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The Hubble Space Telescope image shows the massive galaxy cluster MACS J1206. Embedded within the cluster are the distorted images of distant background galaxies, which look like arcs and speckled features. These distortions are caused by the amount of dark matter in the cluster, the gravity of which bends and amplifies light from distant galaxies. This effect, called gravitational lensing, allows astronomers to study distant galaxies that would otherwise be too faint to see. Many cluster galaxies are massive and dense enough to distort and amplify distant sources. The galaxies in the three retreats are examples of these effects. In the snapshots of the upper right and lower section, two blue galaxies are lensing apart through the front red cluster of galaxies, forming rings and multiple images of distant objects. Red dots around the galaxy in the upper left indicate an emission of hydrogen clouds from a distant source. The source, seen four times through the lens, could be a faint galaxy. These spots were detected by the Multiple Unit Spectral Explorer (MUSE) on the Very Large Telescope (VLT) at the European Southern Observatory in Chile. The points do not appear in the Hubble images. MACS J1206 is part of the Hubble Cluster Lensing and Supernova Survey (CLASH) and is one of three galactic clusters that researchers studied with Hubble and VLT. The Hubble image is a combination of visible and infrared light observations captured in 2011 by Advanced Surveys Camera and Wide Field Camera 3.
Image credit: NASA, European Space Agency, b. Natarajan (Yale University), JC Kamenha (University of Groningen), M. Minghetti (INAF Observatory for Astrophysics and Space Sciences in Bologna), CLASH-VLT / Zooming teams; Endorsement: NASA, ESA, M. Postman (STScI) and the CLASH team
Astronomers have discovered that an element may be missing from our cosmic description of how dark matter behaves.
Astronomers have discovered a discrepancy between theoretical models of how dark matter is distributed in galaxy clusters and observations of the dominance of dark matter over clusters.
Dark matter does not emit, absorb, or reflect light. Its existence is only known for its attractiveness to visible matter in space. So dark matter is still as elusive as the Cheshire cat in Alice in Wonderland, where you only see its smile (in gravity form) but not the animal itself.
One of the ways astronomers can detect dark matter is by measuring how its gravitational tugs distort space, an effect called gravitational lensing.
The researchers found that small concentrations of dark matter in the clusters produced gravitational lensing effects ten times stronger than expected. This evidence is based on unprecedented detailed observations of many massive galaxy clusters. POTit is hubble space telescope And the European Southern Observatory Very large telescope (VLT) in Chile.
Astronomers seem to have discovered puzzling details about the behavior of dark matter. They found small, dense concentrations of dark matter that bent and amplified light with much greater force than expected. Credit: NASA Goddard Space Flight Center
Clusters of galaxies, the largest structures in the universe made up of individual galaxies, are the largest deposits of dark matter. Not only are they closely related to each other by the gravitational pull of dark matter, the individual galaxies in the cluster are also filled with dark matter. Therefore, dark matter is distributed in groups of large and small scales.
“Galactic clusters are ideal laboratories to understand whether computer simulations of the universe reproduce what we can infer about dark matter and its interaction with light matter,” said Massimo Mingetti of the National Institute of Astrophysics – Observatory of Astrophysics and Space Sciences. From Bologna, Italy, lead author of the study.
“We did a lot of rigorous testing comparing the simulations and data from this study, and we continue to uncover the mismatch,” Mengiti continued. “One possible reason for this discrepancy is that we could lose some basic physics in the simulations.”
Priamvada Natarajan Yale university In New Haven, Connecticut, a senior theorist on the team added: “There is a feature of the real universe that we just don’t capture in our current theoretical models. This may indicate a gap in our current understanding of the nature and properties of dark matter, as these impressive data allowed us to probe the detailed distribution of matter. Dark in the smallest scales. “
The team document will appear in the magazine’s September 11 issue. Sciences.
The distribution of dark matter in groups is determined by the curvature of light or the effect of the gravitational lens that produces them. Like a fun mirror, the gravity of dark matter amplifies and distorts light from distant objects in the background, producing distortions and sometimes multiple images of the same distant galaxy. The higher the concentration of dark matter in the cluster, the more dramatic the curvature of the light.
The clear images from Hubble, along with the spectra from the VLT, helped the team produce an accurate, high-resolution map of dark matter. They have identified dozens of galaxies with lenses and duplicate images. By measuring lens distortions, astronomers can track the amount and distribution of dark matter.
The three main galaxy clusters used in the analysis, MACS J1206.2-0847, MACS J0416.1-2403 and Abell S1063 were part of two Hubble scans: boundary fields and supernova and cluster lens scan using Hubble software. (Clash).
To the team’s surprise, the Hubble images also revealed smaller arcs and distorted images interlaced within the wide-range lens distortions at the core of each cluster, where the largest galaxies are located.
The researchers believe that the included lenses are caused by the gravitational pull of the dense concentrations of dark matter associated with individual galaxy clusters. The distribution of dark matter within individual galaxies is known to enhance the overall lensing effect of the cluster.
Tracking the spectral observations that were added to the study by measuring the speed of stars orbiting within many galaxy clusters. “Based on our spectroscopy, we were able to connect galaxies to each cluster and estimate their distances,” said team member Piero Rosati from the University of Ferrara in Italy.
“The speed of the stars gave us an estimate of the mass of each individual galaxy, including the amount of dark matter,” said team member Pietro Bergamini of the INAF Observatory for Astrophysics and Space Sciences in Bologna, Italy.
The team compared the dark matter maps with samples of simulated galaxies of similar masses that are roughly the same distances as the observed clusters. The clusters in the computer simulations did not exhibit the same level of dark matter concentration on the smallest scales – scales associated with individual galaxy clusters seen in the universe.
The team is looking to continue stress testing the standard model of dark matter to determine its intriguing nature.
NASA’s planned Roman Nancy Grace Space Telescope will discover more distant galaxies through gravitational lensing with massive galaxy clusters. The observations will expand the swarms of samples that astronomers can analyze for further testing of dark matter models.
The reference: “An excess of microgravitational lenses observed in galaxy clusters” by Massimo Mingetti, Guido Davoli, Pietro Bergamini, Piero Rosati, Priamvada Natarajan, Carlo Giocoli and Gabriel B. Kamenya, R., Francesco Calura, Claudio Grillo, Amata Mercurio and Eros Vanzella, September 11, 2020, Science.
DOI: 10.1126 / science.aax5164
The Hubble Space Telescope is an international cooperation project between NASA and the European Space Agency (European Space Agency). The telescope is operated by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Astronomical Research in Washington, DC
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