Observations suggest a missing ingredient in the cosmic recipe

This Hubble Space Telescope image shows the massive galaxy cluster MACS J1206. Embedded within the cluster are distorted images of distant background galaxies, seen as arcs and smeared features. These distortions are caused by the amount of dark matter in the cluster, whose gravity increases the light from distant and distant galaxies. This effect, called gravitational lensing, allows astronomers to study distant galaxies that would otherwise be too faint to see. Many of the cluster galaxies are sufficiently massive and dense and extend to distant sources. The galaxies in the three bridges represent examples of such effects. In the top right and bottom snapshots, two distant, blue galaxies are lensed by foreground, redder cluster galaxies, forming multiple images of rings and distant objects. The red one refers to the emission in the upper left from clouds of hydrogen in an upper distant source. The lens, seen four times due to lensing, may be a faint galaxy. These blobs were detected by the Multi-Unit Spectroscopic Explorer (MUSE) at the European Southern Observatory’s Very Large Telescope (VLT) in Chile. The drops are not visible in the Hubble images. The MACS J1206 is part of a cluster licensing and supernova survey with Hubble (CLASH) and is one of the three galaxy clusters the researchers studied with Hubble and VLT. The Hubble image is a combination of visible and infrared-light observations taken by Advanced Camera and Wide Field Camera 3 in 2011.
Credit: NASA, ESA, p. Natarajan (Yale University), g. Camina (University of Groningen), m. Menegetti (INAF-Observatory of Astrophysics and Space Science of Bologna, Clash-VLT / zooming teams); Acknowledgment: NASA, ESA, M. Postman (STScI), CLASH Team

Astronomers have discovered that our cosmic recipe may have a missing component in how dark matter behaves.

Astronomers have uncovered a discrepancy between the theoretical model of how dark matter should be distributed among galaxy clusters, and the observation of dark matter hold over clusters.

Dark matter does not emit, absorb, or reflect light. Its presence is known only through its gravitational pull on the visible matter in space. Therefore, the Dark Matter remains elusive as the Cheshire Cat of Alice in Wonderland – where you see only your grin (as gravity), but not the animal itself.

One way astronomers can detect dark matter is to measure how gravity affects gravity, an effect called gravitational lensing.

Researchers found that small-scale concentrations of dark matter in clumps produce gravitational lensing effects that are 10 times stronger than expected. This evidence is based on unprecedented detailed observations of several large-scale galaxy clusters. NASAOf Hubble Space Telescope And European Southern Observatory Very large telescope (VLT) in Chile.

Astronomers seem to have revealed in great detail the way dark matter behaves. They found small, dense concentrations of dark matter, which bend and amplify light more strongly than expected. Credit: NASA’s Goddard Space Flight Center

The largest repository of the galaxy cluster Dark Matter is the largest structure in the universe made up of galaxies of individual clusters. Not only are they largely held together by the gravity of dark matter, individual cluster galaxies reunite themselves with dark matter. In bunches, dark matter is therefore distributed on both large and small scales.

“If it is understood that computer simulations of the universe reliably reproduce what we can infer about dark matter and luminous matter,” said Massivetti of Astrophysics and Space Science, INAF (National Institute of Astrophysics). Huh. Bologna in Italy, lead author of the study.

“We have done very careful testing in this study comparing simulations and data, and our search for mismatch continues,” Menegaty said. “One possible origin for this discrepancy is that we are missing some key physics in the simulation.”

Priyamvada Natarajan’s Yale University One of the senior theorists in the New Haven, Connecticut, team, stated, “There is a feature of the real universe that we simply do not capture in our current theoretical model. It is our current understanding of the nature and properties of Dark Matter May indicate a difference in understanding, as these exquisite data have allowed us to examine the broad distribution of dark matter at the smallest scales. ”

The team’s paper will appear in the September 11 issue of the journal Science.

The distribution of dark matter in bunches is mapped through the bending of light, or gravitational lensing effects. Dark Matter’s gravity amplifies and heats light from distant background objects, like a funhouse mirror, producing distortions and sometimes multiple images of the same distant galaxy. The higher the concentration of dark matter in a cluster, the more dramatically its light bends.

Hubble’s crisp images, combined with spectra from VLT, help the team create accurate, high-fidelity dark-matter maps. They identified dozens of multiplied, lensed, background galaxies. By measuring lensing distortions, astronomers can detect the volume and distribution of dark matter.

The three major galaxy clusters used in the analysis, MACS J1206.2-0847, MACS J0416.1-2403 and Abel S1063, were part of two Hubble surveys: cluster licensing and supernova surveys with Frontier Fields and Hubble (CLASH). program.

To the team’s surprise, the Hubble images also revealed small-scale arcs and distorted images nested within large-scale lens distortions in the core of each cluster, where the largest-scale galaxies reside.

Researchers believe that embedded lenses are formed by gravity of dense concentrations of dark matter associated with individual cluster galaxies. The distribution of dark matter in the interior regions of individual galaxies is known to increase the overall lensing effect of the cluster.

Subsequent spectroscopic observations were added to the study by measuring the velocity of stars orbiting inside cluster galaxies. “Based on our spectroscopic study, we were able to connect galaxies with each cluster and estimate their distances,” said Piero Rosati, a team member at the University of Ferrara in Italy.

“The motion of the stars gave us an estimate of the mass of each individual galaxy, including the amount of dark matter,” said Pietro Bergamini, a member of the Astro-Observatory and Astronomy team in Bologna, Italy.

The team compared dark matter maps with samples of simulated galaxy clusters with similar masses, which are located at the same distance as the observed clusters. In computer simulations the clusters did not show the same level of dark-matter concentration at the smallest scale – the scales associated with different cluster galaxies seen in the universe.

The team looks forward to continuing its stress-testing of the standard Dark-Matter model to ease its intense nature.

NASA’s planned Nancy Grace Roman Space Telescope will detect even more remote galaxies through gravitational lensing by massive galaxy clusters. The observations will enlarge the sample of clusters that astronomers can analyze to further test the dark-matter model.

References: “Massimo Menegetti, Guido Davoli, Pietro Bergamini, Piero Rosati, Priyamvanda Natarajan, Carlo Giocoli, Gabriel B. Caminha, R. Benton Metcalfe, Elena Rasia, Stefano Borgano,” An additional number of small-scale gravitational lenses of galaxy groups. Is seen in , Francesco Calura, Claudio Grillo, Amata Mercurio and Eros Vanzella, 11 September 2020, Sci.
DOI: 10.1126 / science.ax 5164

The Hubble Space Telescope is a project of international collaboration between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland manages the telescope. The Hubble Science Operations at Space Telescope Science Institute (STScI) in Baltimore. STScI is run for NASA by the Association of Universities for Research in Astronomy in Washington, DC

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