- A brand new research suggests dark matter might have collisional properties, difficult the standard cosmological model.
- The research analyzed the habits of dark matter within the El Gordo cluster, supporting the self-interacting dark matter idea.
- Huge galaxy clusters like El Gordo present precious insights into the collisional properties of dark matter.
Self-interacting dark matter explains El Gordo
Scientists suppose 27% of the universe consists of dark matter, a mysterious however unseen substance. And if dark matter can work together with itself, it might clarify the habits of the largest galaxy clusters within the universe.
That’s the perception Riccardo Valdarnini on the Scuola Internazionale Superiore di Studi Avanzati (SISSA) in Trieste, Italy, reported in a latest evaluation late final month. Valdarnini checked out mass concentrations within the El Gordo galaxy cluster. He discovered the distribution helps a mannequin of self-interacting dark matter (SIDM). The peer-reviewed journal Astronomy and Astrophysics published the research on April 12, 2024.
El Gordo – Spanish for the fats one and cataloged as ACT-CL J0102-4915 – is the most important identified merger of galaxy clusters but noticed. Measurements from the Hubble Area Telescope recommend El Gordo, which sits 9.7 billion light-years from Earth, comprises 3 million billion (3,000,000,000,000,000) instances the mass of our sun. However solely a part of that’s common matter. Most of it – about 90%, in response to Valdarnini – is invisible dark matter.
Chilly dark matter clumps up an excessive amount of
Valdarnini’s work on the mass distribution in El Gordo strongly suggests bits of dark matter are colliding with one another. These interactions helped form El Gordo’s final kind. He defined what he present in a SISSA news release from Could:
The calculations indicated that on this cluster the noticed bodily separation between the factors of most density of dark matter and people of the opposite mass elements could be defined utilizing the so-called SIDM (self-interacting dark matter) mannequin, versus the usual one.
The usual clarification – chilly dark matter (CDM) – says the stuff doesn’t play properly with others. It solely interacts gravitationally with common matter however doesn’t seem to come back into contact with it or with itself. However that’s not what we discover in El Gordo.
Essentially the most vital results of this simulation research is that the relative separations noticed between the totally different mass centroids of the El Gordo cluster are naturally defined if the dark matter is self-interacting.
Invisible mass makes El Gordo lopsided
The mass of El Gordo has three components: galaxies, gasoline and dark matter. Beneath the CDM mannequin, the middle of mass for the galaxies and dark matter needs to be identical. Within the SIDM mannequin, nonetheless, they need to be totally different. And that’s what the mathematical fashions of the El Gordo information exhibits.
A noteworthy characteristic is the height location of the totally different mass elements. At variance with what we see within the Bullet Cluster, one other vital instance of a colliding cluster, the X-ray peak (from El Gordo) precedes the southeast dark matter peak.
Which means, Valdarnini says, we’ve most likely discovered self-interacting dark matter in El Gordo.
For that reason, these findings present an unambiguous signature of a dark matter habits that displays collisional properties in a really energetic high-redshift cluster collision.
But there’s nonetheless work to do, he notes. His simulation numbers for El Gordo don’t fairly match up completely to remark.
This means that current SIDM fashions needs to be thought-about as solely a low order approximation. And the underlying bodily processes that describe the interplay of dark matter in main cluster mergers are extra complicated than could be adequately represented by the generally assumed strategy based mostly on the scattering of dark matter particles.
That stated, Valdarnini’s work gives sturdy proof that dark matter does work together with itself. And realizing that would result in a brand new understanding of an enormous and invisible portion of our universe.
Backside line: A not too long ago printed evaluation of the El Gordo galaxy cluster suggests its inside habits is likely to be a results of self-interacting dark matter (SIDM).
Read more: Dark matter, a mysterious substance … What is it?
Via Scuola Internazionale Superiore di Studi Avanzati (SISSA)
