This multicolored image of colliding galaxy cluster MACS J0416.1–2403 shows optical data from Hubble plus X-ray data (pink) from Chandra and gravitational lensing data (blue) all superimposed together. The effects of gravitational lensing are clearly visible in the distortion of background galaxies behind the cluster. (Credit: NASA, ESA, CXC, NRAO/AUI/NSF, STScI, and G. Ogrean (Stanford University); Acknowledgment: NASA, ESA, J. Lotz (STScI), and the HFF team)
How do normal matter and dark matter separate by so much when galaxy clusters collide? Astronomers find the surprising, unexpected answer.
When galaxy clusters collide, something fascinating happens.
The colliding galaxy cluster “El Gordo,” the largest one known in the observable Universe, shows the same evidence of dark matter and normal matter separating when galaxy clusters collide, as seen in other colliding clusters. If normal matter alone is to explain gravity, its effects must be non-local: where gravity is found where the mass/matter isn’t. (Credit: NASA, ESA, J. Jee (Univ. of California, Davis), J. Hughes (Rutgers Univ.), F. Menanteau (Rutgers Univ. & Univ. of Illinois, Urbana-Champaign), C. Sifon (Leiden Obs.), R. Mandelbum (Carnegie Mellon Univ.), L. Barrientos (Univ. Catolica de Chile), and K. Ng (Univ. of California, Davis))
The individual galaxies and collisionless dark matter simply pass through one another, unscathed.
This Hubble Space Telescope image of galaxy cluster Abell 1689 has had its mass distribution reconstructed via the effects of gravitational lensing, and that map is overlaid atop the optical image in blue. If a major interaction can separate the gas in the intracluster medium from the position of the galaxies, the existence of dark matter can be put to the test. Differences between pre-collisional and post-collisional clusters is key evidence in the conclusion that dark matter is the leading explanation for what we observe in our Universe. (Credit: NASA, ESA, E. Jullo (Jet Propulsion Laboratory), P. Natarajan (Yale University), and J.-P. Kneib (Laboratoire d’Astrophysique de Marseille, CNRS, France); Acknowledgment: H. Ford and N. Benetiz (Johns Hopkins University), and T. Broadhurst (Tel Aviv University))
But the gas within each cluster collides, heats up, and slows down.
By combining data of Pandora’s Cluster, Abell 2744, from the infrared JWST and from the X-ray sensitive Chandra space observatories, scientists were able to identify a number of lensed galaxies, including one that emits copious amounts of X-ray light from very early on in the Universe’s history, despite having extremely little ultraviolet/optical/infrared light. This “overmassive” black hole holds key information about the formation and growth of black holes. (Credits: X-ray: NASA/CXC/SAO/Ákos Bogdán; Infrared: NASA/ESA/CSA/STScI; Image Processing: NASA/CXC/SAO/L. Frattare & K. Arcand; Animation: E. Siegel)
This creates an observed separation between the light-emitting gas and the gravitational effects of overall mass.
