Astrophysicists Detect Difference Between How Dark Matter Behaves in Theory and How It Appears to Act in Reality

Dark Matter Simulation

The universe’s funhouse mirrors are revealing a distinction between how darkish matter behaves in principle and the way it seems to behave in actuality.

Dark matter is the invisible glue that retains stars sure collectively inside a galaxy. It makes up most of a galaxy’s mass and creates an invisible scaffold that tethers galaxies to type clusters.

Dark matter doesn’t emit, take in, or replicate gentle. It doesn’t work together with any recognized particles. Its presence is thought solely by means of its gravitational pull on seen matter in area.

Although darkish matter is flippantly smeared all through the universe, it’s heaped in areas of area referred to as galaxy clusters. Each of those huge clusters, held collectively by gravity, is made up of about 1,000 particular person galaxies — every of which carries its personal dollop of darkish matter.

In a brand new research within the journal Science, Yale astrophysicist Priyamvada Natarajan and a crew of worldwide researchers analyzed Hubble Space Telescope photographs from a number of huge galaxy clusters and located that the smaller dollops of darkish matter related to cluster galaxies had been considerably extra concentrated than predicted by theorists.

The discovering implies there could also be a lacking ingredient in scientists’ understanding of darkish matter.

Hubble Space Telescope MACS J1206 Dark Matter

This Hubble Space Telescope picture exhibits the huge galaxy cluster MACS J1206. Embedded inside the cluster are the distorted photographs of distant background galaxies, seen as arcs and smeared options. These distortions are attributable to the quantity of darkish matter within the cluster, whose gravity bends and magnifies the sunshine from faraway galaxies. This impact, referred to as gravitational lensing, permits astronomers to check distant galaxies that will in any other case be too faint to see. Several of the cluster galaxies are sufficiently huge and dense to additionally distort and enlarge faraway sources. The galaxies within the three pullouts signify examples of such results. In the snapshots at higher proper and backside, two distant, blue galaxies are lensed by the foreground, redder cluster galaxies, forming rings and a number of photographs of the distant objects. The purple blobs across the galaxy at higher left denote emission from clouds of hydrogen in a single distant supply. The supply, seen 4 occasions due to lensing, could also be a faint galaxy. These blobs had been detected by the Multi-Unit Spectroscopic Explorer (MUSE) on the European Southern Observatory’s Very Large Telescope (VLT) in Chile. The blobs don’t seem within the Hubble photographs. MACS J1206 is a part of the Cluster Lensing And Supernova survey with Hubble (CLASH) and is one in all three galaxy clusters the researchers studied with Hubble and the VLT. The Hubble picture is a mixture of visible- and infrared-light observations taken in 2011 by the Advanced Camera for Surveys and Wide Field Camera 3.
Credit: NASA, ESA, P. Natarajan (Yale University), G. Caminha (University of Groningen), M. Meneghetti (INAF-Observatory of Astrophysics and Space Science of Bologna), the CLASH-VLT/Zooming groups; acknowledgment: NASA, ESA, M. Postman (STScI), the CLASH crew

“There’s a feature of the real universe that we are simply not capturing in our current theoretical models,” mentioned Natarajan, a senior writer of the research and a professor of astronomy and physics at Yale. “This could signal a gap in our current understanding of the nature of dark matter and its properties, as this exquisite data has permitted us to probe the detailed distribution of dark matter on the smallest scales.”

Astronomers are in a position to “map” the distribution of darkish matter inside galaxy clusters through the bending of sunshine the galaxies produce — an idea referred to as gravitational lensing. Like a funhouse mirror, gravitational lensing distorts the shapes of background galaxies that seem in telescope photographs of cluster galaxies. The increased the focus of darkish matter in a cluster, the extra dramatic the noticed lensing results.

The researchers used photographs from NASA’s Hubble Space Telescope, coupled with spectroscopy from the European Southern Observatory’s Very Large Telescope, to supply high-fidelity dark-matter maps.

A 3D view of the information confirmed the presence of darkish matter hills, mounds, and valleys. From this angle, the mapped darkish matter seems like a mountain vary, with peaked areas. The peaks are the dollops of darkish matter related to particular person cluster galaxies.

The particularly top quality of the research’s information allowed the researchers to check whether or not these darkish matter landscapes matched theory-based pc simulations of galaxy clusters with comparable plenty, positioned at roughly the identical distances.

What they found was that the simulations didn’t present any of the identical stage of dark-matter focus on the smallest scales — the scales related to particular person cluster galaxies.


Astronomers appear to have revealed a puzzling element in the best way darkish matter behaves. They discovered small, dense concentrations of darkish matter that bend and enlarge gentle way more strongly than anticipated. Credit: NASA’s Goddard Space Flight Center

“To me personally, detecting a gnawing gap — a factor of 10 discrepancy in this case — between an observation and theoretical prediction is very exciting,” Natarajan mentioned. “A key goal of my research has been testing theoretical models with the improving quality of data to find these gaps. It’s these kinds of gaps and anomalies that have often revealed that either we were missing something in the current theory, or it points the way to a brand-new model, which will have more explanatory power.”

Natarajan has spent greater than a decade confronting theoretical fashions of darkish matter with information from gravitational lensing. “The quality of data and the sophistication of models have only now converged to permit stress testing of the cold dark matter paradigm, and it has revealed a crack,” she mentioned.

For extra on this analysis:

Reference: “An excess of small-scale gravitational lenses observed in galaxy clusters” by Massimo Meneghetti, Guido Davoli, Pietro Bergamini, Piero Rosati, Priyamvada Natarajan, Carlo Giocoli, Gabriel B. Caminha, R. Benton Metcalf, Elena Rasia, Stefano Borgani, Francesco Calura, Claudio Grillo, Amata Mercurio and Eros Vanzella, 11 September 2020, Science.
DOI: 10.1126/science.aax5164

Natarajan mentioned the crew, which incorporates researchers from Italy, the Netherlands, and Denmark, plans to proceed stress testing theories of the character of darkish matter. The research’s first writer is Massimo Meneghetti of the Observatory of Astrophysics and Space Science in Bologna, Italy.

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