galaxy is hosted by an invisible Dark Matter halo – a concentrated group of material, a ball-shaped one, that circles the galaxy and is held together by gravitational forces. Recent observations of two ultra-diffuse galaxies, NGC 1052-DF2 (image above) and NGC 1052-DF4, show that very few, none, dark matter, challenging physicists in this pair of galaxies Understanding of galaxy formation. Astronomical observations suggest that NGC 1052-DF2 and NGC 1052-DF4 are likely satellite galaxies of NGC1052 (picture above).

SIDM Forms are Dark-Matter-Deficient Galaxy

Hai-Bo Yu, associate professor of physics and astronomy at UCR, led the study, saying, “It is generally believed that dark matter dominates the overall mass in a galaxy.” NGC 1052-DF2 and -DF4 show observations, however, that their dark matter ratio to their dark mass is about 1, which is 300 times less than expected. To resolve the discrepancy, we assumed that DF2 and DF4 hallows may lose most of their mass through tidal interactions with the massive NGC 1052 galaxy. “

“Missing” – Can Dark Matter Become a Source of Light in the Universe?

Using sophisticated simulations, the UCR-led team reproduced the properties of NGC 1052-DF2 and NGC 1052-DF4 through tidal stripping – away from the material by galactic tidal forces – by NGC 1052. Because satellite galaxies cannot capture the stripped mass with their own gravitational forces, it effectively adds to the mass of NGC 1052.

The researchers considered both CDM and SIDM scenarios. Their results, published in Physical Review Letters, indicate that SIDM makes dark matter-deficient galaxies like NGC 1052-DF2 and -DF4 much more than CDM, because tidal mass loss of the inner halo is more important and stellar distribution is more diffused. is. In SIDM.

“The Invisible World of Hidden Sector Particles” – Rathing Dark Matter

Yu pointed out that both CDM and SIDM can cause large scale losses. In CDM, the internal corona structure is “rigid” and flexible for tidal stripping, which makes it difficult for a typical CDM corona to lose sufficient internal mass in the tidal region to accommodate observations of NGC 1052-DF2 and -DF4 is. Conversely, in SIDM, dark matter self-interaction can push dark matter particles from inner to outer regions, making the inner aura “fulpher” and increasing tidal mass loss accordingly. In addition, the stellar distribution is more diffuse.

“A typical CDM halo remains on a much larger scale in interior areas even after tidal development,” Yu said.

Subsequently, the team will study the NGC 1052 system more extensively and explore newly discovered galaxies, as well as attempting to better understand the nature of dark matter.

The title of the research paper is “Self-Interacting Dark Matter and the Origin of Ultrafied Galaxies NGC1052-DF2 and -DF4”.

The Daily Galaxy, Max Goldberg, University of California via Riverside

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